Doctoral Degrees (Logistics)

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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.
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.
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.
Decision support for threat detection in maritime surveillance
(Stellenbosch : Stellenbosch University, 2014-12) Du Toit, Jacques; Van Vuuren, Jan Harm; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: The policing and monitoring of South Africa's coastline and economic exclusion zone is made di cult not only by the size of the area of interest, but also by the limited resources available for maritime detection and policing. As a consequence, illegal activities, such as smuggling, poaching and illegal border crossings, are often conducted with impunity. Conventional approaches to monitoring coastal areas, such as the use of patrol boats, port inspections and aircraft surveillance, may be augmented by advances in technology that are steadily contributing vast amounts of data related to maritime activity. For example, various South African agencies collect auto- matic identi cation system and vessel monitoring system transmissions, and gather additional kinematic data of maritime vessels through a number of strategically placed coastal radars. A command and control centre for actively monitoring these data (outside of the intelligence community) was established by the South African Navy in 2014. Such centres provide surveillance operators with a real-time picture of a maritime region of interest from which they can identify relevant facts of interest through a reliance on experience and domain knowledge. The e ectiveness of this process may, however, be undermined by the vast quantities of data typically under consideration, by the di culty of identifying long-term trends in vessel kinematic behaviour and by the possibility of operator fatigue brought on by the relatively low incidence levels of activities of interest. E ective decision support tools may play a valuable role in this context by the automatic processing of these vast collections of data, by the identi cation of concepts of interest and by the prediction of future occurrences of interest. It is, however, essential that such tools should be exible enough to adapt to changes in typical vessel behaviour over time and that they should be capable of integrating new trends and new types of behaviours. Various approaches to maritime surveillance are investigated in this dissertation from the perspectives of threat detection and anomaly identi cation, with particular emphasis on a systems approach to decision support. A decision support system framework that utilises rule-based and data-driven mechanisms is proposed as a means to separate the interesting from the uninteresting and to provide early warnings of potentially threatening maritime vessel behaviour to operators. This system framework is primarily concerned with kinematic data and is restricted to the identi cation of certain types of activities. Successful classi cation and, ultimately, timely prediction of potentially threatening behaviour would allow for e ective policing by providing early warning to relevant entities, thus potentially leading to more e ective use of available policing resources.
Design of a weapon assignment subsystem within a ground-based air defence environment
(Stellenbosch : Stellenbosch University, 2017-12) Lotter, Daniel Petrus; Van Vuuren, Jan Harm; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : A number of assets on the ground typically require protection from aerial threats in a military ground-based air defence environment. The problem of defending these assets is twofold: Incoming aircraft rst have to be identied and classied as friendly or hostile, and the level of threat posed to defended assets by each hostile aircraft has to be assessed, after which available ground-based weapon systems secondly have to be assigned to engage aerial threats with a view to scare them away or to neutralise them. The latter problem is known in the military operations research literature as the weapon assignment problem. A re control ocer is responsible for solving both these sub-problems in real time, usually under very stressful conditions. The officer therefore typically employs a computerised threat evaluation and weapon assignment decision support system to aid him in this task. An architecture is put forward in this dissertation for the weapon assignment part of such a decision support system. The proposed architecture contains two subsystems, namely an engagement quantisation subsystem and a weapon assignment subsystem. The purpose of the engagement quantisation subsystem is to quantify single shot hit probabilities achievable by weapon systems in conjunction with other information within the format required by the weapon assignment subsystem. The working of the various components of the engagement quantisation subsystem is illustrated by means of a series of small numerical examples. The weapon assignment subsystem forms the heart of the proposed architecture and a weapon assignment model classication is proposed for use in this subsystem. This classication consists of four classes of weapon assignment models ranging in different levels of complexity. The classes are single-objective static weapon assignment models, multi-objective static weapon assignment models, single-objective dynamic weapon assignment models and multi-objective dynamic weapon assignment models. A model prototype is proposed for default inclusion in each of the aforementioned weapon assignment model classes. The working of each of these models is illustrated by solving it in the context of a hypothetical, but realistic, ground-based air defence environment. A conventional genetic algorithm is used to solve the single-objective static weapon assignment model prototype, while an extension of this algorithm, a nondominated sorting genetic algorithm (specially designed for solving multi-objective optimisation problems) is used to solve the multi-objective static weapon assignment model prototype. The method of simulated annealing is used to solve the single-objective dynamic weapon assignment model prototype, while a variant of the aforementioned nondominated sorting genetic algorithm is used to solve the multi-objective dynamic weapon assignment model prototype. The results returned by the algorithms are discussed and validated by means of three methods, including a subjective face validation, a random benchmark validation and a validation consultation with two independent military experts. It is found that the results are plausible in terms of realism and practical executability. The models also outperform solutions put forward by the military experts when asked to solve the models by hand in the context of the same ground-based air defence scenario.
