Thesis (DEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / The Finite Element Method (FEM) as applied to Computational Electromagnetics (CEM), can beused to solve a large class of Electromagnetics problems with high accuracy and good computational efficiency. For solving wide-band problems time domain solutions are often preferred; while time domain FEM methods are feasible, the Finite Difference Time Domain (FDTD) method is more commonly applied. The FDTD is popular both for its efficiency and its simplicity. The efficiency of the FDTD stems from the fact that it is both explicit (i.e. no matrices need to be solved) and second order accurate in both time and space. The FDTD has limitations when dealing with certain geometrical shapes and when electrically large structures are analysed. The former limitation is caused by stair-casing in the geometrical modelling, the latter by accumulated dispersion error throughout the mesh. The FEM can be seen as a general mathematical framework describing families of concrete numerical method implementations; in fact the FDTD can be described as a particular FETD (Finite Element Time Domain) method. To date the most commonly described FETD CEM methods make use of unstructured, conforming meshes and implicit time stepping schemes. Such meshes deal well with complex geometries while implicit time stepping is required for practical numerical stability. Compared to the FDTD, these methods have the advantages of computational efficiency when dealing with complex geometries and the conceptually straight forward extension to higher orders of accuracy. On the downside, they are much more complicated to implement and less computationally efficient when dealing with regular geometries. The FDTD and implicit FETD have been combined in an implicit/explicit hybrid. By using the implicit FETD in regions of complex geometry and the FDTD elsewhere the advantages of both are combined. However, previous work only addressed mixed first order (i.e. second order accurate) methods. For electrically large problems or when very accurate solutions are required, higher order methods are attractive. In this thesis a novel higher order implicit/explicit FETD method of arbitrary order in space is presented. A higher order explicit FETD method is implemented using Gauss-Lobatto lumping on regular Cartesian hexahedra with central differencing in time applied to a coupled Maxwell’s equation FEM formulation. This can be seen as a spatially higher order generalisation of the FDTD. A convolution-free perfectly matched layer (PML) method is adapted from the FDTD literature to provide mesh termination. A curl conforming hybrid mesh allowing the interconnection of arbitrary order tetrahedra and hexahedra without using intermediate pyramidal or prismatic elements is presented. An unconditionally stable implicit FETD method is implemented using Newmark-Beta time integration and the standard curl-curl FEM formulation. The implicit/explicit hybrid is constructed on the hybrid hexahedral/tetrahedral mesh using the equivalence between the coupled Maxwell’s formulation with central differences and the Newmark-Beta method with Beta = 0 and the element-wise implicitness method. The accuracy and efficiency of this hybrid is numerically demonstrated using several test-problems.

The objectives of this research were to create explicit and implicit measures of prejudice against homeless, and to identify factors associated with negative attitudes toward this population. To meet these objectives several studies collected in four articles were made. In the first article the literature on prejudice against homeless was reviewed. In this study was found that both, in Latin America and in the countries of industrialized West, have been reported stereotypes towards this population related to mental illness and drug addiction, as well as acts of discrimination related to limitations in the use of public space. Article two corresponded to a study of cross-cultural creation and validation of a scale of prejudice against homeless, created with basics of Item Response Theory and the Allport's scale of prejudice. The created scale presented evidence of construct validity, convergent validity and good internal consistency. It was also verified, in part, the Allport's theory of the scale of prejudice. The third article aimed at identifying factors associated with prejudice against homeless, and to build and test a hierarchical model to explain variations in the levels of this prejudice. The proposed model had four levels of prejudice mediations, good fit indices, and included the variables social dominance orientation, basic values, egocentrism, perception of insecurity and quality of contact with homeless people. In the fourth article was described the process of creating an implicit association test about attitudes toward homeless, and was tested scores correlation levels acquired with this test and those acquired with the scale established in article two. The results indicated that there are strong associations between concepts representing the homeless people and negative stereotypes towards this population. No correlation between the scores on the two measures was found, in line with other studies on implicit and explicit measures of stereotypes. / Los objetivos de esta tesis fueron la creación de medidas explícitas e implícitas del prejuicio contra habitantes de calle, y la identificación de algunos factores asociados con actitudes negativas hacia esta población. Para responder a estos objetivos se realizaron varios estudios reunidos en cuatro artículos y presentados en este documento como capítulos. En el primer capítulo, se realizó un estudio de revisión de la literatura sobre el prejuicio contra habitantes de calle. En este estudio se encontró que tanto en Latinoamérica como en los países de occidente industrializado, se han reportado estereotipos hacia esta población relacionados con la enfermedad