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  • 1.
    Arvemo, Tobias
    et al.
    University West, School of Business, Economics and IT, Divison of Law, Economics, Statistics and Politics.
    Gråsjö, Urban
    University West, School of Business, Economics and IT, Divison of Law, Economics, Statistics and Politics.
    Employment and Economic Activity in Different Swedish Border Regions2015In: Uddevalla Symposium 2015. Regional Development in an International Context. Regional, National, Cross Border and International Factors for Growth and Development: Revised papers presented at the 18th Uddevalla Symposium, 11-13 June, Sönderborg, Denmark / [ed] Iréne Bernhard, Trollhättan: University West , 2015, p. 45-57Conference paper (Refereed)
    Abstract [en]

    This study investigate how the effect of cross border activities between Sweden and its three Nordic neighbours influence the Swedish local economies along the border using municipal data from 2009. Two measures for the local economies are examined, economic activity (measured by gross pay per inhabitant) and employment rates. The Swedish border regions where divided into four regions: The Swedish border to Finland, The Swedish border to the part of Norway not included in the Oslo labour market, The Swedish border to the Oslo labour market, and the Swedish-Danish border region. The regression models show how the the regions compare to the Swedish average when controlled for market structure and accessibility to population. For Sweden's border regions to Denmark and the Oslo labour market there are significant improvements in both economic activity and employment rates when the border activity is included. The improvement is highest for the Oslo border regions. For the Swedish border to Finland and to the part of Norway not included inte the Olso labour market the border activity has no significant influence on either economic activity or employment rates.

  • 2.
    Arvemo, Tobias
    et al.
    University West, Department of Economics and IT, Division of Law, Politics and Economics.
    Gråsjö, Urban
    University West, Department of Economics and IT, Division of Law, Politics and Economics.
    University Colleges Effect on Municipal Growth in Swedish Middle-sized Municipalities2008In: Uddevalla Symposium 2008: Spatial Dispersed Production and Network Governance: Revised papers presented at the 11th Uddevalla Symposium, 15-17 May, 2008, Kyoto, Japan / [ed] Iréne Bernhard, Trollhättan: University West , 2008, p. 85-98Conference paper (Refereed)
    Abstract [en]

    The main purpose in this paper is to study to what extent accessibility to R&D is an important factor of explaining municipal economic growth. Of special interests is the question whether, the effect of company (private) R&D efforts on economic growth differ if a university college is present in the municipality or not. Therefore the empirical analysis is conducted on a reduced dataset (92 out of 290 municipalities), containing only middle-sized municipalities without traditional ´old´ universities. The idea of the selection process was to find two sets of comparable municipalities with one containing municipalities with university colleges and one with municipalities without university colleges. In the empirical analysis a knowledge production function is estimated with the difference in Gross Municipal Product, GMP, between 1993 and 2001 as the output. In order to account for the importance of proximity, the explanatory variables are expressed as accessibilities to university and company R&D. The total accessibility is then decomposed into local, intra-regional and inter-regional accessibility to R&D. The main results show that local and intra-regional accessibility to company R&D has positive effects on economic growth. On the other hand, local accessibility to university R&D is of no importance, while there are influential effects of intra-regional university R&D. Moreover, the presence of university college R&D activities decreases the importance of the local accessibilitiy to company R&D or put it differently, local accessibility to company R&D is more important in municipalitites without university college activities.

  • 3.
    Björkholdt, Elise
    et al.
    University West, Department of Technology, Mathematics and Computer Science.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Generalizations of the normal basis theorem2004In: Mathematica Scandinavica, ISSN 0025-5521, E-ISSN 1903-1807, Vol. 94, p. 5p. 185-190Article in journal (Refereed)
  • 4.
    Choquet, Isabelle
    et al.
    University West, Department of Engineering Science.
    Lucquin-Desreux, Brigitte
    University Pierre and Marie Curie, Paris, France.
    Non equilibrium ionization in magnetized two-temperature thermal plasma2011In: Kinetic and Related Models, ISSN 1937-5093, E-ISSN 1937-5077, ISSN 1, Vol. 4, no 3, p. 669-700Article in journal (Refereed)
    Abstract [en]

    A thermal plasma is studied accounting for both impact ionization, and an electromagnetic field. This plasma problem is modeled based on a system of Boltzmann type transport equations. Electron-neutral collisions are assumed to be much more frequently elastic than inelastic, to complete previous investigations of thermal plasma . A viscous hydrodynamic/diffusion limit is derived in two stagesdoing an Hilbert expansion and using the  Chapman-Enskog method. The resultant viscous fluid model is characterized by two temperatures, and non equilibrium ionization. Its diffusion coefficients depend on the magnetic field, and can be computed explicitely.

  • 5.
    Edstorp, Marcus
    University West, Department of Engineering Science, Division of Production Engineering.
    Weld Pool Simulations2008Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This investigation is devoted to the study of welding and its effect on the workpiece, focusing on the thermo and fluid dynamical phenomena occuring during a autogenous or nonautogenous arc fusion welding process. Its aim is to simulate the behaviour of the weld pool and analyze the consequence of the solid-liquid phase change, thus obtaining a methodology for predicting the appearance of weld defects related to solidification and cooling. In order to accomplish this, we solve equations governing a number of continuum mechanical and electromagnetical quantities, as well as consider the motion of the freely moving boundary of the weld pool. Since the state of these quantities is strongly influenced by phenomena such as arc and droplet impingement, non-isothermal phase change, surface tension, Marangoni forces and Lorentz forces, much effort is necessarily devoted to the modelling of the corresponding fluxes and sources, as well as to the implementation of computationally efficient techniques for simulating the geometrical deformation of the workpiece, which in our setting is entirely determined by the motion of the weld pool surface.

