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  • 101.
    Bååk, Linda
    Örebro University, Swedish Business School at Örebro University.
    Varför gör de på detta viset??: En studie om bakgrundsfaktorerna till alkohol- och tobaksbruk bland ungdomar2009Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 102.
    Cai, Yan-an
    et al.
    Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing, China; Wu Wen Tsun Key Laboratory of Mathematics, Chinese Academy of Science, School of Mathematical Sciences, University of Science and Technology of China, Hefei, Anhui, China.
    Liu, Genqiang
    School of Mathematics and Statistics, Henan University, Kaifeng, China.
    Nilsson, Jonathan
    Örebro University, School of Science and Technology. Department of Mathematics.
    Zhao, Kaiming
    College of Mathematics and Information Science, Hebei Normal (Teachers) University, Shijiazhuang, Hebei, China; Department of Mathematics, Wilfrid Laurier University, Waterloo, ON, Canada.
    Generalized Verma modules over sl(n+2) induced from u(h(n))-free sl(n+1)-modules2018In: Journal of Algebra, ISSN 0021-8693, E-ISSN 1090-266X, Vol. 502, p. 146-162Article in journal (Refereed)
    Abstract [en]

    A class of generalized Verma modules over sl(n+2) are constructed from sl(n+1)-modules which are u(h(n))-free modules of rank 1. The necessary and sufficient conditions for these sl(n+2)-modules to be simple are determined. This leads to a class of new simple sl(n+2)-modules.

  • 103.
    Cakmak, Miray
    Örebro University, School of Science and Technology.
    Användning av den interaktiva skrivtavlan i matematikundervisning: Fördelar respektive utmaningar med den interaktiva skrivtavlan2017Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The interactive writing board is a lesson instrument that is available today, in the most Swedish schools. The purpose of the study is to examine how teachers describe its use of interactive writing boards in teaching mathematics and how often they use it. In order to answer my questions, I have done a qualitative study, where I interviewed five teachers who work in grades 1-3 and are using the interactive writing board, but also examined what the literature says. To find out what kind of knowledge the teachers express, I have compared my result of analysis against Shulmans (1986) theory about TPACK - Technical, Pedagogical and Content Knowledge. TPACK has three different areas consisting of technical knowledge, pedagogical knowledge and content knowledge. It's only when these three knowledges interact with each other, that you get a good teaching. These knowledges are important knowledge that teachers need to use interactive writing boards in mathematics teaching, but also to promote students' learning and commitment.

  • 104.
    Calson Öhman, Frida
    et al.
    Örebro University, Örebro University School of Business.
    Lindberg, Mikaela
    Örebro University, Örebro University School of Business.
    Fotbollsklubbars prestationer och deras effekt på aktiekursen: - En statistisk studie om huruvida skillnaden mellan matchresultat och förväntat matchresultat påverkar fotbollsklubbars aktiekurser2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 105.
    Carlsen, Martin
    et al.
    Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Darula, Radoslav
    Aalborg University, Aalborg, Denmark.
    Gravesen, Jens
    Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Hjorth, Poul G.
    Dynamical systems, Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Jørgensen, H. B.
    University of Southern Denmark, Odense, Denmark.
    Nguyen, Dang Manh
    Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Nielsen, Peter Nørtoft
    Geometry, Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Olsen, J.
    Joltech, Sønderborg, Denmark.
    Petersen, H. G.
    University of Southern Denmark, Odense, Denmark.
    Røgen, Peter
    Geometry, Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Ögren, Magnus
    Department of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    Efficiency of a gyroscopic device for conversion of mechanical wave energy to electric energy: Technical report from ESGI-83 workshop in industrial mathematics 20112011Report (Other academic)
    Abstract [en]

    We consider a recently proposed gyroscopic device for conversion of mechanical ocean wave energy to electrical energy. Two models of the device derived from standard engineering mechanics from the literature are analysed, and a model is derived from analytical mechanics considerations. From these models, estimates of the power production, efficiency, forces and moments are made. We find that it is possible to extract a significant amount of energy from an ocean wave using the described device. Further studies are required for a full treatment of the device.

  • 106.
    Carlsson, Fredrik
    Örebro University, Örebro University School of Business.
    Modell för att beräkna förväntad utlåningsvolym till kommuner med ett eget certifikatprogram2012Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 107.
    Carlsson, Lars
    Örebro University, Örebro University School of Business.
    HUR MAN VINNER ÖVER SPELBOLAGEN: Detta är ett examensarbete i Statistik där författaren beskriver oddssättningen samt analyserar svenska elitverksamheten i speedway2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 108.
    Carlsson, Martin
    Örebro University, Örebro University School of Business.
    The Calibration Estimator and Measurement Error in the Auxiliary Information2018Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 109.
    Carlsson, Martin
    Örebro University, Örebro University School of Business.
    Variance Estimation of the Calibration Estimator with Measurement Errors in the Auxiliary Information2018Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
  • 110.
    Carlsson, Sofia
    Örebro University, School of Science and Technology.
    Elevers matematiska mindset: - En undersökning om elevers syn på matematiskt lärande.2018Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The mathematical mindset of pupils affects the way they view mathematical learning which in turn affects their own learning and achievements. However, a pupil’s mathematical mindset is not necessarily fixed but can hold a certain variation. To enable teachers to help their pupils develop a growth mindset and, in that way, promote pupils’ learning, the present study aims to contribute with increased knowledge of various aspects of pupils' mathematical mindset by investigating in what way pupils' mindset can vary. For the survey, a quantitative survey has been used, in which a total of 137 pupils from one elementary school have participated. The result of the study indicates that pupils’ mathematical mindset can vary both between and within the tree components innate ability, effort and mistakes, which together constitutes a mathematical mindset. The variation shows that the pupils possess a more complete growth mindset in relation to the components effort and mistakes compared to the component innate ability. The discussion section discusses, among other things, that the work with sociomathematic norms in classrooms might be an influence on which mathematical mindset the pupils possess to the different components.

