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  • 201.
    Alqaysi, Hiba
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Fedorov, Igor
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Design Exploration of Multi-Camera Dome2019In: ICDSC 2019 Proceedings of the 13th International Conference on Distributed Smart Cameras, New York, NY: ACM Digital Library, 2019, article id Article No. 7aConference paper (Refereed)
    Abstract [en]

    Visual monitoring systems employ distributed smart cameras toeffectively cover a given area satisfying specific objectives. Thechoice of camera sensors and lenses and their deployment affectsdesign cost, accuracy of the monitoring system and the ability toposition objects within the monitored area. Design cost can bereduced by investigating deployment topology such as groupingcameras together to form a dome at a node and optimize it formonitoring constraints. The constraints may include coverage area,number of cameras that can be integrated in a node and pixelresolution at a given distance. This paper presents a method foroptimizing the design cost of multi-camera dome by analyzing tradeoffsbetween monitoring constraints. The proposed method can beused to reduce monitoring cost while fulfilling design objectives.Results show how to increase coverage area for a given cost byrelaxing requirements on design constraints. Multi-camera domescan be used in sky monitoring applications such as monitoring windparks and remote air-traffic control of airports where all-round fieldof view about a point is required to monitor.

  • 202.
    Alricsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Landstad, Bodil
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Romild, Ulla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Gundersen, KT
    Physical activity, health, BMI and body complaints in high school students2008In: Minerva Pediatrica, ISSN 0026-4946, E-ISSN 1827-1715, Vol. 60, no 1, p. 19-25Article in journal (Refereed)
    Abstract [en]

     

    AIM: Children and adolescents in the industrial world are becoming less

    physically active and are adopting a sedentary lifestyle in front of computers

    and TV. The aim of the present investigation was to determine self-related

    health, physical activity, prevalence of overweight and body complaints in

    high school students in Norway, and to compare students in academic

    programs with those in vocational programs. METHODS: Seven hundred and

    two high school students aged 16-19 years were included in the study. A

    questionnaire was completed in three high schools and included questions

    about weight and height, health, physical activity, type of physical

    activity/sport, intensity, possible injuries or complaints during the last three

    months. RESULTS: Twenty three percent of the students suffers from

    overweight/obesity are at risk of being overweight. Males reported better

    health than females (P<0.02). Sixty-six percent of the study group reported

    body complaints during the last three months, a higher number of females

    than males (P=0.001). Students in vocational programs reported poorer selfrelated

    health than those in academic programs and the males reported

    better self-related health generally than females. Furthermore, there were a

    higher level of prevalence of overweight students in vocational programs

    than academic programs (P=0.039). CONCLUSION: It is important to make it

    easy for school children and adolescents to do physical activity at school and

    during leisure time in order to prevent overweight and obesity as well as

    chronic diseases later in life.

     

  • 203.
    Alricsson, Marie
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Landstad, Bodil
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Romild, Ulla
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Werner, Suzanne
    Self-related health, physical activity and complaints in Swedish high school students2006In: Scientific World Journal, ISSN 1537-744X, E-ISSN 1537-744X, Vol. 6, p. 816-826Article in journal (Refereed)
    Abstract [en]

    The aim of this investigation was to study self-related health, physical activity and level of exertion, as well as body complaints in Swedish high school students. A total of 993 high school students aged 16–19 years participated in the study. A questionnaire was completed at school and included questions about self-related health, physical activity behavior, type of physical activity/sport, intensity, duration, possible injuries or complaints, and absence from physical training at school, during the last 3 months. The results showed that 26% of the high school students participated in sports on a regular basis. Males reported significantly better health than females (p < 0.0005). A significantly higher number of females participated in physical activities at a lower level of effort (p < 0.0005) and a higher number of males trained at a higher level of effort (p < 0.005). Sixty-one percent reported body pain during the last 3 months, representing a higher number of females than males (p = 0.03). A higher number of females than males reported complaints from the back (p = 0.002), the knees (p = 0.015), the neck (p = 0.001), and the hip (p = 0.015). Females with body complaints reported poorer health than those without complaints. There was a correlation between poor self-related health and a lower level of physical effort (0.219; p < 0.001). The results showed that the prevalence of musculoskeletal symptoms was high in this population and demonstrated a certain association with self-related health. Therefore, it is important to make it easy for adolescents to perform physical activity at school and during their leisure time in order to prevent chronic diseases.

  • 204.
    Al-Sahli, Firas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Ibrahimson, Maria
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Delaktighetens förutsättningar och begränsningar i förbättringsarbetet2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Participation is an important aspect when it comes to continuous improvements. Participation increases quality and creates support among employees and is a tool for achieving successful quality work. Companies need prerequisites for creating participation, and in successful companies this success is characterized by the creation of participation and motivation among employees. The aim of the study was to describe how production supervisors create opportunities for participation in improvement processes. The method used was a qualitative inductive approach from a life-world perspective. In-depth interviews were conducted with eight production supervisors and qualitative content analysis was used to examine texts to find sentence entetities and categories. Fishbone diagrams were created as a complement to the interviews. The results and the analysis indicated two categories, prerequisites and limitations to create participation in improvement work. This showed that there are difficulties when it comes to interpreting the term participation and even more difficult to specify the tools inuse. In the future it is of great importance to ensure that the research around the creation of participation is in focus.

