The Himalayan Collisional Orogeny: A Metamorphic Perspective

This paper introduces how crustal thickening controls the growth of the Himalaya by summarizing the P-T-t evolution of the Himalayan metamorphic core. The Himalayan orogeny was divided into three stages. Stage 60–40 Ma: The Himalayan crust thickened to ~40 km through Barrovian-type metamorphism (15–25 °C/km), and the Himalaya rose from <0 to ~1000 m. Stage 40–16 Ma: The crust gradually thickened to 60–70 km, resulting in abundant high-grade metamorphism and anatexis (peak-P, 15–25 °C/km; peak-T, >30 °C/km). The three sub-sheets in the Himalayan metamorphic core extruded southward sequentially through imbricate thrusts of the Eo-Himalayan thrust, High Himalayan thrust, and Main Central thrust, and the Himalaya rose to ≥5,000 m. Stage 16–0 Ma: the mountain roots underwent localized delamination, causing asthenospheric upwelling and overprinting of the lower crust by ultra-high-temperature metamorphism (30–50 °C/km), and the Himalaya reached the present elevation of ~6,000 m. Underplating and imbricate thrusting dominated the Himalaya’ growth and topographic rise, conforming to the critical taper wedge model. Localized delamination of mountain roots facilitated further topographic rise. Future Himalayan metamorphic studies should focus on extreme metamorphism and major collisional events, contact metamorphism and rare metal mineralization, metamorphic decarbonation and the carbon cycle in collisional belts.     

基于B-DEM的颗粒聚合体应力计算和破碎路径模拟

结合边界元法和离散元法,提出一种可以进行计算颗粒内部应力和破碎路径的方法。该方法利用离散元法求解颗粒的相互作用和每个颗粒上的荷载。然后利用边界元法计算颗粒的应力分布,为了实现动态平衡,将颗粒的加速度视为恒定大小的体力。但体力导致边界积分方程中出现域积分,故采用直线积分法将域积分转化为边界积分,以保证边界元法降维的优势。为了提高边界元的计算效率,对于几何形状相似的颗粒,以其中一个颗粒作为模板颗粒,只需要计算模板颗粒在局部坐标系中的系数矩阵,其他相似颗粒可以通过局部和全局坐标系之间的映射获得。在得到应力后,基于Hoek-Brown准则来判断颗粒是否破碎。此外,将破坏路径简化为直线,并采用最小二乘法拟合得到破坏路径。     

拉萨地块松多榴辉岩的变质演化过程:NCKMnFMASHTO体系中的相平衡关系

拉萨地块松多榴辉岩主要矿物组合为石榴子石、绿辉石、角闪石、多硅白云母、绿帘石、金红石。石榴子石环带不明显,核部成分均一,从核部到边部,镁铝榴石和钙铝榴石含量降低,可能分别记录了榴辉岩峰期及退变质过程信息。绿辉石显示微弱的成分环带,硬玉含量从核部到边部略有升高,部分绿辉石边部发育韭闪石退变质边,反映了在减压过程中外来流体进入体系的过程。多硅白云母具有高的Si含量(3.5~3.6),其中石榴石包体中的多硅白云母相对基质中的白云母有更高的Si值。本文利用Thermocalc变质相平衡模拟软件,结合详细岩相学观察,在NCKMn FMASHTO体系下,模拟松多含多硅白云母榴辉岩的变质演化过程。其中,榴辉岩峰期矿物组合为g+o+law+phn+ru,石榴石核部最大镁铝榴石值和石榴子石包体中多硅白云母最大Si值确定的榴辉岩峰期温压条件约为620℃,32×105Pa,榴辉岩经历了近等温降压的退变质过程。相平衡模拟结果表明拉萨地块松多榴辉岩经历了超高压变质作用过程,并经历了相对快速的折返过程到中部地壳层次。     

元胞自动机最短路径算法优化

概括了当前GIS中最短路径算法,分析了元胞自动机在最短路径分析算法中的原理及应用现状,并从两个方面对基于元胞自动机的最短路径算法进行优化即直线优化的元胞自动机最短路径算法。(1)将A*算法中的启发函数引入元胞自动机模型,提出了直线优化元胞自动机最短路径模型;(2)考虑道路网特征对最短路径算法的影响,得出具有道路网自适应性的最短路径分析模型。最后选取不同形态特征的shp道路网数据,验证了优化算法在实际应用中的适用性和高效性。     

基于开源pgRouting的WebGIS最短路径算法实现研究

pgRouting作为开源PostGIS空间数据库扩展路径规划项目,是对开源WebGIS中路径规划的创新.本文提出了如何在开源平台,将Dijkstra算法应用到WebGIS最短路径查询的方法.利用PostGIS开源项目pgRouting,结合Openlayers调用和Geoserver发布地图,利用OSM数据实现起始点定位查询最短路径的方法策略,并给出相关流程和配置安装的步骤.最后以昆明市道路数据验证了WebGIS中最短路径的方法.     

