53
53
Jan 29, 2018
01/18
by
G.Staynov
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The article discusses some obstacles to the extraction of energy from sea waves arising from wave theory.
Topics: group velocity, wave group, wave packet
85
85
Sep 10, 2014
09/14
by
Patrick Bruskiewich
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Recently, 250 m highdeep water ocean waves were discovered at a depth of 5,500 metres in the Samoan Channel in the South Pacific. This short paper estimates the velocity of the waves and their characteristic times.
Topics: deep water wave, Samoan Channel, wave velocity, group velocity, characteristic time
108
108
Nov 14, 2013
11/13
by
Chiang C. Mei
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Topics: Physics, Acoustics, Optics and Waves, Waves, Phase Velocity and Group Velocity, Refraction, Physics
Source: http://www.flooved.com/reader/3247
A generalized exact optical bright solitary wave solution in a three dimensional dispersive linear medium is presented. The most interesting property of the solution is that it can exist in the normal group-velocity-dispersion (GVD) region. In addition, another peculiar feature is that it may achieve a condition of 'zero-dispersion' to the media so that a solitary wave of arbitrarily small amplitude may be propagated with no dependence on is pulse width.
Topics: NASA Technical Reports Server (NTRS), VELOCITY DISTRIBUTION, PULSE DURATION, DISPERSING, GROUP...
245
245
May 31, 2011
05/11
by
Kaneshige, John; Gundy-Burlet, Kare
texts
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This paper describes an integrated neural flight and propulsion control system. which uses a neural network based approach for applying alternate sources of control power in the presence of damage or failures. Under normal operating conditions, the system utilizes conventional flight control surfaces. Neural networks are used to provide consistent handling qualities across flight conditions and for different aircraft configurations. Under damage or failure conditions, the system may utilize...
Topics: GALILEO SPACECRAFT, PLANETARY MAGNETIC FIELDS, IO, ION CYCLOTRON RADIATION, IONIC WAVES,...
We are developing LITHO1.0: an updated crust and lithosphere model of the Earth. The overall plan is to take the popular CRUST2.0 model--a global model of crustal structure with a relatively poor representation of the uppermost mantle--and improve its nominal resolution to 1 degree and extend the model to include lithospheric structure. The new model, LITHO 1.0, will be constrained by many different datasets, including extremely large new datasets of relatively short-period group velocity data...
Topics: DTIC Archive, CALIFORNIA UNIV SAN DIEGO LA JOLLA, *MODELS, *SURFACE WAVES, *LITHOSPHERE, OCEANIC...
157
157
Nov 14, 2013
11/13
by
Vladan Vuletic
texts
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Normalization of wavefunctions in free space
Topics: Physics, Acoustics, Optics and Waves, Quantum Physics, Waves, Quantum Mechanics, Phase Velocity and...
Source: http://www.flooved.com/reader/3085
We apply the methods of time-frequency analysis to pulse propagation in a dispersive medium. We give exact expressions for conditional moments and in particular for the contraction and spreading of the pulse, the covariance between position and wave number and other relevant physical quantities. For the contraction time it is shown that the important quantity is the initial correlation between position and group velocity. A simple physical and mathematical model is presented that explains why...
Topics: DTIC Archive, Cohen, Leon, COHEN (LEON) BRONX NY, *WAVE PROPAGATION, *ELECTROMAGNETIC PULSES,...
It is shown that when the temperature in the atmosphere increases linearly with height, the speed of propagation of long waves does not approach a limit with increasing wavelength, as in the case of an atmosphere in which the temperature at great heights is assumed to be constant or decreasing, but increases linearly with the period. The group velocity ultimately also increases linearly with the period and becomes equal to half the phase velocity. The region of maximum energy of the oscillation...
Topics: DTIC Archive, Pekeris, C L, INSTITUTE FOR ADVANCED STUDY PRINCETON NJ, *OSCILLATION, *ATMOSPHERIC...
We report on R&D that is enabling enhancements to the Bayesian Infrasound Source Location (BISL) method for infrasound event location. The focus of this effort is on improving BISL through the development and implementation of physics-based priors. Phase identification in BISL is incorporated through a prior probability density function on group velocity. We report on the development of a distance-dependent prior through a massive simulation effort that will be validated by a ground-truth...
