共查询到19条相似文献，搜索用时 125 毫秒
1.
为了提高定位算法的环境宽容性,聚焦法将环境参数纳入了寻优空间。聚焦法虽然降低了对环境测量的要求,但是反演参数的增加也增加了反演的复杂性。基于海底反射特性,用两个参数对海底进行建模。通过标准的反演测试问题对简化地声模型在浅海聚焦定位中的有效性进行了分析。结果表明:基于简化地声模型的聚焦定位是可行的。在获得正确定位结果的同时,随着地声参数个数的减少,匹配场处理的便捷性得到了提高。文中引入的简化地声模型是聚焦问题中参数最少的地声模型,它可以有效减少聚焦定位参数维数以提升反演的便捷性。同时,简化地声模型在参数敏感性和耦合性上有较好的表现,这些优点可以保证定位结果的稳健性。 相似文献
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浅海海底声参数是影响声场传播的重要参量。文中根据信号的相位特性对反演稳定性的影响进行了数值模拟;并于2002年8月在黄海海区进行了海底声参数反演实验。利用垂直入射脉冲和海底回波数据进行海底声参数反演,由于海底回波信号随穿透深度增加而导致回波信号的信噪比降低,为了有效地增加海底声阻抗反演深度,提出平滑分段抽取冲激响应,重建声阻抗剖面的方法。结合Hamilton经验公式,分离海底声速、密度,反演结果与海底采样样本分析值、经验值吻合较好。 相似文献
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两种基于贝叶斯点估计理论的多声源定位方法研究 总被引：1，自引：1，他引：0
海洋环境参数失配是制约匹配场定位性能的主要因素之一。为了克服环境失配，本文基于贝叶斯理论，将环境参数与声源的距离和深度一起作为未知量进行反演。然而在进行多声源定位时，反演参数的维数几何增长，极大地增加了反演问题的复杂性和计算量。为此本文将声源强度和噪声方差表示成其极大似然估计值，从而将这些参数进行隐式采样，大大降低了反演的维数和难度。文章比较了两种贝叶斯点估计方法，最大后验概率密度方法和最大边缘后验概率密度方法。最大后验概率密度方法的解是令后验概率密度取得最大值的参数组合，可以利用优化算法快速获得。最大边缘后验概率密度法将其他参数积分，得到目标参数的一维边缘概率分布，分布的最大值为反演结果。该方法得到最优估计值的同时可以获取参数估计的不确定信息。在环境参数和声源参数都未知的情况下，利用蒙特卡洛法在不同信噪比情况下对两种声源定位方法进行分析，实验结果表明：(1)对于敏感参数，如声源距离、水深和海水声速，最大边缘后验概率密度法比最大边缘后验概率密度方法的性能好。(2)对于较不敏感的参数，如海底声速、海底密度和海底声衰减，当信噪比较低时，最大边缘后验概率密度方法能较好地平滑噪声，从而比最大边缘后验概率密度法具有更好的性能。由于声源距离和深度是敏感参数，研究表明最大边缘后验概率密度法提供了一种在不确知环境下更可靠的多声源定位方法。 相似文献
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本文基于Amarouche的二阶理论回波模型,导出了带有偏度系数的二阶理论回波模型;针对HY-2A卫星高度计波形特点,引入了奇异值分解滤波,并根据最大似然估计算法反演参数的不同得到6种重跟踪方案;利用其中的五参数方案处理该波形数据,获得海面散射点高度概率密度函数中偏度的合理取值为0.15;将结果分别与浮标、Jason-1和HY-2AIDR有效波高对比,分析6种方案反演有效波高的准确度,确定了MLE4_SVD(波形重跟踪之前进行滤波)对HY-2A高度计重跟踪更适合反演有效波高。 相似文献
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浅地层剖面仪发射的声脉冲能够穿透海底面进入沉积层内部,其回波中携带了丰富的底质信息。地声模型是底质声学与物理性质关系的数学描述,广泛用于海底声学与地声反演研究。本文通过对浅地层剖面数据的处理、解译得到海底反射系数,与考虑底质松密影响的改进Biot-Stoll模型相结合,提出底质反演新方法并开展实例验证。研究结果表明：通过对浅地层剖面原始记录的读取、解译,提取反射波振幅,并结合设备声源级,可有效求取海底反射系数。通过引入相对密度改进孔隙度计算公式,进而在基于Biot-Stoll模型构建海底反射系数和底质平均粒径关系过程中进一步考虑了底质松密的影响。基于山东威海某海域及文献的算例均显示,本文提出的改进地声模型可缩小底质反演与实测结果之间的相对误差、提升基于浅地层剖面数据的海底底质地声反演精度。 相似文献
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本文通过对南海海底沉积物样品的声学物理参数和沉积粒度特征统计分析，发现了高、低含砂量沉积物的声学物理特征存在明显差异，建立了海底沉积物的含砂量与压缩波速度、孔隙度、含水量和密度等经验公式，分析了含砂量变化与沉积物的体积压缩模量和密度变化的关系，从声速理论基础上阐明了含砂量变化引起沉积物压缩波速度变化的内在原因是含砂量变化引起了体积压缩模量和密度发生了变化，说明了含砂量增大引起沉积物压缩波速度增大的内在原因是含砂量增大引起了体积压缩模量变化量大于密度变化量，从而在数据统计和理论分析结合基础上，论证了含砂量是影响海底沉积物压缩波速度的重要因素之一。这一研究对声学方法反演海底沉积物粒度参数和沉积物类型、地声参数转换模型的建立，以及对水声反演海底和海底资源勘探等方面都具有重要理论意义和应用价值。 相似文献
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提出1种将消频散变换应用到海底地声参数反演的方法。对单一水听器接收声压信号进行消频散处理后,根据群延时差建立代价函数,反演得到主要海底参数,最后根据贝叶斯统计理论给出了待反演地声参数的边缘后验概率密度。对单层波导进行仿真证明这种新方法的有效性。 相似文献
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《应用海洋学学报》2015,(4)
