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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.
    Stokkan, Gaute
    Sintef Materials and Chemistry, Trondheim, Norway.
    Looney, Erin
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
    Jensen, Mallory
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
    Lai, Barry
    Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA.
    Rinio, Markus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Di Sabatino, Marisa
    Department of Materials Science and Engineering, NTNU, A. Getz vei 2B, NO-7491 Trondheim, Norway.
    Recombination activity of grain boundaries in high-performance multicrystalline Si during solar cell processing2018Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, nr 5, s. 1-6, artikkel-id 055705Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity.

  • 2.
    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
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Rinio, Markus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    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 Processing2018Inngår i: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 215, nr 2, artikkel-id 1700493Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 3.
    ahmad, waqas
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    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 poäng / 30 hpOppgave
  • 4.
    Aimal, Pir
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Mohsin, Main
    Analyzing Voltage control and reactive power support from full power converter wind turbine2011Independent thesis Advanced level (degree of Master (Two Years)), 80 poäng / 120 hpOppgave
  • 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
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    On dynamical systems approaches and methods in f (R) cosmology2016Inngår i: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, nr 8, artikkel-id 064Artikkel i tidsskrift (Fagfellevurdert)
    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.
    University of Lisbon, Portugal.
    Hell, Juliette
    Free University Berlin, Germany.
    Uggla, Claes
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Global dynamics and asymptotics for monomial scalar field potentials and perfect fluids2015Inngår i: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 32, nr 14, artikkel-id 145005Artikkel i tidsskrift (Fagfellevurdert)
    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
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Global dynamics and inflationary center manifold and slow-roll approximants2015Inngår i: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 56, nr 1, artikkel-id 012502Artikkel i tidsskrift (Fagfellevurdert)
    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.
    Center for Mathematical Analysis, Geometry and Dynamical Systems, Instituto Superior Técnico, Universidade de Lisboa, Portugal.
    Uggla, Claes
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Inflationary alpha-attractor cosmology: A global dynamical systems perspective2017Inngår i: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, nr 8, artikkel-id 083517Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study flat Friedmann-Lemaitre-Robertson-Walker alpha-attractor E- and T-models by introducing a dynamical systems framework that yields regularized unconstrained field equations on two-dimensional compact state spaces. This results in both illustrative figures and a complete description of the entire solution spaces of these models, including asymptotics. In particular, it is shown that observational viability, which requires a sufficient number of e-folds, is associated with a particular solution given by a one-dimensional center manifold of a past asymptotic de Sitter state, where the center manifold structure also explains why nearby solutions are attracted to this "inflationary attractor solution." A center manifold expansion yields a description of the inflationary regime with arbitrary analytic accuracy, where the slow-roll approximation asymptotically describes the tangency condition of the center manifold at the asymptotic de Sitter state.

  • 9.
    Alho, Artur
    et al.
    Univ Lisbon, Inst Super Tecn, Ctr Math Anal Geometry & Dynam Syst, P-1049001 Lisbon, Portugal..
    Uggla, Claes
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Scalar field deformations of Lambda CDM cosmology2015Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 92, nr 10, artikkel-id 103502Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10.
    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
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    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 algorithm2016Inngår i: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 30, nr 5, s. 715-735Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Al-Jaff, Mohammed
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    The ZX-Calculus: A graphical calculus for multipartite qubit systems2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    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.

  • 12. Almotasem, Ahmed
    et al.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Holleboom, Thijs Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    A molecular dynamic study on the influence of carbide particles in ferrite on material transfer during nanoscratching of ferritic iron2016Inngår i: Proceedings of the 10th International Tool Conference: TOOL, 10th International TOOL Conference : 04th to 07th October 2016, Bratislava, Slovakia / [ed] Simancik, Frantisek, 2016Konferansepaper (Fagfellevurdert)
  • 13.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Holleboom, Thijs
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Adhesion between ferrite iron-€“iron/cementite countersurfaces: A molecular dynamics study2016Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 103, s. 113-120Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 14.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Assiut University, Egypt.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Holleboom, Thijs
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Tool microstructure impact on the wear behavior of ferrite iron during nanoscratching: An atomic level simulation2017Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 370-371, s. 39-45Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 15.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). Department of Physics, Faculty of ScienceAssiut University Assiut Egyp.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Krakhmalev, Pavel
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    Holleboom, Thijs Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Atomistic insights on the wear/friction behavior of nanocrystalline ferrite during nanoscratching as revealed by molecular dynamics2017Inngår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, nr 3, s. 101-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 16.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Gåård, Anders
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Influence of chemical composition on adhesion in metallic contacts2016Inngår i: International Journal of Advances in Science Engineering and Technology, ISSN 2321-9009, Vol. 4, nr 3, Spl. Iss. 1, s. 229-231Artikkel i tidsskrift (Fagfellevurdert)
    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%.

