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  • 301. Bjurulf, Veronica
    et al.
    Kilbrink, Nina
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Segolsson, Mikael
    Ämnet teknik i grundskolan - med empiriska exempel2005Conference paper (Refereed)
  • 302.
    Bjurulf, Veronica
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rovio-Johansson, Airi
    External and internal Perspectives on Learning Object: Emergent Knowledge for Teachers Professionalization2009Conference paper (Other (popular science, discussion, etc.))
    Abstract

    The purpose is to investigate how teachers are using the subject content in order to develop students understanding of the learning object and their capabilities according to the curricula. The theoretical and the conceptual frame of the studies is the phenomenographic research approach and the variation theory, a learning theory. The variation theory is a general theory about the specific content. On the one hand the analytical tools of the variation theory are possible to use in the analysis of the teachers way of working with the learning object. On the other hand, the theory sets out to uncover the different ways in which students experiences the learning object (Marton and Booth, 1997; Marton and Tsui, 2004; Lo et al., 2005, Rovio-Johansson, A. and Lumsden, M., 2007). Two examples from different studies are used to illustrate (1) the teachers way of moulding a learning object in teaching technology in compulsory school and (2) students understanding of the learning object identified in a problem solving process in an examination in Management accounting during their second semester at higher education.

    In the first example empirical data are collected from five teachers teaching technology at Swedish junior high schools, pupils aged 13-15 (Bjurulf, 2008). Variation theory was applied as a tool in the analysis of the data from the classroom observations, i.e. the teachers ways of working with the subject matter. The analysis indicated that the most frequently used pattern of variation was contrast. Through the contrast-pattern the teachers managed to contrast better or worse alternatives of construction and the use artefacts. It can be argued that this contrast-pattern of variation is the proper pattern when pupils are working with limited or expensive material. Results also indicated that technology as a school subject was taught in different ways depending on the teachers educational background, the physical learning environment and the size of the school class.

    In the second example, empirical data are collected from a sample of students taking part in a Swedish three year undergraduate programme in Business, during their second semester (Rovio-Johansson and Johansson, 2006). The study uses the theoretical framework of variation theory and focuses on the students understandings of a basic concept in Management accounting during students second semester. Drawing on extensive interview material of semi-structured interviews and students´ solutions of a specific examination problem, the analysis revealed three qualitatively different categories illustrating in which ways the students understood the concept return on investment. The learning object and its critical aspects were identified as qualitative categories of descriptions, hierarchically organised.

    The empirically grounded didactic knowledge indicates that educationally critical aspects of the learning object, observed by the researcher or experienced by the students, may aid educators and teachers how to reorganize curricula, courses and teaching in order to enhance the quality of learning and teaching opportunities offered the students. Implications of the findings are promoted as means to accomplish further investigations of teachers ways of using the subject matter and students understanding of the learning object in subject matter areas.

  • 303.
    Björk, Johannes
    Karlstad University, Faculty of Technology and Science.
    Uppgradering av serviceprogrammet Mule2011Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 304. Björk, T
    et al.
    Berger, M
    Westergård, R
    Hogmark, S
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    New PVD coatings applied to aluminium extrusion dies2001Other (Other (popular science, discussion, etc.))
  • 305. Björk, T.
    et al.
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Hogmark, S.
    Tribological simulation of aluminium hot extrusion1999Other (Other (popular science, discussion, etc.))
  • 306. Björk, T.
    et al.
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Hogmark, S.
    Tribological simulation of aluminium hot extrusion1997Other (Other (popular science, discussion, etc.))
  • 307. Björk, T
    et al.
    Westergård, R
    Hogmark, S
    Bergström, Jens
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Hedenqvist, P
    PVD Duplex coatings for aluminium extrusion dies1999Other (Other (popular science, discussion, etc.))
  • 308.
    Björklund, Erik
    Karlstad University, Faculty of Technology and Science.
    Borsthållare för asynkrona generatorer i vindkraftverk2011Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Abstract 

