A critical investigation of a Future Search Conference as a planned organisational change initiative within the National Health Training Network in Namibia
- Authors: Hausiku, Marthina Ndahepa
- Date: 2006
- Subjects: Future Search Conference National Health Training Network Organizational change -- Namibia Research -- Methodology Interviewing
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1478 , http://hdl.handle.net/10962/d1003359
- Description: “The world is changing faster than the experts” (Weisbord & Janoff, 2000:xi). Change, according to Meyer & Botha (2000:223), is the movement of people from a current state to a defined, different, improved and desired new state. Change is needed in all organisations because it has direct influence on the organisation’s performance, and the National Health Training Network in Namibia is no exception. The Future Search Conference as a powerful organisation development strategy, can help people transform their capacity for action. The National Health Training Network (NHTN), like any other institution, has been experiencing some managerial/administrative problems. I, being a member of the NHTN, together with most of the organisation, was faced with the challenge of not knowing what to do. Learning about approaches that might help organisations to develop, concepts such as organisation development in general and Future Search in particular, I developed an interest especially in the Future Search Conference. My interest was based on successful developmental stories of Future Search Conferences in organisations across the world. I decided to introduce the Future Search Conference to our organisation, which I thought might be a remedy for our problems at a later stage. The aim of the study was to investigate participants' experiences and the perception of the Future Search Conference as an approach to organisational change, through interviews. The study found that Future Search was a new concept/approach to the NHTN as well as to the whole Ministry, and it is different from the traditional strategic planning. The difference is seen in the way Future Search involves all stakeholders in issues of concern, while strategic planning involves only managers. The responses revealed the willingness of participants to implement the Future Search Conference in their organisation. Data also revealed, however, that it was not clear how ready the managers were to carry out this task, as they are the gatekeepers. Participants suggested a separate Future Search Conference with managers, to sensitise them to the approach, so that they can see whether it addresses the values and goals of the organisation and can be implemented for developmental purposes.
- Full Text:
- Date Issued: 2006
- Authors: Hausiku, Marthina Ndahepa
- Date: 2006
- Subjects: Future Search Conference National Health Training Network Organizational change -- Namibia Research -- Methodology Interviewing
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1478 , http://hdl.handle.net/10962/d1003359
- Description: “The world is changing faster than the experts” (Weisbord & Janoff, 2000:xi). Change, according to Meyer & Botha (2000:223), is the movement of people from a current state to a defined, different, improved and desired new state. Change is needed in all organisations because it has direct influence on the organisation’s performance, and the National Health Training Network in Namibia is no exception. The Future Search Conference as a powerful organisation development strategy, can help people transform their capacity for action. The National Health Training Network (NHTN), like any other institution, has been experiencing some managerial/administrative problems. I, being a member of the NHTN, together with most of the organisation, was faced with the challenge of not knowing what to do. Learning about approaches that might help organisations to develop, concepts such as organisation development in general and Future Search in particular, I developed an interest especially in the Future Search Conference. My interest was based on successful developmental stories of Future Search Conferences in organisations across the world. I decided to introduce the Future Search Conference to our organisation, which I thought might be a remedy for our problems at a later stage. The aim of the study was to investigate participants' experiences and the perception of the Future Search Conference as an approach to organisational change, through interviews. The study found that Future Search was a new concept/approach to the NHTN as well as to the whole Ministry, and it is different from the traditional strategic planning. The difference is seen in the way Future Search involves all stakeholders in issues of concern, while strategic planning involves only managers. The responses revealed the willingness of participants to implement the Future Search Conference in their organisation. Data also revealed, however, that it was not clear how ready the managers were to carry out this task, as they are the gatekeepers. Participants suggested a separate Future Search Conference with managers, to sensitise them to the approach, so that they can see whether it addresses the values and goals of the organisation and can be implemented for developmental purposes.
- Full Text:
- Date Issued: 2006
A critical investigation of the effectiveness of warm-ups as technical exercises for the improvement of choral tone : a case study of the Eastern Cape Children's Choir
- Authors: Van Zyl, Lionel
- Date: 2006
- Subjects: Choral singing Studies and exercises , Choral singing -- Instruction and study , Music rehearsals
- Language: English
- Type: Thesis , Masters , MMus
- Identifier: vital:8513 , http://hdl.handle.net/10948/634 , Choral singing Studies and exercises , Choral singing -- Instruction and study , Music rehearsals
- Description: This is a research project based on the author’s experience of more than 20 years as conductor of the Eastern Cape Childrens Choir. It investigates the effectiveness of technical exercises - with special reference to selected “warm-up” exercises - in creating a superior choral tone in the children’s choir. The investigation is motivated by the fact that it is an ongoing challenge to effectively overcome problems with intonation and poor choral tone, problems which are mostly caused by lack of attention to pure vowel formation. Toward this end, a practical “tool box” of vocal exercises for the children’s choir is ultimately proposed. The toolbox is based on one single exercise with different variations. Each variation is designed to address multiple vocal needs and to correct vocal production during singing. In this manner a great many technical aspects are covered with the simplest of means and in the shortest possible time, bearing in mind that the rehearsal session allows limited time to focus on such matters to the exclusion of all else.
- Full Text:
- Date Issued: 2006
- Authors: Van Zyl, Lionel
- Date: 2006
- Subjects: Choral singing Studies and exercises , Choral singing -- Instruction and study , Music rehearsals
- Language: English
- Type: Thesis , Masters , MMus
- Identifier: vital:8513 , http://hdl.handle.net/10948/634 , Choral singing Studies and exercises , Choral singing -- Instruction and study , Music rehearsals
- Description: This is a research project based on the author’s experience of more than 20 years as conductor of the Eastern Cape Childrens Choir. It investigates the effectiveness of technical exercises - with special reference to selected “warm-up” exercises - in creating a superior choral tone in the children’s choir. The investigation is motivated by the fact that it is an ongoing challenge to effectively overcome problems with intonation and poor choral tone, problems which are mostly caused by lack of attention to pure vowel formation. Toward this end, a practical “tool box” of vocal exercises for the children’s choir is ultimately proposed. The toolbox is based on one single exercise with different variations. Each variation is designed to address multiple vocal needs and to correct vocal production during singing. In this manner a great many technical aspects are covered with the simplest of means and in the shortest possible time, bearing in mind that the rehearsal session allows limited time to focus on such matters to the exclusion of all else.
- Full Text:
- Date Issued: 2006
A detailed investigation of interoperability for web services
- Authors: Wright, Madeleine
- Date: 2006
- Subjects: Firefox , Web services , World Wide Web , Computer architecture , C# (Computer program language) , PHP (Computer program language) , Java (Computer program language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4592 , http://hdl.handle.net/10962/d1004832 , Firefox , Web services , World Wide Web , Computer architecture , C# (Computer program language) , PHP (Computer program language) , Java (Computer program language)
- Description: The thesis presents a qualitative survey of web services' interoperability, offering a snapshot of development and trends at the end of 2005. It starts by examining the beginnings of web services in earlier distributed computing and middleware technologies, determining the distance from these approaches evident in current web-services architectures. It establishes a working definition of web services, examining the protocols that now seek to define it and the extent to which they contribute to its most crucial feature, interoperability. The thesis then considers the REST approach to web services as being in a class of its own, concluding that this approach to interoperable distributed computing is not only the simplest but also the most interoperable. It looks briefly at interoperability issues raised by technologies in the wider arena of Service Oriented Architecture. The chapter on protocols is complemented by a chapter that validates the qualitative findings by examining web services in practice. These have been implemented by a variety of toolkits and on different platforms. Included in the study is a preliminary examination of JAX-WS, the replacement for JAX-RPC, which is still under development. Although the main language of implementation is Java, the study includes services in C# and PHP and one implementation of a client using a Firefox extension. The study concludes that different forms of web service may co-exist with earlier middleware technologies. While remaining aware that there are still pitfalls that might yet derail the movement towards greater interoperability, the conclusion sounds an optimistic note that recent cooperation between different vendors may yet result in a solution that achieves interoperability through core web-service standards.
