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The nearest neighbor search algorithm is one of the major factors that influence the efficiency of grid interpolation. This paper introduces a KD-tree that is a two-dimensional index structure for use in grid interpolation. It also proposes an improved J-nearest neighbor search strategy based on ??priority queue?? and ??neighbor lag?? concepts. In the strategy, two types of J-nearest neighbor search algorithms can be used; these algorithms correspond to the consideration of a fixed number of points and a fixed radius. By using the KD-tree and proposed strategy, interpolation can be performed with methods such as Inverse Distance Weighting and Kriging. Experimental results show that the proposed algorithms has high operating efficiency, especially when the data amount is enormous, and high practical value for increasing the efficiency of grid interpolation. 相似文献
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It is well known that the trial process for seeking the safety factor in the shear strength reduction finite element method (SSRFEM) is quite expensive, particularly for large 3-D slope stability analyses. The search algorithm for the safety factor is crucial to the entire solution process for the shear strength reduction finite element method, but few studies have attempted to exploit it. Among search algorithms, the commonly used bracketing and bisection search has not been fully optimised. Consequently, to improve the search scheme for the safety factor associated with the shear strength reduction finite element method, two strategies are suggested. First, a generalised bisection search algorithm is proposed to reduce the possibility of encountering non-convergence from a statistical point of view. To further improve the efficiency, a new two-grid scheme, characterised by a coarse mesh search and followed by a fine mesh search, is developed. Based on the drained or undrained analyses of the 3-D slope examples, the new search algorithm can markedly outperform the commonly used bisection search algorithms based on a single finite element mesh. 相似文献
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Slope stability analysis of soil with a weak layer sandwiched between two strong layers is considered as a complex geotechnical problem. In this problem, the objective function is non‐convex and discontinuous with the presence of multiple strong local minima. Classical optimization techniques fail to converge to a valid solution unless a proper initial trial is adopted. Even though many new optimization algorithms have emerged, they have not been applied to geotechnical problems yet. In the present study, some recent swarm intelligence algorithms are adopted for some complicated example of slope stability problems and benchmarked with the traditional particle swarm optimization algorithm. From the results, it seems the levy flight krill herd algorithm is the most efficient method over proposed algorithms for this kind of problem. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Retaining wall optimization using interior search algorithm with different bound constraint handling 
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下载免费PDF全文 Along with the applicability of optimization algorithms, there are lots of features that can affect the functioning of the optimization techniques. The main purpose of this paper is investigating the significance of boundary constraint handling (BCH) schemes on the performance of optimization algorithms. To this end, numbers of deterministic and probabilistic BCH approaches are applied to one of the most recent proposed optimization techniques, named interior search algorithm (ISA). Apart from the implementing different BCH methods, a sensitivity analysis is conducted to find an appropriate setting for the only parameter of ISA. Concrete cantilever retaining wall design as one of the most important geotechnical problems is tackled to declare proficiency of the ISA algorithm, on the one hand, and benchmark the effect of BCH schemes on the final results, on the contrary. As results demonstrate, various BCH approaches have a perceptible impact on the algorithm performance. In like manner, the essential parameter of ISA can also play a pivotal role in this algorithm's efficiency. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Point-feature cartographic label placement (PFCLP) involves placing labels adjacent to their corresponding point features on a map. A widely accepted goal of PFCLP is to maximize the number of conflict-free labels. This paper presents an algorithm for PFCLP based on the four-slider (4S) model. The algorithm is composed of two phases: an initialization phase during which an initial solution is constructed by an exact algorithm and a heuristic method to maximize the probability of conflict-free labels. The initialization phase is followed by an improvement phase that adopts a backtracking greedy search. The exact algorithm can find a portion of the conflict-free labels in an optimal solution and an extension of the exact algorithm is provided that can find additional conflict-free labels. Computational tests were performed for instances based on standard sets. The two-phase algorithm generated better solutions relative to all methods previously reported in the literature. It also executes at a reasonable speed and is more stable than most other methods. 相似文献
