The present thesis studies the stability of a rotating cylindrical shell containing a co-rotating axial viscous flow. The system can be thought of as a long thin-walled pipe carrying an internal axial flow while the whole is in a frame of reference rotating at a prescribed rate. The equations of the previously solved inviscid model are rederived and the problem is studied further. The results obtained for purely axial flow are reproduced, but as expected from literature, it is impossible to obtain satisfactory results for the system subjected to rotation due to the presence of singularities in the flow pressure solution. A hypothetical physical explanation for these singularities is put forward and has similarities with the phenomenon of atmospheric flow blocking. / Considering the unsuccessful results obtained with the inviscid theory, it is believed that the added realism brought in by the introduction of viscosity in the theory can lead to a successful model. Assuming a travelling-wave perturbation scheme, the linear Donnell-Mushtari thin shell equations are coupled with the fluid stresses obtained by solving numerically the incompressible Navier-Stokes equation for a laminar or turbulent flow. A novel triple-perturbation approach is established to consider the interaction between the fluid and the structure. This triple-perturbation approach is in essence a superposition of three fluid fields caused by the three components of the shell deformation for a given oscillation mode. It is found that the usual technique for linear aeroelasticity studies consisting of applying the fluid boundary conditions at the undeformed position of the wall instead of the instantaneous deformed position greatly alters the stability of the system. To remedy to this problem, three different corrections are applied and tested on the carefully derived model. The dynamics of the system subjected to purely axial flow with no rotation is successfully studied with the viscous model for both laminar and turbulent flow conditions. Because no experimental or previous theoretical data is available, it is impossible to validate the results obtained in the laminar regime. For the turbulent regime, as the Reynolds number is increased, the results tend more and more towards those obtained with the inviscid theory. / The results obtained for small rates of rotation show that both in the laminar and in the turbulent regime, the system tends to be stabilised when subjected to a small rate of rotation. On the other hand, this tendency should be reversed for higher rates of rotation, but it is impossible to show this due to the limitations of the root-finding method employed.

This thesis is concerned with the experimental evaluation of the volumetric deformation of a two-phase medium at the microscopic level. The basic definitions of the significant parameters involved in the mechanical response behaviour of the structured medium are based on the concepts of Probabilistic Micromechanics. A simple phenomenological model and the leading structural parameter $ theta sb{s}$ (Solid phase volume fraction) are discussed briefly. The experimental work makes use of a series of macroscopic tests to attain different states of deformation so that the evolution of the internal microstructural changes can be analyzed. The combined use of ultramicrotomy techniques and the Scanning Electron Microscopy operating in the Backscattered Electron mode allowed the quantification of the microstructural changes at large magnifications. The concepts of practical Stereology were adopted for the quantification of a large number of observation areas representative of the complete phenomenon to determine the leading structural parameter $ theta sb{s}.$ A semi-automatic system was developed for the determination of $ theta sb{s}$ corresponding to each observation area. A fully-automatic image analyzer also was used for the evaluation of the first state of deformation. The experimental procedure employed in this investigation is described in detail and its application is illustrated by the evaluation of $ theta sb{s}$ and its evolution at the microscopic level. The evaluations of the distributions of this parameter also are shown. In the conclusion of this thesis, the obtained results for the Al-Quetol are discussed and general remarks concerning the experimental technique and its application to other structured media are indicated.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1058. Advisers: Jonathan B. Freund; Robert D. Moser. Includes bibliographical references (leaves 110-114) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 3079. Adviser: Petros Sofronis. Includes bibliographical references (leaves 230-243) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3884. Advisers: Ronald J. Adrian; S. Balachandar. Includes bibliographical references (leaves 120-123) Available on microfilm from Pro Quest Information and Learning.

Organizing data into groups using unsupervised learning algorithms such as k-means clustering and GMM are some of the most widely used techniques in data exploration and data mining. As these clustering algorithms are iterative by nature, for big datasets it is increasingly challenging to find clusters quickly. The iterative nature of k-means makes it inherently difficult to optimize such algorithms for modern hardware, especially as pushing data through the memory hierarchy is the main bottleneck in modern systems. Therefore, performing on-the-fly unsupervised learning is particularly challenging. In this thesis, we address this challenge by presenting an ensemble of algorithms to provide hardware-aware clustering along with a road-map for hardware-aware machine learning algorithms. We move beyond simple yet aggressive parallelization useful only for the embarrassingly parallel parts of the algorithms by employing data reduction, re-factoring of the algorithm, as well as, parallelization through SIMD commands of a general purpose processor. We find that careful engineering employing the SIMD instructions available by the processor and hand-tuning reduces response time by about 4 times. Further, by reducing both data dimensionality and data-points by PCA and then coreset-based sampling we get a very good representative sample of the dataset. Running clustering on the reduced dataset, we achieve a significant speedup. This data reduction technique reduces data dimensionality and data-points, effectively reducing the cost of the k-means algorithm by reducing the number of iteration and the total amount of computations. Last but not least, using we can save pre-computed data to compute cluster variations on the fly. Compared to the state of the art using k-means++, our approach offers comparable accuracy while running about 14 times faster, by moving less data fewer times through the memory hierarchy.

