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  • Public defence: 2016-09-29 10:15 Planck, Fysik huset, Linköping
    Radosavljevic, Sonja
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Radosavljevic, Sonja
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Permanence of age-structured populations in a spatio-temporal variable environment2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    It is widely recognized that various biotic and abiotic factors cause changes in the size of a population and its age distribution. Population structure, intra-specific competition, temporal variability and spatial heterogeneity are identified as the most important factors that, alone or in combination, influence population dynamics. Despite being well-known, these factors are difficult to study, both theoretically and empirically. However, in an increasingly variable world, permanence of a growing number of species is threatened by climate changes, habitat fragmentation or reduced habitat quality. For purposes of conservation of species and land management, it is crucially important to have a good analysis of population dynamics, which will increase our theoretical knowledge and provide practical guidelines.

    One way to address the problem of population dynamics is to use mathematical models. The choice of a model depends on what we want to study or what we aim to achieve. For an extensive theoretical study of population processes and for obtaining qualitative results about population growth or decline, analytical models with various level of complexity are used. The competing interests of realism and solvability of the model are always present. This means that, on one hand, we always aim to make a model that will truthfully reflect reality, while on the other hand, we need to keep the model mathematically solvable. This prompts us to carefully choose the most prominent ecological factors relevant to the problem at hand and to incorporate them into a model. Ideally, the results give new insights into population processes and complex interactions between the mentioned factors and population dynamics.

    The objective of the thesis is to formulate, analyze, and apply various mathematical models of population dynamics. We begin with a classical linear age-structured model and gradually add temporal variability, intra-specific competition and spatial heterogeneity. In this way, every subsequent model is more realistic and complex than the previous one. We prove existence and uniqueness of a nonnegative solution to each boundary-initial problem, and continue with investigation of the large time behavior of the solution.

    In the ecological terms, we are establishing conditions under which a population can persist in a certain environment. Since our aim is a qualitative analysis of a solution, we often examine upper and lower bounds of a solution. Their importance is in the fact that they are obtained analytically and parameters in their expression have biological meaning. Thus, instead of analyzing an exact solution (which often proves to be difficult), we analyze the corresponding upper and lower solutions.

    We apply our models to demonstrate the influence of seasonal changes (or some other periodic temporal variation) and spatial structure of the habitat on population persistence. This is particularly important in explaining behavior of migratory birds or populations that inhabits several patches, some of which are of low quality. Our results extend the previously obtained results in some aspects and point out that all factors (age structure, density dependence, spatio-temporal variability) need to be considered when setting up a population model and predicting population growth.

    List of papers
    1. Estimating effective boundaries of population growth in a variable environment
    Open this publication in new window or tab >>Estimating effective boundaries of population growth in a variable environment
    2016 (English)In: Boundary Value Problems, ISSN 1687-2762, E-ISSN 1687-2770, 1-28 p., 2016:172Article in journal (Refereed) Published
    Abstract [en]

    We study the impact of age-structure and temporal environmental variability on the persistence of populations. We use a linear age-structured model with time-dependent vital rates. It is the same as the one presented by Chipot in (Arch. Ration. Mech. Anal. 82(1):13-25, 1983), but the assumptions on the vital rates are slightly different. Our main interest is in describing the large-time behavior of a population provided that we know its initial distribution and transient vital rates. Using upper and lower solutions for the characteristic equation, we define time-dependent upper and lower boundaries for a solution in a constant environment. Moreover, we estimate solutions for the general time-dependent case and also for a special case when the environment is changing periodically.

    National Category
    Probability Theory and Statistics Computational Mathematics
    Identifiers
    urn:nbn:se:liu:diva-131558 (URN)10.1186/s13661-016-0681-9 (DOI)
    Available from: 2016-09-26 Created: 2016-09-26 Last updated: 2016-09-26Bibliographically approved
    2. Persistence analysis of the age-structured population model on several patches
    Open this publication in new window or tab >>Persistence analysis of the age-structured population model on several patches
    2016 (English)In: Proceedings of the 16th International Conference on Mathematical Methods in Science and Engineering, July 4-8, Rota, Cadiz, Spain, Vol. III / [ed] J. Vigo-Aguiar, Universidad de Cádiz , 2016, Vol. 3, 717-727 p.Chapter in book (Refereed)
    Abstract [en]

    We consider a system of nonlinear partial differential equations that describes an age-structured population living in changing environment on $N$ patches. We prove existence and uniqueness of solution and analyze large time behavior of the system in time-independent case and for periodically changing environment. Under the assumption that every patch can be reached from every other patch, directly or through several intermediary patches, and that net reproductive operator has spectral radius larger than one, we prove that population is persistent on all patches. If the spectral radius is less or equal one, extinction on all patches is imminent.

    Place, publisher, year, edition, pages
    Universidad de Cádiz, 2016
    Keyword
    age-structure, persistence, Kermack-McKendrick equation, Lotcka-Volterra equation
    National Category
    Biological Sciences Mathematics
    Identifiers
    urn:nbn:se:liu:diva-130231 (URN)9788460860822 (ISBN)
    Conference
    Conference on Computational and Mathematical Methods in Science and Engineering, CMMSE 2016
    Note

    Associate Editors

    P. Schwerdtfeger (New Zealand), W. Sprößig (Germany), N. Stollenwerk (Portugal), Pino Caballero (Spain), J. Cioslowski (Poland), J. Medina (Spain), I. P. Hamilton (Canada), J. A. Alvarez-Bermejo (Spain)

    Available from: 2016-07-21 Created: 2016-07-21 Last updated: 2016-08-31Bibliographically approved
  • Public defence: 2016-09-29 13:15 ACAS, Hus A, Linköping
    Örnerheim, Mattias
    Linköping University, Department of Management and Engineering, Political Science. Linköping University, Faculty of Arts and Sciences.
    Örnerheim, Mattias
    Linköping University, Department of Management and Engineering, Political Science. Linköping University, Faculty of Arts and Sciences.
    Mellan kunskap och politik: Kvalitetssystem och offentlig kunskapsstyrning i hälso- och sjukvården2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim with this thesis is to describe the quality development in Swedish healthcare from an institutional perspective, analyse implications of the development concerning the relationship between the medical profession and the public administrative system and discuss consequences for political direction and welfare organization. The study is based on four case studies and one conceptual analysis.

    The main conclusion is that the medical quality systems have been imbedded in the political management alongside the development towards a public knowledge management. The analysis has more specifically uncovered that quality registries in healthcare have been influenced by political ideologies, management ideas and ideas of transparency. It is also clear that open comparisons were an ‘unintended consequence’ of the quality registry development that has enhanced the development towards a public knowledge management.

    The analysis also shows that public knowledge management challenges the ideal of democratic enlightened understanding. The development of public knowledge management in the healthcare sector raises the question of who is governing whom in Swedish healthcare.

    List of papers
    1. Explaining Quality Management in the Danish and Swedish Public Health Sectors: Unintended Learning and Deliberate Co-Optation
    Open this publication in new window or tab >>Explaining Quality Management in the Danish and Swedish Public Health Sectors: Unintended Learning and Deliberate Co-Optation
    2016 (English)In: International Journal of Public Administration, ISSN 1532-4265Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    This article examines the development of diverse quality systems in the otherwise quite similar Danish and Swedish public health sectors. After decades of numerous piecemeal medical and managerial quality development programs in both countries, a nationwide mandatory accreditation system was introduced in the Danish health services in 2009. Nationwide quality indicator projects are also found in Sweden, but there has been political attempt to introduce a compulsory system. This article seeks to explain this difference. It argues, first, that resistance from the medical professions blocked the introduction of compulsory, nationwide quality systems in both countries for decades. Second, the implementation of the Danish accreditation system was triggered by a combination of unintended policy learning produced by local reforms in two counties and of the Ministry of Health’s carefully orchestrated policy process that served to co-opt critical voices in the medical profession.

    Place, publisher, year, edition, pages
    Routledge, 2016
    Keyword
    Historical institutionalism; path dependency; policy learning; quality managment systems
    National Category
    Public Administration Studies
    Identifiers
    urn:nbn:se:liu:diva-128223 (URN)10.1080/01900692.2015.1064959 (DOI)
    Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2016-08-31Bibliographically approved
    2. What frames Quality Registers in Swedish Health Care: an institutional approach
    Open this publication in new window or tab >>What frames Quality Registers in Swedish Health Care: an institutional approach
    2011 (English)In: Proceedings from 14th Uddevalla Symposium, 2011 Entrepreneurial Knowledge, Technology and Transformation of Regions / [ed] Iréne Bernhard, Linköping: Linköping University Electronic Press, 2011, 1-19 p.Conference paper (Other academic)
    Abstract [en]

    Quality issues strike the classical conflict in a democratic health-care deliverysystem of different interests among the politicians, the medical profession andpublic officials. This cannot be studied as a cut-off whiz. Quality registers havedeveloped over the past 40 years. Therefore, this paper puts the innovation ofquality registers in an institutional perspective. Two things are essential in thispaper. First, this paper reviews the emergence of quality registers in Swedish healthcare as an effect of institutional arrangements. Second, it analyses the interactionof diverse factors in different institutional settings and logics. The relevant data forthe study was collected from official/unofficial policy documents and key actorinterviews.The empirical findings show that three different waves of development can betraced in history that has highly affected the development of quality registers. Italso shows that medical quality is framed and determined by physicians in line withprofessional knowledge and by the primary institutional logic of quality in medicalcare. However, organisational quality in health care is framed by the logic ofpublic equity of access based on a third party payer and the logic of managerialcontrol. These two paths of quality developments are now federating in aninstitutional logic of transparency. The contribution of this paper is importantbecause it produces insights in different institutional logics, which frames the riseof the two quality paths and the problems they have to face in order to merge. It also enhances the existing knowledge that institutions matter.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2011
    Series
    , Research Reports 2011:05 University West, ISSN 1653-7831 ; 2011:05
    Keyword
    health care, institutional change, quality, innovation
    National Category
    Public Administration Studies
    Identifiers
    urn:nbn:se:liu:diva-88746 (URN)978-91-977943-2-9 (ISBN)
    Conference
    14th Uddevalla Symposium, 2011 Entrepreneurial Knowledge, Technology and Transformation of Regions, June 16-18, Bergamo, Italy
    Available from: 2013-02-19 Created: 2013-02-18 Last updated: 2016-08-31Bibliographically approved
    3. Path Dependence on New Roads. Institutional Development of Quality Registers
    Open this publication in new window or tab >>Path Dependence on New Roads. Institutional Development of Quality Registers
    2014 (English)In: Offentlig Förvaltning. Scandinavian Journal of Public Administration, ISSN 2000-8058, E-ISSN 2001-3310, Vol. 18, no 2, 3-22 p.Article in journal (Refereed) Published
    Abstract [en]

    When explaining social development and changes in public administration, institutional changeis a typical focus. Institutional analysis can combine the analyses of changes on the basis offormal legal and informal arrangements; it commonly shows that institutions lead to inertiawhere changes over time are concerned. Political aims are a guide to how organizations aredesigned and governed. When goals and earlier decisions clearly guide change, path dependenceis a fundamental concept when explaining change. However, this analysis shows how andwhen quality registers appeared as an answer to changes in institutional arrangements in Swedishpublic healthcare. Through three phases, cumulative processes have been visible and theprocesses have been followed by an improved and increased usage of quality registers andother quality systems. This analysis shows that institutional development can be pathdependentin relation to methods and means. Despite changing goals over time, quality registersas a policy tool have been path-dependent and stayed firm. Thus, it is important to see alsoorganisational methods as a development path that can be used to implement even new policyaims.

    Place, publisher, year, edition, pages
    Förlag Göteborgs Universitet, 2014
    Keyword
    Institutional change, quality registers, public governance, path dependence, time
    National Category
    Public Administration Studies
    Identifiers
    urn:nbn:se:liu:diva-114514 (URN)
    Available from: 2015-02-25 Created: 2015-02-25 Last updated: 2016-08-31Bibliographically approved
    4. Policymaking through healthcare registries in Sweden
    Open this publication in new window or tab >>Policymaking through healthcare registries in Sweden
    2016 (English)In: Health Promotion International, ISSN 0957-4824, E-ISSN 1460-2245Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    Healthcare registries, otherwise known in Sweden as national quality registries (NQRs), have progressed from being a patient-focused system supporting medical results to become the basis of a health policy steering instrument called regional comparisons (RCs). This article seeks to explain RCs as an unintended consequence of the NQR development, by utilizing the concepts of policy entrepreneurs and streams of impact: the problem stream (problem perceived), the policy stream (what is valid), and the political stream (governmental objectives). The empirical contribution lies in insights on how the RCs have developed as an unintended consequence of entrepreneurial deliberate action in the process of creating NQRs. These findings are based on documents, interviews, and previous research in the social sciences. The article also argues for a critical understanding of public knowledge management (PKM) related to experiences in the development of NQRs regarding how to use knowledge in healthcare government. This article highlights how knowledge generated in quality systems based on registries could imply a stronger role for authorities in exerting control over the medical profession. It also discusses the potential use of research evidence on NQRs as a base for more efficient policymaking.

    Keyword
    quality registries, stream coupling, policy entrepreneurs, public knowledge management
    National Category
    Political Science
    Identifiers
    urn:nbn:se:liu:diva-131037 (URN)10.1093/heapro/daw064 (DOI)27594141 (PubMedID)
    Available from: 2016-09-06 Created: 2016-09-06 Last updated: 2016-09-12Bibliographically approved
    5. Public quality – for whom and how? Integrating public core values with quality management
    Open this publication in new window or tab >>Public quality – for whom and how? Integrating public core values with quality management
    2015 (English)In: Total quality management and business excellence (Online), ISSN 1478-3363, E-ISSN 1478-3371Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    Quality management (QM) plays an important role in public organisations’ efforts to create better access to, and effectiveness of, specific services. When transferring QM models from market-based firms to public services provided by public organisations, several basic contrasts and even contradictions must be addressed. Core values of the public sector differ from those of the private sector, but what are the consequences of this distinction? In this article we discuss the importance of four central arguments on public services: rights and access have to be considered; equality is an important facet of public services; coerciveness is a unique feature of public services; and legitimacy can be improved by high-quality services. These arguments have not been discussed explicitly in the context of QM. Adding these central aspects of public services to the QM field could generate more sustainable ways for developing quality and QM in public services in particular and the public sector in general.

    Keyword
    public sector; customer; citizen; quality management
    National Category
    Public Administration Studies
    Identifiers
    urn:nbn:se:liu:diva-128224 (URN)10.1080/14783363.2015.1087841 (DOI)
    Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2016-08-31Bibliographically approved
  • Public defence: 2016-09-30 09:00 Hugo Theorellsallen (norra entrén), Linköping
    Maria Marreiros, Filipe Miguel
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Science & Engineering.
    Maria Marreiros, Filipe Miguel
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Science & Engineering.
    Guidance and Visualization for Brain Tumor Surgery2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Image guidance and visualization play an important role in modern surgery to help surgeons perform their surgical procedures. Here, the focus is on neurosurgery applications, in particular brain tumor surgery where a craniotomy (opening of the skull) is performed to access directly the brain region to be treated. In this type of surgery, once the skull is opened the brain can change its shape, and this deformation is known as brain shift. Moreover, the boundaries of many types of tumors are difficult to identify by the naked eye from healthy tissue. The main goal of this work was to study and develop image guidance and visualization methods for tumor surgery in order to overcome the problems faced in this type of surgery.

    Due to brain shift the magnetic resonance dataset acquired before the operation (preoperatively) no longer corresponds to the anatomy of the patient during the operation (intraoperatively). For this reason, in this work methods were studied and developed to compensate for this deformation. To guide the deformation methods, information of the superficial vessel centerlines of the brain was used. A method for accurate (approximately 1 mm) reconstruction of the vessel centerlines using a multiview camera system was developed. It uses geometrical constraints, relaxation labeling, thin plate spline filtering and finally mean shift to find the correct correspondences between the camera images.

    A complete non-rigid deformation pipeline was initially proposed and evaluated with an animal model. From these experiments it was observed that although the traditional non-rigid registration methods (in our case coherent point drift) were able to produce satisfactory vessel correspondences between preoperative and intraoperative vessels, in some specific areas the results were suboptimal. For this reason a new method was proposed that combined the coherent point drift and thin plate spline semilandmarks. This combination resulted in an accurate (below 1 mm) non-rigid registration method, evaluated with simulated data where artificial deformations were performed.

    Besides the non-rigid registration methods, a new rigid registration method to obtain the rigid transformation between the magnetic resonance dataset and the neuronavigation coordinate systems was also developed.

    Once the rigid transformation and the vessel correspondences are known, the thin plate spline can be used to perform the brain shift deformation. To do so, we have used two approaches: a direct and an indirect. With the direct approach, an image is created that represents the deformed data, and with the indirect approach, a new volume is first constructed and only after that can the deformed image be created. A comparison of these two approaches, implemented for the graphics processing units, in terms of performance and image quality, was performed. The indirect method was superior in terms of performance if the sampling along the ray is high, in comparison to the voxel grid, while the direct was superior otherwise. The image quality analysis seemed to indicate that the direct method is superior.

    Furthermore, visualization studies were performed to understand how different rendering methods and parameters influence the perception of the spatial position of enclosed objects (typical situation of a tumor enclosed in the brain). To test these methods a new single-monitor-mirror stereoscopic display was constructed. Using this display, stereo images simulating a tumor inside the brain were presented to the users with two rendering methods (illustrative rendering and simple alpha blending) and different levels of opacity. For the simple alpha blending method an optimal opacity level was found, while for the illustrative rendering method all the opacity levels used seemed to perform similarly.

    In conclusion, this work developed and evaluated 3D reconstruction, registration (rigid and non-rigid) and deformation methods with the purpose of minimizing the brain shift problem. Stereoscopic perception of the spatial position of enclosed objects was also studied using different rendering methods and parameter values.

    List of papers
    1. Superficial vessel reconstruction with a multiview camera system
    Open this publication in new window or tab >>Superficial vessel reconstruction with a multiview camera system
    Show others...
    2016 (English)In: Journal of Medical Imaging, ISSN 2329-4302, E-ISSN 2329-4310, Vol. 3, no 1, 015001-1-015001-13 p.Article in journal (Refereed) Published
    Abstract [en]

    We aim at reconstructing superficial vessels of the brain. Ultimately, they will serve to guide the deformationmethods to compensate for the brain shift. A pipeline for three-dimensional (3-D) vessel reconstructionusing three mono-complementary metal-oxide semiconductor cameras has been developed. Vessel centerlinesare manually selected in the images. Using the properties of the Hessian matrix, the centerline points areassigned direction information. For correspondence matching, a combination of methods was used. The processstarts with epipolar and spatial coherence constraints (geometrical constraints), followed by relaxation labelingand an iterative filtering where the 3-D points are compared to surfaces obtained using the thin-plate spline withdecreasing relaxation parameter. Finally, the points are shifted to their local centroid position. Evaluation invirtual, phantom, and experimental images, including intraoperative data from patient experiments, showsthat, with appropriate camera positions, the error estimates (root-mean square error and mean error) are∼1 mm.