The design principles and success factors for the operation of cross dock facilities in grocery and retail supply chains
(Stellenbosch : Stellenbosch University, 2004-12) Vogt, John Joseph; Pienaar, W. J.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: The dissertation reflects the research done on the design principles and success factors for the operation of cross dock facilities in grocery and retail supply chains. The cross dock is a particular facility in the supply chain where goods are received from suppliers, sorted without storage of the goods, and then efficiently moved to downstream customers. Cross docks are not a new operation. However, the use in high volume grocery and retail operational capabilities is poorly understood and is not uniquely defined. The problem is that cross docks are often seen as extensions of warehouses. The same personnel, systems and processes are applied and the efficiency potential of the cross dock is not achieved. Warehouses are orientated towards storing the full range of product and allowing the pick to be done from this storage buffer to provide any or all of these products to a customer. Cross docks will only handle products that are used in larger quantities and that are sent to most, if not all, the customers. The cross dock is therefore distinct and very different from the traditional warehouse. The published research tends to focus on the technical aspects of the cross dock layout. This research is primarily in the scheduling of the trucks into the yard of the facility; the allocation of trucks to specific doors of the facility; and the allocation of doors to receiving and despatch functions within the facility. Very little information or research reflects the design principles and success factors for the cross dock and its supply chain. The only classification of the cross dock in the literature is whether the barcode is added to the item before or after receipt at the cross dock. For this research work a literature survey was conducted and five major operations were reviewed, in South Africa and the USA. The research empirically drew logical conclusions, which were tested in the operations and found to be correct. This allowed the design principles and success factors to be determined for a successful cross dock. The research extends the knowledge of the cross dock operation and design: - • A new classification for the feasible types of cross docks in the supply chain was developed. Three factors are shown to be of primary importance: - o Where in the supply chain the identification of specific items for a customer is done; o Where the sort is done for the items to be delivered to a customer; and o Whether the supplier is providing one product or multiple products to the sort. From these three factors, eight potential classifications could be defined. However, only three practical types of cross dock can be determined from these eight alternatives. These are named in this research as Cross Dock Managed Load (CML); Joint Managed Load (JML); and the Supplier Managed Load (SML). The cross dock is far more effective than the warehouse when the total work (excluding inventory) is considered. The earlier in the supply chain the product is identified for the use of the entire downstream supply chain, the more effective will be the total supply chain. Thus the greatest supply chain effectiveness possible is with the SML, then the JML and finally the CML. • The operation of a cross dock is very similar to a continuous manufacturing process. There is no buffer of stock to decouple the inbound and outbound processes, and the operation takes place in a restricted area. However, in the retail chain, the workload alters with different orders and different days. Daily load differences vary by as much as 90%. This results in vastly different workloads and variations of throughput. This is similar to a batch operation with highly variable workloads between batches. The literature recommends the use of Just in Time (JIT) practice for cross docks. This is inappropriate as its primary requirements are continuous full volume operation and continuous small improvements to achieve a balanced operation. The most appropriate method of process improvement is the Theory of Constraints (TO C) and not JlT. • The management must have a detailed, disciplined approach. This implies standardised methods of operation, and a high degree of training. Equally there is the requirement for a special type of personnel to operate the cross dock. These operating personnel must be able to operate with precision (i.e. very low error rates) and be able to maintain this capability for continuous periods. • The systems required for a successful operation must include the capabilities of Yard Management, WMS for cross docking, Order Management with Advanced Shipping Notice (ASN) capability and Track and Trace across the supply chain. The items need to be identified by a barcode. The information required on the barcode will be determined by. the information systems capability of the least advanced service provider in the supply chain. If this service provider can receive and transmit all the data required for the supply chain from and to the other members, then the barcode need only be an identification number of the specific item. The data pertaining to the items is then passed from system to system in the supply chain. If data movement is not possible between all the parties in the entire supply chain, then the barcode must contain the information that will identify the item, the origin and the final delivery destination. If the items are delivered as part of a consignment, a further quantum of information is required to identify the total number of items in the consignment and the specific item within the consignment. • The research shows that the overall capability of the cross dock or its maximum capacity is the combination of the capability of the personnel and the cross dock design. Restrictions on either the personnel capability or the design of the cross dock, or both, severely reduces the effectiveness of the cross dock. • The previous research on the sequence of allocation of trucks to specific doors within the cross dock can be enhanced with a new sequencing method. The new method allocates the transport, in sequence of arrival, to the open door that either numrruses the walk distance in the facility; or maximises the completion of the consignments in order to minimise the area required to build the consignments; or a combination of both. The choice of these will be determined by the constraints imposed by the design of the building. This is an important extension as this ties the supply chain into the cross dock operation, rather than looking at the cross dock in isolation as has been done in this previous research. • The factors that influence the design of a cross dock as to its size, shape, number of doors, and the specifically required additional areas, is defined in detail. The principles of these factors and their inter-relationships and dependencies are used in a detailed design for a cross dock. The detailed design process is set out from data analysis through to the actual size calculations and layouts. Measurements of walk distance and sort movement are used to determine the most effective design. The design is shown to be considerably more effective than the older designs. This work has significantly extended the research on the design principles and success factors for implementation of cross docks in retail supply chains. The research derives a unique new classification for cross docks. An improvement is made to existing research on the allocation of the transport to particular doors in the cross dock. The operation, management and personnel are shown to require specific characteristics. The information systems required for effective cross docks is determined and defined. The identification of the individual items by barcode and the information required within the barcode depending on the information sophistication of the service providers in the supply chain is defined. A detail process to design a cross dock is evolved, with the full knowledge of the factors that must be considered and their interrelationships. Measurements to determine the effectiveness of the design are used to choose the most appropriate design. All these are then synthesised into a new design, which is far more effective than any of the other designs researched. The design process will produce a very effective cross dock as has been demonstrated with a new facility.
