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  • 1.
    Graham, A.C.
    et al.
    Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE, United Kingdom.
    Thomas, K.J.
    Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE, United Kingdom.
    Pepper, M.
    Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE, United Kingdom.
    Simmons, M.Y.
    Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE, United Kingdom, School of Physics, University of New South Wales, Sydney, NSW 2052, Australia.
    Ritchie, D.A.
    Cavendish Laboratory, Madingley Road, Cambridge CB3 OHE, United Kingdom.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Jaksch, Peter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Debnarova, Andrea
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Yakimenko, I.I.
    0.7 Analogue structures and exchange interactions in quantum wires2004In: Solid State Communications, ISSN 0038-1098, Vol. 131, no 9-10 SPEC. ISS., 591-597 p.Article in journal (Refereed)
    Abstract [en]

    We present experimental studies of crossings of spin-split one-dimensional subbands in ballistic quantum wires in an in-plane magnetic field B ?. At low electron densities, a spontaneous spin-splitting occurs as subbands cross, which gives rise to additional non-quantised conductance structures called 0.7 analogues. We analyse the data within a spin-density-functional model, which includes exchange interactions in a magnetic field. Focussing on the region of the crossings of spin-split subbands, it is found that the energy levels rearrange as they cross due to exchange interactions. © 2004 Elsevier Ltd. All rights reserved.

  • 2.
    Lundberg, Peter
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radio Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Ekblad, Alf
    Nilsson, Mats
    13C NMR spectroscopy studies of forest soil microbial activity: Glucose uptake and fatty acid biosynthesis2001In: Soil Biology and Biochemistry, ISSN 0038-0717, Vol. 33, no 4-5, 621-632 p.Article in journal (Refereed)
    Abstract [en]

    The intimate association of soil microorganisms with the soil matrix complicates analysis of their metabolism, since thorough separation of intact cells from the matrix is very difficult using standard protocols. Thus, in the study reported here, in situ glucose decomposition and metabolism in humus from a coniferous forest soil was monitored and evaluated using 'solution state' 13C NMR, which can be used in a non-invasive manner. [U-13C] glucose was added at a concentration of 1.73 mmol C g-1 dry organic matter, which is known to allow maximal substrate induced respiration (SIR), and the microbial metabolism of the added C was followed over a period of 28 days. The data showed that ~50% of the added glucose was consumed within three days, coinciding with the appearance of label in CH3, -CH2- and -CH = CH-groups, and in glycerol-carbons, suggesting that olefinic triacylglycerols were being formed, probably located in oil droplets. During days two to three, around 40% of the consumed glucose C was allocated into solid state components, about 40% was respired and about 20% was found as triglycerols. The triacylglycerol signal reached a maximum after 13 days, but subsequently declined by 60%, as the triacylglycerols were apparently consumed, by day 28 of the incubation. Our results indicate there was an initial formation of structural microbial C (solid state carbon) followed by formation of storage lipid C, which subsequently decreased, probably because it was used to provide the organisms with energy when the external energy source (i.e. the glucose) was depleted. The formation of unsaturated triacylglycerols, typical storage metabolites of eucaryotes, suggests that fungi were the most active organisms in the glucose degradation. ⌐ 2001 Elsevier Science Ltd.

  • 3.
    Eriksson, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Johansson, GA
    Hertz, HM
    Gullikson, EM
    Kreissig, U
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    14.5% near-normal incidence reflectance of Cr/Sc x-ray multilayer mirrors for the water window2003In: Optics Letters, ISSN 0146-9592, Vol. 28, no 24, 2494-2496 p.Article in journal (Refereed)
    Abstract [en]

    Cr/Sc multilayer mirrors, synthesized by ion-assisted magnetron sputter deposition, are proved to have a high near-normal reflectivity of R = 14.5% at a grazing angle of 87.5degrees measured at the wavelength A = 3.11 nm, which is an improvement of more than 31% compared with previously published results. Elastic recoil detection analyses show that the mirrors contained as much as 15 at. % of N and traces of C and O. Soft x-ray reflectivity simulations reveal interface widths of sigma = 0.34 nm and an exceptionally small layer thickness drift of similar to1.6 X 10(-5) nm/multilayer period throughout the stack. Simulations show that a reflectivity of R = 25.6% is attainable if impurities and layer thickness drift can be eliminated. The abrupt interfaces are achieved with ion assistance with a low ion energy of 24 eV and high ion-to-metal flux ratios of 7.1 and 23.1 during Cr and Se sputter deposition, respectively. In addition, a near-normal incidence reflectivity of 5.5% for the C VI emission line (lambda = 3.374 nm) from a laser plasma source was verified. (C) 2003 Optical Society of America.

  • 4.
    Seppänen, Timo
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    248 nm cathodoluminescence in Al1-xInxN (0001) thin films grown on lattice-matched Ti1-yZryN (111) seed layers by low temperature magnetron sputter epitaxy2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 18Article in journal (Refereed)
    Abstract [en]

    Single-crystal Al0.8 In0.2 N (0001) thin films were grown epitaxially onto lattice-matched Ti0.2 Zr0.8 N (111) seed layers on MgO(111) substrates at 300 °C by magnetron sputter epitaxy. Low-energy ion-assisted epitaxial growth conditions were achieved by applying a substrate potential of -15 V. Cross-sectional high-resolution electron microscopy verified the epitaxy and high-resolution x-ray diffraction ω -rocking scans of the Al0.8 In0.2 N 0002 peak (full width at half maximum ∼2400 arc sec) indicated a high structural quality of the films. Cathodoluminescence measurements performed in a scanning electron microscope at 5 K revealed Al0.8 In0.2 N luminescence at 248 nm, or equivalently 5.0 eV, showing that Al0.8 In0.2 N is a promising material for deep-ultraviolet optoelectronic devices. © 2006 American Institute of Physics.

  • 5.
    Inganäs, Olle
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Admassie, Shimelis
    University of Addis Ababa, Ethiopia .
    25th Anniversary Article: Organic Photovoltaic Modules and Biopolymer Supercapacitors for Supply of Renewable Electricity: A Perspective from Africa2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 6, 830-847 p.Article, review/survey (Refereed)
    Abstract [en]

    The role of materials in civilization is well demonstrated over the centuries and millennia, as materials have come to serve as the classifier of stages of civilization. With the advent of materials science, this relation has become even more pronounced. The pivotal role of advanced materials in industrial economies has not yet been matched by the influence of advanced materials during the transition from agricultural to modern societies. The role of advanced materials in poverty eradication can be very large, in particular if new trajectories of social and economic development become possible. This is the topic of this essay, different in format from the traditional scientific review, as we try to encompass not only two infant technologies of solar energy conversion and storage by means of organic materials, but also the social conditions for introduction of the technologies. The development of organic-based photovoltaic energy conversion has been rapid, and promises to deliver new alternatives to well-established silicon photovoltaics. Our recent development of organic biopolymer composite electrodes opens avenues towards the use of renewable materials in the construction of wooden batteries or supercapacitors for charge storage. Combining these new elements may give different conditions for introduction of energy technology in areas now lacking electrical grids, but having sufficient solar energy inputs. These areas are found close to the equator, and include some of the poorest regions on earth.

  • 6.
    Patra, Santanu
    et al.
    Indian School Mines, India.
    Roy, Ekta
    Indian School Mines, India.
    Tiwari, Ashutosh
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics.
    Madhuri, Rashmi
    Indian School Mines, India.
    Sharma, Prashant K.
    Indian School Mines, India.
    2-Dimensional graphene as a route for emergence of additional dimension nanomaterials2017In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 89Article in journal (Refereed)
    Abstract [en]

    Dimension has a different and impactful significance in the field of innovation, research and technologies. Starting from one-dimension, now, we all are moving towards 3-D visuals and try to do the things in this dimension. However, we still have some very innovative and widely applicable nanomaterials, which have tremendous potential in the form of 2-D only i.e. graphene. In this review, we have tried to incorporate the reported pathways used so far for modification of 2-D graphene sheets to make is three-dimensional. The modified graphene been applied in many fields like supercapacitors, sensors, catalysis, energy storage devices and many more. In addition, we have also incorporated the conversion of 2-D graphene to their various other dimensions like zero-, one- or three-dimensional nanostructures. (C) 2016 Elsevier B.V. All rights reserved.

  • 7.
    Forsgren, Mikael
    et al.
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.
    Bengtsson, Ann
    Linköping University, Department of Clinical and Experimental Medicine, Rheumatology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Rheumatology.
    Dahlqvist Leinhard, Olof
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Sören, Birgitta
    Linköping University, Department of Medical and Health Sciences, Physiotherapy. Linköping University, Faculty of Health Sciences.
    Brandejsky, Vaclav
    Depts Clinical Research and Radiology, University Bern, Bern, Switzerland.
    Lund, Eva
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Lundberg, Peter
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    31P MRS as a Potential Biomarker for Fibromyalgia2012In: Proceedings of the 20th Annaal Meeting & Exhibition, 5-11 May, Melbourne, Australia, 2012, 1493-1493 p.Conference paper (Refereed)
    Abstract [en]

    Major clinical symptoms in fibromyalgia (FM) are muscle pain, stiffness and fatigue. Studies have shown reduced voluntary strength and exercise capacity, lower endurance and more muscular pain even at low workload. An impaired muscle energy metabolism has therefore been proposed as a result of the disease. An earlier study using magnetic resonance spectroscopy (MRS) showed that at maximal dynamic and static contractions the concentration of inorganic phosphate was lower in FM [1]. A decrease in ATP, ADP and PCr and an increase in AMP and creatine was found in FM biopsies [2]. The purpose of this study was to non-invasively analyze the quantitative content of  phosphagens in the resting muscle in FM in comparison to healthy controls using 31P MRS of the quadriceps muscle.

  • 8.
    Sanjuan, Joseba
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    3G Energy-Efficient Packet Handling Kernel Module for Android2012Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    The use of mobile devices is increasing due to the constant development of more advanced and appealing applications and computing features. However, these new features are very power hungry leading to short battery lifetimes. Research shows that a major reason for fast battery depletion is the excessive and inefficient use of the wireless interfaces. This thesis studies how we can attempt to increase the battery lifetime of the devices without having to sacrifice the usage of these advanced features in some applications.

    The thesis focuses on adapting the traffic pattern characteristics of mobile communication using a widespread wireless communication technology like 3G. Traffic pattern adaptation is performed at packet level in kernel space in Android. The data transfers are scheduled with the knowledge of the energy consumption characteristics of 3G. The performed measurements indicate that our solution can provide energy savings ranging from 7% to 59%.

