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  • Public defence: 2017-02-23 13:15 John von Neumann, Hus B, Linköping
    Haque, Muhammad Fahim Ul
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Pulse-Width Modulated RF Transmitters2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The market for wireless portable devices has grown signicantly over the recent years.Wireless devices with ever-increased functionality require high rate data transmissionand reduced costs. High data rate is achieved through communication standards such asLTE and WLAN, which generate signals with high peak-to-average-power ratio (PAPR),hence requiring a power amplier (PA) that can handle a large dynamic range signal. Tokeep the costs low, modern CMOS processes allow the integration of the digital, analogand radio functions on to a single chip. However, the design of PAs with large dynamicrange and high eciency is challenging due to the low voltage headroom.

    To prolong the battery life, the PAs have to be power-ecient as they consume a sizablepercentage of the total power. For LTE and WLAN, traditional transmitters operatethe PA at back-o power, below their peak efficiency, whereas pulse-width modulation(PWM) transmitters use the PA at their peak power, resulting in a higher efficiency.PWM transmitters can use both linear and SMPAs where the latter are more power efficient and easy to implement in nanometer CMOS. The PWM transmitters have a higher efficiency but suffer from image and aliasing distortion, resulting in a lower dynamic range,amplitude and phase resolution.

    This thesis studies several new transmitter architectures to improve the dynamicrange, amplitude and phase resolution of PWM transmitters with relaxed filtering requirements.The architectures are suited for fully integrated CMOS solutions, in particular forportable applications.

    The first transmitter (MAF-PWMT) eliminates aliasing and image distortions whileallowing the use of SMPAs by combining RF-PWM and band-limited PWM. The transmittercan be implemented using all-digital techniques and exhibits an improved linearity and spectral performance. The approach is validated using a Class-D PA based transmitter where an improvement of 10.2 dB in the dynamic range compared to a PWM transmitter for a 1.4 MHz of LTE signal is achieved.

    The second transmitter (AC-PWMT) compensates for aliasing distortion by combining PWM and outphasing. It can be used with switch-mode PAs (SMPAs) or linear PAs at peak power. The proposed transmitter shows better linearity, improved spectral performanceand increased dynamic range as it does not suffer from AM-AM distortion of the PAs and aliasing distortion due to digital PWM. The idea is validated using push-pull PAs and the proposed transmitter shows an improvement of 9 dB in the dynamic rangeas compared to a PWM transmitter using digital pulse-width modulation for a 1.4 MHzLTE signal.

    The third transmitter (MD-PWMT) is an all-digital implementation of the second transmitter. The PWM is implemented using a Field Programmable Gate Array(FPGA) core, and outphasing is implemented as pulse-position modulation using FPGA transceivers, which drive two class-D PAs. The digital implementation offers the exibility to adapt the transmitter for multi-standard and multi-band signals. From the measurement results, an improvement of 5 dB in the dynamic range is observed as compared to an all-digital PWM transmitter for a 1.4 MHz LTE signal.

    The fourth transmitter (EP-PWMT) improves the phase linearity of an all-digital PWM transmitter using PWM and asymmetric outphasing. The transmitter uses PWM to encode the amplitude, and outphasing for enhanced phase control thus doubling the phase resolution. The measurement setup uses Class-D PAs to amplify a 1.4 MHz LTEup-link signal. An improvement of 2.8 dB in the adjacent channel leakage ratio is observed whereas the EVM is reduced by 3.3 % as compared to an all-digital PWM transmitter.

    The fifth transmitter (CRF-ML-PWMT) combines multilevel and RF-PWM, whereas the sixth transmitter (CRF-MP-PMWT) combines multiphase PWM and RF-PWM. Both transmitters have smaller chip area as compared to the conventional multiphase and multilevel PWM transmitters, as a combiner is not required. The proposed transmitters also show better dynamic range and improved amplitude resolution as compared to conventional RF-PWM transmitters.

    The solutions presented in this thesis aims to enhance the performance and simplify the digital implementation of PWM-based RF transmitters.

    List of papers
    1. Combined RF and Multilevel PWM Switch Mode Power Amplifier
    Open this publication in new window or tab >>Combined RF and Multilevel PWM Switch Mode Power Amplifier
    2013 (English)In: Norchip, IEEE , 2013, 1-4 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel power amplifier (PA) architecture based on the combination of radio frequency pulse width modulation (RFPWM) and multilevel PWM. The architecture provides better dynamic range at high carrier frequency compared to RFPWM. The benefits of this architecture over multilevel PWM are that it only requires a single PA and no combiner. The average efficiency for an 802.11g baseband signal is better than multilevel PWM. Our results also shows that the proposed technique exhibit a constant dynamic range at carrier frequency of 3, 4 and 5 GHz, in contrast to RFPWM which shows a decrease in dynamic range for increase in carrier frequency.

    Place, publisher, year, edition, pages
    IEEE, 2013
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-102929 (URN)10.1109/NORCHIP.2013.6702010 (DOI)978-147991647-4 (ISBN)
    Conference
    NORCHIP 2013; Vilnius; Lithuania
    Available from: 2014-01-08 Created: 2014-01-08 Last updated: 2017-01-18
    2. Combined RF and Multiphase PWM Transmitter
    Open this publication in new window or tab >>Combined RF and Multiphase PWM Transmitter
    2015 (English)In: 2015 European Conference on Circuit Theory and Design (ECCTD), IEEE , 2015, 264-267 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents two novel transmitter architectures based on the combination of radio-frequency pulse-width modulation and multiphase pulse-width modulation. The proposed transmitter architectures provide good amplitude resolution and large dynamic range at high carrier frequency, which is problematic with existing radio-frequency pulse-width modulation based transmitters. They also have better power efficiency and smaller chip area compared to multiphase pulse-width modulation based transmitters.

    Place, publisher, year, edition, pages
    IEEE, 2015
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-122703 (URN)10.1109/ECCTD.2015.7299999 (DOI)000380498200001 ()978-1-4799-9877-7 (ISBN)
    Conference
    2015 European Conference on Circuit Theory and Design (ECCTD), Trondheim, Norway, August 24-26, 2015
    Available from: 2015-11-16 Created: 2015-11-16 Last updated: 2017-01-18Bibliographically approved
  • Public defence: 2017-02-24 09:15 Planck, Linköping
    Stenberg, Pontus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Fluorinated SiC CVD2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    For the emerging semiconductor material silicon carbide (SiC) used in high power devices, chemical vapor deposition (CVD) is the most prominent method to create the electrically active SiC epitaxial layers in the device. The process of growing such epitaxial layers is to use a hydrocarbon and silane diluted in hydrogen flow through a hot chamber where chemical reactions take place in such manner that Si and C finally deposit on the surface creating epitaxial SiC. The addition of chlorine (Cl) to the process has been thoroughly investigated due to its ability to reduce homogeneous nucleation in the gas phase attributed to the stronger Si-Cl bond compared to the Si-Si bond. In this thesis the fluorinated chemistry has been investigated, since the Si-F bond is even stronger than the Si-Cl bond and the fluorinated chemistry for SiC CVD has remained poorly understood.

    Using SiF4 as Si precursor in growth experiments combined with thermal equilibrium calculations of gas phase composition and quantum chemical computations of the surface chemistry first the silicon chemistry in the CVD process has been probed. It is shown that while growth rates on the order of 35 µm/h can be achieved with a fluorinated chemistry, the deposition chemistry is very sensitive to the mass flows of the precursors and not as robust as the chlorinated CVD chemistry which routinely yields 100 µm/h over wide conditions. By using the position for the onset of epitaxial growth along the gas flow direction as a new measurable, together with modeling, it is conclude that SiF is the main Si growth species with SiHF as a minor Si species contributing to growth.

    The carbon chemistry in a fluorinated SiC CVD process has been probed by a similar approach. Here it is found that the slow kinetics of the SiF4 molecule needs to be matched by a carbon precursor with comparable slow kinetics. It is shown that methane is a suitable carbon precursor in combination with SiF4.

    Before a fluorinated CVD chemistry can be adopted in device processing, the effect of fluorine on the dopant incorporation must be understood since dopant incorporation is of paramount importance in semiconductor manufacturing. Dopant incorporation studies for n-type doping with N using N2 and p-type doping with Al using TMAl in fluorinated CVD of homoepitaxial SiC are presented. It is found to be possible to control the doping in SiC epitaxial layers when using a fluorinated CVD chemistry for both n- and p-type material using the C/Si ratio as in standard SiC CVD. However, large area doping uniformity seems to be a challenge for a fluorinated CVD chemistry, most likely due to the very strong Si-F and Al-F bonds. It is found that no additional optically or electrically active defects are created due to the use of fluorine in the CVD process.

    Finally, the fluorinated chemistry is compared to the chlorinated and brominated chemistries for SiC CVD and an overall model for halogen addition to SiC CVD is presented.

    List of papers
    1. Silicon Chemistry in Fluorinated Chemical Vapor Deposition of Silicon Carbide
    Open this publication in new window or tab >>Silicon Chemistry in Fluorinated Chemical Vapor Deposition of Silicon Carbide
    Show others...
    2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 5, 2711-2720 p.Article in journal (Refereed) Published
    Abstract [en]

    The use of chlorinated chemical vapor deposition (CVD) chemistry for growth of homoepitaxial layers of silicon carbide (SiC) has diminished the problem of homogenous gas phase nucleation, mainly the formation of Si droplets, in CVD of SiC by replacing Si-Si bonds with stronger Si-Cl bonds. Employing the even stronger Si-F bond could potentially lead to an even more efficient CVD chemistry, however, fluorinated chemistry is very poorly understood for SiC CVD. Here, we present studies of the poorly understood fluorinated CVD chemistry for homoepitaxial SiC layers using SiF4 as Si precursor. We use a combination of experimental growth studies, thermal equilibrium calculations of gas phase composition and quantum chemical computations (i.e. hybrid density functional theory) of the surface chemistry to probe the silicon chemistry in the CVD process. We show that while growth rates on the order of 35 µm/h can be achieved with a fluorinated chemistry, the deposition chemistry is very sensitive to the mass flows of the precursors and not as robust as the chlorinated CVD chemistry which routinely yields 100 µm/h over wide conditions. By using the position for the onset of epitaxial growth along the gas flow direction as a measurable, together with modeling, we conclude that SiF is the main Si growth species with SiHF as a minor Si species contributing to growth.

