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排序方式: 共有1131条查询结果,搜索用时 15 毫秒
1.
基于BP神经网络的溶洞规模预测及应用 总被引:2,自引:1,他引:1
复杂岩溶地区的溶洞发育规模受地质构造、地区岩性、地下水动力系统等多种因素的影响,具有高度复杂性和非线性的特征。通过对岩溶区溶洞的赋存规律研究,确定影响溶洞发育规模的控制因素进行定量处理,收集已探明溶洞的样本数据。为克服已有研究对溶洞发育规模定性描述的模糊性,文章利用BP(Back Propagation)神经网络对自组织、自适应特性对数据样本的非线性关系揭示的能力,实现对溶洞发育规模的预测,并基于MATLAB实现BP神经网络结构的设计、训练、预测,其结果表明:BP神经网络模型对溶洞规模预测的精度高、收敛性能好。 相似文献
2.
湖南省油菜春季涝渍过程灾变判别指标 总被引:4,自引:1,他引:3
以湖南省油菜为研究对象,综合洪涝与连阴雨的致灾因子,利用历史灾情数据反演涝渍过程样本,构建临灾、受灾状态样本,采用均值t检验方法,定量分析不同降水累积衰减系数w情况下,降水因子差异的显著性,构建有效累积降水量PE。基于Fisher判别准则,计算涝渍灾害临灾与受灾的临界线,构建逐日动态的油菜春季涝渍过程灾变判别指标y,并进行涝渍过程样本反演及独立样本验证。分析春季涝渍受灾频率与相对气象产量的关系,构建灾害影响评价模型。结果表明:当w=0.899时,受灾与临灾样本PE的差异最显著。灾变判别指标y可逐日动态监测涝渍灾变过程及灾害后续影响,为动态监测区域油菜涝渍过程提供了数据支撑;指标指示的灾变范围与实际受灾情况基本一致,为区域防灾减灾提供了科学参考。开花期及结荚期湖南油菜涝渍受灾频率较高,成熟期较低。湖南省油菜春季涝渍灾害影响指数呈东南高西北低,长沙东部、株洲中部及北部、湘潭、永州及郴州中部油菜产量受涝渍灾害影响最重。 相似文献
3.
西南印度洋63.5°E热液区是在超慢速扩张洋脊发现的首个超镁铁质岩热液系统。对取自该区的热液硫化物样品进行了系统的矿物学和地球化学分析,矿物学分析结果表明:该热液区硫化物为富Fe型高温硫化物,且经历了较深程度的氧化蚀变,大量中间态的Fe氧化物充填在硫化物矿物间的孔隙及内部解理中;这些硫化物相以白铁矿为主,其次是等轴古巴矿和少量铜蓝,缺乏黄铁矿、闪锌矿。据推断,该区的热液成矿作用分为4个阶段:低温白铁矿阶段→高温等轴古巴矿阶段→自形白铁矿阶段→后期海底风化阶段(少量铜蓝以及大量的Fe的羟氧化物)。与之相对应,地球化学分析结果表明这些硫化物的Fe含量较高(31.57%~44.59%),Cu含量次之(0.16%~7.24%),而Zn含量普遍较低(0.01%~0.11%);微量元素较为富集Co(328×10-6~2 400×10-6)和Mn(48.5×10-6~1 730×10-6)。该区硫化物中较高含量的Fe、Co与超镁铁质岩热液系统相似,明显高于镁铁质岩热液系统。独特的热液硫化物矿物学特征和元素组成可能与该区普遍出露的地幔岩、橄榄岩蛇纹石化作用以及拆离断层的广泛发育的环境有关。 相似文献
4.