Topics: DTIC Archive, LOS ALAMOS NATIONAL LAB NM, *INFRASOUND, GROUP VELOCITY, MONTE CARLO METHOD,...
Tracking closely space objects with resolution limited sensors is a difficult problem. One way to address this issue is to track these targets individually, and employ relatively complex data association approaches as a means of pairing detections and tracks. The algorithms outlined in this paper takes a different approach, and instead estimates the group velocity using an unscented Kalman Filter (UKF). The UKF state estimate is then employed within a particle filter, which estimates the...
Topics: DTIC Archive, NAVAL SURFACE WARFARE CENTER DAHLGREN VA, *ALGORITHMS, *KALMAN FILTERING, *TARGET...
Slow light refers to the dramatic reduction in group velocity that can be obtained via a number of physical mechanisms. This project is focused on the fundamental principles of slow light in optical nanostructures and devices. Of particular importance is the use of slow light to enhance nonlinear optical processes, and the fundamental limitations thereof. The fundamental component of all slow light embodiments is a resonator, be it a micro-ring resonator, photonic crystal defect, or plasmonic...
Topics: DTIC Archive, UTAH UNIV SALT LAKE CITY, *OPTICAL EQUIPMENT, *LIGHT, PHOTONIC CRYSTALS, RESONANCE,...
A slow group velocity and low group velocity dispersion photonic crystal slab waveguide is designed by using capsule shaped air holes in hexagonal lattice. The theoretical study shows that adjusting the aspect ratio of holes in the innermost rows can fine tune the dispersion tail. The presented design can achieve nearly flat band photonic crystal waveguides with group index of 21-36 over the normalized bandwidth (delta omega/omega) of 1.38%0.4%. We also discuss the effects of the change in the...
Topics: DTIC Archive, TEXAS UNIV AT AUSTIN MICROELECTRONICS RESEARCH CENTER, *SILICON, *PHOTONIC CRYSTALS,...
he AFOSR project on structural composites with tunable chiral elements has produced some impressive results in the past few years. These include (1) electronically tunable overall chiral composites, (2) mechanically tunable chiral composites, (3) flat lenses with soft hyperbolic focusing due to indefinite overall permittivity, (4) a tunable flat lens based on chiral elements with adjustable focal spot based on applied mechanical deformation, and (5) a three-phase periodic composite was created...
Topics: DTIC Archive, CALIFORNIA UNIV SAN DIEGO LA JOLLA DEPT OF MECHANICAL AND AEROSPACE ENGINEERING,...
A new nonlinear optical medium which can support gap solitons is proposed, an asymmetric dual core fiber with opposite signs of the dispersion in its two cores, which can be easily fabricated choosing the carrier wavelength close to the zero-dispersion point. We consider soliton solutions, combining the analysis of the dispersion relation for the linearized system, the variational approximation for the full nonlinear one, and direct numerical methods. We find that in the case when the cores are...
Topics: DTIC Archive, Kaup, D. J., CLARKSON UNIV POTSDAM NY INST FOR NONLINEAR STUDIES, *FIBER OPTICS,...
One of the most difficult problems the manufacturing community has faced during recent years has been to accurately assess the physical state of anisotropic high-performance materials by nondestructive means. In order to advance the design of ultrasonic nondestructive testing systems, a more fundamental understanding of how ultrasonic waves travel and interact within the anisotropic material is needed. The relationship between the ultrasonic and engineering parameters needs to be explored to...
Topics: NASA Technical Reports Server (NTRS), ANISOTROPY, ELASTIC PROPERTIES, GRAPHITE-EPOXY COMPOSITES,...
We have recently performed ambient noise tomography of China using the new national China Seismic Network and surrounding global and regional stations. For most of the station pairs, we can retrieve very good Rayleigh waves from ambient noise correlations using 18- months of continuous data at all distance ranges (100 km to 5000 km) and for periods down to about 8 s. We obtain Rayleigh wave group velocity dispersion measurements using a frequency-time analysis method and construct Rayleigh wave...
Topics: DTIC Archive, Song, Xiaodong, ILLINOIS UNIV AT URBANA DEPT OF GEOLOGY, *AMBIENT NOISE, SURFACE...
