| Digital Signal Processing Techniques for Positioning of Off-Axis Solar Concentrators |
23 OCT 2002 |
9 pages |
| Authors:
Joseph N. Beasley; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE WEST
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 | This paper will discuss the results of using digital signal processing (DSP) techniques to determine the location of the focal point of an off-axis solar concentrator projected onto a visually complex thruster absorber and secondary concentrator. Once the location of the focal spot is located, position control information is generated to move the concentrator to a location that maximizes power transfer. A program that simulates an off-axis solar concentrator is ... |
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| Numerical Simulation of Compressible Viscous Magneto-Hydrodynamics Equations with Chemical Kinetics |
SEP 2002 |
7 pages |
| Authors:
Ramesh K. Agarwal; WICHITA STATE UNIV KS INST FOR AVIATION RESEARCH
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| Most of the objectives of this research project have been achieved. In this first phase of the AFOSR grant (1 October 1998 - 30 September 2002), the principal investigator and his students have developed a 2-D unsteady compressible viscous magnetohydrodynamic code designated MHD2D which has been validated for 2-D internal and external flow & The code solves the coupled MHD equations (mass. momentum and energy equations of fluid flow including ... |
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| Two-Dimensional ESPRIT with Tracking for Radar Imaging and Feature Extraction |
02 AUG 2002 |
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| Authors:
M. L. Burrows; MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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 | ESPRIT processing appears to be the best of the known spectral- analysis techniques. It provides the highest resolution and has no spectral splatter. By applying matrix eigenstructure analysis, it gives a direct answer to the direct question 'What frequencies, real or complex, are present in the data and what are their amplitudes'? Conventional Fourier techniques, as well as some of the other higher-resolution methods, answer the less direct question 'What ... |
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| MODFLOW-2000 for Cylindrical Geometry With Internal Flow Observations and Improved Water Table Simulation |
AUG 2002 |
34 pages |
| Authors:
Tom Clemo; BOISE STATE UNIV ID CENTER FOR THE GEOPHYSICAL INVESTIGATION OF THE SHALLOW SUBSURFACE
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| A modified form of the MODFLOW-2000 code provides a tool to estimate a hydraulic conductivity distribution near a borehole. The modified code allows the effects of wellbore screen intervals, screen clogging, and disturbed zone skin to be taken into account. The primary application has been in an investigation of electromagnetic borehole flow meter measurement interpretation. MODFLOW-2000 was modified to simulate a two-dimensional cylindrical geometry. The two dimensions are vertical and ... |
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| Adaptive System and Method for Responding to Computer Network Security Attacks |
11 JUL 2002 |
15 pages |
| Authors:
Douglas W. Hill; James T. Lynn; MOTOROLA INC SCHAUMBURG IL
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| A dynamic network security system (20) responds to a security attack (92) on a computer network (22) having a multiplicity of computer nodes (24). The security system (20) includes a plurality of security agents (36) that concurrently detect occurrences of security events (50) on associated computer nodes (24). A processor (40) processes the security events (50) that are received from the security agents (36) to form an attack signature (94) ... |
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| Inviscid Global Linear Instability of Compressible Flow on an Elliptic Cone: Algorithmic Developments |
02 JUL 2002 |
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| Authors:
Vassilios Theofilis; NU-MODELING INC GOTTINGEN (GERMANY)
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| The subject of this present effort is numerical developments in support of a BiGlobal linear instability analysis of the compressible three- dimensional steady laminar basic flows obtained within the framework of F61775- 99-WE049. The first objective becomes extraction from the aforementioned results of the appropriate two-dimensional basic flow data. The assumption is made, and is verified in the numerical results to be increasingly applicable as the flow Mach number increases, ... |
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| Photoluminescence Studies of Two-Dimensional Electron Gas in Modulation Doped A1xGa1-xN/GaN Structures Grown on SI 4H-SiC by MOCVD |
JUL 2002 |
11 pages |
| Authors:
