Department of Logistics

Permanent URI for this community

https://scholar.sun.ac.za/handle/10019.1/71

Browse

Now showing 1 - 20 of 152

Advanced analytics strategy formulation
(Stellenbosch : Stellenbosch University, 2014-12) Steyn, H. J.; Nel, J. H.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: Despite the high potential impact of advanced analytics on the performance of businesses around the world, its uptake and application in an integrated and strategically aligned manner has been limited. This problem is more pronounced with specific reference to optimization. Optimization methods lag behind other analytical methods such as data visualization and predictive models in terms of their level of adoption in organizations. This research suggests that part of the problem of limited application and integration lies in an overall inability of companies to develop and implement an effective advanced analytics strategy. The primary objective of this research is therefore to establish an approach for the development of an advanced analytics strategy for a company. Due to the absence of well described examples or published research on the subject it was necessary to generate insight and knowledge using a research approach that allowed for the development, testing, and improvement of a strategy over multiple cycles. Such a research approach presented itself in the form of action research. An initial advanced analytics strategy was developed for one of the subsidiary companies in a group of companies. The subsidiary company specializes in the importation, distribution, and marketing of industrial fasteners and has branches throughout South Africa. The strategy document was presented to the senior decision makers in the holding company for evaluation. The feedback from the evaluation was used to formulate changes to the initial strategy aimed at improving its alignment with the decision makers’ thinking on advanced analytics and increasing the probability of its implementation. The suggested changes from the first research cycle were used to define the second cycle strategy framework. The second cycle strategy framework included a strategy development process that consisted of three main steps: • Establishing business focus and relevance which included an assessment of the value creating potential of the business, identifying and prioritizing of value creating opportunities, and an assessment of key underlying decision processes, • Developing business relevant concept applications which included determining their potential value impact and creating a ranked pipeline of decision optimization applications. • Selecting concept applications and moving them into production. The strategy development process was informed by a number of different models, methods and frameworks. The most important model was a detailed valuation model of the company. The valuation model proved to be invaluable in identifying those aspects of the business where an improvement will result in the highest potential increase in shareholder value. The second cycle strategy framework will be used to develop an improved version of the advanced analytics strategy for the researched company. Moreover, the generic nature of the framework will allow for it to be used in the development of advanced analytics strategies for other companies.
Advanced supply chain planning processes and decision support systems for large-scale petrochemical companies
(Stellenbosch : University of Stellenbosch, 2006-12) Louw, Johannes Jacobus; Pienaar, W. J.; University of Stellenbosch. Faculty of Economic and Management Sciences. Dept. of Logistics.
Conventional supply chain integration concepts focus primarily on the internal and external integration of individual supply chains (can be viewed as intra-supply chain integration). Due to the highly integrated nature of petrochemical value chains, related supply chains should also be integrated by taking account of enterprise/industry-wide synergies and interdependencies (can be viewed as inter-supply chain integration). Inter-supply chain integration can typically develop along three dimensions: - Upstream feed clusters (upstream in the chemical value chain) - Downstream product clusters (downstream in the chemical value chain) - Macro logistics network clusters (within and across related logistics networks for liquid bulk, dry bulk, packaged goods and gases) This dissertation presents a generic framework of applicable intra- and inter-supply chain planning processes that supports related long- (strategic), medium- (tactical) and short-term (operational) supply chain decisions for large-scale petrochemical companies. This type of companies has to manage relative complex supply chains. Highly complex supply chains (due to an extensive product portfolio, supplier base, customer base, manufacturing processes, transportation, and management processes and systems) require far more advanced planning processes than simple supply chains. Advanced supply chain planning processes cover an extended supply chain scope, deal with longer time horizons, and utilize more sophisticated analytical techniques and decision support systems. An extensive literature study, supplemented by empirical research in the South African petrochemical industry, provided the foundation for the advanced supply chain planning framework concluded in this dissertation. Semi-structured interviews and a questionnaire presented to an informed audience constitute the empirical research conducted. The related best practices, concepts, approaches followed, and level of advancement in three supply chain planning dimensions were derived. To guide petrochemical companies along the planning advancement journey, the roadmap developed can be utilized for the application and implementation of the advanced supply chain planning framework. This roadmap articulates the advancement stages, dimensions, characteristics, and triggers to advance. Typical characteristics associated with the advancement stages and dimensions provide the means for a company to assess their level of progression. The essential mechanisms that can enable interventions are also articulated.
Affordability and subsidies in urban public transport: assessing the impact of public transport affordability on subsidy allocation in Cape Town
(Stellenbosch : Stellenbosch University, 2017-12) Piek, Jaco; Van Rensburg, Johann Andre; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : Cape Town is characterised by high commuting costs and high travel times due to a spatial mismatch between housing and jobs, as a result of apartheid planning policies. This dissertation investigated the use of an Intra-City Affordability Index to better understand this mismatch by analysing transport expenditure and potential travel patterns of public transport commuters in Cape Town. The results from the constructed affordability index analysed public transport affordability within this context. In turn, the potential subsidies needed to achieve the 10% policy affordability objective for public transport users in Cape Town, were estimated. One of the main research objectives was to determine the contextual public transport affordability for Cape Town through the construction of an Intra-City Affordability Index. This was done for two different income levels: low to low-medium income and average-income. One of the other main research objectives was to estimate the extent that improved affordability of low to low-medium income commuters affects subsidy requirements. The Intra-City Affordability Index was contextualised to Cape Town by incorporating household socio-demographics, the built environment and relevant policy conditions. Furthermore, the relationship between current public transport affordability levels and potential additional subsidies required to achieve the policy affordability objective was investigated. Lastly, a sensitivity analysis was done using bandwidths of income and affordability levels to test the robustness of the subsidy impact results. The main findings from the Intra-City Affordability Index showed that, overall, lower-income households spend well over 10% of their income on commuting, with some households potentially spending up to 42% of their income on public transport. It was also found that commuting to Cape Town CBD is more affordable than other employment centres, indicating that the transport system has not adapted to serve other employment centres since apartheid. Furthermore, the subsidies required to attain the 10% affordability benchmark were shown to be unfeasible and unrealistic.
