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基于爆炸声传播时间的声速剖面反演 总被引:2,自引:0,他引:2
特征声线搜索以及传播时间测定的精确性是基于声传播时间的声速剖面反演的关键。在具有倾斜海底的三维海域,声线在海底的反射会导致水平偏转,给特征声线搜索和声传播时间计算带来了困难。为此,首先提出了一种三维空间特征声线搜索方法。通过对南海海洋环境反演实验数据的处理,分析了声线的水平偏转对声传播时间的影响,并用爆炸声传播时间作为代价函数,用量子粒子群算法作为优化算法进行了声速剖面反演。结果表明,海底坡度较大时,声线的水平偏转对声传播时间影响较大,考虑声线的水平偏转能有效地减小声传播时间计算的误差,进而使得声速剖面反演的精度得到显著提高。 相似文献
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利用吕宋海峡附近海区温盐数据的数值模型进行声传播模拟计算的方法,根据相应的声速剖面及声传播损失,分析台风对声传播特性的影响。结果显示,2010年第10号台风"莫兰蒂"过境时,海洋环境对台风的响应较为迅速,海洋表层的温度和盐度变化剧烈,而声速及传播损失的变化较温度盐度缓慢。分析表明:台风过境会导致表面声速减小,深海声道最小声速增大,声传播损失增大,深海声道原第一会聚区位置最小声能损失增大5 d B,台风过境导致声线第一反折点位置下移,第一会聚区消失,使声传播距离缩短。 相似文献
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起伏海底对浅海声传播有着极大影响。文章利用一次东海夏季水文数据,结合蒙特卡洛方法统计分析了浅海长距离起伏海底环境下的声场特性,并利用射线模型分析了海底起伏对声场不确定性影响的机理。结果表明,高频声波对海底起伏的变化更为敏感,传播损失的概率分布更为分散。负跃层环境下,当声源位于跃层下方时,起伏海底对位于跃层下方接收点的声传播影响更为明显。等温层环境下,起伏海底对声传播的影响相比于跃层环境影响更小。起伏海底的倾斜度越大,声传播损失越大。对于相同倾斜度的起伏海底,相对起伏的大小,即起伏海底高度与海深的比值,比起伏周期的变化对声传播的影响更大。 相似文献
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从岛礁斜坡地形条件下的声信号衰减和地形阻断效应分析出发,重点针对水下声场分布规律及其对声传播造成的影响开展研究。利用水声模型理论,结合某礁实测地形以及水文数据,建立岛礁斜坡地形下的多途声信道模型,基于Bellhop与RAM声学仿真方法,对不同地形下的声线轨迹、声传播损失以及信号时延等声场特性进行仿真分析,得出岛礁斜坡地形下的声场分布特征。研究结果表明:(1)岛礁斜坡地形是影响其声传播模式的关键因素;(2)斜坡外缘浅海区域的目标不易被岛礁斜坡顶端的声呐所探测; (3)陡坡地形对浅海声源的声传播有利,当声源深度足够大时,缓坡地形下的本征声线数目能够达到在陡坡地形下的5倍,对声传播有利。以上研究结果可为岛礁区水下声场的特性分析以及水下声学对抗等实践应用提供理论基础和技术参考。 相似文献
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针对海洋声速剖面测量成本高、长期观测困难的难题,文章初步研究了利用水下固定参考点与水面已知位置之间的声信号传播时延来反演海水声速剖面的方法,提出了一种等声速分层模型下的声速剖面反演方法。将海水分层,对声信号传播过程进行建模,推导反演声速的非线性方程组;再利用牛顿迭代法,对非线性方程组进行求解。通过仿真和海试试验数据处理,分层数不同时,反演声速与实际声速之间的误差随着分层数的增加而变小,声速误差最小为0.80 m·s-1左右,验证了反演方法的有效性与准确性。 相似文献
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L. Lages Martins A. Silva Ribeiro J. Alves e Sousa Alistair B. Forbes 《International Journal of Thermophysics》2012,33(8-9):1568-1582
This article describes the measurement uncertainty evaluation of the dew-point temperature when using a two-pressure humidity generator as a reference standard. The estimation of the dew-point temperature involves the solution of a non-linear equation for which iterative solution techniques, such as the Newton?CRaphson method, are required. Previous studies have already been carried out using the GUM method and the Monte Carlo method but have not discussed the impact of the approximate numerical method used to provide the temperature estimation. One of the aims of this article is to take this approximation into account. Following the guidelines presented in the GUM Supplement 1, two alternative approaches can be developed: the forward measurement uncertainty propagation by the Monte Carlo method when using the Newton?CRaphson numerical procedure; and the inverse measurement uncertainty propagation by Bayesian inference, based on prior available information regarding the usual dispersion of values obtained by the calibration process. The measurement uncertainties obtained using these two methods can be compared with previous results. Other relevant issues concerning this research are the broad application to measurements that require hygrometric conditions obtained from two-pressure humidity generators and, also, the ability to provide a solution that can be applied to similar iterative models. The research also studied the factors influencing both the use of the Monte Carlo method (such as the seed value and the convergence parameter) and the inverse uncertainty propagation using Bayesian inference (such as the pre-assigned tolerance, prior estimate, and standard deviation) in terms of their accuracy and adequacy. 相似文献
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This paper is concerned with the use of a Monte Carlo method for uncertainty calculation as an implementation of the propagation of distributions. It reviews the basic principles of the propagation of distributions and numerical aspects of a Monte Carlo implementation. It also discusses the possible advantages in some circumstances of the propagation of distributions over the GUM uncertainty framework, and how the results obtained in any particular instance can be compared with those provided by that framework. To illustrate these various aspects, an application to the measurement of neutron dose equivalent rate is given. A key consideration in this application is the manner in which the dominant source of uncertainty, namely that associated with the field-specific correction factor, is treated. The information available concerning this factor constitutes the correction factors for a set of fields of the same type as that in which a measurement is being made. This information is encoded as a probability density function (PDF) for the correction factor. This PDF constitutes an input to both methods of evaluation. 相似文献
