College of Agriculture, Engineering and Science

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A comparative classification of the sourish-mixed bushveld on the farm Roodeplaat (293 JR) using quadrat and point methods.
(1995) Panagos, Michael David.; Westfall, Ribert Howard.; Zacharias, Peter John Kenneth.; Ellis, Roger.
An area and a point-based technique were used together at each of the same 75 sampling sites (stands), on a Sourish-Mixed Bushveld farm, to collect data for the classification and mapping of the vegetation. Both sets of data were synthesized using the same computer program package and the efficacy of the resulting classifications as well as the efficiency of the two field sampling techniques was compared. Following this, a continuous 7 752 point (1 m apart) transect was carried out, traversing the farm, in order to determine the optimum scales at which to sample Sourish-Mixed Bushveld so as to increase classification efficacy and improve community boundary recognition. The results indicated that (1) the arbitrarily chosen sampling scale of 1:8 000 was too large for "farm-scale" studies; (2) the area-based method proved to be satisfactory in that the classification and vegetation map produced with this method were verified spatially and environmentally; (3) the point-based method was deficient as a classificatory and mapping tool at large scales, since too few species were recorded with this method to make any sense of the classification and mapping of the vegetation was not possible; (4) less time per species was spent using the area-based method but because more species per stand were recorded with this method, the point-based method was quicker per stand; (5) the area-based method was easier to use in dense vegetation and irregular terrain; and (6) the optimum sampling scales for Sourish-Mixed Bushveld, as indicated by the synthesis of the continuous transect data, are about 1:12 000, 1:50 000 and 1:250 000.
Investigation of growth potential of alternative eucalyptus species for mid and high altitude sites in the summer rainfall region in South Africa.
(2008) Otim, Christopher Komakech.; Laing, Mark Delmege.
A study was undertaken to compare growth potential of three Eucalyptus species of natural origin in South Eastern Australia, with commercially grown species on mid and high altitude temperate sites in the summer rainfall growing zones in South Africa. The three species were Eucalyptus globulus subsp. bicostata (E. bicostata), Eucalyptus cypellocarpa and Eucalyptus nobilis. Nine sites were selected to represent the growing areas of South Africa experiencing cold winter drought with occasional snow falls. Improved, commercially grown pure Eucalyptus species and interspecific hybrid clones were included as controls in the trials to give comparative growth performances on specific sites. Both balanced and unbalanced lattice designs were used to evaluate the growth potential of the unimproved Australian species and the improved commercial controls incorporated into the trials. Volume production and basal area growth were assessed for the three species at all sites. However, only three sub species E.globulus (E. bicostata, E. maidenii and E. globulus) showed varying levels of disease (Mychosphaerella nobilosa) infestation and this was therefore assessed in trials at 12 and 30 months respectively, and correlation analysis was used to study the relationship between the impact of disease infestation and growth performance. It was found that negative phenotypic correlations existed between the levels of infection and tree growth. ie greater infection slower growth. Evaluation of genotype x environment interaction (GXE) revealed that this did not exist in the E. bicostata nor E. nobilis populations, and therefore one population of each species can be developed for all the sites tested. E. cypellocarpa was the only species that showed some GXE interaction implying that separate populations to be developed for different sites. Contrary to what was expected, unimproved Eucalyptus species being investigated performed equally as well as the improved commercial species included as controls, thus providing potential for commercial deployment with selection and breeding.
Occurrence of cowpea aphid-borne mosaic virus and prospects of improving resistance in local cowpea landraces in Uganda.
(2007) Orawu, Martin.; Melis, Robertus Johannes Maria.
Viral diseases are a major limiting factor to cowpea production in many countries of Africa. In Uganda, studies indicated that the cowpea aphid-borne mosaic virus (CABMV) is common and a potential threat to cowpea production in the region. There have been no efforts to develop cowpea cultivars with resistance to CABMV in Uganda. This work focused on the development of cultivars resistant to CABMV. Production of cowpea in Uganda is constrained by several factors, including a lack of awareness of diseases among the majority of farmers. A participatory rural appraisal (PRA) was conducted to elicit farmers’ indigenous knowledge of cowpea production and also to gain insight into their understanding of viral diseases affecting cowpea in Uganda. PRA tools such as group discussions, transect walks, problem listing and ranking were used to gather information. Insect pests, diseases, low yielding cultivars and the high cost of pesticides were perceived to be the most important production constraints. Farmers were not aware of the problem of virus diseases, but provided descriptive names of symptoms. Only three cowpea cultivars (Ebelat, Ecirikukwai and Blackcowpea) were produced in the area. Seed size and colour were seen as important traits in new varieties. Information about the occurrence, distribution and identity of cowpea viruses is limited in Uganda. The objective of this study was to identify the important cowpea virus diseases occurring naturally in the major cowpea growing regions of Uganda. Surveys were conducted to determine the incidence and severity of virus symptoms in four districts (Soroti, Kumi, Pallisa and Tororo) in 2004 and 2005. The incidence ranged from 40.5 to 94.4% and severity ranged from 15.0 to 30.6% (for Kumi and Pallisa districts, respectively) during the 2004 surveys. In 2005, the incidence ranged from 55.9 to 85.4% and severity ranged from 4.7 to 14.5% (for Tororo and Soroti districts, respectively). The CABMV, cowpea mild mottle virus (CPMMV), cowpea severe mosaic virus (CPSMV) and cucumber mosaic virus (CMV) were serologically detected by double antibody sandwich enzyme- linked immunosorbent assay (DAS-ELISA). Fifty four improved cowpea genotypes were screened for resistance to CABMV during the first season of 2004 at Serere Agricultural and Animal Production Research Institute in Uganda. Further screening was conducted in the second season of 2004 using 27 genotypes. The genotypes were planted in single rows between the rows of the susceptible cultivar, Ebelat. This was to provide high pressure of aphid vector (Aphis craccivora Koch) and CABMV inoculum. In addition, the test genotypes were artificially inoculated with a CABMV extract on fully expanded primary leaves of fourteen day-old seedlings. The CABMV incidence and severity was assessed. Disease severity was assessed on a 0-60% visual estimation scale where 0 = with no symptoms and 60 = with severe symptoms. Serological analysis was conducted using DAS-ELISA. Five genotypes showed good levels of resistance to CABMV, namely MU-93, IT82D-889, IT82D-516-2, IT85F-2841 and SECOW-2W. These resistant lines were crossed with three susceptible local landraces, namely Ebelat, Ecirikukwai and Blackcowpea in a North Carolina II mating design. The F1, F2 and BC1F1 populations and the parents were evaluated in the field to assess the response to CABMV and to study the inheritance of resistance to CABMV. The general combining ability (GCA) and specific combining ability (SCA) effects were significant, indicating that both additive and non-additive genetic factors are important in determining the control of CABMV in cowpea. The proportions (%) of the sum of squares for crosses attributable to GCA and SCA for CABMV severity were 51.4% for GCA due to females, 8.4% for GCA due to males and 40.2% for the SCA. The narrow-sense heritability estimates, obtained by regressing F1 on mid-parents was 0.87 and 0.84, F2 on F1 progenies 0.49 and 0.48, and F2 progenies on mid-parents 0.63 and 0.79, for AUDPC and final disease severity, respectively. Single gene conditioned resistance in seven populations, but resistance was quantitatively inherited and involved many genes in eight populations. Observation of transgressive segregation and moderate to high heritability suggests a quantitative mode of gene action and the importance of additive effects. The predominance of GCA variance, high heritability estimates and observation of transgressive segregation suggested that resistance could be improved by selection.
