Automatic Histogram and Variogram Reproduction in Simulated Annealing Simulation

Simulated annealing simulation (SAS) is a flexible tool for generating stochastic simulations conditioned to data at various scales and precision. However, a number of important drawbacks exists: (1) SAS requires considerable CPU time, (2) it requires experience in setting the so-called cooling schedule to obtain convergence, and (3) its space of uncertainty is not well understood. In this paper, I propose a new simulated annealing method that guarantees histogram and variogram reproduction through the implementation of a novel perturbation mechanism. The novel perturbation method is based on the Metropolis–Hastings sampler for a Markov-type random field. This new annealing method allows removal of the histogram and variogram from the objective function in the simulated annealing procedure. Furthermore, for the proposed method one finds that (1) the uncertainty space can be quantified, (2) the convergence properties can be linked to convergence of stationary Markov chains, and (3) the convergence speed is improved over traditional simulated annealing.     

Time-dependent effects of heat advection and topography on cooling histories during erosion

Both erosion and surface topography cause a time-dependent variation in isotherm geometry that can result in significant errors in estimating natural exhumation rates from geochronologic data. Analytical solutions and two-dimensional numerical modelling are used to investigate the magnitude of these inaccuracies for conditions appropriate to many rapidly exhumed mountain chains of rugged relief. It is readily demonstrated that uplift of the topographic surface has a negligible effect on the cooling history of an exhumed rock sample and cannot be quantified by current geochronologic methods. The topography itself perturbs the isotherms to a depth that depends on both the vertical and horizontal scale of the surface relief. Estimations employing different isotopic systems in the same sample with higher closure temperatures (> 200°C) are not generally influenced by topography. However, direct conversion of cooling rates to exhumation rates assuming a simple constant linear geotherm markedly underestimates peak rates, due to variation of the geothermal gradient in time and space and to the time lag between exhumation and cooling. Estimations based on the altitude variation in apatite fission-track ages are less prone to such inaccuracies in geothermal gradient but are affected by near-surface time-dependent variation in isotherm depth due to advection and topography. In tectonically active mountain belts, high exhumation rates are coupled with rugged topography, and exhumation rates may be markedly overestimated, by factors of 2 or more. Even at lower exhumation rates on the order of 1 mm/a, the shape of the cooling curve is modified by advection and topography. A convex-concave shape to the cooling curve does not necessarily imply a change of exhumation rate; it may also be attained by a more complicated geothermal gradient induced by topographic relief. Very fast cooling below 100°C, often interpreted as reflecting faster exhumation, can be more simply explained by the lateral cooling effect of topographic relief, with samples exhumed in valleys displaying a different near-surface cooling history to those on ridge crests.     

Adaptive hybrid global inversion algorithm

Most geophysical inversions can be regarded as multiparameter, nonlinear, and multiminimum discontinuous optimization problems. An adaptive hybrid global inversion algorithm based on simulated annealing, downhill simplex method, uniform design, and adaptive annealing rule is formulated. Numeral test and model computation show that this algorithm has very fast speed and high efficiency in searching for global minimum. Project sponsored by the National Natural Science Foundation of China (Grant No. 49474232) and Special Foundation under the auspices of president of Chinese Academy of Sciences.     

串行Cauchy机引导的影像镶嵌方法研究

提出的串行Ｃａｕｃｈｙ机引导的影像镶嵌方法，基于灰度特征，综合人机交互优势，可操作性强，精度高，最大误差不超过０．５像素，可满足高精度影像处理需要。     

COMPUTER-GENERATED MULTICOMPONENT CALIBRATION DESIGNS FOR OPTIMAL ANALYSIS SAMPLE PREDICTIONS

This paper utilizes variable step size generalized simulated annealing(VSGSA)to design multicomponentcalibration samples for spectroscopic data.VSGSA is an optimization procedure which is capable ofconverging to exact positions of global optima located on multidimensional continuous functions.On thebasis of analysis sample response vectors,optimally designed calibration concentration matrices areobtained assuming knowledge of components present.The complexity of response surfaces establishedby the optimization criteria is described.     

基于模拟退火和区域划分的海表流场反演算法研究

经典的海洋表面流场迭代反演算法采用固定的校正系数对探测区域进行整体分析和计算,因此耗时较长且反演精度也受到了一定程度的限制。本文提出利用模拟退火算法对反演过程中的校正系数进行优化,使其能根据每一次反演的结果进行自适应的调整和改变,从而减少迭代次数;同时根据流场分布的特点,提出划分探测区域的反演方法,最终,在经典算法的基础上给出了改进的海表流场反演算法。仿真反演实验结果表明,改进后的反演算法,其时效性和精度都有了明显提高。     

Parameter identification for leaky aquifers using global optimization methods

In the past, graphical or computer methods were usually employed to determine the aquifer parameters of the observed data obtained from field pumping tests. Since we employed the computer methods to determine the aquifer parameters, an analytical aquifer model was required to estimate the predicted drawdown. Following this, the gradient‐type approach was used to solve the nonlinear least‐squares equations to obtain the aquifer parameters. This paper proposes a novel approach based on a drawdown model and a global optimization method of simulated annealing (SA) or a genetic algorithm (GA) to determine the best‐fit aquifer parameters for leaky aquifer systems. The aquifer parameters obtained from SA and the GA almost agree with those obtained from the extended Kalman filter and gradient‐type method. Moreover, all results indicate that the SA and GA are robust and yield consistent results when dealing with the parameter identification problems. Copyright © 2006 John Wiley & Sons, Ltd.     

地下工程围岩位移反分析的改进模拟退火算法

本文针对地下工程围岩位移反分析问题的目标函数存在多个局部极值的特点，在对模拟退火算法进程中控制参数，即初始温度、每一温度下的状态选取次数和退火策略的确定方法加以改进的基础上．引进有限元分析手段和自适应的思想，建立了基于改进模拟退火算法的位移反分析方法，并开发了相应的分析程序。工程实践分析表明：本文理论计算结果与实测结果吻合良好，该方法较一般模拟退火算法具有明显的优越性。