No description available.

In recent years there have been a major developments in the computational mechanics community when it comes to modelling of fracture mechanics. There are now several well established numerical methods that are implemented in commercial programs such as: Phase Field Modelling, Enhanced Assumed Strain (EAS), Smeared Crack Methods, Extended Finite Element Method (XFEM) and Partition of Unity Finite Element Method (PUFEM). This work has been based on PUFEM and it has been of interest to investigate if this numerical method can be combined with plastic deformation. The reason for this is that it has been known that complex structural and material phenomenon such as embrittlement of steels or composites show a variation of fracture toughness. Thus more advanced approaches are required to capture the response of such structures and materials. The analysis was split in to three parts. First, a benchmark analysis was done with linear tetrahedral elements and, which has been implemented in previous applications. Thereafter the same analysis was done for quadratic tetrahedral elements. Finally, the interface between plasticity and PUFEM was implemented and was analysed with the same geometries as in the benchmark case. The analysis show that it is possible to combine plasticity in PUFEM setting and that it has a possibility to be used in future applications. / Under dem senaste åren har det skett en massiv utveckling inom beräkningsmekaniken när det kommer till att modellera brottmekaniska fenomen. Det finns nu ett flertal väletablerade numeriska metoder som är implementerade i kommersiella program såsom: Phase Field Modelling, Enhanced Assumed Strain (EAS), Smeared Crack Methods, Extended Finite Element Method (XFEM) and Partition of Unity Finite Element Method (PUFEM). Detta arbete har fokuserat på (PUFEM) och det har varit av intresse att se om denna metod kan kombineras tillsammans med plastisk deformation. Anledningen till att detta har varit av intresse är på grund av att det finns ett flertal komplexa struktur - och materialfenomen såsom försprödning av stål och kompositer som uppvisar en variation i sin duktilitet. Detta medför att mer avancerade metoder behöver tillämpas för att fånga responsen av dessa strukturer och material. Analysen som har genomförts var uppdelad i tre delar. Först analyserades ett problem med linjär tetrahedriska element som ett riktmärke, detta har implementerats i tidigare applikationer. Därefter analyserades samma problem fast med tethraderiska element med kvadratisk interpolation. Slutligen så integrerades plasticitet med PUFEM, där samma geometrier analyserades som riktmärke. Den analysen som har genomfört visar att det går att kombinera plastiska deformation tillsammans med PUFEM och att denna metod har potentialen att användas i framtida applikationer.

The meta-GGA functionals and random phase approximation are tested for phase transitions and a strongly correlated transition metal oxide in this dissertation. One of the latest meta-GGA functionals is also employed to study the van der Waals bound system in surface science. Our main purpose is to reveal the performance of new exchange-correlation functionals on various properties and systems. We are also interested in seeking the possible relationship between the performance of a semilocal functional and its exchange enhancement factor. We have studied the structural phase transitions in crystalline Si (insulator to metal), SiO2 (insulator to insulator) and Zr (metal to metal) systems, as a test of exchange energy semilocal functionals on Jacob's ladder. Our results confirm the energy-geometry dilemma of GGAs in three systems. The most sophisticated non-empirical meta-generalized gradient approximations (meta-GGAs) such as TPSS (Tao-Perdew-Staroveov-Scuseria) and revTPSS (revised TPSS) give better lattice constants than PBE, but the phase transition parameters (energy difference and transition pressure) are smaller and less realistic than those from the latter GGA. However, the recent functionals of meta-GGA made simple family (MGGA_MS) behave differently to those previous meta-GGAs, predicting larger and more realistic phase transition parameters. Meanwhile, MGGA_MS also delivers the equilibrium geometry of crystalline materials similar to previous non-empirical meta-GGAs. In contrast to semilocal functionals, the nonlocal functionals such as the range-separated hybrid functional HSE06 (Heyd-Scuseria-Ernzerhof) and non-self consistent random phase approximation (RPA) are not only able to give the accurate equilibrium