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Cogitator : a parallel, fuzzy, database-driven expert system

  • Authors: Baise, Paul
  • Date: 1994 , 2012-10-08
  • Subjects: Expert systems (Computer science) , Artificial intelligence -- Computer programs , System design , Cogitator (Computer system)
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4667 , http://hdl.handle.net/10962/d1006684 , Expert systems (Computer science) , Artificial intelligence -- Computer programs , System design , Cogitator (Computer system)
  • Description: The quest to build anthropomorphic machines has led researchers to focus on knowledge and the manipulation thereof. Recently, the expert system was proposed as a solution, working well in small, well understood domains. However these initial attempts highlighted the tedious process associated with building systems to display intelligence, the most notable being the Knowledge Acquisition Bottleneck. Attempts to circumvent this problem have led researchers to propose the use of machine learning databases as a source of knowledge. Attempts to utilise databases as sources of knowledge has led to the development Database-Driven Expert Systems. Furthermore, it has been ascertained that a requisite for intelligent systems is powerful computation. In response to these problems and proposals, a new type of database-driven expert system, Cogitator is proposed. It is shown to circumvent the Knowledge Acquisition Bottleneck and posess many other advantages over both traditional expert systems and connectionist systems, whilst having non-serious disadvantages. , KMBT_223
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  • Date Issued: 1994

Characterisation of InAs-based epilayers by FTIR spectroscopy

  • Authors: Baisitse, Tshepiso Revonia
  • Date: 2007
  • Subjects: Fourier transform infrared spectroscopy , Gallium arsenide semiconductors
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10534 , http://hdl.handle.net/10948/474 , Fourier transform infrared spectroscopy , Gallium arsenide semiconductors
  • Description: This study focuses on the characterization of InAs and InAs1-xSbx epitaxial layers by infrared reflectance and transmittance spectroscopy and Hall measurements. Reflectance measurements were performed in order to obtain the dielectric parameters and to extract from these information about the electrical properties (mobility and carrier concentration) of this important III-V material system. The transmittance measurements were used to determine the bandgap of InAsSb. Infrared reflectivity and transmittance measurements were performed in the wavelength range 200 – 2000 cm-1 on InAs and InAsSb layers grown on three types of substrates. A classical two oscillator model that takes into account both the free carriers and the lattice, was used to analyse the reflectance data using the BMDP® computer curve fitting software. The dielectric parameters and the electrical properties (carrier concentration and mobility) were extracted from the simulations. Due to the low free carrier concentration in the epitaxial structures, the plasma resonance frequency (ωp) values obtained from the simulations of reflectance spectra measured above 200 cm-1, were in the order of 20-30 cm-1. These low values were confirmed by direct measurements of ωp in reflectance spectra obtained in the range 15-200 cm-1. The simulated carrier concentration and mobility values determined optically were compared to the values determined by Hall measurements at room temperature and previously reported values by other researchers. The simulated values obtained were in reasonable agreement with the Hall values. The simulated and measured carrier concentrations obtained for InAs layers were significantly higher than the intrinsic carrier concentration for InAs at room temperature, indicating notable concentrations of donors resulting from the growth process.
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  • Date Issued: 2007

The role of protected areas in the conservation and management of fisheries in the Chobe District of Botswana

  • Authors: Bakane, Modiegi
  • Date: 2017
  • Subjects: Cichlids Botswana Chobe District , Protected areas Botswana Chobe District , Fishery management Botswana Chobe District
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/7459 , vital:21262
  • Description: This study was aimed at better understanding the function of protected areas as a management strategy for the Chobe District fishery in Botswana, by first investigating the relative abundance in fish communities in and outside protected areas and secondly, by performing an assessment of the biology of commercially important large cichlid species viz threespot tilapia Oreochromis andersonii, greenhead tilapia Oreochromis macrochir and redbreast tilapia Coptodon rendalli. In this study, data and specimens were collected during seasonal surveys between September 2014 and April 2015, using the standard graded fleets of gillnets employed in other programmes in the region, together with D-nets, angling and electro-fishing. The study demonstrated that fish communities in the floodplain ecosystems in the Chobe District of Botswana were representative of the region, containing some 70 species in 14 families. This study also demonstrated that for all the species collected, the mean Catch Per Unit Effort (CPUE) by weight for all the species was significantly higher in protected areas (Kruskal Wallis Test; P<0.05) namely, Zibadianja Lagoon (38 ± 31 kg/net.night"1 and Savuti River/marsh 25 ± 19 kg/net.night"1) than in the fished Chobe River floodplains CPUE (6 ± 3 kg/net.night-1). Biological contributions were estimates of longevity, growth and maturity for O. andersonii, O. macrochir and C. rendalli. Age and growth were estimated using sectioned sagittal otoliths. The Von Bertalanffy growth equation from otolith derived length at age was Lt(mm) =298 (1-e-0 59(t=- 098)) for O. andersonii and Lt(mm) = 337 (1-e-0'20(t=-235)) for C. rendalli. The results indicated that protected areas enhanced fish longevity, and fish in protected areas were larger and older than those in exploited areas. Maturity estimates for the large cichlids were consistent with other research in the region and the length-at-50% maturity was estimated as 250mm Lt for O. andersonii, 225 mm Lt for O. macrochir and 210 mm Lt for C. rendalli. Management recommendations are therefore to retain gill net mesh size regulations that ensure that these fish reach maturity and can breed before being harvested and to assess the possibility of increasing the number of protected areas in the district.
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  • Date Issued: 2017

