2010—2016年江西省暖季短时强降水特征分析

利用江西省2010—2016年5—9月1597个观测站逐小时降水资料对江西省短时强降水进行统计分析。采用REOF将降水场划分为5个区域：赣北南部（Ⅰ区）,抚州市及赣州中部（Ⅱ区）,赣北北部（Ⅲ区）,赣南南部、北部（Ⅳ区）以及赣中西部（Ⅴ区）。短时强降水高频区主要分布在山地及河谷附近,分别为湘赣交界罗霄山脉东侧、武夷山西侧、信江河谷、乐安河谷和昌江河谷。河谷附近短时强降水频次以昌江河谷最高（16.9次/a）,山地附近最高在罗霄山脉东侧（12.6次/a）,极端短时强降水分别位于上饶市东北部山区（3.7次/a）及九岭山南侧的锦江河谷（3.3次/a）。短时强降水主要发生在5月第3候,6、7月第3~4候以及8月第2~3候。Ⅳ、Ⅴ区具有单峰型的日变化特征;Ⅰ、Ⅱ、Ⅲ区具有双峰型的日变化特征。主峰基本集中在下午17时;次峰在上午08—10时。短时强降水对暴雨贡献率基本在40%以上,Ⅰ、Ⅱ区的暴雨天气过程将近一半是由短时强降水贡献的。信江河谷是暴雨雨量中心,但并不是短时强降水雨量中心;昌江河谷与武夷山西麓既是暴雨中心也是短时强降水中心。     

Macroscopic criteria for Green type porous materials with spheroidal voids: application to double porous materials

Combined effects of matrix plastic compressibility and void shape are investigated for ductile porous materials. To this end, a spheroidal volume containing a confocal spheroidal (prolate or oblate) void subjected to uniform strain rate boundary conditions has been first studied. A Green type matrix is chosen as a prototype for investigating effects of plastic compressibility. This is carried out by using a kinematics limit analysis theory from which a closed‐form expression of the macroscopic criterion is established for the considered class of materials. These results are then extended to ductile porous materials made up of a green matrix containing randomly oriented spheroidal voids. In the framework of a two‐step homogenization procedure, the obtained results are implemented to describe the macroscopic behavior of double porous materials involving spherical voids at the microscale and randomly oriented and distributed spheroidal voids at the mesoscale. For validation purpose, the new derived criteria are assessed and validated by comparing their predictions to available upper bounds and numerical data from literature. Copyright © 2017 John Wiley & Sons, Ltd.     

Numerical analysis of the effect of natural microcracks on the supercritical CO2 fracturing crack network of shale rock based on bonded particle models

The problem of predicting the geometric structure of induced fractures is highly complex and significant in the fracturing stimulation of rock reservoirs. In the traditional continuous fracturing models, the mechanical properties of reservoir rock are input as macroscopic quantities. These models neglect the microcracks and discontinuous characteristics of rock, which are important factors influencing the geometric structure of the induced fractures. In this paper, we simulate supercritical CO₂ fracturing based on the bonded particle model to investigate the effect of original natural microcracks on the induced‐fracture network distribution. The microcracks are simulated explicitly as broken bonds that form and coalesce into macroscopic fractures in the supercritical CO₂ fracturing process. A calculation method for the distribution uniformity index (DUI) is proposed. The influence of the total number and DUI of initial microcracks on the mechanical properties of the rock sample is studied. The DUI of the induced fractures of supercritical CO₂ fracturing and hydraulic fracturing for different DUIs of initial microcracks are compared, holding other conditions constant. The sensitivity of the DUI of the induced fractures to that of initial natural microcracks under different horizontal stress ratios is also probed. The numerical results indicate that the distribution of induced fractures of supercritical CO₂ fracturing is more uniform than that of common hydraulic fracturing when the horizontal stress ratio is small.     

Petrogenetic modelling of strongly residual metapelitic xenoliths within the southern Platreef,Bushveld Complex,South Africa

Xenoliths of quartz‐absent Fe‐rich aluminous metapelite are common within the platinum group element‐rich mafic/ultramafic magmatic rocks of the Platreef. Relative to well‐characterized protoliths, the xenoliths are strongly depleted in K₂O and H₂O, and have lost a substantial amount of melt (>50 vol.%). Mineral equilibria calculations in the NCKFMASHTO system yield results that are consistent with observations in natural samples. Lower‐grade rocks that lack staurolite constrain peak pressures to ～2.5 kbar in the southern Platreef. Smaller xenoliths and the margins of larger xenoliths comprise micro‐diatexite rich in coarse acicular corundum and spinel, which record evidence for the metastable persistence of lower‐grade hydrous phases and rapid melting consequent on a temperature overstep of several hundred degrees following their incorporation in the mafic/ultramafic magmas. In the cores of larger xenoliths, temperatures increased more slowly enabling progressive metamorphism by continuous prograde equilibration and the loss of H₂O by subsolidus dehydration; the H₂O migrated to xenolith margins where it may have promoted increased melting. According to variations in the original compositional layering, layers became aluminosilicate‐ and/or cordierite‐rich, commonly with spinel but only rarely with corundum. The differing mineralogical and microstructural evolution of the xenoliths depends on heating rates (governed by their size and, therefore, proximity to the Platreef magmas) and the pre‐intrusive metamorphic grade of the protoliths. The presence or absence of certain phases, particularly corundum, is strongly influenced by the degree of metastable retention of lower‐grade hydrates in otherwise identical protolith bulk compositions. The preservation of fine‐scale compositional layering that is inferred to be relict bedding in xenolith cores implies that melt loss by compaction was extremely efficient.     