  • 111.
    Carlsson, Sofia
    Örebro University, School of Science and Technology.
    Vad påverkar elevers attityder till matematik?: En systematisk litteraturstudie med fokus på hur positiva attityder kan främjas.2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In society today, mathematics appears to be a boring and difficult subject that only some people can manage. Many students have negative attitudes towards the subject, which means that their interest in what is thought in the math lessons decreases and they are missing out on opportunities to learn. To promote pupils' learning in mathematics and to prevent students from taking their negative attitudes into adulthood, the present study aims to investigate what effects various kinds of influences may have on students’ attitudes towards mathematics and, above all, how they can be positively influenced. For the survey, a systematic literature study has been used and the basis for the compiled research overview has been retrieved from the Web of Science database. The results of the study indicate that there are several types of influences on pupils’ attitudes towards mathematics and that the influence both can have a positive and a negative effect depending on how it is handled and expressed. However, the most important types of influences can be summarized into social factors, the students' perspective on the subject and on who they think can manage it and the student´s believes of mathematics and the teaching as a meaningful subject.

  • 112.
    Chababi, Marie-Joelle
    et al.
    Örebro University, Örebro University School of Business.
    Mustafa, Shpend
    Örebro University, Örebro University School of Business.
    Korruption i de sydeuropeiska EU-länderna: En tillämpning av den strukturella ekvationsmodellen (SEM)2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 113.
    Chammas, Peter
    et al.
    Örebro University, Örebro University School of Business.
    Kacharov, Daniel
    Örebro University, Örebro University School of Business.
    Den sjunde spelaren på isen: En studie av faktorer som påverkar biljettefterfrågan i SHL 2015–2018 och prediktioner över klubbarnas potentiellt missade intäkter.2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 114.
    Chen, Yu
    Örebro University, Örebro University School of Business.
    FORECASTING WITH MIXED FREQUENCY DATA:MIDAS VERSUS STATE SPACE DYNAMIC FACTOR MODEL: AN APPLICATION TO FORECASTING SWEDISH GDP GROWTH2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Most macroeconomic activity series such as Swedish GDP growth are collected quarterly while an important proportion of time series are recorded at a higher frequency. Thus, policy and business decision makers are often confront with the problems of forecasting and assessing current business and economy state via incomplete statistical data due to publication lags. In this paper, we survey a few general methods and examine different models for mixed frequency issues. We mainly compare mixed data sampling regression (MIDAS) and state space dynamic factor model (SS-DFM) by the comparison experiments forecasting Swedish GDP growth with various economic indicators. We find that single-indicator MIDAS is a wise choice when the explanatory variable is coincident with the target series; that an AR term enables MIDAS more promising since it considers autoregressive behaviour of the target series and makes the dynamic construction more flexible; that SS-DFM and M-MIDAS are the most outstanding models and M-MIDAS dominates undoubtedly at short horizons up to 6 months, whereas SS-DFM is more reliable at long predictive horizons. And finally we conclude that there is no perfect winner because each model can dominate in a special situation.

  • 115.
    Cheng, Xiaoliang
    et al.
    Department of Mathematics, Zhejiang University, Hangzhou, Zhejiang, China.
    Lin, Guangliang
    Department of Mathematics, Zhejiang University, Hangzhou, Zhejiang, China.
    Zhang, Ye
    Örebro University, School of Science and Technology. Department of Mathematics.
    Gong, Rongfang
    Department of Mathematics, Nanjing University of Aeronautics and Astronautics, Nanjing, China.
    Gulliksson, Mårten
    Örebro University, School of Science and Technology. Department of Mathematics.
    A modified coupled complex boundary method for an inverse chromatography problem2018In: Journal of Inverse and Ill-Posed Problems, ISSN 0928-0219, E-ISSN 1569-3945, Vol. 26, no 1, p. 33-49Article in journal (Refereed)
    Abstract [en]

    Adsorption isotherms are the most important parameters in rigorous models of chromatographic processes. In this paper, in order to recover adsorption isotherms, we consider a coupled complex boundary method (CCBM), which was previously proposed for solving an inverse source problem [2]. With CCBM, the original boundary fitting problem is transferred to a domain fitting problem. Thus, this method has advantages regarding robustness and computation in reconstruction. In contrast to the traditional CCBM, for the sake of the reduction of computational complexity and computational cost, the recovered adsorption isotherm only corresponds to the real part of the solution of a forward complex initial boundary value problem. Furthermore, we take into account the position of the profiles and apply the momentum criterion to improve the optimization progress. Using Tikhonov regularization, the well-posedness, convergence properties and regularization parameter selection methods are studied. Based on an adjoint technique, we derive the exact Jacobian of the objective function and give an algorithm to reconstruct the adsorption isotherm. Finally, numerical simulations are given to show the feasibility and efficiency of the proposed regularization method.

  • 116.
    Corboz, Philippe
    et al.
    School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Ögren, Magnus
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Kheruntsyan, Karén
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Corney, Joel F.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, The University of Queensland, Brisbane Qld, Australia.
    Phase-space methods for fermions2013In: Quantum Gases: Finite Temperature and Non-Equilibrium Dynamics / [ed] Davis, M.; Gardiner, S.; Proukakis, N.; Szymańska, M., London: Imperial College Press, 2013, p. 407-416Chapter in book (Other academic)
    Abstract [en]

    We review phase-space simulation techniques for fermions, showing how a Gaussian operator basis leads to exact calculations of the evolution of a many-body quantum system in both real and imaginary time. We apply such techniques to the Hubbard model and to the problem of molecular dissociation of bosonic molecules into pairs of fermionic atoms.

