| Holography at the U.S. Army Research Laboratory: Development of Hologram Transform Equations using the Fresnel Approximation |
Sep 2012 |
18 pages |
| Authors:
Jr Klett Karl K; Neal Bambha; Justin Bickford; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
|
 | This report describes the development and use of the Fresnel approximation, which is necessary to transform a digital hologram to an image. The result is that a Fourier transform, common to many image processing applications, may be used to produce the image. The U.S. Army Research Laboratory's (ARL) goal is to investigate applications of holographic interferometry and transform the holographic interference pattern to three-dimensional images. The mathematics described in this ... |
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| Analysis of the Hessian for Inverse Scattering Problems. Part 3. Inverse Medium Scattering of Electromagnetic Waves in Three Dimensions |
Aug 2012 |
17 pages |
| Authors:
Tan Bui-Thanh; Omar Ghattas; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
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| Continuing our previous work [6, Inverse Problems, 2012, 28, 055002] and [5, Inverse Problems, 2012, 28, 055001], we address the ill-posedness of the inverse scattering problem of electromagnetic waves due to an inhomogeneous medium by studying the Hessian of the data mis t. We derive and analyze the Hessian in both H older and Sobolev spaces. Using an integral equation approach based on Newton potential theory and compact embeddings in ... |
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| Calculation of Impedance Matrix Inner Integral to Prescribed Precision for the Magnetic Field Integral Equation |
19 Jul 2012 |
109 pages |
| Authors:
John S Asvestas; Dennis W Richardson; Oliver E Allen; NAVAL AIR WARFARE CENTER AIRCRAFT DIV PATUXENT RIVER MD
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| The Method of Moments (MoM) is a powerful computational electromagnetics method for analyzing antennas in situ. In a previous report, we presented a new method for evaluating the inner integral of the impedance matrix element in the traditional Rao-Wilton-Glisson formulation of MoM for the electric field integral equation. In this report, we extend our method to the magnetic field integral equation. We show how, in this case, the inner integral ... |
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| Stochastic-Integral Models for Propagation-of-Uncertainty Problems in Nondestructive Evaluation (Preprint) |
Jul 2012 |
8 pages |
| Authors:
Jeremy Knopp; Mark P Blodgett; Elias H Sabbagh; R K Murphy; Harold A Sabbagh; John C Aldrin; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH MATERIALS AND MANUFACTURING DIRECTORATE
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| Generalized polynomical chaos (gPC) and the probabilistic collocation method (PCM) are finding considerable application to problems of interest to engineers in which random parameters are an essential feature of the mathematical model. So far the applications have been mainly to stochastic partial differential equations, but we extend the method to volume-integral equations, which have met great success in electromagnetic nondestructive evaluation (NDE), especially with eddy-currents. The problems of main interest ... |
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| Advances in Developing Multiscale Flaw Models for Eddy-Current NDE (Preprint) |
Dec 2011 |
9 pages |
| Authors:
R K Murphy; Harold A Sabbagh; Elias H Sabbagh; John R Bowler; Yuan Ji; John C Aldrin; VICTOR TECHNOLOGIES LLC BLOOMINGTON IN
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| The need to accurately model multiscale phenomena is ubiquitous in eddy-current nondestructive evaluation. By using volume-integral equations, we are able to develop a very simple algorithm for accurately computing the response of a very small anomaly in the presence of a much larger one. We validate the algorithm and its associated code in VIC-3D(copyright) through benchmark data on two test sets: (1) a notch at a bolt hole with an ... |
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| Advances in Statistical and Deterministic Modeling of Wind-Driven Seas |
30 Sep 2011 |
11 pages |
| Authors:
Vladimir E Zakharov; WAVES AND SOLITONS LLC PHOENIX AZ
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| The long-term goal of this research is the development of accurate, fast, and advanced statistical and dynamical nonlinear models of ocean surface waves based on first physical principles. These wave models will improve both long-term ocean surface wave forecasts and the prediction of strongly coherent events, such as freak waves, tsunamis, and wave breaking. The objectives of this project are as follows: (1) finding a physically correct wind input term ... |