    This work confirms that 3G conscious scheduling of network traffic reduces energy consumption, and that, both applications and energy saving libraries are potential directions to be further studied.

  • 9.
    Hall, Henning
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Luckey, Christian
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    3G Transmission Energy Savings through Adaptive Traffic Shaping Policies2014Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This bachelor thesis will explore how two traffic shaping mechanisms can help preserve battery power while retaining a certain Quality of Service (QoS) in an Android based application developed for crisis management. The implemented user-space mechanisms will delay all elastic data requests in order to reduce the number of times the 3G transmission radio enters high power states. This lowers the QoS but extends the user equipment's battery life. The thesis will show that a shaping mechanism has the capability to reduce radio energy usage by up to 50% for the given Android application at the cost of added transmission delays by up to 134 seconds for background traffic. The study also presents two policies that help the application adapt to the current battery level and lower the QoS accordingly, namely one that has a lenient savings effect and one that has an aggressive savings effect.

  • 10.
    Sundberg, Carina
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Al-Soud, Waleed A.
    University of Copenhagen, Denmark .
    Larsson, Madeleine
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Alm, Erik
    SMI, Sweden .
    Shakeri Yekta, Sepehr
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Svensson, Bo
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Sorensen, Soren J.
    University of Copenhagen, Denmark .
    Karlsson, Anna
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    454 pyrosequencing analyses of bacterial and archaeal richness in 21 full-scale biogas digesters2013In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 85, no 3, 612-626 p.Article in journal (Refereed)
    Abstract [en]

    The microbial community of 21 full-scale biogas reactors was examined using 454 pyrosequencing of 16S rRNA gene sequences. These reactors included seven (six mesophilic and one thermophilic) digesting sewage sludge (SS) and 14 (ten mesophilic and four thermophilic) codigesting (CD) various combinations of wastes from slaughterhouses, restaurants, households, etc. The pyrosequencing generated more than 160 000 sequences representing 11 phyla, 23 classes, and 95 genera of Bacteria and Archaea. The bacterial community was always both more abundant and more diverse than the archaeal community. At the phylum level, the foremost populations in the SS reactors included Actinobacteria, Proteobacteria, Chloroflexi, Spirochetes, and Euryarchaeota, while Firmicutes was the most prevalent in the CD reactors. The main bacterial class in all reactors was Clostridia. Acetoclastic methanogens were detected in the SS, but not in the CD reactors. Their absence suggests that methane formation from acetate takes place mainly via syntrophic acetate oxidation in the CD reactors. A principal component analysis of the communities at genus level revealed three clusters: SS reactors, mesophilic CD reactors (including one thermophilic CD and one SS), and thermophilic CD reactors. Thus, the microbial composition was mainly governed by the substrate differences and the process temperature.

  • 11.
    Fredriksson, Alexandru G
    et al.
    Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Zajac, Jakub
    Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Eriksson, Jonatan
    Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology.
    Dyverfeldt, Petter
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Bolger, Ann F
    University of California San Francisco.
    Ebbers, Tino
    Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Carlhäll, Carljohan
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Clinical Physiology UHL. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    4-D blood flow in the human right ventricle2011In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539, Vol. 301, no 6, H2344-H2350 p.Article in journal (Refereed)
    Abstract [en]

    Right ventricular (RV) function is a powerful prognostic indicator in many forms of heart disease, but its assessment remains challenging and inexact. RV dysfunction may alter the normal patterns of RV blood flow, but those patterns have been incompletely characterized. We hypothesized that, based on anatomic differences, the proportions and energetics of RV flow components would differ from those identified in the left ventricle (LV) and that the portion of the RV inflow passing directly to outflow (Direct Flow) would be prepared for effective systolic ejection as a result of preserved kinetic energy (KE) compared with other RV flow components. Three-dimensional, time-resolved phase-contrast velocity, and balanced steady-state free-precession morphological data were acquired in 10 healthy subjects using MRI. A previously validated method was used to separate the RV and LV end-diastolic volumes into four flow components and measure their volume and KE over the cardiac cycle. The RV Direct Flow: 1) followed a smoothly curving route that did not extend into the apical region of the ventricle; 2) had a larger volume and possessed a larger presystolic KE (0.4 +/- 0.3 mJ) than the other flow components (P andlt; 0.001 and P andlt; 0.01, respectively); and 3) represented a larger part of the end-diastolic blood volume compared with the LV Direct Flow (P andlt; 0.01). These findings suggest that diastolic flow patterns distinct to the normal RV create favorable conditions for ensuing systolic ejection of the Direct Flow component. These flow-specific aspects of RV diastolic-systolic coupling provide novel perspectives on RV physiology and may add to the understanding of RV pathophysiology.

  • 12.
    Dyverfeldt, Petter
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Bissell, Malenka
    University of Oxford, England.
    Barker, Alex J.
    Northwestern University, IL 60611 USA.
    Bolger, Ann F
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. University of Calif San Francisco, CA USA.
    Carlhäll, Carljohan
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ebbers, Tino
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Francios, Christopher J.
    University of Wisconsin, WI 53706 USA.
    Frydrychowicz, Alex
    University Hospital Schleswig Holstein, Germany.
    Geiger, Julia
    University of Childrens Hospital Zurich, Switzerland.
    Giese, Daniel
    University Hospital Cologne, Germany.
    Hope, Michael D.
    University of Calif San Francisco, CA USA.
    Kilner, Philip J.
    University of London Imperial Coll Science Technology and Med, England.
    Kozerke, Sebastian
    University of Zurich, Switzerland; ETH, Switzerland.
    Myerson, Saul
    University of Oxford, England.
    Neubauer, Stefan
    University of Oxford, England.
    Wieben, Oliver
    University of Wisconsin, WI 53706 USA.
    Markl, Michael
    Northwestern University, IL 60611 USA; Northwestern University, IL 60611 USA.
    4D flow cardiovascular magnetic resonance consensus statement2015In: Journal of Cardiovascular Magnetic Resonance, ISSN 1097-6647, E-ISSN 1532-429X, Vol. 17, no 72Article, review/survey (Refereed)
    Abstract [en]

    Pulsatile blood flow through the cavities of the heart and great vessels is time-varying and multidirectional. Access to all regions, phases and directions of cardiovascular flows has formerly been limited. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has enabled more comprehensive access to such flows, with typical spatial resolution of 1.5x1.5x1.5 - 3x3x3 mm(3), typical temporal resolution of 30-40 ms, and acquisition times in the order of 5 to 25 min. This consensus paper is the work of physicists, physicians and biomedical engineers, active in the development and implementation of 4D Flow CMR, who have repeatedly met to share experience and ideas. The paper aims to assist understanding of acquisition and analysis methods, and their potential clinical applications with a focus on the heart and greater vessels. We describe that 4D Flow CMR can be clinically advantageous because placement of a single acquisition volume is straightforward and enables flow through any plane across it to be calculated retrospectively and with good accuracy. We also specify research and development goals that have yet to be satisfactorily achieved. Derived flow parameters, generally needing further development or validation for clinical use, include measurements of wall shear stress, pressure difference, turbulent kinetic energy, and intracardiac flow components. The dependence of measurement accuracy on acquisition parameters is considered, as are the uses of different visualization strategies for appropriate representation of time-varying multidirectional flow fields. Finally, we offer suggestions for more consistent, user-friendly implementation of 4D Flow CMR acquisition and data handling with a view to multicenter studies and more widespread adoption of the approach in routine clinical investigations.

  • 13.
    Fredriksson, Alexandru Grigorescu
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Örebrö University Hospital, Örebro, Sweden.
    Svalbring, Emil
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Eriksson, Jonatan
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Dyverfeldt, Petter
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Alehagen, Urban
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Cardiology in Linköping. Linköping University, Faculty of Medicine and Health Sciences.
    Engvall, Jan
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    Ebbers, Tino
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Faculty of Science & Engineering. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Carlhäll, Carl-Johan
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Medicine and Health Sciences.
    4D flow MRI can detect subtle right ventricular dysfunction in primary left ventricular disease.2016In: Journal of Magnetic Resonance Imaging, ISSN 1053-1807, E-ISSN 1522-2586, Vol. 43, no 3, 558-565 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: To investigate whether 4D flow magnetic resonance imaging (MRI) can detect subtle right ventricular (RV) dysfunction in primary left ventricular (LV) disease.

    MATERIALS AND METHODS: 4D flow and morphological 3T MRI data were acquired in 22 patients with mild ischemic heart disease who were stratified into two groups based on LV end-diastolic volume index (EDVI): lower-LVEDVI and higher-LVEDVI, as well as in 11 healthy controls. The RV volume was segmented at end-diastole (ED) and end-systole (ES). Pathlines were emitted from the ED volume and traced forwards and backwards in time to ES. The blood volume was separated into flow components. The Direct Flow (DF) component was defined as RV inflow passing directly to outflow. The kinetic energy (KE) of the DF component was calculated. Echocardiographic conventional RV indices were also assessed.

    RESULTS: The higher-LVEDVI group had larger LVEDVI and lower LV ejection fraction (98 ± 32 ml/m(2) ; 48 ± 13%) compared to the healthy (67 ± 12, P = 0.002; 64 ± 7, P < 0.001) and lower-LVEDI groups (62 ± 10; 68 ± 7, both P < 0.001). The RV 4D flow-specific measures "DF/EDV volume-ratio" and "DF/EDV KE-ratio at ED" were lower in the higher-LVEDVI group (38 ± 5%; 52 ± 6%) compared to the healthy (44 ± 6; 65 ± 7, P = 0.018 and P < 0.001) and lower-LVEDVI groups (44 ± 6; 64 ± 7, P = 0.011 and P < 0.001). There was no difference in any of the conventional MRI and echocardiographic RV indices between the three groups.

    CONCLUSION: We found that in primary LV disease mild impairment of RV function can be detected by 4D flow-specific measures, but not by the conventional MRI and echocardiographic indices. J. Magn. Reson. Imaging 2015.

