This Thesis reports the results of detailed isotopic studies carried out on three main groups of compounds, MMe2(M= Zn,Cd,Hg), MH 4(M= Si,Ge,Sn) and B(OMe)3 (Me&61 12CH 3,13CH3,12CD3). The infrared and Raman spectra of four isotopic species, 12CH 3, 13CH3, 12CD3, 13CD3, of dimethyl zinc, cadmium and mercury have been recorded, the fundamental frequencies corrected for Fermi resonance and anharmonicity and the empirical force field of each compound calculated. By incorporating interaction force constants determined by ab initio methods, semi-empirical force fields have also been calculated for these three compounds. A comparison of the scaled ab initio force fields with the empirical force field shows that properly constructed basis sets which employ effective core potentials are capable of producing results of similar quality to near Hartree-Fock calculations on molecules containing lighter atoms. The absolute infrared intensities in the 12CH3 isotopes of dimethylzinc, cadmium and mercury and in (12CD3)2Zn have been measured and the associated electrooptical parameters and atomic polar tensors calculated. The electrooptical models which appeared capable of explaining hydrocarbon infrared intensities have been shown to be invalid for these organometallic compounds. Atomic polar tensors have proved to be the more satisfactory means of representing infrared intensities generally. The absolute infrared intensities of SiH4, GeH4 and SnH4 have been remeasured in order to clarify the confusion over previous conflicting results. The unusual intensity patterns and the technological importance of these compounds in chemical vapour deposition made more precise intensity data desirable. The link between the gas phase intensities of these compounds and their gas-crystal shifts has been discussed and the electrooptical parameters and atomic polar tensors have been calculated for all three compounds. Three isotopes of trimethoxy boron; B(O12CH3)3, B(O13CH 3)3 and B(O12CD3)3 have been prepared and their infrared and Raman spectra recorded. The new 13C shifts allowed the spectra to be analysed in greater detail than was previously possible. A rudimentary force field of trimethoxy boron has also been calculated.

We consider one-dimensional longitudinal vibrations of a rigid rod with a nonuniform cross-section, fixed at its ends with lumped masses and springs. The cross-section inertia effects are taken into account on the basis of the Rayleigh theory. The equation of motion and the boundary conditions are derived from Hamilton’s variational principle. The characteristic equation is constructed and the eigenvalues for the harmonic vibrations of the rod are calculated. It is shown that the eigenvalues are bounded from above. Two types of the orthogonality of the eigenfunctions corresponding to the eigenvalues are discussed. The Green function is constructed for the problem of forced vibrations of the rod governed by a linear fourth-order partial differential equation, which involves mixed derivatives. Exact solutions of the rod vibration problems are found for rods with constant and conical cross-sections. Rigid isotropic waveguides are often used for generating, transmitting, and amplifying mechanical vibrations, for example, in acoustic transducers. Theoretical investigation of acoustic, mechanical, and electromagnetic waveguides is usually based on the analysis of second-order wave equations. This approach is justified in descriptions of the wave propagation in relatively thin and long rigid rods. As was shown by Rayleigh [1], the error due to the neglect of the transverse motion of the rod is proportional to the square of the ratio of the characteristic section radius to the length of the rod (aspect ratio). For a more accurate analysis of the longitudinal vibrations of a relatively thick and short rod, the rod deformation in the transverse direction must also be taken into account. The approach to the analysis of the vibrations of a thick and short rod used in this study is based on the theory of longitudinal vibrations of a rod, in which the effects due to the transverse motion are taken into account (the corresponding mathematical model is called the Rayleigh rod). The equation of motion and the boundary conditions for the onedimensional longitudinal vibrations of the Rayleigh rod with variable cross section and ends fixed by means of lumped masses and springs are derived from Hamilton’s variational principle. As a result, we arrive at a linear fourth-order partial differential equation with variable coefficients, which involves mixed derivatives. Previously, approximate analytical methods, such as the Galerkin method [2] and the method based on the expansion of the solution in a power series in the Poisson coefficient [3], were used for solving this equation. The frequencies of the natural vibrations of a cylindrical rod with rigidly fixed ends were determined in [4, pp. 159, 160]. In this study we use the method of the separation of variables based on the exact solutions of the equations of motion of the Rayleigh rod, which makes it possible to construct the Green function. A similar approach to an analysis of the longitudinal vibrations of stepped rigid waveguides described by second-order wave equations was applied in [5, 6].