Breeding investigations of finger millet characteristics including blast disease and striga resistance in Western Kenya.
(2008) Oduori, Chrispus O. A.; Derera, John.; Tongoona, Pangirayi.
Finger millet (Eleusine coracana (L.) Gaertn. ssp. coracana) is an important food, food security and cash crop in eastern and southern Africa where small-scale farmers grow it in low input farming systems. The crop has food security, nutritional, cultural, medicinal, and economic value with high industrial potential. Little research and hardly any breeding have been done on the crop leading to low yields and low production. A project was therefore implemented in western Kenya during 2004-2007 seasons to investigate the possible breeding contributions to enhance productivity and production of the crop. The research comprised a social survey, germplasm evaluation, appraisal of ethrel as a chemical hybridising agent (CHA), genetic analysis of yield, and resistance to blast and Striga, and breeding progress in developing new finger millet varieties. A participatory rural appraisal (PRA) was conducted in three districts during 2006 to position finger millet (FM) in the farming systems, production constraints, and variety diversity and farmer preferences. The PRA established the high rating the peasant farmers gave to finger millet among crop enterprises, using it for food, cash, brewing, ceremonies and medicinal purposes. Farmers cultivated many varieties ranging from five to nine in a district, but each district had its own popular variety. Farmers used the following criteria to select new cultivars: high yield potential; early maturity; resistance to blast disease, Striga, birds, drought, and lodging; large head size, dark grain colour, and good taste. This probably indicated the willingness of farmers to adopt new varieties. Farmers identified constraints to production as blast disease, Striga, wild FM, birds, rats, termites, lack of market, labour shortage, and low yield. The farmers’ variety selection criteria and production constraints underscored the need to improve finger millet varieties. Evaluation of 310 accessions for trait variability and association conducted during 2005 long rain (LR) season at two sites revealed wide variation among the accessions for yield and secondary traits. The best accessions grain yield was above the yield potential of 5,000- 6,000kg ha-1 reported in other environments. Accessions KNE 072 (7,833kg ha-1), GBK 028463 (7,085kg ha-1), GBK 029661 (6,666kg ha-1) and FMBT ACC#42 (6,566kg ha-1) were outstanding. The data showed the opportunity to select for yield directly because of its wide variability but indirect selection could also be used to exploit seedling vigour as shown by its high correlation to yield and direct and indirect positive effects on yield through plant height and single plant yield in path analysis. The wide genetic variability among the genotypes for several traits indicated high potential to breed new and better finger millet varieties.
Cowpea seed quality in response to production site and water stress.
(2007) Odindo, Alfred Oduor.; Modi, Albert Thembinkosi.; Southway, Colin.
