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  • 151.
    Brännström, Åke
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Gross, Thilo
    Max-Planck-Institute for Physics of Complex Systems, Nöthnitzer Straße 38, 01187 Dresden, Germany.
    Blasius, Bernd
    Institute for Chemistry and Biology of Marine Environment, Oldenburg University, 26111 Oldenburg, Germany.
    Dieckmann, Ulf
    Evolution and Ecology Program, International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, 2361 Laxenburg, Austria.
    Consequences of fluctuating group size for the evolution of cooperation2011Inngår i: Journal of Mathematical Biology, ISSN 0303-6812, E-ISSN 1432-1416, Vol. 63, nr 2, s. 263-281Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies of cooperation have traditionally focused on discrete games such as the well-known prisoner’s dilemma, in which players choose between two pure strategies: cooperation and defection. Increasingly, however, cooperation is being studied in continuous games that feature a continuum of strategies determining the level of cooperative investment. For the continuous snowdrift game, it has been shown that a gradually evolving monomorphic population may undergo evolutionary branching, resulting in the emergence of a defector strategy that coexists with a cooperator strategy. This phenomenon has been dubbed the ‘tragedy of the commune’. Here we study the effects of fluctuating group size on the tragedy of the commune and derive analytical conditions for evolutionary branching. Our results show that the effects of fluctuating group size on evolutionary dynamics critically depend on the structure of payoff functions. For games with additively separable benefits and costs, fluctuations in group size make evolutionary branching less likely, and sufficiently large fluctuations in group size can always turn an evolutionary branching point into a locally evolutionarily stable strategy. For games with multiplicatively separable benefits and costs, fluctuations in group size can either prevent or induce the tragedy of the commune. For games with general interactions between benefits and costs, we derive a general classification scheme based on second derivatives of the payoff function, to elucidate when fluctuations in group size help or hinder cooperation.

  • 152.
    Brännström, Åke
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Johansson, Jacob
    Lund University.
    von Festenberg, Niels
    The Hitchhiker’s Guide to Adaptive Dynamics2013Inngår i: Games, ISSN 2073-4336, E-ISSN 2073-4336, nr 4, s. 304-328Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adaptive dynamics is a mathematical framework for studying evolution. It extends evolutionary game theory to account for more realistic ecological dynamics and it can incorporate both frequency- and density-dependent selection. This is a practical guide to adaptive dynamics that aims to illustrate how the methodology can be applied to the study of specific systems. The theory is presented in detail for a single, monomorphic, asexually reproducing population. We explain the necessary terminology to understand the basic arguments in models based on adaptive dynamics, including invasion fitness, the selection gradient, pairwise invasibility plots (PIP), evolutionarily singular strategies, and the canonical equation. The presentation is supported with a worked-out example of evolution of arrival times in migratory birds. We show how the adaptive dynamics methodology can be extended to study evolution in polymorphic populations using trait evolution plots (TEPs). We give an overview of literature that generalises adaptive dynamics techniques to other scenarios, such as sexual, diploid populations, and spatially-structured populations. We conclude by discussing how adaptive dynamics relates to evolutionary game theory and how adaptive-dynamics techniques can be used in speciation research.

  • 153.
    Bråting, Kajsa
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen.
    Studies in the Conceptual Development of Mathematical Analysis2009Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This dissertation deals with the development of mathematical concepts from a historical and didactical perspective. In particular, the development of concepts in mathematical analysis during the 19th century is considered. The thesis consists of a summary and three papers. In the first paper we investigate the Swedish mathematician E.G. Björling's contribution to uniform convergence in connection with Cauchy's sum theorem from 1821. In connection to Björling's convergence theory we discuss some modern interpretations of Cauchy's expression x=1/n. We also consider Björling's convergence conditions in view of Grattan-Guinness distinction between history and heritage. In the second paper we study visualizations in mathematics from historical and didactical perspectives. We consider some historical debates regarding the role of intuition and visual thinking in mathematics. We also consider the problem of what a visualization in mathematics can achieve in learning situations. In an empirical study we investigate what mathematical conclusions university students made on the basis of a visualization. In the third paper we consider Cauchy's theorem on power series expansions of complex valued functions on the basis of a paper written by E.G. Björling in 1852. We discuss Björling's, Lamarle's and Cauchy's different conditions for expanding a complex valued function in a power seris. In the third paper we also discuss the problem of the ambiguites of fundamental concpets that existed during the mid-19th century. We argue that Cauchy's and Lamarle's proofs of Cauchy's theorem on power series expansions of complex valued functions are correct on the basis of their own definitions of the fundamental concepts involved.

     

  • 154.
    Bråting, Kajsa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen.
    Pejlare, Johanna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen.
    Visualizations in mathematics2008Inngår i: Erkenntnis, ISSN 0165-0106, E-ISSN 1572-8420, Vol. 68, nr 3, s. 345-358Artikkel i tidsskrift (Fagfellevurdert)
  • 155.
    Bråting, Kajsa
    et al.
    Uppsala universitet.
    Sollervall, Håkan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Stadler, Erika
    Algebra för lärare2017 (oppl. 1)Bok (Annet vitenskapelig)
  • 156.
    Bråting, Kajsa
    et al.
    Uppsala University.
    Sollervall, Håkan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Stadler, Erika
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA), Institutionen för matematikdidaktik (MD). Stockholm University.
    Geometri för lärare2013 (oppl. 1)Bok (Annet vitenskapelig)
  • 157.
    Bråting, Kajsa
    et al.
    Uppsala universitet, Uppsala, Sverige.
    Sollervall, Håkan
    Linnéuniversitetet, Växjö, Sverige.
    Stadler, Erika
    Stockholms universitet, Stockholm, Sverige.
    Geometri för lärare2013 (oppl. 1)Bok (Annet vitenskapelig)
  • 158.
    Bukina, Elena
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Efficient Numerical Solution of PIDEs in Option Pricing2011Independent thesis Advanced level (degree of Master (One Year)), 15 poäng / 22,5 hpOppgave
  • 159.
    Bursell, Moa
    et al.
    Inst Futures Study, Box 591, SE-10131 Stockholm, Sweden..
    Jansson, Fredrik
    Mälardalens högskola, Akademin för utbildning, kultur och kommunikation, Utbildningsvetenskap och Matematik. Stockholm Univ, Ctr Cultural Evolut, SE-10691 Stockholm, Sweden..
    Diversity preferences among employees and ethnoracial workplace segregation2018Inngår i: Social Science Research, ISSN 0049-089X, E-ISSN 1096-0317, Vol. 74, s. 62-76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ethno-racial workplace segregation increases already existing ethno-racial inequality. While previous research has identified discriminatory employers as drivers of workplace segregation, this study addresses the role of the employees. Sociological and social psychological theory suggest that people prefer to surround themselves with people who positively confirm their social identity or who contribute with higher group status. Through web-based surveys, we measure employee attitudes and preferences concerning ethno-racial workplace diversity, to what extent they differ by ethnicity/race, and if they contain intersectional patterns. Thereafter, we use simulation models to analyze the consequences for workplace segregation that these preferences would have, if realized. The main survey results showed that all ethno-racial groups favored their own in-group as colleagues, especially European Americans. As a secondary choice, the respondents preferred the out-group with the highest labor market status. Intersectional patterns were identified, as minority women were preferred as colleagues over minority men. Our simulation model, based on the results of two surveys on stated vs. indirectly revealed preferences, showed that employee preferences were at best not diverse enough to desegregate workplaces. When based on the most common preferences (i.e. excluding a few outliers), the simulations even suggested that these preferences can cause segregation. We relate these findings to Schelling's model of segregation.