    Place, publisher, year, edition, pages
    SPIE - International Society for Optical Engineering, 2016
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-123661 (URN)10.1117/1.JMI.3.1.015001 (DOI)
    Projects
    ARIOR
    Funder
    Swedish Childhood Cancer Foundation, MT2013-0036
    Available from: 2016-01-05 Created: 2016-01-05 Last updated: 2016-09-15Bibliographically approved
    2. Non-rigid Deformation Pipeline for Compensation of Superficial Brain Shift
    Open this publication in new window or tab >>Non-rigid Deformation Pipeline for Compensation of Superficial Brain Shift
    2013 (English)In: Medical Image Computing and Computer-Assisted Intervention, MICCAI 2013: 16th International Conference, Nagoya, Japan, September 22-26, 2013, Proceedings, Part II, Springer Berlin/Heidelberg, 2013, 141-148 p.Conference paper (Refereed)
    Abstract [en]

    The correct visualization of anatomical structures is a critical component of neurosurgical navigation systems, to guide the surgeon to the areas of interest as well as to avoid brain damage. A major challenge for neuronavigation systems is the brain shift, or deformation of the exposed brain in comparison to preoperative Magnetic Resonance (MR) image sets. In this work paper, a non-rigid deformation pipeline is proposed for brain shift compensation of preoperative imaging datasets using superficial blood vessels as landmarks. The input was preoperative and intraoperative 3D image sets of superficial vessel centerlines. The intraoperative vessels (obtained using 3 Near-Infrared cameras) were registered and aligned with preoperative Magnetic Resonance Angiography vessel centerlines using manual interaction for the rigid transformation and, for the non-rigid transformation, the non-rigid point set registration method Coherent Point Drift. The rigid registration transforms the intraoperative points from the camera coordinate system to the preoperative MR coordinate system, and the non-rigid registration deals with local transformations in the MR coordinate system. Finally, the generation of a new deformed volume is achieved with the Thin-Plate Spline (TPS) method using as control points the matches in the MR coordinate system found in the previous step. The method was tested in a rabbit brain exposed via craniotomy, where deformations were produced by a balloon inserted into the brain. There was a good correlation between the real state of the brain and the deformed volume obtained using the pipeline. Maximum displacements were approximately 4.0 mm for the exposed brain alone, and 6.7 mm after balloon inflation.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2013
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743 (print), 1611-3349 (online) ; 8150
    National Category
    Engineering and Technology Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-106901 (URN)10.1007/978-3-642-40763-5_18 (DOI)000342835100018 ()978-3-642-40762-8 (print) (ISBN)978-3-642-40763-5 (online) (ISBN)
    Conference
    16th International Conference on Medical Image Computing and Computer-Assisted Intervention (MICCAI 2013), Nagoya, Japan, September 22-26, 2013
    Available from: 2014-05-23 Created: 2014-05-23 Last updated: 2016-09-15Bibliographically approved
    3. Non-rigid point set registration of curves: registration of the superficial vessel centerlines of the brain
    Open this publication in new window or tab >>Non-rigid point set registration of curves: registration of the superficial vessel centerlines of the brain
    2016 (English)In: Volume 9786 Medical Imaging 2016: Image-Guided Procedures, Robotic Interventions, and Modeling, SPIE - International Society for Optical Engineering, 2016, Vol. 9786, 8 p.978611-1-978611-8 p.Conference paper (Refereed)
    Abstract [en]

    In this study we present a non-rigid point set registration for 3D curves (composed by 3D set of points). Themethod was evaluated in the task of registration of 3D superficial vessels of the brain where it was used to matchvessel centerline points. It consists of a combination of the Coherent Point Drift (CPD) and the Thin-PlateSpline (TPS) semilandmarks. The CPD is used to perform the initial matching of centerline 3D points, whilethe semilandmark method iteratively relaxes/slides the points.

    For the evaluation, a Magnetic Resonance Angiography (MRA) dataset was used. Deformations were appliedto the extracted vessels centerlines to simulate brain bulging and sinking, using a TPS deformation where afew control points were manipulated to obtain the desired transformation (T1). Once the correspondences areknown, the corresponding points are used to define a new TPS deformation(T2). The errors are measured in thedeformed space, by transforming the original points using T1 and T2 and measuring the distance between them.To simulate cases where the deformed vessel data is incomplete, parts of the reference vessels were cut and thendeformed. Furthermore, anisotropic normally distributed noise was added.

    The results show that the error estimates (root mean square error and mean error) are below 1 mm, even inthe presence of noise and incomplete data.

    Place, publisher, year, edition, pages
    SPIE - International Society for Optical Engineering, 2016. 8 p.
    Series
    , Progress in Biomedical Optics, ISSN 1605-7422
    Keyword
    Non-rigid registration, brain shift correction, vessel registration
    National Category
    Medical Image Processing
    Identifiers
    urn:nbn:se:liu:diva-126347 (URN)10.1117/12.2208421 (DOI)
    Conference
    Medical Imaging 2016: Image-Guided Procedures, Robotic Interventions, and Modeling, San Diego, California, United States, February 27, 2016
    Projects
    ARIOR
    Funder
    Swedish Childhood Cancer Foundation, MT2013-0036
    Available from: 2016-03-22 Created: 2016-03-22 Last updated: 2016-09-15Bibliographically approved
    4. GPU-based ray-casting of non-rigid deformations: a comparison between direct and indirect approaches
    Open this publication in new window or tab >>GPU-based ray-casting of non-rigid deformations: a comparison between direct and indirect approaches
    2014 (English)In: Proceedings of SIGRAD 2014, Visual Computing, June 12-13, 2014, Göteborg, Sweden / [ed] Mohammad Obaid; Daniel Sjölie; Erik Sintorn; Morten Fjeld, Linköping University Electronic Press, 2014, 67-74 p.Conference paper (Refereed)
    Abstract [en]

    For ray-casting of non-rigid deformations, the direct approach (as opposed to the traditional indirect approach) does not require the computation of an intermediate volume to be used for the rendering step. The aim of this study was to compare the two approaches in terms of performance (speed) and accuracy (image quality).

    The direct and the indirect approach were carefully implemented to benefit of the massive GPU parallel power, using CUDA. They were then tested with Computed Tomography (CT) datasets of varying sizes and with a synthetic image, the Marschner-Lobb function.

    The results show that the direct approach is dependent on the ray sampling steps, number of landmarks and image resolution. The indirect approach is mainly affected by the number of landmarks, if the volume is large enough.

    These results exclude extreme cases, i.e. if the sampling steps are much smaller than the voxel size and if the image resolution is much higher than the ones used here. For a volume of size 512×512×512, using 100 landmarks and image resolution of 1280×960, the direct method performs better if the ray sampling steps are approximately above 1 voxel. Regarding accuracy, the direct method provides better results for multiple frequencies using the Marschner-Lobb function.

    The conclusion is that the indirect method is superior in terms of performance, if the sampling along the rays is high, in comparison to the voxel grid, while the direct is superior otherwise. The accuracy analysis seems to point out that the direct method is superior, in particular when the implicit function is used.

    Place, publisher, year, edition, pages
    Linköping University Electronic Press, 2014
    Series
    Linköping Electronic Conference Proceedings, ISSN 1650-3686 (print), 1650-3740 (online) ; 106
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-107553 (URN)9789175192123 (ISBN)
    Conference
    Swedish Computer Graphics Association (SIGRAD), Göteborg, Sweden, June 12-13, 2014
    Available from: 2014-06-16 Created: 2014-06-16 Last updated: 2016-09-15Bibliographically approved
    5. Single-Monitor-Mirror Stereoscopic Display
    Open this publication in new window or tab >>Single-Monitor-Mirror Stereoscopic Display
    2013 (English)In: Journal of Graphics Tools, ISSN 2165-347X, Vol. 17, no 3, 85-97 p.Article in journal (Refereed) Published
    Abstract [en]

    A new single-monitor-mirror stereoscopic display is presented. The stereoscopic display system is composed of one monitor and one acrylic first-surface mirror. The mirror reflects one image for one of the eyes. The geometrical transformations to compute correctly the stereo pair are derived and presented. System considerations such as mirror placement and implications are also discussed.

    In contrast to other similar solutions that use fixed configurations, we try to optimize the display area by controlling the mirror placement. Consequently, one of the images needs to be skewed. Advantages of the system include absence of ghosting and flickering.

    We also developed the rendering engine for direct volume rendering (DVR) of volumetric datasets mostly for medical imaging visualization and using OpenGL for polygonal datasets and stereoscopic digital photography. The skewing process in this case is integrated into the ray-casting of DVR. Using geometrical transformations, we can compute precisely the directions of the rays, producing accurate stereo pairs. A similar operation is also performed using OpenGL.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2013
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-120584 (URN)10.1080/2165347X.2015.1028690 (DOI)
    Projects
    arior
    Funder
    Swedish Childhood Cancer Foundation, MT2013-0036Swedish Foundation for Strategic Research VINNOVAVårdal Foundation
    Available from: 2015-08-17 Created: 2015-08-17 Last updated: 2016-09-15Bibliographically approved
    6. Stereoscopic static depth perception of enclosed 3D objects
    Open this publication in new window or tab >>Stereoscopic static depth perception of enclosed 3D objects
    2013 (English)In: SAP '13 Proceedings of the ACM Symposium on Applied Perception, New York, USA: Association for Computing Machinery (ACM), 2013, 15-22 p.Conference paper (Refereed)
    Abstract [en]

    Depth perception of semi-transparent virtual objects and the visu-alization of their spatial layout are crucial in many applications, in particular medical applications. Depth cues for opaque objects have been extensively studied, but this is not the case for stereo-scopic semi-transparent objects, in particular in the case when one 3D object is enclosed within a larger exterior object.

    In this work we explored different stereoscopic rendering methodsto analyze their impact on depth perception accuracy of an enclosed3D object. Two experiments were performed: the first tested the hypotheses that depth perception is dependent on the color blending of objects (opacity - alpha) for each rendering method and that one of two rendering methods used is superior. The second experiment was performed to corroborate the results of the first experiment and to test an extra hypothesis: is depth perception improved if an auxiliary object that provides a relationship between the enclosed objectand the exterior is used?

    The first rendering method used is simple alpha blending with Blinn-Phong shading model, where a segmented brain (exterior object) and a synthetic tumor (enclosed object) were blended. The second rendering method also uses Blinn-Phong, but the shading was modified to preserve silhouettes and to provide an illustrative rendering. Comparing both rendering methods, the brighter regionsof the first rendering method will become more transparent in the second rendering method, thus preserving silhouette areas.

    The results show that depth perception accuracy of an enclosed object rendered with a stereoscopic system is dependent on opacity for some rendering methods (simple alpha blending), but this effect is less pronounced than the dependence on object position in relation to the exterior object. The illustrative rendering method is less dependent on opacity. The different rendering methods also perform slightly differently; an illustrative rendering method was superior and the use of an auxiliary object seems to facilitate depth perception.

    Place, publisher, year, edition, pages
    New York, USA: Association for Computing Machinery (ACM), 2013
    Keyword
    depth perception, stereoscopy, enclosed 3D objects
    National Category
    Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-106896 (URN)10.1145/2492494.2492501 (DOI)978-1-4503-2262-1 (ISBN)
    Conference
    2013 ACM Symposium on Applied Perception, SAP 2013; Dublin, Ireland, August 22 - 23, 2013
    Funder
    VINNOVA
    Available from: 2014-05-23 Created: 2014-05-23 Last updated: 2016-09-15Bibliographically approved
  • Public defence: 2016-09-30 09:00 Originalet, Qulturum, Hus B4, Jönköping
    Ahlander, Britt-Marie
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Ahlander, Britt-Marie
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Magnetic Resonance Imaging of the Heart: Image quality, measurement accuracy and patient experience2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Non-invasive diagnostic imaging of atherosclerotic coronary artery disease (CAD) is frequently carried out with cardiovascular magnetic resonance imaging (CMR) or myocardial perfusion single photon emission computed tomography (MPS). CMR is the gold standard for the evaluation of scar after myocardial infarction and MPS the clinical gold standard for ischemia. Magnetic Resonance Imaging (MRI) is at times difficult for patients and may induce anxiety while patient experience of MPS is largely unknown.

    Aims: To evaluate image quality in CMR with respect to the sequences employed, the influence of atrial fibrillation, myocardial perfusion and the impact of patient information. Further, to study patient experience in relation to MRI with the goal of improving the care of these patients.

    Method: Four study designs have been used. In paper I, experimental cross-over, paper (II) experimental controlled clinical trial, paper (III) psychometric crosssectional study and paper (IV) prospective intervention study. A total of 475 patients ≥ 18 years with primarily cardiac problems (I-IV) except for those referred for MRI of the spine (III) were included in the four studies.

    Result: In patients (n=20) with atrial fibrillation, a single shot steady state free precession (SS-SSFP) sequence showed significantly better image quality than the standard segmented inversion recovery fast gradient echo (IR-FGRE) sequence (I). In first-pass perfusion imaging the gradient echo-echo planar imaging sequence (GREEPI) (n=30) had lower signal-to-noise and contrast–to-noise ratios than the steady state free precession sequence (SSFP) (n=30) but displayed a higher correlation with the MPS results, evaluated both qualitatively and quantitatively (II). The MRIAnxiety Questionnaire (MRI-AQ) was validated on patients, referred for MRI of either the spine (n=193) or the heart (n=54). The final instrument had 15 items divided in two factors regarding Anxiety and Relaxation. The instrument was found to have satisfactory psychometric properties (III). Patients who prior CMR viewed an information video scored significantly (lower) better in the factor Relaxation, than those who received standard information. Patients who underwent MPS scored lower on both factors, Anxiety and Relaxation. The extra video information had no effect on CMR image quality (IV).

    Conclusion: Single shot imaging in atrial fibrillation produced images with less artefact than a segmented sequence. In first-pass perfusion imaging, the sequence GRE-EPI was superior to SSFP. A questionnaire depicting anxiety during MRI showed that video information prior to imaging helped patients relax but did not result in an improvement in image quality.

    List of papers
    1. Image quality and myocardial scar size determined with magnetic resonance imaging in patients with permanent atrial fibrillation: a comparison of two imaging protocols
    Open this publication in new window or tab >>Image quality and myocardial scar size determined with magnetic resonance imaging in patients with permanent atrial fibrillation: a comparison of two imaging protocols
    Show others...
    2010 (English)In: CLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, ISSN 1475-0961, Vol. 30, no 2, 122-129 p.Article in journal (Refereed) Published
    Abstract [en]

    Pandgt;Background: Magnetic resonance imaging (MRI) of the heart generally requires breath holding and a regular rhythm. Single shot 2D steady-state free precession (SS_SSFP) is a fast sequence insensitive to arrhythmia as well as breath holding. Our purpose was to determine image quality, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios and infarct size with a fast single shot and a standard segmented MRI sequence in patients with permanent atrial fibrillation and chronic myocardial infarction. Methods: Twenty patients with chronic myocardial infarction and ongoing atrial fibrillation were examined with inversion recovery SS_SSFP and segmented inversion recovery 2D fast gradient echo (IR_FGRE). Image quality was assessed in four categories: delineation of infarcted and non-infarcted myocardium, occurrence of artefacts and overall image quality. SNR and CNR were calculated. Myocardial volume (ml) and infarct size, expressed as volume (ml) and extent (%), were calculated, and the methodological error was assessed. Results: SS_SSFP had significantly better quality scores in all categories (P = 0 center dot 037, P = 0 center dot 014, P = 0 center dot 021, P = 0 center dot 03). SNRinfarct and SNRblood were significantly better for IR_FGRE than for SS_SSFP (P = 0 center dot 048, P = 0 center dot 018). No significant difference was found in SNRmyocardium and CNR. The myocardial volume was significantly larger with SS_SSFP (170 center dot 7 versus 159 center dot 2 ml, P andlt; 0 center dot 001), but no significant difference was found in infarct volume and infarct extent. Conclusion: SS_SSFP displayed significantly better image quality than IR_FGRE. The infarct size and the error in its determination were equal for both sequences, and the examination time was shorter with SS_SSFP.

    Keyword
    atrial fibrillation, magnetic resonance imaging, myocardial infarction, segmented inversion recovery 2D fast gradient echo, single shot inversion recovery 2D steady-state free precession
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-54159 (URN)10.1111/j.1475-097X.2009.00914.x (DOI)000274438800006 ()
    Available from: 2010-02-26 Created: 2010-02-26 Last updated: 2016-08-24
    2. An echo-planar imaging sequence is superior to a steady-state free precession sequence for visual as well as quantitative assessment of cardiac magnetic resonance stress perfusion
    Open this publication in new window or tab >>An echo-planar imaging sequence is superior to a steady-state free precession sequence for visual as well as quantitative assessment of cardiac magnetic resonance stress perfusion
    Show others...
    2015 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097XArticle in journal (Refereed) Epub ahead of print
    Abstract [en]

    Background To assess myocardial perfusion, steady-state free precession cardiac magnetic resonance (SSFP, CMR) was compared with gradient-echo–echo-planar imaging (GRE-EPI) using myocardial perfusion scintigraphy (MPS) as reference. Methods Cardiac magnetic resonance perfusion was recorded in 30 patients with SSFP and in another 30 patients with GRE-EPI. Timing and extent of inflow delay to the myocardium was visually assessed. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated. Myocardial scar was visualized with a phase-sensitive inversion recovery sequence (PSIR). All scar positive segments were considered pathologic. In MPS, stress and rest images were used as in clinical reporting. The CMR contrast wash-in slope was calculated and compared with the stress score from the MPS examination. CMR scar, CMR perfusion and MPS were assessed separately by one expert for each method who was blinded to other aspects of the study. Results Visual assessment of CMR had a sensitivity for the detection of an abnormal MPS at 78% (SSFP) versus 91% (GRE-EPI) and a specificity of 58% (SSFP) versus 84% (GRE-EPI). Kappa statistics for SSFP and MPS was 0·29, for GRE-EPI and MPS 0·72. The ANOVA of CMR perfusion slopes for all segments versus MPS score (four levels based on MPS) had correlation r = 0·64 (SSFP) and r = 0·96 (GRE-EPI). SNR was for normal segments 35·63 ± 11·80 (SSFP) and 17·98 ± 8·31 (GRE-EPI), while CNR was 28·79 ± 10·43 (SSFP) and 13·06 ± 7·61 (GRE-EPI). Conclusion GRE-EPI displayed higher agreement with the MPS results than SSFP despite significantly lower signal intensity, SNR and CNR.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2015
    Keyword
    cardiac imaging techniques, coronary heart disease, Magnetic Resonance Imaging, nuclear medicine, perfusion
    National Category
    Radiology, Nuclear Medicine and Medical Imaging Medical Laboratory and Measurements Technologies Medical Image Processing Clinical Medicine
    Identifiers
    urn:nbn:se:liu:diva-130795 (URN)10.1111/cpf.12267 (DOI)26147785 (PubMedID)
    Available from: 2016-08-24 Created: 2016-08-24 Last updated: 2016-09-01Bibliographically approved
    3. Development and validation of a questionnaire evaluating patient anxiety during Magnetic Resonance Imaging: the Magnetic Resonance Imaging-Anxiety Questionnaire (MRI-AQ)
    Open this publication in new window or tab >>Development and validation of a questionnaire evaluating patient anxiety during Magnetic Resonance Imaging: the Magnetic Resonance Imaging-Anxiety Questionnaire (MRI-AQ)
    Show others...
    2016 (English)In: Journal of Advanced Nursing, ISSN 0309-2402, E-ISSN 1365-2648, Vol. 72, no 6, 1368-1380 p.Article in journal (Refereed) Published
    Abstract [en]

    Aim. To develop and validate a new instrument measuring patient anxiety during Magnetic Resonance Imaging examinations, Magnetic Resonance Imaging-Anxiety Questionnaire. Background. Questionnaires measuring patients anxiety during Magnetic Resonance Imaging examinations have been the same as used in a wide range of conditions. To learn about patients experience during examination and to evaluate interventions, a specific questionnaire measuring patient anxiety during Magnetic Resonance Imaging is needed. Design. Psychometric cross-sectional study with test-retest design. Methods. A new questionnaire, Magnetic Resonance Imaging-Anxiety Questionnaire, was designed from patient expressions of anxiety in Magnetic Resonance Imaging-scanners. The sample was recruited between October 2012-October 2014. Factor structure was evaluated with exploratory factor analysis and internal consistency with Cronbachs alpha. Criterion-related validity, known-group validity and test-retest was calculated. Results. Patients referred for Magnetic Resonance Imaging of either the spine or the heart, were invited to participate. The development and validation of Magnetic Resonance Imaging-Anxiety Questionnaire resulted in 15 items consisting of two factors. Cronbachs alpha was found to be high. Magnetic Resonance Imaging-Anxiety Questionnaire correlated higher with instruments measuring anxiety than with depression scales. Known-group validity demonstrated a higher level of anxiety for patients undergoing Magnetic Resonance Imaging scan of the heart than for those examining the spine. Test-retest reliability demonstrated acceptable level for the scale. Conclusion. Magnetic Resonance Imaging-Anxiety Questionnaire bridges a gap among existing questionnaires, making it a simple and useful tool for measuring patient anxiety during Magnetic Resonance Imaging examinations.

    Place, publisher, year, edition, pages
    WILEY-BLACKWELL, 2016
    Keyword
    anxiety; instrument development; magnetic resonance imaging; nurse; nursing; reliability; validity
    National Category
    Other Medical Sciences not elsewhere specified
    Identifiers
    urn:nbn:se:liu:diva-129145 (URN)10.1111/jan.12917 (DOI)000376007400014 ()26893007 (PubMedID)
    Note

    Funding Agencies|Swedish Heart and Lung Foundation; Futurum County Council of Jonkoping

    Available from: 2016-06-13 Created: 2016-06-13 Last updated: 2016-08-24
  • Public defence: 2016-09-30 10:15 Visionen, hus B,, Linköping
    Vapen, Anna
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Vapen, Anna
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, Faculty of Science & Engineering.
    Web Authentication using Third-Parties in Untrusted Environments2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the increasing personalization of the Web, many websites allow users to create their own personal accounts. This has resulted in Web users often having many accounts on different websites, to which they need to authenticate in order to gain access. Unfortunately, there are several security problems connected to the use and re-use of passwords, the most prevalent authentication method currently in use, including eavesdropping and replay attacks.

