Doctoral Degrees (Agricultural Engineering)

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An assessment of the feasibility of quality indicators for the postharvest deterioration of sugarcane (Saccharum officinarum L.)
(2014) Sibomana, Milindi Sylver.; Bezuidenhout, Carel Nicolaas.; Workneh, Tilahun Seyoum.; Sobratee, Nafisa.; Rutherford, Richard Stuart.
Sugarcane deterioration remains one of the most important supply chain efficiency leverage points in the South African sugar industry. Cane quality has been identified as an issue that has the potential to improve the overall efficiency of the sugarcane supply chain. A review comparing the postharvest quality management systems and measurements in the South African sugar and fresh produce industries was conducted. The difference in postharvest handling between the two industries was found to be an important factor dictating quality management. Advances in non-destructive quality measurement techniques and sanitation strategies were found in the fresh produce industries, which could be adopted by the South African sugar industry. An empirical study of standard sugar industry cane quality parameters was also performed. Sugarcane quality parameters measured at the Felixton mill were analysed, per ward, using quality control charts and non-parametric statistical approaches. A daily analysis of these parameters, as well as the Pol % Fibre ratio, using Shewhart quality control ( x ) charts revealed that, overall, Monday deliveries were of significantly lower quality (P<0.01). This is a quantitative indicator of logistics (or management) inefficiency over the weekend. Using the Mann-Whitney test, Pol % Fibre was used to generate a grower performance index, based on high levels of statistical significance (P<0.05), which may allow stakeholders to improve operations, through identifying the levels at which individual growers deliver significantly (P≤0.05) lower quality cane in the early part of the week. This study uncovered new and significant statistical trends within the sugar industry's quality database and demonstrates the potential of Pol % Fibre as an indicator of quality inferiority in the cane supply chain. To further investigate cane deterioration in this context, two burn/harvest-to-crush delay trials involving two sugarcane varieties (N12 and N31), which were exposed to ambient environmental conditions for a period of nine days after harvest were performed. On sampling dates, each variety was tested for quality parameters such as total bacterial counts, D-lactate production, and respiration. Standard sugar industry quality parameters and Pol % Fibre were also monitored. Parameters were measured in bottom, middle and top portions of the stalks to evaluate the effect of section on the parameter changes. Trial 1 was conducted on unburnt cane in October 2012 and Trial 2 on burnt cane, April-May 2013. Stalk portion significantly (P<0.001) affected the parameters, with the top and bottom portions showing higher bacterial proliferation, respiration rates and D-lactate production compared to the middle portion in Trial 1. Trial 2 showed no significant variability in stalk portion. In Trial 1, a significant (P<0.05) declining trend was noted for Brix % DM and Pol % Fibre in the top portion. The effect of higher respiration in the cut-ends in Trial 1 was noted in significantly reduced Pol % Fibre in these cut-ends. Environmental conditions were found to be the major factor influencing quality during the cane storage period. The study concludes, from both analysis of CTS data and the results of the BHTCD trials, that Pol % Fibre can be monitored at sugar mills as an additional parameter for signalling inferior quality and deterioration of cane consignments.
Automated processor for optimizing tractor operation.
(1991) Lyne, Peter William Liversedge.; Meiring, Pierre Andre.
The agricultural tractor is designed as a general purpose machine and consequently, does not perform all its tasks at maximum efficiency. Various methods of increasing the field performance of these vehicles have been studied. Traction is one of the main factors limiting the field performance of the modern tractor. The process of developing traction has therefore been investigated by many researchers and although this study has resulted in a better understanding of the mechanics, it has not to any great extent assisted the operator to optimize performance in the field. It was concluded that in order to solve the problem the operator required a control system to maintain the dynamic load and inflation pressure at optimum levels. Work was carried out to develop and evaluate such a system using the Single Wheel Traction Research Vehicle at the USDA's National Soil Dynamics Laboratory in Auburn, Alabama, USA. A computer management system was developed to control the dynamic load, net traction and inflation pressure of the test tyre. During a simulated field operation the system was programmed to cycle the tyre over its operating range of dynamic load and inflation pressure while monitoring tractive efficiency. A tractive efficiency response surface was computed for the particular condition and the surface searched for the dynamic load and inflation pressure levels which resulted in maximum tractive efficiency. The tyre was then controlled and operated at maximum tractive efficiency. Evaluation showed that within the operating range of the tyre, tractive efficiency varied considerably with dynamic load, inflation pressure, net traction and soil condition. The results indicated that a considerable advantage could be obtained by using such an arrangement on a tractor. The system would automatically maximize the tractive efficiency of the tractor under the particular field conditions and with the particular implement being used. Implements could be ballasted and the hitch system used to control the weight transfer to ensure maximum tractive efficiency. Systems such as these would result in a significant improvement in the field performance of the machine and a reduction in management time required to optimize the performance of the tractor implement combination.
Characterization of flour and starch from Zambian cassava cultivars and application in frozen wheat bread dough.
(2019) Chisenga, Shadrack Mubanga.; Workneh, Tilahun Seyoum.; Bultosa, Geremew.
Abstract available in pdf.
Combustion stress in compression-ignition engines.
(1989) Taylor, Andrew Bruce.; Meiring, Pierre Andre.