    This thesis has been accomplished at the faculty of science and technology. The work has been implemented by a student in machine engineering and the course included 22.5 HP. Supervisor at Karlstad University has been Mikael Åsberg and examiner has been Nils Hallbäck.The assigner of this thesis has been Carbex AB in Vadstena Sweden. Carbex has been the largest carbon manufacturer in the Nordic region for many years. Since a few years back Carbex mission has been to move their market positions forward in order to offer customers complete solutions of slip ring systems.The student’s mission has been to develop brush holders for grounding and power transmission for the generators.

    To understand how a carbon brush works, research has been done in this topic; but brushes’ is a very niche product and due to this there were difficulties to find valuable technical documentation. In order to construct a brush holder it is important to be aware of the theory that has been developed by the leading actors in the market.

    The main problems were whether the brush holder works mechanically and electrically. To ensure this, calculations in mechanics and energy techniques were performed. To verify the theory tests has been carried out in laboratory conditions. The tests are well documented and will be the basis for selling and develop the brush holders in the future.In this thesis potential customers has been visited and the main question during meetings has been how Carbex brush holder can compete in terms of cost, compared with other brush holders available on the market today. The target for Carbex solution has been to lower the total cost. That means Carbex solution is more expensive in purchase phase, but will, in the long run, be a more cost effective solution due to reduced maintenance.Two full-scale models have been developed and are used in practical testing and presentation of the project during customer meetings.The power brush holder solution consists of 15 parts and grounding holder consists of 9 different parts. All items have been produced in the CAD program Solid Works, manufacturing drawings and cost-estimates has also been done.

  • 309. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Effect of cooking conditions on ECF bleaching and brightness reversion of birch kraft pulp2005In: Tappi JournalArticle in journal (Refereed)
  • 310. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Formation of AOX and OCI in ECF-bleaching of birch pulp2004In: Tappi Journal 3(2004)8, 7-11Article in journal (Refereed)
  • 311. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    Formation of AOX and OCl in ECF-bleaching of birch pulp2004In: Tappi Journal, Vol. vol 3 no 8Article in journal (Refereed)
  • 312. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    The influence of softwood kraft cooking conditions on the brightness development in ECF- bleaching2004In: Appita Journal, Vol. vol 57 no 3Article in journal (Refereed)
  • 313. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Basta, Jiri
    The influence of softwood kraft cooking conditions on the brightness development in ECF- bleaching2003Conference paper (Refereed)
  • 314. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, Ann-Britt
    AOX formation in ECF bleaching at different kappa numbers ' influence of oxygen delignification and hexenuronic acid content2001Conference paper (Refereed)
  • 315. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, Ann-Britt
    AOX formation in ECF bleaching at different kappa numbers: Influence of oxygen delignification and hexenuronic acid content2002In: Tappi Journal, 1(2002)7, 20-24, Vol. vol 1 no 7Article in journal (Refereed)
    Abstract [en]

    he aim of this study was to determine how oxygen delignification before bleaching and the hexenuronic acid (HexA) content of the pulps influenced the acisorbable organic halogen (AOX) formation in the elemental chlorine free (ECP) bleaching effluent. Softwood industrial chips cooked to different kappa numbers were oxygen defignified, treated in a hot acid stage (A*), or not pretreated at all before ECF bleaching. We compared the AOX levels in the ECF effluents from bleaching of these pulps. There was a higher formation of AOX for oxygen delignified pulps than for non-oxygen delignified pulps compared at the same kappa number before ECF bleaching. The hexenuronic acid (HexA) content of the pulps had a major impact on the AOX levels in the D[0] effluent. The oxygen delignified pulps had a higher HexA content than the non-oxygen delignified pulps compared at the same kappa number. This explains the higher AOX formation from oxygen delignified pulps. The AOX originating from HexA was not stable upon storage. Application, This study gives additional insight on the AOX formation in ECF bleaching. The information may be used to take appropriate measures when addressing environmental issues