  • 160.
    Böörs, Mikael
    et al.
    Linköpings universitet, Matematiska institutionen, Matematisk statistik. Linköpings universitet, Tekniska fakulteten.
    Wängberg, Tobias
    Linköpings universitet, Matematiska institutionen, Matematisk statistik. Linköpings universitet, Tekniska fakulteten.
    Classification by Decomposition: A Partitioning of the Space of 2X2 Symmetric Games2017Independent thesis Basic level (degree of Bachelor), 10,5 poäng / 16 hpOppgave
    Abstract [en]

    Game theory is the study of strategic interaction between rational agents. The need for understanding interaction arises in many different fields, such as: economics, psychology, philosophy, computer science and biology. The purpose of game theory is to analyse the outcomes and strategies of these interactions, in mathematical models called games. Some of these games have stood out from the rest, e.g. Prisoner's Dilemma, Chicken and Stag Hunt. These games, commonly referred to as the standard games, have attracted interest from many fields of research. In order to understand why these games are interesting and how they differ from each other and other games, many have attempted to sort games into interestingly different classes. In this thesis some already existing classifications are reviewed based on their mathematical structure and how well justified they are. Emphasis is put on mathematical simplicity because it makes the classification more generalisable to larger game spaces. From this review we conclude that none of the classifications captures both of these aspects. We therefore propose a classification of symmetric 2x2 games based on decomposition. We show that our proposed method captures everything that the previous classifications caputure. Our method arguably explains the interesting differences between the games, and we justify this claim by computer experiments. Moreover it has a simple mathematical structure. We also provide some results concerning the size of different game spaces.

  • 161.
    Cano, Cédric
    Karlstads universitet, Institutionen för ingenjörsvetenskap, fysik och matematik.
    Integrering av ett främmande språk i matematikundervisningen2009Independent thesis Advanced level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    Content and Language Integrated Learning (CLIL) is a relatively new method for learning a foreign language. CLIL programs are growing in popularity and more and more schools are adopting it all around the world. There is still no special education for the teachers working with CLIL, though research suggests it may be an effective method for achieving good results.To get a realistic view of the work of a CLIL teacher, I have interviewed four different mathematic teachers who work at CLIL international schools in Spain with English as the foreign language. I have compared their methods and experiences with the main ideas of current research in this particular field.The survey shows that the teachers’ views about how CLIL is to be used do not completely correspond to that of the research. My conclusion is therefore that training in CLIL is needed.

  • 162.
    Carlsson, Eva
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för matematikämnets och naturvetenskapsämnenas didaktik.
    Smidiga övergångar inom grundskolan,men hur?: Sex matematiklärares berättelser om övergången mellan skolår 3 och 42014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The study, Mind the Gap between Grade Three and Four is written within the research fields of Mathematics Education. The research interests in the study concerns how to achieve a smooth transition between grade three and four in compulsory school.

    As a mathematics teacher I found out that the transition from one grade to another in compulsory school affects both the pupil and the mathematics teacher and not always in a satisfactory way. Formal meetings concerning handing over information about pupils are not sufficient, and there is a definite difference between what is said about the pupils during a formal meeting and what is said in more informal settings. Are their gaps that occur?

    The aim of this study is to listen to mathematics teachers´ and to illuminate their stories about handing over pupils from grade three and taking over pupils in grade four. I am searching for gaps in their stories. My goal is to safe guard the continuity concerning the changes of grades between grade three and four in compulsory school. The research questions are: What are the important factors for mathematics teacher´s concerning the transition between grade three and four? What themes and gaps concerning the transitions are revealed in their stories?

    The study is based on a theoretical framework made of; Gees (1999) theory about "language-in-use" and "the seven building blocks of language". Social constructions because the idea is to criticize and change the established order regarding the transition between grade three and grade four. I also made a choice to look at the difficulties concerning the transition as external factors and not as the shortcoming of the mathematics teachers´ therefore I use the critical perspective. Discourse is used because this study is about communication, both spoken and written.

    In order to investigate important factors for mathematics teachers concerning the transitions I interview six mathematics teachers. They are asked about the existent transition between grade three and four at their schools and what they think are important factors for transitions overall. I also videotape one formal meeting because when different methods are used it helps me verify 2

    the outcome. The transcriptions from the interviews and the formal meeting are analyzed with help from the discourse analysis based on Gee (1999).

    The analysis/result shows themes that are important and signal about gaps that could be filled by further research. Themes revealed concerns: school organization, formal/informal meetings, teaching, assessment and special pedagogy. Gaps that are visible concern the teachers’ different educations, the school-web and the curriculum, time, relations, communication, assessment, feedback, teaching methods, teaching materials, and pupils in special needs.

    I argue that its´ necessary to create a structure and make guidelines for formal conferences concerning the transition between grade three and four to minimize the discontinuity. It should also be of interest that the gaps mentioned in this study are filled, and one way to begin could be to plan for collegial work between teachers’ in different grades.

  • 163.
    Carrasco, Lena
    Mälardalens högskola, Akademin för utbildning, kultur och kommunikation.
    Konkret material i matematik: Hur ser elever på det?2018Independent thesis Advanced level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syftet med studien är att studera vilken syn sju elever i årskurs fyra och fem har på konkret material i matematikundervisningen. Metoden som användes för att samla in data var sju semistrukturerade elevintervjuer. Resultatet visar att elevernas syn på användning av konkret material är att det ska ge dem ett visuellt stöd för konkretisering av abstrakt matematik där siffror och symboler dominerar. Resultatet visar även att eleverna tycker att konkret material ska ingå i undervisningen. Slutsatser som kan dras från den här studien stämmer överens med det teoretiska ramverk som används i tolkning av data, om eleverna lär sig med hjälp av modeller eller om elever använder sina kunskaper till att konstruera modeller. En konsekvens av denna studie kan vara att lärare behöver utveckla sin ämnesdidaktiska kompetens så att undervisningen harmonierar med centralt innehåll för årskurs fyra till sex i den rådande läroplanen för skolan.

  • 164. Cedervall, Simon
    et al.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Nonlinear observers for unicycle robots with range sensors2007Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 52, nr 7, s. 1325-1329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For nonlinear mobile systems equipped with exteroceptive sensors, the observability does not only depend on the initial conditions, but also on the control and the environment. This presents an interesting issue: how to design an observer together with the exciting control. In this note, the problem of designing an observer based on range sensor readings is studied. A design method based on periodic excitations is proposed for unicycle robotic systems.

  • 165.
    Cheander, Johan
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    CSI:Math: Ett undervisningsförsök med Storyline i matematik2011Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Storyline är en undervisningsmetod som ursprungligen kommer från Skottland. Metoden används i hela världen, men har blivit väldigt populär främst i de nordiska länderna, Danmark och Norge, men också i Sverige. Storyline är ämnesövergripande och används oftast i grundskolan. Syftet med denna studie är att undersöka hur storyline lämpar sig som undervisningsmetod i matematikundervisningen i gymnasieskolan. Undervisningsförsöket är baserat på ett utgångsmaterial som heter CSI:Math. Försöket observeras och utvärderas med en enkät och en efterföljande intervju. Utifrån resultaten av undersökningarna kan slutsatsen dras att storyline inte bara fungerar väl som arbetsmetod, utan också ligger väl i linje med de senaste förändringarna av gymnasiekurserna i matematik Gy2011.

  • 166. Cheng, Daizhan
    et al.
    Wang, Jinhuan
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för datavetenskap och kommunikation (CSC), Centra, Centrum för Autonoma System, CAS.
    An extension of LaSalle's invariance principle and its application to multi-agent consensus2008Inngår i: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 53, nr 7, s. 1765-1770Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the paper, an extension of LaSalle's Invariance Principle to a class of switched linear systems is studied. One of the motivations is the consensus problem in multi-agent systems. Unlike most existing results in which each switching mode in the system needs to be asymptotically stable, this paper allows that the switching modes are only Lyapunov stable. Under certain ergodicity assumptions, an extension of LaSalle's Invariance Principle for global asymptotic stability is obtained. Then it is used to solve the consensus reaching problem of certain multi-agent systems in which each agent is modeled by a double integrator, and the associated interaction graph is switching and is assumed to be only jointly connected.

  • 167. Chicharro, Daniel
    et al.
    Ledberg, Anders
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Centrum för socialvetenskaplig alkohol- och drogforskning (SoRAD).
    Framework to study dynamic dependencies in networks of interacting processes2012Inngår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 86, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The analysis of dynamic dependencies in complex systems such as the brain helps to understand how emerging properties arise from interactions. Here we propose an information-theoretic framework to analyze the dynamic dependencies in multivariate time-evolving systems. This framework constitutes a fully multivariate extension and unification of previous approaches based on bivariate or conditional mutual information and Granger causality or transfer entropy. We define multi-information measures that allow us to study the global statistical structure of the system as a whole, the total dependence between subsystems, and the temporal statistical structure of each subsystem. We develop a stationary and a nonstationary formulation of the framework. We then examine different decompositions of these multi-information measures. The transfer entropy naturally appears as a term in some of these decompositions. This allows us to examine its properties not as an isolated measure of interdependence but in the context of the complete framework. More generally we use causal graphs to study the specificity and sensitivity of all the measures appearing in these decompositions to different sources of statistical dependence arising from the causal connections between the subsystems. We illustrate that there is no straightforward relation between the strength of specific connections and specific terms in the decompositions. Furthermore, causal and noncausal statistical dependencies are not separable. In particular, the transfer entropy can be nonmonotonic in dependence on the connectivity strength between subsystems and is also sensitive to internal changes of the subsystems, so it should not be interpreted as a measure of connectivity strength. Altogether, in comparison to an analysis based on single isolated measures of interdependence, this framework is more powerful to analyze emergent properties in multivariate systems and to characterize functionally relevant changes in the dynamics.