geometry , but also predict the realistic phase transition parameters for Si and SiO2 systems. The ground state of rutile-type vanadium dioxide (R-VO2) represents a great challenge to the current density functional theory. In this dissertation, we investigated the electronic structures and magnetism of R-VO2 using exchange-correlation functionals of all five rungs on Jacob's ladder. Our calculations show that all semilocal functionals (LSDA, GGAs and meta-GGAs) and hybrid functionals (HSE06) stabilize the spin-polarized states (ferromagnetic and anti-ferromagnetic states) over non-magnetic state, which are completely opposite to experimental observation. Surprisingly, LSDA gives the best energetic descriptions for magnetic and non-magnetic phases of R-VO2 among semilocal functionals and HSE06. Otherwise, RPA calculations are highly dependent on the inputs in the spin polarized case. With PBE inputs, RPA also fails, giving lower energies for spin-polarized states than for the non-magnetic phase. Meanwhile, the results are reversed using LSDA inputs. From the computed equilibrium cell volume, we observe the error cancellation in the exchange-correlation hole of most semilocal functionals in the spin-polarized calculations. LSDA and RPA do not fit to this picture. By analyzing the local magnetic moments of vanadium atoms, it is found that the magnetic property predicted from meta-GGA can be related to its exchange enhancement factor. The physisorption of a molecule on a transition metal surface is also another difficult problem in DFT because of the long-range van der Waals interactions. The recently developed MGGA_MS family of density functionals is able to capture a portion of intermediate range dispersion interactions. Therefore, we employed MGGA_MS2 to study the physisorption of CO2 on Pt (111) surface, and the results are compared to those of PBE, PBE+D2 and optB88-vdW methods. The computed binding curves confirm that that MGGA_MS2 indeed captures the van der Waals interactions near the equilibrium binding distance, and the obtained binding distance is also in good agreement with PBE+D2 and optB88-vdW calculations. By computing the electron density difference map (EDDM), we find that the electron densities of CO2 and Pt (111) surface are strongly polarized in optB88-vdW, creating the dipole moments in two subsystems. Such effect is reduced in MGGA_MS2. For PBE, the polarization of electron density is very weak, but not negligible. The α dependence in the exchange enhancement factor of a meta-GGA is the key to capture the intermediate range van der Waals interactions. In summary, a meta-GGA functional can step out of the famous "energy-geometry dilemma" , predicting good lattice constants and phase transition parameters at the same time. With the proper construction, a meta-GGA can even capture a portion of van der Waals interactions. The RPA is usually more accurate than semilocal functionals for many ground state properties. The strongly correlated systems like R-VO2 are still a big challenge to present-day density functional theory. We will continue to seek more accurate exchange-correlation functionals. / Physics

No description available.

In den letzten Jahrzehnten haben Tischlaserquellen eine bemerkenswerte Entwicklung durchlaufen. Sie sind nun in der Lage, maßgeschneiderte ultrakurze Mehrfarben-Laserpulse zu erzeugen, die es ermöglichen, die elektronische Dynamik in Materialien auf ihrer natürlichen Zeitskala von Attosekunden zu untersuchen. In dieser Arbeit werden verschiedene Kombinationen von elektrischen Feldern genutzt, von extrem-ultravioletten (XUV) bis nahinfraroten Wellenlängen, um komplexe Elektronendynamiken in Atomen und chiralen Medien zu erforschen, zu rekonstruieren und zu kontrollieren. Dabei werden grundlegende Konzepte der Licht-Materie-Wechselwirkung eingeführt, einschließlich starker Feldprozesse, die im Kern der Attosekundenspektroskopie liegen. Ein Schwerpunkt liegt auf der Nutzung eines XUV-Pulses in Kombination mit einem nahinfraroten Puls, um den Bevölkerungstransfer zu hohen Drehimpulszuständen in Heliumatomen zu untersuchen. Durch Manipulation der Laserparameter wird die Rolle des AC Stark-Effekts von gebundenen Zuständen in der beobachteten Dynamik identifiziert. Weitere Untersuchungen umfassen die Verwendung eines bicirculären elektrischen Feldes zur Induktion von HHG in Argon, wobei Anzeichen einer starken Feldfangung von Elektronen in angeregten Zuständen im HHG-Spektrum entdeckt werden. Die Arbeit zeigt die entscheidende Rolle angeregter Zustände in der HHG auf. Zusätzlich wird die Anwendung synthetischer chiraler Felder erforscht, um Chiralität auf achirale Objekte wie Atome zu übertragen, und es wird eine Verbindung zwischen synthetischen chiralen Feldern und strukturiertem Licht hergestellt. / In recent decades table-top laser sources have undergone remarkable development and are now capable of generating tailored ultrashort multicolor laser pulses, enabling the study of electronic dynamics in materials on their natural timescale of the attoseconds. In this thesis work various combinations of electric fields spanning from extreme-ultraviolet (XUV) to near-infrared wavelengths are used to investigate, reconstruct and control complex electron dynamics in atoms and chiral media. The initial chapter of this thesis introduces the fundamental concepts underlying light-matter interaction, including strong field processes which lie at the core of attosecond spectroscopy. The second chapter focuses on the utilization of an XUV pulse combined with a near-infrared pulse to study population transfer to high angular momentum states in helium atoms. By manipulating laser parameters, the study identifies the significant role played by the AC Stark shift of bound states in the observed dynamics. In the third chapter a bicircular electric field is employed to induce HHG in argon. Changing the timedelay between the two frequencies, indications of strong field trapping of electrons in excited states are uncovered within the HHG spectrum, confirming the existence of long-lived trajectories lasting multiple optical cycles. The study conclusively demonstrates the crucial role of excited states in HHG. The fourth chapter explores the application of synthetic chiral fields—whose polarization traces a chiral curve over the optical cycle—to imprint chirality on achiral objects such as atoms, both in the low- and strong-field regime. Moreover, the thesis establishes a connection between synthetic chiral fields and structured light, introducing chiral vortex beams with azimuthally varying handedness.

Tesis por compendio / [EN] Fuzzy mathematics has constituted a wide field of research, since L. A. Zadeh introduced in 1965 the concept of fuzzy set. In particular, the problem of constructing a satisfactory theory of fuzzy metric spaces has been investigated by several authors. In 1994, George and Veeramani introduced and studied a notion of fuzzy metric space that constituted a modification of the one given by Kramosil and Michalek. Several authors have contributed to the study of this kind of fuzzy metrics, from the mathematical point of view and for their applications. In this thesis we have contributed to develop the study of these fuzzy metrics, from the mathematical point of view, and we approached the problem of measuring perceptual colour-difference between samples of colour using one of these fuzzy metrics. The contributions of the study carried out in this thesis is summarized as follows: \begin{enumerate} \item[(i)] We have made a detailed study of the fuzzy metric space $(X,M,\cdot)$ where $M$ is given on $X=[0,\infty[$ by $M(x,y,t)=\frac{\min\{x,y\}+t}{\max\{x,y\}+t}$ and others related to it. As a consequence we have introduced five questions in fuzzy metrics related to continuity, extension, contractivity and completion. \item[(ii)] We have answered an open question constructing a fuzzy metric space $(X,M,\ast)$ in which the assignment $f(t)=\lim_n M(a_n,b_n,t)$, where $\{a_n\}$ and $\{b_n\}$ are $M$-Cauchy sequences in $X$, is not a continuous function on $t$. The response to this question has allowed us to characterize the class of completable strong fuzzy metric spaces. \item[(iii)] We have introduced and studied a stronger concept than convergence of sequences in fuzzy metric spaces, which we call $s$-convergence. In our study, we have gotten a characterization of those spaces in which every convergent sequence is $s$-convergent and we have given a classification of fuzzy metrics attending to the behaviour of the fuzzy metric with respect to the different types of convergence. \item[(iv)] We have studied, in the context of fuzzy metric spaces, when certain families of open balls centered at a point are local bases for this point. \item[(v)] We have answered two open questions related to standard convergence, a stronger concept than convergence of sequences in fuzzy metric spaces, introduced in a natural way attending to the concept of standard Cauchy sequence (introduced in \cite{adomain}). These responses have led us to establish conditions under which Cauchyness and convergence should be considered \textit{compatible}. \item[(vi)] As a practical application, we have shown that a certain fuzzy metric is useful for measuring perceptual colour-differences between colour samples. \end{enumerate} / [ES] La matemática fuzzy ha constituido un amplio campo en la investigación, desde que en 1965 L. A. Zadeh introdujo el concepto de conjunto fuzzy. En particular, la construcción de una teoría satisfactoria de espacios métricos fuzzy ha sido un problema investigado por muchos autores. En 1994, George y Veeramani introdujeron y estudiaron una noción de espacio métrico fuzzy que constituía una modificación de la anteriormente dada por Kramosil y Michalek. Muchos autores han contribuido al estudio de este tipo de métricas fuzzy, desde el punto de vista matemático y de sus aplicaciones. En esta tesis hemos contribuido al desarrollo del estudio de estas métricas fuzzy, desde el punto de vista matemático, y hemos abordado el problema de la medida de la diferencia perceptual de color utilizando una de estas métricas. Las contribuciones que aportamos en esta tesis a dicho estudio, se resumen a continuación: \begin{enumerate} \item[(i)] Hemos hecho un estudio detallado del espacio métrico fuzzy $(X,M,\cdot)$ donde $M$ está dada sobre $[0,\infty[$ por la expresión $M(x,y,t)=\frac{\min\{x,y\}+t}{\max\{x,y\}+t}$ y de otros espacios métricos fuzzy relacionados con el. Como consecuencia de este estudio hemos introducido cinco cuestiones en la teoría de las métricas fuzzy relacionadas con continuidad, extensión, contractividad y completación. \item[(ii)] Hemos respondido a una cuestión abierta construyendo un espacio métrico fuzzy $(X,M,\ast)$ en el cual la asignación $f(t)=\lim_n M(a_n,b_n,t)$, donde $\{a_n\}$ y $\{b_n\}$ son sucesiones $M$-Cauchy, no es una función continua sobre $t$. La respuesta a esta cuestión nos ha permitido caracterizar la clase de los espacios métricos fuzzy strong completables. \item[(iii)] Hemos introducido y estudiado un concepto más fuerte que el de convergencia de sucesiones en espacios métricos fuzzy, al que hemos llamado $s$-convergencia. En nuestro estudio hemos conseguido una caracterización de aquellos espacios métricos fuzzy en los cuales toda sucesión convergente es $s$-convergente y hemos dado una clasificación de los espacios métricos fuzzy atendiendo a su comportamiento con respecto a los diferentes tipos de convergencia que se da en él. \item[(iv)] Hemos estudiado, en el contexto de los espacios métricos fuzzy, cuando ciertas familias de bolas abiertas centradas en un punto son base local de este punto. \item[(v)] Hemos respondido a dos cuestiones abiertas relacionadas con la convergencia standard, un concepto más fuerte que el de convergencia de sucesiones en espacios métricos fuzzy, introducido de forma natural a partir del concepto de sucesión de Cauchy standard (introducido en \cite{adomain}). Estas respuestas nos han llevado a establecer unas condiciones bajo las cuales un concepto relacionado con el concepto de sucesión de Cauchy y un concepto relacionado con el de convergencia deberían satisfacer para ser consideradas \textsl{compatibles}. \item[(vi)] Como aplicación práctica, hemos mostrado que una cierta métrica fuzzy es útil para medir diferencia perceptual de color entre muestras de color. \end{enumerate} / [CA] La matemàtica fuzzy ha constituït un ampli camp en la investigació, des que el 1965 L. A. Zadeh va introduir el concepte de conjunt fuzzy. En particular, la construcció d'una teoria satisfactòria d'espais mètrics fuzzy ha estat un problema investigat per molts autors. El 1994, George i Veeramani introduiren i estudiaren una noció d'espai mètric fuzzy que constituïa una modificació de la donada per Kramosil i Michalek anteriorment. Molts autors han contribuït a l'estudi d'aquest tipus de mètriques fuzzy, des del punt de vista matemàtic i de les seves aplicacions. En aquesta tesi hem contribuït al desenvolupament de l'estudi d'aquestes mètriques fuzzy, des del punt de vista matemàtic, i hem abordat el problema de la mesura de la diferència perceptiva de color utilitzant aquestes mètriques. Les contribucions que aportem en aquesta tesi a tal estudi es resumeixen a continuació: \begin{enumerate} \item[(i)] Hem fet un estudi detallat de l'espai mètric fuzzy $(X,M,\cdot)$ on $M$ està donada sobre $[0,\infty[$ per l'expressió $M(x,y,t)=\frac{\min\{x,y\}+t}{\max\{x,y\}+t}$ i d'altres espais mètrics fuzzy relacionats amb ell. Com a conseqüència d'aquest estudi hem introduït cinc qüestions en la teoria de les mètriques fuzzy relacionades amb continuïtat, extensió, contractividad i completació. \item[(ii)] Hem respost a una qüestió oberta construint un espai mètric fuzzy $ (X, M, \ast) $ en el qual l'assignació $ f (t) = \lim_n M (a_n, b_n, t) $, on $ \{a_n\} $ i $ \{b_n \} $ són successions $ M $-Cauchy, no és una funció contínua sobre $ t $. La resposta a aquesta qüestió ens ha permès caracteritzar la classe dels espais mètrics fuzzy strong completables. \item[(iii)] Hem introduït i estudiat un concepte més fort que el de convergència de successions en espais mètrics fuzzy, al qual hem anomenat $ s $-Convergència. En el nostre estudi hem aconseguit una caracterització d'aquells espais mètrics fuzzy en els quals tota successió convergent és $ s $-convergente i hem donat una classificació dels espais mètrics fuzzy atenent al seu comportament respecte als diferents tipus de convergència que es dóna en ell. \item[(iv)] Hem estudiat, en el context dels espais mètrics fuzzy, quan certes famílies de boles obertes centrades en un punt són base local d'aquest punt. \item[(v)] Hem respost a dues qüestions obertes relacionades amb la convergència estàndard, un concepte més fort que el de convergència de successions en espais mètrics fuzzy, introduït de forma natural a partir del concepte de successió de Cauchy estàndard (introduït en \cite{adomain}). Aquestes respostes ens han portat a establir unes condicions sota les quals un concepte relacionat amb el concepte de successió de Cauchy i un concepte relacionat amb el de convergència haurien de satisfer per a ser considerats \textsl{compatibles}. \item[(vi)] Com a aplicació pràctica, hem mostrat que una certa mètrica fuzzy és útil per mesurar la diferència perceptiva de color entre mostres de color. \end{enumerate} / Miñana Prats, JJ. (2015). Fuzzy metric spaces and applications to perceptual colour-differences [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/50612 / Compendio

High harmonic generation (HHG) is an extreme non-linear phenomenon where strong laser fields interact with a medium to produce coherent and high-frequency harmonics of the incident light. It has emerged as a rapidly growing research area in bulk materials since its first observation in ZnO crystals in 2011. Over the past decade, pioneering studies have already been made in understanding the details of the microscopic mechanism behind this phenomenon, like the role of intra- and inter-band transitions, the contribution of the modulus and the phase of the dipole moment to even and odd harmonic peaks, the role of the oscillating dipoles, effects of broken symmetry, etc. However, the role of electron-electron correlations in the HHG from strongly correlated materials is much less understood. In these materials the interactions between electrons play a significant role, leading to complex and intriguing physical behaviors. In this dissertation, on the example of ZnO, perovskites BaTiO3 and BiFeO3, and transition-metal oxide VO2 I will study the role of electron-electron interaction effects in the HH spectra by using the time-dependent density-functional theory (TDDFT) approach with the exchange-correlation kernel obtained with dynamical mean- field theory (DMFT). In DMFT, one takes into account time-resolved on-site electron-electron interactions (neglected in most of other approaches) that are crucial for a larger part of strongly correlated materials. As I demonstrate, correlation effects significantly modify the HH spectrum, e.g., through the ultrafast modification of the spectrum of the system, as it was found for ZnO. As the next step, I explored the effects of electron-electron correlations in the HH spectrum of BaTiO3 perturbed by intense, few-cycle mid-infrared laser excitations. The correlation effects in this system lead to the emergence of "super-harmonics" - periodic enhancements and suppressions of specific harmonic orders that depend on the correlation strength. I extended my analysis to the case of BiFeO3, where in addition to correlation effects the effects of memory in HHG were analyzed. I have found that both correlation effects and memory lead to an extension of the harmonic cutoff. In my final part, I explored the effect of electron correlations on the HH spectrum of VO2 and compared my findings with the experiment. The obtained results may shed light on the often important role of electron correlations in the HH spectra of solids, providing valuable insights into ultrafast dynamics in complex materials, and contributing to advancements in nonlinear optics and strong-field physics, with the potential for novel photonic devices and imaging techniques in the attosecond and femtosecond regimes.

Объектом исследования явился процесс сепарации студентов от их обоих родителей. Предметом исследования стала взаимосвязь процесса сепарации от родительской семьи с уровнем характеристик инфантилизма и волевых качеств. Магистерская диссертация состоит из введения, двух глав, заключения, списка литературы (98 источников) и приложения, включающего в себя бланки применявшихся методик. Объем магистерской диссертации 96 страница, на которых размещены 8 таблиц и 6 рисунков. Во введении раскрывается актуальность проблемы исследования, разработанность проблематики, ставятся цель и задачи исследования, определяются объект и предмет исследования, формулируются основная и дополнительные гипотезы, указываются методы и эмпирическая база, а также этапы проведения исследования, научная новизна, теоретическая и практическая значимость работы. Первая глава включает в себя обзор иностранной и отечественной литературы по следующим темам: психологическая сепарация от родительской семьи, проявление инфантилизма и место волевых качеств в становлении личности. Выводы по первой главе представляют собой итоги по изучению теоретического материала. Вторая глава посвящена эмпирической части исследования. В ней представлено описание организации и методов проведенного исследования и результатов, полученных по всем использованным методикам: опросник для измерения психологической сепарации в адаптации Дзукаевой В. П.; Садовниковой Т. Ю.; опросник волевых качеств личности под авторством Чумакова; опросник уровня выраженности инфантилизма под авторством Серёгиной А. А. Также в главе представлен корреляционный анализ результатов исследования. Выводы по главе 2 включают в себя основные результаты эмпирического исследования. В заключении в обобщенном виде изложены результаты теоретической и эмпирической частей работы, а также выводы по выдвинутым гипотезам, обоснована практическая значимость исследования и описаны возможные перспективы дальнейшей разработки данной проблематики. / The object of the study was the process of separation of students from their both parents. The subject of the study was the relationship of the separation process from the parental family with the level of characteristics of infantilism and volitional qualities. The master's thesis consists of an introduction, two chapters, a conclusion, a list of references (98 sources) and an appendix, which includes forms of the methods used. The volume of the master's thesis is 96 pages, which contain 8 tables and 6 figures. The introduction reveals the relevance of the research problem, the elaboration of the problem, sets the purpose and objectives of the study, defines the object and subject of the study, formulates the main and additional hypotheses, indicates the methods and empirical base, as well as the stages of research, scientific novelty, theoretical and practical significance of the work. The first chapter includes a review of foreign and domestic literature on the following topics: psychological separation from the parental family, the manifestation of infantilism and the place of volitional qualities in the formation of personality. The conclusions of the first chapter represent the results of the study of theoretical material. The second chapter is devoted to the empirical part of the study. It describes the organization and methods of the conducted research and the results obtained using all the methods used: a questionnaire for measuring psychological separation in adaptation by Dzukaeva V. P.; Sadovnikova T. Yu.; a questionnaire of volitional qualities of personality authored by Chumakov; a questionnaire of the level of severity of infantilism authored by Seregina A. A. The chapter also presents a correlation analysis of the results of the study. The conclusions of Chapter 2 include the main results of an empirical study. In conclusion, the results of the theoretical and empirical parts of the work are summarized, as well as conclusions on the proposed.

