Life Orientation, a core subject of the South African secondary school curriculum since 1996, is still not taught successfully in the majority of secondary schools. This study was conducted in former Model C secondary schools in the Nelson Mandela Metropole in order to identify challenges and problems with regard to the management of the teaching of the subject. If the subject were managed properly by principals the Departmental outcomes would have been achieved and problems would not have existed. In this study the managerial challenges of the teaching of Life Orientation have been identified by means of mixed method research, in terms of the four main management tasks, namely leading, planning, organising and controlling. The views of principals were obtained through a questionnaire and semi-structured interviews. The data was synthesised, multi-dimensional management problems were identified and recommendations were made with regard to managing the important subject of Life Orientation. / Educational Leadership and Management / M. Ed. (Education Management)

La cristallisation sous tension (SIC) du caoutchouc naturel (NR) a fait l’objet d’un nombre considérable d’études depuis sa découverte il y a près d’un siècle. Cependant, il existe peu d’informations dans la littérature concernant le comportement du caoutchouc à des vitesses de sollicitation proches des temps caractéristiques de cristallisation. L’objectif de cette thèse est alors de contribuer à la compréhension du phénomène de cristallisation sous tension grâce à des essais dynamiques à grandes vitesses. Pour répondre à cet objectif, nous avons développé une machine de traction permettant de déformer des échantillons d’élastomères à des vitesses de sollicitation pouvant aller jusqu’à 290s-1. Les essais ont été réalisés sur quatre NR avec des taux de soufre variables, deux NR chargés comportant des taux de noir de carbone différents. Nous avons également étudié un matériau synthétique à base de polyisoprène (IR) afin de comparer ses performances à celle du NR. Les essais dynamiques étant relativement difficiles à interpréter, un travail conséquent a donc été d’abord réalisé à basse vitesse. En outre, l’approche expérimentale proposée a été couplée à une approche thermodynamique de la SIC. Les mécanismes généraux associés à la cristallisation que nous identifions sont les suivants: lors d’une traction, la cristallisation consiste en l’apparition de populations cristallines conditionnée par l’hétérogénéité de réticulation des échantillons. Cette cristallisation semble nettement accélérée dès lors que ce cycle est réalisé au-dessus de la déformation de fusion. Nous attribuons ce phénomène à un effet mémoire dû à un alignement permanent des chaînes. Enfin, l’effet de la vitesse est décrit théoriquement en intégrant un terme de diffusion des chaînes dans la cinétique de SIC. Cette approche couplée à des essais mécaniques suggère que la SIC est essentiellement gouvernée par la cinétique de nucléation. Lors des tests dynamiques, la combinaison de l’effet mémoire et d’une accélération de la fusion pendant le cycle entraine une nette diminution voire une disparition de l’hystérèse cristalline. En outre, l’auto-échauffement, qui augmente progressivement avec la fréquence du cycle, tend à supprimer l’effet mémoire en provoquant le passage du cycle en dessous de la déformation de fusion. Lors de ces essais dynamiques, la SIC semble favorisée pour le matériau le moins réticulé. Nous attribuons cet effet au blocage d’enchevêtrements jouant le rôle de sites nucléants pour la SIC. Le matériau chargé semble avoir une moins bonne aptitude à cristalliser à hautes vitesses, par rapport à l’élastomère non chargé, en raison d’un auto-échauffement important à l’interface entre charges et matrice. Enfin, nous notons une convergence des cinétiques de cristallisation du caoutchouc naturel et synthétique à grande déformation et grande vitesse de sollicitation, que nous attribuons à la prédominance du terme énergétique d’origine entropique dans la cinétique de nucléation. / Strain induced crystallization (SIC) of Natural Rubber (NR) has been the subject of a large number of studies since its discovery in 1929. However, the literature is very poor concerning the study of SIC when samples are deformed with a stretching time in the range of the SIC characteristic time (around 10msec-100msec). Thus, the aim of this thesis is to contribute to the understanding of the SIC phenomenon thanks to dynamic tensile tests at high strain rates. To meet this goal, we have developed a dynamic tensile test machine allowing stretching samples of elastomers at strain rates up to 290 s-1. The tests are carried out on four NR with different sulphur amount, two NR with different carbon black filler amounts. We also studied a synthetic rubber made of polyisoprene chains (IR) able to crystallize under strain. Dynamic tests are relatively difficult to interpret; a significant work has thus been first performed at slow strain rate. Moreover, the experiments are coupled with a thermodynamic approach. First, the general mechanisms associated to the crystallization are identified as follows: during mechanical loading or during cooling in the deformed state, SIC is the result of successive appearance of crystallite populations whose nucleation and growth depend on the local network density. Crystallization is enhanced when the cycle is performed above the melting stretching ratio. This phenomenon is attributed to a memory effect due to a permanent alignment of the chains. Finally, the effect of the strain rate is theoretically described thanks to a diffusion term. This approach, coupled with experiments suggests that SIC is mainly governed by the nucleation kinetics. For the dynamic test, the combination of the memory effect and the acceleration of the melting during the cycle lead to a reduction or even disappearance of the crystalline hysteresis. In addition, self-heating, which progressively increases with the frequency of the cycle, causes the delay of the melting stretching ratio. This well explains why the crystallinity index decreases at the minimum stretching ratio of the dynamic cycles when the frequency increases. We finally compared the ability of our different rubbers to crystallize at high strain rates. SIC is enhanced for the weakly crosslinked rubber. This might be related to the dynamics of its free entanglements, these ones acting as supplementary crosslinks at high strain rates. Then, a filled rubber is compared to the unfilled one. We found that the filled sample has a lower ability to crystallize at high strain rates as compared to the unfilled one. This is likely due to the strong self-heating at the interface between the fillers and the rubbery matrix. Finally, we observe a convergence of crystallization kinetics in natural and synthetic rubbers at high strains and high strain rates. This is attributed to the predominance of the entropic energy in the nucleation kinetics in these experimental conditions.

The preparation of polymeric hybrid composite consisting of organic and inorganic fillers is of interest for industries like automotive, construction and packaging. In order to understand and predict the physical and chemical properties of these hybrid composites, it is necessary to fully understand the nature and properties of the employed fillers. In this study, the preparation of polypropylene hybrid composite consisting of wheat straw and clay was investigated. A detailed study was performed on wheat straw from South Western Ontario region. The effect of grinding the straw and compounding it with polypropylene was investigated. Experiments were carried out to identify the thermal stability of the ground wheat straw with respect to their size and composition. It was important to identify a correlation between these properties in order to minimize the straw degradation by processing and also to improve the final properties of the hybrid composite. The composite samples were prepared through melt blending method using a co-rotating twin-screw extruder. Sample test bars were prepared by injection moulding. The composition of the constituents of the hybrid composite; percentages of wheat straw, clay and coupling agent, were varied in order to investigate their influence on thermal stability, water resistance and mechanical properties. The results of the study indicated that grinding the wheat straw with a hammer mill produced particles with different sizes and shapes. It was found that through the grinding system all particles, regardless of their size, had a multi-layered structure similar to the plant structure. Further hammer milling did not produce plant particles with long aspect ratios that would be expected in a defibrillation process. Analysis of the chemical composition of wheat straw particles of different sizes and shapes was used to measure the ratio of hemicelluloses: lignin and the ash content. It was found that the large particles contained more amount of lignin whereas smaller particles had larger amount of ash content. The thermal stability of the particles was found to be a function of particle size rather than the lignin content. Particle size analysis on the wheat straw particles after the extrusion process indicated a reduction in the particle length and aspect ratio. The thermal stability of the composites was found to be enhanced by the addition of clay particles at higher temperature and the addition of coupling agent at lower temperatures. Increasing the amount of wheat straw and clay content increased the flexural modulus and reduced the resistance for water absorption. Increasing the amount of coupling agent also increased the flexural modulus and resistance for water absorption. The morphological study by scanning electron microscopy revealed that coupling agent increased the interfacial interaction between the particles and the polymer matrix.