    Place, publisher, year, edition, pages
    Washington: American Chemical Society (ACS), 2017
    National Category
    Chemical Process Engineering Inorganic Chemistry Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-134247 (URN)10.1021/acs.jpcc.6b10849 (DOI)
    Available from: 2017-01-30 Created: 2017-01-30 Last updated: 2017-02-20Bibliographically approved
  • Public defence: 2017-02-24 10:15 Hörsal K3, Kåkenhus, Norrköping
    Mešić, Nedžad
    Linköping University, REMESO - Institute for Research on Migration, Ethnicity and Society. Linköping University, Faculty of Arts and Sciences.
    Negotiating Solidarity: Collective Actions for Precarious Migrant Workers’ Rights in Sweden2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Precarious migrant workers are today an everyday part of the Swedish labour market. They often work under conditions of vulnerability, on temporary contracts and with few rights. This dissertation examines collective actions aiming to improve the precarious conditions of three categories of workers –discriminated, seasonal and undocumented. The collective actors examined in the dissertation are composed of formal organisations such as non-governmental organisations, organisations founded on ethnic grounds and trade unions, but also more temporary groups and networks. The analysis foregrounds contemporary societal, economical and legal transfigurations that create the conditions for collaboration among the actors and the negotiations which they conduct. The dissertation contains four articles. The first article, addressing the situation of discriminated migrant workers, scrutinises the conditions for the engagement of anti-discrimination agencies. The result of the study illustrates how the actors, as a consequence of state subsidies, alter their original course of conduct by becoming market orientated,which contributes to tensions in relations with other collaborators. The second and third articles focus on the situation of Bulgarian-Roma berry pickers in the 2012 harvesting season. Thesearticles illuminate on the one hand, the driving forces to their labour migration and the challenges faced in Sweden, and on the other, the emergence of different collective actions and their significance for the workers. The fourth article centres on two trade union initiatives for the inclusion of undocumentedmigrant workers. The article analyses the challenges faced by the unions as they seek to extend solidarity to workers who are relegated to informal work. The article also elucidates that this endeavour,nonetheless, may have the potential to transform the political identity of trade unions and, by extension through collaborations with other collective actors, open the doors of solidarity for precarious EU migrants. In sum, the four articles show that there is a broad range of collective actors who are preparedto assist precarious migrant workers and to negotiate and at best improve their labour market conditions.These actors face many and difficult challenges. However, as the dissertation demonstrates, their engagement has made the reality of precarious migrant work visible to the public, legitimised the workers’ needs and enabled them to claim their rights.

    List of papers
    1. Asymmetric Partnership: Migrant organisations, trade unions and equality Ombudsman
    Open this publication in new window or tab >>Asymmetric Partnership: Migrant organisations, trade unions and equality Ombudsman
    2011 (English)In: Revija za Sociologiju / Sociological Review, ISSN 0350-154X, E-ISSN 1846-7954, Vol. 41, no 1, 51-76 p.Article in journal (Refereed) Published
    Abstract [en]

    The study examines civil society agency for social inclusion among Associations Founded on Ethnic Grounds (AFEGs), focusing on their engagement for combating discrimination and enhancing migrant incorporation into the Swedish labour market. The overall rationale of the study investigates the complex institutional conditionality of AFEGs for developing their agency as social movement and civil society actors. The main aim of this study has been to understand how anti-discrimination agencies run by AFEGs, with subsidy support by the state, describe their experiences, and which implications the subsidy may have for the orientation and direction of their actions. The study comprises primarily interviews with anti-discrimination lawyers and heads of two agencies, but also interviews with representatives for the Equality Ombudsman. The greatest challenge for the agencies has been caused by subsidy cutbacks, which have affected both the working conditions of the agencies and other engagements of the AFEGs, such as educational courses among their members, awareness raising concerning the issues of anti-discrimination among different officials, in municipalities, trade unions and among employers. Due to the cutbacks, the civil society actors such as AFEGs have been forced to adapt to market principles by becoming entrepreneurs specialised, in this case, in the field of anti-discrimination law. The study further analyses the effects of this development as well as opportunity structures for collaboration with trade unions and the Equality Ombudsman. Even though these partnerships reveal relational asymmetries, the authors call attention to current and possible future openings in opportunity structures for wider collaboration between AFEGs, trade unions and the Equality Ombudsman.

    Place, publisher, year, edition, pages
    Zagreb: , 2011
    Keyword
    social movement, integration, civil society, immigrant associations
    National Category
    Social Sciences
    Identifiers
    urn:nbn:se:liu:diva-67527 (URN)10.5613/rzs.41.1.4 (DOI)
    Available from: 2011-04-15 Created: 2011-04-15 Last updated: 2017-02-20
    2. Roma berry pickers in Sweden: Economic crisis and new contingents of the austeriat
    Open this publication in new window or tab >>Roma berry pickers in Sweden: Economic crisis and new contingents of the austeriat
    2015 (English)In: Transfer: European Review of Labour and Research, ISSN 1024-2589, Vol. 21, no 1, 37-50 p.Article in journal (Refereed) Published
    Abstract [en]

    In the current era of austerity free movement of labour has produced an ongoing but also contingent flow of migrant labour, an austeriat, moving from poorer crisis-hit regions of Europe to those countries such as Sweden where the crisis has been less severe. This article describes the working and living experiences of Bulgarian Roma berry pickers in Sweden. It argues that, in the context of a previously well-regulated labour market, an erosion of labour standards based on the exploitation of seasonal unskilled labour migrants from Bulgaria is occurring in the Swedish berry industry, in turn posing challenges for labour market actors and regulatory authorities. The article concludes with a discussion of what might be appropriate European and national trade union responses to the issues of labour precariousness which have emerged.

    Place, publisher, year, edition, pages
    Sage Publications, 2015
    Keyword
    Roma, berry pickers, Bulgaria, austeriat, migration, Sweden, free movement
    National Category
    International Migration and Ethnic Relations
    Identifiers
    urn:nbn:se:liu:diva-113558 (URN)10.1177/1024258914561411 (DOI)
    Projects
    Swedish Research Council for Health, Working Life and Welfare
    Available from: 2015-01-22 Created: 2015-01-22 Last updated: 2017-02-21
    3. Paradoxes of European free movement in times of austerity: The role of social movement actors in framing the plight of Roma berry pickers in Sweden
    Open this publication in new window or tab >>Paradoxes of European free movement in times of austerity: The role of social movement actors in framing the plight of Roma berry pickers in Sweden
    2016 (English)In: International journal of sociology and social policy, ISSN 0144-333X, E-ISSN 1758-6720, Vol. 36, no 5, 289-303 p.Article in journal (Refereed) Published
    Abstract [en]

    The purpose of this paper is to provide insight into the capacities of social movement actors (SMAs) and interest groups to negotiate responsibility, heighten issues of accountability and earn legitimacy from authorities and the wider public for the plight of dis-privileged Roma migrant berry pickers in the Swedish labour market. The objective is guided by a multi-sited ethnographical approach to data collection and analysis, which theoretically anchors in social movement frame analysis. The paper proposes that SMAs, in the face of incapacities of state and industry parties, generate the potentiality to leverage immediate humanitarian distress experienced by the workers and to accentuate their political and public visibility. Delimited by the internal organisational structure of a berry industry, partly operating behind informal employment schemes, future studies should devote closer attention in localising/identifying possible “back-stage” data-gathering settings. Policy-makers and special-interest organisations concerned with internal EU labour migration, labour standards and living condition issues, may consider the social and humanitarian implications of persistent responsibility ambiguities. The paper raises issues of informal work and forms of labour exploitation. The paper provides deeper insight into the societal nexus in which a “hard-to-reach group” of seasonal workers faces potential and actual exploitation.

    Place, publisher, year, edition, pages
    Bingley: Emerald Group Publishing Limited, 2016
    Keyword
    Sweden, Bulgaria, Frame analysis, Internal EU seasonal migrants, Roma berry pickers, Social movement actors
    National Category
    Human Geography Political Science (excluding Public Administration Studies and Globalization Studies) Business Administration Work Sciences Social Sciences Interdisciplinary
    Identifiers
    urn:nbn:se:liu:diva-134147 (URN)10.1108/IJSSP-05-2015-0057 (DOI)
    Available from: 2017-01-25 Created: 2017-01-25 Last updated: 2017-02-20Bibliographically approved
    4. Framing solidarity in the unionisation of undocumented migrant workers
    Open this publication in new window or tab >>Framing solidarity in the unionisation of undocumented migrant workers
    2017 (English)In: Reimagineering the nation: essays on twenty-first-century Sweden / [ed] Aleksandra Ålund, Carl-Ulrik Schierup, Anders Neergard, Bern: Peter Lang Publishing Group, 2017, 303-325 p.Chapter in book (Refereed)
    Abstract [en]

    This chapter explores the capacity of two Swedish trade union initiatives, SAC Syndicalists and LO-TCO centre, to extend solidarity to undocumented migrant workers. The author asks what solidarity linkages have been established since the shift of millennia and what obstacles encountered in forging solidarity between workers with strong versus weak legal status. He illuminates the emergence of a transformative form of solidarity, which may open for protection of new groups of disadvantaged workers.

