The dichroism in amorphous As2Se3 induced by a polarized beam of near band-gap light (λ = 632.8 nm) was measured in films that ranged in thickness from 0.25 µm to 1.93 µm. Most noncrystalline materials are initially isotropic and homogeneous. When amorphous As2Se3 (a chalcogenide glass) absorbs an intense pump-beam of polarized light, the absorption coefficient for light polarized in the same direction as the pump-beam is less than for the perpendicular polarization, i.e. the sample becomes anisotropic (dichroic). The induced dichroism is reversible by rotating the polarization of the pump light by 90°. Induced dichroism is potentially useful in various photonic devices including optical switches, optical memory, and photowritable polarizers.<p>Several aspects of photoinduced anisotropy in a-As2Se3 have been analyzed:<p>(i) rate of photoinduced anisotropy buildup as a function of inducing beam intensity and sample thickness, <p>(ii) the kinetics of the photoinduced anisotropy buildup in terms of a stretched exponential curve, <p>(iii) the stretched exponent, β, as a function of inducing beam intensity and sample thickness, <p>(iv) reversibility of the photoinduced anisotropy, (v) saturation level of photoinduced anisotropy as a function of inducing beam intensity and sample thickness.<p>The anisotropy buildup kinetics has been found to follow a stretched exponential behavior and that there exists an inverse relationship between the pump intensity and the time constant, τ. The τ(I) vs intensity (I) relationship more closely follows a logistic dose response curve than a simple straight line or power law relationship. There exists a direct relationship between the time contact  and the sample thickness, where a longer anisotropy buildup time is required as the sample thickness increases. The stretched exponent, β, was found to be approximately 0.6 and has a slight dependence on the inducing light intensity. The correlation of the stretching exponent, β, to sample thickness, L, was found to have a weak inverse relationship, that is β tends to decrease as the sample thickness increases.<p>The findings in this work demonstrate that the anisotropy orientation could be changed indefinitely since it was found that even after 100 orientation changes the anisotropy saturation had no measurable fatiguing. The anisotropy saturation level was found to be independent of the inducing beam intensity and linearly proportional to the sample thickness.

The influence of manganese (Mn) addition on the tensile properties of recovery-annealed aluminum alloy sheet was studied. After 200 ~ 220¢X C annealing, these alloys exhibit hardening as compared to the as-rolled state. Besides the amount of Mn in solution, the presence of Fe and Si in these alloys was also a vital factor responsible for the hardening. These recovery annealed aluminum alloy sheets show increased tensile elongation with increasing annealing temperature, which is mainly due to the contribution of post-uniform elongation (PUE). The plastic deformation during PUE is associated with development of fine slip bands distributed in the gauge length of the specimen. It was noted that after recovery anneal, the alloy with 0.74 wt% Mn exhibit better combination of strength and ductility as compared to alloys with lower Mn content. In general, these alloys in partially annealed condition show poor tensile ductility at RT, which is mainly attributed to the low work hardening rate associated with the UFG structure. These partially annealed aluminum alloys exhibit highly anisotropic tensile properties, specially a rather poor ductility along the direction of 45o or 90o from the rolling direction at RT. The poor ductility in 45o or 90o direction could be related to flow localization associated with intense shear banding. Discontinuous yielding plays a pivotal role to trigger the flow localization which is affected by the strain path change. However, for alloys tested at 77 K in 45¢X or 90¢X direction, the deformation proceeds by the propagation of L&#x00FC;ders band initially and followed by strain hardening. In general, the tensile elongation can be enhanced greatly irrespective of the stress direction, because a higher work hardening rate can be maintained due to reduced dynamic recovery rate. The yield stress is orientation dependent, which is in the order of 90¢X > 0¢X > 45¢X. The anisotropic tensile behavior has its origin in the rolling texture. The Schmid factor analysis indicates that specimens tested in 45o direction would have lower yield strength as compared to those tested in 0o or 90o direction. Both experimental measurements and simulation indicate that after 30% tensile straining, the copper texture in the partially annealed aluminum alloy is enhanced 0¢X test, and the brass texture is enhanced in 90¢X test, while the texture distribution does not change significantly in 45¢X test. It is suggested that the texture evolution during tensile straining has significant effect on the anisotropy of work hardening rate.

Turbidite reservoirs in deep-water depositional systems, such as the oil fields in the offshore Gulf of Mexico and North Sea, are becoming an important exploration target in the petroleum industry. Accurate seismic reservoir characterization, however, is complicated by the heterogeneous of the sand and shale distribution and also by the lack of resolution when imaging thin channel deposits. Amplitude variation with offset (AVO) is a very important technique that is widely applied to locate hydrocarbons. Inaccurate estimates of seismic reflection amplitudes may result in misleading interpretations because of these problems in application to turbidite reservoirs. Therefore, an efficient, accurate, and robust method of modeling seismic responses for such complex reservoirs is crucial and necessary to reduce exploration risk. A fast and accurate approach generating synthetic seismograms for such reservoir models combines wavefront construction ray tracing with composite reflection coefficients in a hybrid modeling algorithm. The wavefront construction approach is a modern, fast implementation of ray tracing that I have extended to model quasishear wave propagation in anisotropic media. Composite reflection coefficients, which are computed using propagator matrix methods, provide the exact seismic reflection amplitude for a stratified reservoir model. This is a distinct improvement over conventional AVO analysis based on a model with only two homogeneous half spaces. I combine the two methods to compute synthetic seismograms for test models of turbidite reservoirs in the Ursa field, Gulf of Mexico, validating the new results against exact calculations using the discrete wavenumber method. The new method, however, can also be used to generate synthetic seismograms for the laterally heterogeneous, complex stratified reservoir models. The results show important frequency dependence that may be useful for exploration. Because turbidite channel systems often display complex vertical and lateral heterogeneity that is difficult to measure directly, stochastic modeling is often used to predict the range of possible seismic responses. Though binary models containing mixtures of sands and shales have been proposed in previous work, log measurements show that these are not good representations of real seismic properties. Therefore, I develop a new approach for generating stochastic turbidite models (STM) from a combination of geological interpretation and well log measurements that are more realistic. Calculations of the composite reflection coefficient and synthetic seismograms predict direct hydrocarbon indicators associated with such turbidite sequences. The STMs provide important insights to predict the seismic responses for the complexity of turbidite reservoirs. Results of AVO responses predict the presence of gas saturation in the sand beds. For example, as the source frequency increases, the uncertainty in AVO responses for brine and gas sands predict the possibility of false interpretation in AVO analysis.