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| Analysis of the Hessian for Inverse Scattering Problems. Part 1: Inverse Shape Scattering of Acoustic Waves |
Jun 2011 |
40 pages |
| Authors:
Tan Bui-Thanh; Omar Ghattas; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
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| We derive expressions for the shape Hessian operator of the data misfit functional corresponding to the inverse problem of inferring the shape of a scatterer from reflected acoustic waves, using a Banach space setting and the Lagrangian approach. The shape Hessian is then analyzed in both Hoelder and Sobolev spaces. Using an integral equation approach and compact embeddings in Hoelder and Sobolev spaces, we show that the shape Hessian can ... |
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| Analysis of the Hessian for Inverse Scattering Problems. Part 2: Inverse Medium Scattering of Acoustic Waves |
Jun 2011 |
22 pages |
| Authors:
Tan Bui-Thanh; Omar Ghattas; TEXAS UNIV AT AUSTIN INST FOR COMPUTATIONAL ENGINEERING AND SCIENCES
|
| We address the inverse problem for scattering of acoustic waves due to an inhomogeneous medium. We derive and analyze the Hessian in both H older and Sobolev spaces. Using an integral equation approach based on Newton potential theory and compact embeddings in Holder and Sobolev spaces, we show that the Hessian can be decomposed into two components, both of which are shown to be compact operators. Numerical examples are presented ... |
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| Computational Electromagnetics |
20 Feb 2011 |
9 pages |
| Authors:
Oscar P Bruno; CALIFORNIA INST OF TECH PASADENA
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| The overall work in the proposed areas for the duration of this effort, through November 2010, is detailed in what follows. In particular, our efforts gave rise to 1) Volumetric propagation and scattering solvers for propagation through thousand of kilometers of realistic three-dimensional atmospheres (completed in 2009); 2) Development of high-order solvers, which do not suffer from restrictive CFL conditions, for solution of time-dependent wave-propagation problems in inhomogeneous media; 3) ... |
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| Three-Dimensional Shape Optimization in Viscous Incompressible Flows |
Feb 2011 |
39 pages |
| Authors:
Michael Zabarankin; STEVENS INST OF TECH HOBOKEN NJ DEPT OF MATHEMATICAL SCIENCES
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| The integral equation constrained optimization approach to finding three-dimensional minimum-drag shapes for bodies translating in viscous incompressible fluid has been developed. The approach relies on the theory of generalized analytic functions for obtaining efficient integral equations for 3D boundary-value problems with linear partial differential equations (PDEs). The theory has been developed in application to 3D Stokes and Oseen flows, two-phase Stokes flows and 3D magnetohydrodynamic (MHD) flows governed by linearized ... |
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| Third-Order Family of Methods in Banach Spaces |
24 Jan 2011 |
15 pages |
| Authors:
Changbum Chun; Pantelimon Stanica; Beny Neta; NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF APPLIED MATHEMATICS
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| Recently, Parida and Gupta (J. Comp. Appl. Math. v206 (2007) p873-877) used Rall's recurrence relations approach (from 1961) to approximate roots of nonlinear equations by developing several methods, the latest of which is free of second derivatives and is of the third order. In this paper, the authors use an idea from Kou and Li (Appl. Math. Comp. v187 (2007), p1027-1032) and modify the approach of Parida and Gupta to ... |
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| On the Nystrom Discretization of Integral Equations on Planar Curves with Corners |
22 Jul 2010 |
22 pages |
| Authors:
James Bremer; CALIFORNIA UNIV DAVIS DEPT OF MATHEMATICS
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| The Nystrom method can produce ill-conditioned systems of linear equations and inaccurate results when applied to integral equations on domains with corners. This defect can already be seen in the simple case of the integral equations arising from the Neumann problem for Laplace's equation. We explain the origin of this instability and show that a straightforward modification to the Nystrom scheme, which renders it mathematically equivalent to Galerkin discretization, corrects ... |
