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 NavierStokes equations (3)
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 Alloy/materials theory (1)
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 Blade (1)
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 Infrared imaging (1)
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 Publication

 Theses and Dissertations (7)
 Mechanical & Aerospace Engineering Theses & Dissertations (4)
 Chemical and Biochemical Engineering Faculty Research & Creative Works (2)
 Duane D. Johnson (2)
 Electrical & Computer Engineering Theses & Dissertations (2)

 Faculty Publications (2)
 Alexander H. King (1)
 Dissertations, Theses, and Masters Projects (1)
 Electrical & Computer Engineering Faculty Publications (1)
 Electrical Engineering Faculty Publications (1)
 Electrical and Computer Engineering Faculty Publications (1)
 ElectroOptics and Photonics Faculty Publications (1)
 Jacek Smurzynski (1)
 Journal of the Arkansas Academy of Science (1)
 Marc A. Fagelson (1)
 Mechanical Engineering Faculty Publications (1)
 Physics  All Scholarship (1)
 Rocky Mountain Conference on Magnetic Resonance (1)
 Publication Type
Articles 1  30 of 31
FullText Articles in Engineering
OpticalFiber Preamplifiers For Ladar Detection And Associated Measurements For Improving The SignalToNoise Ratio, Michael S. Salisbury, Paul F. Mcmanamon, Bradley D. Duncan
OpticalFiber Preamplifiers For Ladar Detection And Associated Measurements For Improving The SignalToNoise Ratio, Michael S. Salisbury, Paul F. Mcmanamon, Bradley D. Duncan
ElectroOptics and Photonics Faculty Publications
In an effort to increase achievable postdetection signaltonoise ratios (SNRs) of continuouswave, 1gm allsolidstate ladar systems, a prototype rareearthdoped opticalfiber amplifier has been included in the optical return signal path of both a heterodyne and a directdetection ladar system. We provide numerical predictions for SNR increases according to our previously developed theory. We also detail our experimental efforts and provide the results of SNR measurements for four distinct cases: direct ladar detection with and without a fiber amplifier, and heterodyne ladar detection with and without a fiber amplifier. Experimentally measured increases in SNRs for ladar systems incorporating an opticalfiber amplifier …
Multispectral Detection Of Ground Targets In Highly Correlated Backgrounds, Jason E. Thomas
Multispectral Detection Of Ground Targets In Highly Correlated Backgrounds, Jason E. Thomas
Theses and Dissertations
Multispectral detection methods attempt to discriminate targets in a dominant clutter background using multiple images of the same realworld scene taken in different narrow spectral bands in the infrared. Detection is possible due to the empirically observed phenomenon that the radiance of manmade objects, such as a tank or truck, often lies off the main spectral correlation axis of that of natural backgrounds. Radiometric measurements of several vehicles and a tree canopy background taken over three days in June. 1994 were used to examine the factors affecting multispectral detection. Results clearly showed that the processes which provide for higher spectral …
Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell
Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell
Theses and Dissertations
The research reported here investigated the use of a shearing interferometer (SI) wavefront sensor to determine the effects of shearlayer turbulence on an optical wavefront. A collimated heliumneon laser beam was propagated through a plane shearlayer produced by mixing helium and nitrogen at different velocities. Since the gases have different indices of refraction, the optical wavefront was distorted by different amounts by each gas. The SI measured the wavefront slope across the sampled area of the wavefront. The shearlayer was viewed from two orthogonal directions. This document contains shadow graphs, interference patterns imaged by each of the SI's six cameras, …
Frame Selection Performance Limits For Statistical Image Reconstruction Of Adaptive Optics Compensated Images, Stephen D. Ford
Frame Selection Performance Limits For Statistical Image Reconstruction Of Adaptive Optics Compensated Images, Stephen D. Ford
Theses and Dissertations
The U.S. Air Force uses adaptive optics systems to collect images of extended objects beyond the atmosphere. These systems use wavefront sensors and deformable mirrors to compensate for atmospheric turbulence induced aberrations. Adaptive optics greatly enhance image quality; however, wavefront aberrations are not completely eliminated. Therefore, postdetection processing techniques are employed to further improve the compensated images. Typically, many short exposure images are collected, recentered to compensate for tilt, and then averaged to overcome randomness in the images and improve signaltonoise ratio. Experience shows that some short exposure images in a data set are better than others. Frame selection exploits …
The Spectral Center Of Gravity Effect And Auditory Filter Bandwidth, Marc Fagelson, Linda M. Thibodeau
The Spectral Center Of Gravity Effect And Auditory Filter Bandwidth, Marc Fagelson, Linda M. Thibodeau
Marc A. Fagelson
Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf ElDin
Simulation Of Active Control Of Asymmetric Flows Around Slender Pointed Forebodies, Hazem Sharaf ElDin
Mechanical & Aerospace Engineering Theses & Dissertations
At high angles of attack, the flowfield over slender forebodies becomes asymmetric with substantial side force, which may exceed the available control capability. The unsteady compressible NavierStokes equations are used to investigate the effectiveness of different active control methods to alleviate and possibly eliminate the flow asymmetry and the subsequent side force. Although the research work focuses on active control methods, a passive control method has been investigated. The implicit, Roe fluxdifference splitting, finite volume scheme is used for the numerical computations. Both locallyconical and threedimensional solutions of the NavierStokes equations are obtained.
The asymmetric flow over fivedegree semiapex angle …
The Current Voltage Characteristics Of Electron Beam Controlled Thin Film Diamond Switches, Christopher Anthony Molina
The Current Voltage Characteristics Of Electron Beam Controlled Thin Film Diamond Switches, Christopher Anthony Molina
Electrical & Computer Engineering Theses & Dissertations
The dark current of natural diamond thin films and the induced current due to electronbeam irradiation was measured up to a range of 7000Ncm'. The contact material was aluminum, annealed and unannealed. Switching experiments were performed with electron energies ranging from 70keV to 172keV. The switching results obtained are strongly dependent on the biasing polarity, incident electron energy, and whether the contact is blocking or Ohmic in nature. A simple model which takes traps into consideration allows us to explain the various switching responses. The range of electrons which define, in part, the switch mode was measured for one sample …
Orientation Induced Scattering Asymmetry, JeeChing Wang, Ronald E. Olson
Orientation Induced Scattering Asymmetry, JeeChing Wang, Ronald E. Olson
Chemical and Biochemical Engineering Faculty Research & Creative Works
Projectile angular scattering is investigated following electron capture by protons from circular Rydberg atoms oriented along a quantization axis perpendicular to the incident projectile direction. We find strong leftright scattering asymmetry as a function of the orientation angle at collision speeds comparable to the electron orbital speed. The capture cross section is dramatically enhanced due to velocity matching when the angular momenta of the proton and the electron are aligned. The scattering asymmetry exhibits characteristic impact parameter dependencies suitable for studying threebody dynamics influenced by both long and short range forces of comparable strength. © 1994 IOP Publishing Ltd.
36th Rocky Mountain Conference On Analytical Chemistry
36th Rocky Mountain Conference On Analytical Chemistry
Rocky Mountain Conference on Magnetic Resonance
Program, abstracts, and information about the 36th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, cosponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 31  August 5, 1994.