  • 168.
    Christoffer, Dahlqvist
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematikdidaktik (MD).
    Spela för nöje eller spela för kunskap?: Lärares uppfattningar av IT-baserade matematikspel och dess konsekvenser på elevers kunskapsutveckling2015Independent thesis Advanced level (degree of Master (One Year)), 10 poäng / 15 hpOppgave
  • 169.
    Cohen Scalie, Natalie
    Högskolan i Halmstad, Sektionen för lärarutbildning (LUT).
    Vilken matematik ligger g(l)ömd?: En studie om matematikens och de övriga ämnenas inbördes förhållande i mellanstadiets kursplaner2012Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    ”Vilken matematik ligger g(l)ömd?” är en studie som syftar till att rannsaka matematiken i den nya läroplanen och om den håller även för övergången till det ämnesintegrerande arbete i skolan som den har för avsikt. Här finner du svaret på hur väl matematikämnets syften och centrala innehåll överensstämmer med eventuell matematik i övriga ämnens syften och centrala innehåll i Lgr 11, årskurs 4-6? Utifrån en hermeneutisk ansats med kritisk-teoretiska inslag gjordes en innehållsanalys deducerad från en övergripande definition av vad matematiken innebar. Den skulle ge kvalitativ förståelse för lärares skoltillvaro och vilken effekt den får för eleverna genom att analyseras idécentrerat. För att förenkla den kontextuella insikten gjordes detta sedan överskådligt med hjälp av en matris byggd på kategorier. De fick bearbeta alla ämnena i läroplanen och utgjordes då av delarna matematiska idéer, matematisk operationalisering och matematiskt angreppssätt samt områdena algebra, geometri och analys, vilka alla ingick i vardera delen. Efter en pilotstudie användes sedan matrisen strukturanalytiskt och förde samman matematiska komponenter av samma sort grundat på beningsbärande koder. Då syntes ett mönster av återkommande matematiska bitar i de övriga ämnena som inte tycktes vara ha någon motsvarighet i matematikämnet. Men med återkoppling till litteratur och ett granskande med hänsyn till och av tolv författares särpräglade teorier utformades en ny klarläggande modell som gick ut på att man beroende på vilket problem man tar sig för får olika vetenskaplig beskaffenhet på de matematiska bitarna algebra och geometri’s teoretiska idéer och praktiska verksamheter på väg mot en lösning. Denna modell bidrog med en ny dimension av undersökningen, som till slut visade att de saknade bitarna i själva verket var av ämnesövergripande slag och att överensstämmelsen tycktes oinskränkt.

  • 170. Cornforth, Daniel M
    et al.
    Sumpter, David J T
    Brown, Sam P
    Brännström, Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Synergy and group size in microbial cooperation2012Inngår i: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, nr 3, s. 296-305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Abstract Microbes produce many molecules that are important for their growth and development, and the exploitation of these secretions by nonproducers has recently become an important paradigm in microbial social evolution. Although the production of these public-goods molecules has been studied intensely, little is known of how the benefits accrued and the costs incurred depend on the quantity of public-goods molecules produced. We focus here on the relationship between the shape of the benefit curve and cellular density, using a model assuming three types of benefit functions: diminishing, accelerating, and sigmoidal (accelerating and then diminishing). We classify the latter two as being synergistic and argue that sigmoidal curves are common in microbial systems. Synergistic benefit curves interact with group sizes to give very different expected evolutionary dynamics. In particular, we show that whether and to what extent microbes evolve to produce public goods depends strongly on group size. We show that synergy can create an "evolutionary trap" that can stymie the establishment and maintenance of cooperation. By allowing density-dependent regulation of production (quorum sensing), we show how this trap may be avoided. We discuss the implications of our results on experimental design.

  • 171.
    Cortas Nordlander, Maria
    et al.
    Vasaskolan, Gävle.
    Nordlander, Edvard
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    A Study of Students’ Ability to Solve Text-Based Mathematical Problems with Irrelevant or Superfluous Information2008Inngår i: Mathematical Views, MAVI 14: Strobl/Salzburg, Austria, May 2008, 2008Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A limited quantitative survey has been performed in order to study the capability of students to solve text-based mathematical problems containing irrelevant or superfluous information, as well as their ability to scrutinize text and sort out the relevant information. The students took a written test with text-based problems of different amount of irrelevant or superfluous information. The capability of understanding such problems was investigated versus degree of maturity and gender. Obtained results indicate a noticeable correlation between the occurrence of irrelevant or superfluous information and ability of solving the problems. Furthermore, the results show that the degree of maturity, expressed in terms of age, has a clear influence on the results. This study has not revealed any significant difference between genders as regards ability of sorting out the relevant information.

  • 172.
    Cortas Nordlander, Maria
    et al.
    Vasaskolan, Gävle.
    Nordlander, Edvard
    Högskolan i Gävle, Institutionen för teknik och byggd miljö, Ämnesavdelningen för elektronik.
    Influence of Student’s Attitudes and Beliefs on the Ability of Solving Mathematical Problems with Irrelevant Information2009Inngår i: Beliefs and attitudes in mathematics education: new research results / [ed] Jürgen Maasz and Wolfgang Schlöglmann, Rotterdam: Sense Publishers , 2009, s. 165-178Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    A limited quantitative survey has been performed in order to study how attitudes, beliefs and feelings of students may influence the ability of solving text-based mathematical problems containing irrelevant information. The survey is also analyzing their capability of scrutinizing texts and sorting out relevant information.

    The students took a written test with text-based problems of different amount of irrelevant information. The capability of understanding such problems was investigated versus degree of mathematical maturity and gender. Obtained results indicate a noticeable correlation between the occurrence of irrelevant information and the ability of solving the problems. Furthermore, attitudes, beliefs, and the degree of mathematical maturity, expressed in terms of age, have a clear influence on the results. On the other hand, this study has not revealed any significant difference between genders as regards the capability of solving text-based problems with irrelevant information.

     

  • 173.
    Cortas Nordlander, Maria
    et al.
    Vasaskolan, Gävle.
    Nordlander, Edvard
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Komplexa tal är inte så komplexa!2010Konferansepaper (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Abstraktion kan ofta utgöra ett hinder för lärande i matematik. Momentet med komplexa tal är inte något undantag. Varför ska man acceptera att i2=-1? Hur kan lärare introducera det på ett pedagogiskt sätt? Visualisering kan vara ett väsentligt led i att underlätta studenters lärande, ge dem en känsla av lägre abstraktion och härigenom vara nyckeln till djupare förståelse. Artikeln beskriver en visuell ansats som uppfyller kravet på lättillgänglighet. Metoden bygger på upprepade rotationer i det komplexa talplanet, vilket åskådliggör och konkretiserar komplexa tal genom visualisering.

