| Signal Modeling of Turbulence-Distorted Imagery |
Sep-2009 |
18 pages |
| Authors:
S S Young; Ron Driggers; Keith Krapels; Richard Espinola; Joseph Reynolds; Jae Cha; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
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 | Understanding turbulence effects on wave propagation and imaging systems has been an active research area for more than 50 years. Conventional atmospheric optics methods use statistical models to analyze image degradation effects that are caused by turbulence. In this paper, we intend to understand atmospheric turbulence effects using a deterministic signal processing and imaging theory point of view and modeling. The model simulates the formed imagery by a lens by ... |
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| North Pacific Acoustic Laboratory: Analysis of Shadow Zone Arrivals and Acoustic Propagation in Numerical Ocean Models |
Feb-2009 |
12 pages |
| Authors:
Brian Dushaw; WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
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| Over the decade 1996-2006, acoustic sources located off central California and north of Kauai transmitted to receivers distributed throughout the northeast and north central Pacific. Some of the observations included shadow-zone arrivals, that appear at travel times aligned with the lower cusps of the acoustic time front predicted by ray calculations, but with the depth of the receiver lies well below the depths of the predicted cusps. Several models for ... |
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| Design and Analysis of Low Frequency Communication System in Persian Gulf |
Sep-2008 |
8 pages |
| Authors:
H Shahbazi; A Karimifard; TEHRAN UNIV (IRAN)
|
| One of the important applications of underwater communication is speech transmission between two divers or between divers and ship or submarine. This paper describes a project designed to investigate and demonstrate underwater communication system in Persian Gulf for speech transmission in a real channel. At first, transmitter is designed, then channel with real data is simulated by neural network and at last receiver is designed. Transmitted data is speech signal ... |
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| HF Over-the-Horizon Radar System Performance Analysis |
SEP 2007 |
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| Authors:
Bin-Yi Liu; NAVAL POSTGRADUATE SCHOOL MONTEREY CA CENTER FOR JOINT SERVICES ELECTRONIC WARFARE
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 | The basic concept of the structure and properties of the ionosphere are discussed to explain how the performance of the over-the-horizon radar (OTHR) system is affected. An overview of the OTHR system characteristics and performance are presented along with some applications currently used around the world, including their geographic location and historical background. The waveforms used for the OTHR systems include simple pulse, pulse Doppler, phased-coded pulse, frequency modulated continuous ... |
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| Sea Clutter Generation and Target Detection |
JUL 2007 |
26 pages |
| Authors:
Stefano M. Canta; Danilo Erricolo; ILLINOIS UNIV AT CHICAGO CIRCLE COLL OF ENGINEERING
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| Propagation model for the electromagnetic field that accounts for the clutter and metallic objects in the sea. Computationally fast, and the complete work will include electromagnetic propagation models and vector antennas. |
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| Computational Electromagnetics |
APR 2007 |
15 pages |
| Authors:
Fernando L. Reitich; MINNESOTA UNIV MINNEAPOLIS SCHOOL OF MATHEMATICS
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| Progress in the development of fast, error-controllable algorithms for the simulation of electromagnetic scattering throughout the frequency spectrum is reported. Advances are described in the development of (1) accelerated, high-order methods for the solution of general, penetrable scattering problems in the low-to-moderate frequency regime; (2) spectral methods for the solution of approximate high-frequency models (geometrical optics -GO-); and (3) general error-controllable high-frequency scattering solvers. Major accomplishments include the completion of ... |
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| NPAL Modeling-Internal Wave Effects/Theory and Modeling of Internal Wave Effects on Acoustic Propagation |
08 FEB 2007 |
3 pages |
| Authors:
Frank S. Henyey; WASHINGTON UNIV SEATTLE APPLIED PHYSICS LAB