- Full Text:
- Date Issued: 2006
- Authors: Wright, Madeleine
- Date: 2006
- Subjects: Firefox , Web services , World Wide Web , Computer architecture , C# (Computer program language) , PHP (Computer program language) , Java (Computer program language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4592 , http://hdl.handle.net/10962/d1004832 , Firefox , Web services , World Wide Web , Computer architecture , C# (Computer program language) , PHP (Computer program language) , Java (Computer program language)
- Description: The thesis presents a qualitative survey of web services' interoperability, offering a snapshot of development and trends at the end of 2005. It starts by examining the beginnings of web services in earlier distributed computing and middleware technologies, determining the distance from these approaches evident in current web-services architectures. It establishes a working definition of web services, examining the protocols that now seek to define it and the extent to which they contribute to its most crucial feature, interoperability. The thesis then considers the REST approach to web services as being in a class of its own, concluding that this approach to interoperable distributed computing is not only the simplest but also the most interoperable. It looks briefly at interoperability issues raised by technologies in the wider arena of Service Oriented Architecture. The chapter on protocols is complemented by a chapter that validates the qualitative findings by examining web services in practice. These have been implemented by a variety of toolkits and on different platforms. Included in the study is a preliminary examination of JAX-WS, the replacement for JAX-RPC, which is still under development. Although the main language of implementation is Java, the study includes services in C# and PHP and one implementation of a client using a Firefox extension. The study concludes that different forms of web service may co-exist with earlier middleware technologies. While remaining aware that there are still pitfalls that might yet derail the movement towards greater interoperability, the conclusion sounds an optimistic note that recent cooperation between different vendors may yet result in a solution that achieves interoperability through core web-service standards.
- Full Text:
- Date Issued: 2006
A Discussion Of Wireless Security Technologies
- Janse van Rensburg, Johanna, Irwin, Barry V W
- Authors: Janse van Rensburg, Johanna , Irwin, Barry V W
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429852 , vital:72645 , https://www.researchgate.net/profile/Barry-Ir-win/publication/228864029_A_DISCUSSION_OF_WIRELESS_SECURITY_TECHNOLOGIES/links/53e9c5190cf28f342f41492b/A-DISCUSSION-OF-WIRELESS-SECURITY-TECHNOLOGIES.pdf
- Description: The 802.11 standard contains a number of problems, ranging from in-terference, co-existence issues, exposed terminal problems and regula-tions to security. Despite all of these it has become a widely deployed technology as an extension of companies’ networks to provide mobility. In this paper the focus will be on the security issues of 802.11. Several solutions for the deployment of 802.11 security exists today, ranging from WEP, WPA, VPN and 802.11 i, each providing a different level of security. These technologies contain pros and cons which need to be understood in order to implement an appropriate solution suited to a specific scenario.
- Full Text:
- Date Issued: 2006
- Authors: Janse van Rensburg, Johanna , Irwin, Barry V W
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/429852 , vital:72645 , https://www.researchgate.net/profile/Barry-Ir-win/publication/228864029_A_DISCUSSION_OF_WIRELESS_SECURITY_TECHNOLOGIES/links/53e9c5190cf28f342f41492b/A-DISCUSSION-OF-WIRELESS-SECURITY-TECHNOLOGIES.pdf
- Description: The 802.11 standard contains a number of problems, ranging from in-terference, co-existence issues, exposed terminal problems and regula-tions to security. Despite all of these it has become a widely deployed technology as an extension of companies’ networks to provide mobility. In this paper the focus will be on the security issues of 802.11. Several solutions for the deployment of 802.11 security exists today, ranging from WEP, WPA, VPN and 802.11 i, each providing a different level of security. These technologies contain pros and cons which need to be understood in order to implement an appropriate solution suited to a specific scenario.
- Full Text:
- Date Issued: 2006
A field investigation of physical workloads imposed on harvesters in South African forestry
- Authors: Christie, Candice Jo-Anne
- Date: 2006
- Subjects: Forests and forestry -- South Africa Employees -- Workload Forest products industry -- South Africa Work -- Physiological aspects Heart rate monitoring Foresters -- South Africa -- Workload Oxygen -- Physiological transport
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5122 , http://hdl.handle.net/10962/d1005200
- Description: The focus of this field investigation was an analysis of the work demands being placed on South African forestry workers, in particular Chainsaw Operators and Stackers. Working postures, physiological and perceptual responses were assessed on a sample of 58 workers (29 Chainsaw Operators and 29 Stackers) during a ‘normal’ working shift. Body mass was measured before and after work in order to determine dehydration levels. Polar heart rate monitors were fitted to six workers each day over a period of two weeks in order to record ‘working’ heart rates. Fluid and food intake was monitored and recorded during this initial data collection phase. The Rating of Perceived Exertion and Body Discomfort Scales were explained in Zulu, their native language, and workers were asked to rate their perceptions of effort at regular intervals during work, while areas and intensity of body discomfort was obtained on completion of work. After completing a work shift, a 30 minute ‘recovery’ period was given, thereafter a portable ergospirometer, the k4b², was attached to the worker who then participated in a progressive, submaximal step test for the purpose of establishing individual, and group, heart rate-oxygen uptake (HR/VO[subscript 2]) regressions for predicting oxygen uptake from ‘working’ heart rate responses. These procedures were repeated four weeks later following the introduction of a fluid and nutritional supplement during work which was delivered to the workers while they were executing their tasks. The results revealed awkward working postures with a predominance of trunk flexion during all the harvesting tasks; these postures, adopted for long periods during work, are very likely to lead to the development of musculoskeletal injuries. The mean working heart rates were 123.3 bt.min[superscript (-1)] and 117.6 bt.min[superscript (-1)] during chainsaw operations and stacking respectively. During the step test, the mean heart rate and oxygen uptake responses were 127.9 bt.min[superscript (-1)] and 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Chainsaw Operators) and 116.9 bt.min[superscript (-1)] and 24.0 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Stackers), revealing no significant difference between the ‘working’ heart rates and the heart rates recorded during the step test. Physiological responses were analyzed over the full work shift which was divided into four quarters. Heart rate and oxygen uptake were significantly higher during the last half of the Chainsaw Operators’ work shift compared to the first half. Heart rate increased from 120.7 bt.min[superscript (-1)] during the first quarter to 127.4 bt.min[superscript (-1)] during the last quarter of chainsaw operations. Likewise, oxygen uptake increased from 19.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] to 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] from the first to the last quarter of work. During stacking the heart rate (mean of 117.6 bt.min[superscript (-1)]) and oxygen uptake (mean of 24.6 ml.kg[superscript (-1)].min[superscript (-1)]) responses remained stable over the duration of the working shift. Workers lost, on average, 2.8% body mass during work while felling and cross-cutting and 3.6% during stacking. This reduced significantly to a loss of 0.4% body mass when re-tested following the introduction of water and food during the work period. Likewise, the energy deficit was significantly improved due to the introduction of a nutritional supplement. Pre-intervention the deficit was 8861.8 kJ (Chainsaw Operators) and 8804.2 kJ (Stackers) while in the post-intervention phase this deficit was reduced by approximately 50% for both groups of workers.
- Full Text:
- Date Issued: 2006
- Authors: Christie, Candice Jo-Anne
- Date: 2006
- Subjects: Forests and forestry -- South Africa Employees -- Workload Forest products industry -- South Africa Work -- Physiological aspects Heart rate monitoring Foresters -- South Africa -- Workload Oxygen -- Physiological transport
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5122 , http://hdl.handle.net/10962/d1005200
- Description: The focus of this field investigation was an analysis of the work demands being placed on South African forestry workers, in particular Chainsaw Operators and Stackers. Working postures, physiological and perceptual responses were assessed on a sample of 58 workers (29 Chainsaw Operators and 29 Stackers) during a ‘normal’ working shift. Body mass was measured before and after work in order to determine dehydration levels. Polar heart rate monitors were fitted to six workers each day over a period of two weeks in order to record ‘working’ heart rates. Fluid and food intake was monitored and recorded during this initial data collection phase. The Rating of Perceived Exertion and Body Discomfort Scales were explained in Zulu, their native language, and workers were asked to rate their perceptions of effort at regular intervals during work, while areas and intensity of body discomfort was obtained on completion of work. After completing a work shift, a 30 minute ‘recovery’ period was given, thereafter a portable ergospirometer, the k4b², was attached to the worker who then participated in a progressive, submaximal step test for the purpose of establishing individual, and group, heart rate-oxygen uptake (HR/VO[subscript 2]) regressions for predicting oxygen uptake from ‘working’ heart rate responses. These procedures were repeated four weeks later following the introduction of a fluid and nutritional supplement during work which was delivered to the workers while they were executing their tasks. The results revealed awkward working postures with a predominance of trunk flexion during all the harvesting tasks; these postures, adopted for long periods during work, are very likely to lead to the development of musculoskeletal injuries. The mean working heart rates were 123.3 bt.min[superscript (-1)] and 117.6 bt.min[superscript (-1)] during chainsaw operations and stacking respectively. During the step test, the mean heart rate and oxygen uptake responses were 127.9 bt.min[superscript (-1)] and 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Chainsaw Operators) and 116.9 bt.min[superscript (-1)] and 24.0 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] (Stackers), revealing no significant difference between the ‘working’ heart rates and the heart rates recorded during the step test. Physiological responses were analyzed over the full work shift which was divided into four quarters. Heart rate and oxygen uptake were significantly higher during the last half of the Chainsaw Operators’ work shift compared to the first half. Heart rate increased from 120.7 bt.min[superscript (-1)] during the first quarter to 127.4 bt.min[superscript (-1)] during the last quarter of chainsaw operations. Likewise, oxygen uptake increased from 19.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] to 22.9 mlO[subscript 2].kg[superscript (-1)].min[superscript (-1)] from the first to the last quarter of work. During stacking the heart rate (mean of 117.6 bt.min[superscript (-1)]) and oxygen uptake (mean of 24.6 ml.kg[superscript (-1)].min[superscript (-1)]) responses remained stable over the duration of the working shift. Workers lost, on average, 2.8% body mass during work while felling and cross-cutting and 3.6% during stacking. This reduced significantly to a loss of 0.4% body mass when re-tested following the introduction of water and food during the work period. Likewise, the energy deficit was significantly improved due to the introduction of a nutritional supplement. Pre-intervention the deficit was 8861.8 kJ (Chainsaw Operators) and 8804.2 kJ (Stackers) while in the post-intervention phase this deficit was reduced by approximately 50% for both groups of workers.