  • 205.
    Alsmo, Ludvig
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Bärlund, Jonathan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Nyttomaximering vid eleffektbrist på lokalnätet: En objektprioritering i en simuleringsansatts2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this study was to study the Styrel concept as an approach to identify electricity users and prioritize them in the event of a power shortage on a power grid. The study has examined and investigated how the priorities of different electricity users go to, how the benefits of manual disconnection change according to the decision makers' different priorities and how interaction between different local networks affects total utility. The features of a community on a local area, also called objects, are divided into eight priority classes depending on the function of the objects. The area for this study has been decision management. The study has been conducted using results from previous studies and theories on decision analysis as the basis for constructing a simulator that simulates how the power of a power failure changes for a local area dependent on the extent of the electricity supply (capacity). The study's findings have shown that prioritization of electricity supply line with higher priority classes should be prioritized than an electricity supply line with lower priority classes. This is also the result of previous studies. On the other hand, the study has shown that the fixed asset for an electricity supply line with lower priority objects is higher than an electricity supply line with higher priority objects, but with less benefit, priority should be given to the electricity supply line of higher priority objects. This study has thus resulted in the fact that electricity supply lines should be prioritized after the benefit if a decision maker is aware of the extent of the deficiency. Current collaboration between local networks showed that this could be dependent on the factors: distance, risk profile of decision makers and change of benefit through collaboration.  

  • 206.
    Alström, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    En annan verklighet2002In: Nyheter 2020 - rapport 2: dagens medieföretag - morgondagens affärsidé, Sundsvall: Mitthögskolan, FSCN , 2002, p. 116-128Chapter in book (Other academic)
  • 207.
    Alström, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Från tidningsföretag till innehållsföretag2000In: På väg mot medievärlden 2020.: [utveckling, teknik, marknad], Lund: Studentlitteratur, 2000, p. 136-Chapter in book (Other academic)
  • 208.
    Alström, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kampen om framtidens läsare2001Report (Other academic)
  • 209.
    Alström, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Medieföretag eller kunskapsföretag2002In: Nyheter 2020 - rapport 2: dagens medieföretag - morgondagens affärsidé, Sundsvall: Mitthögskolan, FSCN , 2002, p. 27-53Chapter in book (Other academic)
  • 210.
    Alström, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    På väg mot samverkan2002In: Nyheter 2020 - rapport 2: dagens medieföretag - morgondagens affärsidé, Sundsvall: Mitthögskolan, FSCN , 2002, p. 8-24Chapter in book (Other academic)
  • 211.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Cepaite, AstaMid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.Hedman, LoweMid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nyheter 2020 - rapport 3: företagsstrategier,reklamutveckling och konsumenternas livsstilar2004Collection (editor) (Other academic)
    Abstract [en]

    Innehåll:

    Börje Alström & Lowe Hedman: Projektet nyheter 2020

    Börje Alström & Lowe Hedman: Ett medieföretags förutsättningar

    Börje Alström & Lowe Hedman: Reklamen i dagspressen

    Asta Cepaite: Förändringar i livsstilar - förändringar i medieanvändning?

     

     

     

  • 212.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Enlund,
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hvitfelt,
    En föränderlig medievärld: teknik, ekonomi och journalistik2001Report (Other academic)
  • 213.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Enlund, Nils
    Johansson, Per-Åke
    Picard, Robert
    Gulliksson, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Sociological and Behavioural Aspects of Printed Media Usage. Ceprint Pre Study2002Report (Other scientific)
  • 214.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Gulliksson, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    De exklusiva magasinen: Tidskriftsförlagens och läsarnas syn på papperskvalitet2006Report (Other academic)
    Abstract [en]

    The pupose of the survey presented in this report has been to search for answers to qustions regarding what controls the periodical publisher´s choice of paper quality and how the readers of the periodicals influence that choice.

  • 215.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Gulliksson, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Magasin i tryck på nätet2006Report (Other academic)
    Abstract [en]

    The purpose of the project is to investigate how peridical publisher use the possibilities offered by the Internet.

  • 216.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Gulliksson, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Medietrender och papperskvalitet2004Report (Other academic)
    Abstract [sv]

    Tvår övergripande frågeställningar-vad styr magasins/tidskriftsförlagens val av papperskvalitet och påverkas läsarna av magasinens/tidskrifternas papperskvalitet. Studien omfattar sju delstudier med olika metoder.

  • 217.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hot och möjligheter i morgondagens medievärld: en explorativ studie2002Report (Other academic)
  • 218.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Landsortstidningens framtida affärsidé2002In: Nyheter 2020 - rapport 2: dagens medieföretag - morgondagens affärsidé, Sundsvall: Mitthögskolan, FSCN , 2002, p. 139-145Chapter in book (Other academic)
  • 219.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Medieföretag utan strategier2008In: På väg mot medievärlden 2020: Journalistik, teknik, marknad, Lund: Studentlitteratur, 2008, p. 109-126Chapter in book (Other academic)
  • 220.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Medieföretag utan strategier2005In: På väg mot medievärlden 2020: Journalistik, teknik, marknad, Lund: Studentlitteratur, 2005, p. 334-Chapter in book (Other academic)
  • 221.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    News Companies in the Future: Pamplona Spanien2003Conference paper (Other academic)
  • 222.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, LoweMid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nyheter 2020 - rapport 2: dagens medieföretag - morgondagens affärsidé2002Collection (editor) (Other academic)
    Abstract [en]

    Innehåll:

    Börje Alström; På väg mot samverkan

    Börje Alström; Medieföretag eller kunskapsföretag

    Lowe Hedman; Medieföretag utan strategier?

