Change search
Refine search result
3456789 251 - 300 of 2917
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 251.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Ericsson, T
    Surfaces of forming tools1997Book (Refereed)
  • 252.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fatigue and Surface Defects in Tools for Cold Forming1997In: / [ed] J Bergström, T Ericsson, 1997Conference paper (Refereed)
  • 253.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fatigue of Cold Work Steels1998Other (Other (popular science, discussion, etc.))
  • 254.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Fatigue of cold work tool steel1999In: Matériaux & Techniques, ISSN 0032-6895, Vol. 87, no 1-2, p. 9-14Article in journal (Refereed)
    Abstract [en]

    One important surface property of forming tools is their resistance to cracking due to fatigue loading. The wide variety of steel grades, material handling, machining operations and surface treatments will give very different fatigue properties. The present article gives examples on the influence of steel grades, EDM machining and surface coating. Initial cracks may be introduced in the tool during the processing to its final shape and surface finish, why a particular interest is given to small cracks introduced by the EDM process.

  • 255.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Johansson, M
    Kotik, Ouliana
    Thuvander, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    The Use of Tool Steels: Experience and Research2002Book (Refereed)
  • 256.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Fredriksson, Gunnel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Persson, A
    Fatigue of tool steel in cold and hot work applications2000Other (Other (popular science, discussion, etc.))
  • 257.
    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 Technology and Science, Department of Mechanical and Materials Engineering.
    Ekengren, Jens
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    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, p. 315-320Conference paper (Refereed)
  • 258.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Krakhmalev, Pavel
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Gåård, Anders
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Lindvall, Fredrik
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Galling in sheet metal forming2008In: Proceedings of the IDDRG 2008 Conference: Best in class stamping, 16-18 June 2008, Olofström: Industriellt utvecklingscentrum i Olofström AB , 2008Conference paper (Other academic)
  • 259.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Rezai-Aria, F
    High temperature fatigue of tool steels2006Conference paper (Refereed)
  • 260.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Sjöström, Johnny
    Persson, A
    Hogmark, S
    Failure modes in field-tested brass die casting dies2004In: Journal of Materials Processing Technology, v 148, n 1, 2004Article in journal (Refereed)
  • 261.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Sundqvist, Martin
    Surface damage in extrusion and die casting1995Other (Other (popular science, discussion, etc.))
  • 262.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Thuvander, F
    Wear of die materials in full scale plastic injection moulding of glassfibre reinforced poluycarbonate2001Other (Other (popular science, discussion, etc.))
  • 263.
    Bergström, Jens
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Thuvander, Fredrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Devos, P.
    Boher, C.
    Wear of die materials in full scale plastic injection moulding of glassfibre reinforced polycarbonate2001In: Wear 251 2001 pp 1511-1521Article in journal (Refereed)
  • 264.
    Bergström, Johannes
    et al.
    Karlstad University, Faculty of Technology and Science.
    Sjöberg, Olle
    Karlstad University, Faculty of Technology and Science.
    Nybyggnation av våtrum: Jämförelse mellan förtillverkat och platsbyggt2009Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Con-Form AS är en norskägd stomentreprenör som projekterar och egentillverkar byggdelarsåsom vägg, bjälklagselement, pelare, balk, trappor och våtrumsmoduler. Att tillverkavåtrumsmoduler är en relativt ny och obeprövad byggteknik i Sverige gentemot platsbyggdavåtrum. Anledningarna till valet av en specifik produkt är priset och kvalitén.Den prisjämförelse som utförts i denna rapport är framtagen utifrån produktion av tjugofyravåtrum. Våtrummet som har kostnadskalkylerats är på 5,9 m2 och består av en toalett, ettduschset med draperi samt ett handfat med tillhörande underskåp och armaturer.Kostnaden för våtrumsmodulen har tagits fram av Con-Form Töcksfors AB och kostnaden fördet platstillverkade våtrummet av NCC Karlstad i samarbete med underentreprenörer. I dettafall blev summan för det platstillverkade våtrummet 52 500 SEK och summan förvåtrumsmodulen 50 900 kr. Vid byggnation av platstillverkade våtrum blir de indirektakostnaderna mer omfattande. Indirekta kostnader är exempelvis ökad material- ochavfallshantering på byggarbetsplatsen. Våtrumsmodulen är därmed det billigare alternativetav de båda.En fördel med det förtillverkade våtrummet är delvis minskad materialhantering påbyggarbetsplatsen då modulen levereras vid inbyggnadstidpunkt och med kranlyft placerasdirekt i byggnaden. En nackdel med våtrumsmoduler är att dessa tidigt behöver komma in iprojekteringen och kunden låser sig därmed vid valt våtrum. Våtrumsmoduler passar därmedbäst i hotell och hyresrätter där det är en och samma beställare som tidigt i projekteringenbeslutar över utseende av våtrummen.En fördel med platsbyggnation är möjligheten att anpassa våtrummet efter kundens tycke ochbehov längre fram i byggskedet. Detta kan vara en avgörande faktor vid försäljning avexempelvis bostadsrätter. Däremot blir kostnaden för våtrummet dyrare vid platstillverkningoch logistik samt materialhantering blir mer omfattande.

