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• 1.
University of Skovde, Jonkoping University.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV). Jonkoping University, Orebro Univ, University University West - Sweden.
An approach towards generating surrogate models by using RBFN with a priori bias2014Inngår i: PROCEEDINGS OF THE ASME INTERNATIONAL DESIGN ENGINEERING TECHNICAL CONFERENCES AND COMPUTERS AND INFORMATION IN ENGINEERING CONFERENCE, 2014, VOL 2B, AMER SOC MECHANICAL ENGINEERS , 2014, Vol. 2BKonferansepaper (Fagfellevurdert)

In this paper, an approach to generate surrogate models constructed by radial basis function networks (RBFN) with a priori bias is presented. RBFN as a weighted combination of radial basis functions only, might become singular and no interpolation is found. The standard approach to avoid this is to add a polynomial bias, where the bias is defined by imposing orthogonality conditions between the weights of the radial basis functions and the polynomial basis functions. Here, in the proposed a priori approach, the regression coefficients of the polynomial bias are simply calculated by using the normal equation without any need of the extra orthogonality prerequisite. In addition to the simplicity of this approach, the method has also proven to predict the actual functions more accurately compared to the RBFN with a posteriori bias. Several test functions, including Rosenbrock, Branin-Hoo, Goldstein-Price functions and two mathematical functions (one large scale), are used to evaluate the performance of the proposed method by conducting a comparison study and error analysis between the RBFN with a priori and a posteriori known biases. Furthermore, the aforementioned approaches are applied to an engineering design problem, that is modeling of the material properties of a three phase spherical graphite iron (SGI). The corresponding surrogate models are presented and compared.

• 2.
Högskolan Väst, Institutionen för ekonomi och it, Avd för juridik, ekonomi, statistik och politik.
Högskolan Väst, Institutionen för ekonomi och it, Avd för juridik, ekonomi, statistik och politik.
Employment and Economic Activity in Different Swedish Border Regions2015Inngår i: 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, s. 45-57Konferansepaper (Fagfellevurdert)

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.

• 3.
Högskolan Väst, Institutionen för ekonomi och it, Avd för juridik, politik och ekonomi. Högskolan Väst, Institutionen för ekonomi och it, Avd för juridik, ekonomi, statistik och politik.
Högskolan Väst, Institutionen för ekonomi och it, Avd för juridik, politik och ekonomi. Högskolan Väst, Institutionen för ekonomi och it, Avd för juridik, ekonomi, statistik och politik.
University Colleges Effect on Municipal Growth in Swedish Middle-sized Municipalities2008Inngår i: 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, s. 85-98Konferansepaper (Fagfellevurdert)

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.

• 4.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
Generalizations of the normal basis theorem2004Inngår i: Mathematica Scandinavica, ISSN 0025-5521, E-ISSN 1903-1807, Vol. 94, s. 5s. 185-190Artikkel i tidsskrift (Fagfellevurdert)
• 5.
Högskolan Väst, Institutionen för ingenjörsvetenskap.
University Pierre and Marie Curie, Paris, France.
Non equilibrium ionization in magnetized two-temperature thermal plasma2011Inngår i: Kinetic and Related Models, ISSN 1937-5093, E-ISSN 1937-5077, ISSN 1, Vol. 4, nr 3, s. 669-700Artikkel i tidsskrift (Fagfellevurdert)

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.

• 6.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för maskinteknik.
A Comparison between Moving Mesh Implementations for Metal Deposition Simulations2006Inngår i: Proceedings of the Nordic COMSOL Conference: Lyngby, Denmark, 2006, s. 107-110Konferansepaper (Annet vitenskapelig)
• 7.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
An Investigation of Mesh Moving Methods for Simulating the Deformation of Incompressible Fluid Bodies2009Inngår i: COMSOL Conference: 14-16 okt. 2009, Milan, 2009Konferansepaper (Annet vitenskapelig)