    Place, publisher, year, edition, pages
    Bern: Peter Lang Publishing Group, 2017
    Series
    Political and Social Change, ISSN 2198-8587
    National Category
    Law (excluding Law and Society) Economic History Work Sciences Law and Society Sociology (excluding Social Work, Social Psychology and Social Anthropology)
    Identifiers
    urn:nbn:se:liu:diva-134360 (URN)10.3726/b10645 (DOI)9783631715185 (ISBN)9783631715208 (ISBN)9783631715192 (ISBN)
    Available from: 2017-02-07 Created: 2017-02-07 Last updated: 2017-02-16Bibliographically approved
  • Public defence: 2017-02-24 10:15 Nobel BL32, B-huset, Linköping
    Lokharu, Evgeniy
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Small-amplitude steady water waves with vorticity2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The problem of describing two-dimensional traveling water waves is considered. The water region is of finite depth and the interface between the region and the air is given by the graph of a function. We assume the flow to be incompressible and neglect the effects of surface tension. However we assume the flow to be rotational so that the vorticity distribution is a given function depending on the values of the stream function of the flow. The presence of vorticity increases the complexity of the problem and also leads to a wider class of solutions.

    First we study unidirectional waves with vorticity and verify the Benjamin-Lighthill conjecture for flows whose Bernoulli constant is close to the critical one. For this purpose it is shown that every wave, whose slope is bounded by a fixed constant, is either a Stokes or a solitary wave. It is proved that the whole set of these waves is uniquely parametrised (up to translation) by the flow force which varies between its values for the supercritical and subcritical shear flows of constant depth. We also study large-amplitude unidirectional waves for which we prove bounds for the free-surface profile and for Bernoulli’s constant.

    Second, we consider small-amplitude waves over flows with counter currents. Such flows admit layers, where the fluid flows in different directions. In this case we prove that the initial nonlinear free-boundary problem can be reduced to a finite-dimensional Hamiltonian system with a stable equilibrium point corresponding to a uniform stream. As an application of this result, we prove the existence of non-symmetric wave profiles. Furthermore, using a different method, we prove the existence of periodic waves with an arbitrary number of crests per period.

    List of papers
    1. On bounds and non-existence in the problem of steady waves with vorticity
    Open this publication in new window or tab >>On bounds and non-existence in the problem of steady waves with vorticity
    2015 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 765, no R1Article in journal (Refereed) Published
    Abstract [en]

    For the problem describing steady gravity waves with vorticity on a two-dimensional unidirectional flow of finite depth the following results are obtained. (i) Bounds are found for the free-surface profile and for Bernoullis constant. (ii) If only one parallel shear flow exists for a given value of Bernoullis constant, then there are no wave solutions provided the vorticity distribution is subject to a certain condition.

    Place, publisher, year, edition, pages
    Cambridge University Press (CUP): STM Journals, 2015
    Keyword
    surface gravity waves; waves/free-surface flows
    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-114417 (URN)10.1017/jfm.2014.747 (DOI)000348130700001 ()
    Note

    Funding Agencies|Swedish Research Council; G.S. Magnusons Foundation of the Royal Swedish Academy of Sciences; Linkoping University

    Available from: 2015-03-02 Created: 2015-02-20 Last updated: 2017-01-30
  • Public defence: 2017-03-03 10:15 Sal K3, Kåkenhus, Norrköping
    Elhag, Sami
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering.
    Chemically Modified Metal Oxide Nanostructures Electrodes for Sensing and Energy Conversion2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The goal of this thesis is the development of scalable, low cost synthesis of metal oxide nanostructures based electrodes and to correlate the chemical modifications with their energy conversion performance. Methods in energy conversion in this thesis have focused on two aspects; a potentiometric chemical sensor was used to determine the analytical concentration of some components of the analyte solution such as dopamine, glucose and glutamate molecules. The second aspect is to fabricate a photo-electrochemical (PEC) cell. The biocompatibility, excellent electro-catalytic activities and fast electron transfer kinetics accompanied with a high surface area to volume ratio; are properties of some metal oxide nanostructures that of a potential for their use in energy conversion. Furthermore, metal oxide nanostructures based electrode can effectively be improved by the physical or a chemical modification of electrode surface. Among these metal oxide nanostructures are cobalt oxide (Co3O4), zinc oxide (ZnO), and bismuth-zincvanadate (BiZn2VO6) have all been studied in this thesis. Metal oxide nanostructures based electrodes are fabricated on gold-coated glass substrate by low temperature (< 100 0C) wet chemicalapproach. X-ray diffraction, x-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the electrodes while ultraviolet-visible absorption and photoluminescence were used to investigate the optical properties of the nanostructures. The resultant modified electrodes were tested for their performance as chemical sensors and for their efficiency in PEC activities. Efficient chemically modified electrodes were demonstrated through doping with organic additives like anionic, nonionic or cationic surfactants. The organic additives are showing a crucial role in the growth process of metal oxide nanocrystals and hence can beused to control the morphology. These organic additives act also as impurities that would significantly change the conductivity of the electrodes. However, no organic compounds dependence was observed to modify the crystallographic structure. The findings in this thesis indicate the importance of the use of controlled nanostructures morphology for developing efficient functional materials.

    List of papers
    1. Incorporating beta-Cyclodextrin with ZnO Nanorods: A Potentiometric Strategy for Selectivity and Detection of Dopamine
    Open this publication in new window or tab >>Incorporating beta-Cyclodextrin with ZnO Nanorods: A Potentiometric Strategy for Selectivity and Detection of Dopamine
    2014 (English)In: Sensors, ISSN 1424-8220, Vol. 14, no 1, 1654-1664 p.Article in journal (Refereed) Published
    Abstract [en]

    We describe a chemical sensor based on a simple synthesis of zinc oxide nanorods (ZNRs) for the detection of dopamine molecules by a potentiometric approach. The polar nature of dopamine leads to a change of surface charges on the ZNR surface via metal ligand bond formation which results in a measurable electrical signal. ZNRs were grown on a gold-coated glass substrate by a low temperature aqueous chemical growth (ACG) method. Polymeric membranes incorporating beta-cyclodextrin (beta-CD) and potassium tetrakis (4-chlorophenyl) borate was immobilized on the ZNR surface. The fabricated electrodes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The grown ZNRs were well aligned and exhibited good crystal quality. The present sensor system displays a stable potential response for the detection of dopamine in 10(-2) mol.L-1 acetic acid/sodium acetate buffer solution at pH 5.45 within a wide concentration range of 1 x 10(-6) M-1 x 10(-1) M, with sensitivity of 49 mV/decade. The electrode shows a good response time (less than 10 s) and excellent repeatability. This finding can contribute to routine analysis in laboratories studying the neuropharmacology of catecholamines. Moreover, the metal-ligand bonds can be further exploited to detect DA receptors, and for bio-imaging applications.

    Place, publisher, year, edition, pages
    MDPI, 2014
    Keyword
    ZnO nanorods; dopamine; potentiometric response; selectivity; stability; repeatability
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-107470 (URN)10.3390/s140101654 (DOI)000336039100087 ()
    Available from: 2014-06-12 Created: 2014-06-12 Last updated: 2017-02-02Bibliographically approved
    2. Habit-modifying additives and their morphological consequences on photoluminescence and glucose sensing properties of ZnO nanostructures, grown via aqueous chemical synthesis
    Open this publication in new window or tab >>Habit-modifying additives and their morphological consequences on photoluminescence and glucose sensing properties of ZnO nanostructures, grown via aqueous chemical synthesis
    Show others...
    2015 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 116, 21-26 p.Article in journal (Refereed) Published
    Abstract [en]

    Generally, the anisotropic shape of inorganic nano-crystal can be influenced by one or more of different parameters i.e. kinetic energy barrier, temperature, time, and the nature of the capping molecules. Here, different surfactants acting as capping molecules were used to assist the aqueous chemical growth of zinc oxide (ZnO) nanostructures on Au coated glass substrates. The morphology, crystal quality and the photoluminescence (PL) properties of the ZnO nanostructures were investigated. The PL properties of the prepared ZnO nanostructures at room temperature showed a dominant UV luminescence peak, while the "green yellow" emissions were essentially suppressed. Moreover, the ZnO nanostructures were investigated for the development of a glucose biosensor. An adsorbed molecule has direct contribution on the glucose oxidase/ZnO/Au sensing properties. We show that the performance of a ZnO-based biosensor can be improved by tailoring the properties of the ZnO biomolecule interface through engineering of the morphology, effective surface area, and adsorption capability.

    Place, publisher, year, edition, pages
    Elsevier, 2015
    Keyword
    ZnO nanostructures; Cationic and anionic molecules; PL spectra; Glucose sensitivity
    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-119245 (URN)10.1016/j.vacuum.2015.02.026 (DOI)000354582900004 ()
    Note

    Funding Agencies|University of Kordofan Grant, El-Obeid, Kordofan Sudan [700]

    Available from: 2015-06-15 Created: 2015-06-12 Last updated: 2017-02-02
    3. Effect of Urea on the Morphology of Co3O4 Nanostructures and Their Application for Potentiometric Glucose Biosensor
    Open this publication in new window or tab >>Effect of Urea on the Morphology of Co3O4 Nanostructures and Their Application for Potentiometric Glucose Biosensor
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    2014 (English)In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 26, no 8, 1773-1781 p.Article in journal (Refereed) Published
    Abstract [en]

