New ultrasonic modeling findings are presented contributing to ten fundamental problems related to low-frequency seismoacoustic wave phenomena resulting from the interaction of underwater acoustic waves with heterogeneous elastic boundaries such as the ice cover and/or ocean bottom. The results are described in ten independent sections covering the following problems: (1) backscattering of Scholte waves and grazing underwater acoustic waves by a trench at a liquid/solid interface, (2)...

Topics: DTIC Archive, Chamuel, Jacques R, SONOQUEST ADVANCED ULTRASONICS RESEARCH WELLESLEY HILLS MA,...

The Proceedings of the 1991 Battlefield Atmospherics Conference was held at Ft. Bliss, Texas on 3-6 Dec 91. Topics covered included Electromagnetic and Acoustic Transmission, Weather Decision Aids, Battle Scale Weather, Remote Sensing, PBL Energy Budget, Poster and Demonstrations Sessions, Weather Decision Aids Posters and Demonstrations, Battle Scale Weather Posters and Demonstrations.

Topics: DTIC Archive, Creegan, Edward, ARMY LAB COMMAND WHITE SANDS MISSILE RANGE NM ATMOSPHERIC SCIENCES...

This report presents a summary of 14 papers published in archival literature, dealing with the issues of nonlinear dynamics of finitely deformed space structure mixed time finite element methods for large rotational motions of constrained multibody systems, and wave propagation in lattice structures.

Topics: DTIC Archive, Atluri, Satya N, GEORGIA INST OF TECH ATLANTA COMPUTATIONAL MECHANICS CENTER,...

The incremental shear modulus is calculated for infinitesimal shear of an incompressible isotropic elastic material in a state of pure homogeneous deformation. Necessary and sufficient conditions that it be positive are obtained. These conditions are related to the Hadamard conditions for propagation of a wave of infinitesimal amplitude in the deformed material. (Author)

Topics: DTIC Archive, Sawyers,K N, LEHIGH UNIV BETHLEHEM PA CENTER FOR THE APPLICATION OF MATHEMATICS,...

This study was conducted to provide a database from which to draw conclusive results on the efficiencies of seismic wave propagation in natural terrain and the resolution and fidelity of multiple frequency signals, and to supplement data for validation of theoretical models of seismic wave propagation. An extensive test program was conducted at White Sands Missile Range, New Mexico, using an electrohydraulic vibrator, an impulse loader, and a vehicle as sources of seismic waves over a 5-m to...

Topics: DTIC Archive, Carnes, Ben L, ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL...

The propagation of rf waves launched in the end cell and central of the tandem mirror propulsion device has been investigated both theoretically and experimentally. Theoretically, a computer code has been developed to study the wave propagation in a nonhomogeneous magnetic field. It was found that the amplitude of the wave excited in the plasma peaked while approaching the resonance, but then damped out, indicating strong absorption of the wave by the plasma. The absorption took place near the...

Topics: DTIC Archive, Chang-Diaz, F R, MASSACHUSETTS INST OF TECH CAMBRIDGE, *HYBRID ROCKET ENGINES,...

A comprehensive set of equations is derived for correlations and spectra of atmospheric turbulence, useful for wave propagation calculations and other applications. Three basic turbulence models are considered: (1) the Gaussian, (2) von Karman, and (3) Kolmogorov models. Two extended forms of the von Karman model are also described: the Mann model for a shear driven atmospheric surface layer, and the Hunt/Graham/Wilson model for a convective boundary layer. A new method for synthesizing random...

Topics: DTIC Archive, Wilson, D K, ARMY RESEARCH LAB ADELPHI MD, *ACOUSTIC WAVES, *ELECTROMAGNETIC WAVE...

This report contains representative examples of analysis and programming assignments executed for RADC technical personnel by staff of the ACRON Corporation. An assortment of analytical and computational problems as well as data processing tasks were performed relevant to Air Force projects requiring signal processing and electromagnetic theory. The core of the work pertained to LORAN-related studies, antenna theory, target detection and tracking problems, and the analysis of acoustic and...

Topics: DTIC Archive, Tichovolsky,Elihu, ARCON CORP WALTHAM MA, *ACOUSTIC WAVES, *COMPUTER PROGRAMMING,...

Topics: Ionospheric radio wave propagation -- periodicals., Radio meteorology -- periodicals.

Topics: Ionospheric radio wave propagation -- periodicals., Radio meteorology -- periodicals.

Topics: Ionospheric radio wave propagation -- periodicals., Radio meteorology -- periodicals.

Topics: Ionospheric radio wave propagation -- periodicals., Radio meteorology -- periodicals.

