Parallelizing Tabu Search on a Cluster of HeterogeneousWorkstations

In this paper, we present the parallelization of tabu search on a network of workstations using PVM. Two parallelization strategies are integrated: functional decomposition strategy and multi-search threads strategy. In addition, domain decomposition strategy is implemented probabilistically. The performance of each strategy is observed and analyzed. The goal of parallelization is to speedup the search in finding better quality solutions. Observations support that both parallelization strategies are beneficial, with functional decomposition producing slightly better results. Experiments were conducted for the VLSI cell placement, an NP-hard problem, and the objective was to achieve the best possible solution in terms of interconnection length, timing performance (circuit speed), and area. The multiobjective nature of this problem is addressed using a fuzzy goal-based cost computation. Key Words: tabu search, parallel tabu search, metaheuristic, functional decomposition, multi-search threads, combinatorial optimization, VLSI, standard cell design, placement, fuzzy logi

Parallelizing Tabu Search on a Cluster of HeterogeneousWorkstations

In this paper, we present the parallelization of tabu search on a network of workstations using PVM. Two parallelization strategies are integrated: functional decomposition strategy and multi-search threads strategy. In addition, domain decomposition strategy is implemented probabilistically. The performance of each strategy is observed and analyzed. The goal of parallelization is to speedup the search in finding better quality solutions. Observations support that both parallelization strategies are beneficial, with functional decomposition producing slightly better results. Experiments were conducted for the VLSI cell placement, an NP-hard problem, and the objective was to achieve the best possible solution in terms of interconnection length, timing performance (circuit speed), and area. The multiobjective nature of this problem is addressed using a fuzzy goal-based cost computation. Key Words: tabu search, parallel tabu search, metaheuristic, functional decomposition, multi-search threads, combinatorial optimization, VLSI, standard cell design, placement, fuzzy logi

A survey of scheduling problems with setup times or costs

Author name used in this publication: C. T. NgAuthor name used in this publication: T. C. E. Cheng2007-2008 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Design of tool management systems for flexible manufacturing systems

The objective of this thesis is to study the design and analysis of tool management system in the automated manufacturing systems. The thesis is focused on two main areas, namely design and experiment. In the first part of the thesis, the design facility created has been reported. The model has been designed using a hybrid approach in which the power of both algorithmic and knowledge based approaches is utilised. Model permits detail, more accurate and complete solutions for the management of tools in a generic manufacturing system. In the second part of the thesis, to add more understanding to the tool management problems, the interactions of the major tool management design parameters have been investigated using a well known design technique, the Taguchi method. For this purpose, a large number of design experiments have been configured where some have been suggested by the Taguchi method and some have been created by the author to add more confidence, using a large body of real industrial data. The experiments results give deeper understanding of TMS problems and allow design guide-lines to be drawn for the designers. The design approach and the experiments have been proven to be an accurate and valid tool for the design of tool management systems for automated manufacturing systems. This is indicated in the conclusion of the thesis

Development of novel electrical power distribution system state estimation and meter placement algorithms suitable for parallel processing

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe increasing penetration of distributed generation, responsive loads and emerging smart metering technologies will continue the transformation of distribution systems from passive to active network conditions. In such active networks, State Estimation (SE) tools will be essential in order to enable extensive monitoring and enhanced control technologies. In future distribution management systems, the novel electrical power distribution system SE requires development in a scalable manner in order to accommodate small to massive size networks, be operable with limited real time measurements and a restricted time frame. Furthermore, a significant phase of new sensor deployment is inevitable to enable distribution system SE, since present-day distribution networks lack the required level of measurement and instrumentation. In the above context, the research presented in this thesis investigates five SE optimization solution methods with various case studies related to expected scenarios of future distribution networks to determine their suitability. Hachtel's Augmented Matrix method is proposed and developed as potential SE optimizer for distribution systems due to its potential performance characteristics with regard to accuracy and convergence. Differential Evolution Algorithm (DEA) and Overlapping Zone Approach (OZA) are investigated to achieve scalability of SE tools; followed by which the network division based OZA is proposed and developed. An OZA requiring additional measurements is also proposed to provide a feasible solution for voltage estimation at a reduced computation cost. Realising the requirement of additional measurements deployment to enable distribution system SE, the development of a novel meter placement algorithm that provides economical and feasible solutions is demonstrated. The algorithm is strongly focused on reducing the voltage estimation errors and is capable of reducing the error below desired threshold with limited measurements. The scalable SE solution and meter placement algorithm are applied on a multi-processor system in order to examine effective reduction of computation time. Significant improvement in computation time is observed in both cases by dividing the problem into smaller segments. However, it is important to note that enhanced network division reduces computation time further at the cost of accuracy of estimation. Different networks including both idealised (16, 77, 356 and 711 node UKGDS) and real (40 and 43 node EG) distribution network data are used as appropriate to the requirement of the applications throughout this thesis.‘High Performance Computing Technologies for Smart Distribution Network Operation' (HiPerDNO) project under Grant FP7 - 248135/2007-2013 (European Community's Seventh Framework Programme)