The Motor Industry Development Programme (MIDP) was implemented on 1 September 1995 in the context of the country's political and economic liberalisation and the major structural shift in government policy and the trade regime. In an intensely competitive global environment, the strategies of a few dominant motor vehicle manufacturers, mainly operating from the Triad regions of North America, Europe and Japan, impact significantly on the developments of the global automotive industry. Over the past decade the small, highly protected and inwardly focused South African automotive industry has become fully integrated in the global strategies of foreign parent companies. As South Africa's leading manufacturing sector, the automotive sector is contributing significantly to the country's economy in terms of exports, investment, employment and the gross domestic product. The objective of the study was to establish and measure the relevance and value of the MIDP as a promotional tool in the global automotive environment by capturing the responses and perceptions of direct automotive industry exporters and stakeholders for * the South African automotive industry in general, and * the companies forming part of the empirical survey. To satisfy the objectives of the study, the research methodology incorporated an extensive primary and secondary research phase (qualitative and quantitative). A structured empirical survey was used to collect the primary data. The survey data were captured and processed by the Bureau for Market Research (BMR), Unisa. The main findings of the study are that: * The promotional relevance and value of the MIDP as a promotional tool is embedded in the programme's ability to trigger interest in the South African automotive industry, to generate business and to attract investments. * The MIDP is successful in contributing to the automotive sector's international competitiveness and is therefore a very important promotional tool for convincing foreign parent companies to consider South Africa as an investment destination. * The South African automotive industry would not be able to cope with global competition without the MIDP. * Different factors impact on the business operations of the South African automotive industry in general and the specific company in particular and the factors are viewed differently by the selected groups based on their demographic details. The process of trade liberalisation is forcing many South African companies to encounter both intensified competition and new forms of competition. The South African government's target of a 6 percent economic growth rate by 2010 will largely depend on the ongoing successes achieved in priority sectors such as the domestic automotive sector. / Business Management / M. Comm. (Business Management)

Résumé : Il est bien connu que les lois marginales d'un vecteur aléatoire ne suffisent pas à caractériser sa distribution. Lorsque les lois marginales du vecteur aléatoire sont continues, le théorème de Sklar garantit l'existence et l'unicité d'une fonction appelée copule, caractérisant la dépendance entre les composantes du vecteur. La loi du vecteur aléatoire est parfaitement définie par la donnée des lois marginales et de la copule. Dans ce travail de thèse, nous proposons deux tests non paramétriques de détection de ruptures dans la distribution d’observations multivariées, particulièrement sensibles à des changements dans la copule des observations. Ils améliorent tous deux des propositions récentes et donnent lieu à des tests plus puissants que leurs prédécesseurs pour des classes d’alternatives pertinentes. Des simulations de Monte Carlo illustrent les performances de ces tests sur des échantillons de taille modérée. Le premier test est fondé sur une statistique à la Cramér-von Mises construite à partir du processus de copule empirique séquentiel. Une procédure de rééchantillonnage à base de multiplicateurs est proposée pour la statistique de test ; sa validité asymptotique sous l’hypothèse nulle est démontrée sous des conditions de mélange fort sur les données. Le second test se focalise sur la détection d’un changement dans le rho de Spearman multivarié des observations. Bien que moins général, il présente de meilleurs résultats en terme de puissance que le premier test pour les alternatives caractérisées par un changement dans le rho de Spearman. Deux stratégies de calcul de la valeur p sont comparées théoriquement et empiriquement : l’une utilise un rééchantillonnage de la statistique, l’autre est fondée sur une estimation de la loi limite de la statistique de test. // Abstract : It is very well-known that the marginal distributions of a random vector do not characterize the distribution of the random vector. When the marginal distributions are continuous, the work of Sklar ensures the existence and uniqueness of a function called copula which can be regarded as capturing the dependence between the components of the random vector. The cumulative distribution function of the vector can then be rewritten using only the copula and the marginal cumulative distribution functions. In this work, we propose two non-parametric tests for change-point detection, particularly sensitive to changes in the copula of multivariate time series. They improve on recent propositions and are more powerful for relevant alternatives involving a change in the copula. The finite-sample behavior of these tests is investigated through Monte Carlo experiments. The first test is based on a Cramér-von Mises statistic and on the sequential empirical copula process. A multiplier resampling scheme is suggested and its asymptotic validity under the null hypothesis is demonstrated under strong mixing conditions. The second test focuses on the detection of a change in Spearman’s rho. Monte Carlo simulations reveal that this test is more powerful than the first test for alternatives characterized by a change in Spearman’s rho. Two approaches to compute approximate p-values for the test are studied empirically and theoretically. The first one is based on resampling, the second one consists of estimating the asymptotic null distribution of the test statistic.