基于ESPO算法的装甲部队城市道路机动路径选择

现代条件下的城市作战,装甲部队的机动性能起着十分重要的作用。由于城市具有纵横交错的道路以及较多的障碍物等特点,使装甲部队的机动性能会受到很大的影响,延误战斗的时间。本文在分析了城市道路对装甲部队机动影响基础上,介绍了ESPO算法的基本原理,建立了装甲部队在城市道路中机动的最短路线选择的数学模型,并通过实验进行验证。     

Mexico's drug networks: Modeling the smuggling routes towards the United States

Drug smuggling routes are chosen to maximize profit while minimizing costs. Routes with the least drug transportation costs and the lowest risk for drug confiscation and gang fight are most preferred. This study attempts to predict the ground trafficking corridors for transporting marijuana and opium derivatives from Mexico to the United States border. The cost surface, representing impedance to transport illicit drugs, is modeled by considering physical, socio-demographic, and drug violence factors. The impedance is then transferred to the road network to represent the cost for moving drugs along the roads, which becomes the main input for network analysis. The results from the routes simulation confirm largely the known territory divisions and the drug trafficking routes of the major Mexican drug organizations. The findings help us understand the development of drug trafficking routes in Mexico, which can potentially enhance our capability to predict the dynamics of drug smuggling routes.     

Comparison of Liquid Water Content Retrievals for Airborne Millimeter-Wave Radar with Different Particle Parameter Schemes

In the application of the physical iterative method to retrieve millimeter-wave radar liquid water content(LWC) and liquid water path(LWP), particle parameter scheme is the main factor affecting retrieval performance. In this paper, synchronous measurements of an airborne millimeter-wave radar and a hot-wire probe in stratus cloud are used to compare the LWC retrievals of the oceanic and continental particle parameter scheme with diameter less than 50μm and the particle parameter scheme with diameter less than 500μm and 1500μm(scheme 1, scheme 2, scheme 3, and scheme4, respectively). The results show that the particle parameter scheme needs to be selected according to the reflectivity factor when using the physical iterative method to retrieve the LWC and LWP. When the reflectivity factor is less than-30 d BZ, the retrieval error of scheme 1 is the minimum. When the reflectivity factor is greater than-30 d BZ, the retrieval error of scheme 4 is the minimum. Based on the reflectance factor value, the LWP retrievals of scheme 4 are closer to the measurements, the average relative bias is 5.2%, and the minimum relative bias is 4.4 %. Compared with other schemes,scheme 4 seems to be more useful for the LWC and LWP retrieval of stratus cloud in China.     

1208号台风“韦森特”异常路径及其对珠三角南部暴雨影响成因分析

利用1°×1°NCEP再分析资料、全省遥测站资料、卫星云图、香港雷达图等资料,分析台风“韦森特”的环流背景场、物理量场特征,找出“韦森特”在南海中北部原地摆动和对珠三角南部强降水过程的物理成因：“韦森特”的原地摆动,与副热带高压、南海中部海温、还有台风内在的云系和风场结构的不对称有关;珠三角地区两侧附近存在弱的水汽通量辐合,在降水中心附近存在明显的上升运动,低层辐合、高层辐散,另外垂直螺旋场与降水中心的第一段降水期具有很好的对应关系.     

浙西南热带气旋强降水主要影响因子

对1950-2010年影响浙西南的热带气旋降水的移动路径、影响时间、强度、西风槽、西南季风以及地形等主要因子进行分析.结果表明:在玉环南-厦门一带登陆的热带气旋是影响浙西南的热带气旋中正面影响浙西南的类型,影响时间和最大平均过程降雨量、最大过程雨量存在着正相关关系,热带气旋的强度与其降水强度相关性较高.西风槽的存在不仅影响着热带气旋路径的变化,其槽前的西南气流也为热带气旋降水提供充足的水汽,同时槽后冷空气与热带气旋相结合,使丽水的西北部出现另一个强降水中心.西南季风为登陆后的热带气旋提供了水汽条件,使降水得到增幅.浙西南独特的地形,使在厦门以北到玉环以南登陆后西进、西北行或西北行后在120°E以西转向北上的热带气旋迎着山脉进入,降水强度明显加强.