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  • 1.
    Adamczyk, Krzysztof
    et al.
    Department of Materials Science and Engineering, Trondheim, Norway.
    Søndenå, Rune
    Department for Solar Energy, IFE, Kjeller, Norway.
    You, Chang Chuan
    Department for Solar Energy, IFE, Kjeller, Norway.
    Stokkan, Gaute
    Sintef Materials and Chemistry, Trondheim, Norway.
    Lindroos, Jeanette
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Rinio, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Di Sabatino, Marisa
    Department of Materials Science and Engineering, Trondheim, Norway.
    Recombination Strength of Dislocations in High-Performance Multicrystalline/Quasi-Mono Hybrid Wafers During Solar Cell Processing2017In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, 1700493Article in journal (Refereed)
    Abstract [en]

    Wafers from a hybrid silicon ingot seeded in part for High Performance Multicrystalline, in part for a quasi-mono structure, are studied in terms of the effect of gettering and hydrogenation on their final Internal Quantum Efficiency.The wafers are thermally processed in different groups – gettered and hydrogenated. Afterwards, a low temperature heterojunction with intrinsic thin layer cell process is applied to minimize the impact of temperature. Such procedure made it possible to study the effect of different processing steps on dislocation clusters in the material using the Light Beam Induced Current technique with a high spatial resolution. The dislocation densities are measuredusing automatic image recognition on polished and etched samples. The dislocation recombination strengths are obtained by a correlation of the IQE with the dislocation density according to the Donolato model. Different clusters are compared after different process steps. The results show that for the middle of the ingot, the gettering step can increase the recombination strength of dislocations by one order of magnitude. A subsequent passivation with layers containing hydrogen can lead to a decrease in the recombination strength to levels lower than in ungettered samples.

  • 2.
    ahmad, waqas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Development of algorithm for li-ion batteries in electric vehicles, taking into account SOC, charge control, cell balancing and SOF.2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 3.
    Aimal, Pir
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Mohsin, Main
    Analyzing Voltage control and reactive power support from full power converter wind turbine2011Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
  • 4.
    Al Motasem, Ahmed
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Assiut University, Egypt.
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Gåård, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Holleboom, Thijs
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Tool microstructure impact on the wear behavior of ferrite iron during nanoscratching: An atomic level simulation2017In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 370-371, 39-45 p.Article in journal (Refereed)
    Abstract [en]

    In the present work, molecular dynamics simulations were used to investigate the impact of the tool microstructure on the wear behavior of ferrite workpiece during nanoscratching. The tool microstructure was modified by varying the carbide (cementite) contents. The simulation results show that dislocations are the primary mechanism for plastic deformation of the workpiece material. It is found that total dislocation length varies significantly depending on the carbide content in the tool. Furthermore, other tribological phenomena were also observed to depend on the carbide contents. For example, the average value of frictional forces decreased while the normal force increases with increasing carbide contents, and hence the friction coefficient was decreased. Additionally, the shape and size of lateral and frontal pileups are lowered. The structural analysis of the pileup region reveals the loss of long range order and start of amorphisation. The temperature distribution of the pileup regions showed an increase of the pileup temperature when carbide is added into tool. The wear volume is considerably reduced when the carbide content increases. The average scratch hardness was found to decrease and the result was analyzed with the theoretical Taylor hardening model.

  • 5.
    Alho, Artur
    et al.
    Univ Lisbon, Ctr Math Anal Geometry & Dynam Syst, Inst Super Tecn, Av Rovisco Pais, P-1049001 Lisbon, Portugal..
    Carloni, Sante
    Univ Lisbon, Ctr Multidisciplinar Astrofis CENTRA, Inst Super Tecn, Av Rovisco Pais, P-1049001 Lisbon, Portugal..
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    On dynamical systems approaches and methods in f (R) cosmology2016In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 8, 064Article in journal (Refereed)
    Abstract [en]

    We discuss dynamical systems approaches and methods applied to flat Robertson Walker models in f(R)-gravity. We argue that a complete description of the solution space of a model requires a global state space analysis that motivates globally covering state space adapted variables. This is shown explicitly by an illustrative example, f(R) = R + alpha R-2, alpha > 0, for which we introduce new regular dynamical systems on global compactly extended state spaces for the Jordan and Einstein frames. This example also allows us to illustrate several local and global dynamical systems techniques involving, e.g., blow ups of nilpotent fixed points, center manifold analysis, averaging, and use of monotone functions. As a result of applying dynamical systems methods to globally state space adapted dynamical systems formulations, we obtain pictures of the entire solution spaces in both the Jordan and the Einstein frames. This shows, e.g., that due to the domain of the conformal transformation between the Jordan and Einstein frames, not all the solutions in the Jordan frame are completely contained in the Einstein frame. We also make comparisons with previous dynamical systems approaches to f (R) cosmology and discuss their advantages and disadvantages.

  • 6.
    Alho, Artur
    et al.
    Portugal.
    Hell, Juliette
    Germany.
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Global dynamics and asymptotics for monomial scalar field potentials and perfect fluids2015In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 32, no 14, 145005Article in journal (Refereed)
    Abstract [en]

    We consider a minimally coupled scalar field with a monomial potential and a perfect fluid in flat Friedmann-Lemaitre-Robertson-Walker cosmology. We apply local and global dynamical systems techniques to a new three-dimensional dynamical systems reformulation of the field equations on a compact state space. This leads to a visual global description of the solution space and asymptotic behavior. At late times we employ averaging techniques to prove statements about how the relationship between the equation of state of the fluid and the monomial exponent of the scalar field affects asymptotic source dominance and asymptotic manifest self-similarity breaking. We also situate the ’attractor’ solution in the three-dimensional state space and show that it corresponds to the one-dimensional unstable center manifold of a de Sitter fixed point, located on an unphysical boundary associated with the dynamics at early times. By deriving a center manifold expansion we obtain approximate expressions for the attractor solution. We subsequently improve the accuracy and range of the approximation by means of Pade approximants and compare with the slow-roll approximation. 

