This thesis inquires into the lived experience of five foster care alumni as they re-member and explore negotiations of time, space, and being made/becoming as young people formerly in government care. Informed by arts-based living inquiry (Irwin & de Cosson, 2004) and a collaborative research ethic, I undertook an emergent, rhizomatic exploration of new ways of viewing/thinking about the culture of care and about problematic representations of youth in care as irrevocably “broken,” “damaged,” and “deficient”. This process of inquiry allowed for movement between tangled lines of power, resistance, becoming, and desire informed by concepts central to the works of Foucault (1982), Deleuze and Guattari (1987), Tuck (2010), and Skott-Myhre (2008). Five foster care alumni explored their inquiry into “being in care” through arts-based methods that included collage, painting and drawing, and individual and group interviews. Important themes identified by participants included being seen/being heard, “foster child,” time, space, labels, disrupting “normal,” becoming complex, becoming political, and the importance of spirituality, belonging, Indigenous ways of knowing, and community. Such layered, complex representations foreground creativity and dignity while troubling the problematic representations of youth in care that permeate dominant discourses, practices, and policies shaping foster care systems and interventions. / Graduate

Denial-of-service attacks (DoS) and distributed denial-of-service attacks (DDoS) attempt to temporarily disrupt users or computer resources to cause service un- availability to legitimate users in the internetworking system. The most common type of DoS attack occurs when adversaries °ood a large amount of bogus data to interfere or disrupt the service on the server. The attack can be either a single-source attack, which originates at only one host, or a multi-source attack, in which multiple hosts coordinate to °ood a large number of packets to the server. Cryptographic mechanisms in authentication schemes are an example ap- proach to help the server to validate malicious tra±c. Since authentication in key establishment protocols requires the veri¯er to spend some resources before successfully detecting the bogus messages, adversaries might be able to exploit this °aw to mount an attack to overwhelm the server resources. The attacker is able to perform this kind of attack because many key establishment protocols incorporate strong authentication at the beginning phase before they can iden- tify the attacks. This is an example of DoS threats in most key establishment protocols because they have been implemented to support con¯dentiality and data integrity, but do not carefully consider other security objectives, such as availability. The main objective of this research is to design denial-of-service resistant mechanisms in key establishment protocols. In particular, we focus on the design of cryptographic protocols related to key establishment protocols that implement client puzzles to protect the server against resource exhaustion attacks. Another objective is to extend formal analysis techniques to include DoS- resistance. Basically, the formal analysis approach is used not only to analyse and verify the security of a cryptographic scheme carefully but also to help in the design stage of new protocols with a high level of security guarantee. In this research, we focus on an analysis technique of Meadows' cost-based framework, and we implement DoS-resistant model using Coloured Petri Nets. Meadows' cost-based framework is directly proposed to assess denial-of-service vulnerabil- ities in the cryptographic protocols using mathematical proof, while Coloured Petri Nets is used to model and verify the communication protocols using inter- active simulations. In addition, Coloured Petri Nets are able to help the protocol designer to clarify and reduce some inconsistency of the protocol speci¯cation. Therefore, the second objective of this research is to explore vulnerabilities in existing DoS-resistant protocols, as well as extend a formal analysis approach to our new framework for improving DoS-resistance and evaluating the performance of the new proposed mechanism. In summary, the speci¯c outcomes of this research include following results; 1. A taxonomy of denial-of-service resistant strategies and techniques used in key establishment protocols; 2. A critical analysis of existing DoS-resistant key exchange and key estab- lishment protocols; 3. An implementation of Meadows's cost-based framework using Coloured Petri Nets for modelling and evaluating DoS-resistant protocols; and 4. A development of new e±cient and practical DoS-resistant mechanisms to improve the resistance to denial-of-service attacks in key establishment protocols.

The problem addressed in this thesis was identified in a real life context in which an attempt was made to re-constitute a BSc Computer Science degree programme. The curriculum was modelled on the ACM/IEEE Computing Curriculum of 2001. It was further required to comply with accreditation requirements as defined by ABET’s Computing Accreditation Commission. Relying on a spreadsheet, the curriculum was iteratively and manually evaluated against the ACM/IEEE curriculum specification. A need was identified to automate or at least semi-automate this process. In this thesis a generalisation of the problem is presented. Curricula are modelled as directed graphs (digraphs) in which graph vertices represent curriculum elements such as topics, knowledge areas, knowledge units year- levels or modules. Edges in the graph represent dependencies between these vertices such as belonging to grouping or pre-requisites. The task of curriculum comparison then abstracts to a task of digraph comparison. A framework, the Graph Comparison Framework, is proposed. The frame- work comprises of components which are used to guide the digraph comparison process. The so-called Graph Trans-morphism algorithm component is the only component in the framework which is mandatory. The algorithm converts the information from one of the digraphs being compared into the structure of the other. This conversion enables the graphs to be compared as graph isomorphisms. All digraphs are modelled as sets of triples, making it possible to subtract one digraph from another using the set minus operator. The resultant difference sets are used by components defined in the framework to quantify and visualise the differences. By modelling curricula as digraphs and applying the framework to the di-graphs, it is possible to compare curricula. This application of the framework to a real-world problem forms the applications research part of the thesis. In this part, domain knowledge of curriculum design is necessary to apply to the curriculum being developed in order to improve it. / Thesis (PhD)--University of Pretoria, 2014. / Computer Science / unrestricted

Sensor networks are being used in several emerging applications not even imagined some years ago due to advances in sensing, computing, and communication techniques. However, these advances also pose various challenges that must be faced. One important challenge is related to the autonomous capability needed to setup and adapt the networks, which decentralizes the control of the network, saving communication and energy resources. Middleware technology helps in addressing this kind of problem, but there is still a need for additional solutions, particularly considering dynamic changes in users' requirements and operation conditions. This paper presents an agent-based framework acting as an integral part of a middleware to support autonomous setup and adaptation of sensor networks. It adds interoperability among heterogeneous nodes in the network, by means of autonomous behavior and reasoning. These features also address the needs for system setup and adaptations in the network, reducing the communication overhead and decentralizing the decision making mechanism. Additionally, preliminary results are also presented.

[pt] O processo de tratamento de tumores por embolização vascular é sensível ao conjunto de partículas poliméricas empregado, ditos agentes embólicos, cujos fatores como tamanho e morfologia influenciam no sucesso do procedimento e podem ocasionar complicações quando mal dimensionados. Partículas esféricas de poli(acetato de vinila-co-metacrilato de metila) apresentam a maioria das características desejadas após tratamento por hidrólise alcalina. Este material é relativamente novo, o que significa que há uma lacuna de conhecimento em relação ao estudo dos fenômenos que regem sua cinética. Dessa forma, o presente trabalho investigou a cinética de copolimerização responsável pela sua produção. No desenvolvimento matemático, o método dos momentos foi utilizado assumindo estado quase-estacionário para as espécies radicalares. Além disso, o modelo considera difusão das moléculas no meio para contabilização dos efeitos viscosos, comumente determinados empiricamente. Constatou-se que as características físicas dos monômeros, assim como os parâmetros cinéticos da homopolimerização, puderam ser utilizados na copolimerização. Entretanto, como relatado na literatura para outros sistemas, os efeitos viscosos se comportam de forma consideravelmente diferente na copolimerização, sendo necessário a reestimação de alguns parâmetros relativos aos mesmos. Assim, foi possível reproduzir de forma adequada perfis de conversão, massas molares médias e composição do copolímero. Concluiu-se que o modelo proposto é capaz de representar a cinética da copolimerização em suspensão do poli(acetato de vinila-co-metacrilato de metila), possibilitando um melhor controle das características do copolímero aplicado ao procedimento de embolização vascular. Até onde se tem conhecimento, este é o primeiro trabalho que investiga e implementa com sucesso a modelagem cinética desse sistema. / [en] The treatment of vascularized tumors through vascular embolization is sensible to the polymeric particles used during procedure. These embolic agents have attributes, like size and morphology, which play a significant role on the success of this technique and can promote complications when not well dimensioned. Among the many options available, spherical particles of poly(vinyl acetate-co-methyl methacrylate) present most desired characteristics after alkalyne hydrolysis treatment. Being relatively new, the literature lack studies related to the kinetics of production of this material. Therefore, this research investigated the copolymerization kinetics of poly(vinyl acetate-co-methyl methacrylate) production. In the mathematical development, the method of moments was used assuming quasi-steady state for the free radical species. Additionally, the model includes the viscous effects through the diffusion of the involved molecules, which is usually accounted empirically. It was possible to use the physical properties of the monomers as well as the homopolymerization kinetic parameters in the copolymerization. However, as reported in the literature, some parameters are sensible to the system and some viscous effects affect the copolymerization differently. Therefore, some parameters were reestimated. It was possible to predict the conversion, average molecular weights and composition. Consequently, the model was capable of representing the kinetics of the suspension copolymerization of poly(vinyl acetate-co-methyl methacrylate), meaning it could be used to improve the production of this polymer as an embolic agent for vascular embolization procedure. As far as known by the author, this is the first study to successfully perform the kinetic modeling of this specific system.

[pt] Nas últimas décadas, grandes investimentos foram feitos no desenvolvimento de modelos e métodos numéricos para prever e analisar os diferentes aspectos do processo de recuperação de óleo e gás. Neste contexto, os simuladores modernos devem ser capazes de incorporar uma grande variedade de opções para responder questões relacionadas ao gerenciamento de reservatórios de forma rápida e precisa. Neste trabalho, nós apresentamos um simulador de reservatórios baseado em uma arquitetura de plugins, onde diferentes formulações, solvers e modelos podem ser desenvolvidos, estendidos e aprimorados. A partir desta abordagem, utilizamos o modelo black-oil para implementar técnicas tradicionais e do estado da arte, como os métodos totalmente e adaptativamente implícito, os métodos de Newton-Raphson e Newton Inexato, controladores heurístico e PID para passo de tempo adaptativo e aproximações de fluxo de um ponto baseados no potencial de fase tradicional e C1-contínuo. Diversas configurações de plugins foram testadas e validadas com simuladores comerciais e seus desempenhos foram utilizados para determinar quais as mais adequadas para resolver problemas de escoamento multifásico. / [en] During the last decades, large investments were made towards the development of numerical models and methods to forecast and analyze the different aspects of oil and gas recovery. In this context, modern simulators must be able to incorporate a wide variety of options to answer questions related to reservoir management accurately and effectively. In this work, we present a reservoir simulator based on a plugin architecture, where different formulations, solvers, and models can be developed, extended, and enhanced. With this approach, we use the black-oil model to implement traditional and state-of-the-art techniques, including fully- and adaptiveimplicit methods, heuristic and PID time-step controllers, Newton-Raphson and Inexact Newton, and C1-continuous and conventional phase-potential single-point upstream weighting. Several plugin configurations were tested and validated with commercial simulators, and their performances were used to determine which are the most suitable to solve multiphase flow problems.

Spinal cord injury (SCI) is an acquired physical disability through traumatic injuries such as car accidents and shooting incidents, and non-traumatic injury such as a tumour on the spinal cord, amongst others. Unlike other parts of the body, the spinal cord does not have the ability to repair itself if it is damaged. Consequently, a person who has acquired an SCI will have a physical disability and will be either a paraplegic – paralysis of the lower part of the body, including the legs, or a quadriplegic, which is paralysis of all four limbs. Acquiring a spinal cord injury (SCI) has devastating long-term negative outcomes for the injured person as well as his/her cohabiting partner on a physical, psychological, psychosocial and socio-economical level. Exposure to such prolonged adversity and resulting negative outcomes calls for resilience, namely the ability to positively adapt despite the adversity being exposed to. Not all individuals have the natural ability to “bounce back”, and consequently resilience promotion is imperative. In South Africa, the focus of service delivery in rehabilitation centres is mainly centred on the injured person and consequently the well-being of the spinal cord injured person’s partner (SCIPP) is neglected. Little information is available on resilience-promoting programmes for SCIPPs; thus the main aim of this study was to design and develop a group resilience-promoting programme (GRPP) for SCIPPs. The researcher mainly followed a qualitative research approach and included a small quantitative component. In the context of applied research, an intervention research model comprising six phases was employed. Phase 1, Problem analysis and project planning, was reported on in section A. Manuscript 1 reports on phase 2 (information gathering and synthesis), and consists of a qualitative research synthesis, and mainly aimed at organizing and synthesizing previous research on resilience-promoting processes in order to inform the design and development of a group resilience-promoting programme (GRPP) for SCIPPs. After a systematic review and quality appraisal a total of 74 papers were selected to be quality appraised after abstracts and titles were assessed for relevance. Twenty-one studies were included and synthesized where after an outline for the content of a GRPP for SCIPPs was formulated. Conclusions and recommendations highlight that the formulated GRPP for SCIPPs needs to be further developed into an intervention that could be implemented with SCIPPs. As such, the researcher therefore proceeded with the study (see manuscript 2), aiming in developing small-group programme content and activities (using knowledge gathered from pre-existing interventions; resilience literature; consultations with experts; people living with spinal cord injury (SCI) and personal experience) to promote resilience in SCIPPs. By means of purposive sampling six advisory panel members from a diverse background were interviewed before and after the pilot study with two SCIPPs and one observer to contribute towards the further development of the GRPP for SCIPPs. A six-session GRPP for SCIPPs was formulated, including the following: (1) Information on SCI and resilience; (2) Help SCIPPs understand that their reactions to/emotions regarding these huge changes are normal; (3) Caretaking and support; (4) My dual role; (5) Own caretaking by SCIPPs; and (6) Termination and way forward. The newly developed GRPP for SCIPPs however had to be formally evaluated. Recommendations were made by professionals in the field that the GRPP for SCIPPs should first be subjected to peer review prior to implementing it with the target population. Therefore in manuscript 3 (reporting on phase 5 – evaluation ) the evaluation purpose was to subject the GRPP for SCIPPs to peer review by means of an empirical study with professional role-players (social workers and psychologists) in the field of spinal cord injury, prior to exhibiting it to the target population. The six group sessions were presented to professional role-players (n=12) working within the field of SCI during two 2-day workshops, whereby they were requested to evaluate the content and procedural elements of the GRPP for SCIPPs mainly by means of qualitative research, with a small numerical (quantitative) component. Thematic content analysis and basic descriptive statistics were employed. Overall positive feedback regarding the newly developed intervention was received, with suggested adjustments that needed to be made to the GRPP for SCIPPs prior to formal evaluation with the target group. The GRPP for SCIPPs will further be subjected to expert review in other provinces in South Africa, as the current participants were all from Gauteng. Furthermore, postgraduate students will be recruited to test the programme with the target-population in South Africa for possible further improvement and suggestions, as well as possible expansion to adjust this intervention to meet the needs of male SCIPPs; SCIPs themselves; children of a parent/s living with SCI; and also for post-injury cohabiting relationships, as this intervention might be a starting point for above-mentioned research-opportunities.

Spinal cord injury (SCI) is an acquired physical disability through traumatic injuries such as car accidents and shooting incidents, and non-traumatic injury such as a tumour on the spinal cord, amongst others. Unlike other parts of the body, the spinal cord does not have the ability to repair itself if it is damaged. Consequently, a person who has acquired an SCI will have a physical disability and will be either a paraplegic – paralysis of the lower part of the body, including the legs, or a quadriplegic, which is paralysis of all four limbs. Acquiring a spinal cord injury (SCI) has devastating long-term negative outcomes for the injured person as well as his/her cohabiting partner on a physical, psychological, psychosocial and socio-economical level. Exposure to such prolonged adversity and resulting negative outcomes calls for resilience, namely the ability to positively adapt despite the adversity being exposed to. Not all individuals have the natural ability to “bounce back”, and consequently resilience promotion is imperative. In South Africa, the focus of service delivery in rehabilitation centres is mainly centred on the injured person and consequently the well-being of the spinal cord injured person’s partner (SCIPP) is neglected. Little information is available on resilience-promoting programmes for SCIPPs; thus the main aim of this study was to design and develop a group resilience-promoting programme (GRPP) for SCIPPs. The researcher mainly followed a qualitative research approach and included a small quantitative component. In the context of applied research, an intervention research model comprising six phases was employed. Phase 1, Problem analysis and project planning, was reported on in section A. Manuscript 1 reports on phase 2 (information gathering and synthesis), and consists of a qualitative research synthesis, and mainly aimed at organizing and synthesizing previous research on resilience-promoting processes in order to inform the design and development of a group resilience-promoting programme (GRPP) for SCIPPs. After a systematic review and quality appraisal a total of 74 papers were selected to be quality appraised after abstracts and titles were assessed for relevance. Twenty-one studies were included and synthesized where after an outline for the content of a GRPP for SCIPPs was formulated. Conclusions and recommendations highlight that the formulated GRPP for SCIPPs needs to be further developed into an intervention that could be implemented with SCIPPs. As such, the researcher therefore proceeded with the study (see manuscript 2), aiming in developing small-group programme content and activities (using knowledge gathered from pre-existing interventions; resilience literature; consultations with experts; people living with spinal cord injury (SCI) and personal experience) to promote resilience in SCIPPs. By means of purposive sampling six advisory panel members