In this article we apply a finite element method for approximating the geometrical deformation of a two dimensional incompressible fluid body the flow velocity of which is not constrained along its top boundary. As a pressure force is applied on the free boundary, the domain occupied by the fluid deforms. There are several well established methods for treating this type of problem. The purpose of the present work is to investigate the computational efficiency of a number domain-mapping methods, which are akin to many solid mechanical applications involving large deformations, in that they employ a mapping of the initial configuration range onto the current. However, in fluid dynamical applications the deformation of the fluid body may be very large and contain several vortices. When employing domain-mapping methods, the spatial representations of the element domains are attached to the motion, and the Lagrange formulation is therefore inadequate. Instead we wish to find a motion which minimizes the element deformations and the computational complexity of the problem, while satisfying the kinematic constraint along the boundaries.

• 8.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för industriell produktion.
Weld Pool Simulations2008Licentiatavhandling, monografi (Annet vitenskapelig)

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

• 9.
Royal Institute of Technology Division of Geodesy .
On the estimation of variance in unstable condition adjustment models2011Inngår i: Acta Geodaetica et Geophysica Hungarica, ISSN 1217-8977, E-ISSN 1587-1037, ISSN 1217-8977, Vol. 46, nr 1, s. 71-83Artikkel i tidsskrift (Fagfellevurdert)

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.

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• 10.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för data-, elektro- och lantmäteriteknik. Royal Institute of Technology, Division of Geodesy, Stockholm, Sweden .
Royal Institute of Technology, Division of Geodesy, Stockholm, Sweden .
The modified best quadratic unbiased non-negative estimator (MBQUNE) of variance components2008Inngår i: Studia Geophysica et Geodaetica, ISSN 0039-3169, E-ISSN 1573-1626, Vol. 52, nr 3, s. 305-320Artikkel i tidsskrift (Fagfellevurdert)

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.

• 11.
Högskolan Väst, Institutionen för ekonomi och it, Avd för informatik.
Technische Hochschule Nürnberg Georg Simon Ohm / University Nuremberg, Germany.
Das älteste gedruckte schwedische Rechenbuch (Aegidius Aurelius, Arithmetica, Uppsala 1614): (Aegidius Aurelius, Arithmetica, Uppsala 1614)2017Inngår i: 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, s. 313-326Konferansepaper (Annet vitenskapelig)
• 12.
Högskolan Väst, Institutionen för ekonomi och it, Avd för datavetenskap och informatik.
M12: Medicinsk statistik2004 (oppl. 1)Bok (Annet vitenskapelig)
• 13.
Högskolan Väst, Institutionen för arbete, ekonomi och hälsa (HTU).
Statistical issues: significantly important in medical research.2002Inngår i: Allergy. European Journal of Allergy and Clinical Immunology, ISSN 0105-4538, E-ISSN 1398-9995, Vol. 57, nr 2, s. 76-82Artikkel, forskningsoversikt (Annet vitenskapelig)
• 14.
Högskolan Väst, Institutionen för ekonomi och it, Avd för datavetenskap och informatik.
Statistiska metoder för kvalitetsutveckling1997 (oppl. 1)Bok (Annet vitenskapelig)
• 15.
Högskolan Väst, Institutionen för ekonomi och it, Avd för datavetenskap och informatik.
Högskolan Väst, Institutionen för ekonomi och it, Avd för datavetenskap och informatik.
Www means win win win in education: some experiences from online courses in applied statistics2010Inngår i: OZCOTS 2010 Proceedings of the 7th Australian Conferenceon Teaching Statistics / [ed] Helen MacGillivray & Brian Phillips, Statistical society of Australia , 2010, s. 51-56Konferansepaper (Fagfellevurdert)

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.

