Artykuły w czasopismach na temat „Shear wave velocity”
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Li, Yu, Qian Lv, Jiayue Dai, Ye Tian i Jianzhong Guo. "Shear Wave Velocity Estimation Using the Real-Time Curve Tracing Method in Ultrasound Elastography". Applied Sciences 11, nr 5 (26.02.2021): 2095. http://dx.doi.org/10.3390/app11052095.
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The estimation of shear wave velocity is very important in ultrasonic shear wave elasticity imaging (SWEI). Since the stability and accuracy of ultrasonic testing equipment have been greatly improved, in order to further improve the accuracy of shear wave velocity estimation and increase the quality of shear wave elasticity maps, we propose a novel real-time curve tracing (RTCT) technique to accurately reconstruct the motion trace of shear wave fronts. Based on the curve fitting of each frame shear wave, the propagation velocity of two-dimensional shear waves can be estimated. In this paper, shear wave velocity estimation and shear wave image reconstruction are implemented for homogeneous regions and stiff spherical inclusion regions with different elasticity, respectively. The experimental result shows that the proposed shear wave velocity estimation method based on the real-time curve tracing method has advantages in accuracy and anti-noise performance. Moreover, by eliminating artifacts of shear wave videos, the velocity map acquired can restore the shape of inclusions better. The real-time curve tracing method can provide a new idea for the estimation of shear wave velocity and elastic parameters.
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Chen, S. T. "Shear‐wave logging with dipole sources". GEOPHYSICS 53, nr 5 (maj 1988): 659–67. http://dx.doi.org/10.1190/1.1442500.
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Laboratory measurements have verified a novel technique for direct shear‐wave logging in hard and soft formations with a dipole source, as recently suggested in theoretical studies. Conventional monopole logging tools are not capable of measuring shear waves directly. In particular, no S waves are recorded in a soft formation with a conventional monopole sonic tool because there are no critically refracted S rays when the S-wave velocity of the rock is less than the acoustic velocity of the borehole fluid. The present studies were conducted in the laboratory with scale models representative of sonic logging conditions in the field. We have used a concrete model to represent hard formations and a plastic model to simulate a soft formation. The dipole source, operating at frequencies lower than those conventionally used in logging, substantially suppressed the P wave and excited a wave train whose first arrival traveled at the S-wave velocity. As a result, one can use a dipole source to log S-wave velocity directly on‐line by picking the first arrival of the full wave train, in a process similar to that used in conventional P-wave logging. Laboratory experiments with a conventional monopole source in a soft formation did not produce S waves. However, the S-wave velocity was accurately estimated by using Biot’s theory, which required measuring the Stoneley‐wave velocity and knowing other borehole parameters.
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Dashottar, Amitabh, Erin Montambault, Jeffrey R. Betz i Kevin D. Evans. "Area Covered for Shear Wave Velocity Calculation Affects the Shear Wave Velocity Values". Journal of Diagnostic Medical Sonography 35, nr 3 (6.03.2019): 182–87. http://dx.doi.org/10.1177/8756479319834255.
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Although ultrasound elastography is established as a reliable and valid tool for assessment of skeletal muscles, guidelines around the technical specifications, data selection, and acquisition parameters still lack consensus. One such parameter is the use of the quantification box (Q-box) that calculates the shear wave velocity/modulus, within a selected region of interest (ROI). Currently, no data compare the effect of the elastographic area within the ROI to the mean shear wave velocity calculations, using a Q-box. In this study, the mean shear wave velocity calculated over a smaller (single Q-box) ROI is compared to the mean shear wave velocity calculated over maximum area of elastogram, within a ROI. Comparison of mean shear wave velocity revealed a significant difference ( t = 2.79, P = .007) between the means calculated over maximum area of elastogram for only nonuniform elastograms. The rater agreement for the classification scheme was assessed (κ = 0.85). To prevent possible overestimation of shear wave velocities, it may be necessary to place the Q-box over the maximum elastographic area.
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Zhou, Jian Ping, Jin Xia Liu, Wen Yang Gao, Zhi Wen Cui, Wei Guo Lv i Ke Xie Wang. "Effect of Anisotropy on Shear Wave Velocity in Wood". Advanced Materials Research 535-537 (czerwiec 2012): 1923–26. http://dx.doi.org/10.4028/www.scientific.net/amr.535-537.1923.
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The velocities of shear waves propagating along radial direction of birch and elmwood specimens are measured in order to study the effect of anisotropy on shear wave velocity. The relationship between the shear wave velocity and the oscillation direction is examined by rotating an ultrasonic sensor. The results indicate that the effect of anisotropy on shear wave velocity in birch and elmwood specimens is similar to Japanese magnolia specimen. When the oscillation direction of the shear wave corresponds to the certain anisotropic direction of the wood specimen, the shear wave velocity decreases sharply and the relationship between shear wave velocity and rotation angle tends to become discontinuous. The intrinsic birefringence due to the anisotropy of birch and elmwood woods is observed. Their texture anisotropies are strong. In an isotropic nylon, on the contrary, the value of shear wave velocity was similar to a circular ring. This investigation is significant meanings in architectural and civil engineering field.
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Dorman, LeRoy M. "Seafloor shear wave velocity variability." Journal of the Acoustical Society of America 91, nr 4 (kwiecień 1992): 2461. http://dx.doi.org/10.1121/1.403035.
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Miwa, Takashi, Kouki Kanzawa, Ryosuke Tomizawa i Yoshiki Yamakoshi. "Phantom Experiments on Shear Wave Velocity Measurement by Virtual Sensing Array Spectrum Estimation". Key Engineering Materials 497 (grudzień 2011): 153–60. http://dx.doi.org/10.4028/www.scientific.net/kem.497.153.
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Quantitative shear wave velocity measurement inside the living tissue is a key technology in future qualitative diagnosis of breast tumor or liver diseases. We develop a novel shear wave velocity measurement system by using running wave number spectrum analysis of the complex displacement of the shear wave propagation excited by a single frequency. The velocity estimation method is demonstrated through the phantom experiments with the developed shear wave displacement measurement system. The validity of the measurement system is demonstrated by comparing with elastic wave simulation results. From the phantom experiments, it is shown that this method has high accuracy of velocity measurement even in the presence of large reflected waves.
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Blewett, J., I. J. Blewett i P. K. Woodward. "Measurement of shear-wave velocity using phase-sensitive detection techniques". Canadian Geotechnical Journal 36, nr 5 (23.11.1999): 934–39. http://dx.doi.org/10.1139/t99-051.
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The development of a phase-sensitive technique to measure the velocity of shear waves propagating through a sand sample situated inside a standard laboratory triaxial testing cell is reported. The technique shows an improvement in convenience and efficiency over conventional time-of-flight methods, facilitating real-time display of shear-wave velocity during testing. The purpose of this paper is to demonstrate the technique by determining the variation in shear-wave velocity during triaxial testing of a loose sand. Key words: shear-wave velocity, phase-sensitive detection, drained shear.
