An economic evaluation of the National Agricultural Advisory Services (NAADS) program in Uganda
- Authors: Leornard, Walusimbi
- Date: 2019
- Subjects: Agricultural development projects -- Uganda , Agriculture -- Economic Aspects -- Uganda
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45624 , vital:38920
- Description: The National Agricultural Advisory Services (NAADS) programme was formed in Uganda in 2001 as a response to previously poor performance of extension services in Uganda. NAADS was formed as a demand-driven extension programme designed to improve farmers’ incomes through increased farm output in agriculture and to solve food insecurity in the country. Given the enormous resources injected into the programme intended to improve the welfare of farmers, the main objective of this study was to determine the economic viability of NAADS throughout the period 2001-2017. The study was conducted in four districts: Mpigi, Mubende, Luwero, and Mukono. Using a non-probability random sampling technique based on convenience and snowball sampling techniques, a sample of 384 participants took part in this study. Cost-Benefit Analysis (CBA) was used to assess the merits of this public investment project. The study also used descriptive methods of analysis such as a 5-point Likert-type scale so as to derive means. In addition, the study practiced the Principal Component Analysis (PCA) technique, and the cronbach alpha coefficient was used to test the reliability of factors in explaining the concerned five dimensions of this study.
- Full Text:
- Date Issued: 2019
- Authors: Leornard, Walusimbi
- Date: 2019
- Subjects: Agricultural development projects -- Uganda , Agriculture -- Economic Aspects -- Uganda
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45624 , vital:38920
- Description: The National Agricultural Advisory Services (NAADS) programme was formed in Uganda in 2001 as a response to previously poor performance of extension services in Uganda. NAADS was formed as a demand-driven extension programme designed to improve farmers’ incomes through increased farm output in agriculture and to solve food insecurity in the country. Given the enormous resources injected into the programme intended to improve the welfare of farmers, the main objective of this study was to determine the economic viability of NAADS throughout the period 2001-2017. The study was conducted in four districts: Mpigi, Mubende, Luwero, and Mukono. Using a non-probability random sampling technique based on convenience and snowball sampling techniques, a sample of 384 participants took part in this study. Cost-Benefit Analysis (CBA) was used to assess the merits of this public investment project. The study also used descriptive methods of analysis such as a 5-point Likert-type scale so as to derive means. In addition, the study practiced the Principal Component Analysis (PCA) technique, and the cronbach alpha coefficient was used to test the reliability of factors in explaining the concerned five dimensions of this study.
- Full Text:
- Date Issued: 2019
Minding your own game : self-regulation and psychological momentum among golfers
- Authors: Kingma, Graham
- Date: 2015
- Subjects: Golf -- Strategic aspects , Golf -- Psychological aspects , Athletes , Self-control , Golfers -- Conduct of life
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3260 , http://hdl.handle.net/10962/d1017883
- Description: Psychological momentum (PM) is often regarded as an important phenomenon that influences athlete performance. Nevertheless, conceptualisations of PM are criticised for being speculative, vague and impractical for scientific inquiry. In contrast, self-regulation is a long-standing, well researched concept used to explain performance outcomes, yet not clearly integrated in current PM conceptualisations. Hence, this thesis explores self-regulation relative to PM. Golf was considered to be an appropriate context for the empirical inquiries on the basis that it serves as a metaphor for managing life’s challenges. Three studies were conducted. The first study entailed a systematic conceptual analysis of PM based on previous conceptualisations and studies in relevant scientific literature. Self-regulatory processes were identified among the key psychological mechanisms and moderators related to PM. The second study aimed to identify key self-regulation strategies in PM experiences among 16 golfers. A mixed method approach including novel “walk-along” and “think aloud” data collection techniques was used. An inductive thematic analysis yielded a comprehensive typology golfing strategies. Nevertheless, the study did not find consistent strategy patterns in positive or negative PM phases. The third study explored the self-regulation of identity (ego-regulation) in relation to PM phases. A staggered multiple-baseline single-case research methodology was used with five golfers (three professionals and two amateurs). Ego-regulation was manipulated through a mindfulness-based schema mode program tailored to golf (Mindfulness for Golf; MFG). Pre-, mid- and post-intervention data showed positive changes among the participants on two dimensions of PM as well as performance outcomes. Overall the results suggest that golfers use idiosyncratic self-regulation processes to facilitate performance, but these are not directly linked to PM phases. Nonetheless, there are promising indications that enhancing ego-regulation through the MFG program facilitates positive momentum among golfers. Based on the results of the studies in this thesis, and for the sake of scientific parsimony and pragmatism, it is recommended that self-regulation models incorporating motivation are used to explain momentum in athletic activity. In this view, PM has the function of describing, not influencing, goal-driven performance
- Full Text:
- Date Issued: 2015
- Authors: Kingma, Graham
- Date: 2015
- Subjects: Golf -- Strategic aspects , Golf -- Psychological aspects , Athletes , Self-control , Golfers -- Conduct of life
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3260 , http://hdl.handle.net/10962/d1017883
- Description: Psychological momentum (PM) is often regarded as an important phenomenon that influences athlete performance. Nevertheless, conceptualisations of PM are criticised for being speculative, vague and impractical for scientific inquiry. In contrast, self-regulation is a long-standing, well researched concept used to explain performance outcomes, yet not clearly integrated in current PM conceptualisations. Hence, this thesis explores self-regulation relative to PM. Golf was considered to be an appropriate context for the empirical inquiries on the basis that it serves as a metaphor for managing life’s challenges. Three studies were conducted. The first study entailed a systematic conceptual analysis of PM based on previous conceptualisations and studies in relevant scientific literature. Self-regulatory processes were identified among the key psychological mechanisms and moderators related to PM. The second study aimed to identify key self-regulation strategies in PM experiences among 16 golfers. A mixed method approach including novel “walk-along” and “think aloud” data collection techniques was used. An inductive thematic analysis yielded a comprehensive typology golfing strategies. Nevertheless, the study did not find consistent strategy patterns in positive or negative PM phases. The third study explored the self-regulation of identity (ego-regulation) in relation to PM phases. A staggered multiple-baseline single-case research methodology was used with five golfers (three professionals and two amateurs). Ego-regulation was manipulated through a mindfulness-based schema mode program tailored to golf (Mindfulness for Golf; MFG). Pre-, mid- and post-intervention data showed positive changes among the participants on two dimensions of PM as well as performance outcomes. Overall the results suggest that golfers use idiosyncratic self-regulation processes to facilitate performance, but these are not directly linked to PM phases. Nonetheless, there are promising indications that enhancing ego-regulation through the MFG program facilitates positive momentum among golfers. Based on the results of the studies in this thesis, and for the sake of scientific parsimony and pragmatism, it is recommended that self-regulation models incorporating motivation are used to explain momentum in athletic activity. In this view, PM has the function of describing, not influencing, goal-driven performance
- Full Text:
- Date Issued: 2015
An investigation of protocol command translation as a means to enable interoperability between networked audio devices
- Authors: Igumbor, Osedum Peter
- Date: 2014
- Subjects: Streaming audio Data transmission systems Computer network protocols Computer networks -- Management Command languages (Computer science)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4689 , http://hdl.handle.net/10962/d1011128
- Description: Digital audio networks allow multiple channels of audio to be streamed between devices. This eliminates the need for many different cables to route audio between devices. An added advantage of digital audio networks is the ability to configure and control the networked devices from a common control point. Common control of networked devices enables a sound engineer to establish and destroy audio stream connections between networked devices that are distances apart. On a digital audio network, an audio transport technology enables the exchange of data streams. Typically, an audio transport technology is capable of transporting both control messages and audio data streams. There exist a number of audio transport technologies. Some of these technologies implement data transport by exchanging OSI/ISO layer 2 data frames, while others transport data within OSI/ISO layer 3 packets. There are some approaches to achieving interoperability between devices that utilize different audio transport technologies. A digital audio device typically implements an audio control protocol, which enables it process configuration and control messages from a remote controller. An audio control protocol also defines the structure of the messages that are exchanged between compliant devices. There are currently a wide range of audio control protocols. Some audio control protocols utilize layer 3 audio transport technology, while others utilize layer 2 audio transport technology. An audio device can only communicate with other devices that implement the same control protocol, irrespective of a common transport technology that connects the devices. The existence of different audio control protocols among devices on a network results in a situation where the devices are unable to communicate with each other. Furthermore, a single control application is unable to establish or destroy audio stream connections between the networked devices, since they implement different control protocols. When an audio engineer is designing an audio network installation, this interoperability challenge restricts the choice of devices that can be included. Even when audio transport interoperability has been achieved, common control of the devices remains a challenge. This research investigates protocol command translation as a means to enable interoperability between networked audio devices that implement different audio control protocols. It proposes the use of a command translator that is capable of receiving messages conforming to one protocol from any of the networked devices, translating the received message to conform to a different control protocol, then transmitting the translated message to the intended target which understands the translated protocol message. In so doing, the command translator enables common control of the networked devices, since a control application is able to configure and control devices that conform to different protocols by utilizing the command translator to perform appropriate protocol translation.