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| Universal Quadratures for Boundary Integral Equations on Two-Dimensional Domains with Corners |
24 Nov 2009 |
21 pages |
| Authors:
J Bremer; V Rokhlin; I Sammis; YALE UNIV NEW HAVEN CT DEPT OF COMPUTER SCIENCE
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| We describe the construction of a collection of quadrature formulae suitable for the efficient discretization of certain boundary integral equations on a very general class of two-dimensional domains with corner points. The resulting quadrature rules allow for the rapid high accuracy solution of Laplace's equation and the Helmholtz equation on such domains. Our approach can be adapted to many other boundary value problems as well as to the case of ... |
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| An Adaptive Fast Direct Solver for Boundary Integral Equations in Two Dimensions |
21 Aug 2009 |
31 pages |
| Authors:
W Y Kong; J Bremer; V Rokhlin; YALE UNIV NEW HAVEN CT DEPT OF COMPUTER SCIENCE
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| We describe an algorithm for the rapid direct solution of linear algebraic systems arising from the discretization of boundary integral equations of potential theory in two dimensions. The algorithm is combined with a scheme that adaptively rearranges the parameterization of the boundary in order to minimize the ranks of the off-diagonal blocks in the discretized operator, thus obviating the need for the user to supply a parameterization r of the ... |
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| THz-Imaging Through-the-Wall Using the Born and Rytov Approximation |
Dec-2008 |
101 pages |
| Authors:
Kwangmoon Lee; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| We investigated an inverse imaging problem by applying the Rytov approximation for Through-the-Wall Imaging using THz waves. In the beginning, we studied some properties of THz waves and the physical conditions for THz imaging in matter. Then we started with Maxwell's equations to derive a model for the transmission of Green's functions and used a Lippman-Schwinger integral equation and Rytov approximation to predict the scattered field. We applied the L-curve ... |
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| Semi-Analytical Approach to Three-Dimensional Shape Optimization Problems |
APR 2008 |
21 pages |
| Authors:
Michael Zabarankin; STEVENS INST OF TECH HOBOKEN NJ
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| A semi-analytical approach to three-dimensional (3-D) shape optimization problems for a viscous incompressible fluid under the assumption of zero (low) Reynolds number has been developed. It couples the theory of generalized analytic functions with the adjoint equations-based method. A solution to Stokes equations governing the behavior of the fluid has been reduced to integral equations based on the Cauchy integral formula for k-harmonically analytic functions. The fluid velocity and boundary ... |
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| Computational Electromagnetics |
25 FEB 2008 |
10 pages |
| Authors:
Oscar P. Bruno; MICHELSON SCIENCE CENTRE/CALTECH PASADENA CA
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| The Objectives are as follows: 1) High-frequency integral equations: Multiple-scattering/ shadowing interactions; 2) Periodic and random surfaces and structures; 3) Canonical Integration: Edge scattering; 4) Canonical Integration: High Frequency; 5) Geometry representation and solution of challenging real-world problems. |
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| Efficient Craig Interpolation for Linear Diophantine (Dis)Equations and Linear Modular Equations |
FEB 2008 |
40 pages |
| Authors:
Himanshu Jain; Edmund M. Clarke; Orna Grumberg; CARNEGIE-MELLON UNIV PITTSBURGH PA SCHOOL OF COMPUTER SCIENCE
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| The use of Craig interpolants has enabled the development of powerful hardware and software model checking techniques. Efficient algorithms are known for computing interpolants in rational and real linear arithmetic. We focus on subsets of integer linear arithmetic. Our main results are polynomial time algorithms for obtaining proofs of unsatisfiability and interpolants for conjunctions of linear diophantine equations linear modular equations (linear congruences), and linear diophantine disequations. We show the ... |
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| Applying Formal Methods to a Certifiably Secure Software System |
FEB 2008 |
18 pages |
| Authors:
Constance L. Heitmeyer; Myla M. Archer; Elizabeth I. Leonard; John D. McLean; NAVAL RESEARCH LAB WASHINGTON DC INFORMATION TECHNOLOGY DIV