  • 14.
    Casas Garcia, Belén
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Lantz, Jonas
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Dyverfeldt, Petter
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV). Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Ebbers, Tino
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Faculty of Science & Engineering. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    4D Flow MRI-Based Pressure Loss Estimation in Stenotic Flows: Evaluation Using Numerical Simulations2016In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 75, no 4, 1808-1821 p.Article in journal (Refereed)
    Abstract [en]

    Purpose: To assess how 4D flow MRI-based pressure and energy loss estimates correspond to net transstenotic pressure gradients (TPG(net)) and their dependence on spatial resolution. Methods: Numerical velocity data of stenotic flow were obtained from computational fluid dynamics (CFD) simulations in geometries with varying stenosis degrees, poststenotic diameters and flow rates. MRI measurements were simulated at different spatial resolutions. The simplified and extended Bernoulli equations, Pressure-Poisson equation (PPE), and integration of turbulent kinetic energy (TKE) and viscous dissipation were compared against the true TPG(net). Results: The simplified Bernoulli equation overestimated the true TPG(net) (8.74 +/- 0.67 versus 6.76 +/- 0.54 mmHg). The extended Bernoulli equation performed better (6.57 +/- 0.53 mmHg), although errors remained at low TPG(net). TPG(net) estimations using the PPE were always close to zero. Total TKE and viscous dissipation correlated strongly with TPG(net) for each geometry (r(2) &gt; 0.93) and moderately considering all geometries (r(2) = 0.756 and r(2) = 0.776, respectively). TKE estimates were accurate and minorly impacted by resolution. Viscous dissipation was overall underestimated and resolution dependent. Conclusion: Several parameters overestimate or are not linearly related to TPG(net) and/or depend on spatial resolution. Considering idealized axisymmetric geometries and in absence of noise, TPG(net) was best estimated using the extended Bernoulli equation. (C) 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.

  • 15.
    Säll, Erik
    et al.
    Linköping University, Department of Electrical Engineering.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering. Linköping University, Department of Electrical Engineering, Electronics System.
    6 bit 1 GHz CMOS silicon-on-insulator flash analog-to-digital converter for read channel applications2005In: Proc. European Conf. on Circuit Theory and Design, ECCTD'05, 2005, I/127-I/130 p.Conference paper (Refereed)
    Abstract [en]

    The purpose of this work is to investigate the possibility to implement analog base band circuitry along with digital circuitry in silicon-on-insulator technology. Hence a 6 bit Nyquist rate flash analog-to-digital converter is designed in a 130 nm CMOS silicon-on-insulator technology. The converter is aimed for read channel or ultra-wideband radio applications. The simulations indicate a 170 mW power consumption at a maximum sampling rate of 1 GHz. The supply voltage is only 1.2 V. The effective number of bit is 5.8 bit and the effective resolution bandwidth is 390 MHz. An energy per conversion step of 3.9 pJ indicate that this converter is as efficient as other state-of-the-art converters, without using interpolation or averaging techniques.

  • 16.
    Du, Chun
    et al.
    Chinese Academy of Science.
    Li, Cuihong
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Li, Weiwei
    Chinese Academy of Science.
    Chen, Xiong
    Chinese Academy of Science.
    Bo, Zhishan
    Beijing Normal University.
    Veit, Clemens
    Fraunhofer Institute for Solar Energy Systems ISE.
    Ma, Zaifei
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wuerfel, Uli
    Fraunhofer Institute for Solar Energy Systems ISE.
    Zhu, Hongfei
    Chinese Academy of Science.
    Hu, Wenping
    Chinese Academy of Science.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    9-Alkylidene-9H-Fluorene-Containing Polymer for High-Efficiency Polymer Solar Cells2011In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 44, no 19, 7617-7624 p.Article in journal (Refereed)
    Abstract [en]

    A novel donor-acceptor copolymer containing 9-alkylidene-9H-fluorene unit in the main chain, poly[9-(1-hexylheptylidene)-2,7-fluorene-alt-5, 5-(4,7-di-2-thienyl-5,6-dialkoxy-2,1,3-benzothiadiazole)] (PAFDTBT), has been synthesized and evaluated in bulk heterojunction polymer solar cells (BHJ PSCs). The polymer possesses a low band gap of 1.84 eV, a low-lying HOMO energy level (5.32 eV), and excellent solubility in common organic solvents. PSCs based on PAFDTBT and (6,6)-phenyl-C(71)-butyric add methyl ester (PC(71)BM) demonstrate a power conversion efficiency (PCE) of 6.2% with a high fill factor (FF) of 0.70, which indicates that 9-alkylidene-9H-fluorene can be a very useful building block for constructing narrow band gap conjugated polymers for high-efficiency BHJ PSCs.

  • 17.
    Harikumar, Prakash
    et al.
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    A 0.4 V, sub-nW, 8-bit 1 kS/s SAR ADC in 65 nm CMOS for Wireless Sensor Applications2016In: IEEE Transactions on Circuits and Systems - II - Express Briefs, ISSN 1549-7747, E-ISSN 1558-3791, Vol. 63, no 8, 743-747 p.Article in journal (Refereed)
    Abstract [en]

    This brief presents an 8-bit 1-kS/s successive approximation register (SAR) analog-to-digital converter (ADC), which is targeted at distributed wireless sensor networks powered by energy harvesting. For such energy-constrained applications, it is imperative that the ADC employs ultralow supply voltages and minimizes power consumption. The 8-bit 1-kS/s ADC was designed and fabricated in 65-nm CMOS and uses a supply voltage of 0.4 V. In order to achieve sufficient linearity, a two-stage charge pump was implemented to boost the gate voltage of the sampling switches. A custom-designed unit capacitor of 1.9 fF was used to realize the capacitive digital-to-analog converters. The ADC achieves an effective number of bits of 7.81 bits while consuming 717 pW and attains a figure of merit of 3.19 fJ/conversion-step. The differential nonlinearity and the integral nonlinearity are 0.35 and 0.36 LSB, respectively. The core area occupied by the ADC is only 0.0126 mm2.

  • 18.
    Harikumar, Prakash
    et al.
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A 10-bit 50 MS/s SAR ADC in 65 nm CMOS with On-Chip Reference Voltage Buffer2015In: Integration, ISSN 0167-9260, E-ISSN 1872-7522, Vol. 50, 28-38 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the design of a 10-bit, 50 MS/s successive approximation register (SAR) analog-to-digital converter (ADC) with an onchip reference voltage buffer implemented in 65 nm CMOS process. The speed limitation on SAR ADCs with off-chip reference voltage and the necessity of a fast-settling reference voltage buffer are elaborated. Design details of a high-speed reference voltage buffer which ensures precise settling of the DAC output voltage in the presence of bondwire inductances are provided. The ADC uses bootstrapped switches for input sampling, a double-tail high-speed dynamic comparator and split binary-weighted capacitive array charge redistribution DACs. The split binary-weighted array DAC topology helps to achieve low area and less capacitive load and thus enhances power efficiency. Top-plate sampling is utilized in the DAC to reduce the number of switches. In post-layout simulation which includes the entire pad frame and associated parasitics, the ADC achieves an ENOB of 9.25 bits at a supply voltage of 1.2 V, typical process corner and sampling frequency of 50 MS/s for near-Nyquist input. Excluding the reference voltage buffer, the ADC consumes 697 μW and achieves an energy efficiency of 25 fJ/conversionstep while occupying a core area of 0.055 mm2.

  • 19.
    Eriksson, Henrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Electronic Devices.
    Larsson-Edefors, Per
    Chalmers.
    Alvandpour, Atila
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Electronic Devices.
    A 2.8 ns 30 uW/MHz area-efficient 32-b Manchester carry-bypass adder.2001In: IEEE International Symposium on Circuits and Systems ISCAS.,2001, Piscataway: IEEE , 2001, Vol. 4, 84-87 p.Conference paper (Refereed)
    Abstract [en]

    A fast and area-efficient 32-b Manchester carry-bypass adder with low energy-delay product is presented in this paper. The high speed is achieved by the use of optimized bypass circuitry and fast repeater elements in the carry path. The fabricated adder has a measured worst-case delay of 2.8 ns and consumes 30 μW/MHz

  • 20.
    Sundström, Timmy
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Svensson, Christer
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A 7.5 ENOB, 1.0 GS/s, 73 mW Pipeline ADC in 65nm CMOSManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents a pipeline analog-to-digital converter achieving 7.5 ENOB at 1.0 GS/s. A single-stage inverter-based amplifier is used and by individually biasing the pMOS and nMOS, symmetrical layout as well as transconductance can be achieved, resulting in increased closed-loop linearity and a THD of -52 dB. With the amplifier in a switched-capacitor configuration, the optimal bias point can be maintained throughout the input range, which minimizes the power overhead of the MDAC. Calibration of the stage gain is digitally controlled through binary weighted capacitors, which removes the need for digital background calibration. With a power dissipation of 73 mW and an FoM of 0.4 pJ/conv-step, high sample-rate is achieved in a medium resolution pipeline ADC without compromising the energy efficiency.

  • 21.
    Thorarensen, Sebastian
    Linköping University, Department of Computer and Information Science, Software and Systems.
    A Back-End for the SkePU Skeleton Programming Library targeting the Low-Power Multicore Vision Processor Myriad 22016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The SkePU skeleton programming library utilises algorithmic skeletons to offer a high-level approach for creating parallel applications. By using different back-ends, SkePU applications can run on multicore systems, GPGPU systems, and computer clusters.

    Myriad 2 is a low-power multicore vision processor for embedded systems, capable of running parallel applications energy-efficiently. Myriad 2 is heterogeneous, containing two different processor architectures and memories with different characteristics.

    In this thesis, we implement a back-end for SkePU, that allows SkePU applications to run on Myriad 2. We describe how the back-end is designed and evaluate the performance of SkePU applications running on Myriad 2. By conducting a series of benchmarks, we show that our back-end achieves enough performance to make SkePU a useful tool for creating applications for Myriad 2. We also show that SkePU applications can run more energy-efficiently on Myriad 2, compared to a GPGPU system.

  • 22.
    Kiflemariam, Jordanos
    Linköping University, Department of Science and Technology.
    A Biomimetic Manganese Model for Artificial Photosynthesis: Q-band Electron Paramagnetic Resonance Study of a Novel Mn2(II,III) Complex2005Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    In natural oxygen-producing photosynthesis solar energy is stored as chemical energy, in carbohydrates, fats and amino acids, using water as electron source. The large transmembrane protein complex, PSII, is the key enzyme in the light-driven reactions. Water oxidation is accomplished by a triad in PSII in which the Mn-cluster plays an important role. In the artificial photosynthetic system, nature’s photosynthesis will be mimicked such that hydrogen, a sustainable energy source, can be produced from solar energy and water alone. Since water oxidiation requires the catalytic activity of a Mn-cluster in photosynthesis, different artificially constructed manganese complexes are investigated.