• 16.
Högskolan Väst, Institutionen för individ och samhälle.
Högskolan Väst, Institutionen för individ och samhälle, Avd för utbildningsvetenskap och språk.
Gymnasielevers problem med procenträkning.2009Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave

• 17.
McMaster University, Department of Chemistry and Chemical Biology.
Pontificia Universidad Catlica de Chile, Facultad de Qumica, Laboratorio de Qumica Terica Computacional (QTC). Pontificia Universidad Catlica de Chile, Facultad de Qumica, Laboratorio de Qumica Terica Computacional (QTC). Högskolan Väst, Institutionen för ekonomi och it, Avd för datavetenskap och informatik. Högskolan Väst, Institutionen för ekonomi och it, Avd för datavetenskap och informatik. McMaster University, Department of Chemistry and Chemical Biology.
Pointing the way to the products Comparison of the stress tensor and the second-derivative tensor of the electron density2011Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 134, nr 23, s. 234106-Artikkel i tidsskrift (Fagfellevurdert)

The eigenvectors of the electronic stress tensor can be used to identify where new bond paths form in a chemical reaction. In cases where the eigenvectors of the stress tensor are not available, the gradient-expansion- approximation suggests using the eigenvalues of the second derivative tensor of the electron density instead; this approximation can be made quantitatively accurate by scaling and shifting the second-derivative tensor, but it has a weaker physical basis and less predictive power for chemical reactivity than the stress tensor. These tools provide an extension of the quantum theory of atoms and molecules from the characterization of molecular electronic structure to the prediction of chemical reactivity. Â© 2011 American Institute of Physics.

• 18.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
A finite element method on composite grids based on Nitsche's method2002Rapport (Annet (populærvitenskap, debatt, mm))
• 19.
Department of Geodesy and Geomatics, Zanjan University, Iran.
Royal Institute of Technology, Stockholm, Sweden.
Estimating variance components of ellipsoidal, orthometric and geoidalheights through the GPS/levelling Network in Iran2008Inngår i: Journal of the Earth and Space Physics, Vol. 34, nr 3, s. 1-13Artikkel i tidsskrift (Fagfellevurdert)

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.

• 20.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för maskinteknik. Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Industriell ekonomi, Elektro- och Maskinteknik.
Competence development through Project-based learning in higher education i Sweden and England2012Inngår i: 40th annual congress of the Nordic Educational Research association, NPFP/NERA: 8-10 mars, 2012, Copenhagen, Aarhus: Department of Eduation, Aarhus University , 2012, s. 286-Konferansepaper (Fagfellevurdert)

The focus of higher education curricula has been changing from factual knowledge acquisition to developing students competences in response to a changing professional environment in the context of a knowledge economy and labour market globalisation.

Despite these social changes, existing teaching and learning strategies in Engineering are still mainly lecture-based.

We investigate competence development using a Project- Based Learning (PrBL) environment on a range of Engineering programmes at Lancaster University, UK and Högskolan VÃ¤st, Sweden. We evaluate the PrBL potential to enhance student employability prospects.

PrBL is an example of collaborative student-focussed learning underpinned by constructivist theory which encourages deeper learning via construction of meaning, connection of ideas and creation of meaningful artefacts. PrBL stimulates collaborative knowledge building among participants and develops a range of skills through creating an informal learning environment. First and second-year students on undergraduate programmes in Engineering departments in both universities with projects as part of their course participated in this study. In the UK the students had to design, build and test two types of robots. The Swedish students were given a project to make calculations for a pump with preset parameters. The projects were designed to help the students acquire competences relevant to their future career. All students worked in small groups. After finishing their projects, the students completed an open-ended questionnaire about their experiences.

The students evaluated PrBL positively, stating that they developed problem solving and analytical skills and the ability to apply mathematical tools. They highly rated collaboration with peers and emphasised the necessity of developing time management, communication and organisational skills.

Higher education systems in Europe including Scandinavia are facing new challenges in developing students' employability. We conclude with recommendations for promoting PrBL in university courses as it contributes to competence development and is an efficient tool when administrative resources are limited and when academic staff are faced with large student numbers.

• 21.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för maskinteknik och naturvetenskap.
Evaluation of a Surrogate Based Method for Global Optimization2015Inngår i: International Journal of Computer, Electrical, Automation, Control and Information Engineering, E-ISSN 1307-6892, Vol. 9, nr 7, s. 1636-1642Artikkel i tidsskrift (Fagfellevurdert)

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.

• 22.
Högskolan Väst, Institutionen för ingenjörsvetenskap.
Robustness analysis of airfoil performance: DETC2010-282612010Inngår i: 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, s. 1-6Konferansepaper (Fagfellevurdert)

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.