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Ensley, Ross Alan. "Evaluation of direct hydrocarbon indicators through comparison of compressional‐ and shear‐wave seismic data: a case study of the Myrnam gas field, Alberta". GEOPHYSICS 50, nr 1 (styczeń 1985): 37–48. http://dx.doi.org/10.1190/1.1441834.
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Shear waves differ from compressional waves in that their velocity is not significantly affected by changes in the fluid content of a rock. Because of this relationship, a gas‐related compressional‐wave “bright spot” or direct hydrocarbon indicator will have no comparable shear‐wave anomaly. In contrast, a lithology‐related compressional‐wave anomaly will have a corresponding shear‐wave anomaly. Thus, it is possible to use shear‐wave seismic data to evaluate compressional‐wave direct hydrocarbon indicators. This case study presents data from Myrnam, Alberta which exhibit the relationship between compressional‐ and shear‐wave seismic data over a gas reservoir and a low‐velocity coal.
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Yan, Li, i Peter M. Byrne. "Simulation of downhole and crosshole seismic tests on sand using the hydraulic gradient similitude method". Canadian Geotechnical Journal 27, nr 4 (1.08.1990): 441–60. http://dx.doi.org/10.1139/t90-060.
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A method of simulating downhole and crosshole seismic shear-wave tests in a model under controlled stress conditionsis described. The downhole and shear wave in horizontal plane (SH) crosshole shear waves are generated and received along the principal stress axes using piezoceramic bender elements. The K0in situ stress conditions, including loading and unloading stress paths, are simulated by the hydraulic gradient similitude method, which allows high stresses simulating field conditions to be obtained. The horizontal stress during the tests is directly measured by a lateral total-stress transducer. The test data are used to evaluate various published empirical equations that relate shear-wave velocity and soil stress state. It is found that although the various empirical equations can predict the in situ shear-wave velocity profile reasonably well, only the equation that relates the shear-wave velocity to the individual principal stresses in the directions of wave propagation and particle motion can predict the variation of the velocity ratio between the downhole and SH crosshole tests. It was also found that the stress ratio has some effects on the downhole (or shear wave in vertical plane (SV) crosshole) shear-wave velocity, but not on the SH crosshole shear-wave velocity. This indicates that it is only the stress ratio in the plane of wave propagation that is important to the shear-wave velocity. Comparison between the downhole and SH crosshole shows that structure anisotropy is in the order of 10%. In addjtion, K0 values are predicted from shear-wave measurement and compared with measured ones. The difficulties in obtaining K0 values from shear-wave measurement are also discussed. Key words: hydraulic gradient, model tests, downhole and crosshole shear-wave tests, sand.
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Bakulin, Andrey, Albena Mateeva, Rodney Calvert, Patsy Jorgensen i Jorge Lopez. "Virtual shear source makes shear waves with air guns". GEOPHYSICS 72, nr 2 (marzec 2007): A7—A11. http://dx.doi.org/10.1190/1.2430563.
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We demonstrate a novel application of the virtual source method to create shear-wave sources at the location of buried geophones. These virtual downhole sources excite shear waves with a different radiation pattern than known sources. They can be useful in various shear-wave applications. Here we focus on the virtual shear check shot to generate accurate shear-velocity profiles in offshore environments using typical acquisition for marine walkaway vertical seismic profiling (VSP). The virtual source method is applied to walkaway VSP data to obtain new traces resembling seismograms acquired with downhole seismic sources at geophone locations, thus bypassing any overburden complexity. The virtual sources can be synthesized to radiate predominantly shear waves by collecting converted-wave energy scattered throughout the overburden. We illustrate the concept in a synthetic layered model and demonstrate the method by estimating accurate P- and S-wave velocity profiles below salt using a walkaway VSP from the deepwater Gulf of Mexico.
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Ruderman, M. S., i M. Goossens. "Surface Alfvén waves of negative energy". Journal of Plasma Physics 54, nr 2 (październik 1995): 149–55. http://dx.doi.org/10.1017/s0022377800018419.
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The stability of an MHD tangential discontinuity is studied in an incompressible plasma where viscosity is taken into account at one side of the discontinuity. When the shear velocity is smaller than the threshold value for the onset of the Kelvin-Helmholtz (KH) instability, two surface waves can propagate along the discontinuity. There is a critical value for the shear velocity, which is smaller than the threshold value for the onset of the KH instability. When the shear velocity is smaller than the critical value, the two surface waves propagate in Opposite directions. When the shear velocity is larger than the critical velocity, the two waves propagate in the same direction, and the wave with smaller phase velocity is a negative-energy wave. Viscosity causes this negative-energy wave to be unstable, and the instability increment is proportional to the viscosity coefficient.
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Le Ngal, Nwai, Subagyo Pramumijoyo, Iman Satyarno, Kirbani Sri Brotopuspito, Junji Kiyono i Eddy Hartantyo. "Multi-channel analysis of surface wave method for geotechnical site characterization in Yogyakarta, Indonesia". E3S Web of Conferences 76 (2019): 03006. http://dx.doi.org/10.1051/e3sconf/20197603006.
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On May 27th 2006, Yogyakarta earthquake happened with 6.3 Mw. It was causing widespread destruction and loss of life and property. The average shear wave velocity to 30 m (Vs30) is useful parameter for classifying sites to predict their potential to amplify seismic shaking (Boore, 2004) [1]. Shear wave velocity is one of the most influential factors of the ground motion. The average shear wave velocity for the top 30 m of soil is referred to as Vs30. In this study, the Vs30 values were calculated by using multichannel analysis of surface waves (MASW) method. The Multichannel Analysis of Surface Waves (MASW) method was introduced by Park et al. (1999). Multi-channel Analysis of Surface Waves (MASW) is non-invasive method of estimating the shear-wave velocity profile. It utilizes the dispersive properties of Rayleigh waves for imaging the subsurface layers. MASW surveys can be divided into active and passive surveys. In active MASW method, surface waves can be easily generated by an impulsive source like a hammer, sledge hammer, weight drops, accelerated weight drops and explosive. Seismic measurements were carried out 44 locations in Yogyakarta province, in Indonesia. The dispersion data of the recorded Rayleigh waves were processed by using Seisimager software to obtain shear wave velocity profiles of the studied area. The average shear wave velocities of the soil obtained are ranging from 200 ms-1 to 988 ms-1, respectively.
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Stevens, Jeffry L., i Steven M. Day. "Shear velocity logging in slow formations using the Stoneley wave". GEOPHYSICS 51, nr 1 (styczeń 1986): 137–47. http://dx.doi.org/10.1190/1.1442027.