    The dinuclear ([Mn2(II,III)L(µ-OAc)2]ClO4), where L is the X-anion of 2-(N,N-Bis(2-methylpyridyl)aminomethyl)-6-(N-(3,5-ditert-butylbenzyl-2-hydroxy)-N-(pyridylmethyl)aminomethyl)-4-methylphenol, an unsymmetric ligand with two coordinating phenolate groups, has been studied. The two Mn-ions are linked via a mono-µ-oxo bridge and two acetate ligands. Q-band Electron Paramagnetic Resonance was conducted on the Unsymmetric Mn2(II,III) Complex. Aquired results show that the complex has a 2600 Gauss broad signal (11 400-14 000 Gauss) with 14-17 lines at g~2 and hyperfines of 120 Gauss. This is consistent with previous X-band studies. Q-band spectra of the Unsymmetric Mn(II,III) display increased hyperfine resolution compared to Qband spectra of the symmetric complex, Mn2(bpmp)(µ-OAC)2. This is noticeable since Unsymmetric Mn2(II,III) and Mn2 (bpmp)(µ-OAC)2 partly overlap in low-frequency experiments (X-band EPR).

    Further investigations are yet to be expected. Nevertheless, the conducted thesis study provides important knowledge in the futuristic goal of building an artificial super-complex.

  • 23.
    Wermelin, Karin
    et al.
    Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine . Linköping University, Faculty of Health Sciences.
    Tengvall, Pentti
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Aspenberg, Per
    Linköping University, Department of Clinical and Experimental Medicine, Orthopaedics and Sports Medicine . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Orthopaedic Centre, Department of Orthopaedics Linköping.
    A bisphosphonate coating improves the bony fixation of stainless steel screws in ovariectomized rats2008Article in journal (Refereed)
    Abstract [en]

    Background: Bisphosphonate coatings improve the fixation of implants in bone. Stainless steels screws inserted in the rat tibia become encapsulated by new bone if they are coated with bisphosphonates in a crosslinked fibrinogen matrix. Thereby, the coating leads to a gradual increase in pull-out force. We now investigate if this bisphosphonate coating is capable to improve the mechanical fixation also in osteoporotic bone.

    Methods: Stainless steel screws were coated with a thin crosslinked fibrinogen matrix. With EDC/NHS coupling technique, pamidronate was bound to carboxylic groups and ibandronate was adsorbed in the fibrinogen matrix. Uncoated stainless steel screws and bisphosphonatecoated screws were inserted bilaterally in the proximal tibia in 10 ovariectomized and 10 sham operated rats. At 2 weeks pull-out force and energy was measured.

    Results: In the ovariectomized rats, pull-out force was 53 % higher for bisphosphonate coated screws compared to control screws. Energy was 44 % higher. The sham operated rats showed a higher variation, and no effect of the coating was found.

    Conclusion: The coating was sufficient to improve fixation in ovariectomized rats

  • 24.
    Quast, Ulrich
    et al.
    Ex University Hospital, Germany.
    Kaulich, Theodor W.
    University Hospital, Germany.
    Alvarez-Romero, Jose T.
    ININ, Mexico.
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Karolinska University Hospital, Sweden.
    Enger, Shirin A.
    McGill University, Canada.
    Medich, David C.
    Worcester Polytech Institute, MA 01609 USA.
    Mourtada, Firas
    Helen F Graham Cancer Centre and Research Institute, DE 19713 USA.
    Perez-Calatayud, Jose
    University Hospital La Fe, Spain; Clin Benidorm, Spain.
    Rivard, Mark J.
    Tufts University, MA 02111 USA.
    Abu Zakaria, G.
    University of Cologne, Germany; Gono University, Bangladesh.
    A brachytherapy photon radiation quality index Q(BT) for probe-type dosimetry2016In: Physica medica (Testo stampato), ISSN 1120-1797, E-ISSN 1724-191X, Vol. 32, no 6, 741-748 p.Article in journal (Refereed)
    Abstract [en]

    Introduction: In photon brachytherapy (BT), experimental dosimetry is needed to verify treatment plans if planning algorithms neglect varying attenuation, absorption or scattering conditions. The detectors response is energy dependent, including the detector material to water dose ratio and the intrinsic mechanisms. The local mean photon energy E(r) must be known or another equivalent energy quality parameter used. We propose the brachytherapy photon radiation quality index Q(BT) ((E) over bar), to characterize the photon radiation quality in view of measurements of distributions of the absorbed dose to water, D-w, around BT sources. Materials and methods: While the external photon beam radiotherapy (EBRT) radiation quality index Q(EBRT) ((E) over bar) = TPR1020((E) over bar) is not applicable to BT, the authors have applied a novel energy dependent parameter, called brachytherapy photon radiation quality index, defined as Q(BT) ((E) over bar) = D-prim(r = 2 cm; theta(0) = 90 degrees)/D-prim(r(0) = 1 cm; theta(0) = 90 degrees), utilizing precise primary absorbed dose data, D-prim, from source reference databases, without additional MC-calculations. Results and discussion: For BT photon sources used clinically, Q(BT) ((E) over bar) enables to determine the effective mean linear attenuation coefficient (mu) over bar (E) and thus the effective energy of the primary photons E-prim(eff)(r(0), theta(0)) at the TG-43 reference position P-ref (r(0) = 1 cm; theta(0) = 90 degrees) being close to the mean total photon energy (E) over bar (tot)(r(0), theta(0)). If one has calibrated detectors, published (E) over bar (tot)(r) and the BT radiation quality correction factor k(Q, Q0)(BT) ((E) over bar, r, theta) for different BT radiation qualities Q and Q(0), the detectors response can be determined and D-w(r, theta) measured in the vicinity of BT photon sources. Conclusions: This novel brachytherapy photon radiation quality index Q(BT) characterizes sufficiently accurate and precise the primary photon` s penetration probability and scattering potential. (C) 2016 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica.

  • 25.
    Lind, Malin
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    Josefsson, Karl Johan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics.
    A CFD Method for Simulation of Gas-Liquid Flow in Cooling Systems: An Eulerian-Eulerian Approach2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When designing modern engines it is important to construct a cooling system that cools the engine structure efficiently. Within the cooling system there is always a certain amount of air which can accumulate and form air pockets in critical areas, such as the water jacket, which can lead to wall degradation. A Computational Fluid Dynamics (CFD) method in STAR-CCM+ from CD-adapco, was derived at Volvo Cars in order to study the accumulation of air bubbles in the water jacket. The method was derived by investigating and evaluating already existing methods. The method initially considered as the best suited was the Eulerian-Eulerian approach. The method was validated against three simpler geometries where experimental data was available. The Eulerian-Eulerian approach treats both phases, liquid and gas, as continuous phases. The idea with the method is to solve the Navier-Stokes equation, the continuity equation and the energy equation for both phases using the Eulerian approach, therefore called Eulerian-Eulerian. The interaction between the two phases was important to model properly which was done by including several interaction models within STAR-CCM+. By tuning different coefficients, which were investigated by a thorough parameter study, the method resembled the experimental data in a satisfying way. The best suited mesh for these simpler geometries was a directed mesh. However, the mesh in the water jacket was automatically generated by STAR-CCM+ and the simpler cases were therefore validated with an automated mesh as well. To capture the experimental data the convection scheme for volume fraction had to be of second order when simulating with automated mesh. This resulted in convergence issues when implementing the method on the water jacket. Instead first order convection scheme, which did not present as satisfying results as second order, had to be implemented. Simulations of the water jacket were performed with two different velocities, that were 10 m/s and 19 m/s, and different flow split ratios for the three outlets. Air with volume fraction 0.1 was injected at the inlet during the first 0.5 s followed by 0.5-1.1 s of further simulation without injecting air. Increased velocity resulted in increased flow through of gas, whereas no big difference could be seen between the different outlet flow split ratios. At two different zones lower pressure was found which resulted in gas holdup. To be able to validate the results from the water jacket, experiments would be necessary to perform in order to provide experimental data for comparison. Velocity profiles from the derived two-phase method resemble the velocity profiles from the one-phase simulation from Volvo, which indicated that the two-phase method did not affect the solution in a remarkable way. Granted that the zones of lower pressure and gas holdup normally coincides, the pressure field from the one-phase simulation could be directly studied, which would lower the computational costs significantly.

  • 26.
    Jogenfors, Jonathan
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    A Classical-Light Attack on Energy-Time Entangled Quantum Key Distribution, and Countermeasures2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Quantum key distribution (QKD) is an application of quantum mechanics that allowstwo parties to communicate with perfect secrecy. Traditional QKD uses polarization of individual photons, but the development of energy-time entanglement could lead to QKD protocols robust against environmental effects. The security proofs of energy-time entangled QKD rely on a violation of the Bell inequality to certify the system as secure. This thesis shows that the Bell violation can be faked in energy-time entangled QKD protocols that involve a postselection step, such as Franson-based setups. Using pulsed and phase-modulated classical light, it is possible to circumvent the Bell test which allows for a local hidden-variable model to give the same predictions as the quantum-mechanical description. We show that this attack works experimentally and also how energy-time-entangled systems can be strengthened to avoid our attack.

    List of papers
    1. Energy-time entanglement, elements of reality, and local realism
    Open this publication in new window or tab >>Energy-time entanglement, elements of reality, and local realism
    2014 (English)In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, E-ISSN 1751-8121, Vol. 47, no 42, 424032- p.Article in journal (Refereed) Published
    Abstract [en]

    The Franson interferometer, proposed in 1989 (Franson 1989 Phys. Rev. Lett. 62 2205-08), beautifully shows the counter-intuitive nature of light. The quantum description predicts sinusoidal interference for specific outcomes of the experiment, and these predictions can be verified in experiment. In the spirit of Einstein, Podolsky, and Rosen it is possible to ask if the quantum-mechanical description (of this setup) can be considered complete. This question will be answered in detail in this paper, by delineating the quite complicated relation between energy-time entanglement experiments and Einstein-Podolsky-Rosen (EPR) elements of reality. The mentioned sinusoidal interference pattern is the same as that giving a violation in the usual Bell experiment. Even so, depending on the precise requirements made on the local realist model, this can imply (a) no violation, (b) smaller violation than usual, or (c) full violation of the appropriate statistical bound. Alternatives include (a) using only the measurement outcomes as EPR elements of reality, (b) using the emission time as EPR element of reality, (c) using path realism, or (d) using a modified setup. This paper discusses the nature of these alternatives and how to choose between them. The subtleties of this discussion needs to be taken into account when designing and setting up experiments intended to test local realism. Furthermore, these considerations are also important for quantum communication, for example in Bell-inequality-based quantum cryptography, especially when aiming for device independence.