  • 7.
    Alho, Artur
    et al.
    Technical University of Lisbon, Portugal.
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Global dynamics and inflationary center manifold and slow-roll approximants2015In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 56, no 1, 012502Article in journal (Refereed)
    Abstract [en]

    We consider the familiar problem of a minimally coupled scalar field with quadratic potential in flat Friedmann-Lemaître-Robertson-Walker cosmology to illustrate a number of techniques and tools, which can be applied to a wide range of scalar field potentials and problems in, e.g., modified gravity. We present a global and regular dynamical systems description that yields a global understanding of the solution space, including asymptotic features. We introduce dynamical systems techniques such as center manifold expansions and use Padé approximants to obtain improved approximations for the “attractor solution” at early times. We also show that future asymptotic behavior is associated with a limit cycle, which shows that manifest self-similarity is asymptotically broken toward the future and gives approximate expressions for this behavior. We then combine these results to obtain global approximations for the attractor solution, which, e.g., might be used in the context of global measures. In addition, we elucidate the connection between slow-roll based approximations and the attractor solution, and compare these approximations with the center manifold based approximants.

  • 8.
    Alho, Artur
    et al.
    Univ Lisbon, Inst Super Tecn, Ctr Math Anal Geometry & Dynam Syst, P-1049001 Lisbon, Portugal..
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Scalar field deformations of Lambda CDM cosmology2015In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 92, no 10, 103502Article in journal (Refereed)
    Abstract [en]

    This paper treats nonrelativistic matter and a scalar field phi with a monotonically decreasing potential minimally coupled to gravity in flat Friedmann-Lemaitre-Robertson-Walker cosmology. The field equations are reformulated as a three-dimensional dynamical system on an extended compact state space, complemented with cosmographic diagrams. A dynamical systems analysis provides global dynamical results describing possible asymptotic behavior. It is shown that one should impose global and asymptotic bounds on lambda = -V-1 dV/d phi to obtain viable cosmological models that continuously deform Lambda CDM cosmology. In particular we introduce a regularized inverse power-law potential as a simple specific example.

  • 9.
    Ali, Asad A.
    et al.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    Hoagg, Jesse B.
    Univ Kentucky, Dept Mech Engn, 151 Ralph G Anderson Bldg, Lexington, KY 40507 USA..
    Mossberg, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Bernstein, Dennis S.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    On the stability and convergence of a sliding-window variable-regularization recursive-least-squares algorithm2016In: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 30, no 5, 715-735 p.Article in journal (Refereed)
    Abstract [en]

    A sliding-window variable-regularization recursive-least-squares algorithm is derived, and its convergence properties, computational complexity, and numerical stability are analyzed. The algorithm operates on a finite data window and allows for time-varying regularization in the weighting and the difference between estimates. Numerical examples are provided to compare the performance of this technique with the least mean squares and affine projection algorithms. Copyright (c) 2015 John Wiley & Sons, Ltd.

  • 10.
    Al-Jaff, Mohammed
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    The ZX-Calculus: A graphical calculus for multipartite qubit systems2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis we will give a presentation of a graphical/diagrammatic calculus for quantum systems involving interacting quantum observables such as multi-partite systems of qubits, the ZX-Calculus. Unlike the Hilbert space formulation of quantum mechanics, the ZX-Calculus is based on category theory, more specically on the notion of a compact dagger symmetric monoidal category and as a consequence the graphical language associated with such a category is inherited by the calculus. This enables us to think about and deal with many calculations in quantum computation and information in a purely graphical and intuitive fashion. Although being formulated in a more general mathematical framework, huge parts of the Hilbert space formulation of quantum mechanics can be extracted from the ZX-calculus. In this thesis we will begin by giving a motivation for the need of such a calculus and then key concepts of category theory will be introduced in an intuitive manner in order to understand the ZX-calculus that will be presented afterwards. We then apply the calculus to'model' and describe certain quantum circuits and quantum teleportation.

  • 11.
    AlMotasem, A
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Department of Physics, Faculty of ScienceAssiut University Assiut Egyp.
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Gåård, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics, Science, Mathematics and Engineering Education Research.
    Holleboom, Thijs Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Atomistic insights on the wear/friction behavior of nanocrystalline ferrite during nanoscratching as revealed by molecular dynamics2017In: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, no 3, 101- p.Article in journal (Refereed)
    Abstract [en]

    Using embedded atom method potential, extensive large-scale molecular dynamics (MD) simulations of nanoindentation/nanoscratching of nanocrystalline (nc) iron have been carried out to explore grain size dependence of wear response. MD results show no clear dependence of the frictional and normal forces on the grain size, and the single-crystal (sc) iron has higher frictional and normal force compared to nc-samples. For all samples, the dislocation- mediated mechanism is the primary cause of plastic deformation in both nanoindentation/nanoscratch. However, secondary cooperative mechanisms are varied significantly according to grain size. Pileup formation was observed in the front of and sideways of the tool, and they exhibit strong dependence on grain orientation rather than grain size. Tip size has significant impact on nanoscratch characteristics; both frictional and normal forces monotonically increase as tip radii increase, while the friction coefficient value drops by about 38%. Additionally, the increase in scratch depth leads to an increase in frictional and normal forces as well as friction coefficient. To elucidate the relevance of indentation/scratch results with mechanical properties, uniaxial tensile test was performed for nc-samples, and the result indicates the existence of both the regular and inverse Hall-Petch relations at critical grain size of 110.9 angstrom. The present results suggest that indentation/scratch hardness has no apparent correlation with the mechanical properties of the substrate, whereas the plastic deformation has.

  • 12.
    AlMotasem, Ahmed
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Gåård, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Holleboom, Thijs
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Adhesion between ferrite iron-€“iron/cementite countersurfaces: A molecular dynamics study2016In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 103, 113-120 p.Article in journal (Refereed)
    Abstract [en]

    The adhesive properties of Fe(110)/Fe(110) and Fe3C(001)/Fe(110) countersurfaces have been investigated by using classical molecular dynamics simulations. The simulation results show that Fe3C/Fe exhibits a relatively lower adhesion compared to the Fe/Fe. Additionally, the temperature dependence of the adhesive properties between 300–700 K has been examined. The results demonstrate that, with increasing the temperature, the values of the adhesion force and the work of adhesion continuously decrease in the case of Fe3C/Fe; they initially slightly increase up to 500 K then decrease in the case of Fe/Fe. Furthermore, the effect of lattice coherency between Fe/Fe has been examined and found to slightly reduce the adhesion. These results explain how carbides improve galling resistance of tool steel observed during dry sliding. 

  • 13. Almotasem, Ahmed
    et al.
    Bergström, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Gåård, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Holleboom, Thijs Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    A molecular dynamic study on the influence of carbide particles in ferrite on material transfer during nanoscratching of ferritic iron2016In: Proceedings of the 10th International Tool Conference: TOOL, 10th International TOOL Conference : 04th to 07th October 2016, Bratislava, Slovakia / [ed] Simancik, Frantisek, 2016Conference paper (Refereed)
  • 14.
    AlMotasem, Ahmed
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Gåård, Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Influence of chemical composition on adhesion in metallic contacts2016In: International Journal of Advances in Science Engineering and Technology, ISSN 2321-9009, Vol. 4, no 3, Spl. Iss. 1, 229-231 p.Article in journal (Refereed)
    Abstract [en]

    - In sheet metal forming operations, adhesive wear is the main causeof tool damage as sheet material is transferred to the tool surface during the forming operation. Means of reducing adhesive wear are of high interest for the metal forming industry.In the present work, molecular dynamics simulations were used to investigate influence of alloying iron with vanadium on adhesive properties in contact with iron. The results showed that adhesion, quantified by the work of adhesion, decreased as the vanadium content increased. Highest reduction was obtained for 10 at.% vanadium which corresponded to a decrease in adhesive work of approximately 10%.

  • 15.
    Alpmarken, Ia
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Studie av tekniska och ekonomiska fördelar av olika lösningar vid instrumentinstallation2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Inom industrin är tendensen att allt mer arbete automatiseras för snabbare, mer kostnadseffektiv samt exaktare tillverkning eller bearbetning. Vid automatisering av en processindustri möts konstruktören av ett flertal utmaningar, i minst att välja vilken installationsmetod som skall användas i det aktuella fallet.Vid en ombyggnation eller tillbyggnad av en existerande processindustri finns ofta begränsningar som styr vilken installationsmetod som kan användas, kunden kan exempelvis önska att den nya installationen utförs på liknande sätt som den tidigare.En nyinstallation kan däremot ge att konstruktören har möjlighet att själv påverka installationsmetod.

    I samarbete med Sweco Industry, ett konsultbolag som bland annat ägnar sig åt att konstruera system för processtyrning åt kunder, samt Valmet, ett företag som konstruerar anläggningar för tillverkning av mjukpapper, har därför en studie utförts för att studera vilken typ av installation som är mest kostnadseffektiv för ett uppbyggt typfall.

    Detta har utförts genom att planera fem installationer för det uppbyggda fallet och jämföra dess delkostnader samt totalkostnader.

    Den installationsmetod som påvisat lägst totalkostnad är en installation med distribuerade I/O-moduler anslutna till styrsystemet via PROFIBUS DP fältbuss.

    Trots en något högre totalkostnad rekommenderas dock en installation medelst fältinstrument anslutna till en fältbuss av lägre nivå då detta medför en störningssäker kommunikation och ger en tidseffektiv installation.

  • 16.
    Andersson, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Different Styles of Laboratory Work - Different Types of Communication: Students’ talk during laboratory work in upper secondary school physicsManuscript (preprint) (Other academic)
  • 17.
    Andersson, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Laborativt arbete i fysikundervisningen: Något som behöver diskuteras!2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [sv]

    Baksidestext

    I gymnasieskolans kursplaner för ämnet fysik framhålls det undersökande arbetssättet genom att betona att eleverna ska ges förutsättningar att utveckla förmågan att söka svar på frågor, planera, genomföra, tolka och redovisa experiment. Eleverna ska dessutom ges möjligheter att använda sina kunskaper i fysik för att kommunicera, argumentera och presentera slutsatser. Utgångspunkten i den här avhandlingen är att laborationsmomentet skapar en speciell diskurs där eleverna blir aktörer och läraren iträder rollen som observatör. I en sådan miljö skapas förutsättningar för att eleverna på ett naturligt sätt får möjlighet att prata och diskutera fysik, utifrån sina egna förutsättningar. Syftet med denna avhandling är att genom praktikbaserade studier tydliggöra hur fysiklaborationens utformning påverkar elevernas kommunikation och vidare hur eleverna använder språket vid laborationstillfället för att skapa förståelse. Detta bidrar till debatten om fysiklaborationens effektivitet, sett både ur ett undervisnings- och inlärningsperspektiv. Resultaten visar att olika laborationsformer är uppbyggda av liknande aktiviteter, men varierar i tid som ägnas åt de olika aktiviteterna. Aktiviteterna i sin tur skapar samtal av olika karaktär. Olika samtalsformer används för skilda syften. Ett analytiskt ramverk har skapats för att ingående kunna studera hur och vad eleverna talar om både på en lingvistisk och kognitiv nivå.

  • 18.
    Andersson, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Learning Physics Through Communication During Laboratory Work: An empirical study at upper secondary school2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Laboratory work as a teaching and learning method is given prominence in the Swedish physics curriculum for upper secondary school. It is emphasised that students should be given opportunities to develop the ability to search for answers to questions, plan, conduct, interpret and present results. Moreover, students should also be encouraged to use their physics knowledge to communicate, argument and present conclusions. This thesis is based on the belief that physics laboratory work creates a special discourse, where the student becomes the actor and the teacher becomes the organiser and observer. Such an environment enables students to naturally engage in physics discussions using their own terms. The aim is to explore students’ laboratory work at upper secondary school in-depth, with respect to its design and influence on students’ communication. Through analysis of students’ communication, the purpose is to better understand the physics laboratory work’s possibilities as a teaching and learning method. This will contribute to ongoing debate about the effectiveness of laboratory work. The results show that laboratory work consists of similar activities but differs in amount of time allocated to the different activities. Different types of talk are used for different purposes. An analytical framework has been created to enable deeper investigations of how and what students are talking about at both a linguistic and cognitive level. Moreover, the analysis shows the importance of students acquiring knowledge about physics and understanding the value of using an investigative approach as well as acquiring core content physics knowledge.