    In this study, an effect of different concentrations of urea on the morphology of cobalt oxide (Co3O4) nanostructures was investigated. The Co3O4 nanostructures are fabricated on gold coated glass substrate by the hydrothermal method. The morphological and structural characterization was performed by scanning electron microscopy, and X-ray diffraction techniques. The Co3O4 nanostructures exhibit morphology of flowers-like and have comprised on nanowires due to the increasing amount of urea. The nanostructures were highly dense on the substrate and possess a good crystalline quality. The Co3O4 nanostructures were successfully used for the development of a sensitive glucose biosensor. The presented glucose biosensor detected a wide range of glucose concentrations from 1 x 10(-6) M to 1 x 10(-2) M with sensitivity of a -56.85 mV/decade and indicated a fast response time of less than 10 s. This performance could be attributed to the heterogeneous catalysis effect at glucose oxidase enzyme, nanoflowers, and nanowires interfaces, which have enhanced the electron transfer process on the electrode surface. Moreover, the reproducibility, repeatability, stability and selectivity were also investigated. All the obtained results indicate the potential use of the developed glucose sensor for monitoring of glucose concentrations at drugs, human serum and food industry related samples.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2014
    Keyword
    Nanostructures; Hydrothermal method; Glucose biosensor
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-110486 (URN)10.1002/elan.201400116 (DOI)000340557700016 ()
    Available from: 2014-09-15 Created: 2014-09-12 Last updated: 2017-02-02Bibliographically approved
    4. Dopamine wide range detection sensor based on modified Co3O4 nanowires electrode
    Open this publication in new window or tab >>Dopamine wide range detection sensor based on modified Co3O4 nanowires electrode
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    2014 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, Vol. 203, 543-549 p.Article in journal (Refereed) Published
    Abstract [en]

    Ultra-thin cobalt oxide (Co3O4) nanowires grown on gold coated glass substrates by the hydrothermal chemical deposition and have been used as a wide range dopamine potentiometric sensor. An anionic surfactant ( sodium dodecylbenzenesulfonate) was used to achieve assisted growth procedure. Moreover, a polymeric membrane containing polyvinyl chloride as plasticized polymer, p-cyclodextrin as ionophore, and potassium tetrakis (4-chlorophenyl) borate as ionic additive were immobilized on the Co3O4 nanostructures through electrostatic adsorption method. X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy were used to characterize the electrodes while ultraviolet-visible absorption was used to investigate the band gap of the Co3O4 nanostructures. The structural characterization showed a cubic crystalline, pure phase, and nanowires morphology of the Co3O4. However, the morphology is altered when the surfactant concentration has been changed. The Co3O4 chemical modified electrodes were used in potentiometric measurements for dopamine in a 10(-2) M acetic acid/sodium acetate solution having a pH of 5.45. For dopamine range from 10(-9) M to 10(-2) M, the potential response of the sensor electrode was linear with a slope of 52 mV/decade. The wide range and high sensitivity of the modified Co3O4 nanowires based sensor for dopamine is attributed to the defects on the metal oxide that is dictated by the used surfactant along with the high surface area-to-volume ratio.

    Place, publisher, year, edition, pages
    Elsevier, 2014
    Keyword
    Potentiometric sensor; Chemically modified electrode; Surfactant; Dopamine chemical sensor
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-111254 (URN)10.1016/j.snb.2014.07.028 (DOI)000341455400072 ()
    Available from: 2014-10-15 Created: 2014-10-14 Last updated: 2017-02-02Bibliographically approved
    5. Efficient Donor Impurities in ZnO Nanorods by Polyethylene Glycol for Enhanced Optical and Glutamate Sensing Properties
    Open this publication in new window or tab >>Efficient Donor Impurities in ZnO Nanorods by Polyethylene Glycol for Enhanced Optical and Glutamate Sensing Properties
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    2016 (English)In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 16, no 2Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we show that the possibility of using polyethylene glycol (EG) as a hydrogen source and it is used to assist the hydrothermal synthesis of ZnO nanorods (ZNRs). EG doping in ZNRs has been found to significantly improve their optical and chemical sensing characteristics toward glutamate. The EG was found to have no role on the structural properties of the ZNRs. However, the x-ray photoelectron spectroscopy (XPS) suggests that the EG could induce donor impurities effect in ZnO. Photoluminescence (PL) and UV-Vis. spectra demonstrated this doping effect. Mott-Schottky analysis at the ZNRs/electrolyte interface was used to investigate the charge density for the doped ZNRs and showed comparable dependence on the used amount of EG. Moreover, the doped ZNRs were used in potentiometric measurements for glutamate for a range from 10(-6) M to 10(-3) M and the potential response of the sensor electrode was linear with a slope of 91.15 mV/decade. The wide range and high sensitivity of the modified ZNRs based glutamate biosensor is attributed to the doping effect on the ZNRs that is dictated by the EG along with the high surface area-to-volume ratio. The findings in the present study suggest new avenues to control the growth of n-ZnO nanostructures and enhance the performance of their sensing devices.

    Place, publisher, year, edition, pages
    MDPI AG, 2016
    Keyword
    potentiometric sensor; ZnO nanorods; glutamate; doping
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering Chemical Sciences Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-126849 (URN)10.3390/s16020222 (DOI)000371787800096 ()26861342 (PubMedID)
    Note

    Funding Agencies|University of Kordofan, El-Obeid, Kordofan Sudan [700]

    Available from: 2016-04-05 Created: 2016-04-05 Last updated: 2017-02-02
    6. Low-temperature growth of polyethylene glycol-doped BiZn2VO6 nanocompounds with enhanced photoelectrochemical properties
    Open this publication in new window or tab >>Low-temperature growth of polyethylene glycol-doped BiZn2VO6 nanocompounds with enhanced photoelectrochemical properties
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    2017 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, no 3, 112-1119 p.Article in journal (Refereed) Published
    Abstract [en]

    We demonstrate scalable, low-cost and low-temperature (<100 °C) aqueous chemical growth of bismuth–zinc vanadate (BiZn2VO6) nanocompounds by BiVO4 growth on ZnO nanobelts (NBs). The nanocompounds were further doped with polyethylene glycol (PEG) to tune the electronic structure of the materials, as a means to lower the charge carrier recombination rate. The chemical composition, morphology, and detailed nanostructure of the BiZn2VO6 nanocompounds were characterized. They exhibit rice-like morphology, are highly dense on the substrate and possess a good crystalline quality. Photoelectrochemical characterization in 0.1 M lithium perchlorate in carbonate propylene shows that BiZn2VO6 nanocompounds are highly suitable as anodes for solar-driven photoelectrochemical applications, providing significantly better performance than with only ZnO NBs. This performance could be attributed to the heterogeneous catalysis effect at nanocompound and ZnO NB interfaces, which have enhanced the electron transfer process on the electrode surface. Furthermore, the charge collection efficiency could be significantly improved through PEG doping of nanocompounds. The photocurrent density of PEG-doped BiZn2VO6 nanocompounds reached values of 2 mA cm−2 at 1.23 V (vs. Ag/AgCl), over 60% larger than that of undoped BiZn2VO6 nanocompounds. Photoluminescence emission experiments confirmed that PEG plays a crucial role in lowering the charge carrier recombination rate. The presented BiZn2VO6 nanocompounds are shown to provide highly competitive performance compared with other state-of-the art photoelectrodes.

    Place, publisher, year, edition, pages
    Cambridge: Royal Society of Chemistry, 2017
    National Category
    Materials Chemistry Condensed Matter Physics Inorganic Chemistry Ceramics
    Identifiers
    urn:nbn:se:liu:diva-134273 (URN)10.1039/C6TA10180A (DOI)
    Available from: 2017-02-02 Created: 2017-02-02 Last updated: 2017-02-10Bibliographically approved
  • Public defence: 2017-03-08 13:15 Visionen, Hus B, Ingång 25, Linköping
    Linder, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Indirect System Identification for Unknown Input Problems: With Applications to Ships2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    System identification is used in engineering sciences to build mathematical models from data. A common issue in system identification problems is that the true inputs to the system are not fully known. In this thesis, existing approaches to unknown input problems are classified and some of their properties are analyzed.

     A new indirect framework is proposed to treat system identification problems with unknown inputs. The effects of the unknown inputs are assumed to be measured through possibly unknown dynamics. Furthermore, the measurements may also be dependent on other known or measured inputs and can in these cases be called indirect input measurements. Typically, these indirect input measurements can arise when a subsystem of a larger system is of interest and only a limited set of sensors is available. Two examples are when it is desired to estimate parts of a mechanical system or parts of a dynamic network without full knowledge of the signals in the system. The input measurements can be used to eliminate the unknown inputs from a mathematical model of the system through algebraic manipulations. The resulting indirect model structure only depends on known and measured signals and can be used to estimate the desired dynamics or properties. The effects of using the input measurements are analyzed in terms of identifiability, consistency and variance properties. It is shown that cancelation of shared dynamics can occur and that the resulting estimation problem is similar to errors-in-variables and closed-loop estimation problems because of the noisy inputs used in the model. In fact, the indirect framework unifies a number of already existing system identification problems that are contained as special cases.

    For completeness, an instrumental variable method is proposed as one possibility for estimating the indirect model. It is shown that multiple datasets can be used to overcome certain identifiability issues and two approaches, the multi-stage and the joint identification approach, are suggested to utilize multiple datasets for estimation of models. Furthermore, the benefits of using the indirect model in filtering and for control synthesis are briefly discussed. 

    To show the applicability, the framework is applied to the roll dynamics of a ship for tracking of the loading conditions. The roll dynamics is very sensitive to changes in these conditions and a worst-case scenario is that the ship will capsize.  It is assumed that only motion measurements from an inertial measurement unit (IMU) together with measurements of the rudder angle are available. The true inputs are thus not available, but the measurements from the IMU can be used to form an indirect model from a well-established ship model. It is shown that only a subset of the unknown parameters can be estimated simultaneously. Data was collected in experiments with a scale ship model in a basin and the joint identification approach was selected for this application due to the properties of the model. The approach was applied to the collected data and gave promising results.

  • Public defence: 2017-03-10 13:15 Visionen, Linköping
    Malmberg, Lisa
    Linköping University, Department of Computer and Information Science, Human-Centered systems. Linköping University, Faculty of Arts and Sciences.
    Building Design Capability in the Public Sector: Expanding the Horizons of Development2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Public sector organizations are in need of new approaches to development and innovation. There is a need to develop a capability to better understand priorities, needs and wishes of public sector service users and become more proactive, in order to meet the demands on keeping costs down and quality high.

