8,325 Works

A theoretical and computational study on active wake control

Luca Cortelezzi
In the first part of this dissertation a two-dimensional unsteady separated flow past a semi-infinite plate with transverse motion is considered. The flow is assumed incompressible and at high Reynolds number. The rolling-up of the separated shear-layer is modelled by a point vortex whose time dependent circulation is predicted by an unsteady Kutta condition. A power-law starting flow is assumed along with a power-law for the transverse motion. The effects of the motion of the...

Computational topology algorithms for discrete 2-manifolds

Zoe Justine Wood
This thesis presents computational topology algorithms for discrete 2-manifolds. Although it is straightforward to compute the genus of a discrete 2-manifold, this topological invariant does not tell us enough for most computer graphics applications where we would like to know: what does the topology look like? Genus is a scalar value with no associated geometric appearance. We can, however, isolate geometric regions of the surface that are topologically interesting. The simplest topologically interesting, and perhaps...

A videomagnetograph study of diffusion of solar magnetic field in weak plage regions

Robert Carroll Smithson
A new instrument for use in astronomical research has been developed. This is the differential video photometer, a device for detecting differences in light intensity between two television pictures. With a suitable source of video, the device is capable of detecting intensity differences of the order of one part in one thousand. It should be useful in many applications, such as colorimetry, polarimetry, motion detection, and doppler shift measurements. It has been used thus far...

Association schemes, codes, and difference sets

Carlos Harold Salazar-Lazaro
This thesis consists of an introductory chapter and three independent chapters. In the first chapter, we give a brief description of the three independent chapters: abelian $n$-adic codes; generalized skew hadamard difference sets; and equivariant incidence structures. In the second chapter, we introduce $n$-adic codes, a generalization of the Duadic Codes studied by Pless and Rushanan, and we solve the corresponding existence problem. We introduce $n$-adic groups, canonical pplitters, and Margarita Codes to generalize the...

Wind tunnel model tests to investigate the effects of boundary layer control

Irving Louis Ashkenas
This thesis presents a study of the results obtained with the Boundary Layer Removal Model of the Guggenheim Aeronautics Laboratory, California Institute of Technology (GALCIT). It is a continuation of work begun here some time past and, as such, contains very little in the way of historical review, the origin of the project, preliminary studies of the problem and experimental technique being contained in previous reports. The attempt, in this series of tests, to find...

The mechanics and control of undulatory robotic locomotion

James Patrick Ostrowski
In this dissertation, we examine a formulation of problems of undulatory robotic locomotion within the context of mechanical systems with nonholonomic constraints and symmetries. Using tools from geometric mechanics, we study the underlying structure found in general problems of locomotion. In doing so, we decompose locomotion into two basic components: internal shape changes and net changes in position and orientation. This decomposition has a natural mathematical interpretation in which the relationship between shape changes and...

Experimental determination of accommodation coefficients as functions of temperature for several metals and gases

Robert Norris Oliver
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The accommodation coefficients for the gases and metals tested vary rapidly in the range where the gas temperature is within approximately 50°C of the filament temperature. When the temperature excess becomes large, the [...] of argon, nitrogen and helium on platinum is approximately .7, .5 and .2, respectively, and on tungsten approximately .5, .35 and .15,...

Commuting Equivalence Relations and Scales on Differentiable Functions

Janet Mary Pavelich
This work consists of two independent chapters: The first is a study of commuting countable Borel equivalence relations, where two equivalence relations R and 5 are said to commute if, as binary relations, they commute with respect to the composition operator , i.e., R ◦ S = S ◦ R. The primary problem considered is, to what extent does the complexity of E = R V S depend on the complexity of R and S...

Bayesian Learning for Earthquake Engineering Applications and Structural Health Monitoring

Chang Kook Oh
Parallel to significant advances in sensor hardware, there have been recent developments of sophisticated methods for quantitative assessment of measured data that explicitly deal with all of the involved uncertainties, including inevitable measurement errors. The existence of these uncertainties often causes numerical instabilities in inverse problems that make them ill-conditioned. The Bayesian methodology is known to provide an efficient way to alleviate this ill-conditioning by incorporating the prior term for regularization of the inverse problem,...