    Common to all arc fusion welding processes is the employment of a welding arc. Many techniques rely on the arc to clean and shield the workpiece during the process, however in this study we consider it to be its main purpose to cause the local increase of thermal energy that is required for the establishment of the weld pool, and also to exert the mechanical forces that provoke the subsequent fluid flow which enhances heat transfer and facilitates weld penetration. The physics of the welding arc itself is quite intricate, and although the modelling of the arc is not the prime objective of this research project, we conclude that arc forces act on the pool surface, and that the investigation of the arc behaviour is important insofar that it provides input to the pool model and thus enables a more accurate prediction of the quality of the weldment that is created once the pool has solidified

  • 6.
    Eshagh, Mehdi
    Royal Institute of Technology Division of Geodesy .
    On the estimation of variance in unstable condition adjustment models2011In: Acta Geodaetica et Geophysica Hungarica, ISSN 1217-8977, E-ISSN 1587-1037, ISSN 1217-8977, Vol. 46, no 1, p. 71-83Article in journal (Refereed)
    Abstract [en]

    Estimation of variance in an ordinary adjustment model is straightforward, but if the model becomes unstable or ill-conditioned its solution and the variance of the solution will be very sensitive to the errors of observations. This sensitivity can be controlled by stabilizing methods but the results will be distorted due to stabilization. In this paper, stabilizing an unstable condition model using Tikhonov regularization, the estimations of variance of unit weight and variance components are investigated. It will be theoretically proved that the estimator of variance or variance components has not the minimum variance property when the model is stabilized, but unbiased estimation of variance is possible. A simple numerical example is provided to show the performance of the theory.

    |

  • 7.
    Eshagh, Mehdi
    et al.
    University West, Department of Engineering Science, Division of Computer, Electrical and Surveying Engineering. Royal Institute of Technology, Division of Geodesy, Stockholm, Sweden .
    Lars E:, Sjöberg
    Royal Institute of Technology, Division of Geodesy, Stockholm, Sweden .
    The modified best quadratic unbiased non-negative estimator (MBQUNE) of variance components2008In: Studia Geophysica et Geodaetica, ISSN 0039-3169, E-ISSN 1573-1626, Vol. 52, no 3, p. 305-320Article in journal (Refereed)
    Abstract [en]

    Estimated variance components may come out as negative numbers without physical meaning. One way out of this problem is to use non-negative methods. Different approaches have been presented for the solution. Sjöberg presented a method of Best Quadratic Unbiased Non-Negative Estimator (BQUNE) in the Gauss-Helmert model. This estimator does not exist in the general case. Here we present the Modified BQUNE (MBQUNE) obtained by a simple transformation from the misclosures used in the BQUE to residuals. In the Gauss-Markov adjustment model the BQUNE and MBQUNE are identical, and they differ in condition and Gauss-Helmert models only by a simple transformation. If the observations are composed of independent/disjunctive groups the MBQUNE exists in any adjustment model and it carries all the properties of the BQUNE (when it exists). The presented variance component models are tested numerically in some simple examples. It is shown that the MBQUNE works well for disjunctive groups of observations.

  • 8.
    Flensburg, Per
    et al.
    University West, School of Business, Economics and IT, Divison of Informatics.
    Holl, Alfred
    Technische Hochschule Nürnberg Georg Simon Ohm / University Nuremberg, Germany.
    Das älteste gedruckte schwedische Rechenbuch (Aegidius Aurelius, Arithmetica, Uppsala 1614): (Aegidius Aurelius, Arithmetica, Uppsala 1614)2017In: Tagungsband zum wissenschaftlichen Kolloquium vom 21.–23. April 2017 in der Berg- und Adam-Ries-Stadt Annaberg-Buchholz / [ed] Gebhardt, Rainer, Annaberg-Buchholz: Adam-Ries-Bund , 2017, p. 313-326Conference paper (Other academic)
  • 9.
    Gellerstedt, Martin
    University West, Department of Economics and IT, Division of Computer Science and Informatics.
    M12: Medicinsk statistik 2004 (ed. 1)Book (Other academic)
  • 10.
    Gellerstedt, Martin
    University West, Department of Economics and IT, Division of Computer Science and Informatics.
    Statistiska metoder för kvalitetsutveckling1997 (ed. 1)Book (Other academic)
  • 11.
    Gellerstedt, Martin
    et al.
    University West, Department of Economics and IT, Division of Computer Science and Informatics.
    Svensson, Lars
    University West, Department of Economics and IT, Division of Computer Science and Informatics.
    Www means win win win in education: some experiences from online courses in applied statistics2010In: OZCOTS 2010 Proceedings of the 7th Australian Conferenceon Teaching Statistics / [ed] Helen MacGillivray & Brian Phillips, Statistical society of Australia , 2010, p. 51-56Conference paper (Refereed)
    Abstract [en]

    This paper reports on the experiences from online courses in applied statistics. The courses were designed with the ambition of making studies in statistics, fun, interesting, useful, not that difficult and directly supported the possibility to combine studies and work. When designing the courses we considered three dimensions: "pedagogies","community" and "structure". Experiences after giving a first-year course three times show that the online course succeeds in attracting new studen ts since 90% of the participants would not be able to follow an on-campus course and 62% worked full time.