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We apply an iterative, linearized inversion method to Stoneley waves recorded on acoustic logs in a borehole. Our objective is to assess inversion of Stoneley wave phase and group velocity as a practical technique for shear velocity logging in slow formations. Indirect techniques for shear logging are of particular importance in this case because there is no shear head wave arrival. Acoustic logs from a long‐spaced sonic tool provided high‐quality, low‐noise data in the 1 to 10 kHz band for this experiment. A shear velocity profile estimated by inversion of a 60 ft (18 ⋅ 3 m) section of full‐wave acoustic data correlates well with the P‐wave log for the section. The inferred shear velocity ranges from 60 to 90 percent of the sound velocity of the fluid. Formal error estimates on the shear velocity are everywhere less than 5 percent. Moreover, application of the same inversion method to synthetic waveforms corroborates these error estimates. Finally, a synthetic acoustic waveform computed from inversion results is an excellent match to the observed waveform. On the basis of these results, we conclude that Stoneley‐wave inversion constitutes a practical, indirect, shear‐logging technique for slow formations. Success of the shear‐logging method depends upon availability of high‐quality, low‐noise waveform data in the 1 to 4 kHz band. Given good prior estimates of compressional velocity and density of the borehole fluid, only rough estimates of borehole radius and formation density and compressional velocity are required. The existing inversion procedure also yields estimates of formation Q inferred from spectral amplitudes of Stoneley waves. This extension of the method is promising, since amplitudes of Stoneley waves in a slow formation are highly sensitive to formation Q. Attenuation caused by formation Q dominates over attenuation caused by fluid viscosity if the viscosity is less than about [Formula: see text]. However, Stoneley‐wave amplitudes are also sensitive to gradients in shear velocity in the direction of propagation. In some cases, correction for the effects of shear‐velocity gradients is required to obtain the formation Q from Stoneley‐wave attenuation.
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Bessason, Bjarni, i Sigurður Erlingsson. "Shear wave velocity in surface sediments". Jökull 61, nr 1 (15.12.2011): 51–64. http://dx.doi.org/10.33799/jokull2011.61.051.
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Surface sediments of different nature are common in Iceland. Natural soil sites and man-made fillings commonly serve as foundations for different types of structures. In Civil engineering work it is fundamental to know the geotechnical properties of these materials in the upper 20–30 m. A seismic method called Spectral Analysis of Surface Waves (SASW) has been used in recent decades in Iceland to measure and evaluate shear wave velocity at different natural sites as well as in man-made fillings. The method is fast and involves low cost equipment. It gives reliable results down to 20 m depth by using sledge as a seismic source and copes with both soft and stiff soil sites. Furthermore, the technique can be applied at coarse grained gravelly sites where it can be difficult to use borehole and penetration methods. We describe the methodology used in these projects and review all SASW measurements carried out in Iceland. The soil strata at all test sites are classified based on sieve analysis when possible. Natural sites and man-made fillings are kept separated. A database and an open web site are introduced where all the SASW results can be viewed and shear wave profiles for different soil types and unlike sites can be compared. The main aim with the database and the webpage is to give scientists and engineers access to this data and enable them to compare stiffness at different sites.
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Tang, X. M., E. C. Reiter i D. R. Burns. "A dispersive‐wave processing technique for estimating formation shear velocity from dipole and Stoneley waveforms". GEOPHYSICS 60, nr 1 (styczeń 1995): 19–28. http://dx.doi.org/10.1190/1.1443747.
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A model‐guided dispersive‐wave processing technique has been developed to estimate formation shear‐wave velocity from borehole acoustic logging waveforms. These waveform data can be the Stoneley waves in monopole logging or the flexural waves in dipole logging. In this technique, the waveform recorded on a given receiver is compared to the waveform from a second receiver that is numerically propagated to the given receiver’s position using a trial formation shear‐wave velocity. The numerical propagation step uses the proper dispersion relation for the wave mode (dipole or Stoneley). The phase difference between the two waveforms is minimized by varying the shear velocity. The velocity value that minimizes the phase difference is chosen as the final shear velocity at which the waveforms attain the optimum phase match. In this procedure the dispersion effect is automatically accounted for by using the model theory and is demonstrated by a comparison with the results of the semblance method. Using this technique with a multiple‐shot scheme to process array acoustic logging data, formation shear velocity can be estimated to the resolution of one receiver spacing [typically 0.5 ft (0.1524 m)]. This result has been demonstrated by a field example in which the improved resolution in the shear velocity log is convincingly supported by the same character in the density log measured at one receiver spacing intervals. Shear velocity logs obtained using field Stoneley and dipole sonic data are also compared to demonstrate the ability of the technique to obtain high‐resolution formation shear velocity logs from the dispersive logging waveforms. The new technique may find very useful applications in the determination of formation shear‐wave properties using acoustic waveform logging.
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Yue, Chongwang, i Xiaopeng Yue. "Influence of Relaxation Frequency on Acoustic Wave in Unconsolidated Sands and Acoustic Logging Simulation". Journal of Theoretical and Computational Acoustics 26, nr 02 (czerwiec 2018): 1850014. http://dx.doi.org/10.1142/s2591728518500147.
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Apart from consolidated rocks, the effect of relaxation on acoustic propagation in unconsolidated sands cannot be neglected. In this paper, we study the influence of relaxation frequency on the propagation of acoustic waves. We compute the frequency-dependent velocities and attenuation of P1-wave, P2-wave, and S-wave at different bulk or shear relaxation frequency for plane wave. In addition, we derive the integral solutions of acoustic field equations in cylindrical coordinate system to simulate acoustic logging. The reflected acoustic waveforms in a borehole are calculated at different bulk or shear relaxation frequency. Calculation results show that the increase of bulk relaxation frequency will cause the velocity of P1-wave to decrease slightly, and the velocity of P2-wave to decrease substantially. The change of bulk relaxation frequency has no effect on the velocity of S-wave. The increase of bulk relaxation frequency will cause the attenuation of P1-wave or P2-wave to decrease or increase in different wave frequency range. The change of bulk relaxation frequency has no effect on the attenuation of S-wave. The increase of shear relaxation frequency will cause the velocity of P1-wave to increase slightly, and the velocity of P2-wave or S-wave to decrease substantially. The increase of the shear relaxation frequency will cause the attenuation of P1-wave, P2-wave or S-wave to decrease. For acoustic field in a borehole surrounded by unconsolidated sands, the effect of bulk or shear relaxation frequency on the velocity of reflected waves in a borehole is negligible at the dimension of the distance from a logging source. The increase of bulk or shear relaxation frequency will cause the amplitude of the reflected waveforms from the borehole wall to increase.
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Saha, Sukumar. "Dispersion of Love Waves in a Composite Layer Resting on Monoclinic Half-Space". Journal of Applied Mathematics 2011 (2011): 1–9. http://dx.doi.org/10.1155/2011/721349.
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Dispersion of Love waves is studied in a fibre-reinforced layer resting on monoclinic half-space. The wave velocity equation has been obtained for a fiber-reinforced layer resting on monoclinic half space. Shear wave velocity ratio curve for Love waves has been shown graphically for fibre reinforced material layer resting on various monoclinic half-spaces. In a similar way, shear wave velocity ratio curve for Love waves has been plotted for an isotropic layer resting on various monoclinic half-spaces. From these curves, it has been observed that the curves are of similar type for a fibre reinforced layer resting on monoclinic half-spaces, and the shear wave velocity ratio ranges from 1.14 to 7.19, whereas for the case isotropic layer, this range varies from 1.0 to 2.19.
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Chen, Ji Hua, Ai Hong Zhou, Qiu Jun Wang i Ying Jiao Xu. "Study on the Influence of Seismic Wave Inputting Interface on the Earthquake Response of Deep Soft Sites". Advanced Materials Research 243-249 (maj 2011): 2523–28. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2523.
