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Dec 9, 2017
12/17

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© IASET

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Microseismic ground motion produced, as Rayleigh-type surface waves in a wide frequency range, by either natural or artificial (man-made cultural) sources can be gainfully employed, for determining the sedimentary structure of layered crust from phase velocity dispersion data acquired, at seismometric arrays. The properties of a large aperture array to resolve long wavelengths, and with station density adequate to suppress wave number aliasing, can be synthesized using smaller arrays in...

Topics: Expanding Seismic Arrays, Microseisms, Phase Velocity, Response, Wave Number

Recent development using compact difference schemes to solve the Navier-Stokes equations show spectral-like accuracy. A study was made of the numerical characteristics of various combinations of the Runge-Kutta (RK) methods and compact difference schemes to calculate the unsteady Euler equations. The accuracy of finite difference schemes is assessed based on the evaluations of dissipative error. The objectives are reducing the numerical damping and, at the same time, preserving numerical...

Topics: NASA Technical Reports Server (NTRS), ALGORITHMS, EULER EQUATIONS OF MOTION, FINITE DIFFERENCE...

Superconducting microwave transmission lines can be designed to have lower loss, lower dispersion, and lower phase velocity than conventional metal lines. These properties make superconducting transmission lines attractive for use in many devices and systems such as filters and analog to digital converters. The problem with designing microwave circuits which utilizes these lines is that accurate circuit models do not exist. This paper present models for the microwave transmission line...

Topics: DTIC Archive, McClay, C P, MITRE CORP BEDFORD MA, *DISPERSING, PARAMETERS, SUPERCONDUCTORS,...

Under this project, UCLA researchers have developed new methods for filtering, prediction and system identification in adaptive optics for high energy laser systems including phased arrays. The research has concentrated on wavefront prediction in digital holography. The methods developed can achieve significant improvements in on-target Strehl ratios and tracking jitter for phased array high energy laser systems. The main contribution of the research is a state-space prediction filter that...

Topics: DTIC Archive, Gibson,Steve, University of California Los Angeles United States, adaptive optics,...

The existence of five different waves fronts in a unidirectional graphite fiber reinforced epoxy composite with energy flux propagation at the angle of 60 deg with respect to the fiber direction is verified by measuring their corresponding group and phase velocities of longitudinal and shear waves using the through transmission technique. The experimental and theoretical values of phase velocities show excellent agreement for all three modes of wave propagation. It is also verified that the...

Topics: NASA Technical Reports Server (NTRS), CARBON FIBER REINFORCED PLASTICS, FLUX DENSITY,...

Theoretical studies have been made on the nonlinear operating regimes of crossed-field vacuum devices, in the nonrelativistic regime. The main interaction is a wave-particle interaction between those drifting electrons whose velocities match the phase velocity of the RF wave in the slow-wave structure. The theory is based on two elementary modes: a DC average background mode and an RF oscillating mode. These elementary modes interact nonlinearly via a nonlinear diffusion process, for which...

Topics: DTIC Archive, Kaup, David J., KAUP INC POTSDAM NY, *PLASMAS(PHYSICS), *CROSSED FIELD DEVICES,...

The results are given a theoretical and experimental investigation of the properties of a shielded helix when used as a transmission line. Such a structure is dispersive and, because of the presence of both TM and Te modes, cannot have a true characteristic impedance. However, such an impedance is defined in terms of a distributed capacitance and inductance. These parameters are determined for the case of infinite wave length for round wire helices. The equations are developed for a uniform...

Topics: DTIC Archive, Kirschbaum, Herbert S., CARNEGIE INST OF TECH PITTSBURGH PA, *TRANSMISSION LINES,...

Seismograms recorded on broadband instruments in Saudi Arabia for events occurring in the Zagros Folded Belt of Iran often show a P phase with an apparent velocity of about 5.7 km/sec. We refer to this phase as P(x). Its amplitude rapidly diminishes along Arabian Shield paths, suggesting it is a guided wave in the sedimentary section of the Arabian Platform. P(x) blockage is observed for event-station paths crossing the Zagros and for some other events that we believe occur below the wave...

Topics: DTIC Archive, Zollweg, J. E., BOISE STATE UNIV ID DEPT OF GEOSCIENCES, *SEISMIC DATA, *SEISMIC...

Most source discriminants make use of the prominent regional phase Lg, so that a complete understanding of the generation and spectral characteristics of Lg from explosions is essential for improved and reliable monitoring of the Comprehensive Test Ban Treaty (CTBT). Our research provides valuable new information regarding the origin of both low and high frequency Lg. The low-frequency (up to about 2 Hz) part of the Lg spectra (including the most prominent peaks and nulls) appears to be due to...

Topics: DTIC Archive, Gupta, Indra N, MULTIMAX INC LARGO MD, *NUCLEAR EXPLOSIONS, *SEISMIC DISCRIMINATION,...

Global surface wave arrival angles (also called polarization data) are extremely useful data to constrain the short wavelength structure in global surface wave phase velocity maps. This paper investigates the feasibility of using such data on a more regional scale to validate regional models. We measure the arrival angles at the Saudi Arabian Seismic Network and compare them with predictions calculated using published phase velocity maps. We find large discrepancies between data and existing...

Topics: DTIC Archive, CALIFORNIA UNIV SAN DIEGO LA JOLLA INST OF GEOPHYSICS AND PLANETARY PHYSICS, *SURFACE...

We are continuing efforts to develop 3-D velocity models for southern Asia through the collection and analysis of broadband waveform data acquired on the Indian subcontinent. The geology of India is diverse, but can be divided into three main regions: the Himalayas, the Indo-Gangetic plain, and the Indian Shield. Our initial focus has been on the southern Indian shield, and we have also completed studies in the trans-Himalayas and the Shillong Plateau. The goal of our work is to determine the...

Topics: DTIC Archive, CAMBRIDGE UNIV (UNITED KINGDOM), *INDIA, *SOUTH ASIA, *SEISMIC DATA, BROADBAND,...

The characteristics of the quasi-static TEM mode of a cylindrical microstrip transmission line are investigated using the finite difference technique. The transmission line consists of two perfectly conducting strips located between two different layers of dielectric materials, and a dielectric notch embedded in the substrate between two strips. The dielectric overlay and substrate are truncated for practical purposes. The formulation of the problem is based on the solution of Laplace's...

Topics: DTIC Archive, Elsherbeni, Atef, MISSISSIPPI UNIV UNIVERSITY DEPT OF ELECTRICAL ENGINEERING,...

This investigation evaluated the feasibility of developing a fast and efficient computational tool for optimized design of advanced, slow-wave, traveling-wave-tube-amplifiers (TWTAs). Because of their high power, broad-bandwidth, compact size, and high efficiency features, TWTAs are relied upon for satellite communications; airborne, shipborne, and ground-based radar; jamming and decoy applications. Because it is crucial to keep the time between conceptualization and finished product to an...

Topics: DTIC Archive, Kory, Carol L, ANALEX CORP TITUSVILLE FL, *TRAVELING WAVE TUBES, *DESIGN CRITERIA,...

The reduction of spaced wind measurements taken over a range of heights is described. The equipment used is a medium frequency radar with one site consisting of a vertically pointing transmitter and space receiving antennas, and two remote receiving sites with spaced antennas. Assuming approximately horizontally stratified scatterers, horizontal winds are thus available at the corners of a triangle of side approx. 20 km in the GRAVNET system.

Topics: NASA Technical Reports Server (NTRS), GRAVITY WAVES, HORIZONTAL ORIENTATION, METEOROLOGICAL RADAR,...

The theoretical and experimental results for a pair of mode-selective directional couplers designed to detect the TE sub 11 and TE sub 12 modes in a multimode circular wavelength are described. A brief description of the design of the couplers is presented, followed by a comparison of their measured and calculated parameters. The couplers were used to measure the characteristics of a circular waveguide mode converter. The results of these measurements are described.

Topics: NASA Technical Reports Server (NTRS), CIRCULAR WAVEGUIDES, DIRECTIONAL COUPLERS, TRANSMISSION LOSS,...

This work is an intercomparison of four tropospheric-stratospheric climate models, the Unified Model (UM) of the U.K. Meteorological Office (UKMO), the model of the Free University in Berlin (FUB). the ARPEGE-climat model of the National Center for Meteorological Research (CNRM), and the Extended UGAMP GCM (EUGCM) of the Center for Global Atmospheric Modelling (CGAM), against the UKMO analyses. This comparison has been made in the framework of the "GSM-Reality Intercomparison Project for...