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Oct 8, 2015
10/15

by
Janaswamy, Ramakrishna.

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Revised: November 1994.

Topic: ELECTROMAGNETIC WAVE PROPAGATION.,FINITE DIFFERENCE THEORY.,RADIO WAVES.

Cover title

Topics: Ionospheric radio wave propagation, Electrons

Extensive interaction formulas and data are given for the infinitely long cylinder and the cylinder of finite length for both E- and H-polarization, together with a comparison between theoretical calculations and Laboratory measurements. The formulation of the problem of two intersecting electrically thin cylinders and that of two non-orthogonally intersecting thin cylinders are described in detail with some representative results. The essential interaction features of two intersecting thick...

Topics: DTIC Archive, King,Ronold W P, DIKEWOOD INDUSTRIES INC ALBUQUERQUE NM, *MATHEMATICAL MODELS,...

An approximate theory of dynamics of rods was formulated by Mindlin and Herrmann in 1951. The unique feature of this theory is that it can model the longitudinal as well as the radial motions of a rod, and yet it can retain the simplicity of a one-dimensional problem in the axial direction. Solutions pertaining to rods of infinite length were also given by Mindlin and Herrmann. This report presents vibration solutions of this rod model with finite lengths. First, the set of two partial...

Topics: DTIC Archive, Wu,J J, ARMY ARMAMENT RESEARCH AND DEVELOPMENT CENTER WATERVLIET NY LARGE CALIBER...

The three invariant elastoplastic constitutive model has been implemented for use in finite difference blast and shock calculations. The model employs two yield surfaces with an independent plastic potential to control shear induced dilatancy. The model is conceptually similar to Lade's cohesionless soil model. Several improvements in the original ARA model have been incorporated during the course of implementation including tensile strength, expansive strain tracking during tensile failure,...

Topics: DTIC Archive, Dass,William C, APPLIED RESEARCH ASSOCIATES INC ALBUQUERQUE NM, *SOIL MECHANICS,...

The T-matrix method, a technique invented by Peter Waterman, (1965, 1969, 1977, 1980) has proven to be valuable for calculating classical scattering from bounded targets. The method is useful for acoustical, electromagnetic and elastic scattering and is based on coupled boundary integral equations and partial wave expansions of relevant physical quantities. Upon truncation of the partial wave expansion, which are in principle in finite, a system of equations is derived that can be expressed in...

Topics: DTIC Archive, Werby, M F, NAVAL RESEARCH LAB STENNIS SPACE CENTER MS, *MATRICES(MATHEMATICS),...

This report contains 4 separate contributions (paragraph 2.1 through 2.4), as well as abstracts of the investigations submitted as quarterly technical reports during FY92 (paragraph 2.5). A systematic analysis of teleseismic P-wave travel time and amplitude variations across the NORSAR array described in paragraph 2.1 reveals that (1) SP time and amplitude anomalies are related, (2) SP and LP time variations are only partially related and (3) LP amplitude variations are very small. It is...

Topics: DTIC Archive, Mykkeltveit, Svein, NORWEGIAN SEISMIC ARRAY (NORSAR) KJELLER, *SEISMIC WAVES,...

This report, together with the proposed Part 2, surveys the literature relevant to the design of a sonar array for imaging mines with a resolution approaching 1 mm. Written as a descriptive and sometimes critical review, the report draws out the connections to mine imaging. Background areas surveyed include acoustic propagation and scattering, signal processing and display. The theory of array beamforming is traced, beginning from basics and including the near field and broadband signals....

Topics: DTIC Archive, Blair, David G, MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA), *ACOUSTIC IMAGES,...

The general goals of this project included the development of new, high-order, adaptive methods for the computer simulation of stress-wave propagation phenomena in solid mechanics, particularly elastodynamics. The motivation for using adaptive methodologies is to control and optimize the computational process, to use a posteriori error estimates to optimize meshes and spectral orders of approximation. Such orchestrated meshing can produce exponential rates of convergence, thereby allowing...

Topics: DTIC Archive, Oden, J. T., TEXAS UNIV AT AUSTIN, *COMPUTERIZED SIMULATION, *TIME DEPENDENCE,...

Partial Contents: Acoustic Vibration of Structures in Liquids; Some Transient Problems of Structures Interfacing with Fluid; Beam Vibrations--A review; and Abstracts from the Current Literature.

Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON D C SHOCK AND VIBRATION INFORMATION CENTER, *VIBRATION,...

An analytical model is developed and numerical simulations are performed for shock wave propagation into a reentrant corner. The analytical and numerical results are compared with shock tube experiments performed in a 100 deg reentrant corner with a moderate strength (P sub 1/P sub 0 = 2.37, shock overpressure 137.9 kPa) incident shock and a weak (P sub 1/P sub 0 = 1.12, shock overpressure 12.41 kPa) incident shock. The analytical model provides an exact solution of the flow field if shock...

Topics: DTIC Archive, Schmitt,J A, ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD, *MATHEMATICAL...

In the static analysis, the hybrid-stress finite element model is used for (1) the study of edge effects in symmetrically-stacked laminates subject to prescribed inplane strain, (2) the development and evaluation of 8-node single-layer plate bending elements for which the traction-free conditions are satisfied along a straight edge, and (3) the elastic-plastic analysis of single layer plates. An analytic study is also presented to determine the nature of the potential 2-D singularity at the...

Topics: DTIC Archive, Spilker,R L, ILLINOIS UNIV AT CHICAGO CIRCLE DEPT OF MATERIALS ENGINEERING, *STRESS...

The main purpose of this study is to consider an uncoupling method for analyzing explosively loaded structures embedded in hysteretic media. The method, which is based on wave propagation considerations, can be viewed as the plane wave approximation extended to nonlinear problems. Free-field data (both traction and velocity vectors) must be known in order to apply the method. Accuracy of the approximation is shown to be quite good when applied to a series of one-dimensional soil-structure...

Topics: DTIC Archive, Wright,J P, WEIDLINGER ASSOCIATES NEW YORK, *Soils, Approximation(Mathematics),...

In order to study seismic wave propagation through laterally varying sea floor structures, a software package has been created to generate synthetic seismograms by finite differences. The elastic wave equation can be solved in two dimensions either for point sources in cylindrical coordinates or for line sources in rectangular coordinates. Vertical and radial variations of the elastic parameters are allowed. The package includes four programs. Input to the system consists of a short file...

Topics: DTIC Archive, Hunt,M M, WOODS HOLE OCEANOGRAPHIC INSTITUTION MA, *Seismic waves, Wave propagation,...

The long-term goal is to develop a nonhydrostatic, parallel ocean simulation tool that is capable of simulating processes on a wide range of scales through use of accurate numerical methods and high-performance computational algorithms. The tool will be applied to study highly nonlinear internal waves in coastal domains to develop an improved understanding of mechanisms that govern their generation, propagation, and dissipation.

Topics: DTIC Archive, Fringer,Oliver B, Department of Civil and Environmental Engineering, Stanford...

The acoustic wave properties of several piezoelectric crystals and a layered structure have been theoretically and experimentally investigated for possible application in microwave acoustic devices. A search was made for crystals and layered structures having one or more of the following properties: (i) temperature compensation, (ii) high piezoelectric coupling, (iii) low power flow angle, (iv) low loss and (v) low or high acoustic wave velocities. The acoustic waves studied were the bulk...

Topics: DTIC Archive, Vetelino,John F, MAINE UNIV ORONO DEPT OF ELECTRICAL ENGINEERING, *SURFACE WAVES,...

The final report gives a summary of all the work completed and under way under this contract covering the period from December 1976 to March 1980. The work covers a broad spectrum including radiometric determination of rain attenuation, wideband millimeter wave communication, effects of transmitter and receiver characteristics, backscattering from turbulence and scatterer, diffusion of pulse in scatterer, and beam waves in random media. The emphasis is directed towards generating new ideas and...

Topics: DTIC Archive, Ishimaru,Akira, WASHINGTON UNIV SEATTLE DEPT OF ELECTRICAL ENGINEERING, *MILLIMETER...

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...

Topics: DTIC Archive, Bell, Timothy F, STANFORD UNIV CA SPACE TELECOMMUNICATIONS AND RADIOSCIENCE LAB...

Eigenanalysis of temperature and wind profiles can reveal distinct resonances at mesoscale wavelengths. Fourier transform methods are well suited to analyze resonant modes such as mountain waves due, in part, to (1) their fast computation speed for large wave number domains compared to numerical forecast models and (2) their requirements for only a coarse horizontal background state. Common traits of Fourier mountain wave models include use of the Boussinesq approximation and neglect of...

Topics: DTIC Archive, Roadcap, John R, AIR FORCE RESEARCH LAB HANSCOM AFB MA, *FOURIER TRANSFORMATION,...

The VHF attenuation measured at two locations on the body during flight at 17,700 ft/sec is compared to theoretical values computed on the basis of equilibrium, nonequilibrium, inviscid- and viscous-flow models. The shock- layer plasma-flow computational procedure included modification of the inviscid- flow properties near the body surface for the effects due to boundary-layer flow, and application of nonequilibrium concepts to the flow along streamlines. Attenuation is computed on the basis of...