  • 316. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, AnnBritt
    TCF and ECF bleaching effluent COD at varying kappa numbers after cooking2003In: Appita Journal, Vol. vol 56 no 3Article in journal (Refereed)
  • 317. Björklund, Magnus
    et al.
    Germgård, Ulf
    Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering.
    Jour, Pia
    Forsström, AnnBritt
    TCF and ECF bleaching effluent COD at varying kappa numbers after cooking2003In: Appita Journal 56(2003)3, 200-205Article in journal (Refereed)
  • 318.
    Björkman, Fredrik
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Runnerström, Tim
    Gestaltningsförslag till ny förskola på Zakrisdal2011Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 319.
    Björnsson, Jonas
    Karlstad University, Faculty of Technology and Science.
    Stretched Membranes2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis deals with relativistic membranes and, in particular, a limit called stretched membranes. The thesis also considers the relation of membranes to the conjectured M-theory and string theory. The thesis is divided into two parts. One introductory part where I introduce areas which are of relevance for the second part.

    The second part consists of the scientific papers.

    In the first part I make a general introduction to string theory. Furthermore, I discuss different limits of membrane theory. Then, I make a short review of the different conjectures of M-theory and briefly mention different consistency checks of these conjectures. The last subject in the first part concerns an area, which is not

    in direct connection to the other chapters in the thesis. This is a short introduction to the general treatment of theories with constraints.

    The second part of the thesis consists of the included articles. The common topic of these is that they give a new approach to the treatment of membranes. We here make a partial gauge-fixing of the constraints which, by choosing an appropriate limit, will yield a perturbation theory around a free string-like theory. The stringlike

    theory is the usual string theory with an extra parameter dependence. This perturbation theory we solve by infinitesimal canonical transformations.

    The corresponding quantum theory is also discussed. We show that a particular ordering gives critical dimensions 27 and 11 for the bosonic and fermionic case respectively.

  • 320.
    Björnsson, Jonas
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Strings, Branes and Non-trivial Space-times2008Doctoral thesis, monograph (Other academic)
  • 321.
    Björnsson, Jonas
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Strings, Branes and Non-trivial Space-times2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis deals with different aspects of string and /p/-brane theories. One of the motivations for string theory is to unify the forces in nature and produce a quantum theory of gravity. /p/-branes and related objects arise in string theory and are related to a non-perturbative definition of the theory. The results of this thesis might help in understanding string theory better. The first part of the thesis introduces and discusses relevant topics for the second part of the thesis which consists of five papers.

    In the three first papers we develop and treat a perturbative approach to relativistic /p/-branes around stretched geometries. The unperturbed theory is described by a string- or particle-like theory. The theory is solved, within perturbation theory, by constructing successive canonical transformations which map the theory to the unperturbed one order by order. The result is used to define a quantum theory which requires for consistency d = 25 + p dimensions for the bosonic /p/-branes and d = 11 for the supermembrane. This is one of the first quantum results for extended objects beyond string theory and is a confirmation of the expectation of an eleven-dimensional quantum membrane.

    The two last papers deal with a gauged WZNW-approach to strings moving on non-trivial space-times. The groups used in the formulation of these models are connected to Hermitian symmetric spaces of non-compact type. We have found that the GKO-construction does not yield a unitary spectrum. We will show that there exists, however, a different approach, the BRST approach, which gives unitarity under certain conditions. This is the first example of a difference between the GKO- and BRST construction. This is one of the first proofs of unitarity of a string theory in a non-trivial non-compact space-time. Furthermore, new critical string theories in dimensions less then 26 or 10 is found for the bosonic and supersymmetric string, respectively.

