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Neuro Fuzzy Reasoning For Pattern Classification And Object Recognition., Jayati Ghosh Dr.

Doctoral Theses

In real world, pattern classification and object recognition problems are faced with fuzzi- ness that is connected with diverse facets of cognitive activity of the human being. An origin of sources of fuzziness is related to labels expressed in feature space as well as to labels of classes taken into account in classification and /or recognition procedures. Though a lot of scientific efforts have already been dedicated to pattern recognition problems, especially to classification procedures, still pattern recognition is confronted with a continuous challenge coming from a human being who can perform lot of ex- tremely complex classification tasks by …

Physical And Chemical Climate In The Nepal Himalaya, Arun Bhakta Shrestha

Doctoral Dissertations

The physical climate of the Himalaya is governed by monsoon circulation, a primary source of moisture to the region. To date, little research has focused on the physical and chemical climate in the Himalaya, while not much is known about the chemical climate there. This dissertation is a first attempt to investigate both the physical and chemical aspects of climate in the Nepal Himalaya with the objective of documenting current conditions and past trends as well as laying the foundation for investigations of their inter-relationship in the future.

Temperature and precipitation records from a network of meteorological station in Nepal …

Evolutionary Effects Of Irradiation In Cataclysmic Variables., Patrick Joseph Mccormick

LSU Historical Dissertations and Theses

We developed a simple stellar computational model consisting of two concentric polytropic shells in order to investigate compact binary evolution. In this thesis we focus the investigation on the effects of irradiation on the orbital evolution of cataclysmic variables (CVs). In these systems, when the companion is illuminated by a fraction of the accretion luminosity, the orbital evolution consists of irradiation-driven limit cycles on thermal timescales. These cycles are superimposed on the secular evolution toward shorter periods due to systemic angular momentum losses. When the irradiation instability is enhanced by consequential angular momentum losses $j\sb{\rm CAML}$ the net effect is …

Photoionization Studies Of Intramolecular Dynamics: A Closer Look., Chuanyong Wu

LSU Historical Dissertations and Theses

Using synchrotron radiation as an excitation source, dispersed fluorescence measurements of two different molecular systems are presented in this dissertation with the intention to study the two fundamental aspects of shape resonances-complexity and completeness. $\rm C\sb6F\sb6$ is a relative large and complex molecule in the sense that nonradiative transitions can take place unimolecularly in the free species. The elucidation of the ionization dynamics of this molecule helps to bridge the gap from simple molecules to matter in condensed phases. In the $\rm 2a\sb{2u}\sp{-1}$ photoionization study of $\rm C\sb6F\sb6,$ the non-Franck-Condon behavior of the vibrational distributions at around 20 eV indicates …

Energy Flow And Non-Guiding Center Effects In The Earth's Magnetotail, Ioannis Dimitrios Kontodinas

Doctoral Dissertations

The purpose of this study is to investigate energy transfer processes in the Earth's magnetotail. An equilibrium, two-dimensional magnetic field model is used to simulate the mid-tail region. Groups of particles are traced in the model magnetic field and the groups are combined to generate a self-consistent two-dimensional current sheet. Two thin current sheets are generated with thicknesses characteristic of a substorm growth phase. One current sheet contains Speiser-type particles only and the other one contains mostly Speiser-type and some trapped particles. It is found that the two current sheets show differences in energy flow processes and pressure anisotropies due …

Fluid-Structure Interaction In Taylor-Couette Flow, Martin Horst Willi Kempf

Doctoral Dissertations

The linear stability of a viscous fluid between two concentric, rotating cylinders is considered. The inner cylinder is a rigid boundary and the outer cylinder has an elastic layer exposed to the fluid. The subject is motivated by flow between two adjoining rollers in a printing press. The governing equations of the fluid layer are the incompressible Navier-Stokes equations, and the governing equations of the elastic layer are Navier's equations. A narrow gap, neutral stability, and axisymmetric disturbances are assumed. The solution involves a novel technique for treating two layer stability problems, where an exact solution in the elastic layer …

Ground State Of (16)O, Bogdan Mihaila

Doctoral Dissertations

We use the coupled cluster expansion (exp(S) method) to solve the many-body Schrodinger equation in configuration space in a configuration space of 35 $\hbar\omega.$ The Hamiltonian includes a nonrelativistic one-body kinetic energy, a realistic two-nucleon potential and a phenomenological three-nucleon potential. Using this formalism we generate the complete ground state correlations due the underlying interactions between nucleons. The resulting ground state wave function is used to calculate the binding energy, the one- and two-body densities for the ground state of $\sp{16}$O. The problem of center-of-mass corrections in calculating observables has been worked out by expanding the center-of-mass correction as many-body …

Spin-Exchange Polarized (3)He Using Optically Pumped Alkali Atoms For Magnetic Resonance Imaging And Neutron Spin-Filters, Vance Reid Pomeroy

Doctoral Dissertations

The past several years have witnessed an increase in applications of polarized noble gases. In particular, the development of high power lasers has enabled the realization of dense, highly polarized samples of $\sp3$He. We report here the development of a system to produce high density, highly polarized samples of $\sp3$He gas. We developed a liquid helium system to cryogenically increase the density of $\sp3$He gas to pressures exceeding 10 atmospheres. We developed a system based on adiabatic fast passage nuclear magnetic resonance to measure and monitor the $\sp3$He nuclear polarization. Polarizations as high as 64% were measured and cells with …

Effects Of Non-Maxwellian Auroral Source Electrons, Eric Edward Dors

Doctoral Dissertations

The auroral current density-voltage and energy flux density-voltage relationships are derived under the assumption that magnetospheric electrons above the auroral acceleration region are described by the $\kappa$ distribution function. To illustrate the effects of this boundary condition on auroral precipitation, a two dimensional model of auroral electrodynamics similar to that of Lyons (1980) has been developed by imposing current continuity in the auroral zone. The current carried by precipitating magnetospheric electrons inside auroral arcs connects to return current regions at the arc edges via ionospheric Pedersen currents. A key feature is the ability to parameterize the magnetospheric boundary electron population …

Source And Acceleration Of Energetic He(+) Ions At The Earth's Bow Shock, Kemei Wang

Doctoral Dissertations

This thesis have presented the first detailed study of the sources and the acceleration of energetic He$\sp+$ ions in front of the Earth's bow shock, using data from AMPTE/IRM and AMPTE/CCE.

Based on observations of energetic He$\sp+$ ions during an event when the bow shock was an almost perfect perpendicular shock, we compared the results of a simulation to the observed event. The model provides a good quantitative description of the phase space distribution of the gyrating ions. A large portion (approximately 63%) of the incident pickup ions are reflected and gain energy in the interaction. It is also consistent …

Measurement Of The Cosmic Diffuse Gamma-Ray Spectrum From 800 Kev To 30 Mev, Srinivas Cheenu Kappadath

Doctoral Dissertations

The Cosmic Diffuse Gamma-Ray (CDG) spectrum between 800 keV and 30 MeV has been measured with the Imaging Compton telescope COMPTEL, aboard the Compton Gamma Ray Observatory. COMPTEL is well suited to measure the CDG flux because of its large detection area, wide field-of-view ($\sim$1.5 sr), low background and long exposure times. The major difficulty in measuring the CDG radiation at MeV energies is the intense instrumental background. The instrumental background in COMPTEL is created mainly in the surrounding material. The striking feature of the pre-COMPTEL CDG spectrum was an apparent flattening between 1 and 10 MeV. A simple power …

Some Observations Of Magnetic Clouds And Simulations Of A Normal Fast Shock Interaction With An Idealized Magnetic Cloud, Laurence X. Janoo

Doctoral Dissertations

We looked at three magnetic clouds observed by the WIND satellite and find that though they are temporally the same, their effects on the Earth were different. The magnetopause is slightly expanded for all the three clouds from its average position during the Bz<0 phase of the clouds and in the Bz<0 phase there was a compression of the magnetopause taking place. During the Bz<0 phase of the October 1995 cloud the bow shock expanded from its average position much more then the January 1997 but the May 1996 cloud hardly affected the Earth's bow shock position during this phase. For the later Bz<0 phase, we find that all three clouds compressed the bow shock closer to the Earth from its average position. We studied a number of discontinuities in the field and plasma observations for the October 18--19, 1995 magnetic cloud. Except for the front cloud boundary, which was a tangential discontinuity, all other discontinuities were rotational. We also could identify 3 different coherent structures within the October 18--19, 1995 cloud. We also found regions for which no coherent structure existed.

From our simulations of a shock with a static force-free Lundquist flux tube, we find that the width of the tube will decrease but the boundaries of the tube were still clearly defined. The magnetic field components retain their original orientation but with an increased amplitude. Depending on the density ratio's between the tube and surrounding …

Magnetic Field Evolution In Neutron Stars., Erik Jordan Young

LSU Historical Dissertations and Theses

Magnetized neutron stars provide the basic model for radio pulsars. They also play a fundamental role in the theory of pulsating X-ray sources and explaining the origin of millisecond radio pulsars. In an effort to better understand these interesting and fundamentally important astrophysical systems, this dissertation studies the magnetic evolution of neutron stars with a dipole field supported in the crust. We explore their evolution both as isolated systems and as accreting objects in binary systems. We investigate how the incorporation of the gravitational field of the neutron star core into the spacetime occupied by a dipole field in the …

Pressure-Induced Changes In Structural And Mechanical Properties Of Gallium Arsenide And Nanophase Silicon Carbide Using Parallel Molecular Dynamics Simulations., Alok Chatterjee

LSU Historical Dissertations and Theses

Large-scale parallel molecular-dynamics (MD) simulations are performed to investigate properties and processes in nanophase silicon carbide (n-SiC) and gallium arsenide (GaAs) under pressure. These simulations involve 10 6 atoms interacting via realistic interatomic potentials. Structure and sintering of crystalline n-SiC are also investigated with neutron scattering experiments performed at the Intense Pulsed Neutron Source Division (IPNS), Argonne National Laboratory. Both MD simulations and neutron scattering experiments indicate the onset of sintering around 1500K. During sintering, the pores shrink in size while maintaining their morphology: Their fractal dimension remains ∼2.4 and their surface roughness exponent is ∼0.45. The pair distribution functions …

High-Frequency Giant Magnetoresistance In Evaporated Cobalt/Copper Multilayers Deposited On Silicon(111) And Silicon(100)., Tim. Rausch

Electronic Theses and Dissertations

We report Giant Magnetoresistance (GMR) in Co/Cu multilayers deposited using high vacuum electron beam evaporation on Si(111) and Si(100). Samples grown on Si(111) show enhanced magnetoresistance and coercivity, which may be attributed to ill-defined interfacial boundaries between successive layers. Previous work exploring the frequency dependency of GMR has been done using microwave techniques to indirectly determine GMR. Our magnetoresistance data was obtained by replacing one side of a square loop antenna with a Co/Cu multilayer and measuring the impedance. No effect on the magnitude of the GMR, due to high frequency test signals, was observed for a frequency range from …

New Relativistic Solutions For Classical Charges In An Electromagnetic Field., Yuan. Yao

Electronic Theses and Dissertations

The well-known Lorentz-force equation is expressed covariantly in a new eigenspinor formalism. The eigenspinor in classical electrodynamics arises as an element of bilinear Lorentz transformations in the framework of the Clifford algebra Cℓ3. The paravector subspace of the algebra, a four-dimensional space defined to contain scalars and spatial vectors, shares the metric structure of Minkowski spacetime. With the flexible advantage of Clifford algebras in vector operations and the almost magical property of idempotent projectors of the algebra, the eigenspinor approach simplifies computations and aids geometrical intuition in problems involving the relativistic motion of charged particles. The eigenspinor method is also …

Calculation Of Hyperfine Shifts Of 2s And 2p States Of Heliumlike Atoms Up To Z = 10., Limin. Pan

Electronic Theses and Dissertations

The hyperfine shifts of 2S and 2P states of heliumlike atoms from helium to neon (both stable and unstable isotopes) have been calculated with accuracy better than 0.1 MHz. The fine structure and hyperfine structure parameters ( CS1,1,CS 1,0,CP1,1, CP1,0,D1, E1,1 and E1,0 ) are calculated using the double-basis-set wavefunctions in Hylleraas coordinates developed by Drake. Hyperfine shifts due to the electric quadrupole interaction, the Breit relativistic, QED and finite nuclear size effects have been included in the calculation. Our results are in good agreement with the recent experimental data.Dept. of Physics. Paper copy at Leddy Library: Theses & Major …

The Structure And Stability Of Selected, 2-D Self-Gravitating Systems., Saied W. Andalib

LSU Historical Dissertations and Theses

Models of radially and vertically extended self-gravitating disks orbiting around a central point mass are relevant to the dynamics of astrophysical systems and are thought to be common in many galaxies. The gravity driven instabilities in these accretion disks are now believed to be a possible mechanism for star formation via disk fragmentation (Shu, Adams, & Lizano 1987, Adams, Rudin & Shu 1989; Christodoulou 1995). We quantify these regions of instability using a simple toroidal model of an accretion disk. We choose the two-dimensional axisymmetric, incompressible slender disks to examine and map out these principal modes of gravity driven instabilities. …

The Selective Digital Integrator: A New Device For Modulated Polarization Spectroscopy., Aljosa Vrancic

LSU Historical Dissertations and Theses

A new device, a selective digital integrator (SDI), for the acquisition of modulated polarization spectroscopy (MPS) signals is described. Special attention is given to the accurate measurement of very small (AC component of interest $<$10$\sp{-3}$ x DC component), rapidly modulated ($\sim$50 kHz) signals at or below noise levels. Various data acquisition methods and problems associated with the collection of modulated signals are discussed. The SDI solves most of these problems and has the following advantages: it provides the average-time resolved profile of a modulated signal; it eliminates errors if the modulation is not sinusoidal; it enables separate measurements of the various phases of the signal modulation cycle; it permits simultaneous measurement of absorption, circular dichroism (CD) and linear dichroism (LD) spectra; it facilitates 3-D absorbance measurements; it has a wide gain-switching-free dynamic range (10 orders of magnitude or more); it offers a constant S/N ratio mode of operation; it eliminates the need for photomultiplier voltage feedback, and it has faster scanning speeds. The time-resolution, selectivity, wide dynamic range, and low-overhead on-the-fly data processing are useful for other modulated spectroscopy (MS) and non-MS experiments such as pulse height distribution and time-resolved pulse counting measurements. The advantages of the MPS-SDI method are tested on the first Rydberg electronic transitions of (+)-3-methylcyclopentanone. The experimental results validate the predicted SDI capabilities. However, they also point to two difficulties that had not been noted previously: the presence of LD in a gaseous sample and a pressure-dependence of the relative peak heights of the CD spectrum. Models for these anomalies are proposed. The presence of the oscillatory LD (but not an LD background) is explained with a sample cell model based on the observed polarization-dependent time-resolved profiles of transmitted light intensity. To obtain expressions for these intensities, a theoretical background, which provides a new approach to the treatment of light/matter interaction, is included as an Appendix. To explain the second anomaly, present only at high optical densities, a model based on the presence of scattered light is introduced and verified. The mode of correction for the scattering problem is outlined.

Nanostructure Modeling In Oxide Ceramics Using Large Scale Parallel Molecular Dynamics Simulations., Timothy J. Campbell

LSU Historical Dissertations and Theses

The purpose of this dissertation is to investigate the properties and processes in nanostructured oxide ceramics using molecular-dynamics (MD) simulations. These simulations are based on realistic interatomic potentials and require scalable and portable multiresolution algorithms implemented on parallel computers. The dynamics of oxidation of aluminum nanoclusters is studied with a MD scheme that can simultaneously treat metallic and oxide systems. Dynamic charge transfer between anions and cations which gives rise to a compute-intensive Coulomb interaction, is treated by the O(N) Fast Multipole Method. Structural and dynamical correlations and local stresses reveal significant charge transfer and stress variations which cause rapid …

Measurement Of The Cross Section For Elastic Scattering Of Electron Neutrinos On Electrons., Neville Dinyar Wadia

LSU Historical Dissertations and Theses

In this dissertation, we measure the cross section for the elastic scattering of electron neutrinos on electrons. We use data from the LSND experiment which is located at the Los Alamos Neutron Scattering Center at Los Alamos National Laboratory, New Mexico. The neutrino beam is produced when an 800 MeV proton beam from a linear accelerator is incident on a target located 29.8 m from the detector. The LSND veto system allows us to reject charged cosmic-ray particles entering the detector with high efficiency. The detector consists of 180 tons of mineral oil, to which a small quantity of scintillator …

M1 Strength Distributions In Deformed Nuclei., Thomas Georg Beuschel

LSU Historical Dissertations and Theses

The Elliott SU(3) Model, extended via pseudo-spin for heavy nuclei, is used to study low-lying magnetic dipole excitations in deformed nuclei which axe known as "scissors" modes. Proton and neutron degrees of freedom are handled explicitly and a system Hamiltonian that preserves SU(3) symmetry and one that includes single particle energies as well as quadrupole-quadrupole and pairing two-body interactions are considered. Starting from a basic nuclear Hamiltonian that preserves SU(3) symmetry, a microscopic interpretation of the "scissors" mode of the Two Rotor Model is realized through a linear mapping between invariants of the rotor group and SU(3). The model allows …

Laser-Induced Fluorescence Studies Of Water By Electron Impact., Tarek Hussein. Harb

Electronic Theses and Dissertations

Using a magnetically collimated electron beam crossed with a jet-cooled molecular beam, the break-up of water into slow ground state OH radicals has been probed using Laser Induced Fluorescence (LIF). Particular attention is given to the near threshold region where the relative cross sections for the production of OH(A, v = 0) and OH(X, v = 0) are obtained and compared to each other. The similarity between the shapes and appearance energies of the two cross sections allow us to conclude that production of the OH(A) and OH(X) states are closely related. The fact that little evidence is obtained for …

Variational Calculations For General Three-Body Systems., Mark Michael. Cassar

Electronic Theses and Dissertations

A general study of the bound states for the quantum mechanical three-body problem is presented over a broad range of particle masses. The purpose is to identify improved methods for constructing the variational wave functions in terms of the Hylleraas interparticle coordinates r 1, r2, and r12. A new nonlinear parameter is introduced so that distance scales can be set independently for all three coordinates. Significant improvements are found, particularly as the particle masses approach equality and mass polarization effects become large. As a pilot project, high precision variational calculations are carried out for the 1s2 1S ground state of …