mental y la adicción a las drogas; así como actos de discriminación relacionados con limitaciones en el uso del espacio público. El capítulo dos corresponde a un estudio de creación y validación transcultural de una escala de prejuicio contra habitantes de calle, fundamentada en la teoría de la respuesta al ítem y en la teoría de la escalada comportamental del prejuicio de Allport. La escala creada presentó evidencias de validez de constructo, validez convergente y buenos índices de consistencia interna. También se comprobó parcialmente la hipótesis de la escala del prejuicio de Allport. En el tercer capítulo se buscó identificar los factores asociados al prejuicio contra habitantes de calle, así como construir y probar un modelo jerárquico para explicar variaciones en los niveles de este prejuicio. El modelo propuesto tuvo cuatro niveles de mediación del prejuicio, buenos índices de ajuste, e incluyó las variables dominancia social, valores básicos, egocentrismo, percepción de inseguridad y calidad del contacto con habitantes de calle. En el cuarto capítulo se describió el proceso de creación de un Test de Asociaciones Implícitas sobre actitudes hacia habitantes de calle, y se probó los niveles de correlación entre los puntajes adquiridos con este test y los adquiridos con la escala creada en el artículo dos. Los resultados indicaron que hubo fuertes asociaciones entre los conceptos que representan a los habitantes de calle y los estereotipos negativos hacia esta población. No se encontró una correlación entre los puntajes en las dos pruebas, acorde con los resultados de otros estudios sobre medidas implícitas y explícitas de estereotipos.

The objectives of this research were to create explicit and implicit measures of prejudice against homeless, and to identify factors associated with negative attitudes toward this population. To meet these objectives several studies collected in four articles were made. In the first article the literature on prejudice against homeless was reviewed. In this study was found that both, in Latin America and in the countries of industrialized West, have been reported stereotypes towards this population related to mental illness and drug addiction, as well as acts of discrimination related to limitations in the use of public space. Article two corresponded to a study of cross-cultural creation and validation of a scale of prejudice against homeless, created with basics of Item Response Theory and the Allport's scale of prejudice. The created scale presented evidence of construct validity, convergent validity and good internal consistency. It was also verified, in part, the Allport's theory of the scale of prejudice. The third article aimed at identifying factors associated with prejudice against homeless, and to build and test a hierarchical model to explain variations in the levels of this prejudice. The proposed model had four levels of prejudice mediations, good fit indices, and included the variables social dominance orientation, basic values, egocentrism, perception of insecurity and quality of contact with homeless people. In the fourth article was described the process of creating an implicit association test about attitudes toward homeless, and was tested scores correlation levels acquired with this test and those acquired with the scale established in article two. The results indicated that there are strong associations between concepts representing the homeless people and negative stereotypes towards this population. No correlation between the scores on the two measures was found, in line with other studies on implicit and explicit measures of stereotypes. / Los objetivos de esta tesis fueron la creación de medidas explícitas e implícitas del prejuicio contra habitantes de calle, y la identificación de algunos factores asociados con actitudes negativas hacia esta población. Para responder a estos objetivos se realizaron varios estudios reunidos en cuatro artículos y presentados en este documento como capítulos. En el primer capítulo, se realizó un estudio de revisión de la literatura sobre el prejuicio contra habitantes de calle. En este estudio se encontró que tanto en Latinoamérica como en los países de occidente industrializado, se han reportado estereotipos hacia esta población relacionados con la enfermedad mental y la adicción a las drogas; así como actos de discriminación relacionados con limitaciones en el uso del espacio público. El capítulo dos corresponde a un estudio de creación y validación transcultural de una escala de prejuicio contra habitantes de calle, fundamentada en la teoría de la respuesta al ítem y en la teoría de la escalada comportamental del prejuicio de Allport. La escala creada presentó evidencias de validez de constructo, validez convergente y buenos índices de consistencia interna. También se comprobó parcialmente la hipótesis de la escala del prejuicio de Allport. En el tercer capítulo se buscó identificar los factores asociados al prejuicio contra habitantes de calle, así como construir y probar un modelo jerárquico para explicar variaciones en los niveles de este prejuicio. El modelo propuesto tuvo cuatro niveles de mediación del prejuicio, buenos índices de ajuste, e incluyó las variables dominancia social, valores básicos, egocentrismo, percepción de inseguridad y calidad del contacto con habitantes de calle. En el cuarto capítulo se describió el proceso de creación de un Test de Asociaciones Implícitas sobre actitudes hacia habitantes de calle, y se probó los niveles de correlación entre los puntajes adquiridos con este test y los adquiridos con la escala creada en el artículo dos. Los resultados indicaron que hubo fuertes asociaciones entre los conceptos que representan a los habitantes de calle y los estereotipos negativos hacia esta población. No se encontró una correlación entre los puntajes en las dos pruebas, acorde con los resultados de otros estudios sobre medidas implícitas y explícitas de estereotipos.