Topics: NASA Technical Reports Server (NTRS), KELVIN WAVES, ATMOSPHERIC MODELS, TROPOSPHERE, ATMOSPHERIC...

The elastic constants of a fiberglass epoxy unidirectional composite are determined by measuring the phase velocities of longitudinal and shear stress waves via the through transmission ultrasonic technique. The waves introduced into the composite specimens were generated by piezoceramic transducers. Geometric lengths and the times required to travel those lengths were used to calculate the phase velocities. The model of the transversely isotropic medium was adopted to relate the velocities and...

Topics: NASA Technical Reports Server (NTRS), EPOXY MATRIX COMPOSITES, FIBER COMPOSITES, GLASS FIBERS,...

Bell System Technical Journal, 53: 7. September 1974 pp 1379-1394. Transverse Coupling in Fiber Optics Part III: Bending Losses. (Arnaud, J.A.)

Topics: fiber, radius, radiation, loss, waveguide, rod, exp, mode, curvature, modes, propagation constant,...

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250

May 23, 2011
05/11

by
Ma, Y. F.; Ke, H. Z.; Jee, W. S. S

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The objects of this study were to determine the responses of a cancellous bone site with a closed growth plate, (the distal tibial metaphysis (DTM), to ovariectomy (OVX) and OVX plus a prostaglandin E(2) treatment, and compare the site's response to previous findings reported for another site, the proximal tibial metaphysis (PTM). Thirty five 3-month old female Sprague-Dawley rats were divided into five groups; basal, sham OVX, and OVX0, 1, or 6 mg PGE(2)/kg/d injected subcutaneously for 3...

Topics: DISPERSING, PHASE VELOCITY, ALUMINUM, STAINLESS STEELS, PROPAGATION MODES, PIEZOELECTRIC...

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Jun 9, 2011
06/11

by
Zhu, Dong-Ming; Miller, Robert A

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The development of low conductivity and high temperature capable thermal barrier coatings requires advanced testing techniques that can accurately and effectively evaluate coating thermal conductivity under future high-performance and low-emission engine heat-flux conditions. In this paper, a unique steady-state CO2 laser (wavelength 10.6 microns) heat-flux approach is described for determining the thermal conductivity and conductivity deduced cyclic durability of ceramic thermal and...

Topics: ELECTROMAGNETIC FIELDS, SINE WAVES, SIMULATION, MAGNETORESISTIVITY, PULSE AMPLITUDE,...

This report contains dielectric property measurement results for five different materials that have been used as fillers for various inert landmines. The original data were collected in the form of the real and imaginary parts of the complex dielectric constant versus frequency utilizing a Hewlett-Packard 8510C Vector Network Analyzer System with an S-Parameter Test Set and a coaxial sample holder. Software developed at the U.S. Army Engineer Waterways Experiment Station was used to convert...

Topics: DTIC Archive, Curtis, John O, ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS, *SAND,...

Bell System Technical Journal, 30: 4. October 1951 pp 956-969. Longitudinal Modes of Elastic Waves in Isotropic Cylinders and Slabs. (Holden, A.N.)

Topics: frequency, elastic, velocity, domain, nickel, decrement, longitudinal, constants, sin, arc, domain...

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 Millstone Hill UHF radar was used as a diagnostic tool for investigating plasma waves and turbulence. During the 15-month interval covered by the first year of this award, experiments were performed using an alternating-code technique in order to assess this capability for use as a plasma diagnostic. Experiments at fixed antenna position and with real-time interaction investigated phenomena near perpendicular flow angle when looking very close to perpendicular magnetic aspect angle...

Topics: DTIC Archive, Foster, John C, HAYSTACK OBSERVATORY WESTFORD MA, *IONOSPHERE, *TURBULENCE, *RADAR,...

The values of phase velocities of ultrasonic waves in transversely isotropic media are presented in terms of the fiber volume fraction of a unidirectional fiberglass epoxy composite with constant matrix properties and the ratio between extensional moduli in the longitudinal and transverse directions of the composite when the properties of the fibers are changed, at a constant fiber volume fraction. The model of a homogeneous transversely isotropic medium is adopted to describe the relations...