  • 322. Björnsson, Jonas
    et al.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    On small tension p-branes2008In: Physics Letters B 662 (2008) 270-274Article in journal (Refereed)
  • 323.
    Björnsson, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    On small tension p-branes2008In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 662, no 3, p. 270-274Article in journal (Refereed)
  • 324.
    Björnsson, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    On the unitarity of gauged non-compact world-sheet supersymmetric WZNW models2009In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 812, no 3, p. 525-539Article in journal (Refereed)
    Abstract [en]

    In this paper we generalize our investigation of the unitarity of non-compact WZNW models connected to Hermitian symmetric spaces to the N=1 world-sheet supersymmetric extension of these models. We will prove that these models have a unitary spectrum in a BRST approach for antidominant highest weight representations if the level and weights of the gauged subalgebra are integers. We will find new critical string theories in 7 and 9 space–time dimensions.

  • 325.
    Björnsson, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science.
    On the unitarity of gauged non-compact WZNW strings2008In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 797, no 3, p. 464-498Article in journal (Refereed)
  • 326. Björnsson, Jonas
    et al.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Stretched Quantum Membranes2005In: Nuclear Physics B727 (2005) 77-98Article in journal (Refereed)
  • 327.
    Björnsson, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science.
    Stretched quantum membranes2005In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 727, no 1-2, p. 77-98Article in journal (Refereed)
  • 328. Björnsson, Jonas
    et al.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    The BRST treatment of stretched membranes2006In: Nuclear Physics B736 (2006) 156-167Article in journal (Refereed)
  • 329.
    Björnsson, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science.
    The BRST treatment of stretched membranes2006In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 736, no 1-2, p. 156-167Article in journal (Refereed)
  • 330.
    Björnsson, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science.
    The membrane as a pertubation around string-like configurations2004In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 689, no 1-2, p. 37-52Article in journal (Refereed)
  • 331.
    Björnsson, Jonas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hwang, Stephen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    The membrane as a perturbation around string-like configurations2004In: Nuclear Physics B 689 (2004) 37-52Article in journal (Refereed)
  • 332.
    Björström, Cecilia M.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Kraków, Poland.
    Rysz, Jakub
    Institute of Physics, Jagiellonian University, Kraków, Poland.
    Budkowski, Andrzej
    Institute of Physics, Jagiellonian University, Kraków, Poland.
    Nilsson, Svante
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Mattias
    Department of Materials and Surface Chemistry/Polymer Technology, Chalmers University of Technology, Göteborg.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Multilayer formation in spin-coated thin films of low-bandgap polyfluorene:PCBM blends2005In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 17, no 50, p. L529-L534Article in journal (Refereed)
    Abstract [en]

    Blends of the low-bandgap polymer poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5- (4',7'-di-2-thienyl-2',1',3'-benzothiadiazole] (APFO-3) and the fullerene derivative [6,6]-phenyl–C61–butyric acid methyl ester (PCBM) were spin-coated from chloroform solution into thin films, which were examined with dynamic secondary ion mass spectrometry. For blends with high PCBM content, the depth profiles show composition waves that were caused by surface-directed phase separation during spin-coating. The formation of such multilayer structures by spontaneous self-stratification is likely to have implications for optimization strategies for the performance of organic solar cells

  • 333.
    Björström, Cecilia M.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Control of phase separation in blends of polyfluorene (co)polymers and the C60-derivative PCBM2005In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 152, no 1-3, p. 109-112Article in journal (Refereed)
    Abstract [en]

    When creating thin films of polymer blends, interesting morphologies are formed because of phaseseparation. In particular for conjugated polymers, which are used as active material in optoelectronic devices, it is very important to understand the parameters that influence the phaseseparation process and to achieve control over the morphology. The overall goal of this blend morphology study is to contribute to the design of device structures with desired performance.

    Here we present results of morphology studies on thin films of polyfluorene-based blends with the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The polymers used are poly(9,9-dioctylfluorene) (F8) and four different copolymers of F8. The thin films are spin coated from chloroform solutions onto silicon substrates and their surface morphology is imaged by tapping mode atomic force microscopy (AFM). We observe that the size and the shape of the domains in the film depend on the structure of the polymer. The nature of the monomer that, together with F8, is building the repeating unit in the copolymers has a strong effect on the phaseseparation in the polymer: PCBMblend. Since phaseseparation is influenced by interactions between components of the blend and the solvent, these results indicate that the degree of chemical interaction between polymer, solvent and PCBM, is different for the different blends. For the systems that form larger domains there is a clear correlation between the domain size (area) and the polymer/PCBMblend ratio. We also observe that the spin speed affects the thickness of the films and that the domain size increases with increasing thickness, primarily due to longer drying times

  • 334.
    Björström, Cecilia M.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Nilsson, Svante
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Poland.
    Budkowski, Andrzej
    Institute of Physics, Jagiellonian University, Poland.
    Andersson, Mats
    Department of Materials and Surface Chemistry/Polymer Technology, Chalmers University of Technology, Göteborg.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Vertical phase separation in spin-coated films of a low bandgap polyfluorene/PCBM blend: Effects of specific substrate interaction2007In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 253, no 8, p. 3906-3912Article in journal (Refereed)
    Abstract [en]

    We report on the effect of the substrate on the vertical phase separation in spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-40,70-di-2-thienyl-20,10,30-benzothiadiazole] (APFO-3) blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Compositional depth profiles of the films are measured by dynamic secondary ion mass spectrometry (SIMS).We found that changing the substrate from silicon to gold affects the composition profile near the substrate interface. This is caused by a specific interaction between the polymer (APFO-3) and the gold surface, as confirmed by X-ray photoelectron spectroscopy (XPS). The composition profile in the area away from the substrate interface, as well as the enrichment of the free surface with APFO-3, remain however unaffected by the choice of substrate. The vertical composition was also analysed for APFO-3:PCBM films spin-coated on indium tin oxide (ITO) coated with a thin layer of (3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS).

  • 335.
    Björström, Cecilia M.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Nilsson, Svante
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Poland.
    Rysz, Jakub
    Institute of Physics, Jagiellonian University, Poland.
    Budkowski, Andrzej
    Institute of Physics, Jagiellonian University, Poland.
    Zhang, Fengling
    Department of Physics, Linköping University, Sweden.
    Inganäs, Olle
    Department of Physics, Linköping University, Sweden.
    Andersson, Mats R.
    Department of Materials and Surface Chemistry / Polymer Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Influence of solvents and substrates on the morphology and the performance of low-bandgap polyfluorene:PCBM photovoltaic devices2006In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 6192, p. 61921X-Article in journal (Refereed)
    Abstract [en]

    Spin-coated thin films of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (APFO-3) blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are used as the active material in polymer photovoltaic cells. Such blends are known for their tendency to phase separate during film formation. Tuning the morphology of the blend in a controlled way is one possible road towards higher efficiency. We studied the effect of adding chlorobenzene to chloroform-based blend solutions before spin-coating on the conversion efficiency of APFO-3:PCBM photodiodes, and related that to the lateral and vertical morphology of thin films of the blend. The lateral morphology is imaged by atomic force microscopy (AFM) and the vertical compositional profile is obtained by dynamic secondary ion mass spectrometry (SIMS). The profiles reveal compositional variations consisting of multilayers of alternating polymer-rich and PCBM-rich domains in the blend film spin-coated from chloroform. The vertical compositional variations are caused by surface-directed spinodal waves and are frozen in during the rapid evaporation of a highly volatile solvent. With addition of the low-vapour pressure solvent chlorobenzene, a more homogeneous vertical composition is found. The conversion efficiency for solar cells of this blend was found to be optimal for chloroform:chlorobenzene mixtures with a volume-ratio of 80:1. We have also investigated the role of the substrate on the morphology. We found that blend films spin-coated from chloroform solutions on PEDOT:PSS-coated ITO show a similar compositional structure as the films on silicon, and that changing the substrate from silicon to gold only affects the vertical phase separation in a region close to the substrate interface