• 23.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för maskinteknik och naturvetenskap.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för maskinteknik och naturvetenskap.
A surrogate model based global optimization method2008Inngår i: 38th International Conference on Computers and Industrial Engineering 2008, 2008, s. 226-232Konferansepaper (Fagfellevurdert)

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.

• 24.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Brauer group rings2004Inngår i: JP Journal of Algebra, Number Theory & Applications, Vol. 4, s. 22s. 465-494Artikkel i tidsskrift (Fagfellevurdert)
• 25.
Högskolan Väst, Institutionen för teknik (HTU).
Cohomology and Self-dual Normal Bases for Infinite Galois Field Extensions2002Inngår i: Journal of Algebra, ISSN 0021-8693, E-ISSN 1090-266X, Vol. 256, s. 531-541Artikkel i tidsskrift (Fagfellevurdert)

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.

• 26.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för matematik och naturvetenskap.
Cohomology and the normal basis theorem2007Inngår i: Indagationes mathematicae, ISSN 0019-3577, E-ISSN 1872-6100, Vol. 18, s. 69-72Artikkel i tidsskrift (Fagfellevurdert)
• 27.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Crossed product algebras defined by separable extensions2005Inngår i: Journal of Algebra, ISSN 0021-8693, E-ISSN 1090-266X, Vol. 283, s. 14s. 723-737Artikkel i tidsskrift (Fagfellevurdert)
• 28.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Fuzzified categories of composition graphs2005Rapport (Annet (populærvitenskap, debatt, mm))

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.

• 29.
Högskolan Väst, Institutionen för teknik (HTU). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
Generalized Brauer Algebras2002Inngår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 30, nr 5, s. 2229-2270Artikkel i tidsskrift (Fagfellevurdert)

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.

• 30.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för naturvetenskap, lantmäteri- och maskinteknik.
Good Magma Gradings On Rings2014Inngår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 42, nr 12, s. 5357-5373Artikkel i tidsskrift (Fagfellevurdert)

Suppose that G and H are magmas and that R is a strongly G-graded ring. We show that there is a bijection between the set of good (zero) H-gradings of R and the set of (zero) magma homomorphisms from G to H. Thereby we generalize a result by Dascalescu, Ion, Nastasescu and Rios Montes from group gradings of matrix rings to strongly magma graded rings. We also show that there is an isomorphism between the preordered set of good (zero) H-filters on R and the preordered set of (zero) submagmas of G \times H. These results are applied to category graded rings and, in particular, to the case when G and H are groupoids. In the latter case, we use this bijection to determine the cardinality of the set of good H-gradings on R.

• 31.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för lantmäteriteknik och matematik.
Hilbert 90 for Rings with ConjugationManuskript (preprint) (Annet vitenskapelig)

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.

• 32.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för lantmäteriteknik och matematik.
Hilbert 90 for algebras with conjugation2012Inngår i: Algebras and Representation Theory, ISSN 1386-923X, E-ISSN 1572-9079, Vol. 15, nr 1, s. 119-135Artikkel i tidsskrift (Fagfellevurdert)

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.

• 33.
Högskolan Väst, Institutionen för teknik (HTU).
Normal Bases for Infinite Galois Ring Extensions1999Inngår i: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 79, s. 235-240Artikkel i tidsskrift (Fagfellevurdert)
• 34.
Högskolan Väst, Institutionen för teknik (HTU). Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för Matematik, Data- och Lantmäteriteknik.
Normal Integral Bases for Infinite Abelian Extensions2001Inngår i: Acta Arithmetica, ISSN 0065-1036, E-ISSN 1730-6264, Vol. 100, s. 79-83Artikkel i tidsskrift (Fagfellevurdert)
• 35.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för lantmäteriteknik och matematik.
Pythagoreiska tripplar på sex olika sätt2008Inngår i: Normat, ISSN 0801-3500, Vol. 56, nr 3, s. 111-119Artikkel i tidsskrift (Fagfellevurdert)

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.