Recent research has established that it is possible to exercise extraordinary control of the velocity of propagation of light pulses through a material system. Both extremely slow propagation (much slower than the velocity of light in vacuum) and fast propagation (exceeding the velocity of light in vacuum) have been observed. This article summarizes this recent research, placing special emphasis on the description of the underlying physical processes leading to the modification of the velocity...
Topics: DTIC Archive, Boyd, Robert W, ROCHESTER UNIV NY INST OF OPTICS, *PROPAGATION, *GROUP VELOCITY,...
The second order nonlinearity present in many crystals can be utilized to convert optical radiation into THz radiation via the optical rectification mechanism. This process becomes efficient if a phase matching condition is satisfied. The short pulses used for optical rectification can be more intense than the longer pulses used for difference frequency generation because of the pulse length dependence of the crystal's damage threshold. However, optical rectification is more complicated than...
Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC, *ELECTROMAGNETIC RADIATION, OPTICAL PROPERTIES,...
Conical refraction phenomena, i.e., the spreading into a hollow cone of an unpolarized light beam entering a biaxial crystal along its optic axis, are fundamental in classical optics and in mathematical physics [1 4]. Originally predicted by Hamilton in 1837 [3] and experimentally observed by Lloyd [4], these phenomena have been intensively studied in recent years by a large community of theorists and experimentalists [1 8]. The physical origin of the phenomenon is associated with the existence...
Topics: DTIC Archive, AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH SENSORS DIR, *ALGEBRA, CONICAL BODIES,...
The propagation and stability of intense laser pulses in a partially-stripped plasma, i.e., in the presence of free and bound electrons, is analyzed. The presence of bound electrons is shown to significantly alter the propagation and stability of intense laser pulses. The bound electrons are represented by a linear and nonlinear susceptibility, while the free electrons, which can support plasma waves, are treated nonlinearly. In the presence of both free and bound electrons, an atomic...
Topics: DTIC Archive, Sprangle, P., NAVAL RESEARCH LAB WASHINGTON DC BEAM PHYSICS BRANCH,...
The purpose of this study is to improve group velocity maps designed to advance the detection and discrimination capabilities for the area encompassed by western China, northern India, and Pakistan. These maps may be used to construct sharply tuned phase-matched filters for extracting weak surface wave signals from background noise and to make better estimates of surface wave spectral magnitudes for small events. We are working now to obtain a greatly expanded data set of short-period...
Topics: DTIC Archive, COLORADO UNIV AT BOULDER, *GROUP VELOCITY, *PERIODIC VARIATIONS, *ASIA, *SHORT...
The present invention is directed toward a unique ultra-fast, all-optical switching device or switch made with readily available, relatively inexpensive, highly nonlinear photonic glasses. These photonic glasses have a sufficiently negative group velocity dispersion and high nonlinear index of refraction to support stable light bullets. The light bullets counterpropagate through, and interact within the waveguide to selectively change each others' directions of propagation into predetermined...
Topics: NASA Technical Reports Server (NTRS), OPTICAL SWITCHING, SWITCHES, NONLINEAR OPTICS, GLASS,...
This effort involved the analysis of low frequency waves as observed by the Galileo spacecraft near the Galilean moon, Io. Io is a significant source of material, especially SO2, and various products of dissociation, and further these atoms and molecules are readily ionized. The initial velocity of the ions is essentially that of the neutral species, i.e., the Keplerian velocity. The plasma, on the other hand is co-rotating, and there is a differential flow of the order 57 km/s between the...
Topics: NASA Technical Reports Server (NTRS), GALILEO SPACECRAFT, IO, ION CYCLOTRON RADIATION, IONIC WAVES,...
This report summarizes the entire research period. In this program, we performed experiments using a femtosecond mid-infrared pump-probe system implemented for QCL samples operating at 4.6 and 5.3 m. We employed femtosecond time-resolved pump-probe measurements to probe the nature of the transport through the laser structure via the dynamics of the gain. The gain recovery was determined by the time-dependent transport of electrons through the cascade heterostructure; as the laser approaches and...