- Full Text:
- Date Issued: 2006
A financial planning model for retirement, taking into account the impact of pre-retirement funding income, age and taxation
- Authors: Barnes, Andrew
- Date: 2006
- Subjects: Retirement -- South Africa Retirement income -- Planning -- South Africa Pensions -- Planning -- South Africa Finance, Personal Investments Income tax -- Law and legislation -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:895 , http://hdl.handle.net/10962/d1004532
- Description: Individuals are often not aware of the required level of contributions needed to fund a retirement savings plan. This problem is compounded by the fact that the assistance provided to these individuals by way of commercially-available retirement planning models does not take into account the effect of income tax on the level of required retirement savings contributions and recent changes in the tax legislation to the income tax payable by individuals has had a significant effect on these required levels. As a preamble to the research process, an exploratory questionnaire was administrated to a sample of individuals, which was designed to measure the level of awareness of these individuals of the contributions to a retirement savings plan needed to fund their postretirement financial needs, and of the impact of age, the level of income and income tax on their contributions. Responses to the questionnaire indicated a low level of awareness of retirement planning amongst these individuals. A retirement planning model was then designed to test the effect of earnings, age and changes in tax legislation on the level of an individual's required monthly contributions to a retirement savings plan. Independent variables of age and income were processed using the model. These same variables were then processed using the Old Mutual and Liberty Life retirement planning models and a comparison was made between the model developed in the research and these commercially developed models, to assess their usefulness and limitations. Based on the above comparison, it appeared that the Old Mutual and Liberty Life retirement models both included the effects of the individual marginal tax rates in their calculations. However, they appeared to be using marginal tax rates which were higher than those reflected in the 2006 individual income tax tables. In addition these models did not include the effect of income tax exemptions and deductions and they therefore provided more conservative estimates than the retirement planning model designed in the research. Recent tax adjustments have had the effect of greatly increasing the after-tax income of individuals and therefore it is important to include the effects of changes in tax legislation in determining the monthly contributions to a retirement savings plan.
- Full Text:
- Date Issued: 2006
- Authors: Barnes, Andrew
- Date: 2006
- Subjects: Retirement -- South Africa Retirement income -- Planning -- South Africa Pensions -- Planning -- South Africa Finance, Personal Investments Income tax -- Law and legislation -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:895 , http://hdl.handle.net/10962/d1004532
- Description: Individuals are often not aware of the required level of contributions needed to fund a retirement savings plan. This problem is compounded by the fact that the assistance provided to these individuals by way of commercially-available retirement planning models does not take into account the effect of income tax on the level of required retirement savings contributions and recent changes in the tax legislation to the income tax payable by individuals has had a significant effect on these required levels. As a preamble to the research process, an exploratory questionnaire was administrated to a sample of individuals, which was designed to measure the level of awareness of these individuals of the contributions to a retirement savings plan needed to fund their postretirement financial needs, and of the impact of age, the level of income and income tax on their contributions. Responses to the questionnaire indicated a low level of awareness of retirement planning amongst these individuals. A retirement planning model was then designed to test the effect of earnings, age and changes in tax legislation on the level of an individual's required monthly contributions to a retirement savings plan. Independent variables of age and income were processed using the model. These same variables were then processed using the Old Mutual and Liberty Life retirement planning models and a comparison was made between the model developed in the research and these commercially developed models, to assess their usefulness and limitations. Based on the above comparison, it appeared that the Old Mutual and Liberty Life retirement models both included the effects of the individual marginal tax rates in their calculations. However, they appeared to be using marginal tax rates which were higher than those reflected in the 2006 individual income tax tables. In addition these models did not include the effect of income tax exemptions and deductions and they therefore provided more conservative estimates than the retirement planning model designed in the research. Recent tax adjustments have had the effect of greatly increasing the after-tax income of individuals and therefore it is important to include the effects of changes in tax legislation in determining the monthly contributions to a retirement savings plan.
- Full Text:
- Date Issued: 2006
A framework for responsive content adaptation in electronic display networks
- Authors: West, Philip
- Date: 2006
- Subjects: Computer networks , Cell phone systems , Wireless communication systems , Mobile communication systems , HTML (Document markup language) , XML (Document markup language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4589 , http://hdl.handle.net/10962/d1004824 , Computer networks , Cell phone systems , Wireless communication systems , Mobile communication systems , HTML (Document markup language) , XML (Document markup language)
- Description: Recent trends show an increase in the availability and functionality of handheld devices, wireless network technology, and electronic display networks. We propose the novel integration of these technologies to provide wireless access to content delivered to large-screen display systems. Content adaptation is used as a method of reformatting web pages to display more appropriately on handheld devices, and to remove unwanted content. A framework is presented that facilitates content adaptation, implemented as an adaptation layer, which is extended to provide personalization of adaptation settings and response to network conditions. The framework is implemented as a proxy server for a wireless network, and handles HTML and XML documents. Once a document has been requested by a user, the HTML/XML is retrieved and parsed, creating a Document Object Model tree representation. It is then altered according to the user’s personal settings or predefined settings, based on current network usage and the network resources available. Three adaptation techniques were implemented; spatial representation, which generates an image map of the document, text summarization, which creates a tree view representation of a document, and tag extraction, which replaces specific tags with links. Three proof-of-concept systems were developed in order to test the robustness of the framework. A system for use with digital slide shows, a digital signage system, and a generalized system for use with the internet were implemented. Testing was performed by accessing sample web pages through the content adaptation proxy server. Tag extraction works correctly for all HTML and XML document structures, whereas spatial representation and text summarization are limited to a controlled subset. Results indicate that the adaptive system has the ability to reduce average bandwidth usage, by decreasing the amount of data on the network, thereby allowing a greater number of users access to content. This suggests that responsive content adaptation has a positive influence on network performance metrics.
- Full Text:
- Date Issued: 2006
- Authors: West, Philip
- Date: 2006
- Subjects: Computer networks , Cell phone systems , Wireless communication systems , Mobile communication systems , HTML (Document markup language) , XML (Document markup language)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4589 , http://hdl.handle.net/10962/d1004824 , Computer networks , Cell phone systems , Wireless communication systems , Mobile communication systems , HTML (Document markup language) , XML (Document markup language)
- Description: Recent trends show an increase in the availability and functionality of handheld devices, wireless network technology, and electronic display networks. We propose the novel integration of these technologies to provide wireless access to content delivered to large-screen display systems. Content adaptation is used as a method of reformatting web pages to display more appropriately on handheld devices, and to remove unwanted content. A framework is presented that facilitates content adaptation, implemented as an adaptation layer, which is extended to provide personalization of adaptation settings and response to network conditions. The framework is implemented as a proxy server for a wireless network, and handles HTML and XML documents. Once a document has been requested by a user, the HTML/XML is retrieved and parsed, creating a Document Object Model tree representation. It is then altered according to the user’s personal settings or predefined settings, based on current network usage and the network resources available. Three adaptation techniques were implemented; spatial representation, which generates an image map of the document, text summarization, which creates a tree view representation of a document, and tag extraction, which replaces specific tags with links. Three proof-of-concept systems were developed in order to test the robustness of the framework. A system for use with digital slide shows, a digital signage system, and a generalized system for use with the internet were implemented. Testing was performed by accessing sample web pages through the content adaptation proxy server. Tag extraction works correctly for all HTML and XML document structures, whereas spatial representation and text summarization are limited to a controlled subset. Results indicate that the adaptive system has the ability to reduce average bandwidth usage, by decreasing the amount of data on the network, thereby allowing a greater number of users access to content. This suggests that responsive content adaptation has a positive influence on network performance metrics.
- Full Text:
- Date Issued: 2006
A framework for secure mobility in wireless overlay networks
- Authors: Chen, Hejun
- Date: 2006
- Subjects: Wireless communication systems , Computer networks
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9778 , http://hdl.handle.net/10948/819 , Wireless communication systems , Computer networks
- Description: Various wireless networks are widely deployed world wide. Current technologies employed in these networks vary widely in terms of bandwidths, latencies, frequencies, and media access methods. Most existing wireless network technologies can be divided into two categories: those that provide a low-bandwidth service over a wide geographic area, for example UMTS, and those that provide a high bandwidth service over a narrow geographic area, for example 802.11. Although it would be desirable to provide a high- bandwidth service over a wide coverage region to mobile users all the time, no single wireless network technology simultaneously satisfies these require- ments. Wireless Overlay Networks, a hierarchical structure of wireless personal area, local area, and wide area data networks, is considered as an efficient and scalable way to solve this problem. Due to the wide deployment of UMTS and 802.11 WLAN, this study attempts to combine them to implement the concept of Wireless Overlay Net- works. Furthermore, the information transmitted over this Wireless Overlay Networks is protected in terms of authentication, integrity and confidentiality. To achieve this goal, this study aims to combine GPRS, Mobile IP and IPSec to propose a framework for secure mobility in Wireless Overlay Networks. The framework is developed in three steps: Firstly, this study addresses the problem of combining GPRS and Mo- bile IP, so that GPRS users are provided with Mobile IP service. This results in presenting a uniform Mobile IP interface to peers regardless of whether mobile users use UMTS or 802.11 WLAN. Secondly, this study discovers the existing problem when combining Mobile IP and IPSec, and proposes a Dual Home Agent Architecture to achieve secure mobility. Finally, based on the output of the previous two steps, a complete framework is proposed, which achieves secure mobility in Wireless Overlay Networks, specifically, in UMTS and 802.11 WLAN. The framework also implements seamless handover when mobile users switch between UMTS and 802.11. This results in UMTS and 802.11 WLAN looking like a single network when participating in this framework, and presents seamless and secure mobility.
- Full Text:
- Date Issued: 2006
- Authors: Chen, Hejun
- Date: 2006
- Subjects: Wireless communication systems , Computer networks
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9778 , http://hdl.handle.net/10948/819 , Wireless communication systems , Computer networks
- Description: Various wireless networks are widely deployed world wide. Current technologies employed in these networks vary widely in terms of bandwidths, latencies, frequencies, and media access methods. Most existing wireless network technologies can be divided into two categories: those that provide a low-bandwidth service over a wide geographic area, for example UMTS, and those that provide a high bandwidth service over a narrow geographic area, for example 802.11. Although it would be desirable to provide a high- bandwidth service over a wide coverage region to mobile users all the time, no single wireless network technology simultaneously satisfies these require- ments. Wireless Overlay Networks, a hierarchical structure of wireless personal area, local area, and wide area data networks, is considered as an efficient and scalable way to solve this problem. Due to the wide deployment of UMTS and 802.11 WLAN, this study attempts to combine them to implement the concept of Wireless Overlay Net- works. Furthermore, the information transmitted over this Wireless Overlay Networks is protected in terms of authentication, integrity and confidentiality. To achieve this goal, this study aims to combine GPRS, Mobile IP and IPSec to propose a framework for secure mobility in Wireless Overlay Networks. The framework is developed in three steps: Firstly, this study addresses the problem of combining GPRS and Mo- bile IP, so that GPRS users are provided with Mobile IP service. This results in presenting a uniform Mobile IP interface to peers regardless of whether mobile users use UMTS or 802.11 WLAN. Secondly, this study discovers the existing problem when combining Mobile IP and IPSec, and proposes a Dual Home Agent Architecture to achieve secure mobility. Finally, based on the output of the previous two steps, a complete framework is proposed, which achieves secure mobility in Wireless Overlay Networks, specifically, in UMTS and 802.11 WLAN. The framework also implements seamless handover when mobile users switch between UMTS and 802.11. This results in UMTS and 802.11 WLAN looking like a single network when participating in this framework, and presents seamless and secure mobility.
- Full Text:
- Date Issued: 2006
A framework proposal for algorithm animation systems
- Authors: Yeh, Chih Lung
- Date: 2006
- Subjects: Computer programming , Computer algorithms , Computer graphics
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10488 , http://hdl.handle.net/10948/d1019680
- Description: The learning and analysis of algorithms and algorithm concepts are challenging to students due to the abstract and conceptual nature of algorithms. Algorithm animation is a form of technological support tool which encourages algorithm comprehension by visualising algorithms in execution. Algorithm animation can potentially be utilised to support students while learning algorithms. Despite widespread acknowledgement for the usefulness of algorithm animation in algorithm courses at tertiary institutions, no recognised framework exists upon which algorithm animation systems can be effectively modelled. This dissertation consequently focuses on the design of an extensible algorithm animation framework to support the generation of interactive algorithm animations. A literature and extant system review forms the basis for the framework design process. The result of the review is a list of requirements for a pedagogically effective algorithm animation system. The proposed framework supports the pedagogic requirements by utilising an independent layer structure to support the generation and display of algorithm animations. The effectiveness of the framework is evaluated through the implementation of a prototype algorithm animation system using sorting algorithms as a case study. This dissertation is successful in proposing a framework to support the development of algorithm animations. The prototype developed will enable the integration of algorithm animations into the Nelson Mandela Metropolitan University’s teaching model, thereby permitting the university to conduct future research relating to the usefulness of algorithm animation in algorithm courses.
- Full Text:
- Date Issued: 2006
- Authors: Yeh, Chih Lung
- Date: 2006
- Subjects: Computer programming , Computer algorithms , Computer graphics
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:10488 , http://hdl.handle.net/10948/d1019680
- Description: The learning and analysis of algorithms and algorithm concepts are challenging to students due to the abstract and conceptual nature of algorithms. Algorithm animation is a form of technological support tool which encourages algorithm comprehension by visualising algorithms in execution. Algorithm animation can potentially be utilised to support students while learning algorithms. Despite widespread acknowledgement for the usefulness of algorithm animation in algorithm courses at tertiary institutions, no recognised framework exists upon which algorithm animation systems can be effectively modelled. This dissertation consequently focuses on the design of an extensible algorithm animation framework to support the generation of interactive algorithm animations. A literature and extant system review forms the basis for the framework design process. The result of the review is a list of requirements for a pedagogically effective algorithm animation system. The proposed framework supports the pedagogic requirements by utilising an independent layer structure to support the generation and display of algorithm animations. The effectiveness of the framework is evaluated through the implementation of a prototype algorithm animation system using sorting algorithms as a case study. This dissertation is successful in proposing a framework to support the development of algorithm animations. The prototype developed will enable the integration of algorithm animations into the Nelson Mandela Metropolitan University’s teaching model, thereby permitting the university to conduct future research relating to the usefulness of algorithm animation in algorithm courses.
- Full Text:
- Date Issued: 2006
A fuzzy logic control system for a friction stir welding process
- Authors: Majara, Khotso Ernest
- Date: 2006
- Subjects: Friction welding , Fuzzy logic , Automatic control , Fuzzy systems
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9594 , http://hdl.handle.net/10948/405 , Friction welding , Fuzzy logic , Automatic control , Fuzzy systems
- Description: FSW is a welding technique invented and patented by The Welding Institute in 1991. This welding technique utilises the benefits of solid-state welding to materials regarded as difficult to weld by fusion processes. The productivity of the process was not optimised as the real-time dynamics of the material and tool changes were not considered. Furthermore, the process has a plastic weld region where no traditional modelling describing the interaction between the tool and work piece is available. Fuzzy logic technology is one of the artificial intelligent strategies used to improve the control of the dynamics of industrial processes. Fuzzy control was proposed as a viable solution to improve the productivity of the FSW process. The simulations indicated that FLC can use feed rate and welding speed to adaptively regulate the feed force and tool temperature respectively, irrespective of varying tool and material change. The simulations presented fuzzy logic technology to be robust enough to regulate FSW process in the absence of accurate mathematical models.