    Several alternative methods have been proposed to address these shortcomings, including the use of hardware authentication devices. However, these more secure authentication methods are often not adapted for mobile Web users who use different devices in different places and in untrusted environments, such as public Wi-Fi networks, to access their accounts.

    We have designed a method for comparing, evaluating and designing authentication solutions suitable for mobile users and untrusted environments. Our method leverages the fact that mobile users often bring their own cell phones, and also takes into account different levels of security adapted for different services on the Web.

    Another important trend in the authentication landscape is that an increasing number of websites use third-party authentication. This is a solution where users have an account on a single system, the identity provider, and this one account can then be used with multiple other websites. In addition to requiring fewer passwords, these services can also in some cases implement authentication with higher security than passwords can provide.

    How websites select their third-party identity providers has privacy and security implications for end users. To better understand the security and privacy risks with these services, we present a data collection methodology that we have used to identify and capture third-party authentication usage on the Web. We have also characterized the third-party authentication landscape based on our collected data, outlining which types of third-parties are used by which types of sites, and how usage differs across the world. Using a combination of large-scale crawling, longitudinal manual testing, and in-depth login tests, our characterization and analysis has also allowed us to discover interesting structural properties of the landscape, differences in the cross-site relationships, and how the use of third-party authentication is changing over time.

    Finally, we have also outlined what information is shared between websites in third-party authentication, dened risk classes based on shared data, and proled privacy leakage risks associated with websites and their identity providers sharing data with each other. Our ndings show how websites can strengthen the privacy of their users based on how these websites select and combine their third-parties and the data they allow to be shared.

    List of papers
    1. Security Levels for Web Authentication using Mobile Phones
    Open this publication in new window or tab >>Security Levels for Web Authentication using Mobile Phones
    2011 (English)In: Privacy and Identity Management for Life / [ed] Simone Fischer-Hübner, Penny Duquenoy, Marit Hansen, Ronald Leenes and Ge Zhang, Boston: Springer , 2011, 130-143 p.Conference paper (Refereed)
    Abstract [en]

    Mobile phones offer unique advantages for secure authentication: they are small and portable, provide multiple data transfer channels, and are nearly ubiquitous. While phones provide a flexible and capable platform, phone designs vary, and the security level of an authentication solution is influenced by the choice of channels and authentication methods. It can be a challenge to get a consistent overview of the strengths and weaknesses of the available alternatives. Existing guidelines for authentication usually do not consider the specific problems in mobile phone authentication. We provide a method for evaluating and designing authentication solutions using mobile phones, using an augmented version of the Electronic Authentication Guideline.

    Place, publisher, year, edition, pages
    Boston: Springer, 2011
    Series
    , IFIP Advances in Information and Communication Technology, ISSN 1868-4238 ; 352
    Keyword
    Authentication, information security, mobile phone, security levels, evaluation method
    National Category
    Computer Science
    Identifiers
    urn:nbn:se:liu:diva-70058 (URN)10.1007/978-3-642-20769-3_11 (DOI)978-3-642-20768-6 (ISBN)
    Conference
    PrimeLife/IFIP Summer School 2010
    Available from: 2011-08-17 Created: 2011-08-17 Last updated: 2016-08-22
    2. 2-clickAuth - Optical Challenge-Response Authentication using Mobile Handsets
    Open this publication in new window or tab >>2-clickAuth - Optical Challenge-Response Authentication using Mobile Handsets
    2011 (English)In: International Journal on Mobile Computing and Multimedia Communications, ISSN 1937-9412, E-ISSN 1937-9404, Vol. 3, no 2, 1-18 p.Article in journal (Refereed) Published
    Abstract [en]

    Internet users often have usernames and passwords at multiple web sites. To simplify things, many sites support federated identity management, which enables users to have a single account allowing them to log on to different sites by authenticating to a single identity provider. Most identity providers perform authentication using a username and password. Should these credentials be compromised, all of the user’s accounts become compromised. Therefore a more secure authentication method is desirable. This paper implements 2-clickAuth, a multimedia-based challenge-response solution which uses a web camera and a camera phone for authentication. Two-dimensional barcodes are used for the communication between phone and computer, which allows 2-clickAuth to transfer relatively large amounts of data in a short period of time. 2-clickAuth is more secure than passwords while easy to use and distribute. 2-clickAuth is a viable alternative to passwords in systems where enhanced security is desired, but availability, ease-of-use, and cost cannot be compromised. This paper implements an identity provider in the OpenID federated identity management system that uses 2-clickAuth for authentication, making 2-clickAuth available to all users of sites that support OpenID, including Facebook, Sourceforge, and MySpace.

    Place, publisher, year, edition, pages
    Hershey, USA: IGI Global, 2011
    Keyword
    Authentication, federated identity management, mobile computing, OpenID, QR code, trusted device
    National Category
    Computer Science
    Identifiers
    urn:nbn:se:liu:diva-70063 (URN)10.4018/jmcmc.2011040101 (DOI)
    Available from: 2011-08-17 Created: 2011-08-17 Last updated: 2016-08-22
    3. Third-party identity management usage on the web
    Open this publication in new window or tab >>Third-party identity management usage on the web
    2014 (English)In: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), Springer Berlin/Heidelberg, 2014, Vol. 8362 LNCS, 151-162 p.Conference paper (Refereed)
    Abstract [en]

    Many websites utilize third-party identity management services to simplify access to their services. Given the privacy and security implications for end users, an important question is how websites select their third-party identity providers and how this impacts the characteristics of the emerging identity management landscape seen by the users. In this paper we first present a novel Selenium-based data collection methodology that identifies and captures the identity management relationships between sites and the intrinsic characteristics of the websites that form these relationships. Second, we present the first large-scale characterization of the third-party identity management landscape and the relationships that makes up this emerging landscape. As a reference point, we compare and contrast our observations with the somewhat more understood third-party content provider landscape. Interesting findings include a much higher skew towards websites selecting popular identity provider sites than is observed among content providers, with sites being more likely to form identity management relationships that have similar cultural, geographic, and general site focus. These findings are both positive and negative. For example, the high skew in usage places greater responsibility on fewer organizations that are responsible for the increased information leakage cost associated with highly aggregated personal information, but also reduces the users control of the access to this information. © 2014 Springer International Publishing Switzerland.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2014
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743 (print), 1611-3349 (online)
    National Category
    Computer and Information Science
    Identifiers
    urn:nbn:se:liu:diva-116404 (URN)10.1007/978-3-319-04918-2_15 (DOI)2-s2.0-84900600203 (ScopusID)9783319049175 (ISBN)
    Conference
    15th International Conference on Passive and Active Measurement, PAM 2014
    Available from: 2015-03-26 Created: 2015-03-26 Last updated: 2016-08-22
    4. A Look at the Third-Party Identity Management Landscape
    Open this publication in new window or tab >>A Look at the Third-Party Identity Management Landscape
    2016 (English)In: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 20, no 2, 18-25 p.Article in journal (Refereed) Published
    Abstract [en]

    Many websites act as relying parties (RPs) by allowing access to their services via third-party identity providers (IDPs), such as Facebook and Google. Using IDPs simplifies account creation, login activity, and information sharing across websites. However, different websites use of IDPs can have significant security and privacy implications for users. Here, the authors provide an overview of third-party identity managements current landscape. Using datasets collected through manual identification and large-scale crawling, they answer questions related to which sites act as RPs, which sites are the most successful IDPs, and how different classes of RPs select their IDPs.

    Place, publisher, year, edition, pages
    IEEE COMPUTER SOC, 2016
    National Category
    Computer and Information Science
    Identifiers
    urn:nbn:se:liu:diva-127053 (URN)10.1109/MIC.2016.38 (DOI)000372015500003 ()
    Available from: 2016-04-13 Created: 2016-04-13 Last updated: 2016-08-22
    5. Information Sharing and User Privacy in the Third-party Identity Management Landscape
    Open this publication in new window or tab >>Information Sharing and User Privacy in the Third-party Identity Management Landscape
    2015 (English)In: ICT Systems Security and Privacy Protection: 30th IFIP TC 11 International Conference, SEC 2015, Hamburg, Germany, May 26-28, 2015, Proceedings / [ed] Hannes Federrath, Dieter Gollmann, Springer, 2015, 174-188 p.Conference paper (Refereed)
    Abstract [en]

    The cross-site information sharing and authorized actions of third-party identity management can have significant privacy implications for the users. In this paper, we use a combination of manual analysis of identified third-party identity management relationships and targeted case studies to (i) capture how the protocol usage and third-party selection is changing, (ii) profile what information is requested to be shared (and actions to be performed) between websites, and (iii) identify privacy issues and practical problems that occur when using multiple accounts (associated with these services). By characterizing and quantifying the third-party relationships based on their cross-site information sharing, the study highlights differences in the privacy leakage risks associated with different classes of websites, and provides concrete evidence for how the privacy risks are increasing. For example, many news and file/video-sharing sites ask users to authorize the site to post information to the third-party website. We also observe a general increase in the breadth of information that is shared across websites, and find that due to usage of multiple third-party websites, in many cases, the user can lose (at least) partial control over which identities they can merge/relate and the information that is shared/posted on their behalf.

    Place, publisher, year, edition, pages
    Springer, 2015
    Series
    , IFIP Advances in Information and Communication Technology, ISSN 1868-4238 ; 455
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-117543 (URN)10.1007/978-3-319-18467-8_12 (DOI)000364779100012 ()978-3-319-18466-1 (print) (ISBN)978-3-319-18467-8 (online) (ISBN)
    Conference
    30th IFIP TC 11 International Conference, SEC 2015, Hamburg, Germany, May 26-28, 2015
    Available from: 2015-05-04 Created: 2015-05-04 Last updated: 2016-08-22Bibliographically approved
    6. Longitudinal Analysis of the Third-party Authentication Landscape
    Open this publication in new window or tab >>Longitudinal Analysis of the Third-party Authentication Landscape
    2016 (English)Conference paper (Refereed)
    Abstract [en]

    Many modern websites offer single sign-on (SSO) services, which allow the user to use an existing account with a third-party website such as Facebook to authenticate. When using SSO the user must approve an app-rights agreement that specifies what data related to the user can be shared between the two websites and any actions (e.g., posting comments) that the origin website is allowed to perform on behalf of the user on the third-party provider (e.g., Facebook). Both cross-site data sharing and actions performed on behalf of the user can have significant privacy implications. In this paper we present a longitudinal study of the third-party authentication landscape, its structure, and the protocol usage, data sharing, and actions associated with individual third-party relationships. The study captures the current state, changes in the structure, protocol usage, and information leakage risks.

    Place, publisher, year, edition, pages
    Internet Society, 2016
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-127301 (URN)10.14722/ueop.2016.23008 (DOI)1-891562-44-4 (ISBN)
    Conference
    NDSS Workshop on Understanding and Enhancing Online Privacy Workshop (UEOP@NDSS).21-24 February 2016 Catamaran Resort Hotel & Spa in San Diego, California
    Available from: 2016-04-19 Created: 2016-04-19 Last updated: 2016-08-22Bibliographically approved
  • Public defence: 2016-09-30 10:15 K1, Kåkenhus, Norrköping
    Ekholm, David
    Linköping University, Department of Social and Welfare Studies, Social Work. Linköping University, Faculty of Arts and Sciences.
    Ekholm, David
    Linköping University, Department of Social and Welfare Studies, Social Work. Linköping University, Faculty of Arts and Sciences.
    Sport as a Means of Responding to Social Problems: Rationales of Government, Welfare and Social Change2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sport has been increasingly recognized in social policy as a means of steering social change and as a method for responding to diverse social problems. The present study examines how rationales of social change are formed through ‘sport as a means of responding to social problems’. Four research questions are posed: (1) How is it that sport can be thought of and articulated as a means of responding to social problems? (2) How are sport practices assumed to operate as a means of responding to social problems? (3) How are social problems represented when sport is promoted as a means of response? (4) What conduct, subjectivity and citizen competences are shaped within this regime of practice? The study focuses on the government of subjects’ conduct, the formation of community and delineation of domains subjected to social change. The gradual shifts in the governmental rationality of the Swedish welfare state provide a framework for the study. Two kinds of empirical material are investigated. Initially, scientific knowledge is analysed; after this, a sport-based intervention, conducted in cooperation between a social entrepreneur, municipality and local sport clubs, is examined. In relation to scientific discourse, research on sport for social objectives would benefit from more theoretically driven constructionist perspectives related to welfare state transformations. In scientific discourse, rationales of social change in sport are conceived of as individual attainment of skills, competences and powers that are presumably transferable to other social spheres. Such discourse represents problems as individual problems. With respect to the sport-based intervention, individual change is promoted by representatives of the social entrepreneur in terms of providing subjects with motivational powers, which are shaped by role models and applied in “choosing the right track”. By representing problems as risks, avoidance is formed as an individual opportunity. This positions subjects as being responsible for their own welfare and inclusion. Municipal policy makers view the intervention as a way to form community and social cohesion in response to tensions in society. They present sport (and the social entrepreneur) as a way to mobilize and activate civil society – which is associated with the potency of voluntarism, authentic leadership and personal relations based on common identity. Consequently, responsibility for responding to social problems is spread and elements of de-professionalized social work are imposed. To conclude, sport is conceptualized as a means of responding to social problems because sport practices are associated with individual agency and with an active civil society and moral community. The technologies and rationality of social change point out ‘the self’, ‘the community’ and ‘the place’ as locations where social change is possible, rather than the whole of society. For instance, the technologies of social change are based on activation and responsibilization of ‘the self’ and of ‘the community’. These rationales of social change are based on a critique of welfarist governmentality and of the idea of governing from ‘the social’ point of view. Arguably, such discourse obscures more profound social reform. The study provides some empirical explorations illustrating how a range of tendencies and mutations in the governmental rationality of the welfare state and of social work are  manifested in ‘sport as a means of responding to social problems’.

    List of papers
    1. Research on Sport as a Means of Crime Prevention in a Swedish Welfare Context: A Literature Review
    Open this publication in new window or tab >>Research on Sport as a Means of Crime Prevention in a Swedish Welfare Context: A Literature Review
    2013 (English)In: Scandinavian Sport Studies Forum, ISSN 2000-088X, Vol. 4, 91-120 p.Article in journal (Refereed) Published
    Abstract [en]

    This article reviews Swedish research literature on sport as a means to realize social objectives related to crime prevention, contextualized by international literature on the subject. The article examines how Swedish research on sport as a means of crime prevention can be understood in light of international research regarding research questions, theoretical approaches, and content. Utilizing content analysis with inductive category development, the article describes current Swedish and international research, identifies certain characteristics in Swedish research, as well as underlying assumptions. Besides a thorough description acknowledging discrepancies between scientific knowledge in literature and a common sense notion in society about sport as a means of crime prevention, the article highlights five results. First, Swedish research shows great similarities with international research regarding content. Second, previous research is greatly concerned with empirically driven approaches. Third, Swedish research is nonexplicit in terms of crime prevention as a social objective and considers social objectives a potential effect of, rather than a premise for, sport practices. Fourth, Swedish research is focused on primary and secondary prevention. Fifth, there is general lack of Swedish research on sport as a means of crime prevention. In conclusion, the article considers future possible directions in research with respect to characteristics in the traditionally upheld Swedish welfare state regime.

    Place, publisher, year, edition, pages
    Malmö University, 2013
    Keyword
    crime reduction, social problem, social work, sport, welfare, youth, leisure, deviancy
    National Category
    Social Sciences
    Identifiers
    urn:nbn:se:liu:diva-99435 (URN)
    Available from: 2013-10-18 Created: 2013-10-18 Last updated: 2016-08-23Bibliographically approved
    2. Sport and crime prevention: Individuality and transferability in research
    Open this publication in new window or tab >>Sport and crime prevention: Individuality and transferability in research
    2013 (English)In: Journal of Sport for Development, ISSN 2330-0574, Vol. 1, no 2Article in journal (Refereed) Published
    Abstract [en]

    Researchers have examined sport practices as a means of crime prevention. The article reviews the international body of literature on this subject from a social constructionist perspective. By exploring the idea of sport as a means of crime prevention, the article considers what is described on the subject and how these descriptions are articulated. Through a content analysis, the article aims to develop categories and provide an analytical discussion of the findings. The descriptive analysis reveals that, although researchers are most notably critical of putting faith in sport for social objectives, there is research that affirms the role of sport in crime prevention. When sport is upheld as a means of crime prevention, two modes of prevention are emphasised, called the averting-mode and the social change-mode. The discussion focuses primarily on how the dominant social change-mode is articulated and how this social change becomes a meaningful concept as portrayed in discourses on individuality and transferability. The importance and potential consequences of framing crime as a social problem and of framing sport as a solution in response are also discussed. Finally, the article sets out the direction for further research on sport as a means of crime prevention.

    Keyword
    Anti-social behaviour, Social problem, Social work, Welfare, Youth
    National Category
    Social Sciences
    Identifiers
    urn:nbn:se:liu:diva-102954 (URN)
    Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2016-08-23Bibliographically approved
  • Public defence: 2016-09-30 13:00 Berzeliussalen, Linköping
    Fältström, Anne
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.
    Fältström, Anne
    Linköping University, Department of Medical and Health Sciences, Division of Physiotherapy. Linköping University, Faculty of Medicine and Health Sciences.
    One Anterior Cruciate Ligament injury is enough!: Focus on female football players2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Anterior cruciate ligament (ACL) injury is a severe and common injury, and females have 2-4 times higher injury risk compared to men. Return to sport (RTS) is a common goal after an ACL reconstruction (ACLR), but only about two thirds of patients RTS. Young patients who RTS may have a 30-40 times increased risk of sustaining an additional ACL injury to the ipsi- or contralateral knee compared with an uninjured person.

    Aims: The overall aim of this thesis was to increase the knowledge about female football players with ACLR, and patients with bilateral ACL injuries, and to identify predictors for additional ipsi- and/or contralateral ACLR.

    Methods: This thesis comprises four studies. Study I and II were cross-sectional, including females who sustained a primary ACL rupture while playing football and underwent ACLR 6–36 months prior to study inclusion. In study I, 182 females were included at a median of 18 months (IQR 13) after ACLR. All players completed a battery of questionnaires. Ninety-four players (52%) returned to football and were playing at the time of completing the questionnaires, and 88 (48%) had not returned. In study II, 77 of the 94 active female football players (from study I) with an ACLR and 77 kneehealthy female football players were included. A battery of tests was used to assess postural control (the Star excursion balance test) and hop performance (the one-leg hop for distance, the five jump test and the side hop). Movement asymmetries in the lower limbs and trunk were assessed with the drop vertical jump and the tuck jump using two-dimensional analyses. Study III, was a cohort study including all patients with a primary ACLR (n=22,429) registered in the Swedish national ACL register between January 2005 and February 2013. Data extracted from the register to identify predictors for additional ACLR were: patient age at primary ACLR, sex, activity performed at the time of ACL injury, primary injury to the right- or left knee, time between injury and primary ACLR, presence of any concomitant injuries, graft type, Knee injury and Osteoarthritis Outcome Score and Euroqol Index Five Dimensions measured pre-operatively. Study IV was cross-sectional. In this study, patient-reported knee function, quality of life and activity level in 66 patients with bilateral ACL injuries was investigated and outcomes were compared with 182 patients with unilateral ACLR.

    Results: Factors associated with returning to football in females were; short time between injury and ACLR (0–3 months, OR 5.6; 3–12 months OR 4.7 vs. reference group >12 months) and high motivation (study I). In all functional tests, the reconstructed and uninvolved limbs did not differ, and players with ACLR and controls differed only minimally. Nine to 49% of the players with ACLR and controls had side-to-side differences and movement asymmetries and only one fifth had results that met the recommended guidelines for successful outcome on all the different tests (study II). Main predictors for revision and contralateral ACLR were younger age (fourfold increased rate for <16 vs. >35-year-old patients), having ACLR early after the primary injury (two to threefold increased rate for ACLR within 3 months vs. >12 months), and incurring the primary injury while playing football (study III). Patients with bilateral ACL injuries reported poorer knee function and quality of life compared to those who had undergone unilateral ACLR. They had a high activity level before their first and second ACL injuries but an impaired activity level at follow-up after their second injury (study IV).

    Conclusions: Female football players who returned to football after an ACLR had high motivation and had undergone ACLR within one year after injury. Players with ACLR had similar functional performance to healthy controls. Movement asymmetries, which in previous studies have been associated with increased risk for primary and secondary ACL injury, occurred to a high degree in both groups. The rate of additional ACLR seemed to be increased in a selected group of young patients who desire to return to strenuous sports like football quickly after primary ACLR. Sustaining a contralateral ACL injury led to impaired knee function and activity level.

    List of papers
    1. Factors associated with playing football after anterior cruciate ligament reconstruction in female football players.
    Open this publication in new window or tab >>Factors associated with playing football after anterior cruciate ligament reconstruction in female football players.
    2015 (English)In: Scandinavian Journal of Medicine and Science in Sports, ISSN 0905-7188, E-ISSN 1600-0838Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    This study investigated whether player-related factors (demographic, personality, or psychological factors) or the characteristics of the anterior cruciate ligament (ACL) injury were associated with the return to playing football in females after ACL reconstruction (ACLR). We also compared current knee function, knee related quality of life and readiness to return to sport between females who returned to football and those who had not returned. Females who sustained a primary ACL rupture while playing football and underwent ACLR 6-36 months ago were eligible. Of the 460 contacted, 274 (60%) completed a battery of questionnaires, and 182 were included a median of 18 months (IQR 13) after ACLR. Of these, 94 (52%) returned to football and were currently playing, and 88 (48%) had not returned. Multiple logistic regression analysis identified two factors associated with returning to football: short time between injury and ACLR (0-3 months, OR 5.6; 3-12 months OR 4.7 vs reference group > 12 months) and high motivation. Current players showed higher ratings for current knee function, knee-related quality of life, and psychological readiness to return to sport (P < 0.001). Undergoing ACLR sooner after injury and high motivation to return to sports may impact a player's return to football after ACLR.

    Place, publisher, year, edition, pages
    Wiley-Blackwell, 2015
    Keyword
    ACL; knee; return to sport; soccer
    National Category
    Physiotherapy
    Identifiers
    urn:nbn:se:liu:diva-123889 (URN)10.1111/sms.12588 (DOI)26589671 (PubMedID)
    Available from: 2016-01-13 Created: 2016-01-13 Last updated: 2016-08-31Bibliographically approved
    2. Predictors for additional anterior cruciate ligament reconstruction: data from the Swedish national ACL register.
    Open this publication in new window or tab >>Predictors for additional anterior cruciate ligament reconstruction: data from the Swedish national ACL register.
    Show others...
    2016 (English)In: Knee Surgery, Sports Traumatology, Arthroscopy, ISSN 0942-2056, E-ISSN 1433-7347, Vol. 24, no 3, 885-894 p.Article in journal (Refereed) Published
    Abstract [en]

    PURPOSE: To identify predictors for additional anterior cruciate ligament (ACL) reconstruction.

    METHODS: Patients from the Swedish national ACL register who underwent ACL reconstruction between January 2005 and February 2013 (follow-up duration 6-104 months) were included. Cox regression analyses included the following independent variables regarding primary injury: age, sex, time between injury and primary ACL reconstruction, activity at primary injury, concomitant injuries, injury side, graft type, and pre-surgery KOOS and EQ-5D scores.

    RESULTS: Among ACL reconstruction procedures, 93 % involved hamstring tendon (HT) autografts. Graft type did not predict additional ACL reconstruction. Final regression models only included patients with HT autograft (n = 20,824). Of these, 702 had revision and 591 contralateral ACL reconstructions. The 5-year post-operative rates of revision and contralateral ACL reconstruction were 4.3 and 3.8 %, respectively. Significant predictors for additional ACL reconstruction were age (fourfold increased rate for <16-year-old patients vs. >35-year-old patients), time between injury and primary surgery (two to threefold increased rate for ACL reconstruction within 0-90 days vs. >365 days), and playing football at primary injury.

    CONCLUSION: This study identified younger age, having ACL reconstruction early after the primary injury, and incurring the primary injury while playing football as the main predictors for revision and contralateral ACL reconstruction. This suggests that the rate of additional ACL reconstruction is increased in a selected group of young patients aiming to return to strenuous sports after primary surgery and should be taken into consideration when discussing primary ACL reconstruction, return to sports, and during post-surgery rehabilitation. LEVEL OF EVIDENCE: II.

    National Category
    Physiotherapy
    Identifiers
    urn:nbn:se:liu:diva-115943 (URN)10.1007/s00167-014-3406-6 (DOI)000371300400036 ()25366191 (PubMedID)
    Note

    Funding agencies:The study was financially supported by Futurum-the academy for healthcare, County Council, Jonkoping, the Faculty of Health Sciences at Linkoping University, and the Swedish National Centre for Research in Sports (CIF).

    Available from: 2015-03-24 Created: 2015-03-24 Last updated: 2016-08-31
    3. Patient-Reported Knee Function, Quality of Life, and Activity Level After Bilateral Anterior Cruciate Ligament Injuries
    Open this publication in new window or tab >>Patient-Reported Knee Function, Quality of Life, and Activity Level After Bilateral Anterior Cruciate Ligament Injuries
    2013 (English)In: American Journal of Sports Medicine, ISSN 0363-5465, E-ISSN 1552-3365, Vol. 41, no 12, 2805-2813 p.Article in journal (Refereed) Published
    Abstract [en]

    Background: About 12% of patients who have undergone primary anterior cruciate ligament (ACL) reconstruction sustain a contralateral ACL injury within 5 years. less thanbrgreater than less thanbrgreater thanPurpose: To investigate patient-reported knee function, quality of life, and activity level in patients with bilateral ACL injuries. less thanbrgreater than less thanbrgreater thanStudy Design: Cohort study; Level of evidence, 3. less thanbrgreater than less thanbrgreater thanMethods: A search of hospital records identified 147 patients, aged 18 to 45 years, with bilateral ACL injuries. Of these, 83 met the inclusion criteria, having had their first ACL injury up to 12 years ago with no other major injuries to the knee joint. Sixty-six of these patients (80% of total; 47% female; mean age, 29.1 7.2 years) answered a questionnaire packet. Patients who had undergone unilateral ACL reconstruction (n = 182) were used for comparison. less thanbrgreater than less thanbrgreater thanResults: Patients with bilateral ACL injuries had a median Lysholm knee score of 82 (range, 34-100). The mean EuroQol index (EQ-5D) score of the overall health status was 0.77 +/- 0.22, and the mean EQ-5D visual analog scale score was 75.5 +/- 17.6. The median Tegner activity level was 9 (range, 1-9) before any injuries, 7 (range, 1-9) before the second ACL injury, and 4 (range, 1-9) at the time of follow-up. The activity level before the second injury was higher compared with the follow-up for patients who had undergone unilateral ACL reconstruction. At follow-up, 23% of the patients with bilateral ACL injuries returned to their previous activity, and 12% of patients returned to the same level as before their injuries compared with 43% (P = .004) and 28% (P = .01) in patients who had undergone unilateral ACL reconstruction, respectively. Patients with bilateral ACL injuries had significantly lower values in the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales for pain, function in sports and recreation, and knee-related quality of life as well as the ACL Deficiency Quality of Life (ACL-QOL) score compared with patients who had undergone unilateral ACL reconstruction. less thanbrgreater than less thanbrgreater thanConclusion: Patients with bilateral ACL injuries reported poorer knee function and quality of life compared with those who had undergone unilateral ACL reconstruction. Their activities had changed, and they were dissatisfied with their current activity level. They had a high activity level before their first and second ACL injuries but an impaired activity level after their contralateral injury at follow-up.

    Place, publisher, year, edition, pages
    SAGE Publications (UK and US): No SAGE Choice, 2013
    Keyword
    knee, ligaments, ACL, contralateral, return to sport, subsequent injury, Tegner activity scale
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-102774 (URN)10.1177/0363546513502309 (DOI)000327473300013 ()
    Note

    Funding Agencies|Futurum-The Academy for Healthcare, Jonkoping County Council||Medical Research Council of Southeast Sweden||Faculty of Health Sciences at Linkoping University||Swedish National Centre for Research in Sports||

    Available from: 2014-01-07 Created: 2013-12-26 Last updated: 2016-08-31
  • Public defence: 2016-09-30 13:15 Visionen, Hus B, Linköping
    Nikkar, Samira
    Linköping University, Department of Mathematics, Computational Mathematics. Linköping University, Faculty of Science & Engineering.
    Nikkar, Samira
    Linköping University, Department of Mathematics, Computational Mathematics. Linköping University, Faculty of Science & Engineering.
    Stable High Order Finite Difference Methods for Wave Propagation and Flow Problems on Deforming Domains2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    We construct stable, accurate and efficient numerical schemes for wave propagation and flow problems posed on spatial geometries that are moving, deforming, erroneously described or non-simply connected. The schemes are on Summation-by-Parts (SBP) form, combined with the Simultaneous Approximation Term (SAT) technique for imposing initial and boundary conditions. The main analytical tool is the energy method, by which well-posedness, stability and conservation are investigated. To handle the deforming domains, time-dependent coordinate transformations are used to map the problem to fixed geometries.

    The discretization is performed in such a way that the Numerical Geometric Conservation Law (NGCL) is satisfied. Additionally, even though the schemes are constructed on fixed domains, time-dependent penalty formulations are necessary, due to the originally moving boundaries. We show how to satisfy the NGCL and present an automatic formulation for the penalty operators, such that the correct number of boundary conditions are imposed, when and where required.

    For problems posed on erroneously described geometries, we investigate how the accuracy of the solution is affected. It is shown that the inaccurate geometry descriptions may lead to wrong wave speeds, a misplacement of the boundary condition, the wrong boundary operator or a mismatch of data. Next, the SBP-SAT technique is extended to time-dependent coupling procedures for deforming interfaces in hyperbolic problems. We prove conservation and stability and show how to formulate the penalty operators such that the coupling procedure is automatically adjusted to the variations of the interface location while the NGCL is preserved.

    Moreover, dual consistent SBP-SAT schemes for the linearized incompressible Navier-Stokes equations posed on deforming domains are investigated. To simplify the derivations of the dual problem and incorporate the motions of the boundaries, the second order formulation is reduced to first order and the problem is transformed to a fixed domain. We prove energy stability and dual consistency. It is shown that the solution as well as the divergence of the solution converge with the design order of accuracy, and that functionals of the solution are superconverging.

    Finally, initial boundary value problems posed on non-simply connected spatial domains are investigated. The new formulation increases the accuracy of the scheme by minimizing the use of multi-block couplings. In order to show stability, the spectrum of the semi-discrete SBP-SAT formulation is studied. We show that the eigenvalues have the correct sign, which implies stability, in combination with the SBP-SAT technique in time.

    List of papers
    1. Fully discrete energy stable high order finite difference methods for hyperbolic problems in deforming domains
    Open this publication in new window or tab >>Fully discrete energy stable high order finite difference methods for hyperbolic problems in deforming domains
    2015 (English)In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 291, 82-98 p.Article in journal (Refereed) Published
    Abstract [en]

    A time-dependent coordinate transformation of a constant coefficient hyperbolic system of equations which results in a variable coefficient system of equations is considered. By applying the energy method, well-posed boundary conditions for the continuous problem are derived. Summation-by-Parts (SBP) operators for the space and time discretization, together with a weak imposition of boundary and initial conditions using Simultaneously Approximation Terms (SATs) lead to a provable fully-discrete energy-stable conservative finite difference scheme. We show how to construct a time-dependent SAT formulation that automatically imposes boundary conditions, when and where they are required. We also prove that a uniform flow field is preserved, i.e. the Numerical Geometric Conservation Law (NGCL) holds automatically by using SBP-SAT in time and space. The developed technique is illustrated by considering an application using the linearized Euler equations: the sound generated by moving boundaries. Numerical calculations corroborate the stability and accuracy of the new fully discrete approximations.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keyword
    Deforming domain; Initial boundary value problems; High order accuracy; Well-posed boundary conditions; Summation-by-parts operators; Stability; Convergence; Conservation; Numerical geometric conservation law; Euler equation; Sound propagation
    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-117360 (URN)10.1016/j.jcp.2015.02.027 (DOI)000352230500006 ()
    Available from: 2015-04-24 Created: 2015-04-24 Last updated: 2016-08-31
    2. Hyperbolic systems of equations posed on erroneous curved domains
    Open this publication in new window or tab >>Hyperbolic systems of equations posed on erroneous curved domains
    2016 (English)In: Journal of Computational Physics, ISSN 0021-9991, E-ISSN 1090-2716, Vol. 308, 438-442 p.Article in journal (Refereed) Published
    Abstract [en]

    The effect of an inaccurate geometry description on the solution accuracy of a hyperbolic problem is discussed. The inaccurate geometry can for example come from an imperfect CAD system, a faulty mesh generator, bad measurements or simply a misconception.

    We show that inaccurate geometry descriptions might lead to the wrong wave speeds, a misplacement of the boundary conditions, to the wrong boundary operator and a mismatch of boundary data.

    The errors caused by an inaccurate geometry description may affect the solution more than the accuracy of the specific discretization techniques used. In extreme cases, the order of accuracy goes to zero. Numerical experiments corroborate the theoretical results.

    Place, publisher, year, edition, pages
    Elsevier, 2016
    Keyword
    Hyperbolic systems; Erroneous curved domains; Inaccurate data; Convergence rate
    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-123918 (URN)10.1016/j.jcp.2015.12.048 (DOI)000369086700021 ()
    Available from: 2016-01-13 Created: 2016-01-13 Last updated: 2016-08-31Bibliographically approved
    3. A fully discrete, stable and conservative summation-by-parts formulation for deforming interfaces
    Open this publication in new window or tab >>A fully discrete, stable and conservative summation-by-parts formulation for deforming interfaces
    2016 (English)Report (Other academic)
    Abstract [en]

    We introduce an interface/coupling procedure for hyperbolic problems posedon time-dependent curved multi-domains. First, we transform the problem from Cartesian to boundary-conforming curvilinear coordinates and apply the energy method to derive well-posed and conservative interface conditions.

    Next, we discretize the problem in space and time by employing finite difference operators that satisfy a summation-by-parts rule. The interface condition is imposed weakly using a penalty formulation. We show how to formulate the penalty operators such that the coupling procedure is automatically adjusted to the movements and deformations of the interface, while both stability and conservation conditions are respected.

    The developed techniques are illustrated by performing numerical experiments on the linearized Euler equations and the Maxwell equations. The results corroborate the stability and accuracy of the fully discrete approximations.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2016. 38 p.
    Series
    LiTH-MAT-R, ISSN 0348-2960 ; 2016:9
    Keyword
    Finite difference, High order accuracy, Deforming domains, Time-dependent interface, Well-posedness, Conservation, Summation-by-parts, Stability, Hyperbolic problems
    National Category
    Computational Mathematics
    Identifiers
    urn:nbn:se:liu:diva-130583 (URN)LiTH-MAT-R--2016/09--SE (ISRN)
    Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2016-09-19Bibliographically approved
    4. A dual consistent summation-by-parts formulation for the linearized incompressible Navier-Stokes equations posed on deforming domains
    Open this publication in new window or tab >>A dual consistent summation-by-parts formulation for the linearized incompressible Navier-Stokes equations posed on deforming domains
    2016 (English)Report (Other academic)
    Abstract [en]

    In this article, well-posedness and dual consistency of the linearized incompressible Navier-Stokes equations posed on time-dependent spatial domains are studied. To simplify the derivation of the dual problem, the second order formulation is transformed to rst order form. Boundary conditions that simultaneously lead to well-posedness of the primal and dual problems are derived.

    We construct fully discrete nite di erence schemes on summation-byparts form, in combination with the simultaneous approximation technique. We prove energy stability and discrete dual consistency. Moreover, we show how to construct the penalty operators such that the scheme automatically adjusts to the variations of the spatial domain, and as a result, stability and discrete dual consistency follow simultaneously.

    The method is illustrated by considering a deforming time-dependent spatial domain in two dimensions. The numerical calculations are performed using high order operators in space and time. The results corroborate the stability of the scheme and the accuracy of the solution. We also show that linear functionals are superconverging. Additionally, we investigate the convergence of non-linear functionals and the divergence of the solution.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2016. 26 p.
    Series
    LiTH-MAT-R, ISSN 0348-2960 ; 2016:10
    Keyword
    Incompressible Navier-Stokes equations, Deforming domain, Stability, Dual consistency, High order accuracy, Superconvergence
    National Category
    Computational Mathematics
    Identifiers
    urn:nbn:se:liu:diva-130584 (URN)LiTH-MAT-R--2016/10--SE (ISRN)
    Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2016-09-19Bibliographically approved
    5. Summation-by-parts operators for non-simply connected domains
    Open this publication in new window or tab >>Summation-by-parts operators for non-simply connected domains
    2016 (English)Report (Other academic)
    Abstract [en]

    We construct fully discrete stable and accurate numerical schemes for solving partial differential equations posed on non-simply connected spatial domains. The schemes are constructed using summation-by-parts operators in combination with a weak imposition of initial and boundary conditions using the simultaneous approximation term technique.

    In the theoretical part, we consider the two dimensional constant coefficient advection equation posed on a rectangular spatial domain with a hole. We construct the new scheme and study well-posedness and stability. Once the theoretical development is done, the technique is extended to more complex non-simply connected geometries.

    Numerical experiments corroborate the theoretical results and show the applicability of the new approach and its advantages over the standard multi-block technique. Finally, an application using the linearized Euler equations for sound propagation is presented.

    Place, publisher, year, edition, pages
    Linköping: Linköping University Electronic Press, 2016. 32 p.
    Series
    LiTH-MAT-R, ISSN 0348-2960 ; 2016:11
    Keyword
    Initial boundary value problems, Stability, Well-posedness, Boundary conditions, Non-simply connected domains, Complex geometries
    National Category
    Computational Mathematics
    Identifiers
    urn:nbn:se:liu:diva-130585 (URN)LiTH-MAT-R--2016/11--SE (ISRN)
    Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2016-08-31Bibliographically approved
  • Public defence: 2016-09-30 13:15 ACAS, Hus A, Linköping
    Granath, Malin
    Linköping University, Department of Management and Engineering, Information Systems. Linköping University, Faculty of Arts and Sciences.
    Granath, Malin
    Linköping University, Department of Management and Engineering, Information Systems. Linköping University, Faculty of Arts and Sciences.
    The Smart City – how smart can ’IT’ be?: Discourses on digitalisation in policy and planning of urban development2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Cities are facing many challenges; challenges linked to world-wide trends like urbanisation, climate changes and globalisation. In parallel to these trends, we have seen a rapid digitalisation in and of different parts of society. Cities and local governments have been appointed an important role in overcoming these world-wide challenges, and subsequently, in policy practices digitalisation is perceived as an important dimension in delivering better and sustainable services to its citizens. As a result, the smart city has emerged as a concept and approach to contemporary urban planning and development. There is still no common understanding of the concept and what components and dimensions it covers. However, in all definitions digitalisation constitutes one dimension, but the role and function of it is still not clear.

    In this study I have examined how different stakeholders talk about digitalisation in policy and planning practices of urban development. The aim has been to identify and analyse different repertoires of discourses on digitalisation to advance our knowledge on how goals related to the smart city and digitalisation are put into practice. The results are based on a qualitative and interpretative case study with a social constructionist approach. An analytical framework based on discourse analysis, stakeholder theory and (new) institutional theory has been constructed to analyse the case.

    Main results show that repertoires on digitalisation are limited in both policy and planning of urban development. In these practices, digitalisation is primarily seen as a means or as a communication infrastructure in relation to two city services/functions; i.e. services related to governance and to environment. Results also show that practices of urban planning and development are institutionalised, where different stakeholders’ salience and stakes in urban development and in digitalisation differ, but it is clear that digitalisation is a secondary issue. Implications of these results are that the taken-for-granted discourses in policy and planning practices of urban development limit both practice and research when developing a smart city.

  • Public defence: 2016-10-04 09:00 K1, Kåkenhus, Norrköping
    Klompstra, Leonie
    Linköping University, Department of Social and Welfare Studies, Division of Nursing Science. Linköping University, Faculty of Medicine and Health Sciences.
    Klompstra, Leonie
    Linköping University, Department of Social and Welfare Studies, Division of Nursing Science. Linköping University, Faculty of Medicine and Health Sciences.
    Physical activity in patients with heart failure: motivations, self-efficacy and the potential of exergaming2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background: Adherence to recommendations for physical activity is low in patients with heart failure (HF). It is essential to explore to what extent and why patients with HF are physically active. Self-efficacy and motivation for physical activity are important in becoming more physically active, but the role of self-efficacy in the relationship between motivation and physical activity in patients with HF is unknown. Alternative approaches to motivate and increase self-efficacy to exercise are needed. One of these alternatives might be using exergames (games to improve physical exercise). Therefore, it is important to obtain more knowledge on the potential of exergaming to increase physical activity.

    The overall aim was to describe the physical activity in patients with HF, with special focus on motivations and self-efficacy in physical activity, and to describe the potential of exergaming to improve exercise capacity.

    Methods: Study I (n = 154) and II (n = 101) in this thesis had a cross-sectional survey design. Study III (n = 32) was a 12-week pilot intervention study, including an exergame platform at home, with a pretest-posttest design. Study IV (n = 14) described the experiences of exergaming in patients who participated in the intervention group of a randomized controlled study in which they had access to an exergame platform at home.