Analysis and modeling of spike train correlations in the lateral geniculate nucleus

Carlos D. Brody
In this thesis I consider the cross-correlation analysis of spike train data, in two parts. In the first part, I consider the question of the proper interpretation of peaks in covariograms: It is known that peaks in the covariogram of the spike trains of two cells are due to covariations, not time-locked to the stimulus, in the responses of the two cells. Such peaks, even when they have widths on the order of 10s of...

Light Scattering in the Clouds on Jupiter

Ulyana Anatolyevna Dyudina
We construct maps of jovian cloud properties from images taken simultaneously by the Galileo solid state imaging system (SSI) and the near-infrared mapping spectrometer (NIMS) at 26 visible and near infrared wavelengths, ranging from 0.41 to 5.2 µm. Three regions - the Great Red Spot (GRS), a 5-micron Hot Spot, and one of the White Ovals - are studied. We perform a principal component analysis (PCA) on the multispectral images. PCA shows that the pixel-to-pixel...

Viscous stratified flow towards a line sink

Robert Ching-yee Koh
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. A theoretical and experimental investigation has been made for the problem of two-dimensional viscous, incompressible, steady, slightly-stratified flow towards a line sink. The analytical solution was obtained from the Navier Stokes equations, the continuity equation, and the diffusion equation by first making a boundary-layer-type assumption and then using a small perturbation technique based on a perturbation...

Diameter bounds on the complex of minimal genus Seifert surfaces for hyperbolic knots

Roberto Carlos Pelayo
Given a link L in the 3-sphere, one can build simplicial complexes MS(L) and IS(L), called the Kakimizu complexes. These complexes have isotopy classes of minimal genus and incompressible Seifert surfaces for L as their vertex sets and have simplicial structures defined via a disjointness property. The Kakimizu complexes enjoy many topological properties and are conjectured to be contractible. Following the work of Gabai on sutured manifolds and Murasugi sums, MS(L) and IS(L) have been...

The elastic scattering of protons from Li^6 nuclei

James A. McCray
The differential elastic scattering cross section for protons from Li^6 nuclei has been measured for energies from 0.45 Mev to 2.9 Mev at six different angles. A measurement was also made of the Li^6(p,α)He^3 reaction cross section in order to determine its absolute value. The scattering data is consistent with an s- and p-wave phase shift analysis with a p-wave 5/2^- state at about E_p(Lab) = 1.84 Mev, with resonant parameters consistent with the parameters...

Design of a granular pressure cell to be used in soils

Jean Maurice Meuris
In preliminary experimentation, a granular pressure cell was built and tested. From the results obtained, an improved method for the production of granular pressure cells was developed and a second pressure cell was built in order to determine the behavior of granular pressure cells, as designed, under variable external temperature conditions. A third pressure cell was built for laboratory testing. A calibration curve was established and the pressure cell was used satisfactorily in simple laboratory...

Incomplete Charge Transfer in Overlapping Gates Charge Coupled Devices

Amr Mohamed Mohsen
We have developed a numerical simulation of the charge transfer in the overlapping gates charge coupled devices. The transport dynamics were analyzed in terms of thermal diffusion, self-induced fields and fringing fields under all the relevant electrodes and the interelectrode regions with time varying gate potentials. We have also developed a lumped circuit model of charge coupled devices. Using this model simple analytic expressions describing the charge transfer with various clocking waveforms are derived. This...

Lateral stability of thin tapered struts

Paul Christian Durup & Joseph Oscar Weisenberg
From the experimental investigation detailed herein it has been determined, at least for two types of struts, that there is a very close correlation between (1) the experimentally determined buckling load which a given strut will sustain and (2) the critical load determined by the use of Southwell’s method, which does not entail loading the strut to its critical load. By using an initial eccentricity and loads considerably less than the original, the critical load...

Nuclear Magnetic Resonance Studies of α-Chymotrypsin. I. NMR Studies of the Binding of Small Molecule Inhibitors to α-Chymotrypsin. II. NMR Studies of the Interaction of N-TFA-D-Tryptophan Semicarbazide with α-Chymotrypsin. III. ^(13)C-NMR Studies of Methylated α-Chymotrypsin. IV. NMR Studies of Acylated Chymotrypsins

Kenneth Lee Gammon
Part I Magnetic resonance studies of the interaction of N-trifluoro-acetyl-D-(and L-)p-fluorophenylalanine and N-trifluoro-acetyl-D-(and L-)tryptophan with α-chymotrypsin have been carried out at pH 5.0-8.0. The effect of enzyme oligomerization and competitive inhibition have been quantitatively accounted for. The trifluoro- acetyl group of the D-isomer of both inhibitors is directed toward the active site of the enzyme, while that of the L-isomers is directed toward Ser 214. The aromatic side chain of all inhibitors resides in the...