  • 17.
    AlMotasem, Ahmed Tamer
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Posselt, Matthias
    Helmholtz Zentrum Dresden-Rossendorf, Germany.
    Bergström, Jens
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Nanoindentation and nanoscratching of a ferrite/austenite iron bi-crystal: An atomistic study2018Inngår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 127, s. 231-239Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular dynamics simulations are applied to investigate the wear/friction behavior of a ferrite/austenite iron bi-crystal, as a model system for duplex stainless steels. The plasticity of the ferrite phase is dominated by dislocations while both dislocations and stacking faults are the primary cause of plastic deformation of the austenite phase. Interestingly, the responses of tribological parameters vary depending on the scratch direction. For instance, the scratch hardness is increased by about 46% whereas the friction coefficient is reduced by about 22% when scratch starts from austenite to ferrite. At the interface, a local softening/hardening occurs because of dislocation-interface interaction. The present results demonstrate that martensitic phase transformation is responsible for experimentally observed high amount of ferrite of the pile-up.

  • 18.
    Almén, Anton
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Importance of atomic force microscopy settings for measuring the diameter of carbon nanotubes2019Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Carbon nanotubes (CNTs) have gathered a lot of interest because of their extraordinary mechanical, electrical and thermal properties and have potential applications in a wide variety of areas such as material-reinforcement and nano-electronics. The properties of nanotubes are dependent on their diameter and methods for determining this using atomic force microscopy (AFM) in tapping mode assume that the measured height of the tubes represent the real diameter. Based on early, faulty calculations, the forces in tapping mode were assumed to be much lower than in contact mode, however it was later shown that forces in tapping mode can at point of impact rival the forces present in contact mode. This means that there is a potential risk of tube deformation during tapping mode measurements, resulting in incorrectly determined diameters. This work studies CNTs deposited on a silicon-substrate to analyze the effect of three common AFM settings (tapping frequency, free oscillation amplitude and setpoint) to determine their effect on measured CNT diameters and recommendations for choosing settings are given.

  • 19.
    Alpmarken, Ia
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Studie av tekniska och ekonomiska fördelar av olika lösningar vid instrumentinstallation2015Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    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.

  • 20.
    Andersson, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Different Styles of Laboratory Work - Different Types of Communication: Students’ talk during laboratory work in upper secondary school physicsManuskript (preprint) (Annet vitenskapelig)
  • 21.
    Andersson, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Laborativt arbete i fysikundervisningen: Något som behöver diskuteras!2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    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.

  • 22.
    Andersson, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Learning Physics Through Communication During Laboratory Work: An empirical study at upper secondary school2017Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 23.
    Andersson, Jan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Open Inquiry-Based Learning in Physics: Students' Communicative Moves Under ScrutinyManuskript (preprint) (Annet vitenskapelig)
  • 24.
    Andersson, Jan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Enghag, Margareta
    Stockholms universitet.
    Different Types of Laboratory Work - Different Types of Communication: Students’ talk during laboratory work in upper secondary school physicsManuskript (preprint) (Annet vitenskapelig)
  • 25.
    Andersson, Jan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Enghag, Margareta
    Stockholms universitet.
    Student talk during the process of laboratory work of linear motion in school physicsManuskript (preprint) (Annet vitenskapelig)
  • 26.
    Andersson, Jan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Enghag, Margareta
    Stockholms universitet.
    The Effectiveness of Laboratory Work in Physics: A Case Study at Upper Secondary School in Sweden2012Inngår i: Proceedings of The World Conference on Physics Education 2012: WCPE 2012 / [ed] Mehmet Fatih Taşar, 2012, s. 729-740Konferansepaper (Fagfellevurdert)
    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. 