Some ionospheric effects observed at sunrise

  • Authors: Baker, D C
  • Date: 1964
  • Subjects: Sun -- Rising and setting , Ionosphere -- Research
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5513 , http://hdl.handle.net/10962/d1009496 , Sun -- Rising and setting , Ionosphere -- Research
  • Description: The study of the ionosphere over the sunrise period is necessary for an understanding of the vtiriations in layer structure with time and has been a topic of research of many workers. On the whole these investigations have been restricted to a study of critical frequency variations with relatively short intervals of a few minutes between successive records, of N-h curves deduced from ionograms with long intervals (15 minutes or so) between successive N-h curves or of continuously monitored single frequency reflections. Not one of the three techniques is entirely satisfactory for a detailed study of ionospheric behaviour over sunrise. The first two do not give a sufficiently clear indication of what happens in the initial stages of layer development, while from the third incomplete data is obtained as to what is happening at a specific electron-density level. For this reason a preliminary investigation of the ionosphere over sunrise was made at Rhodes University during August, 1959. The records were obtained at four-and-a-half minute intervals and scaled by the method of KELSO (1952 ). "Many of t he results were inconclusive but it appeared that records would have to be taken at approximately one minute intervals and reduced to N-h curves by a scaling technique which made full allowance for low-level ionization if useful results were to be obtained. An attempt has been made in this thesis to investigate the behaviour of the ionosphere over sunrise more fully than can be done by the three techniques referred to. A number of observed phenomena are also examined. Part I deals with the theoretical background to ionosphere physics in general and describes the equipment, equipment modifications and experimental procedure. Part II presents the results obtained. The records for a largescale travelling disturbance are analysed. Various observed phenomena are described and discussed. A simple method of obtaining production rates from experimental data is described. The implications of the observed variations of production rates with height and time are discussed. Suggestions for further research and improvement of the methods used arc made in Charter 9.
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  • Date Issued: 1964

Bacterial degradation of the acaricide amitraz

  • Authors: Baker, Penelope Bridget
  • Date: 1976
  • Subjects: Acaricides , Biodegradation , Gas chromatography , Bacteriology -- Cultures and culture media
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4099 , http://hdl.handle.net/10962/d1009498
  • Description: This thesis describes dip tank field trials and laboratory investigations on the acaricide Amitraz. Amitraz is a triazapenta- diene compound which is relatively unstable in fouled dip washes. The field trials were conducted on the farm Sea View according to the "Total Replacement Method" and on the farm Sea Ways according to the "Lime Stabilization Method" of dipping. The results of these trials showed that Amitraz was stable in clean dip washes, and under conditions of high pH resulting from the addition of slaked lime to the dip wash. Using mixed bacterial populations optimum conditions for degradation of Amitraz in the laboratory were determined. Bacterial cultures degraded Amitraz most efficiently in media supplemented with yeast extract or with a high content of sterile cattle faeces. Amitraz concentrations were determined by gas chromatography. A culture. efficient at degrading Amitraz was enriched from a dip tank sludge inoculum. From this culture ten bacterial isolates were identified; nine of these were of the genus Pseudomonas and one was an Achromobacter sp. Experiments with both mixed and pure cultures demonstrated that bacterial degradation of Amitraz was by the process of co-metabolism. The existence of four degradation products was shown using thin layer chromatography. Tentative identification of two of the products was made.
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  • Date Issued: 1976

The use of a silica based coating to reduce moisture absorption of flax fibre reinforced composites

  • Authors: Bala, Sandisiwe
  • Date: 2018
  • Subjects: Chromatographic analysis , Nonwoven fabrics Nanocomposites (Materials)
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/23349 , vital:30534
  • Description: This study deals with the synthesis of silica particles, treatment of flax fabrics with silica, and the preparation and characterization of silica coated flax fibre reinforced phenolic composites treated with silica. Silica particles were successfully prepared by means of a hydrolytic sol-gel route. Two types of silica were prepared by employing either ammonium hydroxide solution as a base catalyst and acetic acid as an acid catalyst. The silica sols were then aged from three to five days in order to determine the effects of aging on the final properties of the silica. The chemical composition of the silica particles was evaluated by fourier transform infrared spectroscopy (FTIR), thermal stability was determined by using thermogravimetric analysis (TGA), and structural and physical properties of the silica particles prepared via two catalysts and aged at different time periods was investigated by x-ray diffraction (XRD). Silica sols, prepared at different conditions were then applied to treat flax fabrics (untreated/scoured) by use of the padding technique. The effects of the silica treatments on flax fabrics were evaluated by FTIR, XRD, determination of moisture content and mechanical properties. The FTIR revealed presence of silica groups on the silica treated flax fabrics, thus resulting in low moisture content for silica treated flax fabrics. XRD analysis revealed that aging the silica sols increases the crystallinity index. Silica treated flax fabrics showed enhanced tensile properties in the weft direction. The thermal, mechanical and water sorption properties of the composites were evaluated. TGA results revealed that the decomposition temperatures of the silica treated composites shifted to higher temperatures. Thus, silica treatments lead to an improvement in thermal stability for composites. A reduction in mechanical properties was also observed for silica treated composites and some composites showed a reduction in water absorption. It was quite evident from this study that the type of catalyst system used in silica preparation has a great influence on the final properties of the silica, which to a large extent changes the thermal, mechanical and water sorption properties of the composites.
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  • Date Issued: 2018

Size-fractionated phytoplankton biomass and primary production in the Southern Ocean