The objectives of this research were to create explicit and implicit measures of prejudice against homeless, and to identify factors associated with negative attitudes toward this population. To meet these objectives several studies collected in four articles were made. In the first article the literature on prejudice against homeless was reviewed. In this study was found that both, in Latin America and in the countries of industrialized West, have been reported stereotypes towards this population related to mental illness and drug addiction, as well as acts of discrimination related to limitations in the use of public space. Article two corresponded to a study of cross-cultural creation and validation of a scale of prejudice against homeless, created with basics of Item Response Theory and the Allport's scale of prejudice. The created scale presented evidence of construct validity, convergent validity and good internal consistency. It was also verified, in part, the Allport's theory of the scale of prejudice. The third article aimed at identifying factors associated with prejudice against homeless, and to build and test a hierarchical model to explain variations in the levels of this prejudice. The proposed model had four levels of prejudice mediations, good fit indices, and included the variables social dominance orientation, basic values, egocentrism, perception of insecurity and quality of contact with homeless people. In the fourth article was described the process of creating an implicit association test about attitudes toward homeless, and was tested scores correlation levels acquired with this test and those acquired with the scale established in article two. The results indicated that there are strong associations between concepts representing the homeless people and negative stereotypes towards this population. No correlation between the scores on the two measures was found, in line with other studies on implicit and explicit measures of stereotypes. / Los objetivos de esta tesis fueron la creación de medidas explícitas e implícitas del prejuicio contra habitantes de calle, y la identificación de algunos factores asociados con actitudes negativas hacia esta población. Para responder a estos objetivos se realizaron varios estudios reunidos en cuatro artículos y presentados en este documento como capítulos. En el primer capítulo, se realizó un estudio de revisión de la literatura sobre el prejuicio contra habitantes de calle. En este estudio se encontró que tanto en Latinoamérica como en los países de occidente industrializado, se han reportado estereotipos hacia esta población relacionados con la enfermedad mental y la adicción a las drogas; así como actos de discriminación relacionados con limitaciones en el uso del espacio público. El capítulo dos corresponde a un estudio de creación y validación transcultural de una escala de prejuicio contra habitantes de calle, fundamentada en la teoría de la respuesta al ítem y en la teoría de la escalada comportamental del prejuicio de Allport. La escala creada presentó evidencias de validez de constructo, validez convergente y buenos índices de consistencia interna. También se comprobó parcialmente la hipótesis de la escala del prejuicio de Allport. En el tercer capítulo se buscó identificar los factores asociados al prejuicio contra habitantes de calle, así como construir y probar un modelo jerárquico para explicar variaciones en los niveles de este prejuicio. El modelo propuesto tuvo cuatro niveles de mediación del prejuicio, buenos índices de ajuste, e incluyó las variables dominancia social, valores básicos, egocentrismo, percepción de inseguridad y calidad del contacto con habitantes de calle. En el cuarto capítulo se describió el proceso de creación de un Test de Asociaciones Implícitas sobre actitudes hacia habitantes de calle, y se probó los niveles de correlación entre los puntajes adquiridos con este test y los adquiridos con la escala creada en el artículo dos. Los resultados indicaron que hubo fuertes asociaciones entre los conceptos que representan a los habitantes de calle y los estereotipos negativos hacia esta población. No se encontró una correlación entre los puntajes en las dos pruebas, acorde con los resultados de otros estudios sobre medidas implícitas y explícitas de estereotipos.