  • 117.
    Daas, Piet
    et al.
    Centraal Bureau voor de Statistiek (CBS), The Hague, The Netherlands.
    Tennekes, Martijn
    Centraal Bureau voor de Statistiek (CBS), The Hague, The Netherlands.
    Ossen, Saskia
    Centraal Bureau voor de Statistiek (CBS), The Hague, The Netherlands.
    Di Bella, Grazia
    Istituto Nazionale di Statistica (ISTAT), Rome, Italy.
    Galiè, Lorena
    Istituto Nazionale di Statistica (ISTAT), Rome, Italy.
    Laitila, Thomas
    Statistiska centralbyrån, Stockholm, Sweden.
    Lennartsson, Daniel
    Statistiska centralbyrån, Stockholm, Sweden.
    Nilsson, Richard
    Statistiska centralbyrån, Stockholm, Sweden.
    Wallgren, Anders
    Statistiska centralbyrån, Stockholm, Sweden.
    Wallgren, Britt
    Statistiska centralbyrån, Stockholm, Sweden.
    Guidelines on the usage of the prototype of the computerized version of QRCA, and Report on the overall evaluation results. (Deliverable WP8.2)2013Report (Refereed)
    Abstract [en]

    In this report the findings of the evaluation of various administrative data sources used by Dutch, Italian and Swedish National Statistical Institutes are reported. Administrative data sources were studied from both the data source quality and input oriented output quality point of view (deliverable 4.2). Since not all of the institutes were able to directly apply the statistical measurement methods implemented in the R-package developed in WP 4 (deliverable 4.3), the measurement methods required were implemented in the (standard) programming language of choice for each institute. The experiences and results obtained by the NSIs involved are generally discussed in this report. In the appendices, the findings of each source foreach individual NSI are included. This report also contains the manual for the methods implemented in the dataquality R-package and the most recent version of the Quality Report Card for Administrative data (QRCA).

  • 118.
    Dahl, Tobias
    et al.
    Örebro University, Department of Business, Economics, Statistics and Informatics.
    Kling, Anna-Maria
    Örebro University, Department of Business, Economics, Statistics and Informatics.
    En utvärdering av det nyutvecklade formuläret BiS med avseende på validitet och reliabilitet2006Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Uppsatsens syfte var att utvärdera ett nyutvecklat formulär, BiS. Formuläret används av Ryggkirurgiska kliniken i Strängnäs för att utvärdera behandlingseffekt efter operation av patienter med ryggbesvär.

    Formuläret har utvärderats med avseende på validitet och reliabilitet med hjälp av statistiska mått för ordningskonsistens och enighet.

    Utifrån den statistiska bearbetningen samt saklogiska resonemang har vi dragit slutsatsen att formuläret har hög validitet och reliabilitet.

  • 119.
    Dai, Xiaoxia
    et al.
    School of Computing Science, Zhejiang University City College, Hangzhou, People’s Republic of China.
    Zhang, Chengwei
    School of Computing Science, Zhejiang University City College, Hangzhou, People’s Republic of China.
    Zhang, Ye
    Örebro University, School of Science and Technology.
    Gulliksson, Mårten
    Örebro University, School of Science and Technology.
    Topology optimization of steady Navier-Stokes flow via a piecewise constant level set method2018In: Structural and multidisciplinary optimization (Print), ISSN 1615-147X, E-ISSN 1615-1488, Vol. 57, no 6, p. 2193-2203Article in journal (Refereed)
    Abstract [en]

    This paper presents a piecewise constant level set method for the topology optimization of steady Navier- Stokes flow. Combining piecewise constant level set functions and artificial friction force, the optimization problem is formulated and analyzed based on a design variable. The topology sensitivities are computed by the adjoint method based on Lagrangian multipliers. In the optimization procedure, the piecewise constant level set function is updated by a new descent method, without the needing to solve the Hamilton-Jacobi equation. To achieve optimization, the piecewise constant level set method does not track the boundaries between the different materials but instead through the regional division, which can easily create small holes without topological derivatives. Furthermore, we make some attempts to avoid updating the Lagrangian multipliers and to deal with the constraints easily. The algorithm is very simple to implement, and it is possible to obtain the optimal solution by iterating a few steps. Several numerical examples for both two- and three-dimensional problems are provided, to demonstrate the validity and efficiency of the proposed method.

  • 120.
    Dai, Yanjiao
    Örebro University, Örebro University School of Business.
    Quantile Analysis on Provincial Household Income and Convergence in China2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 121.
    Danesh, Sabri
    Örebro University, Örebro University School of Business.
    BIG DATA: From hype to reality2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Big data is all of a sudden everywhere. It is too big to ignore!It has been six decades since the computer revolution, four decades after the development of the microchip, and two decades of the modern Internet! More than a decade after the 90s “.com” fizz, can Big Data be the next Big Bang? Big data reveals part of our daily lives. It has the potential to solve virtually any problem for a better urbanized global. Big Data sources are also very interesting from an official statistics point of view. The purpose of this paper is to explore the conceptions of big data and opportunities and challenges associated with using big data especially in official statistics.