    Results: In total, 34% of the patients with HF had a low level of physical activity, 46% had a moderate level, 23% reported a high level. Higher education, higher selfefficacy, and higher motivation were significantly associated with a higher amount of physical activity. Barriers to exercise were reported to be difficult to overcome and psychological motivations were the most important motivations to be physically active. Women had significantly higher total motivation to be physically active. Self-efficacy mediated the relationship between exercise motivation and physical activity; motivation leads to a higher self-efficacy towards physical activity.

    More than half of the patients significantly increased their exercise capacity after 12 weeks of using an exergame platform at home. Lower NYHA-class and shorter time since diagnosis were factors significantly related to the increase in exercise capacity. The mean time spent exergaming was 28 minutes per day. Having grandchildren and being male were related to more time spent exergaming.

    The analysis of the qualitative data resulted in three categories describing patients’ experience of exergaming: (i) making exergaming work, (ii) added value of exergaming, (iii) no appeal of exergaming.

    Conclusion: One-third of the patients with HF had a low level of physical activity in their daily life. Level of education, exercise self-efficacy, and motivation were important factors to take into account when advising patients with HF about physical activity. In addition to a high level of motivation to be physically active, it is important that patients with HF have a high degree of exercise self-efficacy.

    Exergaming has the potential to increase exercise capacity in patients with HF. The results also showed that this technology might be suitable for some patients while others may prefer other kinds of physical activity.

    List of papers
    1. Physical activity in patients with heart failure: barriers and motivations with special focus on sex differences
    Open this publication in new window or tab >>Physical activity in patients with heart failure: barriers and motivations with special focus on sex differences
    2015 (English)In: Patient Preference and Adherence, ISSN 1177-889X, E-ISSN 1177-889X, Vol. 9, 1603-1610 p.Article in journal (Refereed) Published
    Abstract [en]

    Background: Adherence to recommendations for physical activity is low in both male and female patients with heart failure (HF). Men are more physically active than women. In order to successfully promote physical activity, it is therefore essential to explore how much and why HF patients are physically active and if this is related to sex. The aim of this study was therefore to evaluate physical activity in HF patients, to describe the factors related to physical activity, and to examine potential barriers and motivations to physical activity with special focus on sex differences. Methods: The study had a cross-sectional survey design. HF patients living at home received a questionnaire during May-July 2014, with questions on physical activity (from the Short Form-International Physical Activity Questionnaire), and potential barriers and motivations to physical activity. Results: A total of 154 HF patients, 27% women, with a mean age of 70 +/- 10 were included. In total, 23% of the patients reported a high level of physical activity, 46% a moderate level, and 34% a low level. Higher education, self-efficacy, and motivation were significantly associated with a higher amount of physical activity. Symptoms or severity of the disease were not related to physical activity. All the potential barriers to exercise were reported to be of importance. Psychological motivations were most frequently rated as being the most important motivation (41%) to be physically active. Physical motivations (33%) and social motivations were rated as the least important ones (22%). Women had significantly higher total motivation to be physically active. These differences were found in social, physical, and psychological motivations. Discussion: One-third of the HF patients had a low level of physical activity in their daily life. Severity of the disease or symptoms were not related, whereas level of education, exercise self-efficacy, and motivation were important factors to take into account when advising a HF patient about physical activity. Women reported higher motivation to be physically active than men, but there was no difference in the reported level of physical activity.

    Place, publisher, year, edition, pages
    DOVE MEDICAL PRESS LTD, 2015
    Keyword
    barriers; sex differences; heart failure; motivation; physical activity; self-efficacy
    National Category
    Nursing Health Care Service and Management, Health Policy and Services and Health Economy
    Identifiers
    urn:nbn:se:liu:diva-123091 (URN)10.2147/PPA.S90942 (DOI)000364289900001 ()26635469 (PubMedID)
    Available from: 2015-12-03 Created: 2015-12-03 Last updated: 2016-08-31
    2. Exergaming to increase the exercise capacity and daily physical activity in heart failure patients: a pilot study
    Open this publication in new window or tab >>Exergaming to increase the exercise capacity and daily physical activity in heart failure patients: a pilot study
    2014 (English)In: BMC Geriatrics, ISSN 1471-2318, Vol. 14, no 119Article in journal (Refereed) Published
    Abstract [en]

    Background

    Regular daily physical activity is recognised as important in heart failure (HF) patients, but adherence to physical activity is low (<50%). To improve adherence to exercise in HF patients, alternative approaches to motivate and increase self-efficacy to exercise are needed. Therefore, we have studied a new phenomenon: exergames (games to improve physical exercise). The aims of the study were to assess the influence of the exergame platform Nintendo Wii on exercise capacity and daily physical activity in heart failure patients, to study factors related to exercise capacity and daily physical activity, and to assess patients’ adherence to exergaming.

    Methods

    A 12-week pilot study with a pretest-posttest design was conducted. The intervention consisted of an instruction on how to use the Wii and 12 weeks’ access to Wii at home. The main variables tested were exercise capacity (measured with a six-minute walking test), daily physical activity (measured with an activity monitor), and time exergaming (daily self-report with a diary). Bivariate correlations were used to assess associations between symptom experience, self-efficacy, motivation, anxiety, and depression.

    Results

    In total, 32 heart failure patients were included. More than half of the patients (53%) significantly increased their exercise capacity after 12 weeks. No significant difference was found in daily physical activity between baseline and 12 weeks. Lower NYHA class and shorter time since diagnosis were factors significantly related to the increase in exercise capacity. The daily mean time spent exergaming was 28 minutes, and having grandchildren and being male were related to more time spent exergaming.

    Conclusion

    Exergaming has the potential to increase exercise capacity in elderly, chronically ill cardiac patients. Although the daily physical activity did not change over time, exergaming was feasible for heart failure patients and might be a rehabilitation option for patients with heart failure

    Place, publisher, year, edition, pages
    BioMed Central, 2014
    Keyword
    Active video game, Adherence, Exercise capacity, Exergame, Heart failure, Physical activity
    National Category
    Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-112402 (URN)10.1186/1471-2318-14-119 (DOI)000346030500004 ()25407612 (PubMedID)
    Available from: 2014-11-25 Created: 2014-11-25 Last updated: 2016-08-31Bibliographically approved
  • Public defence: 2016-10-07 10:15 ACAS, A-huset, Linköping
    Mignon, Ingrid
    Linköping University, Department of Management and Engineering, Project Innovations and Entrepreneurship. Linköping University, Faculty of Science & Engineering.
    Mignon, Ingrid
    Linköping University, Department of Management and Engineering, Project Innovations and Entrepreneurship. Linköping University, Faculty of Science & Engineering.
    Inducing large-scale diffusion of innovation: An integrated actor- and system-level approach2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In order for the innovation process to be successful, not only do innovations need to be developed and reached the market, but, once they are available for users, they have to spread on a large scale. In the innovation literature, a complete explanation is lacking of why some innovations reach a phase of large-scale diffusion faster than others, including both actor- and system-level components. For instance, what drives and hinders adopters to decide to adopt the innovation on the actor and system levels, and how adopters who participate in the largescale diffusion handle the adoption process and the implementation of the innovation, are questions still unanswered. As a consequence, it remains unclear how the large-scale diffusion process can be facilitated and speeded up.

    This thesis addresses these issues by studying the case of renewable electricity (RE) innovations. After decades of technology development and improvements, RE innovations are now mature enough to be bought off-the-shelf by individuals and organizations. Yet, the pace of their large-scale diffusion is still too slow for countries to reach their RE generation targets and to limit global warming.

    Through qualitative and quantitative methods including 59 semi-structured interviews with adopters, project developers and experts in Sweden, France and Germany as well as a survey sent to the whole population of RE adopters in Sweden, an adopter perspective is taken in order to explore the adoption dynamics shaping large-scale diffusion of innovation. More specifically, the thesis identifies the drivers and challenges of adoption during large-scale diffusion and their impact on adoption decisions and strategies. The outcome of this work is presented in a compiling synthesis and six appended papers.

    Findings show that adopters are heterogeneous with regard to their characteristics, as well as to the drivers, challenges and strategies that affect their adoption processes. Depending on their perceptions, some adopters are more influenced by drivers and challenges than others and, as a consequence, adopters base their adoption decisions on different motives and follow different strategies to implement the innovation.

    Moreover, the results suggest that the dynamics that occur during the large-scale diffusion process does not only come from the actor level and the level of the system where the largescale diffusion takes place, but also from parallel systems, which are related to adopters and their contexts, including both the social networks and the industries they primarily belong. This makes adopters the central drivers of the innovation diffusion process and this distinguishes the dynamics of large-scale diffusion from the dynamics of innovation development and early diffusion, in which the innovation is the central component.

    Based on the findings about the adoption dynamics shaping large-scale diffusion, the thesis raises the need to consider large-scale diffusion as part of a new system, different from the innovation system and that acknowledges the specificities of this process. A tentative model accounting for the central role of adopters and for the interactions between adopters, the diffusion system and parallel systems is introduced.

    Finally, the implications of these findings for policy makers and managers are put forward. In particular, there is a need for policies acknowledging adopters’ heterogeneity as well as the new challenges of large-scale diffusion. Strategies developed by adopters can be a source of inspiration for policy-makers, who can for instance promote the use of intermediaries, of adopters’ task environment and networks, as well as the formation of coalitions among adopters.

    List of papers
    1. Who invests in renewable electricity production?: Empirical evidence and suggestions for further research
    Open this publication in new window or tab >>Who invests in renewable electricity production?: Empirical evidence and suggestions for further research
    2013 (English)In: Energy Policy, ISSN 0301-4215, Vol. 56, 568-581 p.Article in journal (Refereed) Published
    Abstract [en]

    Transforming energy systems to fulfill the needs of a low-carbon economy requires large investments in renewable electricity production (RES-E). Recent literature underlines the need to take a closer look at the composition of the RES-E investor group in order to understand the motives and investment processes of different types of investors. However, existing energy policies generally consider RES-E investments made on a regional or national level, and target investors who evaluate their RES-E investments according to least-cost high-profit criteria. We present empirical evidence to show that RES-E investments are made by a heterogeneous group of investors, that a variety of investors exist and that their formation varies among the different types of renewable sources. This has direct implications for our understanding of the investment process in RES-E and for the study of motives and driving forces of RES-E investors. We introduce a multi-dimensional framework for analyzing differences between categories of investors, which not only considers to the standard economic dimension which is predominant in the contemporary energy literature, but also considers the entrepreneurship, innovation-adoption and institutional dimensions. The framework emphasizes the influence of four main investor-related factors on the investment process which should be studied in future research: motives, background, resources and personal characteristics.

    Place, publisher, year, edition, pages
    Elsevier, 2013
    Keyword
    Energy policy, Renewable electricity production, Tradable Green Certificate, Investor types, Investments, RES-E
    National Category
    Economics and Business
    Identifiers
    urn:nbn:se:liu:diva-89587 (URN)10.1016/j.enpol.2013.01.038 (DOI)000317158400054 ()
    Projects
    NYEL - Nya investerare i förnybar elproduktion
    Funder
    Swedish Energy Agency
    Note

    Highlights

    ► The RES-E investor group is heterogeneous. ► Investors with no traditional background within electricity production make the majority of RES-E investments in Sweden. ► Different types of RES-E investors invest in different renewables. ► A standard economic perspective is not sufficient to understand emerging RES-E investors. ► Motives, background, resources and personal characteristics of RES-E investors matter.

    Available from: 2013-02-27 Created: 2013-02-27 Last updated: 2016-09-06Bibliographically approved
    2. Investments in renewable electricity production: The importance of policy revisited
    Open this publication in new window or tab >>Investments in renewable electricity production: The importance of policy revisited
    2016 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 88, 307-316 p.Article in journal (Refereed) Published
    Abstract [en]

    Finding ways to encourage investments in renewable electricity production is crucial to reach a transition to a sustainable energy system. While in the energy policy literature, investments are usually explained by economic or regulatory policies, recent studies have suggested that some investors are boundedly rational and may respond differently to policies. In this paper, a framework is proposed to make a more complete analysis of the institutional demands influencing emerging investors in renewable electricity production. Based on 35 cases, both formal and informal demands were identified and their impact on emerging investors behavior was analyzed. Results show that besides formal institutional demands, emerging investors were influenced by their task environment and by various informal demands which originated in investors collective and internal contexts. However, different investors were affected by different institutional demands. They also responded in different ways to the same demands; while some perceived a specific demand as imposing, others regarded it as inducing. These findings provide a better understanding of the institutional forces affecting emerging investors in renewable electricity. The paper suggests new policies to handle the heterogeneity of investors and opens up for a new panorama of informal policy channels, where network effects can be utilized to trigger emerging investors decisions. (C) 2015 Elsevier Ltd. All rights reserved.

    Place, publisher, year, edition, pages
    PERGAMON-ELSEVIER SCIENCE LTD, 2016
    Keyword
    Renewable electricity production; Policies; Institutional demands; Investments; Heterogeneity; Sweden
    National Category
    Economics and Business
    Identifiers
    urn:nbn:se:liu:diva-125141 (URN)10.1016/j.renene.2015.11.045 (DOI)000368563900029 ()
    Note

    Funding Agencies|Swedish Energy Agencys AES programme [33685-1]

    Available from: 2016-02-15 Created: 2016-02-15 Last updated: 2016-09-06
    3. System- and actor-level challenges for diffusion of renewable electricity technologies: an international comparison
    Open this publication in new window or tab >>System- and actor-level challenges for diffusion of renewable electricity technologies: an international comparison
    2016 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 128, no SI, 105-115 p.Article in journal (Refereed) Published
    Abstract [en]

    Abstract It has become increasingly clear that a transition to low-carbon energy systems, including a widespread diffusion of renewable energy technologies (RETs), is necessary for the world to handle the challenges of climate change. Previous innovation system oriented research has identified barriers to development and early-stage diffusion of RETs, but more research is needed to understand what kind of institutional frameworks and governance tools are needed to achieve effective large-scale diffusion at a stage when technologies are commercially available and new demand-side actors become involved. The purpose of this paper is, therefore, to identify the main challenges faced by adopters of renewable electricity technologies under different institutional frameworks as well as their strategies for overcoming them. Results based on a qualitative multiple case study of 28 adopters in France and in Sweden show that adopters were faced with system-level challenges, such as market-structure obstacles and lack of institutional routines, as well as actor-level challenges, such as lack of resources or behavioral characteristics. The study also highlights the difference between blocking and restraining challenges and proposes that barriers are better thought of as challenges that can be overcome. It shows the importance for policy makers to consider not only system-level diffusion challenges, but also to understand actor-level contexts, including the behaviors of adopters who contribute to the transition. A further understanding how new entrants have managed to overcome existing challenges may provide new policy tools to facilitate the adoption for new adopters, for instance by encouraging the use of networks or by supplying specific information to potential adopters who lack it.

    Place, publisher, year, edition, pages
    Elsevier, 2016
    Keyword
    Diffusion, Challenges, Renewable energy technology, System-level, Actor-level, Policy
    National Category
    Environmental Management Production Engineering, Human Work Science and Ergonomics Environmental Biotechnology Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-128256 (URN)10.1016/j.jclepro.2015.09.048 (DOI)000378568800009 ()
    Note

    Funding agencies.The funding support of the Swedish Energy Agency (Grant 33685-1 Project New investors in renewable electricity production) is gratefully acknowledged.

    Available from: 2016-05-24 Created: 2016-05-24 Last updated: 2016-09-06Bibliographically approved
    4. The impact of systemic factors on the deployment of cooperative projects within renewable electricity production - An international comparison
    Open this publication in new window or tab >>The impact of systemic factors on the deployment of cooperative projects within renewable electricity production - An international comparison
    2016 (English)In: Renewable and sustainable energy reviews, ISSN 1364-0321, Vol. 65, 478-488 p.Article in journal (Refereed) Published
    Abstract [en]

    While cooperative organizations created with the aim to initiate, develop, and operate renewable electricity (RE) projects have received attention for their roles in the transition to a sustainable energy system, the disparities in the number of RE cooperative projects among countries suggest that institutional contexts may have an impact on their deployment. In order to systematically identify the systemic factors that impact their deployment, we use an established framework, considering the strengths and weaknesses in market structure, infrastructures, institutions, interactions, and capabilities. We compare the deployment context in Germany, France, and Sweden in order to understand which systemic factors have an impact and how they affect RE cooperative projects. Based on a review of the literature and qualitative interviews with experts in RE cooperatives, it appears that, although RE cooperative projects share some obstacles with most new entrants of RE, they are particularly exposed to a lack of financial insfrastructure, a lack of knowledge and interactions, and problems related to a lack of regulatory frameworks facilitating their deployment. Results also show that systemic factors are complementary and dependent on each other; lowering one barrier lowers other barriers, and some obstacles strengthen other obstacles. Drawing on the comparison among Germany, France, and Sweden, we highlight some interesting practices that could be used in the coordination and alignment of systemic conditions for the deployment of RE cooperative projects.

    Keyword
    Systemic obstacles; Renewable electricity; Energy transition; RE cooperatives; Energy policy; Europe
    National Category
    Environmental Management Production Engineering, Human Work Science and Ergonomics Business Administration Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-131014 (URN)10.1016/j.rser.2016.07.026 (DOI)
    Funder
    Swedish Energy Agency, 40642-1
    Available from: 2016-09-05 Created: 2016-09-05 Last updated: 2016-09-06Bibliographically approved
    5. Intermediary-user collaboration during the innovation implementation process
    Open this publication in new window or tab >>Intermediary-user collaboration during the innovation implementation process
    2016 (English)In: Technology Analysis & Strategic Management, ISSN 0953-7325, E-ISSN 1465-3990Article in journal (Refereed) Accepted
    Abstract [en]

    The innovation process is characterized by obstacles faced both by innovation suppliers during development and by users during implementation. Although the literature has underscored the importance of collaboration, how this process occurs during implementation remains understudied. In this study, a cross-case analysis of implementation processes showed that intermediary-user collaborations are characterized by different ways of matching users' demands with intermediaries' services, different formal and informal governance mechanisms, and different implementation outcomes. We propose that these characteristics are due to the specificities of implementation and to the particularities of the intermediary-user relationship. Additionally, there are particularities of the intermediary-user collaborations that both facilitate implementation and create risks for its outcomes. We suggest that the link between the implementation outcome and the collaboration process affects user satisfaction, further investments in the technology, and learning. We conclude by drawing implications of the particularities of intermediary-user collaboration and implementation for theory, managers and further research.

    Keyword
    Collaboration, intermediaries, users, implementation; innovation
    National Category
    Social Sciences Interdisciplinary Economics and Business Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-131016 (URN)10.1080/09537325.2016.1231299 (DOI)
    Funder
    Swedish Energy Agency, 40642-1
    Available from: 2016-09-05 Created: 2016-09-05 Last updated: 2016-09-06
    6. Motives to adopt renewable energy technologies: evidence from Sweden
    Open this publication in new window or tab >>Motives to adopt renewable energy technologies: evidence from Sweden
    2016 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    The diffusion of renewable energy technologies (RETs) has to speed up for countries to reach their, often ambitious, targets for renewable energy generation. This requires a large number of actors to adopt RETs. Policies will most likely be needed to induce adoption, but there is limited knowledge about what motivates RET adoption. The purpose of this paper is to complement and expand the available evidence regarding motives to adopt RETs through a survey to over 600 non-traditional RET adopters in Sweden. The main finding of the study is that although environmental concerns, technology interest, access to a base resource and prospects to make money are important motives in general, RET adopters is a heterogeneous group with regard to motives: there are many different motives to adopt RETs, adopters differ in how large importance they attach to the same motive and each adopter can have several different motives to adopt. There are also differences in motives between RETs (especially wind power vs. solar power) and between adopter categories (especially IPPs vs. individuals and diversified companies). This implies that a variety of policy instruments might be needed to induce further adoption of a variety of RETs by a variety of adopter categories.

    Keyword
    Renewable energy, motive, adoption, diffusion, investment
    National Category
    Business Administration Energy Engineering Energy Systems Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-131034 (URN)
    Available from: 2016-09-06 Created: 2016-09-06 Last updated: 2016-09-06Bibliographically approved
  • Public defence: 2016-10-14 09:15 Planck, Fysikhuset, Linköping
    Tengdelius, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Tengdelius, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Fucoidan-Mimetic Glycopolymers: Synthesis and Biomedical Applications2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The marine polysaccharide fucoidan has demonstrated several interesting biological properties, for instance being antiviral, anticoagulant, anti-inflammatory, anticancer, and platelet activating. Many of these properties are desirable for various biomedical applications. Yet, there are few reports on fucoidan being used in such applications. The reasons for this are primarily the heterogeneity and low structural reproducibility of fucoidan.