Cowpea (Vigna unguiculata. L) is an important African crop. However, it is also an underutilized grain legume. Consequently, there is not enough research data on cowpea seed physiology. Whereas there is evidence of cowpea being a drought tolerant crop, there is no evidence to associate plant drought tolerance with seed quality in response to water stress. This study sought to understand the effect of production site and water stress on cowpea seed quality development with respect to germination capacity and vigour. Patterns of raffinose family of oligosaccharides (RFO) during seed development to mature dry stage were used to physiologically relate seed performance to water stress. The effect of water stress and exogenous ABA on the accumulation of stress LEA proteins (dehydrins) in relation to seed quality development and germination was investigated. RFOs are known for their roles in desiccation sensitivity but no studies have shown their significance in cowpeas. Seeds of six cowpea cultivars were produced at two distinct growth sites characterised by irrigated and dry land conditions. The seeds were assessed during six developmental stages, for water content, dry matter accumulation, and performance. Harvested seeds were then planted in a pot experiment under controlled conditions to examine the effect of water stress on seed quality development and data collected during three developmental stages. Harvested seeds from the pot experiment were subsequently analyzed for changes in RFO accumulation during development using gas chromatography. The seeds were also used to investigate the effect of water stress and ABA on the accumulation of stress LEA proteins (dehydrins) in relation to seed quality development in cowpea. In addition, this study evaluated the use of image analysis as a method that can be used to objectively determine seed coat colour variation in cowpea. Statistical variation in individual seed’s solute leakage for cowpea cultivars differing in seed coat colour and produced under different environmental conditions was explored and correlations were done between seed conductivity test with other aspects of seed performance during germination. Furthermore the results of the conductivity test were compared with accelerated aging test, in relation to seed performance. The study provided evidence that cowpea seed lots produced under different environmental, and possibly management conditions may not differ with respect to seed quality as determined by germination capacity and vigour. However, significant differences between sites with respect to seed maturation patterns determined by water content and dry matter accumulation were observed. Adverse maternal environmental effects on the subsequent performance of seeds in a drought tolerant crop may not necessarily lead to poor performance. Cultivar differences in response to simulated drought conditions at the whole plant and tissue level can be considerable and highly variable; however, these differences may not have adverse effects on the germination and vigour of the seeds. Drought avoidance mechanisms at the whole plant level in cowpea are quite efficient in allowing the species to adapt to simulated drought conditions. These mechanisms may allow the cowpea cultivars to maintain metabolism and restore conditions for their continued growth under water stress; and produce few seeds of high germination capacity and vigour. Stachyose was found to be the predominant member of the raffinose family of oligosaccharides in cowpea. It is suggested that stachyose accumulation could be used as an indicator of stress tolerance in cowpea. However, the relationship between RFO concentration and the acquisition of desiccation remained as a matter of speculation in the present study and is still generally inconclusive. There was no evidence to suggest the acquisition of maximum desiccation tolerance is associated with maximum seed vigour. It is suggested in cowpea, which is drought tolerant, that maximum vigour does not necessarily imply the acquisition of maximum desiccation tolerance; rather there is a minimum level of desiccation tolerance that is required for the development of optimal seed vigour. The use of an in vivo approach in the study of LEA function in cowpea enabled the accurate comparison of two different groups of LEA proteins in developing cowpea seeds under conditions of water stress and in relation to germination and vigour. Both group 1 LEA and group 2 LEA (dehydrin) were shown to increase in concentration in response to water stress. In addition group 1 LEA protein was observed to be relatively abundant in cowpea seeds. A maternal influence on LEA protein gene expression under conditions of water stress, which may induce dehydrin accumulation vii during the earlier stages of seed development, was implied by the observation that dehydrin-like proteins were induced after two weeks of development in cowpea plants subjected to stress during the vegetative phase. In addition, the exogenous application of ABA delayed radicle protrusion; this was associated with a delay in the disappearance of LEA proteins and is suggestive of a relationship between LEA protein accumulation and the acquisition of desiccation tolerance. The study has demonstrated that image analysis can objectively discriminate seed coat colour variation in cowpea. Dark coloured seeds in general performed better than light coloured seeds; however seed coat colour was not always associated with better performance. A newly developed Aging Stress Differential Index (ASDI) has been used in this study to demonstrate a link between seed coat colour and sensitivity to water stress. The ASDI correlated well with the observations relating stress tolerance to stachyose accumulation. The skewed distribution patterns in individual electrical conductivity and the presence of extreme values may have implications with respect to the suitability of using standard statistical analyses which compare mean values to evaluate such data. In addition variation in individual electrical conductivity may also be influenced by cultivar differences and the chemical composition of the seed coat. Therefore associations between seed coat colour and electrical conductivity as a measure of performance should be treated with caution. The AA test does reflect changes in seed vigour, however ranked electrical conductivity values after AA did not consistently reflect differences in seed performance between cultivars and sites, and they did not correlate well with other aspects of performance.
Resprouting and multi-stemming and the role of the persistence niche in the structure and dynamics of subtropical coastal dune forest in KwaZulu-Natal province, South Africa.
(2008) Nzunda, Emmanuel F.; Lawes, Michael John.; Griffiths, Megan Elizabeth.
Resprouting is an important means of plant regeneration especially under conditions that do not favour regeneration through seeding such as frequent disturbances, low productivity, unfavourable soil conditions, extreme cold and limited understorey light availability. Sprouts may be advantageous over seedlings because they have higher survival and growth rates than seedlings, since they use resources from parent plants unlike seedlings that have to acquire their own resources. Resprouting is well documented for ecosystems that experience severe disturbances that damage aboveground biomass. For example, resprouting is important for plant persistence against fire in fire-prone savannas and Mediterranean shrub-lands, and hurricanes and cyclones in tropical forests. In these ecosystems, resprouting often results in multi-stemming, because this dilutes the risk of damage among many stems, improving the chances of individual survival. This study was conducted at coastal dune forest at Cape Vidal in north-eastern South Africa, where there is a high incidence of multi-stemmed trees due to resprouting in response to chronic disturbances of low severity. This study examines (1) the importance of resprouting to tree survival and dynamics in an environment where disturbance severity is low but pervasive, and (2) how this resprouting strategy differs from the more familiar sprouting response to severe disturbances such as fire and hurricanes. Analysis of the relationship between multi-stemming and a number of disturbances potentially causing multi-stemming revealed that stem leaning and substrate erosion were the most important disturbances associated with multi-stemming. There were fewer multistemmed trees on dune slacks that had a stable substrate and were protected from sea winds than on dune crests and slopes that had unstable substrate