根据2014年在南中国海开展声学试验的定深爆炸宽带声信号数据进行海底地声参数反演.考虑到不同海底声参数对不同声场物理参数的敏感程度不同以及不同海底声参数对不同反演方法的敏感程度亦不同,综合应用2种反演方法得到不同底质声参数:(1)根据接收的直达波和海底反射波计算得到关注海域的海底反射系数进而反演得到海底声阻抗;(2)实验海区的海底地形为大陆坡,选取Hamilton总结的关于沉积物声速与沉积物密度关系的经验公式,结合沉积物声阻抗与沉积物声速、沉积物密度的关系,进而反演得到沉积物声速和沉积物密度.沉积物声学参数的取样测量是在实验室条件下进行的,温度为23℃,大气压1×105Pa,由于沉积物孔隙海水是决定沉积物声速的关键且受温度压强变化的影响显著,本研究利用沉积物声速与孔隙海水声速的比值即使在温度压强变化的情况下较稳定的特点,可对沉积物声速在实验室条件和海底原位条件进行校正.校正到海底温度和压强后,反演结果与沉积物取样的实测结果和Hamilton总结的结果吻合得相当好:(1)声阻抗的反演结果为2.065 6×10~5g/(cm2·s),修正后的沉积物取样结果则为2.046 0×10~5g/(cm~2·s),Hamilton总结的结果为2.238 0×10~5g/(cm~2·s);(2)声速的反演结果为1 482.6m/s,修正后的沉积物取样结果为1 467.5 m/s,Hamilton总结的结果为1 502.8 m/s;(3)密度的反演结果为1.393 2 g/cm3,沉积物取样结果为1.400 0 g/cm~3,Hamilton总结的结果为1.489 0 g/cm3. 相似文献
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In this paper, we use matched-field inversion methods to estimate the geoacoustic parameters for three synthetic test cases from the Geoacoustic Inversion Techniques Workshop held in May 2001 in Gulfport, MS. The objective of this work is to use a sparse acoustic data set to obtain estimates of the parameters as well as an indication of their uncertainties. The unknown parameters include the geoacoustic properties of the sea bed (i.e., number of layers, layer thickness, density, compressional speed, and attenuation) and the bathymetry for simplified range-dependent acoustic environments. The acoustic data used to solve the problems are restricted to five frequencies for a single vertical line array of receivers located at one range from the source. Matched-field inversion using simplex simulated annealing optimization is initially used to find a maximum-likelihood (ML) estimate. However, the ML estimate provides no information on the uncertainties or covariance associated with the model parameters. To estimate uncertainties, a Bayesian formulation of matched-field inversion is used to generate posterior probability density distributions for the parameters. The mean, covariance, and marginal distributions are determined using a Gibbs importance sampler based on the cascaded Metropolis algorithm. In most cases, excellent results were obtained for relatively sensitive parameters such as wave speed, layer thickness, and water depth. The variance of the estimates increase for relatively insensitive parameters such as density and wave attenuation, especially when noise is added to the data. 相似文献
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This paper presents the results obtained using the adaptive simulated annealing (ASA) algorithm to invert the test cases from the Geoacoustic Inversion Techniques Workshop held in May 2001. The ASA algorithm was chosen for use in our inversion software for its speed and robustness when searching the geoacoustic parameter solution space to minimize the difference between the observed and the modeled transmission loss (TL). Earlier work has shown that the ASA algorithm is approximately 15 times faster than a modified Boltzmann annealing algorithm, used in prior versions of our TL inversion software, with comparable fits to the measured data. Results are shown for the synthetic test cases, 0 through 3, and for the measured data cases, 4 and 5. The inversion results from the synthetic test cases showed that subtle differences between range-dependent acoustic model