    “A petabyte is the equivalent of 1,000 terabytes, or a quadrillion bytes. One terabyte is a thousand gigabytes. One gigabyte is made up of a thousand megabytes. There are a thousand thousand—i.e., a million—petabytes in a zettabyte” (Shaw 2014). And this is to be continued…

  • 122.
    Danesh, Sabri
    Örebro University, Örebro University School of Business.
    Invandring - vinst eller förlust för kommunerna?: En studie om sambandet mellan kommunernas offentliga finanser och invandring2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 123.
    Daniel, Alberto
    Örebro University, School of Science and Technology.
    An Introduction to Invariant Theory2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This work is an attempt to explain in some detail section III D of the paper:

    N.J.A. Sloane. "Error-correcting codes and Invariant Theory:

    New application of a Nineteenth-Century Technique". For that, we will be concerned with polynomial invariants of  finite groups which come from a group action. We will introduce the basic notions of Invariant Theory to give an almost self-contained proof of Molien's theorem, and also present applications on linear codes.

  • 124. Danielsson, Christina Bodin
    et al.
    Bodin, Lennart
    Örebro University, Swedish Business School at Örebro University.
    Difference in satisfaction with office environment among employees in different office types2009In: Journal of Architectural and Planning Research, ISSN 0738-0895, Vol. 26, no 3, p. 241-257Article in journal (Refereed)
    Abstract [en]

    Differences between office types may have an influence on the employees' satisfaction and psychological responses with respect to different aspects of the office environment. For this study, 469 employees rated their perceptions of and satisfaction with the office environments of seven different office types, which were classified as cell-office, shared-room office, small open-plan office, medium open-plan office, large open-plan office, flex-office, and combi-office. Three domains of environmental factors were analyzed: (1) ambient factors, (2) noise and privacy, and (3) design-related factors. Employee responses were evaluated using multivariate logistic and Poisson regression., Adjustments were made for potential confounders such as age, gender job rank, and line of business. Substantial differences between employees in different office types were found The analysis of frequencies in complaints within the three domains shows that noise and privacy is the domain that causes the most dissatisfaction among office employees. Cell-office employees are most satisfied with the physical environment overall, followed by those in flex-office. However the results for cell-office are not uniformly best, since they score low with regard to the social aspects of design-related factors and, in particular on support of affinity. The most dissatisfaction is reported in medium and large open-plan offices, where the complaints about noise and lack of privacy are especially negative. Architectural and functional features of the offices are discussed as the main explanatory factors for these results.

  • 125.
    Danielsson, Linda
    et al.
    Örebro University, School of Science and Technology.
    Sternefors, Karin
    Örebro University, School of Science and Technology.
    Vad i undervisning genom problemlösning i grupp har forskning visat påverkar elevers matematiska förmågor?2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Problem solving within mathematics teaching has been more highlighted during the last decades. In the Swedish curriculum for primary school problem solving has got a bigger role, being one of five mathematical competencies that students should be given the chance to develop during school. In the Swedish curriculum there is also a focus on communication and how students should get the opportunity to engage in conversations and to reason about mathematics. This can be brought out by letting the students work together with their classmates in different kinds of group constellations. Problem solving in groups can be designed in different ways and affects the development of students’ mathematical competencies. In this systematic literature study three general themes were discovered, on how problem solving in groups can support students in developing their mathematical competencies; how problem solving can be designed, under a longer or shorter period of time, access to supporting structures and tools and the group constellation’s affect.

  • 126.
    Davidsson, Johan
    Örebro University, School of Science and Technology.
    Sobolev Spaces and the Finite Element Method2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this essay we present the Sobolev spaces and some basic properties of them. The Sobolev spaces serve as a theoretical framework for studying solutions to partial differential equations. The finite element method is presented which is a numerical method for solving partial differential equations.

  • 127.
    Demetriades, Lovisa
    et al.
    Örebro University, School of Science and Technology.
    Vikström Björklund, Lisa
    Örebro University, School of Science and Technology.
    Backahallens kombinatoriskaproblem: En undersökning om hur schemaläggningen påverkarinkomsten hos ett racketcenter2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Backahallen är ett racketcenter belägen i Örebro och har en komplex schemaläggning där klubbar, abonnenter och strökunder samsas om de banor och tider hallen erbjuder. Den kundgrupp som betalar minst värderas högst vilket resulterar i att Backahallen får svårt att hålla sin budget om de inte fördelar banorna på korrekt sätt. Genom heltalsoptimering undersöks därför alternativa schemaläggningar för att optimera inkomst och nöjdhet utifrån olika scenarier. Vi undersöker vilka tider som Backahallen bör reglera priser på, hur en utbyggnad påverkar schemaläggningen och därmed nöjdheten hos de mest värderade kunderna och vilket pris samma kunder minst kan betala för att Backahallen fortfarande ska hålla budget. Detta beskrivs, löses och tolkas med hjälp av lämplig optimeringsteori och statistik.

    Resultatet visar på att Backahallen kan påverka sin förväntade inkomst genom att reglera sin schemaläggning och i en del av dessa fall ökar även nöjdheten hos de högst värderade kunderna.

  • 128.
    Demissie, Meaza
    et al.
    Örebro University, Swedish Business School at Örebro University.
    Mascialino, Barbara
    Calza, Stefano
    Pawitan, Yudi
    Unequal group variances in microarray data analyses2008In: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 24, no 9, p. 1168-1174Article in journal (Refereed)
    Abstract [en]

    Motivation: In searching for differentially expressed (DE) genes in microarray data, we often observe a fraction of the genes to have unequal variability between groups. This is not an issue in large samples, where a valid test exists that uses individual variances separately. The problem arises in the small-sample setting, where the approximately valid Welch test lacks sensitivity, while the more sensitive moderated t-test assumes equal variance. Methods: We introduce a moderated Welch test (MWT) that allows unequal variance between groups. It is based on (i) weighting of pooled and unpooled standard errors and (ii) improved estimation of the gene-level variance that exploits the information from across the genes. Results: When a non-trivial proportion of genes has unequal variability, false discovery rate (FDR) estimates based on the standard t and moderated t-tests are often too optimistic, while the standard Welch test has low sensitivity. The MWT is shown to (i) perform better than the standard t, the standard Welch and the moderated t-tests when the variances are unequal between groups and (ii) perform similarly to the moderated t, and better than the standard t and Welch tests when the group variances are equal. These results mean that MWT is more reliable than other existing tests over wider range of data conditions. Availability: R package to perform MWT is available at http://www.meb.ki.se/similar to yudpaw Contact: yudi.pawitan@ki.se Supplementary information: Supplementary data are available at Bioinformatics online.