    Design is increasingly put forward as a potential answer to this need and there are many initiatives taken across the world to encourage the use of a design approach to development and innovation within public sector. In relation to this trend there is a need to improve the understanding of how public sector organizations develop ability to exploit design; how they develop design capability. This is the focus of this thesis, which through an exploratory study has observed the two initiatives aiming to introduce design and develop design capability within healthcare and social service organizations.

    One main contribution of this work is an understanding of the design capability concept based on a structured review of the use of the design capability concept in the literature. The concept has previously been used in relation to different aspects of designs in organizations.

    Another important contribution is the development of an understanding for how design capability is developed based on interpretations founded in the organizational learning perspective of absorptive capacity. The study has identified how different antecedents to development of design capability have influenced this development in the two cases. The findings have identified aspects that both support and impede the development of design capability which are important to acknowledge and address when aiming to develop design capability within a public sector organization.

    In both cases, the set up of the knowledge transferring efforts focus mainly on developing awareness of design. Similar patterns are seen in other prior and parallel initiatives. The findings however suggest that it is also important to ensure that the organization have access to design competence and that structures like routines, processes and culture support and enable the use of design practice, in order to make design a natural part of the continuous development work.

  • Public defence: 2017-03-16 13:00 Elsa Brändström-salen, Linköping
    Petersen, Eline Borch
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Eriksholm Research Centre.
    Neural and Cognitive Effects of Hearing Loss on Speech Processing2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Understanding speech in the presence of noise can be difficult, especially when suffering from a hearing loss. This thesis examined behavioural and electrophysiological measures of speech processing with the aim of establishing how they were influenced by hearing loss (internal degradation) and listening condition (external degradation). The hypothesis that more internal and external degradation of a speech signal would result in higher working memory (WM) involvement was investigated in four studies. The behavioural measure of speech recognition consistently decreased with worse hearing, whereas lower WM capacity only resulted in poorer speech recognition when sound were spatially co-located. Electrophysiological data (EEG) recorded during speech processing, revealed that worse hearing was associated with an increase in inhibitory alpha activity (~10 Hz). This indicates that listeners with worse hearing experienced a higher degree of WM involvement during the listening task. When increasing the level of background noise, listeners with poorer hearing exhibited a breakdown in alpha activity, suggesting that these listeners reached a ceiling at which no more WM resources could be released through neural inhibition. Worse hearing was also associated with a reduced ability to selectively attend to one of two simultaneous talkers, brought on by a reduced neural inhibition of the to-be-ignored speech. Increasing the level of background noise reduced the ability to neurally track the to-be-attended speech. That internal and external degradation affected the tracking of ignored and attended speech, respectively, indicates that the two speech streams were neurally processed as independent objects. This thesis demonstrates for the first time that hearing loss causes changes in the induced neural activity during speech processing. In the last paper of the thesis, it is tentatively suggested that neural activity can be utilized from electrodes positioned in the ear canal (EarEEG) for adapting hearing-aid processing to suite the individual listeners and situation.

    List of papers
    1. Danish Reading Span data from 283 hearing-aid users, including a sub-group analysis of their relationship to speech-in-noise performance
    Open this publication in new window or tab >>Danish Reading Span data from 283 hearing-aid users, including a sub-group analysis of their relationship to speech-in-noise performance
    2016 (English)In: International Journal of Audiology, ISSN 1499-2027, E-ISSN 1708-8186, Vol. 55, no 4, 254-261 p.Article in journal (Refereed) Published
    Abstract [en]

    Objective: This study provides descriptive statistics of the Danish reading span (RS) test for hearing-impaired adults. The combined effect of hearing loss, RS score, and age on speech-in-noise performance in different spatial settings was evaluated in a subset of participants. Design: Data from published and unpublished studies were re-analysed. Data regarding speech-in-noise performance with co-located or spatially separated sound sources were available for a subset of participants. Study sample: RS scores from 283 hearing-impaired participants were extracted from past studies, and 239 of these participants had completed a speech-in-noise test. Results: RS scores (mean = 41.91%, standard deviation = 11.29%) were related to age (p <0.01), but not pure-tone average (PTA) (p = 0.29). Speech-in-noise performance for co-located sound sources was related to PTA and RS score (both p < 0.01, adjusted R-squared = 0.226). Performance for spatially separated sounds was related to PTA (p < 0.01, adjusted R-squared = 0.10) but not RS score (p = 0.484). We found no differences between the standardized coefficients of the two regression models. Conclusions: The distribution of RS scores indicated a high test difficulty. We found that age should be controlled when RS scores are compared across populations. The experimental setup of the speech-in-noise test may influence the relationship between performance and RS score.

    Place, publisher, year, edition, pages
    Taylor & Francis, 2016
    Keyword
    Reading span; hearing impairment; spatially distributed vs. co-located sound sources; speech-in-noise; working memory
    National Category
    Otorhinolaryngology
    Identifiers
    urn:nbn:se:liu:diva-126496 (URN)10.3109/14992027.2015.1125533 (DOI)000371744400008 ()26836955 (PubMedID)
    Available from: 2016-03-29 Created: 2016-03-29 Last updated: 2017-02-07
    2. Hearing loss impacts neural alpha oscillations under adverse listening conditions
    Open this publication in new window or tab >>Hearing loss impacts neural alpha oscillations under adverse listening conditions
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    2015 (English)In: Frontiers in Psychology, ISSN 1664-1078, Vol. 6, no 177Article in journal (Refereed) Published
    Abstract [en]

    Degradations in external, acoustic stimulation have long been suspected to increase the load on working memory (WM). One neural signature of WM load is enhanced power of alpha oscillations (6–12 Hz). However, it is unknown to what extent common internal, auditory degradation, that is, hearing impairment, affects the neural mechanisms of WM when audibility has been ensured via amplification. Using an adapted auditory Sternberg paradigm, we varied the orthogonal factors memory load and background noise level, while the electroencephalogram was recorded. In each trial, participants were presented with 2, 4, or 6 spoken digits embedded in one of three different levels of background noise. After a stimulus-free delay interval, participants indicated whether a probe digit had appeared in the sequence of digits. Participants were healthy older adults (62–86 years), with normal to moderately impaired hearing. Importantly, the background noise levels were individually adjusted and participants were wearing hearing aids to equalize audibility across participants. Irrespective of hearing loss (HL), behavioral performance improved with lower memory load and also with lower levels of background noise. Interestingly, the alpha power in the stimulus-free delay interval was dependent on the interplay between task demands (memory load and noise level) and HL; while alpha power increased with HL during low and intermediate levels of memory load and background noise, it dropped for participants with the relatively most severe HL under the highest memory load and background noise level. These findings suggest that adaptive neural mechanisms for coping with adverse listening conditions break down for higher degrees of HL, even when adequate hearing aid amplification is in place.

    Keyword
    alpha oscillations, hearing loss, hearing aid, cognition, working memory
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-114641 (URN)10.3389/fpsyg.2015.00177 (DOI)000349597100001 ()25745410 (PubMedID)
    Available from: 2015-03-02 Created: 2015-03-02 Last updated: 2017-02-07
    3. Neural tracking of attended versus ignored speech is differentially affected by hearing loss
    Open this publication in new window or tab >>Neural tracking of attended versus ignored speech is differentially affected by hearing loss
    2017 (English)In: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 117, no 1, 18-27 p.Article in journal (Refereed) Published
    Abstract [en]

    Hearing loss manifests as a reduced ability to understand speech, particularly in multitalker situations. In these situations, younger normal-hearing listeners' brains are known to track attended speech through phase-locking of neural activity to the slow-varying envelope of the speech. This study investigates how hearing loss, compensated by hearing aids, affects the neural tracking of the speech-onset envelope in elderly participants with varying degree of hearing loss (n = 27, 62–86 yr; hearing thresholds 11–73 dB hearing level). In an active listening task, a to-be-attended audiobook (signal) was presented either in quiet or against a competing to-be-ignored audiobook (noise) presented at three individualized signal-to-noise ratios (SNRs). The neural tracking of the to-be-attended and to-be-ignored speech was quantified through the cross-correlation of the electroencephalogram (EEG) and the temporal envelope of speech. We primarily investigated the effects of hearing loss and SNR on the neural envelope tracking. First, we found that elderly hearing-impaired listeners' neural responses reliably track the envelope of to-be-attended speech more than to-be-ignored speech. Second, hearing loss relates to the neural tracking of to-be-ignored speech, resulting in a weaker differential neural tracking of to-be-attended vs. to-be-ignored speech in listeners with worse hearing. Third, neural tracking of to-be-attended speech increased with decreasing background noise. Critically, the beneficial effect of reduced noise on neural speech tracking decreased with stronger hearing loss. In sum, our results show that a common sensorineural processing deficit, i.e., hearing loss, interacts with central attention mechanisms and reduces the differential tracking of attended and ignored speech.

