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1
Carmichael, Stephen W. "Imaging Based on Elasticity." Microscopy Today 6, no. 7 (September 1998): 3–4. http://dx.doi.org/10.1017/s1551929500068565.
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There are scores of microscopes that detect different properties of a specimen. Typically we image ‘visible” properties, but, for example, even the commonly-used atomic force microscope detects physical interactions rather than “visible” characteristics, Mostafa Fatemi and James Greenleaf have introduced the principle of imaging the elastic features of a specimen. This is done with sound waves, but we are not talking about just another acoustic microscope.The method demonstrated by Fatemi and Greenleaf uses radiation force to image the acoustic response of a specimen to mechanical excitation. The mechanical excitation results from focusing two coaxial and confocal ultrasound beams of slightly different frequencies onto a selected region of the specimen.
2
Inoue, Kazuko, and Tomio Ariyasu. "Sound waves and shock waves in high-density deuterium." Laser and Particle Beams 9, no. 4 (December 1991): 795–816. http://dx.doi.org/10.1017/s026303460000656x.
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The possibility of compressing the cryogenic hollow pellet of inertial confinement nuclear fusion with multiple adiabatic shock waves is discussed, on the basis of the estimation of the properties of a high-density deuterium plasma (1024−1027 cm−3, 10−1−104 eV), such as the velocity and the attenuation constant of the adiabatic sound wave, the width of the shock wave, and the surface tension.It is found that in the course of compression the wavelength of the adiabatic sound wave and the width of the weak shock wave sometimes become comparable to or exceed the fuel shell width of the pellet, and that the surface tension is negative. These results show that it is rather difficult to compress stably the hollow pellet with successive weak shock waves.
3
Gräff, Dominik, Fabian Walter, and Bradley P. Lipovsky. "Crack wave resonances within the basal water layer." Annals of Glaciology 60, no. 79 (April 25, 2019): 158–66. http://dx.doi.org/10.1017/aog.2019.8.
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ABSTRACTHydraulic processes within and beneath glacial bodies exert a far-reaching control on ice flow through their influence on basal sliding. Within the subglacial system, rapid changes in these processes may excite resonances whose interpretation requires an understanding of the underlying wave mechanics. Here, we explore these mechanics using observations from a kHz-sampled pressure sensor installed in a borehole directly above the hard granite bedrock of a temperate mountain glacier in Switzerland. We apply a previously established theory of wave propagation along thin, water-filled structures such as water-filled voids, basal water layers, or hydraulic fractures. Within such structures, short-wavelength waves experience restoring forces due to compressibility and are composed of sound waves. Long-wavelength resonances, in contrast, experience restoring forces due to elasticity and are composed of anomalously dispersed crack waves or Krauklis waves. Our borehole observations confirm the occurrence of both sound and crack waves within the basal water layer. Using both the resonance frequencies and attenuation of recorded crack waves we estimate thickness, aperture and length of the resonating basal water layer patch into which we drilled. We demonstrate that high-frequency observations of subglacial hydraulic processes provide new insights into this evolving dynamic system.
4
Li, Yueqiu, Peijun Wei, and Changda Wang. "Propagation of thermoelastic waves across an interface with consideration of couple stress and second sound." Mathematics and Mechanics of Solids 24, no. 1 (December 28, 2017): 235–57. http://dx.doi.org/10.1177/1081286517736999.
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The reflection and transmission of thermoelastic waves across an interface between two different couple stress solids are studied based on the thermoelastic Green–Naghdi theory with consideration of second sound. First, some thermodynamic equations of a couple stress elastic solid are formulated and the function of free energy density is postulated. Second, equations of thermal motion and heat conduction of the couple stress elasticity are derived and constitutive relations with thermoelastic coupled effects are obtained. From these equations, four kinds of dispersive waves, namely, thermal-mechanically coupled MT1 wave and MT2 wave, uncoupled SV wave, and an evanescent wave that becomes the surface waves at interface, are derived. Then, the interfacial conditions of couple stress elastic solids with consideration of force stress, couple stress, and thermal effects are used to determine the amplitude ratios of the reflection and transmission waves with respect to the incident wave. The numerical results are validated by consideration of energy conservation.
5
Rousseau, Martine, and Gérard A. Maugin. "Rayleigh surface waves and their canonically associated quasi-particles." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 467, no. 2126 (August 11, 2010): 495–507. http://dx.doi.org/10.1098/rspa.2010.0229.
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Inspired by soliton theory and exploiting the conservation law of wave momentum, it is shown that one can associate with the surface Rayleigh wave of macroscopic elasticity a quasi-particle, a ‘surface phonon’, which is in inertial motion for the standard boundary conditions. The ‘mass’ of this ‘particle’ is determined in terms of the wave properties. Different types of alteration in the boundary conditions are shown to result in perturbations of this inertial motion in various ways. The essential tool in the presented derivation is the exploitation of the canonical equations of conservation, which are consequences of the celebrated Noether theorem of field theory. The results obtained may be useful in the mechanics of surface waves at the nanoscale, in particular in treating perturbations of various kinds.
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Otani, Takahiko. "Modeling of Ultrasonic Wave Propagation Path through Cancellous Bone and Quantitative Estimation of Bone Density and Bone Quality." Key Engineering Materials 321-323 (October 2006): 857–61. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.857.
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Osteoporosis is a disease characterized by decreasing bone density, and is assessed by the bone mass density of cancellous bone. An X-ray method is widely used for noninvasive measurement of bone mass density [mg/cm3]. An ultrasonic method has the potential to evaluate the elastic properties, however measured ultrasonic parameters are the slope of frequency dependent attenuation (BUA [dB/MHz]) and the speed of sound (SOS [m/s]), not the bone mass density [mg/cm3]. In previous study, two longitudinal waves, the fast and slow waves, were observed in cancellous bone. In this study, the propagation path through cancellous bone is modeled to specify the causality between ultrasonic wave parameters and bone density. Then bone density and bone elasticity are quantitatively formulated. A novel ultrasonic bone densitometry, prototype LD-100, have been developed. The bone density [mg/cm3] and the bone elasticity [GPa] are evaluated by ultrasonic parameters based on the fast and slow waves in cancellous bone using a modeling of ultrasonic wave propagation path.
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OU, Z. Y., and D. W. LEE. "EFFECTS OF INTERFACE ENERGY ON MULTIPLE SCATTERING OF PLANE COMPRESSIONAL WAVES BY TWO CYLINDRICAL FIBERS." International Journal of Applied Mechanics 04, no. 04 (December 2012): 1250040. http://dx.doi.org/10.1142/s1758825112500408.
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The multiple scattering of plane compressional waves by two cylindrical fibers with interface effects is investigated. Based on surface elasticity theory, the wave fields in a nanoscale solid medium can be obtained by applying the eigenfunction expansion method and the Graf's addition theorem. Our results indicate that surface energy significantly affects the diffraction of elastic waves, as the radii of the fibers approach nanometers. The dynamic stress concentration factors at the interfaces between the fibers and the matrix under incident plane compressional waves at different frequencies are examined to determine the effects of surface energy, properties of inhomogeneous materials, and the interaction between fibers in multiple scattering phenomena. These results are helpful in understanding the dynamic mechanical properties of nanocomposites, and the proposed method for investigating the multiple scattering of plane compressional waves can be extended to the case of fiber-reinforced composites.
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Sharifineyestani, Elham, and Navid Tahvildari. "A NUMERICAL STUDY ON SURFACE WAVE EVOLUTION OVER VISCOELASTIC MUD." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 64. http://dx.doi.org/10.9753/icce.v36.waves.64.
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A numerical modeling approach is applied to investigate the combined effect of wave-current-mud on the evolution of nonlinear waves. A frequency-domain phase-resolving wave-current model that solves nonlinear wave-wave interactions is used to solve wave evolution. A comparison between the results of numerical wave model and the laboratory experiments confirms the accuracy of the numerical model. The model is then applied to consider the effect of mud properties on nonlinear surface wave evolution. It is shown that resonance effect in viscoelastic mud creates a complex frequency-dependent dissipation pattern. In fact, due to the resonance effect, higher surface wave frequencies can experience higher damping rates over viscoelastic mud compared to viscous mud in both permanent form solution and random wave scenarios. Thus, neglecting mud elasticity can result in inaccuracies in estimating total wave energy and wave shape.