Topics: NASA Technical Reports Server (NTRS), COMPOSITE MATERIALS, DYNAMIC RESPONSE, FIBER COMPOSITES,...

The state of the art in multidimensional combustor modeling as evidenced by the level of sophistication employed in terms of modeling and numerical accuracy considerations, is also dictated by the available computer memory and turnaround times afforded by present-day computers. With the aim of advancing the current multi-dimensional computational tools used in the design of advanced technology combustors, a solution procedure is developed that combines the novelty of the coupled...

Topics: NASA Technical Reports Server (NTRS), PARALLEL PROCESSING (COMPUTERS), TURBULENCE MODELS, TURBULENT...

It is known that mixing enhancement in compressible free shear layer flows with high convective Mach numbers is difficult. One design strategy to get around this is to use multiple nozzles. Extrapolating this design concept in a one dimensional manner, one arrives at an array of parallel rectangular nozzles where the smaller dimension is omega and the longer dimension, b, is taken to be infinite. In this paper, the feasibility of predicting the stability of this type of compressible periodic...

Topics: NASA Technical Reports Server (NTRS), COMPRESSIBLE FLOW, JET FLOW, FLOW STABILITY, PREDICTION...

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RCA Review 1953 dec

Topics: rca, circuit, filter, figure, tube, frequency, aperture, television, impedance, storage, rca...

The development of a high average power FEL for military applications would represent a significant improvement in missile defense, especially shipboard self defense. The LANL regenerative amplifier FEL (RAFEL) is designed to produce an average output power of 1 kW. This FEL represents a significant increase in average power demonstrated in an FEL and also provides a test of the concept of combining the FEL oscillator and amplifier designs. Simulations were performed to better understand the...

Topics: DTIC Archive, Kesselring, Mark D., NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *FREE ELECTRON LASERS,...

The problem of wave propagation in an infinite, fluid-loaded, homogeneous, transversely isotropic cylinder is studied within the framework of the linearized, three-dimensional theory of elasticity. The equations of motion of the cylinder are formulated using the constitutive equations of a transversely isotropic material with a preferred material direction collinear with the longitudinal axis of the cylinder. The equations of motion of the internal and external fluids are formulated using the...

Topics: DTIC Archive, Berliner, Marilyn J., NAVAL UNDERSEA WARFARE CENTER NEWPORT DIV NEW LONDON CT NEW...

This study increases the quantitative understanding of acousto-ultrasonic nondestructive evaluation (NDE) parameters such as the stress wave factor (SWF) and wave propagation in fiber reinforced polymeric, ceramic or metallic composites, which can be modelled as transversely isotropic media. A unidirectional fiberglass epoxy composite specimen is modelled as a homogeneous transversely isotropic continuum plate medium. Acousto-ultrasonic noncontact input-output characterization is studied...

Topics: DTIC Archive, Liao, Peter, MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MECHANICAL ENGINEERING,...

This paper discusses accuracy limitations due to numerical dispersion and time step size for three implicit unconditionally- stable FDTD methods: Alternate-Direction- Implicit (ADI), Crank-Nicolson (CN) and Crank-Nicolson- Douglas-Gunn (CNDG). It is shown that for a uniform mesh, the three methods have the same numerical phase velocity along the axes, but have large differences along the diagonals. The ADI method has two orders-of-magnitude larger anisotropy than that of CN and CNDG. CNDG has...

Topics: DTIC Archive, Sun, Guilin, Trueman, Christopher W., CONCORDIA UNIV MONTREAL (QUEBEC) CA...

As large-distance rays (say, 10 - 24deg) approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large-separation travel times associated...

Topics: NASA Technical Reports Server (NTRS), HELIOSEISMOLOGY, SOLAR GRANULATION, DISTANCE, TIME RESPONSE,...

This memorandum presents a design study of a high power C-band Crestatron Amplifier. While conventional helix traveling-wave tubes (TWT's) are operated in an exponentially growing-wave mode, the Crestatron operates a beating-wave regime where three constant-amplitude voltage waves traveling at different phase velocities along the helix beat together to produce power gain. Although inherently lower in gain than a TWT, the Crestatron can produce high power rf over a surprisingly broad frequency...

Topics: DTIC Archive, Abe, David K, NAVAL RESEARCH LAB WASHINGTON DC VACUUM ELECTRONICS BRANCH,...

We develop a method for regionalization of surface wave magnitudes, replacing the traditional Ms measurement with a new type of magnitude, the scalar moment, derived from the equations for surface waves from point sources in layered media. This has the effect of minimizing the frequency dependence and distance dependence of the magnitude, and allows worldwide regionalization so that the magnitude is a consistent measure of source size for any source and receiver location. Automatic surface wave...

Topics: DTIC Archive, Stevens, J. L., S-CUBED LA JOLLA CA, *SURFACE WAVES, *SEISMIC DISCRIMINATION,...

A model and computer code are presented that simulate the operation of traveling wave tube amplifiers (TWTs). The model is based on the well known parametric theory in which the relevant properties of the interaction circuit are the phase velocity and coupling impedance of the waves supported by the slow wave structure. The model includes a multifrequency description of both the fields of the structure and the space charge fields. This allows for the study of harmonic and intermodulation...

Topics: DTIC Archive, Antonsen, Thomas M., Jr., NAVAL RESEARCH LAB WASHINGTON DC VACUUM ELECTRONICS BRANCH,...

Algorithms based on the global optimization technique of simulated annealing (SA) have proven useful in designing traveling-wave tube (TWT) slow-wave circuits for high RF power efficiency. The characteristic of SA that enables it to determine a globally optimized solution is its ability to accept non-improving moves in a controlled manner. In the initial stages of the optimization, the algorithm moves freely through configuration space, accepting most of the proposed designs. This freedom of...

Topics: NASA Technical Reports Server (NTRS), WAVE PROPAGATION, PHASE VELOCITY, SIMULATED ANNEALING, TUBE...

A new ultrasonic approach for monitoring the anelastic behavior of metals and alloys was presented. The approach poses some problems related to separating the temperature dependence of the anelastic phenomena from the natural wave velocity s susceptibility to temperature changes. However, these effects can be distinguished and separated without much difficulty. Due to its high sensitivity to microstructural changes, the new technique will be quite valuable when used in conjunction with strain...

Topics: NASA Technical Reports Server (NTRS), ANELASTICITY, ULTRASONICS, METALS, ALLOYS, MAGNETOACOUSTICS,...

Our long-term goal is to study the sensitivity behavior of acoustic phase arrival times, as an alternative observable offering increased resolution (compared to peak arrivals), for the recovery of sound-speed perturbations in the ocean. The objective of this work is to study the behavior and sensitivity of ocean acoustic phase arrival times due to sound-speed changes, in comparison to those of peak arrival times. The aim is to derive perturbation relations and sensitivity kernels connecting...

Topics: DTIC Archive, CALIFORNIA UNIV REGENTS LA JOLLA CA SCRIPPS INST OF OCEANOGRAPHY, *ACOUSTIC VELOCITY,...

Noise characteristics in shock-containing jets at an overexpanded jet condition have been investigated. Total temperature ratios of 1.0 (cold), 2.0, and 3.0 are considered. The cold jet is a highly screeching jet. Frequency-wavenumber Fourier analysis is employed to examine the wave characteristics of pressure waves along the lip line and also along a near-field conical surface. It is found that the radiating portion of the pressure wave intensity increases with the jet temperature, but the...

Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC, *JET ENGINE NOISE, *JET FLOW, *NUMERICAL ANALYSIS,...

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Jun 15, 2011
06/11

by
Karpov, N. I., et al

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Vibration measurement of circular cylinder with thickness varying in time

Topics: CROSS CORRELATION, GLOW DISCHARGES, LIGHT EMISSION, OPTICAL PATHS, PLASMA RADIATION,...

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May 23, 2011
05/11

by
Zolensky, Michael E.; Browning, Lauren B.; McSween, Harry Y., Jr., et al

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Three parameters are proposed to determine the relative extent of alteration in CM chondrites. The mineralogic alteration index monitors the relative progress of coupled substitutions in the progressive alteration of cronstedtite to Mg-serpentine, and increases with increasing alteration. To calculate values of this index, an algorithm has been developed to estimate the average matrix phyllosilicate composition in individual CM chondrites. The second parameter is the volume percent of isolated...