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| North Pacific Acoustic Laboratory (NPAL) is the name for a set of experiments on long-range acoustic propagation through the ocean. For a sound to travel far in the ocean, its frequency must be low; sound at 70HZ was frequently used in NPAL experiments. It is common for the propagation of sound to be described in terms of ray tracing, a theory that assumes the frequency is high. An obvious question ... |
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| Reverberation Inversion Enhancements Using BASE 04 Data |
OCT 2006 |
52 pages |
| Authors:
C. Cainan; XWAVE HALIFAX (NOVA SCOTIA)
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| Previous contracts resulted in the development and use of the program BREVER, which performs reverberation inversion using the sonar analysis suite DMOS (DRDC Atlantic Model Operating System). A more recent contract allowed for the expansion of DMOS to incorporate the use of the ray trace program Bellhop as an alternative to the normal mode theory program PMODES. The current contract called for the expansion of BREVER so that it is ... |
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| The ITSIMBW Environment for Simulation and Decision Support |
01 SEP 2006 |
43 pages |
| Authors:
Uwe Beyer; Thomas Zoeller; Philipp Huegelmeyer; Timo Steffens; FRAUNHOFER INST FOR INTELLIGENT ANALYSIS AND INFORMATION SYSTEMS SANKT AUGUSTIN (GERMANY)
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| In this contribution, we give an overview on the military multi-agent simulation environment ITSimBw, which is developed at Fraunhofer IAIS/ART under contract for the department A5 of the IT office of the German Armed Forces (ITAmtBw), where the project is overseen by Captain Thomas Doll. Due to the growing importance of network centric capabilities in military operations, one of the main focus points for the development of ITSimBw is the ... |
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| Radio Propagation Prediction Software for Complex Mixed Path Physical Channels |
14 AUG 2006 |
91 pages |
| Authors:
Stephen A. Fast; REMCOM INC STATE COLLEGE PA
|
| It has become increasingly clear that the customers for the Mixed Path project desire API to the various Wireless InSite calculation engines. Thus the WI engines can be incorporated into tools such as OPNET and QualNet for network analysis or into various signal processing software. For network analysis all that is required is an extremely fast computing propagation model that captures the mixed path propagation at an acceptable resolution and ... |
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| Modeling of Ionospheric Refraction of UHF Radar Signals at High Latitudes |
JUN 2006 |
15 pages |
| Authors:
Brenton Watkins; Sergei Maurits; Anton Kulchitsky; ALASKA UNIV FAIRBANKS GEOPHYSICAL INST
|
| A three-dimensional ray-tracing code has been developed to run in conjunction with the University of Alaska polar ionospheric model. The ionospheric model may be run in a real-time predictive mode and its outputs have been used as an input to the ray tracing code. The objective of this work is to compute refractive effects on UHF radar signals due to time-varying ionospheric structures at high latitudes. Radar range and pointing ... |
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| Seismic Calibration of Group 1 IMS Stations in Eastern Asia for Improved IDC Event Location |
APR 2006 |
144 pages |
| Authors:
J. R. Murphy; W. L. Rodi; M. Johnson; J. D. Sultanov; T. J. Bennett; M. N. Toksoz; V. Ovtchinnikov; B. W. Barker; A. M. Rosca; Y. Shchukin; SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA
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| The determination of accurate seismic locations for detected events is one of the most important functions of nuclear test monitoring because location plays such a key role in nuclear test monitoring. In order to establish a robust nuclear test monitoring capability, it is necessary to calibrate the IMS seismic stations used in monitoring, to account for systematic deviations from the nominal travel time curves. This report presents a summary of ... |
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| Quasi-Analytic Model of OTHR Clutter from Equatorial Bubbles in the Ionosphere |
27 FEB 2006 |
61 pages |
| Authors:
Paul A. Bernhardt; NAVAL RESEARCH LAB WASHINGTON DC PLASMA PHYSICS DIV