    Keyword
    hearing loss, neural tracking, attention, speech-onset envelope, electroencephalography, cross-correlation
    National Category
    Neurosciences
    Identifiers
    urn:nbn:se:liu:diva-133644 (URN)10.1152/jn.00527.2016 (DOI)
    Available from: 2017-01-05 Created: 2017-01-05 Last updated: 2017-02-07
    4. Cognitive Hearing Aids? - Insights and Possibilities
    Open this publication in new window or tab >>Cognitive Hearing Aids? - Insights and Possibilities
    2015 (English)Conference paper (Refereed)
    Abstract [en]

    The working memory plays an important role in successfully overcoming adverse listening conditions and should consequently be considered when designing and testing hearing aids. A number of studies have established the relationship between hearing in noise and working memory involvement, but with the Sentence-final Word Identification and Recall (SWIRL) test, it is possible to show that working memory is also involved in listening under favorable conditions and that noise reduction has a positive influence in situation with very little noise. Although the capacity of the working memory is a finite individual size, its involvement can differ with fatigue and other factors and individualization of hearing aids should take this into account to obtain the best performance. A way of individually adapting hearing aids is based on changes in the electrical activity of the brain (EEG). Here we present the possibilities that arise from using EEG and show that ear-mounted electrodes is able to record useful EEG that can be explored for individualization of hearing aids. Such an adaptation could be done based on changes in the electrical activity of the brain (EEG). Here we present the possibilities that arise from using EEG and show that ear-mounted electrodes is able to record useful EEG that can be explored for individualization of hearing aids.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2015
    Series
    AIP Conference Proceedings, ISSN 0094-243X
    National Category
    Otorhinolaryngology
    Identifiers
    urn:nbn:se:liu:diva-126560 (URN)10.1063/1.4939399 (DOI)000372065400086 ()978-0-7354-1350-4 (ISBN)
    Conference
    12th international workshop in Mechanics of Hearing, Cape Sounio, Greece, 23-29 May 2014
    Available from: 2016-03-30 Created: 2016-03-30 Last updated: 2017-02-07
  • Public defence: 2017-03-17 09:00 Hasselquist, Linköping
    Bahrampour, Shahrzad
    Linköping University, Department of Clinical and Experimental Medicine, Division of Microbiology and Molecular Medicine. Linköping University, Faculty of Medicine and Health Sciences.
    Genetic mechanisms regulating proliferation and cell specification in the Drosophila embryonic CNS2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The central nervous system (CNS) consists of an enormous number of cells, and large cellular variance, integrated into an elaborate network. The CNS is the most complex animal organ, and therefore its establishment must be controlled by many different genetic programs. Considering the high level of complexity in the human CNS, addressing issues related to human neurodevelopment represents a major challenge. Since comparative studies have revealed that neurodevelopmental programs are well conserved through evolution, on both the genetic and functional levels, studies on invertebrate neurodevelopmental programs are often translatable to vertebrates. Indeed, the basis of our current knowledge about vertebrate CNS development has been greatly aided by studies on invertebrates, and in particular on the Drosophila melanogaster (fruit fly) model system.

    This thesis attempted to identify novel genes regulating neural cell specification and proliferation in the CNS, using the Drosophila model system. Moreover, I aimed to address how those genes govern neural progenitor cells (neuroblasts; NBs) to obtain/maintain their stemness identity and proliferation capacity, and how they drive NBs through temporal windows and series of programmed asymmetric division, which gradually reduces their stemness identity in favor of neural differentiation, resulting in appropriate lineage progression. In the first project, we conducted a forward genetic screen in Drosophila embryos, aimed at isolating genes involved in regulation of neural proliferation and specification, at the single cell resolution. By taking advantage of the restricted expression of the neuropeptide FMRFa in the last-born cell of the NB lineage 5-6T, the Ap4 neuron, we could monitor the entire lineage progression. This screen succeeded in identifying 43 novel genes controlling different aspects of CNS development. One of the genes isolated, Ctr9, displayed extra Ap4/FMRFa neurons. Ctr9 encodes a component of the RNA polymerase II complex Paf1, which is involved in a number of transcriptional processes. The Paf1C, including Ctr9, is highly conserved from yeast to human, and in the past couple of years, its importance for transcription has become increasingly appreciated. However, studies in the Drosophila system have been limited. In the screen, we isolated the first mutant of Drosophila Ctr9 and conducted the first detailed phenotypic study on its function in the Drosophila embryonic CNS. Loss of function of Ctr9 leads to extra NB numbers, higher proliferation ratio and lower expression of neuropeptides. Gene expression analysis identified several other genes regulated by Ctr9, which may explain the Ctr9 mutant phenotypes. In summary, we identified Ctr9 as an essential gene for proper CNS development in Drosophila, and this provides a platform for future study on the Drosophila Paf1C. Another interesting gene isolated in the screen was worniou (wor), a member of the Snail family of transcription factors. In contrast to Ctr9, whichdisplayed additional Ap4/FMRFa neurons, wor mutants displayed a loss of these neurons. Previous studies in our group have identified many genes acting to stop NB lineage progression, but how NBs are pushed to proliferate and generate their lineages was not well known. Since wor may constitute a “driver” of proliferation, we decided to study it further. Also, we identified five other transcription factors acting together with Wor as pro-proliferative in both NBs and their daughter cells. These “drivers” are gradually replaced by the previously identified late-acting “stoppers.” Early and late factors regulate each other and the cell cycle, and thereby orchestrate proper neural lineage progression.

    List of papers
    1. Novel Genes Involved in Controlling Specification of Drosophila FMRFamide Neuropeptide Cells
    Open this publication in new window or tab >>Novel Genes Involved in Controlling Specification of Drosophila FMRFamide Neuropeptide Cells
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    2015 (English)In: Genetics, ISSN 0016-6731, E-ISSN 1943-2631, Vol. 200, no 4, 1229-1244 p.Article in journal (Refereed) Published
    Abstract [en]

    The expression of neuropeptides is often extremely restricted in the nervous system, making them powerful markers for addressing cell specification . In the developing Drosophila ventral nerve cord, only six cells, the Ap4 neurons, of some 10,000 neurons, express the neuropeptide FMRFamide (FMRFa). Each Ap4/FMRFa neuron is the last-born cell generated by an identifiable and well-studied progenitor cell, neuroblast 5-6 (NB5-6T). The restricted expression of FMRFa and the wealth of information regarding its gene regulation and Ap4 neuron specification makes FMRFa a valuable readout for addressing many aspects of neural development, i.e., spatial and temporal patterning cues, cell cycle control, cell specification, axon transport, and retrograde signaling. To this end, we have conducted a forward genetic screen utilizing an Ap4-specific FMRFa-eGFP transgenic reporter as our readout. A total of 9781 EMS-mutated chromosomes were screened for perturbations in FMRFa-eGFP expression, and 611 mutants were identified. Seventy-nine of the strongest mutants were mapped down to the affected gene by deficiency mapping or whole-genome sequencing. We isolated novel alleles for previously known FMRFa regulators, confirming the validity of the screen. In addition, we identified novel essential genes, including several with previously undefined functions in neural development. Our identification of genes affecting most major steps required for successful terminal differentiation of Ap4 neurons provides a comprehensive view of the genetic flow controlling the generation of highly unique neuronal cell types in the developing nervous system.

    Place, publisher, year, edition, pages
    Genetics Society of America, 2015
    Keyword
    Drosophila; CNS development; neural cell fate specification; forward genetic screening; FMRFamide
    National Category
    Clinical Medicine
    Identifiers
    urn:nbn:se:liu:diva-121318 (URN)10.1534/genetics.115.178483 (DOI)000359917000020 ()26092715 (PubMedID)
    Available from: 2015-09-16 Created: 2015-09-14 Last updated: 2017-02-14Bibliographically approved
    2. Ctr9, a Key Component of the Paf1 Complex, Affects Proliferation and Terminal Differentiation in the Developing Drosophila Nervous System
    Open this publication in new window or tab >>Ctr9, a Key Component of the Paf1 Complex, Affects Proliferation and Terminal Differentiation in the Developing Drosophila Nervous System
    2016 (English)In: G3: Genes, Genomes, Genetics, ISSN 2160-1836, E-ISSN 2160-1836, Vol. 6, no 10, 3229-3239 p.Article in journal (Refereed) Published
    Abstract [en]

    The Paf1 protein complex (Paf1C) is increasingly recognized as a highly conserved and broadly utilized regulator of a variety of transcriptional processes. These include the promotion of H3K4 and H3K36 trimethylation, H2BK123 ubiquitination, RNA Pol II transcriptional termination, and also RNA-mediated gene silencing. Paf1C contains five canonical protein components, including Paf1 and Ctr9, which are critical for overall complex integrity, as well as Rtf1, Leo1, and Cdc73/Parafibromin(Hrpt2)/Hyrax. In spite of a growing appreciation for the importance of Paf1C from yeast and mammalian studies, there has only been limited work in Drosophila. Here, we provide the first detailed phenotypic study of Ctr9 function in Drosophila. We found that Ctr9 mutants die at late embryogenesis or early larval life, but can be partly rescued by nervous system reexpression of Ctr9. We observed a number of phenotypes in Ctr9 mutants, including increased neuroblast numbers, increased nervous system proliferation, as well as downregulation of many neuropeptide genes. Analysis of cell cycle and regulatory gene expression revealed upregulation of the E2f1 cell cycle factor, as well as changes in Antennapedia and Grainy head expression. We also found reduction of H3K4me3 modification in the embryonic nervous system. Genome-wide transcriptome analysis points to additional downstream genes that may underlie these Ctr9 phenotypes, revealing gene expression changes in Notch pathway target genes, cell cycle genes, and neuropeptide genes. In addition, we find significant effects on the gene expression of metabolic genes. These findings reveal that Ctr9 is an essential gene that is necessary at multiple stages of nervous system development, and provides a starting point for future studies of the Paf1C in Drosophila.

    Place, publisher, year, edition, pages
    Genetics Society of America, 2016
    Keyword
    neuroblast, lineage tree, cell cycle, epigenetics, terminal differentiation, FlyBook
    National Category
    Genetics
    Identifiers
    urn:nbn:se:liu:diva-132856 (URN)10.1534/g3.116.034231 (DOI)000386581200018 ()27520958 (PubMedID)
    Note

    Funding Agencies|Swedish Research Council [621-2013-5258]; Knut and Alice Wallenberg Foundation [KAW2011.0165]; Swedish Cancer Foundation [120531]; Swedish Royal Academy of Sciences

    Available from: 2016-12-06 Created: 2016-11-30 Last updated: 2017-02-14
  • Public defence: 2017-03-17 13:00 Berzeliussalen, Linköping
    Lampi, Maria
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences.
    TRIAGE: Management of the trauma patient2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Triage, derived from the French word for sorting, aims to assess and prioritize injured patients, regardless of whether the injuries are sustained from everyday road traffic accident with few injured or a mass casualty incident. Triage seeks to provide the greatest benefit to the largest number of casualties in order to minimize morbidity and mortality. Triage in a pre-hospital setting entails management and sorting of patients according to an assessment of medical need, prioritization, and evacuation. In-hospital triage aims to rapidly identify the most injured and ensure timely and appropriate treatment according to the patient’s clinical urgency. A number of different systems for performing triage have been established and implemented globally. The methodology is recognized and utilized but there is still a need for an evidence-based strategy to optimize training and the efficacy of the different systems.

    The main aim of this thesis was to determine triage performance among prehospital personnel and investigate the potential advantage of a triage system for trauma patients. The papers included in this thesis evaluated the triage skills of physicians, pre-hospital personnel, and rescue services personnel by testing their performance before and after an educational intervention. The last paper evaluated potential benefits of using a triage system for trauma patients admitted to the emergency department at MOI Teaching and Referral Hospital in Eldoret, Kenya.

    The results presented in this thesis illustrate that triage skills are lacking among physicians. Experienced pre-hospital personnel are more skilled in performing triage than physicians. The triage skills of the rescue services personnel improved significantly after the educational intervention. Moreover, the potential benefit to trauma patients of implementing an in-hospital triage system in a resource-poor environment was shown. In conclusion, health care personnel, especially physicians without experience but highly involved in trauma patient management, seem to be in need of triage training. How to train, how to implement, and how to evaluate triage skills must be considered in order to develop effective training.

    List of papers
    1. Triage performance of Swedish physicians using the ATLS algorithm in a simulated mass casualty incident: a prospective cross-sectional survey
    Open this publication in new window or tab >>Triage performance of Swedish physicians using the ATLS algorithm in a simulated mass casualty incident: a prospective cross-sectional survey
    2013 (English)In: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine, ISSN 1757-7241, Vol. 21, no 90Article in journal (Refereed) Published
    Abstract [en]

    Background: In a mass casualty situation, medical personnel must rapidly assess and prioritize patients for treatment and transport. Triage is an important tool for medical management in disaster situations. Lack of common international and Swedish triage guidelines could lead to confusion. Attending the Advanced Trauma Life Support (ATLS) provider course is becoming compulsory in the northern part of Europe. The aim of the ATLS guidelines is provision of effective management of single critically injured patients, not mass casualties incidents. However, the use of the ABCDE algorithms from ATLS, has been proposed to be valuable, even in a disaster environment. The objective for this study was to determine whether the mnemonic ABCDE as instructed in the ATLS provider course, affects the ability of Swedish physician's to correctly triage patients in a simulated mass casualty incident.Methods: The study group included 169 ATLS provider students from 10 courses and course sites in Sweden; 153 students filled in an anonymous test just before the course and just after the course. The tests contained 3 questions based on overall priority. The assignment was to triage 15 hypothetical patients who had been involved in a bus crash. Triage was performed according to the ABCDE algorithm. In the triage, the ATLS students used a colour-coded algorithm with red for priority 1, yellow for priority 2, green for priority 3 and black for dead. The students were instructed to identify and prioritize 3 of the most critically injured patients, who should be the first to leave the scene. The same test was used before and after the course.Results: The triage section of the test was completed by 142 of the 169 participants both before and after the course. The results indicate that there was no significant difference in triage knowledge among Swedish physicians who attended the ATLS provider course. The results also showed that Swedish physicians have little experience of real mass casualty incidents and exercises.Conclusion: The mnemonic ABCDE doesn't significantly affect the ability of triage among Swedish physicians. Actions to increase Swedish physicians' knowledge of triage, within the ATLS context or separately, are warranted.

    Place, publisher, year, edition, pages
    BioMed Central, 2013
    Keyword
    ATLS; Triage; Disaster; Education; Physicians; Mass casualty incident; Exercises
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-103718 (URN)10.1186/1757-7241-21-90 (DOI)000329181100001 ()
    Available from: 2014-01-24 Created: 2014-01-24 Last updated: 2017-02-20Bibliographically approved
    2. Improved and sustained triage skills in firemen after a short training intervention
    Open this publication in new window or tab >>Improved and sustained triage skills in firemen after a short training intervention
    Show others...
    2015 (English)In: Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine, ISSN 1757-7241, E-ISSN 1757-7241, Vol. 23, no 81, 1-6 p.Article in journal (Refereed) Published
    Abstract [en]

    Background: A previous study has shown no measurable improvement in triage accuracy among physicians attending the Advanced Trauma Life Support (ATLS) course and suggests a curriculum revision regarding triage. Other studies have indicated that cooperative learning helps students acquire knowledge. Objective: The present study was designed to evaluate the effectiveness of trauma cards in triage training for firemen. Methods: Eighty-six firemen were randomly assigned into two groups: the trauma card group and the direct instruction group. Both groups received the same 30-min PowerPoint lecture on how to perform triage according to the Sort Assess Lifesaving interventions Treatment and transport (SALT) Mass Casualty Triage Algorithm. In the trauma card group, the participants were divided into groups of 3-5 and instructed to triage 10 trauma victims according to the descriptions on the trauma cards. In the direct instruction group, written forms about the same 10 victims were used and discussed as a continuation of the PowerPoint lecture. Total training time was 60 min for both groups. A test was distributed before and after the educational intervention to measure the individual triage skills. The same test was applied again 6 months later. Results: There was a significant improvement in triage skills directly after the intervention and this was sustained 6 months later. No significant difference in triage skills was seen between the trauma card group and the direct instruction group. Previous experience of multi-casualty incidents, years in service, level of education or age did not have any measurable effects on triage accuracy. Conclusions: One hour of triage training with the SALT Mass Casualty Triage Algorithm was enough to significantly improve triage accuracy in both groups of firemen with sustained skills 6 months later. Further studies on the first assessment on scene versus patient outcome are necessary to provide evidence that this training can improve casualty outcome. The efficacy and validity of trauma cards for disaster management training need to be tested in future studies.

    Place, publisher, year, edition, pages
    BIOMED CENTRAL LTD, 2015
    Keyword
    Triage; Triage training; SALT Mass Casualty Triage Algorithm; Trauma cards; Direct instruction; Firemen
    National Category
    Other Medical Sciences not elsewhere specified
    Identifiers
    urn:nbn:se:liu:diva-122520 (URN)10.1186/s13049-015-0162-7 (DOI)000363098400002 ()26481218 (PubMedID)
    Note

    Funding Agencies|Swedish Civil Contingencies Agency

    Available from: 2015-11-09 Created: 2015-11-06 Last updated: 2017-02-20
  • Public defence: 2017-03-17 13:15 K1, Kåkenhus, Norrköping
    Dalgren, Sara
    Linköping University, Department of Social and Welfare Studies, Learning, Aesthetics, Natural science. Linköping University, Faculty of Educational Sciences.
    Att göra pedagogisk praktik tillsammans: Socialt samspel i förskolans vardag2017Doctoral thesis, monograph (Other academic)
    Abstract [sv]

    Denna studies övergripande syfte är att åskådliggöra hur social interaktion mellan förskolepedagoger och barn i vardagliga förskoleaktiviteter genomförs och därigenom också visa hur pedagogisk praktik åstadkoms i samspelet. Mer specifikt analyseras hur det går till och vad som händer när interaktionen organiseras genom multimodalt handlande och fråga-svar-sekvenser, och hur dessa interaktionella fenomen kan tjäna pedagogiska syften. Som teoretiska och analytiska utgångspunkter använder sig studien av etnometodologiskt perspektiv och konversationsanalys. Detta innebär att delar av det videofilmade materialet har transkriberats och analyserats i detalj.

    Resultatet presenteras i sex empiriska kapitel och visar konkret och detaljerat hur deltagarna ”gör” förskolepedagogisk praktik tillsammans. Studiens analyser belyser hur pedagoger och barn genomför interaktionella projekt, eftersträvar intersubjektivitet och etablerar organisatoriska principer för gemensamma aktiviteter. Analyserna visar också hur ett yngre förskolebarn kan delta aktivt i måltider utan tal, hur vardagliga aktiviteter transformeras till problemlösningsprojekt och hur lokala pedagogiska praktiker orienterade mot sociala (måltids)normer, språk, fysik och matematik kan genereras spontant i förskolans vardag. Avhandlingen lyfter slutligen begreppet inbäddad undervisning och försöker därigenom definiera och empiriskt konkretisera den typ av undervisning som bedrivs i förskolan.

  • Public defence: 2017-03-23 10:15 C3, C-huset, Linköping
    Johansson, Cristina
    Linköping University, Department of Management and Engineering, Machine Design. Linköping University, Faculty of Science & Engineering.
    Multiobjective Optimization for Safety and Reliability Trade-off: Applications on Early Phases of Aircraft Systems Design2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A strategic issue for any industrial company is to conceive safe and reliable systems while performing all systems’ intended functions at a minimum cost. System safety and reliability are fundamental to system design and involve a quantitative assessment prior to system development. Aircraft design is a multifaceted process that involves several different disciplines, system safety and reliability among them, to obtain o holistic approach of a complex product. During the last decades, the idea of trade-off between safety or reliability goals against other characteristics has become more prominent. Furthermore, while predictions of system performance can be made in early design phases with credible precision, within reasonable tolerances, reliability and system safety are seldom predicted with high accuracy and confidence. Making the right design decisions in the early design phase is vital to the success of a project. Nowadays, it is essential within the design of new products, to increase awareness (knowledge) early in the design phases and keep the design decisions (freedom) open as long as possible, and with that also keep down the allocated costs.

    This thesis presents MOSART (Multiobjective Optimization for Safety and Reliability Trade-off), a method promoting a systematic approach regarding trade-offs between system safety and reliability goals against other contradictory targets, such as weight and cost, in early design phases.