  • 265. Bergström, L.
    et al.
    Sjöberg, M.
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Concentrated Kaolinite Suspensions - Polymer Adsorption and Rheological Properties1996In: in "Science of Whitewares", ed. by V.E. Henkes, G.Y. Onoda and W.M. Carty, American Ceramic Society, Westerville, OH, 1996, pp. 65-77 / [ed] V.E. Henkes, G.Y. Onoda and W.M. Carty, 1996Chapter in book (Refereed)
  • 266. Bergström, U.
    et al.
    Burman, Christer
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Försämrad varmhållfasthet vid långa sintringstider för Si3N4 med Y2O3-tillsats1978Report (Other academic)
  • 267.
    Berndtson, Magnus
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Andersson Frohm, Martin
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Den nya branschstandarden ByggaF: Hur fungerar den i produktionen?2013Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 268.
    Bernhardsson, Erica
    et al.
    Karlstad University, Faculty of Technology and Science.
    Andersson, Anna-Carin
    Karlstad University, Faculty of Technology and Science.
    GROT uttag i Värmlands Län: Extraction of Harvest residues in the County of Värmland2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    On commission by the Swedish Forest Agency a calculation of the forest fuel potential within the county of Värmland shall be made. Forest fuel today mainly consists of harvest residues from final fellings, branches and treetops. Many factors influence the amount of forest fuels after final falling. Big fast growing trees have more branches and foliage biomass.

    In this project we have selected suitable forest types, stands ages and composition in order to obtain the largest possible volume of harvest residues. Nature reserve areas, key biotopes and riparian zones are excluded from the area suitable for forest fuel extraction.

    The result shows that there is approximately 104 000 hectare suitable woodland for forest fuel extraction in Värmland. Out of this you can get 45.4 tons of forest fuels (dry matter/hectare spruce)

    For certain parts of the lumbered areas there has been announced forest fuels extraction to Swedish Forest Agency. These areas were about 5000 hectares and calculated dry matter 31 tons of spruce dry matter/hectare, 8 tons of fir dry matter/hectare and 2.3 tons of birch dry matter/hectare. To show profitability in relation to the distance from roads, MF-curves have been calculated. Within a kilometre you have almost covered the total volume forest fuel that can be extracted, but already after 500 meters you have reached approximately 75 % of the volume.

  • 269.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Boundary Layers and Shock Profiles for the Discrete Boltzmann Equation for Mixtures2012In: Kinetic and Related Models, ISSN 1937-5093, E-ISSN 1937-5077, Vol. 5, no 1, p. 1-19Article in journal (Refereed)
    Abstract [en]

    We consider the discrete Boltzmann equation for binary gas mixtures. Some known results for half-space problems and shock profile solutions of the discrete Boltzmann for single-component gases are extended to the case of two-component gases. These results include well-posedness results for half-space problems for the linearized discrete Boltzmann equation, existence results for half-space problems for the weakly non-linear discrete Boltzmann equation, and existence results for shock profile solutions of the discrete Boltzmann equation. A characteristic number, corresponding to the speed of sound in the continuous case, is calculated for a class of symmetric models. Some explicit calculations are also made for a simplified 6+4 -velocity model.

