共查询到20条相似文献,搜索用时 31 毫秒
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《Oceanic Engineering, IEEE Journal of》2009,34(4):451-458
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《Oceanic Engineering, IEEE Journal of》2009,34(4):407-422
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《Oceanic Engineering, IEEE Journal of》2009,34(1):83-92
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Evaluation of Laser Scanning and Stereo Photography Roughness Measurement Systems Using a Realistic Model Seabed Surface 总被引:1,自引:0,他引:1
《Oceanic Engineering, IEEE Journal of》2009,34(4):466-475
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《Oceanic Engineering, IEEE Journal of》2009,34(4):485-494
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《Oceanic Engineering, IEEE Journal of》2008,33(2):69-88
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《Oceanic Engineering, IEEE Journal of》2008,33(2):224-231
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《Oceanic Engineering, IEEE Journal of》2009,34(4):476-484
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Robb G.B.N. Best A.I. Dix J.K. White P.R. Leighton T.G. Bull J.M. Harris A. 《Oceanic Engineering, IEEE Journal of》2007,32(2):484-496
Geoacoustic inversion requires a generic knowledge of the frequency dependence of compressional wave properties in marine sediments, the nature of which is still under debate. The use of in situ probes to measure sediment acoustic properties introduces a number of experimental difficulties that must be overcome. To this end, a series of well-constrained in situ acoustic transmission experiments were undertaken on intertidal sediments using a purpose-built in situ device, the Sediment Probing Acoustic Detection Equipment (SPADE). Compressional wave speed and attenuation coefficient were measured from 16 to 100 kHz in medium to fine sands and coarse to medium silts. Spreading losses, which were adjusted for sediment type, were incorporated into the data processing, as were a thorough error analysis and an examination of the repeatability of both the acoustic wave emitted by the source and the coupling between probes and sediment. Over the experimental frequency range and source-to-receiver (S-R) separations of 0.99-8.1 m, resulting speeds are accurate to between 1.1% and 4.5% in sands and less than 1.9% in silts, while attenuation coefficients are accurate to between 1 and 7 dBm in both sands and silts. Preliminary results indicate no speed dispersion and an attenuation coefficient that is proportional to frequency. 相似文献
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南黄海海底沉积物声学特性及其影响因素试验研究 总被引:5,自引:2,他引:3
利用自南黄海中西部海底取回的沉积物样品,对其声学特性及其影响因素进行了试验研究,结果显示,研究区海底沉积物的压缩波速为1.359 ~1.695 km/s,剪切波速为12.5 ~70.9 m/s;颗粒较细的沉积物与较低的压缩波速、剪切波速对应,主要集中在研究区东侧水深较深处;沉积物的物理力学性质对其压缩波速、剪切波速的影响较显著,沉积物的温度和换能器的频率对上述声学两参数也具有一定的影响,而沉积物的包含物及薄夹层等影响声波传播的理论计算结果。给出了研究区海底沉积物物理力学各参数与压缩波速、剪切波速之间的回归方程,以期为国防、工程提供基础资料。 相似文献
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Mid- to High-Frequency Acoustic Penetration and Propagation Measurements in a Sandy Sediment 总被引:2,自引:0,他引:2
《Oceanic Engineering, IEEE Journal of》2009,34(4):372-387
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Biot反演在夏威夷钙质沉积物原位测量声速和衰减中的应用 总被引:9,自引:1,他引:9
对夏威夷檀香山岛的两个站(H3和H4)钙质沉积物进行了20~100kHz的原位纵波声速和声衰减测量.它们均有轻微的频散.随频率的增加H3站位声速从1691m/s增加到1708m/s,H4站位的声速从1579m/s增加到1585m/s.随频率的增加H3站位的有效衰减从15dB/m增加到75dB/m,H4站位的有效衰减从22dB/m增加到62dB/m.运用Biot-Stoll模型对所测得的纵波速度和声衰减数据进行了Biot模型未知参数反演,发现粒径较大的H3站的沉积物(孔隙率为45%)比粒径较小的H4站的沉积物(孔隙率为56%)具有曲率小和渗透率及孔隙半径都大的性质. 相似文献
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中国黄渤海沉积物声速与物理性质研究 总被引:1,自引:0,他引:1
In order to investigate the correlation between a sound velocity and sediment bulk properties and explore the influence of frequency dependence of the sound velocity on the prediction of the sediment properties by the sound velocity,a compressional wave velocity is measured at frequencies of 25–250 k Hz on marine sediment samples collected from the Bohai Sea and the Yellow Sea in laboratory,together with the geotechnical parameters of sediments.The results indicate that the sound velocity ranges from 1.232 to 1.721 km/s for the collected sediment samples with a significant dispersion within the series measuring frequency.Poorly sorted sediments are highly dispersive nearly with a positive linear relationship.The porosity shows a better negative logarithmic correlation with the sound velocity compared with other geotechnical parameters.Generally,the sound velocity increases with the increasing of the average particle size,sand content,wet and dry bulk densities,and decreasing of the clay content,and water content.An important point should be demonstrated that the higher correlation can be obtained when the measuring frequency is low within the frequency ranges from 25 to 250 k Hz since the inhomogeneity of sediment properties has a more remarkably influence on the laboratory sound velocity measurement at the high frequency. 相似文献
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Jian-Jun Long 《Marine Georesources & Geotechnology》2013,31(2):176-189