  • 174.
    Cownden, Daniel
    et al.
    University of St Andrews, Scotland.
    Eriksson, Kimmo
    Mälardalens högskola, Akademin för utbildning, kultur och kommunikation, Utbildningsvetenskap och Matematik. Stockholm University, Sweden.
    Strimling, Pontus
    Stockholm University, Sweden.
    The implications of learning across perceptually and strategically distinct situations2018Inngår i: Synthese, ISSN 0039-7857, E-ISSN 1573-0964, Vol. 195, nr 2, s. 511-528Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Game theory is a formal approach to behavior that focuses on the strategic aspect of situations. The game theoretic approach originates in economics but has been embraced by scholars across disciplines, including many philosophers and biologists. This approach has an important weakness: the strategic aspect of a situation, which is its defining quality in game theory, is often not its most salient quality in human (or animal) cognition. Evidence from a wide range of experiments highlights this shortcoming. Previous theoretical and empirical work has sought to address this weakness by considering learning across an ensemble of multiple games simultaneously. Here we extend this framework, incorporating artificial neural networks, to allow for an investigation of the interaction between the perceptual and functional similarity of the games composing the larger ensemble. Using this framework, we conduct a theoretical investigation of a population that encounters both stag hunts and prisoner's dilemmas, two situations that are strategically different but which may or may not be perceptually similar.

  • 175.
    Cox, Sander
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Dynamical modelling2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 176.
    Curic, Vladimir
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion.
    Angulo, Jesus
    Morphological image regularization using adaptive structuring functionsManuskript (preprint) (Annet vitenskapelig)
  • 177. Curic, Vladimir
    et al.
    Heilio, Matti
    Krejic, Natasa
    Nedeljkov, Marko
    Mathematical model for efficient water flow management2010Inngår i: Nonlinear Analysis: Real World ApplicationsArtikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mathematical model for the optimization of pump scheduling in a water distribution system is proposed. The water system we consider works without a large water storage facility and hence the mass balance principle is the base for the model. A result concerning the pressure drop after T-junctions is the main simplification we propose. An optimization problem is formulated and solved by a Branch and Bound method for a real water distribution system using data from a small city in Serbia.

  • 178.
    Curic, Vladimir
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion.
    Hendriks Luengo, Cris L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Adaptive structuring elements based on salience information2012Inngår i: Computer Vision and Graphics / [ed] L. Bolc, K. Wojciechowski, R. Tadeusiewicz, L.J. Chmielewski, Springer, 2012, s. 321-328Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Adaptive structuring elements modify their shape and size according to the image content and may outperform fixed structuring elements. Without any restrictions, they suffer from a high computational complexity, which is often higher than linear with respect to the number of pixels in the image. This paper introduces adaptive structuring elements that have predefined shape, but where the size is adjusted to the local image structures. The size of adaptive structuring elements is determined by the salience map that corresponds to the salience of the edges in the image, which can be computed in linear time. We illustrate the difference between the new adaptive structuring elements and morphological amoebas. As an example of its usefulness, we show how the new adaptive morphological operations can isolate the text in historical documents.

  • 179.
    Curic, Vladimir
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Luengo Hendriks, Cris L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Salience-Based Parabolic Structuring Functions2013Inngår i: Mathematical Morphology and Its Applications to Signal and Image Processing, Springer Berlin/Heidelberg, 2013, s. 183-194Konferansepaper (Fagfellevurdert)
    Abstract [en]

    It has been shown that the use of the salience map based on the salience distance transform can be useful for the construction of spatially adaptive structuring elements. In this paper, we propose salience-based parabolic structuring functions that are defined for a fixed, predefined spatial support, and have low computational complexity. In addition, we discuss how to properly define adjunct morphological operators using the new spatially adaptive structuring functions. It is also possible to obtain flat adaptive structuring elements by thresholding the salience-based parabolic structuring functions.

  • 180.
    Curic, Vladimir
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion.
    Luengo Hendriks, Cris L.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Borgefors, Gunilla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för visuell information och interaktion. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Bildanalys och människa-datorinteraktion.
    Salience adaptive structuring elements2012Inngår i: IEEE Journal on Selected Topics in Signal Processing, ISSN 1932-4553, E-ISSN 1941-0484, Vol. 6, nr 7, s. 809-819Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spatially adaptive structuring elements adjust their shape to the local structures in the image, and are often defined by a ball in a geodesic distance or gray-weighted distance metric space. This paper introduces salience adaptive structuring elements as spatially variant structuring elements that modify not only their shape, but also their size according to the salience of the edges in the image. Morphological operators with salience adaptive structuring elements shift edges with high salience to a less extent than those with low salience. Salience adaptive structuring elements are less flexible than morphological amoebas and their shape is less affected by noise in the image. Consequently, morphological operators using salience adaptive structuring elements have better properties.

  • 181.
    da Silva, Marcio Antonio
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för matematikämnets och naturvetenskapsämnenas didaktik.
    Valero, Paola
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för matematikämnets och naturvetenskapsämnenas didaktik.
    Brazilian high school textbooks: Mathematics and students’ subjectivity2018Inngår i: Proceedings of the 42nd Conference of the International Group for the Psychology of Mathematics Education / [ed] E. Bergqvist, M. Österholm, C. Granberg, L. Sumpter, Umeå, Sweden: PME , 2018, Vol. 4, s. 187-194Konferansepaper (Fagfellevurdert)
  • 182.
    Daag, Madeleine
    et al.
    Högskolan i Jönköping, Högskolan för lärande och kommunikation.
    Andersson, Hanna
    Högskolan i Jönköping, Högskolan för lärande och kommunikation.
    Elever lär med hjälp av varandra: Matematisk problemlösning i små grupper2016Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
  • 183.
    Dahl, Emelie
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Cicek, Pierre
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Att motivera till lärande i matematik: En studie om hur elever kan motiveras i ämnet matematik ur ett lärarperspektiv2017Independent thesis Advanced level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Syftet med den här studien är att se hur lärare i årskurserna 4-6 arbetar med motivation inom ämnet matematik. Syftet är också att se hur lärare skapar ett intresse för matematikämnet i skolan. 

     

    Metoderna som använts för att genomföra studien är intervjuer och observationer. Dessa metoder är båda av kvalitativ art. Intervjuerna har genomförts med fem olika lärare och svaren kommer att användas för att se hur lärare ser på sin undervisning och möjligheter till att motivera elever i matematik. Observationerna användes både för att ha en gemensam grund att utgå ifrån vid intervjun men också för att se hur lärarna faktiskt arbetade med att motivera eleverna.

     

    Det resultat som framkommer är att lärarna arbetar med att variera sin undervisning för att få med alla elever i arbetet. Det är både arbetssätt och arbetsmaterial som lärarna varierar. Resultatet visar också att lärarna utgår ifrån elevens behov och förutsättningar för att skapa en plattform att utgå ifrån i lärandet.

