共查询到19条相似文献，搜索用时 125 毫秒
1.
2.
对地球物理中的非线性反演问题进行了讨论，地球物理反演通常涉及有限参数空间的最优问题，一个地球模型由一组参数描述其一个或多个地球物理性质（例如，穿过地球内部的弹性波速度）。地球模型是在一定的限制条件下，寻找模型预测值和观测值之间的最小失配。最优问题通常是非线性或非线性极强的反演问题，经常导致失配空间出现多重极小，在过去的10年里，全局（随机）最优方法得到了广泛应用，有关模拟退火、遗传算法和进化程序法的讨论已出现在有关的地球物理专业文献中。但是，这些方法在对各参数解的约束评价方面没有引起足够的重视，通常很少涉及这类问题。这里给出一类新的方法，该方法在反演的最优化和误差分析方面均具有潜力。新的方法使用的是计算几何的概念。这里描述的搜索方法对10维以上的问题不太适用。 相似文献
3.
4.
逐步缩小搜索范围的遗传算法 总被引：16，自引：3，他引：16
本文介绍在遗传算法的运行过程中如何逐步缩小搜索范围，使搜索速度与计算精度同时得到提高的方法。文中提出了真值邻域的概念，利用这个概念得到了缩小搜索范围的压缩公式。只要合理选择初始搜索范围（这一点并不难做到），上述压缩公式能确保问题的解始终保留在压缩后的搜索范围内。通过理论模型的检验及与原有遗传算法结果的比较，证实了方法的有效性。 相似文献
5.
提出了一种新的非导数搜索方法，用于在多维参数空间中寻找可较好地拟合观测数据的模型，该方法与模拟退火和遗传算法同属一类，一般情况下，模拟退火和遗传算法是用于解决全局最优问题的。这里的目是寻找参数空间中对数据拟合较好域进行优先采样的模型集合，而不是寻找单一的最优模型（相关的文章涉及集合的定量评价）。新的搜索算法利用Voronoi单元的几何建造在参数空间引导搜索，这些单元是根据适当的距离标准定义的最临近区域，算法的概念是简单的，仅需两个调节参数，并且只使用数据的秩拟合准则，而不是数据值，这样避免了与数据失配函数缩放比例相关的一些困难，并能使用任意组合的数据拟合标准，通过不时地使用最相邻的计算代替正演模拟计算，也显示出了Voronoi单元是如何能增强任何现有直接搜索方法的性能的。通过对理论模型的地壳地震结构接收函数反演的应用，对新的直接搜索算法进行了解释，众所周知，这是一个非线性问题，线性化反演技术强烈地依赖于初始解，新的算法生成复杂的自适应搜索行为，据我们所知以前的算法不具有这种功能。 相似文献
6.
随着并行计算技术的发展,非线性反演计算效率在不断提高,但对于基于单点搜索的非线性反演方法,其并行算法的实现则是一个难题。本文将群体搜索的思想引入到基于单点搜索的非线性反演方法,构建了并行算法,以量子蒙特卡罗方法为例进行了二维地震波速度反演及实际资料波阻抗反演,并测试了使用不同节点数进行计算的效率。计算结果表明:该并行算法在理论和实际资料反演中是可行的和有效的,具有很好的通用性;算法计算效率随着使用节点数的增加而提高,但算法计算效率的提高幅度随着使用节点数的增加逐渐减小。 相似文献
7.
地震救助生命搜索与定位技术研究进展 总被引：1，自引：0，他引：1
生命搜索是地震紧急救援中最重要的问题，由于时间紧迫、环境条件恶劣也是最困难的问题。先进的技术与装备是提高救助成功率，最大限度减轻人员伤亡的技术保障。本文简要介绍了利用国内外目前较为成熟的相关技术，研制开发光学探生仪、声波／振动探生仪、红外热像仪3种先进、轻便、高效、实用的地震救助现场生命搜索与定位技术设备，以及利用系统工程学原理和现代管理理论，开展地震灾害现场生命搜索与救援支持系统的研究，从而初步建立地震救助生命搜索定位技术系统的基本情况。 相似文献
8.
对于借助重力异常进行密度反演来说,一旦反演方法确定,影响反演效果的主要因素在于反演参数和剖分方案的选择,合理的反演参数及剖分方案不仅能够提高反演方法的效率,更能保证反演结果的精度。基于相关系数搜索的黄金分割重力反演方法是位场反演中的物性分布反演的有效方法之一,可用于平地表及起伏地表上的二度体和三度体的物性反演。本文讨论了利用相关搜索黄金分割进行剩余密度反演的基本原理,提出了试探法判断反演结果是否为全局最优,并通过模型试验给出了各反演参数及剖分方案的合理选取原则,提高了剩余密度反演的精度。 相似文献
9.
单台地震自动定位网格搜索法及其MATLAB试验 总被引：3，自引：3，他引：0
提出了一种利用单个地震台站三分向数字地震波形记录进行单台地震自动定位的网格搜索法。该方法以台站为中心,建立辐射状网格,按可变震中距步长和方位角步长进行搜索。对一个检测到的地震事件记录波形,对每个震中距,计算预测波形特征函数与记录波形特征函数的互相关函数值,选其最大值对应的震中距;对每个方位角,合成沿径向和沿横向的波形分量,并计算P波段的径向绝对积分值与横向绝对积分值之差,选其最大值对应的方位。对于选定的方位,如果合成的径向分量与记录垂直分量乘积在P波段的积分值为负,则取该方位角为震中相对于台站的方位角,否则该角要加上180°。在MATLAB环境中对该方法的基本步骤进行了试验,初步结果表明该方法是可行的。 相似文献
10.
基于人工蜂群算法的边坡最危险滑动面搜索 总被引：1，自引：0，他引：1
将用于连续数值优化问题的人工蜂群算法引入边坡稳定分析临界滑动面搜索领域。该方法模拟了蜂群的群体协作采蜜过程,具有自适应收敛的特点,克服了传统方法容易陷入局部最优的缺点,是一种全局优化算法。为进一步改善其在复杂边坡搜索中的效果,将Hooke-Jeeves模式搜索操作引入人工蜂群算法,提出一种用于边坡临界滑动面搜索的模式搜索人工蜂群算法。对土石坝、海堤等4个实例边坡的计算结果表明,人工蜂群算法是一种简洁、高效的边坡临界滑动面搜索方法;对于复杂边坡,所提出算法具有更高的收敛精度和可靠性,为边坡稳定分析临界滑动面搜索和最小安全系数的计算提供了一种新的全局求解策略。 相似文献
11.
12.
Improved Monte Carlo inversion of surface wave data 总被引：2，自引：0，他引：2
Inversion of surface wave data suffers from solution non‐uniqueness and is hence strongly biased by the initial model. The Monte Carlo approach can handle this non‐uniqueness by evidencing the local minima but it is inefficient for high dimensionality problems and makes use of subjective criteria, such as misfit thresholds, to interpret the results. If a smart sampling of the model parameter space, which exploits scale properties of the modal curves, is introduced the method becomes more efficient and with respect to traditional global search methods it avoids the subjective use of control parameters that are barely related to the physical problem. The results are interpreted drawing inference by means of a statistical test that selects an ensemble of feasible shear wave velocity models according to data quality and model parameterization. Tests on synthetic data demonstrate that the application of scale properties concentrates the sampling of model parameter space in high probability density zones and makes it poorly sensitive to the initial boundary of the model parameters. Tests on synthetic and field data, where boreholes are available, prove that the statistical test selects final results that are consistent with the true model and which are sensitive to data quality. The implemented strategies make the Monte Carlo inversion efficient for practical applications and able to effectively retrieve subsoil models even in complex and challenging situations such as velocity inversions. 相似文献
13.
MAHBOUB AL-CHALABI 《Geophysical Prospecting》1972,20(1):1-16
The interpretation of a gravity anomaly in terms of the shape of the anomalous body is a non-linear problem and may, therefore, be carried out using non-linear optimisation techniques. The formulation is extended to include cases where the density contrast and the regional background are also unknown. For a given model the objective function is provided by the discrepancy between the observed anomaly and the calculated anomaly due to the model. Given an initial model, the optimisation procedure searches for a minimum of the objective function by an iterative adjustment of the parameters. A number of suitable objective functions is given. The behaviour of these functions in the parameter hyperspace is quite complex. Accordingly, direct search methods should be employed at the early stages of the search, changing to gradient methods at later stages. The use of constraints is also necessary to ensure the geological feasibility of the model. The required computer time may be largely reduced by careful programming. Two examples of interpretation by optimisation methods are given. 相似文献
14.
Hartvig Christie 《Marine pollution bulletin》1985,16(6):232-235
Excluding the most polluted areas, a general problem to handle in an ecological monitoring context is the recognition of pollution-induced changes as opposed to natural variations always occurring in marine communities. In the search for solutions to this problem, a combination of different methods is suggested. The use of basic ecological community studies, comparison of common patterns on a broad geographical scale, and making predictions from short and long term trend models are the methods that have been tried and discussed. Ecological knowledge and comparison of common patterns are here suggested as the most fruitful tools in an ecological monitoring programme. 相似文献
15.