Designing travel behaviour change interventions: a spatiotemporal perspective
(Stellenbosch : Stellenbosch University, 2017-12) Van Dijk, Justin Tycho; Krygsman, Stephan; Nel, Hannelie; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH SUMMARY : Against the background of unprecedented growth in private vehicle ownership and the entrenchment of the private car in everyday life, the past decades have seen a growing and ongoing academic and policy debate on how to encourage individuals to change to more sustainable ways of travelling; for instance, with voluntary travel behaviour change (VTBC) interventions. VTBC interventions aim to alter travel behaviour by providing information. In recent years, a large body of research has focused on the evaluation of the effectiveness of these programmes. However, no consensus has been reached on the question of whether a broad implementation of VTBC programmes is effective in stimulating people to use more sustainable ways of travelling. This dissertation argues that location-aware technologies, particularly GPSenabled smartphones, could potentially augment the research on VTBC interventions. Smartphones can not only source data (such as place and time of travel or activity) but can also provide individuals with real-time information, feedback, and suggestions for alternative behaviour or travel options.. However, between sourcing the data and relaying feedback to individual commuters, significant research is required on how to obtain, clean, and interpret the data, as well as on how to account for individual spatiotemporal accessibility. GPS data need to be collected and analysed systematically; especially in the context of evaluating the effectiveness of VTBC interventions in which effect sizes are known to be small and inconspicuous. As such, the translation of raw GPS trajectories into activity episodes and the best estimation of a travelled route are pivotal. Methods of activity recognition were explored with advanced machine learning algorithms, and two approaches for identifying travelled routes were proposed. Furthermore, it was demonstrated how spatiotemporal measurements could aid the design of VTBC interventions. Attention was drawn to the time-geographical concepts of activity spaces and potential path areas. Based on the examination of GPS tracks with different two-dimensional operationalisations of activity spaces, it was found that the density of opportunities within an activity space is related to the size of the activity space: larger activity spaces have lower densities of opportunities than smaller activity spaces. This may suggest that individuals who have a low opportunity density are less likely to respond to external stimuli and/or awareness programmes than individuals who have a high opportunity density. In turn, potential path areas were used to establish to what extent individuals have different spatiotemporal opportunities that will enable behavioural change in travel and activity. The findings indicate that location-aware technologies hold great potential to supplement transport geographical-research. Moreover, the results show that the incorporation of spatiotemporal measurements is crucial to consider for the design, implementation, and evaluation of VTBC interventions. The added value of seemingly new technologies, such as GPS, is that they can be easily integrated into a larger spatiotemporal framework of analysis. However, one has to be careful not to consider GPS as a panacea, because GPS data and technology also have some drawbacks. Careful consideration should go into application development, sample selection, site selection, and data imputation.
The development of an integrated supply chain competency model
(Stellenbosch : Stellenbosch University, 2015-12) Cilliers, Willem Wouter; Louw, Johannes Jacobus; Malan, Dirk Johannes; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: Supply chain management is an important contributor to business performance, both financially and in terms of customer service. This is proven by various research reports, ranging from industry research, such as the Gartner Top 25 Supply Chains, an annual study of the world’s top supply chains, to academic research which modelled the financial impact of superior supply chain capabilities. The focus of supply chain management was traditionally on the infrastructure, processes and technology. The people side of supply chain management was overlooked and under researched. A global shortage of talent resulting in an increased focus on human capital and the development of talent contributed towards the focus. A shift in human capital management towards a competency-based approach further contributed towards competency modelling as a key instrument for developing talent. This resulted in many organisations developing competency models. Previous research over 18 months across multiple organisations resulted in a best practice framework for competency modelling. This framework was also used to develop the competency model for the world’s biggest human capital industry association. The development of competency modelling in the supply chain is in its early stages of development. This is supported by limited research on the subject and various models being developed, but all from different perspectives and with different limitations if compared to the best practice framework for competency modelling. The first objective of the research was to develop an integrated supply chain competency model by integrating various models into a single model using the principles of model development. This model was then tested through two phases of Delphi research using two different teams of experts. Once confirmed, the competency model was further enhanced by developing a competency measurement instrument. The competency model was then applied in a multi-national supply chain company using the case-study research methodology. Testing the application of a competency model across multiple companies through survey research was not practical. A sample of job incumbents was selected, who completed an on-line competency assessment. The quality of questions was analysed through discriminative analysis and all poor quality questions were deleted. The balance of the questions was used to assess the level of competency of the job incumbents. A limited contribution towards existing knowledge on supply chain competency modelling was made. The conceptual model can be further tested empirically and the first version of the on-line assessment can be improved through further testing.
Distance-based road user charges as a road cost recovery method : a South African case study
(Stellenbosch : Stellenbosch University, 2024-03) van Rensburg, Johann Andre; Krygsman, S. C.; Booysen, M. J.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH SUMMARY: Transport infrastructure, especially relating to the road sector, is an important pillar to facilitate economic development and growth in any country. Roads, however, are subject to large capital outlays for new construction and upgrades, requiring timely maintenance to ensure transport links that are in a satisfactory condition to meet road user demand, improve accessibility and mobility, and reduce vehicle-operating cost. Despite the background of the infrastructure’s importance, the road sector is continuing to experience funding deficits, meaning that the current financing and funding methods (also known as road cost recovery methods) are unable to meet budgetary requirements. This study argues that distance-based road user charges, using Global Positioning System enabled vehicle tracking devices coupled with a short-run marginal social cost fare structure, could potentially augment the research on road cost recovery for an improved road funding framework given the characteristics of the South African road sector. This hypothesis was tested by assessing i) how the South African road-funding framework currently performs in terms of its ability to secure funding for the road sector. Secondly assessing ii) how it will perform in the future, followed by calculating iii) the correct charges to be levied for road use. Lastly, iv) the public acceptability of road cost recovery methods and v) the operational and economic viability of implementing a distance-based road user charge system in South Africa was assessed. The findings indicate that the South African road funding framework currently collects a large amount of revenue from road users annually, but this is less than what is invested in actual road infrastructure. Compared to select developed countries in terms of how much revenue South Africa collects and spends on road infrastructure as a percentage of Gross Domestic Product, it is definitely not below the norm. The fuel levy, however, although collecting the bulk of the revenue from road users, is becoming increasingly unproductive. It was found that technological and societal trends will have an incremental impact on the future revenue collected from road users in the short to medium term, without necessarily being disruptive. Calculations indicate that the average road user might already be paying more than their fair share of road cost per kilometre of travel and that deriving a short-run marginal social cost fare structure which represents fair and efficient road user charges, as required by the user-pay principle, is by no means an easy endeavour. A public opinion survey indicated that road users in general do not know the amount of costs they pay for using the road network and that they still favour the fuel levy as the main road cost recovery method to be used in South Africa. Simultaneously, they view distance-based road user charges as an acceptable supplementary option. Through a vehicle tracking study, it was determined that a distance-based road user charge system is operationally feasible and economically viable in South Africa and that if implemented with a short-run marginal social cost fare structure could lead to more equitable pricing while possibly increasing the road funding revenue base. It is advised that distance-based road user charges be considered to form part of the current road funding framework in South Africa as a supplementary road cost recovery method. Although there are many issues that should still be addressed, it is an avenue worth considering especially from an equity perspective.
A framework for sustainable road freight decarbonisation in South Africa
(Stellenbosch : Stellenbosch University, 2019-12) Terblanche, Lee-Anne; Havenga, Jan H.; Goedhals-Gerber, Leila Louise; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics. Logistics.
ENGLISH ABSTRACT: Local and international governments are becoming more aware of carbon emission outputs and the damage that these emissions are inflicting on the environment. The definite impact that carbon emissions have on global warming has received public and media attention, which has placed high carbon-intensive companies and products under surveillance. Following electricity, road freight in South Africa is the second-biggest generator of carbon emissions. Thus, this research problem identified the need to decrease South Africa’s road freight emissions through the use of a road freight decarbonisation framework. The research problem entailed applying a framework to South Africa and expanding the structure to include the unique challenges in the South African road freight industry. A mixed methods research design was conducted to include both qualitative and quantitative data for the road freight industry in South Africa. The first objective of the research was to establish which road freight decarbonisation strategy, framework, system or tool would suit South Africa that also provides a holistic approach to decarbonising road freight activities. A literature review and criteria analysis concluded that the McKinnon road freight decarbonisation framework would be best suited to adapt and expand within the South African context. The literature review was followed by qualitative and quantitative data gathering to establish how industry professionals perceived the McKinnon framework, and to determine what further inputs into the framework could be provided. The data gathering consisted of personal interviews with industry professionals and data questionnaires that were sent out to working professionals in the road freight industry. After South African challenges were established and added to the chosen framework, the South African challenges for road freight carbon emission were quantified, through data questionnaires, to determine what total impact these challenges have on total road freight emissions and to quantify the carbon variables on a national basis. The outcome of the research provided the first South African decarbonisation framework, which highlights the road freight challenges South African companies are facing daily. The study identifies what the current main road freight carbon-intensive challenges are in South Africa, so that South Africa can focus on these costly and highly intensive emission influences and be aware that the problems are not isolated events, but can affect all road freight companies in South Africa. Keywords: Road freight, decarbonisation, carbon emissions, challenges
'n Gerekenariseerde logistieke bedryfstelsel vir klein tot mediumgrootte sakeondernemings
(Stellenbosch : Stellenbosch University, 2004-04) Loubser, Jacobus Stephanus; Pienaar, W. J.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: The logistical approach of ERF (Enterprise Resource Planning) software has certain shortcomings with respect to application in small to medium sized enterprises (SMEs) in South Africa. During the course of this study these shortcomings are identified, effective solutions are suggested and a logistical ERF program is provided. This ERF program is aimed at SMEs where stock items are handled, produced and shipped. SMEs experience problems with ERF systems, such as a high total cost of ownership, high complexities and the nature of the systems' design. The cost of international ERF systems is usually determined by stronger international currencies, creating price fluctuations and placing it outside the reach of SMEs. These systems generally comprise of a series of complex functions, of which only a limited quantity applies to local enterprises and logistics. Several configuration steps have to be completed before the advanced logistical functions may be used. ERF systems do not necessarily focus on logistics, but are made up of a combination of finance and other modules. Futhermore, the layout and design of the systems are aimed at a high-level user, which prevent the entry-level user from completing the logistical function with ease. The developed ERF program can be obtained and implemented at a low cost due to the standard base program upon which it lives, as well as the simple nature of the screens and menus. The program provides a logistical focus, with a simple path to electronic logistical functions. The design and supporting material for configuration and execution of the program provide the opportunity to an entry-level user to make use of the program effectively. This decreases the cost of implementing and maintaining the system, thus reducing total cost of ownership.
Heuristics for offline rectangular packing problems
(Stellenbosch : University of Stellenbosch, 2010-03) Ortmann, Frank; Van Vuuren, J. H.; University of Stellenbosch. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: Packing problems are common in industry and there is a large body of literature on the subject. Two packing problems are considered in this dissertation: the strip packing problem and the bin packing problem. The aim in both problems is to pack a speci ed set of small items, the dimensions of which are all known prior to packing (hence giving rise to an o ine problem), into larger objects, called bins. The strip packing problem requires packing these items into a single bin, one dimension of which is unbounded (the bin is therefore referred to as a strip). In two dimensions the width of the strip is typically speci ed and the aim is to pack all the items into the strip, without overlapping, so that the resulting packing height is a minimum. The bin packing problem, on the other hand, is the problem of packing the items into a speci ed set of bins (all of whose dimensions are bounded) so that the wasted space remaining in the bins (which contain items) is a minimum. The bins may all have the same dimensions (in which case the problem is known as the single bin size bin packing problem), or may have di erent dimensions, in which case the problem is called the multiple bin size bin packing problem (MBSBPP). In two dimensions the wasted space is the sum total of areas of the bins (containing items) not covered by items. Many solution methodologies have been developed for above-mentioned problems, but the scope of the solution methodologies considered in this dissertation is restricted to heuristics. Packing heuristics follow a xed set of rules to pack items in such a manner as to nd good, feasible (but not necessarily optimal) solutions to the strip and bin packing problems within as short a time span as possible. Three types of heuristics are considered in this dissertation: (i) those that pack items into levels (the heights of which are determined by the heights of the tallest items in these levels) in such a manner that all items are packed along the bottom of the level, (ii) those that pack items into levels in such a manner that items may be packed anywhere between the horizontal boundaries that de ne the levels, and (iii) those heuristics that do not restrict the packing of items to levels. These three classes of heuristics are known as level algorithms, pseudolevel algorithms and plane algorithms, respectively. A computational approach is adopted in this dissertation in order to evaluate the performances of 218 new heuristics for the strip packing problem in relation to 34 known heuristics from the literature with respect to a set of 1 170 benchmark problem instances. It is found that the new level-packing heuristics do not yield signi cantly better solutions than the known heuristics, but several of the newly proposed pseudolevel heuristics do yield signi cantly better results than the best of the known pseudolevel heuristics in terms of both packing densities achieved and computation times expended. During the evaluation of the plane algorithms two classes of heuristics were identi ed for packing problems, namely sorting-dependent and sortingindependent algorithms. Two new sorting techniques are proposed for the sorting-independent algorithms and one of them yields the best-performing heuristic overall. A new heuristic approach for the MBSBPP is also proposed, which may be combined with level and pseudolevel algorithms for the strip packing problem in order to nd solutions to the problem very rapidly. The best-performing plane-packing heuristic is modi ed to pack items into the largest bins rst, followed by an attempted repacking of the items in those bins into smaller bins with the aim of further minimising wasted space. It is found that the resulting plane-packing algorithm yields the best results in terms of time and packing density, but that the solution di erences between pseudolevel algorithms are not as marked for the MBSBPP as for the strip packing problem.