  • Authors: Balarin, Marianne G
  • Date: 1999
  • Subjects: Biomass -- Analysis , Phytoplankton , Atlantic Ocean
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5765 , http://hdl.handle.net/10962/d1005453 , Biomass -- Analysis , Phytoplankton , Atlantic Ocean
  • Description: The factors controlling primary production in the Southern Ocean were investigated over two years during two cruises of the South African National Antarctic Program (SANAP). The first cruise was conducted to the region of the eastern Atlantic sector of the Southern Ocean during the collaborative Scandinavian/South African Antarctic expedition conducted in austral summer (DecemberIFebruary) 1997-1998. Production studies were conducted in the vicinity of the Marginal Ice Zone (MIZ), Interfrontal Zone (IFZ) and Antarctic Polar Front(APF). The second cruise was conducted during the Third Marion Island Oceanographic Survey (MIOS III) to the region of the Sub-Antarctic Prince Edward Islands in austral autumn (April/May) 1998. Size-fractionated production rates were estimated by 14C incorporation using standard JGOFS protocols. Oceanographic data from the first cruise suggest that the three regions can be divided into two distinct regimes. Stations occupied in the vicinity of the MIZ and the APF were characterised by a shallow mixed layer depth « 40m) while at the IFZ-stations, the mixed layer depth exceeded the 1% light depth. Microphytoplankton dominated integrated chlorophyll-a biomass in the MIZ (total chlorophyll a ranged between 15.4 and 41.3 mg Chi-a. m-2) and at the APF (range between 10.7 and 31.4 mg Chi-a. m-2) , comprising > 50% of total chlorophyll-a at all these stations. Xl Within the IFZ (2 stations), nanophytoplankton dominated total integrated Chl-a biomass (range between 5.6 and 8.8 mg Chi-a. m-2) comprising, on average, 36% of the total. Picophytoplankton comprised an average of 12% of the total Chl-a biomass (range between 3.1 and 5.9 mg Chi-a. m-2) in the MIZ, 36% in the IFZ (range between 6.4 and 7.8 mg Chl-a . m-2) and 20% in the vicinity of the APF (range between 6.8 and 10.6 mg Chi-a. m-2). Total integrated primary production ranged between 316 and 729 mg C . m-2. d-1 at stations occupied in the vicinity of the MIZ, and between 292 and 317 mg C . m·2• d-l within the IFZ. At stations occupied in the region of the APF, total integrated production ranged between 708 and 926 mg C . m-2• dol. The contribution of various size fractions to total productivity generally displayed the same pattern as integrated Chl-a biomass. Microphytoplankton formed the most important contributor to total production at stations occupied in the MIZ and at the APF. Within the IFZ, nanophytoplankton dominated total daily production. Nutrient data suggest that concentrations of macro nutrients within the upper water column were above the threshold where growth would be limited. Preliminary results showed that concentrations of iron (Fe) were highest in the southern region of the MIZ and in the vicinity of the APF. During the second cruise, conducted in the vicinity of the Sub-Antarctic Front (SAF) and in the upstream, inter-island and downstream regions of the Prince Edward Islands, there was evidence of fresh water run-off from the islands, (i.e. decreased salinities and increased concentrations of ammonia and nitrate). Oceanographic data collected at the various production stations indicated that the upper water column was well mixed throughout the survey. Total integrated biomass during the study ranged between 8.5 and 20.1 mg Chi-a. m-2• No distinct patterns in total Chl-a biomass were evident. Picophytoplankton dominated total biomass comprising> 45 % of total pigment at all stations. Nanophytoplankton were the second most important contributor to total integrated biomass. Generally xu microphytoplankton contributed < 10 % of total ChI-a. Total daily integrated production was highest (442.6 mg Chi-a. m-2) at the single station occupied in the vicinity of the SAF. Outside this region, total areal production was lower, ranging from 94.5 to 353.0 mg C . m-2. d-1. With the exception of the station occupied in the vicinity of the SAF, total productivity was dominated by nanophytoplankton, which comprised between 48 and 66% of the total. Concentrations of macronutrients did not appear to be limiting to phytoplankton growth. The absence of a phytoplankton bloom in the vicinity of the islands appears to have been related to water column stability, which was influenced by the prevailing oceanographic regime during the survey. Previous studies have shown that when the SAF lies in close proximity to the islands, advecting forces prevail, resulting in the islands functioning as a flow-through system. During this study, the SAF lay immediately north of the islands. As a consequence no water was trapped in the leeward side of the islands. The results of the two cruises suggest that phytoplankton production in the four systems investigated: the Marginal Ice Zone (MIZ), Antarctic Polar Front (APF), Inter Frontal Zone (IFZ) and Prince Edward Islands (PEl), was largely controlled by water column stability. It is probable that the availability of iron, particularly in the region of the MIZ and APF, may have further contributed to the elevated production recorded in these two regions.
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  • Date Issued: 1999

An investigation into the use of a ceramifiable Ethylene Vinyl Acetate (EVA) co-polymer formulation to aid flame retardency in electrical cables

  • Authors: Bambalaza, Sonwabo Elvis
  • Date: 2014
  • Subjects: Vinyl acetate , Polymeric composites , Inorganic compounds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:10433 , http://hdl.handle.net/10948/d1020159
  • Description: The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.
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  • Date Issued: 2014

Analyses of the simple harmonic oscillator and its variations

  • Authors: Bambiso, Noludwe Patience
  • Date: 2017
  • Subjects: Harmonic analysis Vibration -- Mathematical models Oscillations
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10353/8132 , vital:31530
  • Description: Vibratory motion is fundamental to all natural phenomena. It occurs everywhere in nature, from fundamental particles to the complexity of the life of the smallest cell, to the properties of the cosmos. Its frequency ranges from those of gammarays down the spectrum of X-rays, microwave, optical and radio waves. These are common concepts in everyday life, but their origin and nature are seldom comprehended. In this thesis we look at the mathematical fundamentals and how to apply them. We start with fundamental concepts and extend them to more complicated systems. We consider methods of analysis and applications. In Chapter 2 we consider simple harmonic oscillators and their mathematical analyses and in Chapter 3 we look at applications. Chapter 4 discusses the general form of simple harmonic motion, i.e. damped and forced harmonic motion. We consider simple coupled systems and their analysis. In Chapter 5 we introduce the method of complex functions and its application to complicated compound systems. Chapter 6 introduces a novel application, that of how SHM can be used as a model for advanced effects, or acausality. Chapter 7 presents a summary and conclusion.
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  • Date Issued: 2017

The sorption of Hydrochloric Acid and Potassium Hydroxide by mohair and wool

  • Authors: Bamford, Graeme Reginald Ernest
  • Date: 1959
  • Subjects: Hydrochloric acid -- Absorption and adsorption , Hydroxides -- Absorption and adsorption , Wool , Mohair
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4452 , http://hdl.handle.net/10962/d1009503
  • Description: The main object of the present investigation has been to establish a titration curve for mohair keratin and to compare it with similar data for wool, to determine whether the differences in physical and chemical properties could be attributed in any way to the acidic and basic character of these fibres. As shown in subsequent discussion such measurements provide extremely useful information regarding the chemical structure of proteins in general, and in the technical fields involving processes such as wool scouring, carbonizing and dyeing. The study has been extended to include certain modified wools, i.e. photochemically damaged, and oxidized keratin. The most successful contribution to the titration data of wool keratin is the work of Steinhardt and Harris and subsequent authors have tended to adopt their procedures without modification. In the present study attempts have been made to obtain a clearer understanding of the fundamental processes. New techniques and analytical methods have been introduced to improve the accuracy of the measurements.
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  • Date Issued: 1959

An analysis on the use of web-based ontology to support ubiquitous learning in South African secondary schools

  • Authors: Bamigboye, Oluwatosin Omotoyosi
  • Date: 2018
  • Subjects: Internet in education World Wide Web Ontology
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10353/12859 , vital:39385
  • Description: There is certainly a need to upgrade our educational system and this can be done through technology-enhanced learning. Technology-enhanced learning can be achieved by developing a web-based ontology e-learning platform, which allows learning to take place ubiquitously. In achieving this task, this research is focusing on analyzing the use of web-based ontology to support the design and implementation of a ubiquitous learning system in South Africa. The implemented web-based ontology e-learning system was deployed and tested. The system testing was done on two variables (Information retrieval and Scalability) of localhost and client system, with the following testing metrics: time is taken for information retrieval, request time to process the request, transfer rate, time localhost receives request, time to respond, roundtrip time for request and network usage. The metrics testing was achieved using apache benchmarking console and gnuplot application to generate the data captured and performance graph, while Wireshark was also used to test/analyze round trip time and network usage through the deployed system. The results of the findings in this study show that the relationship between student and learning content becomes explicit when using ontology technology in searching, organizing, gathering and development content. Results obtained from information retrieval show that the transfer rate of information on localhost for 100 request @ current level of 5 is 37169.89kb/s, while on the client’s system, the transfer rate was 48494.36kb/s which was due to multiple request on the client’s side. Results obtained on scalability shows the round trip time which was (time to respond-time to request). The longest roundtrip was 8 seconds as a result of network being congested with multiple packets request from various sources trying to access the localhost at the same time while the fastest was 1 seconds. The implications of this results show that web-based ontology e-learning system has a positive input to teaching and learning processes in schools for content retrieval and network usage. The system furthermore shows the relationship adopted by learners and teachers, and also the match needs that arise in between. The contribution of this study adds to the existing discoveries on the use of web-based and knowledge-based ontology.
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  • Date Issued: 2018

Assessing the outcomes and consequences of large carnivore reintroductions to the Eastern Cape, South Africa

  • Authors: Banasiak, Natalia Matgorzata
  • Date: 2017
  • Subjects: Carnivores -- Reintroduction , Wildlife reintroduction
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/11963 , vital:27011
  • Description: Reintroduction is a potentially powerful tool available to conservationists to cope with species population declines. Nonetheless, it is poorly understood and past reviews tend to indicate poor results. Reintroduction, under the sensu stricto IUCN definition, must have a primary objective of conservation; however species can be released to sites in their indigenous range (reintroduction sensu lato) to meet other objectives. The outcomes of these reintroductions s.l need to be assessed to determine how effectively they achieve their varied objectives. A Web of Science review revealed that only 32.1% of 131 publications on reintroduction provided clearly defined success criteria. Using economic, ecological, conservation and problem animal management objectives as reintroduction s.l. drivers, I developed context-dependent success definitions for each objective to use in reintroduction outcome assessments. These success criteria were then used to assess the reintroductions s.l. of large carnivores, namely lion, leopard, cheetah, African wild dog, spotted hyaena, and brown hyaena, to 16 private- and state-owned reserves in the Eastern Cape Province, South Africa. Ecotourism and ecological restoration were the most common objectives for the reintroduction of top predators to these reserves. Overall the reintroductions of large carnivores have been successful in meeting their objectives. Only African wild dogs have failed to establish in the province. Causes of objective-specific failures for the other species in some reserves included introductions of same-sex populations, lack of breeding events and changes in reserve management objectives. Assessments for leopard and brown hyaena were inconclusive due to lack of monitoring data. The reintroduction of large carnivores to the Eastern Cape Province has also resulted in the emergence of human-carnivore conflict on neighbouring properties. Carnivores have reportedly escaped from 8 reserves (61.5% of reserves) in the Eastern Cape. A total of 75 conflict events on 68 neighbouring properties (36.7% of neighbouring properties) have been reported. There is a major gap in research around conflict resulting from carnivore reintroductions and future research is required to fully understand the situation in the province in order to develop effective mitigation methods. An adaptive management approach to reintroductions is encouraged to improve monitoring and ensure reintroductions continue to meet their objectives. Furthermore, emerging consequences, such as human-wildlife conflict, and related mitigation strategies should be incorporated into management of reintroduced populations. Communities surrounding reintroduction sites should be educated on lifting baselines where conflict-causing species are recovering to ensure continued success of reintroduction undertakings. National management plans should be developed for all large carnivore species to improve the conservation value of small, fenced reserves that are typical of South African conservation, through a managed metapopulation approach. Management plans should include social, political, and economic factors that can influence the success of reintroductions and ultimate conservation outcomes.
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  • Date Issued: 2017

A crowdsensing method for water resource monitoring in smart communities

  • Authors: Banda, Clara Mloza
  • Date: 2019
  • Subjects: Data collection platforms
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/42449 , vital:36658
  • Description: Crowdsensing aims to empower a large group of individuals to collect large amounts of data using their mobile devices, with the goal of sharing the collected data. Existing crowdsensing studies do not consider all the activities and methods of the crowdsensing process and the key success factors related to the process. Nor do they investigate the profile and behaviour of potential participants. The aim of this study was to design a crowdsensing method for water resource monitoring in smart communities. This study opted for an exploratory study using the Engaged Scholarship approach, which allows the study of complex real-world problems based on the different perspectives of key stakeholders. The proposed Crowdsensing Method considers the social, technical and programme design components. The study proposes a programme design for the Crowdsensing Methodwhich is crowdsensing ReferenceFrameworkthat includes Crowdsensing Processwith key success factors and guidelines that should be considered in each phase of the process. The method also uses the Theory of Planned Behaviour (TPB) to investigate citizens’intention to participate in crowdsensing for water resource monitoring and explores their attitudes, norms and perceived behavioural control on these intentions. Understanding the profiles of potential participants can assist with designing crowdsensing systems with appropriate incentive mechanisms to achieve adequate user participation and good service quality. A survey was conducted to validate the theoretical TB model in a real-world context. Regression and correlation analyses demonstrated that the attitudes, norms and perceived behavioural control can be used to predict participants’ intention to participate in crowdsensing for water resource monitoring. The survey results assisted with the development of an Incentive Mechanism as part of the Crowdsensing Method. This mechanism incorporates recruitment and incentive policies, as well as guidelines derived from the literature review and extant system analysis. The policies, called the OverSensepolicies, provide guidance for recruitment and rewarding of participants using the popular Stackelberg technique. The policies were evaluated using simulation experiments with a data set provided by the case study, the Nelson Mandela Bay Municipality. The results of the simulation experiments illustrated that the OverSenserecruitmentpolicycan reduce the computing resources required for the recruitment of participants and that the recruitment policy performs better than random or naïve recruitment policies. The proposed Crowdsensing Method was evaluated using an ecosystem of success factors for mobile-based interventions identified in the literature and the Crowdsensing Method adhered to a majority (90%) of the success factors. This study also contributes information systems design theory by proposing several sets of guidelines for crowdsensing projects and the development of crowdsensing systems. This study fulfils an identified need to study the applicability of crowdsensing for water resource monitoring and explores how a crowdsensing method can create a smart community.
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  • Date Issued: 2019

The use of image processing to determine cell defects in polycrystalline solar modules

  • Authors: Banda, Peter
  • Date: 2019
  • Subjects: Polycrystals
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10948/36573 , vital:33996
  • Description: This research aims to use image processingtodetermine cell defects in polycrystalline solar modules. Image processing is a process of enhancing images for differentapplications. One domain that seems to not yet utilise the use of image processing, is photovoltaics. An increased use of fossil fuels is damaging the earth and a call to protect the earth has resulted in the emergence of pollutant-free technologies such as polycrystalline photovoltaic (PV) cells, which are connected to make up solar modules. However, defects often affect the performance of PV cells and consequently solar modules. Electroluminescence (EL) images are used to examine polycrystalline solar (PV) modules to determine if the modules are defective. The main research question that this research addressed is“How can an image processing technique be used to effectively identify defective polycrystalline PV cells from EL images of such cells?“. The experimental research methodology was used to address the main research question. The initial investigation into the problem revealed that certain sectors within industry, as well as the Physics Department at Nelson Mandela University(NMU), do not currently utiliseimage processing when examining EL images of solar modules. The current process is a tedious, manual process whereby solar modules are manually inspected. An analysis of the current processes enabled the identification of ways in which to automatically examine EL images of solar modules. An analysis of literatureprovided a better understanding of the different techniques that are used to examine solar modules, and it was identified how image processing can be applied to EL images. Further analysis of literatureprovided a better understanding of image processing and how image classification experiments using Deep Learning (DL) as an image processing technique can be used to address the main research question. The outcome of the experiments conducted in this research weredifferentadaptive models(LeNet, MobileNet, Xception)that can classify EL images of PV cellsaccording to known standardsused by the Physics Department at NMU. The known standards yielded four classes; normal, uncritical, critical and very critical, which were used for the classification of EL images of PV cells. The adaptive models were evaluated to obtain the precision, recall and F1–scoreof the models.The precession, recall, and F1–score were required to determine how effective the models were in identifying defective PV cells from EL images.The results indicated that an image processing technique canbe used to identify defective polycrystalline PV cells from EL images of such cells. However, further research needs to be conducted to improve the effectiveness of the adaptive models.
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  • Date Issued: 2019