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将一种新的启发式和谐搜索算法(harmony search algorithm,HS)引入到水文地质领域。在对其音节调整步骤进行改进的基础上,提出快速和谐搜索算法(Fast harmony search algorithm,FHS),并将FHS算法与MODFLOW结合,用于水文地质问题的参数识别。算例研究表明,FHS算法较其他多种算法具有更强的全局搜索能力、更快的收敛速度及求解精度,可用于地下水数值模型的参数反演。 相似文献
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地铁深基坑支护的遗传神经网络位移反分析 总被引：2，自引：0，他引：2
针对目前已有的各种位移反分析方法存在的缺陷,利用神经网络具有的非线性映射能力和遗传算法具有的全局随机搜索能力,提出了一种基于遗传神经网络进行深基坑支护的位移反分析方法。该方法改变了BP算法依赖梯度信息的指导来调整网络权值的方法,而是利用遗传算法全局性搜索的特点,寻找最合适的网络连接权和网络结构等来达到优化的目的。结合地铁深基坑支护位移计算,应用该方法对某一地铁深基坑土体的力学参数进行了反演。结果表明：将位移观测值作为网络输入数据,土体力学参数作为输出数据,在较大的解空间内,该位移反分析方法收敛速度快、解的稳定性好、反演结果精度高,是一种理想的位移反分析方法。最后,采用该软件结合一个工程实例实现了应用遗传神经网络进行的基坑支护位移反分析。 相似文献
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《地学前缘(英文版)》2016,7(1)
Proper quality planning of limestone raw materials is an essential job of maintaining desired feed in cement plant. Rock-type identification is an integrated part of quality planning for limestone mine. In this paper, a computer vision-based rock-type classification algorithm is proposed for fast and reliable identification without human intervention. A laboratory scale vision-based model was developed using probabilistic neural network(PNN) where color histogram features are used as input. The color image histogram-based features that include weighted mean, skewness and kurtosis features are extracted for all three color space red, green, and blue. A total nine features are used as input for the PNN classification model. The smoothing parameter for PNN model is selected judicially to develop an optimal or close to the optimum classification model. The developed PPN is validated using the test data set and results reveal that the proposed vision-based model can perform satisfactorily for classifying limestone rocktypes. Overall the error of mis-classification is below 6%. When compared with other three classification algorithms, it is observed that the proposed method performs substantially better than all three classification algorithms. 相似文献
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水文频率分析在参数估计过程中常采用智能优化适线法,如蚁群算法、遗传算法、粒子群算法、模拟退火算法等,但这些算法模型参数难以有效确定,导致寻优结果存在不稳定的不足。为了克服传统优化适线法的缺陷,在系统阐述群居蜘蛛优化算法基本原理的基础上,将群居蜘蛛优化算法用于水文频率曲线的参数确定中,并与传统的参数估计方法(矩法、权函数法、概率权重矩法、遗传算法)加以比较。实例结果表明,该方法搜索效率高,寻优结果稳定,能较好获得参数的最优解。 相似文献
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针对岩石力学试验中传统的声发射定位算法存在局限性,将灰狼算法(GWO)引入声发射定位研究中,该算法模仿了狼群的领导阶层与狩猎机制,用α、β、δ和ω 4种灰狼来模拟头狼领导,通过搜寻猎物、包围猎物和攻击猎物3个步骤实现目标的发现到捕获的全过程。在原始灰狼算法的基础上,针对其局部搜索能力欠佳的缺陷,修改收敛因子递减方式和淘汰最劣个体,提出基于种群记忆淘汰制的改进灰狼算法(BGWO)。基于预制裂隙岩石试件单轴压缩声发射试验结果,对比分析BGWO、GWO、引力搜索法(GSA)、Geiger算法、最小二乘法(LS)算法等5种定位算法的性能,发现改进后的BGWO算法在声发射定位搜索效率、搜索精度、稳定性和试验结果模拟方面效果优于其他算法。 相似文献
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Simultaneous Estimation of Geologic and Reservoir State Variables Within an Ensemble-Based Multiple-Point Statistic Framework 总被引：1，自引：1，他引：0
Liangping Li Sanjay Srinivasan Haiyan Zhou J. Jaime Gómez-Hernández 《Mathematical Geosciences》2014,46(5):597-623
Assessment of uncertainty due to inadequate data and imperfect geological knowledge is an essential aspect of the subsurface model building process. In this work, a novel methodology for characterizing complex geological structures is presented that integrates dynamic data. The procedure results in the assessment of uncertainty associated with the predictions of flow and transport. The methodology is an extension of a previously developed pattern search-based inverse method that models the spatial variation in flow parameters by searching for patterns in an ensemble of reservoir models. More specifically, the pattern-searching algorithm is extended in two directions: (1) state values (such as piezometric head) and parameters (such as conductivities) are simultaneously and sequentially estimated, which implies that real-time assimilation of dynamic data is possible as in ensemble filtering approaches; and (2) both the estimated parameter and state variables are considered when pattern searching is implemented. The new scheme results in two main advantages—better characterization of parameters, especially for delineating small scale features, and an ensemble of head states that can be used to update the parameter field using the dynamic data at the next instant, without running expensive flow simulations. An efficient algorithm for pattern search is developed, which works with a flexible search radius and can be optimized for the estimation of either large- or small-scale structures. Synthetic examples are employed to demonstrate the effectiveness and robustness of the proposed approach. 相似文献