Fred Semendy; Patrick Folkes; Alfred H. Huang; Michael Wraback; ARMY RESEARCH LAB ADELPHI MD
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| Electron devices with ever-increasing operating speed are used for applications such microwave switches or amplifiers. As the physical dimensions of these devices (e.g., field effect transistors) become smaller, thinner channel layers and higher electron concentrations are required to provide high performance operation. This is because current for faster discharge of capacitance in these microwave device structures is proportional to the carrier velocity as well as the carrier density. This requirement ... |
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| Analysis of a Generic Warhead Part I: Experimental and Computational Assessment of Free Field Overpressure |
JUL 2002 |
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| Authors:
J. G. Anderson; G. Katselis; C. Caputo; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION SALISBURY (AUSTRALIA) SYSTEMS SCIENCES LAB
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| Experimental and numerical results are presented for the free field blast generated by a 7.8 kg cylindrical charge of Composition B high explosive. In the experiments, overpressure and shock front time of arrival measurements have been recorded. Overpressure measurements in the far field provide pressure histories at discrete locations. Peak overpressure in the near field is calculated from time of arrival measurements. In addition, the numerical model was used to ... |
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| Experimental Observation of Fluid Echoes in a Non-Neutral Plasma |
24 JUN 2002 |
6 pages |
| Authors:
Jonathan H. Yu; C. F. Driscoll; CALIFORNIA UNIV SAN DIEGO LA JOLLA
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| Experimental observation of a nonlinear fluid echo is presented which demonstrates the reversible nature of spatial Landau damping, and that non-neutral plasmas behave as nearly ideal 2D fluids. These experiments are performed on UCSD's CamV Penning-Malmberg trap with magnetized electron plasmas. An initial m (sub i) = 2 diocotron wave is excited, and the received wall signal damps away in about 5 wave periods. The density perturbation filaments are observed ... |
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| Shear Reduction of 2D Point Vortex Diffusion |
24 JUN 2002 |
13 pages |
| Authors:
Daniel H. Dubin; C. F. Driscoll; CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF PHYSICS
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| Theory and simulations establish the effects of shear on the collisional diffusion of a 2D point vortex gas. For finite shear, the diffusion is considerably smaller than previous zero-shear theories predict, scaling inversely with the shear. Surprisingly, changing the sign of the applied shear changes the diffusion by an order of magnitude. |
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| Breaking the Azimuthal Symmetry-Jumping Off-aAis or Staying Away from the Axis? |
24 JUN 2002 |
7 pages |
| Authors:
Eli Sarid; Catalin Teodorescu; Phil Marcus; Joel Fajans; CALIFORNIA UNIV BERKELEY DEPT OF PHYSICS
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| We performed experiments with electrons in a Malmberg-Penning trap, as well as 2D fluid simulations, and found conditions that lead to off-axis equilibrium states. We found that unstable initial distributions whose average distance from the axis is larger than about half the wall radius end up in off-axis states. These states consist of a small strong vortex and a large diffuse background, each having about half of the initial charge. ... |
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| Continuously Injected Plasma Columns |
24 JUN 2002 |
6 pages |
| Authors:
Tom Pasquini; Joel Fajans; CALIFORNIA UNIV BERKELEY DEPT OF PHYSICS
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| Electron plasma columns continuously injected into a Malmberg-Penning trap display a rich evolution. Electrons emitted from an illuminated photocathode are trapped in the electrostatic well formed by the negatively biased photocathode and the trap end cylinder. Initially, the injections form cylinders of uniform density. As the density increases, the columns hollow in an attempt to match the potential profile of the equipotential cathode. The hollow columns are subject to the ... |
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| Experimental and Numerical Study of Asymmetric Vortex Merger in a Pure Electron Plasma |
24 JUN 2002 |
5 pages |
| Authors:
M. Amoretti; D. Durkin; J. Fajans; R. Pozzoli; M. Rome; CALIFORNIA UNIV BERKELEY DEPT OF PHYSICS
