Capturefoundry: a gpu accelerated packet capture analysis tool
- Nottingham, Alastair, Richter, John, Irwin, Barry V W
- Authors: Nottingham, Alastair , Richter, John , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430112 , vital:72666 , https://doi.org/10.1145/2389836.2389877
- Description: Packet captures are used to support a variety of tasks, including network administration, fault diagnosis and security and network related research. Despite their usefulness, processing packet capture files is a slow and tedious process that impedes the analysis of large, long-term captures. This paper discusses the primary components and observed performance of CaptureFoundry, a stand-alone capture analysis support tool designed to quickly map, filter and extract packets from large capture files using a combination of indexing techniques and GPU accelerated packet classification. All results are persistent, and may be used to rapidly extract small pre-filtered captures on demand that may be analysed quickly in existing capture analysis applications. Performance results show that CaptureFoundry is capable of generating multiple indexes and classification results for large captures at hundreds of megabytes per second, with minimal CPU and memory overhead and only minor additional storage space requirements.
- Full Text:
- Date Issued: 2012
- Authors: Nottingham, Alastair , Richter, John , Irwin, Barry V W
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430112 , vital:72666 , https://doi.org/10.1145/2389836.2389877
- Description: Packet captures are used to support a variety of tasks, including network administration, fault diagnosis and security and network related research. Despite their usefulness, processing packet capture files is a slow and tedious process that impedes the analysis of large, long-term captures. This paper discusses the primary components and observed performance of CaptureFoundry, a stand-alone capture analysis support tool designed to quickly map, filter and extract packets from large capture files using a combination of indexing techniques and GPU accelerated packet classification. All results are persistent, and may be used to rapidly extract small pre-filtered captures on demand that may be analysed quickly in existing capture analysis applications. Performance results show that CaptureFoundry is capable of generating multiple indexes and classification results for large captures at hundreds of megabytes per second, with minimal CPU and memory overhead and only minor additional storage space requirements.
- Full Text:
- Date Issued: 2012
Cardiovascular disease and metabolic syndrome in health transition and evidence-based medicine: a perspective from Africa
- Authors: Longo-Mbenza, B
- Date: 2012
- Subjects: Cardiovascular Disease Cardiovascular systems -- Diseases -- Treatment
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/11260/1078 , vital:30578
- Description: The Cardiovascular Disease (CVD) pandemic worldwide presents a true challenge today with a high health burden that is only expected to rise. I address the causes and prevention of CVD, as well as CVD rehabilitation and physiology. As a member of the American Heart Association and European Society of cardiology, I practice under the level of evidence and the strength of recommendation of particular treatment options, as outlined in the tables below.
- Full Text:
- Date Issued: 2012
- Authors: Longo-Mbenza, B
- Date: 2012
- Subjects: Cardiovascular Disease Cardiovascular systems -- Diseases -- Treatment
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/11260/1078 , vital:30578
- Description: The Cardiovascular Disease (CVD) pandemic worldwide presents a true challenge today with a high health burden that is only expected to rise. I address the causes and prevention of CVD, as well as CVD rehabilitation and physiology. As a member of the American Heart Association and European Society of cardiology, I practice under the level of evidence and the strength of recommendation of particular treatment options, as outlined in the tables below.
- Full Text:
- Date Issued: 2012
Carriage of goods by sea - from Hague to Rotterdam: safer waters
- Authors: Metuge, Denning N
- Date: 2012
- Subjects: International trade , Transportation
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10235 , http://hdl.handle.net/10948/d1011561 , International trade , Transportation
- Description: The back bone of international trade has always been international transport. Without good transport networks, the movement of goods and services from one frontier to another would be an uphill task, and would greatly hinder development in international trade. The impact of such poor transport networks would reflect negatively on economies that rely on international trade for the growth of their nations. Nevertheless, perfect transport networks would be useless if the performance of the business of carriage was not regulated by a law developed to meet the standards established by time, and that would regulate the relationship of the parties under contracts of carriage, mainly the carrier, consignor and consignee, so as to ensure certainty and equality in the allocation of risks between the parties thereunder. This research focuses on the carriage of goods by sea. Like most other modes of transport, one of the major issues that arises in the business of carriage of goods by sea is the conflict between the carrier, consignor and consignee, with regards to the allocation of risk in the carriage. Over the years, early rules that were developed to regulate the relationship of the parties under contracts of carriage of goods by sea placed the carrier in a dominant position over the consignor. The carrier issued a standard bill of lading which exempted him from almost all liability for damage or loss of the goods in his care. The consignors and bona fide third parties, not satisfied with the terms of carriage contracts brought a lot of pressure to bear on their governments to enact legislation protecting their interests in the transaction. The United States of America were the first to pass such national law revising the position of the parties under contracts of carriage. In 1893 the United States of America passed the Harter Act. This Act aimed at imposing limits of liability on the carrier to which no derogation could be brought. However, this was a dangerous precedence which was going to hinder international trade rather than improve on it, as different nations developing local legislation on carriage meant conflict of laws. In order to avoid the extensive nationalisation of carriage laws, the international maritime community set to develop rules that would regulate carriage by sea. Over the years convention has succeeded convention such that today four international regimes (The Hague Rules, Hague-Visby Rules, Hamburg Rules and Rotterdam Rules), exist regulating carriage of goods by sea. This research takes an in-depth look at these regimes that were developed to regulate carriage by sea, and the author aims to identify a particular regime that meets the standards of modern day practice of carriage of goods, and advocate for the ratification of this regime, to the exclusion of all others so as to foster uniformity, certainty and equality in the business of carriage of goods by sea.
- Full Text:
- Date Issued: 2012
- Authors: Metuge, Denning N
- Date: 2012
- Subjects: International trade , Transportation
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10235 , http://hdl.handle.net/10948/d1011561 , International trade , Transportation
- Description: The back bone of international trade has always been international transport. Without good transport networks, the movement of goods and services from one frontier to another would be an uphill task, and would greatly hinder development in international trade. The impact of such poor transport networks would reflect negatively on economies that rely on international trade for the growth of their nations. Nevertheless, perfect transport networks would be useless if the performance of the business of carriage was not regulated by a law developed to meet the standards established by time, and that would regulate the relationship of the parties under contracts of carriage, mainly the carrier, consignor and consignee, so as to ensure certainty and equality in the allocation of risks between the parties thereunder. This research focuses on the carriage of goods by sea. Like most other modes of transport, one of the major issues that arises in the business of carriage of goods by sea is the conflict between the carrier, consignor and consignee, with regards to the allocation of risk in the carriage. Over the years, early rules that were developed to regulate the relationship of the parties under contracts of carriage of goods by sea placed the carrier in a dominant position over the consignor. The carrier issued a standard bill of lading which exempted him from almost all liability for damage or loss of the goods in his care. The consignors and bona fide third parties, not satisfied with the terms of carriage contracts brought a lot of pressure to bear on their governments to enact legislation protecting their interests in the transaction. The United States of America were the first to pass such national law revising the position of the parties under contracts of carriage. In 1893 the United States of America passed the Harter Act. This Act aimed at imposing limits of liability on the carrier to which no derogation could be brought. However, this was a dangerous precedence which was going to hinder international trade rather than improve on it, as different nations developing local legislation on carriage meant conflict of laws. In order to avoid the extensive nationalisation of carriage laws, the international maritime community set to develop rules that would regulate carriage by sea. Over the years convention has succeeded convention such that today four international regimes (The Hague Rules, Hague-Visby Rules, Hamburg Rules and Rotterdam Rules), exist regulating carriage of goods by sea. This research takes an in-depth look at these regimes that were developed to regulate carriage by sea, and the author aims to identify a particular regime that meets the standards of modern day practice of carriage of goods, and advocate for the ratification of this regime, to the exclusion of all others so as to foster uniformity, certainty and equality in the business of carriage of goods by sea.
- Full Text:
- Date Issued: 2012
Case study of the educational experiences of four teenage mothers in two high schools in the Buffalo City Metropole
- Authors: Adams, Hermie E
- Date: 2012
- Subjects: Teenage girls -- Sexual behavior -- South Africa -- Eastern Cape , High schools -- South Africa -- Eastern Cape -- Social conditions
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:16168 , http://hdl.handle.net/10353/468 , Teenage girls -- Sexual behavior -- South Africa -- Eastern Cape , High schools -- South Africa -- Eastern Cape -- Social conditions
- Description: Teenage pregnancy is a worldwide phenomenon. World Health Organisation (2009) reports that teenage mothers between the ages of 15-19 years account for 11% of births recorded worldwide. In South Africa it has been estimated that teenagers aged 17-19 account for 93% of all teenage pregnancies. A large proportion of these adolescents return to school after giving birth. Research has shown that there is a great deal of controversy about not only pre-marital sex, but also concerning whether teenage mothers should be allowed back in school at all. The aim of this study was to gain some insights into the lived experiences of teenage mothers in schools with particular reference to how they cope with school work and the responsibilities of motherhood. A case study of four teenage mothers who returned to school after giving birth was carried out. In-depth phenomenological interviewing designed to elicit the voices of the selected adolescents was done. There were five main findings. First, all four teenagers were minors, under the age of 18 when they gave birth. Two of them were even under the statutory age of consent. Second, upon return to school, teenage mothers experienced stigmatisation from peers and teachers and this forced them to continually negotiate their dual identities as mothers and learners. Third, teenage mothers experienced psychological emotions of stress; low self-esteem; shame and depression. Fourth, they also had sociological experiences in the form of material, financial and social support from family and friends. In some cases they experienced rejection from peers and abandonment by boyfriends who had made them pregnant. Some educators discriminated against and ridiculed teenage mothers. Fifth, teenage mothers reorganised their lives after childbirth and established routines that enabled them to cope with the demands of school work and the responsibilities of motherhood. iii The study concludes that, although viewed with scepticism by sections of the community and some educators, and given that some pregnancies are a result of abuse and unequal power relations between men and women in society, the policy of allowing teenage mothers back to school after giving birth gives them another chance to re-focus their lives. It is recommended that the voices of teenage mothers who return to school after childbirth should be taken into account to inform any planning for future policies on teenage pregnancy by schools and the state. It is further recommended that all educators should also be trained to be able to assist the teenage mothers instead of alienating them. There should also be counselling services available for the teenage mothers to enable them to deal with psychological and sociological problems they might encounter. For further research, students from different backgrounds should be the target of similar research. Another area of research should focus on academic performance of teenage mothers who return to school after giving birth. Lastly, there should be research that seeks to link what is taught in the Life Orientation curriculum and voices of teenage mothers.
- Full Text:
- Date Issued: 2012
- Authors: Adams, Hermie E
- Date: 2012
- Subjects: Teenage girls -- Sexual behavior -- South Africa -- Eastern Cape , High schools -- South Africa -- Eastern Cape -- Social conditions
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:16168 , http://hdl.handle.net/10353/468 , Teenage girls -- Sexual behavior -- South Africa -- Eastern Cape , High schools -- South Africa -- Eastern Cape -- Social conditions
- Description: Teenage pregnancy is a worldwide phenomenon. World Health Organisation (2009) reports that teenage mothers between the ages of 15-19 years account for 11% of births recorded worldwide. In South Africa it has been estimated that teenagers aged 17-19 account for 93% of all teenage pregnancies. A large proportion of these adolescents return to school after giving birth. Research has shown that there is a great deal of controversy about not only pre-marital sex, but also concerning whether teenage mothers should be allowed back in school at all. The aim of this study was to gain some insights into the lived experiences of teenage mothers in schools with particular reference to how they cope with school work and the responsibilities of motherhood. A case study of four teenage mothers who returned to school after giving birth was carried out. In-depth phenomenological interviewing designed to elicit the voices of the selected adolescents was done. There were five main findings. First, all four teenagers were minors, under the age of 18 when they gave birth. Two of them were even under the statutory age of consent. Second, upon return to school, teenage mothers experienced stigmatisation from peers and teachers and this forced them to continually negotiate their dual identities as mothers and learners. Third, teenage mothers experienced psychological emotions of stress; low self-esteem; shame and depression. Fourth, they also had sociological experiences in the form of material, financial and social support from family and friends. In some cases they experienced rejection from peers and abandonment by boyfriends who had made them pregnant. Some educators discriminated against and ridiculed teenage mothers. Fifth, teenage mothers reorganised their lives after childbirth and established routines that enabled them to cope with the demands of school work and the responsibilities of motherhood. iii The study concludes that, although viewed with scepticism by sections of the community and some educators, and given that some pregnancies are a result of abuse and unequal power relations between men and women in society, the policy of allowing teenage mothers back to school after giving birth gives them another chance to re-focus their lives. It is recommended that the voices of teenage mothers who return to school after childbirth should be taken into account to inform any planning for future policies on teenage pregnancy by schools and the state. It is further recommended that all educators should also be trained to be able to assist the teenage mothers instead of alienating them. There should also be counselling services available for the teenage mothers to enable them to deal with psychological and sociological problems they might encounter. For further research, students from different backgrounds should be the target of similar research. Another area of research should focus on academic performance of teenage mothers who return to school after giving birth. Lastly, there should be research that seeks to link what is taught in the Life Orientation curriculum and voices of teenage mothers.
- Full Text:
- Date Issued: 2012
Cash transfers and poverty reduction in South Africa: a case study of old age pensions
- Authors: Kasere, Gayle Farai
- Date: 2012
- Subjects: Poverty -- Economic aspects -- South Africa -- Eastern Cape Poverty -- Grahamstown -- Eastern Cape Social security -- South Africa Pensions -- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3321 , http://hdl.handle.net/10962/d1003109
- Description: Social assistance in the form of cash grants is a large and fiscally costly component of anti-poverty policy in South Africa. A critical question arises: Are the grants effective tools for reducing poverty in South Africa and, moreover, how significant is their impact on poverty? As a measure of reducing poverty, the government has expanded the social grants system since the advent of the new democracy in 1994. The country's social grant system is quite comprehensive and it is intended to cover vulnerable individuals over their life course from childhood to adulthood and into old age. Policy discourse surrounding the grants centres on the sustainability of the system and its implications for socio-economic development and poverty alleviation. It is therefore important that the significance of grants is identified and assessed particularly in relation to very poor households. This dissertation focuses specifically on one particular grant, namely, the old age pension. It does so in the context of the sustainable livelihoods conceptual framework and the history of the social grant system in South Africa. Statistical data collected by the South African government as well as more localised evidence gathered in the Eastern Cape town of Grahamstown is used to ascertain the significance of old age pensions for poverty reduction. While there is some evidence to suggest that pensions contribute to poverty reduction, this does not translate into poverty alleviation. In fact, there is some unevenness in the impact of pensions on poverty. In this regard, the decision-making structures in poor households regularly influence the way pension money is allocated and used within households. Grant money is normally shared in extended households, such that the pension does not simply benefit the recipient but the recipient's household as a whole. Although there is cause for concern regarding the propensity of social grants to affect people's behaviour negatively, there is a case to be made for retaining grants as an important, though not the only, form of anti-poverty strategy. This highlights the need for continued research on the social grant system and pensions more specifically.
- Full Text:
- Date Issued: 2012
- Authors: Kasere, Gayle Farai
- Date: 2012
- Subjects: Poverty -- Economic aspects -- South Africa -- Eastern Cape Poverty -- Grahamstown -- Eastern Cape Social security -- South Africa Pensions -- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3321 , http://hdl.handle.net/10962/d1003109
- Description: Social assistance in the form of cash grants is a large and fiscally costly component of anti-poverty policy in South Africa. A critical question arises: Are the grants effective tools for reducing poverty in South Africa and, moreover, how significant is their impact on poverty? As a measure of reducing poverty, the government has expanded the social grants system since the advent of the new democracy in 1994. The country's social grant system is quite comprehensive and it is intended to cover vulnerable individuals over their life course from childhood to adulthood and into old age. Policy discourse surrounding the grants centres on the sustainability of the system and its implications for socio-economic development and poverty alleviation. It is therefore important that the significance of grants is identified and assessed particularly in relation to very poor households. This dissertation focuses specifically on one particular grant, namely, the old age pension. It does so in the context of the sustainable livelihoods conceptual framework and the history of the social grant system in South Africa. Statistical data collected by the South African government as well as more localised evidence gathered in the Eastern Cape town of Grahamstown is used to ascertain the significance of old age pensions for poverty reduction. While there is some evidence to suggest that pensions contribute to poverty reduction, this does not translate into poverty alleviation. In fact, there is some unevenness in the impact of pensions on poverty. In this regard, the decision-making structures in poor households regularly influence the way pension money is allocated and used within households. Grant money is normally shared in extended households, such that the pension does not simply benefit the recipient but the recipient's household as a whole. Although there is cause for concern regarding the propensity of social grants to affect people's behaviour negatively, there is a case to be made for retaining grants as an important, though not the only, form of anti-poverty strategy. This highlights the need for continued research on the social grant system and pensions more specifically.
- Full Text:
- Date Issued: 2012
Causes and consequences of early marriage in Lusikisiki: a research paper
- Authors: Jongizulu, Siziwe
- Date: 2012
- Subjects: Teenage marriage -- South Africa -- Eastern Cape , Forced marriage -- South Africa , Children's rights -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9074 , http://hdl.handle.net/10948/d1008414 , Teenage marriage -- South Africa -- Eastern Cape , Forced marriage -- South Africa , Children's rights -- South Africa -- Eastern Cape
- Description: The purpose of the study was to identify causes and consequences of early marriages in Lusikisiki. The population of this study is a convenience sample from Lusikisiki. The researcher thought that this was appropriate because these subjects would be sharing their personal experiences in the form of case studies. The ages of subjects that were interviewed were 40 years & 47 years old (both married early) and those that married late were both 50 years old. The idea that guided the study was an exploratory one aimed at understanding the phenomenon of early marriage. The aim was to explore the following ideas: Young girls are being given into marriage at their early age by their parents because of the bride price (ilobola)Women that are given into marriage early feel victimized by this process early marriage disrupts the school pattern of young girls Men are the main beneficiaries of early marriage.
- Full Text:
- Date Issued: 2012
- Authors: Jongizulu, Siziwe
- Date: 2012
- Subjects: Teenage marriage -- South Africa -- Eastern Cape , Forced marriage -- South Africa , Children's rights -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9074 , http://hdl.handle.net/10948/d1008414 , Teenage marriage -- South Africa -- Eastern Cape , Forced marriage -- South Africa , Children's rights -- South Africa -- Eastern Cape
- Description: The purpose of the study was to identify causes and consequences of early marriages in Lusikisiki. The population of this study is a convenience sample from Lusikisiki. The researcher thought that this was appropriate because these subjects would be sharing their personal experiences in the form of case studies. The ages of subjects that were interviewed were 40 years & 47 years old (both married early) and those that married late were both 50 years old. The idea that guided the study was an exploratory one aimed at understanding the phenomenon of early marriage. The aim was to explore the following ideas: Young girls are being given into marriage at their early age by their parents because of the bride price (ilobola)Women that are given into marriage early feel victimized by this process early marriage disrupts the school pattern of young girls Men are the main beneficiaries of early marriage.
- Full Text:
- Date Issued: 2012
Causes and effects of teachers' job satisfaction or dissatisfaction and their impact on leaner performance: a case study of two schools in the Ngqeleni Area of the Libode Mega-District, Eastern Cape Province of South Africa
- Authors: Dukwana, Mzamo Jeffrey
- Date: 2012
- Subjects: Teachers -- Job satisfaction -- Teaching and learning , South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18433 , http://hdl.handle.net/11260/d1007159
- Description: The study investigated the relationship between teachers' job satisfaction-or dissatisfaction-and learner performance in two schools (one Junior Secondary School and one Senior Secondary School) in the Libode Mega-district, Eastern Cape Province, South Africa. The study is qualitative in nature; the interview was used as the method of collecting data. Six School Management Team (SMT) members and ten teachers were purposively selected from the two schools in the Libode Mega-district. The researcher administered the interview and interviewed the selected SMT members and teachers. The researcher used the video/sound/audio recorder as the research instrument to collect data. To analyze data, the researcher transcribed the recorded interview responses, presented the responses without editing them, interpreted the responses and themes. The findings were derived from the themes. The main findings of the study revealed that there was low morale and job dissatisfaction among teachers. The study`s finding of “low morale and job dissatisfaction among teachers” could be regarded as the reference of the general situation ('picture') of the relationship between teachers` job dissatisfaction and learner performance in the schools of the Libode Mega Education District. The findings have also revealed that there is a proportional relationship between teachers` job satisfaction and learner performance, i.e. the more satisfied teachers are with their jobs the more likely they perform better on their tasks, this results in good leaner performance, while low the levels of job satisfaction among teachers result in poor learner performance. The study recommends that the website- based, electronic information systems should be developed by the National Department of Education in order to grant teachers, or any school stakeholder, absolute anonymity to log or report complaints, dissatisfaction, suggestions, disapproval, appraisals and opinions on matters that concern the education system in South Africa. The study recommends that pupil-teacher ratio policy, and policies on working conditions in schools should be constantly reviewed. The introduction of change- management workshops for teachers to adapt to innovations in the education curriculum is also recommended.
- Full Text:
- Date Issued: 2012
- Authors: Dukwana, Mzamo Jeffrey
- Date: 2012
- Subjects: Teachers -- Job satisfaction -- Teaching and learning , South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18433 , http://hdl.handle.net/11260/d1007159
- Description: The study investigated the relationship between teachers' job satisfaction-or dissatisfaction-and learner performance in two schools (one Junior Secondary School and one Senior Secondary School) in the Libode Mega-district, Eastern Cape Province, South Africa. The study is qualitative in nature; the interview was used as the method of collecting data. Six School Management Team (SMT) members and ten teachers were purposively selected from the two schools in the Libode Mega-district. The researcher administered the interview and interviewed the selected SMT members and teachers. The researcher used the video/sound/audio recorder as the research instrument to collect data. To analyze data, the researcher transcribed the recorded interview responses, presented the responses without editing them, interpreted the responses and themes. The findings were derived from the themes. The main findings of the study revealed that there was low morale and job dissatisfaction among teachers. The study`s finding of “low morale and job dissatisfaction among teachers” could be regarded as the reference of the general situation ('picture') of the relationship between teachers` job dissatisfaction and learner performance in the schools of the Libode Mega Education District. The findings have also revealed that there is a proportional relationship between teachers` job satisfaction and learner performance, i.e. the more satisfied teachers are with their jobs the more likely they perform better on their tasks, this results in good leaner performance, while low the levels of job satisfaction among teachers result in poor learner performance. The study recommends that the website- based, electronic information systems should be developed by the National Department of Education in order to grant teachers, or any school stakeholder, absolute anonymity to log or report complaints, dissatisfaction, suggestions, disapproval, appraisals and opinions on matters that concern the education system in South Africa. The study recommends that pupil-teacher ratio policy, and policies on working conditions in schools should be constantly reviewed. The introduction of change- management workshops for teachers to adapt to innovations in the education curriculum is also recommended.
- Full Text:
- Date Issued: 2012
CdTe quantum dots functionalized with 4-amino-2, 2, 6, 6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion
- Adegoke, Oluwasesan, Hosten, Eric, McCleland, Cedric, Nyokong, Tebello
- Authors: Adegoke, Oluwasesan , Hosten, Eric , McCleland, Cedric , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244393 , vital:51253 , xlink:href="https://doi.org/10.1016/j.aca.2012.01.040"
- Description: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
- Full Text:
- Date Issued: 2012
- Authors: Adegoke, Oluwasesan , Hosten, Eric , McCleland, Cedric , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244393 , vital:51253 , xlink:href="https://doi.org/10.1016/j.aca.2012.01.040"
- Description: A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6 nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13 μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
- Full Text:
- Date Issued: 2012
Challenges experienced in the first year of implementation of a teaching and learning virtual partnership at the University of Namibia
- Mufeti, K, Foster, Greg, Terzoli, Alfredo
- Authors: Mufeti, K , Foster, Greg , Terzoli, Alfredo
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431234 , vital:72756 , https://rcetj.org/index.php/rcetj/article/view/178
- Description: Advances in information and communication technologies are enabling higher educa-tion institutions to build virtual partnerships with other institutions. Virtual partner-ships are defined here as collaborations between geographically dispersed institutions, where interaction between these institutions is enabled mainly by electronic modes of communication. This article reports on the participants’ experiences of the implemen-tation of one such partnership from the perspective of a partner in a developing con-text. It uses the SANTED Virtual Classroom Project (VCP), a virtual partnership initia-tive between the Departments of Computer Science at the University of Namibia (UNAM) and Rhodes University (RU), as a case study. In the VCP, the department at RU was tasked with building teaching and human resource capacity in the department at UNAM. The article focuses on the challenges experienced at UNAM during the first year of implementation of the VCP and lessons learned.
- Full Text:
- Date Issued: 2012
- Authors: Mufeti, K , Foster, Greg , Terzoli, Alfredo
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/431234 , vital:72756 , https://rcetj.org/index.php/rcetj/article/view/178
- Description: Advances in information and communication technologies are enabling higher educa-tion institutions to build virtual partnerships with other institutions. Virtual partner-ships are defined here as collaborations between geographically dispersed institutions, where interaction between these institutions is enabled mainly by electronic modes of communication. This article reports on the participants’ experiences of the implemen-tation of one such partnership from the perspective of a partner in a developing con-text. It uses the SANTED Virtual Classroom Project (VCP), a virtual partnership initia-tive between the Departments of Computer Science at the University of Namibia (UNAM) and Rhodes University (RU), as a case study. In the VCP, the department at RU was tasked with building teaching and human resource capacity in the department at UNAM. The article focuses on the challenges experienced at UNAM during the first year of implementation of the VCP and lessons learned.
- Full Text:
- Date Issued: 2012
Challenges faced by female secondary school principals in the Qumbu Education District of the Eastern Cape Province of South Africa
- Authors: Sobekwa, Jonguxolo
- Date: 2012
- Subjects: School principals -- Education (Secondary) , South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18453 , http://hdl.handle.net/11260/d1007759
- Description: The purpose of this study was to investigate and explore the challenges faced by female secondary school principals when discharging their duties. This study was done because it was not a normal practice before 1994 to have a female person as the head of a learning institution. This was specifically linked to the implementation of equity as enshrined and entrenched in the constitution no.108, of 1996 of the Republic of South Africa. It is almost 18 years since the proclamation of equity in the constitution; it was therefore of great importance to evaluate the ground covered in terms of implementation of this equity. The equity mentioned in Chapter 2, section 9 of the constitution resulted in the formulation of the Employment Equity Act no.55 of 1998 as amended. The implementation of the Employment Equity Act no.55 of 1998 was expected to have an impact on the way the female school secondary principals were received by the community. Currently all departments are compelled to employ women in managerial positions and this receives opposition in some sectors of the population. This study was conducted in Qumbu education district in the Eastern Cape Province of South Africa. It focused on secondary school principals. The study used a quantitative research design to elicit data from the respondents. Data were collected from 46 participants through the use of a questionnaire. 32 questionnaires were returned and the data were processed. The Statistical Package for Social Sciences (SPSS) was used in the analysis of the data. The findings of the study revealed several challenges confronting female secondary school principals both in the workplace and at home. In the workplace, on one hand, female principals are faced with insubordination from male educators; poor parental involvement and cultural stereotypes; and on the other hand, at home, they were confronted by minimal support from their partners/ spouses. In the light of the findings, the researcher recommended that the Department of Basic Education organize capacity-building workshops to develop leadership skills; replacement strategies for ageing principals; women‟s conferences to advocate women‟s rights; and programmes for female principals and their husbands, called Men As Partners (MAP). The study succeeded in portraying a picture of what is presently taking place in secondary schools that are headed by female principals. Some of the limitations encountered by the researcher during the study included the reluctance of the participants to take part in the research, the non-accessibility of schools in deep rural areas, the return rate of completed questionnaires; and the obtaining of permission to undertake the study.