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Earthquake effects of two typical deep soft sites selected from Tianjin(site 1)and Shanghai(site 2) are studied when the vertical inputting earthquake waves are located in different depth of sites. As far as the shear wave velocity of soil layers is concerned, seven kinds of soil layers in site 1 and eight soil layers in site 2 are selected as the vertical imputing interfaces of earthquake waves. Two acceleration waves recorded during Taft earthquake and Northbridge earthquake are selected, and the peak values of two waves are adjusted to be 0.35m/s2、0 70m /s2 and 0 98m /s2, respectively. The earthquake response of sites is calculated by SHAKE91 program. The results are compared to those of site when the input interfaces of earthquake waves are located in bedrock with shear wave velocity larger than 500m/s. The conclusion is as following: With the depth of input position (or shear wave velocity) increasing, the value of the ground acceleration response spectrum gradually closes to the actual data.; For the general building the soil layer with shear wave velocity for 400m/s or so can be chosen as the input interface, and the building with long natural vibration period should be treated seriously, and the soil layer whose shear wave velocity is above 500m/s can be chosen as the input interface.
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Piriyakul, Keeratikan. "Application of the Non-Destructive Testing Method to Determine the Gmax of Bangkok Clay". Applied Mechanics and Materials 418 (wrzesień 2013): 157–60. http://dx.doi.org/10.4028/www.scientific.net/amm.418.157.
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This article presents the application of the non-destructive testing method (so called Bender element test) to measure the shear wave velocity and determine the maximum shear modulus of soft Bangkok clay samples. This research proposes the bender element technique to measure the shear wave velocity by means of piezoelectric ceramic sensors. The details of the bender element test were clearly explained. The laboratory bender element test data of the shear wave velocity were compared with the field test results and show that the field propagating waves pass along layers of higher stiffness while the laboratory test data were performed on small, possible less stiff material. The inversion calculation of the shear wave velocity in the field test is based on a linear elastic isotropic assumption which is not valid for the Bangkok subsoil and might be a second reason for the noticed differences in velocity.
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Addo, K. O., i P. K. Robertson. "Shear-wave velocity measurement of soils using Rayleigh waves". Canadian Geotechnical Journal 29, nr 4 (1.08.1992): 558–68. http://dx.doi.org/10.1139/t92-063.
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A modified version of the spectral analysis of surface waves (SASW) equipment and analysis procedure has been developed to determine in situ shear-wave velocity variation with depth from the ground surface. A microcomputer has been programmed to acquire waveform data and perform the relevant spectral analyses that were previously done by signal analyzers. Experimental dispersion for Rayleigh waves is now obtainable at a site and inverted with a fast algorithm for dispersion computation. Matching experimental and theoretical dispersion curves has been automated in an optimization routine that does not require intermittent operator intervention or experience in dispersion computation. Shear-wave velocity profiles measured by this procedure are compared with results from independent seismic cone penetration tests for selected sites in western Canada. Key words : surface wave, dispersion, inversion, optimization, shear-wave velocity.
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Wen, Li Ping, Guan Xiu Wu i Lan Li Zuo. "Influence of Ancient River Covering Layer Shear-Wave Velocity Variation on Plane Primary Waves". Advanced Materials Research 838-841 (listopad 2013): 948–52. http://dx.doi.org/10.4028/www.scientific.net/amr.838-841.948.
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While using the big circle method, Fourier Bessel series expansion technique, and the coordinate conversion of Graf's addition formula, an analytical solution for the scattering of non concentric arc layered alluvial valleys subjected to plane primary waves was derived. Then the precision of the numerical result was checked up and analyzed. Finally, by using the analytic solution, the surface displacement was analyzed at different shear wave velocity of covering layer. The analysis results show that shear wave velocity change has little effect on the crest value of displacement at lower frequency incidence, however the influence becomes significant with the increase of incident frequency. In general, lower the shear wave velocity is, higher the crest value of displacement will be. Compared with the existing conclusions, the covering thickness variation has little effect on the influence of shear wave velocity change on the scattering of elastic waves.
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Miwa, Takashi, i Yoshiki Yamakoshi. "Anisotropy Evaluation of In Vivo Tissue Elasticity Measurement by Using Wavenumber Filtering". Key Engineering Materials 534 (styczeń 2013): 262–66. http://dx.doi.org/10.4028/www.scientific.net/kem.534.262.
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Tissue elasticity measurements by an ultrasonic wave are a promising technique to qualitative diagnosis of tumor or liver diseases. The elasticity in the soft tissue can quantitatively be estimated by velocity of a shear wave propagating through the tissue. For safer and more accurate estimation of the velocity, an elasticity imaging method using continuous vibration wave excitation has been proposed. This method utilizes wave number vector analysis to individually estimate the velocity of the shear waves generated by multiple reflections. In this paper, applicability of the wave number filtering method is discussed to separate the plural shear waves through a phantom experiment. Then, an in-vivo experiment shows possibility to extract anisotropic information of muscle fiber for applying the tissue elasticity measurement.
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Blewett, J., I. J. Blewett i P. K. Woodward. "Phase and amplitude responses associated with the measurement of shear-wave velocity in sand by bender elements". Canadian Geotechnical Journal 37, nr 6 (1.12.2000): 1348–57. http://dx.doi.org/10.1139/t00-047.
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Shear-wave velocity measured by bender elements in laboratory sand samples is shown to be dependent upon the excitation frequency and exhibits a maximum velocity for a finite frequency. By comparing the relative effects of dispersion due to propagation of shear waves through sand and dispersion due to bender element performance within sand, we show that a combination of the two processes is required to explain the observations. The magnitude of the aggregate response of the bender elements and the sand implies that reliable shear-wave velocity results cannot be obtained from bender element tests without a prior knowledge of the frequency response of the entire system.Key words: shear-wave velocity, phase-sensitive detection, dispersion, attenuation, sand.
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Kimura, Masao. "Shear Wave Velocity in Marine Sediment". Japanese Journal of Applied Physics 45, nr 5B (25.05.2006): 4824–28. http://dx.doi.org/10.1143/jjap.45.4824.
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Kamel, Filali, i Sbartai Badreddine. "Liquefaction Analysis using Shear Wave Velocity". Civil Engineering Journal 6, nr 10 (1.10.2020): 1944–55. http://dx.doi.org/10.28991/cej-2020-03091594.
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The Andrus and Stokoe curves developed based on shear wave velocity case history databases, are the most widely used in the context of the Seed and Idriss simplified procedure as a deterministic model. Theses curves were developed from the database according to the calculate cyclic stress ratio (CSR) proposed by Seed and Idriss in 1971 with the assumption that the dynamic cyclic shear stress (τd) is always less than the simplified cyclic shear stress (τr) deduced by Seed and Idriss based on their simplifying hypotheses (rd= τd / τr <1). Filali and Sbartai in 2017, showed that rd can in many cases be greater than 1, and they have proposed a correction for the CSR in the range where rd >1. In this paper, we will present a probabilistic study based on the Bayesian method for the evaluation of the liquefaction potential of a soil deposit using a case history database based on shear wave velocity measurement. The result of this analysis shows that by using the corrected version of the simplified method, the boundary curve is moved to a new position. Then, the objective of this study is to present an adjusted mathematical model which characterizes the new position of the boundary curve (CRR) and a new formulation for computing the probability of liquefaction based on the probabilistic shape of the CRR curves using the corrected and the original version of the simplified method.
