Effect of a uniform magnetic field on nonlinear magnetocenvection in a rotating fluid spherical shell

Abstract

Dynamic interaction between magnetic field and fluid motion is studied through a numerical experiment of nonlinear three-dimensional magnetoconvection in a rapidly rotating spherical fluid shell to which a uniform magnetic field parallel to its spin axis is applied. The fluid shell is heated by internal heat sources to maintain thermal convection. The mean value of the magnetic Reynolds number in the fluid shell is 22.4 and 10 pairs of axially aligned vortex rolls are stably developed. We found that confinement of magnetic flux into anti-cyclonic vortex rolls was crucial on an abrupt change of the mode of magnetoconvection which occurred at Δ = 1 ～ 2, where A is the Elsasser number. After the mode change, the fluid shell can store a large amount of magnetic flux in itself by changing its convection style, and the magnetostrophic balance among the Coriolis, Lorentz and pressure forces is established. Furthermore, the toroidal/poloidal ratio of the induced magnetic energy becomes less than unity, and the magnetized anti-cyclones are enlarged due to the effect of the magnetic force. Using these key ideas, we investigated the causes of the mode change of magnetoconvection. Considering relatively large magnetic Reynolds number and a rapid rotation rate of this model, we believe that these basic ideas used to interpret the present numerical experiment can be applied to the dynamics in the Earth's and other planetary cores.     

江苏省地电阻率年变化及其差异性探讨

以江苏省江宁地震台、新沂地震台和海安地震台为例,归纳了江苏省地电阻率年变化特征的类型,并对地电阻率年变化差异性的原因做了探讨。通过反演计算指出地电阻率年变化差异性的原因主要是由各观测场地地下电性结构造成的,分析这种不同有益于解决在场地选择中如何得到一个规则年变的场地,以便更好地服务于地震预报的数据处理。     

卧龙湖煤矿岩浆侵入特征及控制因素分析

岩浆侵入对煤矿生产影响极大,淮北煤田卧龙湖煤矿是受岩浆侵入较严重的矿井之一,其地质构造是控制岩浆侵入和岩浆岩展布的重要因素。卧龙湖煤矿自侏罗纪以来岩浆活动剧烈,发生了中性岩浆的侵入,多以岩床形式顺层侵入煤层顶底板及煤层中间。本文基于矿区钻孔数据揭露的岩浆岩分布情况,分析了结果表明卧龙湖矿区岩浆侵入规律,受煤层的形态、结构、理化性质以及产状的控制。     

A modified stochastic neighbor embedding for multi-feature dimension reduction of remote sensing images

In automated remote sensing based image analysis, it is important to consider the multiple features of a certain pixel, such as the spectral signature, morphological property, and shape feature, in both the spatial and spectral domains, to improve the classification accuracy. Therefore, it is essential to consider the complementary properties of the different features and combine them in order to obtain an accurate classification rate. In this paper, we introduce a modified stochastic neighbor embedding (MSNE) algorithm for multiple features dimension reduction (DR) under a probability preserving projection framework. For each feature, a probability distribution is constructed based on t-distributed stochastic neighbor embedding (t-SNE), and we then alternately solve t-SNE and learn the optimal combination coefficients for different features in the proposed multiple features DR optimization. Compared with conventional remote sensing image DR strategies, the suggested algorithm utilizes both the spatial and spectral features of a pixel to achieve a physically meaningful low-dimensional feature representation for the subsequent classification, by automatically learning a combination coefficient for each feature. The classification results using hyperspectral remote sensing images (HSI) show that MSNE can effectively improve RS image classification performance.     

吉林苇厦子金矿床地质特征及深部找矿远景

通过对苇厦子金矿床地质特征及其矿体产出规律的分析,总结了地层、构造、岩浆对成矿的控制作用,为本矿床深部探矿提供了依据。     

马鞍桥金矿床成矿流体特征研究

马鞍桥金矿床产于西秦岭造山带商丹断裂带南缘的E-W脆-韧性剪切带中,矿床空间定位和矿体展布受脆-韧性剪切带控。选择马鞍桥金矿床矿石、地层岩石和二长花岗斑岩的代表性样品,针对性地开展碳-氧和氢-氧同位素分析测试。研究结果证明:成矿早阶段和主阶段成矿流体以变质热液或地层改造热液为主,而晚阶段则主要为大气降水。马鞍桥金矿床矿化地质特征和同位素地球化学组成为广义的类卡林型金矿床或属介于造山型和卡林型金矿床之间的过渡类型。     

甘肃省夏河县隆瓦寺院金矿地质特征及找矿前景分析

隆瓦寺院金矿为多期活动的断裂构造和中酸性脉岩双重控矿的蚀变岩型中型金矿床,矿区内的多条矿化蚀变带,具有宽度大、走向延伸较稳定的特征。通过对该成矿特征及成矿条件分析,该矿体形态较简单,总体厚度变化较稳定,品位变化不太均匀。矿体的形成主要受一套浅变质碎屑岩建造、断裂构造及中酸性侵入岩脉的控制。该矿有利的成矿条件和特定的成矿类型对该地区的找矿具有重要指示意义。     

安徽含山县汤山白云石矿产地质特征及综合利用

随着社会主义经济建设的发展,白云石应用领域不断扩展,广泛用于建材、冶金、化工等行业;寻找白云石矿已成为经济建设不可或缺的一部分.汤山白云石矿的发现,对它的地层、构造、断层等矿床地质特征等的研究,为我们找寻类似白云石矿产指明了一条捷径.     

NaCl-H2O-CO2体系人工合成流体包裹体实验研究

NaCl- H2O-CO2体系流体是热液成矿系统中最常见的流体之一,针对该体系相关特征的研究对理解热液矿床的成矿机制和过程、成矿流体特征等具有重要的理论和实际意义.本文利用愈合人工水晶裂隙的技术,开展100 MPa、800℃条件下NaCl-H2 O-CO2体系流体的人工合成包裹体实验,并对其物理化学性质进行了初步探讨.通过对合成的包裹体进行岩相学观察、显微测温以及喇曼光谱分析,结果表明,在实验温压条件下合成的包裹体捕获了既定组成的流体;人工合成NaCl- H2O-CO2体系流体包裹体与天然流体包裹体具有相似的特征,可以作为天然包裹体的参照物应用于流体包裹体及地质流体的研究,特别是在评价CO2在热液矿床成矿过程中的作用方面,NaCl-H2O-CO2体系人工合成包裹体具有广阔的应用前景.     

赣南淘锡坑钨矿床流体包裹体特征及其地质意义

淘锡坑钨矿是赣南一个重要的大型石英脉型钨多金属矿床。矿床主要矿化阶段含矿石英脉中石英和黄玉中的流体包裹体类型有单一水溶液相H2O-NaCl(Ⅰa型)、富液L+V两相H2O-NaCl(Ⅰb型)、两相H2O-NaCl-CO2体系包裹体(Ⅱa型)和三相H2O-NaCl-CO2包裹体(Ⅱb型)。Ⅰb型包裹体均一温度范围为80~370℃,具有多峰态分布特征,可识别出140~190℃,200~250℃和340~360℃几个峰。成矿流体的盐度相对较低,一般<8w(NaCleq)%。用流体包裹体组合的方法获得四组包体的相关参数,结果表明同一包体组合内不同包体的盐度、均一温度及密度基本一致,而不同包体组合中包体的盐度、均一温度及密度则相差较大,显示出不同包体组合所捕获的流体存在较大的差异。Ⅰb型包裹体均一温度分别分布在329~355℃,214~240℃和141~189℃三个温度区间,经压力校正后的捕获温度分别为400~425℃,275~300℃,210~260℃。这些特征表明,淘锡坑钨矿至少存在三期热液流动,其中前两期为成矿期的热液活动,第三期(次生包体)为成矿后的热液活动。根据Ⅱ型包裹体的CO2部分均一温度与最终均一温度计算出成矿流体的捕获压力67.3~97.8 Mpa,平均压力74.8 Mpa,按静岩压力换算成成矿深度为2.59~3.77 km,平均为2.88 km。