  • 270.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Boundary layers for the nonlinear discrete Boltzmann equation: Condensing vapor flow in the presence of a non-condensable gas2012In: Proceedings of 28th International Symposium on Rarefied Gas Dynamics 2012 / [ed] Michel Mareschal, Andrés Santos, Melville, New York: American Institute of Physics (AIP), 2012, 1, p. 223-230Conference paper (Refereed)
    Abstract [en]

    Half-space problems for the Boltzmann equation are of great importance in the study of the asymptotic behaviorof the solutions of boundary value problems of the Boltzmann equation for small Knudsen numbers. Half-space problems provide the boundary conditions for the fluid-dynamic-type equations and Knudsen-layer corrections to the solution of the fluid-dynamic-type equations in a neighborhood of the boundary. Here we consider a half-space problem of condensation for apure vapor in the presence of a non-condensable gas by using discrete velocity models (DVMs) of the Boltzmann equation. The Boltzmann equation can be approximated by DVMs up to any order, and these DVMs can be applied for numerical methods,but also for mathematical studies to bring deeper understanding and new ideas. For one-dimensional half-space problems,the discrete Boltzmann equation (the general DVM) reduces to a system of ODEs. We obtain that the number of parametersto be specified in the boundary conditions depends on whether the condensing vapor flow is subsonic or supersonic. Thisbehavior has earlier been found numerically. We want to stress that our results are valid for any finite number of velocities.This is an extension of known results for single-component gases (and for binary mixtures of two vapors) to the case when a non-condensable gas is present. The vapor is assumed to tend to an assigned Maxwellian, with a flow velocity towards thecondensed phase, at infinity, while the non-condensable gas tends to zero at infinity. Steady condensation of the vapor takes place at the condensed phase, which is held at a constant temperature. We assume that the vapor is completely absorbed, that the non-condensable gas is diffusively reflected at the condensed phase, and that vapor molecules leaving the condensed phase are distributed according to a given distribution. The conditions, on the given distribution at the condensed phase, needed for the existence of a unique solution of the problem are investigated, assuming that the given distribution at the condensed phase is sufficiently close to the Maxwellian at infinity and that the total mass of the non-condensable gas is sufficiently small. Exact solutions and solvability conditions are found for a specific simplified discrete velocity model (with few velocities).

  • 271.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Discrete Velocity Models and Half-Space Problems2003Licentiate thesis, monograph (Other academic)
    Abstract [en]

    We study some questions related to discrete velocity models (DVMs) of the Boltzmann equation. In the case of plane stationary problems the typical DVM reduces to a dynamical system (system of ODEs). Properties of such systems are studied in this paper in the most general case. In particular, a topological classification of their singular points is made and dimensions of the corresponding stable, unstable and center manifolds are computed. These results are applied to typical half-space problems of rarefied gas dynamics. A classification of well-posed half-space problems for linearized DVMs is made. Exact solutions of a (simplified) linearized kinetic model of BGK type are found as limiting case of corresponding discrete models. The main results of the paper can be also used for moment approximations and other versions of discretizised kinetic equations

  • 272.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Half-Space Problem for the Discrete Boltzmann Equation: Condensing Vapor Flow in the Presence of a Non-condensable Gas2012In: Journal of statistical physics, ISSN 0022-4715, E-ISSN 1572-9613, Vol. 147, no 6, p. 1156-1181Article in journal (Refereed)
    Abstract [en]

    We consider a non-linear half-space problem related to the condensation problem for the discrete Boltzmann equation and extend some known results for a single-component gas to the case when a non-condensable gas is present. The vapor is assumed to tend to an assigned Maxwellian at infinity, as the non-condensable gas tends to zero at infinity. We assume that the vapor is completely absorbed and that the non-condensable gas is diffusively reflected at the condensed phase and that the vapor molecules leaving the condensed phase are distributed according to a given distribution. The conditions, on the given distribution, needed for the existence of a unique solution of the problem are investigated. We also find exact solvability conditions and solutions for a simplified six+four-velocity model, as the given distribution is a Maxwellian at rest, and study a simplified twelve+six-velocitymodel.