  • 19.
    Andersson, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Open Inquiry-Based Learning in Physics: Students' Communicative Moves Under ScrutinyManuscript (preprint) (Other academic)
  • 20.
    Andersson, Jan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Enghag, Margareta
    Stockholms universitet.
    Different Types of Laboratory Work - Different Types of Communication: Students’ talk during laboratory work in upper secondary school physicsManuscript (preprint) (Other academic)
  • 21.
    Andersson, Jan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Enghag, Margareta
    Stockholms universitet.
    Student talk during the process of laboratory work of linear motion in school physicsManuscript (preprint) (Other academic)
  • 22.
    Andersson, Jan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Enghag, Margareta
    Stockholms universitet.
    The Effectiveness of Laboratory Work in Physics: A Case Study at Upper Secondary School in Sweden2012In: Proceedings of The World Conference on Physics Education 2012: WCPE 2012 / [ed] Mehmet Fatih Taşar, 2012, 729-740 p.Conference paper (Refereed)
    Abstract [en]

    The present paper reports on a case study that examined the effectiveness of a practical activity in physics, at a Swedish upper secondary school. A teacher and 19 students participated in the study. The students were observed while working with the topic motion, in a computer based laboratory environment (CBL). This case study is part of an ongoing longitudinal study, about the role of laboratory work with different degrees of freedom. The analysis of interviews, written reports and posttest, shows that the practical work was effective based on Millar’s model. Even so, the students had difficulties expressing what they learned from the activity. This study emphasizes the complexity of planning and conducting laboratory work that is effective, from several different aspects. 

  • 23.
    Andersson, Jan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Enghag, Margareta
    Stockholms universitet.
    The relation between students’ communicative moves during laboratory work in physics and outcomes of their actions2017In: International Journal of Science Education, ISSN 0950-0693, E-ISSN 1464-5289, Vol. 39, no 2, 158-180 p.Article in journal (Refereed)
    Abstract [en]

    In this case study, we explore students’ communication during practical work in physics at an upper secondary school in Sweden from a sociocultural perspective. We investigate the relation between the interaction and content of students’ communication and outcomes of their actions, with the purpose of finding new knowledge for informing teachers in their choice of instruction. We make discourse analysis of how students interact but also of what students are discussing in terms of underlying content at a linguistic and cognitive level. Twenty students divided into five groups were video recorded while performing four practical tasks at different stations during laboratory work about motion. An analytical framework was developed and applied for one group to three parts of the transcripts in which three different talk-types occurred. Discursive, content, action and purposive moves in the process were identified for each talk-type at both linguistic and cognitive levels. These moves represent information concerning what the teacher actually assigns students to do, and how students make meaning of the activities. Through these different communicative moves, students experience how laboratory work can enhance their competence to collaborate in a scientific environment with complex practical and theoretical questions to solve quickly. Implications of the findings are discussed. 

  • 24.
    Andersson, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Jansson, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Analys av solcellsanläggningar påverkan på elnätet2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Sammanfattning

    Examensarbetet handlar om vilka effekter mikroproduktion i form av solcellsenheter har och kommer att ha på Karlstads elnät. Via flera mätserier har här sammanställts vad som händer med elkvaliteten i nätet och vilka krav som ställs på elnätsbolag och framtida mikroproducenter. Genom bred teoretisk kunskap och praktiskt arbete med ett antal dataprogram har denna rapport arbetats fram och sammanställts. Vid ett flertal tillfällen har upphovsmännen bakom denna rapport gett sig ut i fält för att på plats ta del utav dagens former av solkraft samt också iakttagit arbetet bakom och inför elkvalitetsundersökningar.Syftet har i grunden varit att ge kunskap inför ökande volymer av mikroproduktion och att förbereda för framtida förändringar och ombyggnationer i det lokala elnätet. Arbetet har resulterat i en tydlig bild av att dagens elnät har goda möjligheter att möta en ökning av producenter med låga produktionsnivåer. Det har konstaterats att försiktighet bör tas vid inkoppling av anläggningar vad gäller enfas och trefas. Eftersträvansvärt är att använda trefasinkoppling för att undvika snedbelastningar i nätet.

  • 25.
    Andersson, Jonatan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    A lattice model for topological phases2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Matter exists in many different phases, for example in solid state or in liquid phase. There are also phases in which the ordering of atoms is the same, but which differ in some other respect, for example ferromagnetic and paramagnetic states. According to Landau's symmetry breaking theory every phase transition is connected to a symmetry breaking process. A solid material has discrete translational symmetry, while liquid phase has continuous translational symmetry. But it has turned out that there also exist phase transitions that can occur without a symmetry breaking. This phenomenon is called topological order. In this thesis we consider one example of a theoretical model constructed on a two dimensional lattice in which one obtains topological order.

  • 26.
    Andersson, Jonatan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    AFM study of Micro Fibrllated Cellulose, (MFC) in controlled atmosphere2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis, Atomic Force Microscopy (AFM) is used to characterize Micro Fibrillated Cellulose (MFC) produced by two different methods according to their size and shape. For one of these MFC-types, their interaction with the humidity in the atmosphere is investigated and their swelling is calculated. MFC is a relatively new material based on cellulose fibres extracted from wood. This study is performed in co-operation with Stora Enso research centre. Stora Enso is a renewable material company which uses mostly wood based raw materials in their production. The measured swelling is ~ 5 % and depends on the number of elementary fibrils included in the fibre.