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Mahmoudian, Mohammad Sadegh, Yousef Shiri i Ahmad Vaezian. "PREDICTION OF SHEAR WAVE VELOCITY AND MODIFICATION OF CASTAGNA AND CARROLL RELATIONSHIPS IN ONE OF THE IRANIAN OIL FIELDS". Rudarsko-geološko-naftni zbornik 37, nr 4 (2022): 137–44. http://dx.doi.org/10.17794/rgn.2022.4.11.
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Shear wave velocity is one of the essential parameters for describing hydrocarbon reservoirs that have several applications in petrophysical, geophysical, and geomechanical studies. Shear wave velocity usually does not exist in all wells, especially in old oil fields. In the current study, two equations of Carroll and Castagna have been modified, and linear and nonlinear multi-regressions were used to estimate shear wave velocity in an oil reservoir in southwestern Iran. Initially, compressional wave velocity and porosity were determined as the most effective wire-line logs on shear wave velocity by comparing their correlations. Then, two equations of Carroll and Castagna were modified. In addition, new equations based on porosity and compressional wave velocity for estimating the shear wave velocity were obtained. Shear wave velocity was estimated by new exponential equations in the wells of the current oil field with excellent goodness of fit by determination coefficients of 0.80 in the whole well, 0.72 in the Ghar-Shale-1, and 0.78 in Ghar-Shale-3 in X-07 well.
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Bohlen, Thomas, Simone Kugler, Gerald Klein i Friedrich Theilen. "1.5D inversion of lateral variation of Scholte‐wave dispersion". GEOPHYSICS 69, nr 2 (marzec 2004): 330–44. http://dx.doi.org/10.1190/1.1707052.
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Reliable models of in‐situ shear‐wave velocities of shallow‐water marine sediments are important for geotechnical applications, lithological sediment characterization, and seismic exploration studies. We infer the 2D shear‐wave velocity structure of shallow‐water marine sediments from the lateral variation of Scholte‐wave dispersion. Scholte waves are recorded in a common receiver gather generated by an air gun towed behind a ship away from a single stationary ocean‐bottom seismometer. An offset window moves along the common receiver gather to pick up a local wavefield. A slant stack produces a slowness–frequency spectrum of the local wavefield, which contains all modes excited by the air gun. Amplitude maxima (dispersion curves) in the local spectrum are picked and inverted for the shear‐wave velocity depth profile located at the center of the window. As the window continuously moves along the common receiver gather, a 2D shear‐wave velocity section is generated. In a synthetic example the smooth lateral variation of surficial shear‐wave velocity is well reconstructed. The method is applied to two orthogonal common receiver gathers acquired in the Baltic Sea (northern Germany). The inverted 2D models show a strong vertical gradient of shear‐wave velocity at the sea floor. Along one profile significant lateral variation near the sea floor is observed.
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Castagna, J. P., M. L. Batzle i R. L. Eastwood. "Relationships between compressional‐wave and shear‐wave velocities in clastic silicate rocks". GEOPHYSICS 50, nr 4 (kwiecień 1985): 571–81. http://dx.doi.org/10.1190/1.1441933.
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New velocity data in addition to literature data derived from sonic log, seismic, and laboratory measurements are analyzed for clastic silicate rocks. These data demonstrate simple systematic relationships between compressional and shear wave velocities. For water‐saturated clastic silicate rocks, shear wave velocity is approximately linearly related to compressional wave velocity and the compressional‐to‐shear velocity ratio decreases with increasing compressional velocity. Laboratory data for dry sandstones indicate a nearly constant compressional‐to‐shear velocity ratio with rigidity approximately equal to bulk modulus. Ideal models for regular packings of spheres and cracked solids exhibit behavior similar to the observed water‐saturated and dry trends. For dry rigidity equal to dry bulk modulus, Gassmann’s equations predict velocities in close agreement with data from the water‐saturated rock.
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Polet, J., i H. Kanamori. "Upper-mantle shear velocities beneath southern California determined from long-period surface waves". Bulletin of the Seismological Society of America 87, nr 1 (1.02.1997): 200–209. http://dx.doi.org/10.1785/bssa0870010200.
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Abstract We used long-period surface waves from teleseismic earthquakes recorded by the TERRAscope network to determine phase velocity dispersion of Rayleigh waves up to periods of about 170 sec and of Love waves up to about 150 sec. This enabled us to investigate the upper-mantle velocity structure beneath southern California to a depth of about 250 km. Ten and five earthquakes were used for Rayleigh and Love waves, respectively. The observed surface-wave dispersion shows a clear Love/Rayleigh-wave discrepancy that cannot be accounted for by a simple isotropic velocity model with smooth variations of velocity with depth. Separate isotropic inversions for Love- and Rayleigh-wave data yield velocity models that show up to 10% anisotropy (transverse isotropy). However, tests with synthetic Love waves suggest that the relatively high Love-wave phase velocity could be at least partly due to interference of higher-mode Love waves with the fundamental mode. Even after this interference effect is removed, about 4% anisotropy remains in the top 250 km of the mantle. This anisotropy could be due to intrinsic anisotropy of olivine crystals or due to a laminated structure with alternating high- and low-velocity layers. Other possibilities include the following: upper-mantle heterogeneity in southern California (such as the Transverse Range anomaly) may affect Love- and Rayleigh-wave velocities differently so that it yields the apparent anisotropy; higher-mode Love-wave interference has a stronger effect than suggested by our numerical experiments using model 1066A. If the high Love-wave velocity is due to causes other than anisotropy, the Rayleigh-wave velocity model would represent the southern California upper-mantle velocity structure. The shear velocity in the upper mantle (Moho to 250 km) of this structure is, on average, 3 to 4% slower than that of the TNA model determined for western North America.
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Pei, Qiang, i Lei Huan Zhen. "Statistical Analysis on Shear Wave Velocity of Soils in Bohai Gulf". Advanced Materials Research 787 (wrzesień 2013): 750–54. http://dx.doi.org/10.4028/www.scientific.net/amr.787.750.
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The shear wave velocity is an important parameter in the geo-seismic analysis. The corresponding database of shear wave velocity is founded by collecting and sorting out the data of superficial soil layers in Bohai Gulf. The scatter diagrams of soil shear wave velocity and depth are drawn using the software of ORIGIN. The exponential regression equation is selected by adopting the goodness-of-fit for evaluation index; the regression coefficients about shear wave velocity with depth of four categories of soils are fitted. The results show that there is a good relationship in the exponential form between the shear wave velocity and depth of superficial soil layers in Bohai Gulf. The obtained results can be directly provided a reference for the field without shear wave velocity.
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Levin, Franklyn K. "Estimating shear‐wave velocities from P-wave and converted‐wave data". GEOPHYSICS 64, nr 2 (marzec 1999): 504–7. http://dx.doi.org/10.1190/1.1444556.