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| A major problem in verifying the security of code is that the code's large size makes it much too costly to verify in its entirety. This paper describes a novel and practical approach to verifying the security of code which substantially reduces the cost of verification. In this approach, a compact security model containing only information needed to reason about the security properties of interest is constructed and the security ... |
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| Hearing Protection for High-Noise Environments. Part 2: Finite Element Modeling |
31 MAY 2007 |
51 pages |
| Authors:
Elizabeth Bleszynski; Marek Bleszynski; Thomas Jaroszewicz; MONOPOLE RESEARCH THOUSAND OAKS CA
|
| Report developed under STTR contract for topic AF06-T035. The objective of our effort was to develop powerful software tools and to perform high fidelity simulation which would allow identification and understanding of relevant bio-acoustic and psycho-acoustic mechanisms responsible for the transmission of acoustic energy through non-airborne pathways to the cochlea. As the main achievements of our Phase I work we consider: (1) development of a set of algorithms (including non-lossy, ... |
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| Analysis and Design of Ultra Wide-Band and High-Power Microwave Pulse Interactions With Electronic Circuits and Systems |
28 FEB 2007 |
55 pages |
| Authors:
Piergiorgio L. Uslenghi; Danilo Erricolo; Hung-Yu D. Yang; ILLINOIS UNIV AT CHICAGO
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| This research is directed to understanding and modeling the effects of electromagnetic pulse interactions with electronic circuits and systems, and is focused on four major tasks. (1) Characterization of coupling mechanisms responsible for guiding electromagnetic energy from the source to the electronic components, via topology schemes based on a generalized scattering matrix. Frequency-domain and time-domain solvers are developed for large-scale systems. The results are validated via measurements and via comparison ... |
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| Research in Electromagnetic Scattering |
31 JUL 2006 |
8 pages |
| Authors:
Arthur Yaghjian; DEVANEY (AJ) ASSOCIATES HARVARD MA
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| In the main area of Frequency-Domain Electromagnetics, we made significant accomplishments in the sub-areas of Scattering-Matrix Analysis of periodic Arrays, Bandwidth and Quality Factor of Antennas, Supergain Arrays, and Surface Integral Equations. Yaghjian also continued to consult with John Moore of SAIC on his further testing of the source-based ILDC's implemented in recent years into the widely used high-frequency computer code Xpatch. A joint paper with Shore and Moore on ... |
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| Termination of A Half-Width Leaky-Wave Antenna (Preprint) |
JUL 2006 |
6 pages |
| Authors:
Daniel Killips; Michael Corwin; Leo Kempel; Stephen Schneider; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SENSORS DIRECTORATE
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| Leaky-wave antennas offer the potential for a wide operational bandwidth from a very thin antenna. Recently, a leaky-wave antenna that is half the usual width of a planar microstrip leaky-wave antenna was proposed. One of the major advantages of this design is that it requires only a single, rather simple, feed mechanism. To maintain the full potential bandwidth of that antenna, an appropriate termination is required. In this paper, a ... |
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| Excitation of the Magnetospheric Cavity by Space-Based ELF/VLF Transmitters |
30 DEC 2005 |
11 pages |
| Authors:
Timothy F. Bell; STANFORD UNIV CA SPACE TELECOMMUNICATIONS AND RADIOSCIENCE LAB (STAR)
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| During the period of performance, Stanford University completed the development of integral equations describing the distribution of current along a dipole antenna radiating ELF/VLF waves in the magnetospheric cavity. It was found that the radiation resistance was much smaller near the lower-hybrid resonance frequency than previously believed. Stanford University included the effects of ion temperature in the plasma dielectric tensor. It was found that the ion temperature had a first-order ... |
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| Adaptive Protocols for Mobile Wireless Networks |
22 DEC 2005 |
37 pages |
| Authors:
Michael B. Pursley; CLEMSON UNIV SC DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| Results are reported for basic research in mobile wireless communication networks for tactical applications including investigations of new methods for error-control coding and decoding, modulation and demodulation, channel access, adaptive transmission and routing, and broadband antenna design. Research results are presented on adaptive, energy-efficient, distributed protocols for mobile wireless networks that must operate effectively over unreliable communication links in highly dynamic environments and handle multimedia traffic. The dominant feature of ... |
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| Stochastic Representation of the Marcum Q-Function and Associated Radar Detection Probabilities |
DEC 2005 |
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| Authors:
Graham V. Weinberg; DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION EDINBURGH (AUSTRALIA) ELECTRONIC WARFARE AND RADAR DIVISION
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 | This report introduces new research on the generalized Marcum Q-Function, and in particular, the probability of detection of a number of incoherently integrated signals in a Gaussian clutter and noise environment. A new probabilistic association is derived, linking this detection probability with a probability associated with two independent Poisson random variables. Additionally, it is shown that this detection probability is the solution to two stochastic Volterra integral equations. This results ... |
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| Separated Representation for Computational Materials Science |
31 OCT 2005 |
30 pages |
| Authors:
Gregory Beylkin; Martin J. Mohlenkamp; Lucas Monzon; COLORADO UNIV AT BOULDER DEPT OF APPLIED MATHEMATICS
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| Our goal was to develop novel multiparticle computational tools for materials science based on representing operators and functions of many variables as short sums of separable functions. We have extended multiresolution separated representation of free-space Green's functions to those periodic or satisfying boundary conditions, making fast algorithms available for solving integral equations. The problem of incorporating inter-electron cusps within two-particle methods led us to the problem of approximating multivariable functions ... |
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| Velocity Averaging, Kinetic Formulations and Regularizing Effects in Quasilinear PDEs |
31 OCT 2005 |
29 pages |
| Authors:
Eitan Tadmor; Terence Tao; MARYLAND UNIV COLLEGE PARK DEPT OF MATHEMATICS
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| We prove new velocity averaging results for second-order multidimensional equations. In particular, we improve previous regularity statements for nonlinear conservation laws, and we derive completely new regularity results for convection-diffusion and elliptic equations driven by degenerate, non-isotropic diffusion. |
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| Sound Wave Mitigation Through the Design of Surface Impedance |
21 SEP 2005 |
36 pages |
| Authors:
Weng C. Chew; Gong L. Wang; ILLINOIS UNIV AT URBANA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
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| An artificial soft surface is proposed to reduce and attenuate the propagation of acoustic waves along the surface of hard ground. An infinitesimal pressure line source is used as the excitation. Instead of an ideal periodic structure, a quasi-periodic structure is used where a finite number of grooves are incorporated to model exactly the realistic situation. Two boundary integral equation methods are proposed, one is based on the free space ... |
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| Modeling the Electromagnetic Scattering by 3-D Objects in a Layered Media. Electromagnetic Active Detection of Metallic Targets |
24 AUG 2005 |
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| Authors:
Marius S. Birsan; DEFENCE RESEARCH AND DEVELOPMENT ATLANTIC DARTMOUTH (CANADA)
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| The underwater electromagnetic (EM) active detection technique attempts to reveal a stealth iron-hull vessel (submarine or surface warship) located in a horizontal layer of seawater. Our goal is to numerically investigate the EM scattering process in the presence of a metallic vessel of arbitrary shape placed inside a lossy media. To solve the EM scattering problem involving perfectly conducting (PEC) objects we make use of the Method of Moments (MoM) ... |
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| On Improving the Convergence of the Solution of a System of Linear Equations |
AUG 2005 |
22 pages |
| Authors:
Surendra Singh; Klaus Halterman; J. M. Elson; TULSA UNIV OK DEPT OF ELECTRICAL ENGINEERING
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| The computation of electromagnetic scattering from a nanowire requires the solution of a system of linear equations of the form, Ax=b, where the dimension of the matrix A increases with the number of unknowns. Previously, we had implemented a bi-conjugate gradient algorithm to iteratively solve this system of equations. However, this method converges very slowly when the convergence criterion is made stringent. An improved version of the algorithm, namely stabilized ... |
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| Fast Multipole / Wavelet-IML Hybrids for Electromagnetic Analysis |
20 JUL 2005 |
19 pages |
| Authors:
Eric Michielssen; Andreas Cangellaris; Weng Chew; Jianming Jin; ILLINOIS UNIV AT URBANA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| In recent years, a variety of computational schemes have been developed that accelerate the iterative solution of the dense matrix equations that arise upon discretizing boundary integral equations pertinent to the description of electromagnetic scattering problems. These schemes largely fall into two categories: (i) fast multipole methods and (ii) wavelet/multiresolution schemes. The overall goal of this project is to develop and catalogue all practical hybrids between fast multipole solvers and ... |
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| Inversion for Subbottom Sound Velocity Profiles in the Deep and Shallow Ocean |
FEB 2005 |
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| Authors:
Luiz L. Souza; WOODS HOLE OCEANOGRAPHIC INSTITUTION MA
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| We investigate the application of acoustic measurement sin the ocean to measurer the sound velocity profile (svp) in the subbottom. For the deep water ocean, an exact method based on the Gelfand-Levitan integral equation is evaluated. The input data is the complex plane-wave reflection coefficient. We apply the method to experimental acoustic data and estimate the reflection coefficient and the svp in the seabed. |
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| New Numerical Integrators Based on Solvability and Splitting |
03 JAN 2005 |
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| Authors:
Fernando Casas; UNIVERSIDAD JAUME I CASTELLON (SPAIN) DEPARTAMENTO DE INGENIERIA Y CIENCIA DE LOS COMPUTADORES
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| Outline of the Talk: 1. Some (well known) Lie group methods for linear problems (Fer and Magnus expansions); 2. Schemes based on triangular matrices (splitting + solvability); 3. Some methods and practical issues in their construction. |
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| Lie Group Techniques for Neural Learning |
03 JAN 2005 |
37 pages |
| Authors:
Elena Celledoni; SINTEF APPLIED MATHEMATICS OSLO (NORWAY)
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| OUTLINE: 1. Neural Networks: a short introduction; 2. Independent Component Analysis: (a) Stochastic signal processing; (b) Constraint optimization in ICA; 3. Geometric Integration of Learning Equations: (a) Gradient flows and algorithms on manifolds; (b) MEC learning; (c) Newton methods; (d) Diffusion algorithms. |
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| Parameter Estimation Techniques for a Class of Nonlinear Hysteresis Models |
2005 |
16 pages |
| Authors:
Ralph C. Smith; Andrew G. Hatch; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
|
| This paper addresses the development of parameter estimation techniques for a class of models used to characterize hysteresis and constitutive nonlinearities inherent to ferroelectric, ferromagnetic and ferroelastic materials employed in a wide range of actuators and sensors. These models are formulated as integral equations with known kernels and unknown densities to be identified through least squares techniques. Due to the compactness of the integral operators, the resulting discretized models inherit ... |
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| Efficient Analysis of Microwave Devices Based on Polygonal Modeling and WIPL-D Numerical Engine |
2005 |
5 pages |
| Authors:
Miodrag S. Tasic; Branko M. Kolundzija; BELGRADE UNIV (YUGOSLAVIA) FACULTY OF ELECTRICAL ENGINEERING
|
| Surface formulation of method of moments gives the best results in electromagnetic analysis when geometrical modeling is performed with quadrilateral patches. Quadrilateral modeling, however, can be very difficult. Many structures, e.g. different microwave devices, can be easily modeled using polygonal surfaces. This paper presents general method for conversion of polygonal model into quadrilateral model. Proposed method is illustrated on real microwave filter. |
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| High-Order Hybrid Finite Element Technology for Simulation of Large- Scale Array Antennas Embedded in Inhomogeneous Media |
01 NOV 2004 |
25 pages |
| Authors:
Jianming Jin; ILLINOIS UNIV AT URBANA
|
| This report summarizes our research effort on the development of higher-order hybrid finite element techniques that are capable of simulating large array antennas embedded in inhomogeneous media. The effort led to the development of a suite of FEM-based simulation tools to deal with a variety of array antennas, which include (i) infinitely large periodic phased arrays, (ii) array antennas that are finite in one dimension and infinitely periodic in the ... |
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| Dynamic Fracture in Temperature Sensitive Materials With Cohesive Zones: A Discontinuous Galerkin Approach |
NOV 2004 |
16 pages |
| Authors:
Francesco Costanzo; PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF ENGINEERING SCIENCE AND MECHANICS
|
| This project began July 1, 2002 and will expire on November 30, 2004. During the last two years, the primary focus of this effort has been the creation of a reliable computational capability for the solution of elasto- dynamic moving boundary problems. Specifically, the PI, along with a student: 1) has formulated a space-time discontinuous Galerkin finite element (DGFEM) formulation that has been shown to be unconditionally stable and capable ... |
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| Fast Time Domain Integral Equation Solvers for Large-Scale Electromagnetic Analysis |
OCT 2004 |
43 pages |
| Authors:
Eric Michielsssen; Weng C. Chew; Jianming Jin; Balasubramaniam Shanker; ILLINOIS UNIV AT URBANA BOARD OF TRUSTEES
|
| New fast time domain integral equation (TDIE) solvers for analyzing large-scale electromagnetic scattering and radiation phenomena were developed. These solvers were accelerated using a host of new Plane Wave Time Domain (PWTD) algorithms. PWTD augmented TDIE solvers accomplish for the time domain wave equation (and related Maxwell's equations) what fast multipole methods previously achieved for the Poisson and Helmholtz equations, viz. a significant reduction in computational cost of the integral ... |
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| Research in Electromagnetic Scattering and Phase Space Methods in Radiation Propagation |
01 SEP 2004 |
9 pages |
| Authors:
Arthur D. Yaghjian; DEVANEY (A J) ASSOCIATES BOSTON MA
|
| This document constitutes a final report for our research in electromagnetic scattering during the years 2001-2003. The technical research accomplishments during each year divide conveniently into the areas of basic electromagnetic theory, scattering-matrix analysis of antenna arrays, and surface integral equations. Significant contributions were also made in the area of incremental length diffraction coefficients and toward the development of the Air Force cylindrical near-field scanning facility for measuring bistatic RCS. ... |
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| Modal Expansion Functions Combined with EFIE Applied to Air Intake/Engine RCS Computations |
23 APR 2004 |
9 pages |
| Authors:
Andre Barka; Beatrice Fromentin; Sophie Langlet; OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AEROSPATIALES TOULOUSE (FRANCE) DEMR
|
| In this paper we will describe a sub-domain method based on integral equations devoted to the RCS analysis of Air Intake and rotating fans. The accuracy and efficiency of theses techniques will be demonstrated for the CHANNEL 1/4 scaled mock-up. During the computation a set of sub-domain will be calculated and connected in a final step. The RCS results will be compared with measurements on the CHANNEL mock-up for 2 ... |
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| Simulations of Radar Scattering Over a Rough Sea Surface |
MAR 2004 |
46 pages |
| Authors:
Khalid Jamil; Robert J. Burkholder; OHIO STATE UNIV COLUMBUS ELECTROSCIENCE LAB
|
| Forward scattering from a 2D rough sea surface is simulated using the Generalized Forward-Backward (GFB) method in a Monte Carlo fashion. Measurements were performed using a sealed ocean model in the NSWC Carderock Maneuvering and Sea-Keeping (MASK) wavetank facility. The mean, standard deviation and probability density function (PDF) of the computational and experimental data is compared and good agreement is found. Backscattering from a floating target on the rough sea ... |
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| Parameter Estimation Techniques for a Polarization Hysteresis Model |
2004 |
10 pages |
| Authors:
Ralph C. Smith; Andrew Hatch; NORTH CAROLINA STATE UNIV AT RALEIGH CENTER FOR RESEARCH IN SCIENTIFIC COMPUTATION
|
| This paper focuses on the development of parameter estimation techniques for models quantifying hysteresis and constitutive nonlinearities in ferroelectric materials. These models are formulated as integral equations with known kernels and unknown densities to be identified through least squares fit to data. Due to the compactness of the integral operators, the resulting discretized models inherit ill-posedness which often must be accommodated through regularization. The accuracy of regularized finite-dimensional models is ... |
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| Far Field Extrapolation Technique Using CHIEF Enclosing Sphere Deduced Pressures and Velocities |
DEC 2003 |
191 pages |
| Authors:
Robert M. Drake; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| A Combined Helmholtz Integral Equation Formulation (CHIEF)-defined enclosing sphere placed around an acoustic projector is used to calculate far field response data from near field measurements. Pressure response data at a specified frequency is obtained from a near field linear array. Helmholtz integral relations for the enclosing sphere and integrals of the free-space Green's function and its gradient for defined near field point locations are used along with physical assumptions ... |
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| Exploitation of Omnidirectional Reflectivity |
SEP 2003 |
27 pages |
| Authors:
Tri Van; Dennis Nyquist; Leo Kempel; Gang Bao; MISSION RESEARCH CORP SANTA BARBARA CA
|
| In this final report, we have summarized the progress made during the period of September 1. 2002-September 30, 2003. We derive the integral equations for (electric fields propagating in a fiber of arbitrary cross section and arbitrary refractive index. Mathematical analysis of conventional optical fibers is rich and widely available in literature, for example 3, 9, 11 and references therein. It helps the advancement of optical fiber industry in understanding ... |
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| Electromagnetic Backscattering from a Triangular Dielectric Cylinder |
11 JUN 2003 |
2 pages |
| Authors:
Lyudmila N. Illyashenko; AKADEMIYA NAUK USSR KHARKOV INST OF RADIOPHYSICS AND ELECTRONICS
|
| Boundary integral equations (IEs) are an accurate and versatile tool in the electromagnetic scattering by smooth cylinder 1 especially when it is combined with analytical preconditioning 2. An original approach to the E-wave scattering by PEC polygons was developed in 3 to study a triangular prism. Here the boundary of the scatterer was conformally mapped on a circular cylinder 4, and a log-singular IL was treated by a simple moment ... |
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| Resonant Coupling of Cavity-Backed Slots |
11 JUN 2003 |
4 pages |
| Authors:
Aleksandr V. Sulima; RADIO-ASTRONOMY INST KHARKOV (UKRAINE)
|
| A rigorous solution of the problem of a TE wave scattering by a finite number of slots in a PEG plane backed by resonant cavities is given. The scattering problem formulated in terms of system of singular integral equations has been solved by the method of analytical regularization. Application of the regularization procedure allowed obtaining an accurate and numerically efficient solution. |
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| Modeling of Electromagnetic Field from Mobile Phone Distributed in the Human Head Phantom |
11 JUN 2003 |
1 pages |
| Authors:
Victor Goblyk; Yevheniya Yakovenko; NATIONAL UNIV LVIV (UKRAINE)
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| This work is a development of ideas originally presented in 1, 2. In the work 1, a general equation for the modeling of electromagnetic field in a inhomogeneous dielectric environment was given. In the work 2, this approach was used for the hyperthermia problems solution. In our work the modeling of electromagnetic field from a mobile phone distributed in the human head phantom was carried out. The modeling was done ... |
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| Investigation of Composite Materials with Controllable Electrodynamic Properties |
11 JUN 2003 |
3 pages |
| Authors:
Ruslan V. Kornev; Valerij I. Demidtchik; BELARUSSIAN STATE UNIV MINSK DEPT OF RADIOPHYSICS
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| The method of electrodynamic analysis of single conducting fibres having various configuration is offered. Numerical experiments on studying the influence of wire elements geometry on properties of a scattered field are carried out and the possibility to control these properties is shown. |
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INTEGRAL EQUATIONS