The impact of transport accessibility and spatial equity on employment outcomes
(Stellenbosch : Stellenbosch University, 2024-03) Van der Merwe, Jacomina Magdalena; Krygsman, Stephan; Woolard, Ingrid, 1970-; Papps, Kerry; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH SUMMARY: Addressing unemployment and income inequalities in transport and land-use policies is important, particularly in South Africa, which is currently experiencing one of the highest unemployment rates and income inequality in the world. South Africa has also seen a rise in the number of discouraged job seekers, which accounted for 14% of the labour force in 2021. These are individuals who want to work but have become too discouraged to actively search for employment. The primary aim of this research is to understand how transport, measured by accessibility and general transport cost components, such as commuting cost and travel time, affects the labour market in South Africa. It highlights the horizontal and vertical spatial equity impacts and the differentiated impact on different income groups. Previous research has proven the impact of a spatial mismatch on the probability of an individual becoming employed and the link between transport accessibility and employment status, but it ignores its impact on an employee’s decision to remain in employment, as well as the decision to stop searching for a job. This research first highlights the unequal distribution of accessibility across space and different income groups in the City of Cape Town. Using unique tax administrative data together with TomTom road network and speeds data, the research shows that the impact of congestion has a greater effect on access to job opportunities for residents of low-income locations compared to those from high-income locations. This reinforces spatial inequality. The research further focuses on the notion of job seekers becoming discourage and the impact of transport cost on their decision not to search for employment. Third, the research provides evidence that longer commuting distances between an employee’s residence and work location reduce employment duration for lower-income employees. The converse it true for higher income individuals. This shows a positive relationship between commuting distance and employment duration. The differentiated impact that transport has on the labour market for different income groups can be incorporated in transport and land-use policy and planning that aim to improve employment and equity outcomes. Last, the impact of land-use policy on accessibility is investigated in a case study, should affordable housing be provided closer to the two main employment hubs in the City of Cape Town. This could address vertical spatial equity, as measured by accessibility to employment in the city.
Investigating marine cargo insurance claims for signs of climate change through the South African fresh fruit export supply chain
(Stellenbosch : Stellenbosch University, 2024-03) du Plessis, Francois; Goedhals-Gerber, Leila Louise; Van Eeden, Joubert; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH SUMMARY: This dissertation comprises four research articles that collectively explore the intersection of climate change events as a supply chain risk through investigating marine cargo insurance claims, specifically focusing on South Africa. The overarching aim is to gain insight into the impacts of climate-related perils on global supply chains and develop effective risk management strategies. The first article presents a systematic literature review and bibliometric analysis that identifies trends, gaps and limitations in published academic papers on climate change events and fresh fruit export supply chain risks. According to the study, there is insufficient peer-reviewed literature in this area, and a research agenda is proposed for future scientific contributions. The findings underscore the need for the comprehensive understanding and mitigation of risks associated with climate change events and their effect on supply chains. The second article examines the trends, differences and seasonality of weather-related marine cargo insurance claims in South Africa from 2013 to 2022. Through statistical and claims analysis, the research shows a significant increase in weather-related claims over the past decade, resulting in challenges and disruptions to the country’s supply chain network. The study also highlights the higher average values and seasonal patterns of weather-related claims compared to non-weather-related claims. Practical guidelines are provided for supply chain managers and insurers to manage weather-related risks effectively. The third article, based on feedback from a cohort of international participants, delves into understanding the perceptions of marine insurers about their organisation’s involvement in the Supply Chain Risk Management (SCRM) framework for climate change events. The research explores the influence of experience levels and World Bank country income classifications on insurers’ perceptions. The SCRM framework steps show significant variations, indicating different risk management practices within experience groups. Higher country income levels correlate with greater awareness and management of climate change risks. The study emphasises the need for comprehensive involvement in all steps of the SCRM framework to build resilient supply chains. The final article focuses on the interplay between climate change events, South African fruit exports and food safety, providing a comprehensive analysis of fruit damage claims. With the global temperatures witnessing a significant 1.1 °C surge since the pre-industrial times, scrutiny of the vulnerabilities of South Africa’s fruit export sector has increased. This industry contributes over $3 billion to the economy every year. By examining fruit damage claims from 2013 to 2022, the article illuminates distinct categories of claims, highlighting variations driven by elements such as weather patterns. Notably, the research identifies seasonal trends vital for risk mitigation planning. Both Seasonal Autoregressive Integrated Moving Average (SARIMA) and regression analytic models are employed to anticipate future claims. The conclusions drawn highlight the pressing need for tailormade policies, reinforced resilience tactics in maritime supply routes, thorough analysis of different fruit-type vulnerabilities, enriched data gathering, and fortified partnerships with key players. This strategic alignment is crucial to offset potential future damages and to safeguard the prosperity of South Africa’s fruit export sector amid mounting climate adversities. Overall, this dissertation contributes to the growing knowledge of climate change as a supply chain risk. It highlights the urgent need for comprehensive risk management practices and proactive measures to address the increasing frequency and severity of weather-related hazards. The findings offer practical guidelines for supply chain managers, marine insurers and policymakers in mitigating the impacts of climate change on global supply chains, particularly in the context of South Africa. The research also identifies gaps for further investigation and provides a foundation for future scientific contributions in this important study area.
