Wave attenuation

Liquid Level. The most widely used devices for measuring Hquid levels involve detecting the buoyant force on an object or the pressure differential created by the height of Hquid between two taps on the vessel. Consequently, care is required in locating the tap. Other less widely used techniques utilize concepts such as the attenuation of radiation changes in electrical properties, eg, capacitance and impedance and ultrasonic wave attenuation. 

Ahrens, T.J., and O Keefe, J.D. (1977), Equation of State and Impact-Induced Shock-Wave Attenuation on the Moon, in Impact and Explosion Cratering (edited by Roddy D.J. et al.), Pergamon Press, New York, pp. 639-656. 

Y.M. Gupta, Stress Dependence of Elastic-Wave Attenuation in LiF, J. Appl. Phys. 46, 3395-3401 (1975). 

Figure 8.9. The effect of attenuation of the pullback wave signal in an elastic-plastic material. Amplitude of the pullback signal at the recording interface will be diminished due to wave attenuation and will not provide an accurate measure of the material spall strength.

Example 9 Mud Pulse Telemetry—Pressure Wave Attenuation... 

In preparing this figure, the authors of Ref. 28 assumed no wave attenuation through the wall thickness H, so Pr and ir are the normally reflected blast loading parameters on the loaded side of the wall or slab. 

H. J. Liebe, T. Manabe, G. A. Hufford. Millimeter-Wave Attenuation and Delay Rates Due to Fog/Cloud Conditions , IEEE Trans. Antennas Propagat., Vol. 37, pp. 1617-1623, December 1989. 

The blast wave attenuates as it propagates outward from the explosion epicenter. Consequently, the values of peak overpressure and impulse decrease with distance while the duration tends to increase. Values for these blast wave parameters can be... 

H(u) is the Fourier Transform of h(r) and is called the contrast transfer function (CTF). u is a reciprocal-lattice vector that can be expressed by image Fourier coefficients. The CTF is the product of an aperture function A(u), a wave attenuation function E(u) and a lens aberration function B(u) = exp(ix(u)). Typically, a mathematical description of the lens aberration function to lowest orders builds on the Weak Phase Approximation and yields the expression ... 

Lin J., and Pence T.J., 1996, Wave attenuation by Mnetically active phase boundary scattering during displacivephase transformations. Preprint... 

Rayleigh angle as usual. The value of (7.45) has the form of a ratio of impedances multiplied by a ratio of velocities, and it provides a means of relating Rayleigh wave attenuation (due to radiation into the fluid) to the density of the specimen. With the approximation of (7.45), the term in the large curly brackets in (7.42) becomes... 

Hook F, Ray A, Norden B, Kasemo B (2001) Characterization of PNA and DNA immobilization and subsequent hybridization with DNA using acoustic-shear-wave attenuation measurements. Langmuir 17 8305-8312... 

Equation 2.55 indicates the relationship between wave attenuation and power dissipation in the medium attenuation is one-half the ratio of power dissipated to power transmitted by the wave. Note that in the derivations of this section, velocity and attenuation changes depend on ratios of energy and power, not on absolute levels. Consequently, in the small-signal limit, velocity and attenuation changes are independent of wave amplitude. 

AW device sensitivity to viscoelastic parameters and electrical pnqieities can be used to advantage in some film characterization techniques. In these situations, a comparison of the AW device response to a model of the AW/thin film interaction is often crucial to the effective evaluation of thin film parameters. These additional interaction mechanisms typically involve changes in both the wave velocity and the wave attenuation for SAW, APM and FPW devices, and changes in both resonant frequency and admittance magnitude in TSM devices. In contrast, mass loading does not contribute to wave attenuation or decreases in admittance since moving mass involves no power dissipation (see Chapter 3). 

Because of the oscillatory nature of the acoustic wave, probing of polymer viscoelastic properties using AW devices is analogous to the high rate/short time scale probing of polymers mentioned previously. The wave period, which is the inverse of the AW frequency, determines the time scale of the applied strain. Wave attenuation and velocity, or resonant amplitude and frequency, can be monitored at a relatively fixed frequency (rate) while scanning the temperature. 

The results presented here demonstrate that thin films can be characterized based on acoustical monitoring of changes in film mass density, conductivity, and viscoelasticity. Additional sensing mechanisms are available to probe film properties. Some examples are thin-film dielectric constant, stress, and structure (e.g., roughness). Some of these sensing mechanisms will be hard to quantify since they involve a complex interaction (e.g., wave attenuation based on wave scattering due to film roughness) however, they may still be useful to provide a qualitative monitor based on empirical data. 

Figure 1, The Contribution of Mode Conversion Scattering to Longitudinal Stress Wave Attenuation by Spherical Pb Inclusions in Epoxy (Attenuation = 20a log 10(e) = 8.69a)...

Abstract Contribution of the Jahn-Teller system to the elastic moduli and ultrasonic wave attenuation of the diluted crystals is discussed in the frames of phenomenological approach and on the basis of quantum-mechanical theory. Both, resonant and relaxation processes are considered. The procedure of distinguishing the nature of the anomalies (either resonant or relaxation) in the elastic moduli and attenuation of ultrasound as well as generalized method for reconstruction of the relaxation time temperature dependence are described in detail. Particular attention is paid to the physical parameters of the Jahn-Teller complex that could be determined using the ultrasonic technique, namely, the potential barrier, the type of the vibronic modes and their frequency, the tunnelling splitting, the deformation potential and the energy of inevitable strain. The experimental results obtained in some zinc-blende crystals doped with 3d ions are presented. 

For this reason ki(t) is also called the impulse-response function. For excitation of the linear response in NMR, that is, for excitation with small flip-angle pulses, k t) is identical to the FID (Fig. 4.1.1(b)). If the input is a weak continuous wave with adjustable frequency co, then x(t) = exp in>r, and the response is given by the input wave attenuated by the spectrum K (to) of the impulse-response function ki (r),... 

Pogorzelski St, Linde B, Sliwinski A (1984) Capillary wave attenuation on a water surface coated with monolayers of oil-derivative substances. Acoustics Letters 8 5-9... 

Direct measurements of permeabilities in unconsolidated marine sediments are difficult, and only few examples are published. They confine to measurements on discrete samples with a specially developed tool (Lovell 1985), to indirect estimations by resistivity measurements (Lovell 1985), and to consolidation tests on ODP cores using a modified medical tool (Olsen et al. 1985). These measurements are necessary to correct for the elastic rebound (MacKillop et al. 1995) and to determine intrinsic permeabilities at the end of each consolidation step (Fisher et al. 1994). In Section 2.4.2 a numerical modeling and inversion scheme is described which estimates permeabilities from P-wave attenuation and dispersion curves (c.f. also section 3.6). 

Fig. 2.16 Comparison of P-wave attenuation and velocity dispersion data derived from ultrasonic transmission seismograms with theoretical curves based on Biot-Stoll s model for six traces of the turbidite layer of gravity core GeoB1510-2. Permeabilities vary in the model curves according to constant ratios K/a = 0.030, 0.010, 0.003 (K = permeability, a = pore size parameter). The resulting permeabilities are given in each diagram. Modified after Breitzke et al. (1996).

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