Diese Arbeit befasst sich mit der Entwicklung einer Applikation, welche Infrastrukturdaten über Eisenbahnnetze generiert. Dabei bildet die Erzeugung der topologischen Informationen den Schwerpunkt dieser Arbeit. Der Anwender charakterisiert hierfür vorab das gewünschte Eisenbahnnetz, wobei die geforderten Eigenschaften die Randbedingungen darstellen, die bei der Synthese zu beachten sind. Zur Einhaltung dieser Bedingungen wird die Constraint-Programmierung eingesetzt, welche durch ihr spezielles Programmierparadigma konsistente Lösungen effizient erzeugt. Dies wird u.a. durch die Nachnutzung so genannter globaler Constraints erreicht. Aus diesem Grund wird insbesondere auf den Einsatz der Constraint-Programmierung bei der Modellierung und Implementierung der Applikation eingegangen. / This work deals with the development of an application, which generates infrastructure data of railway networks. The focus of this work concentrates on the generation process of topological information. As input for the application a characterization of the intended railway network is given as attributes, which are handled as constraints in the generation process. To satisfy these restrictions constraint programming, a special programming paradigm, which is able to search efficently consistent solutions, is applied. In particular, the use of so-called global constraints improves the computation. For that reason the role of constraint-programming in modelling and implementing these application is discussed in more detail.

Konkurrensen i tillverkningsföretag ökar ständigt och detta medför att det ställs hårda krav på produktkvalitet och förmågan att leverera produkter i tid. För att företag ska kunna nå upp till dessa mål krävs utveckling och ständiga förbättringar i takt med den växande marknaden. Detta uppnås på olika sätt men ett vanligt sätt är att arbeta med förbättringsmetodiker. Val av förbättringsmetodik beror på företagets tillverkning, kunskap inom företaget och resurser inom företaget. Att välja förbättringsmetodik anpassat till den egna organisationen är väldigt svårt för många organisationer och många organisationer ställer sig frågan: ”Vilken metod passar bäst för den egna organisationen?”. Målet med examensarbetet är att undersöka om och hur Lean Production och Theory of Constraints kan användas i företag med high-mix low-volume produktion. Med hjälp av en litteraturstudie och en fallstudie har följande frågor besvarats: 1) hur Lean Prodution och Theory of Constraints används i en HMLV produktion och hur dessa kombineras, 2) hur produktionsflödet styrs enligt Lean Production och Theory of Constraints för att effektivisera en produktionsprocess i ett HMLV företag, 3) vilka personliga paradigm och policys det uppstår enligt Lean Production och Theory of Constraints i HMLV företag och vad sambandet mellan dessa och kvalitet är. Resultat från litteraturstudien och fallstudien visar att Lean Production och dess verktyg går bra att använda kombinerat med Theory of Constraints i HMLV företag med vissa undantag. Dessa undantag är dock inga undantag som säger att Lean Production och dess verktyg inte går att använda i HMLV företag i kombination med Theory of Constraints. Dessa undantag behöver endast anpassas för HMLV produktion. Resultaten visade också att standardiserat arbete i en produktion har en avgörande roll när Lean Production och Theory of Constraints används. Standardiserat arbete bidrar till att fortsatt utveckling och implementering underlättas. Resultaten visar även på att produktionsflödet kan anpassas med hjälp av metoder inom Lean Production och Theory of Constraints och att detta göras bäst när dessa två metodiker kombineras. Vidare visade resultaten att nya investeringar i form av ny utrustning inte är nödvändiga i många fall. Detta förutsätter att flaskhalsar, så som personliga paradigm och policys, identifieras. Resultaten visade även att kvaliteten är direkt kopplad till dessa två flaskhalsar och att en investering i ledarskap är att föredra. / Competition between manufacturing companies is constantly increasing and this causes high demands on product quality and ability to deliver products in time. For companies to be able to reach these goals it is necessary to work with development and continuous improvements and respond to the current pace of the market. This can be achieved in different ways, but a common method is to work with improvement methodologies. Selecting which improvement methodologies to use depends on a company’s manufacturing, knowledge, and resources. Many organisations find it difficult to choose improvement methodologies for their particular organisation and ask the question: “Which method is best suited for our organisation?”. The goal of this study is to examine whether and how Lean Production and Theory of Constraints can be utilized in companies with high-mix low-volume production. By performing a literature review and a case study the following questions have been answered: 1) how Lean production and Theory of constraints are utilized in a HMLV production system and how they can be combined, 2) how the production flow is controlled according to Lean Production and Theory of Constraints to improve the efficiency of a production process in a HMLV company, 3) what personal paradigms and policys arise according to Lean Production and Theory of Constraints in HMLV company and what the relationship between these and quality is. Results from the literature review and case study show that Lean Production and its tools are possible to use in a combination with Theory of Constraints in HMLV companies with some exceptions. However there is no exceptions saying that Lean Production and its tools combined with Theory of Constraints can not be utilized in HMLV companies. These exceptions only need to be adjusted for HMLV production. The results also showed that standardized work in a production process plays a crucial role when combining Lean production with Theory of Constraints. Standardized work contributes to facilitation of further development and implementation. The results show that the production flow can be adjusted using methods from Lean Production and Theory of Constraints, and that this is done best by combining these two methodologies. Furthermore, the results showed that in many cases new investments in the form of new equipment are not necessary. This assumes that bottlenecks, such as personal paradigms and policies are identified. The results showed that quality is directly linked to these two bottlenecks and that an investment in management is preferable.

Three methodologies are associated with production optimisation, namely, Theory of Constraints (TOC), Lean and Six Sigma – and each boasts with a number of success stories. This dissertation addresses the possibility of implementing all three these methodologies in a specific sequence at an organisation and also sets out to determine the impact of this implementation. A literature survey was conducted on all three stand-alone methodologies as well as on the combined methodology, which is called the Theory of Constrains Lean Six Sigma (TLS). TLS literature suggests that TOC should be implemented first with a view to identify the constraint in an organisation. Lean implementation should follow in order to eliminate any waste in the organisation. Lastly, Six Sigma should be implemented to optimise the process variability. TOC literature explains that The Goal of any organisation is to make money. All other objectives are only the means of achieving The Goal. The literature further indicates that the constraint in any organisation determines the drumbeat, and that this constraint should be managed by means of the Drum-Buffer-Rope methodology. Lean literature points towards 14 Management Principles by means of which an organisation should be managed in order to become a Lean organisation, while Six Sigma literature is concerned with the DMAIC (Define-Measure-Analyse-Improve-Control) methodology used for improvement projects and the belt system that is used to manage these improvement projects. Jonker Sailplanes, a sailplanes manufacturer in Potchefstroom, South Africa, was used as a case study for the implementation of TLS. A description is given of the processes and procedures that were followed before and after the implementation of TLS. The TLS methodology had to be adapted in order to meet the specific needs of Jonker Sailplanes into an adapted 14-step TLS implementation plan. After implementing TOC and Lean at Jonker Sailplanes, it was found that the organisation was not ready for the transition from Lean projects to Six Sigma projects. The implementation of Six Sigma was therefore referred for future research. One of the most significant findings of the current study was the very positive impact that the implementation of TLS had on the organisation: the production tempo (throughput) of the organisation has increased while the operating expenses per aircraft have decreased. This confirms that the profit per aircraft has increased. A critical evaluation of the implementation of the TLS methodology can therefore maintain that the implementation of TLS at Jonker Sailplanes was a success since the production tempo (throughput) and the organisational profit were increased and the implementation of the methodology was done with relative ease. In terms of interpreting results it was also necessary to set out how Jonker Sailplanes proceeded from a prototyping environment to a production setup, and how specifically identifying the constraint helped to achieve this transition. Furthermore, is it argued that when Lean is implemented before TOC, this could move the organisation away from The Goal, which is to make money. The interpretation of findings suggests that the procedure followed at Jonker Sailplanes was the most appropriate one. Finally, recommendations are made for future studies in terms of how to further improve the impact of the TLS implementation at Jonker Sailplanes. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2011.

Three methodologies are associated with production optimisation, namely, Theory of Constraints (TOC), Lean and Six Sigma – and each boasts with a number of success stories. This dissertation addresses the possibility of implementing all three these methodologies in a specific sequence at an organisation and also sets out to determine the impact of this implementation. A literature survey was conducted on all three stand-alone methodologies as well as on the combined methodology, which is called the Theory of Constrains Lean Six Sigma (TLS). TLS literature suggests that TOC should be implemented first with a view to identify the constraint in an organisation. Lean implementation should follow in order to eliminate any waste in the organisation. Lastly, Six Sigma should be implemented to optimise the process variability. TOC literature explains that The Goal of any organisation is to make money. All other objectives are only the means of achieving The Goal. The literature further indicates that the constraint in any organisation determines the drumbeat, and that this constraint should be managed by means of the Drum-Buffer-Rope methodology. Lean literature points towards 14 Management Principles by means of which an organisation should be managed in order to become a Lean organisation, while Six Sigma literature is concerned with the DMAIC (Define-Measure-Analyse-Improve-Control) methodology used for improvement projects and the belt system that is used to manage these improvement projects. Jonker Sailplanes, a sailplanes manufacturer in Potchefstroom, South Africa, was used as a case study for the implementation of TLS. A description is given of the processes and procedures that were followed before and after the implementation of TLS. The TLS methodology had to be adapted in order to meet the specific needs of Jonker Sailplanes into an adapted 14-step TLS implementation plan. After implementing TOC and Lean at Jonker Sailplanes, it was found that the organisation was not ready for the transition from Lean projects to Six Sigma projects. The implementation of Six Sigma was therefore referred for future research. One of the most significant findings of the current study was the very positive impact that the implementation of TLS had on the organisation: the production tempo (throughput) of the organisation has increased while the operating expenses per aircraft have decreased. This confirms that the profit per aircraft has increased. A critical evaluation of the implementation of the TLS methodology can therefore maintain that the implementation of TLS at Jonker Sailplanes was a success since the production tempo (throughput) and the organisational profit were increased and the implementation of the methodology was done with relative ease. In terms of interpreting results it was also necessary to set out how Jonker Sailplanes proceeded from a prototyping environment to a production setup, and how specifically identifying the constraint helped to achieve this transition. Furthermore, is it argued that when Lean is implemented before TOC, this could move the organisation away from The Goal, which is to make money. The interpretation of findings suggests that the procedure followed at Jonker Sailplanes was the most appropriate one. Finally, recommendations are made for future studies in terms of how to further improve the impact of the TLS implementation at Jonker Sailplanes. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2011.

When designing controllers with robust performance and stabilization requirements, H-infinity synthesis is a common tool to use. These controllers are often obtained by solving mathematical optimization problems. The controllers that result from these algorithms are typically of very high order, which complicates implementation. Low order controllers are usually desired, since they are considered more reliable than high order controllers. However, if a constraint on the maximum order of the controller is set that is lower than the order of the so-called augmented system, the optimization problem becomes nonconvex and it is relatively difficult to solve. This is true even when the order of the augmented system is low. In this thesis, optimization methods for solving these problems are considered. In contrast to other methods in the literature, the approach used in this thesis is based on formulating the constraint on the maximum order of the controller as a rational function in an equality constraint. Three methods are then suggested for solving this smooth nonconvex optimization problem. The first two methods use the fact that the rational function is nonnegative. The problem is then reformulated as an optimization problem where the rational function is to be minimized over a convex set defined by linear matrix inequalities (LMIs). This problem is then solved using two different interior point methods. In the third method the problem is solved by using a partially augmented Lagrangian formulation where the equality constraint is relaxed and incorporated into the objective function, but where the LMIs are kept as constraints. Again, the feasible set is convex and the objective function is nonconvex. The proposed methods are evaluated and compared with two well-known methods from the literature. The results indicate that the first two suggested methods perform well especially when the number of states in the augmented system is less than 10 and 20, respectively. The third method has comparable performance with two methods from literature when the number of states in the augmented system is less than 25.

Logic-based Benders decomposition (LBBD) is a strategy for solving discrete optimisation problems. In LBBD, the optimisation problem is divided into a master problem and a subproblem and each part is solved separately. LBBD methods that combine mixed-integer programming and constraint programming have been successfully applied to solve large-scale scheduling and resource allocation problems. Such combinations typically solve an assignment-type master problem and a scheduling-type subproblem. However, a challenge with LBBD methods that have feasibility subproblems are that they do not provide a feasible solution until an optimal solution is found.  In this thesis, we show that feasible solutions can be obtained by finding and combining feasible parts of an infeasible master problem assignment. We use these insights to develop an acceleration technique for LBBD that solves a series of subproblems, according to algorithms for constructing a maximal feasible subset of constraints (MaFS). Using a multiprocessor scheduling problem as a benchmark, we study the computational impact from using this technique. We evaluate three variants of LBBD schemes. The first uses MaFS, the second uses irreducible subset of constraints (IIS) and the third combines MaFS with IIS. Computational tests were performed on an instance set of multiprocessor scheduling problems. In total, 83 instances were tested, and their number of tasks varied between 2794 and 10,661. The results showed that when applying our acceleration technique in the decomposition scheme, the pessimistic bounds were strong, but the convergence was slow. The decomposition scheme combining our acceleration technique with the acceleration technique using IIS showed potential to accelerate the method.

<p>Formal methods such as Event-B are a widely used approach for developing critical systems. This thesis demonstrates that creating models and proving the consistency of the models at the requirements level during software (system) development is an effective way to reduce the occurrence of faults and errors in a practical application. An insulin infusion pump (IIP) is a complicated and time critical system. This thesis uses Event-B to specify models for an IIP, based on a draft requirements document developed by the US Food and Drug Administration (FDA). Consequently it demonstrates Event-B can be used effectively to detect the missing properties, the missing quantities, the faults and the errors at the requirements level of a system development. The IIP is an active and reactive time control system. To achieve the goal of handling timing issues in the IIP system, we made extensions of an existing time pattern specified using Event-B to enrich the semantics of the Event-B language. We created several sets to model the activation times of different events and the union of these time sets defines a global time activation set. The tick of global time is specified as a progress tick event. All the actions in an event are triggered only when the global time in the time tick event matches the time specified in the event. Time is deleted from the corresponding time set, but not the corresponding global time set while the event is triggered. A time point is deleted from the global time set only when there are no pending actions for that time point. Through discharging proof obligations using Event-B, we achieved our goal of improving the requirements document.</p> / Master of Computer Science (MCS)

