The Stochastic Diffusion Search (SDS) was developed as a solution to the best-fit search problem. Thus, as a special case it is capable of solving the transform invariant pattern recognition problem. SDS is efficient and, although inherently probabilistic, produces very reliable solutions in widely ranging search conditions. However, to date a systematic formal investigation of its properties has not been carried out. This thesis addresses this problem. The thesis reports results pertaining to the global convergence of SDS as well as characterising its time complexity. However, the main emphasis of the work, reports on the resource allocation aspect of the Stochastic Diffusion Search operations. The thesis introduces a novel model of the algorithm, generalising an Ehrenfest Urn Model from statistical physics. This approach makes it possible to obtain a thorough characterisation of the response of the algorithm in terms of the parameters describing the search conditions in case of a unique best-fit pattern in the search space. This model is further generalised in order to account for different search conditions: two solutions in the search space and search for a unique solution in a noisy search space. Also an approximate solution in the case of two alternative solutions is proposed and compared with predictions of the extended Ehrenfest Urn model. The analysis performed enabled a quantitative characterisation of the Stochastic Diffusion Search in terms of exploration and exploitation of the search space. It appeared that SDS is biased towards the latter mode of operation. This novel perspective on the Stochastic Diffusion Search lead to an investigation of extensions of the standard SDS, which would strike a different balance between these two modes of search space processing. Thus, two novel algorithms were derived from the standard Stochastic Diffusion Search, ‘context-free’ and ‘context-sensitive’ SDS, and their properties were analysed with respect to resource allocation. It appeared that they shared some of the desired features of their predecessor but also possessed some properties not present in the classic SDS. The theory developed in the thesis was illustrated throughout with carefully chosen simulations of a best-fit search for a string pattern, a simple but representative domain, enabling careful control of search conditions.

The thesis first addresses the typology of cutting problems and their relationship to the packing problems. These are categorized (Wascher et al (2005)) according to 5 basic kriteria into the so-called "refined problem types", which is the sufficiently detailed and practical segmentation of cutting problems. The thesis deals with a selected sample of some of the most interesting algorithms from the wide range of those used to solve the cutting problems. The Viswanathan-Bagchi algorithm for the exact solution of constrainted two-dimensional orthogonal Cutting stock probléme with gillotine cuts is briefly described. It enables to process a wide range of additional problem constraints. The body of the thesis concentrates on heuristic algorithms used to solve orthogonal Open dimension problems. The Best-fit algorithm according to Burke et al. (2004) is described in detail. The work introduces two modifications of this algorithm that helped improve the solution in 42 out of the 89 benchmark problems, while a worse solution was achieved only in 10 of them. Moreover, new and more effective data structures and procedures that enable to solve the testing exercise with approx 50 000 rectangles in just about 2,5 seconds have been introduced.

The telecommunication industry is dominating the world. Most recently there have been technological advancements made in mobile telecommunication. There are currently a few telecommunication organizations in South Africa. These organizations each have their own unique approach to service delivery. The strong competitive nature of the telecommunication industry is taking telecommunications in South Africa to greater heights. All these advancements necessitate the need for better security and controls of the telecommunications networks. RICA legislation was brought into effect to accomplish just this. The research focuses on the contingent use of systems development methodologies in the telecommunication industry in South Africa. The study determines how these telecommunication organizations choose a systems development methodology when developing systems. This study looks at how these organizations are currently implementing system development methodologies to keep up with the changes and competition within the industry. An interpretive approach was used to conduct the research. Four of the leading telecommunication organizations in South Africa were studied by using case studies. Each case study focused on a single telecommunication organization to gain in depth data regarding the use of systems development methodologies. The case studies were conducted by using structured interviews to gain data from multiple sources within the organizations. The data was analyzed using ATLAS.ti and a cross case analysis was done to answer the research questions. The results indicate that there is a contingent use of systems development methodologies within telecommunication organizations. The telecommunication organizations each use criteria to determine which systems development methodology to use. The results of the study indicate that there are different levels of contingency, and it examines how this is accomplished by each organization individually. Each of the organizations has a unique approach when selecting systems development methodologies. The systems development methodologies that are used by the telecommunication organizations are also tailored in some cases. / Thesis (M.Sc. (Computer Science))--North-West University, Potchefstroom Campus, 2011.

