Magister Scientiae - MSc / To improve the adsorption capacity of polyacrylonitrile (PAN) fibres, hydrophilic amidoxime fibres were prepared by subsequent conversion of the cyano groups to an amidoxime group by reacting with hydroxylamine at 80°C at an optimum amidoximation time of 2 hrs. The amidoxime fibre was hydrolyzed/alkali treated in a solution of sodium hydroxide to enhance or improve the adsorption properties. This was followed by characterization of the amidoxime and hydrolyzed fibres using Scanning electron microscopy (SEM); Fourier transform Infrared Spectroscopy (FTIR) and exchange capacity (cationic and anionic). SEM showed that the hydrolysis process made the surface of Amidoxime fibre rougher than that of Polyacrylonitrile fibre. FTIR revealed that the hydrolyzed Amidoxime fibres contained conjugated imine (-C=N-) sequences. Functionalization enhanced the sorption of amidoxime fibres by an increase of 20 % in the cationic exchange capacity. This was achieved by the part conversion of the cyano groups into the carboxylic acid groups. The fibres showed faster kinetics largely due the available exchange sites on the surface of the fibres hence the equilibration was achieved much quicker. / South Africa

This thesis is broadly concerned with online-optimizing anti-windup control. These are control structures that implement some online-optimization routines to compensate for the windup effects in constrained control systems. The first part of this thesis examines a general framework for analyzing robust preservation in anti-windup control systems. This framework - the robust Kalman conjecture - is defined for the robust Lur’e problem. This part of the thesis verifies this conjecture for first-order plants perturbed by various norm-bounded unstructured uncertainties. Integral quadratic constraint theory is exploited to classify the appropriate stability multipliers required for verification in these cases. The remaining part of the thesis focusses on accelerated gradient methods. In particular, tight complexity-certificates can be obtained for the Nesterov gradient method, which makes it attractive for implementation of online-optimizing anti-windup control. This part of the thesis presents a proposed algorithm that extends the classical Nesterov gradient method by using available secant information. Numerical results demonstrating the efficiency of the proposed algorithm are analysed with the aid of performance profiles. As the objective function becomes more ill-conditioned, the proposed algorithm becomes significantly more efficient than the classical Nesterov gradient method. The improved performance bodes well for online-optimization anti-windup control since ill-conditioning is common place in constrained control systems. In addition, this thesis explores another subcategory of accelerated gradient methods known as Barzilai-Borwein gradient methods. Here, two algorithms that modify the Barzilai-Borwein gradient method are proposed. Global convergence of the proposed algorithms for all convex functions is established by using discrete Lyapunov theorems.

This research was conducted as part of the formative evaluation of a mother-child interaction intervention, which was incorporated into the Kgolo Mmogo pilot study at the Kalafong Hospital in Tshwane (South Africa). The purpose of the intervention was to encourage the development of parenting skills and to improve mother-child relationships within an HIV context over a six-month period. By promoting more effective interaction between mother and child, child resilience could be enhanced and children could learn the necessary coping skills that would help them deal with the challenges posed by HIV and other life events. The aim of the study was to generate a systemic understanding of families affected by HIV/AIDS. The study explored (1) the effect of HIV on family interaction and (2) the effect of the mother-child interaction intervention on family interaction from the perspective of HIV-infected mothers. The theoretical framework chosen for the study was of a systemic nature and the standpoints, as set out by the Milan family therapy team, were implemented. Ten months after the intervention, four of the HIV-positive mothers who had participated in the intervention were interviewed and encouraged to share their experiences. Circular questions were employed in the interviews as a means of gathering data. A qualitative design was therefore the best option for this study. The research findings of this study coincide with previous literature and research findings; thus, the findings of this study have been consolidated. The current study findings support the importance of bridging the distance that is created by HIV in family relations, particularly between mother and child. Newly-diagnosed mothers often become stuck in their own processes and distance themselves from others in order to make sense of their situation. The broader social stigmas associated with HIV/AIDS contribute further to the sense of isolation that HIV-positive women experience. Often, women perceive HIV to be a disruptive force in their relationships with their partners and children, which creates tension, secrets and uncertainty within the family. HIV-infected mothers generally feel that keeping secrets from their children protects them from being traumatized by the social stigmas surrounding HIV/AIDS. Some HIV-positive mothers also feel that an emotional distance will shield their children from the pain of losing their mother. Because they are grappling with many negative feelings, such as anger and frustration, many HIV-positive mothers resort to strict disciplinary measures and avoid spending time with their children. The children misinterpret their mother’s behaviour and react in a manner that the mother perceives to be both disrespectful and disobedient, thus creating a recurring cycle in which both mothers and children become stuck. The participating mothers perceived the mother-child interaction intervention to focus on their emotional, physical, cognitive and behavioural needs as well as the needs of their children. The mothers experienced the intervention as having been particularly helpful to them and their children. They perceived themselves to be warmer, more supportive, more accepting and to have found meaning in their lives. In addition they felt that their children had begun to behave themselves and were also less avoidant of them. It enhanced their understanding of one another, and strengthened their bond so that they can depend on each other in times of difficulty. Copyright / Dissertation (MA)--University of Pretoria, 2009. / Psychology / unrestricted

Nous donnons un mécanisme de type Calderón-Zygmund concernant la théorie de l’extrapolationpour des opérateurs d’intégrale singulière sur les espaces de tentes. Pour des opérateursde régularité maximale sur les espaces de tentes, nous donnons des résultats optimaux enexploitant la structure des opérateurs intégraux de convolution et en utilisant des estimationsde la décroissance hors-diagonale du semi-groupe ou de la famille résolvante sous-jacente.Nous appliquons des techniques précédentes d’analyse harmonique et fonctionnelle pourestimer sur les espaces de tentes certains opérateurs d’intégrale évolutionnelle, nées de l’étudedes problèmes aux limites elliptiques et des systèmes non-autonomes du premier ordre. / We give a Calderón-Zygmund type machinery concerning the extrapolation theory for thesingular integral operators on tent spaces. For maximal regularity operators on tent space, wegive some optimal results by exploiting the structure of convolution integral operators and byusing the off-diagonal decay estimates of the underlying semigroup or resolvent family.We apply the previous harmonic and functional analysis techniques to estimate on tentspaces certain evolutionary integral operators arisen from the study of boundary value ellipticproblems and first order non-autonomous systems.

[pt] Atualmente, a maioria dos programas para computadores é obtida através da WEB. Como muitas vezes a procedência são fontes desconhecidas, é preciso se certificar de que o código se comporta como o esperado. A solução ideal seria verificar o código contra uma especificação de políticas de segurança ,contudo, isso pode consumir muito tempo.Uma outra alternativa é fazer com que o próprio código prove ser seguro. O conceito de proof-carryng code (PCC)é baseado nessa idéia : um programa carrega consigo uma prova de sua conformidade com certas políticas de segurança. Ou seja ,ele carrega uma prova a respeito de propriedades do próprio código. Portanto, os mesmos métodos froamsi usados para a verificação de programs podem se utilizados para esta tecnolgia. Considerando este fato,neste trabalho é estudado como cálculo de Hoare, em método formal para realizar a verificação de programas, aplicado a códigos-fonte escritos em uma linguagem de programação imperativa, pode ser útil á tecnica de PCC. Conseqüentemente, são pesquisados métodos para a geração de provas de correção de programas utilizando o método citado, para tornar possível a geração de provas de segurança para PCC utilizando o cálculo de Hoare. / [en] Nowdays most computer programs are obtained from the WEB. Since their source is usually unknown, it is necessary to be sure that the code of the program behaves as expected.The ideal solution would be verify the code against a specification of safety policies.However, this can take too much time.Another approach is making the code itself prove that it is safe. The concept os proof-carryng code (PCC) is based on this idea: a program carries a proof of its conformity with certain safety policies. That is , it carries a proof cencerning properties related to the code itself. Therefore, the same formal methods employed in formal verification of programs can be used in this tecnology. Due to this fact, in this work it is studied how Hoare logic applied to source codes written in an imperative programming language, which is a formal methods are researched to generate proofs of program correctness using the method explained, so that it can be possible to generate PCC safety programs with Hoare logic.

Les dispositifs matériels mobiles proposent des capacités de mesure à l'aide de capteurs soit embarqués, soit connectés. Ils ont vocation à être de plus en plus utilisés dans des processus de prises de mesures. Ils présentent un caractère critique dans le sens où ces informations doivent être fiables, car potentiellement utilisées dans un contexte exigeant. Malgré une grande demande, peu d'applications proposent d'assister les utilisateurs lors de relevés exploitant ces capacités. Idéalement, ces applications devraient proposer des méthodes de visualisation, de calcul, des procédures de mesure et des fonctions de communications permettant la prise en charge de capteurs connectés ou encore la génération de rapports. La rareté de ces applications se justifie par les connaissances nécessaires pour permettre la définition de procédures de mesure correctes. Ces éléments sont apportés par la métrologie et la théorie de la mesure et sont rarement présents dans les équipes de développement logiciel. De plus, chaque utilisateur effectue des activités de mesure spécifiques au domaine de son champ d'activités, ce qui implique le développement d'applications spécifiques de qualité pouvant être certifiées par des experts. Ce postulat apporte la question de recherche à laquelle les travaux présentés répondent: Comment proposer une approche pour la conception d’applications adaptées à des procédures de mesures spécifiques. Les procédures de mesure pouvant être configurées par un utilisateur final La réponse développée est une "plateforme" de conception d'applications d'assistance à la mesure. Elle permet d'assurer la conformité des procédures de mesures sans l'intervention d'expert de la métrologie. Pour cela elle est construite en utilisant des concepts issus de la métrologie, de l'Ingénierie Dirigée par les Modèles et de la logique du premier ordre. Une étude du domaine de la métrologie permet de mettre en évidence la nécessité d'une expertise des procédures de mesure impliquées dans les applications. Cette expertise comprend des termes et des règles assurant l'intégrité et la cohérence d'une procédure de mesure. Un modèle conceptuel du domaine de la métrologie est proposé. Ce modèle conceptuel est ensuite intégré au processus de développement d'une application. Cette intégration se fait par un encodage de ce modèle conceptuel sous la forme d'un schéma des connaissances de la métrologie en logique du premier ordre. Il permet, la vérification du respect des contraintes inhérentes à la métrologie dans une procédure de mesure. Cette vérification est réalisée en confrontant les procédures de mesures au schéma sous forme de requêtes. Ces requêtes sont décrites à l'aide d'un langage proposé par le schéma. Les applications d'assistance à la mesure nécessitent d'exposer à l'utilisateur un processus de mesure impliquant relevés et affichages de mesures étape par étape. Cela implique de pouvoir décrire un processus de mesure et d'en définir les interfaces et le schéma d'évolution. Pour cela, un éditeur d'application est proposé. Cet éditeur propose un langage spécifique dédié à la description d'applications d'assistance à la mesure. Ce langage est construit à partir des concepts, formalismes et outils proposés par l'environnement de métamodélisation Diagrammatic Predicate Framework (DPF). Le langage comporte des contraintes syntaxiques prévenant les erreurs de construction au niveau logiciel tout en réduisant l'écart sémantique entre l'architecte logiciel l'utilisant et un potentiel expert de la métrologie. [...] / Mobile devices offer measuring capabilities using embedded or connected sensors. They are more and more used in measuring processes. They are critical because the performed measurements must be reliable because possibly used in rigorous context. Despite a real demand, there are relatively few applications assisting users with their measuring processes that use those sensors. Such assistant should propose methods to visualise and to compute measuring procedures while using communication functions to handle connected sensors or to generate reports. Such rarity of applications arises because of the knowledges required to define correct measuring procedures. Those knowledges are brought by metrology and measurement theory and are rarely found in software development teams. Moreover, every user has specific measuring activities depending on his field of work. That implies many quality applications developments which could request expert certification. These premises bring the research question the presented works answer : What approach enables the conception of applications suitable to specific measurement procedures considering that the measurement procedures could be configured by the final user. The presented works propose a platform for the development of measuring assistant applications. The platform ensure the conformity of measuring processes without involving metrology experts. It is built upon metrology, model driven engineering and first order logic concepts. A study of metrology enables to show the need of applications measuring process expert evaluation. This evaluation encompasses terms and rules that ensure the process integrity and coherence. A conceptual model of the metrology domain is proposed. That model is then employed in the development process of applications. It is encoded into a first order logic knowledge scheme of the metrology concepts. That scheme enables to verify that metrology constraints holds in a given measuring process. The verification is performed by confronting measuring processes to the knowledge scheme in the form of requests. Those requests are described with a request language proposed by the scheme. Measuring assistant applications require to propose to the user a measuring process that sequences measuring activities. This implies to describe a measuring process, and also to define interactive interfaces and sequencing mechanism. An application editor is proposed. That editor uses a domain specific language dedicated to the description of measuring assistant applications. The language is built upon concepts, formalisms and tools proposed by the metamodeling environment : Diagrammatic Predicat Framework (DPF). The language encompasses syntactical constraints that prevent construction errors on the software level while reducing the semantical gap between the software architect using it and a potential metrology expert. Then, mobile platforms need to execute a behaviour conforming to the editor described one. An implementation modelling language is proposed. This language enables to describe measuring procedures as sequences of activities. Activities imply to measure, compute and present values. Quantities are all abstracted by numerical values. This eases their computation and the use of sensors. The implementation model is made up of software agents. A mobile application is also proposed. The application is built upon a framework of agents, an agent network composer and a runtime system. The application is able to consider an implementation model and to build the corresponding agent network in order to propose a behaviour matching the end users needs. This enables to answer to any user needs, considering he can access to the implementation model, without requiring to download several applications.

An abstract knowledge representation of cognitive robots - as used for reasoning and planning - typically relies on symbols denoting objects of the world and states of affairs. The process of creating and maintaining the correct connection between a symbol denoting an object and its corresponding perceptual image (called percept), both referring to the same physical object, is called symbol anchoring. Most current cognitive systems implement an ad hoc solution which may work for the specific, intended application under certain conditions. Conversely, we suggest a formal and general approach to the symbol anchoring problem, which enhances previous approaches in terms of flexibility, applicability and expressiveness, and which completely automates the process of determining and maintaining all plausible hypotheses of correspondences between object symbols and perceptual images of physical objects. Based on the first-order logical Fluent Calculus, our approach inherits its rich expressiveness with respect to knowledge representation and reasoning. Implementing all required symbol anchoring functionalities, our approach also complies with fundamental concepts of phenomenalism, representationalism and the sense-data theory of philosophy of cognition.

The purpose of this research was to trace the first year of progress made towards implementing the new curriculum for basic education in Mozambique and to gain clarity about the process with a view to formulating pertinent recommendations for its successful implementation. This study starts by presenting background information which highlights the need for the curriculum to be more relevant to the sociopolitical changes in Mozambique as the main aim of transforming the basic education curriculum. Secondly, it maps out the national environment in which the new curriculum is operating and the critical factors justifying the changes brought by curriculum transformation. Then it introduces the research questions that essentially explore four issues, namely (1) the nature of the new curriculum and the strategy used to implement it, (2) the perceptions of educators, subject specialists and principals regarding the new curriculum, (3) classroom practices as envisaged in the new education curriculum and (4) efforts towards successful implementation of the new curriculum. Before the research topic is addressed the precepts of curriculum theory and the principles of curriculum development are discussed as the context within which to conceptualize the implementation of the new curriculum in Mozambique. The study under review explores the seven basic conditions for effective change identified by Giacquinta (1998). The researcher has found with due reference to the subject literature that the relevance of these conditions is borne out by the findings of the research under review. This research therefore has the merit that it relates these conditions (referred as factors in the study) to each other, thus serving as an important guide for monitoring and implementing education change of which curriculum reform is a basic element. The study employed mainly quantitative analysis (descriptive statistical analysis and factor analysis) having as research instrument a survey questionnaire designed to gauge educators’ and learners’ opinions regarding implementation of the new Basic Education Curriculum in Mozambican schools. As the main findings of the study, it was clear from participating principals’ and teachers’ responses that school leadership is an essential factor in assuring the presence and maintenance of all the necessary conditions for successful implementation of the new curriculum. The capacity building is another indispensable factor derived from participating principals’ and teachers’ responses concerning successful implementation of the new curriculum, which is viewed as an important condition for creating and maintaining teachers’ confidence in their ability to fulfil new role expectations. In this regard, principals and teachers identified innovative classroom practices as an important condition for successful implementation of the new curriculum. So, principals’ responses showed that it was important to recognise the association between leadership, innovative classroom practices and capacity building, while participating teachers’ responses showed that there was an important link between capacity building and leadership, rewarding and innovative classroom practices. Thus, with the exception of rewarding the same factors were identified as critical by both principals and teachers. A distinct enabling condition for successful implementation of the new curriculum that emerged from participating students’ responses comprised (1) an association of students’ expectations, learning opportunities and outcomes, (2) students’ subject preferences, (3) and a friendly and supportive school environment. This research both contributes to understanding of the curriculum implementation process, and enables the formulation of pertinent recommendations towards successful curriculum implementation. It also enriches the current literature on this matter through critical analysis of a new curriculum implementation, offering empirical evidences of the relevance of school resocialization, which entails restructuring and reculturing. / Thesis (PhD)--University of Pretoria, 2008. / Education Management and Policy Studies / unrestricted

[pt] Esse trabalho apresenta uma abordagem baseada em programação matemática para a solução de problemas de valor inicial de contorno constitutivo elastoplástico. Considerando a plasticidade associativa, as equações constitutivas locais, em sua forma discreta, são formuladas como problemas de otimização cônica. Especificamente, é demonstrado que métodos implícitos de retorno a superfície para os critérios mais conhecidos da literatura, como o de Rankine, von Mises, Tresca, Drucker-Prager e Mohr Coulomb, podem ser expressos como problemas de otimização cônica de segunda ordem e semidefinida. Além disso, um novo método numérico para a determinação do operador elastoplástico consistente, baseado na derivada paramétrica de primeira ordem das soluções ótimas, é proposto. / [en] This work presents a mathematical programming approach for elastoplastic constitutive initial boundary value problems. Considering associative plasticity, the local discrete constitutive equations are formulated as conic programs. Specifically, it is demonstrated that implicit return-mapping schemes for well-known yield criteria, such as the Rankine, von Mises, Tresca, Drucker-Prager, and Mohr-Coulomb criteria, can be expressed as secondorder and semidefinite conic programs. Additionally, a novel scheme for the numerical evaluation of the consistent elastoplastic tangent operator, based on a first-order parameter derivative of the optimal solutions, is proposed.

The Bondi-Metzner-Sachs-van der Burg (BMS) group is the asymptotic symmetry group of radiating asymptotically flat spacetimes. It has recently received renewed interest in the context of the flat holography and the infrared structure of gravity. In this thesis, we investigate the consequences of considering extensions of the BMS group in four dimensions with superrotations. In particular, we apply the covariant phase space methods on a class of first order gauge theories that includes the Cartan formulation of general relativity and specify this analysis to gravity in asymptotically flat spacetime. Furthermore, we renormalize the symplectic structure at null infinity to obtain the generalized BMS charge algebra associated with smooth superrotations. We then study the vacuum structure of the gravitational field, which allows us to relate the so-called superboost transformations to the velocity kick/refraction memory effect. Afterward, we propose a new set of boundary conditions in asymptotically locally (A)dS spacetime that leads to a version of the BMS group in the presence of a non-vanishing cosmological constant, called the Λ-BMS asymptotic symmetry group. Using the holographic renormalization procedure and a diffeomorphism between Bondi and Fefferman-Graham gauges, we construct the phase space of Λ-BMS and show that it reduces to the one of the generalized BMS group in the flat limit. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished