Congestion in ATM communications is a significant issue as it can have a dramatic effect on critical or real-time data. Forward Error Correction (FEC) codes are one class of protocols to decrease this effect. Conventional FEC techniques have a uniform or constant error correction rate, which can result in poor bandwidth utilization. Therefore adaptive techniques are sought. The rationale is to have better bandwidth utilization when congestion occurs. In this thesis, we investigate the related work on FEC in ATM networks. Then we propose an adaptive FEC scheme based on RS codes. This proposed scheme is then studied in different types of environments, wireline and wireless. Simulations are also conducted to measure different performance issues concerning network resources and quality of service. Another crucial issue in ATM communications is security. The proposed FEC scheme has an added feature of being security ready. Moreover it has been shown that the security scheme is computationally secure. Such FEC scheme has significant impact on ATM network resources and switch capacity. This has been investigated further in this work. Switch architectures utilizing FEC schemes are also studied. / Graduate

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Pupils entering High School for the first time experience many problems of orientation and adjustment. This study arose from the conviction that something could be done to alleviate this time of stress to the benefit of both pupil and school alike. A brief review of literature showed that despite a fair amount of research having been done in Britain and the United States, there is still a dearth of information relating directly to the South African situation. Most transition studies differentiate between factors affecting academic adjustment, those relating to personal adjustment after transfer, and those which involve adjustment to environmental factors. In general studies approached orientation pogrammes from two perspectives - those that handled orientation as an event with its concomitant administrative and practical advantages, and those that saw it to be a process which has more person-focussed advantages. Most researchers agree that each school has its own needs and that the orientation programme should reflect those needs. Many favour a problem-solving approach to the design of any programme and emphasize the need for constant evaluation of the programme to maintain relevance and effectiveness. A low-key investigation into adjustment problems faced by new pupils in the High School was conducted by means of a questionnaire. Three main areas of information were investigated: attitude to school; personal adjustment as indicated by the self-concept; and general impression of Secondary School. The results confirmed that problems of orientation and adjustment are experienced by pupils in the South African Education System and revealed a framework upon which an orientation programme could be based. An overview of existing orientation programme objectives stresses the fact that orientation must be concerned with the total adjustment of the child - personal, academic and environmental - and that, of necessity, it involves the whole family. An orientation programme is outlined and expanded upon in order to provide a framework upon which other programmes could be designed, specific to the particular needs of the schools involved. Finally, certain observations are offered which may lead to a better understanding of the demands of the orientation process

Universities are facing growing pressure to contribute towards innovation which has social impact and which contributes to economic development. Researchers mainly in the Science and Engineering fields are the primary sources of innovation outputs from universities and as such their involvement in commercialisation activities directly adds to the growth of innovative outputs from publicly financed research. Technology Transfer Offices (TTO) have been established at universities across South Africa to foster the involvement of researchers in commercialisation activities, to champion the innovation conversation within higher education institutions and to progress innovations from concept to application in society. This study focussed on understanding the factors which enable or create a barrier to the involvement of researchers in commercialisation activities at the Nelson Mandela Metropolitan University. The key elements examined in this study include the researchers’ perception of enablers (monetary and nonmonetary incentives) and barriers to involvement at national, institutional and individual levels. This study undertook to understand the perceptions of researchers of enablers and barriers to involvement in commercialisation at the Nelson Mandela Metropolitan University. Researchers in the two faculties of Science and Engineering, Built Environment and Information Technology were approached to anonymously complete an electronic survey, the questions for which were developed from literature. The results from the survey were analysed using descriptive statistics and hypothesis testing. This study finds that a combination of incentives is necessary to enable researcher involvement and to lower barriers to involvement in commercialisation research. A set of recommendations based on the study are put forward on how such recommendations can be implemented.

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The purpose of this study was to characterize recombinant plasraids carrying Drosophila melanogaster tRNA genes. The two groups of recombinant plasmids studied were those which carried tRNA₄Val genes and those with tRNA₄,₇Ser genes. pDt92 and pDt120, both tRNA₄Val gene-carrying plasmids, were characterized initially to determine the number of inserts they contained and the size of the inserts. For plasmids containing multiple inserts, the insert which carried the tRNA₄Val gene was also determined. These characteristics were studied by HindIII digestion of the plasmid DNA, agarose gel electrophoresis, Southern transfer onto nitrocellulose filters and hybridization to [¹²⁵I] tRNA₄Val. It was found that both, pDt92 and pDt120 contained two inserts each of sizes 0.5kb and 1.7kb,and 2.0kb and 5.*fkb respectively, with the 0.5kb and 2.0kb fragments carrying the tRNA₄Val genes. pDt92 and pDt120 then were recloned so as to contain only the fragments which carried the tRNA₄Val genes, namely the 0.5kb and 2.0kb fragment respectively. pDt92RC and pDt120RC plus three other tRNA₄,₇Ser gene containing plasmids, pDt16, pDt17RC and pDt27RC were further characterized by the technique of in situ hybridization to study the organization of these tRNA genes on the Drosophila genome. Four of these plasmids with the exception of pDt17RC hybridized to only one site on the Drosophila chromosome. Both, pDt92RC and pDt120RC hybridized to the 90BC site on the right arm of the third chromosome; pDt16 and pDt27RC hybridized to the 12DE site on the first or the X chromosome. pDt17RC on the other hand hybridized predominantly to the 12DE site and to a lesser extent to 2}E (2L), 56D (2R), 62D (3L) and 64D (3L) sites. These in situ hybridization results when studied together with those reported by Dunn et al. (1979b) show that genes for a single species of tRNA are located on more than one site on the Drosophila genome. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

L’objectif de cette thèse est de comprendre l’usage et les pratiques modales des individus et saisir les conséquences globales d’un nouveau mode alternatif « tramway » au sein de l’agglomération Rabat- Salé sur une société donnée (marocaine). Cette étude doctorale met en exergue les variables, les logiques individuelles qui interagissent dans un report modal et qui peuvent parfois être la cause des freins et de comportements résistants face au changement et à l’innovation. Les choix modaux se trouvent au cœur d’un processus complexe autour d’une multitude de facteurs et de variables. Un des éléments clés résultant de notre enquête sociologique pour accepter le changement consiste à acquérir de nouvelles compétences en termes de mobilité. Notre travail a été réalisé à l’échelle micro- individuelle qui correspond le mieux à notre problématique pour mieux analyser les pratiques des individus, les émotions, les normes sociales incorporées. La méthode qualitative retenue permet de se concentrer sur les propos des individus, la construction de leurs choix modaux, les représentations et les significations que donnent chaque personne à son choix. Le cadrage méthodologique s’est construit en se concentrant sur la focale « dimension culturelle et symbolique » de la société marocaine interrogée pour mieux saisir les processus de changement dans leur dynamique contextuelle et temporelle. En mêlant recherches bibliographiques épistémologiques, théoriques, enquêtes de terrain et analyse sociologique, cette thèse tente d’apporter des éléments de compréhension pour appréhender l’appropriation et l’adoption de ce nouveau concept de mobilité durable au sein de la société marocaine et contribue donc aussi à mener une réflexion sur le changement vers une mobilité plus durable et viable. / The objective of this thesis is to understand the use and the modal practices of individuals and to seize the global consequences of a means of transport « tramway » within the agglomeration of Rabat-Salé and also the consequence in Moroccan society. This doctoral study highlights the variables, the individual logics which interact in a modal transfer and witch can sometimes be the cause of brakes and resistant behavior to change and innovation. The modal choices are at the heart of a complex process around a multitude of factors and variables. One of the key elements resulting from a sociological analysis of mobility to accept the change consists in acquiring new skills in terms of mobility. Our work was realized at the micro-individual scale which corresponds to the best in order to analyze better the practices of individuals, the feeling and the incorporated social standards. The chosen qualitative method allows to concentrate on the words of people, The construction of their modal choices, the representations and meanings that every person gives to its choice. The methodological framework is built by focusing on the focal length « cultural and symbolic dimension » of the Moroccan society questioned to better understand the process of change in their contextual and temporal dynamics. By combining epistemological literature, theoretical bibliographical researches, inquiries of ground and sociological analysis, this thesis tries to bring elements of understanding to include the appropriation and the adoption of this new concept of sustainable mobility within the Moroccan society and contributes also reflect of the change to a more sustainable mobility.

Includes bibliographical references. / This thesis is concerned with the numerical modelling of the transient nonlinear heat conduction problem in solid continua. The hyperbolic governing equation is specialised to a parabolic equation which is sufficient for most engineering applications. The theoretical development includes the effects of conduction, specific heat, internal heat generation and the boundary conditions of convection, radiation, specified temperatures and flux, as well as point sources in the domain. The finite element spatial semidiscretisation of the equations is formally derived from the weak form of the governing equations. Temporal discretisation is obtained through an implicit/explicit difference scheme. The material properties are allowed to be temperature dependent, and consequently a modified Newton-Raphson iterative scheme is employed to solve the equations. The fully discretised equations are solved by implementing the algorithm in an existing finite element stress analysis code. Modelling is possible using four or eight-noded isoparametric elements, and solution control is possible through choice of time step size and choice of time integration method. Five examples are employed to demonstrate the ability of the program. The results compare well with published analytical solutions.