A mathematical model for the control of Eldana saccharina Walker using the sterile insect technique
(Stellenbosch : Stellenbosch University, 2013-12) Potgieter, Linke; Van Vuuren, J. H.; Conlong, D. E.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: Two mathematical models are formulated in this dissertation for the population growth of an Eldana saccharina Walker infestation of sugarcane under the influence of partially sterile released insects. The first model describes the population growth of and interaction between normal and sterile E. saccharina moths in a temporally variable, but spatially homogeneous environment. The model consists of a deterministic system of difference equations subject to strictly positive initial data. The primary objective of this model is to determine suitable parameters in terms of which the above population growth and interaction may be quantified and according to which E. saccharina infestation levels and the associated sugarcane damage may be measured. The second model describes this growth and interaction under the influence of partially sterile insects which are released in a temporally variable and spatially heterogeneous environment. The model consists of a discretized reaction-diffusion system with variable diffusion coefficients, subject to strictly positive initial data and zero-flux Neumann boundary conditions on a bounded spatial domain. The primary objectives in this case are to establish a model which may be used within an area-wide integrated pest management programme for E. saccharina in order to investigate the efficiency of different sterile moth release strategies in various scenarios without having to conduct formal field experiments, and to present guidelines by which release ratios, frequencies and distributions may be estimated that are expected to lead to suppression of the pest. In addition to the mathematical models formulated, two practical applications of the models are described. The first application is the development of a user-friendly simulation tool for simulating E. saccharina infestation under the influence of sterile insect releases over differently shaped spatial domains. This tool provides the reader with a deeper understanding as to what is involved in applying mathematical models, such as the two described in this dissertation, to real-life scenarios. In the second application, an optimal diversification of sugarcane habitats is considered as an option for minimising average E. saccharina infestation levels, and as a further consequence, improving the cost-efficiency of sterile insect releases. Although many special cases of the above model classes have been used to model the sterile insect technique in the past, few of these models describe the technique for Lepidopteran species with more than one life stage and where F1-sterility is relevant. In addition, none of these models consider the technique when fully sterile females and partially sterile males are being released. The models formulated in this dissertation are also the first to describe the technique applied specifically to E. saccharina, and to consider the economic viability of applying the technique to this species. Furthermore, very few examples exist of such models which go beyond a theoretical description and analysis towards practical, real-life applications as illustrated in this dissertation.
The measurement of supply chain efficiency : theoretical considerations and practical criteria
(Stellenbosch : University of Stellenbosch, 2010-03) Goedhals-Gerber, Leila Louise; Pienaar, W. J.; University of Stellenbosch. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH SUMMARY: In an effort to compete globally, South African supply chains must achieve and maintain a competitive advantage. One way of achieving this is by ensuring that South African supply chains are as efficient as possible. Consequently, steps must be taken to evaluate the efficiency levels of South African supply chains. This dissertation develops the composite supply chain efficiency model using variables specifically identified as problem areas experienced by South African supply chains. The composite supply chain efficiency model evaluates the overall efficiency of a supply chain based on three criteria, namely, reliability efficiency, cost efficiency and speed efficiency. It identifies bottlenecks along the supply chain and in so doing identifies key focus areas for firms if they want to improve their overall efficiency and become more competitive. 3
A model for the sustainability of local suppliers in the South African automotive value chain
(Stellenbosch : Stellenbosch University, 2011-12) Nitschke, Christian; Havenga, Jan; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
What factors influence the economic sustainability of local suppliers in emerging markets in the automotive value chain? The answer to this question is not only influenced by the direct and indirect customers of the automotive component suppliers, but it is also influenced by factors on the macro-, meso- and micro-levels of the supplier‟s environment. In order to investigate the research objective, the South African automotive industry is chosen as a case study in the global automotive value chain. The literature review indicates that variables that influence the economic sustainability of suppliers can be found on the global and regional levels of the automotive industry, as well as on the industry and corporate value chain levels. As the theory does not offer a holistic approach for a problem solution, the identified factors are assembled in a conceptual model that measures the economic sustainability of automotive component suppliers with respect to financial dimensions. The conceptual model is structured according to the macro-, meso- and micro-level influences, and also recognises the impact of governance structures on the government, market, industry and corporate levels. The suggested conceptual model is subsequently tested for totality and alignment with industry features using qualitative methods and is furthermore validated by using quantitative modelling data from primary research in the supplier component industry. The analysis of the quantitative data shows that the majority of factors influencing the economic sustainability of local component suppliers can be found on the micro- and meso-levels (corporate value chain and industry value chain), whereas the qualitative data implies that economic sustainability is mainly influenced by factors on the macro- and meso-levels (industrial policy and labour market). This finding shows that there is a discrepancy between the measurable influences and the automotive component suppliers‟ perception of the research problem. Nevertheless, it can be stated that the conceptual model, as supported by the stakeholder group, can be used for further research. Alongside the development of the conceptual model, the industry data is used for a discussion about the status of the South African automotive component supplier industry in order to point out strengths and issues as well as to identify factors that should change or improve to enable a viable future for suppliers.