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Tessmer and Behle (1988) show that S-wave velocity can be estimated from surface seismic data if both normal P-wave data and converted‐wave data (P-SV) are available. The relation of Tessmer and Behle is [Formula: see text] (1) where [Formula: see text] is the S-wave velocity, [Formula: see text] is the P-wave velocity, and [Formula: see text] is the converted‐wave velocity. The growing body of converted‐wave data suggest a brief examination of the validity of equation (1) for velocities that vary with depth.
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Leong, E. C., J. Cahyadi i H. Rahardjo. "Measuring shear and compression wave velocities of soil using bender–extender elements". Canadian Geotechnical Journal 46, nr 7 (lipiec 2009): 792–812. http://dx.doi.org/10.1139/t09-026.
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Piezoceramic elements have been used for laboratory measurement of wave velocity in soil and rock specimens. Shear-wave piezoceramic elements (bender elements) are commonly used to measure shear wave velocity for the determination of small-strain shear modulus. Compression-wave piezoceramic elements (extender elements), on the other hand, are less commonly used as compression wave velocity is less frequently measured. In this paper, the performance of a pair of bender–extender elements for the determination of both shear and compression wave velocities is examined with respect to the resolution of the recorder, bender–extender element size. and excitation voltage frequency. The evaluation showed that the performance of the bender–extender elements test can be improved by considering the following conditions: (i) the digital oscilloscope used to record the bender–extender element signals should have a high analog to digital (A/D) conversion resolution; (ii) the size of the bender–extender elements plays an important role in the strength and quality of the receiver signal, especially for compression waves; and (iii) using a wave path length to wavelength ratio of 3.33 enables a more reliable determination of shear wave velocity.
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Kim, Dong-Ju, Jung-Doung Yu i Yong-Hoon Byun. "Piezoelectric Ring Bender for Characterization of Shear Waves in Compacted Sandy Soils". Sensors 21, nr 4 (9.02.2021): 1226. http://dx.doi.org/10.3390/s21041226.
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Shear wave velocity and small-strain shear modulus are widely used as the mechanical properties of soil. The objective of this study is to develop a new shear wave monitoring system using a pair of piezoelectric ring benders (RBs) and to evaluate the suitability of RB in compacted soils compared with the bender element and ultrasonic transducer. The RB is a multilayered piezoelectric actuator, which can generate shear waves without disturbing soils. For five compacted soil specimens, the shear waves are monitored by using three different piezoelectric transducers. Results of time-domain response show that the output signals measured from the RB vary according to the water content of the specimen and the frequency of the input signal. Except at the water content of 9.3%, the difference in the resonant frequencies between the three transducers is not significant. The shear wave velocities for the RB are slightly greater than those for the other transducers. For the RB, the exponential relationship between the shear wave velocity and dry unit weight is better established compared with that of the other transducers. The newly proposed piezoelectric transducer RB may be useful for the evaluation of the shear wave velocity and small-strain shear modulus of compacted soils.
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Dong, Yang, Shengchun Piao, Lijia Gong, Guangxue Zheng, Kashif Iqbal, Shizhao Zhang i Xiaohan Wang. "Scholte Wave Dispersion Modeling and Subsequent Application in Seabed Shear-Wave Velocity Profile Inversion". Journal of Marine Science and Engineering 9, nr 8 (2.08.2021): 840. http://dx.doi.org/10.3390/jmse9080840.
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Recent studies have illustrated that the Multichannel Analysis of Surface Waves (MASW) method is an effective geoacoustic parameter inversion tool. This particular tool employs the dispersion property of broadband Scholte-type surface wave signals, which propagate along the interface between the sea water and seafloor. It is of critical importance to establish the theoretical Scholte wave dispersion curve computation model. In this typical study, the stiffness matrix method is introduced to compute the phase speed of the Scholte wave in a layered ocean environment with an elastic bottom. By computing the phase velocity in environments with a typical complexly varying seabed, it is observed that the coupling phenomenon occurs among Scholte waves corresponding to the fundamental mode and the first higher-order mode for the model with a low shear-velocity layer. Afterwards, few differences are highlighted, which should be taken into consideration while applying the MASW method in the seabed. Finally, based on the ingeniously developed nonlinear Bayesian inversion theory, the seafloor shear wave velocity profile in the southern Yellow Sea of China is inverted by employing multi-order Scholte wave dispersion curves. These inversion results illustrate that the shear wave speed is below 700 m/s in the upper layers of bottom sediments. Due to the alternation of argillaceous layers and sandy layers in the experimental area, there are several low-shear-wave-velocity layers in the inversion profile.
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Dong, Hefeng, Thanh-Duong Nguyen i Kenneth Duffaut. "Estimation of seabed shear-wave velocity profiles using shear-wave source data". Journal of the Acoustical Society of America 134, nr 1 (lipiec 2013): 176–84. http://dx.doi.org/10.1121/1.4809719.
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Abuawad, Tareq, Gerald Miller i Kanthasamy Muraleetharan. "Field and laboratory measurements of shear wave velocity in unsaturated soils". E3S Web of Conferences 382 (2023): 03002. http://dx.doi.org/10.1051/e3sconf/202338203002.
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Shear wave velocity measurements in soil are important for assigning site soil profiles to seismic site classes and for calculating other dynamic soil properties. The seismic cone penetration test (SCPT) is commonly used to determine shear wave velocity profiles in the field. In the laboratory, bender elements provide an easy means to measure shear wave velocity of soil specimens from discrete depths. In this study, shear wave velocity measurements obtained from unsaturated soil profiles in the field and on field samples in the laboratory under similar stress conditions were analyzed and compared. Additionally, the influence of seasonal changes on the behavior of shear wave velocity was investigated. Comparisons of shear wave velocities from the field and laboratory were favorable for similar moisture and stress conditions. However, results showed that as the degree of saturation increases and suction decreases the shear wave velocity can decrease significantly.
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Liu, Xin, i Jun Yang. "Shear wave velocity and shear modulus of silty sand". Japanese Geotechnical Society Special Publication 2, nr 24 (2016): 907–10. http://dx.doi.org/10.3208/jgssp.hkg-07.
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Grechka, Vladimir. "Shear-wave group-velocity surfaces in low-symmetry anisotropic media". GEOPHYSICS 80, nr 1 (1.01.2015): C1—C7. http://dx.doi.org/10.1190/geo2014-0156.1.
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Shear waves excited by natural sources constitute a significant part of useful energy recorded in downhole microseismic surveys. In rocks, such as fractured shales, exhibiting symmetries lower than transverse isotropy (TI), the shear wavefronts are always multivalued in certain directions, potentially complicating the data processing and analysis. This paper discusses a basic tool — the computation of the phase and group velocities of all waves propagating along a given ray — that intends to facilitate the understanding of geometries of the shear wavefronts in homogeneous anisotropic media. With this tool, arbitrarily complex group-velocity surfaces can be conveniently analyzed, providing insights into possible challenges to be faced when processing shear waves in anisotropic velocity models that have symmetries lower than TI. Among those challenges are complicated multipathing and the presence of cones of directions, known as internal refraction cones, in which no fast shear waves propagate and the entire shear portion of the body-wave seismic data consists of several branches of the slow shear wavefronts.