  • 273.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    On Half-Space and Shock-Wave Problems for Discrete Velocity Models of the Boltzmann Equation2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    We study some questions related to general discrete velocity (with arbitrarily number of velocities) models (DVMs) of the Boltzmann equation. In the case of plane stationary problems the typical DVM reduces to a dynamical system (system of ODEs). Properties of such systems are studied in the most general case. In particular, a topological classification of their singular points is made and dimensions of the corresponding stable, unstable and center manifolds are computed.

    These results are applied to typical half-space problems of rarefied gas dynamics, including the problems of Milne and Kramer. A classification of well-posed half-space problems for linearized DVMs is made. Exact solutions of a (simplified) linearized kinetic model of BGK type are found as a limiting case of the corresponding discrete models.

    Existence of solutions of weakly non-linear half-space problems for general DVMs are studied. The solutions are assumed to tend to an assigned Maxwellian at infinity, and the data for the outgoing particles at the boundary are assigned, possibly depending on the data for the incoming particles. The conditions, on the data at the boundary, needed for the existence of a unique (in a neighborhood of the assigned Maxwellian) solution of the problem are investigated. Both implicit, in the non-degenerate cases, and sometimes, in both degenerate and non-degenerate cases, explicit conditions are found.

    Shock-waves can be seen as heteroclinic orbits connecting two singular points (Maxwellians) for DVMs. We give a constructive proof for the existence of solutions of the shock-wave problem for the general DVM. This is worked out for shock speeds close to a typical speed, corresponding to the sound speed in the continuous case. We clarify how close the shock speed must be for our theorem to hold, and present an iteration scheme for obtaining the solution.

    The main results of the paper can be used for DVMs for mixtures as well as for DVMs for one species.

  • 274.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    On half-space problems for the discrete Boltzmann equation2010In: Il Nuovo Cimento C, ISSN 2037-4909, 1826-9885, Vol. 33, no 1, p. 47-54Article in journal (Refereed)
    Abstract [en]

    We study typical half-space problems of rarefied gas dynamics, including the problems of Milne and Kramer, for the discrete Boltzmann equation (a general discrete velocity model, DVM, with an arbitrary finite number of velocities). Then the discrete Boltzmann equation reduces to a system of ODEs. The data for the outgoing particles at the boundary are assigned, possibly linearly depending on the data for the incoming particles. A classification of well-posed half-space problems for the homogeneous, as well as the inhomogeneous, linearized discrete Boltzmann equation is made. In the non-linear case the solutions are assumed to tend to an assigned Maxwellian at infinity. The conditions on the data at the boundary needed for the existence of a unique (in a neighborhood of the assigned Maxwellian) solution of the problem are investigated. In the non-degenerate case (corresponding, in the continuous case, to the case when the Mach number at the Maxwellian at infinity is different of -1, 0 and 1) implicit conditions are found. Furthermore, under certain assumptions explicit conditions are found, both in the non-degenerate and degenerate cases. An application to axially symmetric models is also studied

  • 275.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    On half-space problems for the linearized discrete Boltzmann equation2008In: Rivista di Matematica della Universita' di Parma, Vol. (7)9, p. 73-124Article in journal (Refereed)
    Abstract [en]

    In this paper we study typical half-space problems of rarefied gas dynamics, including the problems of Milne and Kramer, for the discrete Boltzmann equation. The discrete Boltzmann equation reduces to a system of ODEs for plane stationary problems. These systems are studied, and for general boundary conditions at the "wall" a classification of well-posed half-space problems for the homogeneous, as well as the inhomogeneous, linearized discrete Boltzmann equation is made. Applications for axially symmetric models are studied in more detail. Exact solutions of a (simplified) linearized kinetic model of BGK type are also found as a limiting case of the corresponding discrete models.