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Tang, Zihan, Yue Chen, and Wei Ye. "Calculation of Surface Properties of Cubic and Hexagonal Crystals through Molecular Statics Simulations." Crystals 10, no. 4 (April 22, 2020): 329. http://dx.doi.org/10.3390/cryst10040329.
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Surface property is an important factor that is widely considered in crystal growth and design. It is also found to play a critical role in changing the constitutive law seen in the classical elasticity theory for nanomaterials. Through molecular static simulations, this work presents the calculation of surface properties (surface energy density, surface stress and surface stiffness) of some typical cubic and hexagonal crystals: face-centered-cubic (FCC) pure metals (Cu, Ni, Pd and Ag), body-centered-cubic (BCC) pure metals (Mo and W), diamond Si, zincblende GaAs and GaN, hexagonal-close-packed (HCP) pure metals (Mg, Zr and Ti), and wurzite GaN. Sound agreements of the bulk and surface properties between this work and the literature are found. New results are first reported for the surface stiffness of BCC pure metals, surface stress and surface stiffness of HCP pure metals, Si, GaAs and GaN. Comparative studies of the surface properties are carried out to uncover trends in their behaviors. The results in this work could be helpful to the investigation of material properties and structure performances of crystals.
10
Mei, Chiang C., and Usama Kadri. "Sound signals of tsunamis from a slender fault." Journal of Fluid Mechanics 836 (December 11, 2017): 352–73. http://dx.doi.org/10.1017/jfm.2017.811.
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Since the speed of sound in water is much greater than that of the surface gravity waves, acoustic signals can be used for early warning of tsunamis. We simplify existing works by treating the sound wave alone without the much slower gravity wave, and derive a two-dimensional theory for signals emanating from a fault of finite length. Under the assumptions of a slender fault and constant sea depth, the asymptotic technique of multiple scales is applied to obtain analytical results. The modal envelopes of the two-dimensional sound waves are found to be governed by the Schrödinger equation and are solved explicitly. An approximate method is described for the inverse estimation of fault properties from the pressure record at a distant hydrophone.
11
Lou, Ching-Wen, Ting-Ting Li, Chien-Lin Huang, Ying-Hsuan Hsu, and Jia-Horng Lin. "Sound-Absorbing and Flame-Retarding Property of Nonwoven Compounded PU foam Planks." Journal of Engineered Fibers and Fabrics 10, no. 3 (September 2015): 155892501501000. http://dx.doi.org/10.1177/155892501501000315.
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A nonwoven is an ideal sound-absorbing material due to its high surface area. Surface area of a nonwoven correlates with fiber denier and packing density, and affects the sound absorbing property. With smaller denier, sound waves have great chance to interact with fibers. Moreover, more fibers would produce friction in-between sound waves at high packing density. Besides, a large amount of fabrics are produced in the current textile industry. During the production process, selvages are cut form fabrics and then abandoned, thus leading to amazing wastes after a long period of discarding. This study used recycled selvage fiber to prepare composite nonwovens, and then compounded with polyurethane foam, forming sound-absorbing/flame-retarding composite planks. Porous and vibration absorbing mechanism was combined for improving sound the absorbing property. And effects of fiber denier, needle-punched density for nonwoven and foam density of PU foam on properties including sound-absorbing and flame-retarding are discussed. Results show that the sound absorption coefficient of the resultant composite plank was above 0.8 at medium frequency. Superficial composite nonwoven achieved the effect of delayed burning time.
12
Lebedev, Maxim, Andrej Bóna, Roman Pevzner, and Boris Gurevich. "Elastic anisotropy estimation from laboratory measurements of velocity and polarization of quasi-P-waves using laser interferometry." GEOPHYSICS 76, no. 3 (May 2011): WA83—WA89. http://dx.doi.org/10.1190/1.3569110.
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A new method for conducting laboratory measurements of the velocities and polarizations of compressional and shear waves in rock samples uses a laser Doppler interferometer (LDI). LDI can measure the particle velocity of a small (0.03 mm2) element of the surface of the sample along the direction of the laser beam. By measuring the particle velocity of the same surface element in three linearly independent directions and then transforming those velocities to Cartesian coordinates, three orthogonal components of the particle-velocity vector are obtained. Thus, LDI can be used as a localized three-component (3C) receiver of ultrasonic waves, and, together with a piezoelectric transducer as a source, it can simulate a 3C seismic experiment in the laboratory. Performing such 3C measurements at various locations on the surface of the sample produces a 3C seismogram, which can be used to separate the P-wave and two S-waves and to find the polarizations and traveltimes of those waves. Then, the elasticity tensor of the medium can be obtained by minimizing the misfit between measured and predicted polarizations and traveltimes. Computation of the polarizations and traveltimes of body waves inside a sample with a given elasticity tensor is based on the Christoffel equation. The predicted polarizations on the surface then are obtained using the anisotropic Zoeppritz equations. The type of velocity measured (phase or group velocity) depends on the acquisition geometry and the material properties. This is taken into account in the inversion procedure. A “walkaway” laboratory experiment demonstrates the high accuracy of this method.
13
Lapčík, Lubomír, Martin Vašina, Barbora Lapčíková, David Hui, Eva Otyepková, Richard W. Greenwood, Kristian E. Waters, and Jakub Vlček. "Materials characterization of advanced fillers for composites engineering applications." Nanotechnology Reviews 8, no. 1 (December 31, 2019): 503–12. http://dx.doi.org/10.1515/ntrev-2019-0045.
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Abstract Four different minerals were investigated; hollow spheres of calcium carbonate, platy mica, needle like wollastonite and glassy perlite and characterized via iGC for surface energy, Freeman powder rheology for flow characterization, cyclic uniaxial die compaction for modulus of elasticity and frequency dependent sound absorption properties. Particle surface energy and particle shape strongly affected the packing density of powder beds. In the case of higher porosity and thus lower bulk density, the powders acoustic absorption was higher in comparison with higher packing density materials. Surface energy profiles and surface energy distributions revealed clear convergence with powder rheology data, where the character of the powder flow at defined consolidation stresses was mirroring either the high cohesion powders properties connected with the high surface energy or powder free flowing characteristics, as reflected in low cohesion of the powder matrix.
14
Ziemann, A., K. Arnold, and A. Raabe. "Acoustic tomography in the atmospheric surface layer." Annales Geophysicae 17, no. 1 (January 31, 1999): 139–48. http://dx.doi.org/10.1007/s00585-999-0139-9.
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Abstract. Acoustic tomography is presented as a technique for remote monitoring of meteorological quantities. This method and a special algorithm of analysis can directly produce area-averaged values of meteorological parameters. As a result consistent data will be obtained for validation of numerical atmospheric micro-scale models. Such a measuring system can complement conventional point measurements over different surfaces. The procedure of acoustic tomography uses the horizontal propagation of sound waves in the atmospheric surface layer. Therefore, to provide a general overview of sound propagation under various atmospheric conditions a two-dimensional ray-tracing model according to a modified version of Snell's law is used. The state of the crossed atmosphere can be estimated from measurements of acoustic travel time between sources and receivers at different points. Derivation of area-averaged values of the sound speed and furthermore of air temperature results from the inversion of travel time values for all acoustic paths. Thereby, the applied straight ray two-dimensional tomographic model using SIRT (simultaneous iterative reconstruction technique) is characterised as a method with small computational requirements, satisfactory convergence and stability properties as well as simple handling, especially, during online evaluation.Key words. Meteorology and atmospheric dynamics (turbulence; instruments and techniques).
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Diez, A., and O. Eisen. "Seismic wave propagation in anisotropic ice – Part 1: Elasticity tensor and derived quantities from ice-core properties." Cryosphere 9, no. 1 (February 20, 2015): 367–84. http://dx.doi.org/10.5194/tc-9-367-2015.
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Abstract. A preferred orientation of the anisotropic ice crystals influences the viscosity of the ice bulk and the dynamic behaviour of glaciers and ice sheets. Knowledge about the distribution of crystal anisotropy is mainly provided by crystal orientation fabric (COF) data from ice cores. However, the developed anisotropic fabric influences not only the flow behaviour of ice but also the propagation of seismic waves. Two effects are important: (i) sudden changes in COF lead to englacial reflections, and (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. A framework is presented here to connect COF data from ice cores with the elasticity tensor to determine seismic velocities and reflection coefficients for cone and girdle fabrics. We connect the microscopic anisotropy of the crystals with the macroscopic anisotropy of the ice mass, observable with seismic methods. Elasticity tensors for different fabrics are calculated and used to investigate the influence of the anisotropic ice fabric on seismic velocities and reflection coefficients, englacially as well as for the ice–bed contact. Hence, it is possible to remotely determine the bulk ice anisotropy.