Compositional ShortRange Ordering In Metallic Alloys: BandFilling, ChargeTransfer, And Size Effects From A FirstPrinciples AllElectron LandauType Theory, J. B. Staunton, Duane D. Johnson, F. J. Pinski
Compositional ShortRange Ordering In Metallic Alloys: BandFilling, ChargeTransfer, And Size Effects From A FirstPrinciples AllElectron LandauType Theory, J. B. Staunton, Duane D. Johnson, F. J. Pinski
Duane D. Johnson
Using a meanfield statistical description, we derive a general formalism to investigate atomic shortrange order in alloys based on a densityfunctional description of the finitetemperature, grand potential of the random alloy. This ‘‘firstprinciples,’’ Landautype approach attempts to treat several contributions (electronic structure, Fermi surface, electrostatics, magnetism, etc.) to the electronic energy on an equal footing. An important ingredient for the statistical averaging is the replacement of the molecular mean fields (Weiss fields) with Onsager cavity fields, which forces the diagonal part of the fluctuationdissipation theorem to be obeyed. To show its general applicability and usefulness, we apply the theory to …
FirstPrinciples AllElectron Theory Of Atomic ShortRange Ordering In Metallic Alloys: D022 Versus L12Like Correlations, Duane D. Johnson, J. B. Staunton, F. J. Pinski
FirstPrinciples AllElectron Theory Of Atomic ShortRange Ordering In Metallic Alloys: D022 Versus L12Like Correlations, Duane D. Johnson, J. B. Staunton, F. J. Pinski
Duane D. Johnson
We use a ‘‘firstprinciples’’ concentrationwave approach based on a finitetemperature, electronic densityfunctional, meanfield, grand potential of the random alloy to investigate the hightemperature atomic shortrange order (ASRO) in Ni75V25 and Pd75V25 solid solutions. Experimentally, these similar alloys both develop D022type longrange order at low temperatures but different ASRO at high temperatures. Our calculations describe the measured ASRO well. We compare these results with those found for a hypothetical Co75Ti25 solid solution. Since this alloy orders directly from the melt into the L12 phase, it should exhibit strong L12like ASRO, as we find in our calculations. We analyze the features in …
SurfaceInduced Ordering In Asymmetric Block Copolymers, Y. Liu, W. Zhao, X. Zheng, Alexander H. King, A. Sing, M. H. Rafailovich, J. Sokolov, K. H. Dai, E. J. Kramer, S. A. Schwarz, O. Gebizlioglu, S. K. Sinha
SurfaceInduced Ordering In Asymmetric Block Copolymers, Y. Liu, W. Zhao, X. Zheng, Alexander H. King, A. Sing, M. H. Rafailovich, J. Sokolov, K. H. Dai, E. J. Kramer, S. A. Schwarz, O. Gebizlioglu, S. K. Sinha
Alexander H. King
The surfaceinduced ordering in thin films of asymmetric deuterated polystyrene (dPS) poly(viny1pyridine) (PVP) diblock and triblock copolymers of comparable polymerization index and PVP volume fraction  0.25) was studied using transmission electron microscopy, atomic force microscopy, secondary ion massspectrometry, and neutron reflectivity. The morphology of both di and triblock copolymer films was found to be cylindrical except for the layer adjacent to the silicon oxide surface, which due to the strong interaction of silica with PVP, was lamellar. The spacing between adjacent cylindrical layers was found to be consistent with mean field theory predictions. In the triblock copolymer films the …
Direct Relation Between Fresnel's Interface Reflection Coefficients For The Parallel And Perpendicular Polarizations: Erratum 2, R. M.A. Azzam
Direct Relation Between Fresnel's Interface Reflection Coefficients For The Parallel And Perpendicular Polarizations: Erratum 2, R. M.A. Azzam
Electrical Engineering Faculty Publications
The record is set straight concerning two equations that determine the reflection phase shifts at a single interface from the intensity reflectances forp and spolarized light at one angle of incidence. These equations appeared previously in this journal [J. Opt. Soc. Am. 69, 1007 (1979); erratum, J. Opt. Soc. Am. 70, 261 (1980)].