  • 276.
    Bernhoff, Niclas
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    On half-space problems for the weakly non-linear discrete Boltzmann equation2010In: Kinetic and Related Models, ISSN 1937-5093, E-ISSN 1937-5077, Vol. 3, no 2, p. 195-222Article in journal (Refereed)
    Abstract [en]

    Existence of solutions of weakly non-linear half-space problems for the general discrete velocity (with arbitrarily finite number of velocities) model of the Boltzmann equation are studied. The solutions are assumed to tend to an assigned Maxwellian at infinity, and the data for the outgoing particles at the boundary are assigned, possibly linearly depending on the data for the incoming particles. The conditions, on the data at the boundary, needed for the existence of a unique (in a neighborhood of the assigned Maxwellian) solution of the problem are investigated. In the non-degenerate case (corresponding, in the continuous case, to the case when the Mach number at infinity is different of -1, 0 and 1) implicit conditions are found. Furthermore, under certain assumptions explicit conditions are found, both in the non-degenerate and degenerate cases. Applications to axially symmetric models are studied in more detail

  • 277.
    Bernhoff, Niclas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Bobylev, Alexander
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Weak Shock Wave Solutions for the Discrete Boltzmann Equation2007In: Rarefied Gas Dynamics: 25th International Symposium on Rarefied Gas Dynamics, Saint-Petersburg, Russia, July 21-28, 2006 (M.S. Ivanov and A.K. Rebrov, eds), Novosibirsk: Publishing House of the Siberian Branch of the Russian Academy of Sciences , 2007, p. 173-178Conference paper (Refereed)
    Abstract [en]

    The analytically difficult problem of existence of shock wave solutions is studied for the general discrete velocity model (DVM) with an arbitrary finite number of velocities (the discrete Boltzmann equation in terminology of H. Cabannes). For the shock wave problem the discrete Boltzmann equation becomes a system of ordinary differential equations (dynamical system). Then the shock waves can be seen as heteroclinic orbits connecting two singular points (Maxwellians). In this work we give a constructive proof for the existence of solutions in the case of weak shocks. We assume that a given Maxwellian is approached at infinity, and consider shock speeds close to a typical speed , corresponding to the sound speed in the continuous case. The existence of a non-negative locally unique (up to a shift in the independent variable) bounded solution is proved by using contraction mapping arguments (after a suitable decomposition of the system). This solution is then shown to tend to a Maxwellian at minus infinity. Existence of weak shock wave solutions for DVMs was proved by Bose, Illner and Ukai in 1998 [1]. In their technical proof Bose et al. are following the lines of the pioneering work for the continuous Boltzmann equation by Caflisch and Nicolaenko [2]. In this work, we follow a more straightforward way, suiting the discrete case. Our approach is based on results by the authors on the main characteristics (dimensions of corresponding stable, unstable and center manifolds) for singular points [3] to general dynamical systems of the same type as in the shock wave problem for DVMs. Our proof is constructive, and it is also shown (at least implicitly) how close to the typical speed , the shock speed must be for our results to be valid. All results are mathematically rigorous. Our results are also applicable for DVMs for mixtures. ACKNOWLEDGEMENTS. The support by the Swedish Research Council grant 20035357 are gratefully acknowledged by both of the authors.REFERENCES[1] C. Bose, R. Illner, S. Ukai, Transp. Th. Stat. Phys., 27, 35-66 (1998) [2] R.E. Caflisch, B. Nicolaenko, Comm. Math. Phys., 86, 161-194 (1982)[3] A.V. Bobylev, N. Bernhoff, Lecture Notes on the Discretization of the Boltzmann Equation, World Scientific, 2003, pp. 203-222

  • 278.
    Bernhoff, Niclas
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Bobylev, Alexander
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Weak shock waves for the general discrete velocity model of the Boltzmann equation2007In: Communications in Mathematical Sciences, ISSN 1539-6746, E-ISSN 1945-0796, Vol. 5, no 4, p. 815-832Article in journal (Refereed)
    Abstract [en]