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VORONOVICH, VYACHESLAV V., DMITRY E. PELINOVSKY i VICTOR I. SHRIRA. "On internal wave–shear flow resonance in shallow water". Journal of Fluid Mechanics 354 (10.01.1998): 209–37. http://dx.doi.org/10.1017/s0022112097007593.
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The work is concerned with long nonlinear internal waves interacting with a shear flow localized near the sea surface. The study is focused on the most intense resonant interaction occurring when the phase velocity of internal waves matches the flow velocity at the surface. The perturbations of the shear flow are considered as ‘vorticity waves’, which enables us to treat the wave–flow resonance as the resonant wave–wave interaction between an internal gravity mode and the vorticity mode. Within the weakly nonlinear long-wave approximation a system of evolution equations governing the nonlinear dynamics of the waves in resonance is derived and an asymptotic solution to the basic equations is constructed. At resonance the nonlinearity of the internal wave dynamics is due to the interaction with the vorticity mode, while the wave's own nonlinearity proves to be negligible. The equations derived are found to possess solitary wave solutions of different polarities propagating slightly faster or slower than the surface velocity of the shear flow. The amplitudes of the ‘fast’ solitary waves are limited from above; the crest of the limiting wave forms a sharp corner. The solitary waves of amplitude smaller than a certain threshold are shown to be stable; ‘subcritical’ localized pulses tend to such solutions. The localized pulses of amplitude exceeding this threshold form infinite slopes in finite time, which indicates wave breaking.
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Tao, Xingming, Lihua Fang, Luchao Lin, Ruirui Du i Yinyu Song. "Simulation of Optical Coherence Elastography in Agar Based on Finite Element Analysis". E3S Web of Conferences 271 (2021): 04025. http://dx.doi.org/10.1051/e3sconf/202127104025.
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The finite element method is used to simulate the optical coherent elastic imaging in Agar. The shear wave velocity in Agar was measured by ARF-OCE system, and then the Agar model was established by finite element method, and then the shear wave velocity in Agar model was measured. The shear wave velocity in experiment and finite element simulation were compared and analyzed. The shear wave velocity obtained in the experiment is 2.50 m/s, and the range of shear wave velocity obtained in the finite element simulation is 2.4802m/s, and the average wave velocity is 2.5167m/s. The finite element method can express tissue elasticity directly and clearly, and it plays a great guiding role in corneal elastography.
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Sasitharan, S., P. K. Robertson i D. C. Sego. "Sample disturbance from shear wave velocity measurements". Canadian Geotechnical Journal 31, nr 1 (1.02.1994): 119–24. http://dx.doi.org/10.1139/t94-013.
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Effective techniques are currently available to obtain undisturbed samples of cohesive soils. However, little advance has been made in the procurement of undisturbed samples of cohesionless soils such as sands, silty sands, and clayey sands. In the area of earthquake design and liquefaction, researchers and practitioners are becoming increasingly aware of the importance of obtaining high-quality undisturbed samples of cohesionless soils. In situ ground-freezing techniques can be used to obtain undisturbed samples of cohesionless soils. However, there is still concern regarding the possibility of disturbance during the freezing and thawing of the samples. Shear wave velocity is a direct measurement of the stiffness of the soil skeleton at small strains (<10−4%). Hence, shear wave velocity can be a sensitive measurement to detect changes in void ratio and soil structure due to freezing and thawing. A laboratory study has been performed to evaluate the use of shear wave velocity measurements to detect sample disturbance due to freezing and thawing of cohesionless soils. Samples prepared with different amounts and type of fines were frozen using uniaxial freezing techniques and subsequently thawed. Shear wave velocity measurements were made before and after freezing and thawing of the reconstituted samples. The measured shear wave velocities were unchanged for samples that did not heave (undisturbed) during the freeze–thaw cycle. Samples that heaved (disturbed) showed an associated change in shear wave velocity. Hence, measurements of shear wave velocities in situ and in the laboratory have the potential to identify sample disturbance in granular soils. Key words : in situ, sampling, freezing, disturbance, shear wave velocity.
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Bawadi, Nor Faizah, Nur Jihan Syamimi Jafri, Ahmad Faizal Mansor i Mohd Asri Ab Rahim. "Relationship between Shear Wave Velocity and SPT-N Value for Residual Soils". MATEC Web of Conferences 203 (2018): 04009. http://dx.doi.org/10.1051/matecconf/201820304009.
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The shear wave velocity (Vs) is an important dynamic parameter in the field of geotechnical engineering. One of the surface wave methods is Spectral Analysis of Surface Wave (SASW) has received attention in obtaining the shear wave velocity (Vs) profile by analysing the dispersion curve. SASW is a non-destructive test, fast and time-effective for field survey. Thus, this paper proposed the application of SASW method to obtain the shear wave velocity (Vs) to represent the soil profile. This paper aims to determine the shear wave velocity (Vs) profile using SASW method, where the testing has been conducted at three site of residual soils located in Damansara, Kuala Lumpur and Nilai area. In this study, it shows that the soil profile obtained from shear wave velocity value is similar pattern with profile that obtained using Standard Penetration Testing (SPT), which conventional used in field. The shear wave velocity are proportionally increase with depth.
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Cherepetskaya, Elena B., Alexander A. Karabutov, Vladimir A. Makarov, Elena A. Mironova, Ivan A. Shibaev, Nikolay G. Vysotin i Dmitry V. Morozov. "Internal Structure Research of Shungite by Broadband Ultrasonic Spectroscopy". Key Engineering Materials 755 (wrzesień 2017): 242–47. http://dx.doi.org/10.4028/www.scientific.net/kem.755.242.
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The internal structure of plane-parallel plates of shungite is studied. The broadband ultrasonic pulses are used to measure the velocities of longitudinal and shear elastic ultrasonic waves. The accuracy of measurements is 0.3% in the case of longitudinal wave velocity and 0.5% in the case of shear wave velocity (scanning pitch over the surface of specimens was 0.5 mm). Local elastic moduli of shungite (Young modulus, shear modulus and Poisson's ratio) are uniquely determined from the velocities of elastic waves.
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Di, Sheng Jie, Zhi Gang Shan i Xue Yong Xu. "Estimation Study on Shear Wave Velocity of Seabed Using GRNN". Applied Mechanics and Materials 580-583 (lipiec 2014): 264–67. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.264.
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Characterization of the shear wave velocity of soils is an integral component of various seismic analysis, including site classification, hazard analysis, site response analysis, and soil-structure interaction. Shear wave velocity at offshore sites of the coastal regions can be measured by the suspension logging method according to the economic applicability. The study presents some methods for estimating the shear wave velocity profiles in the absence of site-specific shear wave velocity data. By applying generalized regression neural network (GRNN) for the estimation of in-situ shear wave velocity, it shows good performances. Therefore, this estimation method is worthy of being recommended in the later engineering practice.