16
Pierce, A. D. "Waves on Fluid-Loaded Inhomogeneous Elastic Shells of Arbitrary Shape." Journal of Vibration and Acoustics 115, no. 4 (October 1, 1993): 384–90. http://dx.doi.org/10.1115/1.2930361.
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A generalization of the Donnell model for a thin shell of arbitrary shape, and with position-dependent elastic and geometric properties, is used to formulate a wave theory for quasi-straight-crested waves of constant frequency propagating over the shell’s surface. The principal restriction on the theory is that the wavenumber components must be large compared with the two principal curvatures. A simple method for including fluid loading in the model yields a finite local specific radiation impedance even when the waves on the surface are moving with the fluid’s sound speed. The overall model is then used to derive a general dispersion relation which connects frequency and wavenumber components for the fundamental waves of the fluid-shell system.
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Qu, Renhao, Jingwen Guo, Yi Fang, and Siyang Zhong. "Sound reflection of acoustic porous metasurfaces under uniform mean flow." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 4 (August 1, 2021): 2601–8. http://dx.doi.org/10.3397/in-2021-2182.
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Acoustic metasurfaces are artificial 2D structures with a sub-wavelength thickness that can realize some exotic properties such as non-trivial refraction, broadband and low frequency absorption. However, most relevant studies are still in a static medium, hindering their realistic applications in aviation, where background flow exists. To address it, the effects of mean flow on the acoustic performance of metasurfaces, which is designed based on the generalized Snell's law (GSL) to achieve anomalous reflections, are systemically studied. Firstly, an analytical model of GSL taking the effect of background uniform mean flow into account is built, in which the wavenumbers of both incident and reflected waves are corrected. Then, taking an acoustic porous metasurface for instance, the effectiveness of the derived model is validated by numerical simulations. Results reveal that the reflected waves are deflected in the presence of background flow. The critical incident angle, at which the incident sound wave is converted to surface wave, decreases with the increasing flow velocity. Since the converted surface wave can only propagate along the metasurface, there is little sound energy radiated into far field, which is benefit for the noise attenuation in the presence of flow.
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Guliyev, H., Kh Aghayev, F. Mehraliyev, and E. Ahmadova. "DETERMINATION OF THE PHYSICAL PROPERTIES OF COMPLEXLY CONSTRUCTED MEDIA USING NEAR-SURFACE CROSSWELL METHOD." Visnyk of Taras Shevchenko National University of Kyiv. Geology, no. 3 (86) (2019): 13–20. http://dx.doi.org/10.17721/1728-2713.86.02.
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In case when the upper part of the medium has complex geological structure and geodynamic processes occur in it, the necessity of these data increases in projecting of the object under construction. Purpose. Studying of acoustic, elastic and anisotropic properties of the upper part of section of complicatedly constructed geological media. Methodology. Seismic observations are conducted in shallow wells in the areas of construction objects located in various seismogeological conditions by NSCW (Near-Surface Cross Well testing) method. Field seismic records are processed. Kinematic and dynamic parameters of pressure and differently polarized shear waves are determined. Thin-layered one-dimensional models of physical properties of the medium are created and interpreted on the basis of nonlinear theory of elastodynamics. Results. It is determined that the medium with high porous, water saturated rocks and anomalous high reservoir pressure has anomalous low value of velocities and gradient of their increase with depth. When this medium was re-examined after deep piles were built there, the overestimated seismic velocities are obtained, which is explained by a decrease in the section of anomalously high reservoir pressure and, accordingly, the porosity of the rocks after piles were built. When the hollowness is increased in unsaturated pebble rocks, the negative value of Poisson's ratio is obtained on the standard method. Seismic anisotropy related with the direction of the grains packing of the rocks is revealed on velocities of shear waves. The change of property of rocks on depth is manifested clearer on frequencies of waves than on their amplitudes. Scientific novelty. The elasticity moduli of the 3rd order are determined which are more sensible to variability of nonlinear elastic properties of rocks of the medium than the moduli of the 2nd order. The values of Poisson's ratio are recalculated for one and the same rocks located in different conditions of rock pressure on the basis of nonclassical theory of deformation. Practical importance. The obtained results can be applied to study the media characterized by complex seismogeological hydrodynamic conditions with clay-sandy rocks of high porosity and water saturation.
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Diez, A., and O. Eisen. "Seismic wave propagation in anisotropic ice – Part 1: Elasticity tensor and derived quantities from ice-core properties." Cryosphere Discussions 8, no. 4 (August 4, 2014): 4349–95. http://dx.doi.org/10.5194/tcd-8-4349-2014.
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Abstract. A preferred orientation of the anisotropic ice crystals influences the viscosity of the ice bulk and the dynamic behaviour of glaciers and ice sheets. Knowledge about the distribution of crystal anisotropy, to understand its contribution to ice dynamics, is mainly provided by crystal orientation fabric (COF) data from ice cores. However, the developed anisotropic fabric does not only influence the flow behaviour of ice, but also the propagation of seismic waves. Two effects are important: (i) sudden changes in COF lead to englacial reflections and (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, also recorded traveltimes. A framework is presented here to connect COF data with the elasticity tensor to determine seismic velocities and reflection coefficients for cone and girdle fabrics from ice-core data. We connect the microscopic anisotropy of the crystals with the macroscopic anisotropy of the ice mass, observable with seismic methods. Elasticity tensors for different fabrics are calculated and used to investigate the influence of the anisotropic ice fabric on seismic velocities and reflection coefficients, englacially as well as for the ice-bed contact. Our work, therefore, provides a contribution to remotely determine the state of bulk ice anisotropy.
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Li, Chunhui, Guangying Guan, Roberto Reif, Zhihong Huang, and Ruikang K. Wang. "Determining elastic properties of skin by measuring surface waves from an impulse mechanical stimulus using phase-sensitive optical coherence tomography." Journal of The Royal Society Interface 9, no. 70 (November 2, 2011): 831–41. http://dx.doi.org/10.1098/rsif.2011.0583.
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The mechanical properties of skin are important tissue parameters that are useful for understanding skin patho-physiology, which can aid disease diagnosis and treatment. This paper presents an innovative method that employs phase-sensitive spectral-domain optical coherence tomography (PhS-OCT) to characterize the biomechanical properties of skin by measuring surface waves induced by short impulses from a home-made shaker. Experiments are carried out on single and double-layer agar–agar phantoms, of different concentrations and thickness, and on in vivo human skin, at the forearm and the palm. For each experiment, the surface wave phase-velocity dispersion curves were calculated, from which the elasticity of each layer of the sample was determined. It is demonstrated that the experimental results agree well with previous work. This study provides a novel combination of PhS-OCT technology with a simple and an inexpensive mechanical impulse surface wave stimulation that can be used to non-invasively evaluate the mechanical properties of skin in vivo , and may offer potential use in clinical situations.
21
Zhong, Siyang, and Xin Zhang. "A sound extrapolation method for aeroacoustics far-field prediction in presence of vortical waves." Journal of Fluid Mechanics 820 (May 8, 2017): 424–50. http://dx.doi.org/10.1017/jfm.2017.219.
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Off-surface integral solutions to an inhomogeneous wave equation based on acoustic analogy could suffer from spurious wave contamination when volume integrals are ignored for computation efficiency and vortical/turbulent gusts are convected across the integration surfaces, leading to erroneous far-field directivity predictions. Vortical gusts often exist in aerodynamic flows and it is inevitable their effects are present on the integration surface. In this work, we propose a new sound extrapolation method for acoustic far-field directivity prediction in the presence of vortical gusts, which overcomes the deficiencies in the existing methods. The Euler equations are rearranged to an alternative form in terms of fluctuation variables that contains the possible acoustical and vortical waves. Then the equations are manipulated to an inhomogeneous wave equation with source terms corresponding to surface and volume integrals. With the new formulation, spurious monopole and dipole noise produced by vortical gusts can be suppressed on account of the solenoidal property of the vortical waves and a simple convection process. It is therefore valid to ignore the volume integrals and preserve the sound properties. The resulting new acoustic inhomogeneous convected wave equations could be solved by means of the Green’s function method. Validation and verification cases are investigated, and the proposed method shows a capacity of accurate sound prediction for these cases. The new method is also applied to the challenging airfoil leading edge noise problems by injecting vortical waves into the computational domain and performing aeroacoustic studies at both subsonic and transonic speeds. In the case of a transonic airfoil leading edge noise problem, shocks are present on the airfoil surface. Good agreements of the directivity patterns are obtained compared with direct computation results.
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Belakova, D., A. Seile, S. Kukle, and T. Plamus. "Non-Wovens as Sound Reducers." Latvian Journal of Physics and Technical Sciences 55, no. 2 (April 1, 2018): 64–76. http://dx.doi.org/10.2478/lpts-2018-0014.
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Abstract Within the present study, the effect of hemp (40 wt%) and polyactide (60 wt%), non-woven surface density, thickness and number of fibre web layers on the sound absorption coefficient and the sound transmission loss in the frequency range from 50 to 5000 Hz is analysed. The sound insulation properties of the experimental samples have been determined, compared to the ones in practical use, and the possible use of material has been defined. Non-woven materials are ideally suited for use in acoustic insulation products because the arrangement of fibres produces a porous material structure, which leads to a greater interaction between sound waves and fibre structure. Of all the tested samples (A, B and D), the non-woven variant B exceeded the surface density of sample A by 1.22 times and 1.15 times that of sample D. By placing non-wovens one above the other in 2 layers, it is possible to increase the absorption coefficient of the material, which depending on the frequency corresponds to C, D, and E sound absorption classes. Sample A demonstrates the best sound absorption of all the three samples in the frequency range from 250 to 2000 Hz. In the test frequency range from 50 to 5000 Hz, the sound transmission loss varies from 0.76 (Sample D at 63 Hz) to 3.90 (Sample B at 5000 Hz).
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Singh, Dilbag, Davinder Kumar, and S. K. Tomar. "Plane harmonic waves in a thermoelastic solid with double porosity." Mathematics and Mechanics of Solids 25, no. 4 (January 10, 2020): 869–86. http://dx.doi.org/10.1177/1081286519890053.
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Propagation of time harmonic plane waves in an infinite thermoelastic solid medium with double porosity is studied in this paper. It is found that there may exist five basic waves consisting of four sets of coupled longitudinal waves and an independent transverse wave traveling at different speeds. Each set of coupled longitudinal waves is found to be dispersive, attenuating and depends upon the presence of both types of voids and thermal properties in the medium. The lone transverse wave is found to be non-dispersive and non-attenuating, and does not depend on the presence of voids and thermal properties, and travels with the speed of the shear wave of classical elasticity. Two sets of the coupled longitudinal waves face critical frequencies, below which these waves do not propagate in the medium. These critical frequencies depend upon the presence of voids and thermal parameters of the medium. The reflection phenomenon of a set of incident coupled longitudinal wave from the stress-free and thermally insulated boundary surface of a half-space has been studied. For a particular model, the phase speeds, attenuation coefficients, amplitude ratios and energy ratios have been computed numerically, presented graphically and discussed.
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Barnes, G., and P. S. Cally. "Frequency Dependent Ray Paths in Local Helioseismology." Publications of the Astronomical Society of Australia 18, no. 3 (2001): 243–51. http://dx.doi.org/10.1071/as01040.
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AbstractThe surface of the Sun is continually oscillating due to sound waves encroaching on it from the interior. Measurements of the surface velocity are used to infer some of the properties of the regions through which the sound waves have propagated. Traditionally, this has been done by using a modal decomposition of the surface disturbances. However, the use of ray descriptions, in the form of acoustic holography or time–distance helioseismology, provides an alternative approach which may reveal more detailed information about the properties of local phenomena such as sunspots and active regions. Fundamental to any such treatment is determining the correct ray paths in a given atmosphere. In the simplest approach, the ray paths are constructed to minimise the travel time between two points (Fermat's principle). However, such an approach is only valid in the high frequency limit, ω » ωc, N, where ωc is the acoustic cut-off and N the Brunt-VÄisÄlÄ frequency. Although ωc is often included in time– distance calculations, and N occasionally, the same is not true of acoustic holography. We argue that this raises concerns about image sharpness. As illustrations, representative ray paths are integrated in a realistic solar model to show that the Fermat approximation performs poorly for frequencies of helioseismic interest. We also briefly discuss the importance of the Brunt-VÄisÄlÄ frequency to the time–distance diagram.
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McCall, K. R., and R. A. Guyer. "A new theoretical paradigm to describe hysteresis, discrete memory and nonlinear elastic wave propagation in rock." Nonlinear Processes in Geophysics 3, no. 2 (June 30, 1996): 89–101. http://dx.doi.org/10.5194/npg-3-89-1996.
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Abstract. The velocity of sound in rock is a strong function of pressure, indicating that wave propagation in rocks is very nonlinear. The quasistatic elastic properties of rocks axe hysteretic, possessing discrete memory. In this paper a new theory is developed, placing all of these properties (nonlinearity, hysteresis, and memory) on equal footing. The starting point of the new theory is closer to a microscopic description of a rock than the starting point of the traditional five-constant theory of nonlinear elasticity. However, this starting point (the number density ρ of generic mechanical elements in an abstract space) is deliberately independent of a specific microscopic model. No prejudice is imposed as to the mechanism causing nonlinear response in the microscopic mechanical elements. The new theory (1) relates suitable stress-strain measurements to the number density ρ and (2) uses the number density ρ to find the behaviour of nonlinear elastic waves. Thus the new theory provides for the synthesis of the full spectrum of elastic behaviours of a rock. Early development of the new theory is sketched in this contribution.
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Ailawalia, Praveen, and Priyanka. "Wave propagation in a temperature rate-dependent semiconducting medium with hydrostatic initial stress." International Journal of Computational Materials Science and Engineering 10, no. 02 (June 2021): 2150011. http://dx.doi.org/10.1142/s2047684121500111.
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The aim of this paper is to investigate the effect of hydrostatic initial stress and temperature dependence of the modulus of elasticity on surface wave propagation in the semiconducting medium under photothermal theory. An infinite elastic half-space is overlying the infinite semiconducting medium and a mechanical force of constant magnitude is applied along with the interface. Surface wave solutions are used to solve the coupled plasma, thermal, and elastic wave equations. The effect of hydrostatic initial stress and temperature dependent properties have been studied and depicted graphically on the penetration depths of the waves and the components of stresses, displacement, temperature distribution and carrier density. It is observed that the effect of hydrostatic initial stress on the penetration depths is prominent in temperature independent semiconducting medium.
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Miranda, Edson, Clodualdo Aranas, Samuel Rodrigues, Hélio Silva, Gedeon Reis, Antônio Paiva, and José Dos Santos. "Dispersion Diagram of Trigonal Piezoelectric Phononic Structures with Langasite Inclusions." Crystals 11, no. 5 (April 28, 2021): 491. http://dx.doi.org/10.3390/cryst11050491.
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The dispersion relation of elastic Bloch waves in 1-3 piezoelectric phononic structures (PPnSs) with Langasite (La3Ga5SiO14) inclusions in a polymeric matrix is reported. Langasite presents promising material properties, for instance good temperature behaviour, high piezoelectric coupling, low acoustic loss and high quality factor. Furthermore, Langasite belongs to the point group 32 and has a trigonal structure. Thus, the 2-D bulk wave propagation in periodic systems with Langasite inclusions cannot be decoupled into XY and Z modes. The improved plane wave expansion (IPWE) is used to obtain the dispersion diagram of the bulk Bloch waves in 1-3 PPnSs considering the classical elasticity theory and D3 symmetry. Full band gaps are obtained for a broad range of frequency. The piezoelectricity enhances significantly the band gap widths and opens up a narrow band gap in lower frequencies for a filling fraction of 0.5. This study should be useful for surface acoustic wave (SAW) filter and 1-3 piezocomposite transducer design using PPnSs with Langasite.
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Diez, A., O. Eisen, C. Hofstede, A. Lambrecht, C. Mayer, H. Miller, D. Steinhage, T. Binder, and I. Weikusat. "Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data." Cryosphere 9, no. 1 (February 20, 2015): 385–98. http://dx.doi.org/10.5194/tc-9-385-2015.
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Abstract. We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. Velocities calculated from the polycrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monocrystal elasticity tensor used for the calculation of the polycrystal properties. We make use of abrupt changes in COF as a common reflection mechanism for seismic and radar data below the firn–ice transition to determine COF-induced reflections in either data set by joint comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic experiments to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred crystal orientations.
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Diez, A., O. Eisen, C. Hofstede, A. Lambrecht, C. Mayer, H. Miller, D. Steinhage, T. Binder, and I. Weikusat. "Seismic wave propagation in anisotropic ice – Part 2: Effects of crystal anisotropy in geophysical data." Cryosphere Discussions 8, no. 4 (August 4, 2014): 4397–430. http://dx.doi.org/10.5194/tcd-8-4397-2014.
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Abstract. We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded traveltimes. Velocities calculated from the polycrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from a vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monocrystal elasticity tensor used for the calculation of the polycrystal properties. With this validation of seismic velocities we make use of abrupt changes in COF as common reflection mechanism for seismic and radar data below the firn–ice transition to investigate their occurrence by comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic deployment to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous viscosity from preferred crystal orientations.
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Baev, A. R., A. L. Mayorov, M. V. Asadchaya, V. N. Levkovich, and K. G. Zhavoronkov. "Features of the Surface and Subsurface Waves Application for Ultrasonic Evaluation of Physicomechanical Properties of Solids. Part 1. Influence of the Geometrical Parameters." Devices and Methods of Measurements 9, no. 4 (December 17, 2018): 325–26. http://dx.doi.org/10.21122/2220-9506-2018-9-4-325-326.
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Application of surface and subsurface waves for control of objects with a double-layer structure allows to extend possibilities of diagnostics of their physico-mechanical properties. The purpose of work was to determine conditions and offer recommendations providing measuring of ultrasonic velocity and amplitude of the former modes in protective layers and in basis of object at one-sided access to its surface.The analysis of an acoustic path of a measuring system in relation to ultrasonic evaluation of the objects having the restricted sizes and the protective coating according to velocity data of the surface and subsurface waves propagation is made. On the basis of representations of beam acoustics the dependences connecting a wavelength of the excited surface and subsurface modes, thickness and width of a controlled object, acoustic base of a sounding are defined. There are to provide a condition leveling of the influence of an acoustical noise created by the reflected and accompanying waves on parameters of acoustic signal with the given quantity of oscillations in an impulse.The principle opportunity is shown and conditions for determination of velocity of subsurface body waves in the base material which is under a protective coating layer are established. For these purposes on the basis of use of the block of ultrasonic probes the optimum scheme of a sounding is offered and the analytical expression for calculation of required velocity considering varying of thickness of a covering is received.The method of acoustical measuring realized by a direct and reverse sounding of the objects with small aperture and angle probes was analysed and formulas for determination of speed of subsurface wave under protective layer of the wedge form have been got. An ultrasonic device is suggested for the excitationreception of subsurface waves with different speed in objects (on 20–35 %) using for the acoustic concordance of environments of metallic sound duct as a wedge. Possibility of leveling of interference in a protective layer to control efects in basis of material by a volume wave by creation of supporting echo-signal of longitudinal wave of the set frequency and entered normally to the surface of object was studied.
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Singh, B., L. Singh, and S. Deswal. "Reflection of Plane Waves in a Rotating Temperature-Dependent Thermoelastic Solid with Diffusion." Journal of Mechanics 28, no. 4 (October 16, 2012): 599–606. http://dx.doi.org/10.1017/jmech.2012.101.
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ABSTRACTThe governing equations of a model of rotating generalized thermoelastic diffusion in an isotropic medium with temperature-dependent mechanical properties are formulated in context of Lord-Shulman theory of generalized thermoelasticity. The modulus of elasticity is taken as a linear function of reference temperature. The solution of the governing equations indicates the existence of four coupled plane waves in x-z plane. The reflection of plane waves from the free surface of a rotating temperature-dependent thermoelastic solid half-space with diffusion is considered. The required boundary conditions are satisfied by the appropriate potentials for incident and reflected waves in the half-space to obtain a system of four non-homogeneous equations in the reflection coefficients. The expressions for energy ratios of the reflected waves are also obtained. The reflection coefficients and energy ratios are found to depend upon the angle of incidence, reference temperature, thermodiffusion and rotation parameters. Aluminum material is modeled as the half-space to compute the absolute values of the reflection coefficients and the energy ratios. Effects of temperature dependence and rotation parameters on the reflection coefficients and energy ratios are shown graphically for a certain range of the angle of incidence of the incident plane wave.
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Kozaczka, Eugeniusz, and Grażyna Grelowska. "Theoretical Model of Acoustic Wave Propagation in Shallow Water." Polish Maritime Research 24, no. 2 (June 27, 2017): 48–55. http://dx.doi.org/10.1515/pomr-2017-0049.
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Abstract The work is devoted to the propagation of low frequency waves in a shallow sea. As a source of acoustic waves, underwater disturbances generated by ships were adopted. A specific feature of the propagation of acoustic waves in shallow water is the proximity of boundaries of the limiting media characterised by different impedance properties, which affects the acoustic field coming from a source situated in the water layer “deformed” by different phenomena. The acoustic field distribution in the real shallow sea is affected not only by multiple reflections, but also by stochastic changes in the free surface shape, and statistical changes in the seabed shape and impedance. The paper discusses fundamental problems of modal sound propagation in the water layer over different types of bottom sediments. The basic task in this case was to determine the acoustic pressure level as a function of distance and depth. The results of the conducted investigation can be useful in indirect determination of the type of bottom.
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Manasseh, Richard, Alexander V. Babanin, Cameron Forbes, Kate Rickards, Irena Bobevski, and Andrew Ooi. "Passive Acoustic Determination of Wave-Breaking Events and Their Severity across the Spectrum." Journal of Atmospheric and Oceanic Technology 23, no. 4 (April 1, 2006): 599–618. http://dx.doi.org/10.1175/jtech1853.1.
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Abstract A passive acoustic method of detecting breaking waves of different scales has been developed. The method also showed promise for measuring breaking severity. Sounds were measured by a subsurface hydrophone in various wind and wave states. A video record of the surface was made simultaneously. Individual sound pulses corresponding to the many individual bubble formations during wave-breaking events typically last only a few tens of milliseconds. Each time a sound-level threshold was exceeded, the acoustic signal was captured over a brief window typical of a bubble formation pulse, registering one count. Each pulse was also analyzed to determine the likely bubble size generating the pulse. Using the time series of counts and visual observations of the video record, the sound-level threshold that detected bubble formations at a rate optimally discriminating between breaking and nonbreaking waves was determined by a classification-accuracy analysis. This diagnosis of breaking waves was found to be approximately 70%–75% accurate once the optimum threshold had been determined. The method was then used for detailed analysis of wave-breaking properties across the spectrum. When applied to real field data, a breaking probability distribution could be obtained. This is the rate of occurrence of wave-breaking events at different wave scales. With support from a separate, laboratory experiment, the estimated bubble size is argued to be dependent on the severity of wave breaking and thus to provide information on the energy loss due to the breaking at the measured spectral frequencies. A combination of the breaking probability distribution and the bubble size could lead to direct estimates of spectral distribution of wave dissipation.
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Józefczak, Arkadiusz, Tomasz Hornowski, Anita Król, Matúš Molčan, Błażej Leszczyński, and Milan Timko. "The Effect of Sonication on Acoustic Properties of Biogenic Ferroparticle Suspension." Archives of Acoustics 41, no. 1 (March 1, 2016): 161–68. http://dx.doi.org/10.1515/aoa-2016-0016.
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Abstract Superparamagnetic iron oxide nanoparticles (SPION) synthesised chemically usually need the modification of the particle surface. Other natural sources of magnetic particles are various magnetotactic bacteria. Magnetosomes isolated from magnetotactic bacteria are organelles consisting of magnetite (Fe3O4) or greigite (Fe3S4) crystals enclosed by a biological membrane. Magnetotactic bacteria produce their magnetic particles in chains. The process of isolation of magnetosome chains from the body of bacteria consists of a series of cycles of centrifugation and magnetic decantation. Using a high-energy ultrasound it is possible to break the magnetosome chains into individual nanoparticles – magnetosomes. This study presents the effect of sonication of magnetosome suspension on their acoustic properties, that is speed and attenuation of the sound. Acoustic propagation parameters are measured using ultrasonic spectroscopy based on FFT spectral analysis of the received pulses. The speed and attenuation of ultrasonic waves in magnetosome suspensions are analysed as a function of frequency, temperature, magnetic field intensity, and the angle between the direction of the wave and the direction of the field.
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Li, Qing Tian. "Electron Micro Technology Study on BN Fiber’s Microcosmic Structure and Mechanics Properties." Advanced Materials Research 588-589 (November 2012): 104–7. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.104.
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This paper uses transmission electron microscope technology, studies microcosmic structure’ s feature of BN fiber, clarifies existing crystal structure’s state of BN fiber during its producing and transform course. It is studied that BN fiber has a sound mechanical properties, which most of crystalline phase is turbine layer phase and whose nitrogen is high and size is small .During the course of BN fiber’s producing, adding suitable tension from axial can promote directional arrange of BN fiber’s surface crystalline grain and put forward the improving direction of manufacturing technology in order to improve materials’ mechanical properties. BN fiber(indicated by BNf) is a kind of new inorganic material. Because of its fine stable, corrosion-resisting, anti-oxidant properties and high ability of absorbing neutron and so on, it is attached more and more importance and it get constant development and usefulness. BNf and ceramics, metal, various compound materials made of resin material can be used in metallurgy, electron, aviation etc science and technology fields. But the intensity of BNf and its elasticity modulus are lower than basic fundamental material. When BNf’s compound material get fine properties above mentioned, the mechanics properties of the material will drop. So its application degree will be limited to a certain extent. In order to improve and raise BNf’s mechanics properties, this essay makes use of electron micro analytical technology to study its microcosmic structure and mechanics properties, providing scientific basis for designing reasonable manufacturing technology.
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Candelier, Julien, Stéphane Le Dizès, and Christophe Millet. "Inviscid instability of a stably stratified compressible boundary layer on an inclined surface." Journal of Fluid Mechanics 694 (February 2, 2012): 524–39. http://dx.doi.org/10.1017/jfm.2012.7.
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AbstractThe three-dimensional stability of an inflection-free boundary layer flow of length scale$L$and maximum velocity${U}_{0} $in a stably stratified and compressible fluid of constant Brunt–Väisälä frequency$N$, sound speed${c}_{s} $and stratification length$H$is examined in an inviscid framework. The shear plane of the boundary layer is assumed to be inclined at an angle$\theta $with respect to the vertical direction of stratification. The stability analysis is performed using both numerical and theoretical methods for all the values of$\theta $and Froude number$F= {U}_{0} / (LN)$. When non-Boussinesq and compressible effects are negligible ($L/ H\ll 1$and${U}_{0} / {c}_{s} \ll 1$), the boundary layer flow is found to be unstable for any$F$as soon as$\theta \not = 0$. Compressible and non-Boussinesq effects are considered in the strongly stratified limit: they are shown to have no influence on the stability properties of an inclined boundary layer (when$F/ \sin \theta \ll 1$). In this limit, the instability is associated with the emission of internal-acoustic waves.
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TARYANA, NANDANG. "Sonolog Test Sumur Minyak menggunakan Alat Total Well Management Echometer sebagai Well Analyzer Sumur di Pertamina EP Subang." ELKOMIKA: Jurnal Teknik Energi Elektrik, Teknik Telekomunikasi, & Teknik Elektronika 2, no. 2 (July 1, 2014): 152. http://dx.doi.org/10.26760/elkomika.v2i2.152.
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ABSTRAK Metoda Sonolog Tes adalah metoda dengan menggunakan sifat refleksi gelombang bunyi, digunakan untuk analisa sumur. Metoda Sonolog Tes menggunakan alat Total Well Managemen (TWM) sebagai Well Analyzer yang digunakan untuk memperoleh data keperluan analisa performance sumur. Informasi tentang data sumur ini dapat diperoleh dengan menggunakan gas gun sebagai sumber gelombang bunyi yang ditembakan ke sumur. Hasil refleksi dari dalam sumur direkam dalam bentuk grafik yang direkam di komputer. Refleksi yang kuat (down kick) dari gelombang bunyi tercatat pada 14.827 detik yang mengindikasikan puncak cairan berada di kedalaman 9161.24 feet dari permukaan. Tekanan casing terukur sebesar 33.8 psig masih lebih rendah dibandingkan tekanan pump intake hasil perhitungan sebesar 486 psig sehingga tekanan casing tersebut tidak menggganggu produksi sumur. Analisa pantulan akustik tubing collar rata rata of 31.19 ft tiap tubing, dan kecepatan gelombang bunyi gas pada annulus sebesar 1236 ft/sec, dan dapat diketahui bahwa kecepatan gelombang gas di annulus berhubungan langsung dengan densitas gas. Aplikasi Well Analyzer dari Echometer pada Metoda Sonolog Tes, membantu melihat peluang peningkatan produksi lebih lanjut seperti dengan menganalisa tinggi puncak cairan pada sumur yang datanya terlihat di komputer.Kata kunci: Gelombang bunyi, acoustic, Sonolog Test, Total Well Management, Well Analyzer ABSTRACT Sonolog Test Method is a method using reflection properties of sound waves, is used for the analysis of the well. Sonolog Test Method using a Total Well Management (TWM) as Well Analyzer is used to obtain data for analysis of performance well. Information on well data can be obtained by using a gas gun as a source of sound waves that were fired into the well. Results reflection of the well recorded in the form of graphs recorded in the computer. Strong reflection (kick down) from the sound waves recorded on 14 827 seconds indicating fluid peak at a depth of 9161.24 feet from the surface. Casing pressure of 33.8 psig measured is lower than the pump intake pressure of 486 psig calculation results so that the casing pressure does not interfere with the production wells. Analysis of acoustic tubing collar reflection average of 31.19 ft each tubing, and a sound wave velocity of gas in the annulus of 1236 ft / sec, and it can be seen that the wave velocity in the annular gas directly related to the density of the gas. Well Analyzer of Echometer on Sonolog Test Method, helped see further opportunities to increase production as by analyzing the peak height of fluid in the well for which data is visible on the computer.Keywords: sound waves, acoustic, Sonolog Test, Total Well Management, Well Analyzer
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Khokhryakova, C. A., A. I. Shmyrova, I. A. Mizeva, and A. V. Shmyrov. "The experimental study of ferrocolloid surface tension in a magnetic field." Вестник Пермского университета. Физика, no. 3 (2020): 56–64. http://dx.doi.org/10.17072/1994-3598-2020-3-56-64.
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Direct measurements of surface tension, viscosity and surface elasticity under the action of external forces are often impossible. In many tasks, the magnetic fluid surface tension is considered to be independent of the magnitude of the applied magnetic field and is determined by the properties of the base fluid. The anisotropy of the magnetic properties at the interface due to the jump in the fluid’s magnetization suggests the dependence of the surface tension tensor on the magnetic field. In this paper, we propose a new experimental method for studying the surface tension of a magnetic fluid in an external uniform magnetic field, depending on the orientation of the magnetic field intensity towards the liquid-gas interface. The study was carried out with the help of modified capillary wave method in a magnetic field orthogonal to the liquid surface and with the ring detachment method in the case of a longitudinal field. It was shown experimentally that the surface tension of a ferrocolloid fluid base (kerosene) does not depend either on the frequency of capillary waves excitation or on intensity of an applied external magnetic field, and corresponds to the value determined with the help of a commercial tensiometer by the standard method of ring detachment. The surface tension of the ferrofluid decreases with increasing intensity of the orthogonal magnetic field interface and with increasing frequency of acoustic vibrations. However, an increase in the field strength longitudinally directed to the interface, provokes an increase in the surface tension of the magnetic fluid. The experimental results are in qualitative agreement with theoretical predictions by A. V. Zhukov: the eigenvalues of the surface tension tensor monotonically increase with the tangential magnetic field component and monotonically decrease with an increase in its normal component.
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Japsen, Peter, Anders Bruun, Ida L. Fabricius, and Gary Mavko. "Identification of hydrocarbons in chalk reservoirs from surface seismic data: South Arne field, North Sea." Geological Survey of Denmark and Greenland (GEUS) Bulletin 7 (July 29, 2005): 13–16. http://dx.doi.org/10.34194/geusb.v7.4823.