and were exposed to sea winds. Trees resprouted and became multi-stemmed from an early stage to increase their chances of survival against leaning caused by strong sea winds and erosion, and occasional slumping of the unstable dune sand substrate. These low severity disturbances are persistent and are referred to as chronic disturbances in this thesis. As a result of these chronic disturbances, both single and multi-stemmed trees had short stature because taller individuals that emerged above the tree canopy would be exposed to wind damage. Under chronic disturbances plants may manifest a phylogenetically determined sprouting response. However, in this study resprouting and multi-stemming were the results of the tree-disturbance interaction and not a property of a plant or species and were not phylogenetically constrained. Because the disturbances are predominantly of low severity, leaning trees were able to regain the vertical orientation of the growing section by turning upward (a process referred to as ‘turning up’ in this study) and hence survive without resprouting. Species that were prone to turning upward had a low incidence and degree of leaning of their individuals, low frequency of loss of primary stems and high abundance of individuals. Although turning up is less costly to the individual than resprouting, it could only be used by leaning trees that had small angles of inclination and were not eroded. High intensities of the latter require that individuals resprout to survive. The form and function of resprouting varied between seedlings and juvenile and mature trees. Resprouting in seedlings resulted in a single replacement shoot, unlike sprouting in juvenile and mature trees that resulted in multi-stemmed trees. Like sprouting in juvenile and mature trees, sprouting in seedlings was not phylogenetically constrained. Resprouting in seedlings increased seedling persistence; hence species with more sprout seedlings had larger individual seedlings and seedling banks. Resprouting in seedlings increased the chances of seedling recruitment, whereas resprouting in juvenile and mature trees increased the chances of an established plant maintaining its position in the habitat. After disturbances of high severity, which destroy the photosynthesizing parts, plants resprout using carbohydrates stored below- or above ground. In this study, good resprouters stored more carbohydrates both below- and above ground than poor resprouters. The carbohydrates were mobilized for resprouting after disturbance. More carbohydrates were stored in stems than in roots because the prevailing disturbances were mostly of low severity and hence above ground resources were readily available. Similar to storage by plants in severely disturbed habitats, carbohydrates were stored by reserve formation, which competes for carbohydrates with growth and maintenance and forms permanent storage, rather than accumulation, which temporarily stores carbohydrates in excess of demands for growth and maintenance. Stored carbohydrates are not necessary for resprouting of plants after disturbances of low severity because they can resprout using resources remobilized directly from the disturbed photosynthesizing parts. However, in this study, stored carbohydrates served as a bet-hedge against occasional severe disturbances that occurred in addition to chronic disturbances. Allocation of carbohydrates to permanent storage diverts them from growth and reproduction and hence good resprouters had lower growth rates, seed output, seed size and seedling recruitment than poor resprouters. However, the costs of these traits that resulted in low recruitment from seed by good resprouters, were compensated for by high persistence of established individuals of good resprouters through recruitment of sprout stems. This study demonstrates that resprouting is not only advantageous in severely disturbed environments, but also in environments where disturbances are of low severity but nevertheless confer an advantage on individuals that persist. Thus in forest environments where aboveground biomass is seldom destroyed and individuals are relatively long-lived, resprouting can confer significant fitness and selective advantage on individuals.
Voltage dip performance analysis.
(2009) Nzimande, Timothy M.; Ijumba, Nelson Mutatina.; Koch, Robert G.
The power quality performance of South African utilities has been regulated through the application of NRS 048-2 standard. The earliest edition of the power quality standard (NRS 048- 2:1996) defines compatibility levels for voltage dips in the form of annual dip limits for each voltage dip type. Actual measured utility dip performance has consistently resulted in higher dip numbers than the limits imposed in the standard. On the other hand, the dip limits were considered to be less restrictive by industrial customers. The revised power quality standard addresses the difficulties in managing voltage dip performance based on dip limits as specified in the first edition of NRS 048-2. This new philosophy does not define dip limits; instead, utilities are required to develop specific strategies to manage dip performance according to customer requirements. This research work develops an alternative approach to the management of dip performance as opposed to the application of dip limits. The study analyses measured voltage dip records for a steel-processing plant and a pulp and paper plant. The supply network for each plant is modelled to define dip influence zones as a function of fault locations. The principal results of this study are critical circuits, causes of dips, dip influence zones and the key elements of the proposed approach in communicating dip performance. The optimised approach was presented to and adopted by the customers involved.
Optimal placement of shunt capacitor banks on a sub-transmission network.
(2009) Ntusi, M.; Mbuli, M.
The optimal capacitor placement problem is the determination of the optimal location of the shunt capacitors on the sub-transmission networks such that energy losses are minimised, the power factor and the network voltage profile are improved. During this period when Eskom is experiencing an unacceptably low generation reserve margin, it’s quite critical that the electrical Transmission and Distribution network losses be kept to a minimum to optimise on the scarce generation that is available to supply South Africa’s current and future power demand. One of the ways of minimising technical losses is through the optimal placement or installation of capacitor banks on the network. The placement of shunt capacitors on a bulk Transmission network is essentially to improve the voltage profile on the network, increase system security and reduce transmission losses. The optimal placement of shunt capacitors with the above objectives would assist in minimising the cost of the investment whilst maximising the return on investment to the utility. This research subject is treated as an optimization problem and hence optimization solutions were considered to address the “Optimal capacitor placement problem”. This optimisation problem is solved for all loading levels i.e. peak, standard and off peak periods and for different seasons in a given typical year. This thesis investigates the capability of Genetic Algorithms technique in solving this optimisation problem. Genetic algorithms utilize a guided search principle to develop a robust solution to this research problem. Given their capability to traverse the complicated search space with a multivariate objective function, Genetic Algorithm are versatile and robust to locate the global optimum of the objective function. These Genetic Algorithms (GA’s) were implemented on real sub transmission networks modelled on DigSilent/ Powerfactory. The modelled GA’s on DigSilent were then tested on different network types i.e. commercial, mining, residential and industrial load mixes. The solutions determined by the different GA’s are then compared in terms of time taken to locate the solution, reliability and robustness. The most reliable GA is then identified and recommended as the preferred optimisation approach. A methodology of using GA’s to solve the above mentioned problem is therefore proposed
A detailed kinetic and mechanistic investigation into the rate of chloride substitution from chloro terpyridine platinum (II) and analogous complexes by a series of azole nucleophiles.
(2010) Gillham, Kate J.; Reddy, Desigan.; Jaganyi, Deogratius.
The influence of soil properties on the vegetation dynamics of Hluhluwe iMfolozi Park, KwaZulu-Natal.
(2009) Harrison, Rowena Louise.; Hughes, Jeffrey Colin.