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Didebulidze, G. G., i L. N. Lomidze. "The formation of sporadic E layers by a vortical perturbation excited in a horizontal wind shear flow". Annales Geophysicae 26, nr 7 (24.06.2008): 1741–49. http://dx.doi.org/10.5194/angeo-26-1741-2008.
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Abstract. The formation of the mid-latitude sporadic E layers (Es layers) by an atmospheric vortical perturbation excited in a horizontal shear flow (horizontal wind with a horizontal linear shear) is investigated. A three-dimensional atmospheric vortical perturbation (atmospheric shear waves), whose velocity vector is in the horizontal plane and has a vertical wavenumber kz≠0, can provide a vertical shear of the horizontal wind. The shear waves influence the vertical transport of heavy metallic ions and their convergence into thin and dense horizontal layers. The proposed mechanism takes into account the dynamical influence of the shear wave velocity in the horizontal wind on the vertical drift velocity of the ions. It also can explain the multi-layer structure of Es layers. The pattern of the multi-layer structure depends on the value of the shear-wave vertical wavelength, the ion-neutral collision frequency and the direction of the background horizontal wind. The modelling of formation of sporadic E layers with a single and a double peak is presented. Also, the importance of shear wave coupling with short-period atmospheric gravity waves (AGWs) on the variations of sporadic E layer ion density is examined and discussed.
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Jo. "Evaluation of ground characteristics near underground rainfall storage facilities using shear wave velocity". Journal of Korean Tunnelling and Underground Space Association 16, nr 2 (2014): 225. http://dx.doi.org/10.9711/ktaj.2014.16.2.225.
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Drijkoningen, Guy, Nihed el Allouche, Jan Thorbecke i Gábor Bada. "Nongeometrically converted shear waves in marine streamer data". GEOPHYSICS 77, nr 6 (1.11.2012): P45—P56. http://dx.doi.org/10.1190/geo2012-0037.1.
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Under certain circumstances, marine streamer data contain nongeometrical shear body wave arrivals that can be used for imaging. These shear waves are generated via an evanescent compressional wave in the water and convert to propagating shear waves at the water bottom. They are called “nongeometrical” because the evanescent part in the water does not satisfy Snell’s law for real angles, but only for complex angles. The propagating shear waves then undergo reflection and refraction in the subsurface, and arrive at the receivers via an evanescent compressional wave. The required circumstances are that sources and receivers are near the water bottom, irrespective of the total water depth, and that the shear-wave velocity of the water bottom is smaller than the P-wave velocity in the water, most often the normal situation. This claim has been tested during a seismic experiment in the river Danube, south of Budapest, Hungary. To show that the shear-related arrivals are body rather than surface waves, a borehole was drilled and used for multicomponent recordings. The streamer data indeed show evidence of shear waves propagating as body waves, and the borehole data confirm that these arrivals are refracted shear waves. To illustrate the effect, finite-difference modeling has been performed and it confirmed the presence of such shear waves. The streamer data were subsequently processed to obtain a shear-wave refraction section; this was obtained by removing the Scholte wave arrival, separating the wavefield into different refracted arrivals, stacking and depth-converting each refracted arrival before adding the different depth sections together. The obtained section can be compared directly with the standard P-wave reflection section. The comparison shows that this approach can deliver refracted-shear-wave sections from streamer data in an efficient manner, because neither the source nor receivers need to be situated on the water bottom.
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YOON, HYUNG-KOO, JONG-SUB LEE, YOUNG-UK KIM i SUNGSOO YOON. "FORK BLADE-TYPE FIELD VELOCITY PROBE FOR MEASURING SHEAR WAVES". Modern Physics Letters B 22, nr 11 (10.05.2008): 965–69. http://dx.doi.org/10.1142/s0217984908015681.
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The reasonable assessment of the shear wave velocity of soft soils in the laboratory is difficult due to the soil disturbance. This study presents a new apparatus, the blade-type field velocity probe, FVP, which overcomes several limitations of commonly used shear wave measurement methods in the field. The shear wave velocity of the FVP is simply calculated by using the travel distance and the travel time without inversion process. The FVP are carried out in clay soils up to 30m in depth. In addition, the dissipation of excess pore water pressure is investigated. The shear wave velocity is measured every 10cm. The velocity profiles with depth show the consolidation of the upper part of the soft clay. The shear wave velocity approaches asymptotic value after 50 minutes later due to the dissipation of excess pore water pressure. This study suggests that the blade-type FVP may be an effective device for measuring the shear wave velocity with minimized soil disturbance in the field.
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Grechka, Vladimir, Linbin Zhang i James W. Rector. "Shear waves in acoustic anisotropic media". GEOPHYSICS 69, nr 2 (marzec 2004): 576–82. http://dx.doi.org/10.1190/1.1707077.
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Acoustic transversely isotropic (TI) media are defined by artificially setting the shear‐wave velocity in the direction of symmetry axis, VS0, to zero. Contrary to conventional wisdom that equating VS0 = 0 eliminates shear waves, we demonstrate their presence and examine their properties. Specifically, we show that SV‐waves generally have finite nonzero phase and group velocities in acoustic TI media. In fact, these waves have been observed in full waveform modeling, but apparently they were not understood and labeled as numerical artifacts. Acoustic TI media are characterized by extreme, in some sense infinite strength of anisotropy. It makes the following unusual wave phenomena possible: (1) there are propagation directions, where the SV‐ray is orthogonal to the corresponding wavefront normal, (2) the SV‐wave whose ray propagates along the symmetry axis is polarized parallel to the P‐wave propagating in the same direction, (3) P‐wave singularities, that is, directions where P‐ and SV‐wave phase velocities coincide might exist in acoustic TI media. We also briefly discuss some aspects of wave propagation in low‐symmetry acoustic anisotropic models. Extreme anisotropy in those media creates bizarre phase‐ and group‐velocity surfaces that might bring intellectual delight to an anisotropic guru.
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Abdul Aziz, Qahtan, i Hassan Abdul Hussein. "Development a Statistical Relationship between Compressional Wave Velocity and Petrophysical Properties from Logs Data for JERIBE Formation ASMARI Reservoir in FAUQI Oil Field". Iraqi Journal of Chemical and petroleum Engineering 22, nr 3 (30.09.2021): 1–9. http://dx.doi.org/10.31699/ijcpe.2021.3.1.
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The Compressional-wave (Vp) data are useful for reservoir exploration, drilling operations, stimulation, hydraulic fracturing employment, and development plans for a specific reservoir. Due to the different nature and behavior of the influencing parameters, more complex nonlinearity exists for Vp modeling purposes. In this study, a statistical relationship between compressional wave velocity and petrophysical parameters was developed from wireline log data for Jeribe formation in Fauqi oil field south Est Iraq, which is studied using single and multiple linear regressions. The model concentrated on predicting compressional wave velocity from petrophysical parameters and any pair of shear waves velocity, porosity, density, and fluid saturation in carbonate rocks. A strong linear correlation between P-wave velocity and S-wave velocity and between P-wave velocity and density rock was found. The resulting linear equations can be used to estimate P-wave velocity from the S-wave velocity in the case of both. The results of multiple regression analysis indicated that the density, porosity, water-saturated, and shear wave velocity (VS) are strongly related to Vp.