| 题名 | 海底地声参数的混合反演方法 |
| 作者 | 张学磊 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-27 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 混合反演方法 遗传算法 贝叶斯统计推断理论 后验概率密度 |
| 其他题名 | A hybrid geoacoustic inversion scheme |
| 学位专业 | 声学 |
| 中文摘要 | 地声参数，如海水中的声速分布、海底的声速、密度、衰减系数及分层结构，是浅海声场预报的关键环境参数。然而大部分地声参数（特别是声速和吸收系数）很难进行直接采样测量，且费用昂贵，因此声学反演方法受到了广泛的重视。本文针对地声参数反演问题进了研究。本文主要的工作及创新点包括以下几个方面： 1. 全面阐述了地声反演的流程。重点研究了全局优化算法性能的选取和性能改进。针对遗传算法（GA）早熟、局部搜索能力差的缺点，对GA进行了改进，使得改进后的遗传算法能较好的收敛于全局最优值。 2. 根据贝叶斯统计反演理论确定了地声反演中先验概率分布的选取方法，并对不同情况下的似然函数进行了推导，得到了不同条件下的似然函数。改进了待反演参数后验概率密度（PPD）的数值求解方法，使得在保证PPD计算精度的同时，大大提高速度。 3. 利用2005年和2006年在黄海进行的两次海上实验数据，提出了一种利用简正波频散特征，结合随距离连续的声传播损失，反演地声参数的混合反演方法，并用后验概率分析方法，对反演结果进行了有效性评估。首次尝试用实验船的航行辐射噪声反演了海底吸收系数，并得到了很好的结果。 4. 研究了用匹配场处理方法反演地声参数。数值分析了不同参数对声场的敏感性，并发现沉积层密度在某些频段对匹配场反演的代价函数较为敏感，这与以往的结论略有不同。根据参数敏感性不同，采用了用匹配场处理方法中进行分步反演，并通过数值仿真和实验数据验证了这种方法的可行性。 |
| 英文摘要 | Geoacoustic parameters including the profile of seabottom sound speed, density and attenuation coefficient, are the key environment parameters in predicting the acoustic phenomenon in shallow water. 1However, the geoacoustic parameters, especially the sound speed and the attenuation coefficient of seabottom, are really very hard to be measured directly. Moreover, the direct measurement is time-consuming and expensive. Therefore, the acoustic inversion method has been paid much attention. A hybrid geoacoustic inversion scheme is presented in this dissertation. The major contents and contributions are summarized as follows: 1. The process of geoacoustic inversion is given firstly. Much effort was given to improve the performance of global optimization algorithm (genetic algorithm, GA) to overcome its shortcomings, such as the prematurity and poor local search ability. The improved GA has a better convergence to the global optimum value than the original one. 2. Based on the Bayesian inversion theory, the a priori probability distribution for the geoacoustic inversion is selected, and the likelihood function under different conditions is derived. The modified version of numerical solution method of a posteriori probability density (PPD) in geoacoustic inversion is given. This modification can greatly enhance the computation speed of PPD and ensure computation accuracy. 3. A hybrid inversion scheme of geoacoustic parameters, which combines dispersion characteristics of normal modes with transmission loss, has been proposed based on the facts that different parameters have different effects on sound field. The scheme has been verified by using the data from two shallow water experiments conducted in the same ocean area. And the validity of inversion is evaluated by the PPD. It is worth to mention that the attenuation coefficient of seabottom was tentatively inverted using sound field radiated form a ship noise for the first time. 4. The sensitivities of ocean environment parameters on matched field processing inversion were numerically analyzed. It was found that the density of sediment may be very sensitive for some frequency bands in MFP inversion, which is different from the traditional results. Based on analysis results, a multistep inversion scheme using matched field processing was proposed, and the feasibility of the scheme was validated by numerical simulation and experimental data. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 59393 |
| 内容类型 | 学位论文 |
| 源URL | [http://159.226.59.140/handle/311008/452]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 张学磊. 海底地声参数的混合反演方法[D]. 声学研究所. 中国科学院声学研究所. 2009. |
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