Topics: WATER WAVES, WAVE PROPAGATION, VIDEO EQUIPMENT, BANDPASS FILTERS, PHASE VELOCITY, FREQUENCY...

The purpose of the investigation is to study the interaction between an obliquely incident, plane electromagnetic wave and a plane, semi infinite dielectric medium, the dielectric constant of which contains a space- and time- varying component. Let us first consider a medium, the dielectric constant of which is periodically fluctuating only in time. It can then be shown that one gets parametric resonance when the angular frequency, w1, of the incident electro-magnetic wave is equal to half the...

Topics: DTIC Archive, Thomasson, A R, CHALMERS UNIV OF TECHNOLOGY GOETEBORG (SWEDEN), *ELECTROMAGNETIC WAVE...

Ultrasonic measurements were performed on MIL-W-81381/7, /12, and /21 wire, a polyimide (Kapton) insulated wire. The phase velocity for the 20-gauge MIL-W-81381/7 wire had a baseline value of 3023 plus or minus 78 m/s. After exposure to high temperatures, the wire's phase velocity rapidly increased, and reached an asymptotic value of 3598 plus or minus 20 m/s after 100 hours exposure. Similar responses were measured in other gauges. The baseline measurements of Young's moduli resulted in values...

Topics: NASA Technical Reports Server (NTRS), POLYIMIDES, ULTRASONICS, WIRE, TENSILE TESTS, DAMAGE, HIGH...

Surface wind waves play an important role in the air-sea transfer of momentum, mass and heat. Several field experiments reported that wave age, C/u. (Cp is the wave phase velocity at spectral peak), is an important parameter for determining air-sea drag coefficient, Cd, or surface roughness length, Zg (Donelan 1990; Geemaert et al. 1987; Smith et al. 1992; Lin 2000; Lin et al. 2002). Other theoretical or modeling studies (Janssen 1989,1991) also suggested that wave age is a controlling factor...

Topics: DTIC Archive, Lin, Weiqi, NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEAN SCIENCES BRANCH,...

The pressure disturbances generated by an instability wave in the shear layer of a supersonic jet are studied for an axisymmetric jet inside a lined cylindrical duct. For the supersonic jet, locally linear stability analysis with duct wall boundary conditions is used to calculate the eigenvalues and the eigenfunctions. These values are used to determine the growth rates and phase velocities of the instability waves and the radial pressure disturbance patterns. The study is confined to the...

Topics: NASA Technical Reports Server (NTRS), SUPERSONIC JET FLOW, CYLINDRICAL BODIES, STABILITY TESTS,...

Journal of Research of the National Bureau of Standards

Topics: very-low-frequency emissions, stream velocity, phase velocity, traveling wave tubes, wave...

A laboratory measurement program was conducted to explore the fundamental electrical properties of organic contaminants and contaminant/soil mixtures. Complex reflection and transmission coefficients measured by a vector network analyzer system for samples contained in coaxial sample holders were used to generate electrical properties of the pure substances and the mixtures. The frequencies covered by these experiments ranged from 43 MHz to 26.5 GHz, and sample temperatures were held fixed at...

Topics: DTIC Archive, Curtis, John O., ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS...

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509

May 23, 2011
05/11

by
Farassat, F.; Myers, M. K

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In this paper we discuss two problems of classical duct acoustics: (1) wave propagation in infinite ducts with uniform flow based on a graphical approach, and (2) detection of mode radiation from a duct by an external circular microphone array. In (1) we show that the wave number vectors for a given flow Mach number form an ellipse whose center and shape depend on the Mach number only. We construct graphically the upstream and downstream wave number vectors of modes that propagate in the duct....

Topics: PHASE VELOCITY, BOUNDARY CONDITIONS, ULTRASONIC WAVE TRANSDUCERS, PIEZOELECTRIC TRANSDUCERS,...

This report contains dielectric property measurement results for soils. The original data were collected in the form of the real and imaginary parts of the complex dielectric constant versus frequency. The data collection apparatus was a Hewlet-Packard 85l0C Vector Network Analyzer System with an S-Parameter Test Set. Software developed at the U.S. Army Engineer Waterways Experiment Station was used to convert S-parameter measurements at selected frequencies into a complex dielectric constant....

Topics: DTIC Archive, Curtis, John O, ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS, *DIELECTRIC...