Isotropic radiators are known to be a useful tool across a wide range of applications, from applications in light dosimetry in human/animal tissue to calibration of sensitive laboratory equipment. While the bene ts are known, constructing such a tool has proven to be di cult. Currently, there are no commercially available isotropic or nearly isotropic radiators. Previous attempts at constructing an isotropic radiator have been limited to a 10% isotropy level. This thesis covers the design, construction, and analysis of a nearly isotropic optical light source. The constructed source has extrema anisotropies, over a solid angle of approximately 3 steradians, of +\-3% (with 95% of that solid angle being within +\- 2.5% anisotropy). / Graduate

No description available.

No description available.

<p> The semi-classical path-integral method for finding the magnetoconductivity is specialised to cubic one-electron metals having a spherical Fermi surface, isotropic effective mass and anisotropic scattering times. Properties of the conductivity and resistivity tensors are deduced for this special case, in more detail for high magnetic fields. The magnetoconductivity for potassium, and the quantities derived from it - magnetoresistance and induced torque - are calculated as functions of temperature, field strength, impurity concentration and crystal orientation. Comparison is made with experimental results.</p> / Thesis / Master of Science (MSc)

The production of an isotropic source or detector by fixing a small resin sphere onto one end of an optical fibre is discussed. The potential application of these fibres to Photochemotherapy is reviewed. Isotropic fibres are used as both sources and detectors in experiments designed to measure the amount of light loss in a 1% solution of Neutralipid (an intravenous nutrient supply). Determination of light loss in this solution is important in one application of Photochemotherapy where an estimate of the irradiation time is required. / Thesis / Master of Science (MSc)

Unbound granular materials are generally used in road pavements as base and subbase layers. The granular materials provide load distribution through aggregate contacts to a level that can help the subgrade to withstand the applied loads. Several research studies have shown that unbound pavement layers exhibit anisotropic properties. Anisotropy is caused by the preferred orientation of aggregates and compaction forces. The result is unbound pavement layers that have higher stiffness in the vertical direction than in the horizontal direction. This behavior is not accounted for in the design and analysis procedures included in the proposed AASHTO 2002 design guide. One of the objectives of this study is to conduct a comparative analysis of flexible pavement response using different models for unbound pavement layers: linear isotropic, nonlinear isotropic, linear anisotropic and nonlinear anisotropic. Pavement response is computed using a finite element program. The computations from nonlinear isotropic and anisotropic models of unbound layers are compared to the AASHO field experimental measurements. The second objective is to analyze the influence of using isotropic and anisotropic properties for the pavement layers on the performance of flexible pavements calculated using the AASHTO 2002 models. Finally, a comprehensive sensitivity analysis of the proposed AASHTO 2002 performance models to the properties of the unbound pavement layers is conducted. The sensitivity analysis includes different types of base materials, base layer thicknesses, hot mix asphalt type and thickness, environmental conditions, and subgrade materials.

Diffusion can be classified as either normal or anomalous. A variety of experimental systems are evaluated to classify diffusion. Potential regressions and step size distributions are analysed. Nor-mal diffusion holds except where flocculation takes place, or where concentrations of cationic starches are high or with cationic starches and latex together. In these cases, subdiffusion takes place. Furthermore, limiting values are used to calculate diffusion coefficients. Diffusion of non-spherical particles is covered as well, here tested on microcrystalline cellulose.

Unbound granular materials are generally used in road pavements as base and subbase layers. The granular materials provide load distribution through aggregate contacts to a level that can help the subgrade to withstand the applied loads. Several research studies have shown that unbound pavement layers exhibit anisotropic properties. Anisotropy is caused by the preferred orientation of aggregates and compaction forces. The result is unbound pavement layers that have higher stiffness in the vertical direction than in the horizontal direction. This behavior is not accounted for in the design and analysis procedures included in the proposed AASHTO 2002 design guide. One of the objectives of this study is to conduct a comparative analysis of flexible pavement response using different models for unbound pavement layers: linear isotropic, nonlinear isotropic, linear anisotropic and nonlinear anisotropic. Pavement response is computed using a finite element program. The computations from nonlinear isotropic and anisotropic models of unbound layers are compared to the AASHO field experimental measurements. The second objective is to analyze the influence of using isotropic and anisotropic properties for the pavement layers on the performance of flexible pavements calculated using the AASHTO 2002 models. Finally, a comprehensive sensitivity analysis of the proposed AASHTO 2002 performance models to the properties of the unbound pavement layers is conducted. The sensitivity analysis includes different types of base materials, base layer thicknesses, hot mix asphalt type and thickness, environmental conditions, and subgrade materials.