Topics: DTIC Archive, MICHIGAN UNIV ANN ARBOR CENTER FOR ULTRAFAST OPTICAL SCIENCE, *LASERS, QUANTUM...
Ionization processes limit the accelerating gradient and place an upper limit on the pulse duration of the electromagnetic driver in the Inverse Cherenkov Accelerator (ICA). Group velocity slippage, i.e., pulse lethargy, on the other hand, imposes a lower limit on the pulse duration. These limits are obtained for two ICA configurations in which the electromagnetic driver (e.g., laser or millimeter wave source) is propagated in a waveguide that is, (i) lined with a dielectric material or (ii)...
Topics: DTIC Archive, Sprangle, P., NAVAL RESEARCH LAB WASHINGTON DC BEAM PHYSICS BRANCH, *LASER PUMPING,...
Suitably configured whispering-gallery-mode (WGM) optical resonators have been proposed as delay lines for trains of short light pulses. Until now, it has been common practice to implement an optical delay line as a coiled long optical fiber, which is bulky and tends to be noisy. An alternative has been to implement an optical delay line as a coupled-resonator optical waveguide (a chain of coupled optical resonators), which is compact but limits the width of the pulse spectrum to the width of...
Topics: NASA Technical Reports Server (NTRS), OPTICAL RESONATORS, OPTICAL WAVEGUIDES, DELAY LINES, OPTICAL...
A new identification of groups and clusters in the CfAl Catalog of Huchra, et al. (1983) is presented, using a percolation algorithm to identify density enhancements. The procedure differs from that of the original Geller and Huchra (1983; GH) catalog in several important respects; galaxy distances are calculated from the Virgo-Great Attractor flow model of Faber and Burnstein (1988), the adopted distance linkage criteria is only approx. 1/4 as large as in the Geller and Huchra catalog, the sky...
Topics: NASA Technical Reports Server (NTRS), ASTRONOMICAL CATALOGS, FLOW DISTRIBUTION, GROUP VELOCITY,...
Long period Rayleigh wave and Love wave dispersion data, particularly for oceanic areas, were not simultaneously satisfied by an isotropic structure. Available phase and group velocity data are inverted by a procedure which includes the effects of transverse anisotropy, an elastic dispersion, sphericity, and gravity. The resulting models, for the average Earth, average ocean and oceanic regions divided according to the age of the ocean floor, are quite different from previous results which...
Topics: NASA Technical Reports Server (NTRS), GROUP VELOCITY, LITHOSPHERE, LOVE WAVES, OCEANS, RAYLEIGH...
Propagation of acoustic waves (linear arid nonlinear, time harmonic and pulsed) in a broad class of periodically nonuniform wave guides is investigated theoretically and experimentally. It is shown that the linear, time harmonic solution wave functions are Bloch wave functions. Expressions for parameters characterizing Bloch waves (such as the Bloch wave number) are derived and the features of their band structure determined. Propagation of linear Bloch wave pulses is investigated using the...
Topics: DTIC Archive, Bradley, Charles E., TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS, *WAVEGUIDES, *SOUND...
Edge states and their transport in a quantum wire exposed to a perpendicular non-homogeneous magnetic field are investigated. Systems are studied where the magnetic field exhibits a discontinuous jump in the transverse direction. The energy spectra and wave functions of these systems the corresponding group velocities along the interface and the particle average positions normal to the interface are calculated. The resistance of the quantum wire is obtained both in the ballistic and in the...
Topics: DTIC Archive, Badalyan, S. M., Peters, F. M., ANTWERP UNIV WILRIJK (BELGIUM) DEPT OFPHYSICS*,...
205
205
May 26, 2011
05/11
by
Bada, Jeffrey L.; McDonald, Gene D., et al
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Understanding the events that led to the origin of life on Earth is complicated by the lack of geological evidence from the period around four billion years (4 Gyr) ago when the transition from prebiotic chemistry to biochemistry is believed to be occurred. Although erosion and plate tectonics have since erased the terrestrial geological record from the time of the origin of life, there is possibility that information about this period of Earth history may still be preserved on Mars. A major...
Topics: EULER EQUATIONS OF MOTION, RIGID STRUCTURES, BOUNDARY CONDITIONS, BOUNDARY LAYER CONTROL, BOUNDARY...
