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No description available.

This thesis presents an analytical method based on classical matrix methods for computing the dynamic response of elastic-plastic multi-storey building frames. The method developed is comparatively simple and is of much use for building frames having large number of storeys. By this method, response of multi-storey build­ings could be calculated on high-speed digital computers of high storage capacity. The computer program developed saves huge storage locations and thus makes it possible to analyze multi-storey frames which till now were con­sidered as very difficult. Dynamic response of a two-storey and six-storey frame are shown to demonstrate the utility of the method. / Thesis / Master of Engineering (ME)

This thesis investigates Raman spectra of novel glasses and their correlation with structure for Raman gain applications. Raman gain for all-optical amplification by fibers depends significantly on the cross section for spontaneous Raman scattering allowing to compare signal strength and spectral coverage. We also investigate the relationship between glass structure and the Boson peak (enhancement of the low-frequency vibrational density of states) and report new inelastic neutron scattering spectra for niobium-phosphate glasses. Polarization resolved Raman spectra of glasses based on tellurite and phosphate formers have been measured from 6 – 1500 cm-1 using an excitation wavelength of 514 nm. The Tellurite glasses exhibit Raman Spectra at least 10 times more intense, are more spectrally uniform and possess spectral bandwidths more than a factor of two wider than fused silica. Assignments of the vibrational bands are presented and the compositional dependence of the spectra is discussed with respect to the molecular structure. Significantly high Boson peaks were found in the frequency range from 30-100 cm-1. The Raman gain curves were calculated from the polarized spontaneous Raman spectra. In particular, they show broad and flat band in the low frequency region (50-400 cm-1) suggesting that these glasses may be useful for Raman gain applications extending to very low frequencies. The inelastic neutron scattering spectra of the niobium-phosphate glasses display a pronounced low-frequency enhancement of the vibrational density of states. By averaging over the full accessible wavevector range we obtain an approximate spectral distribution of the vibrational modes. Through direct comparison with the Raman spectra we determine the Raman coupling function which shows a linear behavior near the Boson peak maximum. Possible mechanisms contributing to the low frequency Raman band such as disorder-induced irregular vibrational states are discussed.

This thesis presents the results of an investigation of a multiple degree of freedom (MDOF) structure with hyperelastic bracing using nonlinear and incremental dynamic analysis. New analytical software is implemented in the investigation of the structure, and the study seeks to investigate the effectiveness of hyperelastic bracing as a seismic protection device. Hyperelastic braces incorporate a new idea of a nonlinear elastic material that gains stiffness as the brace deforms. Structural behaviors of particular concern for an MDOF frame are stability, residual displacement, base shear, and dispersion. The structure is analyzed under two ground motion records of varying content, and for two separate P-Delta cases of varying severity. Two sets of hyperelastic braces are investigated for their influence under the two ground motions and two P-Delta cases. Each scenario is analyzed using nonlinear dynamic analyses to investigate the response histories, and Incremental Dynamic Analysis (IDA) to investigate dispersion and the behavior of specific response measures as ground motion intensity increases. IDA curves are created for interstory drift and base shear for comparison between the two response measures. The research shows that the inclusion of hyperelastic braces in the MDOF frame improves the overall stability of the structure and reduces the amount of dispersion and residual displacement. The hyperelastic braces are shown to give positive performance characteristics while not detrimentally increasing system forces under regular service loads. The results highlight the benefit of the unique stiffening properties of hyperelastic braces as a seismic protection device. / Master of Science

<p> A Matrix Stiffness-Modification Technique has been proposed for the inelastic analysis of ·reinforced concrete frames subjected to short term or sustained loads. To check the applicability of the analytical method, two large scale concrete frames were tested under short-term loads and sustained-loads respectively. In addition, data for twenty-two frame tests from other sources has also been compared with the non-linear analysis. Close agreement has. been observed for all the frames considered. It was further concluded that a conventional elastic matrix method using stiffnesses based on a cracked transformed section of concrete does net yield accurate results, especially in the case of sustained loading conditions. From the method developed, comments can therefore be made on present column design practice. </p> / Thesis / Master of Engineering (MEngr)

This work is the result of two separate lines of study into the family of frustrated rare-earth pyrochlores with ferromagnetic interactions. The first is an examination of Yb2Ti2O7 and Ho2Ti2O7 through small angle neutron scattering (SANS) techniques. The sensitivity to anisotropic ferromagnetic correlations of SANS makes it an ideal tool to investigate the anomalous scattering of Yb2Ti2O7 , and to take a closer look into the low Q region of the spin ice Ho2Ti2O7 , where long range dipolar effects modify magnetic scattering. We show that in Yb2Ti2O7 the ferromagnetic order observed by other researchers coexists with short range HHH correlations to 0.03 K. We identify a new feature in Yb2Ti2O7 , a medium range (on the order of 100 ̊A) ferromagnetic correlation which appears to correlate well with the systems heat capacity anomaly. In Ho2Ti2O7 , we observe isotropic magnetic scattering in the low Q region that correlates to the system heat capacity anomaly. The second research project involves the system Ho2Sn2−xTixO7 with x=0,0.5,1,1.5,2. We use SQUID magnetometry and inelastic neutron scattering to examine the effects of B-site disorder on the spin ice system. We find some discrepancies with previous generation instrument results for the crystal electric field (CEF) Hamiltonian, and find results consistent with our previously hypothesized picture of the effects of B-site disorder on the CEF levels. We also observe increased spin dynamics in the disordered compounds, which is consistent with recent theory work predicting a transition to a quantum spin liquid phase in disordered non-kramers spin ice compounds. / Thesis / Master of Science (MSc)

No description available.

No description available.

A three-dimensional finite element code to analyze coupled thermomechanical deformations of composites has been developed. It incorporates geometric nonlinearities, delamination between adjoining layers, and damage due to fiber breakage, fiber/matrix debonding, and matrix cracking. The three damage modes are modeled using the theory of internal variables and the delamination by postulating a failure envelope in terms of the transverse stresses; the damage degrades elastic moduli. The delamination of adjoining layers is simulated by the nodal release technique. Coupled nonlinear partial differential equations governing deformations of a composite, and the pertinent initial and boundary conditions are first reduced to coupled ordinary differential equations (ODEs) by the Galerkin method. These are integrated with respect to time with the Livermore solver for ODEs. After each time step, the damage in an element is computed, and material properties modified. The code has been used to analyze several static and transient problems; computed results have been found to compare well with the corresponding test results. The effect of various factors such as the fiber orientation, ply stacking sequence, and laminate thickness on composite's resistance to shock loads induced by underwater explosions has been delineated. / Ph. D.