- Full Text:
- Date Issued: 2014
- Authors: Igumbor, Osedum Peter
- Date: 2014
- Subjects: Streaming audio Data transmission systems Computer network protocols Computer networks -- Management Command languages (Computer science)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4689 , http://hdl.handle.net/10962/d1011128
- Description: Digital audio networks allow multiple channels of audio to be streamed between devices. This eliminates the need for many different cables to route audio between devices. An added advantage of digital audio networks is the ability to configure and control the networked devices from a common control point. Common control of networked devices enables a sound engineer to establish and destroy audio stream connections between networked devices that are distances apart. On a digital audio network, an audio transport technology enables the exchange of data streams. Typically, an audio transport technology is capable of transporting both control messages and audio data streams. There exist a number of audio transport technologies. Some of these technologies implement data transport by exchanging OSI/ISO layer 2 data frames, while others transport data within OSI/ISO layer 3 packets. There are some approaches to achieving interoperability between devices that utilize different audio transport technologies. A digital audio device typically implements an audio control protocol, which enables it process configuration and control messages from a remote controller. An audio control protocol also defines the structure of the messages that are exchanged between compliant devices. There are currently a wide range of audio control protocols. Some audio control protocols utilize layer 3 audio transport technology, while others utilize layer 2 audio transport technology. An audio device can only communicate with other devices that implement the same control protocol, irrespective of a common transport technology that connects the devices. The existence of different audio control protocols among devices on a network results in a situation where the devices are unable to communicate with each other. Furthermore, a single control application is unable to establish or destroy audio stream connections between the networked devices, since they implement different control protocols. When an audio engineer is designing an audio network installation, this interoperability challenge restricts the choice of devices that can be included. Even when audio transport interoperability has been achieved, common control of the devices remains a challenge. This research investigates protocol command translation as a means to enable interoperability between networked audio devices that implement different audio control protocols. It proposes the use of a command translator that is capable of receiving messages conforming to one protocol from any of the networked devices, translating the received message to conform to a different control protocol, then transmitting the translated message to the intended target which understands the translated protocol message. In so doing, the command translator enables common control of the networked devices, since a control application is able to configure and control devices that conform to different protocols by utilizing the command translator to perform appropriate protocol translation.
- Full Text:
- Date Issued: 2014
Effectiveness of irrigation water management institutions in Zimbabwe: a new institutional economics theory approach
- Authors: Nhundu, Kenneth
- Date: 2013
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11195 , http://hdl.handle.net/10353/d1006784
- Description: Despite considerable advances in technology across the world, some scholars (Bratton, 1987; Namara et al., 2010) have argued that declining agricultural productivity among smallholder farmers in Africa remains a major bottleneck in the development of the continent. Unganai (1993) indicates that about 60% of the southern African region is semi-arid or arid and suffers from periodic droughts. In addition, World Bank (2003) notes that agricultural production is dominated by rain-fed agriculture and irrigation systems are limited. This is compounded by the scarcity and poor management of irrigation water resources. Water scarcity in agriculture has large impacts on the population, especially in rural areas, where more than 60 percent of the population are engaged in agriculture which represents their main source of food and income (FAO, 2008). On the macroeconomic level, agricultural share of the GDP is about 37 percent and 75 percent of the export value is generated from the agricultural sector globally. To this effect, management of agricultural water particularly in rain-fed systems remains imperative for improved farm level yields because the bulk of the food comes from rain-fed agriculture (FAO, 2008; Namara et al., 2010). However, increasing water scarcity and poor accessibility may become a limiting factor not only for agricultural production and the welfare of rural population but also for the entire economy. Improving the management of water resources and an efficient use of water by all sectors, including agricultural production, are therefore important if the welfare and health of the population, particularly in rural areas, are to be maintained and improved (Nyong & Kanaroglou, 1999).
- Full Text:
- Date Issued: 2013
- Authors: Nhundu, Kenneth
- Date: 2013
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11195 , http://hdl.handle.net/10353/d1006784
- Description: Despite considerable advances in technology across the world, some scholars (Bratton, 1987; Namara et al., 2010) have argued that declining agricultural productivity among smallholder farmers in Africa remains a major bottleneck in the development of the continent. Unganai (1993) indicates that about 60% of the southern African region is semi-arid or arid and suffers from periodic droughts. In addition, World Bank (2003) notes that agricultural production is dominated by rain-fed agriculture and irrigation systems are limited. This is compounded by the scarcity and poor management of irrigation water resources. Water scarcity in agriculture has large impacts on the population, especially in rural areas, where more than 60 percent of the population are engaged in agriculture which represents their main source of food and income (FAO, 2008). On the macroeconomic level, agricultural share of the GDP is about 37 percent and 75 percent of the export value is generated from the agricultural sector globally. To this effect, management of agricultural water particularly in rain-fed systems remains imperative for improved farm level yields because the bulk of the food comes from rain-fed agriculture (FAO, 2008; Namara et al., 2010). However, increasing water scarcity and poor accessibility may become a limiting factor not only for agricultural production and the welfare of rural population but also for the entire economy. Improving the management of water resources and an efficient use of water by all sectors, including agricultural production, are therefore important if the welfare and health of the population, particularly in rural areas, are to be maintained and improved (Nyong & Kanaroglou, 1999).
- Full Text:
- Date Issued: 2013
Electrochemical sensing and immunosensing using metallophthalocyanines and biomolecular modified surfaces
- Authors: Mashazi, Philani Nkosinathi
- Date: 2012
- Subjects: Phthalocyanines , Electrochemistry , Electrodes, Enzyme , Measles -- Measurement
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5580 , http://hdl.handle.net/10962/d1018248
- Description: The synthesis of cobalt and manganese phthalocyanine complexes bearing eight hexylthio and four amino substituents was carried out. The formation of thin films of these complexes using different modification methods was also studied. Hexylthio functionalized metallophthalocyanine complexes were immobilized onto gold electrode surfaces using the self-assembly techniques. Surface modifications using cobalt and manganese tetraamino phthalocyanine as polymers, monolayers (onto electrografted surfaces) and as carbon nanotube – metallophthalocyanine conjugates was also carried out. The new method of modifying gold electrodes with metal tetraamino phthalocyanine complexes was investigated. The modified electrode surfaces were studied for their electrocatalytic properties and as potential electrochemical sensors for the detection of hydrogen peroxide (H₂O₂). The limits of detection for the H₂O₂ were of the orders of ~10⁻⁷ M for all the modified electrodes. The modified electrodes gave very good analytical parameters; such as good sensitivity, linearity at studied concentration range and well-defined analytical peaks with increased current densities. The modification methods were reproducible, highly conducting thin films were formed and the modified electrodes were very stable. The design of electrochemical immunosensors for the detection of measles-specific antibodies was also carried out. The modified surface with measles-antigen as sensing element was accomplished using covalent immobilization for an intimate connection of the measles-antigen as a sensing layer onto an electrode surface. Two methods of detecting measles-specific antibodies were investigated and these methods were based on electrochemical impedance, i.e. label-free detection, and voltammetric method using horse-radish peroxidase (HRP) labeled antibody as a reporter. The detection of measles-specific antibodies was accomplished using both these methods. The potential applications of the designed immunosensor were evaluated in real samples (human and newborn calf serum) and the electrodes could detect the antibodies in the complex sample matrix with ease.
- Full Text:
- Date Issued: 2012
- Authors: Mashazi, Philani Nkosinathi
- Date: 2012
- Subjects: Phthalocyanines , Electrochemistry , Electrodes, Enzyme , Measles -- Measurement
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5580 , http://hdl.handle.net/10962/d1018248
- Description: The synthesis of cobalt and manganese phthalocyanine complexes bearing eight hexylthio and four amino substituents was carried out. The formation of thin films of these complexes using different modification methods was also studied. Hexylthio functionalized metallophthalocyanine complexes were immobilized onto gold electrode surfaces using the self-assembly techniques. Surface modifications using cobalt and manganese tetraamino phthalocyanine as polymers, monolayers (onto electrografted surfaces) and as carbon nanotube – metallophthalocyanine conjugates was also carried out. The new method of modifying gold electrodes with metal tetraamino phthalocyanine complexes was investigated. The modified electrode surfaces were studied for their electrocatalytic properties and as potential electrochemical sensors for the detection of hydrogen peroxide (H₂O₂). The limits of detection for the H₂O₂ were of the orders of ~10⁻⁷ M for all the modified electrodes. The modified electrodes gave very good analytical parameters; such as good sensitivity, linearity at studied concentration range and well-defined analytical peaks with increased current densities. The modification methods were reproducible, highly conducting thin films were formed and the modified electrodes were very stable. The design of electrochemical immunosensors for the detection of measles-specific antibodies was also carried out. The modified surface with measles-antigen as sensing element was accomplished using covalent immobilization for an intimate connection of the measles-antigen as a sensing layer onto an electrode surface. Two methods of detecting measles-specific antibodies were investigated and these methods were based on electrochemical impedance, i.e. label-free detection, and voltammetric method using horse-radish peroxidase (HRP) labeled antibody as a reporter. The detection of measles-specific antibodies was accomplished using both these methods. The potential applications of the designed immunosensor were evaluated in real samples (human and newborn calf serum) and the electrodes could detect the antibodies in the complex sample matrix with ease.
- Full Text:
- Date Issued: 2012
An investigation into the state-of-practice of information security within Zambian copper mines: a case study
- Authors: Lukweza, Chishala
- Date: 2011
- Subjects: Computer security -- Zambia -- Management Case studies , Computer networks -- Security measures -- Zambia Case studies , Copper mines and mining -- Computer networks -- Security measures -- Zambia Case studies , Information technology -- Zambia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1146 , http://hdl.handle.net/10962/d1002776 , Computer security -- Zambia -- Management Case studies , Computer networks -- Security measures -- Zambia Case studies , Copper mines and mining -- Computer networks -- Security measures -- Zambia Case studies , Information technology -- Zambia
- Description: Zambian copper mines have embraced the use of information technologies for strategic operations and competitive advantage. This dependence on these technologies has not only been seen in the physical aspects of business operations but also in the use of information systems such as Enterprise Resource Planning Systems (ERPs) for strategic decision making and increased usage of Industrial Control Systems (ICS’) that are meant to enhance operational efficiency in production areas. A survey was conducted to explore leadership perceptions on information security practices in Zambian copper mines and an ISO/IEC 27002 Audit Tool was administered to middle management in a particular mine for an in-depth analysis of their information security practices. Results revealed that although information security controls may have been put in place in these organisations, there are still areas that require attention. Senior management and middle management have different perceptions as to the extent to which information security practices are conducted in these copper mines. This implies that management may not be fully involved in certain aspects of these organisations’ information security practices. The results concluded that management needs to be fully involved and provide support for information security programs. Furthermore, these information security programs should be standardised so as to effectively protect these organisations’ information assets. This should also include the involvement of personnel as key players in the information security process.
- Full Text:
- Date Issued: 2011
- Authors: Lukweza, Chishala
- Date: 2011
- Subjects: Computer security -- Zambia -- Management Case studies , Computer networks -- Security measures -- Zambia Case studies , Copper mines and mining -- Computer networks -- Security measures -- Zambia Case studies , Information technology -- Zambia
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1146 , http://hdl.handle.net/10962/d1002776 , Computer security -- Zambia -- Management Case studies , Computer networks -- Security measures -- Zambia Case studies , Copper mines and mining -- Computer networks -- Security measures -- Zambia Case studies , Information technology -- Zambia
- Description: Zambian copper mines have embraced the use of information technologies for strategic operations and competitive advantage. This dependence on these technologies has not only been seen in the physical aspects of business operations but also in the use of information systems such as Enterprise Resource Planning Systems (ERPs) for strategic decision making and increased usage of Industrial Control Systems (ICS’) that are meant to enhance operational efficiency in production areas. A survey was conducted to explore leadership perceptions on information security practices in Zambian copper mines and an ISO/IEC 27002 Audit Tool was administered to middle management in a particular mine for an in-depth analysis of their information security practices. Results revealed that although information security controls may have been put in place in these organisations, there are still areas that require attention. Senior management and middle management have different perceptions as to the extent to which information security practices are conducted in these copper mines. This implies that management may not be fully involved in certain aspects of these organisations’ information security practices. The results concluded that management needs to be fully involved and provide support for information security programs. Furthermore, these information security programs should be standardised so as to effectively protect these organisations’ information assets. This should also include the involvement of personnel as key players in the information security process.
- Full Text:
- Date Issued: 2011
Evaluating uncertainty in water resources estimation in Southern Africa : a case study of South Africa
- Authors: Sawunyama, Tendai
- Date: 2009
- Subjects: Water supply -- South Africa , Water supply -- Africa, Southern , Hydrology -- South Africa , Hydrology -- Africa, Southern , Hydrologic models , Hydrology research -- South Africa , Hydrology research -- Africa, Southern , Rain and rainfall -- Mathematical models , Runoff -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6035 , http://hdl.handle.net/10962/d1006176
- Description: Hydrological models are widely used tools in water resources estimation, but they are simple representations of reality and are frequently based on inadequate input data and uncertainties in parameter values. Data observation networks are expensive to establish and maintain and often beyond the resources of most developing countries. Consequently, measurements are difficult to obtain and observation networks in many countries are shrinking, hence obtaining representative observations in space and time remains a challenge. This study presents some guidelines on the identification, quantification and reduction of sources of uncertainty in water resources estimation in southern Africa, a data scarce region. The analyses are based on example sub-basins drawn from South Africa and the application of the Pitman hydrological model. While it has always been recognised that estimates of water resources availability for the region are subject to possible errors, the quantification of these uncertainties has never been explicitly incorporated into the methods used in the region. The motivation for this study was therefore to contribute to the future development of a revised framework for water resources estimation that does include uncertainty. The focus was on uncertainties associated with climate input data, parameter estimation (and recognizing the uncertainty due model structure deficiencies) methods and water use data. In addition to variance based measures of uncertainty, this study also used a reservoir yield based statistic to evaluate model output uncertainty, which represents an integrated measure of flow regime variations and one that can be more easily understood by water resources managers. Through a sensitivity analysis approach, the results of the individual contribution of each source of uncertainty suggest regional differences and that clear statements about which source of uncertainty is likely to dominate are not generally possible. Parameter sensitivity analysis was used in identifying parameters which are important withinspecific sub-basins and therefore those to focus on in uncertainty analysis. The study used a simple framework for evaluating the combined contribution of uncertainty sources to model outputs that is consistent with the model limitations and data available, and that allows direct quantitative comparison between model outputs obtained by using different sources of information and methods within Spatial and Time Series Information Modelling (SPATSIM) software. The results from combining the sources of uncertainties showed that parameter uncertainty dominates the contribution to model output uncertainty. However, in some parts of the country especially those with complex topography, which tend to experience high rainfall spatial variability, rainfall uncertainty is equally dominant, while the contributions of evaporation and water use data uncertainty are relatively small. While the results of this study are encouraging, the weaknesses of the methods used to quantify uncertainty (especially subjectivity involved in evaluating parameter uncertainty) should not be neglected and require further evaluations. An effort to reduce data and parameter uncertainty shows that this can only be achieved if data access at appropriate scale and quality improves. Perhaps the focus should be on maintaining existing networks and concentrating research efforts on making the most out of the emerging data products derived from remote sensing platforms. While this study presents some initial guidelines for evaluating uncertainty in South Africa, there is need to overcome several constraints which are related to data availability and accuracy, the models used and the capacity or willingness to adopt new methods that incorporate uncertainty. The study has provided a starting point for the development of new approaches to modelling water resources in the region that include uncertain estimates.
- Full Text:
- Date Issued: 2009
- Authors: Sawunyama, Tendai
- Date: 2009
- Subjects: Water supply -- South Africa , Water supply -- Africa, Southern , Hydrology -- South Africa , Hydrology -- Africa, Southern , Hydrologic models , Hydrology research -- South Africa , Hydrology research -- Africa, Southern , Rain and rainfall -- Mathematical models , Runoff -- Mathematical models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6035 , http://hdl.handle.net/10962/d1006176
- Description: Hydrological models are widely used tools in water resources estimation, but they are simple representations of reality and are frequently based on inadequate input data and uncertainties in parameter values. Data observation networks are expensive to establish and maintain and often beyond the resources of most developing countries. Consequently, measurements are difficult to obtain and observation networks in many countries are shrinking, hence obtaining representative observations in space and time remains a challenge. This study presents some guidelines on the identification, quantification and reduction of sources of uncertainty in water resources estimation in southern Africa, a data scarce region. The analyses are based on example sub-basins drawn from South Africa and the application of the Pitman hydrological model. While it has always been recognised that estimates of water resources availability for the region are subject to possible errors, the quantification of these uncertainties has never been explicitly incorporated into the methods used in the region. The motivation for this study was therefore to contribute to the future development of a revised framework for water resources estimation that does include uncertainty. The focus was on uncertainties associated with climate input data, parameter estimation (and recognizing the uncertainty due model structure deficiencies) methods and water use data. In addition to variance based measures of uncertainty, this study also used a reservoir yield based statistic to evaluate model output uncertainty, which represents an integrated measure of flow regime variations and one that can be more easily understood by water resources managers. Through a sensitivity analysis approach, the results of the individual contribution of each source of uncertainty suggest regional differences and that clear statements about which source of uncertainty is likely to dominate are not generally possible. Parameter sensitivity analysis was used in identifying parameters which are important withinspecific sub-basins and therefore those to focus on in uncertainty analysis. The study used a simple framework for evaluating the combined contribution of uncertainty sources to model outputs that is consistent with the model limitations and data available, and that allows direct quantitative comparison between model outputs obtained by using different sources of information and methods within Spatial and Time Series Information Modelling (SPATSIM) software. The results from combining the sources of uncertainties showed that parameter uncertainty dominates the contribution to model output uncertainty. However, in some parts of the country especially those with complex topography, which tend to experience high rainfall spatial variability, rainfall uncertainty is equally dominant, while the contributions of evaporation and water use data uncertainty are relatively small. While the results of this study are encouraging, the weaknesses of the methods used to quantify uncertainty (especially subjectivity involved in evaluating parameter uncertainty) should not be neglected and require further evaluations. An effort to reduce data and parameter uncertainty shows that this can only be achieved if data access at appropriate scale and quality improves. Perhaps the focus should be on maintaining existing networks and concentrating research efforts on making the most out of the emerging data products derived from remote sensing platforms. While this study presents some initial guidelines for evaluating uncertainty in South Africa, there is need to overcome several constraints which are related to data availability and accuracy, the models used and the capacity or willingness to adopt new methods that incorporate uncertainty. The study has provided a starting point for the development of new approaches to modelling water resources in the region that include uncertain estimates.
- Full Text:
- Date Issued: 2009
Metallophthalocyanines as photocatalysts for transformation of chlorophenols and self-assembled monolayers for electrochemical detection of thiols and cyanides
- Authors: Ozoemena, Kenneth Ikechukwu
- Date: 2003
- Subjects: Electrochemistry Cyanides Thiols Chlorophenols Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4089 , http://hdl.handle.net/10962/d1007709
- Description: Photochemical properties of sulphonated phthalocyanine complexes of aluminium, zinc, tin and silicon, and octa-carboxyphthalocyanine complexes of aluminium and zinc have been investigated. These water-soluble metallophthalocyanine (MPc) complexes, especially the sulphonated aluminium and zinc phthalocyanines, were found to be good photosensitisers for the transformation of the toxic mono-, tri- and penta-chlorophenols in aqueous solutions. The efficiency of MPc sensitiser towards photo-transformation of chlorophenols depends on its effectiveness to generate singlet oxygen as well as its photostability. Octa-substituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were synthesized and their spectral and electrochemical properties investigated. The photochemical properties ofthe zinc phthalocyanine complexes in non-aqueous solutions were comparable to those in literature. Ultrathin films of the octasubstituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were, for the first time, immobilized onto gold electrodes using the self-assembling technique. Surface electrochemistry indicates that the ultrathin films are surface-confined self-assembled monolayer (SAM) species. Gold electrodes modified with the redox-active SAMs of cobalt and iron phthalocyanine complexes proved to be potential electrochemical sensors for the detection of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in aqueous solutions (pH 4). The limits of detection for the thiols and thiocyanate were in the range of ∼ 10⁻⁷ and 10⁻⁶ mol dm⁻³, respectively. The modification process was reproducible and the modified electrodes showed good stability and, if stored in pH 4 buffer solutions, could be used for the analysis of thiols and thiocyanate for about a month without the need for recalibration. Etching of gold marred electrochemical detection of cyanide with the MPc-SAM-modified gold electrodes. Interestingly, however, kinetic and equilibria studies revealed strong interaction of octabutylthiophthalocyaninatoiron (II), FeOBTPc, with cyanide in both DMF and DMSO solutions.
- Full Text:
- Date Issued: 2003
- Authors: Ozoemena, Kenneth Ikechukwu
- Date: 2003
- Subjects: Electrochemistry Cyanides Thiols Chlorophenols Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4089 , http://hdl.handle.net/10962/d1007709
- Description: Photochemical properties of sulphonated phthalocyanine complexes of aluminium, zinc, tin and silicon, and octa-carboxyphthalocyanine complexes of aluminium and zinc have been investigated. These water-soluble metallophthalocyanine (MPc) complexes, especially the sulphonated aluminium and zinc phthalocyanines, were found to be good photosensitisers for the transformation of the toxic mono-, tri- and penta-chlorophenols in aqueous solutions. The efficiency of MPc sensitiser towards photo-transformation of chlorophenols depends on its effectiveness to generate singlet oxygen as well as its photostability. Octa-substituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were synthesized and their spectral and electrochemical properties investigated. The photochemical properties ofthe zinc phthalocyanine complexes in non-aqueous solutions were comparable to those in literature. Ultrathin films of the octasubstituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were, for the first time, immobilized onto gold electrodes using the self-assembling technique. Surface electrochemistry indicates that the ultrathin films are surface-confined self-assembled monolayer (SAM) species. Gold electrodes modified with the redox-active SAMs of cobalt and iron phthalocyanine complexes proved to be potential electrochemical sensors for the detection of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in aqueous solutions (pH 4). The limits of detection for the thiols and thiocyanate were in the range of ∼ 10⁻⁷ and 10⁻⁶ mol dm⁻³, respectively. The modification process was reproducible and the modified electrodes showed good stability and, if stored in pH 4 buffer solutions, could be used for the analysis of thiols and thiocyanate for about a month without the need for recalibration. Etching of gold marred electrochemical detection of cyanide with the MPc-SAM-modified gold electrodes. Interestingly, however, kinetic and equilibria studies revealed strong interaction of octabutylthiophthalocyaninatoiron (II), FeOBTPc, with cyanide in both DMF and DMSO solutions.
- Full Text:
- Date Issued: 2003
A study of irradiation effects in solids
- Authors: Brown, Michael Ewart
- Date: 1966
- Subjects: Decomposition (Chemistry) , Crystals -- Thermal properties , Oxalates -- Thermal properties , Solids -- Effect of radiation on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4509 , http://hdl.handle.net/10962/d1013387
- Description: One of the primary objects of this research was to determine, if possible, the nature of the radiation damage prior to thermal decomposition. The X-ray study has not wholly achieved this although more information has been derived from it than from similar work on AgMnO₄ However, the diffuse reflections obtained do indicate, quite strongly, the creation of point defects during irradiation. This is of value since such assumptions have been made in the explanation of the kinetics of decomposition of a number of irradiated solids (BaN₆,CaN₆). In addition the X-ray work has suggested future research which should produce useful information; namely, a precise study of the diffuse reflections. Another object of the research was to attempt to determine what characteristics, if any, of the kinetics of the decomposition of an unirradiated solid would predetermine a marked irradiation effect. It is obvious that the type of nuclear growth which occurs e.g. branching chain, or power law, does not characterise a substance with regard to a possible irradiation effect . The photosensitivity, or otherwise, also does not determine whether there will be an irradiation effect. However, the one property that the substances which have been studied, have in common, is a polyatomic anion, but here again ammonium dichromate does not show an acceleration of the decomposition after irradiation. Consequently it is considered that it is not possible to say, a priori, whether a solid will undergo an accelerated decomposition after irradiation. Each new solid, unless it belongs to a particular class e.g. the alkaline earth azides , must be considered afresh. Nevertheless it does appear that the irradiation effect can take two forms: - (i) the production of an unstable compound e.g. nickel oxalate, the decomposition of which affects the normal pyrolysis; and (ii) the production of point defects which determine the nature of the subsequent thermal decomposition e.g . CaN₆ . It is possible that the effect requires an interaction of the created point defects with the existing line defects.
- Full Text:
- Date Issued: 1966
- Authors: Brown, Michael Ewart
- Date: 1966
- Subjects: Decomposition (Chemistry) , Crystals -- Thermal properties , Oxalates -- Thermal properties , Solids -- Effect of radiation on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4509 , http://hdl.handle.net/10962/d1013387
- Description: One of the primary objects of this research was to determine, if possible, the nature of the radiation damage prior to thermal decomposition. The X-ray study has not wholly achieved this although more information has been derived from it than from similar work on AgMnO₄ However, the diffuse reflections obtained do indicate, quite strongly, the creation of point defects during irradiation. This is of value since such assumptions have been made in the explanation of the kinetics of decomposition of a number of irradiated solids (BaN₆,CaN₆). In addition the X-ray work has suggested future research which should produce useful information; namely, a precise study of the diffuse reflections. Another object of the research was to attempt to determine what characteristics, if any, of the kinetics of the decomposition of an unirradiated solid would predetermine a marked irradiation effect. It is obvious that the type of nuclear growth which occurs e.g. branching chain, or power law, does not characterise a substance with regard to a possible irradiation effect . The photosensitivity, or otherwise, also does not determine whether there will be an irradiation effect. However, the one property that the substances which have been studied, have in common, is a polyatomic anion, but here again ammonium dichromate does not show an acceleration of the decomposition after irradiation. Consequently it is considered that it is not possible to say, a priori, whether a solid will undergo an accelerated decomposition after irradiation. Each new solid, unless it belongs to a particular class e.g. the alkaline earth azides , must be considered afresh. Nevertheless it does appear that the irradiation effect can take two forms: - (i) the production of an unstable compound e.g. nickel oxalate, the decomposition of which affects the normal pyrolysis; and (ii) the production of point defects which determine the nature of the subsequent thermal decomposition e.g . CaN₆ . It is possible that the effect requires an interaction of the created point defects with the existing line defects.
- Full Text:
- Date Issued: 1966
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