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| Ground clutter for the over-the-horizon radar (OTHR) sky wave becomes Doppler shifted because of the ionosphere through which the radio rays are propagating changes. One source of these changes is ionospheric bubbles, which rise vertically through a horizontally stratified plasma near the equator. The rising plume structures are formed when gravity, neutral winds, or external electric fields act on the F-region plasma. The effect of these ionospheric disturbances can be ... |
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| DMOS - Bellhop Extension |
FEB 2006 |
32 pages |
| Authors:
C. Calnan; XWAVE HALIFAX (NOVA SCOTIA)
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| The current contract contains requirements to enhance the sonar analysis suite DMOS to incorporate the use of the ray trace program Bellhop, and then to produce an updated version of the DMOS User s Guide. The current document is a report on the project in general, describing the enhancement of DMOS and indicating changes made to existing members of that analysis suite necessitated by the addition of Bellhop. An updated ... |
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| An Adjoint State Method for Three-Dimensional Transmission Traveltime Tomography Using First-Arrivals |
30 JAN 2006 |
23 pages |
| Authors:
Shingyu Leung; Jianliang Qian; CALIFORNIA UNIV LOS ANGELES DEPT OF MATHEMATICS
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| Traditional transmission travel-time tomography hinges on ray tracing techniques. We propose a PDE-based Eulerian approach to travel-time tomography so that we can avoid the cumbersome ray-tracing. We start from the eikonal equation, define a mismatching functional and derive the gradient of the nonlinear functional by an adjoint state method. The resulting forward and adjoint problems can be efficiently solved by using the fast sweeping method; a limited memory BFGS method ... |
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| Electronically Reconfigurable Microwave Lens Antennas |
13 DEC 2005 |
54 pages |
| Authors:
Liang Xue; Vincent Fusco; QUEEN'S UNIV BELFAST (NORTHERN IRELAND)
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| The purpose of this report is to present the results of further investigations into the operation and design of two-dimensional Luneburg Lenses at 24 GHz, with the possibility for electronic control of their behavior. Various lens design techniques are illustrated; these include a holey dielectric lens (drilled dielectric), and a holey plate lens (etched holes on the upper metal plate). Ray tracing theory is presented which shows the general properties ... |
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| Limits to the Extraction of Information from Multi-Hop Skywave Radar Signals |
14 APR 2005 |
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| Authors:
Stuart Anderson; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION SALISBURY (AUSTRALIA)
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| The performance of high-frequency skywave radar systems is customarily referred to in terms of single-hop propagations, a mechanism which provides illumination of the earth's surface out to ranges of around 4000 kilometers. In practice, the process of ionospheric reflection often supports multiple hops, though the signals are inevitably subjected to much greater distortion and contamination. In this paper, the author addresses the issue of adequacy of conventional models of multi-hop ... |
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| Probing of the Artificial Hole in the Ionosphere with the HF Skywave Radar |
14 APR 2005 |
6 pages |
| Authors:
Pei-Nan Jiao; Tie-Han Ma; Guo-Liang Xu; Zong-Qiang Li; Xin-Sheng Zhang; Fei Xu; CHINA RESEARCH INST OF RADIOWAVE PROPAGATION XINXIANG (CHINA)
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| This paper describes an experiment in which high-frequency sky wave radar probed the artificial ionospheric hole that was caused by the flames of a rocket that was vertically launched and that penetrated the ionosphere. After the rocket had passed through the ionosphere the minimum time delay P(sub min)-f on the backscatter ionograms showed wave and focusing stripes resulting from the irregular structure. The results indicated a low electron density zone ... |
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| Imaging and Forecasting of Ionospheric Structures and Their System Impacts |
27 JAN 2005 |
76 pages |
| Authors:
Bodo Reinisch; Gary Sales; Paul Song; MASSACHUSETTS UNIV LOWELL CENTER FOR ATMOSPHERIC RESEARCH
|
| The COPEX attention was focused on the details of the early stages in the development of ionospheric (F-region) instabilities that precede the growth of equatorial bubbles. We continued our work on ground VLF station monitoring with the RPI/IMAGE instrument. We carried out RPI measurements using specifically designed operational modes with lower receiver gains. In the past year, several Radiation Belt Remediation (RBR) studies were done and many of them remain ... |