A practice based learning environment for engineering students: Acquiring competencies for working on advanced manufacturing engineering

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.In this thesis the author describes the design and operation of a learning environment aimed at imparting technical, technological and managerial knowledge, developing understanding of the underlying issues and enhancing team work skills for an advanced technology future. He offers an analysis of learning, education and training and compares group work with individual tasks, presents a major case study and illustrates the features which distinguish the approach from role play, simulation and experiential learning. When staff at Brunel University were faced with the problem of teaching Computer Integrated Manufacturing (CIM) to engineering students on thin sandwich type undergraduate degree programmes the writer suggested the use of an approach he would later describe as 'practice based learning' or 'real life simulation'. The fourth year course in CIM is designed as a double option for the complementary undergraduate courses, Brunel Manufacturing Engineering (BME) and Special Engineering Programmes (SEP). It is an extension of the Manufacturing Design and Practice course in years one to three of the BME course and of the Design strand on SEP, both of which restrict students' work to the use of individual machine tools and stand alone computing facilities. A wide range of teaching methods is used on the CIM course, including lectures by course staff, presentations by experts and, as the major element, a large group project involving all the students on the course, organised in a management matrix, coordinated by the students and supported by the staff acting as experts. The students also undertake assignment work alongside the technical tasks, to focus their thinking and to improve written communication skills. While the course described cannot replace more than a small proportion of the more conventional lecture, laboratory and tutorial teaching on an engineering programme, it provides a setting where students can experiment and learn about their own strengths and weaknesses in a realistic situation and in the context of teamwork. It also offers a space where they can make quite serious mistakes without direct consequences to their careers. The experience of seven years leads the author to believe that advanced manufacturing technologies and the associated management techniques should be taught in a project based environment with clear and real targets and realistic constraints, offering students challenges to which they can only rise through close and creative team work. The management of task execution must be left largely in the students' own hands. A high level of "consultant" type support is essential though, allied to an assessment scheme which promises and ensures fair treatment of the individual. The different parts of the thesis will be relevant to readers depending on their interest and background. Chapter 1 sets the scene and outlines the approach taken. Following this broad outline of the scope of the dissertation the author places Computer Integrated Manufacturing in a wider context in chapter 2, by providing an introduction to the underlying issues of computer integration and human factors. He puts forward a case for new approaches to the education and training of engineers and managers who will be working in Computer Integrated Manufacturing and Advanced Manufacturing Environments in general. Chapter 3 is devoted to the management of projects while chapter 4 is used to question the role of the engineer. Chapters 5 and 6 provide an introduction to theories of knowledge, teaching, learning and motivation. Chapters 7 and 8 are devoted to particular aspects of engineering education, while chapter 9 reviews the approach used at Brunel University. The topical issues of competence and its relevance to engineering education is discussed in chapter 10, leading into chapters 11 and 12 which deal with aspects of the CIM course. Chapters 13 and 14 are devoted to case-studies and particular tools. The key question of assessment of a practice oriented and team based course is addressed in chapter 15, followed by an evaluation of the CIM process and its application to engineering education of a full time nature which is included in chapters 17 and 18.Funding was obtained from The General Electric Company Prize 1993: Manufacturing Systems Engineering

Boundary-crossing learning in agricultural learning systems: formative interventions for water and seed provision in southern Africa