  • 129.
    Denk, Thomas
    et al.
    Department of Political Science, Åbo Akademi University, Turku, Finland.
    Lehtinen, Sarah
    Department of Political Science, Åbo Akademi University, Turku, Finland.
    Two modes of democratisation: transition and state-formation2016In: Quality & Quantity: International Journal of Methodology, ISSN 0033-5177, Vol. 50, no 6, p. 2331-2346Article in journal (Refereed)
    Abstract [en]

    Previous studies about democracies on a global level have assumed that democratisation occurs when an autocratic regime moves toward becoming a democratic regime. This article recognises an alternative mode to democratic transition: democratisation by state-formation, which occurs when democratic regimes are established in new states as an outcome of state-formation. The article describes how cases of democratisation can be classified according the two modes of democratisation. Furthermore, the classification is applied in illustrative analyses of democratisation on the global level during 1800-2007. The analyses describe how transition and state-formation have affected the global number of democracies. These analyses indicate that both modes of democratisation have empirical relevance and that the classification provides a more complete description of the global development of democracies than previous studies. The main conclusion of this article is therefore a proposal for future studies to include both modes to understand and explain democratisation on the global level.

  • 130.
    Desaling Germay, Meron
    Örebro University, Örebro University School of Business.
    Modeling and Forecasting Unemployment Rate In Sweden using various Econometric Measures2016Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 131.
    Ding, Shutong
    Örebro University, Örebro University School of Business.
    Bayesian VAR models with asymmetric lagsManuscript (preprint) (Other academic)
    Abstract [en]

    Most studies estimate the VAR models with equal lag length. Little attention has been paid to the issue of lag specifications. In this paper we propose VAR models with asymmetric lags via Bayesian sparse learning. Three popular sparse priors, L1-penalized Lasso, the mixture of L1 and L2 penalties elastic net, and spike and slab type are developed using hierarchical Bayes formulation. The model identification performance is assessed with Monte Carlo experiment and the forecasting performance is evaluated with US macroeconomic data.

  • 132.
    Ding, Shutong
    Örebro University, Örebro University School of Business.
    Model choice in Bayesian VAR models2014Doctoral thesis, comprehensive summary (Other academic)
    List of papers
    1. Model averaging and variable selection in VAR models
    Open this publication in new window or tab >>Model averaging and variable selection in VAR models
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Bayesian model averaging and model selection is based on the marginal likelihoods of the competing models. This can, however, not be used directly in VAR models when one of the issues is which - and how many - variables to include in the model since the likelihoods will be for different groups of variables and not directly comparable. One possible solution is to consider the marginal likelihood for a core subset of variables that are always included in the model. This is similar in spirit to a recent proposal for forecast combination based on the predictive likelihood. The two approaches are contrasted and their performance is evaluated in a simulation study and a forecasting exercise. 

    Keywords
    Bayesian model averaging, marginalized likelihood, predictive likelihood
    National Category
    Probability Theory and Statistics
    Research subject
    Statistics
    Identifiers
    urn:nbn:se:oru:diva-35873 (URN)
    Available from: 2014-08-07 Created: 2014-08-07 Last updated: 2017-10-17Bibliographically approved
    2. Bayesian forecasting combination in VAR models with many predictors
    Open this publication in new window or tab >>Bayesian forecasting combination in VAR models with many predictors
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    This paper is motivated by the findings of our previous work, that is forecasting VAR models in the cases of small and medium-sized datasets, both marginalized marginal likelihood and predictive likelihood based averaging approaches tend to produce superior forecasts than the Bayesian VAR methods using shrinkage priors. With an efficient reversible-jump MCMC algorithm, We extend the forecast combination and model averaging of VAR models to the context of large datasets (more than hundred predictors), and consider a range of competitive alternative methods to compare and examine their forecast performance. Our empirical results show that the Bayesian model averaging approach outperforms the various alternatives.

    Keywords
    Bayesian model averaging, large datasets, marginalized marginal likelihood, reversible-jump MCMC
    National Category
    Probability Theory and Statistics
    Research subject
    Statistics
    Identifiers
    urn:nbn:se:oru:diva-35874 (URN)
    Available from: 2014-08-07 Created: 2014-08-07 Last updated: 2017-10-17Bibliographically approved
    3. Bayesian forecasting using reduced rank VARs
    Open this publication in new window or tab >>Bayesian forecasting using reduced rank VARs
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Reduced rank regression has a long tradition as a technique to achieve a parsimonious parameterization in multivariate regression models. Recently this has been applied in the Bayesian VAR framework where the rich parameterization is a common concern in applied work. We advocate a parameterization of the reduced rank VAR which leads to a natural interpretation in terms of a dynamic factor model. Without additional restrictions on the parameters the reduced rank model is unidentified and we consider two identification schemes. The traditional ad-hoc identification with the first rows of one of the reduced rank parameter matrices being the identity matrix and a semi-orthogonal identification originally proposed in the context of cointegrated VAR models with the advantage that it does not depend on the ordering of the variables. Borrowing from the cointegration literature, we propose efficient MCMC algorithms for the evaluation of the posterior distribution given the two identification schemes. The determination of the rank of the reduced rank VAR is an important practical issue and we study the performance of different criteria for determining the rank. Finally, the forecasting performance of the reduced rank VAR model is evaluated in comparison with other popular forecasting models for large data sets.

    Keywords
    Model selection, Bayesian VAR model, Reduced rank regression, Markov chain Monte Carlo
    National Category
    Probability Theory and Statistics
    Research subject
    Statistics
    Identifiers
    urn:nbn:se:oru:diva-35875 (URN)
    Available from: 2014-08-07 Created: 2014-08-07 Last updated: 2017-10-17Bibliographically approved
    4. Bayesian VAR models with asymmetric lags
    Open this publication in new window or tab >>Bayesian VAR models with asymmetric lags
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Most studies estimate the VAR models with equal lag length. Little attention has been paid to the issue of lag specifications. In this paper we propose VAR models with asymmetric lags via Bayesian sparse learning. Three popular sparse priors, L1-penalized Lasso, the mixture of L1 and L2 penalties elastic net, and spike and slab type are developed using hierarchical Bayes formulation. The model identification performance is assessed with Monte Carlo experiment and the forecasting performance is evaluated with US macroeconomic data.

    Keywords
    Bayesian shrinkage, vector autoregression, sparsity, Lasso, elastic net, spike and slab prior, asymmetric lags
    National Category
    Probability Theory and Statistics
    Research subject
    Statistics
    Identifiers
    urn:nbn:se:oru:diva-35876 (URN)
    Available from: 2014-08-07 Created: 2014-08-07 Last updated: 2017-10-17Bibliographically approved
  • 133.
    Ding, Shutong
    Örebro University, Swedish Business School at Örebro University.
    Restrictions on Calibrated Weights2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 134.
    Ding, Shutong
    et al.
    Örebro University, Örebro University School of Business.
    Karlsson, Sune
    Örebro University, Örebro University School of Business.
    Bayesian forecasting combination in VAR models with many predictorsManuscript (preprint) (Other academic)
    Abstract [en]

    This paper is motivated by the findings of our previous work, that is forecasting VAR models in the cases of small and medium-sized datasets, both marginalized marginal likelihood and predictive likelihood based averaging approaches tend to produce superior forecasts than the Bayesian VAR methods using shrinkage priors. With an efficient reversible-jump MCMC algorithm, We extend the forecast combination and model averaging of VAR models to the context of large datasets (more than hundred predictors), and consider a range of competitive alternative methods to compare and examine their forecast performance. Our empirical results show that the Bayesian model averaging approach outperforms the various alternatives.

  • 135.
    Ding, Shutong
    et al.
    Örebro University, Örebro University School of Business.
    Karlsson, Sune
    Örebro University, Örebro University School of Business.
    Bayesian forecasting using reduced rank VARsManuscript (preprint) (Other academic)
    Abstract [en]

    Reduced rank regression has a long tradition as a technique to achieve a parsimonious parameterization in multivariate regression models. Recently this has been applied in the Bayesian VAR framework where the rich parameterization is a common concern in applied work. We advocate a parameterization of the reduced rank VAR which leads to a natural interpretation in terms of a dynamic factor model. Without additional restrictions on the parameters the reduced rank model is unidentified and we consider two identification schemes. The traditional ad-hoc identification with the first rows of one of the reduced rank parameter matrices being the identity matrix and a semi-orthogonal identification originally proposed in the context of cointegrated VAR models with the advantage that it does not depend on the ordering of the variables. Borrowing from the cointegration literature, we propose efficient MCMC algorithms for the evaluation of the posterior distribution given the two identification schemes. The determination of the rank of the reduced rank VAR is an important practical issue and we study the performance of different criteria for determining the rank. Finally, the forecasting performance of the reduced rank VAR model is evaluated in comparison with other popular forecasting models for large data sets.

  • 136.
    Ding, Shutong
    et al.
    Örebro University, Örebro University School of Business.
    Karlsson, Sune
    Örebro University, Örebro University School of Business.
    Model averaging and variable selection in VAR modelsManuscript (preprint) (Other academic)
    Abstract [en]

    Bayesian model averaging and model selection is based on the marginal likelihoods of the competing models. This can, however, not be used directly in VAR models when one of the issues is which - and how many - variables to include in the model since the likelihoods will be for different groups of variables and not directly comparable. One possible solution is to consider the marginal likelihood for a core subset of variables that are always included in the model. This is similar in spirit to a recent proposal for forecast combination based on the predictive likelihood. The two approaches are contrasted and their performance is evaluated in a simulation study and a forecasting exercise. 

  • 137.
    Dmytryshyn, Andrii
    Umeå universitet, Institutionen för datavetenskap.
    Miniversal deformations of pairs of skew-symmetric matrices under congruence2016In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 506, p. 506-534Article in journal (Refereed)
    Abstract [en]

    Miniversal deformations for pairs of skew-symmetric matrices under congruence are constructed. To be precise, for each such a pair (A, B) we provide a normal form with a minimal number of independent parameters to which all pairs of skew-symmetric matrices ((A) over tilde (,) (B) over tilde), close to (A, B) can be reduced by congruence transformation which smoothly depends on the entries of the matrices in the pair ((A) over tilde (,) (B) over tilde). An upper bound on the distance from such a miniversal deformation to (A, B) is derived too. We also present an example of using miniversal deformations for analyzing changes in the canonical structure information (i.e. eigenvalues and minimal indices) of skew-symmetric matrix pairs under perturbations.