version 1.5, used to generate the test cases, and parabolic equation (PE) 5.0, used as the propagation loss model for the inversion, were significant enough to result in the inversion algorithm finding a geoacoustic environment that produced a better match to the synthetic data than the true environment. The measured data cases resulted in better fits using ASTRAL automated signal excess prediction system TL 5.0 than using the more sophisticated PE 5.0 as a result of the inherent range averaging present in the ASTRAL 5.0 predictions. 相似文献
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Matched-fieId inversion (MFI) undertakes to estimate the geometric and geoacoustic parameters in an ocean acoustic scenario by matching acoustic field data recorded at hydrophone array with numerical calculations of the field. The model which provides the best fit to the data is the estimate of the actual experimental scenario. MFI provides a comparatively inexpensive method for estimating ocean bottom parameters over an extensive area. The basic components of the inversion process are a sound propagation model and matching (minimization) algorithm. Since a typical MFI problem requires a large number of computationally intensive sound propagation calculations, both of these components have to be efficient. In this study, a hybrid inversion algorithm which uses a parabolic equation propagation model and combines the downhill simplex algorithm with genetic algorithms is introduced. The algorithm is demonstrated on synthetic range-dependent shallow-water data generated using the parabolic equation propagation model. The performance for estimating the model parameters is compared for realistic signal-to-noise ratios in the synthetic data 相似文献
14.
《Oceanic Engineering, IEEE Journal of》2009,34(1):51-62
15.
Estimates of geoacoustic model parameters from inversions of horizontal and vertical line array data
This paper describes results from geoacoustic inversion of low-frequency acoustic data recorded at a receiving array divided into two sections, a sparse bottom laid horizontal array (HLA) and a vertical array (VLA) deployed in shallow water. The data are from an experiment conducted by the Norwegian Defence Research Establishment (FFI) in the Barents Sea, using broadband explosives (shot) sources. A two-layer range-independent geoacoustic model, consistent with seismic profiles from the area, described the environment. Inversion for geoacoustic model parameters was carried out using a fast implementation of the hybrid adaptive simplex simulated annealing (ASSA) inversion algorithm, with replica fields computed by the ORCA normal mode code. Low-frequency (40-128 Hz) data from six shot sources at ranges 3-9 km from the array were considered. Estimates of sediment and substrate p-wave velocities and sediment thickness were found to be consistent between independent inversions of data from the two sections of the array. 相似文献
16.
