A fundamental understanding of the process of devolatilization requires extensive knowledge of not only the intrinsic properties of the parent coal and its subsequent formed products (tars, gases and chars), but also its characteristic reaction rate behaviour. Devolatilization behaviour has been extensively addressed in literature with the use of powdered coal samples, which normally do not adhere to particle size constraints of coal conversion processes utilizing lump coal. The aim of this investigation was therefore to assess the devolatilization behaviour (with respect to product yield and -quality; and reaction rate modelling) of four typical South African coals (UMZ, INY, G#5 and TSH) confined to the large particle regime. All four coals were found to be bituminous in rank, with vitrinite contents ranging between 24.4 vol.% and 69.2 vol.% (mineral matter free basis). Two were inertinite-rich coals (UMZ and INY) and the other two were vitrinite-rich coals (G#5 and TSH). From thermoplasticity measurements it was evident that only coal TSH displayed extensive thermoplastic behaviour, while a comparison between molecular properties confirmed the higher abundance of poly-condensed aromatic structures (aromaticity of 81%) present in this coal. Product evolution was evaluated under atmospheric conditions in a self-constructed, large particle, fixed-bed reactor, on two particle sizes (5 mm and 20 mm) at two isothermal reactor temperatures (450°C and 750°C) using a combination of both GC and MS techniques for gas species measurement, while standard gravimetric methods were used to quantify tar- and char yield respectively. Elucidation of tar- and char structural features involved the use of both conventional- and advanced analytical techniques. From the results it could be concluded that temperature was the dominating factor controlling product yield- and quality, with significant increases in both volatile- and gas yield observed for an increase in temperature. Tar yields ranged between 3.6 wt.% and 10.1 wt.% and increased in the order UMZ < INY < TSH < G#5, with higher tar yields obtained for coal G#5, being ascribed to larger abundances of vitrinite and liptinite present in this coal. For coal TSH, lower tar yields could mainly be attributed to the higher aromaticity and extensive swelling nature of this coal. Evolved gases were found to be mainly composed of H2, CH4, CO and CO2, low molecular weight olefins and paraffins; and some C4 homologues. Advanced analytical techniques (NMR, SEC, GC-MS, XRD, etc.) revealed the progressive increase of the aromatic nature of both tars and chars with increasing temperature; as well as subsequent differences in tar composition between the different parent coals. In all cases, an increase in devolatilization temperature led to the evolution of larger amounts of aromatic compounds such as alkyl-naphthalenes and PAHs, while significant decreases in the amount of aliphatics and mixed compounds could be observed. From 13C NMR, HRTEM and XRD carbon crystallite results it was clear that an increase in temperature led to the formation of progressively larger, more aromatic and structurally orientated polycondensed carbon structures. Reaction rate studies involved the use of non-isothermal (5-40 K/min) and isothermal (350- 900°C) thermogravimetry of both powdered (-200 μm) and large particle samples (20 mm) in order to assess intrinsic kinetics and large particle rate behaviour, respectively. Evaluation of the intrinsic kinetic parameters of each coal involved the numerical regression of non-isothermal rate data in MATLAB® 7.1.1 according to a pseudo-component modelling philosophy. Modelling results indicated that the intrinsic devolatilization behaviour of each coal could be adequately described by using a total number of eight pseudo-components, while reported activation energies were found to range between 22.3 kJ/mol and 244.3 kJ/mol. Description of the rate of large particle devolatilization involved the evaluation of a novel, comprehensive rate model accounting for derived kinetics, heat and mass transport effects, as well as physical changes due to particle swelling/shrinkage. Evaluation of the proposed model with the aid of the COMSOL Multiphysics 4.3 simulation software provided a suitable fit to the experimental data of all four coals, while simulation studies highlighted the relevant importance of not only the effect of particle size, but also the importance of including terms affecting for heat losses due to particle swelling/shrinkage, transport of volatile products through the porous char structure, heat of reaction and heat of vaporization of water. / Thesis (PhD (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013