  • 27.
    Andersson, Oscar
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Influence of primary precipitate shape, size volume fraction and distribution in PM tool steels on galling resistance2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In sheet metal forming (SMF), the major failure reason is galling. Galling is a process of different wear stages that leads to destruction of both the forming tool and the sheet metal working piece and is, because of that, of big economic importance for the SMF industries. Therefore, investigations and researches about how tool steels microstructure affect the tool steels galling resistance is of high priority. In the present work, different carbide properties were studied to find out how their properties affected the tool materials galling resistance. The investigated carbide properties were:

    • Shape and size of the carbides  
    • Carbide volume fraction
    • Carbide distribution in the microstructure

    The investigation included three tools, all made of the PM tool steel S390, that were heattreated differently in order to achieve different carbide properties but still maintain the same hardness. The tools were galling tested in a slider-on-flat-surface (SOFS) tribometer to determine their galling resistances. In a scanning surface electron microscope (SEM) the tools galling marks were analyzed to find explanations for the SOFS tribometer results and the connection to the tools different carbide properties. 

    The investigations most galling resistant tool was the tool that had the microstructure with largest carbides which were distributed at grain boundaries and the second highest carbide volume fraction among the investigated tools.

  • 28.
    Andersson, Stig
    et al.
    Göteborgs Universitet.
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Excitation and desorption of physisorbed H2 via the 2Σu electron scattering resonance.2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, 114703-1-114703-11 p., 114703Article in journal (Refereed)
    Abstract [en]

    Our high-resolution electron energy-loss measurements concern physisorbed H2 and comprise dif- ferential cross sections for the excitation of the internal H2 modes and the H2-surface bonding mode and their combinations and extend over the electron impact energy range of the classical low-energy H2 2Σu resonance. Comparison with corresponding data for the excitation of the internal modes of gas phase H2 reveals that strong elastic electron reflectivity from the Cu(100) substrate profoundly distorts the inelastic scattering pattern for physisorbed H2. We find that this influence can be corrected for and that the resulting peak cross sections agree with the H2 gas phase data, in accordance with theoretical predictions for the excitation of the internal H2 vibration. We have used corrected cross sections for the rotational mode spectra of physisorbed H2, HD, and D2 in a model concerning elec- tron induced desorption via rotation-translation energy conversion. These spectra include transitions from the ground state as well as excited levels of the physisorption potential well. H2 and HD can desorb from all levels while D2, for energetic reason, can only desorb from the excited levels. This model gives a satisfactory account of the observed desorption cross sections and predicts character- istic velocity distributions of the desorbing molecules. The cross section data for H2 and HD reveals that direct bound-free transitions also contribute to the electron induced desorption. 

  • 29.
    Annebäck, Jenny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    A Minor Field Study on development of recycling service for used PET bottles at hotels in Uganda2013Independent thesis Basic level (professional degree), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Through interviews, research, observations and the use of service design methods the author of this report, Jenny Annebäck, executed a Minor Field Study within the field of recycling of PET bottles in Uganda. The project work resulted in thorough studies of service design thinking and methodology, sustainable development, the market and situation in Uganda as well as the consumer group concerned about sustainable development. The result was a pre-study of a future development of a recycling service, visualized through two stakeholder maps, personas and a customer journey map. These three tools constitutes a beginning and a solid ground for further work with developing the service. A service that can contribute to a more sustainable development in the country of Uganda. In the report, examples are stated how to continue with the project as well as how it can be applied in other developing countries.

    The project work of this Minor Field Study(MFS) lasted from November 2011 until June 2012, as a degree project of 22,5 ECTS credits for the Degree of Bachelor of Science in Innovation and Design Engineering at Karlstad University. The MFS program is organized by the Swedish International Programme Office for Education and Training and financed by the Swedish International Development Cooperation Agency, enabling graduating students to perform a thesis in a developing country.

    Jenny Annebäck spent the first two months of the project time in Jinja, Uganda, together with her project partner Olga Sabirova Höjerström, both students at Karlstad University. The two project group members performed this Minor Field Study together with Sarah Keller, industrial designer and general manager at Uganda Innovation Factory(UIF). UIF is a product and graphic design company situated in Jinja, working with local designers to encourage Ugandan design and production for the global market. The supervising teacher of this project has been Monica Jakobsson and the examiner professor Fredrik Thuvander, both belonging to the Faculty of Technology and Science at Karlstad University. 

  • 30.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Materials aspects in spin-coated films for polymer photovoltaics2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Polymer-based photovoltaics have the potential to contribute to boosting photovoltaic energy conversion overall. Besides allowing large-area inexpensive processing, polymeric materials have the added benefit of opening new market applications for photovoltaics due to their low-weight and interesting mechanical properties. The energy conversion efficiency values of polymer photovoltaics have reached new record values over the past years. It is however crucial that stability issues are addressed together with efficiency optimization. Understanding fundamental materials aspects is key in both areas.

    In the work presented in this thesis, the morphology of polymer:fullerene films and its influence on device performance was studied, as well as the effect of light exposure on the surface of fullerene films. Several polyfluorene copolymers were used for the morphology studies, where the effects of changing spin-coating solvent and of side chain engineering were investigated with dynamic secondary ion mass spectrometry (dSIMS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Polymer-enriched surfaces were found in all blend films, even in the cases with homogeneous distributions in the bulk. Side chain engineering of the polymer led to gradual changes in the compositional variations perpendicular to the surface, and to slight variations in the photocurrent. The electronic structure of the fullerene derivative PCBM was studied in detail and the spectroscopic fingerprint of the materials was analysed by comparison with theoretically simulated spectra. Photo-stability studies done in air showed that the surface of fullerene films underwent severe damages at the molecular level, which is evident from changes in the valence band and X-ray absorption spectra. These changes were explained by transitions from sp2-type to sp3 hybridization of the carbon atoms in the cage that resulted in the destruction of the fullerene cage.