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| COLISEUM: An Application Programming Interface for 3D Plasma Simulations |
20 DEC 2004 |
19 pages |
| Authors:
Douglas VanGilder; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
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| APPROACH: A new 3D plasma simulation system (COLISEUM) is being developed: * Allows easy implementation of various plasma simulation modules for quicker code development & controllable fidelity * Using COTS extensively. CURRENT STATUS: * Low-fidelity plume (prescribed plume & ray tracing) * High- fidelity plume (AQUILA & DRACO) * Thruster modeling (HET & Colloid). FUTURE WORK: * DRACO (charging, sputtering, surface contamination) * AQUILA (parallel, generalized collisions) * Device modeling ... |
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| Simulation of Wireless Propagation in a High-Rise Building |
DEC 2004 |
97 pages |
| Authors:
Lotfi Boukraa; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| With the introduction of wireless Local Area Networks (WLANs) in many organizations, it became much easier to intercept confidential files and personal health records. The present study focused on radio frequency propagation in a high-rise building, specifically, the attenuation between floors, and the possibility of intercepting signals through the floors. The current work is based on simulations using the Urbana software tool. It is used to predict the contour of ... |
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| Simulations of Diversity Techniques for Urban UAV Data Links |
DEC 2004 |
115 pages |
| Authors:
Seng Cheong Telly Poh; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| In urbanized terrain, radiowave propagation is subjected to fading on large-scales and small-scales that would impede on the quality and reliability of data link transmission. This would have implications in many military applications. One example is the performance of unmanned aerial vehicle (UAV) data and communications links in complex urban environments. The purpose of this research is to study the effectiveness of diversity techniques on the performance of urban UAV ... |
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| High Order Electromagnetic Modeling for High Frequency |
15 OCT 2004 |
59 pages |
| Authors:
John T. Moore; SCIENCE APPLICATIONS INTERNATIONAL CORPCHAMPAIGN IL RESEARCH AND DEVELOPMENTDIV
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| The goals of this project were to insert mature physical theory of diffraction (PTD) based phenomenology models into the Xpatch computational electromagnetics (CEM) prediction codes and analysis tools. Several incremental length diffraction coefficient derivations were identified as candidates for inclusion. The shadow boundary incremental length diffraction coefficient (ILDC) capability was integrated based on the significant correction it applies to the physical optics current discontinuity in the neighborhood of the shadow ... |
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| Solar Thermal Propulsion for Microsatellite Manoeuvring |
SEP 2004 |
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| Authors:
F. G. Kennedy; SURREY UNIV GUILDFORD (UNITED KINGDOM)
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| The thesis will trace the development of the microsatellite solar thermal engine from conception through mission analysis design, modelling, fabrication, component, and system testing. On-sun testing of 14-cm and 56-cm diameter solar concentrating mirrors has clearly validated initial optical ray trace modelling and suggests that there is significant performance margin built into test concentrators. Electrical heating tests on two solar cavity receivers the Mk. I and Mk. II, have demonstrated ... |
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| Synthetic Vision: Visual Perception for Computer Generated Forces Using the Programmable Graphics Pipeline |
SEP 2004 |
115 pages |
| Authors:
Eugene R. Pursel; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| In visual simulations, the human must make most of her decisions based on the visual cues rendered to her display. On the other hand, synthetic forces have the luxury of basing their decisions on the data contained in the simulation's model. Line of sight calculations are often examples of the synthetic player's excess of information. Current methodologies for determining a synthetic player's line of sight to a target are generally ... |