    We study the shock wave problem for the general discrete velocity model (DVM), with an arbitrary finite number of velocities. In this case the discrete Boltzmann equation becomes a system of ordinary differential equations (dynamical system). Then the shock waves can be seen as heteroclinic orbits connecting two singular points (Maxwellians). In this paper we give a constructive proof for the existence of solutions in the case of weak shocks. We assume that a given Maxwellian is approached at infinity, and consider shock speeds close to a typical speed c, corresponding to the sound speed in the continuous case. The existence of a non-negative locally unique (up to a shift in the independent variable) bounded solution is proved by using contraction mapping arguments (after a suitable decomposition of the system). This solution is shown to tend to a Maxwellian at minus infinity. Existence of weak shock wave solutions for DVMs was proved by Bose, Illner and Ukai in 1998. In this paper, we give a constructive proof following a more straightforward way, suiting the discrete case. Our approach is based on earlier results by the authors on the main characteristics (dimensions of corresponding stable, unstable and center manifolds) for singular points to general dynamical systems of the same type as in the shock wave problem for DVMs. The same approach can also be applied for DVMs for mixtures

  • 279.
    Bernström, Annelie
    Karlstad University, Faculty of Technology and Science.
    Leksaker baserade på teknik sedda ur ett genusperspektiv: En studie om 6-åringars preferenser och användande av könsstereotypa konstruktionsleksaker2007Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [en]

    Through interviews with children in preschool class and through inquiries by questionnaire with their teachers, I have received answers of my question at issue about boys, girls and their choices of technical toys. The purpose was to see if there were any differences in choosing and using these toys, and also to find out if and why the children have different preferences.

    The results indicate that for the children in this preschool class the choice of construction toys is common in the activities. All the children play with these toys, but still there are different preferences among girls and boys, both at home and in preschool class. There are differences in opinion among earlier researchers what causes boys and girls to differ in preferences of toys, but the main theory is still that gender differences depend on the family and the community.

    Pedagogical conclusions are that as a teacher of young children, you have to work with awareness when it comes to toys and gender. You must never forget the important role toys play in the development of the children.

    Keywords: gender, technical, toys, preferences

  • 280. Bhaskar Dutt, G.
    et al.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences. Karlstad University, Faculty of Technology and Science, Materials Science.
    De Schryver, FC
    Are Aqueous Sodium Dodecyl Sulfate Micelles in the Presence of Added Salt Polydisperse? A Time-Resolved Fluorescence Quenching Study with Global Analysis1997In: Langmuir, 1997, 13, 1957-1963Article in journal (Refereed)
  • 281.
    Birgmark, Anja
    Karlstad University, Faculty of Technology and Science.
    Wear of Coater Blades2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 282. Bjorklund, R.B.
    et al.
    Arwin, H.
    Järnström, Lars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Paper Surface Centre. Karlstad University, Faculty of Technology and Science, Department of Chemical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Adsorption of Anionic and Cationic Polymers on Porous and Non-Porous Calcium Carbonate Surfaces1994In: Appl.Surf.Sci.,75,197(1994)Article in journal (Refereed)
  • 283.
    Bjurheden, Eva
    Karlstad University, Faculty of Technology and Science.
    Utveckling och utvärdering av ett fidelitetssystem för DNA polymeraser2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A published method for testing the accuracy of DNA polymerases has been evaluated. The method is based on in vitro replication of the lacZα gene in pUC18 and identification of mutations by blue white selection for transformation of the reaction product. It was shown that the production of the template for the polymerase reaction can be done by the protocol, but the yield was low. The polymerase reaction with the prepared template worked as described, but the amount of product obtained was too small to give colonies after the transformation. Before the method can be used, larger amounts of template for the polymerase reaction are needed. One possibility to improve the yield is a better procedure for the extraction of the desired fragment from the agarose gel.

