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The object ofthe present work is to experimentally study thecase ofa turbulent boundary layer subjected to an AdversePressure Gradient (APG) with separation and reattachment. Thisconstitutes a good test case for advanced turbulence modeling.The work consists ofde sign of a wind-tunnel setup, developmentofP article Image Velocimetry (PIV) measurements and evaluationtechniques for boundary layer flows, investigations ofs calingofb oundary layers with APG and separation and studies oftheturbulence structure ofthe separating boundary layer withcontrol by means ofs treamwise vortices. The accuracy ofP IV isinvestigated in the near-wall region ofa zero pressure-gradientturbulent boundary layer at high Reynolds number. It is shownthat, by careful design oft he experiment and correctly appliedvalidation criteria, PIV is a serious alternative toconventional techniques for well-resolved accurate turbulencemeasurements. The results from peak-locking simulationsconstitute useful guide-lines for the effect on the turbulencestatistics. Its symptoms are identified and criteria for whenthis needs to be considered are presented. Different velocityscalings are tested against the new data base on a separatingAPG boundary layer. It is shown that a velocity scale relatedto the local pressure gradient gives similarity not only forthe mean velocity but also to some extent for the Reynoldsshear-stress. Another velocity scale, which is claimed to berelated to the maximum Reynolds shear-stress, gives the samedegree of similarity which connects the two scalings. However,profile similarity achieved within an experiment is notuniversal and this flow is obviously governed by parameterswhich are still not accounted for. Turbulent boundary layerseparation control by means ofs treamwise vortices isinvestigated. The instantaneous interaction between thevortices and the boundary layer and the change in the boundarylayer and turbulence structure is presented. The vortices aregrowing with the boundary layer and the maximum vorticity isdecreased as the circulation is conserved. The vortices arenon-stationary and subjected to vortex stretching. Themovements contribute to large levels ofthe Reynolds stresses.Initially non-equidistant vortices become and remainequidistant and are con- fined to the boundary layer. Theamount ofi nitial streamwise circulationwas found to be acrucial parameter for successful separation control whereas thevortex generator position and size is ofseco ndary importance.At symmetry planes the turbulence is relaxed to a nearisotropic state and the turbulence kinetic energy is decreasedcompared to the case without vortices. <b>Keywords:</b>Turbulence, Boundary layer, Separation,Adverse Pressure Gradient (APG), PIV, control, streamwisevortices, velocity scaling.

¡§Phononic crystal,¡¨ a binary-composite medium composed of a square array of parallel circular steel cylinders in a air matrix is studied. Phononic crystal exists full band-gaps phenomenon which is caused by strongly constructive interference of Bragg reflection in their acoustic transmission spectrum. The Bragg reflection theorem is also a basis for searching the full band-gaps in this thesis. This thesis applies the boundary element simulation software BEASY to analyze the sound field characteristics of solid/fluid composite medium, phononic crystal. The forbidden bands of the band gap are shown by the relative amplitude in the incidence before and after. First, the study by Varadan and Faran aims at scattering sound field of the single rigid sphere and the circular cylinder in water which constructed a simulation of the boundary element model. It is compared to under the different kr change result of its scattering sound field and it has demonstrated that our simulation work was feasible. Second, the study constructs the boundary element model for a two-dimensional phononic crystal which was studied by S&#x00E1;nchez-P&#x00E9;rez etc. with experimentation, constituted of rectangular and triangular array of parallel circular stainless steel and aluminum cylinders in air. The study is compared with the forbidden bands of the band gap in the reference which performs the simulations with the mono-frequency by sweep. The full band gaps are determined from the combination of the results in both the [100] and [110] direction. Finally, the study aimed at the scattering pattern of sound field in phononic crystal to make discussion. In order to understand the sound source acts on the phononic crystal, the status of the sound pressure is distributed over the spatial. So it could get up to reduce the influence of the noise by way of the improvement the structure in phononic crystal. The study has successfully shown the boundary element simulation for the solid/fluid phononic crystal. The study of experiment in the reference is compared with the BEM simulation in this thesis. The results have demonstrated that the boundary element method is a good tool for the design of phononic crystal in application to new type sound absorption (isolation) material in the future.