Viral infections, such as HIV, are often treated with orally administered antiviral medications that are dosed at particular intervals, leading to periodic drug levels and hence periodic inhibition of viral replication. These drugs generally bind to viral proteins and inhibit particular steps in the viral lifecycle, and resistance often evolves due to point mutations in the virus that prevent the drug from binding its target. However, it has been proposed (Wahl \& Nowak, Proc Roy Soc B, 2000) that a completely different ``cryptic'' mechanism for resistance could exist: the virus population may evolve towards synchronizing its lifecycle with the pattern of drug treatment. If the lifecycle of the virus is a multiple of the dosing interval, it is possible that over time the bulk of the virus population will replicate during trough concentrations of the drug. In this thesis, we use stochastic mathematical models of viral dynamics to demonstrate that cryptic resistance could plausibly provide a powerful fitness advantage to a wide variety of viral strains whose expected lifecycle times are slightly less than the expected time between doses of an antiviral drug, allowing them to survive drug regimes that would otherwise drive infected cell populations to extinction. This in turn suggests that continuously-administered antiviral drug treatments may be significantly more effective than periodically-administered treatments in combatting viral infections. / Applied Mathematics

We have constructed a model for the kinetics of rupture of membranes under tension, applying physical principles relevant to lipid bilayers held together by hydrophobic interactions. The membrane is characterized by the bulk compressibility (for expansion) K and the thickness 2ht of the hydrophobic part of the bilayer. The model is a lattice model which incorporates stress relaxation, and considers the nucleation of pores at constant area, constant temperature, and constant particle number. The particle number is conserved by allowing multiple occupancy of the sites. A value for the rigidity of the phopholipid tails in the Lalpha liquid phase are found for saturated and unsaturated lipids, and long diblock copolymers. An equilibrium "phase diagram" is constructed as a function of temperature and strain with the pores total surface and distribution as the order parameters. With parameters relevant to saturated phosphatidylcholine (PC) lipid membranes, well defined regions of "no pores", "protopores (non-critical pores)", "rupture" are found. The model also reproduces recent results on super-thick membranes, and on membranes in presence of peptides. Free energy curves as a function of total pore surface are presented for various values of tension and temperature, and the fractal dimension of the pore edge is evaluated.

The purpose of the present investigation was to determine the net passive elastic joint moment and the angular damping coefficient of the human knee joint in full range flexion-extension. A secondary purpose was to develop regression equations to predict the measured passive properties from anthropometric data. The passive elastic moments increased exponentially as the limits of either flexion or extension were approached. The midrange of joint motion was a low moment (5 N$\cdot$m), low stiffness region. Considerable variability in the magnitudes of the passive elastic moments existed across subjects. At 140$\sp\circ$ of flexion, between about 5 N$\cdot$m and 86 N$\cdot$m was measured while the range at full extension (0$\sp\circ$) was about 6 N$\cdot$m to 22 N$\cdot$m. The angular damping coefficient was a nonlinear function (approximately quadratic) of the knee joint angle. The variability was not quite as high compared to the elastic component. Application of the data to the late swing phase of walking indicated that, for some subjects, the passive moments may contribute (or oppose) significantly to the net joint moment. (Abstract shortened by UMI.)

The study makes use of a variation of the Finite-Difference Time-Domain (FDTD) method as first proposed by Yee to simulate electromagnetic field distribution and propagation in an open waveguide structure. In order to prove that this new method is valid, a reflection coefficient is calculated with simulation data and compared to measurements. The agreement between measurement and simulation data, while not exact, is enough to establish the veracity of the new method. This study contains a detailed discussion of the discrepancies which were observed. Also presented are colour images of the simulation which give the reader an idea as to the nature and level of detail of the information which can be obtained from the simulation.