     

  • 184.
    Dahlin, Malin
    Karlstads universitet.
    Digitala verktyg i matematik på lågstadiet2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
  • 185.
    Dahne, Joel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Enclosing Zeros for Systems of Two Analytic Functions2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 186.
    Dalarsson, Mariana
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Emadi, Seyed Mohamad Hadi
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Norgren, Martin
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Perturbation Approach to Reconstructing Deformations in a Coaxial Cylindrical Waveguide2015Inngår i: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, artikkel-id 915497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study a detection method for continuous mechanical deformations of coaxial cylindrical waveguide boundaries, using perturbation theory. The inner boundary of the waveguide is described as a continuous PEC structure with deformations modeled by suitable continuous functions. In the present approach, the computation complexity is significantly reduced compared to discrete conductor models studied in our previous work. If the mechanically deformed metallic structure is irradiated by the microwave fields of appropriate frequencies, then, by means of measurements of the scattered fields at both ends, we can reconstruct the continuous deformation function. We apply the first-order perturbation method to the inverse problem of reconstruction of boundary deformations, using the dominant TEM-mode of the microwave radiation. Different orders of Tikhonov regularization, using the L-curve criterion, are investigated. Using reflection data, we obtain reconstruction results that indicate an agreement between the reconstructed and true continuous deformations of waveguide boundaries.

  • 187.
    Danielsson, Stina
    Högskolan Dalarna, Akademin Utbildning och humaniora, Matematikdidaktik.
    Håller din lärobok i matematik måttet?: En modell för granskning av hur läroböcker i matematik förhåller sig till rådande styrdokuments centrala innehåll2012Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
  • 188.
    D'Ariano, Mauro
    et al.
    University of Pavia, Italy.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Melucci, Massimo
    University of Padua, Italy.
    Special Issue "Quantum Mechanics: From Foundations to Information Technologies"2018Inngår i: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 20, nr 6Artikkel i tidsskrift (Fagfellevurdert)
  • 189.
    de Barra, Mícheál
    et al.
    Centre for the Study of Cultural Evolution, Stockholm, Sweden.
    Eriksson, Kimmo
    Centre for the Study of Cultural Evolution, Stockholm, Sweden.
    Strimling, Pontus
    Centre for the Study of Cultural Evolution, Stockholm, Sweden.
    How feedback biases give ineffective medical treatments a good reputation.2014Inngår i: Journal of medical Internet research, ISSN 1438-8871, Vol. 16, nr 8, s. e193-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND: Medical treatments with no direct effect (like homeopathy) or that cause harm (like bloodletting) are common across cultures and throughout history. How do such treatments spread and persist? Most medical treatments result in a range of outcomes: some people improve while others deteriorate. If the people who improve are more inclined to tell others about their experiences than the people who deteriorate, ineffective or even harmful treatments can maintain a good reputation.

    OBJECTIVE: The intent of this study was to test the hypothesis that positive outcomes are overrepresented in online medical product reviews, to examine if this reputational distortion is large enough to bias people's decisions, and to explore the implications of this bias for the cultural evolution of medical treatments.

    METHODS: We compared outcomes of weight loss treatments and fertility treatments in clinical trials to outcomes reported in 1901 reviews on Amazon. Then, in a series of experiments, we evaluated people's choice of weight loss diet after reading different reviews. Finally, a mathematical model was used to examine if this bias could result in less effective treatments having a better reputation than more effective treatments.

    RESULTS: Data are consistent with the hypothesis that people with better outcomes are more inclined to write reviews. After 6 months on the diet, 93% (64/69) of online reviewers reported a weight loss of 10 kg or more while just 27% (19/71) of clinical trial participants experienced this level of weight change. A similar positive distortion was found in fertility treatment reviews. In a series of experiments, we show that people are more inclined to begin a diet with many positive reviews, than a diet with reviews that are representative of the diet's true effect. A mathematical model of medical cultural evolution shows that the size of the positive distortion critically depends on the shape of the outcome distribution.

    CONCLUSIONS: Online reviews overestimate the benefits of medical treatments, probably because people with negative outcomes are less inclined to tell others about their experiences. This bias can enable ineffective medical treatments to maintain a good reputation.