     

  • 284.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    An example of what one teacher focuses when teaching the technology subject in Swedish compulsory school2005Conference paper (Refereed)
  • 285.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    En levande tradition: Teknik i år 7, 8 och 92005In: KAPET, 1(1), 43-58Article in journal (Other academic)
  • 286.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Holistic learning in the dual education system: A study of technical vocational education in upper secondary school2010Conference paper (Refereed)
  • 287.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Holistiskt lärande i dubbelt utbildningssystem: En studie av teknisk gymnasial yrkesutbildning2010Conference paper (Other (popular science, discussion, etc.))
  • 288.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Reasons for choosing a technically oriented education: An interview study within the fields of pipefitting and industry2012In: International journal of technology and design education, ISSN 0957-7572, E-ISSN 1573-1804, Vol. 22, no 3, p. 377-397Article in journal (Refereed)
    Abstract [en]

    The article examines how professionals within technical businesses describe their ways into their trade and why they have remained. Semi-structured interviews, analyzed by analysis of narratives, have been conducted with six informants within pipefitting and industrial work aiming to understand how technically oriented professions can attract young potentials into the field. The results from the study are thus a contribution within the field of vocational education, in order to understand why youths should consider to study the Energy Programme or the Industry Programme at upper secondary school. The results show that factors that influence people to start working within technically oriented trades are:

    1. to use your hands to screw things together,
    2. to get an income and
    3. if relatives work in the branch.

    Based on the study it is not obvious to young people what they want to do when they have graduated. But the study also shows that even though the choice of careers is not obvious from the beginning people who chose the field of pipefitting or industry remain for many years.This implies that programmes for recruitment could use the advantages shown in this study for arguments to increase the amount of students who chose the technically oriented educations. The reasons for staying in the professions are:

    1. variation and freedom,
    2. creativity and influence and
    3. you get to work with your hands.

    This significant content within the technically oriented trades contribute with specific arguments for promotion of the plumbing and industrial work in particular and also for the technical trades and technical education in general.

  • 289.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Same syllabus - different kinds of subject2007Conference paper (Refereed)
  • 290.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Teknikdidaktik2011Book (Refereed)
  • 291.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Teknikundervisning i den svenska grundskolan: elever, lärare och styrdokumenten2004Conference paper (Other (popular science, discussion, etc.))
  • 292.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Teknikundervisning i den svenska skolan2004In: Utbilder, 1, p. 10-11Article in journal (Other (popular science, discussion, etc.))
  • 293.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Teknikämnets gestaltningar: En studie av lärares arbete i skolämnet teknik2008Doctoral thesis, monograph (Other academic)
    Abstract [sv]

    Teknikämnets gestaltningar handlar om lärares arbete med skolämnet teknik i den svenska grundskolans senare år (7-9). Studien bygger på intervjuer med fem lärare och på observationer av deras undervisningspraktik. Studien undersöker hur lärare förstår begreppet teknik och skolämnet teknik. Den undersöker också vad lärare väljer för ämnesinnehåll i teknik och hur de arbetar med detta samt vilka förmågor elever erbjuds att utveckla i ämnet teknik. Avhandlingens forskningsansats är empiriskt grundad i teknikämnets undervisningspraktik och studiens empiriska analyser grundas i narrativ analys och variationsteori.

    Det fanns ett gemensamt element i lärarnas sätt att förstå begreppet teknik: Teknik är saker som människan utvecklat för att uppfylla praktiska behov. När det gäller lärarnas sätt att förstå skolämnet teknik skiljde de sig åt mellan att förstå syftet med teknikämnet som att: (1) träna hantverksskicklighet, (2) förbereda eleverna för framtida karriärer som ingenjörer, (3) tillämpa naturvetenskap, (4) stärka flickors självförtroende och (5) intressera framtida tekniker och uppfinnare.

    Vidare tyder studien på att teknikundervisningen specifikt bidrar till att utveckla tre förmågor hos eleverna: (1) att värdera och testa funktionalitet, (2) precision och noggrannhet och (3) att bygga, konstruera och montera. De tre förmågorna tränades enbart med undervisningsinnehåll av praktisk karaktär. Den variationsteoretiska analysen visar att variationsmönstret kontrastering lämpar sig bra i ett produktionsperspektiv där det kostar att göra fel.

    Studiens övergripande resultat visar att lärares tolkningar av de officiella styrdokumenten, i kombination med deras val av undervisningsinnehåll och undervisningsmetoder, påverkar vad elever erbjuds att lära i skolämnet teknik.

    Den här studien visar att det saknas verklighetsanknytning i grundskolans teknikundervisning. För att elever ska få möjlighet att utveckla en medvetenhet om vikten av utbildning i teknikämnet, som en nyckelfaktor för framtida utveckling vad gäller natur, människa och samhälle, är det uppenbart att betydelsen av den svenska grundskolans teknikämne behöver mer uppmärksamhet från de nationella utbildningsmyndigheterna.

  • 294.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Vad, varför och hur?: En studie av handledning av examensarbeten inom naturvetenskap och teknik2010Conference paper (Other (popular science, discussion, etc.))
  • 295.
    Bjurulf, Veronica
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    What kinds of variation are made available in technology education?2006Conference paper (Refereed)
    Abstract [en]

    Five teachers from the Swedish compulsory school were interviewed about technology

    and technology as a subject in school. One field of work for each of the teachers was

    observed. The analysis is under work based on the variation theory. The aim of this

    paper is to present what kinds of variation that are made available in two teachers

    classrooms. Examples from the data show that there are different kinds of variation in

    Johns1 and Gustavs teaching, but one kind more frequent than others. In Gustavs case

    the principle-apply variation is most common, which means that there is a

    fundamental idea needed to be understood by the students, for them to be capable to

    make suitable choices and/or acts. In Johns case the most frequent kind of variation is

    the example variation. It means that the examples of a specific aspect vary. Interesting

    to discuss is how these results affect the shape of the technology subject in the two

    teachers classrooms

  • 296.
    Bjurulf, Veronica
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Kilbrink, Nina
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Enineering.
    Different kinds of transfer in Technical Vocational Education2011In: PATT25: Cript 8: Perspectives on Learning in Design & Technology Education / [ed] Kay, Stables; Clare Benson; Marc de Vries, London: Goldsmiths University of London , 2011, p. 231-235Conference paper (Other academic)
  • 297.
    Bjurulf, Veronica
    et al.
    Linköping University.
    Kilbrink, Nina
    Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Hands-on material in technology education: The first cycle of a learning study2012In: Technology education in the 21st century / [ed] T. Ginner, J. Hallström & M. Hultén, Linköping University Electronic Press, 2012, p. 89-95Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to describe the first cycle of a learning study in technology education, using a hands-on material, in a Swedish preschool class, i.e. pupils at the age of six. The study was conducted by three teachers and two researchers during fall 2011. Within a learning study, the pupils’ learning is in focus in order to find out the opportunities and obstacles in teaching. The teachers and researchers are working in close cooperation when planning, observing, analysing and revising a specific lesson in which a specific learning object is dealt with. The learning study described in this paper, was carried out with starting-point in the revised Swedish curricula, launched in fall 2011. The results show that the use of a hands-on material may obstruct the view of the learning object, if the pupils are not able to manage the material. The results also indicate that an unsupported practical oriented task could prevent the intended learning object to appear for the pupils.

  • 298.
    Bjurulf, Veronica
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Kilbrink, Nina
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    Technology in Education: Ongoing research2006Conference paper (Refereed)
  • 299.
    Bjurulf, Veronica
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Kilbrink, Nina
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Mechanical and Materials Engineering.
    The Importance of Interweaving Theoretical and Practical Tasks in Technology education2008In: Exploring technology education: solutions to issues in a globalised world : proceedings of the 5th Biennial International Conference on Technology Education Research held at the Crowne Plaza Surfers Paradise, Australia, 27-29 November 2008, Griffith University , 2008, p. 27-34Conference paper (Refereed)
  • 300.
    Bjurulf, Veronica
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Kilbrink, Nina
    Karlstad University, Faculty of Arts and Education, Department of Education.
    Segolsson, Mikael
    Ämnet teknik i grundskolan - med empiriska exempel2009In: Ämnesdidaktiska brobyggen: didaktiska perspektiv inom lärande och forskning, Karlstad: Karlstad University Press , 2009, p. 100-109Chapter in book (Other academic)
3456789 251 - 300 of 2917
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf