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2001

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Articles 481 - 490 of 490

Full-Text Articles in Physics

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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Comparing Classical And Quantum Dynamics Of Strong-Field Double Ionization, R. Panfili, J. H. Eberly, Stanley L. Haan Jan 2001

Comparing Classical And Quantum Dynamics Of Strong-Field Double Ionization, R. Panfili, J. H. Eberly, Stanley L. Haan

University Faculty Publications and Creative Works

We compare quantum mechanical and fully classical treatments of electron dynamics accompanying strong field double ionization. The major features seen in quantum mechanical simulations, including the double-ionization jets, are reproduced when using a classical ensemble of two-particle trajectories.

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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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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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Probing The Strong Boundary Shape Dependence Of The Casimir Force, Thorsten Emig, Andreas Hanke, Ramin Golestanian, Mehran Kardar Jan 2001

Probing The Strong Boundary Shape Dependence Of The Casimir Force, Thorsten Emig, Andreas Hanke, Ramin Golestanian, Mehran Kardar

Physics & Astronomy Faculty Publications

We study the geometry dependence of the Casimir energy for deformed metal plates by a path integral quantization of the electromagnetic field. For the first time, we give a complete analytical result for the deformation induced change in Casimir energy δE in an experimentally testable, nontrivial geometry, consisting of a flat and a corrugated plate. Our results show an interesting crossover for δE as a function of the ratio of the mean plate distance H, to the corrugation length λ: For λ≪H we find a slower decay ∼H−4, compared to the H−5 behavior predicted by the commonly used pairwise summation …

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Chemical Transferability Of Single- And Multiple-Scattering Exafs Debye-Waller Factors, Nicholas Dimakis, Grant Bunker Jan 2001

Chemical Transferability Of Single- And Multiple-Scattering Exafs Debye-Waller Factors, Nicholas Dimakis, Grant Bunker

Physics & Astronomy Faculty Publications

Single- and multiple-scattering EXAFS Debye-Waller factors are amplitude reduction parameters that appear in the EXAFS x(k) equation accounting for the structural and thermal disorder of a given sample. These parameters must be known accurately in order to obtain quantitative agreement between theory and experiment. Since experimental data can only support a limited number of fitted parameters these factors must be known from another source. Although various approaches have been considered in the past with a variety of results, the self-consistent ab initio Density functional theory stands for the most accurate and reliable method regardless of molecular symmetry or other specific …

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Teaching Effectiveness In An Introductory High School Honors Physics Course As Measured By The Force Concept Inventory, April Crawford Moore Jan 2001

Teaching Effectiveness In An Introductory High School Honors Physics Course As Measured By The Force Concept Inventory, April Crawford Moore

Dissertations and Theses @ UNI

Of importance to many teachers is that students emerge from a course of study with an acceptable level of comprehension of the subject matter presented and that students' course grades reflect that understanding. The primary question of this research was, "How effective in promoting comprehension of Newtonian concepts is this teacher's use of selected interactive strategies?" Secondary questions were: 1. What modifications to instruction, if any, have to be made for implementation of interactive-engagement strategies? 2. Following instruction in mechanics, which misconceptions probed by the Force Concept Inventory (FCI) are retained by students, and which misconceptions are corrected? 3. How …

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Semiclassical Application Of The Mo/Ller Operators In Reactive Scattering, Sophya V. Garashchuk, J. C. Light Jan 2001

Semiclassical Application Of The Mo/Ller Operators In Reactive Scattering, Sophya V. Garashchuk, J. C. Light

Faculty Publications

Mo/ller operators in the formulation of reaction probabilities in terms of wave packet correlation functions allow us to define the wave packets in the interaction region rather than in the asymptotic region of the potential surface. We combine Mo/ller operators with the semiclassical propagator of Herman and Kluk. This does not involve further approximations and can be used with any initial value representation (IVR) semiclassical propagator. Time propagation in asymptotic regions of the potential due to Mo/ller operators reduces the oscillations of the propagator integrand and improves convergence of the results with respect to the number of trajectories. The effectiveness …

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Electron Cyclotron Resonance Heating In Spherical Plasmas: O-X-Ebw Mode Conversion In Mast, Josef Preinhaelter, M. A. Irzak, Linda L. Vahala, George Vahala Jan 2001

Electron Cyclotron Resonance Heating In Spherical Plasmas: O-X-Ebw Mode Conversion In Mast, Josef Preinhaelter, M. A. Irzak, Linda L. Vahala, George Vahala

Electrical & Computer Engineering Faculty Publications

Using a full wave solution, the O-X-EBW mode conversion is examined for density and magnetic profiles in MAST. The effects of magnetic shear and the sharp density pedestal for H-mode operation are considered with an eye to understanding both electron cyclotron emission (ECE) and electron cyclotron resonance heating (ECRH).

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Multilayer Mim Inversion Of Aem Data: Theory And Field Example, Clyde J. Bergeron Jr, Juliette W. Ioup, Yan Wu, George E. Ioup, Kenneth W. Holladay Jan 2001

Multilayer Mim Inversion Of Aem Data: Theory And Field Example, Clyde J. Bergeron Jr, Juliette W. Ioup, Yan Wu, George E. Ioup, Kenneth W. Holladay

Physics Faculty Publications

This paper presents a multilayer generalization of an algebraic method of inverting frequency-doma in airborne active electromagnetic (AEM) data in terms of 1-D layered earth models. The processing of the AEM data, which includes a recalibration procedure, is also outlined. The inversion is applied to synthetic fields generated from a multilayer model which is intended to approximate a measured conductivity profile of the water column in the Gulf of Mexico and to measured AEM data from a survey of the Barataria Bay estuary region of the Louisiana Gulf of Mexico coast. The inversion results from the synthetic data are in …

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