Ti3Al based intermetallic alloys are attractive for aerospace and aircraft applications due to their superior high temperature properties. Excellent high temperature superplasticity in the Ti3Al-Nb based alloy has been widely published. However, the alloys become brittle and hard to deform at temperatures below 600oC so that low temperature superplasticity is difficult to develop. In the current super

Interference for adjacent wells may be beneficial to Coalbed-Methane production. The effect is the acceleration of de-watering which should lead to earlier and higher gas rate peaks. It is inherent that permeability anisotropy exists in the coalbed methane formation. It means that the placement of wells (wells configuration) has an effect on the development of coalbed methane field. The effect of Palmer-Mansoori Theory is increasing effective permeability at lower pressures due to matrix shrinkage during desorption. This effect should increase the gas recovery of coalbed methane production. Palmer and Mansoori model should be considered and included to coalbed methane reservoir simulation. These effects and phenomena can be modeled with the CMG simulator. A systematic sensitivity study of various reservoir and operating parameters will result in generalized guidelines for operating these reservoirs more effectively.

Recently, Iwamoto[1] has proposed a passive-matrix LCD called VA-STN-LCD (Verically Aligned Super Twist Nemetic LCD), in which excellent electro-optic (EO) performance under high-multiplexing conditions has been demonstrated. It was pointed out that such a high EO performance was realized by achieving a pretilt angle of about 80 degree. In this study, we want to learn the different EO characteristic of separate pretilt angle and separate chiral-doped concentration of Negative Dielectric Anisotropy nemetic liquid crystal in vertically aligned cell.

Rubbing alignment has been used popularly in display industry. However, the alignment mechanisms of rubbed polymer are still not well understood. The purpose of this study is to investigate the relationship between anisotropy of rubbed polyimide thin film and liquid crystal alignment. In this study, we discuss the effects of surface energy and RAS on the surface roughness and pretilt angle of liquid crystal molecules. RAS is a non-contact optical probing technique developed originally for real-time, in situ monitoring of semiconductor growth . In this technique the normalized difference in reflectivity along two orthogonal directions is measured. Recently, the prospect of using RAS for process control in the fabrication of liquid crystal devices is investigated. On the other hand, we have known that the magnitude of surface energy is related to the strength of molecular bond. We can obtain the variation of surface properties by measuring the difference of surface energy. We found that the RA signal, pretilt angle and surface roughness are increasing with an increase in rubbing strength, but surface energy was decreased..

<p>The recent development in the marine industry with largerships built in sandwich construction and also the use of moreadvanced materials has enforced improvements of design criteriaregarding wrinkling. The commonly used Hoff’s formula isnot suited for the highly anisotropic fibre reinforced sandwichface sheets of today.</p><p>The work presented herein investigates the wrinklingphenomenon. A solution to wrinkling of anisotropic sandwichplates subjected to multi-axial loading is presented. Thesolution includes the possibility of skew wrinkling where thewrinkling waves are not perpendicular to the principal loaddirection. The wrinkling angle is obtained from the solutiontogether with the maximum wrinkling load. This method has beensupported with tests of anisotropic plates subjected touni-axial and bi-axial loading.</p><p>The effect of the face sheet local bending stiffness showsthe importance of including the face sheet stacking sequence inthe wrinkling analysis. The work points out the influence ofthe face sheet local bending stiffness on wrinkling. Threedifferent means of improving the wrinkling load except changingcore material is evaluated. The effect of the differentapproaches is evaluated theoretically and also throughcomparative testing. The transition between wrinkling and pureface sheet compression failure is investigated. Theoreticaldiscussions are compared with compressive test results of twodifferent face sheet types on seven different core densities.The failure modes are investigated using fractography. Theresults clearly show how the actual sandwich compressionfailure mode is influenced by the choice of core material,changing from wrinkling failure to face sheet micro bucklingfailure as the modulus density increases.</p><p>Finally, a new approach is presented where the wrinklingproblem is transferred from a pure stability problem to amaterial strength criterion. The developed theory providesmeans on how to decide which sandwich constituent will failfirst and at which load it will fail. The method give insightto and develop the overall understanding of the wrinklingphenomenon. A very good correlation is found when the developedtheory is compared with both finite element calculations and toexperimental tests.</p><p><b>Keywords:</b>wrinkling, local buckling, imperfection,stability, anisotropy, sandwich</p>

Thesis (M.S.)--Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 96-101).