An agent-based simulation modelling approach to assessing various refuge strategies in Bt sugarcane
(Stellenbosch : Stellenbosch University, 2019-12) Human, Dirk Johannes; Potgieter, Linke; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : Crops expressing genes from the bacterium Bacillus Thuringiensis (Bt) produce a protein toxic to members of the order Lepidoptera and are a popular alternative to sprayed insecticides. Although these Bt crops are considered to be an effective pest control method, careless usage may add selective pressure on the pest population to develop resistance to the protein over time. One method of limiting the rate of resistance development is to keep small portions of the cultivated land planted with the non-GMO crop which then acts as a refuge area for susceptible pests, limiting its exposure to the protein. Varieties of Bt sugarcane for the South African market that should limit the damage caused by the stalk borer moth, Eldana Saccharina Walker, are being developed, and a prerequisite to releasing such a product is to manage resistance development. Refuge areas are the primary way of managing resistance, but a recommendation is required on the size and layout of the refuge areas to be planted, as an area too small may not curb the rate of resistance development enough, but an area too large may not be economically viable for the industry. An agent-based simulation model is presented where individual moths are modelled as agents on an underlying sugarcane field that can either be Bt or refuge. The spatial aspect of the simulation model allows for testing the effectiveness of different shapes of refuge and not just the size. To reduce the complexity of the model, the field is divided into a series of smaller cells that can interact with each other, which allows us to model the impact of a severe infestation on an area the size of an average sugarcane farm. The simulation divides the simulated space into two grids representing the layers of the sugarcane that the different life stages of the insect move in. The first layer is the ground layer, representing the lower portions of the sugarcane where the eggs, larvae, pupae and egg-laying female moths are found. These cells are smaller as the immature life stages are nearly stationary and the female moth is assumed to have a much lower dispersal rate when searching for sights to lay eggs. The second layer is the sky layer with larger cells, where adult males and unmated females are able to move over larger distances to find mates. To further reduce complexity, every cluster of eggs laid by a female moth is modelled as a single agent that progresses as a unit through the immature life stages before being converted to many individual moth agents when they mature. The model is then applied to three hypothetical case studies, each focussing on a specific aspect of refuge planning. The first case study focusses on the size and distribution of refuge, the second on the shape of the refuge, and the third assumes that the Bt sugarcane is introduced gradually and how this may affect the refuge strategy. The results from these case studies as well as those obtained from the sensitivity analysis are then summarised in the form of a decision support tool (DST), which provides some recommendations for refugia planning and highlights the risk factors for resistance development identified during the course of this study. Combining the recommendations with the risk factors that may be associated with a given scenario should provide the growers with a starting point of how to plan their refugia.
An algorithmic approach to the 2D oriented strip packing problem
(Stellenbosch : Stellenbosch University, 2007-12) Ntene, Nthabiseng; Van Vuuren, J. H.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: Packing problems in industry may be categorised into the two classes of bin packing and strip packing problems. The former involves packing items into the minimum number of fixed sized bins, while in the latter the items are packed into a single open-ended bin (referred to as a strip) such that the total packing height is minimised. The items in both problem categories may not overlap. The entire set of items may be known in advance in which case the problem is referred to as an offiine problem. On the other hand, in online packing problems, only one item is available at a time and the next item only becomes available once the current item has been packed. Problems where some information about the items to be packed (such as a sorting) is available in advance are referred to as almost online packing problems. Offiine strip packing problems may be solved using exact algorithms, level heuristics or plane heuristics while online packing problems may be solved using level heuristics, shelf heuristics or plane heuristics. In level heuristics the strip is divided into horizontal levels whose heights are equal to the heights of the tallest items packed on the levels, whereas in shelf algorithms the strip is also partitioned into horizontal levels, but with additional space above the tallest rectangles on the levels to cater for future variation of item heights. On the other hand, in plane algorithms, the strip is not partitioned-items may be packed anywhere within the strip. Both online and offl.ine two-dimensional rectangle strip packing problems are considered in this dissertation, and the rectangles may not be rotated. An algorithmic approach is employed whereby several algorithms (heuristic and exact) are implemented. A new offl.ine level algorithm is introduced which seeks to fully utilise available space within a level. For online packing problems, a new approach is proposed when creating additional space via shelf algorithms. A new online plane algorithm is also presented. The study aims to find (among the new and a host of known algorithms) the best algorithm to use for different instances of two-dimensional strip packing problems. In reality, such problems often involve a large number of items-therefore the need arises for a computerised decision support system. Such a system, implementing all the (known and new) algorithms described and tested is also presented in this dissertation.
Algoritmes vir die maksimering van konvekse en verwante knapsakprobleme
(Stellenbosch : University of Stellenbosch, 2007-03) Visagie, Stephan E.; De Kock, H. C.; University of Stellenbosch. Faculty of Economic and Management Sciences. Dept. of Logistics.