Packet-switched on-chip FPGA overlay networks

Nachiket Ganesh Kapre
As we scale to larger chip capacities, it becomes possible to map large, concurrent applications to programmable fabrics. These applications often have irregular and dynamic communication requirements. Packet-switched networks provide efficient implementations for such applications on these fabrics. In this research, we show how to engineer high-performance packet-switched on-chip networks and provide quantitative comparisons between different kinds of these networks. We analyse different network topologies and justify selection of topologies based on experimental results. We...

Cohesive models of fatigue crack growth and stress-corrosion cracking

Olivier Thanh Nguyen
The aim of this dissertation was to develop models of fatigue crack growth and stress-corrosion cracking by investigating cohesive theories of fracture. These models were integrated in a finite-element framework embedding a contact algorithm and techniques of remeshing and adaptive meshing. For the fatigue model, we developed a phenomenological cohesive law which exhibits unloading-reloading hysteresis. This model qualitatively predicts fatigue crack growth rates in metals under constant amplitude regime for short and long cracks, as...

Optical Fiber Taper Coupled Glass Microsphere Resonators

Ming Cai
This thesis studies optical fiber taper coupled dielectric microsphere resonators and their applications. Fundamental properties including ideal coupling and critical coupling in an optical fiber taper to fused silica glass microsphere coupling system is investigated both theoretically and experimentally. A symmetrical dual-taper coupling configuration is proposed to obtain highly efficient power transfer from the taper coupler to the microsphere resonator. Applications as channel add/drop filters and microsphere lasers are also demonstrated. The physical essence of...

Burial environment, diagenesis, mineralogy, and MG & SR contents of skeletal carbonates in the Buckhorn asphalt of Middle Pennsylvanian age, Arbuckle Mountains, Oklahoma

Richard Lane Squires
The Buckhorn asphalt quarry in the northern part of the Arbuckle Mountains, Oklahoma, contains chemically well preserved marine invertebrate fossils of Middle Pennsylvanian age. The main purpose of this investigation was to study the chemistry of these fossils, and at the same time analyze the geologic setting of the deposits containing the fossils. Due to early sealing by oil, many of the shells still have the original aragonite and nacreous luster. The oil prevented the...

Part I. The Structure of 1, 2-Dimethylnorbornyl Cation. Part II. The Relative Stabilities of Some Tertiary Aliphatic Cations.

James Thomas McFarland
Part I. The pmr spectrum of 1,2-dimethylnorbornyl cation indicates that the Wagner-Meerwein rearrangement is rapid on the nmr time scale at -100° C. Furthermore the protons at C-6 are deshielded by 1.3 ppm with respect to the protons at C-5. This is consistent with the nonclassical structure for this cation. Part II. Mixtures of organic chlorides have been forced to compete for less than one equivalent of antimony penta-fluoride in order to judge relative cation...

Topics in the Analysis, Measurement, and Design of High-Performance Switching Regulators

Arthur Raymond Brown
This thesis treats several issues in the analysis, measurements and design of high-performance switching regulator systems. In Part 1 the high-frequency capabilities of two switching regulator modeling techniques, state-space averaging and discrete modeling, are compared, using the subharmonic instability in current-programmed regulators as a test. As a result of this comparison, a new small-signal, linear, time-invariant modeling technique, called sampled-data modeling, is developed. This new method retains the continuous form of state-space averaging but also...

Lower hybrid current drive experiments on the encore tokamak

Lawrence Henry Sverdrup
The work of this thesis concerns a technological aspect of a tokamak fusion power reactor. A toroidal current in tokamaks is necessary for plasma equilibrium. Ohmic heated tokamaks are inherently pulsed devices since the toroidal plasma current is essentially a single turn secondary of a transformer. A pulsed power reactor is undesirable for a number of reasons including thermal fatigue to material structures and other mechanical cycling effects. Various means to drive a continuous current...

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