- Full Text:
- Date Issued: 2012
- Authors: Sobekwa, Jonguxolo
- Date: 2012
- Subjects: School principals -- Education (Secondary) , South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18453 , http://hdl.handle.net/11260/d1007759
- Description: The purpose of this study was to investigate and explore the challenges faced by female secondary school principals when discharging their duties. This study was done because it was not a normal practice before 1994 to have a female person as the head of a learning institution. This was specifically linked to the implementation of equity as enshrined and entrenched in the constitution no.108, of 1996 of the Republic of South Africa. It is almost 18 years since the proclamation of equity in the constitution; it was therefore of great importance to evaluate the ground covered in terms of implementation of this equity. The equity mentioned in Chapter 2, section 9 of the constitution resulted in the formulation of the Employment Equity Act no.55 of 1998 as amended. The implementation of the Employment Equity Act no.55 of 1998 was expected to have an impact on the way the female school secondary principals were received by the community. Currently all departments are compelled to employ women in managerial positions and this receives opposition in some sectors of the population. This study was conducted in Qumbu education district in the Eastern Cape Province of South Africa. It focused on secondary school principals. The study used a quantitative research design to elicit data from the respondents. Data were collected from 46 participants through the use of a questionnaire. 32 questionnaires were returned and the data were processed. The Statistical Package for Social Sciences (SPSS) was used in the analysis of the data. The findings of the study revealed several challenges confronting female secondary school principals both in the workplace and at home. In the workplace, on one hand, female principals are faced with insubordination from male educators; poor parental involvement and cultural stereotypes; and on the other hand, at home, they were confronted by minimal support from their partners/ spouses. In the light of the findings, the researcher recommended that the Department of Basic Education organize capacity-building workshops to develop leadership skills; replacement strategies for ageing principals; women‟s conferences to advocate women‟s rights; and programmes for female principals and their husbands, called Men As Partners (MAP). The study succeeded in portraying a picture of what is presently taking place in secondary schools that are headed by female principals. Some of the limitations encountered by the researcher during the study included the reluctance of the participants to take part in the research, the non-accessibility of schools in deep rural areas, the return rate of completed questionnaires; and the obtaining of permission to undertake the study.
- Full Text:
- Date Issued: 2012
Challenges faced by high school managers in dealing with pregnant learners in their schools: a case study of selected high schools in the Idutywa district, Eastern Cape Region
- Authors: Tyumre, Nocawe
- Date: 2012
- Subjects: School principals -- Pregnant teenagers -- Education (Secondary) , South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18448 , http://hdl.handle.net/11260/d1007300
- Description: The purpose of the study was to investigate the challenges faced by high school managers in dealing with pregnant learners in their schools and also ways of dealing with such challenges in selected Senior Secondary Schools in the Idutywa Education District (IED) in the Eastern Cape Province. The study mainly focused on rural schools. Qualitative research method was used and a Case Study design was used to conduct the study. The sample constituted of 16 high School Management Team (SMT) members from the four chosen high schools. An interview schedule designed by the researcher was used to gather data. The collected data were analysed using codes, segments, categories and themes. The researcher interpreted the data and the findings of the study showed that pregnancy changed the behaviour of female learners as a result, School Management Teams (SMT) found it difficult to deal with pregnant learner behaviours in terms of punishing them or expelling them due to South African Schools Act (1996). The study showed that, the School Management Teams in the four selected high schools felt that there should be parental involvement in schools when dealing with learner behaviours. The study showed that pregnant learners dropout of school before they completed their matriculation and they returned anytime after giving birth and SMT had no choice but to accept them even if they returned in the middle of the year. The study further showed that teachers had to assist pregnant learners by organizing catch up programmes so that they produce good results at the end of the year. According to the findings of the study it was clear that pregnancy really affected school policies in terms of learner discipline, learner absenteeism, school dropout and learner overall results. The researcher recommended that, the Department of Education should formulate a policy on pregnant learners that will not allow pregnant learners to attend school while being pregnant in order to assist School Management Teams in schools. The formulated policy should allow School Management Teams to expel pregnant learners in school.
- Full Text:
- Date Issued: 2012
- Authors: Tyumre, Nocawe
- Date: 2012
- Subjects: School principals -- Pregnant teenagers -- Education (Secondary) , South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , M Ed
- Identifier: vital:18448 , http://hdl.handle.net/11260/d1007300
- Description: The purpose of the study was to investigate the challenges faced by high school managers in dealing with pregnant learners in their schools and also ways of dealing with such challenges in selected Senior Secondary Schools in the Idutywa Education District (IED) in the Eastern Cape Province. The study mainly focused on rural schools. Qualitative research method was used and a Case Study design was used to conduct the study. The sample constituted of 16 high School Management Team (SMT) members from the four chosen high schools. An interview schedule designed by the researcher was used to gather data. The collected data were analysed using codes, segments, categories and themes. The researcher interpreted the data and the findings of the study showed that pregnancy changed the behaviour of female learners as a result, School Management Teams (SMT) found it difficult to deal with pregnant learner behaviours in terms of punishing them or expelling them due to South African Schools Act (1996). The study showed that, the School Management Teams in the four selected high schools felt that there should be parental involvement in schools when dealing with learner behaviours. The study showed that pregnant learners dropout of school before they completed their matriculation and they returned anytime after giving birth and SMT had no choice but to accept them even if they returned in the middle of the year. The study further showed that teachers had to assist pregnant learners by organizing catch up programmes so that they produce good results at the end of the year. According to the findings of the study it was clear that pregnancy really affected school policies in terms of learner discipline, learner absenteeism, school dropout and learner overall results. The researcher recommended that, the Department of Education should formulate a policy on pregnant learners that will not allow pregnant learners to attend school while being pregnant in order to assist School Management Teams in schools. The formulated policy should allow School Management Teams to expel pregnant learners in school.
- Full Text:
- Date Issued: 2012
Challenges of instructional leadership in historically disadvantaged schools in South Africa
- Authors: Tshazibana, Vukile Shadrack
- Date: 2012
- Subjects: School management and organization -- South Africa , Educational leadership -- South Africa , Children with social disabilities -- Education -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9565 , http://hdl.handle.net/10948/d1016059
- Description: The research presented in this thesis investigates challenges faced by principals in historically disadvantaged schools in terms of their role as instructional leaders facilitating the implementation of curriculum policies. The study consists of two parts. The first study sampled 25 school principals, 80 teachers and 11 department of education officials from the Uitenhage and Port Elizabeth education districts in the Eastern Cape. Data obtained in the first study were generated by administering a pen-and-paper questionnaire and individual interviews to selected participants. The second study employed an online questionnaire that was open to principals, teachers and departmental officials in all provinces of South Africa in order to generate data over as wide a geographic range as possible. Mixed methods were used to analyse the qualitative and quantitative data from the two studies. Thematic analysis techniques were employed to categorise qualitative data and the quantitative data were subjected to analytical techniques to provide descriptive and inferential statistics. The data revealed that school principals view themselves as change agents who should be in the forefront of change and curriculum implementation, and that they believe that they know what is expected of them in this regard. However, they recognise that they are not adequately prepared for the task of instructional leadership. The data also suggest that teachers have expectations that principals should be trained in instructional leadership and work closely with departmental officials in order to provide guidance and leadership at school level to address their professional needs. Problems related to capacity and skills of subject advisors and other district officials were revealed by the study. These issues are generally and informally recognised, but have not been formally raised within the Department of Education. The findings of the study also highlight the fact that, after nearly two decades in the new political dispensation, there are still vast differences within the South African schooling system between school types. These differences are most evident between ex-Model C schools and historically disadvantaged ex-DET schools, and it is recognised that principals in ex-DET schools need support tailored to their particular circumstances and context. The findings in this study support the notion that much needs to be done in South Africa in terms of empowering school principals; especially those from historically disadvantaged schools. The data provide insights into some of the constraints of local context, which enables better understandings of the challenges of instructional leadership in historically disadvantaged schools. These understandings should be of value when considering strategies to support principals in their role of instructional leaders.
- Full Text:
- Date Issued: 2012
- Authors: Tshazibana, Vukile Shadrack
- Date: 2012
- Subjects: School management and organization -- South Africa , Educational leadership -- South Africa , Children with social disabilities -- Education -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9565 , http://hdl.handle.net/10948/d1016059
- Description: The research presented in this thesis investigates challenges faced by principals in historically disadvantaged schools in terms of their role as instructional leaders facilitating the implementation of curriculum policies. The study consists of two parts. The first study sampled 25 school principals, 80 teachers and 11 department of education officials from the Uitenhage and Port Elizabeth education districts in the Eastern Cape. Data obtained in the first study were generated by administering a pen-and-paper questionnaire and individual interviews to selected participants. The second study employed an online questionnaire that was open to principals, teachers and departmental officials in all provinces of South Africa in order to generate data over as wide a geographic range as possible. Mixed methods were used to analyse the qualitative and quantitative data from the two studies. Thematic analysis techniques were employed to categorise qualitative data and the quantitative data were subjected to analytical techniques to provide descriptive and inferential statistics. The data revealed that school principals view themselves as change agents who should be in the forefront of change and curriculum implementation, and that they believe that they know what is expected of them in this regard. However, they recognise that they are not adequately prepared for the task of instructional leadership. The data also suggest that teachers have expectations that principals should be trained in instructional leadership and work closely with departmental officials in order to provide guidance and leadership at school level to address their professional needs. Problems related to capacity and skills of subject advisors and other district officials were revealed by the study. These issues are generally and informally recognised, but have not been formally raised within the Department of Education. The findings of the study also highlight the fact that, after nearly two decades in the new political dispensation, there are still vast differences within the South African schooling system between school types. These differences are most evident between ex-Model C schools and historically disadvantaged ex-DET schools, and it is recognised that principals in ex-DET schools need support tailored to their particular circumstances and context. The findings in this study support the notion that much needs to be done in South Africa in terms of empowering school principals; especially those from historically disadvantaged schools. The data provide insights into some of the constraints of local context, which enables better understandings of the challenges of instructional leadership in historically disadvantaged schools. These understandings should be of value when considering strategies to support principals in their role of instructional leaders.
- Full Text:
- Date Issued: 2012
Changing sediment yield and sediment dynamics in the Karoo uplands, South Africa : post-European impacts
- Foster, I D L, Rowntree, Kate M, Boardman, J, Mighall, T M
- Authors: Foster, I D L , Rowntree, Kate M , Boardman, J , Mighall, T M
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6684 , http://hdl.handle.net/10962/d1006683
- Description: We provide an overview of published results and a significant body of new data from an ongoing research programme designed to reconstruct sediment yields and sources in small (<60 km2) catchments in the Eastern Cape, South Africa over the last 150 years. Our analysis of four catchments has determined that sediment yield increased significantly in the latter half of the 20th Century but that the exact timing of these increases was different in each of the four catchments. In two high altitude locations, sediment yield increases were not associated with a significant change in sediment source, although in one case areas of former cultivation appear to have made a slightly greater contribution since the 1960s. In a third catchment, increases in sediment yield appear to have been driven by the development of badlands and by an increase in connectivity between the badlands and the main channel network in the 1960s. In the fourth catchment, increased connectivity between the main catchment and dam occurred as a result of the construction of a causeway to carry a main road and by the construction of culverts beneath the road. Occasional changes in sediment source have also been identified in the sedimentary record but these were not linked directly to road construction. Research to date shows the complexity of sediment delivery in these semi-arid catchment systems and emphasises the need to combine sediment yield with source ascription in order to better understand the dynamics of these systems.
- Full Text:
- Date Issued: 2012
- Authors: Foster, I D L , Rowntree, Kate M , Boardman, J , Mighall, T M
- Date: 2012
- Language: English
- Type: Article
- Identifier: vital:6684 , http://hdl.handle.net/10962/d1006683
- Description: We provide an overview of published results and a significant body of new data from an ongoing research programme designed to reconstruct sediment yields and sources in small (<60 km2) catchments in the Eastern Cape, South Africa over the last 150 years. Our analysis of four catchments has determined that sediment yield increased significantly in the latter half of the 20th Century but that the exact timing of these increases was different in each of the four catchments. In two high altitude locations, sediment yield increases were not associated with a significant change in sediment source, although in one case areas of former cultivation appear to have made a slightly greater contribution since the 1960s. In a third catchment, increases in sediment yield appear to have been driven by the development of badlands and by an increase in connectivity between the badlands and the main channel network in the 1960s. In the fourth catchment, increased connectivity between the main catchment and dam occurred as a result of the construction of a causeway to carry a main road and by the construction of culverts beneath the road. Occasional changes in sediment source have also been identified in the sedimentary record but these were not linked directly to road construction. Research to date shows the complexity of sediment delivery in these semi-arid catchment systems and emphasises the need to combine sediment yield with source ascription in order to better understand the dynamics of these systems.
- Full Text:
- Date Issued: 2012
Characterisation and optimisation of waterjet impact forces and energy parameters during hydroentanglement
- Authors: Moyo, Doice
- Date: 2012
- Subjects: Textile chemistry , Nonwoven fabrics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10453 , http://hdl.handle.net/10948/d1020134
- Description: Hydroentanglement is an important technique of bonding fibres to produce nonwovens using high velocity waterjets as the primary bonding tool. The work reported in this thesis addresses the gap in scientific knowledge and understanding, both theoretical and experimental, related to the impact forces and energy of the waterjets used in the hydroentanglement process. The current study focused on the impact forces and energy involved in, and the optimisation of, the hydroentanglement process. The results of the experimentally measured waterjet impact forces have been used to characterise the waterjets as well as to verify empirically the theoretical models currently available for explaining the mechanics of the hydroentanglement process. Since the process of supplying pressurised waterjets consumes a great deal of energy, the study of energy consumption and efficiency of the system has been critical. A method was proposed and used to determine the coefficients of velocity and water discharge of an industrial machine set-up, helping explain the mechanism of energy transfer during hydroentanglement and to concurrently optimise the process. Furthermore, a response surface experimental design was used to optimise the hydroentanglement of viscose and Polylactic acid (PLA) fibres into nonwovens. The selected Box-Behnken design, with four factors, namely the waterjet force, machine processing speed, input weight and fibre type, was employed to investigate the multivariate process factors and their interactive effects on physical and mechanical properties of nonwovens. Two sets of experiments, the later for validation, were performed to study the energy transfer efficiency. The results of the relative energy transfer to bond the fibrous web showed that it was possible to produce nonwovens using lower input energy without compromising the quality of the products. The optimum waterjet pressure and machine speed used to produce the Abstract nonwoven with the highest tensile strength for the least amount of energy supplied were identified.
- Full Text:
- Date Issued: 2012
- Authors: Moyo, Doice
- Date: 2012
- Subjects: Textile chemistry , Nonwoven fabrics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10453 , http://hdl.handle.net/10948/d1020134
- Description: Hydroentanglement is an important technique of bonding fibres to produce nonwovens using high velocity waterjets as the primary bonding tool. The work reported in this thesis addresses the gap in scientific knowledge and understanding, both theoretical and experimental, related to the impact forces and energy of the waterjets used in the hydroentanglement process. The current study focused on the impact forces and energy involved in, and the optimisation of, the hydroentanglement process. The results of the experimentally measured waterjet impact forces have been used to characterise the waterjets as well as to verify empirically the theoretical models currently available for explaining the mechanics of the hydroentanglement process. Since the process of supplying pressurised waterjets consumes a great deal of energy, the study of energy consumption and efficiency of the system has been critical. A method was proposed and used to determine the coefficients of velocity and water discharge of an industrial machine set-up, helping explain the mechanism of energy transfer during hydroentanglement and to concurrently optimise the process. Furthermore, a response surface experimental design was used to optimise the hydroentanglement of viscose and Polylactic acid (PLA) fibres into nonwovens. The selected Box-Behnken design, with four factors, namely the waterjet force, machine processing speed, input weight and fibre type, was employed to investigate the multivariate process factors and their interactive effects on physical and mechanical properties of nonwovens. Two sets of experiments, the later for validation, were performed to study the energy transfer efficiency. The results of the relative energy transfer to bond the fibrous web showed that it was possible to produce nonwovens using lower input energy without compromising the quality of the products. The optimum waterjet pressure and machine speed used to produce the Abstract nonwoven with the highest tensile strength for the least amount of energy supplied were identified.
- Full Text:
- Date Issued: 2012
Characterising the stress-life response of mechanical and laser formed titanium components
- Authors: Fidder, Herman
- Date: 2012
- Subjects: Titanium alloys -- Fatigue , Titanium --- Fatigue , Materials -- Mechanical properties
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9634 , http://hdl.handle.net/10948/d1018462
- Description: This dissertation involves the experimental investigation of commercially pure titanium (CP Ti) which was subjected to laser forming and mechanical forming processes. Commercially pure titanium grade 2 was formed to a radius of curvature of approximately 120 mm using three forming procedures, i.e. i) laser forming; ii) mechanical forming (stretched forming) and iii) a combined forming process (laser-mechanical forming). Fatigue testing revealed, for all the forming processes, that samples produced by laser forming performed the best at high load settings. However, mechanically formed specimens performed the best at low load settings, whereas the laser-mechanical process resulted in midway performance between laser and mechanical processing. Considering microstructure vs fatigue; impact vs fatigue; and residual stress vs fatigue; at high load settings it is evident that the microstructure is the dominant contributor to crack initiation and growth. Crack morphology of fatigue samples revealed that secondary cracks (parallel to main crack front) followed the grain boundaries of the Widmanstätten microstructure, whereas irregular secondary cracks grew parallel and through the twinning planes and along the grain boundaries of the equiaxed microstructure. Laser forming resulted in microstructural changes from equiaxed grains to a Widmanstätten structure due to fast cooling rates. Excessive twinning is developed within the equiaxed microstructure after the mechanical forming procedure. This is due to cold working / strain hardening. The combined process shows a combination of equiaxed grains and Widmanstätten microstructure. Residual stress relieved for all forming processes revealed an increase in the magnitude of the residual stress compared to the parent plate and that the maximum values were obtained at the inner radius of curvature (i.e. 118.4 mm). Laser forming revealed the highest values in residual stress whereas the other two processes i.e. mechanical and laser-mechanical forming exhibited an increase midway between the parent plate and laser forming. The second most influential factor with regards to fatigue was the magnitude of the residual stress, especially at medium to low load settings. When considering theoretical models to predict fatigue life it was found that the Goodman model showed the closest relation to the actual fatigue data when considering the entire theoretical curve. Vickers microhardness profiling was applied to the thickness of the samples for the parent plate and all forming processes. No significant hardening occurred due to the forming processes and differences in hardness were considered negligible. Charpy impact testing revealed that the laser formed specimens exhibited the most brittle behaviour when compared to the parent plate results. Mechanical formed specimens showed a slight increase in brittleness compared to parent plate whereas the combined process yielded results midway between the laser and mechanically formed specimens. Mathematical equations are formulated and presented for predicting the fatigue life of CP Ti grade 2 for the parent plate and the three forming processes. This study proved that the laser forming process can be successfully used as a production stage in the forming of CP Ti grade 2.