The physical and chemical properties of soils can greatly influence the vegetation patterns in a landscape. This is especially so through the effect that particular characteristics of soils have on the water balance and nutrient cycling in savanna ecosystems. Areas in the savanna environment found in Hluhluwe iMfolozi Park have experienced a number of changes in the vegetation patterns observed. This study, therefore, looks at the effect that soil characteristics may have on the vegetation growth in this area and on the changes that have taken place over time. Fixed-point photographs, taken every four years, were used to choose fourteen sites in the Park, which showed either a ‘change’ or ‘no-change’ in vegetation from 1974 to 1997. The sites consisted of four which had ‘no-change’ in vegetation, two sites with a slight increase (5- 20%) in tree density, three sites with a greater increase in tree density (>20%), two sites with a slight decrease in tree density (5-20%), and three sites with a greater decrease in tree density (>20%). Transects were then carried out at each site, in which the soil was classified to the form and family level. Each horizon was then sampled and the field texture, structure, Munsell colour and depth of each horizon and profile recorded. The data recorded in the field were statistically analysed through a principal component analysis (PCA). The type of horizon, horizon boundary, structure type, colour group and depth for the top and subsoil were included in the models and were analysed with the number given to each site for each of the three sections of the Park, namely Hluhluwe, the Corridor and iMfolozi. The most prominent textures at all sites were sandy loam, loam, clay loam and silt loam for both the top and subsoil for all site categories. The texture classes were also compared across the Hluhluwe, Corridor and iMfolozi sections. The dominant textures in the Hluhluwe and Corridor sections are loam, clay loam and silt loam for both top and subsoils. Sites sampled in the iMfolozi section appear to have textures mainly associated with the clay loam and sandy loam classes. The structure classes of the soil including sub-angular blocky, granular and crumb which are associated with a moderate structure appear to be the most dominant type in all categories for the topsoil; single-grain and sub-angular blocky classes the main types for the subsoil. Generally the colour of the soil at all the sites sampled was yellower than 2.5YR and the values and chromas mostly fell within the range of 3-5 and 2-6, respectively. This is also shown in the PCA results obtained, which associate particular soil characteristics with the various sites sampled for the different vegetation change categories investigated. The samples collected were also analysed in the laboratory after being air-dried. The laboratory analysis included measurements of pH, exchangeable acidity, organic carbon, extractable phosphorus, particle size distribution and cation exchange capacity (CEC). The data recorded in the laboratory were also analysed by PCA. This was used to determine which soil properties are associated with the particular sites investigated. The pH of the soil, in all areas, fell within a wide range. The pH is influenced by the rainfall in the area and thus sites sampled in the Hluhluwe section are more acidic than those sampled in the Corridor and iMfolozi sections. The topsoils had a higher pH for all the samples and were in the range between 5 and 7. The exchangeable acidity measurements were low, although they were higher in the subsoil as opposed to the topsoil. The nutrient contents did not appear to vary greatly between the different sites in the Park. Generally extractable phosphorus, CEC and organic carbon were low across the Park. The particle size analysis showed that the clay percentage increases between the top and subsoil for all the sites sampled. The silt and various fractions of sand percentages vary across all sites and are lower than the clay percentage at all sites except the A horizon of the ‘slight increase’ sites. The ‘no-change’, and ‘increase’ sites have a higher percentage of clay as compared to the silt and sand fraction for both the A and B horizon. The ‘slight increase’ sites have a higher percentage of sand in the A and B horizon, the ‘slight decrease’ sites have a more equal percentage between the sand, silt and clay fractions in the A horizon and a greater percentage of clay in the B horizon. The ‘decrease’ sites have a greater percentage of clay and silt in the A and B horizon. While certain soil properties have a definite effect on the plant growth, no relationship between specific soil properties and vegetation changes was shown. However, it is likely that the soil structure and texture affect the vegetation patterns, through their influences on the water and nutrient holding capacity. With an increase in the clay percentage and more strongly structured soils, plants can access more water and nutrients and this will increase the tree density in an area. However, the recent changes in the vegetation patterns observed in the Park appear to be more associated with other environmental factors. The soil properties analysed would have generally been more constant at the sites sampled, particularly over the relatively short period of time in this study. Therefore, the changes which were recorded in the fixed-point photographs would have been enhanced by other factors experienced in the Park, including fire and the effect that grazers and browsers have on the vegetation.
The development of a latent heat thermal energy storage system using a phase change material for solar energy application.
(2010) Zulu, Njabulo Mziwandile.; Arnold, David R.
This investigation forms part of an attempt to provide an alternative to conventional power generation technologies that use fossil fuels which have impact on global warming. The field of this investigation covers the development of a latent heat thermal storage system which has a potential of conserving available solar energy. The advantages of using thermal energy storage that have been found previously include reduced energy cost, energy consumption, equipment size and pollutant emissions, also increased flexibility of operation, efficiency and effectiveness of equipment utilization. Traditionally, available heat has been stored in the form of sensible heat (typically by raising the temperature of the energy storage medium) for later use. Latent heat storage on the other hand, is a young and developing technology which has found considerable interest in recent times due to its advantages over sensible heat storage which include smaller temperature swing, smaller size and lower weight per unit of storage capacity. It has been demonstrated that, for the development of a latent heat thermal energy storage system, the choice of the phase change material (PCM) as well as the heat transfer mechanism in the PCM play important roles. In this study, a suitable phase change material and an appropriate heat transfer enhancement technique are identified for utilization in a proposed latent heat thermal energy storage system. Also included, is the design of the proposed heat storage system.
The use of spatial analysis and participatory approaches in strategic environmental assessment (SEA) : identifying and predicting the ecological impacts of development on the KwaZulu-Natal North Coast of South Africa.
(2010) Ahmed, Fathima.; Bob, Urmilla.; Ahmed, Fethi B.