Determining and analysing the emergent behaviour from context-aware devices

  • Authors: Bandason, Vivian
  • Date: 2017
  • Subjects: Context-aware computing Mobile computing
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10353/7907 , vital:30805
  • Description: With the continued miniaturization of technology and the incorporation of Moore’s law, smartphones are more powerful. These mobile devices contain technologies that add other functionalities to them. Technologies such as sensors constantly provide information to the device. The constant stream of information from these sensors often leads to information overload of relevant and irrelevant information. To work towards solving this problem context-aware computing was introduced. Our major concern is that context information in context aware computing is not completely being utilized. The aggregation of context information could unlock more possibilities. This research seeks to aggregate the context of multiple devices such that, through analysis, some emergent behaviour can be observed. In this research context information from the sensors of devices is collected using an Android application and a central Server. The context information is used for pattern analysis. A pattern analysis algorithm is designed and used to observe patterns throughout the data set. It shows patterns that are similar within the dataset. In the case that the pattern observed has no similar pattern or few similar patterns this behaviour can be stated as emergent in the dataset. Further study of this emergent behaviour can be performed were a classifier can be used to give the exact activities that were being performed at that time. The research found this was possible and has many uses. One of these is in disaster prevention were the behaviour of a group of individuals may be monitored to observe any random changes such as masses running at the same time. This could be used as a first warning to natural disasters.
  • Full Text:
  • Date Issued: 2017

Parallel implementation of a virtual reality system on a transputer architecture

  • Authors: Bangay, Shaun Douglas
  • Date: 1994 , 2012-10-11
  • Subjects: Virtual reality , Computer simulation , Transputers
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4668 , http://hdl.handle.net/10962/d1006687 , Virtual reality , Computer simulation , Transputers
  • Description: A Virtual Reality is a computer model of an environment, actual or imagined, presented to a user in as realistic a fashion as possible. Stereo goggles may be used to provide the user with a view of the modelled environment from within the environment, while a data-glove is used to interact with the environment. To simulate reality on a computer, the machine has to produce realistic images rapidly. Such a requirement usually necessitates expensive equipment. This thesis presents an implementation of a virtual reality system on a transputer architecture. The system is general, and is intended to provide support for the development of various virtual environments. The three main components of the system are the output device drivers, the input device drivers, and the virtual world kernel. This last component is responsible for the simulation of the virtual world. The rendering system is described in detail. Various methods for implementing the components of the graphics pipeline are discussed. These are then generalised to make use of the facilities provided by the transputer processor for parallel processing. A number of different decomposition techniques are implemented and compared. The emphasis in this section is on the speed at which the world can be rendered, and the interaction latency involved. In the best case, where almost linear speedup is obtained, a world containing over 250 polygons is rendered at 32 frames/second. The bandwidth of the transputer links is the major factor limiting speedup. A description is given of an input device driver which makes use of a powerglove. Techniques for overcoming the limitations of this device, and for interacting with the virtual world, are discussed. The virtual world kernel is designed to make extensive use of the parallel processing facilities provided by transputers. It is capable of providing support for mUltiple worlds concurrently, and for multiple users interacting with these worlds. Two applications are described that were successfully implemented using this system. The design of the system is compared with other recently developed virtual reality systems. Features that are common or advantageous in each of the systems are discussed. The system described in this thesis compares favourably, particularly in its use of parallel processors. , KMBT_223
  • Full Text:
  • Date Issued: 1994

Developing a citizen technician based approach to suspended sediment monitoring in the Tsitsa River catchment, Eastern Cape, South Africa

  • Authors: Bannatyne, Laura Joan
  • Date: 2018
  • Subjects: Sediments (Geology) -- Management , Sediments (Geology) -- South Africa -- Eastern Cape , Watersheds -- South Africa -- Eastern Cape , Suspended sediments -- South Africa -- Eastern Cape , Suspended sediments -- Monitoring -- Citizen participation , Tsitsa River
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/62593 , vital:28211
  • Description: Suspended sediment (SS) in channels is spatiotemporally heterogeneous and, over the long term, is known to be moved predominantly by flood flows with return periods of ~1 - 1.5 years. Flood flows in the Tsitsa catchment (Eastern Cape Province, South Africa) are unpredictable, and display a wide range of discharges. Direct, flood-focused SS sampling at sub-catchment scale was required to provide a SS baseline against which to monitor the impact on SS of catchment rehabilitation interventions, to determine the relative contributions of sub-catchments to SS loads and yields at the site of the proposed Ntabelanga Dam wall, and to verify modelled SS baselines, loads and yields. Approaches to SS sampling relying on researcher presence and/or installed equipment to adequately monitor SS through flood flows were precluded by cost, and the physical and socioeconomic conditions in the project area. A citizen technician (CT)-based flood-focused approach to direct SS sampling was developed and implemented. It was assessed in terms of its efficiency and effectiveness, the proficiency of the laboratory analysis methods, and the accuracy of the resulting SS data. A basic laboratory protocol for SSC analysis was developed, but is not the focus of this thesis. Using basic sampling equipment and smartphone-based reporting protocols, local residents at eleven points on the Tsitsa River and its major tributaries were employed as CTs. They were paid to take water samples during daylight hours at sub-daily timestep, with the emphasis on sampling through flood flows. The method was innovative in that it opted for manual sampling against a global trend towards instrumentation. Whilst the management of CTs formed a significant project component, the CTs benefitted directly through remuneration and work experience opportunities. The sampling method was evaluated at four sites from December 2015 - May 2016. The CTs were found to have efficiently and effectively sampled SS through a range of water levels, particularly in the main Tsitsa channel. An acceptable level of proficiency and accuracy was achieved, and many flood events were successfully defined by multiple data points. The method was chiefly limited by the inability of CTs to sample overnight rises and peaks occurring as a result of afternoon thunderstorms, particularly in small tributaries. The laboratory process was responsible for some losses in proficiency and accuracy. Improved laboratory quality control was therefore recommended. The CT-based approach can be adapted to other spatial and temporal scales in other areas, and to other environmental monitoring applications.
  • Full Text:
  • Date Issued: 2018

Thermodynamic and electrical performance monitoring of a domestic split-type air conditioner and development of a simulation based R22 permanent replacement

  • Authors: Bantan, Mafor Glory
  • Date: 2017
  • Subjects: Air conditioning
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10353/4857 , vital:28537
  • Description: The difficulty that exists in accurately monitoring the performance of air conditioners has made performance prediction an arduous task. Nevertheless, the performance still needs to be monitored and predicted as it helps solve a lot of problems resulting from this technology like effect of the technology on the grid, energy consumption, water utilisation and GHGs emission. With the introduction of regression modelling as a means of system monitoring and prediction some years ago, the accuracy was still a call for concern. It is worth realising that increasing the number of predictors will enhance this method’s accuracy. As such, this document intends to increase the accuracy of this method’s monitoring and predicting ability by increasing the number of predictors to cut across system thermal, environmental and human behavioural variation. These predictors experimentally gotten are used to build an environ-behavioural model that monitors the coefficient of performance and energy consumption of a domestic split-type air conditioner with higher accuracy. Refrigerants have undergone evolution in the past decades in a bid to come up with a refrigerant that has zero ODP, lower – than – R22 GWP and much better than R22 thermodynamic performance. No pure refrigerant has been found to possess these qualities as such mixtures or blends are the best shot at the moment. R410A could stand the test of time to be the long term R22 replacement but for the fact that besides R410A’s higher GWP than that of R22, the former’s system performance is lower than that of the latter’s due to the lower thermodynamic performance of the former. This means the search continues. In this document, a combination of carefully chosen refrigerant components are carefully blended to come up with a simulation based R22 long term replacement, which will be referred to in this document as BTEP.
  • Full Text:
  • Date Issued: 2017

Design, formulation and evalauation of liposomes co-loaded with human serum Albumin and Rifampicin

  • Authors: Bapolisi, Alain Murhimalika
  • Date: 2020
  • Subjects: Liposomes , Serum albumin , Rifampin , Mycobacterium tuberculosis
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/161780 , vital:40670
  • Description: Tuberculosis (TB) is a devastating infectious disease caused by Mycobacterium tuberculosis and is the leading cause of death from a single infectious agent. The high morbidity and mortality rates of TB are partly due to factors such as the lengthy regimen (of 6–24 months), the development of drug resistance, and the pathogen location within the macrophages. These, with poor physiochemical properties of existing drugs hamper the effectiveness of the treatment despite the existence of potent antibiotics such as Rifampicin (Rif). Hydrophobicity plagues many drugs, including Rif, which are then particularly affected due to inherently poor intracellular availability. Novel drug delivery approaches are therefore needed in order to optimize the cytotoxic potential of said antitubercular drugs. To improve the bioavailability of hydrophobic drugs, numerous delivery strategies have been developed. Amongst these, the coordination of cytotoxic drugs to therapeutic proteins have shown some success for improved efficacy in the management of illnesses including infectious diseases. Of therapeutic proteins, Human Serum Albumin (HSA) is an attractive drug carrier with interestingbenefits such as low immunogenicity, antioxidant properties and improving cellular uptake ofdrugs through HSA-specific binding sites which are expressed on most cells including macrophages, where M. tuberculosis often resides. Hence, combination of Rif to HSA (Rif-HSA)seems a promising approach for improved intracellular delivery of Rif. However, the in vivo stability of colloidal protein-based therapeutics is mostly challenging and an effective vehicle is needed to control the biological fate of such conjugates.Liposomes seem to be appropriate carriers for the Rif-HSA complex due to their reputable applicability for encapsulating diverse materials (i.e., hydrophobic and hydrophilic compounds or small and complex molecules) and preventing chemical and biological degradation of the cargo. Therefore, the main objective of this study was to simultaneously encapsulate Rif and HSA in liposomes, which, to the best of our knowledge, has not been done before. The dual liposomes (Rif-HSA-lip) were made by a modified “Reverse Phase Evaporation” method (REV), following a Design of Experiments (DOE) approach to determine which factors impact the formulation. In addition, liposomes were made from crude soybean lecithin (CSL), rather than expensive and highly purified lipids. The liposomes were fully characterised, and the encapsulation efficiency (î) was monitored using high-performance liquid chromatography (HPLC). The results were correlated with factors such as organic and aqueous phase composition, as well as the in vitro release profile of Rif. Transmission electron microscopy (TEM) results confirmed the formation of spherical dual liposomes nanoparticles of roughly 200 nm. Dynamic light scattering (DLS) and Zeta potential measurements showed a negative charge (<–45 mV) and with satisfactory polydispersity (PDI<0.5). HSA dramatically improved the aqueous solubility of Rif (from1.9 mg/ml in water to around 4.3 mg/ml in HSA 10% solution) mainly due to Rif-HSA hydrophobic interactions. This resulted in a good î of almost 60% for Rif, despite the presence of bulky HSA in the lipid bilayer. These details were confirmed using proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, energy dispersive X-ray (EDX) and DLS data suggested the presence of HSA poking out on the surface of liposomes, which is encouraging for potential targeted delivery in the future. The in vitro release studies also depicted a substantial improvement in the diffusion of Rif in dual liposomes versus free Rif, from 65% after 12 hours for free Rif to 95% after only 5 hours for Rif- HSA-lip. Finally, stability studies conducted over 30 days at room temperature, showed that the freeze-dried formulations of Rif-HSA-lip exhibited good shelf stability over liposomes with no HSA. This study represents an illustrative example of co-loading of antibiotics and proteins into liposomes, which could encourage further development of novel nanoparticulate tools for the effective management of both drug-susceptible and -resistant infectious diseases such as TB.
  • Full Text:
  • Date Issued: 2020

Design, formulation and evaluation of liposomes co-loaded with human serum albumin and rifampicin

  • Authors: Bapolisi, Alain Murhimalika
  • Date: 2020
  • Subjects: Liposomes , Rifampin , Antitubercular agents , Serum albumin , Albumins , Tuberculosis -- Treatment
  • Language: English
  • Type: text , Thesis , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/163179 , vital:41016
  • Description: Tuberculosis (TB) is a devastating infectious disease caused by Mycobacterium tuberculosis and is the leading cause of death from a single infectious agent. The high morbidity and mortality rates of TB are partly due to factors such as the lengthy regimen (of 6–24 months), the development of drug resistance, and the pathogen location within the macrophages. These, with poor physiochemical properties of existing drugs hamper the effectiveness of the treatment despite the existence of potent antibiotics such as Rifampicin (Rif). Hydrophobicity plagues many drugs, including Rif, which are then particularly affected due to inherently poor intracellular availability. Novel drug delivery approaches are therefore needed in order to optimize the cytotoxic potential of said antitubercular drugs. To improve the bioavailability of hydrophobic drugs, numerous delivery strategies have been developed. Amongst these, the coordination of cytotoxic drugs to therapeutic proteins have shown some success for improved efficacy in the management of illnesses including infectious diseases. Of therapeutic proteins, Human Serum Albumin (HSA) is an attractive drug carrier with interesting benefits such as low immunogenicity, antioxidant properties and improving cellular uptake of drugs through HSA-specific binding sites which are expressed on most cells including macrophages, where M. tuberculosis often resides. Hence, combination of Rif to HSA (Rif-HSA) seems a promising approach for improved intracellular delivery of Rif. However, the in vivo stability of colloidal protein-based therapeutics is mostly challenging and an effective vehicle is needed to control the biological fate of such conjugates. Liposomes seem to be appropriate carriers for the Rif-HSA complex due to their reputable applicability for encapsulating diverse materials (i.e., hydrophobic and hydrophilic compounds or small and complex molecules) and preventing chemical and biological degradation of the cargo. Therefore, the main objective of this study was to simultaneously encapsulate Rif and HSA in liposomes, which, to the best of our knowledge, has not been done before. The dual liposomes (Rif-HSA-lip) were made by a modified “Reverse Phase Evaporation” method (REV), following a Design of Experiments (DOE) approach to determine which factors impact the formulation. In addition, liposomes were made from crude soybean lecithin (CSL), rather than expensive and highly purified lipids. iv The liposomes were fully characterised, and the encapsulation efficiency (î) was monitored using high-performance liquid chromatography (HPLC). The results were correlated with factors such as organic and aqueous phase composition, as well as the in vitro release profile of Rif. Transmission electron microscopy (TEM) results confirmed the formation of spherical dual liposomes nanoparticles of roughly 200 nm. Dynamic light scattering (DLS) and Zeta potential measurements showed a negative charge (<–45 mV) and with satisfactory polydispersity (PDI<0.5). HSA dramatically improved the aqueous solubility of Rif (from1.9 mg/ml in water to around 4.3 mg/ml in HSA 10% solution) mainly due to Rif-HSA hydrophobic interactions. This resulted in a good î of almost 60% for Rif, despite the presence of bulky HSA in the lipid bilayer. These details were confirmed using proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR). Furthermore, energy dispersive X-ray (EDX) and DLS data suggested the presence of HSA poking out on the surface of liposomes, which is encouraging for potential targeted delivery in the future. The in vitro release studies also depicted a substantial improvement in the diffusion of Rif in dual liposomes versus free Rif, from 65% after 12 hours for free Rif to 95% after only 5 hours for Rif- HSA-lip. Finally, stability studies conducted over 30 days at room temperature, showed that the freeze-dried formulations of Rif-HSA-lip exhibited good shelf stability over liposomes with no HSA. This study represents an illustrative example of co-loading of antibiotics and proteins into liposomes, which could encourage further development of novel nanoparticulate tools for the effective management of both drug-susceptible and -resistant infectious diseases such as TB.
  • Full Text:
  • Date Issued: 2020
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