A fundamental understanding of the process of devolatilization requires extensive knowledge of not only the intrinsic properties of the parent coal and its subsequent formed products (tars, gases and chars), but also its characteristic reaction rate behaviour. Devolatilization behaviour has been extensively addressed in literature with the use of powdered coal samples, which normally do not adhere to particle size constraints of coal conversion processes utilizing lump coal. The aim of this investigation was therefore to assess the devolatilization behaviour (with respect to product yield and -quality; and reaction rate modelling) of four typical South African coals (UMZ, INY, G#5 and TSH) confined to the large particle regime. All four coals were found to be bituminous in rank, with vitrinite contents ranging between 24.4 vol.% and 69.2 vol.% (mineral matter free basis). Two were inertinite-rich coals (UMZ and INY) and the other two were vitrinite-rich coals (G#5 and TSH). From thermoplasticity measurements it was evident that only coal TSH displayed extensive thermoplastic behaviour, while a comparison between molecular properties confirmed the higher abundance of poly-condensed aromatic structures (aromaticity of 81%) present in this coal. Product evolution was evaluated under atmospheric conditions in a self-constructed, large particle, fixed-bed reactor, on two particle sizes (5 mm and 20 mm) at two isothermal reactor temperatures (450°C and 750°C) using a combination of both GC and MS techniques for gas species measurement, while standard gravimetric methods were used to quantify tar- and char yield respectively. Elucidation of tar- and char structural features involved the use of both conventional- and advanced analytical techniques. From the results it could be concluded that temperature was the dominating factor controlling product yield- and quality, with significant increases in both volatile- and gas yield observed for an increase in temperature. Tar yields ranged between 3.6 wt.% and 10.1 wt.% and increased in the order UMZ < INY < TSH < G#5, with higher tar yields obtained for coal G#5, being ascribed to larger abundances of vitrinite and liptinite present in this coal. For coal TSH, lower tar yields could mainly be attributed to the higher aromaticity and extensive swelling nature of this coal. Evolved gases were found to be mainly composed of H2, CH4, CO and CO2, low molecular weight olefins and paraffins; and some C4 homologues. Advanced analytical techniques (NMR, SEC, GC-MS, XRD, etc.) revealed the progressive increase of the aromatic nature of both tars and chars with increasing temperature; as well as subsequent differences in tar composition between the different parent coals. In all cases, an increase in devolatilization temperature led to the evolution of larger amounts of aromatic compounds such as alkyl-naphthalenes and PAHs, while significant decreases in the amount of aliphatics and mixed compounds could be observed. From 13C NMR, HRTEM and XRD carbon crystallite results it was clear that an increase in temperature led to the formation of progressively larger, more aromatic and structurally orientated polycondensed carbon structures. Reaction rate studies involved the use of non-isothermal (5-40 K/min) and isothermal (350- 900°C) thermogravimetry of both powdered (-200 μm) and large particle samples (20 mm) in order to assess intrinsic kinetics and large particle rate behaviour, respectively. Evaluation of the intrinsic kinetic parameters of each coal involved the numerical regression of non-isothermal rate data in MATLAB® 7.1.1 according to a pseudo-component modelling philosophy. Modelling results indicated that the intrinsic devolatilization behaviour of each coal could be adequately described by using a total number of eight pseudo-components, while reported activation energies were found to range between 22.3 kJ/mol and 244.3 kJ/mol. Description of the rate of large particle devolatilization involved the evaluation of a novel, comprehensive rate model accounting for derived kinetics, heat and mass transport effects, as well as physical changes due to particle swelling/shrinkage. Evaluation of the proposed model with the aid of the COMSOL Multiphysics 4.3 simulation software provided a suitable fit to the experimental data of all four coals, while simulation studies highlighted the relevant importance of not only the effect of particle size, but also the importance of including terms affecting for heat losses due to particle swelling/shrinkage, transport of volatile products through the porous char structure, heat of reaction and heat of vaporization of water. / Thesis (PhD (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013

Thesis (doctoral)--Universität, Freiburg, 2005/2006.

Proefschrift Universiteit Maastricht. / Met lit. opg. - Met samenvatting in het Nederlands.

After suffering heavy losses at the hands of the warriors of Zulu King Dingane (c. 1795-1840), a Voortrekker commando advanced against the former in December 1838. As it was evident that they would be faced by superior enemy numbers, the Voortrekkers were induced by A.W.J. Pretorius (1798-1853) and S.A. Cilliers (1801-1871), to enter into a covenant with God. Its exact words were not recorded, but eyewitnesses' later versions concurred that God had been requested to assist them in vanquishing the Zulu Army. Should they be victorious, the Voortrekkers undertook that they and their descendants would annually dedicate the day of the conquest to the glory of God alone. The Battle of Blood River took place on 16 December 1838, marking the Voortrekkers' desired victory. On the same day, the Covenant was fulfilled for the first time on the very battlefield. Thus the oldest Afrikaner national celebration, later known as Dingaan's Day or Day of the Covenant, came about. Initially the Covenant was commemorated in a small way by families and religious associates. In 1864 the General Synod of the Afrikaners' Natal Churches agreed that 16 December would henceforth be celebrated as ecclesiastical day of thanksgiving by all its congregations. This was the result of the efforts of two Dutch clergymen and supporters of Revival Theology, namely Revs. D.P.M. Huet (1827-1895) and F.L. Cachet (1835-1899). In 1865 the Executive Counsel of the South African Republic declared 16 December to be a public holiday in this Boer Republic. During the Anglo Transvaal (1880-1881) and Anglo Boer Wars (1899-1902), the commemoration of the Covenant inspired Afrikaners. The celebrations acquired a deeply nationalistic significance. A growing number of Covenant ceremonies were annually being organised throughout the Boer Republics and northern Natal. In 1894 the Government of the Free State also declared 16 December to be a public holiday. English-speaking compatriots and members of other races in general attached little importance to the Covenant, normally utilising 16 December for recreational purposes only. In 1910 an act was passed by Parliament according to which 16 December would be celebrated as a national holiday (Dingaan's Day) throughout the Union of South Africa, as of 1911. The celebration of the Covenant of 1838 has had an inestimable influence on Afrikaner and even South African cultural history. It played an important religious, national, social and educational role in everyday life, stimulating and shaping the Afrikaner's creativity, historical consciousness, ethics and intercultural relations. In 1952 the name of the day was changed from Dingaan's Day to Day of the Covenant. After 1994, in post-apartheid South Africa, it has still remained a public holiday, even though it is now known as Day of Reconciliation. The fact that it has been retained as a holiday is regarded as a significant gesture of goodwill towards Afrikaners. A study of South Africans' diverse attitudes towards the celebration of the Covenant of 1838, starting with the earliest commemorations between 1838 and 1910, may contribute towards mutual understanding and harmony. / Dissertation (MHCS)--University of Pretoria, 2004. / Historical and Heritage Studies / unrestricted

No description available.

Based on the author's Thesis (doctoral)--University of Oxford. / Includes bibliographical references and index.

No description available.

À partir de l'observation de pratiques artistiques relationnelles, ce mémoire vise à la fois à identifier la relation comme un enjeu majeur de l'art actuel et à la définir comme concept opératoire pour l'analyse critique de ces pratiques en fonction de leur spécificité. Cette recherche est fondée sur la réévaluation de deux cadres conceptuels: d'une part, la théorie esthétique développée par Nicolas Bourriaud dans l'Esthétique relationnelle (1998) et, d'autre part, la problématique de l'in situ, qui est considérée comme un ancrage historique pour l'analyse des pratiques relationnelles. Proposant de revenir au fondement de la relation pour la définir comme espace de négociation entre soi et l'autre, cette étude permet de considérer les pratiques relationnelles en dehors de l'emprise conceptuelle exercée par l'Esthétique relationnelle de Nicolas Bourriaud. Elle propose également, à partir d'une conception anthropologique de la relation, de dépasser une analyse des pratiques relationnelles qui a souvent été effectuée en fonction de la notion d'in situ en histoire de l'art, en insistant sur la nécessité de considérer qu'un glissement s'opère, du site à la relation, quant à l'ancrage de l'art dans le champ social. La contribution de ce mémoire est de pointer la nature conflictuelle de la relation comme fondement d'une analyse critique des pratiques relationnelles, à partir d'exemples qui explorent la relation comme expérience vécue, en fonction de son altérité et de son effectivité. Cette recherche s'appuie sur cinq études de cas, afin de montrer qu'envisager la relation comme espace de négociation fait émerger de nouvelles questions, directement liées à la rencontre entre des individus. Par l'exploration de la relation à partir d'une reconnaissance de sa dimension hétérogène et conflictuelle, les pratiques de Devora Neumark, de Raphaëlle de Groot, de David Dupont, d'ATSA et d'Artur Zmijewski, sont étudiées dans la mesure où elles mettent en oeuvre des situations d'altérité qui contribuent à redéfinir la notion d'identité et à repenser l'idée de communauté en plus d'être investies d'une dimension intrinsèquement politique. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Art relationnel, Art d'intervention, In situ, Artur Zmijewski, Action terroriste socialement acceptable (ATSA), David Dupont, Devora Neumark, Raphaëlle de Groot.

The aim of this study is to determine the value of the Big 5 from a visitor’s perspective. This study will focus on determining the stated preference or contingent value (CV) of the Big 5 through a survey of tourists’, visiting the Kruger National Park, willingness to pay (WTP) for the conservation. The CV method is based on the principle of stated preferences, since participants are asked to state how much they are willing to pay for specific goods or services. Literature indicates that there is a relationship between education, income, professional standing, marital status, age, characteristics of visit, number of children and nationality and a tourist’s willingness to pay. By estimating the effect these variables have on a tourist’s willingness to pay will assist parks and private game reserves in future decisions concerning the conservation of wildlife. Additionally this information is also invaluable for marketing as well as pricing purposes since it gives a specific monetary value. The study found that visitors to the Kruger National Park (KNP) assigned a significant amount (34.64%) of total average spending to experience the Big 5. The value per species also differed. The main determinants of visitors’ willingness-to-pay for simply viewing the Big 5 include age, the marital status and the role of the Big 5 during decision to visit the KNP. Noticeable differences between international literature and this research are the determinants like education, income, age and country of residence. / Thesis (MCom (Economics))--North-West University, Potchefstroom Campus, 2013.