The goal of this project was to develop a new global magnetohydrodynamic model of the interaction of the Jovian magnetosphere with the solar wind. Observations from 28 orbits of Jupiter by Galileo along with those from previous spacecraft at Jupiter, Pioneer 10 and 11, Voyager I and 2 and Ulysses, have revealed that the Jovian magnetosphere is a vast, complicated system. The Jovian aurora also has been monitored for several years. Like auroral observations at Earth, these measurements provide...
Topics: NASA Technical Reports Server (NTRS), MAGNETOHYDRODYNAMICS, MODELS, EARTH MAGNETOSPHERE, GROUP...
A description is presented of the theoretical and experimental work performed on the propagation of electromagnetic waves along plasma columns in logitudinal magnetic fields. Theoretical work includes: completion of the basic theory for propagation along plasma columns in magnetic fields; derivation of Brillouin diagrams; and discussion of particularly significant limits and preliminary analyses of the non-uniform plasma case. Experimental work includes: measurements of basic propagation...
Topics: DTIC Archive, Gilardini, A, SELENIA INDUSTRIE ELETTRONICHE ASSOCIATE S P A ROME (ITALY),...
This report presents a tomographic analysis of surface-wave group velocity dispersion through the Arabian Plate and studies on the usefulness of genetic algorithms for the inversion of surface-wave waveforms for earth structure. The raw group velocity dispersion measurements are available by anonymous ftp to ftp.eas.slu.edu in the directory pub/rbh/ARABIA.
Topics: DTIC Archive, Herrmann, R B, SAINT LOUIS UNIV MO DEPT OF EARTH AND ATMOSPHERIC SCIENCES, *SURFACE...
The receptivity theory of Goldstein and Ruban is extended within the nonasymptotic (quasi-parallel) framework of Zavol'skii et al to predict the roughness-induced generation of stationary and nonstationary instability waves in three-dimensional, incompressible boundary layers. The influence of acoustic-wave orientation, as well as that of different types of roughness geometries, including isolated roughness elements, periodic arrays, and two-dimensional lattices of compact roughness shapes, as...
Topics: NASA Technical Reports Server (NTRS), INCOMPRESSIBLE BOUNDARY LAYER, SOUND WAVES, SURFACE...
An experimental study was conducted to investigate dynamic load transfer and wave propagation in particulate assemblies containing damaged particles. The assembly was simulated by a one-dimensional array of circular disks, and the damage itself, by a natural crack or drilled boles. The assembly was explosively loaded and the dynamic load transfer process observed using dynamic photoelasticity and strain gages. Attention was focused on the influence of damage size and orientation on the group...
Topics: DTIC Archive, Shukla, Arun, RHODE ISLAND UNIV KINGSTON DEPT OF MECHANICAL ENGINEERING AND APPLIED...
Bell System Technical Journal, 33: 6. November 1954 pp 1343-1372. The Wave Picture of Microwave Tubes. (Pierce, J.R.)
Topics: wave, electron, waves, beam, tubes, phase, power, velocity, coupling, slow, electron stream, bell...
Bell System Technical Journal, 55: 6. July-August 1976 pp 777-802. Mode Mixing With Reduced Losses in Parabolic-Index Fibers. (Marcuse, D.)
Topics: mode, fiber, modes, pulse, filters, guided, fibers, coupling, propagation, coupled, mode boundary,...
The first navigators to encounter the Arctic and Antartic ice margins rapidly became aware the penetration of ocean waves into ice-fields. These waves are termed as flexural-gravity waves (or coupled ice-ocean waves) whose dispersion and energy decay are determined by the character of the ice as well as the water beneath. The ultimate energy source for the flexural-gravity wave is the atmospheric pressure fluctuations generated by winds. However, this wind effect has not been included into the...
Topics: DTIC Archive, NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF OCEANOGRAPHY, *ICE, *GRAVITY WAVES,...
Evidence for Rossby-gravity waves in tropical data fields produced by the European Center for Medium Range Weather Forecasts (ECMWF) was recently reported. Similar features are observable in fields of total column ozone from the Total Ozone Mapping Spectrometer (TOMS) satellite instrument. The observed features are episodic, have zonal (east-west) wavelengths of 6,000-10,000 km, and oscillate with periods of 5-10 days. In accord with simple linear theory, the modes exhibit westward phase...