动态遗传算法及其在P波初动震源机制解中的应用 总被引：9，自引：0，他引：9
利用动态遗传算法对Ｐ波初动震源机制解进行反演计算，并与前人常用的反演计算方法对比，认为遗传算法在Ｐ波初动 震源机制解中的应用是有很有效的。 相似文献
16.
Surface wave methods are becoming increasingly popular in many geotechnical applications and in earthquake seismology due to their noninvasive characteristics.Inverse surface wave dispersion curves are a crucial step in most surface wave methods.Many inversion methods have been applied to surface wave dispersion curve inversion,including linearized inversion and nonlinearized inversion methods.In this study,a hybrid inversion method of Damped Least Squares(DLS) with Very Fast Simulated Annealing(VFSA) is developed for multi-mode Rayleigh wave dispersion curve inversion.Both synthetic and in situ fi eld data were used to verify the validity of the proposed method.The results show that the proposed method is superior to the conventional VFSA method in aiming at global minimum,especially when parameter searching space is adjacent to real values of the parameters.The advantage of the new method is that it retains both the merits of VFSA for global search and DLS for local search.At high temperatures,the global search dominates the runs,while at a low temperatures,the local search dominates the runs.Thus,at low temperatures,the proposed method can almost directly approach the actual model. 相似文献
17.
A. Boud 《Journal of Geodynamics》1987,7(3-4)
Interdisciplinary interpretation of satellite and geologic-geophysical data can be applied to East Africa as a cost-effective means of regional tectonic evaluation. All available data sources: geologic and geophysical maps and remote sensing images should be used. Remote sensing methods are very efficient for the “synoptic overlook” necessary to pinpoint areas for more detailed investigation.The use of satellite imagery is a way of applying and testing structural frameworks for mineral potential as surface reflections of deep tectonic features can be recognized. Mineralization can be correlated with tectonic lineaments that are probably related to persistent discontinuities in the upper mantle. The outlining of these discontinuities would be of value in the search for the understanding of riftogenesis and in the search for mineralization.This paper is a review of such work with a specific example from Canada, and how the approach can be applied to Africa for continuing research on recent crustal movements. 相似文献
18.
At-sea detection of marine debris: overview of technologies, processes, issues, and options 总被引：1，自引：0，他引：1
Mace TH 《Marine pollution bulletin》2012,65(1-3):23-27
At-sea detection of marine debris presents a difficult problem, as the debris items are often relatively small and partially submerged. However, they may accumulate in water parcel boundaries or eddy lines. The application of models, satellite radar and multispectral data, and airborne remote sensing (particularly radar) to focus the search on eddies and convergence zones in the open ocean appear to be a productive avenue of investigation. A multistage modeling and remote sensing approach is proposed for the identification of areas of the open ocean where debris items are more likely to congregate. A path forward may best be achieved through the refinement of the Ghost Net procedures with the addition of a final search stage using airborne radar from an UAS simulator aircraft to detect zones of potential accumulation for direct search. Sampling strategies, direct versus indirect measurements, remote sensing resolution, sensor/platform considerations, and future state are addressed. 相似文献
19.
Anders U. Waldeland Tiago A. Coimbra Jorge H. Faccipieri Anne H. Schistad Solberg Leiv-J. Gelius 《Geophysical Prospecting》2019,67(5):1163-1183
We present a method for fast estimation of finite offset common reflection surface parameters. Firstly, the derivatives with respect to offset are derived from the velocity guide. Secondly, we apply structure tensors to extract the derivatives with respect to midpoint from stacked common offset sections. Finally, the mixed derivative is estimated using a one-parametric semblance search. The proposed method is compared to the global five-parametric semblance search and the pragmatic sequential two-parametric semblance search on one synthetic and one real data set. The experiments show that the proposed method is more robust against noise than the pragmatic search and have comparable robustness with the global search. The proposed method smoothes parameter estimates in a local window, and the window size is set to give the best trade-off between detail and robustness. Since the proposed method is dependent on a velocity guide, the quality of the other parameter estimates may be influenced by any inaccuracies in the guide. The main advantage of the proposed method is the computational efficiency. When compared with a gridded implementation of the semblance search, the proposed method is 10 and 400 times faster than the pragmatic and global search. Alternative search strategies significantly reduce the computational cost of the global search. However, since more than 99% of the computational cost of the proposed method comes from the semblance search to estimate the mixed derivative, it is expected that such techniques also reduce the computational cost for the proposed method. 相似文献