    The pedagogies were highly appreciated because focusing on the interpretation of results and using computer analyses really changed the prejudices about statistics. Structure and prompt feedback was experienced as important factors. It was possible to combine online studies with employment, and the student completion rate was (84%, 55% and 61%), with a potential for further improvements.

  • 12.
    Gillerstedt, Monica
    et al.
    University West, Department of Social and Behavioural Studies.
    Isaksson, Anders
    University West, Department of Social and Behavioural Studies, Division for Educational Science and Languages.
    Gymnasielevers problem med procenträkning.2009Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Undersökningen handlar om gymnasieelevers svårigheter med procentavsnittet i matematik. Syftet var att undersöka vilka svårigheter eleverna har att lösa olika sorters räkneuppgifter av procentkaraktär. Vi ville även veta om det skiljer i svårighet att lösa sifferuppgifter respektive textuppgifter samt hur det är med den matematiska begreppsförståelsen. Studien är gjord på två gymnasieskolor i Västsverige och omfattar 68 elever från fyra olika klasser i årskurs 1 på teknikprogrammet. Samtliga elever har svarat på ett skriftligt test i form av ett diagnostiskt prov och av dessa har sedan 19 elever också intervjuats. Den skriftliga diagnosen bestod av uppgifter av följande fem typer: Att räkna ut delen, då det hela och procenttalet är kända. Att räkna ut det hela, då delen och procenttalet är kända. Att räkna ut procenttalet, då delen och det hela är kända. Begreppen procent och procentenheter. Kombinationer och räkning med procent i flera steg. Elevernas svar har granskats och analyserats med utgångspunkt från Kilpatrick, Swafford och Bradfords (2001) samt Mölleheds (2001) forskning vars arbeten lyfter fram olika färdigheter och påverkansfaktorer som har betydelse för elevernas resultat vid problemlösning i matematik. Vi har funnit att de flesta elever inte har så stora problem när det gäller de enklare uppgifterna. De problem som finns här består mest av missförstånd av texten, låg uppmärksamhet och bristande räkneförmåga. De lite mer krävande uppgifterna avslöjar desto fler svårigheter. Både antalet svårigheter och antalet elever med svårigheter ökar. I diagnosen finner vi exempel på osäkerhet kring Kilpatricks et al. (2001) alla matematiska färdigheter samt flera av Mölleheds (2001) påverkansfaktorer. Svårigheterna består i osäkerhet att räkna på rätt sätt och att tolka det uträknade värdet för att kunna svara på den ställda frågan. En textuppgift med helheter och delar som måste byta relation under lösningen av problemet ställer till bekymmer för många. Ingen av de undersökta eleverna har ritat upp och visualiserat i sina uträkningar vilket är en brist då det hade förenklat förståelsen av texten. Vi har även funnit att det finns problem med att på ett korrekt sätt ställa upp det bråk som räknar ut procenttalet, då delen och det hela är kända. En del elever vill gärna ha den stora delen i nämnaren oavsett fråga. Det finns även brister i den matematiska begreppsförståelsen vilken är av stor betydelse för problemlösning. Skillnaden mellan procent och procentenheter är ett sådant exempel. Begreppet procentenheter har gett stora svårigheter för eleverna att tolka och beräkna liksom behandlingen av olika förändringsfaktorer.

  • 13.
    Hansbo, Anita
    et al.
    University West, Department of Technology, Mathematics and Computer Science.
    Hansbo, Peter
    Hansson, Mats G.
    A finite element method on composite grids based on Nitsche's method2002Report (Other (popular science, discussion, etc.))
  • 14.
    Kiamehr, Ramin
    et al.
    Department of Geodesy and Geomatics, Zanjan University, Iran.
    Eshagh, Mehdi
    Royal Institute of Technology, Stockholm, Sweden.
    Estimating variance components of ellipsoidal, orthometric and geoidalheights through the GPS/levelling Network in Iran2008In: Journal of the Earth and Space Physics, Vol. 34, no 3, p. 1-13Article in journal (Refereed)
    Abstract [en]

    The Best Quadratic Unbiased Estimation (BQUE) of variance components in the Gauss-Helmert model is used to combine adjustment of GPS/levelling and geoid to determinethe individual variance components for each of the three height types. Through theresearch, different reasons for achievement of the negative variance components werediscussed and a new modified version of the Best Quadratic Unbiased Non-negativeEstimator (MBQUNE) was successfully developed and applied. This estimation could beuseful for estimating the absolute accuracy level which can be achieved using theGPS/levelling method. A general MATLAB function is presented for numericalestimation of variance components by using the different parametric models. Themodified BQUNE and developed software was successfully applied for estimating thevariance components through the sample GPS/levelling network in Iran. In the followingresearch, we used the 75 outlier free and well distributed GPS/levelling data. Threecorrective surface models based on the 4, 5 and 7 parameter models were used throughthe combined adjustment of the GPS/levelling and geoidal heights. Using the 7-parametermodel, the standard deviation indexes of the geoidal, geodetic and orthometric heights inIran were estimated to be about 27, 39 and 35 cm, respectively.

  • 15.
    Lindström, David
    University West, Department of Engineering Science, Division of Mechanical Engineering and Natural Sciences.
    Evaluation of a Surrogate Based Method for Global Optimization2015In: International Journal of Computer, Electrical, Automation, Control and Information Engineering, E-ISSN 1307-6892, Vol. 9, no 7, p. 1636-1642Article in journal (Refereed)
    Abstract [en]

    We evaluate the performance of a numerical method for global optimization of expensive functions. The method is using a response surface to guide the search for the global optimum. This metamodel could be based on radial basis functions, kriging, or a combination of different models. We discuss how to set the cyclic parameters of the optimization method to get a balance between local and global search. We also discuss the eventual problem with Runge oscillations in the response surface.

  • 16.
    Lindström, David
    University West, Department of Engineering Science.
    Robustness analysis of airfoil performance: DETC2010-282612010In: Proceedings of the ASME 2010 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference: August 15-18, 2010, Montreal, Quebec, Canada, ASME, the American Society of Mechanical Engineers , 2010, p. 1-6Conference paper (Refereed)
    Abstract [en]

    We demonstrate a technique to evaluate the aerodynamic robustness of a given blade profile which it is exposed to stochastic geometrical variation. The technique is based on random fields, with geometrical deviations continuously defined over the entire structure, with a prescribed statistical distribution function and a given correlation between these deviations. Control points are defined on the blade surface to model the blade geometry disturbances. At each control point a stochastic deviation is defined, which acts in the normal direction of the blade. By modeling disturbances in the normal direction instead of in the separate Cartesian directions, we automatically reduce the number of stochastic variables by a factor two. The perturbation variables are transformed via Karhunen-Loève eigenvalue decomposition, giving stochastically independent variables. The robustness is finally estimated by a Monte Carlo simulation, where computational fluid dynamic simulations are performed to evaluate the resulting change in blade performance for given geometrical perturbations.

  • 17.
    Lindström, David
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering and Natural Sciences.
    Eriksson, Kenneth
    University West, Department of Engineering Science, Division of Mechanical Engineering and Natural Sciences.
    A surrogate model based global optimization method2008In: 38th International Conference on Computers and Industrial Engineering 2008, 2008, p. 226-232Conference paper (Refereed)
    Abstract [en]

    A new surrogate model based algorithm for global optimization is derived. A metamodel such as a kriging model or a radial basis function model is used to build an interpolant of the objective function. Evaluation points are chosen in such a way that local search and global exploration is balanced. Instead of putting the next point exactly where it is most likely to find the global optimum, the new method also prepares for steps to come by minimizing the total uncertainty of the interpolated function within the most interesting areas of the search space.

  • 18.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Brauer group rings2004In: JP Journal of Algebra, Number Theory & Applications, Vol. 4, p. 22p. 465-494Article in journal (Refereed)
  • 19.
    Lundström, Patrik
    University West, Department of Technology.
    Cohomology and Self-dual Normal Bases for Infinite Galois Field Extensions2002In: Journal of Algebra, ISSN 0021-8693, E-ISSN 1090-266X, Vol. 256, p. 531-541Article in journal (Refereed)
    Abstract [en]

    We generalize an injectivity result obtained by Bayer-Fluckiger and Lenstra concerning pointed cohomology sets, defined by norm-one groups of finite-dimensional algebras with involution over fields k of characteristic different from 2, to the case of inverse limits of finite-dimensional k-algebras with involution. We use this generalization to obtain a result about self-dual normal bases for infinite Galois field extensions.

  • 20.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science, Division for Mathematics and Sciences.
    Cohomology and the normal basis theorem2007In: Indagationes mathematicae, ISSN 0019-3577, E-ISSN 1872-6100, Vol. 18, p. 69-72Article in journal (Refereed)
  • 21.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Crossed product algebras defined by separable extensions2005In: Journal of Algebra, ISSN 0021-8693, E-ISSN 1090-266X, Vol. 283, p. 14p. 723-737Article in journal (Refereed)
  • 22.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Fuzzified categories of composition graphs2005Report (Other (popular science, discussion, etc.))
    Abstract [en]

    Serving as a generalization of many examples of fuzzy algebraical systems equipped with a binary operation, we introduce fuzzy composition graphs and show that categories formed by such graphs are, in the sense of Wyler [10], top categories. By using this, we investigate projective and injective objects in such categories, and we determine when various limits and colimits, such as terminal and initial objects, products, coproducts, pullbacks, pushouts, equalizers, coequalizers, kernels and cokernels, exist in categories of this type and what they look like. These results are then applied to the categories of fuzzy sets, fuzzy categories, fuzzy groupoids, fuzzy monoids, fuzzy groups and fuzzy abelian groups.

  • 23.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science, Division for Mathematics and Sciences.
    Galois Module Structure of Field Extensions2007In: International Electronic Journal of Algebra, ISSN 1306-6048, E-ISSN 1306-6048, Vol. 2, no 8, p. 100-105Article in journal (Refereed)
    Abstract [en]

    We show, in two different ways, that every finite field extension has a basis with the property that the Galois group of the extension acts faithfully on it. We use this to prove a Galois correspondence theorem for general finite field extensions. We also show that if the characteristic of the base field is different from two and the field extension has a normal closure of odd degree, then the extension has a self-dual basis upon which the Galois group acts faithfully.

  • 24.
    Lundström, Patrik
    University West, Department of Technology.
    Generalized Brauer Algebras2002In: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 30, no 5, p. 2229-2270Article in journal (Refereed)
    Abstract [en]

    Using some ideas of Brauer, we introduce what we call generalized Brauer algebras and, as a special case, Brauer orders. We show that many well-known classes of so-called crossed product algebras, and in particular, the well-known crossed product orders, can be obtained as special instances of our construction. We prove several results showing when Brauer orders are Azumaya, maximal, hereditary or Gorenstein.

  • 25.
    Lundström, Patrik
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Hilbert 90 for Rings with ConjugationManuscript (preprint) (Other academic)
    Abstract [en]

    We show a version of Hilbert 90 that is valid for a large class ofalgebras many of which are not commutative, distributive orassociative. This class contains the n:th iteration of theConway-Smith doubling procedure. We use our version of Hilbert 90 toparametrize all solutions in ordered fields to the norm one equation for such algebras.

  • 26.
    Lundström, Patrik
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Hilbert 90 for algebras with conjugation2012In: Algebras and Representation Theory, ISSN 1386-923X, E-ISSN 1572-9079, Vol. 15, no 1, p. 119-135Article in journal (Refereed)
    Abstract [en]

    We show a version of Hilbert 90 that is valid for a large class ofalgebras many of which are not commutative, distributive orassociative. This class contains the n:th iteration of theConway-Smith doubling procedure. We use our version of Hilbert 90 toparametrize all solutions in ordered fields to the norm one equation for such algebras.

  • 27.
    Lundström, Patrik
    University West, Department of Technology.
    Normal Bases for Infinite Galois Ring Extensions1999In: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 79, p. 235-240Article in journal (Refereed)
  • 28.
    Lundström, Patrik
    University West, Department of Technology.
    Normal Integral Bases for Infinite Abelian Extensions2001In: Acta Arithmetica, ISSN 0065-1036, E-ISSN 1730-6264, Vol. 100, p. 79-83Article in journal (Refereed)
  • 29.
    Lundström, Patrik
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Pythagoreiska tripplar på sex olika sätt2008In: Normat, ISSN 0801-3500, Vol. 56, no 3, p. 111-119Article in journal (Refereed)
    Abstract [en]

    Six different ways of parametrising Pythagorean triplets are presented, from the elementary arguments supplied by the Greek, via trigonometry to Gaussian integers and applications of Hilbers 90th theorem.

  • 30.
    Lundström, Patrik
    University West, Department of Technology.
    Self-dual Normal Bases for Infinite Galois Field Extensions1998In: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 26, p. 4331-4341Article in journal (Refereed)
  • 31.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Self-dual normal bases for infinite odd abelian Galois ring extensions2006In: Acta Arithmetica, ISSN 0065-1036, E-ISSN 1730-6264, Vol. 123, no 1, p. 1-8Article in journal (Refereed)
  • 32.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Self-dual Normal Integral Bases for Infinite Unramified Extensions2002In: Journal of Number Theory, ISSN 0022-314X, E-ISSN 1096-1658, Vol. 97, no 2, p. 350-367Article in journal (Refereed)
    Abstract [en]

    We prove a generalization to infinite Galois extensions of local fields, of a classical result by Noether on the existence of normal integral bases for finite tamely ramified Galois extensions. We also prove a self-dual normal integral basis theorem for infinite unramified Galois field extensions of local fields with finite residue fields of characteristic different from 2. This generalizes a result by Fainsilber for the finite case. To do this, we obtain an injectivity result concerning pointed cohomology sets, defined by inverse limits of norm-one groups of free finite-dimensional algebras with involution over complete discrete valuation rings.

  • 33.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science, Division for Mathematics and Sciences.
    Separable Groupoid Rings2006In: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 34, no 8, p. 3029-3041Article in journal (Refereed)
    Abstract [en]

    We show that groupoid rings are separable over their ring of coefficients if and only if the groupoid is finite and the orders of the associated principal groups are invertible in the ring of coefficients. We use this to show that if we are given a finite groupoid, then the associated groupoid ring is semisimple (or hereditary) if and only if the ring of coefficients is semisimple (or hereditary) and the orders of the principal groups are invertible in the ring of coefficients. To this end, we extend parts of the theory of graded rings and modules from the group graded case to the category graded, and, hence, groupoid graded situation. In particular, we show that strongly groupoid graded rings are separable over their principal components if and only if the image of the trace map contains the identity

  • 34.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Separable groupoid rings2006In: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 34, p. 13p. 3029-3041Article in journal (Other (popular science, discussion, etc.))
  • 35.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    The category of groupoid graded modules2004In: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 100, p. 15p. 195-211Article in journal (Refereed)
  • 36.
    Lundström, Patrik
    University West, Department of Engineering Science.
    The Picard Groupoid and Strongly Groupoid Graded Modules2006In: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 106, p. 1-13Article in journal (Refereed)
  • 37.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    The Picard Groupoid and Strongly Groupoid Graded Modules2006In: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 106, p. 1-13Article in journal (Refereed)
  • 38.
    Lundström, Patrik
    University West, Department of Technology, Mathematics and Computer Science.
    Von Neumann finite endomorphism rings2003In: Indagationes mathematicae, ISSN 0019-3577, E-ISSN 1872-6100, Vol. 14, p. 9p. 223-232Article in journal (Refereed)
  • 39.
    Lundström, Patrik
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Weak topological functors2008In: Journal of Generalized Lie Theory and Applications, ISSN 1736-5279, E-ISSN 1736-4337, Vol. 2, no 3, p. 211-215Article in journal (Refereed)
    Abstract [en]

    We introduce weak topological functors and show that they lift and preserve weak limits and weak colimits. We also show that if then the induced functor of Wyler’s top categories and in particular to functor categories of fuzzy maps, fuzzy relations, fuzzy topological spaces and fuzzy measurable spaces. A ! B is a topological functor and J is a category,AJ ! BJ is topological. These results are applied to a generalization

  • 40.
    Lundström, Patrik
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Öinert, Johan
    Commutativity and Ideals in Category Crossed Products2010In: Proceedings of the Estonian Academy of Sciences: Physics, Mathematics, ISSN 1406-0086, E-ISSN 2228-0685, Vol. 59, no 4, p. 338-346Article in journal (Refereed)
  • 41.
    Lundström, Patrik
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Öinert, Johan
    LTH.
    Miyashita Action in Strongly Groupoid Graded RingsManuscript (preprint) (Other academic)
    Abstract [en]

    We determine the commutant of homogeneous subringsin strongly groupoid graded rings in terms of an action on the ring induced by the grading. Thereby we generalize a classical result of Miyashita from the groupgraded case to the groupoid graded situation. In the end of the article we exemplify this result. To this end, we show, by an explicit construction,that given a finite groupoid $G$, equipped with a nonidentitymorphism t : d(t) -> c(t), there is a strongly G-graded ring R with the properties that each R_s, for s in G, is nonzero and R_t is a nonfree left R_c(t)-module.

  • 42.
    Lundström, Patrik
    et al.
    University West, Department of Engineering Science.
    Öinert, Johan
    LTH.
    Miyashita Action in Strongly Groupoid Graded Rings2012In: International Electronic Journal of Algebra, ISSN 1306-6048, E-ISSN 1306-6048, Vol. 11, p. 46-63Article in journal (Refereed)
    Abstract [en]

    We determine the commutant of homogeneous subrings in strongly groupoid graded rings in terms of an action on the ring induced by the grading. Thereby we generalize a classical result of Miyashita from the groupgraded case to the groupoid graded situation. In the end of the article we exemplify this result. To this end, we show, by an explicit construction,that given a finite groupoid $G$, equipped with a nonidentitymorphism t : d(t) -> c(t), there is a strongly G-graded ring R with the properties that each R_s, for s in G, is nonzero and R_t is a nonfree left R_c(t)-module.

  • 43.
    Lundström, Patrik
    et al.
    University West, Department of Engineering Science, Division of Natural Sciences and Electrical and Surveying Engineering.
    Öinert, Johan
    Köpenhamns Universitet.
    Skew category algebras associated with partially defined dynamical systems2012In: International Journal of Mathematics, ISSN 0129-167X, Vol. 23, no 4, p. 16-Article in journal (Refereed)
    Abstract [en]

    We introduce partially defined dynamical systems defined on a topological space. To each such system we associate a functor s from a category G to Top^op and show that it defines what we call a skew category algebra AxG. We study the connection between topological freeness of s and, on the one hand, ideal properties of AxG and, on the other hand, maximal commutativity of A in AxG. In particular, we show that if G is a groupoid and for each e in ob(G) the group of all morphisms from e to e is countable and the topological space s(e) is Tychonoff and Baire, then the following assertions are equivalent: (i) s is topologically free; (ii) A has the ideal intersection property, that is if I is a nonzero ideal of AxG, then I \cap A is not equal to zero; (iii) the ring A is a maximal abelian complex subalgebra of AxG. Thereby, we generalize a result by Svensson, Silvestrov and de Jeu from the additive group of integers to a large class of groupoids.

  • 44.
    Lundström, Patrik
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Öinert, Johan
    LTH.
    The Ideal Intersection Property for Groupoid Graded Rings2012In: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 40, no 5, p. 1860-1871Article in journal (Refereed)
    Abstract [en]

    We show that if a groupoid graded ring hasa certain nonzero ideal property, then the commutant of the center of the principal component of the ringhas the ideal intersection property, that is it intersects nontrivially every nonzero ideal of the ring. Furthermore, we show that for skew groupoid algebras withcommutative principal component, the principal componentis maximal commutative if and only if it has the ideal intersection property.

  • 45.
    Mark, Sigyn
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Holm, Sture
    Göteborg University, Department of Mathematics.
    Test and prediction in factorial models with independent variance estimates2008In: Journal of Applied Statistics, ISSN 0266-4763, E-ISSN 1360-0532, Vol. 35, no 7, p. 773-782Article in journal (Refereed)
  • 46.
    Nilsson, Galina
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Peer-Assisted Learning in Mathematics in Higher Education. 2010In: LTH:s Pedagogiska Inspirationskonferens: 6:e Pedagogiska inspirationskonferensen, dec 2010. Lund, 2010Conference paper (Other academic)
    Abstract [en]

    This paper explores opportunities for implementing a peer-tutoring system in mathematics in two contrasting settings: a traditional classroom environment with a teacher-centred educational process and the higher education environment where a range of student-centred teaching and learning methods has already been introduced. After a series of PAL sessions a questionnaire was distributed and in-depth interviews with the peer tutors were conducted. The analysis of the impact of peer-assisted learning (PAL) on the students' learning experience showed that the majority of students positively evaluated their PAL experience. The students felt that they were more actively engaged with and more in control of the learning process than during a traditional tutorial. This study demonstrated that the size of the groups, timing and the number of PAL sessions are crucial for successful implementation of PAL. The paper concludes with the recommendations for using PAL in a variety of educational settings.The higher education sector has been experiencing a dramatic change during the past decade: it is rapidly expanding both in the number and diversity of students. Student to staff ratio has enormously increased. The students are coming from different ethnic, social, and cultural backgrounds and have different levels of knowledge. The change in higher education from an "elite" to a "mass" system creates new challenges for educators. At the same time, the main features of the modern knowledge-based society, the society we live in, are the fast pace of technological advancements, interdisciplinary work organisation and globalisation of the work market. Educators in Europe are facing new challenges in preparing young people for their social and professional integration, successful career and personal development.