The preparation of polymeric hybrid composite consisting of organic and inorganic fillers is of interest for industries like automotive, construction and packaging. In order to understand and predict the physical and chemical properties of these hybrid composites, it is necessary to fully understand the nature and properties of the employed fillers. In this study, the preparation of polypropylene hybrid composite consisting of wheat straw and clay was investigated. A detailed study was performed on wheat straw from South Western Ontario region. The effect of grinding the straw and compounding it with polypropylene was investigated. Experiments were carried out to identify the thermal stability of the ground wheat straw with respect to their size and composition. It was important to identify a correlation between these properties in order to minimize the straw degradation by processing and also to improve the final properties of the hybrid composite. The composite samples were prepared through melt blending method using a co-rotating twin-screw extruder. Sample test bars were prepared by injection moulding. The composition of the constituents of the hybrid composite; percentages of wheat straw, clay and coupling agent, were varied in order to investigate their influence on thermal stability, water resistance and mechanical properties. The results of the study indicated that grinding the wheat straw with a hammer mill produced particles with different sizes and shapes. It was found that through the grinding system all particles, regardless of their size, had a multi-layered structure similar to the plant structure. Further hammer milling did not produce plant particles with long aspect ratios that would be expected in a defibrillation process. Analysis of the chemical composition of wheat straw particles of different sizes and shapes was used to measure the ratio of hemicelluloses: lignin and the ash content. It was found that the large particles contained more amount of lignin whereas smaller particles had larger amount of ash content. The thermal stability of the particles was found to be a function of particle size rather than the lignin content. Particle size analysis on the wheat straw particles after the extrusion process indicated a reduction in the particle length and aspect ratio. The thermal stability of the composites was found to be enhanced by the addition of clay particles at higher temperature and the addition of coupling agent at lower temperatures. Increasing the amount of wheat straw and clay content increased the flexural modulus and reduced the resistance for water absorption. Increasing the amount of coupling agent also increased the flexural modulus and resistance for water absorption. The morphological study by scanning electron microscopy revealed that coupling agent increased the interfacial interaction between the particles and the polymer matrix.

Life Orientation, a core subject of the South African secondary school curriculum since 1996, is still not taught successfully in the majority of secondary schools. This study was conducted in former Model C secondary schools in the Nelson Mandela Metropole in order to identify challenges and problems with regard to the management of the teaching of the subject. If the subject were managed properly by principals the Departmental outcomes would have been achieved and problems would not have existed. In this study the managerial challenges of the teaching of Life Orientation have been identified by means of mixed method research, in terms of the four main management tasks, namely leading, planning, organising and controlling. The views of principals were obtained through a questionnaire and semi-structured interviews. The data was synthesised, multi-dimensional management problems were identified and recommendations were made with regard to managing the important subject of Life Orientation. / Educational Leadership and Management / M. Ed. (Education Management)