    This thesis describes the synthesis of polymers with pendant saccharides bearing the key structural features of fucoidan. These glycopolymers were synthesized via different radical polymerization techniques yielding polymers of different chain lengths and dispersity. These glycopolymers showed antiviral and platelet activating properties similar to those of natural fucoidan, thus making them fucoidan-mimetic glycopolymers. However, compared to fucoidan from natural sources, the fucoidan-mimetic glycopolymers had homogeneous and reproducible structures making them suitable for biomedical applications.

    Further studies demonstrated that platelet activation, caused by these glycopolymers, showed dose-response curves almost identical to fucoidan. The platelet activation was induced via intracellular signaling and caused platelet surface changes similar to those of fucoidan. Fucoidan-mimetic glycopolymers can therefore be used as unique biomolecular tools for studying the molecular and cellular responses of human platelets.

    Fucoidan-mimetic glycopolymers generally assert their antiviral activity by blocking viral entry to host cells, thus inhibiting spreading of the viral infection but not acting virucidal, i.e. not killing the viruses. Introduction of hydrophobic groups to the polymer’s chain ends improved the antiviral properties significantly and is an important step towards yielding glycopolymers with virucidal properties.

    The fucoidan-mimetic glycopolymers were also applied as capping agents when synthesizing gold nanoparticles. These fucoidan-mimetic glycopolymer coated gold nanoparticles showed improved colloidal stability compared to uncapped gold nanoparticles. Furthermore, the nanoparticles also demonstrated selective cytotoxicity against a human colon cancer cell line over fibroblast cells.

    List of papers
    1. Synthesis and biological evaluation of fucoidan-mimetic glycopolymers through cyanoxyl-mediated free-radical polymerization
    Open this publication in new window or tab >>Synthesis and biological evaluation of fucoidan-mimetic glycopolymers through cyanoxyl-mediated free-radical polymerization
    Show others...
    2014 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 7, 2359-2368 p.Article in journal (Refereed) Published
    Abstract [en]

    The sulfated marine polysaccharide fucoidan has been reported to have health benefits ranging from antivirus and anticancer properties to modulation of high blood pressure. Hence, they could enhance the biological function of materials for biomedical applications. However, the incorporation of fucoidan into biomaterials has been difficult, possibly due to its complex structure and lack of suitable functional groups for covalent anchoring to biomaterials. We have developed an approach for a rapid synthesis of fucoidanmimetic glycopolymer chains through cyanoxyl-mediated free-radical polymerization, a method suitable for chain-end functionalizing and subsequent linkage to biomaterials. The resulting sulfated and nonsulfated methacrylamido alpha-L-fucoside glycopolymers fucoidan-mimetic properties were studied in HSV-1 infection and platelet activation assays. The sulfated glycopolymer showed similar properties to natural fucoidan in inducing platelet activation and inhibiting HSV-1 binding and entry to cells, thus indicating successful syntheses of fucoidan-mimetic glycopolymers.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2014
    National Category
    Chemical Sciences Clinical Medicine Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-109382 (URN)10.1021/bm5002312 (DOI)000339090500003 ()24813544 (PubMedID)
    Available from: 2014-08-15 Created: 2014-08-15 Last updated: 2016-09-08Bibliographically approved
    2. Synthesis and anticancer properties of fucoidan-mimetic glycopolymer coated gold nanoparticles
    Open this publication in new window or tab >>Synthesis and anticancer properties of fucoidan-mimetic glycopolymer coated gold nanoparticles
    Show others...
    2015 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 40, 8532-8535 p.Article in journal (Refereed) Published
    Abstract [en]

    Gold nanoparticles coated with fucoidan-mimetic glycopolymers were synthesized that displayed good colloidal stability and promising anti-cancer properties. Fucoidan mimetic glycopolymers on their own were nontoxic, while glycopolymer coated gold nanoparticles displayed selective cytotoxicity to human colon cancer cell lines (HCT116) while it was non-toxic to mouse fibroblast cells (NIH3T3).

    Place, publisher, year, edition, pages
    ROYAL SOC CHEMISTRY, 2015
    National Category
    Chemical Sciences Clinical Medicine
    Identifiers
    urn:nbn:se:liu:diva-119269 (URN)10.1039/c5cc02387d (DOI)000354043200034 ()25892661 (PubMedID)
    Note

    Funding Agencies|Swedish Strategic Research StemTherapy

    Available from: 2015-06-12 Created: 2015-06-12 Last updated: 2016-09-08
  • Public defence: 2016-10-14 13:15 K1, Kåkenhus, Norrköping
    Ekström, Veronica
    Linköping University, Department of Social and Welfare Studies, Social Work. Linköping University, Faculty of Arts and Sciences.
    Ekström, Veronica
    Linköping University, Department of Social and Welfare Studies, Social Work. Linköping University, Faculty of Arts and Sciences.
    Det besvärliga våldet: Socialtjänstens stöd till kvinnor som utsatts för våld i nära relationer2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis analyses how the needs of abused women are interpreted, renegotiated and adapted for handling within the social services. The overarching research questions concern support and needs, the significance of the social services organisation, and the role of social workers’ own discretion. The material consists of qualitative analyses of government bills, and interviews with social workers as well as with female victims of domestic violence. The theoretical framework includes Fraser's (1989) perspective on society's interpretations of people/groups in need of support, neo-institutional theory and the theory of street level bureaucracy. The thesis shows that social workers’ interpretations are central for how abused women's needs and their right to support will be understood. An important result is the wide variation in the kinds of support offered, deriving from the fact that there appears to be no uniform approach across the municipal social services; social workers in the different offices set up different requirements/thresholds for women to receive support. No answers are given in quantitative terms of how this diversity is distributed, but examples are presented to illustrate the range manifested. In  municipalities where specialisation means that the social workers primarily investigate needs and make formal decisions about measures to be taken, there must also be adequate interventions in place to decide upon and distribute. The thesis shows that both mutual knowledge and mutual understanding of social problems are central for the cooperation within in the specialised social services and ultimately for what kind of support people will be offered.

    List of papers
    1. Inte bara kvinna. Våldsutsatta kvinnor och deras behov av stöd - konstruktioner och komplikationer i svenskt offentligt tryck
    Open this publication in new window or tab >>Inte bara kvinna. Våldsutsatta kvinnor och deras behov av stöd - konstruktioner och komplikationer i svenskt offentligt tryck
    2012 (Swedish)In: Retfærd. Nordisk Juridisk Tidsskrift, ISSN 0105-1121, Vol. 35, no 3, 51-68 p.Article in journal (Refereed) Published
    Abstract [sv]

    Med startpunkt i Kvinnofridspropositionen från 1997 undersöks i den här artikeln sex statliga propositioner utifrån ett intersektionellt perspektiv. I artikeln diskuteras hur mäns våld mot kvinnor i nära relationer framställs som problem, hur de våldsutsatta kvinnorna framställs och konstrueras samt hur dessa framställningar förhåller sig till lagstiftarens motiveringar till lagstadgat stöd till dessa kvinnor. Analysen fokuseras kring hur kategorier som klass, kön och etnicitet synliggörs i det studerade materialet och hur detta kan förstås i relation till det lagstiftade stöd som formuleras för kvinnorna. I artikeln framkommer att de våldsutsatta kvinnorna framförallt beskrivs som kvinnor. I en del av texterna lyfts grupper av kvinnor (utländska, äldre, missbrukande t ex) upp som särskilt stödbehövande. Det handlar dock inte om en förståelse av hur olika maktstrukturer påverkar kvinnornas utsatthet för våld och deras skilda erfarenheter av konsekvenserna av våldet. Framställningen av den våldsutsatta kvinnan som å ena sidan ”vem som helst” och å andra sidan ”den andra” bidrar sannolikt till att det stöd som formuleras riskerar att inte möta de reella behov av stöd som våldsutsatta kvinnor har.

    Place, publisher, year, edition, pages
    DJØF forlag, 2012
    Keyword
    Socialtjänstlagen, kvinnomisshandel, mäns våld mot kvinnor, våld i nära relationer, stöd, insatser, socialt arbete, intersektionalitet
    National Category
    Social Work
    Identifiers
    urn:nbn:se:liu:diva-88377 (URN)
    Available from: 2013-03-13 Created: 2013-02-04 Last updated: 2016-08-31Bibliographically approved
    2. Carriers of the Troublesome Violence: The Social Services’ Support for Female Victims of Domestic Violence.
    Open this publication in new window or tab >>Carriers of the Troublesome Violence: The Social Services’ Support for Female Victims of Domestic Violence.
    (English)In: European Journal of Social Work, ISSN 1369-1457, E-ISSN 1468-2664Article in journal (Refereed) Accepted
    Abstract [en]

    In Sweden, the social services’ responsibility for abused women has been reinforced and clarified on several occasions since the 1990s. At the same time, the knowledge of their work is undeveloped. This article analyses the social services’ support for female victims of domestic violence with a focus on organisation, based on the concepts of specialisation and specialists. The study consists of qualitative interviews with 16 social workers in eleven municipalities. The study shows great organisational variation between the municipalities, although most have some sort of specialised units or person-bound specialisation. Colleagues, training and  external supervision are factors the social workers emphasise as important in working with female victims of violence, a social problem described as both special and difficult. The different forms of organisation and specialisation influence the support the social services offer abused women.

    Place, publisher, year, edition, pages
    Routledge
    Keyword
    IPV, domestic violence, social services, crime victims, specialisation
    National Category
    Social Work
    Identifiers
    urn:nbn:se:liu:diva-128994 (URN)
    Available from: 2016-06-08 Created: 2016-06-08 Last updated: 2016-08-31Bibliographically approved
    3. Negotiating and Justifying Social Services’ Support for Female Victims of Domestic Violence
    Open this publication in new window or tab >>Negotiating and Justifying Social Services’ Support for Female Victims of Domestic Violence
    2016 (English)In: Nordic Social Work Research, ISSN 2156-857X, E-ISSN 2156-8588Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    The social services in Sweden have become key actors in the field of support for female victims of domestic violence. However, knowledge about what kind of support the social services offer is underdeveloped. The aim of this article is to examine social workers’ perceptions of the needs they meet among female victims of domestic violence, what kind of support they offer to meet these needs, and how they use their discretion to negotiate and justify their work. The article builds on a qualitative analysis of interviews with social workers. The analysis shows that the social workers have a great deal of discretion, as a result of framework legislation and a high status among local politicians and managers. However, both specialization and a lack of available services limit their discretion. What an abused woman is offered or is entitled to is negotiated and justified depending on, for example, which services are available, whether the woman is considered to have own resources (not only financial but also emotional and practical), and if the social worker is available. Three main strategies for reducing workload are identified: increasing demands for authority decisions, transferring responsibility to others, and placing requirements on the abused women’s actions and attitudes.

    Place, publisher, year, edition, pages
    Routledge, 2016
    Keyword
    social services, domestic violence, IPV, discretion, street-level bureaucrats
    National Category
    Social Work
    Identifiers
    urn:nbn:se:liu:diva-128995 (URN)10.1080/2156857X.2016.1203813 (DOI)
    Available from: 2016-06-08 Created: 2016-06-08 Last updated: 2016-08-31Bibliographically approved
    4. Violence against women - social services support during legal proceedings: [Kvinnor utsatta för våld i nära relationer—socialtjänstens stöd under rättsprocessen]
    Open this publication in new window or tab >>Violence against women - social services support during legal proceedings: [Kvinnor utsatta för våld i nära relationer—socialtjänstens stöd under rättsprocessen]
    2015 (English)In: European Journal of Social Work, ISSN 1369-1457, E-ISSN 1468-2664, Vol. 18, no 5, 661-674 p.Article in journal (Refereed) Published
    Abstract [en]

    Social workers and social work have been criticized for failing to address violence against women in adequate ways, of blaming the victim and failing to recognize domestic violence as a problem. At the same time, it is the social services that are responsible for support to abused women, according to amendments in the Social Services Act (2001). This article examines abused women’s own experiences of support in connection with the police investigation of domestic violence. It is a qualitative study with six women who all have received support from the Relationship Violence Center (RVC) in Stockholm. The main findings in the article suggest that support in connection with the judicial process is important. Women’s earlier experiences or preconceptions of the social services might prevent them from accepting support or turning to the social services for help.

     

    Abstract [sv]

    Socialarbetare och socialt arbete har blivit kritiserade för att misslyckas med att ge stöd till våldsutsatta kvinnor på ett adekvat sätt, för att lägga skulden på kvinnan och för att inte se våld mot kvinnor i nära relationer som ett problem. Samtidigt är det socialtjänsten som är ansvarig för att ge stöd till misshandlade kvinnor enligt tilläggen i socialtjänstlagen (2001). I den här artikeln undersöks våldsutsatta kvinnors egna erfarenheter av stöd i samband med polisutredningar om våld i nära relationer. Studien är kvalitativ och baseras på intervjuer med sex kvinnor som har fått stöd från Relationsvåldscentrum (RVC). De huvudsakliga resultaten i artikeln visar att stöd i samband med rättsprocessen är viktigt. Kvinnors tidigare erfarenheter eller uppfattningar om socialtjänsten kan hindra dem från att ta hjälp från eller vända sig till socialtjänsten för stöd.

    Place, publisher, year, edition, pages
    London: Routledge, 2015
    Keyword
    men´s violence against women; abused women; battered women; domestic violence; support
    National Category
    Social Work
    Identifiers
    urn:nbn:se:liu:diva-110765 (URN)10.1080/13691457.2014.951600 (DOI)000369907600003 ()
    Available from: 2014-09-22 Created: 2014-09-22 Last updated: 2016-08-31Bibliographically approved
  • Public defence: 2016-10-18 10:15 TP2, Täppan, Norrköping
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    He, Qing
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    A Comprehensive Analysis of Optimal Link Scheduling for Emptying a Wireless Network2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless communications have become an important part of modern life. The ubiquitous wireless networks and connectivities generate exponentially increasing data traffic. In view of this, wireless network optimization, which aims at utilizing the limited resource, especially spectrum and energy, as efficiently as possible from a network perspective, is essential for performance improvement and sustainable development of wireless communications.

    In the dissertation, we focus on a fundamental problem of wireless network optimization, link scheduling, as well as its subproblem, link activation. The problem type arises because of the nature of wireless media and hence it is of relevance to a wide range of networks with multiple access. We freshen these classic problems up by novel extensions incorporating new technologies of interference management or with new performance metrics. We also revisit the problems in their classic setup to gain new theoretical results and insights for problem-solving. Throughout the study, we consider the problems with a general setup, such that the insights presented in this dissertation are not constrained to a specific technology or network type. Since link activation and scheduling are key elements of access coordination in wireless communications, the study opens up new approaches that significantly improve network performance, and eventually benefit practical applications.

    The dissertation consists of five research papers. The first paper addresses maximum link activation with cooperative transmission and interference cancellation. Papers II and III investigate the minimum-time link scheduling problem in general and a particular class of networks, respectively. In Paper IV, we consider the scheduling problem of emptying a network in its broad form and provide a general optimality condition. In Paper V, we study the scheduling problem with respect to age of information.

    List of papers
    1. Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    Open this publication in new window or tab >>Maximum Link Activation with Cooperative Transmission and Interference Cancellation in Wireless Networks
    2016 (English)In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, 1-1 p.Article in journal (Other academic) Published
    Abstract [en]

    We address the maximum link activation problem in wireless networks with new features, namely when the transmitters can perform cooperative transmission, and the receivers are able to perform successive interference cancellation. In this new problem setting, which transmitters should transmit and to whom, as well as the optimal cancellation patterns at the receivers, are strongly intertwined. We present contributions along three lines. First, we provide a thorough tractability analysis, proving the NP-hardness as well as identifying tractable cases. Second, for benchmarking purposes, we deploy integer linear programming for achieving global optimum using off-theshelf optimization methods. Third, to overcome the scalability issue of integer programming, we design a sub-optimal but efficient optimization algorithm for the problem in its general form, by embedding maximum-weighted bipartite matching into local search. Numerical results are presented for performance evaluation, to validate the benefit of cooperative transmission and interference cancellation for maximum link activation and to demonstrate the effectiveness of the proposed algorithm.

    Place, publisher, year, edition, pages
    IEEE, 2016
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112447 (URN)10.1109/TMC.2016.2546906 (DOI)
    Conference
    2014 IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), September 2-5, Washington DC, DC, USA
    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2016-09-19Bibliographically approved
    2. Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    Open this publication in new window or tab >>Minimum-Time Link Scheduling for Emptying Wireless Systems: Solution Characterization and Algorithmic Framework
    2014 (English)In: IEEE Transactions on Information Theory, ISSN 0018-9448, Vol. 60, no 2, 1083-1100 p.Article in journal (Refereed) Published
    Abstract [en]

    We consider a set of transmitter-receiver pairs, or links, that share a wireless medium and address the problem of emptying backlogged queues with given initial size at the transmitters in minimum time. The problem amounts to determining activation subsets of links, and their time durations, to form a minimum-time schedule. Scheduling in wireless networks has been studied under various formulations before. In this paper, we present fundamental insights and solution characterizations that include: 1) showing that the complexity of the problem remains high for any continuous and increasing rate function; 2) formulating and proving sufficient and necessary optimality conditions of two baseline scheduling strategies that correspond to emptying the queues using one-at-a-time or all-at-once strategies; and 3) presenting and proving the tractability of the special case in which the transmission rates are functions only of the cardinality of the link activation sets. These results are independent of physical-layer system specifications and are valid for any form of rate function. We then develop an algorithmic framework for the solution to this problem. The framework encompasses exact as well as sub-optimal, but fast, scheduling algorithms, all under a unified principle design. Through computational experiments, we finally investigate the performance of several specific algorithms from this framework.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2014
    Keyword
    Algorithm; optimality; scheduling; wireless networks
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-104836 (URN)10.1109/TIT.2013.2292065 (DOI)000330286100022 ()
    Available from: 2014-02-28 Created: 2014-02-28 Last updated: 2016-09-15
    3. Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    Open this publication in new window or tab >>Polynomial Complexity Minimum-Time Scheduling in a Class of Wireless Networks
    2015 (English)In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870 (Print), 2325-5870 (online), Vol. 3, no 3, 322-331 p.Article in journal (Other academic) Epub ahead of print
    Abstract [en]

    We consider a wireless network with a set of transmitter-receiver pairs, or links, that share a common channel, and address the problem of emptying finite traffic volume from the transmitters in minimum time. This, so called, minimum-time scheduling problem has been proved to be NP-hard in general. In this paper, we study a class of minimum-time scheduling problems in which the link rates have a particular structure. We show that global optimality can be reached in polynomial time and derive optimality conditions. Then we consider a more general case in which we apply the same approach and obtain an approximation as well as lower and upper bounds to the optimal solution. Simulation results confirm and validate our approach.

    Place, publisher, year, edition, pages
    Institute of Electrical and Electronics Engineers (IEEE), 2015
    Keyword
    algorithm, interference, optimality, scheduling, wireless networks
    National Category
    Communication Systems Telecommunications
    Identifiers
    urn:nbn:se:liu:diva-112446 (URN)10.1109/TCNS.2015.2512678 (DOI)
    Note

    At the time for thesis presentation publication was in status: Manuscript

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2016-09-16Bibliographically approved
    4. A general optimality condition of link scheduling for emptying a wireless network
    Open this publication in new window or tab >>A general optimality condition of link scheduling for emptying a wireless network
    2016 (English)Conference paper (Refereed)
    Abstract [en]

    We consider link scheduling in wireless networks for emptying the queues of the source nodes, and provide a unified mathematical formulation that accommodates all meaningful settings of link transmission rates and network configurations. We prove that, any scheduling problem is equivalent to solving a convex problem defined over the convex hull of the rate region. Based on the fundamental insight, a general optimality condition is derived, that yields a unified treatment of optimal scheduling. Furthermore, we demonstrate the implications and usefulness of the result. Specifically, by applying the theoretical insight to optimality characterization and complexity analysis of scheduling problems, we can both unify and extend previously obtained results.

    Place, publisher, year, edition, pages
    IEEE, 2016
    Series
    , IEEE International Symposium on Information Theory. Proceedings, ISSN 2157-8095 (Print), 2157-8117 (online) ; 2016
    Keyword
    convex programming;radio links;radio networks;telecommunication scheduling;convex hull;convex problem;general optimality condition;link scheduling;link transmission rates;network configurations;optimal scheduling;source nodes;wireless network;Complexity theory;Information theory;Interference;Optimal scheduling;Processor scheduling;Scheduling;Wireless networks;complexity;optimality;scheduling;wireless networks
    National Category
    Computer Engineering Information Systems Software Engineering
    Identifiers
    urn:nbn:se:liu:diva-131357 (URN)10.1109/ISIT.2016.7541538 (DOI)
    Conference
    IEEE International Symposium on Information Theory (ISIT), 2016, Universitat Pompeu Fabra, Barcelona, Spain, July l0-l5, 2016
    Available from: 2016-09-15 Created: 2016-09-15 Last updated: 2016-09-15Bibliographically approved
  • Public defence: 2016-10-21 10:15 ACAS, A-Huset, Linköping
    Fenton, Paul
    Linköping University, Department of Management and Engineering, Environmental Technology and Management. Linköping University, Faculty of Science & Engineering.
    Fenton, Paul
    Linköping University, Department of Management and Engineering, Environmental Technology and Management. Linköping University, Faculty of Science & Engineering.
    Sustainability · Strategy · Space – exploring influences on governing for urban sustainability in municipalities2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The pursuit of urban sustainability is considered central to sustainable development and is a key objective of the global Sustainable Development Goals (2015) and the New Urban Agenda (2016). This thesis aims to contribute to debates on urban sustainability by providing insights as to the role of actors participating in processes of governing for urban sustainability, with particular focus on the municipal organisation.