The Excitation Mechanism Of PraseodymiumDoped Semiconductors, Paul L. Thee
The Excitation Mechanism Of PraseodymiumDoped Semiconductors, Paul L. Thee
Theses and Dissertations
This study on praseodymium Pr luminescence in Al_{x}Ga_{1x}As was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 10^{12} to 5 x 10^{13} sq cm into Al_{x}Ga_{1x}As x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Arion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra4f transitions of 1G4 yielding 3H5 …
SpatioTemporal Pattern Recognition Using Hidden Markov Models, Kenneth H. Fielding
SpatioTemporal Pattern Recognition Using Hidden Markov Models, Kenneth H. Fielding
Theses and Dissertations
A new spatiotemporal method for identifying 3D objects found in 2D image sequences is presented. The Hidden Markov Model technique is used as a spatiotemporal classification algorithm to identify 3D objects by the temporal changes in observed shape features. A new information theoretic argument is developed that proves identifying objects based on image sequences can lead to higher classification accuracies than single look methods. A new distance measure is proposed that analyzes the performance of Hidden Markov Models in a multiclass pattern recognition problem. A three class problem identifying moving light display objects provides experimental verification of the sequence processing …
A DiffractionBased Model Of Anisoplanatism Effects In Adaptive Optic Systems, Steven E. Troxel
A DiffractionBased Model Of Anisoplanatism Effects In Adaptive Optic Systems, Steven E. Troxel
Theses and Dissertations
This dissertation presents a new model for computing the angle dependent performance measures of an adaptiveoptics system. By incorporating diffraction caused by the indexofrefraction variations of the atmosphere, the phase and amplitude fluctuations of the propagating wave are computed. New theory is presented, that uses the diffractionbased propagation model to yield optical transfer function (OTF) expressions that are more accurate as compared to current theory that neglects diffraction. An evaluation method for calculating the OTF is presented that utilizes a layered atmospheric model and normalized OTF expressions. The diffraction model is also used to present the first OTF signaltonoise ratio …
Flow Simulations About SteadyComplex And Unsteady Moving Configurations Using StructuredOverlapped And Unstructured Grids, James Charles Newman Iii
Flow Simulations About SteadyComplex And Unsteady Moving Configurations Using StructuredOverlapped And Unstructured Grids, James Charles Newman Iii
Mechanical & Aerospace Engineering Theses & Dissertations
The limiting factor in simulating flows past realistic configurations of interest has been the discretization of the physical domain on which the governing equations of fluid flow may be solved. In an attempt to circumvent this problem, many Computational Fluid Dynamic (CFD) methodologies that are based on different grid generation and domain decomposition techniques have been developed. However, due to the costs involved and expertise required, very few comparative studies between these methods have been performed. In the present work, the two CFD methodologies which show the most promise for treating complex threedimensional configurations as well as unsteady moving boundary …
Unsteady Flow Simulations About Moving Boundary Configurations Using Dynamic Domain Decomposition Techniques, GuanWei Yen
Unsteady Flow Simulations About Moving Boundary Configurations Using Dynamic Domain Decomposition Techniques, GuanWei Yen
Mechanical & Aerospace Engineering Theses & Dissertations
A computational method is developed to solve the coupled governing equations of an unsteady flowfield and those of rigidbody dynamics in six degreesoffreedom (6DOF). This method is capable of simulating the unsteady flowfields around multiple component configurations with at least one of the components in relative motion with respect to the others. Two of the important phenomena that such analyses can help us to understand are the unsteady aerodynamic interference and the boundaryinduced component of such a flowfield. By hybridizing two dynamic domain decomposition techniques, the grid generation task is simplified, the computer memory requirement is reduced, and the governing …
Derivative Absorption Spectroscopy With Tunable Laser Diodes, Andrew D. Jackson
Derivative Absorption Spectroscopy With Tunable Laser Diodes, Andrew D. Jackson
Electrical & Computer Engineering Theses & Dissertations
Derivative Absorption Spectroscopy using tunable diode lasers provides a non intrusive, sensitive, and convenient method for monitoring gaseous characteristics such as concentration, temperature, and flow velocity. In addition, the specie type can be identified, and if the equation of state is known, pressure may be deduced.
This technique was used on molecular oxygen, in which the rovibronic transitions of the Aband ( b^{ 1 }∑_{g} ^{+ }← X ^{3 }∑g ^{} ; v^{II } = O, v^{I } = O) were probed. Phase sensitive detection with a lockin amplifier provides the flexibility to examine lineshape derivatives; several such derivative …
Feasibility Analysis For Predicting A Kinetic Kill Zone For Aircraft Homing Missile Defense, Mark E. Ennis
Feasibility Analysis For Predicting A Kinetic Kill Zone For Aircraft Homing Missile Defense, Mark E. Ennis
Theses and Dissertations
An extended Kalman filter is used to predict a kinetic kill zone for use in aircraft self defense versus homing missiles. The analysis is limited to an intheplane analysis and focuses on finding the model parameters which have the largest impact on the predicted kill zone. No attempt is made to optimize the design of the filter model itself. The analysis computes the kill zone relative to an assumed aircraft trajectory using strictly filter computed statistics. No MonteCarlo simulations are used throughout the thesis. The filter assumed to be on the evading aircraft, uses an onboard laser radar (ladar) to …
Rank Conditioned Rank Selection Filters For Signal Restoration, Russell C. Hardie, Kenneth E. Barner
Rank Conditioned Rank Selection Filters For Signal Restoration, Russell C. Hardie, Kenneth E. Barner
Electrical and Computer Engineering Faculty Publications
A class of nonlinear filters called rank conditioned rank selection (RCRS) filters is developed and analyzed in this paper. The RCRS filters are developed within the general framework of rank selection(RS) filters, which are filters constrained to output an order statistic from the observation set. Many previously proposed rank order based filters can be formulated as RS filters. The only difference between such filters is in the information used in deciding which order statistic to output. The information used by RCRS filters is the ranks of selected input samples, hence the name rank conditioned rank selection filters. The number of …
Click‐Evoked Otoacoustic Emissions In Normal‐Hearing Children, Jacek Smurzynski
Click‐Evoked Otoacoustic Emissions In Normal‐Hearing Children, Jacek Smurzynski
Jacek Smurzynski
Gravity And Electromagnetism In Noncommutative Geometry, Giovanni Landi, Nguyen Ai Viet, Kameshwar C. Wali
Gravity And Electromagnetism In Noncommutative Geometry, Giovanni Landi, Nguyen Ai Viet, Kameshwar C. Wali
Physics  All Scholarship
We present a unified description of gravity and electromagnetism in the framework of a Z 2 noncommutative differential calculus. It can be considered as a “discrete version” of KaluzaKlein theory, where the fifth continuous dimension is replaced by two discrete points. We derive an action which coincides with the dimensionally reduced one of the ordinary KaluzaKlein theory.
A Fringe Center Detection Technique Based On A SubPixel Resolution, And Its Applications Using Sinusoidal Gratings, Ming Chang, Paul P. Lin, Wen Chih Tai
A Fringe Center Detection Technique Based On A SubPixel Resolution, And Its Applications Using Sinusoidal Gratings, Ming Chang, Paul P. Lin, Wen Chih Tai
Mechanical Engineering Faculty Publications
A common problem in optical profilometry is the accuracy in locating fringe centers. This paper presents an accurate fringe center detection technique based on subpixel resolution using the fringe projection method. An optimum reconstruction filter is developed which has low sensitivity to noise. In fringe center detection, computer simulation results of using onepixel and subpixel resolutions are compared. The detection technique is then applied to radius measurement of cylindrical objects and surface profile measurement of diffuse objects. The experimental results thus obtained through the proposed optimum reconstruction filter show significant improvement in measurement accuracy.