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-09T18:16:27Z No. of bitstreams: 1 SANDRO MARTINS DOLGHI - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1349252 bytes, checksum: 7e20e2840dc2a5d2e873cd9b77ed0100 (MD5) / Made available in DSpace on 2018-04-09T18:16:27Z (GMT). No. of bitstreams: 1 SANDRO MARTINS DOLGHI - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1349252 bytes, checksum: 7e20e2840dc2a5d2e873cd9b77ed0100 (MD5) Previous issue date: 2014-12-19 / O culto à beleza está em evidência no Brasil e no mundo, levando ao crescente aumento de técnicas e procedimentos para corrigir defeitos estéticos e minimizar os efeitos do envelhecimento. Diversas substâncias preenchedoras com fluidos de alta viscosidade ou partículas de polímeros em suspensão têm sido utilizadas em larga escala em procedimentos cosméticos e correção de lipodistrofia de pacientes HIV positivos, submetidos à terapia antirretroviral de alta atividade. O uso de polimetilmetacrilato (PMMA) como substância de preenchimento dérmico tem crescido vertiginosamente, assim como o número de reações adversas decorrentes de seu uso. O PMMA vem sendo utilizado, amplamente como matéria prima na fabricação de diversos dispositivos e produtos médicos desde a década de 40, especialmente em função de sua biocompatibilidade, entretanto, ainda há carência de informações e estudos sobre migração e resposta inflamatória das substâncias comercializadas no Brasil para fins de preenchimento dérmico. Este trabalho teve como objetivo avaliar as características físico-químicas de implantes de PMMA comercializados no Brasil para procedimentos de bioplastia, em três apresentações comerciais do produto com diferentes concentrações, visando delimitar limites aceitáveis para fins de registro destes produtos na Agência Nacional de Vigilância Sanitária (Anvisa), com foco na segurança sanitária. As amostras foram caracterizadas por Difração de Raios X (DRX), Espectroscopia na região do infravermelho com transformada de Fourier (FTIR), Microscopia Eletrônica de Varredura (MEV), Espectroscopia por Energia Dispersiva de Raios X (EDS), análise de Calorimetria Exploratória Diferencial (DSC), caracterização por Microscopia Óptica (MO). A técnica de DRX mostrou comportamento semicristalino do PMMA. Com a técnica de FTIR constatou-se os grupos funcionais presentes nos implantes. Por meio das técnicas de MO e MEV foi possível perceber a não homogeneidade em relação ao tamanho das microesferas de PMMA. Pôde-se concluir com os resultados de DSC que o pico endotérmico aumentou de acordo com as variações de concentração do PMMA. A partir dos dados obtidos neste trabalho constata-se que o consumidor está sujeito a riscos, visto que a irregularidade das superfícies e variações nos tamanhos das microesferas pode ocasionar reações adversas, em função da fagocitose das microesferas com tamanho inferior a 20 μm. O crescente uso das técnicas de preenchimento com implantes de PMMA, bem como sua indicação para uso em demais especialidades da medicina, o coloca como material a ser ainda amplamente estudado nas mais diversas aplicações do produto na área médica. / The cult of beauty is in evidence in Brazil and in the world, leading to increasing techniques and procedures to correct aesthetic defects and minimize the effects of aging. Several dermal fillers with high viscosity or polymer particles in suspension fluids have been used in large scale in cosmetic procedures and lipodystrophy correction of HIV-positive patients undergoing HAART activity. The use of polymethylmethacrylate (PMMA) as dermal filler substance has grown dramatically, and the number of adverse reactions arising from its use. PMMA has been used widely as a raw material in manufacturing various medical devices and products since the 40s, especially due to its biocompatibility, however, there is still a lack of information and studies on migration and inflammatory response of substances marketed in Brazil dermal filler purposes. This study aimed to evaluate the physical and chemical characteristics of PMMA implants sold in Brazil for bioplasty procedures in three commercial presentations of the product with different concentrations, in order to delimit acceptable limits for registration of these products at ANVISA, with focus on security health. The samples were characterized by X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Spectroscopy Energy Dispersive X-ray (EDS) analysis of Differential Scanning Calorimetry (DSC), characterized by Optical Microscopy (OM). The XRD technique showed semi-crystalline behavior of PMMA. FTIR technique found the functional groups present on the implants. Through OM and SEM techniques we saw the inhomogeneity relative to the size of the PMMA microspheres. One can conclude from the results of the DSC endothermic peak increased in accordance with changes in the concentration of PMMA. From the data obtained in this study it appears that the consumer is subject to risks as uneven surfaces and variations in size of the microspheres can cause adverse reactions, depending on the phagocytosis of microspheres with size less than 20 microns. The increasing use of technical fill with PMMA implants, as well as indications for use in other specialties of medicine, places it as material to be still widely studied in various product applications in the medical field.

