Texte remanié de: Th.--Mathématiques--Eindhoven--Eindhoven University of technology, 1988. / Bibliogr. p. 97-100. Index.

Th. Ph. D.--Department of business administration--University of Stockholm, 1992. / Bibliogr. p. 286-315.

A comprehensive study on the application of flow cytometry (FCM) for the analysis of biofilms has been undertaken and the results presented in this thesis have shown that flow cytometry can been successfully used to enumerate, sort and image the bacteria and amoebae in biofilms and water distribution systems as a rapid and sensitive semiautomated technique compared with conventional microbiology. It has been shown that the results of flow cytometric analysis of total Legionella pneumophila cells have a strong statistical correlation with the numbers of Legionella cfu by BCYE plate counting (BCYE PC) methods for biofilms and planktonic phases. There are also strong statistical correlations between flow cytometric analysis and epifluorescent microscopic (EFM) analysis (direct counting) for determination of bacteria, including Legionella, Escherichia coli, Salmonella, Pseudomonas and amoebae, and total and viable cells in pure cultures, water distribution systems and biofilms. The flow cytometric protocols have been set up and optimised for the analysis of environmental microorganisms. The novel fluorescent dyes and immunofluorescence antibodies from the most current commercial dyes also have been screened and the staining protocols have been optimised and adopted for flow cytometric analysis and direct counting by epifluorescent microscopy. The tap water biofilms and river water biofilms were analysed by the flow cytometer and direct counting methods as well as by conventional microbiological methods (plate counting). The bacterial populations in real water distribution systems have been fully investigated and the total, viable bacteria were determined by the above methods. The findings of this work have practical implications with respect to the rapid and automatic detection and predictions of Legionella spp. and the risk assessment from biofilms and water environments.

Distribution and parallelism are historically important approaches for the implementation of artificial intelligence systems. Research in distributed problem solving considers the approach of solving a particular problem by sharing the problem across a number of cooperatively acting processing agents. Communicating problem solvers can cooperate by exchanging partial solutions to converge on global results. The purpose of this research programme is to make a contribution to the field of Artificial Intelligence by developing a knowledge representation language. The project has attempted to create a computational model using an underlying theory of cognition to address the problem of finding clusters of relevant problem solving agents to provide appropriate partial solutions, which when put together provide the overall solution for a given complex problem. To prove the validity of this approach to problem solving, a model of a distributed production system has been created. A model of a supporting parallel architecture for the proposed distributed production problem solving system (DPSS) is described, along with the mechanism for inference processing. The architecture should offer sufficient computing power to cope with the larger search space required by the knowledge representation, and the required faster methods of processing. The inference engine mechanism, which is a combination of task sharing and result sharing perspectives, is distinguished into three phases of initialising, clustering and integrating. Based on a fitness measure derived to balance the communication and computation for the clusters, new clusters are assembled using genetic operators. The algorithm is also guided by the knowledge expert. A cost model for fitness values has been used, parameterised by computation ration and communication performance. Following the establishment of this knowledge representation scheme and identification of a supporting parallel architecture, a simulation of the array of PEs has been developed to emulate the behaviour of such a system. The thesis reports on findings from a series of tests used to assess its potential gains. The performance of the DPSS has been evaluated to verify the validity of this approach by measuring the gain in speed of execution in a parallel environment as compared with serial processing. The evaluation of test results shows the validity of the proposed approach in constructing large knowledge based systems.