Yes / Assessment of children for school readiness is a crucial process that requires extensive effort to select the sequence of tests most appropriate for the particular case to be investigated. Indeed, the success of the assessment depends highly on the diversity, flexibility, and comprehensiveness of the tests available and the ability of the applied system to decide on the specific sequence of tests to be utilized for each child based on his/her skills which should be discovered dynam- ically as the assessment progresses. Given the huge search space for the test cases to be utilized in the assessment process, it is preferred to apply an optimization technique capable of finding an appropriate test case that better fits the skills of a given child. It was decided to use a genetic algorithm (GA)-based approach for the optimization process. Any other optimization technique could have been used and utilizing the GA is a personal decision to complement the framework developed for this paper. GAs have been widely and successfully used in various application domains. Fortunately, the results reported in this paper demonstrate the effective- ness of the utilized GA in handling the assessment process to decide on school readiness. Assessment of a person’s abilities and skills is an important task for organizations. Examples include evaluating a child’s readiness for school or determining an employee’s aptitude for a position. The assessment involves various parameters related to the test subject’s aptitude, such as motor skills, linguistic development, or deductive capabilities, among others. The assessment may be conducted by various bodies, such as public education systems, commercial testing companies, and recruiters. To facilitate the assessment process in a systematic way less influenced by the attitude of a specific domain expert, it is preferred to develop and employ web-based assessment systems which integrate the skills of professional domain experts. A recent innovation is an adaptive web-based stealth assessment that analyzes the subject’s skill and dynamically adapts the assessment tests accordingly. A web-based stealth assessment is used for evaluating school readiness of a child by having the child play a series of games comparing the child’s per- formance with a database of performance results for a population. The web-based stealth assessment includes a processor for processing the child’s performance data, for comparing the performance data with the performance results of the population, and for applying a GA to determine the most appropriate next test for the child.

The main contribution of this thesis is the implementation of manufacturing constraints in shape and topology optimization. Fabrication limitations related to the casting process are formulated as mathematical constraints and introduced in the optimization algorithm. In addition, based on the same theoretical and modelization tools, we propose a novel formulation for multi-phase optimization problems, which can be extended to the optimization of structures with functionally-graded properties. A key ingredient for the mathematical formulation of most problems throughout our work is the notion of the signed distance function to a domain. This work is divided into three parts. The rst part is bibliographical and contains the necessary background material for the understanding of the thesis' main core. It includes the rst two chapters. Chapter 1 provides a synopsis of shape and topology optimization methods and emphasizes the combination of shape sensitivity analysis and the level-set method for tracking a shape's boundary. In Chapter 2 we give a short description of the casting process, from which all our manufacturing constraints derive. We explain how industrial designers account for these limitations and propose a strategy to incorporate them in shape and topology optimization algorithms. The second part is about the mathematical formulation of manufacturing constraints. It starts with Chapter 3, where the control of thickness is discussed. Based on the signed distance function, we formulate three constraints to ensure a maximum and minimm feature size, as well as a minimal distance between structural members. Then, in Chapter 4, we propose ways to handle molding direction constraints and combine them with thickness constraints. Finally, a thermal constraint coming from the solidi cation of cast parts is treated in Chapter 5 using several thermal models. Multi-phase optimization is discussed in the third part. The general problem of shape and topology optimization using multiple phases is presented in detail in Chapter 6. A "smoothed-interface" approach, based again on the signed distance function, is proposed to avoid numerical di culties related to classical "sharp-interface" problems and a shape derivative is calculated. An extension of this novel formulation to general types of material properties' gradation is shown in the Appendix A.

Over the last three decades, the impact of dramatic change in the social, religious, political and economic environment has led to a rapid expansion in the number of women entering the paid labour force in Sri Lanka as elsewhere. However, their identities and workload continue to be defined around caring work, especially for children. Not surprisingly, employed mothers endeavour to balance these two central spheres of their life, family and work. This research focuses on the contradictions of mothers' work-life balance. It does so through an analysis of how successfully (or unsuccessfully) professional and managerial mothers in Sri Lanka combine motherhood with paid work, and how they understand this in terms of gendered identities and social norms. This example also allows an evaluation of western derived theories about mothers' decision making in the context of a developing, Asian country. Grounded theory was used to examine mothers' narratives about life in the family and at work, drawn from in-depth qualitative interviews, along with data from some representative secondary sources, in order to explore these questions. This thesis demonstrates that working women's mothering leads to the formation of a gendered identity which varies according to different socio-cultural and religious opportunities and constraints. Using the Bourdieu approach the research suggests how everyday life operates in terms of habitus, field and capital. However, these working mothers have low capacity to achieve a work-life balance and this may lead to complex social problems.