In this dissertation original algorithms are introduced to solve separable resource allocation problems (RAPs) with increasing nonlinear functions in the objective function, and lower and upper bounds on each variable. Algorithms are introduced in three special cases. The first case arises when the objective function of the RAP consists of the sum of convex functions and all the variables for these functions range over the same interval. In the second case RAPs with the sum of convex functions in the objective function are considered, but the variables of these functions can range over different intervals. In the last special case RAPs with an objective function comprising the sum of convex and concave functions are considered. In this case the intervals of the variables can range over different values. In the first case two new algorithms, namely the fraction and the slope algorithm are presented to solve the RAPs adhering to the conditions of the case. Both these algorithms yield far better solution times than the existing branch and bound algorithm. A new heuristic and three new algorithms are presented to solve RAPs falling into the second case. The iso-bound heuristic yields, on average, good solutions relative to the optimal objective function value in faster times than exact algorithms. The three algorithms, namely the iso-bound algorithm, the branch and cut algorithm and the iso-bound branch and cut algorithm also yield considerably beter solution times than the existing branch and bound algorithm. It is shown that, on average, the iso-bound branch and cut algorithm yields the fastest solution times, followed by the iso-bound algorithm and then by die branch and cut algorithm. In the third case the necessary and sufficient conditions for optimality are considered. From this, the conclusion is drawn that search techniques for points complying with the necessary conditions will take too long relative to branch and bound techniques. Thus three new algorithms, namely the KL, SKL and IKL algorithms are introduced to solve RAPs falling into this case. These algorithms are generalisations of the branch and bound, branch and cut, and iso-bound algorithms respectively. The KL algorithm was then used as a benchmark. Only the IKL algorithm yields a considerable improvement on the KL algorithm.
Allocating commodity volumes in the citrus export cold chain: A case for the Port of Durban
(Stellenbosch : Stellenbosch University, 2021-03) Darley-Waddilove, Joshua Ian; Goedhals-Gerber, Leila Louise; Thiart, Jeanette; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics
ENGLISH ABSTRACT: In this study, the feasibility of using “forced” allocation as a mechanism to aide in alleviating capacity challenges at the Port of Durban is explored and insights on the impact of reallocation to the citrus export cold chain is provided. The use of the mechanism is explored by limiting the allowable citrus throughput that may be handled at the Port of Durban for varying through put scenarios, and using allocation techniques to allocate the allowable citrus throughput amongst the competing production regions. An allocation model framework is formulated to optimally allocate the total citrus export volumes in a season to each of the South African ports that export citrus, taking into account the allowable port throughput constraint at the Port of Durban. The allocation model framework is modelled as a minimum cost transport problem and is solved using linear programming. The results of the 2019 actual export season for citrus exports is compared to the results of the 2019 forecasted export season to determine if there is a single suitable allocation technique that can be used to allocate the allowable port throughput to the production regions in the allocation model framework for future export seasons. The results show that there is no single suitable allocation technique, and so allocations on forecasted citrus export volumes must be done on a case-by-case basis. A possible export plan for the 2021 forecasted export season is calculated using the allocation model framework for each scenario to provide a baseline export plan for the different allowable throughput scenario’s at the Port of Durban. The forecasted citrus export volumes are forecasted using a four period double moving average forecasting model. The feasibility of using “forced” allocation as mechanism to alleviate capacity challenges faced at the Port of Durban is assessed on two criteria, namely the availability of theoretical excess capacity at the alternate ports to handle the citrus volumes reallocated and the change in total transport cost to the citrus export cold chain. The assessment of the criteria, and the analysis of the results, indicate that the use of “forced” allocation is feasible in the majority of, but not in all of the port throughput scenarios. Even though it is feasible in terms of the available capacity, there is, however, an increased transport cost to the citrus export cold chain in the majority of the scenario’s analysed. This additional transport cost must be weighed up against the cost of congestion and lost time, and will have to be absorbed by the citrus export cold chain. Eventhough there is an increase in transport cost, which can affect the total citrus export cold chain by as much as +35.2% (in the worst case scenario), the mechanism is deemed feasible as the impact of the increased transport cost is a relative measure that will have a varying impact amongst the different stakeholders of the citrus export cold chain and so each stakeholder will have to decide independently if it is feasible to them. The study achieved its primary aim of alleviating capacity pressures at the Port of Durban by reallocating citrus volumes to all South African ports that can handle citrus under different levels of available capacity at the Port of Durban. Therefore, “forced” allocation is deemed a good alternative solution to the current congested situation.
An analysis of temperature breaks in the summer fruit export cold chain from pack house to vessel
(Stellenbosch : Stellenbosch University, 2013-12) Haasbroek, Laura Marchand; Goedhals-Gerber, Leila Louise; Van Dyk, Frances Elizabeth; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: There is great concern in the fruit industry that too much fruit and money is lost each year due to breaks occurring in the export cold chain of fresh fruit. Therefore, the CSIR (Council for Scientific and Industrial Research) and Stellenbosch University were approached to do research on this problem. This particular study focuses on the cold chains of table grapes, summer pears and plums as these fruit are especially sensitive to temperature. Observations were made on fruit farms, in pack houses, in cold stores as well as in the Port of Cape Town. From these observations it was clear that protocols are not always followed and fruit quality is sometimes neglected because of pressure to speed up the exporting process. In order to analyse the export cold chains of these fruit types, temperature trials were conducted and temperature data received from exporting companies was analysed. The data was analysed from the cold store up to the point where the vessel sailed out of the Port of Cape Town. From the analysis it became clear that too many cold chain breaks occur during fruit exports from South Africa, especially during the loading of containers at cold stores. As a final output to the study, a good cold chain practice guide for the export of table grapes was developed with the aim of assisting the fruit industry in minimizing these cold chain breaks. The guide was developed with simplicity to ensure easy understanding under all role-players in the industry. This study was a small step in the right direction, but it should be highlighted that the complexity of the problems in the fruit cold chains are substantial and further research will have to be done in order to eliminate the occurrence of these cold chain breaks.
Analysis of the efficiency of the transport logistics supply chain with specific reference to liner shipping in South Africa
(Stellenbosch : Stellenbosch University, 2000-12) Qukula, Temba; Van Niekerk, H. C.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics .
ENGLISH ABSTRACT: Liner shipping supplies a frequent scheduled transport service between designated ports to meet the needs of importers and exporters. Those needs are becoming more specific as a result of increasing competition attributable to globalisation of trade while importers and exporters are requiring more exacting services from the liner operators. The elements of service which most concern the importers and exporters are obviously the costs they must bear for the conveyance of the cargo and the time taken for its delivery. In order to meet the requirements of importers and exporters and at the same time enable the operators of the services to remain in business in the face of increasing competition within the industry, liner shipping worldwide is undergoing major changes. These changes are intended to increase the economies of scale and to extend control of the liner operators over the landside transport services. A discussion on liner shipping and current developments is contained in Chapter 3. Liner shipping plays an indispensable role in the economy of South Africa because almost 50% by value of South African imports are containerised. That equates to 8% of South African imports by volume (Moving South Africa: 1998), although it must be borne in mind that some of the cargo moving through South African ports is ultimately destined for countries in SADC (Southern African Development Community). According to Drewry Shipping Consultants, containerised cargo worldwide has been growing at the rate of about 8% per annum since 1980 and the South African trade has experienced a similarly high growth. The actual transport of containers, by sea is only one of the elements in the transport logistics supply chain (TLSC) between exporters in one country and importers in another with which liner operators must concern themselves. A conceptual background explaining the entire TLSC is provided in Chapter 2. In that chapter, the TLSe is defined and two models are used to identify key elements of the TLSC as well as interaction between them. Inefficiencies existing in individual elements of the TLSC as well as suggested solutions to the underlying problems are discussed in Chapter 4. Emphasis is placed on the need to use information technology as a vehicle to integrate the individual elements of the TLSe and as a means of saving costs and time. A discussion of the economic benefits of an efficient TLSe is contained in Chapter 5, while Chapter 6 includes a discussion on local and regional developments that have a bearing on the efficiency of the TLSe. The conclusions of the study together with recommended action are contained in Chapter 7.
Application of long short-term memory artificial neural networks to forecast water supply and demand in the Lake Chad Basin
(Stellenbosch : Stellenbosch University, 2020-12) Fouotsa Manfouo, Noe Careme; Potgieter, Linke; Nel, Johanna H.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH ABSTRACT: The implementation of effective water resources management in developing countries in general and in the Lake Chad Basin in particular, is hindered by the absence of reliable information on both the net water supply, as well as on the agricultural water demand. The main purpose of this research is to provide a methodology to determine and forecast total water supply and water demand in the context of scarce data for water resources management. In order to develop a forecasting methodology, a literature survey is first performed to understand the current environment and methodology of water resources management in the Lake Chad Basin, to highlight the main problems faced within the context, and to identify the opportunity for applied research. As part of this investigation, different stakeholders were visited during a field trip to the Lake Chad Basin. The main water users identified in the Lake Chad Basin do not have historical data on agricultural water demands, making it difficult to understand current water demand requirements or estimate future demand in the Lake Chad Basin. Literature available on the Lake Chad Basin were also considered. A hydrological model was developed in 2011 by Bader, Lemoalle, and Leblanc and reported on in the paper Modèle hydrologique du Lac Tchad [16]. The model provides information on the lake storage for the period 1956 to 2011, however, it does not consider upstream diversion. Therefore, the output of the model does not allow an exhaustive estimation of water supply in the Lake Chad Basin. In addition, the model is data intensive and uses variables that are neither easy to obtain, nor straightforward to compute, and requires expert hydrological knowledge to extend the use of the model for future water supply estimation beyond 2011. Moreover, there are currently no model developed for estimating water demand in the Lake Chad Basin. Long short-term memory is an artificial recurrent neural network that have been shown to perform exceptionally well in the context of time series forecasting, due to its ability to incorporate lags of unknown duration in the network structure. Despite the good track record of this methodology in forecasting time series, it is not widely used in the literature for water supply and demand estimation. In this dissertation, multivariate time series forecasting with long short-term memory is investigated as an alternative methodology for different aspects of water supply and demand estimation. Pearson correlation, random forest, extra trees classifiers and principal component analysis are investigated as input selection approaches to increase prediction accuracy. For water supply estimation, a lake storage forecasting model as well as a streamflow forecasting model are developed. Results indicate that long short-term memory can be used to predict Lake Chad Basin storage, with better performances than the state of the art results, obtained from artificial neural networks and support vector regression. The multivariate approach indicates that atmospheric data are both good and easily obtainable data for lake storage forecasting. The input variables, selected with both the principal component analysis and random forest approach are recommended for streamflow forecasting in the Lake Chad Basin. Random forest occupies the second position, by producing better predictions in the Ndjamena gauging station. A long-term temperature forecasting model as well as a precipitation forecasting model were developed and the outputs were used as input in the CROPWAT software to determine the irrigation water requirement per hectare per crop type. A comparison between the widely used statistical downscaling model and the forecasting models for long-term temperatures and precipitations developed in this research indicate better accuracy using the multivariate long short-term memory approach. Both the root mean square error and the mean absolute percentage error used to check the performances of the models indicate commendable accuracy. Four population dynamics models, namely the malthusian growth model; the logistic growth models with both constant and dynamic rates, as well a logistic growth model with dynamic rate and species interaction, are developed to estimate the size of land used for both crop and livestock, and to finally predict the total agricultural water demand in the Lake Chad Basin. The models are parameterised using long short-term memory. A case by case investigation of prediction performances across the three countries indicates that the malthusian growth approach produces better performances in 9 cases, the logistic growth model with constant rate performs better in 4 cases, and the logistic growth model with dynamic rate performs better in 7 cases. The malthusian approach is more suitable for variables with unstable trends, the logistic model with constant rate is more suitable for variables with almost concave or convex shapes and the logistic growth with dynamic rate is the most useful long-term crop land-use and livestock population forecasting. Finally, the best performing models for crop land-use and livestock population are downscaled to main water users level, in order to estimate total water demand per crop type and per livestock type. The investigation of the four population dynamics models, on both the crop land-use and livestock population dynamics, the characterisation of the competition type between species in the Lake Chad Basin case study as well as the estimation of water demand at water users’ level is a new contribution to literature.