A procedure to evaluate the leaching properties of radionuclides from irradiated graphite waste has been developed by combining ANSI 16.1 (USA) and NEN 7345 (Netherlands) standardised diffusion leaching techniques. The ANSI 16.1 standard has been followed to the acquire the leachates and to determine the leach rate/ diffusion coefficient and NEN 7345 standard technique has been used to determine the diffusion mechanism of radionuclides. The investigation employs simulated Drigg groundwater as a leachant using semi-dynamic technique for the production of leachate specimens. From gamma spectroscopy analysis the principal radionuclides present in terms of activity were 60Co, 137Cs, 134Cs, 155Eu, 133Ba and 46Sc. The dominant radionuclides are 60Co, 134Cs and 133Ba which together account for about 91 % of the total activity. The 91 % can be broken down into 73.4 % 60Co, 9.1 % 134Cs and 8.1 % 133Ba. Analysis of total beta and total beta without tritium activity release from Magnox graphite was measured using liquid scintillating counting. Preliminary results show that there is an initial high release of activity and decreases when the leaching period increases. This may be due to the depletion of contaminants which were absorbed by the internal pore networks and the surface. During the leaching test approximately 275.33 ± 18.20 Bq of 3H and 106.26 ± 7.01 Bq of 14C was released into the leachant within 91 days. Irradiation induced damages to the nuclear graphite crystal structure have been shown to cause disruption of the bonding across the basal planes. Moreover, the closures of Mrozowski cracks have been observed in nuclear graphite, the bulk property are governed by the porosity, in particular, at the nanometre scale. Therefore, knowledge of the crystallite structure and porosity distribution is very important; as it will assist in understand the affects of irradiated damage and location and the mechanism of the leaching of radionuclides. The work reported herein contributed several key findings to the international work on graphite leaching to offer guidance leading toward obtaining leaching data in the future: (a) the effective diffusion coefficient for 14C from graphite waste has been determined. The diffusion process for 14C has two stages resulting two different values of diffusion coefficient, i.e., for the fast and slow components; (b) the controlling leaching mechanism for 3H radionuclide from graphite is shown to be surface wash–off; and for that of 14C radionuclide the initial controlling leaching mechanism is surface wash-off following by diffusion which is the major transport mechanism ; (c) The weight loss originates from the open pore structure which has been opened up by radiolytic oxidation; at the higher weight losses much of the closed porosity in the graphite has been opened. The investigation indicates that weigh loss has a major influence on the leaching of elements from the irradiated graphite; and (d) the analysis of the pores in nuclear graphite can be categorised into three types. These three types of pores are: (1) small pores narrow which are slit-shaped pores in the binder phase or matrix, (2) gas evolution pores or gas entrapment pores within the binder phase or matrix and (3) lenticular pores which are large cracks within the filler particles. It is shown in this thesis that by using tomography to study the morphology of the different pores coupled with the distribution of impurities an understanding of the role of porosity in leaching is possible.

Work describes the relationship between structure and mechanical properties in case of hybrid mixtures. They are composed from polyurethane matrices (eventually polyurethane-urea or polyurethane-inorganic filler mixtures), different rubber fractions as filler and eventually reinforcement made from PET monofilaments. Mechanical behaviour was studied by tensile testing. Studied mechanical properties include tensile modulus, ultimate strength and strain and also specific energy need neccessary for ultimate strength achievement. Prepared materials are naturally porous. Therefore their mechanical behaviour has to be described generally for porous composites. The porosity occurence means, that it is difficult to describe them by models valid for mechanical behaviour (mainly elastic modulus) of nonporous composites. Models are also based on idealized structures on microscopic level. In case of porous composites, it is very difficult to create any idealized structure. The structure is changed with modifications of composition (change of components or their rates). These conditions have lead to utilizing of different approach how to describe the relationship between structure and mentioned mechanical properties. The chosen approach comes from knewledge about structural parametres coming from porosity. Structural parameters describe the structure on macroscopic level. They include interspace volume (volume lying between filler particles), interspace filling (how the matrix fills the interspace volume) and matrix volume fraction. Proposed parameters are used in relations, where they are fitted by exponents to interlay values of chosen mechanical properties for composites containing discrete matrix and filler. Found exponents are then described by properties of matrices to obtain relations describing properties of filled porous materials. Very similar approach was chosen for description in the case of reinforced composites. Proposed relation are potentially valid for materials containing binding matrix, infinity count of fillers and one kind of reinforcement.

The proposed golf resort is situated near the village of Nevcehle in the sloping terrain. It is a brick building of concrete blocks with contact thermal insulation and with concrete floor structure. The building has two floors. House is based on plain concrete foundations. Roof is made up of metal plate-connected timber truss with metal roofing.

Aim of this diploma thesis is to choose new pattern wax for Fimes a.s. foundry. New wax should substitute old not fully satisfactory pattern wax which caused problems in technological process resulting in increased number of rejects. New pattern wax should eliminate current problems and help foundry with producing large, thin-walled, high-quality castings. Numbers of pattern waxes supplied by world’s leading wax manufacturers were subjected to laboratory tests and pilot study. This diploma thesis is part of project Alfa TA01010766: „Research and development of production technology large, thin and high quality castings of aluminium alloys “