This research performs an experimental study of a trailing edge blowing system that can adapt to variations in flow parameters and reduce the unsteady stator-rotor interaction at all engine operating conditions. The fan rotor of a 1/14 scale turbofan propulsion simulator is subjected to spatially periodic, circumferential inlet flow distortions. The distortions are generated by four struts that support a centerbody in the inlet mounted onto the simulator. To reduce the unsteady effects of the strut wakes on the rotor blades, the wake is re-energized by injecting mass from the trailing edge of the strut. Each strut is provided with discrete blowing holes that open out through the strut trailing edge. Each blowing hole is connected to a MEMS based microvalve, which controls the blowing rate of the hole. The microvalve is actuated by a signal voltage, generated by a PID controller that accepts free stream and wake axial flow velocities as inputs and minimizes their difference. To quantify the effectiveness of trailing edge blowing the far-field noise is measured in an anechoic chamber. The experiments are performed for two simulator test speeds, 29,500 rpm and 40,000 rpm, with and without trailing edge blowing. The maximum reduction recorded at 29,500 rpm is 8.2 dB, and at 40,000 rpm is 7.3 dB. Reductions of 2.9 dB and greater are observed at the first five harmonics of the blade passing frequency. The sound power level at the blade passing frequency, calculated from measured far-field directivity, is reduced by 4.4 dB at 29,500 rpm and by 2.9 dB at 40,000 rpm. The feasibility and advantage of active control is demonstrated by the ability of the system to respond to a step change in the inlet flow velocity, and achieve optimum wake filling in approximately 8 seconds. / Master of Science

Este trabalho trata da uniformização local, que é um passo do método de Zariski para provar resolução de singularidades em variedades algébricas. O método consiste numa abordagem por teoria de valorizações, e esta dissertação se baseia no artigo [NS], de Novacoski e Spivakovsky, que consiste em reduzir a prova da uniformização local para valorizações de qualquer posto, a provar apenas para os casos de posto um. / This work deals with local uniformization, which is a step in the method of Zariski to prove resolution of singularities for algebraic varieties. The method consists in an approach using valuation theory and this dissertation is based on the paper [NS], by Novacoski and Spivakovsky, which consists in reduce the proof of local uniformization for all cases to prove only the cases of rank one.

O uso de sopro lateral a partir da ponta de uma asa, desloca para fora seus vórtices de ponta, aumentando sua envergadura efetiva. Este aumento reflete em incremento na sustentação da asa e redução em seu arrasto induzido. O presente estudo pesquisou, através de ensaios em túnel de vento, uma configuração de sopro lateral a partir da ponta de asa, cujo sopro foi efetuado através de três fendas dispostas ao longo da corda da ponta de um modelo de asa. Cada fenda era individual, ou seja, sua alimentação de ar, regulagem da intensidade do sopro e posicionamento do ângulo de saída do jato em relação ao plano da asa, eram independentes. Desta forma, ensaiaram-se vários posicionamentos angulares relativos entre as fendas e configurações com um, dois ou três sopro(s). Os resultados obtidos demonstraram que todas as configurações ensaiadas promoveram incrementos na sustentação e reduções no arrasto da asa e, geralmente, quanto maior o número de sopros, maiores foram os ganhos. Entretanto, algumas configurações com sopros duplos apresentaram benefícios aerodinâmicos superiores àqueles demonstrados pelos sopros triplos. Portanto, pode-se obter benefícios aerodinâmicos com configurações de sopro que demandem menor massa de ar e, no caso de uma aeronave equipada com tal dispositivo, significar-se-á menor sangria de ar do(s) motor(es). / Lateral wing tip blowing device displaces wing tip vortices outboard and increases the effective span of the wing. The increase in wing span increases lift and reduces induced drag. This study, which included tests in the wind tunnel, tested a lateral wing tip blowing device in which the jets flow exit was from three longitudinal slots on a wing tip model. Jet intensity and angular position could be individually regulated for each slot. Various angular positions of the slots were tested and were also tested one, two or three plenum chambers operating. Results shown that all the blowing configurations increased lift and reduced drag. Some double jet configurations, using reduced jet coefficient, demonstrated aerodynamic improvements than those with triple jets. Therefore, localized lateral wing tip blowing devices provides aerodynamic improvement than full cord lateral jets and yet, uses less engine bleed air.

