The influence of the major environmental forces on the attitude response of gravity gradient satellites is investigated using analytical and numerical techniques. The study establishes not only the effect of these forces on system performance but also their relative importance. The problem is investigated in the order of increasing difficulty which corresponds to a systematic reduction in altitude. In general, the non-linear, non-autonomous nature of the system renders the determination of a closed form solution virtually impossible. Hence, numerical techniques are employed, in conjunction with invariant surfaces or integral manifolds, to analyse the system. For a given set of parameters, the largest such surface defines the bound of stable motion; on the other hand, the smallest surface that can be found (i.e., a line or set of lines) represents the dominant periodic solution with which these manifolds are associated. The analysis establishes the importance of periodic solutions as they provide the 'frame' about which stability charts are built. Furthermore, a variational stability analysis of these solutions, using Floquet theory, accurately determines the termination of the spikes and establishes the critical eccentricity for stable motion. Phase I investigates the attitude dynamics of satellites at high altitudes where gravity gradient and direct solar radiation constitute the predominant torques. The approximate closed form solution, obtained using the WKBJ and Harmonic Balance methods, was found to predict the librational response of a satellite with considerable accuracy. As the satellites requiring station keeping permit only small amplitude motion, the analytical results are of sufficient accuracy to be useful during preliminary design stages. The response and stability bounds of the system, obtained numerically, are shown through the use of 'system plots' and 'stability charts'. The results indicate a considerable effect due to solar radiation on the attitude dynamics of a satellite. The use of solar radiation in controlling the satellite attitude is explored. The optimized results show this system to be quite effective, being capable of providing a pointing accuracy of 0-5° depending on orbit eccentricity. The extension of the analysis to the intermediate altitude ranges, where direct earth radiation, its albedo and shadow become significant, is undertaken in phase II. A comprehensive investigation was made possible by the determination of closed form expressions for earth radiation forces. This was accomplished through the concept of cutting plane distance ratios. The analysis shows only local variations due to earth radiations without substantially affecting the maximum librational amplitude or mainland stability area. Hence, for all practical purposes, direct earth radiation, its albedo and shadow can be neglected in such studies. Phase III investigates the dynamics of close earth satellites in the presence of aerodynamic and radiation forces, thus covering the remaining altitude range. The results show that a precise dynamic analysis requires the consideration of both aerodynamic and direct solar radiation forces. The investigation helps in establishing an altitude range in which a pure gravity gradient analysis is likely to be most applicable. The application of this analysis to the representative gravity gradient satellite, GEOS-A, over the entire altitude range, exemplifies the findings of the parametric study. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The effect of specific active environment on the fracture strength of glass and polymethyl methacrylate was investigated using an indirect tensile testing technique. The strength of glass was not affected by exposure to dry gaseous N₂ and CO₂. At low water vapour coverages, (<1/3 monolayer), the tensile strength of glass was reduced by approximately 50%. Further increase in water vapour pressure did not weaken the solid to a much greater extent. The existence of surface microcracks governs the absolute tensile fracture strength, and any process which varies the flaw geometry acts to vary the tensile fracture strength. Soaking in the liquid has the same effect as adsorption from the vapour phase near saturation. All vapour adsorbates caused a weakening, the magnitude of the decrease increasing with increasing ability of the adsorbate to screen the surface Si++++ cores. Moisture was the most active environment encountered. Polymethyl methacrylate did not weaken in the vapour phase despite multilayer adsorption, but stressing in wetting liquids did cause drastic failure, with a 57% decrease in tensile strength. Non-wetting liquids do not affect the strength of the acrylic plastics. Fracture experiments on a quartzitic rock in aqueous solutions of surfactant, (quartenary ammonium salts), show that the weakening due to surfactant adsorption is negligible, since water itself causes the maximum strength reduction. The adsorption of surfactant is only a secondary effect. A mechanism has been proposed for the stress-environmental failure of brittle solids. This mechanism recognizes the existence of micro-cracks, regards the stable crack propagation stage of the fracture process to be environment sensitive, and involves the strain-activated adsorption resulting in a decrease in cohesion at the flaw apex. The magnitude of the weakening is critically dependent on the nature of the bonding in the solid surface. A literature review of stress-sorption cracking, with an emphasis on non-metallic systems, is included. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

THE AREA OF CONCERN This thesis looks at two actual neighbourhoods within Vancouver - a high density urban, and a low density suburban environment. Using these neighbourhood environments, an attempt is made to see if children act or are affected in ways which can be traced to the layout and amenities of the physical environment. Data has been gathered concerning the physical structure of the environments, and is examined in relation to how the children use these environments, and in relation to the attitudes that parents, or institutions responsible for child socialization, have towards the effect of these environments on the children and themselves. THE METHODS OF INVESTIGATION This data has been gathered by my own observations, by interviewing children and key resource people who work or reside in the neighourhood, and by handing out questionnaires to parents involved with raising children in the sample areas. CONCLUSIONS The data shows that in different types of neighbourhood communities, children use and interact with the environment in different ways. It shows that the behaviour of children is modified because of the physical environment they grow up within. It shows that children of different ages and sexes have differing needs, and that their use of the environment is constantly changing as they grow and search for ways to satisfy these needs. The analysis of this data begins to show deficiencies and strengths in the planning and layout of the physical environments, and how these potentially affect children. From this analysis certain proposed solutions have been arrived at - solutions which the author feels can make the child’s environment more appropriate to his developmental needs,and more in keeping with the desires of his family and self. / Applied Science, Faculty of / Architecture and Landscape Architecture (SALA), School of / Graduate

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The aim of the diploma thesis is to analyse the influence of the concept of the institutional care in children's homes on clients. The introduction chapter provides the description of the psychological condition of the clients and how it is influenced by the institutional upbringing. The following chapters deal with the realization of the state education in children's homes and with the description of the system of the intitutional care and its development. The research has found out how a group of clients evaluates the changes in the concept of the institutional care and how this changes come into operation in their own life. The research was based on the immediate observation, analysis of the records and conversations with clients. The final evaluation of the research presents recommendations for further development of the improvement of the children care in the institutional care.