  • 336.
    Björström, Cecilia M.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    Institute of Physics, Jagiellonian University, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Poland.
    Budkowski, Andrzej
    Institute of Physics, Jagiellonian University, Poland.
    Zhang, Fengling
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Inganäs, Olle
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Nelson, Jenny
    Imperial College, London, U.K..
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Device Performance of APFO-3/PCBM Solar Cells with controlled morphologyManuscript (Other academic)
  • 337.
    Björström Svanström, Cecilia
    Karlstad University, Faculty of Technology and Science.
    Thin films of polyfluorene:fullerene blends - Morphology and its role in solar cell performance2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The sun provides us daily with large quantities of energy in the form of light. With the world’s increasing demand of electrical energy the prospect of converting this solar light into electricity is highly tempting. In the strive towards mass-production and low cost solar cells, new types of solar cells are being developed, e.g. solar cells completely based on organic molecules and polymers. These materials offer a promising potential of low cost and large scale manufacturing and have the additional advantage that they can be produced on flexible and light weight substrate which opens for new and innovating application areas, e.g. integration with paper or textiles, or as building materials. In polymer solar cells a combination of two materials are used, an electron donor and an electron acceptor. The three dimensional distribution of the donor and acceptor in the active layer of the device, i.e. the morphology, is known to have larger influence of the solar cell performance. For the optimal morphology there is a trade-off between sometimes conflicting criteria for the various steps of the energy conversion process. The dissociation of photogenerated excitons takes place at an interface between the donor and acceptor materials. Therefore an efficient generation of charges requires a large interface between the two components. However, for charge transport and collection at the electrodes, continuous pathways for the charges to the electrodes are required.

    In this thesis, results from morphology studies by atomic force microscopy (AFM) and dynamic secondary ion mass spectrometry (SIMS) of spin-coated blend and bilayer thin films of polyfluorene co-polymers, especially poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4´,7´-di-2-thienyl-2´,1´,3´-benzothiadiazole)] APFO-3, and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are presented. It is shown that by varying the blend ratio, the spin.-coating solvent, and/or the substrate, different morphologies can be obtained, e.g. diffuse bilayer structures, spontaneously formed multilayer structures and homogeneous blends. The connection between these different morphologies and the performance of solar cells is also analysed. The results indicate that nano-scale engineering of the morphology in the active layer may be an important factor in the optimization of the performance of polymer solar cells.

  • 338.
    Björström Svanström, Cecilia M.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    Institute of Physics, Jagiellonian University, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Poland.
    Budkowski, Andrzej
    Institute of Physics, Jagiellonian University, Poland.
    Zhang, Fengling
    nic Electronic (COE), Linköping University, Sweden.
    Inganäs, Olle
    IFM and Center of Organic Electronic (COE), Linköping University, Sweden.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Benson-Smith, Jessica
    Department of Physics, Imperial College, London, U.K..
    Nelson, Jenny
    Department of Physics, Imperial College, London, U.K..
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Device performance of APFO-3/PCBM solar cells with controlled morphology2009In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 21, no 43, p. 4398-4403Article in journal (Refereed)
    Abstract [en]

    Polymer/fullerene solar cells with three different device structures: A) diffuse bilayer, B) spontaneously formed multilayer, and C) vertically homogenous thin films, are fabricated. The photocurrent/voltage performance is compared and it is found that the self-stratified structure (B) yields the highest energy conversion efficiency.