  • 190.
    de Pierrefeu, Amicie
    et al.
    NeuroSpin, CEA, Gif-sur-Yvette, France.
    Löfstedt, Tommy
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Laidi, C.
    NeuroSpin, CEA, Gif-sur-Yvette, France; Institut National de la Santé et de la Recherche Médicale (INSERM), U955, Institut Mondor de Recherche Biomédicale, Psychiatrie Translationnelle, Créteil, France; Fondation Fondamental, Créteil, France; Pôle de Psychiatrie, Assistance Publique–Hôpitaux de Paris (AP-HP), Faculté, de Médecine de Créteil, DHU PePsy, Hôpitaux Universitaires Mondor, Créteil, France.
    Hadj-Selem, Fouad
    Energy Transition Institute: VeDeCoM, Versailles, France.
    Bourgin, Julie
    Department of Psychiatry, Louis-Mourier Hospital, AP-HP, Colombes, France; INSERM U894, Centre for Psychiatry and Neurosciences, Paris, France.
    Hajek, Tomas
    Department of Psychiatry, Dalhousie University, Halifax, NS, Canada; National Institute of Mental Health, Klecany, Czech Republic.
    Spaniel, Filip
    National Institute of Mental Health, Klecany, Czech Republic.
    Kolenic, Marian
    National Institute of Mental Health, Klecany, Czech Republic.
    Ciuciu, Philippe
    NeuroSpin, CEA, Gif-sur-Yvette, France; INRIA, CEA, Parietal team, University of Paris-Saclay, France.
    Hamdani, Nora
    Institut National de la Santé et de la Recherche Médicale (INSERM), U955, Institut Mondor de Recherche Biomédicale, Psychiatrie Translationnelle, Créteil, France; Fondation Fondamental, Créteil, France; Pôle de Psychiatrie, Assistance Publique–Hôpitaux de Paris (AP-HP), Faculté, de Médecine de Créteil, DHU PePsy, Hôpitaux Universitaires Mondor, Créteil, France.
    Leboyer, Marion
    Institut National de la Santé et de la Recherche Médicale (INSERM), U955, Institut Mondor de Recherche Biomédicale, Psychiatrie Translationnelle, Créteil, France; Fondation Fondamental, Créteil, France; Pôle de Psychiatrie, Assistance Publique–Hôpitaux de Paris (AP-HP), Faculté, de Médecine de Créteil, DHU PePsy, Hôpitaux Universitaires Mondor, Créteil, France.
    Fovet, Thomas
    Laboratoire de Sciences Cognitives et Sciences Affectives (SCALab-PsyCHIC), CNRS UMR 9193, University of Lille; Pôle de Psychiatrie, Unité CURE, CHU Lille, Lille, France.
    Jardri, Renaud
    INRIA, CEA, Parietal team, University of Paris-Saclay, France; Laboratoire de Sciences Cognitives et Sciences Affectives (SCALab-PsyCHIC), CNRS UMR 9193, University of Lille; Pôle de Psychiatrie, Unité CURE, CHU Lille, Lille, France.
    Houenou, Josselin
    NeuroSpin, CEA, Gif-sur-Yvette, France; Institut National de la Santé et de la Recherche Médicale (INSERM), U955, Institut Mondor de Recherche Biomédicale, Psychiatrie Translationnelle, Créteil, France; Fondation Fondamental, Créteil, France; Pôle de Psychiatrie, Assistance Publique–Hôpitaux de Paris (AP-HP), Faculté, de Médecine de Créteil, DHU PePsy, Hôpitaux Universitaires Mondor, Créteil, France.
    Duchesnay, Edouard
    NeuroSpin, CEA, Gif-sur-Yvette, France.
    Identifying a neuroanatomical signature of schizophrenia, reproducible across sites and stages, using machine-learning with structured sparsity2018Inngår i: Acta Psychiatrica Scandinavica, ISSN 0001-690X, E-ISSN 1600-0447, Vol. 138, s. 571-580Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ObjectiveStructural MRI (sMRI) increasingly offers insight into abnormalities inherent to schizophrenia. Previous machine learning applications suggest that individual classification is feasible and reliable and, however, is focused on the predictive performance of the clinical status in cross‐sectional designs, which has limited biological perspectives. Moreover, most studies depend on relatively small cohorts or single recruiting site. Finally, no study controlled for disease stage or medication's effect. These elements cast doubt on previous findings’ reproducibility.

    MethodWe propose a machine learning algorithm that provides an interpretable brain signature. Using large datasets collected from 4 sites (276 schizophrenia patients, 330 controls), we assessed cross‐site prediction reproducibility and associated predictive signature. For the first time, we evaluated the predictive signature regarding medication and illness duration using an independent dataset of first‐episode patients.

    ResultsMachine learning classifiers based on neuroanatomical features yield significant intersite prediction accuracies (72%) together with an excellent predictive signature stability. This signature provides a neural score significantly correlated with symptom severity and the extent of cognitive impairments. Moreover, this signature demonstrates its efficiency on first‐episode psychosis patients (73% accuracy).

    ConclusionThese results highlight the existence of a common neuroanatomical signature for schizophrenia, shared by a majority of patients even from an early stage of the disorder.

  • 191.
    de Woul, Jonas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Matematisk fysik.
    Langmann, Edwin
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Matematisk fysik.
    Gauge invariance, correlated fermions, and Meissner effect in 2+1 dimensionsArtikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    We present a 2+1 dimensional quantum gauge theory model with correlated fermions that is exactly solvable by bosonization. This model gives an effective description of partially gapped fermions on a square lattice that have density-density interactions and are coupled to photons. We show that the photons in this model are massive due to gauge-invariant normal-ordering, similarly as in the Schwinger model. Moreover, the exact excitation spectrum of the model has two gapped and one gapless mode. We also compute the magnetic field induced by an external current and show that there is a Meissner effect. We find that the transverse photons have significant effects on the low-energy properties of the model even if the fermion-photon coupling is small.

  • 192.
    de Woul, Jonas
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Matematisk fysik.
    Langmann, Edwin
    KTH, Skolan för teknikvetenskap (SCI), Teoretisk fysik, Matematisk fysik.
    Partial continuum limit of the 2D Hubbard modelArtikkel i tidsskrift (Annet vitenskapelig)
  • 193.
    Dejby, Jesper
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Larsson, Josef
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik.
    Optimizing production line sequence to minimize waste: A paint shop problem2016Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    In the competitive automobile manufacturing industry only the most efficient and profitable companies will survive. Companies search for ways to cut costs and increase production without lower their standards of quality. In the field of optimization research such problems can be formulated as combinatorial optimization problems. The Car Sequencing problem (CSP) tries to find the optimal production sequence which increases the number of produced units. Parrello et al. (1986) where the first one to formulate the problem with respect to an assembly line in a automobile factory. Volvo GTO in Umeå desires to minimize their paint consumption in the paint shop. By formulating paint process in the top coat, which is the last part of the paint shop, as a Integer Linear Program the number of color changes can be minimized. Hence the paint consumption is reduced which leads to lower costs. Using a greedy approach while simulating the process the number of color changes can be reduced based on historical data. This result is based on a somewhat simplified model of a real life problem. The number of parameters in the model can be increased to reflect the complexity of the paint shop. The purpose of this thesis is to present a way to decrease the paint consumption

  • 194.
    Demin, Mikhail
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Tillämpad matematik och fysik (MPE-lab).
    Finite Volume Methods for Option Pricing2011Independent thesis Advanced level (degree of Master (One Year)), 15 poäng / 22,5 hpOppgave
  • 195.
    Dendani, Linda
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematikdidaktik (MD).
    Miljö och matematik i förskolan: En studie om förskollärarens syn på innemiljöns betydelse för den matematiska inlärningen på en Reggio Emilia-inspirerad förskola2014Independent thesis Basic level (professional degree), 210 hpOppgave
    Abstract [sv]