South Africa produces alternative fuels from a number of different sources. The properties of a fuel are known to affect the nature of combustion in compression-ignition engines significantly, and have occasionally resulted in engine failures. Combustion analyses have been conducted on a wide range of fuels and combustion has been thoroughly quantified. However, the role played by the different combustion variables in failures was not known. The result was that it was not possible to predict the implications of variations in the nature of combustion. There was thus a need to investigate the relative role of combustion variables in the failure of engines. The mechanisms of combustion and engine failure were studied. All the variables required to determine combustion and engine durability were measured simultaneously. This research required the development of a complete engine research facility as well as specialized transducers. Fast response surface thermocouples were designed and constructed in order to monitor transient surface temperatures. Heat transfer rates were then calculated with the aid of Fourier analysis. Dynamic stresses were monitored by strain-gauges applied to the engine. A special high speed data acquisition system was developed. An existing heat release model was modified and used to calculate combustion rates. A comprehensive finite element model was developed to calculate piston temperatures and stresses. The role of each combustion variable in stress and durability was investigated by statistical analysis. The results successfully identified the causes of combustion related engine failures. The primary cause of engine failure was found to be thermal loading. The principal cause of any variation in thermal loading and thus engine durability was maximum cylinder pressure. The life of the engine was proved to be determined almost entirely by peak cylinder pressure. The role of the rate of pressure rise was proved to be insignificant. All the implications of variations in the nature of combustion can now be determined accurately. It will thus be possible to optimise engine modifications and fuel properties before validation by durability testing.
A comprehensive qualitative and quantitative assessment of harvesting and other sugarcane supply chain disruptions within the Eston Mill supply area.
(2014) Kadwa, Muhammad.; Bezuidenhout, Carel Nicolaas.; Ortmann, Gerald Friedel.
The Eston Mill, which was established in 1994, is the newest in the KwaZulu-Natal sugar belt. Like for most other mills, it can be argued that there are inefficiencies in the supply chain due to systemic issues, which reduce optimum performance. The literature study involved a review of the factors which cause inconsistencies in sugarcane supply chains and the strategies implemented for improvement. This research study involved five main aims. First, a novice qualitative diagnostic analysis of the Eston sugarcane system, to identify a range of systemic issues and one pertinent problem, involving pay-weekends and subsequent labour absenteeism, was isolated for further investigation. This was conducted through explorative interviews and network analysis approaches. Secondly, based on the information from the diagnostic analysis, a model that predicts and quantifies the factors which influence daily crush rate disruptions at Eston, was developed, validated and verified. Thirdly, the extent of the pay-weekend problem area was systematically estimated in terms of frequency, variability and predictability. Fourthly, the cost of cutter absenteeism was conservatively quantified, based on two factors, namely, sugar recovery and mill operational costs. Lastly, a case study was carried out, which involved the feasibility of a mechanical harvesting system, to mitigate the impacts of labour absenteeism. The model involved the calibration of parameters for mill maintenance and operational stops, rainfall events and days in the week when slow crush rates occurred. The model captures approximately 64% of the variation observed in daily crush rates. Subsequent to the development of the model, additional cane supply disruptions, caused by cutter absenteeism, were also investigated. It was statistically verified that a significantly detectable degree of labour absenteeism occurs immediately after pay-weekends. There has been a general increased trend in cutter absenteeism from about 2007 until 2010. An economic analysis estimated the costs associated with cutter absenteeism to be approximately R1.3 million per season, for the Eston region. The alternative harvesting system case-study solution, was found to be risky. However, acquiring second-hand equipment, which was available on the market, is estimated to make the solution more feasible. Based on a literature search, this research is considered to be the most comprehensive analyses of sugarcane supply consistency at mill-scale worldwide. The model developed can be utilized to critically evaluate different sugarcane milling areas and could potentially make significant contributions to commercial sugarcane operations. The effectiveness of the model is dependent on usage in other milling areas, as well as other industries. In addition, the specific labour absenteeism coefficients for each season can possibly be investigated using other industries as well.
Computational and numerical analysis of differential equations using spectral based collocation method.
(2019) Samuel, Mutua.; Motsa, Sandile Sydney.
In this thesis, we develop accurate and computationally eﬃcient spectral collocation-based methods, both modiﬁed and new, and apply them to solve diﬀerential equations. Spectral collocation-based methods are the most commonly used methods for approximating smooth solutions of diﬀerential equations deﬁned over simple geometries. Procedurally, these methods entail transforming the gov erning diﬀerential equation(s) into a system of linear algebraic equations that can be solved directly. Owing to the complexity of expanding the numerical algorithms to higher dimensions, as reported in the literature, researchers often transform their models to reduce the number of variables or narrow them down to problems with fewer dimensions. Such a process is accomplished by making a series of assumptions that limit the scope of the study. To address this deﬁciency, the present study explores the development of numerical algorithms for solving ordinary and partial diﬀerential equations deﬁned over simple geometries. The solutions of the diﬀerential equations considered are approximated using interpolating polynomials that satisfy the given diﬀerential equation at se lected distinct collocation points preferably the Chebyshev-Gauss-Lobatto points. The size of the computational domain is particularly emphasized as it plays a key role in determining the number of grid points that are used; a feature that dictates the accuracy and the computational expense of the spectral method. To solve diﬀerential equations deﬁned on large computational domains much eﬀort is devoted to the development and application of new multidomain approaches, based on decomposing large spatial domain(s) into a sequence of overlapping subintervals and a large time interval into equal non-overlapping subintervals. The rigorous analysis of the numerical results con ﬁrms the superiority of these multiple domain techniques in terms of accuracy and computational eﬃciency over the single domain approach when applied to problems deﬁned over large domains. The structure of the thesis indicates a smooth sequence of constructing spectral collocation method algorithms for problems across diﬀerent dimensions. The process of switching between dimensions is explained by presenting the work in chronological order from a simple one-dimensional problem to more complex higher-dimensional problems. The preliminary chapter explores solutions of or dinary diﬀerential equations. Subsequent chapters then build on solutions to partial diﬀerential i equations in order of increasing computational complexity. The transition between intermediate dimensions is demonstrated and reinforced while highlighting the computational complexities in volved. Discussions of the numerical methods terminate with development and application of a new method namely; the trivariate spectral collocation method for solving two-dimensional initial boundary value problems. Finally, the new error bound theorems on polynomial interpolation are presented with rigorous proofs in each chapter to benchmark the adoption of the diﬀerent numerical algorithms. The numerical results of the study conﬁrm that incorporating domain decomposition techniques in spectral collocation methods work eﬀectively for all dimensions, as we report highly accurate results obtained in a computationally eﬃcient manner for problems deﬁned on large do mains. The ﬁndings of this study thus lay a solid foundation to overcome major challenges that numerical analysts might encounter.