Seabed sediment microstructure has an influence on its acousto-physical properties, and the properties in a length of the sediment column reflect an aspect of the macroscopic behavior of the microstructure. An original measurement method of the sound attenuation within small distance cross sections in a sediment column, and the corresponding approach in data processing to attain an attenuation factor are detailed in the paper. This method was used to measure the compressional wave in series of points with a small distance in the sediment column, and it is shown that exponential attenuation is a type of compressional wave attenuation model for a sediment column in its full length. It indicates that there are various models of compressional wave attenuation in seabed sediments in the South China Sea after comparison of data from other literature. The method of measuring sound attenuation satisfies the sampling space interval in the acoustical forward and inverse problems in seabed sediments, and the original method provides a new approach for finding out sound attenuation mechanism in seabed sediments on small length scale. 相似文献
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A new system for logging the geophysical properties of marine sediment cores allows both whole cores and split cores to be
measured in a nondestructive fashion. The current sensor configuration measures compressional (P) wave velocity (500 kHz),
bulk density (using gamma-ray attenuation), and magnetic susceptibility at user-defined sample intervals down the core. Split-core
logging gives more reliable results than whole core logging as it mostly eliminates core-slumping effects that can lead to
spurious results; it also gives higher resolution magnetic susceptibility readings.
Received: 16 May 1997 / Revision received: 24 October 1997 相似文献
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A technique for measuring in-situ compressional wave speed dispersion in marine sediments 总被引:1,自引:0,他引:1
Compressional speed dispersion exists in all marine sediments. If the dispersion is great enough it may play a significant role in acoustic interaction with the seabed. On the other hand if dispersion is weak, seabed models and databases can be substantially simpler. The ocean acoustics community is divided on this issue, in part because of the lack of observations. One of the experimental challenges has been to measure speed over several decades of frequency using a single technique so that observed speed changes cannot be due to different biases in the techniques. A simple in-situ experimental approach was developed that measures the critical angle as a function of frequency and thus infers the speed dispersion. Measurements on the mid to outer continental shelf (Malta Plateau and the New Jersey Shelf STRATAFORM area) show a weak dispersion over the band from /spl sim/10/sup 2/-10/sup 4/ Hz. This implies (via the Kramers-Kronig relations) that the compressional wave attenuation for these sediments is small and/or approximately linear over this band. 相似文献
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Comparison of sound speed and attenuation measured in a sandy sediment to predictions based on the Biot theory of porous media 总被引:2,自引:0,他引:2
Williams K.L. Jackson D.R. Thorsos E.I. Dajun Tang Schock S.G. 《Oceanic Engineering, IEEE Journal of》2002,27(3):413-428
During the sediment acoustics experiment in 1999 (SAX99), several researchers measured sound speed and attenuation. Together, the measurements span the frequency range of about 125 Hz-400 kHz. The data are unique both for the frequency range spanned at a common location, and for the extensive environmental characterization that was carried out as part of SAX99. Environmental measurements were sufficient to determine or bound the values of almost all the sediment and pore water physical property input parameters of the Biot poroelastic model for sediment. However, the measurement uncertainties for some of the parameters result in significant uncertainties for Biot-model predictions. Here, measured sound-speed and attenuation results are compared to the frequency dependence predicted by Biot theory and a simpler "effective density" fluid model derived from Biot theory. Model/data comparisons are shown where the uncertainty in Biot predictions due to the measurement uncertainties for values of each input parameter are quantified. A final set of parameter values, for use in other modeling applications e.g., in modeling backscattering (Williams et al., 2002) are given, that optimize the fit of the Biot and effective density fluid models to the sound-speed dispersion and attenuation measured during SAX99. The results indicate that the variation of sound speed with frequency is fairly well modeled by Biot theory but the variation of attenuation with frequency deviates from Biot theory predictions for homogeneous sediment as frequency increases. This deviation may be due to scattering from volume heterogeneity. Another possibility for this deviation is shearing at grain contacts hypothesized by Buckingham; comparisons are also made with this model. 相似文献