    Syftet med denna studie var att undersöka vad förskollärare har för syn på innemiljöns betydelse för den matematiska inlärningen, samt hur de arbetar för att synliggöra matematiken i innemiljön. Studien utfördes på en Reggio Emilia-inspirerad förskola, detta för att miljön står i fokus inom denna pedagogiska filosofi, och kallas för ”den tredje pedagogen”. De metoder som användes för att erhålla information till studien var intervjuer med tre förskollärare som arbetade på förskolan, samt en observation av innemiljön.Resultatet visade att matematiken finns överallt i innemiljön och synliggörs genom ett stort utbud av material, som är tillgängligt och på barnens nivå. Under intervjuerna visade det sig att förskollärarna har en stor medvetenhet kring innemiljöns betydelse för det matematiska lärandet och att de planerat sin innemiljö för att främja barnens lärande. Dock har de inte alltid matematiken i åtanke när de förändrar miljön, utan utgår från barngruppens intresse. Under mitt besök på förskolan uppgav de att sortering och klassificering var den mest populära aktiviteten och därför var det mycket fokus på den delen av matematiken i förskolans innemiljö.En slutsats som kan dras från studien är att förskolan som undersökts är en förskola som tror på det kompetenta barnet. Detta då förskolan har en mycket genomtänkt och bearbetad innemiljö. Förskollärarna såg dock bristfällig planeringstid som ett hinder i arbetet med att bygga upp en föränderlig och god innemiljö.

  • 196.
    Derevyanchuk, E.
    et al.
    Russia .
    Smirnov, Yurij
    Russia.
    Shestopalov, Yuri
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Permittivity determination of thin multi-sectional diaphragms in a rectangular waveguide2013Inngår i: Proceedings of the International Conference Days on Diffraction 2013, 2013, s. 32-35, artikkel-id 6712799Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we consider the inverse problem of the permittivity determination of thin multisectional diaphragm in a rectangular waveguide. We perform a detailed analysis for one-, two- and three-sectional thin diaphragms. Numerical results are presented.

  • 197.
    Djechiche, Boualem
    et al.
    KTH Royal Institute of Technology.
    Hilbert, Astrid
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Nassar, Hiba
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    On the Functional Hodrick-Prescott Filter with Non-compact Operators2016Inngår i: Random Operators and Stochastic Equations, ISSN 0926-6364, E-ISSN 1569-397X, Vol. 24, nr 1, s. 33-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study a version of the functional Hodrick-Prescott filter where the associated operator is not necessarily compact, but merely closed and densely defined with closed range. We show that the associate doptimal smoothing operator preserves the structure obtained in the compact case, when the underlying distribution of the data is Gaussian.

  • 198.
    Dougherty, Mark
    KTH, Tidigare Institutioner, Farkost- och flygteknik.
    What has literature to offer computer science?2004Inngår i: Human IT, ISSN 1402-1501, E-ISSN 1402-151X, Vol. 7, nr 1, s. 74-91Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    In this paper I ask the question: what has literature to offer computer science? Can a bilateral programme of research be started with the aim of discovering the same kind of deep intertwining of ideas between computer science and literature, as already exists between computer science and linguistics? What practical use could such results yield? I begin by studying a classic forum for some of the most unintelligible pieces of prose ever written, the computer manual. Why are these books so hard to understand? Could a richer diet of metaphor and onomatopoeia help me get my laser printer working? I then dig down a little deeper and explore computer programs themselves as literature. Do they exhibit aesthetics, emotion and all the other multifarious aspects of true literature? If so, does this support their purpose and understandability? Finally I explore the link between computer code and the human writer. Rather than write large amounts of code directly, we encourage students to write algorithms as pseudo-code as a first step. Pseudo-code tells a story within a semi-formalised framework of conventions. Is this the intertwining we should be looking for?

  • 199.
    Dragovich, Branko
    et al.
    University of Belgrade, Serbia ; Serbian Academy of Arts and Sciences, Serbia.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Mišić, Nata Ž.
    Lola Institute, Serbia.
    Ultrametrics in the genetic code and the genome2017Inngår i: Applied Mathematics and Computation, ISSN 0096-3003, E-ISSN 1873-5649, Vol. 309, s. 350-358Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ultrametric approach to the genetic code and the genome is considered and developed. p-Adic degeneracy of the genetic code is pointed out. Ultrametric tree of the codon space is presented. It is shown that codons and amino acids can be treated as p-adic ultrametric networks. Ultrametric modification of the Hamming distance is defined and noted how it can be useful. Ultrametric approach with p-adic distance is an attractive and promising trend towards investigation of bioinformation. © 2017 Elsevier Inc.

  • 200.
    Duits, R.
    et al.
    Eindhoven University of Technology, Netherlands.
    Ghosh, Arpan
    Linköpings universitet, Matematiska institutionen, Matematik och tillämpad matematik. Linköpings universitet, Tekniska fakulteten.
    Dela Haije, T. C. J.
    Eindhoven University of Technology, Netherlands.
    Mashtakov, A.
    Eindhoven University of Technology, Netherlands.
    On Sub-Riemannian Geodesics in SE(3) Whose Spatial Projections do not Have Cusps2016Inngår i: Journal of dynamical and control systems, ISSN 1079-2724, E-ISSN 1573-8698, Vol. 22, nr 4, s. 771-805Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We consider the problem P (c u r v e) of minimizing for a curve x in with fixed boundary points and directions. Here, the total length Laeyen0 is free, s denotes the arclength parameter, kappa denotes the absolute curvature of x, and xi amp;gt; 0 is constant. We lift problem P (c u r v e) on to a sub-Riemannian problem P (m e c) on SE(3)/({0}xSO(2)). Here, for admissible boundary conditions, the spatial projections of sub-Riemannian geodesics do not exhibit cusps and they solve problem P (c u r v e) . We apply the Pontryagin Maximum Principle (PMP) and prove Liouville integrability of the Hamiltonian system. We derive explicit analytic formulas for such sub-Riemannian geodesics, relying on the co-adjoint orbit structure, an underlying Cartan connection, and the matrix representation of SE(3) arising in the Cartan-matrix. These formulas allow us to extract geometrical properties of the sub-Riemannian geodesics with cuspless projection, such as planarity conditions, explicit bounds on their torsion, and their symmetries. Furthermore, they allow us to parameterize all admissible boundary conditions reachable by geodesics with cuspless spatial projection. Such projections lay in the upper half space. We prove this for most cases, and the rest is checked numerically. Finally, we employ the formulas to numerically solve the boundary value problem, and visualize the set of admissible boundary conditions.

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