Topics: NASA Technical Reports Server (NTRS), ATMOSPHERIC GENERAL CIRCULATION MODELS, GRAVITY WAVES,...
Bell System Technical Journal, 35: 1 January 1956 pp 35-65. Waveguide Investigations with Millimicrosecond Pulses (Beck, A.C.)
Topics: pulse, mode, pulses, waveguide, teoi, conversion, piston, frequency, trace, distortion, round trip,...
Use of regional phase spectral ratios as discriminants involves parameterization of differences in the relative spectral shape of regional phase signals from different source types. This research program has been directed at improved understanding of the influences of source excitation and propagation on the transportability of regional phase spectral ratio discriminants. For use in these investigations, high quality digital waveform data from regional seismic stations have been compiled for...
Topics: DTIC Archive, Bennett, Theron J., MAXWELL TECHNOLOGIES INC SAN DIEGO CA, *NUCLEAR EXPLOSION...
Bell System Technical Journal, 29: 2. April 1950 pp 189-250. Traveling-Wave Tubes (Second Installment). (Pierce, J.R.)
Topics: field, circuit, phase, resonators, circuits, stored, frequency, velocity, electron, transverse,...
Bell System Technical Journal, 53: 8. October 1974 pp 1599-1618. Pulse Spreading in Multimode, Planar, Optical Fibers. (Arnaud, J.A.)
Topics: pulse, slab, optical, spreading, modes, thickness, fibers, ray, axis, dielectric, wave number,...
We performed ambient noise tomography of China using the data from the China National Seismic Network and surrounding global and PASSCAL-type stations. For most of the station pairs, we retrieve good Rayleigh waveforms from ambient noise correlations using a few months to several years of continuous data at all distance ranges across the entire region (over 5000 km) and for periods from about 70 s down to about 8 s. We obtained a total number of 33,800 station-pairs (paths) and measured...
Topics: DTIC Archive, ILLINOIS UNIV AT URBANA-CHAMAPAIGN, *RAYLEIGH WAVES, *TOMOGRAPHY, *AMBIENT NOISE,...
Bell System Technical Journal, 50: 6. July-August 1971 pp 1741-1759. Linearized Dispersion Relation and Green's Function for Discrete-Charge-Transfer Devices with Incomplete Transfer . (Joyce, W.B.; Bertram, W.J.)
Topics: equation, charge, discrete, distribution, devices, signal, station, binomial, spatial, probability,...
The second order nonlinearity present in many crystals can be utilized to convert optical radiation into THz radiation via the optical rectification mechanism. This process becomes efficient if a phase matching condition is satisfied. The short pulses used for optical rectification can be more intense that the longer pulses used for difference frequency generation because of the pulse length dependence of the crystal's damage threshold. However, optical rectification is more complicated than...
Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC BEAM PHYSICS BRANCH, *ELECTROMAGNETIC RADIATION,...
During the past few decades, considerable interest has been generated in the production of efficient, high power, high frequency coherent electromagnetic sources. Several devices exist in which coherent microwaves can be generated, such as the relativistic magnetron, klystrons gyro-Klystrons magnetically insulated line oscillators (MILOs), virtual cathode oscillators (VIRCATORS), backward wave oscillators (BWOs), electron cyclotron resonance masers, the cusptron, as well as many others. The...
Topics: DTIC Archive, Spencer, Thomas A., MICHIGAN UNIV ANN ARBOR DEPT OF NUCLEAR ENGINEERING, *MASERS,...
The report describes the status and results to reduce the magnitude threshold for which surface waves can be identified and measured reliably, and to improve the accuracy of surface wave measurements, using phase-matched filtering, development of global regionalized earth and dispersion models, and other techniques. We have focused on improvements to global earth models and dispersion maps, and improved techniques for measuring surface wave amplitudes. Completed work on implementation and...
Topics: DTIC Archive, Stevens, J L, SCIENCE APPLICATIONS INTERNATIONAL CORPSAN DIEGO CA, *SURFACE WAVES,...