The Gulf of Suez Basin is a very mature and extremely prospective petroleum province.Many heavy oil fields have been found in the Basin, and such reserves are abundant.Characteristics and models of heavy oil are analyzed in this study based on tectonic, basin evolution, stratigraphic distribution and geochemical data. The best reservoirs of heavy oil are Miocene sandstone and limestone formations.Source rocks of hydrocarbon include deep limestone and shale of the Brown Limestone, the Thebes Formation and the Rudeis Formation. Thick evaporite rocks with rock salts and anhydrites deposited broadly throughout the basin are the most impor-tant regional seals, whereas Miocene shales are intraformational and regional seals that cover small areas.Heavy oil could be directly generated or densified during vertical migration along faults and reservoir accumulation. The heavy oil accumulation model is a mixed model that includes three mechanisms:fault dispersal, sulfocom-pound reactions and hydrocarbons generated from immature source rock.After analyzing the model and the dis-tribution of source rocks, reservoirs, heavy oil fields and structures, it is concluded that the potential heavy oil area is at the center of the basin. 相似文献
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通过对中国萤石矿床的成矿作用研究,综合考虑萤石矿床的成因类型和工业类型,将中国萤石矿床划分为沉积改造型、热液充填型和伴生型3种矿床类型。在全面分析萤石矿典型矿床的成矿条件、控矿因素和成矿作用的基础上,总结成矿要素,以相同或相似的二级成矿必要要素组合确定沉积改造型、热液充填型萤石矿床的亚类型,沉积改造型进一步划分出2个矿床式,热液充填型划分出5个矿床式,伴生型按伴生主矿种划分出4个矿床式。文章分析了每一个矿床式的成矿地质背景,成矿条件、矿床特征、控矿因素和成矿作用,总结了每一个矿床式的二级成矿必要要素。 相似文献
7.
Tongwen Zhang Yujiang YuanWenshou Wei Shulong YuRuibo Zhang Feng ChenHuaming Shang Li Qin 《Quaternary Research》2014
August–July precipitation has been reconstructed back to AD 1724 for the Mohe region in the northern Greater Higgnan Mountains, China, using Pinus sylvestris var. mongolica tree-ring width. The reconstruction explains 39% of the variance in the precipitation observed from AD 1960–2008. Some droughts noted in historical documents are precisely captured in our reconstruction. Wet periods occurred during the periods of AD 1734–1785, AD 1805–1830, AD 1863–1880, AD 1922–1961, and AD 1983–1998; while the periods of AD 1786–1804, AD 1831–1862, AD 1881–1921, and AD 1962–1982 were relatively dry. Power spectral and wavelet analyses demonstrated the existence of significant 24-yr, 12-yr, and 2-yr cycles of variability. The results of the spatial correlations suggest that our reconstruction contains climatic signals for the southern Stanovoy Range and the northern Greater Higgnan Mountains. The positive correlations between the new reconstructed precipitation series and two precipitation reconstructions indicate that our precipitation reconstruction captures broad-scale regional climatic variations. A comparison between the weakening tendency of summer monsoon and the dry period of our reconstruction reveals that the annual precipitation in the Mohe region is partly influenced by the East Asian Summer Monsoon. 相似文献
8.
In flowing water the incipient motion of sediment can be affected by the presence of microbial biofilm growth. This article documents a series of flume experiments using non‐uniform sediments, in which sediment entrainment was investigated for cases where the sediment was immersed in deionized water, so that no biofilm developed, and for cases where a bio‐sediment was cultivated by placing the sediment in a mixture of natural water and nutrient solution. Differences in entrainment and the velocity at incipient motion were measured over an eight week period, as biofilm grew. It was found that the incipient motion phenomena were quite distinct between the two kinds of sediment. Sediment with biofilm was more stable and, over time, incipient velocity increased to a threshold level, before declining. Biofilm development is clearly an important control on the stability of sediments, especially in eutrophic water bodies. Two incipient velocity formulas were derived for sliding and rolling conditions. Film water theory was utilized to describe the cohesive force between sediment particles and the adhesive force generated by biofilm was introduced into the formula derivation; the time variation characteristics of biofilm strength and the features of the substrate were also taken into consideration. Such analyses can help to predict sediment transport changes due to biofilm presence in nutrient‐rich water bodies. 相似文献
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老工业区产业结构转型与用地结构转型互动机制及优化路径——以上海市宝山区为例 总被引:1,自引:0,他引:1
尝试理清老工业区产业结构转型与用地结构转型内涵,提出其转型效率的函数表达,分析二者间的互动关系;并运用改进的动态变化度及偏离系数,对上海市宝山区进行实证研究。结果表明:(1)宝山区产业结构与用地结构变化度逐渐增加,工业和第三产业动态度分别由1996年的2.48%和5.36%上升至2012年的4.75%和5.51%,用地结构动态度由11.16%上升至13.53%;(2)宝山区三次产业结构总体趋于优化,但产业内部并未优化,仍以重化工业和传统服务业为主导;(3)宝山区用地结构与产业结构不协调并处于加剧的状态。老工业区产业结构与用地结构存在较强的互动关系,改进的动态变化度及偏离系数方法为老工业区产业结构转型与用地结构转型问题提供了一种研究思路。提出宝山区产业结构转型与用地结构转型的优化路径。 相似文献