Executable and Translatable UML (xtUML) is the next abstraction level in software development, where both programming language and software architecture have been abstracted away. xtUML is a well defined UML profile, extended with precise action semantics. This allows the developers to define a problem area, domain, in such a detail that it can be executed. By defining the system with xtUML-models, domains, the system functionality can be verified early in the development process. Translation to code can be done in different ways and this work will be performed in an environment where code is automatically generated with a model compiler. The goal with a domain is that it should be independent of other domains, reused without modification and exchanged with another domain solving the same problem. However a domain can make assumptions that certain functionality is available and these assumptions are requirements for another domain. To fulfil these goals there must be a minimal coupling between the domains. This can be solved with the technique Implicit Bridging, where the bridge dependency between domains is defined in a bridge. The dependency is in the form of mappings/coupling between elements in both domains. By defining a bridge interface for a server domain a client domain can use the resources offered by the server domain. The work performed shows how an implementation of Implicit Bridging could be realized by applying the technique in a microwave oven system. From the system design five different mapping types have been implemented. The applicability and the quality of the implementation have been verified by testing the generated system functionality and also verifying the goals, exchangeability and reuse of domains, of the system.

No description available.

En analys av en studie gjord av Lorenz och Heinitz (2014) på autistiska personers uppfattning om sig själva, sina förmågor och behov och en kartläggningsrapport av Specialpedagogiska skolmyndigheten från 2013 har belyst hur det hos dessa individer finns en potential långt utöver det normala. Skolmyndigheten (2013) rapporterar om att lärare saknar verktyg för att förstå elever med neuropsykiatriska funktionsvariationer, framförallt vid autismspektrumtillstånd där sådana verktyg ofta behöver vara individanpassade och därför varierar från elev till elev. Önskan om att hitta metoder för att använda tillgängliga läromedel eller önskan om handledning för att förstå eleverna bättre är någonting som lyfts upp då lärare menar sig vara vilsna kring vad man ska göra i den egna undervisningen med de metoder som finns. Med detta som grund motiverades jag till att utforma ett fortbildningsmaterial för lärare inom matematik som förhoppningsvis ska kunna stötta lärarna i deras kommunikation med elever med autismspektrumtillstånd. Som ett led i utvecklingsarbetet gjordes djupintervjuer med två lärare inom matematik och teknik och med fyra personer diagnosticerade med AST. Därefter analyserades intervjuerna med hjälp av tematisk analys för att sedan användas som underlag för diskussion kring några faktorer som påverkar elevens lärande. Faktorer som framkom var lärarnas undervisningsform, föreställningar av sin och elevens roll i lärandet och hur lärarens relation till de övriga lärare i kollegieteamet påverkar kvalitén av lärarens undervisning. Resultatet från djupintervjuerna visade att det hos elever med AST finns behov av tydlighet, struktur och tidsplanering. Vill man som lärare säkerställa en bra kommunikation med dessa elever behöver en förståelse för hur läraren kan förmedla förväntningar uppmärksammas. Sådana förväntningar kan vara såväl implicita och explicita. Förväntningar som t.ex. kan vara att läraren tilldelar uppgifter som befinner sig på en lägre nivå än elevens egen föreställning av sin förmåga. Läraren behöver också vara införstådd i elevens problematik och för det krävs ett mer omfattande arbete inom kollegiet som läraren är en del av. Detta eftersom ett bra stöd för eleven inte kan förväntas ges enbart av elevens egna lärare då elevens behov av stöd kräver insatser från flera olika yrkesgrupper. Vidare visade resultat från djupintervjuerna hur det hos elever med AST finns ett behov av social inkludering, däremot var det mindre tydligt hur eleverna skulle uppnå detta. Man hänvisade till att läraren saknar kunskap om hur elevens personligheter och intressen måste beaktas tillsammans innan man sammanför grupper. Också underströks hur eleven behöver lära sig hantera vissa sociala situationer, vad den ska säga och hur. Om inte det sker vågar eleven sällan inleda samtal med övriga klasskamrater och det i sin tur har jag kunnat visa påverka elevens fortsatta förståelse av matematik. Utvärdering av det utvecklade fortbildningsmaterialet gav värdefull återkoppling för att förbättra materialet. Utvärderingen genomfördes bland tre verksamma lärare. En lärare hade förstått det avsedda syftet och angav att materialet gav hen idéer om hur undervisning kan genomföras, t.ex. genom att omformulera sina uppgifter eller addera material inför vissa moment som kan göra det lättare för AST-elever att sätta sig in i dem. För de andra två lärarna var syftet otydligt och de angav att det saknades tillräckligt med uppgifter som läraren kunde använda för sina elever med AST, men att de förslagen som gavs ändå var uppskattade. / A study conducted by Lorenz and Heinitz (2014) on the view that autistic people have of themselves, their attributes as well as a survey done by Specialpedagogiska Skolmyndigheten (2013) suggest that a lot of individuals on the spectrum may own a potential far beyond what is considered normal. The report from Skolmyndigheten (2013) paints an image of how present material for students with neuropsychiatric disorders are lacking, especially for those students who are on the autistic spectrum. These students are specially a challenge since every individual on the spectrum and thus a one-way solution is considered virtually impossible. Using this knowledge as a building block, I was motivated to construct an introductory material for teachers in mathematics to effectively communicate with students on the autistic spectrum. The material is based on surveys done in the form of deep interviews. These deep interviews were conducted with 2 teachers in math and technology and with 4 people diagnosed with ASD. Furthermore, the data from the interviews were analysed with the help of a tool called thematic analysis. Afterwards the data was used to discuss some of the factors that affect students learning. The factors involved in my discussion were the specific form of teaching, preconceptions about ones and students’ involvement in their own learning and how teacher interaction with the other teachers in the colleague team may impact the quality of student learning. Looking at the results from the deep interviews, we see that for people with ASD there is a desire for precision, structure and adequate time-planning. Good communication with these students requires the teachers’ understanding of how she can convey her conceptions, explicit as well as implicit, by her form of teaching, for example by recognizing how the distribution of lower level problems could downgrade a students’ perception of their own10ability. Teachers need to consider and understand the problems of specific students and in order to do that a more extensive cooperation is required with the rest of the team. Such cooperation is required since one need to consider how a complex diagnosis such as autism spectrum involves appropriate intervention regulated and influenced by people in different occupation groups. The final results concerned the opinions received by teachers regarding the realization of the introductory material. With regards to the intention to construct a material which can support understanding of the communication problems associated with autism, the results of evaluation from three teachers in mathematics and technology showed mix of responses. One of the three teachers had understood the purpose and commented on how the material inspired his own taking on how to teach for these students, for instance by reformulating problems or add material in the making of problems to make it easier for students on the autistic spectrum to engage with them. The other two teachers mentioned the lack of sufficient amount of math problems which could be of any use in their own teaching, although they saw how some of the parts were useful for other purposes. I suggest that the responses were mixed as an effect of misunderstanding of the real purpose of the introductory material. Since the making of a new introductory material given the feedback was not tested, the conclusions regarding how well this material meets the context cannot be properly validated.