• 36.
Högskolan Väst, Institutionen för teknik (HTU).
Self-dual Normal Bases for Infinite Galois Field Extensions1998Inngår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 26, s. 4331-4341Artikkel i tidsskrift (Fagfellevurdert)
• 37.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Self-dual normal bases for infinite odd abelian Galois ring extensions2006Inngår i: Acta Arithmetica, ISSN 0065-1036, E-ISSN 1730-6264, Vol. 123, nr 1, s. 1-8Artikkel i tidsskrift (Fagfellevurdert)
• 38.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Self-dual Normal Integral Bases for Infinite Unramified Extensions2002Inngår i: Journal of Number Theory, ISSN 0022-314X, E-ISSN 1096-1658, Vol. 97, nr 2, s. 350-367Artikkel i tidsskrift (Fagfellevurdert)

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.

• 39.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap, Avd för matematik och naturvetenskap.
Separable Groupoid Rings2006Inngår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 34, nr 8, s. 3029-3041Artikkel i tidsskrift (Fagfellevurdert)

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

• 40.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Separable groupoid rings2006Inngår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 34, s. 13s. 3029-3041Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
• 41.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
The category of groupoid graded modules2004Inngår i: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 100, s. 15s. 195-211Artikkel i tidsskrift (Fagfellevurdert)
• 42.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
The Picard Groupoid and Strongly Groupoid Graded Modules2006Inngår i: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 106, s. 1-13Artikkel i tidsskrift (Fagfellevurdert)
• 43.
Högskolan Väst, Institutionen för ingenjörsvetenskap.
The Picard Groupoid and Strongly Groupoid Graded Modules2006Inngår i: Colloquium Mathematicum, ISSN 0010-1354, E-ISSN 1730-6302, Vol. 106, s. 1-13Artikkel i tidsskrift (Fagfellevurdert)
• 44.
Högskolan Väst, Institutionen för teknik, matematik och datavetenskap.
Von Neumann finite endomorphism rings2003Inngår i: Indagationes mathematicae, ISSN 0019-3577, E-ISSN 1872-6100, Vol. 14, s. 9s. 223-232Artikkel i tidsskrift (Fagfellevurdert)
• 45.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för lantmäteriteknik och matematik.
Weak topological functors2008Inngår i: Journal of Generalized Lie Theory and Applications, ISSN 1736-5279, E-ISSN 1736-4337, Vol. 2, nr 3, s. 211-215Artikkel i tidsskrift (Fagfellevurdert)

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

• 46.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för lantmäteriteknik och matematik.
Commutativity and Ideals in Category Crossed Products2010Inngår i: Proceedings of the Estonian Academy of Sciences: Physics, Mathematics, ISSN 1406-0086, E-ISSN 2228-0685, Vol. 59, nr 4, s. 338-346Artikkel i tidsskrift (Fagfellevurdert)
• 47.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för lantmäteriteknik och matematik.
LTH.
Miyashita Action in Strongly Groupoid Graded RingsManuskript (preprint) (Annet vitenskapelig)

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.

• 48.
Högskolan Väst, Institutionen för ingenjörsvetenskap.
LTH.
Miyashita Action in Strongly Groupoid Graded Rings2012Inngår i: International Electronic Journal of Algebra, ISSN 1306-6048, E-ISSN 1306-6048, Vol. 11, s. 46-63Artikkel i tidsskrift (Fagfellevurdert)

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.

• 49.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för elektro, lantmäteri och naturvetenskap.
Köpenhamns Universitet.
Skew category algebras associated with partially defined dynamical systems2012Inngår i: International Journal of Mathematics, ISSN 0129-167X, Vol. 23, nr 4, s. 16-Artikkel i tidsskrift (Fagfellevurdert)

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.

• 50.
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avd för lantmäteriteknik och matematik.
LTH.
The Ideal Intersection Property for Groupoid Graded Rings2012Inngår i: Communications in Algebra, ISSN 0092-7872, E-ISSN 1532-4125, Vol. 40, nr 5, s. 1860-1871Artikkel i tidsskrift (Fagfellevurdert)

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.

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