The telecommunication industry is dominating the world. Most recently there have been technological advancements made in mobile telecommunication. There are currently a few telecommunication organizations in South Africa. These organizations each have their own unique approach to service delivery. The strong competitive nature of the telecommunication industry is taking telecommunications in South Africa to greater heights. All these advancements necessitate the need for better security and controls of the telecommunications networks. RICA legislation was brought into effect to accomplish just this. The research focuses on the contingent use of systems development methodologies in the telecommunication industry in South Africa. The study determines how these telecommunication organizations choose a systems development methodology when developing systems. This study looks at how these organizations are currently implementing system development methodologies to keep up with the changes and competition within the industry. An interpretive approach was used to conduct the research. Four of the leading telecommunication organizations in South Africa were studied by using case studies. Each case study focused on a single telecommunication organization to gain in depth data regarding the use of systems development methodologies. The case studies were conducted by using structured interviews to gain data from multiple sources within the organizations. The data was analyzed using ATLAS.ti and a cross case analysis was done to answer the research questions. The results indicate that there is a contingent use of systems development methodologies within telecommunication organizations. The telecommunication organizations each use criteria to determine which systems development methodology to use. The results of the study indicate that there are different levels of contingency, and it examines how this is accomplished by each organization individually. Each of the organizations has a unique approach when selecting systems development methodologies. The systems development methodologies that are used by the telecommunication organizations are also tailored in some cases. / Thesis (M.Sc. (Computer Science))--North-West University, Potchefstroom Campus, 2011.

Although Wireless Sensor Networks (WSNs) have found a niche in numerous applications, they are constrained by numerous factors. One of these important factors is security in WSNs. There are various types of security attacks that WSNs are susceptible to. The focus of this study is centred on Sybil attacks, a denial of service attack. In this type of attack, rogue nodes impersonate valid nodes by falsely claiming to possess authentic identities, thereby rendering numerous core WSN operations ineffective. The diverse nature of existing solutions poses a difficult problem for system engineers wanting to employ a best fit countermeasure. This problem is the largely unanswered question posed to all system engineers and developers alike whose goal is to design/develop a secure WSN. Resolving this dilemma proves to be quite a fascinating task, since there are numerous factors to consider and more especially one cannot assume that every application is affected by all identified factors. A framework methodology presented in this study addresses the abovementioned challenges by evaluating countermeasure effectiveness based on theoretical and practical security factors. Furthermore, a process is outlined to determine the application’s engineering requirements and the framework also suggests what security components the system engineer ought to incorporate into the application, depending on the application’s risk profile. The framework then numerically aligns these considerations, ensuring an accurate and fairly unbiased best fit countermeasure selection. Although the framework concentrates on Sybil countermeasures, the methodology can be applied to other classes of countermeasures since it answers the question of how to objectively study and compare security mechanisms that are both diverse and intended for different application environments. The report documents the design and development of a comparative framework that can be used to evaluate countermeasures against Sybil attacks in wireless sensor networks based on various criteria that will be discussed in detail. This report looks briefly at the aims and description of the research. Following this, a literature survey on the body of knowledge concerning WSN security and a discussion on the proposed methodology of a specific design approach are given. Assumptions and a short list of factors that were considered are then described. Metrics, the taxonomy for WSN countermeasures, the framework and a formal model are developed. Risk analysis and the best fit methodology are also discussed. Finally, the results and recommendations are shown for the research, after which the document is concluded. / Dissertation (MEng)--University of Pretoria, 2011. / Electrical, Electronic and Computer Engineering / unrestricted

Retail work constitutes an estimated 10.5 per cent of the UK workforce (British Retail Consortium, 2011). The literature suggests homogeneity in the nature of HRM in the retail industry with low formal skills, pay and trade union density associated with this context (Skillsmart Retail, 2010; Department for Business Innovation and Skills, 2010). Furthermore, the downward pressure on the working conditions of employees is observed across front-line work in general and this, seemingly does not improve with competitive strategy (Kelliher and Perrett, 2001; Lloyd, 2005; Lloyd, Warhurst and Dutton, 2013). However, the service work literature reveals diversity at the workplace level in the performance of emotional labour (Bolton, 2000) and the different types of customer (Bolton and Houlihan, 2005). Yet there are gaps in the literature related to how the performance of emotional labour compares and contrasts across retail organisations through different management control mechanisms as well as how the employee-customer interaction may explain diversity at the workplace level. The thesis draws on a comparative case approach of four case study organisations in the retail industry each reflecting different market positions in clothing and electrical product markets. A total of 37 semi-structured interviews were conducted with managers and employees across the case study stores. In addition the methodology also included the analysis of the customer perspective which is traditionally missing in the work and employment relations literature (Korczynski, 2009) This included collecting data using eighteen customer shopping reports, a method based on qualitative diaries. The overall aim of the study was to compare and contrast management, employee and customer perspectives across different retail organisation contexts and explore how the nature of HR and the performance of emotional labour are framed and reframed by the dynamics and negotiations that take place between these three actors. The findings reveal homogeneity in the nature of HRM with no improvement in recruitment and selection, training, pay and collective employee involvement going up the quality chain in the retail industry. This confirms other studies in the service industry more generally (Kelliher and Perrett, 2001; Lloyd, 2005; Lloyd et al, 2013). However within this downward pressure on the nature of HRM there were elements of diversity in the management requirements for the performance of emotional labour and the conceptualisation of the customer which shaped the employee-customer interaction in much broader terms than Strategic HR theorists might have assumed. To understand diversity across the retail organisations it was necessary to analyse the nature of employee-customer interactions within the context of management performance strategies. This revealed that many of the nuances between the case study retailers related to the ways the customer shapes, and is shaped, by the performance of emotional labour. The thesis will argue for the continued relevance of the concept of triangular relations which has been recently criticised (Belanger and Edwards, 2013) because it recognises the three actors that shape the performance of emotional labour at the level of workplace relations.

This thesis explores and explains a method using discrete curvature as a feature to find regions of vertices that can be classified as being likely to indicate the presence of an underlying tumor on a kidney surface mesh. Vertices are tagged based on curvature type and mathematical morphology is used to form regions on the mesh. The size and location of the tumor is approximated by fitting a sphere to this region. The method is intended to be employed in noninvasive radiotherapy with a dynamic soft tissue model. It could also provide an alternative to volumetric methods used to segment tumors. A validation is made using the images from which the kidney mesh was constructed, the tumor is visible as a comparison to the method result. The dynamic kidney model is validated using the Hausdorff distance and it is explained how this can be computed in an effective way using bounding volume hierarchies. Both the tumor finding method and the dynamic model show promising results since they lie within the limit used by practitioners during therapy.

This bachelor’s thesis was written in the context of a joint research group, which developed a framework for finding and providing the best-fit web service for a user. The problem of the research group lays in testing their developed framework sufficiently. The framework can either be tested with test data produced by real web services which costs money or by generated test data based on a simulation of web service behavior. The second attempt has been developed within this scientific paper in the form of a test data generator. The generator simulates a web service request by defining internal services, whereas each service has an own internal graph which considers the structure of a service. A service can be atomic or can be compose of other services that are called in a specific manner (sequential, loop, conditional). The generation of the test data is done by randomly going through the services which result in variable response times, since the graph structure changes every time the system has been initialized. The implementation process displayed problems which have not been solved within the time frame. Those problems are displaying interesting challenges for the dynamical generation of random graphs. Those challenges should be targeted in further research.

Residence time distributions have become an important analytical tool in the analysis of many types of flow systems. Residence time distributions have proven to be effective for analysing trickle bed reactors, as it allows determination of parameters under operating conditions allowing no interference of these conditions. By studying the residence time distribution a great amount of information can be obtained and therefore used to determine a number of hydrodynamic parameters. Due to recent findings that prewetting has a tremendous effect on a number of hydrodynamic parameters such as holdup, wetting efficiency and pressure drop, it is therefore the aim of this study to investigate the effect of trickle flow morphology or prewetting on a trickle bed reactor. The residence time distribution is obtained whereby hydrodynamic parameters are determined and therefore the effect the flow morphology has on various hydrodynamic parameters is highlighted. A number of methods were used to determine these parameters, namely that of the best-fit method, whereby the PDE model was used, and the method of moments. Operating conditions included varying gas and liquid flow rates for porous and non-porous catalyst particles at atmospheric pressure. The different prewetting procedures used during this work included the following: <ul><li>Non-wetted </li> <li>Levec-wetted </li> <li>Super-wetted</li></ul> From this investigation the following conclusions were made: <li>Prewetting has a great effect on the hydrodynamic parameters of trickle bed reactors</li> <li>The differences in prewetting can be attributed to differing flow morphologies for the different prewetted beds i.e. the dominant flow morphology for a non-wetted bed is that of rivulets and for prewetted beds that of film flow</li> <li>It was also found that at low liquid flow rates the flow morphology in prewetted beds changes from film flow to a combination of rivulet and film flow</li> <li>The different flow morphologies for prewetted and non prewetted beds was confirmed by the residence time distributions and various parameters obtained there from</li> <li>At low liquid flow rates the flow morphology becomes a more predominant factor in creating the tailing effect present in residence time distribution for prewetted beds</li> <li>The tailing effect in residence time distributions is a result of both internal diffusion and liquid flow morphology, where the liquid flow morphology is the more dominant factor</li> <li>The use of residence time distributions to determine a number of hydrodynamic parameters proved to be very useful and accurate by means of different methods, i.e. method of moments and best-fit method</li> <li>Differences in the liquid holdup determined from the method of moments and the weighing method confirmed that different flow morphologies exist for different prewetted beds</li> <li>An increase in the dispersion coefficient with prewetting was observed indicating that the amount of micro mixing is different for the different prewetted beds</li> <li>Differences in residence times and high values for the dynamic holdup, for the porous packing, confirmed that the PDE model does not model well the porous packing response curves due to the lack of internal diffusion and internal holdup in this model</li> <li>The dynamic-static mass transfer showed that film flow, as in prewetted beds, results in slower mass transfer as opposed to rivulet flow and therefore it is concluded that prewetting results in different flow morphologies.</li></ul> Following this study it is recommended that a residence time distribution model be used or developed that incorporates the effects of internal diffusion and internal holdup as present in porous catalyst particles. In addition, it was found that very few correlations could accurately predict hydrodynamic parameters due to the absence of the effect of prewetting and therefore it is recommended that correlations be developed that incorporate the effect of prewetting. / Dissertation (MEng)--University of Pretoria, 2008. / Chemical Engineering / unrestricted

M. Ing. / The report presents and analyses allocation methods for assigning limited resources to project tasks. The report is partitioned into five chapters beginning with an introductory chapter. Chapter 1 summarises the problem and describes the process followed in addressing the problem. A literature chapter covers the literature for the development and analysis of the methods presented in the report. Chapter three presents the allocation methods and discusses the role of the methods in single and multi-project resource allocation. Two commercial methods (Hu’s Algorithm; and Coffman’s and Munt’s Algorithm) along with a recipe for implementation are discussed. It is followed by the introduction and formulation of two additional methods that base their resource allocation on critical and least slack chains (Least Slack and Least Slack Ancestors First methods). A final method, based on locating the best possible solution, is presented and formulated (Best Fit method). A case study is presented in chapter four which is applied to each of the formulated methods in chapter three. Key metrics are derived and necessary compassions among the methods are performed. Chapter 4 concludes with an analysis of the comparisons. Finally Chapter five presents a conclusion to the report summarising the results of chapters three and four. Future recommendations are also discussed with the main emphasis on a possible investigation of a hybrid method stemming from the application and analysis in chapter four.