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Resonant excitation of coupled Rayleigh waves in a short and narrow fluid channel clad between two identical metal plates

Description: This article studies the transmission of ultrasonic waves through a slit between two water immersed brass plates for sub-wavelength plate thicknesses and slit apertures.
Date: July 14, 2014
Creator: Garcia-Chocano, Victor M.; Lopez-Rios, Tomas; Krokhin, Arkadii A. & Sanchez-Dehesa, Jose
Partner: UNT College of Arts and Sciences

Radio-frequency actuated polymer-based phononic meta-materials for control of ultrasonic waves

Description: This article describes the achievement of radio-frequency control of a n ultrasonic phononic crystal by encapsulating it in a composite of high k-10% KF-doped BaTiO₃ dielectric nanoparticles with poly(N-isopropylacrylamide) (PNIP Am)-based hydrogel.
Date: July 14, 2016
Creator: Walker, Ezekiel; Wang, Zhiming & Neogi, Arup
Partner: UNT College of Arts and Sciences

A Model Designed to Predict the Motion of Objects Translated by Classical Blast Waves

Description: From Introduction: "The purpose of this report is to describe, step by step, the theoretical studies that have resulted in a mathematical model capable of predicting the motion of objects utilizing selected basic blast parameters."
Date: January 1961
Creator: Bowen, I. Gerald; Albright, Ray W.; Fletcher, E. Royce & White, Clayton S.
Partner: UNT Libraries Government Documents Department

Investigation of the Attenuation of Plane Shock Waves Moving over very Rough Surfaces

Description: Experimental measurements of the attenuation of plane shock waves moving over rough walls have been made in a shock tube. Measurements of the boundary-layer characteristics, including thickness and velocity distribution behind the shock, have also been made with the aid of new cal techniques which provide direct information on the local boundary-layer conditions at the rough walls. Measurements of shock speed and shock pressure ratio are presented for both smooth-wall and rough-wall flow over lengths of machined-smooth and rough strips which lined all four walls of the shock tube. A simplified theory based on Von Karman's expression for skin-friction coefficient for flow over rough walls, along with a wave-model concept and extensions to include time effects, is presented. In this theory, the shock-tube flow is assumed to be one-dimensional at all times and the wave-model concept is used to relate the local layer growth to decreases in shock strength. This concept assumes that local boundary-layer growths act as local mass-flow sinks, which give rise to expansion waves which, in turn, overtake the shock and lower its mass flow accordingly.
Date: June 16, 1953
Creator: Huber, Paul W.; McFarland, Donald R. & Levine, Philip
Partner: UNT Libraries Government Documents Department

Boundary Disturbances in High Explosive Shock Tubes

Description: From abstract: High velocity disturbances are observed to propagate along the walls of a high explosive operated shock tube in advance of the plane shock. Experiments are presented which determine the dependence of the geometry, energy, and velocity of the disturbance on such variables as the gas contained in the shock tube, the shock strength, and the roughness and composition of the supporting boundary. A model is constructed to explain the flow within the disturbance. Arguments are presented which show the disturbance to result from radiation originating in the luminous plane shock...The purpose of this paper is to present the results of initial investigations made in an effort to describe the phenomenon of strong shocks developed in a shock tube by the detonation of high explosive charge.
Date: May 26, 1952
Creator: Shreffler, R. G. & Christian, R. H.
Partner: UNT Libraries Government Documents Department

Boundary Disturbances in High Explosive Shock Tubes

Description: Abstract: High Velocity disturbance are observed to propagate in advance of the plane shock front along the walls of a high-explosive-operated shock tube. Experiments were performed which indicate that the disturbance proceeds at a constant velocity relative to the shock front, and carries a considerable amount of energy as evidenced by its ability to penetrate metal plates. The velocity of a similar disturbance observed along a rod placed on the axis of the shock tube normal to the plane shock front was essentially independent of the rod material and diameter. This phenomenon was observed when shock tubes were filled with argon or chlorine but was absent when air or helium was used.
Date: March 31, 1952
Creator: Shreffler, R. G.
Partner: UNT Libraries Government Documents Department

A study of the transient behavior of shock waves in transonic channels flows

Description: Report presenting an investigation of the accuracy of the result obtained in a fundamental paper by Kantrowitz that a small short-time lowering of the back pressure in steady, shock-free, transonic diffuser flow causes a stationary or trapped shock to form near the critical shock channel throat.
Date: October 1952
Creator: Hess, Robert V.
Partner: UNT Libraries Government Documents Department

Visual observations of the shock wave in flight

Description: From Summary: "This report presents the results of pilot observations and photographs of the compression shock wave on the wing of an airplane in flight. A detailed description of the test conditions necessary and the procedure to be following in producing the visible shock are presented. The pilot's observations of the occurrence of an oscillating shock wave and its possible relationship with the airplane buffeting are also presented."
Date: May 24, 1948
Creator: Cooper, George E. & Rathert, George A., Jr.
Partner: UNT Libraries Government Documents Department

Preseismic Velocity Changes Observed from Active Source Monitoringat the Parkfield SAFOD Drill Site

Description: Measuring stress changes within seismically active fault zones has been a long-sought goal of seismology. Here we show that such stress changes are measurable by exploiting the stress dependence of seismic wave speed from an active source cross-well experiment conducted at the SAFOD drill site. Over a two-month period we observed an excellent anti-correlation between changes in the time required for an S wave to travel through the rock along a fixed pathway--a few microseconds--and variations in barometric pressure. We also observed two large excursions in the traveltime data that are coincident with two earthquakes that are among those predicted to produce the largest coseismic stress changes at SAFOD. Interestingly, the two excursions started approximately 10 and 2 hours before the events, respectively, suggesting that they may be related to pre-rupture stress induced changes in crack properties, as observed in early laboratory studies.
Date: June 10, 2008
Creator: Daley, Thomas; Niu, Fenglin; Silver, Paul G.; Daley, Thomas M.; Cheng, Xin & Majer, Ernest L.
Partner: UNT Libraries Government Documents Department

The Use of Compensation With Directional Couplers

Description: Abstract: The accurate measurement of voltage standing wave ratio (VSWR) is of prime importance in the production of microwave systems. The work reported in this memorandum was undertaken in the development of a faster system for measuring VSWR.
Date: January 1961
Creator: Lincoln, Roland Alan
Partner: UNT Libraries Government Documents Department

Theory of Near-Field Phased Arrays for Electromagnetic Susceptibility Testing

Description: From introduction: The feasibility of using a near-field array for electromagnetic susceptibility testing is studied. The basic objective is to control the element weightings such that a plane wave is generated within the test volume. The basic theory is developed for arbitrary array geometries, and numerical results are obtained for finite planar arrays. A general near-field array synthesis technique is developed, and the technique minimizes the mean square error in the test volume while constraining the array excitations. The constraint prevents large excitations and is useful in minimizing the fields outside the test volume. The basic idea looks promising, but some practical considerations, such as bandwidth and angular scanning limitations, require further theoretical and experimental investigation.
Date: February 1984
Creator: Hill, D. A.
Partner: UNT Libraries Government Documents Department

K{sub s} K{sub s} System at 800 GeV/c

Description: Results are presented from a partial wave analysis of a sample of centrally produced mesons in the reaction pp {yields} p{sub slow}(K{sub s} K{sub s})p{sub fast} , with 800 GeV/c protons incident on a liquid hydrogen target. The meson system is found to be predominantly S-wave in the mass range between K{sub s} K{sub s} threshold and 1.58 GeV/c{sup 2} . The f{sub 0}(1500) is clearly observed in this region. Above 1.58 GeV/c{sup 2} two solutions are possible, one with mainly S-wave and another with mainly D-wave. This ambiguity prevents a unique determination of the spin of the f{sub J} (1710) meson.
Date: December 1, 1997
Creator: Reyes, M.A. & others, and
Partner: UNT Libraries Government Documents Department

Alfven Continuum and Alfven Eigenmodes in the National Compact Stellarator Experiment

Description: The Alfven continuum (AC) in the National Compact Stellarator Experiment (NCSX) is investigated with the AC code COBRA. The resonant interaction of Alfven eigenmodes and the fast ions produced by neutral beam injection is analyzed. Alfven eigenmodes residing in one of the widest gaps of the NCSX AC, the ellipticity-induced gap, are studied with the code BOA-E.
Date: September 17, 2004
Creator: O.P. Fesenyuk, Ya.I. Kolesnichenko, V.V. Lutsenko, R.B. White, and Yu.V. Yakovenko
Partner: UNT Libraries Government Documents Department

Kinetic Damping of Toroidal Alfven Eigenmodes

Description: The damping of Toroidal Alfven Eigenmodes in JET plasmas is investigated by using a reduced kinetic model. Typically no significant damping is found to occur near the center of the plasma due to mode conversion to kinetic Alfven waves. In contrast, continuum damping from resonance near the plasma edge may be significant, and when it is, it gives rise to damping rates that are compatible with the experimental observations.
Date: May 3, 2005
Creator: Fu, G.Y.; Berk, H.L. & Pletzer, A.
Partner: UNT Libraries Government Documents Department