Huang Hongyan. / "February 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (p. 134-142). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

A concept for the mathematical modeling of multiple repairable equipment and logistic systems (MREAL systems) is developed; These systems consist of multiple populations of repairable equipment, and their associated design, procurement, maintenance, and supply support. MREAL systems present management and design problems which parallel the·management and design of multiple, consumable item inventory systems. However, the MREAL system is more complex since it has a repair component. The MREAL system concept is described in a classification hierarchy which attempts to categorize the components of such systems. A specific mathematical model (MREAL1) is developed for a subset of these components. Included in MREAL1 are representations of the equipment reliability and maintainability design problem, the maintenance capacity problem, the retirement age problem, and the population size problem, for each of the multiple populations. MREAL1 models the steady state stochastic behavior of the equipment repair facilities using an approximation which is based upon the finite source, multiple server queuing system. System performance measures included in MREAL1 are: the expected MREAL total system life cycle cost (including a shortage cost penalty); the steady state expected number of shortages; the probability of catastrophic failure in each equipment population; and two budget based measures of effectiveness. Two optimization methods are described for a test problem developed for MREAL1. The first method computes values of the objective function and the constraints for a specified subset of the solution space. The best feasible solution found is recorded. This method can also examine all possible solutions, or can be used in a manual search. The second optimization method performs an exhaustive enumeration. of the combinatorial programming portion of MREAL1, which represents equipment design. For each enumerated design combination, an attempt is made to find the optimal solution to the remaining nonlinear discrete programming problem. A sequential unconstrained minimization technique is used which is based on an augmented Lagrangian penalty function adapted to the integer nature of MREAL1. The unconstrained minimization is performed by a combination of Rosenbrock's search technique, the steepest descent method, and Fibonacci line searches, adapted to the integer nature of the search. Since the model contains many discrete local minima, the sequential unconstrained minimization is repeated from different starting solutions, based upon a heuristic selection procedure. A gradient projection method provides the termination criteria for each unconstrained minimization. / Ph. D.

published_or_final_version / Computer Science and Information Systems / Master / Master of Philosophy

M. Tech. (Department of Information and Communication Technology, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Crude oil is among the most in-demand and desirable commodities across the world today. The multiple uses of crude oil are widespread, ranging from the generation of energy to its use as fuel for the petrochemical and transportation sectors. Because of the high use of and demand for crude oil worldwide, the petroleum industry (also known as the oil and gas industry) is a significantly role player in the world economy. Libya‘s oil and gas industry is deemed the most essential and important sector in this country, as Libya is mainly dependent on proceeds from this sector. However, existing information technologies are not always optimally applied and utilised. This, together with the challenge that information technologies in the supply chain system and logistics processes of some of Libya‘s oil and gas companies are not always sufficient, the productivity of the country‘s oil and gas supply chain is compromised, and this results in revenue losses because of wasteful expenditure. This research therefore aimed to determine what innovative information technologies should be considered by Zueitina Oil Company (as case study) in Libya to enhance its supply chain and logistics processes. Two primary research questions (PRQs) were formulated for this research, namely: (i) What is the current status of Libya‘s oil and gas sector in terms of oil production and export? (ii) What innovative information technologies need to be considered by Zueitina Oil Company in Libya to contribute towards optimising its supply chain and logistics processes? This study followed the qualitative research methodology, as the data collected were qualitative and the research design was inductive. A case study strategy was adopted, with Zueitina Oil Company in Libya as the case under study. The primary sources for the research were the management of the supply chain and logistics departments of Zueitina Oil Company. The qualitative data collection method selected was a survey conducted by means of telephone and focus group interviews. The data were analysed using thematic analysis. In total, five themes and six sub-themes emerged from the findings obtained from the analysis. This research contributes to the scientific body of knowledge by proposing an Information Technology Optimisation Model for the Supply Chain of Zueitina Oil Company in Libya in order to achieve increased revenues, reduced costs, and improved customer services, among others.