from a diverse background were interviewed before and after the pilot study with two SCIPPs and one observer to contribute towards the further development of the GRPP for SCIPPs. A six-session GRPP for SCIPPs was formulated, including the following: (1) Information on SCI and resilience; (2) Help SCIPPs understand that their reactions to/emotions regarding these huge changes are normal; (3) Caretaking and support; (4) My dual role; (5) Own caretaking by SCIPPs; and (6) Termination and way forward. The newly developed GRPP for SCIPPs however had to be formally evaluated. Recommendations were made by professionals in the field that the GRPP for SCIPPs should first be subjected to peer review prior to implementing it with the target population. Therefore in manuscript 3 (reporting on phase 5 – evaluation ) the evaluation purpose was to subject the GRPP for SCIPPs to peer review by means of an empirical study with professional role-players (social workers and psychologists) in the field of spinal cord injury, prior to exhibiting it to the target population. The six group sessions were presented to professional role-players (n=12) working within the field of SCI during two 2-day workshops, whereby they were requested to evaluate the content and procedural elements of the GRPP for SCIPPs mainly by means of qualitative research, with a small numerical (quantitative) component. Thematic content analysis and basic descriptive statistics were employed. Overall positive feedback regarding the newly developed intervention was received, with suggested adjustments that needed to be made to the GRPP for SCIPPs prior to formal evaluation with the target group. The GRPP for SCIPPs will further be subjected to expert review in other provinces in South Africa, as the current participants were all from Gauteng. Furthermore, postgraduate students will be recruited to test the programme with the target-population in South Africa for possible further improvement and suggestions, as well as possible expansion to adjust this intervention to meet the needs of male SCIPPs; SCIPs themselves; children of a parent/s living with SCI; and also for post-injury cohabiting relationships, as this intervention might be a starting point for above-mentioned research-opportunities.

A pragmatic method for selecting components and devices from a database or parameterized models is developed in this thesis. The quantitative framework presented here is sufficiently general to accommodate an entire device assembly, a component, or a sub-assembly. The details pertaining to a device or a component are classified into three sets of variables: (i) user-specifications, s (ii) device parameters, p , and (iii) device characteristics, c . Functional, practical, and performance-related attributes that a user can provide comprise user-specifications. Since, most often, a specification cannot be specified as a single number, we allow the user to enter a range with lower and upper bounds. Device parameters comprise the geometry and material properties, and device characteristics include functional requirements and performance criteria. Thus, for a device, all its functional and utility attributes are contained in the union of sets s and c , whereas the geometry and the material properties are in set p . The equations governing the physical behavior of the device are written in terms of s , p , and c . These equations may sometimes be readily available; when they are not, it may be necessary to formulate them as required. By solving the governing equations along with the inequalities that arise from the lower and upper bounds on s , we obtain feasible ranges on p and c . Then, for any pair of device characteristics, a 2D feasible map is drawn, to visually portray the consequences of user-specifications. If the feasible map is null, small, or large, it indicates that the user-specifications are infeasible, stringent, or there is much scope for design, respectively. This can be inferred even before the designs are considered. Juxtaposed on the feasible map are points or lozenges corresponding to the quantitative attributes of the entries in the database. The ones that lie inside the feasible map can be reckoned as meeting the user-specifications and thus, enabling selection. On the other hand, if there is no database or none of the devices in the database lie inside the feasible map, we can identify the feasible ranges of all the design parameters for every point inside the feasible map. This information is useful to the designer to redesign and arrive at feasible designs by using parameterized models of the device. A Graphical User Interface (GUI) is developed to facilitate the user-interaction. The utility of the selection framework is demonstrated with a variety of case-studies including miniature pumps, heat pulse-based soil-moisture sensors, springs, flywheels, compliant mechanisms, micromechanical suspensions, etc. The latter two use kineto-elastic characteristics of deformable components. The framework, when used for materials selection, can be seen as an extension of Ashby’s materials selection method. This is also illustrated with two examples.

[pt] Métodos computacionais em engenharia são usados na solução de problemas físicos que não possuem solução analítica ou sua perfeita representação matemática é inviável. Técnicas de métodos numéricos, incluindo o amplamente usado método dos elementos finitos, podem exigir a solução de sistemas lineares com centenas de milhares de equações, demandando altos recursos computacionais (memória e tempo). Nesta tese, nós apresentamos um sistema baseado em plugins para análise numérica em larga escala. O sistema é usado como uma ferramenta original na solução de problemas de otimização topológica usando o método dos elementos finitos com milhões de elementos. Nossa estratégia utiliza uma técnica elemento-por-elemento para implementar um código altamente paralelo para um solver iterativo com baixo consumo de memória. Além disso, a abordagem de plugin proporciona um ambiente completamente flexível e fácil de estender, onde diferentes aplicações, exigindo diferentes tipos de elementos finitos, materiais, solvers lineares e formulações podem ser desenvolvidos e melhorados. O kernel do sistema é mínimo, com apenas um módulo gerenciador de plugin, responsável por carregar os plugins desejados em tempo real usando um arquivo de configuração de entrada. Todas as funcionalidades necessárias para uma determinada aplicação são definidas dentro dos plugins, sem a necessidade de mudar o kernel. Plugins podem disponibilizar ou exigir interfaces adicionais especializadas, onde outros plugins podem ser conectados para compor um sistema mais complexo e completo. Nós apresentamos resultados para uma análise estrutural estática linear elástica e para uma análise estrutural de otimização topológica. As simulações utilizam elementos Q4, hexagonal (Brick8) e prisma hexagonal (Honeycomb), com solvers diretos e iterativos usando computação sequencial, paralela e distribuída. Nós investigamos o desempenho com relação ao uso de memória e escalabilidade da solução para problemas com diferentes tamanhos, de exemplos pequenos a muito grandes em apenas uma máquina e em um cluster. Foi simulado um exemplo de análise estática linear elástica com 500 milhões de elementos em 300 máquinas. / [en] Computational methods in engineering are used to solve physical problems that do not have analytical solution or their perfect mathematical representation is unfeasible. Numerical techniques, including the largely used finite element method, require the solution of linear systems with hundreds of thousands equations, demanding high computational resources (memory and time). In this thesis, we present a plugin-based framework for large-scale numerical analysis. The framework is used as an original tool to solve topology optimization problems using the finite element method with millions of elements. Our strategy uses an element-by-element technique to implement a highly parallel code for an iterative solver with low memory consumption. Besides, the plugin approach provides a fully flexible and easy to extend environment, where different types of applications, requiring different types of finite elements, materials, linear solvers, and formulations, can be developed and improved. The kernel of the framework is minimum with only a plugin manager module, responsible to load the desired plugins during runtime using an input configuration file. All the features required for a specific application are defined inside plugins, with no need to change the kernel. Plugins may provide or require additional specialized interfaces, where other plugins may be connected to compose a more complex and complete system. We present results for a structural linear elastic static analysis and for a structural topology optimization analysis. The simulations use elements Q4, hexahedron (Brick8), and hexagonal prism (Honeycomb), with direct and iterative solvers using sequential, parallel and distributed computing. We investigate the performance regarding the use of memory and the scalability of the solution for problems with different sizes, from small to very large examples on a single machine and on a cluster. We simulated a linear elastic static example with 500 million elements on 300 machines.