- Full Text:
- Date Issued: 2006
- Authors: Majara, Khotso Ernest
- Date: 2006
- Subjects: Friction welding , Fuzzy logic , Automatic control , Fuzzy systems
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9594 , http://hdl.handle.net/10948/405 , Friction welding , Fuzzy logic , Automatic control , Fuzzy systems
- Description: FSW is a welding technique invented and patented by The Welding Institute in 1991. This welding technique utilises the benefits of solid-state welding to materials regarded as difficult to weld by fusion processes. The productivity of the process was not optimised as the real-time dynamics of the material and tool changes were not considered. Furthermore, the process has a plastic weld region where no traditional modelling describing the interaction between the tool and work piece is available. Fuzzy logic technology is one of the artificial intelligent strategies used to improve the control of the dynamics of industrial processes. Fuzzy control was proposed as a viable solution to improve the productivity of the FSW process. The simulations indicated that FLC can use feed rate and welding speed to adaptively regulate the feed force and tool temperature respectively, irrespective of varying tool and material change. The simulations presented fuzzy logic technology to be robust enough to regulate FSW process in the absence of accurate mathematical models.
- Full Text:
- Date Issued: 2006
A generic database and spatial interface for the application of hydrological and water resource models
- Hughes, Denis A, Forsyth, D A
- Authors: Hughes, Denis A , Forsyth, D A
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7080 , http://hdl.handle.net/10962/d1012333
- Description: The paper discusses a software package that has been designed to enhance the efficiency of applying a range of hydrological and water resource simulation models. The SPATSIM (SPatial and Time Series Information Modeling) system has been developed in Delphi using MapObjects and incorporates a spatial data interface for access to the different types of information commonly associated with water resource analyses. All of the information is stored within database tables (Paradox by default) with generic structures. The structure and components of the system are briefly described and some example applications provided. The discussion identifies some of the criticisms that have been leveled at the software, the approach of the developers to user support and some possible future developments. The conclusions suggest that the development can be considered successful in that it has substantially improved the efficiency of the Institute for Water Research to undertake one of its core functions of hydrological model development and application.
- Full Text:
- Date Issued: 2006
- Authors: Hughes, Denis A , Forsyth, D A
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:7080 , http://hdl.handle.net/10962/d1012333
- Description: The paper discusses a software package that has been designed to enhance the efficiency of applying a range of hydrological and water resource simulation models. The SPATSIM (SPatial and Time Series Information Modeling) system has been developed in Delphi using MapObjects and incorporates a spatial data interface for access to the different types of information commonly associated with water resource analyses. All of the information is stored within database tables (Paradox by default) with generic structures. The structure and components of the system are briefly described and some example applications provided. The discussion identifies some of the criticisms that have been leveled at the software, the approach of the developers to user support and some possible future developments. The conclusions suggest that the development can be considered successful in that it has substantially improved the efficiency of the Institute for Water Research to undertake one of its core functions of hydrological model development and application.
- Full Text:
- Date Issued: 2006
A genetic and ecophysiological comparison of co-occuring indigenous (Perna perna) and invasive (Mytilus galloprovincialis) intertidal mussels
- Authors: Zardi, G I
- Date: 2006
- Subjects: Perna -- South Africa Mytilus galloprovincialis -- South Africa Mussels -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5613 , http://hdl.handle.net/10962/d1003066
- Description: The Mediterranean mussel Mytilus galloprovincialis is the most successful marine invasive species in South Africa. Its presence has had significant ecological consequences on the intertidal communities of the west coast. On the south coast, M galloprovincialis co-exists and competes with the indigenous intertidal mussel Perna perna in the lower balanoid zone, where they show partial habitat segregation. The upper and the lower mussel zones are dominated by M. galloprovincialis and P. perna respectively while they co-occur in the mid zone. In this thesis M. galloprovincialis and P. perna are compared in terms of their population genetics and their ecophysiology. The success of an invader depends on its ability to react to new environmental factors, especially when compared to indigenous species. The distribution and diversity of intertidal species throughout the world are strongly influenced by periodic sand inundation and hydrodynamic stress. Occupying the lower intertidal zone, P. perna is more strongly influenced by sand (burial and sand in suspension) than M. galioprovincialis. Despite this, P. perna is more vulnerable to the effects of sand, showing higher mortality rates under experimental conditions in both the laboratory and the field. M. galioprovincialis has longer labial palps than P. perna, indicating a better ability to sort particles. This, and a higher tolerance to anoxia, explains its lower mortality rates when exposed to burial or suspended sand. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. The ability of a mussel to withstand wave-generated hydrodynamic stress depends mainly on its byssal attachment strength. The higher attachment strength of P. perna compared to M. galioprovincialis and of solitary mussels compared to mussels living within a bed (bed mussels) can be explained by more and thicker byssal threads. M galloprovincialis also has a wider shell, is subjected to higher hydrodynamic loads than P. perna and shows a higher theoretical probability of dislodgement, this is borne out under field conditions. The attachment strength of both species increased from higher to lower shore, in parallel to a gradient of a stronger wave action. Monthly measurements showed that P. perna is always more strongly attached than M. galloprovincialis and revealed seasonal fluctuations of attachment strength for both species in response to wave height. The gonad index of both species was negatively cross-correlated with attachment strength. The results are discussed in the context of the evolutionary strategy of the alien mussel, which directs most of its energy to fast growth and high reproductive output, apparently at the cost of reduced attachment strength. This raises the prediction that its invasive impact will be more pronounced at sites subjected to low or moderate wave action at heavily exposed sites. The potential of a species for invasion is also determined by the ability of the invader to disperse. Population genetics provide indirect information about dispersal through a direct measurement of gene flow. The low genetic divergence (measured as mtDNA) of M. galloprovincialis confirms its recent arrival in South Africa. In contrast, the population genetics structure of P. perna revealed strong divergence on the south-east coast, resulting in a western lineage (straddling the distributional gap of the Benguela System), and an eastern lineage, with an overlap region of the two on the south coast between Kenton-on-Sea and Haga Haga. This genetic disjunction may be caused by Agulhas Current acting as an oceanographic barrier to larval dispersal, or by different environmental selective forces acting on regional populations. Over the last ten years, M. galloprovincialis has shown a decrease or cessation of its spread to the east in exactly the region of the genetic disjunction in P. perna, again suggesting either an oceanographic barrier to larval dispersal, or increasing selection driven by sharp gradients in environmental conditions.
- Full Text:
- Date Issued: 2006
- Authors: Zardi, G I
- Date: 2006
- Subjects: Perna -- South Africa Mytilus galloprovincialis -- South Africa Mussels -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5613 , http://hdl.handle.net/10962/d1003066
- Description: The Mediterranean mussel Mytilus galloprovincialis is the most successful marine invasive species in South Africa. Its presence has had significant ecological consequences on the intertidal communities of the west coast. On the south coast, M galloprovincialis co-exists and competes with the indigenous intertidal mussel Perna perna in the lower balanoid zone, where they show partial habitat segregation. The upper and the lower mussel zones are dominated by M. galloprovincialis and P. perna respectively while they co-occur in the mid zone. In this thesis M. galloprovincialis and P. perna are compared in terms of their population genetics and their ecophysiology. The success of an invader depends on its ability to react to new environmental factors, especially when compared to indigenous species. The distribution and diversity of intertidal species throughout the world are strongly influenced by periodic sand inundation and hydrodynamic stress. Occupying the lower intertidal zone, P. perna is more strongly influenced by sand (burial and sand in suspension) than M. galioprovincialis. Despite this, P. perna is more vulnerable to the effects of sand, showing higher mortality rates under experimental conditions in both the laboratory and the field. M. galioprovincialis has longer labial palps than P. perna, indicating a better ability to sort particles. This, and a higher tolerance to anoxia, explains its lower mortality rates when exposed to burial or suspended sand. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. The ability of a mussel to withstand wave-generated hydrodynamic stress depends mainly on its byssal attachment strength. The higher attachment strength of P. perna compared to M. galioprovincialis and of solitary mussels compared to mussels living within a bed (bed mussels) can be explained by more and thicker byssal threads. M galloprovincialis also has a wider shell, is subjected to higher hydrodynamic loads than P. perna and shows a higher theoretical probability of dislodgement, this is borne out under field conditions. The attachment strength of both species increased from higher to lower shore, in parallel to a gradient of a stronger wave action. Monthly measurements showed that P. perna is always more strongly attached than M. galloprovincialis and revealed seasonal fluctuations of attachment strength for both species in response to wave height. The gonad index of both species was negatively cross-correlated with attachment strength. The results are discussed in the context of the evolutionary strategy of the alien mussel, which directs most of its energy to fast growth and high reproductive output, apparently at the cost of reduced attachment strength. This raises the prediction that its invasive impact will be more pronounced at sites subjected to low or moderate wave action at heavily exposed sites. The potential of a species for invasion is also determined by the ability of the invader to disperse. Population genetics provide indirect information about dispersal through a direct measurement of gene flow. The low genetic divergence (measured as mtDNA) of M. galloprovincialis confirms its recent arrival in South Africa. In contrast, the population genetics structure of P. perna revealed strong divergence on the south-east coast, resulting in a western lineage (straddling the distributional gap of the Benguela System), and an eastern lineage, with an overlap region of the two on the south coast between Kenton-on-Sea and Haga Haga. This genetic disjunction may be caused by Agulhas Current acting as an oceanographic barrier to larval dispersal, or by different environmental selective forces acting on regional populations. Over the last ten years, M. galloprovincialis has shown a decrease or cessation of its spread to the east in exactly the region of the genetic disjunction in P. perna, again suggesting either an oceanographic barrier to larval dispersal, or increasing selection driven by sharp gradients in environmental conditions.
- Full Text:
- Date Issued: 2006
A Geographic Information System for the African Coelacanth Ecosystem Programme
- Authors: Scott, Lucy E P
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7129 , http://hdl.handle.net/10962/d1010639
- Description: The African Coelacanth Ecosystem Programme (ACEP) Geographic Information System (GIS) has been developed to integrate, analyse and map all spatial data generated within the ACEP programme. A GIS is a multidisciplinary tool, and within ACEP the GIS has been used to integrate information from marine biology studies, oceanographic surveys, geophysical exploration as well as the observations made and footage taken from a research submersible. The core data in the GIS are based on deep marine ecosystems and the programme’s flagship species, Latimeria chalumnae (the coelacanth). Over and above the utility of the GIS as a tool for science through its considerable information storage, analysis and display capabilities, the ACEP GIS has been used for interactive environmental education purposes and to generate public awareness of the programme at various meetings, training events and conferences.
- Full Text:
- Date Issued: 2006
- Authors: Scott, Lucy E P
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7129 , http://hdl.handle.net/10962/d1010639
- Description: The African Coelacanth Ecosystem Programme (ACEP) Geographic Information System (GIS) has been developed to integrate, analyse and map all spatial data generated within the ACEP programme. A GIS is a multidisciplinary tool, and within ACEP the GIS has been used to integrate information from marine biology studies, oceanographic surveys, geophysical exploration as well as the observations made and footage taken from a research submersible. The core data in the GIS are based on deep marine ecosystems and the programme’s flagship species, Latimeria chalumnae (the coelacanth). Over and above the utility of the GIS as a tool for science through its considerable information storage, analysis and display capabilities, the ACEP GIS has been used for interactive environmental education purposes and to generate public awareness of the programme at various meetings, training events and conferences.
- Full Text:
- Date Issued: 2006
A Geographic Information System for the African Coelacanth Ecosystem Programme
- Authors: Scott, Lucy E P
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7159 , http://hdl.handle.net/10962/d1011886
- Description: The African Coelacanth Ecosystem Programme (ACEP) Geographic Information System (GIS) has been developed to integrate, analyse and map all spatial data generated within the ACEP programme. A GIS is a multidisciplinary tool, and within ACEP the GIS has been used to integrate information from marine biology studies, oceanographic surveys, geophysical exploration as well as the observations made and footage taken from a research submersible. The core data in the GIS are based on deep marine ecosystems and the programme’s flagship species, Latimeria chalumnae (the coelacanth). Over and above the utility of the GIS as a tool for science through its considerable information storage, analysis and display capabilities, the ACEP GIS has been used for interactive environmental education purposes and to generate public awareness of the programme at various meetings, training events and conferences.
- Full Text:
- Date Issued: 2006
- Authors: Scott, Lucy E P
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:7159 , http://hdl.handle.net/10962/d1011886
- Description: The African Coelacanth Ecosystem Programme (ACEP) Geographic Information System (GIS) has been developed to integrate, analyse and map all spatial data generated within the ACEP programme. A GIS is a multidisciplinary tool, and within ACEP the GIS has been used to integrate information from marine biology studies, oceanographic surveys, geophysical exploration as well as the observations made and footage taken from a research submersible. The core data in the GIS are based on deep marine ecosystems and the programme’s flagship species, Latimeria chalumnae (the coelacanth). Over and above the utility of the GIS as a tool for science through its considerable information storage, analysis and display capabilities, the ACEP GIS has been used for interactive environmental education purposes and to generate public awareness of the programme at various meetings, training events and conferences.
- Full Text:
- Date Issued: 2006
A global ionospheric F2 region peak electron density model using neural networks and extended geophysically relevant inputs
- Authors: Oyeyemi, Elijah Oyedola
- Date: 2006
- Subjects: Neural networks (Computer science) Ionospheric electron density Ionosphere Ionosphere -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5470 , http://hdl.handle.net/10962/d1005255
- Description: This thesis presents my research on the development of a neural network (NN) based global empirical model of the ionospheric F2 region peak electron density using extended geophysically relevant inputs. The main principle behind this approach has been to utilize parameters other than simple geographic co-ordinates, on which the F2 peak electron density is known to depend, and to exploit the technique of NNs, thereby establishing and modeling the non-linear dynamic processes (both in space and time)associated with the F2 region electron density on a global scale. Four different models have been developed in this work. These are the foF2 NN model, M(3000)F2 NN model, short-term forecasting foF2 NN, and a near-real time foF2 NN model. Data used in the training of the NNs were obtained from the worldwide ionosonde stations spanning the period 1964 to 1986 based on availability, which included all periods of calm and disturbed magnetic activity. Common input parameters used in the training of all 4 models are day number (day of the year, DN), Universal Time (UT), a 2 month running mean of the sunspot number (R2), a 2 day running mean of the 3-hour planetary magnetic index ap (A16), solar zenith angle (CHI), geographic latitude (q), magnetic dip angle (I), angle of magnetic declination (D), angle of meridian relative to subsolar point (M). For the short-term and near-real time foF2 models, additional input parameters related to recent past observations of foF2 itself were included in the training of the NNs. The results of the foF2 NN model and M(3000)F2 NN model presented in this work, which compare favourably with the IRI (International Reference Ionosphere) model successfully demonstrate the potential of NNs for spatial and temporal modeling of the ionospheric parameters foF2 and M(3000)F2 globally. The results obtained from the short-term foF2 NN model and nearreal time foF2 NN model reveal that, in addition to the temporal and spatial input variables, short-term forecasting of foF2 is much improved by including past observations of foF2 itself. Results obtained from the near-real time foF2 NN model also reveal that there exists a correlation between measured foF2 values at different locations across the globe. Again, comparisons of the foF2 NN model and M(3000)F2 NN model predictions with that of the IRI model predictions and observed values at some selected high latitude stations, suggest that the NN technique can successfully be employed to model the complex irregularities associated with the high latitude regions. Based on the results obtained in this research and the comparison made with the IRI model (URSI and CCIR coefficients), these results justify consideration of the NN technique for the prediction of global ionospheric parameters. I believe that, after consideration by the IRI community, these models will prove to be valuable to both the high frequency (HF) communication and worldwide ionospheric communities.
- Full Text:
- Date Issued: 2006
- Authors: Oyeyemi, Elijah Oyedola
- Date: 2006
- Subjects: Neural networks (Computer science) Ionospheric electron density Ionosphere Ionosphere -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5470 , http://hdl.handle.net/10962/d1005255
- Description: This thesis presents my research on the development of a neural network (NN) based global empirical model of the ionospheric F2 region peak electron density using extended geophysically relevant inputs. The main principle behind this approach has been to utilize parameters other than simple geographic co-ordinates, on which the F2 peak electron density is known to depend, and to exploit the technique of NNs, thereby establishing and modeling the non-linear dynamic processes (both in space and time)associated with the F2 region electron density on a global scale. Four different models have been developed in this work. These are the foF2 NN model, M(3000)F2 NN model, short-term forecasting foF2 NN, and a near-real time foF2 NN model. Data used in the training of the NNs were obtained from the worldwide ionosonde stations spanning the period 1964 to 1986 based on availability, which included all periods of calm and disturbed magnetic activity. Common input parameters used in the training of all 4 models are day number (day of the year, DN), Universal Time (UT), a 2 month running mean of the sunspot number (R2), a 2 day running mean of the 3-hour planetary magnetic index ap (A16), solar zenith angle (CHI), geographic latitude (q), magnetic dip angle (I), angle of magnetic declination (D), angle of meridian relative to subsolar point (M). For the short-term and near-real time foF2 models, additional input parameters related to recent past observations of foF2 itself were included in the training of the NNs. The results of the foF2 NN model and M(3000)F2 NN model presented in this work, which compare favourably with the IRI (International Reference Ionosphere) model successfully demonstrate the potential of NNs for spatial and temporal modeling of the ionospheric parameters foF2 and M(3000)F2 globally. The results obtained from the short-term foF2 NN model and nearreal time foF2 NN model reveal that, in addition to the temporal and spatial input variables, short-term forecasting of foF2 is much improved by including past observations of foF2 itself. Results obtained from the near-real time foF2 NN model also reveal that there exists a correlation between measured foF2 values at different locations across the globe. Again, comparisons of the foF2 NN model and M(3000)F2 NN model predictions with that of the IRI model predictions and observed values at some selected high latitude stations, suggest that the NN technique can successfully be employed to model the complex irregularities associated with the high latitude regions. Based on the results obtained in this research and the comparison made with the IRI model (URSI and CCIR coefficients), these results justify consideration of the NN technique for the prediction of global ionospheric parameters. I believe that, after consideration by the IRI community, these models will prove to be valuable to both the high frequency (HF) communication and worldwide ionospheric communities.
- Full Text:
- Date Issued: 2006
A Hall-effect study of as-grown and hydrogenerated n-type ZnO layers grown by MOCVD
- Somhlahlo, Nomabali Nelisiwe
- Authors: Somhlahlo, Nomabali Nelisiwe
- Date: 2006
- Subjects: Hall effect , Electric currents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10535 , http://hdl.handle.net/10948/444 , http://hdl.handle.net/10948/d1012014 , Hall effect , Electric currents
- Description: A series of as-grown ZnO layers have been electrically characterised by the temperature dependent (20 – 300 K) Hall-effect technique. The ZnO layers were grown by metal organic chemical vapour deposition (MOCVD) on glass substrates under various growth conditions. The temperature dependent Hall-effect technique produced mobility and carrier concentration measurements. These measurements were found to be reproducible and reliable. The carrier concentration data for the layers was fitted by the charge balance equation to accurately determine the donor level and corresponding donor concentration as well as the acceptor concentration for each sample. The measured donor levels were found to vary from sample to sample and there is evidence from the results that the variations are related to the differing growth conditions of the layers. The mobility data was also fitted to establish the dominant electron scattering mechanisms in the layers. The dominant scattering mechanisms were found to vary from sample to sample. For most of the layers studied, the dominant scattering mechanism was found to be both the ionised impurity scattering at low temperatures (20 – 100 K) and grain boundary scattering at higher temperatures (100 – 300 K). The effects of exposing the ZnO layers to hydrogen plasma were also investigated by the temperature dependent Hall-effect technique. Findings indicate that hydrogen is readily incorporated in ZnO, leading always to an increased carrier concentration. It was further noted that incorporating hydrogen into ZnO in some layers increased the mobility while in other layers it caused a decrease in the mobility. The hydrogenated samples were subsequently annealed at 600 °C for 1 hour in argon ambient resulting in the carrier concentration reducing to its original value. This effect is attributed to hydrogen diffusing out of ZnO.
- Full Text:
- Date Issued: 2006
- Authors: Somhlahlo, Nomabali Nelisiwe
- Date: 2006
- Subjects: Hall effect , Electric currents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10535 , http://hdl.handle.net/10948/444 , http://hdl.handle.net/10948/d1012014 , Hall effect , Electric currents
- Description: A series of as-grown ZnO layers have been electrically characterised by the temperature dependent (20 – 300 K) Hall-effect technique. The ZnO layers were grown by metal organic chemical vapour deposition (MOCVD) on glass substrates under various growth conditions. The temperature dependent Hall-effect technique produced mobility and carrier concentration measurements. These measurements were found to be reproducible and reliable. The carrier concentration data for the layers was fitted by the charge balance equation to accurately determine the donor level and corresponding donor concentration as well as the acceptor concentration for each sample. The measured donor levels were found to vary from sample to sample and there is evidence from the results that the variations are related to the differing growth conditions of the layers. The mobility data was also fitted to establish the dominant electron scattering mechanisms in the layers. The dominant scattering mechanisms were found to vary from sample to sample. For most of the layers studied, the dominant scattering mechanism was found to be both the ionised impurity scattering at low temperatures (20 – 100 K) and grain boundary scattering at higher temperatures (100 – 300 K). The effects of exposing the ZnO layers to hydrogen plasma were also investigated by the temperature dependent Hall-effect technique. Findings indicate that hydrogen is readily incorporated in ZnO, leading always to an increased carrier concentration. It was further noted that incorporating hydrogen into ZnO in some layers increased the mobility while in other layers it caused a decrease in the mobility. The hydrogenated samples were subsequently annealed at 600 °C for 1 hour in argon ambient resulting in the carrier concentration reducing to its original value. This effect is attributed to hydrogen diffusing out of ZnO.
- Full Text:
- Date Issued: 2006
A Herefordshire life : the life and times of Leslie Evans, bell ringer, musician, craftsman and countryman : book review
- Authors: Lewis, Colin A
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6171 , http://hdl.handle.net/10962/d1012362 , http://www.ringingworld.co.uk
- Description: Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He is the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa.
- Full Text:
- Date Issued: 2006
- Authors: Lewis, Colin A
- Date: 2006
- Language: English
- Type: Article
- Identifier: vital:6171 , http://hdl.handle.net/10962/d1012362 , http://www.ringingworld.co.uk
- Description: Colin Lewis was Professor of Geography at Rhodes University, Grahamstown, South Africa from 1989 until his retirement at the end of 2007. In 1990, with the strong support of the incumbent Vice-Chancellor, Dr Derek Henderson, he instigated the Certificate in Change Ringing (Church Bell Ringing) in the Rhodes University Department of Music and Musicology - the first such course to be offered in Africa. Since that date he has lectured in the basic theory, and taught the practice of change ringing. He is the Ringing Master of the Cathedral of St Michael and St George, Grahamstown, South Africa.
- Full Text:
- Date Issued: 2006
A history of southern African research relevant to forensic entomology
- Williams, K A, Villet, Martin H
- Authors: Williams, K A , Villet, Martin H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6909 , http://hdl.handle.net/10962/d1011862
- Description: Entomological forensic evidence has been used in southern Africa for decades but explicitly forensic research began in southern Africa only 26 years ago. Although applicable local research has accumulated since 1921, it is scattered in a diverse literature or unpublished. Some overseas research has also touched on local species. This review uses a historical approach to synthesize the southern African literature and to illustrate the cross-disciplinary, opportunistic nature of forensic entomology. Distinct phases of research focused on agriculture (1921-1950), medicine (1952- 1965), ecology (1968-1990) and forensics (1980-2005), but systematics spanned the entire period and tended to be ad hoc. Few scientists were involved, situated at geographically distant locations and with widely disparate research interests. The review concludes with an overview of southern African entomologists who have been involved in medico-legal investigations, and a critical evaluation of the past and future of the discipline locally.
- Full Text:
- Date Issued: 2006
- Authors: Williams, K A , Villet, Martin H
- Date: 2006
- Language: English
- Type: text , Article
- Identifier: vital:6909 , http://hdl.handle.net/10962/d1011862
- Description: Entomological forensic evidence has been used in southern Africa for decades but explicitly forensic research began in southern Africa only 26 years ago. Although applicable local research has accumulated since 1921, it is scattered in a diverse literature or unpublished. Some overseas research has also touched on local species. This review uses a historical approach to synthesize the southern African literature and to illustrate the cross-disciplinary, opportunistic nature of forensic entomology. Distinct phases of research focused on agriculture (1921-1950), medicine (1952- 1965), ecology (1968-1990) and forensics (1980-2005), but systematics spanned the entire period and tended to be ad hoc. Few scientists were involved, situated at geographically distant locations and with widely disparate research interests. The review concludes with an overview of southern African entomologists who have been involved in medico-legal investigations, and a critical evaluation of the past and future of the discipline locally.
- Full Text:
- Date Issued: 2006
A holistic approach to consumption analysis in the popular music market
- Authors: Scheckter, Jonathan
- Date: 2006
- Subjects: Consumption (Economics) -- Moral and ethical aspects , Music trade -- South Africa , Popular music -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:981 , http://hdl.handle.net/10962/d1002715 , Consumption (Economics) -- Moral and ethical aspects , Music trade -- South Africa , Popular music -- Economic aspects -- South Africa
- Description: This thesis seeks to gain a holistic understanding of consumption issues in the popular music market, such that it needs to account for the influence of 1) technological factors, 2) institutional factors, 3) cultural factors, and 4) an ontological aspect; as these are identified to be the most prominent aspects in the literature on the market. While there is a bourgeoning literature on the market, there has been little formal attempt to link such issues in a comprehensive fashion. The methodology applied provides a critique of the literature on specific consumption theories which have apparent pertinence to the music market. Each of the sociological, psychological, and economic theories (neoclassical and radical) is found to be too generalized to provide such an understanding, in that many issues concerning the music market would need to be eschewed if these theories were to be applied in an orthodox fashion. Moreover, the theories tend to point towards each other for the possibility of a credible, holistic consumption analysis. The most useful and all-encompassing consumption theory reviewed is the systems of provision approach advanced by Fine and Leopold (1993), in that the approach aims to be sensitive to the difference between commodities in terms of the economic and social processes and structures by which they become commodities, and thus it can allow one to consider adequately the four requirements identified above for a holistic understanding of the market. This approach is then applied to the western music market with the aim of 1) testing the approach identified, and 2) making a specific comment of the market. The market is found to be characterized historically by three distinct periods, each with distinct systems of provision (i.e. each with the four factors identified above relating to each other in a certain manner). It is proposed that preference formations in the final period identified have been institutionalized to a large extent, and there is a low probability of change occurring. The systems of provision approach is argued to be beneficial in highlighting which aspects of the existing consumption theories are relevant to the market at a point in time, and to what extent. Thus the richness of the approach stems from its ability to gain a holistic understanding, and to identify theoretical discussion topics, such as those concerning political economy. The approach is then applied to the South African music market, using the same historical methodology, in conjunction with current empirical evidence from the market. Doing this allows one to test the generality of the systems of provision approach, and to attempt to make a comment on the South African market. The techniques for obtaining empirical evidence are argued to be sound, but resource constraints prevented the research from reflecting a holistic view of the market. Nonetheless, a rich perspective is provided from interviews with prominent agents in the market, and thus the chapter is argued to provide the beginning of an understanding of preference formations in the South African music market, in which little research has been conducted (Stella, 2005).
- Full Text:
- Date Issued: 2006
- Authors: Scheckter, Jonathan
- Date: 2006
- Subjects: Consumption (Economics) -- Moral and ethical aspects , Music trade -- South Africa , Popular music -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:981 , http://hdl.handle.net/10962/d1002715 , Consumption (Economics) -- Moral and ethical aspects , Music trade -- South Africa , Popular music -- Economic aspects -- South Africa
- Description: This thesis seeks to gain a holistic understanding of consumption issues in the popular music market, such that it needs to account for the influence of 1) technological factors, 2) institutional factors, 3) cultural factors, and 4) an ontological aspect; as these are identified to be the most prominent aspects in the literature on the market. While there is a bourgeoning literature on the market, there has been little formal attempt to link such issues in a comprehensive fashion. The methodology applied provides a critique of the literature on specific consumption theories which have apparent pertinence to the music market. Each of the sociological, psychological, and economic theories (neoclassical and radical) is found to be too generalized to provide such an understanding, in that many issues concerning the music market would need to be eschewed if these theories were to be applied in an orthodox fashion. Moreover, the theories tend to point towards each other for the possibility of a credible, holistic consumption analysis. The most useful and all-encompassing consumption theory reviewed is the systems of provision approach advanced by Fine and Leopold (1993), in that the approach aims to be sensitive to the difference between commodities in terms of the economic and social processes and structures by which they become commodities, and thus it can allow one to consider adequately the four requirements identified above for a holistic understanding of the market. This approach is then applied to the western music market with the aim of 1) testing the approach identified, and 2) making a specific comment of the market. The market is found to be characterized historically by three distinct periods, each with distinct systems of provision (i.e. each with the four factors identified above relating to each other in a certain manner). It is proposed that preference formations in the final period identified have been institutionalized to a large extent, and there is a low probability of change occurring. The systems of provision approach is argued to be beneficial in highlighting which aspects of the existing consumption theories are relevant to the market at a point in time, and to what extent. Thus the richness of the approach stems from its ability to gain a holistic understanding, and to identify theoretical discussion topics, such as those concerning political economy. The approach is then applied to the South African music market, using the same historical methodology, in conjunction with current empirical evidence from the market. Doing this allows one to test the generality of the systems of provision approach, and to attempt to make a comment on the South African market. The techniques for obtaining empirical evidence are argued to be sound, but resource constraints prevented the research from reflecting a holistic view of the market. Nonetheless, a rich perspective is provided from interviews with prominent agents in the market, and thus the chapter is argued to provide the beginning of an understanding of preference formations in the South African music market, in which little research has been conducted (Stella, 2005).
- Full Text:
- Date Issued: 2006
A holistic approach to network security in OGSA-based grid systems
- Authors: Loutsios, Demetrios
- Date: 2006
- Subjects: Computer networks -- Security measures
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9736 , http://hdl.handle.net/10948/550 , Computer networks -- Security measures
- Description: Grid computing technologies facilitate complex scientific collaborations between globally dispersed parties, which make use of heterogeneous technologies and computing systems. However, in recent years the commercial sector has developed a growing interest in Grid technologies. Prominent Grid researchers have predicted Grids will grow into the commercial mainstream, even though its origins were in scientific research. This is much the same way as the Internet started as a vehicle for research collaboration between universities and government institutions, and grew into a technology with large commercial applications. Grids facilitate complex trust relationships between globally dispersed business partners, research groups, and non-profit organizations. Almost any dispersed “virtual organization” willing to share computing resources can make use of Grid technologies. Grid computing facilitates the networking of shared services; the inter-connection of a potentially unlimited number of computing resources within a “Grid” is possible. Grid technologies leverage a range of open standards and technologies to provide interoperability between heterogeneous computing systems. Newer Grids build on key capabilities of Web-Service technologies to provide easy and dynamic publishing and discovery of Grid resources. Due to the inter-organisational nature of Grid systems, there is a need to provide adequate security to Grid users and to Grid resources. This research proposes a framework, using a specific brokered pattern, which addresses several common Grid security challenges, which include: Providing secure and consistent cross-site Authentication and Authorization; Single-sign on capabilities to Grid users; Abstract iii; Underlying platform and runtime security, and; Grid network communications and messaging security. These Grid security challenges can be viewed as comprising two (proposed) logical layers of a Grid. These layers are: a Common Grid Layer (higher level Grid interactions), and a Local Resource Layer (Lower level technology security concerns). This research is concerned with providing a generic and holistic security framework to secure both layers. This research makes extensive use of STRIDE - an acronym for Microsoft approach to addressing security threats - as part of a holistic Grid security framework. STRIDE and key Grid related standards, such as Open Grid Service Architecture (OGSA), Web-Service Resource Framework (WS-RF), and the Globus Toolkit are used to formulate the proposed framework.
- Full Text:
- Date Issued: 2006
- Authors: Loutsios, Demetrios
- Date: 2006
- Subjects: Computer networks -- Security measures
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9736 , http://hdl.handle.net/10948/550 , Computer networks -- Security measures
- Description: Grid computing technologies facilitate complex scientific collaborations between globally dispersed parties, which make use of heterogeneous technologies and computing systems. However, in recent years the commercial sector has developed a growing interest in Grid technologies. Prominent Grid researchers have predicted Grids will grow into the commercial mainstream, even though its origins were in scientific research. This is much the same way as the Internet started as a vehicle for research collaboration between universities and government institutions, and grew into a technology with large commercial applications. Grids facilitate complex trust relationships between globally dispersed business partners, research groups, and non-profit organizations. Almost any dispersed “virtual organization” willing to share computing resources can make use of Grid technologies. Grid computing facilitates the networking of shared services; the inter-connection of a potentially unlimited number of computing resources within a “Grid” is possible. Grid technologies leverage a range of open standards and technologies to provide interoperability between heterogeneous computing systems. Newer Grids build on key capabilities of Web-Service technologies to provide easy and dynamic publishing and discovery of Grid resources. Due to the inter-organisational nature of Grid systems, there is a need to provide adequate security to Grid users and to Grid resources. This research proposes a framework, using a specific brokered pattern, which addresses several common Grid security challenges, which include: Providing secure and consistent cross-site Authentication and Authorization; Single-sign on capabilities to Grid users; Abstract iii; Underlying platform and runtime security, and; Grid network communications and messaging security. These Grid security challenges can be viewed as comprising two (proposed) logical layers of a Grid. These layers are: a Common Grid Layer (higher level Grid interactions), and a Local Resource Layer (Lower level technology security concerns). This research is concerned with providing a generic and holistic security framework to secure both layers. This research makes extensive use of STRIDE - an acronym for Microsoft approach to addressing security threats - as part of a holistic Grid security framework. STRIDE and key Grid related standards, such as Open Grid Service Architecture (OGSA), Web-Service Resource Framework (WS-RF), and the Globus Toolkit are used to formulate the proposed framework.
- Full Text:
- Date Issued: 2006