    Place, publisher, year, edition, pages
    IOP Publishing: Hybrid Open Access, 2014
    Keyword
    bell inequalities; energy-time entanglement; elements of reality
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-112643 (URN)10.1088/1751-8113/47/42/424032 (DOI)000344222200033 ()
    Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2017-10-20
    2. Hacking the Bell test using classical light in energy-time entanglement–based quantum key distribution
    Open this publication in new window or tab >>Hacking the Bell test using classical light in energy-time entanglement–based quantum key distribution
    Show others...
    2015 (English)In: Science Advances, ISSN 2375-2548, Vol. 1, no 11, 1-7 p., e1500793Article in journal (Refereed) Published
    Abstract [en]

    Photonic systems based on energy-time entanglement have been proposed to test local realism using the Bell inequality. A violation of this inequality normally also certifies security of device-independent quantum key distribution (QKD) so that an attacker cannot eavesdrop or control the system. We show how this security test can be circumvented in energy-time entangled systems when using standard avalanche photodetectors, allowing an attacker to compromise the system without leaving a trace. We reach Bell values up to 3.63 at 97.6% faked detector efficiency using tailored pulses of classical light, which exceeds even the quantum prediction. This is the first demonstration of a violation-faking source that gives both tunable violation and high faked detector efficiency. The implications are severe: the standard Clauser-Horne-Shimony-Holt inequality cannot be used to show device-independent security for energy-time entanglement setups based on Franson’s configuration. However, device-independent security can be reestablished, and we conclude by listing a number of improved tests and experimental setups that would protect against all current and future attacks of this type.

    Place, publisher, year, edition, pages
    American Association for the Advancement of Science, 2015
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-114210 (URN)10.1126/sciadv.1500793 (DOI)
    Note

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

    At the time for thesis presentation name of publication was: A Classical-Light Attack on Energy-Time Entangled Quantum Key Distribution, and Countermeasures

    Available from: 2015-02-13 Created: 2015-02-13 Last updated: 2017-10-20Bibliographically approved
  • 27.
    Schmitz, Marcus
    et al.
    Dept. of Electronics and Computer Science University of Southampton.
    Al Hashimi, Bashir M.
    Dept. of Electronics and Computer Science University of Southampton.
    Eles, Petru Ion
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    A Co-Design Methodology for Energy-Efficient Multi-Mode Embedded Systems with Consideration of Mode Execution Probabilities2003In: Design Automation and Test in Europe DATE 2003 Conference,2003, Munich, Germany: IEEE Computer Society Press , 2003, 960- p.Conference paper (Refereed)
    Abstract [en]

    Multi-mode systems are characterised by a set of interacting operational modes to support different functionalities and standards. In this paper, we present a co-design methodology for multi-mode embedded systems that produces energy-efficient implementations. Based on the key observation that operational modes are executed with different probabilities, i.e., the system spends uneven amounts of time in the different modes, we develop a novel codesign technique that exploits this property to significantly reduce energy dissipation. We conduct several experi-ments, including a smart phone real-life example, that demonstrate the effectiveness of our approach. Reductions in power consumption of up to 64% are reported.

  • 28.
    Field, M. R.
    et al.
    RMIT University, Australia.
    Carlsson, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Partridge, J. G.
    RMIT University, Australia.
    McCulloch, D. G.
    RMIT University, Australia.
    McKenzie, D. R.
    University of Sydney, Australia.
    Bilek, M. M. M.
    University of Sydney, Australia.
    A combinatorial comparison of DC and high power impulse magnetron sputtered Cr2AlC2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 259, 746-750 p.Article in journal (Refereed)
    Abstract [en]

    Using a combinatorial approach, Cr, Al and C have been deposited onto sapphire wafer substrates by High Power Impulse Magnetron Sputtering (HiPIMS) and DC magnetron sputtering. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and X-ray diffraction were employed to determine the composition and microstructure of the coatings and confirm the presence of the Cr2AlC MAX phase within both coatings. One location in both the DCMS and HiPIMS coatings contained only MAX phase Cr2AlC. The electrical resistivity was also found to be nearly identical at this location and close to that reported from the bulk, indicating that the additional energy in the HiPIMS plasma was not required to form high quality MAX phase Cr2AlC.

  • 29.
    Strömdahl, Helge
    Linköping University, Faculty of Educational Sciences. Linköping University, Department of Social and Welfare Studies, Natural Science - Medicine - Esthetics - Communication .
    A commentary on the attainment of the scientific concept energy1996In: 5:e Nordiska forskarsymposiet om undervisning i naturvetenskap i skolan,1996, Kristianstad: Fagus Förlag, Högskolan Kristianstad, ISBN 91972 88403 , 1996, 489- p.Conference paper (Refereed)
    Abstract [en]

      

  • 30.
    Elwing, B
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Department of Health and Society, Division of Preventive and Social Medicine and Public Health Science.
    Kullberg, C
    Kucinskiene, Z
    Björegren, M
    Abaravicius, A
    Kristenson, Margareta
    Linköping University, Faculty of Health Sciences. Linköping University, Department of health and environment.
    A comparative study of food intake between Lithuanian and Swedish middle-aged men: The LiVicordia study2001In: Scandinavian Journal of Nutrition/Næringsforskning, ISSN 1102-6480, Vol. 45, no 3, 126-130 p.Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Background: In 1994, the mortality in coronary heart disease was four times higher among Lithuanian middle-aged men than among Swedish men. Over the period 1993-1995, the LiVicordia study investigated possible causes for this difference. We have earlier reported lower serum levels of cholesterol and higher susceptibility of low-density lipoprotein cholesterol for oxidation among Lithuanian men. Objective: In this part of the study, the aim was to compare mean estimates of food intake. Design: Cross-sectional study of random samples of 50-year-old men from each of the cities of Link÷ping, Sweden and Vilnius, Lithuania (n=150). The volunteers were interviewed about their food intake with the 24-hour recall method. Results: We found no differences in total energy intake, but Vilnius men had a higher energy intake from fat. Vilnius men consumed more fat from meat and less vegetable fat, while fat intake from dairy products was almost the same. Also, Vilnius men had a higher intake of vegetables, while Link÷ping men had a higher intake of fruit and berries. Conclusion: The observed differences in food consumption and dietary composition are partly consistent with the higher CHD mortality among Lithuanian men. However, data on biomarkers indicate that other dietary and lifestyle factors play a role.

  • 31.
    Hook, F.F
    et al.
    Department of Applied Physics, Chalmers Institute of Technology, SE-412 96 Göteborg, Sweden.
    Voros, J.
    Vörös, J., Laboratory for Surface Science and Technology, Department of Materials, Swiss Federal Institute of Technology, CH-8092 Zürich, Switzerland.
    Rodahl, M.
    Department of Applied Physics, Chalmers Institute of Technology, SE-412 96 Göteborg, Sweden.
    Kurrat, R.
    Laboratory for Surface Science and Technology, Department of Materials, Swiss Federal Institute of Technology, CH-8092 Zürich, Switzerland.
    Boni, P.
    Böni, P., Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
    Ramsden, J.J.
    Department of Biophysical Chemistry, Biocenter of the University, CH-4056 Basel, Switzerland.
    Textor, M.
    Laboratory for Surface Science and Technology, Department of Materials, Swiss Federal Institute of Technology, CH-8092 Zürich, Switzerland.
    Spencer, N.D.
    Laboratory for Surface Science and Technology, Department of Materials, Swiss Federal Institute of Technology, CH-8092 Zürich, Switzerland.
    Tengvall, Pentti
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Gold, J.
    Department of Applied Physics, Chalmers Institute of Technology, SE-412 96 Göteborg, Sweden.
    Kasemo, B.
    Department of Applied Physics, Chalmers Institute of Technology, SE-412 96 Göteborg, Sweden.
    A comparative study of protein adsorption on titanium oxide surfaces using in situ ellipsometry, optical waveguide lightmode spectroscopy, and quartz crystal microbalance/dissipation2002In: Colloids and Surfaces B: Biointerfaces, ISSN 0927-7765, Vol. 24, no 2, 155-170 p.Article in journal (Refereed)
    Abstract [en]

    The adsorption kinetics of three model proteins - human serum albumin, fibrinogen and hemoglobin - has been measured and compared using three different experimental techniques: optical waveguide lightmode spectroscopy (OWLS), ellipsometry (ELM) and quartz crystal microbalance (QCM-D). The studies were complemented by also monitoring the corresponding antibody interactions with the pre-adsorbed protein layer. All measurements were performed with identically prepared titanium oxide coated substrates. All three techniques are suitable to follow in-situ kinetics of protein-surface and protein-antibody interactions, and provide quantitative values of the adsorbed adlayer mass. The results have, however, different physical contents. The optical techniques OWLS and ELM provide in most cases consistent and comparable results, which can be straightforwardly converted to adsorbed protein molar ('dry') mass. QCM-D, on the other hand, produces measured values that are generally higher in terms of mass. This, in turn, provides valuable, complementary information in two respects: (i) the mass calculated from the resonance frequency shift includes both protein mass and water that binds or hydrodynamically couples to the protein adlayer, and (ii) analysis of the energy dissipation in the adlayer and its magnitude in relation to the frequency shift (c.f. adsorbed mass) provides insight about the mechanical/structural properties such as viscoelasticity. © 2002 Elsevier Science B.V. All rights reserved.

  • 32. Olafsson, HO
    et al.
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Sveinbjornsson, EO
    A comparison between SiO2/4H-SiC interface traps on (0001) and (1120) faces2004In: Materials Science Forum, ISSN 0255-5476, Vol. 457-460, 1305-1308 p.Article in journal (Refereed)
    Abstract [en]

    We present thermally stimulated current (TSC) measurements made on metal-oxide-semiconductor (MOS) structures fabricated on off-axis (0001) or on-axis (1120) face n-type 4H-SiC with wet or dry oxides. The TSC measurements show the interface trap spectra of traps with activation energies in the range from 0.1 to 0.6 eV. Varying the charging and discharging conditions, we are able to distinguish between two types of traps which are both present on (0001) and (1120) face samples. One type is sensitive to the electric field during discharging but is insensitive to the charging temperature, while the other type is insensitive to the electric field during discharging but can not capture electrons at low temperatures. We find that, compared to the (0001) face, the traps at the (1120) face are shifted in energy about 0.1 eV towards higher activation energies. In all cases, For wet or dry oxides made on the (0001) or the (1120) face, the number density of traps is above 7x10(12) cm(-2).

  • 33. Alfredsson, Maria
    et al.
    Ojamae, Lars
    Hermansson, Kersti
    Uppsala universitet, Strukturkemi.
    A comparison of Hartree-Fock, MP2, and DFT results for the HCN dimer and crystal1996In: INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Vol. 60, no 3, 767-777 p.Article in journal (Refereed)
    Abstract [en]

    A number of hydrogen-bond related quantities-geometries, interaction energies, dipole moments, dipole moment derivatives, and harmonic vibrational frequencies-were calculated at the Hartree-Fock, MP2, and different DFT levels for the HCN dimer and the pe

  • 34.
    Burgard, W.
    et al.
    University of Freiburg.
    Stachniss, C.
    University of Freiburg.
    Grisetti, G.
    University of Freiburg.
    Steder, B.
    University of Freiburg.
    Kümmerle, R.
    University of Freiburg.
    Dornhege, C.
    University of Freiburg.
    Ruhnke, M.
    University of Freiburg.
    Kleiner, Alexander
    University of Freiburg.
    Tardós, Juan D.
    University of Freiburg.
    A Comparison of SLAM Algorithms Based on a Graph of Relations2009In: IEEE/RSJ Int. Conf. on Intelligent Robots and Systems (IROS), IEEE conference proceedings, 2009, 2089-2095 p.Conference paper (Refereed)
    Abstract [en]

    In this paper, we address the problem of creating an objective benchmark for comparing SLAM approaches. We propose a framework for analyzing the results of SLAM approaches based on a metric for measuring the error of the corrected trajectory. The metric uses only relative relations between poses and does not rely on a global reference frame. The idea is related to graph-based SLAM approaches, namely to consider the energy that is needed to deform the trajectory estimated by a SLAM approach into the ground truth trajectory. Our method enables us to compare SLAM approaches that use different estimation techniques or different sensor modalities since all computations are made based on the corrected trajectory of the robot. We provide sets of relative relations needed to compute our metric for an extensive set of datasets frequently used in the SLAM community. The relations have been obtained by manually matching laser-range observations to avoid the errors caused by matching algorithms. Our benchmark framework allows the user an easy analysis and objective comparisons between different SLAM approaches.

  • 35.
    Öberg, Lasse
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Xu, Youzhi
    A Complete Energy Dissipation Model for Wireless Sensor Networks2007In: In Proceedings of the International Conference on Sensor Technologies and Applications, Valencia, Spain, October 14-20, IEEE , 2007, 531-540 p.Conference paper (Refereed)
    Abstract [en]

    Advances in both microelectronics and wireless commu- nication technology have made it possible to develop and manufacture low cost and energy efficient sensor nodes. To compare different designs and protocols with respect to both energy and delay constraints an energy dissipation model is needed that takes these aspects into account. In this paper we propose a complete energy dissipation model for wire- less sensor networks that uses four operation states. These states are based on the basic sensor nodes architecture and actual working conditions of a sensor node. It also takes into account the transition between the operation states, such that a decision to change operation state can be more accurately determined. In this paper we also present mea- sured values for both the power consumed in each operation state and the time it takes to complete a transition between two operation states.

  • 36.
    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
    2017 (English)In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 16, no 2, 408-421 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, 2017
    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
    Note

    Funding agencies: Swedish Research Council; EU FP7 Marie Curie [324515, 329313]; National Science Foundation [CCF-0728966, CCF-1420651]; ONR [N000141410107]

    Available from: 2014-11-27 Created: 2014-11-27 Last updated: 2017-03-27Bibliographically 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, Vol. 3, no 3, 322-331 p.Article in journal (Other academic) Published
    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: 2016-11-25Bibliographically 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)In: 2016 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, IEEE , 2016, 1446-1450 p.Conference paper, Published 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, E-ISSN 2157-8117
    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)000390098701102 ()
    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: 2017-01-30Bibliographically approved
  • 37.
    Karlsson, Fredrik
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Moshfegh, Bahram
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    A comprehensive investigation of a low-energy building in Sweden2007In: Renewable Energy, ISSN 0960-1481, Vol. 32, no 11, 1830-1841 p.Article in journal (Refereed)
    Abstract [en]

    In Sweden, the building sector alone accounts for almost 40% of the total energy demand and people spend more than 80% of their time indoors. Reducing energy demand in the buildings is essential to the achievement of a sustainable built environment. At the same time, it is important to not deteriorate people's health, well-being and comfort in buildings. Thus, designing healthy and energy efficient buildings are one of the most challenging tasks for building scientists. A low-energy building that uses less than half of the purchased energy of a comparable typical Swedish building has been investigated from different viewpoints in an attempt to represent the building at different system levels. First, the ventilation performance in different rooms using the tracer gas method is reported. Second, results from simulations and in situ measurements are used to analyse the building's power demand and energy performance. The household's behaviour and their impact on energy usage as well as acceptance are reported. Finally, the CO2 emissions with regard to the energy usage are analysed on the basis of different supply energy forms from surrounding energy systems, for example a Swedish and European electricity mix, or district heating as a substitute for electrical heating.

  • 38.
    Johansson, Jonas
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Belov, Ilja
    Jönköping University, School of Engineering, Department of Mechanical Engineering, Jönköping.
    Johnson, Erland
    SP Technical Research Institute of Sweden, Borås, Sweden.
    Leisner, Peter
    SP Technical Research Institute of Sweden, Borås, Sweden.
    A computational method for evaluating the damage in a solder joint of an electronic package subjected to thermal loadsManuscript (preprint) (Other academic)
    Abstract [en]

    Purpose – The purpose of this paper is to introduce a novel computational method to evaluate damage accumulation in a solder joint of an electronic package, when exposed to operating temperature environment. A procedure to implement the method is suggested, and a discussion of the method and its possible applications is provided in the paper.

    Originality/value – The method enables increased accuracy in thermal fatigue life prediction of solder joints. Combined with other failure mechanisms, it may contribute to the accuracy of reliability assessment of electronic packages.

    Design/methodology/approach – Methodologically, interpolated response surfaces based on specially designed finite element simulation runs, are employed to compute a damage metric at regular time intervals of an operating temperature profile. The developed method has been evaluated on a finite-element model of a lead-free PBGA256 package, and accumulated creep strain energy density has been chosen as damage metric.

    Findings – The method has proven to be two orders of magnitude more computationally efficient compared to finite element simulation. A general agreement within 3% has been found between the results predicted with the new method, and finite element simulations when tested on a number of temperature profiles from an avionic application. The solder joint temperature ranges between +25°C and +75°C.

    Practical implications – The method can be implemented as part of reliability assessment of electronic packages in the design phase.

  • 39.
    Svensson, Klas
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Rohdin, Patrik
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Moshfegh, Bahram
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    A computational parametric study on the development of confluent round jet arrays2015In: European journal of mechanics. B, Fluids, ISSN 0997-7546, E-ISSN 1873-7390, Vol. 53, 129-147 p.Article in journal (Refereed)
    Abstract [en]

    In this study, Computational Fluid Dynamics (CFD) and response surface methodology is employed in a parametrical investigation of an in-line array of confluent round jets. Confluent round jet arrays are common within several fields of engineering, as detailed knowledge of the flow field development of confluent round jets is of great importance to design engineers working with, for example, chemical mixing, multiple jet burners, waste water disposal systems or ventilation supply devices. In this paper, five independent factors affecting flow field development are investigated with a multi-variable approach using a Box–Behnken design method.

    The results include decay of maximum velocity, turbulence intensity, location of merging and combined points and development of volumetric flow rate. Dimensionless nozzle spacing, S/d0S/d0, is an important design parameter and has a large impact on several properties, such as merging and combined points, decay of maximum velocity, and development of turbulence intensity. Other factors, such as the number of jets per row and inlet velocity, are also of importance. The analysis of decay in maximum velocity led to the definition of a new zone of development, referred to as the Confluent Core Zone (CCZ), as its behaviour is reminiscent of the potential core of a single jet. The CCZ has uniform velocity, lacks considerable decay in streamwise velocity and has a rather low turbulence intensity. The CCZ has a characteristic footprint in confluent round jet arrays, and its properties are investigated in detail.

    The development of volumetric flow can be divided into two regions. The initial region, close to the nozzles, features a high entrainment but decreasing entrainment rate. As the jets combine, the entrainment rate is lower, but rather constant. While S/d0S/d0 is generally an important design parameter, there is no direct correlation between S/d0S/d0 and entrainment rate of the combined jet.

  • 40.
    Daneva, Maria
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Optimization .
    Lindberg, Per Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Optimization .
    A Conjugate Direction Frank-Wolfe Method with Applications to the Traffic Assignment Problem2003In: Operations Research Proceedings 2002: Selected Papers of the International Conference on Operations Research (SOR 2002), Klagenfurt, September 2-5, 2002" / [ed] Leopold-Wildburger, U, Springer , 2003, -550 p.Chapter in book (Other academic)
    Abstract [en]

    This proceedings volume contains a selection of papers presented at the International Conference on Operations Research (SOR 2002).The contributions cover the broad interdisciplinary spectrum of Operations Research and present recent advances in theory, development of methods, and applications in practice. Subjects covered are Production, Logistics and Supply Chain Production, Marketing and Data Analysis, Transportation and Traffic, Scheduling and Project Management, Telecommunication and Information Technology, Energy and Environment, Public Economy, Health, Agriculture, Education, Banking, Finance, Insurance, Risk Management, Continuous Optimization, Discrete and Combinatorial Optimization, Stochastic and Dynamic Programming, Simulation, Control Theory, Systems Dynamics, Dynamic Games, Game Theory, Auctioning and Bidding, Experimental Economics, Econometrics, Statistics and Mathematical Economics, Fuzzy Logic, Multicriteria Decision Making, Decision Theory.

  • 41.
    Sharifimajd, Babak
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    A Continuum Framework for Modeling the Excitation–Contraction Coupling of Smooth Muscle2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Excitation-contraction coupling of smooth muscle refers to a chain of coupled physiological processes which convert a stimulus to a mechanical response. These processes can be disassociated into ionic transport during cell membrane excitation, activation of myosin light chains, and muscle contraction caused by actin-myosin interaction (filament sliding). This thesis concerns the development of a framework which allows to model the smooth muscle excitation-contraction coupling constitutively by applying the principle of virtual power and dissipation inequality. In doing so, the transport of ions through membrane channels is characterized by an ionic flux and an ionic supply, both governed by an electrochemical potential energy. By letting the Helmholtz free energy to be dependent on the myosin light chain configurations during contraction, the myosin light chain activation process, i.e., myosin phosphorylation, is included. The activation process links the membrane excitation to the filament sliding. A contractile element is presented to replicate the active deformation caused by the filament sliding within the smooth muscle cell. This deformation is coupled to the overall deformation of the muscle tissue by assuming a distinct principal alignment for the contractile elements.

    By employing this framework, an electro-chemo-mechanical model is derived by which the mechanical response of smooth muscle to an electrical stimulus is determined. This model is evaluated by comparing the model response to the experimental isometric stress data obtained from rat uterine smooth muscle tissue. By implementing this model in a finite element program, human uterine contractions during labor are simulated. This simulation determines important clinical factors, e.g., intrauterine pressure and provides the opportunity to investigate the effect of physiological and structural parameters on the uterine contractility.