- Full Text:
- Date Issued: 2012
- Authors: Fidder, Herman
- Date: 2012
- Subjects: Titanium alloys -- Fatigue , Titanium --- Fatigue , Materials -- Mechanical properties
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9634 , http://hdl.handle.net/10948/d1018462
- Description: This dissertation involves the experimental investigation of commercially pure titanium (CP Ti) which was subjected to laser forming and mechanical forming processes. Commercially pure titanium grade 2 was formed to a radius of curvature of approximately 120 mm using three forming procedures, i.e. i) laser forming; ii) mechanical forming (stretched forming) and iii) a combined forming process (laser-mechanical forming). Fatigue testing revealed, for all the forming processes, that samples produced by laser forming performed the best at high load settings. However, mechanically formed specimens performed the best at low load settings, whereas the laser-mechanical process resulted in midway performance between laser and mechanical processing. Considering microstructure vs fatigue; impact vs fatigue; and residual stress vs fatigue; at high load settings it is evident that the microstructure is the dominant contributor to crack initiation and growth. Crack morphology of fatigue samples revealed that secondary cracks (parallel to main crack front) followed the grain boundaries of the Widmanstätten microstructure, whereas irregular secondary cracks grew parallel and through the twinning planes and along the grain boundaries of the equiaxed microstructure. Laser forming resulted in microstructural changes from equiaxed grains to a Widmanstätten structure due to fast cooling rates. Excessive twinning is developed within the equiaxed microstructure after the mechanical forming procedure. This is due to cold working / strain hardening. The combined process shows a combination of equiaxed grains and Widmanstätten microstructure. Residual stress relieved for all forming processes revealed an increase in the magnitude of the residual stress compared to the parent plate and that the maximum values were obtained at the inner radius of curvature (i.e. 118.4 mm). Laser forming revealed the highest values in residual stress whereas the other two processes i.e. mechanical and laser-mechanical forming exhibited an increase midway between the parent plate and laser forming. The second most influential factor with regards to fatigue was the magnitude of the residual stress, especially at medium to low load settings. When considering theoretical models to predict fatigue life it was found that the Goodman model showed the closest relation to the actual fatigue data when considering the entire theoretical curve. Vickers microhardness profiling was applied to the thickness of the samples for the parent plate and all forming processes. No significant hardening occurred due to the forming processes and differences in hardness were considered negligible. Charpy impact testing revealed that the laser formed specimens exhibited the most brittle behaviour when compared to the parent plate results. Mechanical formed specimens showed a slight increase in brittleness compared to parent plate whereas the combined process yielded results midway between the laser and mechanically formed specimens. Mathematical equations are formulated and presented for predicting the fatigue life of CP Ti grade 2 for the parent plate and the three forming processes. This study proved that the laser forming process can be successfully used as a production stage in the forming of CP Ti grade 2.
- Full Text:
- Date Issued: 2012
Characterising the stress-life response of mechanical formed AISI-1008 steel plate components
- Authors: Müller, Ruan
- Date: 2012
- Subjects: Materials -- Fatigue -- Testing , Metals -- Fatigue , Mechanical wear -- Measurement , Mechanical engineering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9616 , http://hdl.handle.net/10948/d1008102 , Materials -- Fatigue -- Testing , Metals -- Fatigue , Mechanical wear -- Measurement , Mechanical engineering
- Description: The main purpose of this research project was to determine the fatigue-life behaviour of AISI 1008 sheet steel which has been mechanically formed to a radius of curvature of 120mm and then to correlate the fatigue-life behaviour to that of the parent or “as manufactured” material. During the forming process it was felt important to induce plastic strain through stretch-bending by clamping the sides of a plate sample’s (width) edges in the bending fixture before being bent by a single acting mechanical press. It was determined through actual testing that there was a decrease in fatigue-life when the mechanical formed data was compared to fatigue data of the parent material. Standard fatigue mathematical models were used to relate the actual fatigue data. Due to the material being cold formed to a radius of curvature of 120mm, residual stresses induced during the forming process played an essential role during the fatigue-life prediction calculations. The maximum relieved stress in the parent material was compressive in nature having a magnitude of 11percent of the “as manufactured” yield strength (265 MPa). For the mechanical formed material compressive residual stresses were measured on the outer surface while tensile stresses were measured on the inner surface. The difference between actual number of cycles to failure to that calculated using the standard mathematical models for the parent material, ranged between 48 percent and 18 percent and for the mechanical formed samples between 35 percent and 1percent, depending on the strain amplitude used. An important aspect of this study was to determine the criteria required for mathematical modelling of the parent material as testing occurred between the limit of proportionality and yield point. Although this aspect requires further investigation the mathematical results obtained during this study were considered to be acceptable.
- Full Text:
- Date Issued: 2012
- Authors: Müller, Ruan
- Date: 2012
- Subjects: Materials -- Fatigue -- Testing , Metals -- Fatigue , Mechanical wear -- Measurement , Mechanical engineering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9616 , http://hdl.handle.net/10948/d1008102 , Materials -- Fatigue -- Testing , Metals -- Fatigue , Mechanical wear -- Measurement , Mechanical engineering
- Description: The main purpose of this research project was to determine the fatigue-life behaviour of AISI 1008 sheet steel which has been mechanically formed to a radius of curvature of 120mm and then to correlate the fatigue-life behaviour to that of the parent or “as manufactured” material. During the forming process it was felt important to induce plastic strain through stretch-bending by clamping the sides of a plate sample’s (width) edges in the bending fixture before being bent by a single acting mechanical press. It was determined through actual testing that there was a decrease in fatigue-life when the mechanical formed data was compared to fatigue data of the parent material. Standard fatigue mathematical models were used to relate the actual fatigue data. Due to the material being cold formed to a radius of curvature of 120mm, residual stresses induced during the forming process played an essential role during the fatigue-life prediction calculations. The maximum relieved stress in the parent material was compressive in nature having a magnitude of 11percent of the “as manufactured” yield strength (265 MPa). For the mechanical formed material compressive residual stresses were measured on the outer surface while tensile stresses were measured on the inner surface. The difference between actual number of cycles to failure to that calculated using the standard mathematical models for the parent material, ranged between 48 percent and 18 percent and for the mechanical formed samples between 35 percent and 1percent, depending on the strain amplitude used. An important aspect of this study was to determine the criteria required for mathematical modelling of the parent material as testing occurred between the limit of proportionality and yield point. Although this aspect requires further investigation the mathematical results obtained during this study were considered to be acceptable.
- Full Text:
- Date Issued: 2012
Characterising the structural integrity of mechanical formed low carbon steel
- Authors: Victor, Ngea Njoume
- Date: 2012
- Subjects: Carbon steel , Structural analysis (Engineering) , Steel, Structural
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9627 , http://hdl.handle.net/10948/d1012089 , Carbon steel , Structural analysis (Engineering) , Steel, Structural
- Description: The contribution of the clamping force in the technique used in this study to stretch-bend low carbon steel samples was investigated to support the subsequent changes in the microstructure and properties of the formed material with regard to parent material. Although plastic deformation by cold working is known to induce texture or preferred orientation to the grains of a formed material while decreasing its ductility and increasing the strength, as well as inducing residual stress, it is not known how the different directions (rolling, transverse and oblique/45°) of the sheet steel will respond to this stretch bending technique. The first part of the research work involved a thorough literature review on sheet metal forming processes and their effect on the formed material with interest on the above mentioned directions of the sheet. It became clear from the literature overview that cold working of a material will induce strain-hardening which varies with the magnitude of cold work, resulting in changes in the strength and ductility of the material. Besides, when plastic deformation is not uniform (e.g., tensile and compressive) throughout the entire cross section of the formed part, residual stresses remain in the material with the grains been elongated along the direction of the maximum strain. The main parameters that were considered and controlled in this study are as follows: strain experienced / stress induced into the form sample, the sample direction, the stroke length and the clamping torque, the generated radius of curvature. The chapters that follow the literature review, deal with the set-up of the different equipment used in this study, the specimen preparation as well as the recording, the calculation and interpretation of the results. It was found that the stress magnitude that generated the different radii of curvature (120 mm, 150 mm and 185 mm) was between 1 percent & 13 percent higher than the parent material’s yield strength with the lower stress been associated to the smaller radius of curvature and the higher stress to the higher radius. The stress induced into the sample during forming was not only proportional to the stroke length but also to the distance between the punch’s tip and the sample and the sample to the die’s nadir. The clamping torque adopted was restricted to the manual capacity of the operator who used a preset torque wrench to fasten the plate sample into the jig. Plate samples of low carbon steel were cut to angles of 0°, 45°, and 90° to the rolling direction of the sheet material and stretch-bent on a single-action mechanical press to 120 mm, 150 mm, and 185 mm radii of curvature. The preliminary results indicate that stretch-bent samples had increased hardness to the parent plate, in particular below the surface layers up to around 1.1 mm depth. Since there is a well established relationship between hardness, yield and tensile strengths for steel, the yield and tensile strengths of the formed material were estimated using the Nobre et al [34] incremental relation, which relates the linearity between relative increments of hardness and yield strength. Changes were not noticeable at the microstructural level of the formed samples. Meanwhile, samples from which higher plastic deformation stress values were calculated were not those absorbing higher impact energy when Charpy specimen cut from plate and stretch-bent samples were tested. The maximum relieved residual stress in the parent material was predominantly compressive and represents in magnitude approximately 12 percent (average for the three directions) of its original yield strength. In the stretch-bent samples, the relieved residual stress was compressive in the outer curved section with a magnitude about 50 percent of the parent material yield strength and tensile in the inner curved section with a magnitude approximately 25 percent of the parent material yield strength.
- Full Text:
- Date Issued: 2012
- Authors: Victor, Ngea Njoume
- Date: 2012
- Subjects: Carbon steel , Structural analysis (Engineering) , Steel, Structural
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9627 , http://hdl.handle.net/10948/d1012089 , Carbon steel , Structural analysis (Engineering) , Steel, Structural
- Description: The contribution of the clamping force in the technique used in this study to stretch-bend low carbon steel samples was investigated to support the subsequent changes in the microstructure and properties of the formed material with regard to parent material. Although plastic deformation by cold working is known to induce texture or preferred orientation to the grains of a formed material while decreasing its ductility and increasing the strength, as well as inducing residual stress, it is not known how the different directions (rolling, transverse and oblique/45°) of the sheet steel will respond to this stretch bending technique. The first part of the research work involved a thorough literature review on sheet metal forming processes and their effect on the formed material with interest on the above mentioned directions of the sheet. It became clear from the literature overview that cold working of a material will induce strain-hardening which varies with the magnitude of cold work, resulting in changes in the strength and ductility of the material. Besides, when plastic deformation is not uniform (e.g., tensile and compressive) throughout the entire cross section of the formed part, residual stresses remain in the material with the grains been elongated along the direction of the maximum strain. The main parameters that were considered and controlled in this study are as follows: strain experienced / stress induced into the form sample, the sample direction, the stroke length and the clamping torque, the generated radius of curvature. The chapters that follow the literature review, deal with the set-up of the different equipment used in this study, the specimen preparation as well as the recording, the calculation and interpretation of the results. It was found that the stress magnitude that generated the different radii of curvature (120 mm, 150 mm and 185 mm) was between 1 percent & 13 percent higher than the parent material’s yield strength with the lower stress been associated to the smaller radius of curvature and the higher stress to the higher radius. The stress induced into the sample during forming was not only proportional to the stroke length but also to the distance between the punch’s tip and the sample and the sample to the die’s nadir. The clamping torque adopted was restricted to the manual capacity of the operator who used a preset torque wrench to fasten the plate sample into the jig. Plate samples of low carbon steel were cut to angles of 0°, 45°, and 90° to the rolling direction of the sheet material and stretch-bent on a single-action mechanical press to 120 mm, 150 mm, and 185 mm radii of curvature. The preliminary results indicate that stretch-bent samples had increased hardness to the parent plate, in particular below the surface layers up to around 1.1 mm depth. Since there is a well established relationship between hardness, yield and tensile strengths for steel, the yield and tensile strengths of the formed material were estimated using the Nobre et al [34] incremental relation, which relates the linearity between relative increments of hardness and yield strength. Changes were not noticeable at the microstructural level of the formed samples. Meanwhile, samples from which higher plastic deformation stress values were calculated were not those absorbing higher impact energy when Charpy specimen cut from plate and stretch-bent samples were tested. The maximum relieved residual stress in the parent material was predominantly compressive and represents in magnitude approximately 12 percent (average for the three directions) of its original yield strength. In the stretch-bent samples, the relieved residual stress was compressive in the outer curved section with a magnitude about 50 percent of the parent material yield strength and tensile in the inner curved section with a magnitude approximately 25 percent of the parent material yield strength.
- Full Text:
- Date Issued: 2012
Characteristics of the modern toursist in the Nelson Mandela Metropolitan area
- Authors: Shrosbree, Laura Tania
- Date: 2012
- Subjects: Sustainable tourism -- South Africa -- Nelson Mandela Bay , Tourism -- South Africa -- Nelson Mandela Bay , Tourism -- Social aspects , Civilization, Modern
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9369 , http://hdl.handle.net/10948/d1012110 , Sustainable tourism -- South Africa -- Nelson Mandela Bay , Tourism -- South Africa -- Nelson Mandela Bay , Tourism -- Social aspects , Civilization, Modern
- Description: Until the nineteenth century, travel was undertaken only by the elite. With the introduction of rail, mass travel was available for the first time, and new faraway destinations became accessible to all. During the 20th century travel became more destination-orientated. And now, in the 21st century, travel is a new economy, resulting in the tourism industry. The focus of the tourism industry has shifted from air travel, weekend getaways and day trips, to a total experience of the destination. A new era in tourism has arrived with a new kind of tourism experience, one that is sustainable, socially responsible and flexible. At the forefront of this industry is a tourist who is more educated, experienced, knowledgeable, independent and demanding. This tourist demands new or different products/services, is harder to please than the traditional tourist, is well-informed and knows what he/she wants and where he/she wants to go. This is the modern tourist. The objectives of the study were to identify the typical characteristics of the so-called modern consumer, determine which of these characteristics were prevalent among consumers living in the Nelson Mandela Metropolitan Area and whether these characteristics could be used to cluster respondents into segments. The results of the study will assist organisations, within the tourism industry, in dealing with the changing demands of the modern tourist. The literature study contextualised the modern tourist within the tourism industry and provides an overview of the demographic and behavioural factors, which form the basis of the modern tourist‟s development. The demographic factors discussed were age, education, income, gender and household size. The non demographic factors identified and explained were variety seeking, quest for self-identity, quest for authenticity, knowledgeable, experience sharing and time poor. The empirical information was obtained via self-administered questionnaires. Two hundred useable questionnaires were completed by respondents in the Nelson Mandela Metropolitan Area. Statistica version 10 was used to analyse the data received. The principal component factor analysis yielded six behavioural factors, namely meaningful experiences, time poor, knowledge, authenticity and experience sharing. Until the nineteenth century, travel was undertaken only by the elite. With the introduction of rail, mass travel was available for the first time, and new faraway destinations became accessible to all. During the 20th century travel became more destination-orientated. And now, in the 21st century, travel is a new economy, resulting in the tourism industry. The focus of the tourism industry has shifted from air travel, weekend getaways and day trips, to a total experience of the destination. A new era in tourism has arrived with a new kind of tourism experience, one that is sustainable, socially responsible and flexible. At the forefront of this industry is a tourist who is more educated, experienced, knowledgeable, independent and demanding. This tourist demands new or different products/services, is harder to please than the traditional tourist, is well-informed and knows what he/she wants and where he/she wants to go. This is the modern tourist. The objectives of the study were to identify the typical characteristics of the so-called modern consumer, determine which of these characteristics were prevalent among consumers living in the Nelson Mandela Metropolitan Area and whether these characteristics could be used to cluster respondents into segments. The results of the study will assist organisations, within the tourism industry, in dealing with the changing demands of the modern tourist. The literature study contextualised the modern tourist within the tourism industry and provides an overview of the demographic and behavioural factors, which form the basis of the modern tourist‟s development. The demographic factors discussed were age, education, income, gender and household size. The non demographic factors identified and explained were variety seeking, quest for self-identity, quest for authenticity, knowledgeable, experience sharing and time poor. The empirical information was obtained via self-administered questionnaires. Two hundred useable questionnaires were completed by respondents in the Nelson Mandela Metropolitan Area. Statistica version 10 was used to analyse the data received. The principal component factor analysis yielded six behavioural factors, namely meaningful experiences, time poor, knowledge, authenticity and experience sharing. The data analysis revealed three distinct clusters, namely Postmodernists, Traditionalists and Modernists. Each cluster had unique demographic and behavioural characteristics with the result that modern tourists could be grouped into distinct clusters according to their demographic and behavioural characteristics. This will enable the tourism industry to tailor-make their marketing strategies according to these clusters.he data analysis revealed three distinct clusters, namely Postmodernists, Traditionalists and Modernists. Each cluster had unique demographic and behavioural characteristics with the result that modern tourists could be grouped into distinct clusters according to their demographic and behavioural characteristics. This will enable the tourism industry to tailor-make their marketing strategies according to these clusters.
- Full Text:
- Date Issued: 2012
- Authors: Shrosbree, Laura Tania
- Date: 2012
- Subjects: Sustainable tourism -- South Africa -- Nelson Mandela Bay , Tourism -- South Africa -- Nelson Mandela Bay , Tourism -- Social aspects , Civilization, Modern
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9369 , http://hdl.handle.net/10948/d1012110 , Sustainable tourism -- South Africa -- Nelson Mandela Bay , Tourism -- South Africa -- Nelson Mandela Bay , Tourism -- Social aspects , Civilization, Modern
- Description: Until the nineteenth century, travel was undertaken only by the elite. With the introduction of rail, mass travel was available for the first time, and new faraway destinations became accessible to all. During the 20th century travel became more destination-orientated. And now, in the 21st century, travel is a new economy, resulting in the tourism industry. The focus of the tourism industry has shifted from air travel, weekend getaways and day trips, to a total experience of the destination. A new era in tourism has arrived with a new kind of tourism experience, one that is sustainable, socially responsible and flexible. At the forefront of this industry is a tourist who is more educated, experienced, knowledgeable, independent and demanding. This tourist demands new or different products/services, is harder to please than the traditional tourist, is well-informed and knows what he/she wants and where he/she wants to go. This is the modern tourist. The objectives of the study were to identify the typical characteristics of the so-called modern consumer, determine which of these characteristics were prevalent among consumers living in the Nelson Mandela Metropolitan Area and whether these characteristics could be used to cluster respondents into segments. The results of the study will assist organisations, within the tourism industry, in dealing with the changing demands of the modern tourist. The literature study contextualised the modern tourist within the tourism industry and provides an overview of the demographic and behavioural factors, which form the basis of the modern tourist‟s development. The demographic factors discussed were age, education, income, gender and household size. The non demographic factors identified and explained were variety seeking, quest for self-identity, quest for authenticity, knowledgeable, experience sharing and time poor. The empirical information was obtained via self-administered questionnaires. Two hundred useable questionnaires were completed by respondents in the Nelson Mandela Metropolitan Area. Statistica version 10 was used to analyse the data received. The principal component factor analysis yielded six behavioural factors, namely meaningful experiences, time poor, knowledge, authenticity and experience sharing. Until the nineteenth century, travel was undertaken only by the elite. With the introduction of rail, mass travel was available for the first time, and new faraway destinations became accessible to all. During the 20th century travel became more destination-orientated. And now, in the 21st century, travel is a new economy, resulting in the tourism industry. The focus of the tourism industry has shifted from air travel, weekend getaways and day trips, to a total experience of the destination. A new era in tourism has arrived with a new kind of tourism experience, one that is sustainable, socially responsible and flexible. At the forefront of this industry is a tourist who is more educated, experienced, knowledgeable, independent and demanding. This tourist demands new or different products/services, is harder to please than the traditional tourist, is well-informed and knows what he/she wants and where he/she wants to go. This is the modern tourist. The objectives of the study were to identify the typical characteristics of the so-called modern consumer, determine which of these characteristics were prevalent among consumers living in the Nelson Mandela Metropolitan Area and whether these characteristics could be used to cluster respondents into segments. The results of the study will assist organisations, within the tourism industry, in dealing with the changing demands of the modern tourist. The literature study contextualised the modern tourist within the tourism industry and provides an overview of the demographic and behavioural factors, which form the basis of the modern tourist‟s development. The demographic factors discussed were age, education, income, gender and household size. The non demographic factors identified and explained were variety seeking, quest for self-identity, quest for authenticity, knowledgeable, experience sharing and time poor. The empirical information was obtained via self-administered questionnaires. Two hundred useable questionnaires were completed by respondents in the Nelson Mandela Metropolitan Area. Statistica version 10 was used to analyse the data received. The principal component factor analysis yielded six behavioural factors, namely meaningful experiences, time poor, knowledge, authenticity and experience sharing. The data analysis revealed three distinct clusters, namely Postmodernists, Traditionalists and Modernists. Each cluster had unique demographic and behavioural characteristics with the result that modern tourists could be grouped into distinct clusters according to their demographic and behavioural characteristics. This will enable the tourism industry to tailor-make their marketing strategies according to these clusters.he data analysis revealed three distinct clusters, namely Postmodernists, Traditionalists and Modernists. Each cluster had unique demographic and behavioural characteristics with the result that modern tourists could be grouped into distinct clusters according to their demographic and behavioural characteristics. This will enable the tourism industry to tailor-make their marketing strategies according to these clusters.
- Full Text:
- Date Issued: 2012
Characterization of 2,(3)-tetra-(4-oxo-benzamide) phthalocyaninato cobalt (II)—single walled carbon nanotube conjugate platforms and their use in electrocatalysis of amitrole
- Mugadza, Tawanda, Arslanoğlu, Yasin, Nyokong, Tebello
- Authors: Mugadza, Tawanda , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244382 , vital:51252 , xlink:href="https://doi.org/10.1016/j.electacta.2012.02.041"
- Description: In this paper we report on the use of carboxylic acid functionalized single walled carbon nanotubes (SWCNT) in the synthesis of 2,(3)-tetra-(4-oxo-benzamide)phthalocyaninato cobalt (II)–single walled carbon nanotube conjugates (CoTOBPc–SWCNT), their characterization and application in the electrocatalytic oxidation of amitrole. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used for the detection of amitrole on the modified glassy carbon electrode. The catalytic rate constant was 1.6 × 103 M−1 s−1 and the apparent electron rate transfer constant was 1.5 × 10−5 cm s−1. The linear dynamic range was 1.0 × 10−6–3.0 × 10−5 M, with a sensitivity of ∼1.13 A mol−1 L cm−2.
- Full Text:
- Date Issued: 2012
- Authors: Mugadza, Tawanda , Arslanoğlu, Yasin , Nyokong, Tebello
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/244382 , vital:51252 , xlink:href="https://doi.org/10.1016/j.electacta.2012.02.041"
- Description: In this paper we report on the use of carboxylic acid functionalized single walled carbon nanotubes (SWCNT) in the synthesis of 2,(3)-tetra-(4-oxo-benzamide)phthalocyaninato cobalt (II)–single walled carbon nanotube conjugates (CoTOBPc–SWCNT), their characterization and application in the electrocatalytic oxidation of amitrole. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used for the detection of amitrole on the modified glassy carbon electrode. The catalytic rate constant was 1.6 × 103 M−1 s−1 and the apparent electron rate transfer constant was 1.5 × 10−5 cm s−1. The linear dynamic range was 1.0 × 10−6–3.0 × 10−5 M, with a sensitivity of ∼1.13 A mol−1 L cm−2.
- Full Text:
- Date Issued: 2012
Characterization of cell mismatch in photovoltaic modules using electroluminescence and associated electro-optic techniques
- Authors: Crozier, Jacqueline Louise
- Date: 2012
- Subjects: Photovoltaic cells , Solar cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10545 , http://hdl.handle.net/10948/d1015059
- Description: Solar cells allow the energy from the sun to be converted into electrical energy; this makes solar energy much more environmentally friendly than fossil fuel energy sources. These solar cells are connected together in a photovoltaic (PV) module to provide the higher current, voltage and power outputs necessary for electrical applications. However, the performance of the PV module is limited by the performance of the individual cells. Cell mismatch occurs when some cells are damaged or shaded and produce lower current output than the other cells in the series connected string. The cell mismatch lowers the module performance and can result in further damage as the weak cells are reverse biased and dissipate heat. Bypass diodes can be connected into the module to increase the module current output and prevent further damage. Since cell mismatch results in a significant decrease in the performance of deployed modules it is important to fully understand and characterise its effect on PV modules. PV modules can be characterised using various techniques, each providing important information about the performance of the module. Most commonly the current-voltage (I-V) characteristic curve of a module is measured in outdoor, fully illuminated conditions. This allows performance parameters such as short circuit current (Isc), open circuit voltage (Voc) and maximum power (Pmax) to be determined. In addition to this the shape of the curve allows device parameters like series and shunt resistances to be determined using parameter extraction algorithms like Particle Swarm Optimisation (PSO). The extracted parameters can be entered into the diode equation to model the I-V curve of the module. The I-V characteristic of the module can also be used to identify poor current producing cells in the module by using the worst-case cell determination method. In this technique a cell is shaded and the greater the drop in current in the whole module the better the current production of the shaded cell. The photoresponse of cells in a module can be determined by the Large-area Light Beam Induced Current (LA-LBIC) technique which involves scanning a module with a laser beam and recording the current generated. Electroluminescence (EL) is emitted by a forward biased PV module and is used to identify defects in cell material. Defects such as cracks and broken fingers can be detected as well as material features such as grain boundaries. These techniques are used to in conjunction to characterise the modules used in this study. The modules investigated in this study each exhibit cell mismatch resulting from different causes. Each module is characterised using a combination of characterisation techniques which allows the effect of cell mismatch be investigated. EL imaging enabled cracks and defects, invisible to the naked eye, to be detected allowing the reduced performance observed in I-V curves to be explained. It was seen that the cracked cells have a significant effect on the current produced by a string, while the effect of delaminated areas is less severe. Hot spots are observed on weak cells indicating they are in reverse bias conditions and will degrade further with time. PSO parameter extraction from I-V curves revealed that the effect of module degradation of device parameters like series and shunt resistances. A module with cracked cells and degradation of the antireflective coating has low shunt resistance indicating current losses due to shunting. Similar shunting is observed in a module with delamination and moisture ingress. The extracted parameters are used to simulate the I-V curves of modules with reasonable fit. The fit could be improved around the “knee” of the I-V curve by improving the methods of parameter extraction. This study has shown the effects of cell mismatch on the performance and I-V curves of the PV modules. The different causes of cell mismatch are discussed and modules with different cell configuration and damage are characterised. The characterisation techniques used on each module provide information about the photoresponse, current generation, material properties and cell defects. A comprehensive understanding of these techniques allows the cell mismatch in the modules to be fully characterized.
- Full Text:
- Date Issued: 2012
- Authors: Crozier, Jacqueline Louise
- Date: 2012
- Subjects: Photovoltaic cells , Solar cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10545 , http://hdl.handle.net/10948/d1015059
- Description: Solar cells allow the energy from the sun to be converted into electrical energy; this makes solar energy much more environmentally friendly than fossil fuel energy sources. These solar cells are connected together in a photovoltaic (PV) module to provide the higher current, voltage and power outputs necessary for electrical applications. However, the performance of the PV module is limited by the performance of the individual cells. Cell mismatch occurs when some cells are damaged or shaded and produce lower current output than the other cells in the series connected string. The cell mismatch lowers the module performance and can result in further damage as the weak cells are reverse biased and dissipate heat. Bypass diodes can be connected into the module to increase the module current output and prevent further damage. Since cell mismatch results in a significant decrease in the performance of deployed modules it is important to fully understand and characterise its effect on PV modules. PV modules can be characterised using various techniques, each providing important information about the performance of the module. Most commonly the current-voltage (I-V) characteristic curve of a module is measured in outdoor, fully illuminated conditions. This allows performance parameters such as short circuit current (Isc), open circuit voltage (Voc) and maximum power (Pmax) to be determined. In addition to this the shape of the curve allows device parameters like series and shunt resistances to be determined using parameter extraction algorithms like Particle Swarm Optimisation (PSO). The extracted parameters can be entered into the diode equation to model the I-V curve of the module. The I-V characteristic of the module can also be used to identify poor current producing cells in the module by using the worst-case cell determination method. In this technique a cell is shaded and the greater the drop in current in the whole module the better the current production of the shaded cell. The photoresponse of cells in a module can be determined by the Large-area Light Beam Induced Current (LA-LBIC) technique which involves scanning a module with a laser beam and recording the current generated. Electroluminescence (EL) is emitted by a forward biased PV module and is used to identify defects in cell material. Defects such as cracks and broken fingers can be detected as well as material features such as grain boundaries. These techniques are used to in conjunction to characterise the modules used in this study. The modules investigated in this study each exhibit cell mismatch resulting from different causes. Each module is characterised using a combination of characterisation techniques which allows the effect of cell mismatch be investigated. EL imaging enabled cracks and defects, invisible to the naked eye, to be detected allowing the reduced performance observed in I-V curves to be explained. It was seen that the cracked cells have a significant effect on the current produced by a string, while the effect of delaminated areas is less severe. Hot spots are observed on weak cells indicating they are in reverse bias conditions and will degrade further with time. PSO parameter extraction from I-V curves revealed that the effect of module degradation of device parameters like series and shunt resistances. A module with cracked cells and degradation of the antireflective coating has low shunt resistance indicating current losses due to shunting. Similar shunting is observed in a module with delamination and moisture ingress. The extracted parameters are used to simulate the I-V curves of modules with reasonable fit. The fit could be improved around the “knee” of the I-V curve by improving the methods of parameter extraction. This study has shown the effects of cell mismatch on the performance and I-V curves of the PV modules. The different causes of cell mismatch are discussed and modules with different cell configuration and damage are characterised. The characterisation techniques used on each module provide information about the photoresponse, current generation, material properties and cell defects. A comprehensive understanding of these techniques allows the cell mismatch in the modules to be fully characterized.
- Full Text:
- Date Issued: 2012