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91.
远东热点:朝鲜半岛形势分析 总被引:1,自引:0,他引:1
朝鲜半岛独特的地理位置,无论对周边的中,俄,日三国,还是对大洋彼岸的美国都具有十分重要的地缘战略意义。如果说这里是四大国利益相互交错的唯一地区,那么解决朝鲜半岛问题便不仅取决于半岛内部北,南双方的互动关系,而且取决于四大四的立场及东北亚政治地理格局的演变态势。近年来随着朝鲜北,南双方首脑的成功会晤,朝鲜半岛的和平统一进程迈出了实质性步伐。但由于朝鲜半岛问题牵涉面广,影响因素复杂,从而使半岛的和平统一进程出现了一波三折的复杂局面,本文从政治地理学角度对半岛形势进行了分析。供关心朝鲜半岛局势的同仁参考。 相似文献
92.
One of the main factors that affects the performance of MLP neural networks trained using the backpropagation algorithm in mineral-potential mapping isthe paucity of deposit relative to barren training patterns. To overcome this problem, random noise is added to the original training patterns in order to create additional synthetic deposit training data. Experiments on the effect of the number of deposits available for training in the Kalgoorlie Terrane orogenic gold province show that both the classification performance of a trained network and the quality of the resultant prospectivity map increasesignificantly with increased numbers of deposit patterns. Experiments are conducted to determine the optimum amount of noise using both uniform and normally distributed random noise. Through the addition of noise to the original deposit training data, the number of deposit training patterns is increased from approximately 50 to 1000. The percentage of correct classifications significantly improves for the independent test set as well as for deposit patterns in the test set. For example, using ±40% uniform random noise, the test-set classification performance increases from 67.9% and 68.0% to 72.8% and 77.1% (for test-set overall and test-set deposit patterns, respectively). Indices for the quality of the resultant prospectivity map, (i.e. D/A, D × (D/A), where D is the percentage of deposits and A is the percentage of the total area for the highest prospectivity map-class, and area under an ROC curve) also increase from 8.2, 105, 0.79 to 17.9, 226, 0.87, respectively. Increasing the size of the training-stop data set results in a further increase in classification performance to 73.5%, 77.4%, 14.7, 296, 0.87 for test-set overall and test-set deposit patterns, D/A, D × (D/A), and area under the ROC curve, respectively. 相似文献
93.
Joseph S. Duval 《Natural Resources Research》2003,12(2):121-126
The U.S. Geological Survey has developed a technique that allows mineral resource experts to apply economic filters to estimates of undiscovered mineral resources. This technique builds on previous work that developed quantitative methods for mineral resource assessments. A Monte-Carlo calculation uses mineral deposit models to estimate commodity grades and tonnages of undiscovered deposits. The results then are analyzed using simple estimates of capital expenditures and daily operating costs for a mine and associated mill. The daily operating costs and the value of the ore are used to calculate the net present value of the deposit, which is compared to the capital expenditures to determine whether the deposit is economic. Repetition of these calculations for many deposits produces a table that can be interpreted in terms of the probability of there being deposits that have anet present value exceeding some specified amount. Sample calculations indicate that applying economic filters to simulated mineral resources might change the perception of the results compared to presenting the calculations in terms of the expected mean gross-in-place value of the minerals. 相似文献
94.
Use of GIS layers, in which the cell values represent fuzzy membership variables, is an effective method of combining subjective geological knowledge with empirical data in a neural network approach to mineral-prospectivity mapping. In this study, multilayer perceptron (MLP), neural networks are used to combine up to 17 regional exploration variables to predict the potential for orogenic gold deposits in the form of prospectivity maps in the Archean Kalgoorlie Terrane of Western Australia. Two types of fuzzy membership layers are used. In the first type of layer, the statistical relationships between known gold deposits and variables in the GIS thematic layer are used to determine fuzzy membership values. For example, GIS layers depicting solid geology and rock-type combinations of categorical data at the nearest lithological boundary for each cell are converted to fuzzy membership layers representing favorable lithologies and favorable lithological boundaries, respectively. This type of fuzzy-membership input is a useful alternative to the 1-of-N coding used for categorical inputs, particularly if there are a large number of classes. Rheological contrast at lithological boundaries is modeled using a second type of fuzzy membership layer, in which the assignment of fuzzy membership value, although based on geological field data, is subjective. The methods used here could be applied to a large range of subjective data (e.g., favorability of tectonic environment, host stratigraphy, or reactivation along major faults) currently used in regional exploration programs, but which normally would not be included as inputs in an empirical neural network approach. 相似文献
95.
广西德保矿区产出的结晶为双锥状的臭葱石的主要化学成分为Fe2O3 34.5%,As2O5 47.75%;而呈葡萄状的臭葱石含Fe2O3 26.67%,As2O5 44.28%, 它们的FeAs≈1,与理想分子式FeAsO4*2H2O接近.根据该矿物(德保)的粉晶X射线分析数据用最小二乘法计算的晶胞参数为a0=10.28(A),b0=10.00(A),c0=8.90(A).Z=8,为斜方晶系,空间群为Pcab.红外吸收光谱分析显示有波数为3505、3420、3000、820、720、490、470、435、415(cm-1)等吸收带.差热分析显示有256℃、945℃和980℃三个明显的吸热谷,还显示有520℃、725℃两个小的放热峰. 相似文献
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97.
我国钴矿矿产资源及其成矿作用 总被引:10,自引:0,他引:10
钴广泛应用于军事、钢铁、电器、机械等方面,它具有亲铁亲硫的双重性,在各类岩浆岩中的分布不均匀,由超基性岩向酸性岩,钴的含量迅速降低。我国钻矿资源呈现富矿少、贫矿多的特点,并且铬矿主要分布在甘肃、青海、新疆、吉林、陕西、云南、四川等地。按照矿床形成的成矿环境、矿床岩石组合,矿床类型划分为:与镁铁质-超镁铁质岩有关的硫化物钻矿、与海相火山喷发有关的钻多金属矿、与斑岩有关的铜钻矿、与砂岩有关的钻矿、与中酸性侵入岩有关的矽卡岩铁钻矿、与风化作用有关的钴矿等六类。 相似文献
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100.
研究和发现更多的成矿环境和岩石建造,有助于扩大找矿领域,提高找矿成效。笔者试从中国的区域成矿特色出发,提出近期应注意的几种地质成矿环境。中国区域成矿的主要特征是:①古陆边缘矿床集中;②多重成矿作用发育;③叠加和改造成矿显著;④热液矿床丰富多彩;⑤有机成矿和无机成矿的复合;⑥矿床形成后变化与保存条件复杂。具有较大成矿潜力、可能有所发现的地质环境和岩石建造有:①黑色岩系;②暗色岩系;③复合沉积盆地;④古湖盆区与构造—岩浆带的复合;⑤叠加成矿的多种形式;⑥构造体制转折期与转折部位;⑦地球化学块体的成矿潜力;⑧深部探矿和矿化垂直分带。论文最后提出找寻新矿床的若干方法途径。 相似文献