    Finally, a methodology to accommodate individualized parameters from intrauterine pressure measurements is established. This methodology allows to develop models with potentials of being used clinically to diagnose difficulties during labor and delivery.

    List of papers
    1. A continuum model for skeletal muscle contraction at homogeneous finite deformations
    Open this publication in new window or tab >>A continuum model for skeletal muscle contraction at homogeneous finite deformations
    2013 (English)In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 12, no 5, 965-973 p.Article in journal (Refereed) Published
    Abstract [en]

    The contractile force in skeletal muscle models is commonly postulated to be the isometric force multiplied by a set of experimentally motivated functions which account for the muscle’s active properties. Although both flexible and simple, this approach does not automatically guarantee a thermodynamically consistent behavior. In contrast, the continuum mechanical model proposed herein is derived from fundamental principles in mechanics and guarantees a dissipative behavior. Further, the contractile force is associated with a friction clutch which provides a simple and well-defined macroscopic model for cycling cross-bridges. To show the performance of the model, it is specialized to standard experiments for rabbit tibialis anterior muscle. The results show that the model is able to capture important characteristics of skeletal muscle.

    Place, publisher, year, edition, pages
    Springer, 2013
    Keyword
    Skeletal muscle, Contractile element, Dissipation inequality, Strain-energy function, Continuum model
    National Category
    Other Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-85805 (URN)10.1007/s10237-012-0456-x (DOI)000324378900008 ()
    Funder
    Swedish Research Council
    Available from: 2012-11-28 Created: 2012-11-28 Last updated: 2015-09-02Bibliographically approved
    2. A continuum model for excitation–contraction of smooth muscle under finite deformations
    Open this publication in new window or tab >>A continuum model for excitation–contraction of smooth muscle under finite deformations
    2014 (English)In: Journal of Theoretical Biology, ISSN 0022-5193, E-ISSN 1095-8541, Vol. 355, 1-9 p.Article in journal (Refereed) Published
    Abstract [en]

    The main focus in most of continuum based muscle models is the muscle contraction dynamics while other physiological processes governing muscle contraction, e.g., the cell membrane excitation and the activation, are ignored. These latter processes are essential to initiate contraction and to determine the amount of generated force, and by excluding them, the developed model cannot replicate the true behavior of the muscle in question. The aim of this study is to establish a thermodynamically and physiologically consistent framework which allows to model smooth muscle contraction by including cell membrane excitability and kinetics of myosin phosphorylation, along with dynamics of smooth muscle contraction. The model accounts for these processes through a set of coupled dissipative constitutive equations derived by applying the first principles. To show the performance of the derived model, it is evaluated for two different cases: a mechanochemical study of pig taenia coli cells where the excitation process is excluded, and a complete excitation–contraction process of rat myometrium. The results show that the model is able to replicate important aspects of the smooth muscle EC process acceptably.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keyword
    Smooth muscle excitation–contraction, Smooth muscle continuum model, The membrane model, Hodgkin-Huxley model, Hai-Murphy model
    National Category
    Other Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-100778 (URN)10.1016/j.jtbi.2014.03.016 (DOI)000337865100001 ()
    Available from: 2013-11-12 Created: 2013-11-12 Last updated: 2015-09-02Bibliographically approved
    3. Simulating uterine contraction by using an electro-chemo-mechanical model
    Open this publication in new window or tab >>Simulating uterine contraction by using an electro-chemo-mechanical model
    2016 (English)In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 15, no 3, 497-510 p.Article in journal (Refereed) Published
    Abstract [en]

    Contractions of uterine smooth muscle cells consist of a chain of physiological processes. These contractions provide the required force to expel the fetus from the uterus. The inclusion of these physiological processes is, therefore, imperative when studying uterine contractions. In this study, an electro-chemo-mechanical model to replicate the excitation, activation, and contraction of uterine smooth muscle cells is developed. The presented modeling strategy enables efficient integration of knowledge about physiological processes at the cellular level to the organ level. The model is implemented in a three-dimensional finite element setting to simulate uterus contraction during labor in response to electrical discharges generated by pacemaker cells and propagated within the myometrium via gap junctions. Important clinical factors, such as uterine electrical activity and intrauterine pressure, are predicted using this simulation. The predictions are in agreement with clinically measured data reported in the literature. A parameter study is also carried out to investigate the impact of physiologically related parameters on the uterine contractility.

    Place, publisher, year, edition, pages
    Springer, 2016
    Keyword
    Excitation-contraction model of uterine smooth muscle; Uterus contraction; Intrauterine pressure; Uterine electrical activity
    National Category
    Applied Mechanics
    Identifiers
    urn:nbn:se:liu:diva-121013 (URN)10.1007/s10237-015-0703-z (DOI)000376014800002 ()26162461 (PubMedID)
    Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2016-06-13Bibliographically approved
    4. Identification of the mechanical parameters for the human uterus in vivo using intrauterine pressure measurements
    Open this publication in new window or tab >>Identification of the mechanical parameters for the human uterus in vivo using intrauterine pressure measurements
    2017 (English)In: International Journal for Numerical Methods in Biomedical Engineering, ISSN 2040-7939, E-ISSN 2040-7947, Vol. 33, no 1, 1-11 p.Article in journal (Refereed) Published
    Abstract [en]

    There are limited experimental data to characterize the mechanical response of human myometrium. A method is presented in this work to identify mechanical parameters describing the active response of human myometrium from the in vivo intrauterine pressure measurements. A finite element model is developed to compute the intrauterine pressure during labor in response to an increase in the intracellular calcium ion concentration within myometrial smooth muscle cells. The finite element model provides the opportunity to tune mechanical parameters in order to fit the computed intrauterine pressure to in vivo measurements. Since the model is computationally expensive, a cheaper meta-model is generated to approximate the model response. By fitting the meta-model response to the in vivo measurements, the parameters used to determine the active response of human myometrial smooth muscle are identified.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2017
    Keyword
    human uterine smooth muscle mechanics, intrauterine pressure, parameter identification, response surface methodology
    National Category
    Applied Mechanics Mechanical Engineering
    Identifiers
    urn:nbn:se:liu:diva-121014 (URN)10.1002/cnm.2778 (DOI)000393964900001 ()26915913 (PubMedID)2-s2.0-84962638845 (Scopus ID)
    Note

    At the time of the thesis presentation this publication was in status Manuscript.

    Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2017-03-27Bibliographically approved
  • 42.
    Sharifimajd, Babak
    et al.
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    Stålhand, Jonas
    Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
    A continuum model for skeletal muscle contraction at homogeneous finite deformations2013In: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 12, no 5, 965-973 p.Article in journal (Refereed)
    Abstract [en]

    The contractile force in skeletal muscle models is commonly postulated to be the isometric force multiplied by a set of experimentally motivated functions which account for the muscle’s active properties. Although both flexible and simple, this approach does not automatically guarantee a thermodynamically consistent behavior. In contrast, the continuum mechanical model proposed herein is derived from fundamental principles in mechanics and guarantees a dissipative behavior. Further, the contractile force is associated with a friction clutch which provides a simple and well-defined macroscopic model for cycling cross-bridges. To show the performance of the model, it is specialized to standard experiments for rabbit tibialis anterior muscle. The results show that the model is able to capture important characteristics of skeletal muscle.

  • 43.
    Sciarretta, A.
    et al.
    IFP Energies Nouvelles, France .
    Serrao, L.
    Dana Corporation, Italy.
    Dewangan, P.C.
    IFP Energies Nouvelles, France; IFP School, France .
    Tona, P.
    IFP Energies Nouvelles, France .
    Bergshoeff, E.N. D.
    TU Eindhoven, Netherlands.
    Bordons, C.
    University of Seville, Spain .
    Charmpa, L.
    IFP Sch, France Continental, France .
    Elbert, Ph.
    ETH Zurich, Switzerland.
    Eriksson, Lars
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Hofman, T.
    TU Eindhoven, Netherlands .
    Hubacher, M.
    TU Eindhoven, Netherlands .
    Isenegger, R.
    TU Eindhoven, Netherlands .
    Lacandia, F.
    Ohio State University, USA.
    Laveau, A.
    IFP School, France.
    Li, H.
    IFP School, France.
    Marcos, D.
    University of Seville, Spain .
    Nueesch, T.
    ETH Zurich, Switzerland.
    Onori, S.
    Ohio State University, USA .
    Pisu, P.
    Clemson University, USA .
    Rios, J.
    Clemson University, USA .
    Silvas, E.
    TU Eindhoven, Netherlands .
    Sivertsson, Martin
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    Tribioli, L.
    Ohio State University, USA .
    van der Hoeven, A.-J.
    TU Eindhoven, Netherlands .
    Wu, M.
    IFP School, France.
    A control benchmark on the energy management of a plug-in hybrid electric vehicle2014In: Control Engineering Practice, ISSN 0967-0661, Vol. 29, 287-298 p.Article in journal (Refereed)
    Abstract [en]

    A benchmark control problem was developed for a special session of the IFAC Workshop on Engine and Powertrain Control, Simulation and Modeling (E-COSM 12), held in Rueil-Malmaison, France, in October 2012. The online energy management of a plug-in hybrid-electric vehicle was to be developed by the benchmark participants. The simulator, provided by the benchmark organizers, implements a model of the GM Voltec powertrain. Each solution was evaluated according to several metrics, comprising of energy and fuel economy on two driving profiles unknown to the participants, acceleration and braking performance, computational performance. The nine solutions received are analyzed in terms of the control technique adopted (heuristic rule-based energy management vs. equivalent consumption minimization strategies, ECMS), battery discharge strategy (charge depleting-charge sustaining vs. blended mode), ECMS implementation (vector-based vs. map-based), ways to improve the implementation and improve the computational performance. The solution having achieved the best combined score is compared with a global optimal solution calculated offline using the Pontryagins minimum principle-derived optimization tool HOT.

  • 44.
    Ruggiero, Martino
    et al.
    DEIS University of Bologna, Italy.
    Gioia, Pari
    DEIS University of Bologna, Italy.
    Alessio, Guerri
    DEIS University of Bologna, Italy.
    Benini, Luca
    DEIS University of Bologna, Italy.
    Michela, Milano
    DEIS University of Bologna, Italy.
    Bertozzi, Davide
    ENDIF University of Ferrara, Italy.
    Andrei, Alexandru
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    A Cooperative, Accurate Solving Framework for Optimal Allocation, Scheduling and Frequency Selection on Energy-Efficient MPSoCs2006In: Intl. Symposium on System-on-Chip SOC06,2006, 2006Conference paper (Refereed)
    Abstract [en]

    Most problems addressed by the software optimization flow for multi-processor systems-on-chip (MPSoCs) are NP-complete, and have been traditionally tackled by means of heuristics and highlevel approximations. Complete approaches have been effectively deployed only under unrealistic simplifying assumptions. We propose a novel methodology to formulate and solve to optimality the allocation, scheduling and discrete voltage selection problem for variable voltage/frequency MPSoCs, minimizing the system energy dissipation and the overhead for frequency switching. We integrate the optimization and validation steps to increase the accuracy of cost models and the confidence in quality of results. Two demonstrators are used to show the viability of the proposed methodology.