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A Kriging-based surrogate model provides a logically strict and efficient tool to evaluate the system reliability of a slope. However, the constant trend function adopted in the ordinary Kriging (OK) cannot always well capture the nonlinear non-smooth properties of a slope stability problem. Although the universal Kriging (UK) with a linear or a quadratic trend function could be an alternative for some cases, a higher order nonlinear trend function is preferable for some more complicated nonlinear non-smooth cases in the slope stability analysis. To address this problem, a genetic algorithm (GA) optimized Taylor Kriging (TK) surrogate model is proposed for the system reliability analysis of soil slopes in this paper. The proposed surrogate model allows a unified framework of the Kriging, considering different extents of nonlinear properties according to the Taylor expansion order (e.g., can be as high as the fourth order). The GA is introduced to search for the optimal correlation parameters, of which the effectiveness is verified by an analytical example. The feasibility of the proposed surrogate model is then validated by two analytical examples before its application to the practical slope reliability analyses. The results show that the UK model can be incorporated into the TK model, and the TK model provides a higher accuracy and efficiency when facing the highly nonlinear slope stability problems. It is also found that the UK model cannot fully capture the potential nonlinear properties existed in a slope stability model as compared with the higher order TK model. 相似文献
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针对传统算法效率低的问题,将隐式双时间步法应用于求解二维浅水方程,建立了非结构网格下高效的有限体积模型。在应用双时间步法时,虚拟时间层中的定常问题采用高效的隐式LU-SGS（Lower-Upper Symmetric Gauss-Seidel）方法进行迭代求解。通过模拟计算4个典型算例以及与传统显式算法进行比较,对模型精度、效率及处理实际问题能力进行检验,分析了时间步长、内迭代次数对模型性能的影响。结果表明,双时间步法放宽了稳定性对时间步长的限制,时间步长可取到显式格式10倍以上,计算耗时减少了50%以上,模型具有良好精度与适应性,具有较好的推广应用价值。 相似文献
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含水层参的反演是一个复杂的非线性优化问题，针对传统二进制遗传算法收敛性能差的缺陷，提出了反演含水层参数的十进制遗传算法.以直线隔水边界附近的井流模型为例，讨论了十进制遗传算法在含水层参数反演中的应用，并与二进制遗传算法的进行比较.结果表明，该方法在含水层参数的反演中不仅是可行的，而且具有较好的确定性和较高的精度;与二进制遗传算法相比，十进制遗传算法的收敛性较好，省时高效，且表示较为自然，容易引入相关领域知识.同时，结合实例的分析结果得出种群的规模对算法的收敛性没有明显的影响。 相似文献
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Slope stability optimization, in the presence of a band of a weak layer between two strong layers, is accounted for in complicated geotechnical problems. Classical optimization algorithms are not suitable for solving such problems as they need a proper preliminary solution to converge to a valid result. Therefore, it is necessary to find a proper algorithm which is capable of finding the best global solution. Recently a lot of metaheuristic algorithms have been proposed which are able to evade local minima effectively. In this study four evolutionary algorithms, including well‐known and recent ones, such as genetic algorithm, differential evolution, evolutionary strategy and biogeography‐based optimization (BBO), are applied in slope stability analysis and their efficiencies are explored by three benchmark case studies. Result show BBO is the most efficient among these evolutionary algorithms and other proposed algorithms applied to this problem. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Various constitutive models have been proposed, and previous studies focused on identifying parameters of specified models. To develop the smart construction, this paper proposes a novel optimization-based intelligent model selection procedure in which parameter identification is also performed during staged excavation. To conduct the model selection, a database of seven constitutive models accounting for isotropic or anisotropic yield surface, isotropic or anisotropic elasticity, or small strain stiffness for clayey soils is established, with each model numbered and deemed as one additional parameter for optimization. A newly developed real-coded genetic algorithm is adopted to evaluate the performance of simulation against field measurement. As the process of optimization goes on, the soil model exhibiting good performance during simulation survives from the database and model parameters are also optimized. For each excavation stage, with the selected model and optimized parameters, wall deflection and ground surface settlement of the subsequent unexcavated stage are predicted. The proposed procedure is repeated until the entire excavation is finished. This proposed procedure is applied to a real staged excavation with field data, which demonstrates its effectiveness and efficiency in engineering practice with highlighting the importance of anisotropic elasticity and small strain stiffness in simulating excavation. All results demonstrate that the current study has both academic significance and practical significance in providing an efficient and effective approach of adaptive optimization-based model selection with parameters updating in engineering applications.
相似文献18.
The paper presents an optimization routine especially developed for the identification of model parameters in soil plasticity on the basis of different soil tests. Main focus is put on the mathematical aspects and the experience from application of this optimization routine. Mathematically, for the optimization, an objective function and a search strategy are needed. Some alternative expressions for the objective function are formulated. They capture the overall soil behaviour and can be used in a simultaneous optimization against several laboratory tests. Two different search strategies, Rosenbrock's method and the Simplex method, both belonging to the category of direct search methods, are utilized in the routine. Direct search methods have generally proved to be reliable and their relative simplicity make them quite easy to program into workable codes. The Rosenbrock and simplex methods are modified to make the search strategies as efficient and user‐friendly as possible for the type of optimization problem addressed here. Since these search strategies are of a heuristic nature, which makes it difficult (or even impossible) to analyse their performance in a theoretical way, representative optimization examples against both simulated experimental results as well as performed triaxial tests are presented to show the efficiency of the optimization routine. From these examples, it has been concluded that the optimization routine is able to locate a minimum with a good accuracy, fast enough to be a very useful tool for identification of model parameters in soil plasticity. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Optimization techniques for identifying soil parameters in geotechnical engineering: Comparative study and enhancement 下载免费PDF全文
下载免费PDF全文 A comparative study of optimization techniques for identifying soil parameters in geotechnical engineering was first presented. The identification methodology with its 3 main parts, error function, search strategy, and identification procedure, was introduced and summarized. Then, current optimization methods were reviewed and classified into 3 categories with an introduction to their basic principles and applications in geotechnical engineering. A comparative study on the identification of model parameters from a synthetic pressuremeter and an excavation tests was then performed by using 5 among the mostly common optimization methods, including genetic algorithms, particle swarm optimization, simulated annealing, the differential evolution algorithm and the artificial bee colony algorithm. The results demonstrated that the differential evolution had the strongest search ability but the slowest convergence speed. All the selected methods could reach approximate solutions with very small objective errors, but these solutions were different from the preset parameters. To improve the identification performance, an enhanced algorithm was developed by implementing the Nelder‐Mead simplex method in a differential algorithm to accelerate the convergence speed with strong reliable search ability. The performance of the enhanced optimization algorithm was finally highlighted by identifying the Mohr‐Coulomb parameters from the 2 same synthetic cases and from 2 real pressuremeter tests in sand, and ANICREEP parameters from 2 real pressuremeter tests in soft clay. 相似文献
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为了解决传统的Theis配线法在求参过程中无法利用全部抽水试验数据、手动配线效率较低、求参过程受人为主观因素影响较大等问题，利用抽水试验数据，以Theis公式和叠加原理为理论基础，以理论计算降深与实测降深的Nach-Sutcliffe效率系数值达到最大为目标函数，基于Matlab软件编程，再利用遍历搜索算法对导水系数（T）、贮水系数（S）在其对应范围内进行遍历，实现了水文地质参数的自动精确求解。将遍历搜索算法应用于2个抽水试验实例的水文地质参数求解，并与传统求参方法的计算结果进行比较分析。结果表明：利用遍历搜索算法求参的计算结果与传统求参方法的计算结果相近，表明利用遍历搜索算法求解水文地质参数有效可靠；2个抽水实例利用遍历搜索算法得到的参数对应的理论计算降深与实测降深的Nach-Sutcliffe效率系数值分别为0.996 5、0.970 8，且相比传统的求参方法而言更接近1.000 0，说明其拟合程度更好。 相似文献