    The appropriate choice of teaching methods which meet the demands of the knowledge-based society, influence the learning process and accommodate the needs of young generation is crucial in achieving these tasks. Implementing student-centred approaches in the educational process creates the learning environment which stimulates students' learning developing their ability of independent and deep learning. 

  • 47.
    Nilsson, Galina
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics. University West, Department of Engineering Science, Division of Mathematics, Computer and Surveying Engineering.
    Luchinskaya, D.
    Provision of maths support for student in higher education institutions2012In: The 40th Annual Congress of the Nordic Educational Research Association: March 8-10, 2012, Copenhagen, Aarhus: Department of Eduation, Aarhus University , 2012, p. 283-Conference paper (Refereed)
    Abstract [en]

    European countries including Scandinavian countries are facing a crisis in preparing qualified staff for working in science and engineering. Declining numbers of students pursuing careers in these areas and poor quality of maths education in secondary schools are the principal factors contributing to this problem.

    Students entering universities have a diverse level of maths knowledge which is often below university requirements. University teachers face a challenging and complex task of teaching such a diverse student body. One of the most common ways to tackle this problem and to raise the level of students' maths knowledge to the required standard is to introduce a maths foundation course prior to mainstream teaching. However, this is not always possible because of academic staff availability and/or time and cost constraints.

    Another solution is to provide additional help with maths-related problems by running drop-in sessions, workshops and/or tutorials.

    This study analyses the efficiency of maths support provision in two universities: Leeds Metropolitan University, UK and Högskolan Väst, Sweden. This is an on-going collaboration between two universities and in this paper we present the results of this study focussing on the academic staff prospective, using questionnaires, observations and interviews with tutors.

    Based on the collected data we concluded that often students are not fully engaged during workshops. They prefer a 'solve this for me' approach which they try to achieve during individual sessions and which is not always possible with the course tutor. However, implementing methods which increase students' engagement with the learning process (e.g. problem-based learning andpeer-assisted learning) can be more useful. Running subject-specific workshops (e.g. for nurses, business students or teachers) helps to focus on students' particular needs, and individual tutorials can accommodate other needs.

    The paper concludes with recommendations for improving the efficiency of maths support for students.

  • 48.
    Nilsson, Galina
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics. University West, Department of Engineering Science.
    Luchinskaya, E
    Developing generic and subject specific competences through non-traditional teaching methods2009In: European Educational Research Association conference: ECER 2009, 25-30 september, Vienna, 2009Conference paper (Other academic)
  • 49.
    Nilsson, Galina
    et al.
    University West, Department of Engineering Science, Division of Land Surveying and Mathematics.
    Luchinskaya, E
    Enhancing student employability prospects through competence development: using non-traditional methods in teaching mathematics in higher education2010In: NERA ‘ s 38 th Congress: Malmö, 11-13 March 2010, Malmö University School of Teacher Education, Malmö: Nordic Educational Research Association (NERA) , 2010, p. 144-144Conference paper (Other academic)
    Abstract [en]

    Research topic/aim: This paper analyses student and academic experience in generic and subject specific competence development to evaluate the potential of using problem-based learning (PBL) and peer-assisted learning (PAL) in raising student employability prospects. The fast pace of technological advancements, interdisciplinary work organisation and globalisation of the work market are the main features of the modern knowledge-based society. Equipping students with competences that are required for their social and professional integration, successful career and personal development is becoming a key mission of the higher education sector. Fostering effective teaching and learning methods facilitates the acquisition of professional skills and competences. This paper explores the opportunities for implementing PBL and PAL in delivering mathematics on a range of programmes at the University Väst in Sweden focusing on the development of generic and subject specific competences. Theoretical framework: This study is underpinned by the socio-cultural theory of the learning processes which was originally formulated by Vygotsky and is currently experiences a tremendous peak of its popularity. PBL encourages deeper learning via meaning construction and connecting ideas. It stimulates collaborative knowledge building process among participants and develops self-directed learning. PAL is an example of a student-to student support scheme grounded in collaborative learning. PAL is aimed to improve student performance and develop a range of study skills through creating an informal environment for learning. The introduction of both methods into the educational process independently and at the same has a broad potential. Methodology/research design: Our study was carried out in the University Väst, Sweden in 2005-2009. The first year students on the ‘Land Surveyors’ and ‘Computer Science’ undergraduate programme participated in this study. Two pedagogical methods — PBL and a combination of PBL and PAL were incorporated into the mathematics modules delivery. The lectures were delivered in a traditional way; PBL and PAL were used throughout tutorials. The students were solving applied mathematical problems working in small groups. The problems selected were aimed to acquire a set of competences relevant to their future career. To evaluate the outcomes of this study, a questionnaire consisted of multiple choice and openended questions was designed where the students could comment on their learning experience. The interviews with tutors were conducted. The study has drawn a comparison between the development of particular competences and the use of PBL, PAL and traditional methods. Expected conclusions/findings: The results showed that the students evaluated PAL and PBL methods as useful and valuable. The students indicated that have developed problem solving skills, advanced their analytical skills and ability to apply mathematical tools. These competences are important for their future employment. The students highly rated collaboration with peers. It was noted that the selection of the problems, the number of students enrolled on the course, the choice of peer tutors, the way how training sessions are organised, the number and timing of the sessions are crucial for the successful implementation of PAL and PBL. Relevance for Nordic Educational research: Higher education systems in Europe including Scandinavia are facing new challenges in raising employability of students. The appropriate choice of teaching methods is instrumental to a successful implementation of this task. The paper concludes with recommendations for fostering PAL and PBL as they represent a useful educational tool which encourages the development of generic and subject specific competences.

