The need for improved cloud parameterisations in a road surface temperature model is demonstrated. Case studies from early 1994 are used to investigate methods of tracking cloud cover using satellite imagery and upper level geostrophic flow. Two of these studies are included in this thesis. Errors encountered in cloud tracking methods were investigated as well as relationships between cloud height and pixel brightness in satellite imagery. For the first time, a one dimensional energy balance model is developed to investigate the effects of erroneous cloud forecasts on surface temperature. The model is used to determine detailed dependency of surface freezing onset time and minimum temperature on cloud cover. Case studies from the 1995/96 winter in Devon are undertaken to determine effects of differing scenarios of cloud cover change. From each study, an algorithm for predicting road surface temperature is constructed which could be used in future occurrences of the corresponding scenario of the case study. Emphasis is strongly placed on accuracy of predictions of surface freezing onset time and minimum surface temperature. The role o f surface and upper level geostrophic flow, humidity and surface wetness in temperature prediction is also investigated. In selected case studies, mesoscale data are also analysed and compared with observations to determine feasibility of using mesoscale models to predict air temperature. Finally, the algorithms constructed from the 1995/96 studies are tested using case studies from the 1996/97 winter. This winter was significantly different from its preceding one which consequently meant that the algorithm from only one scenario of the 1995/96 winter could be tested. An algorithm is also constructed from a 1996/97 winter case study involving a completely different scenario Recommendations for future research suggest testing of existing algorithms with guidance on additional scenarios.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 265-272).

Professional paper (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Abigail Richards. Includes bibliographical references (leaves 53-58).

Thesis (M.S.) in Electrical Engineering--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 79-82).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Un procédé de création de surfaces poreuses sur deux aciers inoxydables respectivement austénitique et ferritique a été étudié. Ce procédé est en deux étapes. Une couche d’oxyde, dont l’épaisseur et la composition sont contrôlées, est d’abord générée par de la vapeur d’eau à 1100 °C. Puis cette couche est ensuite réduite par du dihydrogène à haute température. Ces travaux ont pour objectifs de mieux comprendre les mécanismes de formation des pores ainsi que l’influence des divers paramètres de réaction, tant pour l’oxydation que pour la réduction.Une caractérisation complète des couches d’oxydes a été d’abord réalisée. Le principal paramètre influent est la structure de l’alliage, austénitique ou ferritique. Par la suite, les surfaces poreuses ont été étudiées afin d’établir, étape par étape, les mécanismes mis en jeu.Il a été établi que la non-stœchiométrie des oxydes de fer préalablement formés sur l’acier austénitique est à l’origine de la formation des pores sur la surface de cet acier.Un nouveau type de porosité a pu être obtenu par la formation préalable de couches d’oxydes riches en chrome formées sur l’acier ferritique. Les morphologies ainsi que les mécanismes sont ici totalement différents. Un processus de formation des pores spécifique a été proposé. / A process for pore creation on the surface of two stainless steels, respectively austenitic and ferritic, has been investigated. That process follows two steps. An oxide scale with controlled thickness and composition is firstly generated by water vapour exposition at 1100 °C. That layer is subsequently reduced at high temperature by dihydrogen. The present work aims to better understand the mechanisms of pore formation and the influence of various reaction parameters on both oxidation and reduction course.A comprehensive characterisation of the oxide layers has been first performed. The main parameter is the alloy structure, austenitic or ferritic. The porous surfaces have been thereafter studied to establish step by step the formation mechanisms involved.It was demonstrated that the non-stoichiometry of iron oxides formerly developed on the austenitic steel is behind the pore growth mechanism on that steel.A new kind of porosity could be obtained through the preliminary building of chromium-rich oxide scales on the ferritic steel. The morphologies are in that case completely different as well as the pore formation mechanism. A specific process for the pore growth has been proposed.

By defined structuring of sliding surfaces at dynamic contact seals friction and leakage can be reduced. Compared to macro-structures, micro-structures have the advantage of a quasi-homogeneous influence on the fluid behavior in the sealing gap. The development of suitable microstructures based on prototypes, whose properties are studied on the test bench, is very expensive and time-consuming due to the challenging manufacturing process and measuring technologies, which are necessary to investigate the complex rheological behavior within the sealing gap. A simulation-based development of microstructured sealing surfaces offers a cost- and time-saving alternative. This paper presents a method for simulative design and optimization of microstructured sealing surfaces at the example of a microstructured mechanical face seal.

The purpose of this thesis was to study the influence of manufacturing variations on gear performance. The manufacturing variations inherent in different manufacturing methods were studied to include the effect of real surfaces. Real surfaces have surface irregularities at least on some scale, which can significantly influence how loads are transmitted at the gear contact. To some extent, the lubricant design can help to prevent contact that could lead to tooth failures by forming a protective surface boundary layer. An experimental study was used to consider the compositions of these layers with a surface analysis method. In Paper A a robust design approach was used to find out to what extent the current standard for calculation of surface durability treats manufacturing variations and the choice of lubricant. The results show that the simplest calculation method used is not enough to predict the effect of these on surface durability. Additionally, the standard quality levels are poorly incorporated in the standard calculating procedures for surface durability, and the quality of the gear tooth is restricted to include only a few parameters. In Paper B a pin-on-disc machine was used to evaluate the tribofilm formation by the additives and the corresponding wear occurring in the boundary lubrication regime in environmentally adapted lubricants. Studies of the additive and base fluid interaction were carried out using glow discharge-optical emission spectroscopy. It was found that the chemically reacted surface boundary layers played an important role in terms of wear. More specifically, the oxide layer thickness had significant influence on wear. The findings also demonstrate the complexity of lubrication design formulations coupled to these layers. For example, it was found that the pre-existing surface boundary layer (before any lubricant had been added) played an important role in allowing the lubricant to react properly with the surfaces. The aim of Paper C was to contribute to the knowledge of how different surface topographies, tied to manufacturing methods, influence the early life contact conditions in gears. Topographical measurements of differently manufactured tooth flanks were used as data input to a contact analysis program. The variation in surface topography inherent in the manufacturing method was found to have a strong influence on the contact area ratio.

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