  • 138.
    Dmytryshyn, Andrii
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Miniversal deformations of pairs of symmetric matrices under congruence2019In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 568, p. 84-105Article in journal (Refereed)
    Abstract [en]

    For each pair of complex symmetric matrices (A, B) we provide a normal form with a minimal number of independent parameters, to which all pairs of complex symmetric matrices ((A) over tilde (B) over tilde), close to (A, B) can be reduced by congruence transformation that smoothly depends on the entries of (A ) over tilde and (B) over tilde. Such a normal form is called a miniversal deformation of (A, B) under congruence. A number of independent parameters in the miniversal deformation of a symmetric matrix pencil is equal to the codimension of the congruence orbit of this symmetric matrix pencil and is computed too. We also provide an upper bound on the distance from (A, B) to its miniversal deformation.

  • 139.
    Dmytryshyn, Andrii
    Örebro University, School of Science and Technology. Department of Computing Science, Umeå University, Umeå, Sweden.
    Skew-symmetric matrix pencils: stratification theory and tools2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Investigating the properties, explaining, and predicting the behaviour of a physical system described by a system (matrix) pencil often require the understanding of how canonical structure information of the system pencil may change, e.g., how eigenvalues coalesce or split apart, due to perturbations in the matrix pencil elements. Often these system pencils have different block-partitioning and / or symmetries. We study changes of the congruence canonical form of a complex skew-symmetric matrix pencil under small perturbations. The problem of computing the congruence canonical form is known to be ill-posed: both the canonical form and the reduction transformation depend discontinuously on the entries of a pencil. Thus it is important to know the canonical forms of all such pencils that are close to the investigated pencil. One way to investigate this problem is to construct the stratification of orbits and bundles of the pencils. To be precise, for any problem dimension we construct the closure hierarchy graph for congruence orbits or bundles. Each node (vertex) of the graph represents an orbit (or a bundle) and each edge represents the cover/closure relation. Such a relation means that there is a path from one node to another node if and only if a skew-symmetric matrix pencil corresponding to the first node can be transformed by an arbitrarily small perturbation to a skew-symmetric matrix pencil corresponding to the second node. From the graph it is straightforward to identify more degenerate and more generic nearby canonical structures. A necessary (but not sufficient) condition for one orbit being in the closure of another is that the first orbit has larger codimension than the second one. Therefore we compute the codimensions of the congruence orbits (or bundles). It is done via the solutions of an associated homogeneous system of matrix equations. The complete stratification is done by proving the relation between equivalence and congruence for the skew-symmetric matrix pencils. This relation allows us to use the known result about the stratifications of general matrix pencils (under strict equivalence) in order to stratify skew-symmetric matrix pencils under congruence. Matlab functions to work with skew-symmetric matrix pencils and a number of other types of symmetries for matrices and matrix pencils are developed and included in the Matrix Canonical Structure (MCS) Toolbox.

  • 140.
    Dmytryshyn, Andrii
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Structure preserving stratification of skew-symmetric matrix polynomials2015Report (Other academic)
    Abstract [en]

    We study how elementary divisors and minimal indices of a skew-symmetric matrix polynomial of odd degree may change under small perturbations of the matrix coefficients. We investigate these changes qualitatively by constructing the stratifications (closure hierarchy graphs) of orbits and bundles for skew-symmetric linearizations. We also derive the necessary and sufficient conditions for the existence of a skew-symmetric matrix polynomial with prescribed degree, elementary divisors, and minimal indices.

  • 141.
    Dmytryshyn, Andrii
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Structure preserving stratification of skew-symmetric matrix polynomials2017In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 532, p. 266-286Article in journal (Refereed)
    Abstract [en]

    We study how elementary divisors and minimal indices of a skew-symmetric matrix polynomial of odd degree may change under small perturbations of the matrix coefficients. We investigate these changes qualitatively by constructing the stratifications (closure hierarchy graphs) of orbits and bundles for skew-symmetric linearizations. We also derive the necessary and sufficient conditions for the existence of a skew-symmetric matrix polynomial with prescribed degree, elementary divisors, and minimal indices.

  • 142.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Dopico, Froilán M.
    Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain.
    Generic complete eigenstructures for sets of matrix polynomials with bounded rank and degree2017In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 535, p. 213-230Article in journal (Refereed)
    Abstract [en]

    The set POLd,rm×n of m×n complex matrix polynomials of grade d and (normal) rank at most r in a complex (d+1)mn dimensional space is studied. For r=1,...,min{m,n}−1, we show that POLd,rm×n is the union of the closures of the rd+1 sets of matrix polynomials with rank r, degree exactly d, and explicitly described complete eigenstructures. In addition, for the full-rank rectangular polynomials, i.e. r=min{m,n} and mn, we show that POLd,rm×n coincides with the closure of a single set of the polynomials with rank r, degree exactly d, and the described complete eigenstructure. These complete eigenstructures correspond to generic m×n matrix polynomials of grade d and rank at most r.

  • 143.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Dopico, Froilán M.
    Departamento de Matemáticas, Universidad Carlos III de Madrid.
    Generic matrix polynomials with fixed rank and fixed degree2016Report (Other academic)
  • 144.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Dopico, Froilán M.
    Departamento de Matemáticas, Universidad Carlos III de Madrid, Leganés, Spain.
    Generic skew-symmetric matrix polynomials with fixed rank and fixed odd grade2018In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 536, p. 1-18Article in journal (Refereed)
    Abstract [en]

    We show that the set of m×m complex skew-symmetric matrix polynomials of odd grade d, i.e., of degree at most d, and (normal) rank at most 2r is the closure of the single set of matrix polynomials with the certain, explicitly described, complete eigenstructure. This complete eigenstructure corresponds to the most generic m×m complex skew-symmetric matrix polynomials of odd grade d and rank at most 2r. In particular, this result includes the case of skew-symmetric matrix pencils (d=1).

  • 145.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Klymchuk, Tetiana
    Universitat Politècnica de Catalunya, Barcelona, Spain; Taras Shevchenko National University, Kiev, Ukraine.
    Sergeichuk, Vladimir V.
    Institute of Mathematics, Kiev, Ukraine.
    Generalization of Roth's solvability criteria to systems of matrix equations2017In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 527, p. 294-302Article in journal (Refereed)
    Abstract [en]

    W.E. Roth (1952) proved that the matrix equation AX - XB = C has a solution if and only if the matrices [Graphics] and [Graphics] are similar. A. Dmytryshyn and B. Kagstrom (2015) extended Roth's criterion to systems of matrix equations A(i)X(i')M(i) - (NiXi"Bi)-B-sigma i = Ci (i = 1,..., s) with unknown matrices X1,, X-t, in which every X-sigma is X, X-T, or X*. We extend their criterion to systems of complex matrix equations that include the complex conjugation of unknown matrices. We also prove an analogous criterion for systems of quaternion matrix equations. (C) 2017 Elsevier Inc. All rights reserved.

  • 146.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Kågström, Bo
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Klimenko, Lena
    National Technical University of Ukraine “Kyiv Polytechnic Institute”, Kiev, Ukraine.
    Sergeichuk, Vladimir
    Institute of Mathematics, Kiev, Ukraine.
    Change of the congruence canonical form of 2-by-2 and 3-by-3 matrices under perturbations and bundles of matrices under congruence2015In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 469, p. 305-334Article in journal (Refereed)
    Abstract [en]

    We construct the Hasse diagrams G2 and G3 for the closure ordering on the sets of congruence classes of 2 × 2 and 3 × 3 complex matrices. In other words, we construct two directed graphs whose vertices are 2 × 2 or, respectively, 3 × 3 canonical matrices under congruence, and there is a directed path from A to B if and only if A can be transformed by an arbitrarily small perturbation to a matrix that is congruent to B. A bundle of matrices under congruence is defined as a set of square matrices A for which the pencils A + λAT belong to the same bundle under strict equivalence. In support of this definition, we show that all matrices in a congruence bundle of 2 × 2 or 3 × 3 matrices have the same properties with respect to perturbations. We construct the Hasse diagrams G2 B and G3 B for the closure ordering on the sets of congruence bundles of 2 × 2 and, respectively, 3 × 3 matrices. We find the isometry groups of 2 × 2 and 3 × 3 congruence canonical matrices.

  • 147.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Sergeichuk, Vladimir
    Institute of Mathematics, Kiev, Ukraine.
    Miniversal deformations of matrices of bilinear forms2012In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 436, no 7, p. 2670-2700Article in journal (Refereed)
    Abstract [en]

    Arnold [V.I. Arnold, On matrices depending on parameters, Russian Math. Surveys 26 (2) (1971) 29–43] constructed miniversal deformations of square complex matrices under similarity; that is, a simple normal form to which not only a given square matrix A but all matrices B close to it can be reduced by similarity transformations that smoothly depend on the entries of B. We construct miniversal deformations of matrices under congruence.

  • 148.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Futorny, Vyacheslav
    Department of Mathematics, University of São Paulo, São Paulo, Brazil.
    Sergeichuk, Vladimir
    Institute of Mathematics, Kiev, Ukraine.
    Miniversal deformations of matrices under *congruence and reducing transformations2014In: Linear Algebra and its Applications, ISSN 0024-3795, E-ISSN 1873-1856, Vol. 446, no April, p. 388-420Article in journal (Refereed)
    Abstract [en]

    Arnold (1971) [1] constructed a miniversal deformation of a square complex matrix under similarity; that is, a simple normal form to which not only a given square matrix A but all matrices B close to it can be reduced by similarity transformations that smoothly depend on the entries of B. We give miniversal deformations of matrices of sesquilinear forms; that is, of square complex matrices under *congruence, and construct an analytic reducing transformation to a miniversal deformation. Analogous results for matrices under congruence were obtained by Dmytryshyn, Futorny, and Sergeichuk (2012) [11].

  • 149.
    Dmytryshyn, Andrii
    et al.
    Dept. Computing Science, Umeå University, Umeå, Sweden.
    Johansson, Stefan
    Dept. Computing Science, Umeå University, Umeå, Sweden.
    Kågström, Bo
    Dept. Computing Science, Umeå University, Umeå, Sweden.
    Canonical structure transitions of system pencils2015Report (Other academic)
    Abstract [en]

    We investigate the changes under small perturbations of the canonical structure information for a system pencil (A B C D) − s (E 0 0 0), det(E) ≠ 0, associated with a (generalized) linear time-invariant state-space system. The equivalence class of the pencil is taken with respect to feedback-injection equivalence transformation. The results allow to track possible changes under small perturbations of important linear system characteristics.

  • 150.
    Dmytryshyn, Andrii
    et al.
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Johansson, Stefan
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Kågström, Bo
    Department of Computing Science and HPC2N, Umeå University, Umeå, Sweden.
    Canonical structure transitions of system pencils2017In: SIAM Journal on Matrix Analysis and Applications, ISSN 0895-4798, E-ISSN 1095-7162, Vol. 38, no 4, p. 1249-1267Article in journal (Refereed)
    Abstract [en]

    We investigate the changes of the canonical structure information under small perturbations for a system pencil associated with a (generalized) linear time-invariant state-space system. The equivalence class of the pencil is taken with respect to feedback-injection equivalence transformations. The results allow us to track possible changes of important linear system characteristics under small perturbations.

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