The purpose of this study is to evaluate the effects and importance of different cross–section representations and energy group structures for steady state and transient analysis. More energy groups may be more accurate, but the calculation becomes much more expensive, hence a balance between accuracy and calculation effort must be find. This study is aimed at comparing a multi–group energy dynamics code, MGT (Multi–group TINTE) with TINTE (TIme Dependent Neutronics and TEmperatures). TINTE’s original version (version 204d) only distinguishes between two energy group structures, namely thermal and fast region with a polynomial reconstruction of cross–sections pre–calculated as a function of different conditions and temperatures. MGT is a TINTE derivative that has been developed, allowing a variable number of broad energy groups. The MGT code will be benchmarked against the OECD PBMR coupled neutronics/thermal hydraulics transient benchmark: the PBMR–400 core design. This comparative study reveals the variations in the results when using two different methods for cross–section generation and multi–group energy structure. Inputs and results received from PBMR (Pty) Ltd. were used to do the comparison. A comparison was done between two–group TINTE and the equivalent two energy groups in MGT as well as between 4, 6 and 8 energy groups in MGT with the different cross–section generation methods, namely inline spectrum– and tabulated cross–section method. The characteristics that are compared are reactor power, moderation– and maximum fuel temperatures and k–effective (only steady state case). This study revealed that a balance between accuracy and calculation effort can be met by using a 4–group energy group structure. A larger part of the available increase in accuracy can be obtained with 4–groups, at the cost of only a small increase in CPU time. The changing of the group structures in the steady state case from 2 to 8 groups has a greater influence on the variation in the results than the cross–section generation method that was used to obtain the results. In the case of a transient calculation, the cross–section generation method has a greater influence on the variation in the results than on the steady state case and has a similar effect to the number of energy groups. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

The purpose of this study is to evaluate the effects and importance of different cross–section representations and energy group structures for steady state and transient analysis. More energy groups may be more accurate, but the calculation becomes much more expensive, hence a balance between accuracy and calculation effort must be find. This study is aimed at comparing a multi–group energy dynamics code, MGT (Multi–group TINTE) with TINTE (TIme Dependent Neutronics and TEmperatures). TINTE’s original version (version 204d) only distinguishes between two energy group structures, namely thermal and fast region with a polynomial reconstruction of cross–sections pre–calculated as a function of different conditions and temperatures. MGT is a TINTE derivative that has been developed, allowing a variable number of broad energy groups. The MGT code will be benchmarked against the OECD PBMR coupled neutronics/thermal hydraulics transient benchmark: the PBMR–400 core design. This comparative study reveals the variations in the results when using two different methods for cross–section generation and multi–group energy structure. Inputs and results received from PBMR (Pty) Ltd. were used to do the comparison. A comparison was done between two–group TINTE and the equivalent two energy groups in MGT as well as between 4, 6 and 8 energy groups in MGT with the different cross–section generation methods, namely inline spectrum– and tabulated cross–section method. The characteristics that are compared are reactor power, moderation– and maximum fuel temperatures and k–effective (only steady state case). This study revealed that a balance between accuracy and calculation effort can be met by using a 4–group energy group structure. A larger part of the available increase in accuracy can be obtained with 4–groups, at the cost of only a small increase in CPU time. The changing of the group structures in the steady state case from 2 to 8 groups has a greater influence on the variation in the results than the cross–section generation method that was used to obtain the results. In the case of a transient calculation, the cross–section generation method has a greater influence on the variation in the results than on the steady state case and has a similar effect to the number of energy groups. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2011.

Researchers often benefit from gathering data from participants without any regard for the participants’ needs. In other words, the data gathering process is often not reciprocal in nature, as the researcher is often the only beneficiary. The Mmogo-method® is proposed as a data gathering method that also benefits participants. Three distinct phases are distinguished in applying the Mmogo-method®. During the first phase the researcher gains entry into the research context an ethically sensitive manner. Participants are asked to arrange themselves into groups (not more than eight to ten people participate in a session). They are duly informed of the nature of the research topic and what it entails; namely that they will be requested to make visual representations of specific experiences by using unstructured materials such as malleable clay, dried straw and different colours and sizes of beads. The participants are also informed that only partial confidentially of the information that they share can be ensured because of the group context in which the data are obtained. The participants are, however, asked to treat all shared information as confidential. The Mmogo-method® is usually applied in a group context to allows the dynamics of group processes to inform and enrich the research context. The second phase is introduced by an open-ended prompt that requests the participants to use the unstructured material to visually represent their experiences. In this study, mental health workers were asked to visually represent their coping strategies. On completion of the visual representations, the third phase is initiated. A team of researchers (including counsellors and if needed interpreters) engage in a process of individual and group discussions. Individual participants explain the meaning of each object and action(s); the relationship between the objects and the relevance of the objects in relation to the research prompt; and finally the symbolic value of the objects. After the individual participant has explained the visual representation, the rest of the group is asked to complement the individual participant’s explanation with their perceptions or experiences. Little or no literature is available on how participants experience a visual research method (Mmogo-method®). In this study, the researcher used the Mmogo-method® to elicit mental health workers' coping strategies from a positive participatory perspective and to describe the participants’ experiences of participating in the Mmogo-method® as a data gathering method to elicit the coping strategies of the mental health workers. Mental health workers (telephone counsellors, trauma counsellors, social workers, social auxiliary workers and other professionals) are required to engage with the challenges their clients face and to assist them by means of psycho-social interventions on a daily basis. The mental health workers from Childline who work with children deal with clients who undergo various traumatic experiences, such as severe violence and neglect; physical, emotional and sexual abuse; abduction, homelessness and prostitution. The coping of these mental health workers is important because violence against children is one of the most prominent manifestations of violence in South Africa. More than half of the reported cases against children during the financial year of 2010 were sexual offences. There is a significant shortage of mental health workers to address children’s psycho-social needs in South Africa. Due to the traumatic nature of the mental health workers’ work, they often experience burnout, vicarious traumatisation and compassion fatigue. The management of Childline requested an investigation into the coping strategies of their mental health workers. Childline is a non-governmental organisation that provides a 24-hour toll-free helpline, as well as online counselling services to children and their families. Permission to conduct the research was obtained from the North-West University’s ethical committee, as well as from the heads of departments of the relevant mental health workers. The mental health workers from Childline were invited to participate in the research. The Mmogo-method® was specifically applied from a positive participatory approach and allowed for the positively focused subjective contributions of research participants to the research process. Qualitative research with a case study design was applied. Textual and visual data were gathered and analysed in two phases. First, by the researcher and participants during the research process, and second, by using thematic analysis for the textual data, and visual data analysis of the visual data. Findings revealed themes related to the coping strategies of the mental health workers on an intrapersonal and an interpersonal level, which is not the focus of this study. In terms of the application of the Mmogo-method®, the mental health workers experienced the research context of unconditional positive regard and acceptance as a therapeutic intervention. The applied method supported the mental health workers in making a positive appraisal of their coping strategies and environment. They gained insight into their level of appreciation for their current occupation and interpersonal relationships. They also became more aware of their coping strategies in these contexts. The positive and supportive research context, the material used in applying the method and the group processes experienced were identified as factors contributing to the therapeutic experience of the process. These aspects lead the mental health workers to awareness, maintaining their focus and allowing for shared experience. The findings highlighted that research is not only a matter of obtaining data from participants, but should also allow participants to benefit from the process. Further research is recommended to explore other methodologies that could serve a dual purpose of addressing the needs of both the researcher and participant. / MSc (Clinical Psychology), North-West University, Potchefstroom Campus, 2014

Researchers often benefit from gathering data from participants without any regard for the participants’ needs. In other words, the data gathering process is often not reciprocal in nature, as the researcher is often the only beneficiary. The Mmogo-method® is proposed as a data gathering method that also benefits participants. Three distinct phases are distinguished in applying the Mmogo-method®. During the first phase the researcher gains entry into the research context an ethically sensitive manner. Participants are asked to arrange themselves into groups (not more than eight to ten people participate in a session). They are duly informed of the nature of the research topic and what it entails; namely that they will be requested to make visual representations of specific experiences by using unstructured materials such as malleable clay, dried straw and different colours and sizes of beads. The participants are also informed that only partial confidentially of the information that they share can be ensured because of the group context in which the data are obtained. The participants are, however, asked to treat all shared information as confidential. The Mmogo-method® is usually applied in a group context to allows the dynamics of group processes to inform and enrich the research context. The second phase is introduced by an open-ended prompt that requests the participants to use the unstructured material to visually represent their experiences. In this study, mental health workers were asked to visually represent their coping strategies. On completion of the visual representations, the third phase is initiated. A team of researchers (including counsellors and if needed interpreters) engage in a process of individual and group discussions. Individual participants explain the meaning of each object and action(s); the relationship between the objects and the relevance of the objects in relation to the research prompt; and finally the symbolic value of the objects. After the individual participant has explained the visual representation, the rest of the group is asked to complement the individual participant’s explanation with their perceptions or experiences. Little or no literature is available on how participants experience a visual research method (Mmogo-method®). In this study, the researcher used the Mmogo-method® to elicit mental health workers' coping strategies from a positive participatory perspective and to describe the participants’ experiences of participating in the Mmogo-method® as a data gathering method to elicit the coping strategies of the mental health workers. Mental health workers (telephone counsellors, trauma counsellors, social workers, social auxiliary workers and other professionals) are required to engage with the challenges their clients face and to assist them by means of psycho-social interventions on a daily basis. The mental health workers from Childline who work with children deal with clients who undergo various traumatic experiences, such as severe violence and neglect; physical, emotional and sexual abuse; abduction, homelessness and prostitution. The coping of these mental health workers is important because violence against children is one of the most prominent manifestations of violence in South Africa. More than half of the reported cases against children during the financial year of 2010 were sexual offences. There is a significant shortage of mental health workers to address children’s psycho-social needs in South Africa. Due to the traumatic nature of the mental health workers’ work, they often experience burnout, vicarious traumatisation and compassion fatigue. The management of Childline requested an investigation into the coping strategies of their mental health workers. Childline is a non-governmental organisation that provides a 24-hour toll-free helpline, as well as online counselling services to children and their families. Permission to conduct the research was obtained from the North-West University’s ethical committee, as well as from the heads of departments of the relevant mental health workers. The mental health workers from Childline were invited to participate in the research. The Mmogo-method® was specifically applied from a positive participatory approach and allowed for the positively focused subjective contributions of research participants to the research process. Qualitative research with a case study design was applied. Textual and visual data were gathered and analysed in two phases. First, by the researcher and participants during the research process, and second, by using thematic analysis for the textual data, and visual data analysis of the visual data. Findings revealed themes related to the coping strategies of the mental health workers on an intrapersonal and an interpersonal level, which is not the focus of this study. In terms of the application of the Mmogo-method®, the mental health workers experienced the research context of unconditional positive regard and acceptance as a therapeutic intervention. The applied method supported the mental health workers in making a positive appraisal of their coping strategies and environment. They gained insight into their level of appreciation for their current occupation and interpersonal relationships. They also became more aware of their coping strategies in these contexts. The positive and supportive research context, the material used in applying the method and the group processes experienced were identified as factors contributing to the therapeutic experience of the process. These aspects lead the mental health workers to awareness, maintaining their focus and allowing for shared experience. The findings highlighted that research is not only a matter of obtaining data from participants, but should also allow participants to benefit from the process. Further research is recommended to explore other methodologies that could serve a dual purpose of addressing the needs of both the researcher and participant. / MSc (Clinical Psychology), North-West University, Potchefstroom Campus, 2014

Emotions play an important role in the lives of human beings and, without doubt, emotions form an inherent part of the workplace (Ashkanasy, Zerbe, Charmine & Hartel, 2002). Studying emotions within the South African context is relevant for applied psychology. South Africa comprises eleven official languages which are representative of the general population in the working environment. As a result, knowledge and understanding of emotions is useful since it forms part of social interaction at work. The understanding of one’s own as well as others’ emotions and the ability to deal with those emotions contribute to the productivity and cooperation among employees in the working environment. The objective of this research was to determine the conceptualization of emotion and culture according to the literature study, to determine the different and representative emotion words within the isiNdebele speaking group, to determine the relevant and representative prototypical emotion words that have been encoded in this group, to determine the cognitive emotion structure of this group and lastly, to determine the interrater reliability of the raters and reliability of the measurement instrument as well as the dimensions of emotion structure in the isiNdebele speaking group in Mpumalanga province. A survey design with convenience sample was used to achieve the research objectives in a series of three independent studies. The study population of the first phase (N=126) consisted of a convenience sample of the isiNdebele speaking group who have metric and are working in the South African Police Service in Mpumalanga province. The study population of the second phase consisted of a convenience sample of Language Experts with degrees and diplomas (N=51) in isiNdebele language from different occupations. The study population of the third phase consisted of a convenience sample of the experts (educators) in isiNdebele speaking group (N=183) from different schools in the former KwaNdebele homeland in Mpumalanga province. In this study, free listing, prototypicality and similarity rating questionnaires were administered by a qualified psychometrist. Statistical methods and procedures (Multidimensional Scaling and Descriptive Statistics) were used and Cronbach alpha coefficients were determined to analyse the results of the isiNdebele speaking group. The results of the free listing task indicated the words with the highest frequency as cry (lila), happy (thaba), laugh (hleka), angry (kwata), disappointed (swaba), confused (hlangahlangana), depressed (gandeleleka), pain (ubuhlungu), tired (dinwa), and abused (hlukumezeka). The results of this phase also indicated the basic emotion concepts of happiness (thaba) and angry (kwata) as the only emotion terms which mostly came to mind to the isiNdebele speaking group. The results of the prototypicality rating task indicated the emotion terms ranked as the ten (10) most prototypical emotion terms for the isiNdebele speaking group (N=51) were “ukuthaba khulu” (exhilaration), “itukuthelo/ ukukwata” (anger), “ithabo elikhulu” (euphoria), “ukuthaba” (cheerfulness), “ithabo” (happiness), “ukudana” (dejection), “ukutlhuwa/ ukudana”(glumness), “ukuthaba” (joviality), “ukulila/isililo” (cry), “ithabo” (joy). A multi– dimensional scaling was conducted to determine the cognitive structure of emotion concepts whereby a two– dimensional structure (evaluation and power) was identified to the isiNdebele speaking group. Recommendations for future research to the organisation as well as recommendations for future research were suggested. / http://hdl.handle.net/10394/7044 / http://hdl.handle.net/10394/7044 / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2012.

Emotions play an important role in the lives of human beings and, without doubt, emotions form an inherent part of the workplace (Ashkanasy, Zerbe, Charmine & Hartel, 2002). Studying emotions within the South African context is relevant for applied psychology. South Africa comprises eleven official languages which are representative of the general population in the working environment. As a result, knowledge and understanding of emotions is useful since it forms part of social interaction at work. The understanding of one’s own as well as others’ emotions and the ability to deal with those emotions contribute to the productivity and cooperation among employees in the working environment. The objective of this research was to determine the conceptualization of emotion and culture according to the literature study, to determine the different and representative emotion words within the isiNdebele speaking group, to determine the relevant and representative prototypical emotion words that have been encoded in this group, to determine the cognitive emotion structure of this group and lastly, to determine the interrater reliability of the raters and reliability of the measurement instrument as well as the dimensions of emotion structure in the isiNdebele speaking group in Mpumalanga province. A survey design with convenience sample was used to achieve the research objectives in a series of three independent studies. The study population of the first phase (N=126) consisted of a convenience sample of the isiNdebele speaking group who have metric and are working in the South African Police Service in Mpumalanga province. The study population of the second phase consisted of a convenience sample of Language Experts with degrees and diplomas (N=51) in isiNdebele language from different occupations. The study population of the third phase consisted of a convenience sample of the experts (educators) in isiNdebele speaking group (N=183) from different schools in the former KwaNdebele homeland in Mpumalanga province. In this study, free listing, prototypicality and similarity rating questionnaires were administered by a qualified psychometrist. Statistical methods and procedures (Multidimensional Scaling and Descriptive Statistics) were used and Cronbach alpha coefficients were determined to analyse the results of the isiNdebele speaking group. The results of the free listing task indicated the words with the highest frequency as cry (lila), happy (thaba), laugh (hleka), angry (kwata), disappointed (swaba), confused (hlangahlangana), depressed (gandeleleka), pain (ubuhlungu), tired (dinwa), and abused (hlukumezeka). The results of this phase also indicated the basic emotion concepts of happiness (thaba) and angry (kwata) as the only emotion terms which mostly came to mind to the isiNdebele speaking group. The results of the prototypicality rating task indicated the emotion terms ranked as the ten (10) most prototypical emotion terms for the isiNdebele speaking group (N=51) were “ukuthaba khulu” (exhilaration), “itukuthelo/ ukukwata” (anger), “ithabo elikhulu” (euphoria), “ukuthaba” (cheerfulness), “ithabo” (happiness), “ukudana” (dejection), “ukutlhuwa/ ukudana”(glumness), “ukuthaba” (joviality), “ukulila/isililo” (cry), “ithabo” (joy). A multi– dimensional scaling was conducted to determine the cognitive structure of emotion concepts whereby a two– dimensional structure (evaluation and power) was identified to the isiNdebele speaking group. Recommendations for future research to the organisation as well as recommendations for future research were suggested. / http://hdl.handle.net/10394/7044 / http://hdl.handle.net/10394/7044 / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2012.

The aim of this study was to explore, from a group dynamics perspective, the adult learners' experiences in a learnership program structured to include employed and unemployed learners. A secondary aim was to develop guidelines for practitioners regarding the implementation of learnerships that are structured to include employed and unemployed learners, taking into account the group dynamics at play. The case study played out within a pharmaceutical distribution company within South Africa. A qualitative, constructivist grounded theory method was used to analyse the data that were collected by means of questionnaires and focus groups. The data collected were transcribed and uploaded into Atlas.ti, which is a visual qualitative data analysis and theorybuilding software program that contributes to the management of qualitative data. It was used to complete a rigorous inductive-abductive analysis. The final code list contained 277 codes linked to 29 code families which in turn were linked to 8 super families. These super families were described and the experiences of the learners were then interpreted by means of a number of group dynamics theories and adult learning theories that were discussed in the preceding literature chapters. In the case study the exploration of the learners' experience indicated that certain group dynamics were not taken into consideration and this led to an emotionally burdened experience. If one considers the adult learning theory, these experiences could influence the learning effectiveness. The implementation of a learnership program taking the group dynamics into consideration prior to implementation thereof, could contribute towards a more successful learnership. Guidelines were given based on the conclusions of the research for example: <ul> <li> Ensure that all the relevant parties including management, supervisors, employed learners, unemployed learners, employed staff, SETA etc. strive towards the same goal right from the start.</li> <li> Integrate the employed and unemployed learners' rights from the start so that the unemployed learners are accepted as part of the system.</li> <li> Make it very clear to the employed staff that the unemployed learners are not a threat to their employment within the company as the unemployed learners have not been given a commitment that they will be employed after the learnership.</li> <li> Make sure that the training facilitators are well trained and equipped to deal with the group dynamics that can develop in the classroom environment so that they can contribute to the containment of emotions and to alert the company of the events.</li> <li> Ensure that change agents are available to monitor and manage these group dynamics.</li> <li> Explain the differences and similarities that might exist between the groups and assist the groups to realise their mutually dependent relationship.</li> </ul> The guidelines obtained from this study can be used to stimulate the thinking process when planning and managing the implementation of a learnership program in order to be aware of consequential implications that group dynamics can have on the successful implementation of such a learning program. The conclusions and guidelines will be useful to human resources practitioners, training providers and line managers that are planning to implement similar learnership programs. AFRIKAANS: Die doel van die studie was om volwasse leerders betrokke by ‘n leerlingskapprogram wat gestruktureer is om bestaande werkers en werklose leerders in te sluit, se ervaring vanuit ‘n groepdinamika perspektief te ondersoek. ‘n Sekondêre doelwit was om riglyne te ontwikkel vir mense in die praktyk met betrekking tot die implementering van ‘n leerlingskapprogram vir volwasse leerders bestaande uit werklose leerders en leerders in diens van ‘n bepaalde maatskappy, met in agneming van die groepdinamika daarby betrokke. Die gevallestudie het plaasgevind binne ‘n farmaseutiese verspreidingsmaatskappy in Suid-Afrika. ‘n Kwalitatiewe, konstruktiwistiese metode is gebruik om die data te analiseer wat deur vraelyste en fokusgroepe versamel is. Die data is getranskribeer en ingelees in Atlas.ti, wat ‘n visuele kwalitatiewe data-analise en teoretiese gebaseerde sagtewareprogram is wat bydra tot die bestuur van kwalitatiewe data. Hierdie program is gebruik om ‘n indringende gebaseerde teorieanalise te doen. Die finale kodelys bestaan uit 277 kodes gekoppel aan 29 kode families wat weer op hul beurt gekoppel is aan 8 hooffamilies. Hierdie hooffamilies is beskryf en die navorsingsgebeure van die studie is by wyse van groepdinamikateorieë en volwasseleerteorieë (wat in die vorige literatuur hoofstukke van die studie bespreek is) geïnterpreteer. In hierdie gevallestudie het die interpretasie van die ervarings van die leerders wat ondersoek is, daarop gewys dat sekere groepdinamika nie oorweeg is nie en dat dit gelei het tot ‘n emosionele stresvolle ervaring. Volwasseleerteorie dui aan dat hierdie ervarings die leereffektiwiteit kon beïnvloed het. Die implementering van ‘n leerlingskap program waar die groepdinamika in ag geneem word voor die implementering kan bydra tot die sukses van soortgelyke leerlingskapprogramme. Die riglyne wat deur hierdie studie verkry is, kan gebruik word om die denkproses te stimuleer tydens die beplanning en die bestuur van die implementering van soortgelyke leerlingskapprogramme. Dit sal veroorsaak dat die betrokke persone bewus is van die invloed van groepdinamika kan hê met betrekking tot die suksesvolle implementering van ‘n leerlingskap program. Die navorsingsinligting wat ingewin is, sal bruikbaar wees vir menslike hulpbronne praktisyne, opleidingsvoorsieners en lynbestuurders wat beplan om ‘n soortgelyke leerlingskapprogram te implementeer. Copyright 2010, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Ward, ME 2010, A group dynamics perspective of the experiences of adult learners taking part in a learnership program, MCom dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02152012-114353 / > C12/4/124/gm / Dissertation (MCom)--University of Pretoria, 2010. / Human Resource Management / unrestricted

The world energy supply and demand, together with limited available resources have resulted in the need to develop alternative energy sources to ensure sustainable and expanding economies. Hydrogen is being considered a viable option with particular application to fuel cells. The Hybrid Sulphur cycle has been identified as a process to produce clean hydrogen (carbon free process) and can have economic benefits when coupled to nuclear reactors (High Temperature Gas Reactor) or solar heaters for the supply of the required process energy. The sulphur trioxide decomposition reactor producing sulphur dioxide for the electrolytic cells in a closed loop system has been examined, but it is clear that development with respect to a more durable active catalyst in a reactor operating under severe conditions needs to be investigated. A suitable sulphur trioxide reactor needs to operate at a high temperature with efficient heating in view of the endothermic reaction, and has to consist of special materials of construction to handle the very corrosive reactants and products. This investigation was undertaken to address (1) the synthesis, characterisation, reactivity and stability of a suitable catalyst (2), determination the reaction rate of the chosen catalyst with a suitable micro reactor (3) construction and evaluation of a packed bed reactor for the required reaction, and (4) the development and validation of a reactor model using computational fluid dynamics with associated chemical reactions. A supported catalyst consisting of 0.5 wt% platinum and 0.5 wt% palladium on rutile (TiO2, titania) was prepared by the sintering of an anatase/rutile supported catalyst with the same noble metal composition, synthesized according to an incipient impregnation procedure using cylindrical porous pellets (±1.7 mm diameter and ±5 mm long). Characterization involving: surface area, porosity, metal composition, - dispersion, - particle size, support phase and sulphur content was carried out and it was found from reactivity determinations that the sintered catalyst, which was very different from the synthesized catalyst, had an acceptable activity and stability which was suitable for further evaluation. A micro pellet reactor was constructed and operated and consisted of a small number of pellets (five) placed apart from each other in a two-stage quartz reactor with sulphur trioxide generated from sulphuric acid in the first stage and the conversion of sulphur trioxide in the second stage, respectively. Attention was only confined to the second stage involving the conversion of sulphur trioxide with the supported catalyst. The overall reaction kinetics of the pellets involving momentum, heat and mass transfer and chemical reaction was evaluated and validated with constants obtained from literature and with an unknown reaction rate equation for which constants were obtained by regression. As result of the complexity of the flow, mass and heat transfer fields in the micro pellet reactor it was necessary to use a CFD model with chemical reactions which was accomplished with a commercial code COMSOL MultiPhysics® 4.3b. A reversible reaction rate equation was used and a least squares regression procedure was used to evaluate the activation energy and pre-exponential factor. The activation energy obtained for the first order forward reaction was higher than values obtained from literature for a first order reaction rate (irreversible reaction) for the platinum group metals on titania catalysts. Detailed analyses of the velocity, temperature and concentration profile revealed the importance of using a complex model for determination of the reaction parameters. A fixed bed reactor system consisting of a sulphuric acid vaporizer, a single reactor tube (1 m length, 25 mm OD) heated with a surrounding electrical furnace followed, by a series of condensers for the analysis of the products was constructed and operated. Three process variables were investigated, which included the inlet temperature, the weight hourly velocity and the residence time in order to assess the performance of the reactor and generate results for developing a model. The results obtained included the wall and reactor centreline temperature profiles together with average conversion. As a result of the complexity of the chemistry and the phases present containing the products from the reactor a detailed calculation was done using vapour/liquid equilibrium with the accompanying mass balance (Aspen-Plus®) to determine the distribution of sulphur trioxide, sulphur dioxide, oxygen and steam. A mass balance was successfully completed with analyses including SO2 with a GC, O2 with a paramagnetic cell analyser, acid/base titrations with sodium hydroxide, SO2 titrations with iodine and measurement of condensables (mass and volume). The results obtained showed that a steady state (constant conversion) was obtained after approximately six hours and that it was possible to obtain sulphur trioxide conversion approaching equilibrium conditions for bed lengths of 100 mm with very low weight hourly space velocities. A heterogeneous 2D model consisting of the relevant continuity, momentum, heat transfer and mass transfer and the reaction rate equation determined in this investigation was developed and solved with the use of the commercial code COMSOL MultiPhysics® 4.3b with an appropriate mesh structure. The geometry of the packed bed (geometry) was accomplished by generating a randomly packed bed with a commercial package DigiPac™. The model predicted results that agreed with experimental results with conversions up to 56%, obtained over the following ranges: weight hourly space velocity equal to 15 h-1, temperatures between 903 K and 1053 K and residence times between 0.1 and 0.07 seconds. The post-processing results were most useful for assessing the effect of the controlling mechanisms and associated parameters. / PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2014

The world energy supply and demand, together with limited available resources have resulted in the need to develop alternative energy sources to ensure sustainable and expanding economies. Hydrogen is being considered a viable option with particular application to fuel cells. The Hybrid Sulphur cycle has been identified as a process to produce clean hydrogen (carbon free process) and can have economic benefits when coupled to nuclear reactors (High Temperature Gas Reactor) or solar heaters for the supply of the required process energy. The sulphur trioxide decomposition reactor producing sulphur dioxide for the electrolytic cells in a closed loop system has been examined, but it is clear that development with respect to a more durable active catalyst in a reactor operating under severe conditions needs to be investigated. A suitable sulphur trioxide reactor needs to operate at a high temperature with efficient heating in view of the endothermic reaction, and has to consist of special materials of construction to handle the very corrosive reactants and products. This investigation was undertaken to address (1) the synthesis, characterisation, reactivity and stability of a suitable catalyst (2), determination the reaction rate of the chosen catalyst with a suitable micro reactor (3) construction and evaluation of a packed bed reactor for the required reaction, and (4) the development and validation of a reactor model using computational fluid dynamics with associated chemical reactions. A supported catalyst consisting of 0.5 wt% platinum and 0.5 wt% palladium on rutile (TiO2, titania) was prepared by the sintering of an anatase/rutile supported catalyst with the same noble metal composition, synthesized according to an incipient impregnation procedure using cylindrical porous pellets (±1.7 mm diameter and ±5 mm long). Characterization involving: surface area, porosity, metal composition, - dispersion, - particle size, support phase and sulphur content was carried out and it was found from reactivity determinations that the sintered catalyst, which was very different from the synthesized catalyst, had an acceptable activity and stability which was suitable for further evaluation. A micro pellet reactor was constructed and operated and consisted of a small number of pellets (five) placed apart from each other in a two-stage quartz reactor with sulphur trioxide generated from sulphuric acid in the first stage and the conversion of sulphur trioxide in the second stage, respectively. Attention was only confined to the second stage involving the conversion of sulphur trioxide with the supported catalyst. The overall reaction kinetics of the pellets involving momentum, heat and mass transfer and chemical reaction was evaluated and validated with constants obtained from literature and with an unknown reaction rate equation for which constants were obtained by regression. As result of the complexity of the flow, mass and heat transfer fields in the micro pellet reactor it was necessary to use a CFD model with chemical reactions which was accomplished with a commercial code COMSOL MultiPhysics® 4.3b. A reversible reaction rate equation was used and a least squares regression procedure was used to evaluate the activation energy and pre-exponential factor. The activation energy obtained for the first order forward reaction was higher than values obtained from literature for a first order reaction rate (irreversible reaction) for the platinum group metals on titania catalysts. Detailed analyses of the velocity, temperature and concentration profile revealed the importance of using a complex model for determination of the reaction parameters. A fixed bed reactor system consisting of a sulphuric acid vaporizer, a single reactor tube (1 m length, 25 mm OD) heated with a surrounding electrical furnace followed, by a series of condensers for the analysis of the products was constructed and operated. Three process variables were investigated, which included the inlet temperature, the weight hourly velocity and the residence time in order to assess the performance of the reactor and generate results for developing a model. The results obtained included the wall and reactor centreline temperature profiles together with average conversion. As a result of the complexity of the chemistry and the phases present containing the products from the reactor a detailed calculation was done using vapour/liquid equilibrium with the accompanying mass balance (Aspen-Plus®) to determine the distribution of sulphur trioxide, sulphur dioxide, oxygen and steam. A mass balance was successfully completed with analyses including SO2 with a GC, O2 with a paramagnetic cell analyser, acid/base titrations with sodium hydroxide, SO2 titrations with iodine and measurement of condensables (mass and volume). The results obtained showed that a steady state (constant conversion) was obtained after approximately six hours and that it was possible to obtain sulphur trioxide conversion approaching equilibrium conditions for bed lengths of 100 mm with very low weight hourly space velocities. A heterogeneous 2D model consisting of the relevant continuity, momentum, heat transfer and mass transfer and the reaction rate equation determined in this investigation was developed and solved with the use of the commercial code COMSOL MultiPhysics® 4.3b with an appropriate mesh structure. The geometry of the packed bed (geometry) was accomplished by generating a randomly packed bed with a commercial package DigiPac™. The model predicted results that agreed with experimental results with conversions up to 56%, obtained over the following ranges: weight hourly space velocity equal to 15 h-1, temperatures between 903 K and 1053 K and residence times between 0.1 and 0.07 seconds. The post-processing results were most useful for assessing the effect of the controlling mechanisms and associated parameters. / PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2014

This thesis is an account of our study of two branches of dynamical systems theory, namely the mean and pointwise ergodic theory. In our work on mean ergodic theorems, we investigate the spectral theory of integrable actions of a locally compact abelian group on a locally convex vector space. We start with an analysis of various spectral subspaces induced by the action of the group. This is applied to analyse the spectral theory of operators on the space generated by measures on the group. We apply these results to derive general Tauberian theorems that apply to arbitrary locally compact abelian groups acting on a large class of locally convex vector spaces which includes Fr echet spaces. We show how these theorems simplify the derivation of Mean Ergodic theorems. Next we turn to the topic of pointwise ergodic theorems. We analyse the Transfer Principle, which is used to generate weak type maximal inequalities for ergodic operators, and extend it to the general case of -compact locally compact Hausdor groups acting measure-preservingly on - nite measure spaces. We show how the techniques developed here generate various weak type maximal inequalities on di erent Banach function spaces, and how the properties of these function spaces in- uence the weak type inequalities that can be obtained. Finally, we demonstrate how the techniques developed imply almost sure pointwise convergence of a wide class of ergodic averages. Our investigations of these two parts of ergodic theory are uni ed by the techniques used - locally convex vector spaces, harmonic analysis, measure theory - and by the strong interaction of the nal results, which are obtained in greater generality than hitherto achieved. / PhD (Mathematics), North-West University, Potchefstroom Campus, 2014