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| The merging of an intense localized vortex with an extended vortex is investigated by means of an experimental analysis performed on a Malmberg-Penning trap with photocathode, and numerical simulations with a two-dimensional (2D) particle in cell (PIC) code. The study is restricted to highly nonlinear conditions, where the perturbative approach does not hold. A very good agreement between experimental results and simulations is obtained. It is found that the localized ... |
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| Characteristics and Generation Mechanism of Holes in an Extended Electron Vortex |
24 JUN 2002 |
6 pages |
| Authors:
Akio Sanpei; Kiyokazu Ito; Yukihiro Soga; Yasuhito Kiwamoto; KYOTO UNIV (JAPAN)
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| In nonneutral plasma, depleted regions (holes) in the vorticity often play a controlling role in the evolution of two dimensional turbulence. We report experimental investigations of the generation process of ring holes (three-dimensionally annular depletion) surrounding a strongly-peaked clump of vorticity (point vortex) immersed in the background of a spatially extended vorticity distribution, and determine the empirical scaling for the generation time of the ring holes. Moreover, we report geometrical ... |
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| Two-Dimensional Modeling of Aluminum Gallium Nitride/Gallium Nitride High Electron Mobility Transistor |
JUN 2002 |
79 pages |
| Authors:
Kenneth L. Holmes; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Gallium Nitride (GaN) High Electron Mobility Transistors (HEMT's) are microwave power devices that have the performance characteristics to improve the capabilities of current and future Navy radar and communication systems. The Office of Naval Research (ONR) is funding research for the development of GaN- based microwave power amplifiers for use in future radar and communication systems. This thesis studies the effects of AIGaN/GaN HEMTs' polarization, piezoelectric (PZ) and spontaneous, properties ... |
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| Acoustic Scattering by Axisymmetric Finite-Length Bodies with Application to Fish: Measurement and Modeling |
JUN 2002 |
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| Authors:
D. Reeder; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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| This thesis investigates the complexities of acoustic scattering by finite bodies in general and by fish in particular through the development of an advanced acoustic scattering model and detailed laboratory acoustic measurements. A general acoustic scattering model is developed that is accurate and numerically efficient for a wide range of frequencies, angles of orientation, irregular axisymmetric shapes and boundary conditions The model presented is an extension of a two-dimensional conformal ... |
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| Defining Paths for Driver Models with Hermite Parametric Curves |
JUN 2002 |
18 pages |
| Authors:
Wesley Bylsma; ARMY TANK-AUTOMOTIVE AND ARMAMENTS COMMAND WARREN MI
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| In determining ground vehicle dynamic performance it is generally accepted that comparisons between simulated and test results will be compared for precision and accuracy. The test environment will define a particular course that will be used to define the excitation to the vehicle. In the simulation environment the same course must be replicated to excite the dynamics of the model. Each course used may have different characteristics that excite the ... |
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| 2-D and 3-D Digital Analysis of Breast Calcifications: A Technique to Improve Mammographic Specificity |
JUN 2002 |
48 pages |
| Authors:
Andrew D. Maidment; THOMAS JEFFERSON UNIV PHILADELPHIA PA
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| A method of imaging breast calcifications in 3D was developed. The method is based upon the principles of limited-view image reconstruction. Each calcification is manually identified in multiple views of the breast, and is then semi-automatically segmented. The identified position in 3D is calculated geometrically. The segmented views of each calcification are used to generate a 3D model of each calcification. The calcifications are rendered with custom viewing software that ... |
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| Lattice Boltzmann Equation on a 2D Rectangular Grid |
JUN 2002 |
18 pages |
| Authors:
M'Hamed Bouzidi; Dominique D'Humieres; Pierre Lallemand; Li-Shi Luo; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
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| We construct a multi-relaxation lattice Boltzmann model on a two- dimensional rectangular grid. The model is partly inspired by a previous work of Koelman to construct a lattice BGK model on a two-dimensional rectangular grid. The linearized disperson equation is analyzed to obtain the constraints on the isotropy of the transport coefficients and Galilean in variance for various wave propagations in the model. The linear stability of the model is ... |
