3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Scheduling in the South African construction industry(1989) Rudzinske, Paul EricThis research report investigates the use and sophistication of scheduling by the South African construction industry, by means of a postal survey and personal interviews. Furthermore, the construction industry's past and present use of scheduling is comparatively analyzed with that of selected overseas countries. A brief description of the various scheduling techniques is provided, together with the histories of these techniques. The primary conclusion of the research work was that the larger companies showed greater dedication to their scheduling, as well as implementing more advanced scheduling techniques. The emergence of cheaper computer systems showed definite impacts on the sophistication and effectiveness of scheduling, and indications of future impacts by computers were also found. The use of network-type scheduling techniques had also expanded, and further growth in the use of network-type schedules was indicated.Item Stochastic programs and their value over deterministic programs(1998) Corrigall, StuartReal-life decision-making problems can often be modelled by mathematical programs (or optimization models). It is common for there to be uncertainty about the parameters of such optimization models. Usually, this uncertainty is ignored and a simplified deterministic program is obtained. Stochastic programs take account of this uncertainty by including a probabilistic description of the uncertain parameters in the model. Stochastic programs are therefore more appropriate or valuable than deterministic programs in many situations, and this is emphasized throughout the dissertation. The dissertation contains a development of the theory of stochastic programming, and a number of illustrative examples are formulated and solved. As a real-life application, a stochastic model for the unit commitment problem facing Eskom (one of the world's largest producers of electricity) is formulated and solved, and the solution is compared with that of the current strategy employed by Eskom.Item General solution methods for mixed integer quadratic programming and derivative free mixed integer non-linear programming problems(2013-07-29) Newby, EricIn a number of situations the derivative of the objective function of an optimization problem is not available. This thesis presents a novel algorithm for solving mixed integer programs when this is the case. The algorithm is the first developed for problems of this type which uses a trust region methodology. Three implementations of the algorithm are developed and deterministic proofs of convergence to local minima are provided for two of the implementations. In the development of the algorithm several other contributions are made. The derivative free algorithm requires the solution of several mixed integer quadratic programming subproblems and novel methods for solving nonconvex instances of these problems are developed in this thesis. Additionally, it is shown that the current definitions of local minima for mixed integer programs are deficient and a rigorous approach to developing possible definitions is proposed. Using this approach we propose a new definition which improves on those currently used in the literature. Other components of this thesis are an overview of derivative based mixed integer non-linear programming, extensive reviews of mixed integer quadratic programming and deterministic derivative free optimization and extensive computational results illustrating the effectiveness of the contributions mentioned in the previous paragraphs.