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Seismic data are mainly used to map out structures in the subsurface, but are also increasingly used to detect differences in porosity and in the fluids that occupy the pore space in sedimentary rocks. Hydrocarbons are generally lighter than brine, and the bulk density and sonic velocity (speed of pressure waves or P-wave velocity) of hydrocarbon-bearing sedimentary rocks are therefore reduced compared to non-reservoir rocks. However, sound is transmitted in different wave forms through the rock, and the shear velocity (speed of shear waves or S-wave velocity) is hardly affected by the density of the pore fluid. In order to detect the presence of hydrocarbons from seismic data, it is thus necessary to investigate how porosity and pore fluids affect the acoustic properties of a sedimentary rock. Much previous research has focused on describing such effects in sandstone (see Mavko et al. 1998), and only in recent years have corresponding studies on the rock physics of chalk appeared (e.g. Walls et al. 1998; Røgen 2002; Fabricius 2003; Gommesen 2003; Japsen et al. 2004). In the North Sea, chalk of the Danian Ekofisk Formation and the Maastrichtian Tor Formation are important reservoir rocks. More information could no doubt be extracted from seismic data if the fundamental physical properties of chalk were better understood. The presence of gas in chalk is known to cause a phase reversal in the seismic signal (Megson 1992), but the presence of oil in chalk has only recently been demonstrated to have an effect on surface seismic data (Japsen et al. 2004). The need for a better link between chalk reservoir parameters and geophysical observations has, however, strongly increased since the discovery of the Halfdan field proved major reserves outside four-way dip closures (Jacobsen et al. 1999; Vejbæk & Kristensen 2000).
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Gacem, Amel, A. Doghmane, and Z. Hadjoub. "Quantification the Effect of the Thickness of Thin Films on their Elastic Parameters." Advanced Materials Research 324 (August 2011): 93–96. http://dx.doi.org/10.4028/www.scientific.net/amr.324.93.
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The determination of the characteristics and properties of thin films deposited on substrates is necessary in any device application in various fields. Adequate mechanical properties are highly required for the majority of surface waves and semiconductor devices. In this context, modelling the ultrasonic-material interaction, we present results of simulation curves of acoustic signatures for multiple thin film/substrate combinations. The results obtained on several structures (Al, SiO2, ZnO, Cu, AlN, SiC and Cr)/(Al2O3, Si, Cu or Quartz) showed a velocity dispersion of the Rayleigh wave as a function of layer thickness. The development of a theoretical calculation model based on the acoustic behaviour of these structures has enabled us to quantify the dispersive evolution (positive and negative) density. Thus, we have established a universal relationship describing the density-thickness variation. In addition, networks of dispersion curves, representing the evolution of elasticity modulus (Young and shear), were determined. These charts can be used to extract the influence of thickness of layers on the variation of elastic constants
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Zheng, Lu, Hui Dong, Xiaoyu Wu, Yen-Lin Huang, Wenbo Wang, Weida Wu, Zheng Wang, and Keji Lai. "Interferometric imaging of nonlocal electromechanical power transduction in ferroelectric domains." Proceedings of the National Academy of Sciences 115, no. 21 (May 7, 2018): 5338–42. http://dx.doi.org/10.1073/pnas.1722499115.
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The electrical generation and detection of elastic waves are the foundation for acoustoelectronic and acoustooptic systems. For surface acoustic wave devices, microelectromechanical/nanoelectromechanical systems, and phononic crystals, tailoring the spatial variation of material properties such as piezoelectric and elastic tensors may bring significant improvements to the system performance. Due to the much slower speed of sound than speed of light in solids, it is desirable to study various electroacoustic behaviors at the mesoscopic length scale. In this work, we demonstrate the interferometric imaging of electromechanical power transduction in ferroelectric lithium niobate domain structures by microwave impedance microscopy. In sharp contrast to the traditional standing-wave patterns caused by the superposition of counterpropagating waves, the constructive and destructive fringes in microwave dissipation images exhibit an intriguing one-wavelength periodicity. We show that such unusual interference patterns, which are fundamentally different from the acoustic displacement fields, stem from the nonlocal interaction between electric fields and elastic waves. The results are corroborated by numerical simulations taking into account the sign reversal of piezoelectric tensor in oppositely polarized domains. Our work paves ways to probe nanoscale electroacoustic phenomena in complex structures by near-field electromagnetic imaging.
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Chanda, Ayan, and Swaroop Nandan Bora. "Propagation of Oblique Waves Over a Small Undulating Elastic Bottom Topography in a Two-Layer Fluid Flowing Through a Channel." International Journal of Applied Mechanics 12, no. 02 (March 2020): 2050023. http://dx.doi.org/10.1142/s1758825120500234.
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A hydrodynamic model, with the incorporation of elasticity, is considered to study oblique incident waves propagating over a small undulation on an elastic bed in a two-layer fluid, where the upper layer fluid is bounded above by a rigid lid, which is an approximation to the free surface. Following the Euler–Bernoulli beam equation, the elastic bed is approximated as a thin elastic plate. The surface tension at the interface of the layers is completely ignored since its contribution will be minimal. The behavior and properties of the roots of the dispersion relation are analyzed using counting argument and contour plot. In this case, time-harmonic waves propagate with only one wavenumber. Considering an irrotational motion in an incompressible and inviscid fluid, and applying perturbation technique, the first-order corrections to the velocity potentials are evaluated by an appropriate application of Fourier transform and, subsequently, the corresponding reflection and transmission coefficients are computed through integrals containing a shape function which depicts the bottom undulation. To validate the theory developed, two particular undulating bottom topography are taken up as examples in order to evaluate the hydrodynamic coefficients which are represented through graphs. It is noted that the reflection coefficient shows an oscillatory pattern, when the wavenumber of the undulating bed takes a value almost double the wavenumber of the incident wave. When the ratio of the wavenumber of the undulating bed and the wavenumber of the incident wave approaches 2, the theory predicts existence of resonance between the undulating elastic bed and the interface of the layers. It is worthwhile to note that reflected wave energy of the incident wave is higher if the number of ripples of the bottom undulation is large. It is further noted that the reflected energy increases in response to an increase in the values of the elastic parameters of the ocean bed. The results for a patch of sinusoidal ripples having different wavenumbers are found to be similar. Further, the reflected energy decreases for an increase in the angle of incidence. It is noted that reasonable changes in elasticity, ripple wavenumber and the number of the ripples of the bed have a remarkable effect when the propagating wave passing through a channel encounters a small bottom undulation. When results are compared with the available results, good agreement is observed.
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Kalinova, Klara. "Sound absorptive light comprising nanofibrous resonant membrane applicable in room acoustics." Building Services Engineering Research and Technology 39, no. 3 (September 29, 2017): 362–70. http://dx.doi.org/10.1177/0143624417733404.
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Room acoustic solutions are based on measurements of the acoustic power of the room and acoustic elements with different functions (absorption tiles, absorption ceilings, absorption bodies, diffusers, barriers). This work is focused only on absorption elements with an emphasis on addressing lower-middle frequencies. The design of the material is based on broad band noise. Damping of lower frequencies is restricted to a certain extent by the final thickness of the acoustic material. Nanofibrous resonant membranes will be used in the design to achieve higher sound absorption at lower frequencies in comparison with commercially available materials. The principle of the acoustic system is to use combination of a perforated sheet covered by a nanofibrous resonant membrane, which is brought into forced vibration upon impact of sound waves of low frequency. Practical application:To absorb sounds of high frequencies, porous materials are used. To absorb sounds of low frequencies, resonant membranes are employed. However, these structures absorb only sounds of certain frequency. Nanofibrous layers have unique acoustic properties due to the large specific surface area of the nanofibres, where viscous losses may occur, and also the ability to resonate at its own frequency. The advantage of this technology is the space between the acoustic element with a thickness of 1–2 mm and the wall/ceiling, which can be used for the installation of lighting/audio speakers, etc. The acoustic light prototype has been made.
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ZAKIR’YANOVA, G. K., and L. A. ALEXEYEVA. "The first boundary value problem of the dynamics of an anisotropic elastic half-space under the action of subsonic transport loads." Bulletin of the National Engineering Academy of the Republic of Kazakhstan 4, no. 78 (December 15, 2020): 45–52. http://dx.doi.org/10.47533/2020.1606-146x.31.
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The first boundary value problem of the theory of elasticity for an anisotropic elastic half-space is solved when a transport load moves along its surface. The subsonic Raleigh case is considered, when the velocity of motion is less than the velocity of propagation of bulk and surface elastic waves. The Green’s tensor of the transport boundary value problem is constructed and on its basis the solution of boundary value problems for a wide class of distributed traffic loads is given. To solve the problem, the methods of tensor and linear algebra, integral Fourier transform, and operator method for solving systems of differential equations were used. The obtained solution makes it possible to investigate the dynamics of the rock mass for a wide class of transport loads, in a wide range of velocities, both low velocities and high velocities, and to evaluate the strength properties of the rock mass under the influence of road transport. In particular, determine the permissible velocities of its movement and carrying capacity. In addition, a investigation on its basis of the movement of the day surface along the route will make it possible to establish criteria for the seismic resistance of ground structures and the permissible distances of their location from the route.