  • 339.
    Blazinic, Vanja
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Ericsson, Leif
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Stability of TQ1:N2200 active layers for all-polymer solar cellsManuscript (preprint) (Other academic)
  • 340.
    Blomberg, Andreas
    et al.
    Karlstad University, Faculty of Technology and Science.
    Stöllman, Johan
    Karlstad University, Faculty of Technology and Science.
    Haspelsystemet Camcoil 15002008Independent thesis Basic level (professional degree), 15 points / 22,5 hpStudent thesis
    Abstract [en]

    Our employer Camatec Industriteknik AB gave us the assignments to increase theirs range of versions on Camcoil that is their own patent product. Camcoil is a capstan system that is used when steel band fabricated. Exist for example in production lines their steel band should be annealed. Our goal with this work is to come up with a completed production basis on a Camcoil for heavy industry. The basis should contain calculations, 3D-constructions, drawings and cost proposal on manufacturing and detail purchase.

    Demands on this project:

    1. 15 ton load

    2. Strip width up to 1500 mm

    3. Head diameter 610 mm

    4. Production speed 35 m/min

    5. Economy manufacturing

    6. Be simple

    Several concepts were decided out of the feasibility study. The concepts were compared against each other and finally only one was left. Result of the design concept became one shaft with three capstan heads and a support function.

    One conceivable working process was planed with a Gantt-table. A decision was made that the work of the Camcoil should be separated in several details. Earlier work on Camcoil was study to increase our understanding for the work.

    Some of the examined parts were shaft dimensions, bearings, head shape, tripod, support function and hydraulic cylinder for the capstan and support.

    Some of the calculations have been made in Ansys. Directional deformation, Von Mises stress for the shaft, length of the hydraulic cylinder in the capstan heads and the stress for tripod and support function was calculated.

    Analytic calculations were made on some parts. Frequency analysis for the system was made with Dunkerleys method. The reaction forces in the bearings were calculated with a combination of elementary case. Lifecycle of the bearings can with this be appreciated. Hydraulic cylinder strength in capstan heads and support function, locking assemblies, sheet metal thickness and control off beam dimensions in support was also decided with analytic calculations.

    3D models were made on several details in the system. Models like lock rings, engines and bearings were taken from the supplier.

    After the modeling assemble drawings and detail drawings were made for the whole capstan system. The drawings were sending to manufacturer for a cost proposal.

  • 341.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Analysis of fatty acids by capillary electrophoresis,1999In: Lipid Technology, 11, (1999) 140-142Article in journal (Refereed)
  • 342.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Current Aspects of Stationary Phases for Gas Chromatography, (Guest editorial)1998In: LC/GC Int., 11 (1998) 760-762Article in journal (Refereed)
  • 343.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Effects and nature of buffer ion enrichment in electrical field assisted liquid chromatography2004Licentiate thesis, monograph (Other academic)
  • 344.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    In-line application of electric field in capillary separation systems2006Doctoral thesis, monograph (Other academic)
  • 345.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Models in chemistry education - A study of teaching and learning acids and bases in Swedish upper secondary schools2007Doctoral thesis, monograph (Other academic)
  • 346.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Professional supervision of doctoral education in science2010In: Strömstad akademi, Vision och verklighet / [ed] A. Ott och C.E. Olivestam, Strömstad: Strömstad akademi , 2010, p. 91-112Chapter in book (Other academic)
  • 347.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Silicone stationary phases for gas chromatography,2001In: LC/GC Europe, 14 (2001) 106-112Article in journal (Refereed)
  • 348.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Textbooks, teachers, and students understanding of models used to explain acid-base reactions2005Licentiate thesis, monograph (Other academic)
  • 349.
    Blomberg, Lars G
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Two new techniques for sample preparation in bioanalysis: Microextraction in packed sorbent (MEPS) and use of a bonded monolith as sorbent for sample preparation in polypropylene tips for 96-well plates2009In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 393, no 3, p. 797-807Article in journal (Refereed)
  • 350.
    Blomberg, Lars G
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Abdel-rehim, M
    Current advances in microextraction by packed sorbent (MEPS) for bioanalysis applications2009In: LCGC Europé, ISSN 1471-6577, Vol. 22, no 1, p. 8-19Article in journal (Refereed)
45678910 301 - 350 of 2917
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