Feasibility Analysis of the Use of Binary Genetic Algorithms as Importance Samplers Application to a 1-D DC Resistivity Inverse Problem

DC resistivity inverse problems are ill-posed. For the Vertical Electrical Sounding method the acceptable solutions lie in very narrow elongated-shape regions in the model space. To characterize this ensemble of solutions is a central question. In a Bayesian framework this issue is solved adopting as solution the so-called model posterior probability distribution. However, due to the nonlinearity of the problem, this distribution is not explicitly known, or it is difficult to calculate. Therefore, algorithms that efficiently sample the model space according to it (importance sampling) are very desirable. The main goal of this paper is to numerically explore the performance of binary genetic algorithms as posterior importance sampling strategies. Their behavior will be firstly analyzed using 2D synthetic posterior test functions bearing the relevant properties of the real geo-electrical inverse problem. The conclusions will be again checked through the histogram reconstruction of parameters in a synthetic VES case, and eventually, in a real, higher dimensional, sea-water coastal intrusion problem, by comparing the results with those obtained with a theoretically correct Metropolis-Hasting importance sampler (simulated annealing without cooling). Percentile curves are introduced as an effective tool for risk assessment. We show that binary genetic algorithms perform well under very general assumptions. When the roulette wheel is the selection method used, mutation is over 10%, and the algorithm does not incorporate elitism. The results do not depend on the values of the remaining tuning parameters. Finally, to improve the efficiency of the sampling strategy, we introduce a binary genetic algorithm with oriented search space. This is done with the help of linearization of the forward operator and singular value decomposition around the maximum posterior estimate. It is shown, also, that the logarithmic model parameterization is adequate for this task.     

Present geotemperature and its suggestion to natural gas generation in Xujiaweizi fault-depression of the northern Songliao Basin

According to stastistic of present geotemperatures at the depths of 1000, 2000, 3000 and 4000 m, respectively in the Xujiaweizi fault-depression of the north Songliao Basin, the result indicates that Xujiaweizi fault-depression falls in the high geotemperature area, with the higher geothermal gradient in the depression layer than that in the fault-depression layer. The geothermal gradient decreases with the increasing of the depth. The thermal conductivity of rock greatly controls the geothermal gradient. The main factors constraining the current geotemperature include thermal configuration of the earth’s crust, deep faults, distribution and abundance of radioelements. The high geotemperature is in favour of generation of deep gas.     

毛乌素沙漠砂土地基处理效果分析

在对毛乌素沙漠南缘风积砂进行水坠砂（静水沉积和浸水饱和分层碾压）、振冲密实法（振冲砂桩）及强夯等现场试验的基础上,对不同地基处理方式后风积砂的物理特性和地基承载力进行了对比分析,提出了风积砂不同地基处理方式的优缺点,并对不同地基处理方式的机理进行了探讨。     

强夯法加固砂土地基效果的检测分析

针对强夯法在加固效果的检测与评价方面较为欠缺这一现状,结合工程实例,对某强夯加固砂土地基与天然状态砂层采用多种方法进行检测和对比分析,对强夯法加固的砂土地基做出了比较客观的评价,并探讨了影响强夯加固效果的因素。为强夯法加固砂土地基的检测积累了经验,对提高强夯法在设计、施工中的应用具有重要的理论价值和现实意义。     

The preg-robbing of gold and silver by clays during cyanidation under agitation and heap leaching conditions

Laboratory scale leaching tests were carried out in different experimental conditions, with monitoring of gold and silver recovery, the concentration of cyanide used in leaching, solution pH, and precious metal adsorption onto clay. Evidence for the adsorption or re-precipitation of gold from cyanide solutions onto clay minerals is conclusive and indicates that adsorption contributes to the total gold loss from conventional cyanidation. The loss is related to the type of clay, and appears to be affected by the extent of time cyanidation. It was observed that silver adsorption capacity was above 80% and that the degree of adsorption for gold oscillated between 1.68% and 7.49%, depending on the type and characteristics of the evaluated clay.     

Distribution of gold in igneous granitoid complexes in the central and southwestern areas of eastern Transbaikalia

The distribution of gold in rocks from some igneous complexes of the central and southwestern areas of eastern Transbaikalia (Daurian, Aga, and Argun structure-formational zones) was studied by quantitative extraction–atomic-absorption analysis and mass spectrometry with inductively coupled plasma (Element-2 mass spectrometer). High gold concentrations (on average, 0.0043 ppm) are typical of the most widespread hornblende-biotite granodiorites and granites of the main phases of batholith intrusions in the Upper Paleozoic Unda complex in the east of the study area and in the Triassic–Middle Jurassic Kyra complex in the west. The rocks of the Early–Middle Jurassic (Sokhondo) and Middle–Upper Jurassic (Shakhtama, Kharalga, and Kukul’bei) complexes have much lower Au concentrations (mainly 0.0014–0.0030 ppm), with the minimum ones established in the Shakhtama complex. During the magmatic differentiation of granitoid intrusions, the concentrations of gold in the late leucogranite differentiates decreased.The Au concentrations in the studied complexes do not depend on the composition of the host terrigenous rocks of different ages, which evidences the endogenous nature of the revealed differences in Au concentrations in the regional granitoids. Abnormally high concentrations of gold in some studied samples are observed mainly in the regional hydrothermal mineralization occurrences.The classification R-type cluster analysis showed that all variables of the studied igneous rocks are subdivided into three groups by the degree of correlation. Gold shows a distinct tendency to the correlation with siderophile oxy- and sulfurophile groups of metals. The Q-type analysis generally confirmed the correctness of the known formational classification of the regional granitoids.     

The off-focus photograph technique for low dispersion spectra

We have developed a photograph filtering technique to search for QSOs with objective prism plates. After off-focus reproduction, the signal-to-noise ratio increases and some spectral lines in the prism spectra may be recognized by eye against the noise. Principle of this technique is discussed.     

青藏高原北部地区未来3～5年内强震形势研究

应用统计分析、有序性分析、干支预测模型、可公度模型等方法,对青藏高原北部地区7级强震以及青海省M≥6级强震的危险性进行预测估计。结果表明,目前该区累积发震概率已达60％,到2000年初将达到75％,2000年前后有可能发生7级强震,青海省1998年前后有可能发生M≥6．5级强震。     

Alleviating the effect of collinearity in geographically weighted regression

Geographically weighted regression (GWR) is a popular technique to deal with spatially varying relationships between a response variable and predictors. Problems, however, have been pointed out (see Wheeler and Tiefelsdorf in J Geogr Syst 7(2):161–187, 2005), which appear to be related to locally poor designs, with severe impact on the estimation of coefficients. Different remedies have been proposed. We propose two regularization methods. The first one is generalized ridge regression, which can also be seen as an empirical Bayes method. We show that it can be implemented using ordinary GWR software with an appropriate choice of the weights. The second one augments the local sample as needed while running GWR. We illustrate both methods along with ordinary GWR on an example of housing prices in the city of Bilbao (Spain) and using simulations.