Assessing the adoption and utilization of e-hailing services : the case of Cape Town, South Africa
(Stellenbosch : Stellenbosch University, 2021-03) Smith, Lee-Thomas; Van Rensburg, Johann; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: E-hailing services have gained large attention on media platforms due to their dynamic nature. The spread of smartphone applications with GPS-based location technology has led to the growth of new application-based platforms that offer on-demand transport for their users.The following dissertation introduces e-hailing services in chapter one. The background and motivation of the research is discussed and a suitable conceptual model is created. The aims, objectives and research contribution are further outlined. Following the introduction, chapter two provides an in-depth literature review of notable existing studies and frameworks that provide the basis for the research methodology. Key concepts are defined and literature from existing studies is highlighted and discussed. The literature used in Chapter two formed a baseline for the creation of two surveys, one for e-hailing users and non-users and one for e-hailing drivers. Chapter three introduces a descriptive case study, whereby Cape Towns’ contextual factors are discussed and under three sections which include: household socio-demographics, the built environment and the policy environment. The first section, regarding household socio-demographics, a descriptive analysis of the City’s population, income and employment is discussed for background on the area of the case study. The built environment follows and describes the land-use characteristics and public transport system of Cape Town. Various transport modes and options are discussed. The policy environment is then discussed about road transport legislation and e-hailing service provisions. This is followed by chapter four, which includes the chosen methodology and hypothesis development for the study. Within this chapter, multiple methodologies are discussed to achieve the research objectives in terms of their design, objectives and associated limitations. It further includes the research design and data collection process. Within this chapter, two surveys were created after a review of existing e-hailing literature and the survey distribution is discussed. Chapter five represents the research findings from both surveys, whereby the data is visualised using SMARTPLS 3.0 software, SPS Sand descriptive analysis. Chapter six concludes with a discussion of the research findings.The adoption and utilization of e-hailing services are described, future research prospects are discussed and policy recommendations are given. The limitations of the research methodology are discussed and potential areas for additional research are outlined.
Assessing the costs and benefits of a speed limit for freight trains during night-time operations : a generic model for the Netherlands
(Stellenbosch : Stellenbosch University, 2020-03) Bingel, Christopher; Van der Merwe, Jacomien; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : Noise pollution is a severe issue for numerous individuals, especially when it occurs consistently and throughout the entire day. As a major source of emissions, transportation has long been in the focus of policy makers hoping to alleviate affected persons from negative effects on health and wellbeing. In such an attempt, the Dutch Ministry of Infrastructure and Water Management plans to reduce the maximum allowed speed for freight trains between 11pm and 7am to either 40 km/h or 60 km/h. In order to assess and compare the total economic advantages and disadvantages of such a policy, the Ministry commissioned a study to explore the resulting effects. This research thesis therefore set out to answer the questions if and how much a nightly speed limit reduction for freight trains in the Netherlands will reduce the noise levels and influence the operations of these services. Distinguishing between three different production systems (block trains, wagonload trains and combined transport) and different transportation distances, it is found that operating costs will increase between 0.3% and 5.0%. It is expected that as freight trains becomes more costly to operate, consignors will opt for transportation alternatives on roads and inland waterways. Thus, the second purpose of this study is to determine the demand behaviour and a potential modal shift in the Dutch rail freight market. In order to do so, 13 industry experts from railway operators, freight forwarders and consignors were interviewed. From these interviews, quantitative and qualitative indications were used to calculate price elasticities for rail freight services in the relevant market. These elasticities, again depending on the production system, the transport distance and the level of cost increase, vary between 0.1 and 2.6, which is consistent with previous research. The final question to answer concerns the feasibility of a case study. In an economic cost-benefit analysis, this paper investigates a train line between the Dutch towns of Meteren and Boxtel. It is found that although noise and air pollutant emissions related to freight trains decrease, there are negative effects outweighing the benefits. During the time period from 2030 to 2040, total costs exceed the total benefits by around 3.73 €m (alternative 1, reduction to 40 km/h) and 1.35 €m in 2019 values. This corresponds to a benefit-cost ratio of 0.274 and 0.353 respectively. This paper shows that a speed reduction does in deed reduce costs to society that stem from noise emitted by freight trains. However, this measure has side effects, as traffic volumes will shift to trucks and barges as the railway freight product becomes more and more unattractive. Operational cost increases and external costs (e.g. higher air pollution by trucks or higher probability of accidents) outweigh the benefits to society. Therefore, the author recommends to reject the suggested speed limit reduction for freight trains between 11pm and 7am in the Netherlands.
Assessing the need for a dry port to alleviate congestion surrounding the Port of Durban : a citrus case
(Stellenbosch : Stellenbosch University, 2024-03) Mkhabele, Nkensani Keneth; Krygsman, Stephanus Christiaan; Goedhals-Gerber, Leila Louise; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH SUMMARY: Port congestion poses a critical challenge to the efficient export of citrus fruits, thus impacting global trade and supply chain resilience within the industry. This research investigates the multifaceted dimensions of port congestion at the port of Durban within the context of the South African citrus industry. The primary objective is to evaluate the feasibility and potential benefits of establishing a dry port as a strategic intervention to mitigate existing logistical challenges faced at the port with the aim of providing a framework that aids in facilitating more efficient international trade. While employing a pragmatic mixed-method approach, the study analyses the implications of port congestion on key stakeholders, including shipping companies, industry associations, and regulatory bodies. The research encompasses a literature review, providing insights into global dry port management strategies, the role of dry ports, the importance of international trade, the citrus industry in South Africa as well as broader topics that fuel the readers’ understanding of the research. Through an analysis of primary data, including interviews with 17 industry experts and stakeholders, the study uncovers the specific challenges faced by the citrus industry in navigating port congestion, affecting export schedules, quality control, and market competitiveness. Data from the Ports Regulator of South Africa provides the quantitative data utilised within the study. The research findings highlight the need for strategic interventions, leading to a series of recommendations aimed at enhancing railway capacity and fostering government investment in port infrastructure. The exploration of long-term Public-Private Partnerships (PPPs) and the adoption of development-attracting methods, such as Special Economic Zones (SEZs), emerge as additional recommended strategies for mitigating congestion-related disruptions and avoiding future bottlenecks. This research contributes to the existing body of knowledge by illustrating how the strategic establishment of a dry port can address logistical challenges and stimulate economic growth within the perishable domain. The implications extend beyond congestion relief, encompassing economic stimulation, job creation, and a repositioning of South Africa favourably within global trade networks. The study highlights the necessity for ongoing research into the optimal location, design, and governance of dry ports within South Africa. Lastly, this research provides a practical framework for addressing operational inefficiencies in the citrus supply chain, emphasising the potential transformative impact of a dry port on trade dynamics and economic development for the Republic of South Africa.
Assessing the potential of blockchain technology as an information-sharing platform in the major fruit export supply chains of South Africa
(Stellenbosch : Stellenbosch University, 2022-12) Beuting, Wout Lean; Kussing, Ulrike; Freiboth, Heinrich; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH SUMMARY: Supply chain management has become increasingly complicated with the deepening of globalisation. Supply chains and their stakeholders of first-tier and second-tier organisations have become significantly more versatile, at a time when there is an expanding relevance for delivery times, product quality, and efficiency. Information technologies are potentially supportive to the storage and exchange of data, and make the supply chain more easily manageable. This research study aims to assess the potential of blockchain technology for the major fruit export supply chains of South Africa, which are citrus, pome fruit, and table grapes. This research study follows a deductive approach and utilises a research methodology guided by a three-stage process. First, a systematic literature review was conducted to get a better understanding of blockchain technology and its potential for agricultural supply chains. Second, a qualitative multimethod data collection approach has been followed in the form of an industry case study. This research method has been adopted to get a better understanding of the information flows throughout the fruit export industry and how data is managed. Finally, in the analysis phase, the results of the previous two stages are combined to assess the potential of blockchain technology as an information-sharing platform in the South African fruit export industry. The results of the systematic literature review and the industry case study revealed the shortcomings of blockchain technology and the complexity of the South African fruit export supply chains. Both the produce exporter and the freight forwarder fulfil key roles when it comes to data management and the exchange of data elements. The decentralised systems of blockchain technology look very promising but they are still in the early phase of development. Despite its rapid improvements, the adoption of blockchain technology comes with many uncertainties which exposes its early stage of development at this stage. The analysis phase shows that neither blockchain technology nor the South African fruit export industry, is yet ready for the adoption of this system. The adoption of a decentralised system such as this brings a high degree of uncertainty as many challenges still need to be overcome. Besides that, the system requires a high-quality internet infrastructure which is not presently available for either entity. Nevertheless, the results show the relevance of supply chain transparency, visibility, and data quality on supply chain performance and their contribution to better-grounded decision-making processes. The recommendations given are intended to prepare the industry for the adoption of blockchain in the future. Investments are needed for further improvements of the domestic internet infrastructure in order to achieve blockchain’s potential. The improvements of blockchain technology are proceeding rapidly. It is recommended to follow these developments closely until blockchain is ready for industry-wide adoption. Until such time, recommendations are given on how to increase transparency, visibility, and data quality as these contribute significantly to supply chain performance and decision-making processes.
The assessment of improvements made in the freight logistics costing methodology in South Africa from a macroeconomic perspective
(2008) De Jager, Daniel; Havenga, J. H.; University of Stellenbosch. Faculty of Economic and Management Sciences. Dept. of Logistics.