Using The Cern ProgramLibrary Graphics And Interactive Data Display, Morgan T. Burks, Wilson H. Howe, Christine A. Byrd, Wilfred J. Braithwaite
Using The Cern ProgramLibrary Graphics And Interactive Data Display, Morgan T. Burks, Wilson H. Howe, Christine A. Byrd, Wilfred J. Braithwaite
Journal of the Arkansas Academy of Science
Small scale Monte Carlo programming is growing rapidly due to the ease with which complex problems may be formulated by any programmer. These programmers may choose to exploit graphics and interactive displays available in the program library developed and maintained by CERN (the Center for European Nuclear Research). This paper outlines the use of graphics and interactive data display features of the CERN program library, developed for visualizing simulated data events in particle detectors. One example uses GEANT, CERN's Monte Carlo modeling program, to simulate 300 MeV/c protons incident on a silicon slab. Display packages for GEANT are available both …
Multigrid Acceleration Of TimeDependent Solutions Of NavierStokes Equations, Sarafa Oladele Ibraheem
Multigrid Acceleration Of TimeDependent Solutions Of NavierStokes Equations, Sarafa Oladele Ibraheem
Mechanical & Aerospace Engineering Theses & Dissertations
Recent progress in Computational Fluid Dynamics is encouraging scientists to look at fine details of flow physics of problems in which natural unsteady phenomena have hitherto been neglected. The acceleration methods that have proven very successful in steady state computations can be explored for time dependent computations. In this work, an efficient multigrid methods is developed to solve the timedependent Euler and NavierStokes equations. The BeamWarming ADI method is used as the base algorithm for time stepping calculations. Application of the developed algorithm proved very efficient in selected steady and unsteady test problems. For instance, the inherent unsteadiness present in …
Dominance Of The Thomas Mechanism For Electron Capture From Orientated Rydberg Atoms, JeeChing Wang, Ronald E. Olson
Dominance Of The Thomas Mechanism For Electron Capture From Orientated Rydberg Atoms, JeeChing Wang, Ronald E. Olson
Chemical and Biochemical Engineering Faculty Research & Creative Works
We investigate electron capture from initially oriented circular Rydberg atoms by proton impact at collision speeds comparable to the electron orbital speed. The Thomas double scattering mechanism is observed even at these low relative speeds. Furthermore, we find evidence for the dominance of a quasi Thomas capture mechanism in the form of not a single peak, but a doublepeaked structure in the differential cross section when the plane of the circular orbit is nearly perpendicular to the incident direction of the projectile. © 1994 The American Physical Society.
Models For Water Outgassing From Metal Surfaces, Minxu Li
Models For Water Outgassing From Metal Surfaces, Minxu Li
Dissertations, Theses, and Masters Projects
In this study, the outgassing rate from an electropolished stainless steel surface following exposures to H{dollar}\sb2{dollar}O vapor under various conditions was measured. The results of the experiments showed that the outgassing rate is proportional to {dollar}p\sb0\sp{lcub}n{rcub}{dollar}, where {dollar}p\sb0{dollar} is the H{dollar}\sb2{dollar}O exposure pressure and n is about 0.25. The outgassing rate is not as strongly dependent on the system temperature as one would expect if the temperature is kept the same during exposure and pumpdown. The outgassing rate is also a function of the exposure time for the first several hours of exposure, indicating that the adsorption saturation time is …
Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu
Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu
Faculty Publications
A ressessment of existing theories for calculating the strength of random and quasirandom fiber composites is presented. Fundamental aspects regarding the physical model, macromechanics analysis, fiber distribution functions, generalized failure criterion, and progressive versus sudden failure models are covered first. Progressive ductile failure, progressive brittle failure, and sudden brittle failure are treated in detail. In each case, the original theory is briefly reviewed, and then its extensions accompanied by numerical examples are presented. Several limitations originally imposed by Hahn, such as the monotonically nonincreasing requirement on the failure strain curve, are lifted and the mathematical formulations are generalized. Some common …
Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu
Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu
Faculty Publications
No abstract provided.