Hydrogen fuel cells are devices used to generate electricity from the electrochemical reaction between air and hydrogen gas. An attractive advantage of these devices is that their byproduct is water, which is very safe to the environment. However, hydrogen fuel cells still lack some improvements in terms of increasing their life time and electricity production, decreasing power losses, and optimizing their operating conditions. In this thesis, the cathode part of the hydrogen fuel cell will be considered. This part mainly consists of an air gas channel and a gas diffusion layer. To simulate the fluid dynamics taking place in the cathode, we present two models, a general model and a simple model both based on a set of conservation laws governing the fluid dynamics and chemical reactions. A numerical method to solve these models is presented and verified in terms of accuracy. We also show that both models give similar results and validate the simple model by recovering a polarization curve obtained experimentally. Next, a shape optimization problem is introduced to find an optimal design of the air gas channel. This problem is defined from the simple model and a cost functional, $E$, that measures efficiency factors. The objective of this functional is to maximize the electricity production, uniformize the reaction rate in the catalytic layer and minimize the pressure drop in the gas channel. The impact of the gas channel shape optimization is investigated with a series of test cases in long and short fuel cell geometries. In most instances, the optimal design improves efficiency in on- and off-design operating conditions by shifting the polarization curve vertically and to the right. The second primary goal of the thesis is to analyze mathematical issues related to the introduced shape optimization problem. This involves existence and uniqueness of the solution for the presented model and differentiability of the state variables with respect to the domain of the air channel. The optimization problem is solved using the gradient method, and hence the gradient of $E$ must be found. The gradient of $E$ is obtained by introducing an adjoint system of equations, which is coupled with the state problem, namely the simple model of the fuel cell. The existence and uniqueness of the solution for the adjoint system is shown, and the shape differentiability of the cost functional $E$ is proved.

While there have been numerous studies directed at addressing the female Generation Y cohort’s fashion consumption patterns, there is a dearth of published research focused on male consumer fashion conscious behaviour, especially not that of the African Generation Y (hereafter referred to as black Generation Y) males. There are global indications that contemporary males are engaging in fashion apparel shopping more frequently than ever before. Moreover, unlike past generations, today’s male consumers have become increasingly fashion aware and fashion conscious, taking care of their looks and developing their own fashion style. Born between 1986 and 2005, in 2013, black Generation Y individuals made up approximately 83 percent of South Africa’s total Generation Y cohort and 38 percent of the country’s 52 981 991 population. In 2013, black Generation Y males accounted for an estimated 42 percent of the South African population. As a consequence of its size, the black Generation Y male market segment represents a potentially lucrative and attractive market for apparel retailers and fashion marketers. Marketers are particularly interested in those individuals pursuing tertiary qualifications given that a higher education ultimately acts as a predictor of their higher future spending potential and an indication of their social standing and influence within a society. The aim of this study was to determine the causal relationships between black Generation Y male students’ need for uniqueness, fashion awareness, fashion consciousness and fashion conscious behaviour in order to model the determinants of black Generation Y male students fashion conscious behaviour. A self-administered questionnaire was administered on a single cross-sectional sample of 400 black Generation Y male students at three university campuses in the Gauteng province in 2013 – one from a comprehensive university, one from a university of technology and one from a traditional university. From the administered questionnaires, 213 were completed and returned as usable. The collected data was analysed by means of exploratory factor analysis, reliability and validity analysis, descriptive statistics and correlation analysis. In addition, structural equation modelling (SEM) was applied to test a proposed model derived from the literature. According to the results of the SEM analysis, black Generation Y males’ fashion awareness has a significant positive influence on their fashion consciousness, and their fashion consciousness has a significant positive influence on their fashion conscious behaviour. In terms of the dimensions of the need for uniqueness, unpopular choice has a significant positive influence on black Generation Y male students’ fashion awareness, whilst creative choice has a significant positive influence on their fashion consciousness, and avoidance of similarity has a direct significant positive influence on their fashion conscious behaviour. Furthermore, the findings suggest that their fashion consciousness is reliant on their fashion awareness, which in turn influences their fashion conscious behaviour. Findings from this study will aid marketers’ in better understanding black Generation Y male students’ fashion conscious behaviour. Furthermore, the recommendations provided suggest marketing strategy guidelines tailored at effectively targeting this market segment. / PhD (Marketing Management)--North-West University, Vaal Triangle Campus, 2015

While there have been numerous studies directed at addressing the female Generation Y cohort’s fashion consumption patterns, there is a dearth of published research focused on male consumer fashion conscious behaviour, especially not that of the African Generation Y (hereafter referred to as black Generation Y) males. There are global indications that contemporary males are engaging in fashion apparel shopping more frequently than ever before. Moreover, unlike past generations, today’s male consumers have become increasingly fashion aware and fashion conscious, taking care of their looks and developing their own fashion style. Born between 1986 and 2005, in 2013, black Generation Y individuals made up approximately 83 percent of South Africa’s total Generation Y cohort and 38 percent of the country’s 52 981 991 population. In 2013, black Generation Y males accounted for an estimated 42 percent of the South African population. As a consequence of its size, the black Generation Y male market segment represents a potentially lucrative and attractive market for apparel retailers and fashion marketers. Marketers are particularly interested in those individuals pursuing tertiary qualifications given that a higher education ultimately acts as a predictor of their higher future spending potential and an indication of their social standing and influence within a society. The aim of this study was to determine the causal relationships between black Generation Y male students’ need for uniqueness, fashion awareness, fashion consciousness and fashion conscious behaviour in order to model the determinants of black Generation Y male students fashion conscious behaviour. A self-administered questionnaire was administered on a single cross-sectional sample of 400 black Generation Y male students at three university campuses in the Gauteng province in 2013 – one from a comprehensive university, one from a university of technology and one from a traditional university. From the administered questionnaires, 213 were completed and returned as usable. The collected data was analysed by means of exploratory factor analysis, reliability and validity analysis, descriptive statistics and correlation analysis. In addition, structural equation modelling (SEM) was applied to test a proposed model derived from the literature. According to the results of the SEM analysis, black Generation Y males’ fashion awareness has a significant positive influence on their fashion consciousness, and their fashion consciousness has a significant positive influence on their fashion conscious behaviour. In terms of the dimensions of the need for uniqueness, unpopular choice has a significant positive influence on black Generation Y male students’ fashion awareness, whilst creative choice has a significant positive influence on their fashion consciousness, and avoidance of similarity has a direct significant positive influence on their fashion conscious behaviour. Furthermore, the findings suggest that their fashion consciousness is reliant on their fashion awareness, which in turn influences their fashion conscious behaviour. Findings from this study will aid marketers’ in better understanding black Generation Y male students’ fashion conscious behaviour. Furthermore, the recommendations provided suggest marketing strategy guidelines tailored at effectively targeting this market segment. / PhD (Marketing Management)--North-West University, Vaal Triangle Campus, 2015

Handwriting as a unique expression of human behaviour has evoked continuous interest as a means of analyzing and studying personality – a study known as Graphology. Research in graphology has shown diverse results, ranging from negative to highly favourable. Many of the studies disregarding the value of graphology can be criticized on the grounds of their research methodology as well as the method used in handwriting analysis, namely the ‘trait-method’ whereby isolated graphological features are simplistically linked to personality as opposed to a more encompassing, holistic approach. In the present study the special link between personality and graphology is illustrated as well as the decisive influence the gestalt and form standard of a writing have on the interpretation of that particular writing. The approach to the graphological analyses was holistic, as it complements the complex uniqueness of personality. The study also focuses on the recommended methodology of handwriting analysis, by offering a tailor-made personality ‘picture’ of the individual. Graphological findings were compared to the clinical findings of the same client/patient according to the Diagnostic and Statistical Manual of Mental Diseases IV-TRTM (DSM-IV-TRTM). Five (5) case studies have been reported in this qualitative research study. The analyses of the writings were done by an independent graphologist. The objective graphological findings show similarities with clinical findings of the same clients/patients. The holistic approach to handwriting analysis deems to have diagnostic value and is promising in providing guidelines for psychotherapy. Graphology can thus be regarded as a useful and viable tool in psycho-educational assessment. / Education / D.Ed. (Psychology of Education)

The last decade has seen the transition from single-core processors to multi-cores and many-cores. This move has by and large shifted the responsibility from chip manufacturers to programmers to keep up with ever-increasing expectations on performance. In the single-core era, improvements in hardware capacity could immediately be leveraged by an application: faster machine - faster program. In the age of the multi-cores, this is no longer the case. Programs must be written in specific ways to utilize available parallel hardware resources. Programming language support for concurrent and parallel programming is poor in most popular object-oriented programming languages. Shared memory, threads and locks is the most common concurrency model provided. Threads and locks are hard to understand, error-prone and inflexible; they break encapsulation - the very foundation of the object-oriented approach. This makes it hard to break large complex problems into smaller pieces which can be solved independently and composed to make a whole. Ubiquitous parallelism and object-orientation, seemingly, do not match. Actors, or active objects, have been proposed as a concurrency model better fit for object-oriented programming than threads and locks. Asynchronous message passing between actors each with a logical thread of control preserves encapsulation as objects themselves decide when messages are executed. Unfortunately most implementations of active objects do not prevent sharing of mutable objects across actors. Sharing, whether on purpose or by accident, exposes objects to multiple threads of control, destroying object encapsulation. In this thesis we show techniques for compiler-enforced isolation of active objects, while allowing sharing and zero-copy communication of mutable data in the cases where it is safe to do so. We also show how the same techniques that enforce isolation can be utilized internal to an active object to allow data race-free parallel message processing and data race-free structured parallel computations. This overcomes the coarse-grained nature of active object parallelism without compromising safety. / UPMARC

En optimisation les conditions d’optimalité jouent un rôle primordial pour détecter les solutions optimales et leur étude occupe une place significative dans la recherche actuelle. Afin d’exprimer adéquatement des conditions d’optimalité les chercheurs ont introduit diverses notions de dérivées généralisées non seulement pour des fonctions non lisses, mais aussi pour des fonctions à valeurs ensemblistes, dites applications multivoques ou multifonctions. Cette thèse porte sur l’application des deux nouveaux concepts de dérivées généralisées: les ensembles variationnels de Khanh-Tuan et les approximations de Jourani-Thibault, aux problèmes d’optimisation multiobjectif et aux problèmes d’équilibre vectoriel. L’enjeu principal est d’obtenir des conditions d’optimalité du premier et du second ordre pour les problèmes ayant des données multivoques ou univoques non lisses et pas forcément continues, et des conditions assurant l’unicité des solutions dans les problèmes d’équilibre vectoriel. / Optimality conditions for nonsmooth optimization have become one of the most important topics in the study of optimization-related problems. Various notions of generalized derivatives have been introduced to establish optimality conditions. Besides establishing optimality conditions, generalized derivatives also is an important tool for studying the local uniqueness of solutions. During the last three decades, these topics have been being developed, generalized and applied to many elds of mathematics by many authors all over the world. The purpose of this thesis is to investigate the above topics. It consists of ve chapters. In Chapter 1, we develop elements of calculus of variational sets for set-valued mappings, which were recently introduced in Khanh and Tuan (2008). Most of the usual calculus rules, from chain and sum rules to rules for unions, intersections, products and other operations on mappings, are established. As applications we provide a direct employment of sum rules to establishing an explicit formula for a variational set of the solution map to a parametrized variational inequality in terms of variational sets of the data. Furthermore, chain rules and sum or product rules are also used to prove optimality conditions for weak solutions of some vector optimization problems. In Chapter 2, we propose notions of higher-order outer and inner radial derivatives of set-valued maps and obtain main calculus rules. Some direct applications of these rules in proving optimality conditions for particular optimization problems are provided. Then, we establish higher-order optimality necessary conditions and sufficient ones for a general set-valued vector optimization problem with inequality constraints. Chapter 3 is devoted to using first and second-order approximations, which were introduced by Jourani and Thibault (1993) and Allali and Amaroq (1997), as generalized derivatives, to establish both necessary and sufficient optimality conditions for various kinds of solutions to nonsmooth vector equilibrium problems with functional constraints. Our rst-order conditions are shown to be applicable in many cases, where existing ones cannot be applied. The second-order conditions are new. In Chapter 4, we consider nonsmooth multi-objective fractional programming on normed spaces. Using rst and second-order approximations as generalized derivatives, rst and second-order optimality conditions are established. For sufficient conditions no convexity is needed. Our results can be applied even in innite dimensional cases involving innitely discontinuousmaps. In Chapter 5, we establish sufficient conditions for the local uniqueness of solutions to nonsmooth strong and weak vector equilibrium problems. Also by using approximations, our results are valid even in cases where the maps involved in the problems suffer innite discontinuity at the considered point.

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In the present work we investigate the solution of the univalent twistor equation on an isolated horizon that serves for the definition of the so-called Penrose mass. We start our discussion with the construction of adapted co- ordinates to the isolated horizon and summarizing the main results in this field that are needed for our work. We include a chapter devoted to the extre- mal isolated horizons and prove an important result concerning uniqueness of geometry therein. It is a generalization of the paper by Lewandowski and Pawlowski (Class. Quantum Grav. 31 (17), 2014), which states that the ex- tremal isolated horizons are necessarily isometric to the intrinsic geometry of the Kerr-Newmann black hole. Further we proceed to investigation of the twistor equation on the isolated horizon. We analyze conditions of integra- bility and derive the time dependent solution. Consequently we solve the 2-surface twistor equation and briefly discuss the general approach to the problem of defining the Penrose charge. 1

The development of social media has increased the usage and prevalence of content marketing. This have enhanced the pressures on marketers to manage and leverage this tool. Also, consumers interaction with valuable content leads to a stronger relationship with the brand which further might enhance the brand image. Hence, this paper carries out a quantitative research with the purpose to explain if questionable content marketing on social media have a negative impact on brand image. The researchers used questionnaires as their method for collection of empirical data. The respondents were gathered based on a convenience sampling. The questionnaires were out sent out to 204 participants, were the aim was to investigate if the respondents view of a brand changes negatively, after being exposed to scenarios that were constituted by questionable content marketing. It was analyzed through an ANOVA test. The overall conclusions after gathering and analyzing the data, implicate that questionable content marketing have a negative effect on brand image. Therefore, it becomes important for managers to carefully evaluate their content marketing strategy on social media in order to avoid questionable content marketing.

Handwriting as a unique expression of human behaviour has evoked continuous interest as a means of analyzing and studying personality – a study known as Graphology. Research in graphology has shown diverse results, ranging from negative to highly favourable. Many of the studies disregarding the value of graphology can be criticized on the grounds of their research methodology as well as the method used in handwriting analysis, namely the ‘trait-method’ whereby isolated graphological features are simplistically linked to personality as opposed to a more encompassing, holistic approach. In the present study the special link between personality and graphology is illustrated as well as the decisive influence the gestalt and form standard of a writing have on the interpretation of that particular writing. The approach to the graphological analyses was holistic, as it complements the complex uniqueness of personality. The study also focuses on the recommended methodology of handwriting analysis, by offering a tailor-made personality ‘picture’ of the individual. Graphological findings were compared to the clinical findings of the same client/patient according to the Diagnostic and Statistical Manual of Mental Diseases IV-TRTM (DSM-IV-TRTM). Five (5) case studies have been reported in this qualitative research study. The analyses of the writings were done by an independent graphologist. The objective graphological findings show similarities with clinical findings of the same clients/patients. The holistic approach to handwriting analysis deems to have diagnostic value and is promising in providing guidelines for psychotherapy. Graphology can thus be regarded as a useful and viable tool in psycho-educational assessment. / Education / D.Ed. (Psychology of Education)