Crop water requirements for irrigation planning in South Africa.
(1988) Dent, Mark Clifford.; Schulze, Roland Edgar.
Irrigation in 1980 accounted for approximately 52 per cent of the water consumed in Southern Africa. The need for planning water resources in the agricultural sector is therefore apparent. Much of Southern Africa's arable farming is carried out on land which, in terms of soil moisture availability to crops, can be described as marginal. Information on soil moisture is therefore valuable to the agriculturalist for planning irrigation schemes and for dryland farming. The objectives of this study were to provide the information mentioned above. This was achieved by producing a detailed delimitation of 712 zones throughout Southern Africa, of more or less homogeneous climate and by providing estimates of crop water requirements under dryland and irrigated conditions in each zone. At the same time the bulk of information which is normally forthcoming from such an analysis involving a large number of combinations of possible input, i.e. crops, soils and planting dates, was reduced, whilst the essential information content was retained. The study provided inter alia an estimate of the frequency of non-exceedance of certain levels of irrigation requirement, based on analyses of soil moisture budgets using long daily rainfall records. The soil moisture budgeting models which were used to estimate the above information were verified inter alia using field measurements of soil moisture. The irrigation analysis was designed such that the results should not became redundant when the inevitable improvement occurs in the estimation of crop factors or soil moisture variables nor if the farming practices change with respect to planting dates. A dryland soil moisture budget analysis for a range of crops and soils was performed in addition to the abovementioned irrigation analysis. The need for this latter study stemmed from the belief that irrigation should not be considered in isolation but rather as one of a range of options, many of them involving dryland farming, facing the agriculturalist. In addition to the dissertation, this study produced a map of Southern Africa on which the 712 homogeneous climate zones are depicted. For each of these zones four pages of computer printout were produced. These pages contain the results of the crop water requirements study for irrigated conditions and the crop water requirement deficit, runoff and an index of stress days for a range of crops, soils and planting dates, under dryland conditions.
Determining an integrated solid waste management action plan for urban Harare city, Zimbabwe: a system dynamics approach.
(2021) Kwenda, Phyllis Rumbidzai.; Lagerwall, Gareth.; Eker, Sibel.; Van Ruijven, Bas.
Abstract available in PDF.
Developing a diagnostic heuristic for integrated sugarcane supply and processing systems.
(2019) Shongwe, Mduduzi Innocent.; Bezuidenhout, Carel Nicolaas.; Bodhanya, Shamim Ahmed.
Innovation is a valuable asset that gives supply chains a competitive edge. Moreover, the adoption of innovative research recommendations in agricultural value chains and integrated sugarcane supply and processing systems (ISSPS) in particular has been relatively slow when compared with other industries such as electronics and automotive. The slow adoption is attributed to the complex, multidimensional nature of ISSPS and the perceived lack of a holistic approach when dealing with certain issues. Most of the interventions into ISSPS often view the system as characterised by tame problems hence, the widespread application of traditional operations research approaches. Integrated sugarcane supply and processing systems are, nonetheless, also characterised by wicked problems. Interventions into such contexts should therefore, embrace tame and/or wicked issues. Systemic approaches are important and have in the past identified several system-scale opportunities within ISSPS. Such interventions are multidisciplinary and employ a range of methodologies spanning across paradigms. The large number of methodologies available, however, makes choosing the right method or a combination thereof difficult. In this context, a novel overarching diagnostic heuristic for ISSPS was developed in this research. The heuristic will be used todiagnose relatively small, but pertinent ISSPS constraints and opportunities. The heuristic includes a causal model that determines and ranks linkages between the many domains that govern integrated agricultural supply and processing systems (IASPS) viz. biophysical, collaboration, culture, economics, environment, future strategy, information sharing, political forces, and structures. Furthermore, a diagnostic toolkit based on the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) was developed. The toolkit comprises a diagnostic criteria and a suite of systemic tools. The toolkit, in addition, determines thesuitability of each tool to diagnose any of the IASPS domains. Overall, the diagnostic criteria include accessibility, interactiveness, transparency, iterativeness, feedback, cause-and-effect logic, and time delays. The tools considered for the toolkit were current reality trees, fuzzy cognitive maps (FCMs), network analysis approaches, rich pictures (RP), stock and flow diagrams, cause and effect diagrams (CEDs), and causal loop diagrams (CLDs). Results from the causal model indicate that collaboration, structure and information sharing had a high direct leverage over the other domains as these were associated with a larger number of linkages. Collaboration and structure further provided dynamic leverage as these were also part of feedback loops. Political forces and the culture domain in contrast, provided lowleverage as these domains were only directly linked to collaboration. It was further revealed that each tool provides a different facet to complexity hence, the need for methodological pluralism. All the tools except RP could be applied, to a certain extent, across both appreciation and analysis criteria. Rich pictures do not have causal analysis capabilities viz. cause-and-effect logic, time delays and feedback. Stock and flow diagrams and CLDs conversely, met all criteria. All the diagnostic tools in the toolkit could be used across all the system domains except for FCMs. Fuzzy cognitive maps are explicitly subjective and their contribution lies outside the objective world. Caution should therefore be practiced when FCMs areapplied within the biophysical domain. The heuristic is only an aid to decision making. The decision to select a tool or a combination thereof remains with the user(s). Even though the heuristic was demonstrated at Mhlume sugarcane milling area, it is recommended that other areas be considered for future research. The heuristic itself should continuously be updated with criteria, tools and other domain dimensions.