La thèse est structurée en cinq chapitres. Le premier chapitre met en évidence le contexte actuel du marché de l’énergie et du GN sur lequel porte la recherche. L’histoire du marché du GN est présentée en focalisant la distribution, où les nouvelles règles édictées pour l’ensemble du marché de l’énergie, ont créé un nouvel environnement concurrentiel. Celui-ci est le résultat du changement de structure du secteur, passé d’un monopole public à la compétition privée. On ymontre le besoin d’outils de gestion plus performants, tels que les options réelles. De même, on peut voir que les systèmes de distribution flexibles deviennent un atout important pour le déploiement d’un réseau de distribution.Le deuxième chapitre présente la structure générale de la recherche empirique. Il discute l’épistémologie de la recherche et l’approche abductive qui y est utilisée. Cette dernière, basée sur Thiétart (2001), permet que la recherche puisse avanceravec les interactions entre le terrain de recherche et la théorie de façon simultanée. On montre aussi que l’approche méthodologique systématique (Grawitz, 2001) est celle qui s’adapte le mieux à la recherche.Le troisième chapitre expose le cadre d’analyse de la recherche. Il exploite les aspects importants de l’approche par les options réelles pour l’analyse du système de distribution de GN. L’objectif ici est de montrer l’état de la recherche sur lesoptions réelles et les contributions que l’approche optionnelle peut offrir à la gestion de la distribution du GN. / The thesis is structured in five chapters. The first chapter brings to light the current context of the market of the energy and the GN which the research concerns. The history of the market of the GN is presented by focusing the distribution, where the new rules promulgated for the whole market of the energy, created a new competitive environment.This one is the result of the change of structure of the sector, go from a public monopoly to the private competition. We show the more successful need of management tools, such as the real options.Also, we can see that the flexible systems of distribution become an asset important for the deployment of a distribution network. The second chapter presents the general structure of the empirical research. It discusses the epistemology of the research and the abductive approach which is used there. This last one, based on Thiétart ( 2001 ), allows that the research can advance with the interactions enter the ground of research And the theory in a simultaneous way. We also show that the systematic methodological approach (Grawitz,2001) is the one which adapts itself best to the research.The third chapter exposes the frame of analysis of the research. It exploits the important aspects of the approach by the real options for the analysis of the system of distribution of GN. The objective here is to show the state of the research on the real options and the contributions which the optional approach can offer to the management of the distribution of the GN.

No description available.

Search engines have revolutionised the access to information to the general public. Today search engines are the most important promotional method on the Internet. Sponsored search dominates the revenue model behind this growth. The rise in popularity and the auction pricing mechanism of sponsored advertising have increased the average cost-per-click. Marketing managers need tools to enable them to increase return on investment in this medium. The application of Anderson’s (2004) long tail distribution holds great promise to solve this dilemma. The current study used causal research in a two by two factorial design. Here data from an online property portal in a developing market was collected in order to examine the effect of a long tail (LT) distribution in keyword selection on return on investment (ROI) with sponsored search. Sponsored search allows for individualised targeting of the users behaviour. The application of the long tail (LT) enables further matching the advert text to the users search query. The results provide strong support for the significant impact on cost-per-click and by implication the return on investment that keyword selection and targeted advert text have when used in conjunction with the principles of the long tail. The interaction of the independent variables of long tail and sponsored search is significant, contributing to a 430% increase in click-through (CTR) rates and 61% reduction in cost-per-click, translating into a 61% increase in return on investment. / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted

No description available.

[No abstract available] / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The object of this thesis is to find a method for locating transient as well as permanent faults on transmission lines. Transient faults are those lasting for a fraction of a second or so which do not cause serious enough damage to necessitate immediate repairs before the line may be reenergized. However, transient faults such as insulator flashovers may cause enough damage to be a potential permanent outage. It is thus desirable to be able to locate the position of the fault, and to inspect the line and insulators so that they may be repaired if necessary when the line can be conveniently removed from service. The method that seemed most desirable was based on the echo-ranging principle such as is used in radar. This method has the advantages of accuracy and ease of interpretation. A damped sine wave pulse is generated at short intervals and fed onto the transmission line by means of a coupling capacitor. This pulse travels along the line and is partially reflected from any discontinuity such as a flashover to ground. The transmitted pulse, and pulses reflected from the end of the line and the fault are shown on a viewing tube; the distance to the fault being found by proportion. The line is pulsed only on the occurrence of a fault; thus any interference with radio is eliminated. The pulse generator is tripped by zero-sequence current or from the surge created by the fault itself. The pulses were to be recorded on a skiatron or memory tube which holds the trace on the tube until it is erased at will by the operator. This eliminates the necessity of photographic equipment and the disadvantages of delay and inconvenience of developing the film. The work accomplished on the project included the theory of wave propagation along transmission lines and the reflection to be expected for arcing ground faults. A pulse generator was built to produce either a damped sine wave or a sharp-fronted wave with exponential decay. Experiments were -carried out on coaxial cable with carbon and oil arcs as the fault, but no experiments were carried out on actual transmission lines as no line was available. The results of these experiments and the theory indicate that the method should be satisfactory on transmission lines. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate