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2001

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Articles 481 - 490 of 490

Full-Text Articles in Physics

Investigation Of Optical Interference Effects In The Generalized Eikonal Formalism, Nyok Fah Thong Jan 2001

Investigation Of Optical Interference Effects In The Generalized Eikonal Formalism, Nyok Fah Thong

Student Works (2000-2009)

In recent studies, the generalized eikonal equation and the equation of continuity had been shown able to describe wave phenomena, which cannot be obtained by simple geometrical optics. The time dependent generalized eikonal equation, derived from the time dependent Maxwell wave equation, is able to describe dispersion and soliton effects. This method was exten4ed to include diffraction, self-trapping and self-focusing in linear and non-linear media for stationary waves. For cases that have no analytical solution, the generalized eikonal equation and the equation of continuity are solved numerically. The solutions are in good agreement with the solutions obtained from the Fresnel-Kirchhoff …

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The Effect Of Aluminium Oxide And Cerium Oxide As Dispersoids In Chitosan-Lithium Acetate Complexes, Hoi Mien Leow Jan 2001

The Effect Of Aluminium Oxide And Cerium Oxide As Dispersoids In Chitosan-Lithium Acetate Complexes, Hoi Mien Leow

Student Works (2000-2009)

In this study, chitosan with 85% deacetylation was used with Ni(OAc)₂·2H₂O as doping salt and Al₂O₃, or CeO₂ as dispersoid. They were mixed in certain weight percentages and dissolved in 100ml of 0.5% acetic acid solution. These solutions were poured into petri dishes and left at room temperature for film formation. Infrared Spectroscopy has shown that there is interaction between chitosan and LiOAc with and without dispersoid. The peaks are shifted. broadened. split and differs in intensity. The electrical conductivity of all samples was calculated using the bulk resistance value obtained from the complex admittance plot. The highest electrical conductivity …

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Photoelectron Spectroscopy And The Dipole Approximation, Oliver Hemmers, Dennis W. Lindle Jan 2001

Photoelectron Spectroscopy And The Dipole Approximation, Oliver Hemmers, Dennis W. Lindle

Environmental Studies Faculty Publications

Over the past three decades, the dipole approximation has facilitated a basic understanding of the photoionization process in atoms and molecules. Advances in gas-phase photoemission experiments using synchrotron radiation have recently highlighted nondipole effects at relatively low photon energies while probing the limits of the dipole approximation. Breakdowns in this approximation are manifested primarily as deviations from dipolar angular distributions of photoelectrons. Detailed new results demonstrate nondipolar angular-distribution effects are easily observable in atomic gases at energies well below 1 keV, and, in molecules, a previously unexpected phenomenon greatly enhances the breakdown of the dipole approximation just above the core-level …

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Experimental Investigation Of Steel Corrosion In Lead Bismuth Eutectic (Lbe): Characterization, Species Identification, And Chemical Reactions, John Farley, Dale L. Perry Jan 2001

Experimental Investigation Of Steel Corrosion In Lead Bismuth Eutectic (Lbe): Characterization, Species Identification, And Chemical Reactions, John Farley, Dale L. Perry

Transmutation Sciences Materials (TRP)

The goal of the present research is to achieve a basic understanding of corrosion of steels by Lead Bismuth Eutectic (LBE). Liquid LBE is under consideration in the transmuter as both a coolant and a target material. There have been studies of LBE, especially by the Russians, but a fundamental understanding and verification of its role in the corrosion of steels is still very 2 incomplete. Post-experiment testing and analysis will be performed on steel samples that have been in intimate contact with LBE. Chemical alterations and resulting chemical species will be measured at the steel surface. Techniques to be …

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The Procedure For Determining And Quality Assurance Program For The Calculation Of Dose Coefficients Using Dcal Software, A. Arndt, John P. Shanahan, C. Gold, R. Brey, T. Gesell, Phillip W. Patton, Mark Rudin, K. Eckerman, V. Rusetski, S. Pagava Jan 2001

The Procedure For Determining And Quality Assurance Program For The Calculation Of Dose Coefficients Using Dcal Software, A. Arndt, John P. Shanahan, C. Gold, R. Brey, T. Gesell, Phillip W. Patton, Mark Rudin, K. Eckerman, V. Rusetski, S. Pagava

Transmutation Sciences Physics (TRP)

The development of a spallation neutron source with a mercury target may lead to the production of rare radionuclides. The dose coefficients for many of these radionuclides have not yet been published. A collaboration of universities and national labs has taken on the task of calculating dose coefficients for the rare radionuclides using the software package: DCAL. The working group developed a procedure for calculating dose coefficients and a quality assurance (QA) program to verify the calculations completed. The first portion of this QA program was to verify that each participating group could independently reproduce the dose coefficients for a …

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Apex Version 2.0: Latest Version Of The Cross-Platform Analysis Program For Exafs, Nicholas Dimakis, Grant Bunker Jan 2001

Apex Version 2.0: Latest Version Of The Cross-Platform Analysis Program For Exafs, Nicholas Dimakis, Grant Bunker

Physics & Astronomy Faculty Publications

This report describes recent progress on APEX, a free, open source, cross platform set of EXAFS data analysis software. In a previous report we described APEX 1.0 (Dimakis, N. and Bunker, G., 1999), a free and open source code suite of basic X-Ray Absorption Fine Structure (XAFS) data analysis programs for classical data reduction and single scattering analysis. The first version of APEX was the only cross platform (linux/irix/windows/MacOS) EXAFS analysis program to our knowledge, but it lacked important features like multiple scattering fitting, generic format conversion from ASCII to University of Washington (UW) binary-type files, and user friendly interactive …

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Polymer Depletion Interaction Between Two Parallel Repulsive Walls, F. Schlesener, Andreas Hanke, R. Kimpel, S. Dietrich Jan 2001

Polymer Depletion Interaction Between Two Parallel Repulsive Walls, F. Schlesener, Andreas Hanke, R. Kimpel, S. Dietrich

Physics & Astronomy Faculty Publications

The depletion interaction between two parallel repulsive walls confining a dilute solution of long and flexible polymer chains is studied by field-theoretic methods. Special attention is paid to self-avoidance between chain monomers relevant for polymers in a good solvent. Our direct approach avoids the mapping of the actual polymer chains on effective hard or soft spheres. We compare our results with recent Monte Carlo simulations [A. Milchev and K. Binder, Eur. Phys. J. B 3, 477 (1998)] and with experimental results for the depletion interaction between a spherical colloidal particle and a planar wall in a dilute solution of nonionic …

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Controlling The Optical Properties Of A Conjugated Co-Polymer Through Variation Of Backbone Isomerism And The Introduction Of Carbon Nanotubes, A. Dalton, J. Coleman, M. In Het Panhuis, B. Mccarthy, A. Drury, W. Blau, J. Nunzi, Hugh Byrne Jan 2001

Controlling The Optical Properties Of A Conjugated Co-Polymer Through Variation Of Backbone Isomerism And The Introduction Of Carbon Nanotubes, A. Dalton, J. Coleman, M. In Het Panhuis, B. Mccarthy, A. Drury, W. Blau, J. Nunzi, Hugh Byrne

Articles

The need to control the formation of weakly emitting species in polymers such as aggregates and excimers, which are normally detrimental to device performance, is illustrated for the example of the polymer poly(m-phenylenevinylene-co-2,5-dioctyloxy-p-phenylenevinylene), using the model compound, 2,5-dioctyloxy-p-distyrylbenzene as a comparison. Two different methods, namely a Homer-Emmons polycondensation in dimethylformamide (DMF) and a Wittig polycondensation in dry toluene, have been used during synthesis resulting in a polymer with a predominantly trans-vinylene backbone and a polymer with a predominantly cis-vinylene backbone, respectively. Photoluminescence and absorption spectroscopy indicate that the polymer forms aggregate species in solution with spectra that are distinctly red-shifted …

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A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali Jan 2001

A New Compensating Element For A Femtosecond Photoelectron Gun, Bao-Liang Qian, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Design and analysis of a new compensating element for improving the electron pulse front and compressing the pulse duration in a femtosecond photoelectron gun are described. The compensating element is a small metallic cylindrical cavity in which an external voltage is applied in such a way that a special electric field forms and interacts with the electron pulse. This electric field reduces the distances between the faster and slower electrons inside the cavity and efficiently compensates for electron pulse broadening caused by the photoelectron energy spread and space charge effects. Poisson's equation and the equation of motion are solved to …

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Modified Critical Correlations Close To Modulated And Rough Surfaces, Andreas Hanke, Mehran Kardar Jan 2001

Modified Critical Correlations Close To Modulated And Rough Surfaces, Andreas Hanke, Mehran Kardar

Physics & Astronomy Faculty Publications

Correlation functions are sensitive to the presence of a boundary. Surface modulations give rise to modified near surface correlations, which can be measured by scattering probes. To determine these correlations, we develop a perturbative calculation in deformations in height from a flat surface. The results, combined with a renormalization group around four dimensions, are also used to predict critical behavior near a self-affine rough surface. We find that a large enough roughness exponent can modify surface critical behavior.

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