Development and application of decision support systems for improved planning and operation of large dams along the White Nile.
(2015) Zaake, Benon Tamukedde.; Smithers, Jeffrey Colin.
In this study the regulation of Lakes Victoria, Kyoga and Albert in East Africa are investigated with the objective of maximising hydropower production subject to system constraints for existing and future planned dams along the Upper White Nile in Uganda. A Decision Support System (DSS) has been assembled and applied to search for efficient lake-reservoir operating rules for this basin. Elements of the DSS include power plant functions, a simulation model of the Upper Nile Equatorial Lake Basin, the Stochastic Analysis Modelling and Simulation (SAMS) computer software package for analysing hydrologic time series and the Colorado State University Dynamic Programming (CSUDP) model for solution of the optimisation problem. A concurrent record of observed lake levels and outflows for the three lakes during the reference period 1899 – 2008 has been constructed from various long term monitoring stations and utilised to derive net basin supply or net inflow time series at a monthly and annual time scale. Statistical tests confirmed the non-stationarity of the annual lake net basin supply time series. A justification to model the stochastic process of the monthly inflows as a Markov process was also reached. A Univariate Shifting Mean model was fitted to the annual historical data in tandem with a model for temporal disaggregation of annual to monthly net basin supplies for the purposes of generating synthetic flow series. The model performed well in terms of preserving the statistical characteristics of the historical reference set for each lake. The synthetic time series are considered to be a useful reference data set for future research in generating reservoir operating rules. Two Dynamic Programming (DP) models that may be used to generate reservoir operating rules were investigated. The desired scope of optimization was however curtailed by the well-known dimensionality problem of DP. Application of the deterministic method of Incremental Dynamic Programming (IDP) to the optimisation problem could only be carried out on a monthly time step and for single years separately. Annual time step optimization could only be carried out for the historic net inflows. The 1000 stochastically generated time series of net basin supplies could not be utilized within the implicit framework of deriving operating rules due to impractical computational requirements. The IDP however, yielded a realistic set of optimal operating policies at an annual time scale for the historical reference period (1898 – 2008). The beginning of year lake levels and annual release magnitudes obtained were compared against similar data for natural unregulated lake conditions. It is concluded that, in general, lake regulation would yield desirable benefits in terms of hydropower generation but would lead to marked deviation from natural lake levels and more variable outflows. The Stochastic Dynamic Programing (SDP) model was only applied to Lake Victoria in single reservoir optimization scheme due to limitations imposed by the large dimensionality of the problem and difficulty of simultaneously incorporating multiple lake reservoir transition probability matrices in the model. Application of the model for Lake Victoria showed that, it was feasible to define final storage levels for discretized initial storage and previous period inflow class combinations. The results from the study indicate that realistic heuristic operation rules can be inferred from the results of applying the IDP models and SDP algorithm.
Development and assessment of regionalised approaches to design flood estimation in South Africa.
(2020) Calitz, Johannes Pieter.; Smithers, Jeffrey Colin.; Kjeldsen, Thomas Rodding.; Gericke, Ockert Jacobus.
Engineers rely on design hydrological information for the design of hydraulic structures, such as dams, bridges, and drainage culverts. No single Design Flood Estimation (DFE) method has been identified internationally as the most appropriate method to use and, in many texts and manuals, the use of a combination of these are recommended. In South Africa, some of the currently recommended and widely used methods were developed outside of South Africa with little or no local adaptation or assessment, and most of the recommended methods were developed prior to 1990. The development of new and updated methods can therefore benefit from the use of much longer observed data sets and new and innovative approaches applied internationally. Four Regional Flood Frequency Analysis (RFFA) approaches widely adopted internationally are direct quantile estimation methods, Probabilistic Rational Method (PRM), Index Flood (IF), and Regional Growth Curve (RGC) methods. The Standard Design Flood (SDF) method is a locally developed PRM. However, the method has been recommended for review in a number of studies, and the IF has been shown to have potential for implementation at a national scale in South Africa. The aim of this study was to develop and assess RFFA approaches for the estimation of design flood quantiles within South Africa utilising the currently available data. This process required the compilation of a hydrological descriptors database, including quality controlled gauged flow data. This data was then utilised to identify a suitable probability distribution for FFA in South Africa, which can be applied at a regional scale through the identification of homogeneous flood producing regions and regional flood models. DFE methods require a range of catchment descriptors to be determined for use in models. Considering the literature reviewed and the available datasets, 17 catchment descriptors were selected for inclusion in the study. The descriptors range from geographic and catchment descriptors to design rainfall quantiles. After data screening, a total of 383 stations were utilised, in the study. The available record lengths and number of gauges were compared to prominent studies undertaken previously and was found to be comparative to the data availability in Australia and the United Kingdom. Linear moments (LM) were adopted for the estimation of the distribution parameters. Five distributions were selected for evaluation based on local recommendations as well as recent international developments: (i) General Extreme Value (GEV), (ii) Generalised Pareto (GPA), (iii) 3-parameter Kappa (KAP3), (iv) Log Pearson Type III (LP3) and (v) Pearson Type III (PE3). The evaluation process relied on an iterative elimination approach, reviewing