  • 31.
    Bai, Chengming
    et al.
    Republic of China.
    Fuchs, JürgenKarlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.Huang, Yi-ZhiUSA.Kong, LiangRepublic of China.Runkel, IngoGermany.Schweigert, ChristophGermany.
    Conformal Field Theories and Tensor Categories: Proceedings of a Workshop Held at Beijing International Center for Mathematical Research2014Conference proceedings (editor) (Refereed)
    Abstract [en]

    The present volume is a collection of seven papers that are either based on the talks presented at the workshop "Conformal field theories and tensor categories" held June 13 to June 17, 2011 at theBeijing International Center for Mathematical Research, Peking University,  or are extensions of the material presented in the talks at the workshop. These papers present new developments beyond rational conformal field theories and modular tensor categories and new applications in mathematics and physics. The topics covered include tensor categories from representation categories of Hopf algebras, applications of conformal field theories and tensor categories to topological phases and gapped systems, logarithmic conformal field theories and the corresponding non-semisimple tensor categories, and new developments in the representation theory of vertex operator algebras. Some of the papers contain detailed introductory material that is helpful for graduate students and researchers looking for an introduction to these research directions. The papers also discuss exciting recent developments in the area of conformal field theories, tensor categories and their applications and will be extremely useful for researchers working in these areas.

  • 32.
    Berg, Elin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Utveckling av ergonomiskt armstöd för dentala operatörsstolar: Ett produktutvecklingsprojekt på uppdrag av Support Design AB2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This report treats a product development project conducted in the course Degree Project for the Degree of Bachelor of Science in Innovation and Design Engineering, MSGC12, at Karlstads University. The course is a part of the faculty of heath, sciences and engineering. The report is written by the student Elin Berg, the supervisor of the project is Kristina Gullander and the examnier is Leo de Vin.

    The assignment is provided by Support Design, a Swedish company in Sunne that manufactures and distributes ergnomic chairs. The chairs are mainly sold to clients working in the dental and medical markets, but also office workers. Customers often sit on the chairs for long workdays, and several users sometimes perform precision work that requires relief for the arms and shoulders. Today, Support Design does not manufacture its own armrests but buys these from the US and China.

    The aim of the project is to develop an ergonomic armrest for dental operator chairs where the target group is dentists, dental hygienists and dentist assistants. The armrest should have functions that relieve, provide support and are flexible in order for the user to change the working position. The purpose of the project is to expand the Support Designs business by introducing its own armrest production. Eventually, this would give the company competitive advantages, facilitate logistics and result in better margins.

    The work process follows the methods that are part of a product development process. The phases of the project are project start, project planning, research, product specification, concept generation, concept selection, sub-report, design, final prototype, opposition, presentation, and exhibition. The research is the most important phase in identifying the user's needs, thus developing ergonomic armrests that fulfill the necessary functions.

  • 33.
    Berg, Marcus
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Buchberger, Igor
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ghilencea, D.M.
    CERN, Switzerland.
    Petersson, Christoffer
    Université Libre de Bruxelles, Belgium.
    Higgs diphoton rate enhancement from supersymmetric physics beyond the MSSM2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, no 2Article in journal (Refereed)
    Abstract [en]

    We show that supersymmetric ‘‘new physics’’ beyond the minimal supersymmetric standard model can naturally accommodate a Higgs mass near 126 GeV and enhance the signal rate in the h to gamma gamma channel, while the signal rates in all the other Higgs decay channels coincide with Standard Model expectations, except possibly the h to Z gamma channel. The new physics that corrects the relevant Higgs couplings can be captured by two supersymmetric effective operators. We provide a simple example of an underlying model in which these operators are simultaneously generated. The scale of new physics that generates these operators can be around 5 TeV or larger, and outside the reach of the LHC.

  • 34.
    Berg, Marcus
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Buchberger, Igor
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Schlotterer, Oliver
    Max Planck Institut, Potsdam, Germany.
    From maximal to minimal supersymmetry in string loop amplitudes2017In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 163Article in journal (Refereed)
  • 35.
    Berg, Marcus
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Stockholm University.
    Conlon, Joseph
    Oxford University, UK.
    Marsh, David
    Cornell University, USA.
    Witkowski, Lukas
    Oxford University, UK.
    Superpotential de-sequestering in string models2013In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 18, no FebruaryArticle in journal (Refereed)
    Abstract [en]

    Non-perturbative superpotential cross-couplings between visible sector matter and Kähler moduli can lead to significant flavour-changing neutral currents in compactifications of type IIB string theory. Here, we compute corrections to Yukawa couplings in orbifold models with chiral matter localised on D3-branes and non-perturbative effects on distant D7-branes. By evaluating a threshold correction to the D7-brane gauge coupling, we determine conditions under which the non-perturbative corrections to the Yukawa couplings appear. The flavour structure of the induced Yukawa coupling generically fails to be aligned with the tree-level flavour structure. We check our results by also evaluating a correlation function of two D7-brane gauginos and a D3-brane Yukawa coupling. Finally, by calculating a string amplitude between n hidden scalars and visible matter we show how non-vanishing vacuum expectation values of distant D7-brane scalars, if present, may correct visible Yukawa couplings with a flavour structure that differs from the tree-level flavour structure.

  • 36.
    Berg, Marcus
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Haack, Michael
    LMU München.
    Kang, Jin U
    Kim Il Sung University.
    One-Loop Kähler Metric of D-Branes at Angles2012In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 1211, 091- p.Article in journal (Refereed)
    Abstract [en]

    We evaluate string one-loop contributions to the Kahler metric of D-brane moduli (positions and Wilson lines), in toroidal orientifolds with branes at angles. Contributions due to bulk states in the loop are known, so we focus on the contributions due to states localized at intersections of orientifold images. We show that these quantum corrections vanish. This does not follow from the usual nonrenormalization theorems of supersymmetric field theory.