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浅海海底模型对低频声传播的影响 总被引:1,自引:0,他引:1
海底参数特性是影响浅海低频水声传播的重要因素。理论上需要知道海底所有深度的参数特性才能确定水声传播,这在实践中很不现实。如果在误差的允许范围内只需要知道某个深度以上的海底参数特性,而这个深度以下的海底参数特性可以忽略,这个深度就定义为海底最大深度。低频声波能够穿透海底更深,最大深度能够达到几十米深,对比较高频率只有几米深。海水声速剖面也能影响声波穿透海底深度,声速剖面为负梯度时海底最大深度比等声速要深。在低频声传播过程中,海底横波对声场影响也很大,尤其是在超低频100Hz以下,2002年5月的南海试验也证实了这一点。 相似文献
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Earthquake loss estimation procedures exhibit aleatory and epistemic uncertainty imbedded in their various components; i.e. seismic hazard, structural fragility, and inventory data. Since these uncertainties significantly affect decision-making, they have to be considered in loss estimation to inform decision- and policymakers and to ensure a balanced view of the various threats to which society may be subjected. This paper reviews the uncertainties that affect earthquake loss estimation and proposes a simple framework for probabilistic uncertainty assessment suitable for use after obtaining impact results from existing software, such as HAZUS-MH. To avoid the extensive calculations required for Monte Carlo simulation-based approaches, this study develops an approximate method for uncertainty propagation based on modifying the quantile arithmetic methodology, which allows for acceptable uncertainty estimates with limited computational effort. A verification example shows that the results by the approximation approach are in good agreement with the equivalent Monte Carlo simulation outcome. Finally, the paper demonstrates the proposed procedure for probabilistic loss assessment through a comparison with HAZUS-MH results. It is confirmed that the proposed procedure consistently gives reasonable estimates. 相似文献
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随机浅海环境中声传播起伏的研究,对于随机海洋环境声场预报及海洋环境参数反演和遥测都有十分重要的意义。文中对随机浅海中声传播的简正波起伏进行了研究,利用L.B.Dozier统计耦合模式方程,通过MonteCarlo数值模拟分析声速场随机变化所产生的声场起伏规律。随机声速场模型由海上温度链测量数据统计规律分析得到。结果表明,声速场随机起伏所导致的简正波幅度起伏远高于声压的起伏;当声源处在某一阶简正波的敏感深度位置时,该阶简正波的闪烁系数会比简正波幅度起伏方差高2~3个量级;在所分析随机声速场模型下,声压起伏方差、简正波幅度起伏方差及简正波闪烁系数随距离的增加基本上是线性增大。 相似文献
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针对经验正交函数(Empirical Orthogonal Function,EOF)建模反演得到的声速剖面(Sound Speed Profile,SSP)估计值分辨率比较低的问题,文章采用字典学习方法中的K-奇异值分解(K-Singular Value Decomposition,K-SVD)算法生成声速剖面的非正交原子,研究了该方法生成的学习字典(Learning Dictionary,LD)对声速剖面的重建性能。首先,采用K-SVD算法从获得的数据中训练SSP字典,然后利用正交匹配追踪(Orthogonal Matching Pursuit,OMP)的稀疏方法给出训练信号的稀疏向量,最后通过得到的最优学习字典和稀疏向量反演得到SSP的估计值。结果表明,K-SVD算法比EOF算法使用更少的基函数即可很好地描述SSP的变化,获得更高的反演精度。 相似文献
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Badri Hiriyur Haim Waisman George Deodatis 《International journal for numerical methods in engineering》2011,88(3):257-278
An extended finite element method (XFEM) coupled with a Monte Carlo approach is proposed to quantify the uncertainty in the homogenized effective elastic properties of multiphase materials. The methodology allows for an arbitrary number, aspect ratio, location and orientation of elliptic inclusions within a matrix, without the need for fine meshes in the vicinity of tightly packed inclusions and especially without the need to remesh for every different generated realization of the microstructure. Moreover, the number of degrees of freedom in the enriched elements is dynamically reallocated for each Monte Carlo sample run based on the given volume fraction. The main advantage of the proposed XFEM‐based methodology is a major reduction in the computational effort in extensive Monte Carlo simulations compared with the standard FEM approach. Monte Carlo and XFEM appear to work extremely efficiently together. The Monte Carlo approach allows for the modeling of the size, aspect ratios, orientations, and spatial distribution of the elliptical inclusions as random variables with any prescribed probability distributions. Numerical results are presented and the uncertainty of the homogenized elastic properties is discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献