A model to forecast the impact of road accessibility on the economic development potential of industrial land in urban areas
(Stellenbosch : Stellenbosch University, 2003) Botes, Francois Jacobus; Pienaar, W. J.; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics.
ENGLISH ABSTRACT: The dissertation firstly outlines the findings of recent studies that have recorded the relationship between transport and economic development. This includes the assessment of a number of economic evaluation techniques that are available to predict the impact of improvements in transport on economic development. An historic overview is provided of the role that transport has played in the development of Cape Town. Due to the fact that the phases of development followed international development trends, it is concluded that development in Cape Town will follow the global trend. A number of economic growth scenarios are developed for Cape Town to assess how the City will be able to cope with the socio-demographic challenges facing it in the next century. The relationship between land price and the economic development potential of land is outlined, as are the factors that determine industrial land price, namely the demand and supply of industrial land. The process of determining the economic value of industrial land is described. This includes the collection and analysis of occupation rent of industrial townships in Cape Town, the calculation of property values and the calculation of the shadow price of land. A procedure of determining accessibility to industrial townships in Cape Town was developed. Firstly, accessibility was defined in broad terms. This was followed by a discussion of each of the elements of accessibility namely proximity, access and mobility in order to understand the factors that may impact on the level of accessibility. Finally, the level of accessibility is quantified in terms of generalised cost. A regression analysis was undertaken to establish a statistical relationship between the economic value of industrial land and accessibility to the industrial townships. The development of a numerical model was based on the regression analyses to forecast changes in industrial land price given a change in accessibility. The model was then tested on a case study. The main conclusions of the study are as follows: (a) The accessibility of industrial land in Cape Town is linked closely to its CSD I Port (it was not possible to separate the CSD and the port), which is typical of a monocentric city structure. (b) There is a positive, significant, quantifiable relationship between accessibility as quantified by means of generalised cost and the economic value of industrial land, which was calculated by means of the shadow price technique. (c) There are a number of conditions that should be met for an increase in local industrial production potential to be translated into an equal amount of economic output.
A multi-objective approach towards geospatial facility location
(Stellenbosch : Stellenbosch University, 2016-03) Heyns, Andries M.; Van Vuuren, Jan; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Logistics
ENGLISH ABSTRACT: Applications of the sub-discipline of location science within the larger discipline of operations research include the location of important facilities, such as hospitals, re stations, libraries and depots. Existing facility location resolution techniques are generally based on commercial and transportation modelling criteria with little or no consideration given to the characteristics and in uence of surrounding terrain. Recent technological advances have, however, resulted in a sub- eld of location science rapidly increasing in popularity | the eld of geospatial facility location. Geospatial facility location science places a strong emphasis on terrain and environmental factors in the search for suitable sites for facilities with complex location requirements. Examples of such facilities include radars, telecommunication towers, watchtowers and wind turbines. The applications in which geospatial facility location solution approaches are relevant generally include only one type of facility. As a result, problem-speci c solution approaches tailored to the speci c facility type considered are usually adopted. On closer inspection, however, the solution approaches followed for these facility location problems reveal striking similarities which may be exploited in a generic manner in order to provide more e cient solution tradeo alternatives. By removing the problem-speci c approach to facility location modelling and the design of the associated solution techniques, there is an opportunity to develop a generic, dynamically implementable geospatial facility location framework which may be applied to identify facility location trade-o alternatives in various applications. Moreover, networks of multiple facility types may be considered in such a framework | something that is a rarity in the current geospatial facility location literature. In view of the continual advancement of technology, a generic geospatial facility location framework may even prove to be applicable to future facility location problems in which the placement criteria are currently unknown. The design of a generic geospatial facility location framework is therefore pursued in this dissertation. A dynamic mathematical foundation, which eliminates facility-specific solution methodologies, is established. A computerised concept demonstrator based on this framework is implemented within a generic solution paradigm. This concept demonstrator accommodates as special cases a variety of popular facility location problems from the literature. The geospatial facility location framework is demonstrated to be a dynamic and useful tool for solving complex facility location problems that have not previously been encountered due to the limitations of problem-specific solution search designs.

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