  • 37.
    Berg, Marcus
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Haack, Michael
    LMU München.
    Pajer, Enrico
    LMU München.
    Perturbative quantum corrections and flux compactifications2008In: Fortschritte der Physik, ISSN 0015-8208, E-ISSN 1521-3978, Vol. 56, 356-362 p.Article in journal (Refereed)
  • 38.
    Bergh, Gustav
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Förslitning av fräsverktyg2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 39.
    Bergstrom, Jens
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Burman, Christer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Svensson, Jonas
    Atlas Copco Rock Drills AB, Klerkgatan 21, SE-70225 Orebro, Sweden..
    Jansson, Andreas
    Atlas Copco Rock Drills AB, Klerkgatan 21, SE-70225 Orebro, Sweden..
    Ivansson, Charlotta
    Atlas Copco Rock Drills AB, Klerkgatan 21, SE-70225 Orebro, Sweden..
    Zhou, Jing
    Atlas Copco Rock Drills AB, Klerkgatan 21, SE-70225 Orebro, Sweden..
    Valizadeh, Sima
    Atlas Copco Rock Drills AB, Klerkgatan 21, SE-70225 Orebro, Sweden..
    Very High Cycle Fatigue of Two Ductile Iron Grades2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, no 5, 614-621 p.Article in journal (Refereed)
    Abstract [en]

    Two ductile iron grades, EN-GJS-600-3 a ferritic-pearlitic grade, and EN-GJS-600-10 a silicon strengthened ferritic nodular iron grade, are studied in the very high cycle fatigue range using a 20kHz ultrasonic test equipment. Fatigue strengths and SN-curves are achieved, and fracture surfaces and microstructures are investigated. The ferritic grade with higher ductility displays a lower fatigue strength at 10(8) load cycles than the ferritic-pearlitic grade, 142 and 167MPa, respectively. Examination of fracture surfaces shows that fatigue failures are controlled by micropores in both of the ductile iron grades, while the graphite nodule distributions do not seem to influence the difference in fatigue strengths. Prediction of the fatigue strengths, using a model for ductile iron proposed by Endo and Yanase, indicates a large potential for improvement in particular for the ferritic grade.

  • 40.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Kazymyrovych, Vitaliy
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Burman, Christer
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ekengren, Jens
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Test specimen geometry, stress calculation and mean stress in 20kHz testing in the very long fatigue life region2011In: VHCF5 5thInternational Conference on Very High Cycle Fatigue / [ed] Christina Berger, Hans-Jurgen Christ, Berlin: Deutcher Verband fur Materialforschung und prufung , 2011, 315-320 p.Conference paper (Refereed)
  • 41.
    Bertoni, M. I.
    et al.
    Arizona State Univ, USA.
    Sarau, G.
    Germany.
    Fenning, D. P.
    Rinio, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Frauenhofer ISE, Germany.
    Rose, V.
    USA.
    Maser, J.
    USA.
    Buonassisi, T.
    USA.
    Nano-XRF and micro-Raman Studies of Metal Impurity Decoration around Dislocations in Multicrystalline Silicon2012In: 2012 38TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), New York, USA: IEEE, 2012, 1613-1616 p.Conference paper (Refereed)
    Abstract [en]

    We push the resolution limits of synchrotron-based nano-X-ray fluorescence mapping below 100 nm to investigate the fundamental differences between benign and deleterious dislocations in multicystalline silicon solar cells. We observe that after processing recombination-active dislocations contain a high degree of nanoscale iron and copper decoration, while recombination-inactive dislocations appear clean. To study the origins of the distinct metal decorations around different dislocations we analyze as-grown samples as well as specimens at different stages of processing. We complement our X-ray studies with micro-Raman mapping to understand the relationship between metallic decoration and stress fields around dislocations.

  • 42.
    Bjornsson, Jonas
    et al.
    Univ Cambridge, Dept Appl Math & Theoret Phys, Cambridge CB3 0WA, England..
    Hwang, Stephen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Karlstad Univ, Dept Phys, SE-65188 Karlstad, Sweden..
    Gauged non-compact WZNW models, revisited2010In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 832, no 1-2, 52-88 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of the present paper is to investigate the necessary conditions for unitarity of the spectrum of non-compact gauged WZNW models to some depth. In particular, we would like to investigate the necessity of integer weights and level. We will learn that the problem is very complex and we have not found any simple and general way to formulate the necessary conditions. Instead one must resort to studying the problem almost case by case. The only nearly complete conditions that we will find, is for the case g = su(n, 1). Furthermore, the horizontal part of the case g = su(p, g) is nearly completed as well. In other cases, we will find conditions associated with certain subalgebras and nodes in the Dynkin diagram close to the one corresponding to the non-compact root. In these examples we can give conditions for the horizontal part of the algebra. As a by-product of our investigation we will prove some nice formulae of character identities and explicit branching functions for these representations. (C) 2010 Elsevier B.V. All rights reserved.

  • 43.
    Boudreau, Jonna
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Mossberg, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Barbier, Christophe
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Experiments to Find On-line Measurements of the Structure of the Tissue Paper SurfaceArticle in journal (Refereed)
    Abstract [en]

    The structure of tissue paper has great influence on the quality of the resulting paper produced. One method of measuring the crepe wavelength on-line is sought in order to improve process control as well as to promote greater precision and uniform quality of the end product. In this study, a probe was used to read the surface of the paper whilst the paper travelled at a low speed. Light from a light emitting diode was emitted at a specific angle and collected at the corresponding reflecting angle, from the paper surface.

     

    Focusing the lenses at 45º angle produced results matching closest to the expected wavelength, and such measurements were made on a numerous commercial papers to validate the method. The collected signal contains a lot of information from the surface of the paper and from reflected signals inside the paper. The signal was processed using a mathematical approach to extract the most common wavelengths for each paper. The measured wavelength was found to closely match measurements made with commercial off-line equipment. This new method has a good initial potential to work on-line, however further investigation regarding the effects of high speeds upon the sampling still has to be carried out. 

  • 44.
    Boulfrad, Yacine
    et al.
    Aalto University.
    Lindroos, Jeanette
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Aalto University.
    Inglese, Alessandro
    Aalto University.
    Yli-Koski, Marko
    Aalto University.
    Savin, Hele
    Aalto University.
    Reduction of Light-induced Degradation of Boron-doped Solar-grade Czochralski Silicon by Corona Charging2013In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 38, 531-535 p.Article in journal (Refereed)
    Abstract [en]

    Abstract This study aims at the reduction of light-induced degradation of boron-doped solar-grade Czochralski silicon wafers by corona charging. The method consists of deposition of negative charges on both surface sides of wafer and keeping the wafer in dark for 24 hours to allow the diffusion of positively-charged interstitial copper towards the surfaces. This method proves to be useful to reduce or eliminate light-induced degradation caused by copper. The degradation was significantly reduced in both intentionally (copper-contaminated) and “clean” samples. The amount of the negative charge was found to be proportional to the reduction strength

  • 45.
    Bovin, Jimmy
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Rapid Exchange Solution (RES): En mekanisk omlastningslösning för horisontell överföring av containrar mellan olika transportmedel2013Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This Bachelor of Science thesis was carried out in spring 2013 at Karlstad University for a company called TD Rail and Industry placed in Västerås, Sweden. The project included mapping of current transferring solutions of unit loads between railway and road transports, and the development of a conceptual transferring solution with the focus to increase the flexibility of the railway transport. The importance was to develop a well-made overall concept rather than small detailed parts of it.

    The project followed the design process methodology and included parts like: pre-study, requirements specification, idea generation, concept selection etc.The result was a further development of an already existing system called CCT based on horizontal transferring technology and therefore allow transferring of units directly under the overhead contact line. Thanks to this, together with its low investment / operating costs RES opens new opportunities for additional strategic transferring places along the railway, thereby increasing the flexibility of rail transports.

    The difference between RES and CCT is that you no longer need to rebuild the railway cars or the truckchassis , which was one of CCTs major weaknesses, instead the lifting mechanism is replaced by two hydraulic "technique plates".

    As a further development of the RES a partnership with CCT is proposed.

  • 46.
    Brumboiu, Iulia Emilia
    et al.
    Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden.
    Ericsson, Leif K.E.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden.
    Brena, Barbara
    Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden.
    The influence of oxygen adsorption on the NEXAFS and core-level XPS spectra of the C60 derivative PCBM2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, 054306- p.Article in journal (Refereed)
  • 47.
    Buchberger, Igor
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Strings, Gravitons, and Effective Field Theories2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns a range of aspects of theoretical physics. It is composed of two parts. In the first part we motivate our line of research, and introduce and discuss the relevant concepts. In the second part, four research papers are collected. The first paper deals with a possible extension of general relativity, namely the recently discovered classically consistent bimetric theory. In this paper we study the behavior of perturbations of the metric(s) around cosmologically viable background solutions. In the second paper, we explore possibilities for particle physics with low-scale supersymmetry. In particular we consider the addition of supersymmetric higher-dimensional operators to the minimal supersymmetric standard model, and study collider phenomenology in this class of models. The third paper deals with a possible extension of the notion of Lie algebras within category theory. Considering Lie algebras as objects in additive symmetric ribbon categories we define the proper Killing form morphism and explore its role towards a structure theory of Lie algebras in this setting. Finally, the last paper is concerned with the computation of string amplitudes in four dimensional models with reduced supersymmetry. In particular, we develop general techniques to compute amplitudes involving gauge bosons and gravitons and explicitly compute the corresponding three- and four-point functions. On the one hand, these results can be used to extract important pieces of the effective actions that string theory dictates, on the other they can be used as a tool to compute the corresponding field theory amplitudes.

  • 48.
    Buchberger, Igor
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Karlstads Univ, Teoret Fys, S-65188 Karlstad, Sweden..
    Fuchs, Jürgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    On the Killing form of Lie Algebras in Symmetric Ribbon Categories2015In: SIGMA. Symmetry, Integrability and Geometry, ISSN 1815-0659, E-ISSN 1815-0659, Vol. 11, 017Article in journal (Refereed)
    Abstract [en]

    As a step towards the structure theory of Lie algebras in symmetric monoidal categories we establish results involving the Killing form. The proper categorical setting for discussing these issues are symmetric ribbon categories.

  • 49.
    Calles, Linus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Development of ergonomic seating for dental operator chair2017Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    This report covers the examination of course Degree of Bachelor of Science in Innovation and Design MSGC12. The course is given on the Innovation and Design Program at the Faculty of Health, Science and Technology at Karlstad University. The course corresponds to 22.5 credits and extends over the spring semester in 2017. Examiner is Leo de Vin and supervisor is Kristina Gullander.

    The project is carried out on behalf of Support Design AB, which manufactures and distributes handmade ergonomic chairs. The company is aiming primarily at the dental and medical industry, where they have discovered a great interest in flexible and ergonomic chairs. There are today competing brands that manufacture chairs whose seats are similar to Support Designs. The company now wishes to expand its range of seating in order to differ from market competitors. Need for a more concrete foundation in research on sitting in the dental sector is also something they are looking for.

    The assignment therefore consists of developing an ergonomically designed seat for dental operator chairs, which has a strong foundation in research on sitting in the dental industry and has got a unique design.

    The project's pre-study starts with a literature study, with a large emphasis on trying to define what a good and ergonomic sitting posture is. This is done to provide a basis for a subsequent analysis of interviews and observations by dental staff. To survey the needs of the users, 15 interviews are performed with dental staff to gain an insight into their views of the workplaces and existing operator chairs. Structured observations are carried out at 11 patient visits in connection with the interviews to find motion patterns and review their work positions. The result of the preliminary study shows that many in dental care experience or has experienced work-related pain, especially shoulders, neck and back. A wide legged and relatively ergonomic working position is commonly observed in narrow operating rooms.

     

    The project results in 15 different concepts where four qualify for prototype manufacturing and testing. One concept is perceived to be the most comfortable while another is perceived to be the most unique. One concept meets ergonomic criteria best and another does not meet all the important requirements that the pre-study generated. 

  • 50.
    Carlson, Philip
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics, Science, Mathematics and Engineering Education Research.
    Konstruktions- och Materialförbättring hos Superkritiska Ventiler2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
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