The high pressures for coastal development, translated as prolific land cover transformation, coupled with the weaknesses of management to protect the environment has led to the gradual deterioration of environmental conditions in many coastal areas. Land use decisions in coastal areas are based on opportunities and constraints affected by both biophysical and socio-economic drivers, and hence present one of the main issues integrating the large debate on sustainable development in coastal zones (Lourenço and Machado, 2007: 1). The aim of this study is to investigate the effectiveness of the integration of spatial analysis and participatory approaches in SEA (particularly its ability to identify and predict ecological impacts) on the KwaZulu-Natal north coast of South Africa. The study adopted a conceptual framework based on landscape ecology, which was underpinned within the overarching political ecology framework. The former underscores the importance of integration, while the latter critiques the institutionalization of environmental concerns, which are characterized by inequalities in terms of social and political power and of how problems are defined, mediated and resolved. Hence this conceptual framework was considered appropriate to assess the strategic environmental issues pertaining to the coastal zone on the KwaZulu-Natal north coast. The researcher used participatory methods, primarily focus group discussions (which included venn diagramming, ranking exercises and participatory mapping) which were triangulated with both quantitative and qualitative methods as part of an integrated impact assessment. These relate to the use of semistructured questionnaires which were administered to a purposive sample of six key stakeholder interest groups within the study area. A spatial GIS time series analysis of land use and cover change was employed to determine baseline conditions, changes in the state of key ecosystems, key development drivers and emerging threats. Additionally, a policy and institutional review was undertaken. The analysis revealed that major natural land cover classes are in decline in the study area,within a time period of less than 10 years. The most sensitive ecosystems were found to be grasslands (-19.99%), coastal forest (-40%), wetlands (-37.49%) and secondary dunes (- 21.44%). Furthermore, agriculture and forestry are also indicating severe declines. The reasons attributed to this transformation of land cover are increasingly being linked with economic motives such as individual private land-owner dynamics, tourism growth and development in the area. Furthermore, the policy agendas are clearly economically motivated. These losses signify the cumulative decline in ecosystem goods and services, and could undermine pose risks to the society that relies on them either directly or indirectly. One of the main considerations in this research endeavor was to formulate a Strategic Environmental Assessment (SEA) Framework to inform future ICZM in the study area. SEA is planning with a long-term perspective, with a focus on a spatial rather than a project level, an element that is clearly lacking in the current development scenario of this coastline. It is critical that the SEA Framework advocated in this study include a range of variables that will permit short-term, medium-term and long-term monitoring and evaluation aimed at ensuring sustainable planning in the area.
A vapour-liquid equilibrium study on sub-critical systems using a static apparatus.
(2009) Wilson, Etienne P.; Ramjugernath, Deresh.; Naidoo, Paramespri.
High pressure vapour-liquid equilibrium experiments were undertaken with a static high-pressure apparatus designed by Prof. J. D. Raal and commissioned by Prof. D. Ramjugernath. Isothermal VLE binary data data was measured at moderate temperatures and pressures ranging from atmospheric to 7.2 bar. The equipment had a combined operating pressure and temperature limit of approximately 150 bar and 215° C respectively. The apparatus was initially designed for the measurement of gas-liquid binary systems- where one of the components was supercritical at the operating conditions. Test data were measured for the pentane + ethanol system at 100.41°C. The 2-methyl-2-butene + TAME, hydrocarbon + olefin system, was observed at 70°C, 94.6°C and 104.5°C. The apparatus was modified for the measurement of binary systems containing sub-critical components at the operating conditions specified. An injection port was installed on the apparatus assembly such that the second component of the binary system could be introduced into the equilibrium cell. The binary VLE data was regressed using various thermodynamic models. The direct method or phi-phi approach was considered. The equations of state models used in the regression were the Peng-Robinson-Stryjek-Vera (PRSV) and Soave-Redlich-Kwong (SRK). The 1-fluid van der Waals, Wong and Sandler mixing rules were selected to estimate binary interactions. The excess Gibbs energy equations coupled with the Wong and Sandler mixing rules were the NRTL and WILSON equations.
Globalisation, development and community-based tourism in developing countries : a case study of Pondonland, Eastern Cape.
(2010) Giampiccoli, Andrea.; Moodley, Vadivelu.; Brooks, Shirley.
Contemporary globalisation in developing countries is circumscribed by neo-liberal development approaches, while community-based development seeks to create alternative development strategies. This thesis brings together research in tourism with theoretical perspectives from Gramscian social analysis in order to explore contemporary conflict between these two strategies in the tourism sector. The purpose is to investigate the influence the hegemonic global milieu has exerted on an alternative community-based tourism (CBT) strategy that was initially formally/institutionally supported. Concepts of hegemony, globalisation and divergence/convergence, together with development theories, are explored and applied to the international tourism sector and CBT in particular. A theoretical structure is proposed in which the relationships between hegemony, globalisation, and processes of divergence/convergence are explicated in relation to the tourism sector, and CBT in particular. Global-local linkages, conceptualised in terms of the theoretical framework, are explored in a particular geographical context, namely the Pondoland coast of South Africa. South Africa has recently rejoined the global socio-economic milieu after the isolation of the apartheid period and a European Union-supported tourism project in the Pondoland region is studied in detail. The case study serves to empirically substantiate the proposed theoretical framework. The investigation contributes to ‘initiate’ a global – local oriented paradigm in tourism study that focuses on the relationship between globalisation processes and a CBT development approach by exploiting and conjoining the correlation of the concepts of the proposed theoretical framework. Globalisation processes are set against a specific and local form of tourism, i.e. community-based tourism. The proposition is a ‘new’ double level of interlinkage. General and global policies are interlinked and cross each other with specific and local policies to evaluate a CBT project outcome. The study intends to go beyond existing literature of CBT management and project development. This is achieved by providing an investigation on the ‘unseen’ working mechanisms and influence of globalisation processes in relation to a specific CBT local project supported by a global actor in international cooperation, thus verifying interpretations and commitment on CBT development approaches. The case study findings elucidate and highlight the final effects of the theoretical proposition at a practical level by clarifying and showing the level of influence on, and re-adjustment of, the case study end result in comparison with its initial plan. A shift in the case study project development is individuated and commented on in relation to the proposed theoretical framework. The investigation results allow validating the proposed conceptual basis of the study. Based on the findings, this thesis a proposal is made to construct the interrelationship between development and CBT understanding. A typology and specific nomenclature of CBT approaches is advanced together with their correlation to development concepts. The conclusion also gives further general and specific recommendations by providing possible strategies to permit proper development and better exploitation of CBT possibilities.