This research was conducted in the Amathole rural district of the Eastern Cape Province of South Africa, and in Zvishavane and Zhombe rural districts of the Midlands Province of Zimbabwe over a period of four years. In the first two years of this period I was involved in co-engaged boundary-crossing expansive learning processes with research participants from agricultural education (agricultural college lecturers, principals and university lecturers), extension services (extension officers, advisors and workers), small-scale farmers and a local economic development (LED) agency as agricultural learning activity systems. The latter was applicable only to the South African nested case while the rest applied to both country nested cases. The study focusses on the boundary-crossing learning of sustainable agricultural water relevant for small-scale farming contexts under rain-fed and climate constrained conditions with specific attention to rainwater harvesting and conservation and climate-adaptive seed. The study employed cultural-historical activity theory (CHAT) and developmental work research methodology developed by Yrjö Engeström and his colleagues at the Centre for Researching Activity Development and Learning (CRADLE) at the University of Helsinki in Finland. The study was guided by three objectives. The first objective was to find out how the different groups represented across the activity systems listed above learn together to mediate and communicate sustainable agricultural water and seed saving. To address this objective I conducted focus groups and interviews with key informants, made observations and analysed documents. The second objective was to explore and document the socio-ecological histories of rainwater harvesting and conservation, locally-adaptive seed systems and associated value chains, and socio-cultural histories of agricultural learning systems in the context of small-scale farming using historical and ethnographic research techniques. The third objective was to understand how learning, curriculum innovation and mediation tools for agricultural extension education and farmer training that can expand learning of rainwater harvesting and conservation sustainable practices for improved local agricultural water and climate-adaptive non-formal seed systems in agricultural education and small-scale farmer activity systems could be co-generated. This third objective constituted the boundary-crossing expansive learning that emerged from change laboratory workshops carefully designed to explore the common water for food object across the different but related activity systems. The study reveals historically-persisting tensions and contradictions in the work of agricultural college lecturers, small-scale farmers and extension workers that limit their ability to work together relationally leaving them operating in isolated ‘silos’. The industrially-driven agricultural college curriculum promoting conventional irrigated agriculture conflicted with the college’s objective of producing extension workers who will work with resource-poor small-scale farmers in rain-fed farming systems. This conflict was aggravated by the work of extension workers who had little to no knowledge regarding how to support small-scale farmers facing persistent drought and consequent crop failure due to poor and erratic rainfall. At the same time extension services promoting genetically modified (GMO) seed in South Africa were in conflict with some small-scale farmers’ demands for seed that was adapted to their changing climate and their ability to operate independently with access to and ownership of land. This study shows that the work of agricultural colleges and extension services often defeats its intended structural objectives due to historically-constituted power relations around knowledge. This study has demonstrated the effectiveness of co-generative formative interventions in boundary-crossing scenarios in learning network contexts for expansion of activity in farming communities, agricultural colleges and extension services, with emphasis of transformed activity towards engaging a collective object of rainwater harvesting and conservation for more sustainable agriculture and poverty alleviation. The study shows that diverse combinations of change practice courses, change laboratories, demonstration sites and media engagements as mediation processes in the context of learning networks strengthened the possibility for boundary-crossing expansive learning across activity systems of agricultural college lecturers, smallholder farmers, extension workers and local economic development agency facilitators. Three of the five mediation processes emerged out of the formative intervention processes in both the South African and Zimbabwean case studies while two were not realised in the Zimbabwean case study, namely the change practice course and media engagements, due to different formative intervention conditions, inadequate time and resources. Boundary-crossing was enabled by a variety of actions including understanding and identifying with the context of the other (i.e. developing empathy) as a result of change laboratory workshops that also ensured confrontation with relational contradictions. The study concludes that it is possible for historically-constituted contradictions around water for food to be resolved when participants from different agricultural learning systems co-engage as equals in boundary-crossing change laboratory fora mediated by appropriate tools and processes. The study contributes to innovation in agricultural learning systems in southern Africa, in particular to means of engaging across boundaries of previously largely disconnected activity systems in ways that benefit smallholder farmers who have previously been marginalised from mainstream agricultural learning systems