    The thesis employs an interdisciplinary approach to illustrate divergent approaches to governing for urban sustainability, with reference to empirical studies of strategic planning processes in municipalities in selected North-western European countries – Sweden, Switzerland and The Netherlands.

    These studies address themes including climate change, sustainable transport and multi-level governance. The thesis provides a broad overview of theoretical discussions related to governing, strategy and planning, the role of actors in governing for urban sustainability, and the particular importance of climate change as a challenge for urban sustainability.

    A number of research gaps are identified and addressed in two research questions, focusing on the organisation and practice of processes of governing for urban sustainability, and the factors influencing actors participating in such processes. The thesis responds to these research questions with reference to five appended papers, which illustrate different dimensions of governing for urban sustainability.

    The first paper concerns the organisation of processes to develop energy and climate strategies in Swedish municipalities, and the second paper highlights the experiences of actors participating in such processes. The third paper presents results from a survey illustrating the expectations of stakeholders active in governing transport in the city of Norrköping, Sweden.

    In the fourth paper, the development and implementation of policies aiming for sustainable transport and urban sustainability in Basel, Switzerland, are discussed. In the final paper, cooperation through transnational municipal networks is explored with reference to the World Ports Climate Declaration, an initiative of the city of Rotterdam.

    The thesis confirms the presence of five factors – capacity, mandate, resources, scope and will – that shape the “strategy space” of actors and play an important role in conditioning the form and content of processes of governing for urban sustainability. The thesis suggests that the ways in which a municipal organisation perceive and mobilise the five factors will strongly determine the extent of its sustainability strategy space.

    In sum, municipal organisations and other actors participating in processes of governing for urban sustainability need to mobilise the five factors and expand their strategy space, in order to achieve vertical and horizontal alignment of strategic objectives and facilitate implementation that delivers transformative change.

    List of papers
    1. Sustainable energy and climate strategies: lessons from planning processes in five Swedish municipalities
    Open this publication in new window or tab >>Sustainable energy and climate strategies: lessons from planning processes in five Swedish municipalities
    2015 (English)In: Journal of Cleaner Production, ISSN 0959-6526, Vol. 98, 213-221 p.Article in journal (Refereed) Published
    Abstract [en]

    Swedish municipalities have traditionally had significant powers and played a major role in implementing national energy strategies. This paper describes the factors influencing development of municipal climate and energy plans in five Swedish municipalities and assesses the relevance and importance of these factors from theoretical and practical perspectives. The questions raised in the paper are: what are the characteristics of municipal climate and energy planning processes in the five municipalities, do these municipalities include stakeholders in the process, if so how, and do the stakeholders influence the content of strategies? Results suggest that a number of factors influence the development of municipal climate and energy strategies and their content. These include the importance of a clear, shared vision and engaged politicians; the size and organisational structure of the municipality and its willingness and capability to act; the organisation of the process and extent to which stakeholders not only have been involved but also felt included; the need for clarity about financial aspects, such as planned financing of implementation; and the need for greater clarity concerning selection of targets and their relevance to global climate and energy trends. The study and its results may be used to inform policy-makers on the national and local levels about factors influencing municipal energy planning and also contribute to a discussion on benefits and problems of involving stakeholders and citizens in the strategic work to reduce climate impacts and energy consumption.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keyword
    Energy and climate strategies, municipalities, stakeholders, planning processes
    National Category
    Social Sciences
    Identifiers
    urn:nbn:se:liu:diva-104464 (URN)10.1016/j.jclepro.2014.08.001 (DOI)000356194300022 ()
    Projects
    HEKSA - Sustainable Energy and Climate Strategies
    Funder
    Swedish Energy Agency
    Available from: 2014-02-17 Created: 2014-02-17 Last updated: 2016-06-21Bibliographically approved
    2. Stakeholder participation in municipal energy and climate planning – experiences from Sweden
    Open this publication in new window or tab >>Stakeholder participation in municipal energy and climate planning – experiences from Sweden
    2016 (English)In: Local Environment: the International Journal of Justice and Sustainability, ISSN 1354-9839, E-ISSN 1469-6711, Vol. 21, no 3, 272-289 p.Article in journal (Refereed) Published
    Abstract [en]

    This article analyses the factors influencing stakeholder participation in municipal energy and climate planning, together with stakeholder experiences of participation in such processes. The article presents findings from a survey of 60 Swedish municipalities and detailed case studies of energy and climate planning in five Swedish municipalities to explore which stakeholders are involved, how and why they are involved, and the impacts of participation on both stakeholder experiences. The results of this study provide insight into the role of stakeholders in municipal energy and climate planning.The study proceeds as follows: the Introduction is followed by a discussion of theoretical perspectives on stakeholder participation and energy and climate planning. The Methods used to conduct the study are presented, followed by Results and Analysis. In the subsequent Discussion, the authors propose a conceptual approach that may assist municipalities in development of energy and climate strategies. The Analysis and Discussion inform Conclusions in which the authors advocate early and active stakeholder engagement in energy and climate strategy planning and emphasise the possible utility of their conceptual approach in supporting stakeholder participation.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2016
    Keyword
    Energy and climate strategies; municipalities; participation; stakeholders
    National Category
    Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-104465 (URN)10.1080/13549839.2014.946400 (DOI)
    Projects
    HEKSA - Sustainable Energy and Climate Strategies
    Funder
    Swedish Energy Agency
    Note

    On the day of the defence date the status of this article was Manuscript.

    Available from: 2014-02-17 Created: 2014-02-17 Last updated: 2016-06-21Bibliographically approved
    3. Contesting sustainability in urban transport — perspectives from a Swedish town
    Open this publication in new window or tab >>Contesting sustainability in urban transport — perspectives from a Swedish town
    2015 (English)In: Natural resources forum (Print), ISSN 0165-0203, E-ISSN 1477-8947, Vol. 39, no 1, 15-26 p.Article in journal (Refereed) Published
    Abstract [en]

    This paper presents findings from a document study, survey, and workshops held in a Swedish municipality. The empirical focus of the study is on the role of transport in municipal planning and transport's potential contribution to urban sustainability in the municipality. The case study highlights a problem familiar to many municipalities — a transport sector largely dependent on fossil fuel private vehicles that generates significant impacts on the climate and environment, along with other economic and social costs. However, despite awareness of these negative impacts, it is difficult to implement measures to reduce the use of private vehicles and enable a transition towards a sustainable transport sector. In Sweden, municipalities have exclusive planning monopolies and an extensive range of other powers. Despite this, many municipalities are struggling to reduce car dependency and enable sustainable mobility. This paper questions the extent to which the municipality and its governance processes are capable of contributing toward sustainable development, both locally and globally, in the absence of radical measures. In particular, the paper considers why, despite having adopted objectives to promote sustainable mobility, does the municipality struggle with the implementation of measures to enable sustainable mobility? Why is there a difference between words and actions?

    Keyword
    Municipalities; sustainable development; transport; mobility; decision-making; governance
    National Category
    Social Sciences
    Identifiers
    urn:nbn:se:liu:diva-114291 (URN)10.1111/1477-8947.12061 (DOI)000351775600003 ()
    Projects
    Hållbara Norrköping
    Available from: 2015-02-17 Created: 2015-02-17 Last updated: 2016-06-21
    4. Sustainable mobility as Swiss cheese?: – Exploring influences on urban transport strategy in Basel
    Open this publication in new window or tab >>Sustainable mobility as Swiss cheese?: – Exploring influences on urban transport strategy in Basel
    2016 (English)In: Natural resources forum (Print), ISSN 0165-0203, E-ISSN 1477-8947Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    This paper explores the development and implementation of strategies for sustainable mobility in Basel, Switzerland. Basel (Bâle, Basilea, Basle) has been identified as a ‘relatively successful’ practitioner of sustainable mobility, with an urban form that is not only conducive to walking and cycling, but also has an extensive public transport system and high levels of commuting using these sustainable modes of transport. With a low share of journeys by motor vehicles compared to many other European cities – combined with a legally-binding objective to reduce vehicle traffic by a further 10% from 2010 to 2020 – Basel appears to be a forerunner with regard to sustainable mobility policy and practice. Five years after this objective was passed into law – following a public vote, as Basel is part of the Swiss confederation and practices direct democracy – this study aims to assess the extent of policy implementation and reflect on challenges and opportunities for the future. The paper presents findings from a series of interviews with stakeholders in Basel on the theme of sustainable mobility. Key questions include: is it possible to develop coherent strategies and policies to further reduce the role of motor vehicles and in doing so, achieve a modal shift? How does participation in a direct democracy influence strategy and policy development and outcomes? Do compromises and trade-offs mean strategies and policies promoting sustainable mobility are, like Swiss cheese, riddled with holes? By illustrating challenges and opportunities when advancing sustainable mobility in a participative culture, the study provides insights for policymakers and researchers in other contexts. Among the conclusions is an emphasis on the importance of committed individuals capable of expanding the ‘strategy space’ of processes. Participation provides one such opportunity, yet may also generate divergent or contradictory trends causing incrementalism. A rapid transition to sustainable mobility is thus likely to require increased politicisation of the topic by both politicians and civil servants.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2016
    Keyword
    Sustainable mobility, governance, strategy, policy, participation, direct democracy, Canton Basel-Stadt
    National Category
    Environmental Sciences Transport Systems and Logistics
    Identifiers
    urn:nbn:se:liu:diva-129371 (URN)10.1111/1477-8947.12093 (DOI)
    Available from: 2016-06-17 Created: 2016-06-17 Last updated: 2016-06-29
    5. The role of port cities and transnational municipal networks in efforts to reduce greenhouse gas emissions on land and at sea from shipping - an assessment of the World Ports Climate Initiative
    Open this publication in new window or tab >>The role of port cities and transnational municipal networks in efforts to reduce greenhouse gas emissions on land and at sea from shipping - an assessment of the World Ports Climate Initiative
    2015 (English)In: Marine Policy, ISSN 0308-597X, E-ISSN 1872-9460Article in journal (Refereed) In press
    Abstract [en]

    In 2008, 55 of the world's largest ports voluntarily adopted the World Ports Climate Declaration (WPCD) and the International Association of Ports and Harbours committed to long-term work on implementation through the World Ports Climate Initiative (WPCI). This article assesses the work of WPCI since 2008 and makes five recommendations that, if implemented, could support efforts to reduce the climate and environmental impacts of port operations and international shipping. In particular, as the impetus for the WPCD came from a port city – Rotterdam – and their engagement with a transnational municipal network – the C40 Large Cities Climate Leadership Group – the paper considers the role of cities and transnational municipal networks in governance, and the potential for cities to play a more active and influential role in the maritime sector. The article presents an overview of literature on the role and function of transnational municipal networks, the background and development of the WPCD, analysis of the work of WPCI, and a discussion concerning the potential of cities and transnational municipal networks to support and add value to WPCI or similar initiatives in the maritime sector. This informs the conclusions and recommendations to marine policy-makers and port stakeholders.

    Keyword
    Ports; Shipping;Transnational municipal networks; Climate change; Governance
    National Category
    Social Sciences Interdisciplinary Other Social Sciences not elsewhere specified
    Identifiers
    urn:nbn:se:liu:diva-123628 (URN)10.1016/j.marpol.2015.12.012 (DOI)
    Available from: 2016-01-01 Created: 2016-01-01 Last updated: 2016-06-21Bibliographically approved
  • Public defence: 2016-10-21 10:15 Plank, Fysikhuset, Linköping
    Fashandi, Hossein
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Fashandi, Hossein
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Novel Layered and 2D Materials for Functionality Enhancement of Contacts and Gas Sensors2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Chemical gas sensors are widely-used electronic devices for detecting or measuring the density levels of desired gas species. In this study, materials with established or potential applications for gas sensors are treated. For the case of high-temperature applications (≈ 600 °C), semiconductor-based gas sensors suffer from rapid oxidation of the metallic ohmic contacts, the same cause-of-failure as for the general case of high-temperature semiconductor electronics. 4H-SiC is an ideal semiconductor for high-temperature applications. Ti3SiC2 is a known ohmic contact to 4H-SiC with the known two-step synthesis process of post-annealing of pre-deposited Ti/Al multilayers or sputter-deposition of Ti3SiC2 films at > 900 °C. Here, sputter-deposition of Ti on 4H-SiC at > 900 °C is presented as a novel single-step method for the synthesis of Ti3SiC2 ohmic contacts, based on a concurrent reaction between sputter-deposited Ti and 4HSiC. Ti3SiC2, similar to any other known ohmic contact, degrade rapidly in high-temperature oxidizing ambient. To try to overcome this obstacle, noble metal diffusion into Ti3SiC2 has been s studied with the goal to retain ohmic properties of Ti3SiC2 and harnessing oxidation resistivity of noble metals. A novel exchange intercalation between Ti3SiC2 and Au is discovered which results in the almost complete exchange of Si with Au giving rise to novel Ti3AuC2 and Ti3Au2C2. Ti3IrC2 is also synthesized through exchange intercalation of Ir into Ti3Au2C2. All the aforementioned phases showed ohmic properties to 4H-SiC. This technique is also studied based on Ti2AlC and Ti3AlC2 resulting in the synthesis of novel Ti2Au2C and Ti3Au2C2, respectively. Using Ti3AuC2 and an Au/IrOx capping layer, an ohmic contact was manufactured, which maintained ohmic properties and showed no structural defects after 1000 h of aging at 600 °C air.

    Ti3SiC2 is a member of a large family of materials known as Mn+1AXn phases. While exchange reactions of Si (or Al) planes in Ti3SiC2 (Ti2AlC and Ti3AlC2) is presented here, a world-wide research already exists on chemical removal of the same atomic planes from different Mn+1AXn phases and the synthesis of Mn+1Xn sheets known as MXenes. I performed a theoretical study regarding simulation of electronic and structural properties of more than120 different possible MXene phases. The results show that some MXene phases, when terminated by particular gas species, turn into Dirac materials. That is, they possess massless Dirac fermions with different properties compared to graphene such as higher number of Dirac points at the Fermi level, giant spin orbit splitting, and preserved 2D-type electronic properties by extending the dimensionality. The general substantial change of the electronic properties of MXenes under different gas adsorption configurations stands out and can thus be harnessed for sensing applications.

    Growth of monolayer iron oxide on porous Pt sensing layers is another novel approach used in this study for applying the unique properties of 2D materials for gas sensors. A low temperature shift in CO oxidation characteristics is presented. The approach is similar to that previously reported using bulk single crystal Pt substrate, the latter being an unrealistic model for sensors and catalysts. Monolayer-coated Pt sensing layers were fabricated as the metal component of a metal oxide semiconductor (MOS) capacitor device, whereby the electrical response of the MOS device could be used to map out the catalytic properties of the sensing layer. The monolayer-coated Pt surface showed to be stable with retained improved catalytic properties for > 200 h. The MOS device measurements are here utilized as a handy method for in-situ monitoring of the surface chemical properties of the monolayer-coated Pt and the approach is highly functional for use and characterization of monolayer coatings of widely used sensingor catalytic layers.

    List of papers
    1. Single-step synthesis process of Ti3SiC2 ohmic contacts on 4H-SiC by sputter-deposition of Ti
    Open this publication in new window or tab >>Single-step synthesis process of Ti3SiC2 ohmic contacts on 4H-SiC by sputter-deposition of Ti
    Show others...
    2015 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 99, 53-56 p.Article in journal (Refereed) Published
    Abstract [en]

    We report a single-step procedure for growth of ohmic Ti3SiC2 on 4H-SiC by sputter-deposition of Ti at 960 °C, based on the Ti–SiC solid-state reaction during deposition. X-ray diffraction and electron microscopy show the growth of interfacial Ti3SiC2. The as-deposited contacts are ohmic, in contrast to multistep processes with deposition followed by rapid thermal annealing. This procedure also offers the possibility of direct synthesis of oxygen-barrier capping layers before exposure to air, potentially improving contact stability in high-temperature and high-power devices.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keyword
    Silicon carbide, MAX phase, Physical vapor deposition, High temperature
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-113760 (URN)10.1016/j.scriptamat.2014.11.025 (DOI)000348881100014 ()
    Note

    We acknowledge the support from the VINN Excellence Center in research and innovation on Functional Nanoscale Materials (FunMat) by the Swedish Governmental Agency for Innovation Systems. P.E and J.L. also acknowledge support from the Swedish Foundation for Strategic Research through the Future Research Leaders 5 program and the Synergy Grant FUNCASE, Functional Carbides and Advanced Surface Engineering. In addition, we thank Dr. Hans Hogberg, Dr. Arni Sigurdur Ingason and Dr. Fredrik Eriksson for discussions and help with experiments.

    Available from: 2015-01-30 Created: 2015-01-30 Last updated: 2016-09-22Bibliographically approved
    2. Dirac points with giant spin-orbit splitting in the electronic structure of two-dimensional transition-metal carbides
    Open this publication in new window or tab >>Dirac points with giant spin-orbit splitting in the electronic structure of two-dimensional transition-metal carbides
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    2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 15Article in journal (Refereed) Published
    Abstract [en]

    We investigated the structural and electrical properties of 2D MXene sheets by means of firstprinciples density functional theory (DFT) calculations. To describe the Kohn-Sham states, plane wave basis set and projector augmented wave method (PAW) were used as implemented in the Vienna ab initio Simulation Package (VASP). We applied PBE parameterization of the generalized gradient approximation of the exchange and correlation energy functional to account for many-body effects of the interacting electron system. Convergent sampling of the Brillouin-zone was achieved by a Γ-centered 15×15×1 grid. In order to model a single sheet of MXene we ensured at least 30 Å vacuum between the periodically repeated sheets. For the structural optimization 1×10−3 eV/Å force criteria was used. The relativistic spin-orbit coupling effects were also included in our simulations regarding band structure and density of states.

    Keyword
    Cone-point, MAX phase, MXene, Dirac fermion, Spin-orbit coupling
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-113761 (URN)10.1103/PhysRevB.92.155142 (DOI)000363512700002 ()
    Available from: 2015-05-01 Created: 2015-01-30 Last updated: 2016-09-22Bibliographically approved
  • Public defence: 2016-10-21 13:15 Visionen, Hus B, Linköping
    Forsblad (Kristiansson), Mattias
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Arts and Sciences.
    Forsblad (Kristiansson), Mattias
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Arts and Sciences.
    Distributed cognition in home environments: The prospective memory and cognitive practices of older adults2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In this thesis I explore how older people make use of, and interact with, their physical environment in home and near-by settings to manage cognitive situations, specifically prospective memory situations. Older adults have in past research been shown to perform better on prospective memory in real-life settings than what findings in laboratory-like settings predict. An explanation for this paradox is that older adults has a more developed skill of using the environment for prospective memory than younger adults. However, research investigating this explanation has primarily been based on self-reports.

    I contribute to the understanding of this skill by doing two related things. First I introduce distributed cognition, a theoretical perspective that primarily has been used within professional and socio-technical environments, to the research field of prospective memory in everyday life. Second I present a cognitive ethnography conducted during two years across eight home, and near-by, environments and old-age retired persons, for which I have used theoretical concepts from distributed cognition to analyze observations.

    The analysis shows rich variations in how participants use common cultural cognitive tools, invent their own cognitive tools, deliberately and incidentally shape more or less functional spaces, make use of other physical features, orient themselves toward and make sense of cognitive resources. I complement both prospective memory and distributed cognition research by describing both the intelligent shaping and use of space. Furthermore, by taking a distributed cognitive perspective I show that prospective memory processes in home environments involve properties, and the management, of a multipurpose environment.

    Altogether this supports the understanding of distributed cognition as a perspective on all cognition. Distributed cognition is not a reflection of particular work practices, instead it is a formulation of the general features of human cognition. Prospective memory in everyday life can be understood as an ability persons have. However, in this thesis I show that prospective memory can also be understood as a process that takes place between persons, arrangements of space, and tools.

  • Public defence: 2016-10-27 09:00 Berzeliussalen, Linköping
    Rohini Rajan, Meenu
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Rohini Rajan, Meenu
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Unraveling Mechanisms of Insulin Resistance in Type 2 Diabetes in Human Aidpocytes: Role of extracelluar signal kinase 1/2 (ERK1/2) and farkhead box protein 01 (FOX01)2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Type 2 Diabetes is characterized by hyperglycemia primarily caused due to insulin resistance in insulin responsive tissues and insufficient production of insulin by the β-cells. Insulin resistance appears to develop first in the expanding adipose tissue during caloric surplus and affects other tissues like liver and muscle by ectopic fat accumulation. In spite of significant research in field of insulin signaling, very little has been known about the mechanisms that lead to insulin resistance and T2D.

    We aim for network-wide knowledge of insulin signaling in human adipocytes and to identify mechanisms that can induce insulin resistance in diabetic individuals. We have herein focused on the transcriptional control of insulin via ERK and FOXO1, and have used mathematical modelling to gain a systems-level understanding of insulin signaling network.

    Through the work in this thesis, we present for the first time a dynamic comprehensive model for insulin signaling for the adipocytes, for both metabolic and transcriptional control, and that can simulate data from both normal and diabetic individuals. We described insulin regulation of ERK phosphorylation and showed that both its insulin sensitivity and maxima  response to insulin was curtailed in adipocytes from diabetic individuals (Paper I). Our findings indicate that insulin regulated ERK pathway exerts control on transcription not only through phosphorylation of Elk-1 but also through phosphorylation of FOXO1 and exerts translational control via phosphorylation of ribosomal protein S6 (Paper I, II). Furthermore, we showed that insulin-induced FOXO1 phosphorylation or its insulin sensitivity was not impaired in diabetic individuals, although FOXO1 protein level was reduced by 45% in adipocytes from patients with type 2 diabetes. Comprehensive analysis of the detailed insulin signaling model showed that attenuation of the feedback from mTORC1 to IRS1-Ser307 explained dominant part of the insulin resistance seen in adipocytes from diabetic individuals (Paper II). More interestingly, inhibition of FOXO1 with a dominant negative construct of FOXO1, mimicked the diabetic state in the adipocytes, with the similarity extending to both insulin signaling as well as the reduced protein levels, as seen in the diabetic adipocytes. We also show that mTORC1 and FOXO1 maintain each other’s expression/activity in the human adipocytes (Paper II, III). Our findings thus demonstrate that the interplay between mTORC1 and FOXO1 maintains normal insulin signaling in the human adipocytes.

    List of papers
    1. A Single Mechanism Can Explain Network-wide Insulin Resistance in Adipocytes from Obese Patients with Type 2 Diabetes
    Open this publication in new window or tab >>A Single Mechanism Can Explain Network-wide Insulin Resistance in Adipocytes from Obese Patients with Type 2 Diabetes
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    2014 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 289, no 48, 33215-33230 p.Article in journal (Refereed) Published
    Abstract [en]

    The response to insulin is impaired in type 2 diabetes. Much information is available about insulin signaling, but understanding of the cellular mechanisms causing impaired signaling and insulin resistance is hampered by fragmented data, mainly obtained from different cell lines and animals. We have collected quantitative and systems-wide dynamic data on insulin signaling in primary adipocytes and compared cells isolated from healthy and diabetic individuals. Mathematical modeling and experimental verification identified mechanisms of insulin control of the MAPKs ERK1/2. We found that in human adipocytes, insulin stimulates phosphorylation of the ribosomal protein S6 and hence protein synthesis about equally via ERK1/2 and mTORC1. Using mathematical modeling, we examined the signaling network as a whole and show that a single mechanism can explain the insulin resistance of type 2 diabetes throughout the network, involving signaling both through IRS1, PKB, and mTOR and via ERK1/2 to the nuclear transcription factor Elk1. The most important part of the insulin resistance mechanism is an attenuated feedback from the protein kinase mTORC1 to IRS1, which spreads signal attenuation to all parts of the insulin signaling network. Experimental inhibition of mTORC1 using rapamycin in adipocytes from non-diabetic individuals induced and thus confirmed the predicted network-wide insulin resistance.

    Place, publisher, year, edition, pages
    American Society for Biochemistry and Molecular Biology, 2014
    National Category
    Clinical Medicine
    Identifiers
    urn:nbn:se:liu:diva-113198 (URN)10.1074/jbc.M114.608927 (DOI)000345636600015 ()25320095 (PubMedID)
    Note

    Funding Agencies|Swedish Diabetes Fund; University of Linkoping; Swedish Research Council

    Available from: 2015-01-13 Created: 2015-01-12 Last updated: 2016-09-19
    2. Systems-wide Experimental and Modeling Analysis of Insulin Signaling through Forkhead Box Protein O1 (FOXO1) in Human Adipocytes, Normally and in Type 2 Diabetes
    Open this publication in new window or tab >>Systems-wide Experimental and Modeling Analysis of Insulin Signaling through Forkhead Box Protein O1 (FOXO1) in Human Adipocytes, Normally and in Type 2 Diabetes
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    2016 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 291, no 30, 15806-15819 p.Article in journal (Refereed) Published
    Abstract [en]

    Insulin resistance is a major aspect of type 2 diabetes (T2D), which results from impaired insulin signaling in target cells. Signaling to regulate forkhead box protein O1 (FOXO1) may be the most important mechanism for insulin to control transcription. Despite this, little is known about how insulin regulates FOXO1 and how FOXO1 may contribute to insulin resistance in adipocytes, which are the most critical cell type in the development of insulin resistance. We report a detailed mechanistic analysis of insulin control of FOXO1 in human adipocytes obtained from non-diabetic subjects and from patients with T2D. We show that FOXO1 is mainly phosphorylated through mTORC2-mediated phosphorylation of protein kinase B at Ser(473) and that this mechanism is unperturbed in T2D. We also demonstrate a cross-talk from the MAPK branch of insulin signaling to stimulate phosphorylation of FOXO1. The cellular abundance and consequently activity of FOXO1 are halved in T2D. Interestingly, inhibition of mTORC1 with rapamycin reduces the abundance of FOXO1 to the levels in T2D. This suggests that the reduction of the concentration of FOXO1 is a consequence of attenuation of mTORC1, which defines much of the diabetic state in human adipocytes. We integrate insulin control of FOXO1 in a network-wide mathematical model of insulin signaling dynamics based on compatible data from human adipocytes. The diabetic state is network-wide explained by attenuation of an mTORC1-to-insulin receptor substrate-1 (IRS1) feedback and reduced abundances of insulin receptor, GLUT4, AS160, ribosomal protein S6, and FOXO1. The model demonstrates that attenuation of the mTORC1-to-IRS1 feedback is a major mechanism of insulin resistance in the diabetic state.

    Place, publisher, year, edition, pages
    Rockville, Maryland: American Society for Biochemistry and Molecular Biology, 2016
    National Category
    Endocrinology and Diabetes
    Identifiers
    urn:nbn:se:liu:diva-130998 (URN)10.1074/jbc.M116.715763 (DOI)000380584200033 ()27226562 (PubMedID)
    Note

    Funding agencies|Swedish Diabetes Fund, University of Linköping; Swedish Research Council; AstraZeneca

    Available from: 2016-09-02 Created: 2016-09-02 Last updated: 2016-09-19Bibliographically approved
  • Public defence: 2016-10-28 13:00 K2, Hus Kåkenhus, Norrköping
    Nordh, Jonas
    Linköping University, Department of Social and Welfare Studies, NISAL - National Institute for the Study of Ageing and Later Life. Linköping University, Faculty of Arts and Sciences.
    Nordh, Jonas
    Linköping University, Department of Social and Welfare Studies, NISAL - National Institute for the Study of Ageing and Later Life. Linköping University, Faculty of Arts and Sciences.
    Social citizenship and people with dementia: Designing social care policies in Sweden2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    People with dementia are commonly in need of some form of social care from the social services in order to manage their everyday situations. However, social services are shaped by the construction of policy targets. The aim of this dissertation is to explore the social citizenship for people with dementia. Social citizenship for people with dementia is explored by studying how people with dementia, in policy documents, have been constructed as a target group and also by studying how policies are enacted in practice by care managers, in their work and in their meetings with people with dementia. This is illustrated by studying policy documents from national level which range over nearly 40 years and 19 interviews with care managers. It is shown that, if and when, people with dementia are visible in policy documents, they commonly have a negative construction based on their cognitive and communicative abilities, as a burden, disturbing and incapable. It is further investigated how street-level bureaucrats, in this case care managers, experience meeting with people with dementia when they apply for social services. It is shown that care-managers experience difficulties concerning this group comprised of the exchange of information between care managers and people with dementia, refusal of social services by the person, the influence of relatives and other professions as well as moral dilemmas, such as the relations between the person with dementia and their relatives. The study shows that care managers have little support from policies, e.g. legislation and guidelines, in how to handle these dilemmas, and must thus create their own local ways of handling these situations. Care managers are thus influential policy actors concerning the policy target group of people with dementia. The policy processes which this dissertation illustrates, affect the social citizenship of people with dementia. It is shown that they, to an extent, have difficulties in influencing their own everyday situation concerning social services. Finally, the policy processes, will affect their possibility to influence their social citizenship.

    List of papers
    1. Crafting citizen(ship) for people with dementia: How policy narratives at national level in Sweden informed politics of time from 1975 to 2013
    Open this publication in new window or tab >>Crafting citizen(ship) for people with dementia: How policy narratives at national level in Sweden informed politics of time from 1975 to 2013
    2015 (English)In: Journal of Aging Studies, ISSN 0890-4065, E-ISSN 1879-193X, Vol. 34, 123-133 p.Article in journal (Refereed) Published
    Abstract [en]

    This article explores how policy narratives in national policy documents in Sweden inform associated politics on people with dementia. This is disentangled in terms of how people with dementia have been defined, what the problems and their imminent solutions have been, and if and how these have differed overtime. Based on a textual analysis of policy documents at national level in Sweden, covering nearly 40 years the study shows how divergent policy narratives shape the construction of citizens with dementia as policy target groups. This study shows the temporal character of people with dementia as a political problem, the implications of policy narratives on people with dementia as a citizen group, and policy narratives as something being crafted rather than shaped by fixed pre-existing "facts". Dementia, and further citizens living with dementia, does not have a once and for all stabilised meaning. Instead, the meanings behind the categories continue to evolve and to be crafted, which affects the construction of citizens living with dementia, the space in which to exercise their citizenship and further belonging to the society.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keyword
    Dementia; Citizenship; Policy narratives; Policy-making; Social construction; Sweden
    National Category
    Sociology
    Identifiers
    urn:nbn:se:liu:diva-120866 (URN)10.1016/j.jaging.2015.06.003 (DOI)000359029400013 ()26162732 (PubMedID)
    Note

    Funding Agencies|bank of Sweden Tercentenary Foundation as part of the programme Dementia: Agency, Personhood and Everyday Life [M10-0187:1]

    Available from: 2015-08-28 Created: 2015-08-28 Last updated: 2016-09-22
    2. To Coordinate Information in Practice: Dilemmas and Strategies in Care Management for Citizens with Dementia
    Open this publication in new window or tab >>To Coordinate Information in Practice: Dilemmas and Strategies in Care Management for Citizens with Dementia
    2016 (English)In: Journal of social service research, ISSN 0148-8376, E-ISSN 1540-7314, 1-17 p.Article in journal (Refereed) Epub ahead of print
    Abstract [en]

    This qualitative study, based on 19 interviews with care managers, explores the experiences of care-managers involved in assessing the need for social services for people with dementia. The study shows that social workers, as care managers, face several dilemmas in their practice concerning people with dementia, in relation to the exchange of information and in regards to conflicting interests between different actors involved in the assessment of the need for support for people with dementia. Strategies used to handle problematic situations that arise in their work are using other sources for information (e.g., relatives and actors from other professions), persuading, and pursuing creative forms of consent. However, the study shows that dilemmas and strategies used generate other, prominently moral, dilemmas for care managers in their practice, which relate to participation and self-determination by the person with dementia. The study shed light on the problematic situation for care managers in their work to coordinate information and further the new “realities“ that they encounter as well as on how to handle these new situations. This study suggests possible ways to improve the everyday work of care managers, as well as how policies concerning social work and people with dementia can be improved.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2016
    National Category
    Social Work Other Social Sciences not elsewhere specified Nursing Health Care Service and Management, Health Policy and Services and Health Economy Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-131476 (URN)10.1080/01488376.2016.1217580 (DOI)
    Available from: 2016-09-22 Created: 2016-09-22 Last updated: 2016-09-22Bibliographically approved
  • Public defence: 2016-11-09 10:15 Planck, Fysikhuset, Linköping
    Kumar Yalamanchili, Phani
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Kumar Yalamanchili, Phani
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Multiscale materials design of hard coatings for improved fracture resistance and thermal stability2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Physical vapor deposited hard coatings comprised of cubic (c) transition metal (TM)-Al-N, and (TM)-Si-N are the current workhorse materials for a large number of metal cutting and wear resistant applications to fight against the extreme conditions of temperature and stress simultaneously. In spite of a high degree of sophistication in terms of material choice and microstructural design, a lower fracture resistance and limited thermal stability of the coatings remains a technological challenge in the field. The lower fracture resistance of the coating is an inherent material property. Limited thermal stability in the TM-Al-N system is associated with the transformation of metastable c -AlN to its stable wurtzite (w)-AlN phase at a temperature above 900 oC resulting an undesirable hardness drop.

    The current work shows how to overcome these challenges by manipulating the coating material at different length scales, i.e. microstructure, crystal and interface structure, and alloy design. The endeavor of multiscale materials design is achieved by converging a deeper material and process knowledge to result specific structural modification over multiple length scales by alloying transition metal nitrides with AlN and SiNx as following.

    Microstructure variation is achieved in ZrN coating by alloying it with SiNx, where the surface segregated SiNx breaks down the columnar structure and evolves a selforganized nanocomposite structure with a hardness variation from 37 ±2 GPa to 26 ±1 GPa. The indentation induced fracture studies reveal crack deflection for the columnar coating, likely along the column boundaries. The crack deflection offers additional energy dissipative mechanisms that make the columnar structured coating more fracture resistant, which is not the case for the nanocomposite coating in spite of its lower hardness.

    Crystal structure of AlN is varied between stable wurtzite structure to metastable cubic structure in the ZrAlN alloy by adapting a multilayer structure and tuning the layer thickness. The multilayer consisting c-AlN layer shows a hardness of 34 ±1 GPa and a twofold enhancement in the critical force to cause an indentation induced surface crack compared to the multilayer containing w-AlN in spite of a lower hardness for the later case. The higher fracture resistance is discovered to be caused by stress- induced transformation of AlN from its metastable cubic structure to its thermodynamically stable wurtzite structure associated with a molar volume expansion of 20% that builds up local compressive stress zones delaying the onset and propagation of the cracks. This is in fact the first experimental data point for the stress-induced transformation toughening in a hard coating.

    The current work also demonstrates a concept of improving the thermal stability of the TM-Al-N by modifying the interface structure between w-AlN and c-TMN. A popular belief in the field is that AlN in its stable wurtzite structure is detrimental to coating hardness, and hence the current material design strategy is to force AlN in metastable cubic phase that confines the application temperature (~ 900 oC). In contrast, here it is shown that the w-AlN offers a high hardness provided if it is grown (semi-)coherent to c-TMN. This is experimentally shown for the multilayer system of TiN/ZrAlN. The interface structure between the c-TiN, c-ZrN and w-AlN is transformed from incoherent to (semi-)coherent structure by tuning the growth conditions under a favorable crystallographic template. Furthermore, the low energy (semi-) coherent interface structure between w-AlN and c- TiN, c- ZrN display a high thermal stability, causing a high and more stable hardness up to an annealing temperature of 1150 oC with a value of 34± 1.5 GPa. This value is 50 % higher compared to the state-of-the-art monolithic and multilayered Ti-Al-N and Zr-Al-N coating containing incoherent w-AlN.

    Finally, an entropy based alloy design concept is explored to form a thermodynamically stable solid solution in the TM-Al-N material system that has a positive enthalpy of mixing. Multi-principal element alloys of (AlTiVCrNb)N are formed in a near ideal cubic solid solution. The high configurational entropy in the alloy is predicted to overcome positive enthalpy of mixing, there by an entropy stabilized solid solution formation is expected at a temperature above 1000 K. However, at elevated temperature, optimization between the minimization of interaction energy and maximization of configurational randomness causes precipitation of AlN in its stable wurtzite structure and the cubic solid solution is only confined between TiN, CrN, VN and NbN that have a low enthalpy of mixing.

    In summary, this work provides technological solutions to the two outstanding issues in the field. A significant enhancement in fracture resistance of the coating is achieved with appropriate material choice and microstructural design by invoking crack deflection and stress induced transformation toughening mechanisms. A remarkable thermal stability enhancement of the TM-Al-N coating is achieved by a new structural archetype consisting c-TMN and thermodynamically stable w-AlN with a low energy (semi-)coherent interface structure.

    List of papers
    1. Structure, deformation and fracture of arc evaporated Zr-Si-N ternary hard films
    Open this publication in new window or tab >>Structure, deformation and fracture of arc evaporated Zr-Si-N ternary hard films
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    2014 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 258, 1100-1107 p.Article in journal (Refereed) Published
    Abstract [en]

    Zr-Si-N films with varying Si contents were grown on WC-Co substrates with an industrial scale reactive cathodic arc deposition technique. The microstructural changes correlate to variation in mechanical properties with different deformation mechanisms dominating for different structures. Si forms a substitutional solid solution in the cubic ZrN lattice up to 1.8 at. % in a fine columnar structure. Further Si additions results in precipitation of an amorphous (a)-SiNX phase and evolution of a nanocomposite structure (nc ZrN-a SiNX) which has completely suppressed the columnar structure at 6.3 at. % Si. The rotation-induced artificial layering during film growth was used as a marker to visualize the deformation of the film. A dislocation-based homogeneous plastic deformation mechanism dominates the columnar structure, while grain boundary sliding is the active mechanism mediating heterogeneous plastic deformation in the nanocomposite structure. Film hardness increases with increasing Si content in the columnar structure due to an effective solid solution strengthening. The deformation mechanism of localized grain boundary sliding in the nanocomposite structure results in lower hardness. When cracking is induced by indentation, the fine columnar structure exhibits pronounced crack deflection that results in higher fracture resistance compared to the nanocomposite films.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-106760 (URN)10.1016/j.surfcoat.2014.07.024 (DOI)000346895000134 ()
    Available from: 2014-05-21 Created: 2014-05-21 Last updated: 2016-09-19Bibliographically approved
    2. Tuning hardness and fracture resistance of ZrN/Zr0.63Al0.37N nanoscale multilayers by stress-induced transformation toughening
    Open this publication in new window or tab >>Tuning hardness and fracture resistance of ZrN/Zr0.63Al0.37N nanoscale multilayers by stress-induced transformation toughening
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    2015 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 89, 22-31 p.Article in journal (Refereed) Published
    Abstract [en]

    Structure and mechanical properties of nanoscale multilayers of ZrN/Zr0.63Al0.37N grown by reactive magnetron sputtering on MgO (0 0 1) substrates at a temperature of 700 degrees C are investigated as a function of the Zr0.63Al0.37N layer thickness. The Zr0.63Al0.37N undergoes in situ chemical segregation into ZrN-rich and AlN-rich domains. The AlN-rich domains undergo transition from cubic to wurtzite crystal structure as a function of Zr0.63Al0.37N layer thickness. Such structural transformation allows systematic variation of hardness as well as fracture resistance of the films. A maximum fracture resistance is achieved for 2 nm thick Zr0.63Al0.37N layers where the AlN-rich domains are epitaxially stabilized in the metastable cubic phase. The metastable cubic-AlN phase undergoes stress-induced transformation to wurtzite-AlN when subjected to indentation, which results in the enhanced fracture resistance. A maximum hardness of 34 GPa is obtained for 10 nm thick Zr0.63Al0.37N layers where the wurtzite-AlN and cubic-ZrN rich domains form semi-coherent interfaces.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keyword
    Nitride multilayer thin films; Mechanical properties; Fracture toughness
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-118029 (URN)10.1016/j.actamat.2015.01.066 (DOI)000353249100003 ()
    Note

    Funding Agencies|European Unions Erasmus-Mundus graduate school in Material Science and Engineering (DocMASE); Swedish Foundation for Strategic Research (SSF) through the grant Designed Multicomponent Coatings (MultiFilms); Swedish Governmental Agency for Innovation Systems (Vinnova) through the VINN Excellence Centre FunMat; VINNMER Grant [2011-03464]; EU [C/4-EFRE-13/2009/Br]; DFG; federal state government of Saarland [INST 256/298-1 FUGG]

    Available from: 2015-05-21 Created: 2015-05-20 Last updated: 2016-09-19Bibliographically approved