  • 45.
    Kissavos, Andreas E.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Shallcross, Sam
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Meded, V.
    Department of Physics, Uppsala University, Uppsala, Sweden.
    Kaufman, L.
    Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    A critical test of ab initio and CALPHAD methods: The structural energy difference between bcc and hcp molybdenum2005In: Calphad, ISSN 0364-5916, Vol. 29, no 1, 17-23 p.Article in journal (Refereed)
    Abstract [en]

    Ab initio calculations of the enthalpy of formation of bcc, fcc, and hcp Ru–Mo alloys have been performed for random, ordered, and partially ordered structures. The lattice stability of the bcc and hcp forms of Mo is isolated in order to compare the hcp–bcc difference calculated by ab initio and CALPHAD methods with experimental measurements of the enthalpy of formation of Ru–Mo alloys. The significance of this comparison in calculating the Mo–Ru phase diagram is illustrated. The results of these considerations suggest a rational method for coupling ab initio and CALPHAD techniques might be utilization of the ab initio methods for calculation of the isostructural energies of formation for binary bcc, hcp, and fcc solutions while retaining the CALPHAD lattice stabilities in the calculation of phase diagrams.

  • 46.
    Keshmiri, Vahid
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Larsen, C.
    Umeå University, Sweden.
    Edman, L.
    Umeå University, Sweden.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Tu, Deyu
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    A Current Supply with Single Organic Thin-Film Transistor for Charging Supercapacitors2016In: THIN FILM TRANSISTORS 13 (TFT 13), ELECTROCHEMICAL SOC INC , 2016, Vol. 75, no 10, 217-222 p.Conference paper (Refereed)
    Abstract [en]

    We present a current supply, comprising a single organic thin-film transistor (OTFT), for the charging of supercapacitors. The current supply takes power from the electric grid (115 V AC, US standard), converts the AC voltage to a quasi-constant DC current (similar to 0.1 mA) regardless of the impedance of the load, and charges the supercapacitor. Solution-processed OTFTs based on the popular polymeric semiconductor poly(3-hexylthiophene- 2,5-diyl) have been developed to rectify the 115 V AC voltage. A diodeconfigured OTFT was used as a half-wave rectifier. The single OTFT current supply was demonstrated to charge a 220 mF supercapacitor to 1 V directly using 115 V AC voltage as the input. This work paves the road towards all-printable supercapacitor energy-storage systems with integrated chargers, which enable direct charging from a power outlet.

  • 47.
    Öberg, Per
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
    A DAE Formulation for Multi-Zone Thermodynamic Models and its Application to CVCP Engines2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the automotive area there are ever increasing demands from legislators and customers on low emissions and good fuel economy. In the process of developing and investigating new technologies, that can meet these demands, modeling and simulation have become important as standard engineering tools. To improve the modeling process new concepts and tools are also being developed.

    A formulation of a differential algebraic equation (DAE) that can be used for simulation of multi-zone in-cylinder models is extended and analyzed. Special emphasis is placed on the separation between thermodynamic state equations and the thermodynamic properties. This enables implementations with easy reuse of model components and analysis of simulation results in a structured manner which gives the possibility to use the formulation in a large number of applications. The introduction and depletion of zones are handled and it is shown that the DAE formulation has a unique solution as long as the gas model fulfills a number of basic criteria. Further, an example setup is used to validate that energy, mass, and volume are preserved when using the formulation in computer simulations. In other words, the numerical solution obeys the thermodynamic state equation and the first law of thermodynamics, and the results are consistent and converge as tolerances are tightened. As example applications, the DAE formulation is used to simulate spark ignited SI and Diesel engines as well as simple control volumes and 1-dimensional pipes. It is thus shown that the DAE formulation is able to adapt to the different requirements of the SI and Diesel engine models.

    An interesting application is the SI engine with continuously variable cam phasing (CVCP), which is a technology that reduces the fuel consumption. It influences the amount of air and residual gases in the engine in a non trivial manner and this SI application is used to evaluate three control oriented models for cylinder air charge and residual mass fraction for a CVCP-engine both for static and transient conditions. The models are: a simple generalized flow restriction model created with physical insight and two variants of a model that is based on an energy balance at intake valve closing (IVC). The two latter models require measurement of cylinder pressure and one also requires an air mass flow measurement. Using the SI model as reference it is shown that transients in cam positions have a large impact on air charge and residual mass fraction, and the ability of the models to capture these effects is evaluated. The main advantages of the generalized flow restriction model are that it is simple and does not require measurement of the cylinder pressure but it is also the model with the largest errors for static operating points and highest sensitivity in transients. The two models that use an energy balance at IVC both handle the transient cycles well. They are, however, sensitive to the temperature at IVC. For static cycles it is therefore advantageous to use the model with air mass flow measurement since it is less sensitive to input data. During transients however, if the external measurement is delayed, it is better to use the model that does not require the air mass flow.

    The conclusion is that the DAE formulation is a flexible, robust, tool, and that it is well suited for multi-zone in-cylinder models as well as models for manifolds and pipes outside the cylinder.

    List of papers
    1. Control Oriented Modeling of the Gas Exchange Process in Variable Cam Timing Engines
    Open this publication in new window or tab >>Control Oriented Modeling of the Gas Exchange Process in Variable Cam Timing Engines
    2006 (English)In: SAE Technical Paper 2006-01-0660, SAE , 2006Conference paper, Published paper (Refereed)
    Abstract [en]

    Variable cam timing engines pose new questions for engine control system designers. The cam timing directly influences cylinder air charge and residual mass fraction. Three models that predict residual mass fraction are investigated for a turbocharged dual independent Variable Cam Timing (VCT) engine. The three models (Fox et. al. 1993, Ponti et. al. 2002, and Mladek et. al. 2000) that all have real time capabilities are evaluated and validated against data from a crank angle based reference model. None of these models have previously been validated to cover this engine type. It is shown that all three models can be extended to dual independent VCT engines and that they also give a good description of the residual gas fraction. However, it is shown that the two most advanced models, based on a thermodynamic energy balance, are very sensitive to the model inputs and proper care must therefore be taken when these models are used

    Place, publisher, year, edition, pages
    SAE, 2006
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-18306 (URN)
    Available from: 2009-05-18 Created: 2009-05-18 Last updated: 2009-10-14Bibliographically approved
    2. Control Oriented Gas Exchange Models for CVCP Engines and their Transient Sensitivity
    Open this publication in new window or tab >>Control Oriented Gas Exchange Models for CVCP Engines and their Transient Sensitivity
    2007 (English)In: Oil & gas science and technology, ISSN 1294-4475, Vol. 62, no 4, 573-584 p.Article in journal (Refereed) Published
    Abstract [en]

    The paper analyzes a set of control oriented models for the gas exchange phase in engines with continuously variable cam phasing (CVCP). These models describe the mass flow of fresh gases and the residual gases caught in the cylinder during the gas exchange phase. Simulations with CVCP transients are also performed to analyze the models performance during transients.

    Place, publisher, year, edition, pages
    IFP, 2007
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-18307 (URN)10.2516/ogst:2007041 (DOI)
    Available from: 2009-05-18 Created: 2009-05-18 Last updated: 2009-05-18Bibliographically approved
  • 48.
    Durbeej, Bo
    et al.
    Uppsala University, Sweden.
    Eriksson, Leif A.
    Uppsala University, Sweden.
    A density functional theory study of coniferyl alcohol intermonomeric cross linkages in lignin – three-dimensional structures, stabilities and the thermodynamic control hypothesis2003In: Holzforschung, ISSN 0018-3830, Vol. 57, no 2, 150-164 p.Article in journal (Refereed)
    Abstract [en]

    Density functional theory methods are utilized to investigate structural features and stabilities of the most common lignin dimerization products. It is found that intra-molecular hydrogen bonding acts as a stabilizing force in the lowest-energy conformer(s) of several different dimeric lignin structures. Furthermore, the calculations show that the hypothesis of thermodynamic control of monolignol dimerization accounts for some of the results obtained in experimental studies aimed at determining the ratios of intermonomeric linkages. A quantitative correlation between experimentally observed ratios and calculated relative energies cannot, however, be pointed out.

  • 49.
    Virojanadara, Chariya
    et al.
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Hetzel, M
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Starke, Ulrich
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    A diagonal cut through the SiC bulk unit cell: Structure and composition of the 4H-SiC(1-102) surface2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 6, 061902- p.Article in journal (Refereed)
    Abstract [en]

    The atomic and electronic structure of 4H-SiC(102) surfaces was investigated using low-energy electron diffraction, scanning tunneling microscopy, and photoelectron spectroscopy. Three well ordered phases can be prepared by Si deposition and annealing. The (2×1) phase is Si enriched and terminated by an ordered array of Si-adatom chains which contribute an anisotropic electronic surface state. The c(2×2) phase has a surface composition close to SiC bulk and possesses adatoms in the periodicity of the superlattice. At high temperatures, a (1×1) phase develops with a graphitelike composition.

  • 50.
    Backenius, Erik
    et al.
    Linköping University, Department of Electrical Engineering.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering. Linköping University, Department of Electrical Engineering, Electronics System.
    A digital circuit with relaxed clocking2004In: Proc. Swedish System-on-Chip Conf., SSoCC'04, 2004Conference paper (Other academic)
    Abstract [en]

    A clock with adjustable rise and fall time is used in conjunction with a D flip-flop that operates well with this clock. Its intended use is to relax the design of the clock network in digital circuits and to alleviate the problems with simultaneous switching noise in mixed-signal circuits. A test chip has been designed in a 0.35 μm CMOS process. The chip consists of a clock driver with adjustable rise and fall times, and an FIR filter that uses the special D flip-flop in the registers. According to measurements, the digital circuit works well when the rise and fall times of the clock is varied from 0.5 ns to 10 ns. This makes the propagation delay in the critical path to vary between 13.0 ns and 13.7 ns, and the energy dissipation to vary between 1.5 pJ and 1.7 pJ, for an input signal with a transition activity of 0.4.

1234567 1 - 50 of 5207
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