    Asta Cepaite; Den föreställda framtiden

    Mikael Gulliksson; Ladsortsjournalister i nyhetsflödet

    Börje Alström; En annan verklighet

    Per Mattsson; Mobila redaktioner

    Börje Alström coh Love Hedman; Larsortstidningens framtida affärsidé

     

  • 223.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hedman, Lowe
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Projektet nyheter 20202004In: Nyheter 2020 - Rapport 3: Företagsstrategier, reklamutveckling och konsumenternas livsstilar, Sundsvall: Mitthögskolan FSCN , 2004, p. 5-9Chapter in book (Other academic)
    Abstract [sv]

    Detta avsnitt utgör en kort beskrivning och introduktion till forsknings- och utvecklingsprojektet "Nyheter 2020 - En studie av hur strategier och utbud möter sin publik och marknad i morgondagens medievärld"

    Innehåll:

    Undersökningens syfte

    Delprojekt 1: Medieföretags strategival vid förändringar av produktutbudet

    Delprojekt 2: Konsumenternas syn på och anpassning till ny informationsteknik

    Delprojekt 3; Annonsmarknadens förändring och annonsärernas attityder

    Metod

    Deltagande företag

    Forskningsorganisation

    Tidsplan

  • 224.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nord, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Den skånska modellen: en VD, två kulturer, tre tidningar och fyra bröder2003Book (Other scientific)
    Abstract [sv]

    En analys av den största tidningsfusionen inom svensk landsortspress i nordvästra Skåne 2002

  • 225.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nord, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Expedition Mångfald: båda tidningarna kvar på ön2002Book (Other academic)
  • 226.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nord, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Två små ger mer än en stor: en rapport om en tidningsfusion i Ångermanland2000Book (Other scientific)
  • 227.
    Alström, Börje
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Sjöblom Nordgren, Åsa
    Kommunikationseffektivitet och ickemateriella tillgångar i offentlig verksamhet: Ett samarbete mellan Jämtlands Läns Landsting, Sveriges Informationsförening, Landstingsförbundet & Mitthögskolan : Slutrapport 4(4).1999Report (Other academic)
  • 228.
    Altin, Gustaf
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Industrial Design.
    Ljusbärare genom tiderna2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna rapport handlar om järnljusstakarnas/ järnljusbärarnas historia och nutid i Sverige.Den tar upp framkomsten av de första oljelamporna, vedstickestakarna och de ljusstakar sombörjade utvecklas när de moderna vax, talg och stearinljusen började uppstå. De mer modernaljusstakarna tas också upp och hur det kommer sig att de ser ut på de sätt de gör.Ljusstakar/ljusbärare bär även på mycket information genom sitt formspråk. Rapporten tar upp detsom ligger bakom detta. Varför ser de ut som de gör? Varför har just den utformningen uppstått?Olika varmsmidestekniker tas också upp för att visa på hur man på ett mer ”traditionellt” sätt genomdessa kan påverka utseendet på en ljusstake/ljusbärare.Resultatet blev att det är flera faktorer som spelar in kring varför ljusstakarna/ljusbärarna serut som de gör. Ljusens utformning och andra faktorer som ekonomi, vidskeplighet, religion ochnaturalism har gjort intryck och varit med och styrt utformningen.I slutet av rapporten blir det en diskussion kring det moderna smidets uppkomst, där blandannat järnvalsningen och svetsningen nämns som tänkta bidragande orsaker till att det modernasmidet i många fall ser ut som det gör. Rapporten avslutas med en bildbilaga. Det har gjorts för attman ska få en bättre förståelse för hur ljusstakarna/ljusbärarna och de olika smidesteknikerna ser ut.

  • 229.
    Altomani, Andrea
    et al.
    Université du Luxembourg.
    Hill, C. Denson
    SUNY Stony Brook, New York.
    Nacinovich, Mauro
    Universitá Roma Tor Vergata.
    Porten, Egmont
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Complex vector fields and hypolleptic partial differential operators2010In: Annales de l'Institut Fourier, ISSN 0373-0956, E-ISSN 1777-5310, Vol. 60, no 3, p. 39p. 987-1034Article in journal (Refereed)
    Abstract [en]

    We prove a subelliptic estimate for systems of complex vector fields under some assumptions that generalize the essential pseudoconcavity for CR manifolds, that was first introduced by two of the authors; and the Hormander's bracket condition for real vector fields. Applications are given to prove the hypoellipticity of first order systems and second order partial differential operators. Finally we describe a class of compact homogeneous CR manifolds for which the distribution of (0,1) vector fields satisfies a subelliptic estimate.

  • 230. Altomani, Andrea
    et al.
    Hill, C. Denson
    Nacinovich, Mauro
    Porten, Egmont
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Holomorphic Extension from Weakly Pseudoconcave CR Manifolds2010In: Rendiconti del Seminario Matematico della Universita di Padova, ISSN 0041-8994, E-ISSN 2240-2926, Vol. 123, p. 69-90Article in journal (Refereed)
    Abstract [en]

    Let M be a smooth locally embeddable CR manifold, having some CR dimension M and some CR codimension d. We find an improved local geometric condition on M which guarantees, at a point p on M, that germs of CR distributions are smooth functions, and have extensions to germs of holomorphic functions on a full ambient neighborhood of p. Our condition is a form of weak pseudoconcavity, closely related to essential pseudoconcavity as introduced in [HN1]. Applications are made to CR meromorphic functions and mappings. Explicit examples are given which satisfy our new condition, but which are not pseudoconcave in the strong sense. These results demonstrate that for codimension d > 1 there are additional phenomena, which are invisible when d = 1.

  • 231.
    Altskog, Tomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Customized Analytics Software: Investigating efficient development of an application2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Google Analytics is the most widely used web traffic analytics program in the world with a wide array of functionality which serve several different purposes for its users. However the cost of training employees in the usage of Google Analytics can be expensive and time consuming due to the generality of the software. The purpose of this thesis is to explore an alternative solution to hav- ing employees learn the default Google Analytics interface and thus possibly re- ducing training expenses. A prototype written in the Java programming lan- guage is developed which implements the MVC and facade software patterns for the purpose of making the development process more efficient. It contains a feature for retrieving custom reports from Google Analytics using Google’s Core Reporting API in addition to two web pages are integrated into the proto- type using the Google Embed API. In the result the prototype is used along with the software estimation method COCOMO to make an estimation of the amount of effort required to develop a similar program. This is done by counting the prototype’s source lines of code manually, following the guidelines given by the COCOMO manual, and then implementing the result in the COCOMO estima- tion formula. The count of lines of code for the entire prototype is 567 and the count which considers reused code is 466. The value retrieved from the formula is 1.61±0.14 person months for the estimation of the entire program and 1.31± 0.16 for a program with reused code. The conclusion of the thesis is that the res- ult from the estimation has several weaknesses and further research is necessary in order to improve the accuracy of the result.