O uso de sopro lateral a partir da ponta de uma asa, desloca para fora seus vórtices de ponta, aumentando sua envergadura efetiva. Este aumento reflete em incremento na sustentação da asa e redução em seu arrasto induzido. O presente estudo pesquisou, através de ensaios em túnel de vento, uma configuração de sopro lateral a partir da ponta de asa, cujo sopro foi efetuado através de três fendas dispostas ao longo da corda da ponta de um modelo de asa. Cada fenda era individual, ou seja, sua alimentação de ar, regulagem da intensidade do sopro e posicionamento do ângulo de saída do jato em relação ao plano da asa, eram independentes. Desta forma, ensaiaram-se vários posicionamentos angulares relativos entre as fendas e configurações com um, dois ou três sopro(s). Os resultados obtidos demonstraram que todas as configurações ensaiadas promoveram incrementos na sustentação e reduções no arrasto da asa e, geralmente, quanto maior o número de sopros, maiores foram os ganhos. Entretanto, algumas configurações com sopros duplos apresentaram benefícios aerodinâmicos superiores àqueles demonstrados pelos sopros triplos. Portanto, pode-se obter benefícios aerodinâmicos com configurações de sopro que demandem menor massa de ar e, no caso de uma aeronave equipada com tal dispositivo, significar-se-á menor sangria de ar do(s) motor(es). / Lateral wing tip blowing device displaces wing tip vortices outboard and increases the effective span of the wing. The increase in wing span increases lift and reduces induced drag. This study, which included tests in the wind tunnel, tested a lateral wing tip blowing device in which the jets flow exit was from three longitudinal slots on a wing tip model. Jet intensity and angular position could be individually regulated for each slot. Various angular positions of the slots were tested and were also tested one, two or three plenum chambers operating. Results shown that all the blowing configurations increased lift and reduced drag. Some double jet configurations, using reduced jet coefficient, demonstrated aerodynamic improvements than those with triple jets. Therefore, localized lateral wing tip blowing devices provides aerodynamic improvement than full cord lateral jets and yet, uses less engine bleed air.

Este trabalho trata da uniformização local, que é um passo do método de Zariski para provar resolução de singularidades em variedades algébricas. O método consiste numa abordagem por teoria de valorizações, e esta dissertação se baseia no artigo [NS], de Novacoski e Spivakovsky, que consiste em reduzir a prova da uniformização local para valorizações de qualquer posto, a provar apenas para os casos de posto um. / This work deals with local uniformization, which is a step in the method of Zariski to prove resolution of singularities for algebraic varieties. The method consists in an approach using valuation theory and this dissertation is based on the paper [NS], by Novacoski and Spivakovsky, which consists in reduce the proof of local uniformization for all cases to prove only the cases of rank one.

Active control of the flow over an airfoil is an area of heightened interest in the aerospace community. Previous research on flow control design processes heavily depended on trial and error and the designers knowledge and intuition. Such an approach cannot always meet the growing demands of higher design quality in less time. Successful application of computational fluid dynamics (CFD) to this kind of control problem critically depends on an efficient searching algorithm for design optimization. CFD in conjunction with Genetic Algorithms (GA) potentially offers an efficient and robust optimization method and is a promising solution for current flow control designs. But the traditional binary GA and its operators need to be transformed or re-defined to meet the requirements of real world engineering problems. Current research has combined different existing GA techniques and proposed a realcoded Explicit Adaptive Range Normal Distribution (EARND) genetic algorithm with diversity control to solve the convergence problems. First, a traditional binary-coded GA is replaced by a real-coded algorithm in which the corresponding design variables are encoded into a vector of real numbers that is conceptually closest to the real design space. Second, to address the convergence speed problem, an additional normal distribution scheme is added into the basic GA in order to monitor the global optimization process; meanwhile, design parameters boundaries are explicitly updated to eliminate unnecessary evaluations (computation) in un-promising areas to balance the workload between the global and local searching process. Third, during the initial 20% evolution (search process), the diversity of the individuals within each generation are controlled by a formula in order to conquer the problem of preliminary convergence to the local optimum. In order to better understand the two-jet control optimization results and process, at first, a single jet with a width of 2.5% the chord length is placed on a NACA 0012 airfoils upper surface simulating the blowing and suction control under Re=500,000 and angle of attack 18 degree. Nearly 300 numerical simulations are conducted over a range of parameters (jet location, amplitude and angle). The physical mechanisms that govern suction and blowing flow control are determined and analyzed, and the critical values of suction and blowing locations, amplitudes, and angles are discussed. Moreover, based on the results of single suction/blowing jet control on a NACA 0012 airfoil, the design parameters of a two-jet system are proposed. Our proposed algorithm is built on top of the CFD code, guiding the movement of two jets along the airfoils upper surface. The reasonable optimum control values are determined within the control parameter range. The current study of Genetic Algorithms on airfoil flow control has been demonstrated to be a successful optimization application.

This thesis compares ash collected from different boilers cleaned using infrasound cleaning. The samples were evaluated from their physical properties, in an attempt to find connections between the difficulty to remove ash and its physical appearance. To get a deeper understanding of the mechanisms behind adhesion and fouling, and possibly explain results from the study of the ash samples, a literature review was carried out. The ash was also evaluated to see if any connections could be drawn between the physical properties of the ash and its fouling capabilities. A strong connection was found between ash density and its fouling capabilities. It was found that no dry ash with a density higher than 0.4 g/ml were difficult to remove with infrasound cleaning, and no ash with lower density was easy to remove. The ash density was calculated from a measurement of the weight of a certain volume of ash on a scale. Optical microscopy was used to study the ash samples, and gave an estimation of particle size, shape, and porosity. However, no clear connection could be observed with this method between the different samples and which were difficult to remove. The particle size for a few of the samples were also measured by a wet laser sieving method, and while it does give a good picture of particle size, the size was not found to be a useful prediction of the ash fouling behaviour. The exact mechanism giving rise to the density dependence need to be further investigated.

The author examined whether contextual variables impact internal auditors' self-assessed likelihood of whistleblowing. The author synthesized a theoretical framework and developed research hypotheses that predict relationships between the self-assessed likelihood of whistleblowing and (1) magnitude of the consequences (2) channels of communication and (3) type of wrongdoing. To test these hypotheses, the author provided internal auditors (n=123) with a scenario and asked them to self-assess the likelihood of reporting evidence of a malfacation to their internal audit director even though their audit manager told them to ignore the wrongdoing.

This study examines the effects of reputation threats and anonymous whistle-blowing channels on Chief Audit Executives’ (CAEs) decisions to investigate whistle-blowing allegations. Participants were 94 CAEs and Deputy CAEs from publicly traded companies in the eastern half of the United States. Participants received whistle-blowing reports from either an anonymous or a non-anonymous source. In the high reputation threat condition the whistle-blowing report alleged that the wrongdoing was perpetrated by the exploitation of substantial weaknesses in internal controls that had been previously evaluated by external auditors and the internal audit function. The report in the lower threat condition alleged that the wrongdoing was accomplished by the circumvention of internal controls. Findings show that CAEs found anonymous whistle-blowing reports to be significantly less credible than non-anonymous reports. Although CAEs assessed lower credibility ratings for the reports alleging wrongdoing by the exploitation of substantial weaknesses in internal controls, they perceived greater personal and departmental responsibility in this condition. CAEs did not, however, perceive a significant reputation threat in either the Exploitation or Circumvention condition. Regardless of report source credibility, perceived reputation threat, or felt responsibility, CAEs’ resource allocation decisions consistently demonstrated a determination to thoroughly investigate the allegations of wrongdoing and uncover the truth.

Wang Yi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 61-63). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.4 / Chapter 2 --- Some Preparations --- p.10 / Chapter 3 --- Proof of Theorem 1.1 --- p.24 / Chapter 4 --- Location of Blow-up Points (for n=2) --- p.26 / Chapter 5 --- Location of Blow-up Points (for General n) --- p.35 / Chapter 6 --- Asymptotic behavior of solutions near blow-up point --- p.46 / Chapter 7 --- Appendix --- p.57 / Bibliography --- p.61