  • 27.
    Andersson, Jan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Enghag, Margareta
    Stockholm Univ, Dept Math & Sci Educ, Sci Educ, Stockholm, Sweden.
    The laboratory work style's influence on students' communication2017Inngår i: Journal of Baltic Science Education, ISSN 1648-3898, E-ISSN 2538-7138, Vol. 16, nr 6, s. 958-979Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    More knowledge of how the actual design of the laboratory work influence students' communication, is needed to design and implement physics laboratory work lessons. The aim with this quantitative research, conducted at a Swedish upper secondary school, was to explore how the design of the laboratory work affects students' communication. Twenty students divided into five groups participated in this natural case study and were video recorded while performing four practical tasks with the theme uniformly accelerated motion, designed by their teacher. The four workstations were categorised based on three predefined descriptors: outcome, approach and procedure. Students' work at each workstation was coded according to five defined activities: planning, preparing equipment, collecting data, processing data and analysis of results. The activities were thereafter divided into shorter episodes that were coded for three different types of communication: disputational talk, cumulative talk and exploratory talk. The result shows that the amount of exploratory talk students engaged in are influenced by the style of the laboratory work and the character of the activity. Based on these research results, teachers can better accustom the laboratory work to facilitate fruitful physics discussions which endorse students' learning.

  • 28.
    Andersson, Jan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Enghag, Margareta
    Stockholms universitet.
    The relation between students’ communicative moves during laboratory work in physics and outcomes of their actions2017Inngår i: International Journal of Science Education, ISSN 0950-0693, E-ISSN 1464-5289, Vol. 39, nr 2, s. 158-180Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 29.
    Andersson, Jan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). SMEER.
    Haglund, Jesper
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). SMEER.
    Lärarstudenter konkretiserar energi genom energiteater2019Inngår i: Forum för forskningsbaserad NT-undervisning: Bidrag från konferensen FobasNT18 13 – 14 mars 2018 i Norrköping / [ed] Karin Stolpe, Gunnar Höst och Andreas Larsson, Linköping: Linköping University Electronic Press, 2019, s. 23-38Konferansepaper (Annet vitenskapelig)
    Abstract [sv]

    Vid Karlstads universitet har vi sedan hösten 2017 infört energiteater som en aktivitet i fysikkurser på samtliga grund- och ämneslärarutbildningar. Energiteater kan betraktas som en kompletterande undervisnings- och inlärningsform, där studenter förväntas att i mindre grupper tillsammans diskutera och sedan gestalta förekommande energiformer och energiomvandlingar i olika vardagsscenarier. I den här studien har videoinspelningar av en grupps gestaltningar kring två skilda scenarier analyserats i syfte att klargöra på vilket sätt energiteater stimulerar studenternas kommunikation och interaktion. Scenarierna involverarde energiomvandlingar som sker då en studsboll studsar mot marken, respektive de energiomvandlingar som sker i ett snurrande änglaspel. Resultatet visar att energiteater i stor utsträckning stimulerar utforskande samtal mellan studenterna, vilket kan betraktas somen meningsskapande dialog. Aktivitetens karaktär bidrar till att alla deltagare blir aktiva och förtrogna med förekommande energiformer och energiomvandlingar. Planerandet och genomförandet av gestaltningen skapar spontana kvalitativa diskussioner kring flödet av energi mellan olika system, som på ett naturligt sätt motiverar studenterna att vidareutveckla själva gestaltningen. Vi menar att energiteater kan stärka lärarstudenternas egen förståelse av energi, men att den även kan erbjuda en möjlig alternativ undervisningsansats för lärarstudenterna i sin blivande roll som lärare i skolan.

  • 30.
    Andersson, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Jansson, Ulf
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Analys av solcellsanläggningar påverkan på elnätet2015Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    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.

  • 31.
    Andersson, Jonatan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    A lattice model for topological phases2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    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.

  • 32.
    Andersson, Jonatan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    AFM study of Micro Fibrllated Cellulose, (MFC) in controlled atmosphere2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    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.

  • 33.
    Andersson, Oscar
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Influence of primary precipitate shape, size volume fraction and distribution in PM tool steels on galling resistance2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    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.

  • 34.
    Andersson, Stig
    et al.
    Göteborgs Universitet.
    Svensson, Krister
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Excitation and desorption of physisorbed H2 via the 2Σu electron scattering resonance.2017Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, s. 114703-1-114703-11, artikkel-id 114703Artikkel i tidsskrift (Fagfellevurdert)
    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. 

  • 35.
    Annebäck, Jenny
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    A Minor Field Study on development of recycling service for used PET bottles at hotels in Uganda2013Independent thesis Basic level (professional degree), 15 poäng / 22,5 hpOppgave
    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. 