Diffusion imaging is a relatively recent branch of magnetic resonance imaging that produces images of human physiology through diffusion of water molecules within the body. One difficulty in calculating diffusion coefficients, particularly in the brain, is the multitude of natural barriers to water diffusion, such as cell membranes, myelin sheaths, and fiber tracts. These barriers mean that water diffusion is not a homogeneous random process. Due to the complexity of modeling these structures, a simplifying assumption made in some methods of data analysis is that there are no barriers to water diffusion. We develop tools to simulate the diffusion of water in an inhomogeneous medium, which may then be used to test the accuracy of this assumption. The inherent difficulty (and computational cost) of including barriers (e.g., cell membranes) can be lessened by employing the immersed boundary (IB) method to represent these structures without the need for complicated computational grids. The contribution of this thesis is the implementation and validation of an IB method that allows for diffusion across semi-permeable membranes. The method is tested for a square interface aligned with the computational grid by comparing it to a second numerical scheme that uses standard finite differences. We also calculate the rate of convergence for the IB method to assess the numerical accuracy. To demonstrate the flexibility of the IB method to simulate diffusion with any interface shape, we also present simulations for irregular interfaces. / UOIT

The goal of this research is to develop an equation describing the two, dimensional motion of an inviscid incompressible fluid in the rectangular wavemaker of constant depth. The boundary value problem of the rectangle is transformed to the upper half plane with the use of Jacobian elliptical functions. The boundary value problem is then transformed to the unit disc. The solution to the mixed value problem of the disc is found using a general solution satisfying the Laplace equation in polar coordinates. In order to solve the coefficients of the general solution, a system of equations is developed using a method similar to the one applied for the coefficients of a Fourier series. The system is converted to matrix form and the coefficients are calculated using Mathematica. Four approximate solutions are calculated for depths of 3.96 m and 4.42 m with N equal to 2 and 10. / Graduation date: 1993

The boundary scan standard which has been in existence since the early nineties is widely used to test printed circuit boards (PCB). It is primarily aimed at providing increased physical test access to surface mounted devices on printed circuit boards (PCB). Using boundary scan avoids using functional testing and In-circuit-techniques like 'bed of nails' for structurally testing PCBs as increasing densities and complexities made opting for them a herculean task. Though the standard has had a revolutionizing effect on board testing conducted during the development and production phases, there is a lack of a standardized mechanism to allow IEEE 1149.1 to be used in a system post installation. This has led to problems typically encountered during field test runs, like the issue of high number of No-Fault-Found (NFF), being left unaddressed. The solution lies in conducting a structural test after a given module has already been installed in the system. This can be done by embedding the programmability features of the boundary scan test mechanism into the Unit under test (UUT) thereby enabling the UUT to conduct boundary scan based self tests without the need of external stimuli. In this thesis, a test and debug framework, which aims to use boundary-scan in post system-installation, is the subject of a study and subsequent enhancement. The framework allows embedding much of the test vector deployment and debug mechanism onto the Unit under test (UUT) to enable its remote testing and debug. The framework mainly consists of a prototype board which, along with the UUT, comprise the 'embedded system'. The following document is a description of the phased development of above said framework and its intended usage in the field.

The no-slip boundary condition is the foundation of traditional lubrication theory. It says that fluid adjacent to a solid boundary has zero velocity relative to that solid surface. For most practical applications the no-slip boundary condition is a good model for predicting fluid behavior. However, recent experimental research has found that for special engineered surfaces the no-slip boundary condition is not applicable. Measured velocity profiles suggest that slip is occurring at the interface. In the present study, it is found that judicious application of slip to a bearings surface can lead to improved bearing performance. The focus of this thesis is to analyze the effect an engineered slip/no-slip surface could have on hydrodynamic bearing performance. A heterogeneous pattern is applied to the bearing surface in which slip occurs in certain regions and is absent in others. Analysis is performed numerically for both plane pad slider bearings and journal bearings. The performance parameters evaluated for the bearings are load carrying capacity, side leakage rate and friction force. Fluid slip is assumed to occur according to the Navier relation and the effect of a critical value for slip onset is considered.