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| Investigation into the Discrepancies Between Computational Fluid Dynamic Lift Predictions and Experimental Results |
JUN 2002 |
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| Authors:
Randall S. Fairman; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN ENGINEERING
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| An analysis of current computational fluid dynamics capabilities in predicting mean lift forces for two dimensional foils is conducted. It is shown that both integral boundary layer theory and Reynolds Averaged Navier Stokes algorithms provide the same over-prediction of lift forces when properly converged. It is also shown that the over-prediction is insensitive to turbulence model details. Experimentation and computational fluid dynamics modeling show that discrete vortices are shed with ... |
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| Mezzanine User Manual |
20 MAY 2002 |
30 pages |
| Authors:
Andrew Howard; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES INST FOR ROBOTICS AND INTELLIGENT SYSTEMS
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| Mezzanine is an overhead 2D visual tracking package intended primarily for use as a mobile robot metrology system. It uses a camera to track objects marked with color-coded ducials, and infers the pose (position and orientation) of these objects in world coordinates. Mezzanine will work with most color cameras (even the really cheap ones), and can correct for the barrel distortion produced by wide-angle-lenses. Mezzanine is language and architecture neutral: ... |
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| Discovery of Protein Markers in Breast Cancer by Mass Spectrometry |
MAY 2002 |
13 pages |
| Authors:
Steven H. Seeholzer; FOX CHASE CANCER CENTER PHILADELPHIA PA
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| One of the earliest common changes in the development of breast cancer occurs when some breast epithelial cells begin to grow and proliferate independently of estradiol (E2). We are conducting studies on model breast epithelial cell lines: MCF7 cells, whose proliferation is dependent on estradiol; and LCCl cells, a cell line derived from MCF7 with an acquired E2 independence for growth. We continue to apply proteomics techniques (two dimensional electrophoresis, ... |
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| Imaging of Early-Stage Breast Cancers Using Pulsed Confocal Microwave Technology |
MAY 2002 |
46 pages |
| Authors:
Milica Popovic; Allen Taflove; NORTHWESTERN UNIV EVANSTON IL
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| The work presented in this report is motivated by the need to calibrate a new pulsed-microwave breast tumor detection system for patient- specific skin parameters. A two-dimensional time-domain inverse-scattering algorithm based upon the finite-difference time-domain method is presented for determining the skin thickness and the relative permittivity and electric conductivity of skin in the microwave range. The algorithm traces a search trajectory in the two-dimensional parameter space. The minimal parameter ... |
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| Accuracy of Currents Produced by the Locally-Corrected Nystrom Method and the Method of Moments when used with Higher-Order Representations |
03 APR 2002 |
10 pages |
| Authors:
Andrew F. Peterson; GEORGIA INST OF TECH ATLANTA SCHOOL OFELECTRICAL AND COMPUTER ENGINEERING
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| The locally-corrected Nystrom method is described, and the accuracy of the currents produced by it and the method of moments are compared. Results suggest that when the underlying representation has the same degree, the methods are comparable in accuracy. Additional results are presented to illustrate the Nystrom approach, and advantages and disadvantages of the method are reported. |
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| Object Detection Using a Background Anomaly Approach for Electro-Optic Identification Sensors |
APR 2002 |
9 pages |
| Authors:
Andrew Nevis; James Bryan; J. S. Taylor; Brett Cordes; NAVAL SURFACE WARFARE CENTER PANAMA CITY FL
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| Electro-optic identification (EOID) sensors are transitioning to the fleet and will be used as a short-range identification tool for mine-like contacts from long-range sensors. The present operation of the EOID sensors uses an operator for identification. Whereas the human operator is unparalleled in detecting and recognizing objects of interest, there are still some limitations which may be needed to distinguish between mine types, such as differentiating a 68 inch object ... |
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| Comparisons and Evaluation of Hall Thruster Models |
20 MAR 2002 |
19 pages |
| Authors:
J. Bareilles; G. J. Hagelaar; L. Garrigues; J. P. Boeuf; TOULOUSE-3 UNIV (FRANCE)
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| The aim of the project is to compare, evaluate, and possibly improve the following two SPT models: 1) The two-dimensional hybrid model developed at the MIT between 1994 and 1998, by Mike Fife and Manuel Martinez-Sanchez. 2) The two-dimensional hybrid model developed at the CPAT from 2000 to present, by the authors of this report. Both models attempt to provide a complete simulation of the temporal and spatial behavior of ... |
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| Study of 2D and 3D Boundary Layer of Moving Walls by Embedded LDV Measurements (CD-ROM) |
10 MAR 2002 |
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| Authors:
Christian Maresca; Eric Berton; Daniel Favier; Amine Benyahia; MEDITERRANEE UNIV CEDEX (FRANCE) LAB D'AERODYNAMIQUE ET DE BIOMECANIQUE DU MOUVEMENT
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| ELECTRONIC FILE CHARACTERISTICS: 1,189 files; text and images; Adobe .PDF, MS Word .DOC, Photoshop and JPEG. PHYSICAL DESCRIPTION: 1 computer laser optical disc (CD-ROM); 4 3/4 in.; 378 MB. SYSTEMS DETAIL NOTE: IBM-clone PC-compatible. ABSTRACT: The present final report concerns the extension of the seed contract to more new 2D and 3D tests in order to provide the Aeromechanics of the Army/NASA Rotorcraft Division with experimental results on BL velocity ... |
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| The Investigation of Hypervelocity Gouging |
01 MAR 2002 |
199 pages |
| Authors:
David J. Laird; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| The slipper/rail interface of a hypervelocity rocket sled is subject to immense forces due to dynamic loads and impact of the slipper with the rail, and tremendous heating due to aerodynamic and frictional effects is produced at the interface. Under these severe loading conditions, the material in the rail will sometimes experience large non-linear deformations known as gouging. Hydrocodes are computational solvers designed to handle such non-linear, large deformation, high ... |
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| Influence of 2D Finite Element Modeling Assumptions on Debonding Prediction for Composite Skin-Stiffener Specimens Subjected to Tension and Bending |
MAR 2002 |
35 pages |
| Authors:
Ronald Krueger; Pierre J. Minguet; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
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| The influence of two-dimensional finite element modeling assumptions on the debonding prediction for skin-stiffener specimens was investigated. Geometrically nonlinear finite element analyses using two-dimensional plane- stress and plane-strain elements as well as three different generalized plane strain type approaches were performed. The computed deflections, skin and flange strains, transverse tensile stresses and energy release rates were compared to results obtained from three-dimensional simulations. The study showed that for strains and ... |
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| Study of 2D and 3D Boundary Layer of Moving Walls by Embedded LDV measurements |
MAR 2002 |
40 pages |
| Authors:
Christian Maresca; Eric Berton; Daniel Favier; Amine Benyahia; MEDITERRANEE UNIV CEDEX (FRANCE) LAB D'AERODYNAMIQUE ET DE BIOMECANIQUE DU MOUVEMENT
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| The present final report concerns the extension of the seed contract to more new 2D and 3D tests in order to provide the Aeromechanics of the Army/ NASA Rotorcraft Division with experimental results on BL velocity profiles and on the structure of unsteady separated 2D and 3D flows Smoke visualization and embedded laser velocimeter (2D and 3D) operating in the backscatter mode were used to survey the separation bubble and ... |
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| Percutaneous Absorption of Chemical Mixtures Relevant to the Gulf War |
FEB 2002 |
163 pages |
| Authors:
Jim E. Riviere; NORTH CAROLINA STATE UNIV AT RALEIGH
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| The focus of this research was to quantitate the dermal absorption and cutaneous toxicity of chemical mixtures relevant to the Gulf War Illness. These studies employed in vitro porcine skin models, as well as inert membrane and human epidermal keratinocyte cell cultures. Percutaneous absorption of topically dosed N,N-Diethyl-m-toluamide (DEET) and (14)C-permethrin was assessed after co-exposure to infused pyridostigmine bromide, diisopropylfluorphosphate (DFP); and/or topical exposure to ethanol/water vehicles, low-level sulfur mustard ... |
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| Mine Impact Burial Prediction Experiment |
15-Jan-2002 |
11 pages |
| Authors:
Peter C Chu; Steven D Haeger; Timothy B Smith; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Mine Impact Burial Prediction Experiment "MIBEX" was conducted at Monterey Bay on May 23, 2000 using a simulated mine. During the experiment, we carefully observe mine track and mine burial depth while simultaneously taking gravity cores. After analyzing the gravity cores, we obtain the bottom sediment shear strength data set. Such synchronous mine burial depth and shear strength data were used to evaluate the Navy's Impact Burial Prediction Model "IBPM" ... |
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| Properties of 2D and 3D Dielectric Structures Fabricated by Electrochemical Dissolution of III-V Compounds |
JAN 2002 |
6 pages |
| Authors:
I. M. Tiginyanu; S. Langa; M. Christophersen; J. Carstensen; V. Sergentu; CHRISTIAN-ALBRECHTS UNIV KIEL (GERMANY)
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| Porous layers and membranes representing 2D and 3D dielectric structures were fabricated on different III-V compounds (GaAs, InP, GaP) by electrochemical etching techniques. Nonlithographically fabricated ordered nanopore arrays in InP are reported for the first time. We show that the reflectance from nanostructured InP is lower than that from bulk InP in the spectral interval 1.5 - 2.2 eV. The artificial anisotropy induced by nanotexturization was studied in porous GaP ... |
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| Optical Study of 2D Photonic Crystals in an InP/GaInAsP Slab Waveguide Structure |
JAN 2002 |
6 pages |
| Authors:
Rolando Ferrini; David Leuenberger; Mikael Mulot; Min Qiu; Jurgen Moosburger; WUERZBURG UNIV (GERMANY F R)
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| We report on the optical properties of two dimensional (2D) photonic crystals (PCs) deeply etched in an InP/GaInAsP step-index waveguide. Transmission (T) measurements through simple PC slabs and through one-dimensional (1D) Fabry-Perot (FP)) cavities between PC mirrors are reported and compared to theory. A 2D finite difference time-domain (FDTD) method combined to a phenomenological out-of-plane loss model is used to assess different loss contributions. The PC optical properties are deduced ... |
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| Electron Scattering in Two-Dimensional Disordered Heterostructures |
JAN 2002 |
5 pages |
| Authors:
I. Gomez; E. Diez; F. Dominguez-Adame; P. Orellana; UNIVERSIDAD COMPLUTENSE DE MADRID (SPAIN)
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| The main aim of this work is to study electron scattering in imperfect semiconductor heterostructures. The source of unintentional disorder is the interface roughness at the heterojunctions occurring during growth. In order to achieve this goal we solve numerically the two-dimensional Ben Daniel-Duke equation for the electron scattering problem. Our model assumes open boundary conditions along the growth direction and periodic ones parallel to the heterojunctions. We then compute the ... |
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| Physics of GaN-based High-Power Lasers |
2002 |
5 pages |
| Authors:
Joachim Piprek; Shuji Makamura; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Advanced device simulation is used to analyze performance and device physics of milestone nitride laser diodes. These lasers exhibit the highest room-temperature continuous- wave output power measured thus far. The laser model self-consistently combines band structure and free-carrier gain calculations with two-dimensional simulations of wave guiding, carrier transport, and heat flux. Material parameters used in the model are carefully evaluated. Excellent agreement between simulations and measurements is achieved. The maximum ... |
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| Metachromatic Materials |
2002 |
15 pages |
| Authors:
P. G. Van Patten; OHIO UNIV ATHENS
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| The primary goal of the work performed under this contract was to study the feasibility of using metal nanoparticles as contrast agents (ink) in full-color, flexible, reflective, low-power, electronic displays. The concept is based on the tunability of the plasmon absorption peak in metal nanoparticle ensembles. Well-separated, nanometer-sized fragments of Au, Ag, or Cu have intense plasmon absorptions in the visible part of the spectrum. The extinction coefficient, the frequency ... |
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| Identification of Materiel Damage in Two Dimensional Domains Using Squid Based NDE System |
2002 |
32 pages |
| Authors:
H. T. Banks; F. Kojima; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