  • 36.
    Anselmo, Ana Sofia
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Materials aspects in spin-coated films for polymer photovoltaics2013Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

  • 37.
    Anselmo, Ana Sofia
    et al.
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik. Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Materialvetenskap.
    Dzwilewski, Andrzej
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Svensson, Krister
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Moons, Ellen
    Karlstads universitet, Fakulteten för teknik- och naturvetenskap, Avdelningen för fysik och elektroteknik.
    Photodegradation of the electronic structure of PCBM and C60 films in air2016Inngår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 652, s. 220-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Fullerenes are common electron acceptors in organic solar cells. Here the photostability in air of the electronic structures of spin-coated PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) and evaporated C60 films are studied using ultraviolet photoelectron spectroscopy (UPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. After exposing these materials in air to simulated sunlight, the filled and empty molecular orbitals are strongly altered, indicating that the conjugated π-system of the C60-cage has degraded. Even a few minutes in normal lab light induces changes. These results stress the importance of protecting fullerene-based films from light and air during processing, operation, and storage.

  • 38.
    Arnberg, Johanna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    Torrsubstansförluster vid lagring och hantering av träspån vid Härjeåns Energi AB2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Härjeåns Energi AB är ett företag beläget i Sveg, som består av ett helt nytt kraftvärmeverk samt en biobränslefabrik där företaget producerar bland annat pellets av träspån. Innan pelletering lagras spånet i en stor stack. Företaget hade dock noterat att mängden inlevererat spån till spånstacken minus spånet som tas från stacken till pelleteringen inte stämde överens med hur mycket spån som fanns kvar i stacken. Någon gång under lagringen och hanteringen av spånet har stora mängder spån försvunnit. Syftet med detta arbete är att undersöka hur och när torrsubstansförlusterna uppstår samt storleksordningen på dessa förluster, i två olika avseenden: torrsubstansförlusten kopplade till lagringen samt hanteringen av träspånet. Det för företaget viktigaste målet var att skapa en ekvation som beskriver hur mycket torrsubstans som rimligtvis borde försvinna från stacken beroende på hur länge spånet lagrats. Syftet och målen besvarades genom att utföra en litteraturstudie över ämnet, studera företagets spånbokföring och deras sätt att hantera spånet samt bygga två simuleringsmodeller över torrsubstansförlusterna i företagets spånstack.

    Torrsubstansförluster vid lagring uppstår till följd av nedbrytningsmekanismerna; cellandning, biologisk nedbrytning samt termisk och kemisk nedbrytning. Det kan även uppstå via hantering av materialet. Men lagringens effekt på bränslekvaliteten är komplex. Lagringstid, klimatförhållanden, artssammansättning och biomassans form, allt från stockar till spån, samt lagringshögens geometri och struktur är några faktorer som påverkar förändringen hos biomassans egenskaper.

    Denna nedbrytning bidrar, tillsammans med hur företaget hanterar spånet, till torrsubstansförluster. Den största faktorn bidrar dock lagringen med. Några orsaker till torrsubstansförlusterna är stackens storlek, att den blivit kompakterad samt att spånet lagras helt utan täckning. När modelleringen gjordes över dessa torrsubstansförluster visade det sig att resultatet stämde väl överens med det som faktiskt försvunnit enligt spånbokföringen, under de undersökta åren 2013–2017.

    Att i framtiden till exempel minska maximala höjden på spånstacken till max 5–7 meter samt använda sig av sist-in-först-ut-metoden gällande granspånet, medan furuspånet kan lagras längre, skulle det garanterat bidra till minskade torrsubstansförluster och därmed även minskade ekonomiska förluster.

    I framtiden bör det satsas på forskning inom lagring av trä i fraktionsstorleken spån, samt lagring av trä i stackar som är större än att de har en maxhöjd på 5–7 meter. Idag finns ingen forskning alls inom dessa två kategorier, men om det fanns skulle det kunna underlätta för många energiproducerande företag.

  • 39.
    Axelsson, Jan
    et al.
    Karlstads universitet, Fakulteten för humaniora och samhällsvetenskap (from 2013), Institutionen för pedagogiska studier (from 2013).
    Kilbrink, Nina
    Karlstads universitet, Fakulteten för humaniora och samhällsvetenskap (from 2013), Institutionen för pedagogiska studier (from 2013). Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013), Science, Mathematics and Engineering Education Research (SMEER).
    Asplund, Stig-Börje
    Karlstads universitet, Estetisk-filosofiska fakulteten, Avdelningen för utbildningsvetenskap. Karlstads universitet, Fakulteten för humaniora och samhällsvetenskap (from 2013), Institutionen för pedagogiska studier (from 2013).
    Learning study i svetsundervisning: en yrkeslärares professionsutveckling2019Konferansepaper (Fagfellevurdert)
  • 40.
    Bai, Chengming
    et al.
    Republic of China.
    Fuchs, JürgenKarlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.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 Research2014Konferanseproceedings (Fagfellevurdert)
    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.