The impact of food aid on maize production in Swaziland.
(2007) Mabuza, Majola Lawrence.; Hendriks, Sheryl Lee.; Ortmann, Gerald Friedel.; Sithole, Moses M.
The objective of the study was to provide empirical evidence on whether food aid leads to depressed domestic maize prices and reduced maize production in subsequent years in Swaziland. Similar impact studies have been carried out in a number of sub-Saharan African countries but no evidence is available for Swaziland. The lack of empirical evidence has often resulted in premature negative conclusions on the impact of food aid on Swaziland’s maize industry. The study used secondary national data from 1985 to 2006 to analyse the impact of food aid on maize producer prices and quantity of maize produced. Variables used in the analysis included quantity of cereal food aid; quantity of commercial maize imports; quantity of locally produced maize; official maize producer price; open market maize producer price; fertilizer price; fuel price; rainfall; and total area planted to maize. The impact of food aid was measured using the reduced form market equilibrium model that consisted of maize quantity and maize producer price functions estimated simultaneously using the above variables through the two-stage least square method (2SLS) method. Analytical results revealed that food aid to Swaziland does not lower prices of domestic maize and has no significant negative effect on the quantity of maize produced in subsequent seasons. This means that food aid received by Swaziland over the study years has been appropriately targeted and distributed to the food insecure households. If this were not so, the demand for food from commercial outlets would have been reduced, leading to an adverse impact on maize producer prices, and subsequent local maize production. Notwithstanding the above results, Swaziland should still commit resources towards reducing the national food gap. This calls for increased investment in rural irrigation development, improved farmer institutional support services, and the implementation of pro-poor development programs aimed at improving individual household income to reduce the need for food aid, improve food self-sufficiency and vulnerability to food security.
Measurement and thermodynamic interpretation of high pressure vapour-liquid equilibrium data.
(1990) Muhlbauer, Andreas Lorenz.
.. Detailed experimental and thermodynamic studies of. the isothermal phase equilibria for the
A study of the phenomenon of bridging of sugarcane bagasse
(1996) Bernhardt, Herbert Wolfgang
This work reports the results of a systematic study of the factors that affect the bridging behaviour of bagasse. It shows that traditional bulk solids theory is inappropriate for predicting bagasse flow mainly because of the impossibility of obtaining a reliable measure of internal friction. It demonstrates the significant influence of fibre length and moisture content on its handling charateristics. Correlations of pertinent bulk properties such as compactibility, tensile strength, surface friction and translation of vertical into horizontal pressure have been developed. These were derived as a result of measurements in equipment that was designed for the purpose. Finally, an empirical model utilising these correlations is proposed by which the likelihood of bridge formation in any piece of bagasse handling equipment can be determined. The validity of the model is assessed by comparison with bridging tests that were performed under controlled conditions.
Intersex in four South African racial groups in Durban.
(1970) Grace, Hatherley James.; Bain, Peter G.
Chapter I The ontogeny of sex development is introduced and a definition of the intersexual state is given. A resume of intersexes recorded in South Africa is presented together with figures showing the increased demand for cytogenetic services in the country. The motivation for this study is discussed. Chapter II The biological concept of sex is outlined together with notes on the evolution of the dioecious state in animals. Thereafter a brief account of the normal and abnormal intersex states in invertebrates and vertebrates is given. Chapter III Examples of some of the abundant references to ambisexual individuals found in the classical literature, history and mythology are listed and the status of intersexes in modern society is discussed: it does not vary much from the times of ancient Greece and Rome. Chapter IV A summary of the events which led to the establishment of cytogenetics as an independent discipline is given. The discovery of nuclear sex dimorphism is noted and methods of investigation of intersexual patients are described. A detailed description is given of cytogenetic technical. "methods, ; and leads to a diagrammatic explanation of the differential diagnosis of intersexes. This is used as a basis for the classification and accordingly a simplified, unambiguous system is proposed and defended. The sources and numbers of pat~ ients recorded in this thesis are explained. Chapter V The sex chromatin is described in detail? with a description of the methods used for its demonstration and evaluation. A pilot study of normal women of the four races established that there is no inter-racial variation in chromatin frequency. Reasons are given for disregarding nuclear appendages as an accurate indication of 'sex '. Chapter VI Embryological stage s i n the development of the human urogenital tracts are recounted after considering the mechanisms of sex determination. Pathogenesis of intersexuality is considered briefly. Chapter VII Gonadal dysgenesis of the female, including Turner's syndrome and phenotypes of both male and female are presented. The classification, pathology, aetiological and cytogenetic factors are described. Illustrative case reports and extensive discussion of the syndrome are presented. Chapter VIII The Klinefelter syndrome occurs in males with supernumerary X chromosomes; a number of chromatin negative, hypogonadal conditions mimic the syndrome: they are described, with notes on the classification, pathology, aetiology and the cytogenetic features. A series of case reports demonstrate both chromatin positive and negative types. Special reference is made to the dermatoglyphic profiles which were discovered to differentiate the XY males into two groups. Chapter IX Three syndromes, the XXX, XYY and agonadism, were not encountered in this study and are consequently not discussed. Chapter X The adrenogenital syndrome has several distinctive signs which are mimicked by induced virilization; these are described and a number of case reports are presented to illustrate the syndromes. Chapter XI Male intersexes occur in several different forms: the classification of the group is explained and a distinction is made between intersexes and those with simple, or 'pseudo-intersexual', defects. The signs of the different syndromes are detailed, together with data concerning the aetiology and cytogenetics. A series of patients' case histories is used to illustrate the various syndromes. Chapter XII Idiopathic female intersexuality is defined and a short explanation of the classification is given. The signs found in this syndrome are detailed and a single case report, which is of exceptional interest because of severe masculinization and the formation of a phallic urethra, is presented. Chapter XIII Hermaphroditism is defined and the subgroups are explained. The variability of signs is discussed and details of anatomy and histology of the genital tract are given . A single hermaphrodite was encountered during the survey and the case is described. Three other patients, all infants, were suspected of being hermaphroditic but because gonadal biopsy was not undertaken they were discharged from hospital without a diagnosis having been made. Discussion of the aetiological mechanisms is presented and the need for early diagnosis and treatment is emphasized. Chapter XIV Some of the simple genital anomalies and somatic defects which resemble intersex are mentioned and are illustrated by attenuated case reports. Chapter XV The incidence of those intersexual conditions recognizable at birth by anatomical deformity is calculated from a total population of 21,000 live births recorded during the calendar year, 1969. The incidence was very low (1:7000) and does not permit analysis of inter-racial distribution. Prevalence is calculated from the number of new patients seen by the author during 1969 in Durban. Some interesting observations were made but the primary objective, to determine whether or not intersexuality is more prevalent in the Bantu than any other race, could not be answered with certainty because of the small number of patients. Hermaphroditism was shown not to be the most common type of intersex syndrome in the Bantu. Chapter XVI An outline is given of the normal dermatoglyphic features of the finger prints and palms. Some references of the patterns in Turner's and Klinefelter's syndromes are available from the literature and are compared with the profiles of patients from this series. A distinct dimorphism was found in chromatin negative hypogonadal males and was thought to distinguish between those with congenital or acquired pathology. Normal values for South Africans have not been established satisfactorily and the urgent need for this information is stressed. Chapter XVII A general discussion of the highlights of this study of the epidemiology, clinical presentation and cytogenetics of intersexuality is given and a number of conclusions are drawn .
PLC implementation of online, PRBS-based tests for mechanical system parameter estimation.
(2009) Rampersad, Vaughan.; Burton, Bruce.
This thesis investigates the use of correlation techniques to perform system identification tests, with the objective of developing online test methods to perform mechanical parameter extraction as well as machine diagnostics. More specifically, these test methods must be implemented on a Programmable Logic Controller (PLC) in combination with Variable Speed Drives (VSD). Models for motor-based mechanical systems are derived and other documented methods for parameter identification of mechanical systems are discussed. An investigation is undertaken into the principle that the impulse response of a system may be obtained when a test signal with an impulsive autocorrelation is injected into the system. The theory of using correlation functions to determine the numerical impulse response of a system is presented. Suitable test signals, pseudorandom binary sequences (PRBS) are analysed, and their generation and properties are discussed. Simulations are presented as to how the various properties of the PRBS test signals influence the resulting impulse response curve. Further simulations are presented that demonstrate how PRBS-based tests in conjunction with a curve-fitting method, in this case the method of linear least squares, can provide a fair estimation of the parameters of a mechanical system. The implementation of a correlation based online testing routine on a PLC is presented. Results from these tests are reviewed and discussed. A SCADA system that has been designed is discussed and it is shown how this system allows the user to perform diagnostics on networked drives in a distributed automation system. Identification of other mechanical phenomena such as elasticity and the non-linearity introduced by the presence of backlash is also investigated.
Production of activated carbon from South African sugarcane bagasse.
(2005) Mwasiswebe, Denny.; Arnold, David R.
South Africa has an annual sugarcane milling capacity of about 22 million tonnes on average producing about 3.3 million tonnes of dry bagasse, of which one third is surplus to factory requirements. Currently surplus bagasse is used for furfural, pulp and paper and cogeneration but significant amounts still remain . This prompted the need to find viable alternative and appropriate technology to utilize the surplus. A laboratory pilot plant was used to investigate the production of activated carbon from bagasse. Experiments were carried out to investigate conditions for making the best activated carbon in a rotary batch kiln, and also to examine potential ene rgy recovery from process gases using Gas Chromatography. Derived results from the laboratory experiments were used to develop a conceptual design for a demonstration plant sited within a sugar mill. The conceptual design was evaluated for economic and environmental impacts using a robust Excel spreadsheet and GABI-3 modelling software respectively. Excellent activated carbon was produced from sugarcane bagasse by a two-stage physical process involving pyrolysis and gasification with steam. The best operating conditions were pyrolysis at 700°C for 1 hr and activation at 850°C for 1hr, a heating rate of 10°C/min and a steam flow of 15g/g of char per hour. The active carbon yield was 7% on dry bagasse basis with a Methylene Blue Number of 257mglg of carbon. The active carbon had a sugar decolourisation capacity of 20% at a carbon dosage rate of 0.7 wt% on Brix using clear juice (l2°Brix) and 70% at 0.5 wt% on Brix using brown liquor (65°Brix) . The Freundlich isotherm showed that the bagasse-based activated carbon was a suitable adsorbent for sugar colour bodies. Gas analysis results revealed that the off gases from the pyrolysis and activation stages had calorific values of about 63MJ and 31MJ per kg of activated carbon respectively . The total combustion energy of 94 MJ/kg of active carbon was enough to satisfy the process energy requirements for drying, pyrolysis and activation. By burning combustibles like tar, methane, carbon monoxide, ethylene and hydrogen for process thermal energy needs, the environmental impact of the manufacturing process was reduced to a Global Warming Potential of llkg CO2 Equiv per kg of carbon produced. The demonstration plant requires a capital investment of US$lOA million to give a competitive bagasse-based activated carbon (BPAC) selling price of US$1.80 per kg and IRR, ROI and Investment payback time of 17.93%, 23.93% and 3.80 years respectively. A sensitivity analysis was also carried out to investigate the effect of possible variation in the main project forecasts which are BPAe selling price , bagasse buying price, capital investment and production costs on IRR, ROI and payback time . The benefits of process integration within a sugar mill would be expected to improve the business feasibility ; If bagasse was free the IRR would increase to 28.59% and even better to 32.12% if extra boiler and electricity capacity was also available at the mill.

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