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ZAKIR’YANOVA, G. K., and L. A. ALEXEYEVA. "The first boundary value problem of the dynamics of an anisotropic elastic half-space under the action of subsonic transport loads." Bulletin of the National Engineering Academy of the Republic of Kazakhstan 4, no. 78 (December 15, 2020): 45–52. http://dx.doi.org/10.47533/2020.1606-146x.31.
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The first boundary value problem of the theory of elasticity for an anisotropic elastic half-space is solved when a transport load moves along its surface. The subsonic Raleigh case is considered, when the velocity of motion is less than the velocity of propagation of bulk and surface elastic waves. The Green’s tensor of the transport boundary value problem is constructed and on its basis the solution of boundary value problems for a wide class of distributed traffic loads is given. To solve the problem, the methods of tensor and linear algebra, integral Fourier transform, and operator method for solving systems of differential equations were used. The obtained solution makes it possible to investigate the dynamics of the rock mass for a wide class of transport loads, in a wide range of velocities, both low velocities and high velocities, and to evaluate the strength properties of the rock mass under the influence of road transport. In particular, determine the permissible velocities of its movement and carrying capacity. In addition, a investigation on its basis of the movement of the day surface along the route will make it possible to establish criteria for the seismic resistance of ground structures and the permissible distances of their location from the route.
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González, Genaro, Albert Samper, and Blas Herrera. "ACOUSTIC SIMULATION OF THE CENTRAL HALL IN PALAU GÜELL BY GAUDÍ." Architecture and Engineering 6, no. 2 (2021): 18–30. http://dx.doi.org/10.23968/2500-0055-2021-6-2-18-30.
Full textAbstract:
Introduction: Quadric surfaces are commonly used in buildings due to their geometric ability to distribute and focus sound waves. The Central Hall in Palau Güell — a UNESCO World Heritage Site — is topped by an ellipsoidal dome. Antoni Gaudí envisaged this room as a concert hall where the organ and the dome play a lead role. Methods: The two previously mentioned elements are the main subject of our paper, which serves two purposes: 1) determining the values of the acoustic parameters of the hall through onsite measurement and also through simulation, and 2) using the geometric parameters of the quadric surface, which best fits the dome, in order to check whether it is possible to improve the acoustics of the hall by placing a new emission source at the focus of the dome’s ellipsoid. Results and Discussion: Contrary to the authors’ expectations, due to the focal reflection properties of the quadric surface, some acoustic parameters on the listening plane do not improve significantly. Therefore, we conclude that Gaudí took the acoustical impact into account when designing this hall.
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BUCKINGHAM, MICHAEL J., ERIC M. GIDDENS, FERNANDO SIMONET, and THOMAS R. HAHN. "PROPELLER NOISE FROM A LIGHT AIRCRAFT FOR LOW-FREQUENCY MEASUREMENTS OF THE SPEED OF SOUND IN A MARINE SEDIMENT." Journal of Computational Acoustics 10, no. 04 (December 2002): 445–64. http://dx.doi.org/10.1142/s0218396x02001760.
Full textAbstract:
The sound from a light aircraft in flight is generated primarily by the propeller, which produces a sequence of harmonics in the frequency band between about 80 Hz and 1 kHz. Such an airborne sound source has potential in underwater acoustics applications, including inversion procedures for determining the wave properties of marine sediments. A series of experiments has recently been performed off the coast of La Jolla, California, in which a light aircraft was flown over a sensor station located in a shallow (approximately 15 m deep) ocean channel. The sound from the aircraft was monitored with a microphone above the sea surface, a vertical array of eight hydrophones in the water column, and two sensors, a hydrophone and a bender intended for detecting shear waves, buried 75 cm deep in the very-fine-sand sediment. The propeller harmonics were detected on all the sensors, although the s-wave was masked by the p-wave on the buried bender. Significant Doppler shifts of the order of 17%, were observed on the microphone as the aircraft approached and departed from the sensor station. Doppler shifting was also evident in the hydrophone data from the water column and the sediment, but to a lesser extent than in the atmosphere. The magnitude of the Doppler shift depends on the local speed of sound in the medium in which the sensor is located. A technique is described in which the Doppler difference frequency between aircraft approach and departure is used to determine the speed of sound at low-frequencies (80 Hz to 1 kHz) in each of the three environments, the atmosphere, the ocean and the sediment. Several experimental results are presented, including the speed of sound in the very fine sand sediment at a nominal frequency of 600 Hz, which was found from the Doppler difference frequency of the seventh propeller harmonic to be 1617 m/s.
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Squire, V. A., P. J. Langhorne, W. H. Robinson, A. J. Heine, and T. G. Haskell. "Moving loads on sea ice." Polar Record 23, no. 146 (May 1987): 569–75. http://dx.doi.org/10.1017/s0032247400008068.
Full textAbstract:
ABSTRACTA load moving on sea ice, whether the weight of a vehicle or the pressure exerted by a low-flying aircraft, produces a deflection which can in extreme cases cause ice failure. The magnitude and shape of the deflection profile depends on the weight and speed of the vehicle) and also the the ice thickness and properties, with flexuralgraviry waves radiating from the source at speeds above a critical value. This wave pattern was studied in detail on flat, snow-free sea ice in McMurdo Sound, Antarctica. Surface strain was measured directly and microcracking activity monitored to correlate measured strain with possible generation of dangerous cracks. Speeds of up to 28 m sec-1(60 mph) were achieved with a pickup truck, and up to 80 m sec-1with a US Navy C131 aircraft. Initial comparison between theory and experimental results is very encouraging.
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Clark, Alfred V. "Ultrasonic Characterization of Texture and Formability." MRS Bulletin 13, no. 4 (April 1988): 40–43. http://dx.doi.org/10.1557/s088376940006588x.
Full textAbstract:
There are now theories which predict the effect of texture on elastic properties and hence on the velocities of bulk, surface, and guided ultrasonic waves. Furthermore, there is a relation between texture and formability. These relationships can be potentially exploited to make ultrasonic measurements of formability, and partial pole figures can be made with ultrasonic techniques.This article presents results of various ultrasonic measurements made to characterize the formability of rolled steel and aluminum alloy sheet. A good correlation generally exists between ultrasonic velocity measurements and formability. Furthermore, there is a good possibility of on-line formability measurement using a noncontacting ultrasonic transducer.The influence of texture on material properties has been long recognized, and several excellent texts have been wholly or partly devoted to the subject. Texture classically has been measured with either x-rays or neutron diffraction. Lately, there has been interest in characterizing texture with ultrasound (high-frequency sound) as well.Ultrasound has several potential advantages over x-ray and neutron diffraction techniques. Ultrasonic systems are nondestructive, can rapidly scan large volumes of material, require no radiation sources, and can be devised to measure either surface or bulk textures. There is a distinct possibility that ultrasonic texture monitoring can be implemented in real-time in a production environment such as a rolling mill.
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Liang, S. M., and J. C. Yuan. "Numerical Simulation of Blast-Wave Propagation in a Small Two-Medium Duct." Journal of Mechanics 25, no. 3 (September 2009): 313–22. http://dx.doi.org/10.1017/s172771910000277x.
Full textAbstract:
AbstractIn this study, a small two-medium duct with blast-wave propagation is numerically investigated by a high-resolution Euler/Navier-Stokes solver. The solver has a feature of treatment of the Tait equations of state for two media. One of the two media is water which is envisaged as a blood. The second medium is another liquid, used to simulate body's clot or tissue. The duct wall has a mass diffusion effect in addition to viscous effects. Since two different media are considered, the reflection and transmission of an underwater blast wave passing through the interfaces of the two media with different sound impedances are inevitable. The different properties of liquids may cause numerical oscillation at interfaces for very weak blast waves for a high-resolution scheme such as a 5th-order WENO scheme. In order to overcome this difficulty of numerical fictitious oscillation, a third-order WENO scheme was used. It was found that computed pressures of the transmitted blast wave for four kinds of simulated tissues are in good agreements with those obtained by the acoustic principle. Moreover, for the case of a simulated clot, the pressure force and impulse acted on the clot surface are investigated for different intensities of blast waves.