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| Problems on the identification of two-dimensional spatial domains arising in the detection and characterization of material damage are considered. For electromagnetic nondestructive evaluation systems, observations of the magnetic flux from the front surface are used in a output least-square approach. Parameter estimation techniques based on the method of mappings are discussed and approximation schemes are developed applying a finite-element Galerkin approach. Theoretical convergence results for computational techniques are given and ... |
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| Directional Distributions and Mean Square Slopes of Surface Waves |
2002 |
9 pages |
| Authors:
Paul A. Hwang; David W. Wang; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
|
| Field observations show that the crosswind component constitutes a significant portion of the ocean surface mean square slope. The average ratio between the crosswind and upwind mean square slope components is 0.88 in slick- covered ocean surfaces. This large crosswind slope component cannot be explained satisfactorily based on our present models of ocean wave directional distributions. Two-dimensional spectral analysis of 3D ocean surface topography reveals that bimodal directional distribution is ... |
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| Numerical Simulation of Flows Near and Through a Two-Dimensional Array of Buildings |
DEC 2001 |
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| Authors:
Eugene Yee; Fue-Sang Lien; Yonghua Cheng; DEFENCE RESEARCH ESTABLISHMENT SUFFIELDRALSTON (ALBERTA)
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| A numerical simulation has been performed of turbulent flow near and through a two-dimensional array of rectangular buildings (bluff bodies) in a neutrally stratified background flow. The model used for the simulation was the steady-state Reynolds-averaged Navier-Stokes equations with an isotropic, linear eddy viscosity formulation for the Reynolds stresses; and, the eddy viscosity was determined using a high-Reynolds number form of the kappa-epsilon turbulence-closure model with the boundary conditions at ... |
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| High Order WENO Schemes for Hamilton-Jacobi Equations on Triangular Meshes |
DEC 2001 |
34 pages |
| Authors:
Zhang Yong-Tso; Shu Chi-Wang; INSTITUTE FOR COMPUTER APPLICATIONS IN SCIENCE AND ENGINEERING HAMPTON VA
|
| In this paper we construct high order weighted essentially non- oscillatory (WENO) schems for solving the nonlinear Hamilton-Jacobi equations on two-dimensional unstructured meshes. The main ideas are nodal based approximations, the usage of monotone Hamiltonians as building blocks on unstructured meshes, nonlinear weights using smooth indicators of second and higher derivatives, and a strategy to choose diversified smaller stencils to make up the bigger stencil in the WENO procedure. Both ... |
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| AASERT 98: Ultrafast GaAs Photoconductivity and Applications for Radiation-Hard Electronics |
DEC 2001 |
21 pages |
| Authors:
John F. Whitaker; MICHIGAN UNIV ANN ARBOR
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| Finally, in the last year of the AASERT and during a no-cost extension period, an effort was made to demonstrate how pulsed, single-cycle terahertz beams generated and detected by nonstoichiometric-GaAs dipole antennas - could be employed as a tool for the imaging of metal and dielectric objects. This was accomplished through the use of the time-reversal and back-propagation of time-domain signals scattered from objects through off-axis diffraction. Experimental methods were ... |
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| Ultrafast Optical Wavelength Shuffling Based on Nonlinear Photonic Crystals |
30 NOV 2001 |
4 pages |
| Authors:
Lean McCaughan; WISCONSIN UNIV-MADISON
|
| At the time of this proposal we had developed the theoretical foundation for analyzing 2D periodic second order nonlinearities, from which we developed demonstration of simultaneous optical wavelength interchange I. shown that a properly designed 2-D quadratic nonlinear lattice can be used to produce a simultaneous, one-step, interchange of data between two carrier wavelengths XPj^)^^ (Fig. 1). The two DFG processes essentially "diffract" ^ the Interconverted signals from the unconverted ... |
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| Robust GPS-Based Synchronization of CDMA Mobile Networks |
01-Nov-2001 |
8 pages |
| Authors:
Dominik Schneuwly; OSCILLOQUARTZ S A NEUCHATEL (SWITZERLAND)
|
| Mobile communication networks based on the cdmaOne and cdma2000 standards require that the base-stations of their radio access networks be synchronized. All the base-stations of the network need a 1PPS phase reference with an accuracy of 3 microsecs. The Global Positioning System (GPS) is currently the only practical way of implementing this type of synchronization. This paper proposes a two-fold protection concept for the base-station's phase clock. In case of ... |
