No description available.

No description available.

One major limitation in the use of externally pressurized air bearings (EPB) is their susceptibility to vibrations problems. The most destructive vibration that develops in a gas bearing is self-excited whirl, which commences when the damping force in the bearing becomes zero. The main aim of this research was to undertake a theoretical investigation of cylindrical whirl in a balanced vertical axis EPB, and ways of delaying its onset. In order to do this, it was necessary firstly to find the bearing static stiffness and damping coefficients by means of a compressible flow analysis of the gas. To do this, by employing Mathematica, a novel approach used the 'shooting method' in order to solve the governing differential equation (which included functions of a complex variable). The results obtained compared very favourably with previous theoretical published work that had employed finite difference methods. Having found the bearing coefficients, it was possible to solve the bearing dynamic differential equations and thus create stability maps. This procedure was carried out on various bearing arrangements aimed at raising the stability threshold. These included: A series arrangement involving a non-rotating externally pressurized sleeve round the rotor as well as a series arrangement in parallel with the main bearing. The series-parallel configuration resulted in a bearing with a threshold speed and stiffness between the extremes of a simple EPS and a series EPB, all three designs being of the same length. An optimum adjustment of the series-parallel geometry, created threshold speeds three to four times that of a simple version. This in itself was an excellent achievement. Finally, a further increase in threshold frequency, up to seven times that of an equivalent simple EPB, was attained by an additional novel design round the sleeve of a passive eddy current magnetic damper.

Thesis (M.S.)--Ohio University, March 2004. / Title from PDF t.p. Includes bibliographical references (leaves 84-85).

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 211-214).

Starting in the 1990s, the aerospace industry was challenged to produce products and systems Better, faster, Cheaper. In this paper, we examine some of the underlying reasons for BFC and offer some thoughts to help frame the thinking and action of aerospace industry professionals in this new era. / Lean Aerospace Initiative

No description available.

This thesis involves the experimental wind tunnel testing of a 0.127m by 0.127m square-base bluff body to test the effectiveness of trailing edge tabulations to reduce drag in the Cal Poly 0.912m by 1.219 m low-speed wind tunnel. To accomplish this, the boundary layer was first measured on the trailing edge of the model for the three speeds at 10, 20, and 30 m/s, with Re = 8.3e4, 1.6e5 and 2.5e5 respectively, without the tabs. Three different tests were performed to determine the effectiveness of the tabs. These tests included base pressure measurements, total drag force measurements and hotwire velocity fluctuation measurements. These tests were repeated with tabs on the model’s trailing edge at the three different tab heights and without tabs at all three test speeds. The base pressure measurements showed a decrease in average base pressure with the addition of tabs which signifies an increase in drag. The total drag measurements confirmed this by showing that the overall force increases with the addition of the tabs. The hotwire tests further confirm this by showing that the vortex is present for every configuration tested. This thesis showed that the addition of tabs was unsuccessful in reducing the effects of the vortex shedding for a square-base bluff body. The addition of low, medium, and high tabs to the square base of the bluff body all showed an increase in vortex strength and overall drag. Further study is required to determine if drag savings are feasible for tabs all around the square base of the bluff body and at different locations.

Introdução: Os principais serviços disponibilizados nos aeroportos foram convertidos em indicadores pelo Conselho Internacional de Aeroportos (ACI), uma organização global comercial de autoridades aeroportuárias, e mensurados nos aeroportos brasileiros a partir da FIFA World Cup 2014. Objetivo: Comparar os indicadores de qualidade de desempenho operacional dos serviços prestados aos usuários de 15 aeroportos brasileiros, no período 2013- 2016. Métodos: Os 48 indicadores de qualidade de desempenho operacional de serviços aeroportuários, avaliados pelos usuários segundo escala Likert de 5 pontos, foram agregados em dez índices intermediários e, após, em cinco índices de desempenho operacional (tangibilidade, agilidade, confiabilidade, garantia e empatia). Resultados: No quadriênio de 2013 a 2016, entre os dez índices intermediários, Competência foi o item melhor avaliado pelos usuários (média de 4,42) e Custos foi o pior (média de 2,61). Entre os cinco índices, Agilidade e Confiabilidade foram os melhores avaliados (médias de 4,25 e 4,15, respectivamente), enquanto que Empatia recebeu a pior avaliação (média de 3,82). Na avaliação dos cinco índices de desempenho conforme os setores aeroportuários, as companhias aéreas e os órgãos públicos foram os setores mais bem avaliadas, enquanto o setor de aeroporto comercial foi o pior avaliado. Curitiba foi o aeroporto de melhor avaliação (4,29), seguido de Campinas (4,15) e Natal (4,12), ao passo que o aeroporto de Cuiabá apresentou a pior avaliação pelos usuários (3,64), seguido de Guarulhos/SP (3,79). Conclusão: Os índices de desempenho dos serviços aeroportuários na média das categorias foram melhor avaliados pelos usuários, nas categorias de pequeno e grande porte na gestão privada dos Aeroportos Internacionais de Natal e Brasília, respectivamente. Entre os aeroportos de médio porte, a gestão pública do Aeroporto de Internacional de Curitiba apresentou uma melhor avaliação nos índices de desempenho de prestação de serviços aeroportuários aos usuários, sendo seguida pelos aeroportos sob gestão privada. / Introduction: The main services provided at airports were converted into indicators by the International Airport Council (ACI), a global commercial organization of airport authorities, and measured at Brazilian airports starting with the FIFA World Cup 2014. Objective: To compare the quality indicators of operational performance of services provided to users of 15 Brazilian airports in the period 2013-2016. Methods: The 48 indicators of operational performance quality of airport services, evaluated by users in 15 airports under study, according to a Likert scale of 5 points, were aggregated in ten intermediate indices and, in a second time, five operational performance indices (tangibility, agility, reliability, guarantee and empathy). Results: In the four-year period from 2013 to 2016, among the ten intermediate indices, Competence was the item best evaluated by the users (average of 4.42) and Costs was the worst (average of 2.61). Among the five indexes, Agility and Reliability were the best evaluated (averages of 4.25 and 4.15, respectively), while Empathy was the worst evaluation (mean of 3.82). In the evaluation of the five performance indices according to the airport sectors, airlines and public agencies were the sectors best evaluated, while the commercial airport sector was the worst evaluated. Curitiba was the airport with the best evaluation (4.29), followed by Campinas (4.15) and Natal (4.12), while Cuiabá airport presented the worst evaluation by users (3.64), followed by Guarulhos / SP (3,79). Conclusion: The performance indexes of the airport services in the average category were better evaluated by the users, in categories I and III of small and large ports in the private management of the International Airports of Natal and Brasilia, respectively. Among category II airports, the public management of the Curitiba International Airport presented a better evaluation of the performance indexes for the provision of airport services to users, followed by airports under private management.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The placement of two antennas on an air vehicle is one possible practice for overcoming signal obstruction created by vehicle maneuvering during air-to-ground transmission. Unfortunately, for vehicle attitudes where both antennas have a clear path to the receiving station, this practice also leads to self-interference nulls, resulting in dramatic degradation in the average signal integrity. This paper discusses application of unitary space-time codes such as the Alamouti transmit diversity scheme and unitary differential space-time codes to overcome the self-interference effect observed in such systems.