AFRIKAANSE OPSOMMING: In 2006 het F.J. Botes, C.G. Jacobs en W.J. Pienaar van die Universiteit van Stellenbosch artikel gepubliseer oor die Logistieke Koste Model getitel “A model to calculate the cost of logistics at a macro level: a case study for South Africa”. Die Logistieke Koste Model was op daardie stadium al baan breek werk gewees in Suid Afrika en het gelei na die publikasie van die eerste “State of Logistics Survey for South Africa” deur die Wetenskaplike en Nywerheidsnavorsingsraad (WNNR). Sedertdien is die metodologie in die Logistieke Koste Model oor die jare verbeter, veral in 2008 toe nuwe metodes van padvervoer koste berekening op baie gedetailleerde vlak toegepas is, asook nuwe metodes van voorraad drakoste. Dit is hierdie en ander verbeteringe in die Logistieke Koste Model sedertdien die vorige publikasie deur Botes et al wat in hierdie tesis uitgelig word. Tekortkominge en moontlike metodes om die model te verbeter word ook uitgewys. Dit is van mening dat hierdie dokumentasie belangrik van aard is aangesien die Logistieke Koste Model deur die Sentrum vir Voorsieningskettingbestuur (Universiteit van Stellenbosch) gebruik word om te konsulteer aan Transnet, die WNNR en ander vragvervoer diens leweransiers. Die “State of Logistics Survey for South Africa” publikasie deur die WNNR word ook deur publieke asook private ondernemings gebruik in die maak van makro-ekonomiese strategiese besluite. Hierdie navorsing lig ook die uitkomste van die 2008 Logistieke Koste Model opdatering uit. Maniere waarop hierdie uitkomste geïnterpreteer kan word deur industrie om wyse strategiese investeringsbesluite te neem van makro-ekonomiese aard word ook uitgewys.
Automated examination timetabling with application to Stellenbosch University
(Stellenbosch : Stellenbosch University, 2018-12) Van Rooyen, Charles; Nieuwoudt, Isabelle; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : The examination timetabling problem (ETP) consists of scheduling the examination papers of students in such a way that no student is required to write two or more examination papers at the same time in an examination period. It is well known that this problem is NP–complete, which makes it an interesting research topic for researcher. There exist many different variants of the ETP, and the one focused on in this project is the variant that can be applied to Stellenbosch University. The purpose of this project is to find examination timetables that will spread most students’ examination papers more or less equally over the full duration of the examination period. Stellenbosch University is used as case study. The primary objective of any algorithm is to satisfy the hard constraints provided by Stellenbosch University. For example, one hard constraint is that certain examination papers must be scheduled on fixed timeslots. Graph colouring is used in a two–phase heuristic algorithm to obtain a feasible initial solution. In the first phase an examination timetable is sought where no student is required to write more than one examination paper during any timeslot. After the first phase, the number of examination papers scheduled during each timeslot is balanced in the second phase of the algorithm. This is to ensure that amongst others, enough lecture halls are available during each timeslot to accommodate all students. After a feasible initial solution is obtained, hill climbing and the great deluge algorithm (GDA) are used to improve upon the equally spread of students’ examination papers as much as possible over the entire examination period. Three moves are defined in this project to move from solution to solution in the solution space. The first move moves one module in the timetable to another timeslots, the second move swaps all of the modules in two timeslots and the third move is to swap two modules that are in different timeslots. To evaluate how well students’ examination papers are spread over the entire examination period for each timetable, a newly derived cost function is used. The cost function strives to be fair towards all students. Parameter calibration is done on the parameters used in the cost function and the search algorithms. The resulting timetables when using hill climbing and the GDA are compared, and it is found that the GDA outperforms hill climbing. Furthermore, the cost function used in this project is compared to the cost function of the 2nd International Timetabling Competition (ITC). Using Stellenbosch University’s variant of the ETP, it is found that the cost function of this project outperforms the cost function used in the ITC.
Automated payment fraud detection using logistic regression and support vector machines
(Stellenbosch : Stellenbosch University, 2021-03) Thetard, Heinrich Mathias; Nel, J. H.; Stellenbosch University. Faculty of Economic and Management Science. Dept. of Logistics.
ENGLISH ABSTRACT: The financial technology sector is a fast moving environment. There are many innovations I nthe automation and efficiency spheres where human intervention is required less and processing speed is rapidly increasing. In the payments space this is evident as payments are processed faster each year with the vast majority of these transactions driven automatically. This has opened up a platform for fraudsters to operate on. The use of Machine Learning (ML) in fraud detection has grown in popularity. Two methods, logistic regression (LR) and support vector machines (SVMs), are used to identify fraud and are investigated in this thesis. LR is less complex as compared to SVMs, but SVMs have unique situations where it will outperform any other ML model [31]. Either method is assessed based on application conditions and measured based on a certain set of confusion matrix based metrics. The two methods are applied to a data set from a bank which participates in the automated payment environment. It was evident that the sample proportions selected had a major impact on the model performance especially with regards to sensitivity and specificity. This was an exercise of fraud identification where sensitivity is the most important. This may not be the case for all data sets and environments as the cost to investigate false positives may be higher than the actual cost of fraud prevented. Condition testing and post model application diagnostics were applied in this research. It was evident principle component analysis (PCA) feature selection was inferior to stepwise feature selection. The relatively poor performance of the PCA feature selection models is due to a loss of information when variables are removed when choosing the components. When considering the odds ratios for LR, there were several variables that were protective factors and others that were risk factors. These factors either increased or decreased the odds of a case being fraudulent. It was found that when a debit order (DO) was associated with an older person it was more likely to be fraudulent than when the DO was associated with a younger person. It was also found that if a DO had a value of R99 or R45 then the odds of the case being fraudulent would increase several-fold. LR models produced equivalent results to the more complex SVM models with a much better run time. From a practical point of view, this means that LR is preferred on larger data sets.
Carton and volume forecasting from picking lines
(Stellenbosch : Stellenbosch University, 2017-03) Samuels, Jason; Visagie, Stephan E.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : Supply chains consist of many stages and all these stages need to be managed. Being able to predict stock flow at any stage can be cost effective for the whole supply chain. In this thesis data from the Pepstores Ltd (PEP) distribution centre in Kuilsrivier, Cape Town are used to predict number of cartons and volume of stock that a hub in their supply chain owned by Pepkor logistics (PKL) will receive. These forecasts will help PKL to schedule delivery trucks and routes to stores with more accurate data and thus lower transportation costs. Simple linear regression (SLR) and multiple linear regression (MLR) are used to predict cartons and volume, but heteroscedasticity is obtained in the residuals. Different types of transformations on the SLR model are introduced and used on dependent and independent variables. A logarithmic weighted transformation could overcome these problems and is thus used along with polynomial regression to predict the number of cartons and volume of stock. The carton prediction model uses a polynomial regression model with order 2 and the volume prediction model uses a SLR model on the logarithmic weighted variables. Accuracy tests show that the models predict the number of cartons and volumes of stock well. A case study on actual data to forecast volume and cartons is presented. These predictions were then compared to the actual values and the forecast that was sent to the hub from the DC over a two week period. It is concluded that PEP can use these models within their systems, but coecients need to be reviewed periodically in order to take into account the different types of products.
A cellular automation model of Eldana saccharina Walker infestation in sugarcane to improve the spatio-temporal planning of sugarcane planting and harvesting
(Stellenbosch : Stellenbosch University, 2020-12) De Wet, Pieter; Potgieter, Linke; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : Farmers are being increasingly challenged to use management techniques that reduce the negative impacts of farming. One of the main areas where the environment is negatively impacted by farming practices is pest management when using chemical pesticides. The manipulation of harvesting schedules has long been recognised to impact pest populations in agricultural crops and plays an important role in establishing an integrated pest management (IPM) system. In this study, the impact of di erently con gured sugarcane agricultural landscapes in terms of crop age, and the resulting di erent harvesting times, on the infestation dynamics of Eldana saccharina Walker, were considered. The dynamics of Eldana saccharina Walker infestation in sugarcane were simulated using a cellular automaton approach. The main objective was to identify generic eld con gurations (in terms of crop age) where infestation levels are minimised, and subsequently sucrose yield was maximised. The results obtained indicate that larger groupings of same aged crops tend to provide higher sucrose yields, compared to con gurations where many same aged small elds were scattered across the landscape. It was also determined that harvesting spread over the entire harvesting season with various aged crops tended to outperform scenarios with bulk harvesting of crops only at certain times during the harvesting season. In addition, an earlier harvesting age was found to be better, indicating that if possible, sugarcane should not be carried over during the period when sugarcane mills are closed.
Choosing optimal reverse channel structures for the collection of used products
(Stellenbosch : Stellenbosch University, 2017-03) Hofmann, Flora; Visagie, S. E.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : The re-manufacturing of used products has become more important in literature and practice. Governmental legislation forces manufacturers to take care of their end-of-life products. Additionally, re-manufacturing may increase a companies' revenue through direct savings in production costs by the recovery of valuable material. With these external and internal developments, there is a growing interest of manufacturers in determining an optimal channel for the collection of used products. The overall objective of this optimisation lies in the maximisation of the companies' profit. Therefore, the problem of increasing waste streams of end-of-life products need to be addressed by identifying the most protable reverse channel structure to collect and re-manufacture used products. Three different collection channel options are modelled as decentralised decision-making systems. Therefore, a game theory approach is applied. The first channel is the manufacturer carrying out the collection. The retailer making use of the retail store network to collect from customers and sell back to the manufacturer describes the second channel. A third-party logistics service provider acts as a third channel for collecting and selling returns. The thesis focuses on the detailed cost of collection that each potential collecting agent accommodates. A non-cooperative game between the three collecting agents is modelled first, followed by the extension to a cooperative game. The cooperation can be caused by external in influences like legislative regulations or by a change in perspective. The stability of both versions of the game is evaluated by changing single parameters. Additionally, by changing the market scenario, the influence of the market environment on the channel choice is investigated in particular. The benchmark scenario of the non-cooperative and cooperative version of the game is stable in its parameters. In general, changes in single parameters influence the level of the highest payoff achievable by each player. In the non-cooperative version of the game the manufacturer gains the highest payoffs followed by the retailer, as both benet from the sales of new products. If the market scenario is changed, this ranking only shifts with a change in the market area size. Therefore, the retailer obtains a prot higher than the manufacturer. The third-party is able to work with different clients, turning the collection of returns into a successful business. The results of the cooperative version of the game are consistent with the observations in the non-cooperative game. Forming the grand coalition is the best option to obtain the highest payoffs if collection rate fees are imposed externally. With a change of perception to the manufacturer, the same customer density identifies the retailer as an optimal collection channel. However, subcontracting the third-party obtains the highest payoff in the benchmark scenario as well as in the larger market areas. In conclusion, a cooperation between different options should be taken into account while designing optimal reverse channel structures for every scenario. Additionally, the point of view is crucial in choosing the partner to obtain the highest payoff.

Browse

Browsing Department of Logistics by browse.metadata.type "Thesis"

Results Per Page

Sort Options