graphical fits to theoretical distributions, Goodness-of-fit (GoF) criteria, model fit criteria and model uncertainty to identify the most suitable distribution. The graphical fit favoured the GPA, KAP3 and LP3 distributions equally, with the GoF methods ranking LP3 as the most suitable method. Conversely, the GPA was ranked highest for the model fit criterion and displayed the least model uncertainty and is thus recommended as the most suitable distribution for general FFA in South Africa. Two regionalisation approaches were considered to undertake the formation of the pooling groups, i.e. Clustering, and Region of Influence (RoI). For each regionalisation approach the hydrological descriptors were grouped into parameter sets, that constituted all potential descriptor combinations, which were tested for homogeneity as a selection criterion. Using the RoI approach, a maximum of 51% of the regions identified were relatively homogeneous. The super region approach was also applied to identify five dominant regions within which the RoI was applied in an attempt to refine the RoI approach. Using the combination of super regions and RoI provided little additional benefit, increasing the percentage of relatively homogeneous regions identified to only 52.6%. Conversely, the Clustering approach was able to identify 42 relatively homogeneous clusters in South Africa. To assess the suitability of Quantile Regression Technique (QRT) and Parameter Regression Technique (PRT) models in South Africa, four models were developed: (i) a QRT model, (ii) IF with equal station weighting (IF1), (iii) IF with station weighting applied (IF2) and (iv) PRM. Regression models were developed at two scales to estimate the required Scaling Factors, i.e. national and regional, with regional models performing best based on the Nash- Sutcliffe model Efficiency (NSE) coefficient. Six key performance indicators were utilised to assess the quantile estimation of the developed models: (i) NSE, (ii) Relative Error (RE), (iii) Root Mean Square Error (RMSE), (iv) Relative RMSE (RMSEr), (v) BIAS, and (iii) BIASr. The models that performed best in the RE assessment were the IF1 for both regionalisation schemes and the IF2 and PRM models using the RoI. When comparing the BIAS and RMSE of the four best performing clustering and RoI based models, the IF1 and QRT using Clustering models are the dominant models when considering both the RMSEr and the BIASr, the models improved on the results of the remaining models by up to a factor of two. The IF1 and QRT using Clustering models are therefore the best performing models on a national scale. The IF1 however has the added advantage of being able to estimate the entire growth curve as to the predefined QRT models. The IF1 is therefore the recommended model at a national scale, however cognisance needs to be taken when applying the model on the eastern coast due to poor BIASr performance. The new knowledge generated by the study can be divided into data, in the form of potentially the largest database of design flood specific descriptors concentrating on South Africa, and theoretical applications thereof. The theoretical knowledge generated ranges from the investigation into the most suitable frequency distribution to use for FFA in South Africa, to the application of multi-variate regionalisation approaches, which have not been applied in South Africa before. However, one of the key contributions was the development and performance assessment of four DFE models at multiple scales for South Africa for the estimation of peak design flood values.
The development and evaluation of a performance-based standards approach for regulating the use of heavy vehicles in South Africa.
(2013) Nordengen, Paul Anthony.; Lyne, Peter William Liversedge.; Bezuidenhout, Carel Nicolaas.
The regulation of the use of vehicles on the road network is aimed at ensuring acceptable safety and recovery of road maintenance costs, as well as minimising congestion, road wear, excessive noise and air pollution. The traditional approach of regulating heavy vehicles is prescriptive, i.e. enforcing regulations that primarily limit the mass and dimensions of these vehicles. This approach is generally favoured because such regulations are easy to understand and enforce. However, an underlying disadvantage is that the prescriptive approach does not always adequately safeguard the dynamic performance of heavy vehicles while travelling on the road. Principle-based and performance-based standards are primarily aimed at specifying desired outcomes, rather than how these outcomes should be achieved. Under a performance-based standards (PBS) approach, performance measures (such as low-speed swept path, rearward amplification, load transfer ratio and high-speed offtracking) are utilised to specify the performance required from vehicles. Although more complex to regulate, a PBS approach has a number of potential benefits such as: (a) improved vehicle safety, (b) improved productivity, (c) reduced infrastructure wear and emissions, (d) a more optimal use of the existing road network, and (e) the encouragement of innovation in vehicle design. The aim of this research was to apply, refine and demonstrate an alternative approach to the design and operation of heavy vehicles in South Africa with improved outcomes in terms of road transport productivity, vehicle safety performance, emissions, congestion and preservation of road infrastructure. The research included the development and implementation of a PBS demonstration project in South Africa and the monitoring and evaluation of PBS demonstration vehicles operating in the forestry industry in the provinces of KwaZulu-Natal and Mpumalanga. Evaluation focused on improvements in productivity (fuel efficiency and trip reduction) and load control with reference to initial results regarding road wear and safety performance. Results show a significant improvement in payload control and fuel efficiency of the PBS vehicles compared with the baseline vehicles. This also resulted in a reduction in CO2 emissions per ton.km. Road wear assessments of PBS and baseline vehicles showed that in some cases a reduction in road wear of up to 200% per ton of payload can be achieved through the use of PBS vehicles. Safety assessment results of four PBS vehicle designs showed various shortcomings of prescriptive baseline vehicles in terms of the performance standards.
Development and optimization of an integrated post-harvest management system for the handling and storage of fresh tomatoes in South African supply chains.
(2017) Cherono, Kipchumba.; Workneh, Tilahun Seyoum.
Abstract available in PDF file.