Topics: DTIC Archive, Huber, Paul W, NATIONAL AERONAUTICS AND SPACE ADMIN LANGLEY RESEARCH CENTER HAMPTON...

This report documents canonical pulsed power simulation problems designed to be performed with the two-and-one-half dimensional, particle-in-cell code, MAGIC. The problems were created to furnish new users of MAGIC with experience in the application of simulation techniques to realistic pulsed power problems. The problems range from simple electromagnetic propagation to self-consistent diode operation. Each problem is presented in three parts: (1) a problem description, complete and...

Topics: DTIC Archive, Coplen, Bruce, MISSION RESEARCH CORP ALEXANDRIA VA, *ELECTROMAGNETIC FIELDS,...

This research is directed at studying the effects on the auditory system of exposure to high levels of reverberant impulse noise using an animal (chinchilla) model. The blast waves were generated by a three inch diameter shock tube (source III), which produced wave signatures having spectral energy concentrated in the 12 kHz region. The waves were discharged into a reverberant chamber within which animals were individually exposed. Animals were exposed to either 150, 155 or 160 dB peak SPL...

Topics: DTIC Archive, Hamernik, Roger P, STATE UNIV OF NEW YORK COLL AT PLATTSBURGH AUDITORY RESEARCH LAB,...

Three split-step PE rough surface models-mixed transform (MT), surface loss function (SLF), and approximate solution (AS)-were investigated and compared with a reference waveguide model called MLAYER. The MT and SLF models are shown to agree well with MLAYER; the AS model, however, generally showed poor agreement. The ML model, though the most accurate, is the most time- consuming of the three. The AS model, the most numerically efficient, shows the poorest match to MLAYER. In using one of...

Topics: DTIC Archive, Barrios, Amalia E, NAVAL COMMAND CONTROL AND OCEAN SURVEILLANCE CENTER RDT AND E DIV...

We are investigating new low-power confocal microwave technology to detect and image early-stage breast cancers. The new technology exploits the dielectric-property contrasts between normal breast tissues and malignant tumors and surrounding vascularization at microwave frequencies. The tumor-detection system employs a miniaturized, planar pulsed antenna array contacting only one side of the breast. The digital signal processing for the system is founded upon time-shifting and summing of the...

Topics: DTIC Archive, Popovic, Milica, NORTHWESTERN UNIV EVANSTON IL, *SIGNAL PROCESSING, *MICROWAVE...

The scalar time-dependent equation of radiative transfer in cylindrical coordinates was used to develop several new theories- both rigorous and approximate- for propagation and scattering of beam wave pulse trains in vegetation modeled as a random medium of discrete scatterers. Plots of specific intensity and received power in the random medium (vegetation) showed distortion due to pulse broadening, angular spread, power attenuation (especially at large penetration depths), and out-of-beam...

Topics: DTIC Archive, Whitman, Gerald M, NEW JERSEY INST OF TECH NEWARK, *MODELS, *THEORY, *WAVE...

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169

Nov 14, 2013
11/13

by
Chiang C. Mei

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Topics: Physics, Special Relativity, General Relativity and Gravitation, Gravitational Waves, Wave...

Source: http://www.flooved.com/reader/2045

We report on a search for Alfven waves in the solar wind during solar particle events. During the period June 6-8, 1979, we find clear signatures of outgoing Alfven waves which could have been released from the sun simultaneously with the initial release of energetic particles. The waves are soliton-like, with durations of 200-900 seconds. An isolated square Alfven solution is also seen when the first particles (with E approximately 57 MeV) are detected: the width of this solution is...

Topics: DTIC Archive, Mullan,D J, FRANKLIN INST NEWARK DE BARTOL RESEARCH FOUNDATION, *ELECTROMAGNETIC WAVE...

As result of recent studies, it has become apparent that most available data on free-field particle motion associated with underground chemical and nuclear explosions exhibit nonelastic behavior even at rather large scaled distances from the source. This observation casts suspicion on the usefulness of reduced displacement potential (RDP) calculations based upon these close range data for the purpose of defining a seismic source function (Bache et al, 1981). Experimental measurements on...

Topics: DTIC Archive, Tittmann, B R, ROCKWELL INTERNATIONAL CORP THOUSAND OAKS CA SCIENCE CENTER,...

This project is a part of research into the detection of radar signals at ranges well beyond the horizon by exploiting the effect of tropospheric scattering. A result of this work is a program written in C language which enables the distortion of the envelope of a given radar pulse, which occurs as a result of propagating over any path by tropospheric scattering, to be predicted.

Topics: DTIC Archive, Ozerova, Marina, DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION CANBERRA (AUSTRALIA),...

U.S. Army Training Circular # TC 9-64 Communications-Electronics Fundamentals: Wave Propagation, Transmission Lines, and Antennas. 2004-07. Preface ix Chapter 1 WAVE PROPAGATION 1-1 Learning Objectives 1-1 What is Propagation? 1-2 Principles of Wave Motion 1 -2 Sound Waves 1-15 Lightwaves 1-23 Electromagnetic Spectrum 1 -30 Electromagnetic Waves 1 -32 Summary 1-39 Chapter 2 RADIO WAVE PROPAGATION 2-1 Learning Objectives 2-1 Electromagnetic Fields 2-2 Radio Waves 2-6 Summary 2-38 Chapter 3...

Topics: Electronics, Ham Radio, Radio Propagation, Antennas, Amateur Radio, United States. -- Army --...

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Nov 29, 2012
11/12

by
Nupen, Wilhelm

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Topic: Tropospheric radio wave propagation--Bibliography.

This study was conducted to provide reliable values of the stiffness and damping properties of frozen soils subjected to vibratory loads and to define the significant factors affecting these parameters. A laboratory test was conducted on prepared specimens of frozen soils wherein a right circular cylinder was subjected to steady-state sinusoidal vibration. The material was considered to be linearly viscoelastic. Analysis of test data based on one- dimensional wave propagation yielded the...

Topics: DTIC Archive, Stevens, Henry W, COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH, *COLD...

During a meeting of the AGARD Fluid Dynamics Panel held in Rome, Italy in September 1974, one day was devoted to a review of activities in various countries in the field of multiple flow of solids and gases. Five survey papers were presented by representatives of France, West Germany, United Kingdom, Belgium and the United States. This document includes edited versions of these five papers, which are printed in the order of their presentation at the meeting.

Topics: DTIC Archive, Rudinger,G, ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT PARIS (FRANCE),...

This memorandum describes NUSL Program S1441 written in FORTRAN V. This program uses normal mode theory to predict acoustic propagtion over a flat homogeneous ocean bottom.

Topics: DTIC Archive, Kanabis,William G, NAVY UNDERWATER SOUND LAB NEW LONDON CONN, *COMPUTER PROGRAMS,...

The final report summarizes the results of a 3-year model study to evaluate how well a parallel-plate transmission-line structure simulates an electromagnetic pulse with a plane-wave front. The amplitude and phase of the electric field inside the model simulator have been measured at two high frequencies for which transmission-line theory does not apply. An approximate theoretical representation of the field is used to interpret the measured data. Differences between the actual field and the...

Topics: DTIC Archive, Wu, T. T., HARVARD UNIV CAMBRIDGE MA GORDON MCKAYLAB, *ELECTRIC FIELDS,...

The results of an investigation to select a satisfactory numerical method for calculating the propagation of steep fronted shock like waveforms in a solid rocket motor combusion chamber are presented. A number of different numerical schemes were evaluated by comparing the results obtained for three problems: the shock tube problem, the linear wave equation, and nonlinear wave propagation in a closed tube. The most promising method--a combination of the Lax-Wendroff, Hybrid and Artificial...

Topics: DTIC Archive, Baum,Joseph D, DAYTON UNIV OH RESEARCH INST, *FINITE DIFFERENCE THEORY, *WAVE...

It is shown that the complex cepstrum technique is most effective when simple signals are removed from the observed waveform in the order of their arrival. Cepstrum analysis of teleseismic short-period P-waves from fifteen presumed peaceful nuclear explosions in Eurasia suggests that nine contained more than one direct phase. This may indicate the possible multiple explosions or may well be just due to the surface reverberations. Five of these events contained presumed depth phases of amplitude...

Topics: DTIC Archive, Lane, Stephen S, TEXAS INSTRUMENTS INC DALLAS EQUIPMENT GROUP, *CEPSTRUM TECHNIQUE,...

It is shown that the complex cepstrum technique is most effective when simple signals are removed from the observed waveform in the order of their arrival. Cepstrum analysis of teleseismic short-period P-waves from fifteen presumed peaceful nuclear explosions in Eurasia suggests that nine contained more than one direct phase. This may indicate the possible multiple explosions or may well be just due to the surface reverberations. Five of these events contained presumed depth phases of amplitude...

Topics: DTIC Archive, Lane, Stephen S, TEXAS INSTRUMENTS INC DALLAS EQUIPMENT GROUP, *CEPSTRUM TECHNIQUE,...