Matched-field inversion is used to, estimate geoacoustic properties from data obtained in an experiment with a vertical line array (VLA). The experiment was carried out using broad-band sources (shots) in water depths of about 200 m on the continental shelf off Vancouver Island. The data were processed to obtain spectral components of the field for frequencies near the bubble frequency for the shot. The ocean bottom in this region consists of a layer of mainly sandy sediments (about 100 m thick) overlying older consolidated material. Consequently, the inversion was designed to estimate the parameters of a two-layer elastic sediment model. In the inversion, an adaptive global search algorithm was used to investigate the multidimensional space of geoacoustic models in order to determine the set of values corresponding to the best replica field. Convergence is driven by adaptively guiding the search to regions of the parameter space associated with above-average values of the matched field correlation between the measured and replica fields. The geoacoustic profile estimated by the inversion consisted of a 125-m layer with compressional speed ~1700 m/s and shear speed ~400 m/s, overlying a layer with compressional speed ~1900 m/s. This model is consistent with the results from conventional seismic experiments carried out in the same region 相似文献
17.
A method is described for the estimation of geoacoustic model parameters by the inversion of acoustic field data using a nonlinear optimization procedure based on simulated annealing. The cost function used by the algorithm is the Bartlett matched-field processor (MFP), which related the measured acoustic field with replica fields calculated by the SAFARI fast field program. Model parameters are perturbed randomly, and the algorithm searches the multidimensional parameter space of geoacoustic models to determine the parameter set that optimizes the output of the MFP. Convergence is driven by adaptively guiding the search to regions of the parameter space associated with above-average values of the MFP. The performance of the algorithm is demonstrated for a vertical line array in a shallow water enviornment where the bottom consists of homogeneous elastic solid layers. Simulated data are used to determine the limits on estimation performance due to error in experimental geometry and to noise contamination. The results indicate that reasonable estimates are obtained for moderate conditions of noise and uncertainty in experimental geometry 相似文献
18.
This paper presents an adaptive hybrid algorithm to invert ocean acoustic field measurements for seabed geoacoustic parameters. The inversion combines a global search (simulated annealing) and a local method (downhill simplex), employing an adaptive approach to control the trade off between random variation and gradient-based information in the inversion. The result is an efficient and effective algorithm that successfully navigates challenging parameter spaces including large numbers of local minima, strongly correlated parameters, and a wide range of parameter sensitivities. The algorithm is applied to a set of benchmark test cases, which includes inversion of simulated measurements with and without noise, and cases where the model parameterization is known and where the parameterization most be determined as part of the inversion. For accurate data, the adaptive inversion often produces a model with a Bartlett mismatch lower than the numerical error of the propagation model used to compute the replica fields. For noisy synthetic data, the inversion produces a model with a mismatch that is lower than that for the true parameters. Comparison with previous inversions indicates that the adaptive hybrid method provides the best results to date for the benchmark cases 相似文献
19.
Fallat M.R. Nielsen P.L. Dosso S.E. Siderius M. 《Oceanic Engineering, IEEE Journal of》2005,30(1):198-206
This paper examines geoacoustic inversion over a range-dependent multiple-layer seabed using a towed acoustic source and towed horizontal array. The approach is based on combining the results of a series of short-range, range-independent inversions to form a range-dependent representation of the environment. The data were collected in the Strait of Sicily during the MAPEX 2000 experiment. Issues such as the resolvability of multilayer structure and the sensitivity of various geoacoustic parameters are investigated by inversion of simulated data and by comparison of the MAPEX 2000 inversion results to a high-resolution seismic profile and to sediment core measurements. It appears that two, and in some cases possibly three, sediment layers can be resolved. 相似文献