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| BRL-CAD Tutorial Series: Volume IV Converting Geometry Between BRLCAD and Other Formats |
MAY 2004 |
54 pages |
| Authors:
John R. Anderson; Eric W. Edwards; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD SURVIVABILITY LETHALITY ANALYSIS DIRECTORATE
|
| Since 1979, the U.S. Army Research Laboratory has been developing and distributing the BRL-CAD constructive solid geometry (CSG) modeling package for a wide range of military and industrial applications. The package includes a large collection of tools and utilities, including an interactive three- dimensional geometry editor, raytracing and generic framebuffer libraries, network-distributed image-processing and signal-processing capabilities, and an embedded scripting language. As part of this effort, a multivolume tutorial series ... |
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| User's Manual for Long-Range Swell Forecasting Model |
27 FEB 2004 |
22 pages |
| Authors:
Y. L. Hsu; James D. Dykes; William C. O'Reilly; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| At many parts of the world's coasts, swell waves arriving from a distant generation region are an important part of the local wave climate. To provide accurate swell forecasting, a ray tracing swell model was developed using directional wave spectra from a global wave model as input. The model propagates swell energy from source regions to the forecast sites along great circle routes. The effect of island blocking is considered ... |
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| Exploitation of Microdoppler and Multiple Scattering Phenomena for Radar Target Recognition |
15 JAN 2004 |
69 pages |
| Authors:
Hao Ling; TEXAS UNIV AT AUSTIN DEPT OF ELECTRICALAND COMPUTER ENGINEERING
|
| This report summarizes the scientific progress on the research grant "Exploitation of MicroDoppler and Multiple Scattering Phenomena for Radar Target Recognition" during the period 1 October 2002 - 30 September 2003. Research on the construction of a microDoppler radar and the resulting data collection and signal processing is presented. Additional research into ray tracing simulation, inverse scattering and time reversal imaging is also reported. |
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| BRL-CAD Tutorial Series: Volume III - Principles of Effective Modeling |
SEP 2003 |
88 pages |
| Authors:
Lee A. Butler; Eric W. Edwards; Dwayne L. Kregel; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| Since 1979, tbe U.S. Army Research Laboratory has been developing and distributing the BRL-CAD constructive solid geometry (CSG) modeling package for a wide range of military and industrial applications. The package includes a large collection of tools and utilities, including an interactive geometry editor, raytracing and generic framebuffer libraries, network-distributed image- processing and signal-processing capabilities, and an embedded scripting language. As part of this effort, a multivolume tutorial series is ... |
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| High-frequency Broadband Matched Field Processing in the 8-16 kHz Band |
Sep-2003 |
8 pages |
| Authors:
Paul Hursky; Michael B Porter; Martin Siderius; Vincent K McDonald; SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA
|
| We will show model-based localization results at 8-16 kHz using a single hydrophone in several shallow water environments, with successful tracking out to 3 km. It is very difficult to produce accurate replicas of the field at these high frequencies, due to sensitivity to small bathymetric features, surface motion (waves), and water column fluctuations. To reduce this sensitivity, we match the envelope of the field in the time domain, using ... |
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| Flexible Three-Dimensional Modeling of Electric Thrusters in Vacuum Chambers |
25 JUN 2003 |
10 pages |
| Authors:
M. R. Gibbons; D. E. Kirtley; D. B. VanGilder; J. M. Fife; ENGINEERING RESEARCH AND CONSULTING INC(ERC INC) EDWARDS AFB CA
|
| A national team of researchers is developing a software system, COLISEUM, which performs calculations of plasma propagation and interaction with arbitrary 3%D surfaces. The applications of COLISEUM are wide- ranging, hut include simulating engine test configurations inside vacuum chambers and predicting sputtering and re-deposition on spacecraft surfaces. COLISEUM allows users to easily define complicated 3-D geometries using off the shelf CAD software, then select from a set of plasma expansion ... |
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| Measuring Electrodynamics of the Ionosphere by Digital Ionosondes and Other HF Techniques |
20 JAN 2003 |
30 pages |
| Authors:
Bodo Reinisch; Gary Sales; MASSACHUSETTS UNIV LOWELL CENTER FOR ATMOSPHERIC RESEARCH
|
| We conducted a general investigation into radiowave propagation modeling and ionospheric structure in the equatorial region. Techniques were developed to track ionospheric bubbles that form after sunset at or near the magnetic equator. These bubbles were identified as a source of satellite scintillation at 250 MHz. Drift speeds averaging around 100 m/s were observed during the test period in South America. HF propagation on a global scale was modeled using ... |
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| 3-D Computation of Surface Sputtering and Redeposition Due to Hall Thruster Plumes |
23 DEC 2002 |
11 pages |
| Authors:
J. M. Fife; M. R. Gibbons; W. A. Hargus; D. B. VanGilder; D. E. Kirtley; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| A 3-D computational plasma interaction modeling system is being developed to predict the interaction of electric propulsion plumes with surfaces. The system, named COLISEUM, Is designed to be flexible, usable, and expandable, allowing users to define surfaces with their choice of off-the-shelf 3-D solid modeling packages. These surfaces are then loaded into COLISEUM, which calculates plasma expansion from electric thrusters using a variety of functional modules. Functional modules are interchangeable, ... |
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| Development of High Frequency Numerical Simulation Tools for Electromagnetic Scattering and Radiation Problems in Frequency and Time Domain |
04 NOV 2002 |
85 pages |
| Authors:
Elizabeth H. Bleszynski; Marek K. Bleszynski; Thomas Jaroszewicz; MONOPOLE RESEARCH THOUSAND OAKS CA
|
| Report developed under STTR contract for topic AF01-T009. The main objective of the Phase I effort was to setup a framework for the wavefront (WF) evolution technique and to investigate the feasibility of incorporating, in a fashion consistent with reciprocity, of the edge diffraction effects into the WF approach. A wavefront is defined as a surface on which the propagating fields have a constant phase. Main advantages of the WF ... |
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| A Three-Dimensional Ray Tracing Simulation of a Synthetic Aperture Ground Penetrating Radar System |
OCT 2002 |
146 pages |
| Authors:
James W. Jeter III; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH
|
| Ground Penetrating Radar (GPR) is a useful tool for imaging the area below the Earth's surface. GPR works on the same principle as traditional radar, evaluating the electromagnetic returns reflected from an object or scene of interest to determine characteristics of the object that reflected the signal. Synthetic Aperture Radar (SAR) is a technique which combines radar returns of a given scene collected at several positions. By compiling the information ... |
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| Sensitivity Analysis of Limited Area Ocean Model |
AUG 2002 |
57 pages |
| Authors:
Dubar K. Kamara; JOHNS HOPKINS UNIV BALTIMORE MD
|
| The boundary data for a data assimilation problem for a limited-area ocean model can either be supplied by its global model or from observations interpolated from a conventional observing network. In this study, the sensitivity of the ocean model to variations in the boundary data is investigated. Additionally, the authors look at how predictions of wave height are affected by variations in basin depth. Two models are used to carry ... |
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| Herriott Cell Interferometery for Millimeter-Scale Plasma Measurements |
03 JUL 2002 |
21 pages |
| Authors:
Erik L. Antonsen; Rodney L. Burton; Gregory G. Spanjers; Scott F. Engelman; AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE WEST
|
| A Herriott Cell consists of two concave mirrors positioned on opposite sides of plasma so as to create multiple laser paths through the plasma. Added to a traditional interferometry diagnostic, the Herriott Cell multiplies the effective path length through the medium and thereby increases instrument resolution. Previous work validated the use of Herriott Cells in interferometer applications where the numerous mirror reflections will significantly degrade the phase front quality. The ... |
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| The Development of a Flexible, Usable Plasma Interaction Modeling System |
13 JUN 2002 |
10 pages |
| Authors:
J. M. Fife; M. R. Gibbons; D. B. VanGilder; D. E. Kirtley; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| A 3-D computational plasma interaction modeling system is being developed to predict the interaction of electric propulsion plumes with surfaces. The system, named COLISEUM, is designed to be flexible, usable, and expandable, allowing users to define surfaces with their choice of off-the-shelf 3-D solid modeling packages. These surfaces are then loaded into COLISEUM which performs plasma operations based on user commands. Functional modules are interchangeable, and can range from simple ... |
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| Algorithm and Code to Calculate Specular Reflection of Light from a Wavy Water Surface |
22 MAY 2002 |
10 pages |
| Authors:
Vladimir Haltrin; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
|
| In studying light and image transfer in sea water the influence of Fresnel surface reflection is as significant as scattering and absorption phenomena. In these cases a knowledge of the reflective properties of sea surface at different wind speeds is very important. At present, little is published about these properties. We present here results of numerical modeling of Fresnel light reflection coefficient of sea water as a function of solar ... |
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| A Study of Window Focusing Effects on Laser Ignition for Medium-Caliber Systems |
MAY 2002 |
34 pages |
| Authors:
Jeffrey B. Morris; Richard A. Beyer; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| One proposed implementation of medium-caliber laser ignition em ploys a focusing ball to replace the conventional electric primer. The effects of ball size and igniter stand-off distance have been characterized experimentally with black powder pellets. Ignition threshold and delay experiments were carried out using 4 mm and 6 mm diameter glass beads with standoffs up to 1.5 mm. Ray tracing was used to model the energy distribution of a top-hat ... |
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| Architecture and Initial Results of a 3-D Plasma Simulation System for Spacecraft-Thruster Interaction Assessment |
13 MAR 2002 |
10 pages |
| Authors:
J. M. Fife; M. R. Gibbons; D. B. VanGilder; D. E. Kirtley; AIR FORCE RESEARCH LAB EDWARDS AFB CA SPACE AND MISSILE PROPULSION DIV
|
| A 3-D Plasma Interaction Modeling System (PIMS) is being developed to predict the interaction of electric propulsion plumes with surfaces. The system is designed to be flexible, usable, and expandable, allowing users to define and mesh surfaces with their choice of off-the-shelf 3-D solid modeling packages. These surfaces are then loaded into PIMS, which performs plasma operations based on user commands. Functional PIMS modules will range from simple (prescribed plume ... |
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| Simulation of Passive Imaging of Underwater Objects |
NOV 2001 |
|
| Authors:
A. Kouzoubov; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) AERONAUTICAL AND MARITIME RESEARCH LAB
|
| A computer model simulating performance of passive optical sensors for imaging underwater objects from above-water paltforms is described. The model is based on the models of sun and sky spectral radiance, wavy sea surface, light propagation in seawater and is able to render images of underwater objects as seen through the air-water interface. |
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| Turbulence Simulation: On Phase and Deflector Screen Generation |
OCT 2001 |
68 pages |
| Authors:
David H. Tofsted; ARMY RESEARCH LAB WHITE SANDS NM COMPUTATIONAL AND INFORMATION SCIENCE DIRECTORATE
|
| This report examines the topic of phase screen generation and introduces an alternative method of modeling propagation through turbulence based on an extended raytrace method involving passage through three- dimensionally varying refractive turbulence. The mathematics of propagation through turbulence are thoroughly detailed, including several derivations often left as exercises for the reader in other documentation. Chapter 2 contains an analysis of the interrelationships between Fourier transforms, Fourier series, and Fast ... |
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| Applied Computational Electromagnetics Society Journal, Volume 16, Number 1, March 2001 |
MAR 2001 |
|
| Authors:
MISSISSIPPI UNIV UNIVERSITY DEPT OF ELECTRICAL ENGINEERING
|
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| Attenuation and Refraction of an Electromagnetic Wave in an Electron Beam Generated Plasma |
FEB 2001 |
166 pages |
| Authors:
Nathaniel P. Lockwood; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Artificially generated plasmas may be employed to alter the propagation characteristics of electromagnetic waves. The purpose of this report is to study the propagation of electromagnetic waves in an electron beam generated plasma. To understand the physics related to this concept requires the development of computational tools dealing with a plasma created by an electron beam, an assessment of the temporal and spatial evolution of the plasma, and a characterization ... |
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| Dynamic RCS: A Geometrical/Eulerian Approach to Computing High Frequency Radar Cross Sections |
2001 |
28 pages |
| Authors:
Stanley Osher; John Steinhoff; LEVEL SET SYSTEMS INC PACIFIC PALASIDESCA
|
| Level Set Systems (LSS) has developed a 3D-Eulerian, time-domain method for computing the propagation and scattering of short electromagnetic pulses over arbitrarily long distances. Efforts accommodated includes variation of index of refraction and scattering from complex features including tanks and aircraft. LSS developed a level set method for the construction of wavefronts that handles resolution, multivalued solutions, reflection and refraction. The key idea involves an Eulerian, fixed grid solver involving ... |
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| A Class for Run Time Computation of Shadows for Polygonal Objects |
AUG 2000 |
35 pages |
| Authors:
Mark A. Thomas; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD ADVANCED COMPUTATIONAL AND INFORMATION SCIENCES DIRECTORATE
|
| The development of realistic synthetic environments for dismounted soldier visualization requires attention to environmental cues. Effects such as shadows provide the soldier information about time of day and orientation. Graphical databases that do not have shadows must compute them at run time. Various methods of computing and displaying shadows exist. This report presents a simple method that is based on bounding volumes. The method provides ... |
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| Notes On Improved Exponential Troposphere Model |
17 APR 2000 |
42 pages |
| Authors:
Junho Choi; Sung Kwak; NAVAL RESEARCH LAB WASHINGTON DC COMMAND CONTROL COMMUNICATIONS COMPUTERS AND INTELLIGENCE
|
| Atmospheric data extraction and processing procedures are presented for four different Databases: ECM, HIRAS, MRF, and FNL. Details of database utility are described for application of geolocation measure and semi-major/ semi-minor axis EEP plot generation with miss-distance calculation procedure. New improved Exponential troposphere model algorithm has great utility reducing in processing time as well as improving geolocation accuracy by more than 50% for both ... |
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| User's Guide for the Sound Intensity Prediction System (SIPS) as Installed at the Naval Exposure Ordnance Disposal Technology Division (NAVEODTECHDIV) |
FEB 2000 |
21 pages |
| Authors:
Dean A. Pollet; Micheal M. Kordich; NAVAL SURFACE WARFARE CENTER DAHLGREN DIV VA DEPT OF WEAPONS SYSTEMS
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| The Sound Intensity Prediction System (SIPS) is a noise-complaint management tool for range commanders to help control the impact of noise from explosive operations on surrounding communities. SIPS uses acoustic ray-tracing techniques to predict areas of sound intensification and reduction caused by atmospheric refraction. The predictions coupled with operational procedures allow for a `GO' or "NO GO decision. SIPS has been used at the Naval Surface Warfare Center, Dahlgren Division ... |
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| Applied Computational Electromagnetics Society Journal. Special Issue on Computational Electromagnetic Techniques in Mobile Wireless Communications. Volume 15, Number 3, 2000 |
2000 |
145 pages |
| Authors:
Ray Perez; Chris Holloway; Ahmed Kishk; Allen Glisson; MISSISSIPPI UNIV UNIVERSITY DEPT OF ELECTRICAL ENGINEERING
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| TABLE OF CONTENTS: A Random Phase Assisted Ray Tracing Technique for Wireless Channel Modeling; Nanocells Intrasystem Interference Realistic Worst Case Analysis for Open Site Personnal Communication Scenarios; Designing Embedded Antennas for Bluetooth Protocol; Analysis and Design of Tapered Meander Line Antennas for Mobile Communications; A Cole-Cole Diagram Representation of Micro strip Structure; Enhancement of Numerical Computation Methods Useful for Radio Communication Antenna Systems; Time and Frequency Domain Wave Propagators; Ray ... |
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RAY TRACING