  • 50.
    Nilsson, Galina
    et al.
    University West, Department of Engineering Science.
    Luchinskaya, E
    University West, Department of Engineering Science.
    Using Problem-based and Peer-assisted Learning in Teaching Mathematics to University Students: Focus on Competence Development2009In: British Educational Research Association conference: BERA 2009, Manchester University, Manchester, UK, 2-5 September 2009, 2009Conference paper (Other academic)
    Abstract [en]

    The harmonisation and internationalisation of higher education systems in Europe driven by the principles encapsulated in the Bologna Declaration [1] are offering new agendas for educators. The shift towards a student centred educational paradigm with the focus on learning outcomes and acquired competences highlights various ways in which this process can be mediated. An appropriate choice of teaching methods is instrumental to a successful educational process. The use of different teaching and learning styles such as discussions, group work, case studies, problem-based learning (PBL), peer-assisted learning (PAL) and critical thinking enables deeper engagement of learners within the learning process and at the same time facilitates the acquisition of professional skills and competences [2, 3].

    The paper assesses the impact of PAL and PBL methods applied in teaching Mathematics to students on the 'Land Surveyors' programme, on student experience across generic and subject specific competence development.

    The carried out research had the following objectives:

    To plan and select tasks for tutorials where students can practise PBL;To design and implement several PAL sessions to facilitate the development of problem solving skills;To design questionnaires to evaluate the quality of student experience;To analyse the challenges university teachers face in implementing innovative approaches to teaching and the competence development.

    There is a substantial body of literature on the PAL [e.g. 4] and PBL methodology [e.g. 5, 6]. PAL is an example of a student-to student support scheme grounded in collaborative learning. PAL  is aimed to improve student performance and  develop a range of study skills through creating an informal environment for learning. At the same time PBL encourages deeper learning via meaning construction and connecting ideas. It stimulates collaborative knowledge building process among participants and develops self-directed learning. The introduction of both methods into the educational process at the same has a broad potential.

    Our study was carried out in the University Väst, Sweden during 9 weeks in 2008. The 'Core  Mathematics' module (7.5 credits) is one of the cornerstone modules of the 'Land Surveyors' programme curriculum. The competences acquired by students while on this module are fundamental for the future study. 42 first year students on the 'Land Surveyors' undergraduate programme participated in this study. Two pedagogical methods – PAL and PBL have been incorporated into the programme delivery. PBL method has been already introduced before in University Vast in Computer Science programmes [7] and this method was highly appreciated by students. In order to introduce PBL and PAL methods into the course design and to stimulate student involvement in the educational process, it was decided to keep a traditional layout of lectures but to change the way seminars were conducted. PBL method was used throughout the tutorials but three PAL sessions were introduced at the end of the course.

    The students were solving applied mathematical problems working in small groups of five. The selection of problems was based on the relevance of the competences acquired through this activity to their future career. The introduction of PAL and PBL methods was focused in particular on the developing problem-solving and analytical skills as well as developing ability to formulate the problem mathematically. A peer tutor from the same student cohort was assigned to each group and training sessions for them were organised. To evaluate the outcomes of this study, the questionnaire was designed where the students could evaluate their learning experience. In addition, the peer tutors were interviewed. The results of the survey were statistically analysed. The results showed that the students evaluated PAL and PBL methods as useful and valuable. The students positively evaluated the peer tutors' performance. They thought that the group leaders were well-prepared, competent and could clearly explain the problems to peers.

    The analysed data indicated that over 60 percent of the students estimated that have developed problem solving skills, while 35 percent indicated that they advanced their analytical skills and ability to apply mathematical tools. The students highly rated working in groups and commented on the positive effects of collaboration with peers. In their comments they pointed out that it was easier for them to ask questions, get support and explanation The students perceived the use of PAL and PBL approaches as a useful contribution to their learning experience.

    The introduction of non-traditional methods into educational process creates new challenges for tutors. The selection of the problems, the number of students enrolled on the course, the choice of peer tutors, the way how training sessions are organised, the number and timing of the sessions are crucial for the successful implementation of the PAL and PBL.

    In conclusion, this study demonstrates that the use PAL and PBL was rewarding and overall well received by the students at University Vast. The results of the final exams showed an improvement in student grades compared to previous years. The opportunity of implementing a more individual and flexible approach to the educational process led to improved generic and subject specific competences.

    References

     

    1. The Bologna Declaration of 19 June 1999 http://www.ond.vlaanderen.be/hogeronderwijs/bologna/documents/MDC/BOLOGNA_DECLARATION1.pdf

    2. Moon, J. (2002) The module and programme development handbook. London: Kogan Page.

    3. Ramsden, P. (2003) Learning to teach in higher education (2nd ed). New York: Routledge Falmer.

    4. Peer Assisted Learning, Topping, K. and Ehly, S. (Eds.),  Lawrence Erlbaum, 1998

    5. Dahlgren, M. (2003) PBL through the looking glass: Comparing applications in computer engineering, psychology, physiotherapy. International Journal of Engineering Education, 19 (5), 672-681.

    6. Dahlgren. L. O. (1998) "Problembaserat lärande - Idé, Praktik Och Effeter", Linköpings Universitet.

    Nilsson G. and Luchinskaya E. "Developing Competences Using Problem-based Learning: a Case Study of Teaching Mathematics to Computer Science Students", Journal of Research in Teacher Education, 2007, No 3. p 13-21. 

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