  • 232.
    Alves, L.
    et al.
    University of Coimbra, Department of Chemistry, Coimbra, Portugal .
    Medronho, B.
    Faculty of Sciences and Technology, Centre for Mediterranean Bioresources and Food, University of Algarve, Ed. 8, Campus de Gambelas, Faro, Portugal .
    Antunes, F. E.
    University of Coimbra, Department of Chemistry, Coimbra, Portugal .
    Fernández-García, M. P.
    IFIMUP and in - Institute of Nanoscience and Nanotechnology, Department of Physics and Astronomy, Faculty of Science, University of Porto, Porto, Portugal .
    Ventura, J.
    IFIMUP and in - Institute of Nanoscience and Nanotechnology, Department of Physics and Astronomy, Faculty of Science, University of Porto, Porto, Portugal .
    Araújo, J. P.
    IFIMUP and in - Institute of Nanoscience and Nanotechnology, Department of Physics and Astronomy, Faculty of Science, University of Porto, Porto, Portugal .
    Romano, A.
    Faculty of Sciences and Technology, Centre for Mediterranean Bioresources and Food, University of Algarve, Ed. 8, Campus de Gambelas, Faro, Portugal .
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore .
    Unusual extraction and characterization of nanocrystalline cellulose from cellulose derivatives2015In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 210, p. 106-112Article in journal (Refereed)
    Abstract [en]

    Unlike many nanomaterials, nanocrystalline cellulose (CNC) is not synthesized from molecular or atomic components but rather extracted from naturally occurring cellulose. Undoubtedly, the exploitation of CNCs will become a bridge between nanoscience and natural resource products, which could play a major role in reviving the forest industry. In this work, CNC was successfully extracted from unusual sources, hydroxypropyl methylcellulose (HPMC) and carboxymethylcellulose (CMC). The extracted crystallites were purified and further characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and dynamic light scattering (DLS). The average size of the CNCs extracted from HPMC and CMC was found to be less (and with lower zeta potential) than the ones extracted from microcrystalline cellulose (MCC). On the other hand, FTIR and XRD revealed that native HPMC and CMC are unexpectedly highly crystalline and hence can be used as a source for CNCs. © 2014 Elsevier B.V.All rights reserved.

  • 233.
    Alves, Luis
    et al.
    CQC, University of Coimbra, Portugal.
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. CQC, University of Coimbra, Portugal; Lund University.
    Klotz, Björn
    BASF Personal Care and Nutrition GmbH, Düsseldorf, Germany.
    Böttcher, Axel
    BASF Personal Care and Nutrition GmbH, Düsseldorf, Germany.
    Haake, Hans-Martin
    BASF Personal Care and Nutrition GmbH, Düsseldorf, Germany.
    Antunes, Filipe E.
    CQC, University of Coimbra, Portugal.
    On the rheology of mixed systems of hydrophobically modified polyacrylate microgels and surfactants: Role of the surfactant architecture2018In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 513, p. 489-496Article in journal (Refereed)
    Abstract [en]

    Hypothesis The rheological control of suspensions is of key interest in the formulation design. A chemically cross-linked hydrophobically modified poly(acrylic acid) (HMCL-PAA), used as rheology modifier, is pH sensitive and shows swelling behavior above a critical pH due to the ionization of the acrylic acid groups. At low pH, HMCL-PAA suspensions are liquid and turbid. The binding of surfactants to HMCL-PAA, at low pH conditions, can result in significant changes on rheology and transparency of the polymeric suspensions, due to the swelling of the microgel particles. Experiments The influence of surfactants addition on the rheological properties and transparency of HMCL-PAA suspensions was determined. A systematic study was performed using different types of surfactants (ionic, non-ionic and zwitterionic). Findings The gelation efficiency of HMCL-PAA suspensions at low pH is strongly dependent on surfactant architecture: ionic surfactants are found to be much more efficient than non-ionic or zwitterionic surfactants. Ionic surfactants lead to a liquid-to-gel transition accompanied by an increase of transparency of the suspensions. Among the ionic surfactants, anionics show stronger interactions with the polymer. Also the surfactant hydrophobicity is relevant; the more hydrophobic the surfactant, the stronger is the binding to the polymer and thus the larger the particle swelling. 

  • 234.
    Alves, Luis
    et al.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Medronho, Bruno
    Univ Algarve, Fac Sci & Technol MEDITBIO, Campus Gambelas,Ed 8, P-8005139 Faro, Portugal..
    Antunes, Filipe E.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Topgaard, Daniel
    Lund Univ, Ctr Chem & Chem Engn, Dept Chem, Div Phys Chem, S-22100 Lund, Sweden..
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Nanyang Technol Univ, Mat Sci & Engn, Singapore 639798, Singapore.
    Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents2016In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 1, p. 247-258Article in journal (Refereed)
    Abstract [en]

    The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.

  • 235.
    Alves, Luis
    et al.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Medronho, Bruno
    Univ Algarve, Fac Sci & Technol MEDITBIO, Campus Gambelas,Ed 8, P-8005139 Faro, Portugal..
    Antunes, Filipe E.
    Univ Coimbra, Dept Chem, P-3004535 Coimbra, Portugal..
    Topgaard, Daniel
    Lund Univ, Ctr Chem & Chem Engn, Dept Chem, Div Phys Chem, SE-22100 Lund, Sweden..
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Nanyang Technol Univ, Mat Sci & Engn, Singapore 639798, Singapore.
    Dissolution state of cellulose in aqueous systems. 2. Acidic solvents2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 151, p. 707-715Article in journal (Refereed)
    Abstract [en]

    Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated. The studied solvent systems are capable to efficiently dissolve cellulose, although degradation occurs to some extent. PT ssNMR is capable to identify the liquid and solid fractions of cellulose, the degradation products and it is also sensitive to gelation. The materials regenerated from the acidic dopes were found to be highly sensitive to the solvent system and to the presence of amphiphilic additives in solution.

  • 236.
    Alves, Luis
    et al.
    Univ Coimbra, Coimbra, Portugal.
    Medronho, Bruno
    Univ Algarve, Faro, Portugal.
    Filipe, Alexandra
    Univ Algarve, Faro, Portugal.
    Antunes, Filipe E.
    Univ Coimbra, Coimbra, Portugal.
    Lindman, Björn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Univ Coimbra, Coimbra, Portugal; Lund Univ, Lund.
    Topgaard, Daniel
    Lund Univ, Lund.
    Davidovich, Irina
    Technion Israel Inst Technol, Haifa, Israel.
    Talmon, Yeshayahu
    Technion Israel Inst Technol, Haifa, Israel.
    New Insights on the Role of Urea on the Dissolution and Thermally-Induced Gelation of Cellulose in Aqueous Alkali2018In: GELS, ISSN 2310-2861, Vol. 4, no 4, article id 87Article in journal (Refereed)
    Abstract [en]

    The gelation of cellulose in alkali solutions is quite relevant, but still a poorly understood process. Moreover, the role of certain additives, such as urea, is not consensual among the community. Therefore, in this work, an unusual set of characterization methods for cellulose solutions, such as cryo-transmission electronic microscopy (cryo-TEM), polarization transfer solid-state nuclear magnetic resonance (PTssNMR) and diffusion wave spectroscopy (DWS) were employed to study the role of urea on the dissolution and gelation processes of cellulose in aqueous alkali. Cryo-TEM reveals that the addition of urea generally reduces the presence of undissolved cellulose fibrils in solution. These results are consistent with PTssNMR data, which show the reduction and in some cases the absence of crystalline portions of cellulose in solution, suggesting a pronounced positive effect of the urea on the dissolution efficiency of cellulose. Both conventional mechanical macrorheology and microrheology (DWS) indicate a significant delay of gelation induced by urea, being absent until ca. 60 degrees C for a system containing 5wt % cellulose, while a system without urea gels at a lower temperature. For higher cellulose concentrations, the samples containing urea form gels even at room temperature. It is argued that since urea facilitates cellulose dissolution, the high entanglement of the cellulose chains in solution (above the critical concentration, C*) results in a strong three-dimensional network.

  • 237.
    Ambatipudi, Radhika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    High Frequency (MHz) Planar Transformers for Next Generation Switch Mode Power Supplies2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Increasing the power density of power electronic converters while reducing or maintaining the same cost, offers a higher potential to meet the current trend inrelation to various power electronic applications. High power density converters can be achieved by increasing the switching frequency, due to which the bulkiest parts, such as transformer, inductors and the capacitor's size in the convertercircuit can be drastically reduced. In this regard, highly integrated planar magnetics are considered as an effective approach compared to the conventional wire wound transformers in modern switch mode power supplies (SMPS). However, as the operating frequency of the transformers increase from several hundred kHz to MHz, numerous problems arise such as skin and proximity effects due to the induced eddy currents in the windings, leakage inductance and unbalanced magnetic flux distribution. In addition to this, the core losses whichare functional dependent on frequency gets elevated as the operating frequency increases. Therefore, this thesis provides an insight towards the problems related to the high frequency magnetics and proposes a solution with regards to different aspects in relation to designing high power density, energy efficient transformers.The first part of the thesis concentrates on the investigation of high power density and highly energy efficient coreless printed circuit board (PCB) step-down transformers useful for stringent height DC-DC converter applications, where the core losses are being completely eliminated. These transformers also maintain the advantages offered by existing core based transformers such as, high coupling coefficient, sufficient input impedance, high energy efficiency and wide frequencyband width with the assistance of a resonant technique. In this regard, several coreless PCB step down transformers of different turn’s ratio for power transfer applications have been designed and evaluated. The designed multilayered coreless PCB transformers for telecom and PoE applications of 8,15 and 30W show that the volume reduction of approximately 40 - 90% is possible when compared to its existing core based counterparts while maintaining the energy efficiency of the transformers in the range of 90 - 97%. The estimation of EMI emissions from the designed transformers for the given power transfer application proves that the amount of radiated EMI from a multilayered transformer is lessthan that of the two layered transformer because of the decreased radius for thesame amount of inductance.The design guidelines for the multilayered coreless PCB step-down transformer for the given power transfer application has been proposed. The designed transformer of 10mm radius has been characterized up to the power level of 50Wand possesses a record power density of 107W/cm3 with a peak energy efficiency of 96%. In addition to this, the design guidelines of the signal transformer fordriving the high side MOSFET in double ended converter topologies have been proposed. The measured power consumption of the high side gate drive circuitvitogether with the designed signal transformer is 0.37W. Both these signal andpower transformers have been successfully implemented in a resonant converter topology in the switching frequency range of 2.4 – 2.75MHz for the maximum load power of 34.5W resulting in the peak energy efficiency of converter as 86.5%.This thesis also investigates the indirect effect of the dielectric laminate on the magnetic field intensity and current density distribution in the planar power transformers with the assistance of finite element analysis (FEA). The significanceof the high frequency dielectric laminate compared to FR-4 laminate in terms of energy efficiency of planar power transformers in MHz frequency region is also explored.The investigations were also conducted on different winding strategies such as conventional solid winding and the parallel winding strategies, which play an important role in the design and development of a high frequency transformer and suggested a better choice in the case of transformers operating in the MHz frequency region.In the second part of the thesis, a novel planar power transformer with hybrid core structure has been designed and evaluated in the MHz frequency region. The design guidelines of the energy efficient high frequency planar power transformerfor the given power transfer application have been proposed. The designed corebased planar transformer has been characterized up to the power level of 50W and possess a power density of 47W/cm3 with maximum energy efficiency of 97%. This transformer has been evaluated successfully in the resonant converter topology within the switching frequency range of 3 – 4.5MHz. The peak energy efficiency ofthe converter is reported to be 92% and the converter has been tested for the maximum power level of 45W, which is suitable for consumer applications such as laptop adapters. In addition to this, a record power density transformer has been designed with a custom made pot core and has been characterized in thefrequency range of 1 - 10MHz. The power density of this custom core transformer operating at 6.78MHz frequency is 67W/cm3 and with the peak energy efficiency of 98%.In conclusion, the research in this dissertation proposed a solution for obtaining high power density converters by designing the highly integrated, high frequency(1 - 10MHz) coreless and core based planar magnetics with energy efficiencies inthe range of 92 - 97%. This solution together with the latest semiconductor GaN/SiC switching devices provides an excellent choice to meet the requirements of the next generation ultra flat low profile switch mode power supplies (SMPS).

  • 238.
    Ambatipudi, Radhika
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Multilayered Coreless Printed Circuit Board (PCB) Step-down Transformers for High Frequency Switch Mode Power Supplies (SMPS)2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Power Supply Unit (PSU) plays a vital role in almost all electronic equipment. The continuous efforts applied to the improvement of semiconductor devices such as MOSFETS, diodes, controllers and MOSFET drivers have led to the increased switching speeds of power supplies. By increasing the switching frequency of the converter, the size of passive elements such as inductors, transformers and capacitors can be reduced. Hence, the high frequency transformer has become the backbone in isolated AC/DC and DC/DC converters. The main features of transformers are to provide isolation for safety purpose, multiple outputs such as in telecom applications, to build step down/step up converters and so on. The core based transformers, when operated at higher frequencies, do have limitations such as core losses which are proportional to the operating frequency. Even though the core materials are available in a few MHz frequency regions, because of the copper losses in the windings of the transformers those which are commercially available were limited from a few hundred kHz to 1MHz. The skin and proximity effects because of induced eddy currents act as major drawbacks while operating these transformers at higher frequencies. Therefore, it is necessary to mitigate these core losses, skin and proximity effects while operating the transformers at very high frequencies. This can be achieved by eliminating the magnetic cores of transformers and by introducing a proper winding structure.

    A new multi-layered coreless printed circuit board (PCB) step down transformer for power transfer applications has been designed and this maintains the advantages offered by existing core based transformers such as, high voltage gain, high coupling coefficient, sufficient input impedance and high energy efficiency with the assistance of a resonant technique. In addition, different winding structures have been studied and analysed for higher step down ratios in order to reduce copper losses in the windings and to achieve a higher coupling coefficient. The advantage of increasing the layer for the given power transfer application in terms of the coupling coefficient, resistance and energy efficiency has been reported. The maximum energy efficiency of the designed three layered transformers was found to be within the range of 90%-97% for power transfer applications operated in a few MHz frequency regions. The designed multi-layered coreless PCB transformers for given power applications of 8, 15 and 30W show that the volume reduction of approximately 40-90% is possible when compared to its existing core based counterparts. The estimation of EMI emissions from the designed transformers proves that the amount of radiated EMI from a three layered transformer is less than that of the two layered transformer because of the decreased radius for the same amount of inductance.

    Multi-layered coreless PCB gate drive transformers were designed for signal transfer applications and have successfully driven the double ended topologies such as the half bridge, the two switch flyback converter and resonant converters with low gate drive power consumption of about half a watt. The performance characteristics of these transformers have also been evaluated using the high frequency magnetic material made up of NiZn and operated in the 2-4MHz frequency region.

    These multi-layered coreless PCB power and signal transformers together with the latest semiconductor switching devices such as SiC and GaN MOSFETs and the SiC schottky diode are an excellent choice for the next generation compact SMPS.

  • 239.
    Ambatipudi, Radhika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kotte, Hari Babu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Comparison of Two Layered and Three Layered Coreless Printed Circuit Board Step-Down Power Transformers2011In: 2011 INTERNATIONAL CONFERENCE ON INSTRUMENTATION, MEASUREMENT, CIRCUITS AND SYSTEMS (ICIMCS 2011), VOL 2: FUTURE COMMUNICATION AND NETWORKING, Shenzhen: IEEE conference proceedings, 2011, p. 59-62Conference paper (Refereed)
    Abstract [en]

    In this paper the comparative results of two layered and three layered coreless Printed Circuit Board (PCB) step down 2:1 power transformers operating in MHz frequency were addressed. The  two different step down transformers approximately having same self inductances, one in two layer and the other in three layer were designed and evaluated for the given power transfer application. The performance characteristics of these transformers under similar conditions were measured and the comparative parameters of these transformers in terms of their resistances, self, leakage, mutual inductances, and coupling coefficient are analyzed. For the given output power, the measured energy efficiency of the three layered transformer is improved by 3% and the area is reduced by 32% compared to two layered transformer. The efficiency of the three layered transformer is 94.5% approximately for an output power level of 25W at an operating frequency of 2.5MHz

  • 240.
    Ambatipudi, Radhika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kotte, Hari Babu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Coreless Printed Circuit Board (PCB) StepdownTransformers for DC-DC ConverterApplications2010In: PROCEEDINGS OF WORLD ACADEMY OF SCIENCE, ENGINEERING AND TECHNOLOGY, ISSUE 70, OCTOBER 2010, ISSN:1307-6892, France: World Academy of Science Engineering and Technology , 2010, p. 380-389Conference paper (Refereed)
    Abstract [en]

    In this paper, multilayered coreless printed circuit board (PCB) step-down power transformers for DC-DC converter applications have been designed, manufactured and evaluated. A set of two different circular spiral step-down transformers were fabricated in the four layered PCB. These transformers have been modelled with the assistance of high frequency equivalent circuit and characterized with both sinusoidal and square wave excitation. This paper provides the comparative results of these two different transformers in te rms of their resistances, self, leakage, mutual inductances, coupling coefficient and also their energy efficiencies. The operating regions for optimal performance of these transformers for power transfer applications are determined. These transformers were tested for the output power levels of about 30 Watts within the input voltage range of 12-50 Vrms. The energy efficiency for these step down transformers is observed to be in the range of 90%-97% in MHz frequency region.

  • 241.
    Ambatipudi, Radhika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kotte, Hari Babu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Effect of Air Gap on the Performance of Hybrid Planar Power Transformer in High Frequency (MHz) Switch Mode Power Supplies (SMPS)2012In: Proceedings of INDUCTICA 2012, Coil Winding, Insulation and Electrical Manufacturing International Conference and Exhibition (CWIEME), Berlin, Germany 26-28 June 2012, 2012Conference paper (Refereed)
    Abstract [en]

    A half bridge transformer with novel winding strategy was designed and tested up to the output power level of 50W with a maximum energy efficiency of 98% in 1-6 MHz frequency region. In this paper, the effect of air gap on the performance of the designed transformer for high frequency (MHz) Switch Mode Power Supplies (SMPS) was studied and analyzed. The air gap of the transformer was varied from 0 – 2mm and the effect on self, leakage, mutual inductances, coupling coefficient and power transfer capability was recorded in 1 - 6MHz. The parameters of the transformer with different air gaps were extracted using network analyzer. The transformer was excited with sinusoidal voltages using power amplifier and the performance characteristics such as input impedance, power transfer capability and hence the energy efficiency was measured. At a particular operating frequency of 3MHz, the maximum power transferred for the given excitation voltage with 0mm air gap was found to be 22W whereas it is only 8W with the 2mm air gap . The measured energy efficiency of the transformer at 3MHz with 0mm and 2mm air gap was found to be 93% and 79% respectively. With this study, for the given power transfer application, at a particular high frequency operation of converter, an optimum air gap without sacrificing the energy efficiency and core saturation was proposed

  • 242.
    Ambatipudi, Radhika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kotte, Hari Babu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Effect of Dielectric Material on the Performance of Planar Power Transformers in MHz Frequency Region2012In: Proceedings of INDUCTICA 2012, Coil Winding, Insulation and Electrical Manufacturing International Conference and Exhibition (CWIEME), Berlin, Germany 26-28 June 2012, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper, the effect of two different dielectric materials in planar printed circuit board (PCB) transformers applicable for power transfer applications in MHz frequency region is discussed. The 2-D model of the planar transformer was developed and the effect of the dielectric material on the magnetic field and the current distribution in the transformer was analyzed. Based on the FEA analysis, the power transformers of two different dielectric materials were designed, manufactured and characterized by using ‘S’ parameters obtained from network analyzer in order to determine the performance of dielectrics at high frequencies. The electrical parameters such as inductances, capacitances and resistances of the transformers were obtained and the changes in these parameters with the variation of the dielectric material were analyzed in the MHz frequency. This paper discusses the effect of dielectric material on the magnetic field distribution and the current density which results in the variation of the coupling coefficient and the eddy current losses of the transformer. By changing the dielectric material from a traditional FR-4 to a Rogers, the coupling coefficient was improved by a maximum of 5% and the copper losses of transformer were also decreased in the MHz frequency region. The power gain/energy efficiency obtained from the network analyzer with a resonant capacitor is verified with those obtained using a power amplifier and the simulations. An overall energy efficiency improvement of about 2-5% was achieved with a Rogers’s material in MHz frequency region compared to traditional FR-4 laminate.

     

  • 243.
    Ambatipudi, Radhika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Kotte, Hari Babu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    High Performance Planar Power Transformer with High Power Density in MHz Frequency Region for Next Generation Switch Mode Power Supplies2013In: 2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference And Exposition (APEC 2013), IEEE conference proceedings, 2013, p. 2139-2143Conference paper (Refereed)
    Abstract [en]

    The authors report the utilization of the core based transformer for power transfer applications with high power density and high energy efficiency in the MHz frequency region. A custom made POT core center tapped transformer of 4:1:1 turn’s ratio using novel winding strategy with the core diameter of 16mm is designed and evaluated. The designed transformer has been characterized using sinusoidal excitation for a given output power in the frequency range of 1 – 10MHz and determined the operating frequency region of the transformer. The power tests of the transformer has been carried out up to the power level of 62W at an operating frequency of 6.78MHz with a peak energy efficiency of 98.5% resulting in the record power density of ~1100W/in3. The designed transformer has been characterized using class E isolated DC-DC converter topology at an output power of approximately 18W. The simulated energy efficiency of the converter is 88.5% under the full load condition. This work provides the significant step for the development of next generation high power density isolated converters (both AC/DC and DC/DC) in MHz frequency region

  • 244.
    Ambatipudi, Radhika
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kotte, Hari Babu
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Radiated Emissions of Multilayered Coreless Printed Circuit Board Step-Down Power Transformers in Switch Mode Power Supplies2011In: 8th International Conference on Power Electronics - ECCE Asia: "Green World with Power Electronics", ICPE 2011-ECCE Asia 2011, IEEE conference proceedings, 2011, p. 960-965Conference paper (Refereed)
    Abstract [en]

    This paper addressesradiatedEMI issues in Coreless PCB step-down transformers used for power transfer applications. In case of SMPS circuits, since the waveforms are not sinusoidal in nature, most of theradiatedemissionsare not only from fundamental frequency component but also from harmonic contents. According to antenna theory,radiatedEMI for three different power transformers of different radii were estimated for fundamental frequency of 2MHz to 300MHz. The computations were made for both sinusoidal and square wave excitations and at a load power of 20W. The calculatedradiatedpower obtained for simulated waveforms and for practical measured current waveforms are in good agreement with each other up to certain bandwidth. These computational results confirm thatradiatedpower can be reduced in three layered 2:1 transformer compared to two layered 2:1 transformer. Also theradiatedemissionsare negligible in case of sinusoidal excitations compared to square wave excitations. © 2011 IEEE.

  • 245.
    Amcoff Nyström, Christina
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
    Asproth, Viveca
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
    Virtual Teams - Support for Technical Communication2013In: Journal of Organizational Transformation and Social Change, ISSN 1477-9633, Vol. 10, no 1, p. 87-103Article in journal (Refereed)
    Abstract [en]

    To work together in virtual teams has increasingly become a natural change

    in how organizations work. Due to demands from the environment,

    organizations have had to transform from traditional ways of working to

    becoming more flexible and adaptive. The aim of this article is to identify

    obstacles, problems, and presumptions in order to enable the virtual team to

    be successful. A project — The TIC-project — is described, and results from

    a study concerning collaboration and networking among companies within

    Technical Communication are presented. Results show that, to a great

    extent, experiences from networking are lacking. Furthermore, trust must be

    embedded in the teams, meaning that personal meetings must precede

    virtual meetings. Most interviewees declared a wish to collaborate despite

    being competitors. Finally, questions and topics for further research are

    presented.

  • 246.
    Amcoff Nyström, Christina
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
    Asproth, Viveca
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
    Persson Slumpi, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
    Olsson, Hanna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System science.
    Boundless collaboration: Distributed concurrent design in an inter-regional collaboration between emergency authorities2014In: Proceedings of the DESIGN 2014 13th International Design Conference / [ed] Marjanović, D.; Štorga, M.; Pavković, N.; Bojčetić, N., The Design Society, 2014, p. 1621-1630Conference paper (Refereed)
    Abstract [en]

    The aim of the article is to evaluate how Distributed Concurrent Design works during collaboration in a distributed system development project. We studied collaboration between emergency authorities in Sweden and Norway developing a demonstrator for emergency training. Evaluation criteria were people, processes, and tools. We have used a multi-method approach with the evaluation criterion as a lens. Findings has so far shown that distributed concurrent design works as a method in system development projects but much effort must be put on planning, management and training in available tools.

  • 247.
    Amcoff Nyström, Christina
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Olsson, Hanna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Asproth, Viveca
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Assumptions for Distributed Concurrent Design and Decision Making2012In: Proceedings of International Design Conference, DESIGN / [ed] Marjanović D., Štorga M., Pavković N., Bojčetić N., Dubrovnik, Croatia, 2012, p. 543-550Conference paper (Refereed)
  • 248. Amenitsch, Hans
    et al.
    Edlund, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Khan, Ali
    Marques, Eduardo
    La Mesa, Camilo
    Bile Salts Form Lyotropic Liquid Crystals2003In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 213, no 1, p. 79-92Article in journal (Refereed)
    Abstract [en]

    A reinvestigation of the phase diagrams relative to some conjugated and non-conjugated bile salts in water has demonstrated the formation of lyotropic liquid crystalline phases, in contradiction with generally accepted statements. The phase behaviour is complex and the phase diagrams are unusual, compared to most surfactants and lipids. In particular, coexistence of liquid crystalline phases with crystals has been observed. The formation of liquid crystalline phases requires very long equilibration times and the thermal stability of the lyotropic phases is moderate. The observed structure is tentatively assumed to be of the reverse hexagonal type. Structural relations with currently accepted models for the organisation of bile salts into micelles and solid form have been found.

  • 249.
    Amir, Yousaf Muhammad
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    High Precision Laser Scanning of Metallic Surfaces2017In: International Journal of Optics, ISSN 1687-9384, E-ISSN 1687-9392, article id 4134205Article in journal (Refereed)
    Abstract [en]

    Speckle noise, dynamic range of light intensity, and spurious reflections are major challenges when laser scanners are used for 3D surface acquisition. In this work, a series of image processing operations, that is, Spatial Compound Imaging, High Dynamic Range Extension, Gray Level Transformation, and Most Similar Nearest Neighbor are proposed to overcome the challenges coming from the target surface. A prototype scanner for metallic surfaces is designed to explore combinations of these image processing operations. The main goal is to find the combination of operations thatwill lead to the highest possible robustness andmeasurement precision at the lowest possible computational load. Inspection of metallic tools where the surface of its edge must be measured at micrometer precision is our test case. Precision of heights measured without using the proposed image processing is firstly analyzed to be +/- 7.6 mu m at 68% confidence level. The best achieved height precision was +/- 4.2 mu m. This improvement comes at 24 times longer processing time and five times longer scanning time. Dynamic range extension of the image capture improves robustness since the numbers of saturated or underexposed pixels are substantially reduced. Using a high dynamic range (HDR) camera offers a compromise between processing time, robustness, and precision.

  • 250.
    Amjadian, Sanna
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Design.
    My friend is always with me: The emotional connection between human and plants2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The vision of this project is to change peoples life style by improving their daily connection with plants. The goal of this project is to design a physical product that makes a strong everyday connection between human being and nature. A piece of nature is going to be carried in this product.

    The user study will be designed as an online questionnaire for different group of society and observation in the lab and in an ordinary room. Primary modles were made by acrylic and cartoon and tested by users in tow different stages. Participants were collected among different age, gender, with and without disabilities. Both plant lovers and non-plant lovers participated in this user study.

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