Ce travail est consacré à la modélisation mathématique et numérique des écoulements eau-air en conduite qui interviennent notamment dans les centrales de production d’électricité ou les réseaux d’eaux usées. On s’intéresse particulièrement aux écoulements mixtes caractérisés par la présence de régimes stratifiés pilotés par des ondes gravitaires lentes, de régimes en charge ou secs (conduite remplie d’eau ou d’air) pilotés par des ondes acoustiques rapides, et de poches d’air piégées. Une modélisation précise de ces écoulements est nécessaire afin de garantir le bon fonctionnement du circuit hydraulique sous-jacent. Alors que la plupart des modèles disponibles dans la littérature se concentrent sur la phase eau en négligeant la présence de l’air, un modèle bicouche compressible prenant en compte les interactions eau-air est proposé dans cette thèse. Sa construction réside dans l’intégration des équations d’Euler barotropes sur la hauteur de chaque phase et dans l’application de la contrainte hydrostatique sur le gradient de pression de l’eau. Le modèle obtenu est hyperbolique et satisfait une inégalité d’entropie en plus d’autres propriétés mathématiques notables, telles que l’unicité des relations de saut ou la positivité des hauteurs et densités de chaque phase. Au niveau discret, la simulation d’écoulements mixtes avec le modèle bicouche compressible soulève plusieurs défis en raison de la disparité des vitesses d’ondes caractérisant chaque régime, des processus de relaxation rapide sous-jacents, et de la disparition de l’une des phases dans les régimes en charge ou sec. Une méthode à pas fractionnaires implicite-explicite est alors développée en s’appuyant sur la relaxation rapide en pression et sur le mimétisme avec les équations de Saint-Venant pour la dynamique lente de la phase eau. En particulier, une approche par relaxation permet d’obtenir une stabilisation du schéma en fonction du régime d’écoulement. Plusieurs cas tests sont traités et démontrent la capacité du modèle proposé à gérer des écoulements mixtes incluant la présence de poches d’air piégées. / The present work is dedicated to the mathematical and numerical modelling of transient air-water flows in pipes which occur in piping systems of several industrial areas such as nuclear or hydroelectric power plants or sewage pipelines. It deals more specifically with the so-called mixed flows which involve stratified regimes driven by slow gravity waves, pressurized or dry regimes (pipe full of water or air) driven by fast acoustic waves and entrapped air pockets. An accurate modelling of these flows is necessary to guarantee the operability of the related hydraulic system. While most of available models in the literature focus on the water phase neglecting the air phase, a compressible two-layer model which accounts for air-water interactions is proposed herein. The derivation process relies on a depth averaging of the isentropic Euler set of equations for both phases where the hydrostatic constraint is applied on the water pressure gradient. The resulting system is hyperbolic and satisfies an entropy inequality in addition to other significant mathematical properties, including the uniqueness of jump conditions and the positivity of heights and densities for each layer. Regarding the discrete level, the simulation of mixed flows with the compressible two-layer model raises key challenges due to the discrepancy of wave speeds characterizing each regime combined with the fast underlying relaxation processes and with phase vanishing when the flow becomes pressurized or dry. Thus, an implicit-explicit fractional step method is derived. It relies on the fast pressure relaxation in addition to a mimetic approach with the shallow water equations for the slow dynamics of the water phase. In particular, a relaxation method provides stabilization terms activated according to the flow regime. Several test cases are performed and attest the ability of the compressible two-layer model to deal with mixed flows in pipes involving air pocket entrapment.

On étudie dans le cadre de la thèse une famille de schémas numériques permettant de résoudre les équations de Saint-Venant. Ces schémas utilisent une décomposition d'opérateur de type Lagrange-projection afin de séparer les ondes de gravité et les ondes de transport. Un traitement implicite du système acoustique (relié aux ondes de gravité) permet aux schémas de rester stable avec de grands pas de temps. La correction des flux de pression rend possible l'obtention d'une solution approchée précise quel que soit le régime d'écoulement vis-à-vis du nombre de Froude. Une attention toute particulière est portée sur le traitement du terme source qui permet la prise en compte de l'influence de la topographie. On obtient notamment la propriété dite équilibre permettant de conserver exactement certains états stationnaires, appelés état du "lac au repos". Des versions 1D et 2D sur maillages non-structurés de ces méthodes ont été étudiées et implémentées dans un cadre volumes finis. Enfin, une extension vers des méthodes ordres élevés Galerkin discontinue a été proposée en 1D avec des limiteurs classiques ainsi que combinée avec une boucle MOOD de limitation a posteriori. / In this thesis we study a family of numerical schemes solving the shallow water equations system. These schemes use a Lagrange-projection like splitting operator technique in order to separate the gravity waves and the transport waves. An implicit-explicit treatment of the acoustic system (linked to the gravity waves) allows the schemes to stay stable with large time step. The correction of the pressure fluxes enables the obtain of a precise approximation solution whatever the regime flow is with respect to the Froude number. A particular attention has been paid over the source term treatment which permits to take the topography into account. We especially obtain the so-called well-balanced property giving the exact conservation of some steady states, namely the "lake at rest" state. 1D and 2D versions of this methods have been studied and implemented in the finite volumes framework. Finally, a high order discontinuous Galerkin extension has been proposed in 1D with classical limiters along with a combined MOOD loop a posteriori limiting strategy.