Development of a solar powered indirect air cooling combined with direct evaporative cooling system for storage of fruits and vegetables in Sub-Saharan Africa.
(2019) Sibanda, Sipho.; Workneh, Tilahun Seyoum.
Abstract available in PDF.
The development of the Water-Energy-Food Nexus Index and its application to the Southern African Development Community.
(2020) Simpson, Gareth Beresford.; Jewitt, Graham Paul Wyndham.
This thesis commences with a review of the development and relevance of the water-energy-food (WEF) nexus as a framework for achieving resource security. Based on academic and grey literature it includes an assessment of what the WEF nexus is, a review of its novelty (or lack thereof), and describes the challenges associated with integrating and optimising the WEF nexus. The criticism that several WEF nexus conceptualisations neglect distributional justice is considered, followed by a reflection on governance aspects associated with the approach. Four short WEF nexus case studies illustrate nexus considerations. The research subsequently assesses the status quo of opinion within the WEF nexus fraternity. The approach is not yet a decade old, and several practitioners have called for a shift in focus from ‘nexus thinking’ to ‘nexus doing.’ Various research tools to support nexus action are presented. Next, a comprehensive WEF nexus case study that includes indicators and GIS-base maps is offered. The case study is the Mpumalanga Province in South Africa, which represents a melting pot for the WEF nexus. Within this province is a strategic water area, extensive coal mining for energy generation and a considerable portion of the nation’s high potential agricultural land. This nexus assessment yields a radar chart that represents a visualisation of six water-, energy- and food-related indicators. An anthropogenic WEF nexus framework is subsequently motivated and presented. This framework has been utilised to develop the core output of this research project, namely, the development of a country-level composite indicator that has been established for 170 nations. Following an assessment of 87 globally applicable water-, energy- and food-related indicators, 21 were selected to constitute the WEF Nexus Index. This index provides a quantitative perspective of this multi-centric lens for evaluating trade-offs necessary to achieve sustainable development. To this end, it can be utilised for assessing national progress relating to integrated resource management as well as supporting decision making and policy development. The relevance and usefulness of the outcomes are demonstrated through a detailed discourse of the findings for selected regions and countries. An extended analysis is provided for the Southern African Development Community (SADC). WEF nexus assessments in the decade leading up to the 2030 Sustainable Development Goal (SDG) target year must be more comprehensive. Qualitative studies must be conducted in parallel with quantitative assessments. There is no one-size-fits-all method for integrated resource management utilising the WEF nexus. Instead, the approach must be tailored for each unique situation, and the WEF Nexus Index can be a catalyst and entry-point for such studies. By evaluating a subset of the SDGs, the index is complementary to the SDGs. The WEF Nexus Index is not a silver bullet that will solve all the significant development or environmental challenges facing humanity. This approach can, however, be added to the sustainability toolbox that is being utilised to engineer ‘the future we want’.
Development of updated design norms for soil and water conservation structures in the sugar industry of South Africa.
(2020) Otim, Daniel.; Smithers, Jeffrey Colin.
Sugarcane in South Africa is grown on wide-ranging soils, sometimes in non-ideal climates and on steep topographies where soils are vulnerable to erosion. A consequence of unsustainable soil loss is reduction in field production capacity. Sugarcane fields are protected against erosion through, inter alia, the use of engineered contour banks, waterways and spill-over roads. A comparison of design norms in the National Soil Conservation Manual and norms used in the sugar industry clearly shows discrepancies (e.g. maximum slope and cover factor of sugarcane) that need to be investigated. Furthermore, the sugar industry design nomograph was developed based on an unsustainable soil loss limit, does not include any regional variations of climate and the impact on soil erosion and runoff and does not include vulnerability during break cropping. The aim of this research was to develop updated design norms for soil and water conservation structures in the sugar industry of South Africa. Many soil loss models exist, of which empirical models are the most robust and provide stable performances. The Modified Universal Soil Loss Equation (MUSLE) which is embedded in the Agricultural Catchments Research Unit (ACRU) model, estimates event-based soil erosion and, given that the majority of soil erosion occurs during a few extreme events annually, the design norms were updated using the MUSLE. The ACRU model is a daily time step, physical- conceptual agrohydrological model. Runoff volume, peak discharge and sediment yield were simulated with the ACRU model and verified against the respective observed data. The results showed good correlations and the ACRU model can be confidently applied in the development of updated design norms for soil and water conservation structures in the sugar industry of South Africa. The ACRU model was used to conduct simulations for the different practices in the sugar industry and the results used to build the updated tool for the design of soil and water conservation structures in the sugar industry of South Africa, using MS Access with a background database and a graphical user interface. The updated tool is robust, based on sustainable soil loss limits, includes regional variations of climate and their impact on soil erosion and runoff and also includes vulnerability during break cropping. It is more representative of conditions in the sugar industry of South Africa and therefore recommended for use in place of the current sugar industry design norms. The results also indicate that soil and water conservation structures result in insignificant reductions in stream flow and would not likely necessitate their declaration as Stream Flow Reduction (SFR) activities as contained in the National Water Act of South Africa. Consequently, a 20 year return period is recommended for the design of soil and water conservation structures and the cost implication of varying design return periods from the minimum 10 year return period to the 20 year return period ranges from 16% to 35% across the four homogenous regions in the sugar industry of South Africa.
A diagnostic quasi-dimensional model of heat transfer and combustion in compression-ignition engines.
(1989) Hansen, Alan Christopher.; Meiring, Pierre Andre.