    A theoretical framework and context are presented in the first part of the thesis, including system safety and reliability methods and optimization techniques. The second and third parts are dedicated to contributions and papers, where seven papers are included. These papers approach different aspects of MOSART, from the basic idea to the implementation and usage of the method in the conceptual phase of aircraft systems design. Several aspects regarding the choice of system safety and reliability methods in early design phases are also included in the papers, e.g. evaluation of applicability of reliability methods in early design phases, considerations around the usage of these methods within the MOSART framework and a proposal of a guideline for how to choose the right reliability method. All the examples used in the papers are chosen from basic aircraft sub-systems.

    List of papers
    1. On the Usage of Reliability Methods in Early Design Phases
    Open this publication in new window or tab >>On the Usage of Reliability Methods in Early Design Phases
    2012 (English)In: Proceedings of the 11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012 (PSAM11 ESREL 2012), Curran Associates, Inc., 2012, 769-778 p.Conference paper (Refereed)
    Abstract [en]

    One important challenge in the early phases of product development is to apply reliability methods for estimating the safety and reliability of the system when information about the chosen equipment and components is limited. For systems consisting of units with several degraded states, and not only “up” and “down”, the results from reliability and system safety analysis are often difficult to interpret and use. The main contribution of this paper is to evaluate the applicability of different reliability methods for analyzing an overall system concept in early development stages. Furthermore, the paper constitutes the first step of a methodology intended to address the issues outlined above from a practical point of view. In the paper, two static methods, Reliability Block Diagram and Fault Tree Analysis, and one dynamic method, Markov Analysis, have been applied to conceptual design of an aircraft electrical system. These three methods have been evaluated regarding usefulness, modeling possibilities and applicability in the conceptual design. Each method is, from a practical point of view, dependent on the limitations of the software that is used. In order to overcome this issue the calculations and partly the modeling have been performed in three different software tools.

    Two iterations have been performed for Markov Analysis, and the results are used to evaluate the method regarding applicability and possibilities of modeling the system and to find out what results can be gained by extending the model.

    Place, publisher, year, edition, pages
    Curran Associates, Inc., 2012
    Keyword
    System Reliability, Markov Analysis, Reliability Block Diagram, Fault Tree
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-94350 (URN)978-1-62276-436-5 (ISBN)
    Conference
    11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012 (PSAM11 ESREL 2012), 25-29 June, Helsinki, Finland
    Available from: 2013-06-25 Created: 2013-06-25 Last updated: 2017-02-20Bibliographically approved
    2. Choosing the reliability approach: A guideline for selecting the appropriate reliability method in the design process
    Open this publication in new window or tab >>Choosing the reliability approach: A guideline for selecting the appropriate reliability method in the design process
    2013 (English)In: Proceedings of the 20th Advances in Risk and Reliability Technology Symposium 21–23 May 2013 / [ed] Lisa Jackson and John Andrews, Loughborough: Loughborough University, UK , 2013, 366-378 p.Conference paper (Other academic)
    Abstract [en]

    The main objective of a reliability study should always be to provide information as a basis for decisions, e.g. concept choice, design requirements, investment, choice of suppliers, design changes or guaranty claims. The choice of reliability method depends on the time allocated for the reliability study, the design stage, the problem at hand and the competence and resources available.

    During a reliability study the engineer focuses on providing a graphical means of evaluating the relationships between different parts of the system, gathering or assessing the reliability data for the components and interpreting the results of the analyses. Even though the commercial software tools available claim to provide answers to most reliability questions, choosing which method is best suited is not an easy task. Often several methods can be applied and none of them will fit the purpose perfectly.

    This paper presents a guideline for choosing the best suited reliability method in early design phases from two aspects: objective and system characteristics. The methods studied are the most common methods available in commercial software tools: Reliability Block Diagram (RBD), Fault Tree (FT), Event Tree (ET), Markov Analysis (MA) and Stochastic Petri Network (SPN). The guideline considers two aspects: the characteristics of the system studied and the scope of the analysis. The applicability of each of the five chosen methods is assessed for all possible combinations of system characteristics and objective. A study has been made at Saab Aeronautics to evaluate the practical use of the analysed methods and how this guideline can improve the selection of appropriate reliability methods in early design phases.

    Place, publisher, year, edition, pages
    Loughborough: Loughborough University, UK, 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-94352 (URN)9781907382611 (ISBN)
    Conference
    The 20th Advances in Risk and Reliability Technology Symposium, 21st – 23rd May 2013, Burleigh Court Conference Centre, Loughborough, Leicestershire, UK
    Available from: 2013-06-25 Created: 2013-06-25 Last updated: 2017-02-20Bibliographically approved
    3. Cost optimization with focus on reliability and system safety
    Open this publication in new window or tab >>Cost optimization with focus on reliability and system safety
    2013 (English)In: Safety, Reliability and Risk AnalysisBeyond the Horizon / [ed] R. D. J. M. Steenbergen , P. H. A. J. M. van Gelder , S. Miraglia and A. C. W. M. Ton. Vrouwenvelder, CRC Press, 2013, 2723-2730 p.Conference paper (Refereed)
    Abstract [en]

    When developing a safety critical system, there are many aspects that need to be balanced against each other in order to reach an optimal design such as safety requirements, reliability goal, performance specifications and budget constraints. In an early design stage, it is vital to be able to screen the design space for a set of promising design alternatives for further studies. This paper proposes an approach capable of investigating the trade-offs described above, combining the techniques for system safety and reliability analysis with optimization methods. Markov analysis is employed for modeling the system safety and reliability characteristics and a Genetic Algorithm is used for optimization. The proposed method is applied to the design of an electric supply system for an aircraft, involving selection of components from different suppliers. First a model is built for each objective, i.e. cost, safety, and reliability. The models are validated and optimization is performed. The obtained result is the selection of suppliers for each component in the system in order to achieve a balance between system safety, reliability, and other design objectives.

    Place, publisher, year, edition, pages
    CRC Press, 2013
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-94353 (URN)10.1201/b15938-413 (DOI)9781138001237 (ISBN)9781315815596 (ISBN)
    Conference
    ESREL2013, 29 Sep-02 October, Amsterdam, Holland
    Available from: 2013-06-25 Created: 2013-06-25 Last updated: 2017-02-20Bibliographically approved
    4. An Industrial Implementation of an Optimization Based Method for Balancing Safety, Reliability and Weight of Aircraft Systems
    Open this publication in new window or tab >>An Industrial Implementation of an Optimization Based Method for Balancing Safety, Reliability and Weight of Aircraft Systems
    Show others...
    2016 (English)In: Risk, Reliability and Safety: Innovating Theory and Practice: Proceedings of ESREL 2016 (Glasgow, Scotland, 25-29 September 2016) / [ed] Lesley Walls, Matthew Revie and Tim Bedford, CRC Press, 2016, 1707-1713 p.Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to show how a method able of trade-offs such as system safety, reliability, weight and cost can be practically implemented in industry (SAAB Aeronautics). The scope is to facilitate the decision-making on the optimal design in early design phases. The method consists of several steps guiding the user to model each objective, verify and validate the models, perform optimization and finally visualize and select the results. Within the practical implementation of this method, several challenges are addressed and solved. For example, one challenge is to implement the trade-off method using the existing programs. Another challenge is the user friendliness of the implementation. In order to solve these challenges, the analysis is started and performed in Matlab. A Graphical User Interface guides the user to select the analysis to perform, budgets/requirements for each objective and parameters with influence on end-result. Data regarding the safety and reliability objectives, exported from Reliability Workbench program to Excel, is imported to Matlab, where the analysis is performed. The results are extracted into an Excel file, where the user can work further on visualization and selection. Two small examples are used to demonstrate this practical implementation of the trade-off method. Lessons learned are presented, strengths, limitations and development potential.

    Place, publisher, year, edition, pages
    CRC Press, 2016
    National Category
    Computer Systems Embedded Systems Software Engineering
    Identifiers
    urn:nbn:se:liu:diva-134590 (URN)9781138029972 (ISBN)9781315374987 (ISBN)
    Conference
    ESREL 2016, Glasgow, Scotland, 25-29 September 2016
    Available from: 2017-02-20 Created: 2017-02-20 Last updated: 2017-02-20Bibliographically approved
    5. How to use an Optimization-based Method Capable of Balancing Safety, Reliability, and Weight in an Aircraft Design Process
    Open this publication in new window or tab >>How to use an Optimization-based Method Capable of Balancing Safety, Reliability, and Weight in an Aircraft Design Process
    2017 (English)In: Nuclear engineering and technology : an international journal of the Korean Nuclear Society, ISSN 1738-5733, E-ISSN 2234-358XArticle in journal (Refereed) Epub ahead of print
    Abstract [en]

    In order to help decision-makers in the early design phase to improve and make more cost-efficient system safety and reliability baselines of aircraft design concepts, a method (Multi-objective Optimization for Safety and Reliability Trade-off) that is able to handle trade-offs such as system safety, system reliability, and other characteristics, for instance weight and cost, is used. Multi-objective Optimization for Safety and Reliability Trade-off has been developed and implemented at SAAB Aeronautics. The aim of this paper is to demonstrate how the implemented method might work to aid the selection of optimal design alternatives. The method is a three-step method: step 1 involves the modelling of each considered target, step 2 is optimization, and step 3 is the visualization and selection of results (results processing). The analysis is performed within Architecture Design and Preliminary Design steps, according to the company’s Product Development Process. The lessons learned regarding the use of the implemented trade-off method in the three cases are presented. The results are a handful of solutions, a basis to aid in the selection of a design alternative. While the implementation of the trade-off method is performed for companies, there is nothing to prevent adapting this method, with minimal modifications, for use in other industrial applications.

    Keyword
    Aircraft Design, Early Design Phases, MOSART, Safety, Reliability, Trade-off
    National Category
    Production Engineering, Human Work Science and Ergonomics Embedded Systems Computer Science Computer Systems Reliability and Maintenance
    Identifiers
    urn:nbn:se:liu:diva-134591 (URN)10.1016/j.net.2017.01.006 (DOI)
    Available from: 2017-02-20 Created: 2017-02-20 Last updated: 2017-02-20Bibliographically approved