An advanced ascent guidance algorithm for rocket-powered launch vehicles is developed. The ascent guidance function is responsible for commanding attitude, throttle and setting during the powered ascent phase of flight so that the vehicle attains target cutoff conditions in a near-optimal manner while satisfying path constraints such as maximum allowed bending moment and maximum allowed axial acceleration. This algorithm cyclically solves the calculus-of-variations two-point boundary-value problem starting at vertical rise completion through orbit insertion. This is different from traditional ascent guidance algorithms which operate in an open-loop mode until the high dynamic pressure portion of the trajectory is over, at which time there is a switch to a closed loop guidance mode that operates under the assumption of negligible aerodynamic forces. The main contribution of this research is an algorithm of the predictor-corrector type wherein the state/costate system is propagated with known (navigated) initial state and guessed initial costate to predict the state/costate at engine cutoff. The initial costate guess is corrected, using a multi-dimensional Newtons method, based on errors in the terminal state constraints and the transversality conditions. Path constraints are enforced within the propagation process. A modified multiple shooting method is shown to be a very effective numerical technique for this application. Results for a single stage to orbit launch vehicle are given. In addition, the formulation for the free final time multi-arc trajectory optimization problem is given. Results for a two-stage launch vehicle burn-coast-burn ascent to orbit in a closed-loop guidance mode are shown. An abort to landing site formulation of the algorithm and numerical results are presented. A technique for numerically treating the transversality conditions is discussed that eliminates part of the analytical and coding burden associated with optimal control theory.

Atherosclerosis is a systemic disease occurring in specific sections of the cardiovascular tree such as the carotid and the coronary arteries. Previous studies proposed a strong correlation between plaque localization and blood flow patterns in specific sections of the arteries. In order to elucidate cellular mechanisms that contribute to atherosclerosis, standard cone-and-plate devices are widely used in experiments to reproduce in vitro the effect of different hemodynamic conditions on endothelial cells. In this study, a novel computational fluid dynamic (CFD) numerical code based on the immersed boundary method is developed to simulate this microscopic flow field under different geometries and flow conditions. A comprehensive validation of the CFD code is performed. Once validated, the code is used to analyze the flow field in the cone-and-plate device simulating conditions typically employed in endothelial cell experiments. No previous studies have yet been performed on the fluid dynamics of the cone-and-plate device when surfaces representing actual endothelial cell contours are modeled on the plate surface. This represents a great opportunity to correlate the fluid dynamics in the experimental device and the biochemical properties of the cells under specific flow conditions. The challenging aspect of the problem is represented by its different length scales. While the size of the cone-and-plate device is of the order of millimeters, the endothelial cells laying on the plate surface have size of the order of microns. The goal is to obtain a spatial resolution smaller than the height of the single cell. This allows us to investigate the biological features of the endothelial cells under shear stress in different areas of their membrane surface. This feature must be incorporated in the numerical grid, representing a challenging computational problem and is expected to be a major contribution of the research.

After the surge of Hakka movement in 1980s, Hakka identity has become a public issue. As the Commission of Hakka Affairs in every level of government was constructed and Hakka colleges were founded in several universities in the following years, the category of Hakka people has been institutionalized. But in the meantime, less and less young generation of Hakka people lost the proficiency of the Hakka dialect, which was widely seen as a crucial element of the Hakka identity. This thesis aims to explore how Hakka young generation built their ethnic identity under the paradoxical situation in which the rise of Hakka identify in the public domain has been interwoven with the loss of Hakka proficiency. The author focused on three Hakka groups, including the association of young Hakka in Meinon, the organizations of I-Min Temple (Temple of the Righteous) in Kaohsiung City, and a Hakka dialect classes held by Kaohsiung Municipal government. The author also interview with young Hakka who has no affiliation with any group. The research result found the following results. First, all of the interviewees unanimously refer patrimonial lineage as the criteria of Hakka membership. Second, different groups have different understandings of the contents of Hakka culture. The members in the association of Hakka younger generation in Meinon tend to connect the Hakka identity with local identity, while the interviewees of the organizations of I-Min Temple emphasize the religious practices. The members of the Hakka dialect classes are more responsive to the official version of Hakka identity. Those interviewees without affiliation do not have clear patter and Hakka identity is even not meaningful for many. The study shows that although the public version of Hakka identity emphasizes the diverse sources of identity, but the patrimonial lineage is perceived as the main criteria of Hakka identity. On the other hand, the official category of Hakka does not imply a unified understanding of Hakka ethnicity. This thesis shows the limitation of ¡§groupism¡¨ assumption of which ethnic categories are naturally identical with social groups and social practices. Students of Hakka studies should pay more attention to the complicated relationships between ethnic categories and practices.