Investigations into the combustion of alternative fuels in compression-ignition engines in South Africa have underlined the inadequacies of existing zero-dimensional combustion models. The major aspect of concern in these models was the computation of heat transfer which had been singled out by a number of researchers as the leading cause of inaccuracies in heat release computations. The main objective of this research was to develop a combustion model that was less empirically based than the existing zerodimensional models for use in evaluating the combustion and resulting thermal stresses generated by alternative fuels. in diesel engines. Particular attention was paid to the development of a spatial and temporal model of convective heat transfer that was based on gas flow characteristics and to the introduction of a radiation heat transfer model that made use of fuel properties and fuel-air ratio. The combustion process was divided into two zones representing burnt and unburnt constituents and the resulting temperatures in each zone were used in the calculations of convective and radiative heat transfer. The complete model was formulated in such a way that it could be applied with the aid of a micro-computer. Calibration and verification of the gas flow sub-models which involved the squish, swirl and turbulence components necessitated the use of published data. Good agreement for the squish and swirl components was obtained between the present model and the experimental data from three engines, two with a bowl-in-piston and the other with a flat piston. These gas flow components dominated the gas velocities in the combustion chamber and provided a reliable foundation for the calculation of convective heat transfer. In spite of the well documented difficulties of characterising turbulence, after calibration the model generated turbulence levels with acceptable trends and magnitudes. Tests were carried out on a naturally aspirated ADE 236 engine involving the measurement of cylinder pressure and heat flux at a single point. Motored engine data were used to verify the convective heat transfer rates and to ascertain the effects of soot deposition on the heat flux probe. Close correlation between predicted and measured heat flux was achieved after accounting for the effects of chamber geometry at the probe site. Soot deposition on the probe caused a significant attenuation of the heat flux within a short period of the engine running under fired conditions. The results from fired engine tests showed that the two zone combustion model was providing plausible trends in the burnt and unburnt zone temperatures and that the model generated combined heat transfer rates which were credible not only on a global basis but also in terms of point predictions in the combustion chamber. The results also highlighted the considerable variation in heat transfer that could occur from one point in the chamber to another. Such variations added considerable weight to the objective of moving away from a zero-dimensional model to a quasi-dimensional type where predictions could be made on a more localised rather than global basis. It was concluded that the model was a definite improvement over zero-dimensional models and competed favourably with existing quasi-dimensional models with advantages in both simplicity and accuracy.
Effect of maturity and postharvest handling of prunus persica ‘landrace’ produced in KwaZulu-Natal: case study of physicochemical properties, tunnel solar drying and quality of processed products.
(2017) Mkhathini, Khangelani Maxwell.; Workneh, Tilahun Seyoum.; Mwithiga, Gikuru.; Magwaza, Lembe Samukelo.
Farmers in KwaZulu-Natal produce peach fruit. However, they are faced with overwhelming losses of the fruit due to lack of proper handling techniques, skills and facility during postharvest. In addition, these farmers have limited formal markets where they could sell fresh fruit immediately after harvesting. Thus, they are forced to consume the least they can and leave the rest of the fruit hanging on the tree. As a result, they lose close to 45% of their fruit. The literature review congruently pointed out such challenges of food losses in less developed countries and South Africa is not an exception. With a limited understanding of peach properties, it becomes increasingly difficult for farmers to handle the fruit. The cost of storage and processing facilities (such as sophisticated refrigeration) is very high and a decision table was used to determine which affordable method can be employed to process the peach fruit. The study is significantly important for the reduction of massive losses of fresh produce in the small-scale household farming sector as whole in South Africa. This study had three main aims to address. Firstly, it aimed to understand the physiological maturity and ripening of the peach fruit by determining physicochemical properties such as days to maturity, mass, volume, shape, moisture, pH, total soluble solids, colour (CIELab) and firmness. Secondly, the study aimed to install and test a tunnel solar dryer according to a decision table criteria that used to decide on a fruit processing method. Thirdly, the study aimed to process the fruit into dried peach slice with pre-treatments of lemon juice (LJ), ascorbic acid (AA) and a control, using a tunnel solar dryer. In addition, the study also aimed to process the peach into dried peach leather also using a tunnel solar dryer. This study included both objective and subjective methods to test the quality of the peach slice and leather products processed. Fruits reached maturity 129 days after full bloom (DAFB) and this coincided with fruit mass, volume and moisture content at respective averages of 80.00 g, 66.10 cm3, and 83%. Fruit firmness decreased significantly from 79.00 N to 24.70 N with increasing ripeness. Total soluble solids increased significantly from 13.50 to 19.00 °Brix during ripening. The pH value significantly increased from 3.40 to 4.00 indicating that acidity decreased with ripening. The TSS: TA ratio increased from 21.11 to 35.84. Moreover, it has been statistically verified that due the colour, yellow peach fruit produced the best products (as seen by the receipt of the highest sensory evaluation overall acceptability scores and based on the texture profile analysis results provided by Texture Analyser instrument). The utilisation of treatment such as AA or LJ did not have a significant effect in the overall drying between the yellow and white landraces. Ascorbic acid had a tendency to perform better than LJ which was also better than the untreated slices (control) in terms of the taste and overall acceptabilty. The experiment revealed that white leather moisture was approximately 7% and received the lowest overall acceptability scores from panellists. Less quality results were also received according to the texture profile analysis, in contrast to the yellow peach leather, which had 13% of moisture content. Yellow leather received the highest overall acceptability scores by both texture profile analysis and sensory evaluation tests. Thus, this study suggests that drying is possible in the KwaZulu-Natal Midlands. Overall, the results developed from the current study demonstrate that the fruit produced in small-scale farming sector is of good quality regardless of low yields because fertilizers and pesticides are not used. More importantly, this study reveals the significant potential of solar drying to be used by small-scale farmers to develop on-farm interventions aiming to add value to their produce and thus be able to preserve, use and sell later. It was concluded that DAFB, firmness, mass, TSS, volume, TTS: TA ratio are potential parameters to be used for maturity indexing of white peach ‘landrace’. Regardless of the misty conditions that prevail during the period of harvesting fruits, it was concluded by a statistical significant difference that the tunnel solar drying is a possibility in the KwaZulu-Natal Midlands. Days after full bloom, firmness, TSS, pH and mass have a critical role to play since they significantly differ between different ripeness degrees. These can be used to monitor peach growth stages and estimate yield for the small-scale peach grower in the area. The DAFB are a good tool that farmers can stick to without the use of advance technologies other than monitoring the number of days. Firmness is also a very important parameter for farmers in the area as the fruit hardly changes colour but can be soft showing signs of ripeness. The study has also devised a step-by-step process, which can be followed by small-scale processors in order to reduce losses using solar dryer to process fruit into leather and slice.
Estimating traffic induced sugarcane losses for various harvesting, loading and infield transport operations in South Africa.
(2016) Tweddle, Peter Brian.; Lyne, Peter William Liversedge.; Lagerwall, Gareth.
Infield traffic has been understood to cause adverse field conditions for crop growth. Literature containing traffic induced yield responses for sugarcane was reviewed and synthesised to better estimate the impact of infield traffic on sugarcane yields. Approximately 128 sugarcane yield responses to infield traffic treatments from local and international trials were collated and analysed. The impact of soil compaction effects on soil properties were not considered as there is a substantial body of knowledge on this topic. The results confirm that traffic on a sugarcane row is more detrimental than inter-row traffic. Soil water content at the time of infield traffic and infield traffic load intensity are further critical factors affecting soil compaction and sugarcane yield. Further aggregation of the data by soil textural groups was found to establish yield response trends useful for modelling of infield traffic scenarios, but were not statistically significant. Infield traffic paths of equipment movements were surveyed and mapped for a range of typical harvesting systems found commercially in the South African sugarcane industry. The maps were analysed to proportion the field area by row traffic, inter-row traffic and remaining non traffic areas for each machine component used infield. Yield losses based on vehicle traffic impacts were assigned to each corresponding component as determined from the results of the literature synthesis. The traffic induced yield loss was apportioned to the areas trafficked to determine a field based yield loss estimate for each of the harvesting and extraction systems and a corresponding economic impact reported. The ranking of system costs, reported off a mechanisation costing base, altered when the additional field traffic induced yield loss components were added, particularly when yield losses were compounded across multiple ratoons within a cropping cycle. Systems operating with low impact vehicles, of low traffic extent combined with controlled traffic practices resulted in the lowest yield losses on a field basis and also resulted in the lowest overall cost. Controlled traffic practices reduce the impact of heavy infield equipment on yields. The significance of this work is that the yield losses due to infield traffic can now be attributed to systems to allow for improved costing analyses and system comparisons to be conducted. It is proposed that this new contribution be incorporated into standard mechanisation costing methodologies to allow for such crop yield losses to be accounted for.
Flood disaster preparedness and impacts on rural households: a comparative study of Mwandi District of Zambia and Eastern Zambezi Region of Namibia.
(2019) Mabuku, Monde Patrina.; Senzanje, Aidan.; Mudhara, Maxwell.; Jewitt, Graham Paul Wyndham.; Mulwafu, Wapulumuka O.
The Zambezi Basin is considered vulnerable to climate variability as evidenced by the recurrent floods. The increased occurrence and severity of floods in recent years in areas previously not flooded has inundated parts of Eastern Zambezi Region of Namibia and Mwandi District of Zambia. The magnitude and frequency of these floods, coupled with poor disaster preparedness and lack of effective adaptation strategies, is believed to have negative impacts on rural households. Therefore, a cross country case study was carried out in order to assess the impacts of floods on income, crop production and livestock ownership; to determine the level of flood disaster preparedness; to assess coping and adaptation strategies undertaken by the rural households, and to develop a Household Flood Disaster Resilience Framework (HFDRF). Furthermore, the factors influencing the choice of different adaptation strategies and preparedness level were determined. Data were collected through structured and semi- structured questionnaire survey, focus group discussions, literature reviews and observations. The results indicated that floods had statistically significant impacts on income, crop production and livestock ownership of flooded rural households in both Namibia and Zambia. Rural households depended on both short-term coping and long-term adaptation strategies in order to minimize the negative impacts of floods and flood disasters. Households coped with floods through charcoal production, sale of firewood, sale of grass and reeds, collection of wild food and receipt of food aid. Long-term adaptation strategies included planting trees, fish farming, and flood water harvesting, temporary relocation to higher ground, and changing planting dates, among others. A majority of the households were well prepared (52%) for flood hazards in Namibia, whilst a minority were well prepared (9%) in Zambia. Furthermore, flood preparedness was influenced by sense of community, risk perception, self-efficacy, responsibility efficacy, outcome expectancy, education level, marital status, access and size of land. The study concludes that a variety of factors influence level of flood preparedness and adaptation strategy choices. For policy purposes, this suggests that relevant stakeholders’ interventions should consider these factors in order to enhance the rural households’ adaptive capacity to flooding. Furthermore, results on the impacts of floods on rural households could help in targeting the most vulnerable households in responding effectively to food disasters. This study informs decision makers and practitioners who aim to strengthen disaster risk reduction and management in the two countries and under similar environments, on the status quo of flood impacts, adaptation, and preparedness. The Household Flood Disaster Resilience Framework can be used as a tool for monitoring rural households’ flood resilience.

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