济阳坳陷上第三系的沉积特征及沉积相的纵向演化规律

本文根据岩性特征、沉积构造、砂体厚度和测井曲线特征等资料，对4口岩心井进行了沉积相分析，详细研究了不同时期的河流类型及沉积相的演化规律，从而认为济阳凹陷上第三系沉积大体经历了3个阶段：早期的冲积扇一辫状河阶段，中期的辫状河一低弯度曲流河阶段及晚期的高弯度曲流河阶段，同时分析了不同砂体的油气储集性能。     

五矩二流太阳风等离子体特性的数值研究

本文数值求解了各向同性二流太阳风的五矩方程组,得出了1 R_s-2AU区域内太阳风密度、速度、电子和质子温度、它们的热流通量密度q以及非麦克斯韦分布尾部粒子过剩量ξ随日心距离的变化关系.文中比较了二流太阳风五矩模型、四矩模型（ξ=0）和低阶矩模型（不包括q和ξ二个矩方程）的等离子体特性,着重讨论了量ξ对质子温度及其热流通量的影响.结果表明,包括言的五矩方程可改善T_e/T_p和q_e/q_p的计算值与观测值的符合程度.     

多孔材料声衰减的实验研究

本文旨在研究多孔岩石声衰减机制及衰减和频率的关系,用共振法测量了人工多孔材料10~5Hz以下的弯曲振动能量损耗,发展了前人测量弹性模量的方法.实验结果表明:干燥试样的内耗基本上与频率无关:水饱和试样的内耗比干燥试样的大得多,并在24.0kHz有显著的弛豫峰;饱和试样的内耗主要产生于固体骨架与孔隙流体之间的相对运动.实验结果与Riot理论和局部流体流动机制一致,但未看到Dunn预言的“边界效应”.     

Study of the crust and mantle using magnetic surveys by Magsat and other satellites

Among the first measurements made from near-Earth orbiting satellites were measurements of the magnetic field. The sources of that field lie both within the Earth, in its core and crust, and in the surrounding ionosphere and magnetosphere. This article summarizes some of the methodology and results for studies of the Earth’s mantle and crust. Mantle conductivity studies can be made either by studying signals impressed on the Earth from outside, e.g., the ionosphere or magnetosphere, or by studying signals originating in the core and transmitted through the mantle. Crustal field studies begin with a careful selection of the data and subsequent removal of core and external fields by some sort of filtering. Average maps from different local times sometimes differ, presumably due to the remaining presence of fields of external origin. Several techniques for further filtering are discussed. Where large-area aeromagnetic maps are available, crustal maps derived from satellite data can be compared with upward continued data. In general, the comparisons show agreement, with some differences, particularly in and near the auroral belts. The satellite data are further reduced by various methods of inverse and forward modelling, sometimes including reduction to the pole (RTP). These techniques are generally unstable at the equator. Common methods of stabilizing the inversions include principle components analysis and ridge regression. Because of the presence of the core field, the entire crustal contribution from the field is not known. Also, there is a basic nonuniqueness to the inverse solutions. Nevertheless, magnetizations that are interpretable can be derived.     

A simple method of estimating rock mass porosity and permeability

Conclusion A simple method of estimating fracture porosity and permeability based on empirical relations between fracture aperture andJRC andJCS can be developed. This shows very close correlation with existing data, using simple discontinuity models. There is quite a good correlation between fracture porosity and permeability and depth for larger initial apertures.     

THERMODYNAMIC PROPERTIES AND ROLE OF THERMALS IN THE STRATUS-TOPPED BOUNDARY LAYER

From results of two large-eddy simulation of stratus-topped boundary layer,the structure,thermodynamic prop-erties and role of thermals are investigated by using conditional sampling methods,which divided the thermals into thewarm/moist,cool/dry,warm/dry and cool/moist events.The results show that the main turbulent circulation in thestratus-topped boundary layer is composed of the warm/moist updraft and cool/dry downdraft.Below entrainmentregion,the warm/moist updrafts and cool/dry downdrafts are,respectively,positively and negatively buoyant andcontribute most to total fluxes and variances.Evaporative cooling has important effect on the structure and thermodynamic properties of thermals instratus-topped boundary layer.