  • 41.
    Berg, Elin
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Utveckling av ergonomiskt armstöd för dentala operatörsstolar: Ett produktutvecklingsprojekt på uppdrag av Support Design AB2017Independent thesis Basic level (university diploma), 15 poäng / 22,5 hpOppgave
    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.

  • 42.
    Berg, Henrik
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Radiation exposure to personnel during CT procedures2018Independent thesis Basic level (degree of Bachelor), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    During X-ray examinations a large part of the radiation is scattered from the patient, contributing to larger radiation doses to medical staff operating inside the examination room. Ionizing radiation contributes to the risk of developing cancer and hereditary diseases but also to the risk of developing cataract.

     

    The aim of this thesis was to investigate the radiation environment and construct three-dimensional maps of the dose distribution, in a Computed Tomography (CT) room during examinations. 

     

    Air kerma was measured with real time dosimeters while irradiating an anthropomorphic phantom, using the X-ray tube voltages 100, 120 and 140 kV. The effective dose received by protected and unprotected medical staff inside the CT room during radiation exposure was estimated by using spectra from scattered X-ray radiation, a simulation of X-ray spectra and the dose evaluation program PCXMC. The equivalent dose to the eye lens was estimated by using spectra from scattered X-ray radiation and tabulated conversion factors from air kerma to the personal dose equivalent at 0.07 mm depth, Hp(0.07). From the estimated values of the effective dose and equivalent eye lens dose received by medical staff inside the room, three-dimensional dose distribution maps were constructed. The shielding effectiveness of a lead apron regularly used in the room was examined using tube voltages of 100, 120 and 140 kV.

     

    The radiation dose distributions have a maximum closest to the irradiated phantom for most heights except at eye level where the maximum is shifted outwards along the patient table due to strong shielding by the gantry at eye level. The strong shielding of the gantry is noticed for all energy levels and at all heights but is exceptionally noticeable at eye level. The shielding of the patient table is strongest for the lower heights but is also noticeable at eye level which may seem surprising since there were no objects between the phantom and that point. The dose distribution along directions with minimal shielding seems to follow the inverse square law well. The lead apron is effective but its efficiency decreases for higher photon energies which is expected.

     

    From information about the frequency and durations of CT-guided procedures, the estimated annual effective dose is 1.6-2.3 mSv for protected and 14.3-19.8 mSv for unprotected personnel at the operator position. The estimated annual equivalent eye lens dose is 4.7-7.8 mSv at the operator position. All annual doses at the operator position are below the annual threshold values of 20 mSv set by the ICRP.

  • 43.
    Berg, Marcus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Buchberger, Igor
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Ghilencea, D.M.
    CERN, Switzerland.
    Petersson, Christoffer
    Université Libre de Bruxelles, Belgium.
    Higgs diphoton rate enhancement from supersymmetric physics beyond the MSSM2013Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 44.
    Berg, Marcus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Buchberger, Igor
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Schlotterer, Oliver
    Max Planck Institut, Potsdam, Germany.
    From maximal to minimal supersymmetry in string loop amplitudes2017Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 163Artikkel i tidsskrift (Fagfellevurdert)
  • 45.
    Berg, Marcus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Buchberger, Igor
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Schlotterer, Oliver
    ax-Planck-Institut für Gravitationsphysik, Germany.
    String-motivated one-loop amplitudes in gauge theories with half-maximal supersymmetry2017Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 7, artikkel-id 138Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We compute one-loop amplitudes in six-dimensional Yang-Mills theory with half-maximal supersymmetry from first principles: imposing gauge invariance and locality on an ansatz made from string-theory inspired kinematic building blocks yields unique expressions for the 3- and 4-point amplitudes. We check that the results are reproduced in the field-theory limit alpha' -> 0 of string amplitudes in K3 orbifolds, using simplifications made in a companion string-theory paper.

  • 46.
    Berg, Marcus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik. Stockholm University.
    Conlon, Joseph
    Oxford University, UK.
    Marsh, David
    Cornell University, USA.
    Witkowski, Lukas
    Oxford University, UK.
    Superpotential de-sequestering in string models2013Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 18, nr FebruaryArtikkel i tidsskrift (Fagfellevurdert)
    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.

  • 47.
    Berg, Marcus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Conlon, Joseph P.
    Rudolf Peierls Centre for Theoretical Physics, UK.
    Day, Francesca
    Rudolf Peierls Centre for Theoretical Physics, UK.
    Jennings, Nicholas
    Rudolf Peierls Centre for Theoretical Physics, UK.
    Krippendorf, Sven
    Rudolf Peierls Centre for Theoretical Physics, UK.
    Powell, Andrew J.
    Rudolf Peierls Centre for Theoretical Physics, UK.
    Rummel, Markus
    Rudolf Peierls Centre for Theoretical Physics, UK.
    Constraints on Axion-Like Particles from X-ray Observations of NGC12752017Inngår i: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 847, nr 101, s. 1-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Axion-like particle s(ALPs) can induce localized oscillatory modulations in the spectra of photon sources passingthrough astrophysical magneticfields. Ultra-deep Chandraobservations of the Perseus cluster contain over 5 x 105counts from the active galactic nucleus (AGN) of the central cluster galaxy NGC1275 and represent a dataset of extraordinary quality for ALP searches. We use this data set to search for X-ray spectral irregularities fromthe AGN.

  • 48.
    Berg, Marcus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Haack, Michael
    LMU München.
    Kang, Jin U
    Kim Il Sung University.
    One-Loop Kähler Metric of D-Branes at Angles2012Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 1211, s. 091-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 49.
    Berg, Marcus
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik.
    Haack, Michael
    LMU München.
    Pajer, Enrico
    LMU München.
    Perturbative quantum corrections and flux compactifications2008Inngår i: Fortschritte der Physik, ISSN 0015-8208, E-ISSN 1521-3978, Vol. 56, s. 356-362Artikkel i tidsskrift (Fagfellevurdert)
  • 50.
    Berggren, Mats
    et al.
    Tiundaskolan, Uppsala.
    Isleborn, Helena
    Tiundaskolan, Uppsala.
    Haglund, Jesper
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013). SMEER; Institutionen för pedagogik, didaktik och utbildningsstudier, Uppsala universitet.
    Kärnkraftsdebatt ger möjlighet till kritiskt tänkande i högstadiefysiken2019Konferansepaper (Annet vitenskapelig)
    Abstract [sv]

    I skolans styrdokument betonas vikten av att elever ges möjlighet att utveckla sitt kritiska tänkande. Detta är inte minst angeläget i dessa tider av tillgång till sociala medier och spridande av så kallade alternativa fakta. Trots sin positiva klang finns det dock ingen etablerad konsensus kring vad kritiskt tänkande egentligen är. Inom ramen för ett skolutvecklingsprojekt i samverkan mellan Uppsala universitet och Tiundaskolan, en 4-9-skola i Uppsala, utforskar vi hur kritiskt tänkande kan uttryckas i undervisningspraktiken i ämnena svenska, historia, matematik och fysik. Som exempel har vi i fysikämnet designat, genomfört och analyserat en undervisningssekvens utifrån kärnkraft som tema, där elever i årskurs 9 gavs möjlighet att anamma olika åsikter och argument i frågan genom rollspel. Eleverna genomförde en debatt, där de representerade olika parter: boende nära Forsmark, miljöorganisationen Grön Fred, och företag som utvecklar kärnkraft, respektive vindkraft. Före och efter debatten skrev eleverna individuella texter där de argumenterade för sin personliga åsikt i frågan: Ska kärnkraften bevaras som den är, läggas ner, eller utvecklas? Vi fann att de genom debatten fick goda möjligheter att utveckla och visa kunskaper motsvarande flera kunskapskrav i kursplanen i fysik som annars sällan berörs i fysikklassrummet, såsom, för betyg A: ”Eleven kan samtala om och diskutera frågor som rör energi, teknik, miljö och samhälle och skiljer då fakta från värderingar och formulerar ställningstaganden med välutvecklade motiveringar samt beskriver några tänkbara konsekvenser.” Som exempel på naturvetenskapligt förankrade argument utnyttjade eleverna genererad energi per utsläppt mängd koldioxid som ett mått vid jämförelser mellan kärnkraft och andra energikällor. I de individuella texterna höll de flesta eleverna fast vid sina åsikter från innan de arbetade med temat även efteråt, men nu med fler och mer nyanserade argument.

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