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| Two-Dimensional Processing for Radar Systems |
NOV 2001 |
123 pages |
| Authors:
Jaime R. Roman; Dennis W. Davis; Qingwen Zhang; SCIENTIFIC STUDIES CORP PALM BEACH GARDENS FL
|
| This report presents algorithms and methodologies for space-time adaptive processing (STAP) and detection in airborne surveillance phased array radar systems. Two approaches are considered for the know-signal case: weight vectors for multichannel one-dimensional (MC1D) data representations, and parametric models for single-channel (scalar) two-dimensional (SC2D) data representations. For the MC1D approach, a generic architecture that covers a wide variety of weight vector algorithms and associated detection rules is presented. Algorithms covered ... |
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| An Extending Fitts' Law for Human Upper Limb Performance Evaluation |
25 OCT 2001 |
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| Authors:
N. F. Yang; D. W. Jin; M. Zhang; C. H. Huang; R. C. Wang; TSINGHUA UNIV BEIJING (CHINA) DEPT OF PRECISION INSTRUMENTS
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| Human motor behavior is complex and is challenging to understand. Fitts' Law presented a relationship between speed, accuracy, amplitude of movement and target size in upper extremity tasks. In this paper, Fitts' Law was extended from one- dimensional motion to two-dimensional motion in the polar coordinate system for the human upper limb performance. Based on this, a set of indices were proposed. The index of difficulty and the index of ... |
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| A Three-Dimensional Model of the Mandible Using Two-Dimensional CT images |
25 OCT 2001 |
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| Authors:
L. Mutlu-Sagesen; R. Roroslu; L. Parnas; S. Suca; MIDDLE EAST TECHNICAL UNIV ANKARA (TURKEY) DEPT OF MECHANICAL ENGINEERING
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| In dentistry, instead of conventional prosthetic applications, dental implant prosthesis has recently been used in edentate patients. Biomechanical effects are known to be one of the most important factors in the failure of these implants. In this work, a three-dimensional model of the edentate mandible is formed to use in three-dimensional finite element method for the stress analysis of chewing forces. The computerized three-dimensional solid geometric mandible model is formed ... |
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| Dynamic Edge Tracing for 2D Image Segmentation |
25 OCT 2001 |
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| Authors:
D. J. Withey; Z. J. Koles; W. Pedrycz; ALBERTA UNIV EDMONTON
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| A novel segmentation technique which may be useful for two dimensional (2D) magnetic resonance (MR) image segmentation is presented. The technique utilizes a dynamic target tracking algorithm and a Kalman filter and permits edges to be followed in the presence of intensity variation similar to that found in MR images. Segmentation of two synthetic test images, one with intensity nonuniformity and one without, is performed. Fuzzy c-means clustering with pixel ... |
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| Blood Flow Visualization in Immersive Environment Based on Color Doppler Images |
25 OCT 2001 |
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| Authors:
M. Imura; T. Kuroda; O. Oshiro; K. Chihara; J. Brandberg; P. Ask; NARA INST OF SCIENCE AND TECH (JAPAN) GRADUATE SCHOOL OF INFORMATION SCIENCE
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| An accurate grasp of blood flow patterns in a human heart is important to evaluate cardiac diseases of patients. Doppler ultrasound method is widely used to visualize blood flow patterns and has obtained excellent results in diagnosis. However, the output from Doppler ultrasound method is usually represented as a two-dimensional image, though blood flow patterns have three- dimensional complex structure and change dynamically. Therefore, improvement of both data acquisition and ... |
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| Periodic Lattices of Interacting Self-Assembled Quantum Dots |
SEP 2001 |
25 pages |
| Authors:
James S. Speck; Pierre M. Petroff; Glenn E. Beltz; CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS
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| Overall, in this program, we developed high quality 2D and 3D periodic quantum dot lattices that show strong photoluminescence. In the initial stages of the program, we worked on QD growth on a periodic stressor lattice formed by ordered subsurface dislocations. The dislocation grid was formed by twist bonding. |
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Reports by Keyword(s)
TWO DIMENSIONAL
