Study of charge structure and radiation characteristic of intracloud discharge in thunderstorms of Qinghai-Tibet Plateau

The comprehensive observations on lightning discharges were conducted in Naqu area of Qinghai-Tibet Plateau in summer of 2002. The electric structures of thunderstorms and the characteristics of lightning discharges at initial stage were analyzed by using the observation data. The results show that most of intracloud (IC) lightning flashes were polarities inverted in thunderstorms with tripole electric charge structure and occurred between negative charge region located in the middle of the thunderstorm and positive charge region located at the bottom of the thunderstorm. The radiation characteristics of discharge processes in cloud with longer lasting time involved in Cloud-to-Ground (CG) lightning flashes were similar to that of IC discharges.A lot of radiation pulses were produced in these discharge processes. Because the IC discharges took place at the bottom of thundercloud and were near the ground, they may produce more serious damage to equipment on the ground therefore should not be neglected in lightning protection.     

Experimental research on reservoir sensitivity to stress and impacts on productivity in Kela 2 Gas Field

Kela 2 Gas Field, with high formation pressure (74.35MPa), high pressure coefficient (2.022) and difficulty of potential test and evaluation, is the largest integrated proved dry gas reservoir in China so far and the principal source for West-East Gas Development Project. In order to correctly evaluate the elastic-plastic deformation of rocks caused by the pressure decline during production, some researches, as the experiment on reservoir sensitivity to stress of gas filed with abnormal high pressure, are made. By testing the rock mechanic properties, porosities and permeabilities at different temperature and pressure of 342 core samples from 5 wells in this area, the variations of petro-physical properties at changing pressure are analyzed, and the applicable inspection relationship is concluded. The average productivity curve with the reservoir sensitivity to stress is plotted on the basis of the research, integrated with the field-wide productivity equation. The knowledge lays a foundation for the gas well productivity evaluation in the field and the gas field development plan, and provides effective techniques and measures for basic research on the development of similar gas fields.     

类石材料--灰泥的冻融过程

Serious failure on the slope of rock ground can be caused by a cyclic action of freezing and thawing in the cold regions. The frost susceptibility and the effect of freezing and thawing onthe rock material, however, have not been well investigated. In order to find out the freezing effect on the rock materials, mortar specimens are frozen as a pseudo-rock material under the constant rate of freezing by means of controlling the temperature of both ends of specimen. The freezing process is given one-dimensionally to the cylindrical samples in the laboratory to simulate the in-situ freezing phenomena in the natural ground. Formation of ice lens, frost heave and water intake during freezing process are observed on the mortar specimen under constant freezing rate, which probably causes cracks or large deformation in the real rock ground. The values of the velocity of elastic wave propagation are compared before and after freezing process to estimate the degree of weathering due to freezing and thawing.     

A comparative study on the illite crystallinity and the clay mineral reflectance spectral index for subdividing the very low-grade metamorphic belt along the Lizhou-Hekou geological section in the Youjiang sedimentary basin, Guangxi, China

To examine the application potential of hyperspectral remote sensing techniques in classifying very low-grade metamorphic belts, the composition of clay minerals and the cyrstallinity of illite from mudstones were measured using XRD and VIS-SWIR (400-2500 nm) reflectance spectroscopy. Based on the illite cyrstallinity, Kubler Index (KI), the Early Triassic LuoLou Group and the Middle Triassic lower Baifeng Formation were classified as the lower Epizone with KI△2θ° ranging from 0.22 to 0.25, the upper Baifeng Formation as upper anchizone with KI△2θ°ranging from 0.26 to 0.33, and the Hekou Formation as lower anchizone with KI△2θ° ranging from 0.38 to 0.40. According to a KI△2θ° value of 0.43, it is possible that there may exist a local diagenetic zone in the upper strata. The illite cyrstallinity Kubler index and the metamorphic grade increase from the bottom to the top of the stratigraphic sequence. The metamorphic grade boundaries nearly match the stratigraphic boundaries, indicating a burial metamorphism nature for the stratigraphic sequence. From the bottom to the top of the sequence, the spectral absorption band center of clay minerals from fresh rocks is around 2200 nm. The absorption band centers change towards shorter wavelengths: the Luolou Group being at 2220 nm, the Baifeng Formation at 2217-2213 nm, the lower member of the Hekou Formation at 2214-2206 nm, and the upper member of the Hekou Formation at 2205-2197 nm. The spectral absorption band center of illite shows the same change pattern. These results indicate that very low-grade metamorphic belts can be subdivided using spectral indices of clay minerals, which are measured by using field portable spectroradiometers. However, it may not work well with satellite and airborne sensors.     

天山山区近40a年降水变化特征与南、北疆的比较

本文分析了天山山区近40 a来年降水变化的基本特征，并与南疆、北疆进行了比较，所得的主要结果如下：(1)天山山区在年降水量干湿变化阶段上与北疆的相似性强于南疆。(2)年降水量的空间分布的同步变化性以北疆为最好，南疆最差，天山山区居中，而年降水量的空间分布的反向变化性，以天山山区为最大，北疆最小，南疆居中。(3)天山山区与南疆从60年代到90年代，年降水均表现出了持续的增加的趋势，北疆年降水从60年代到90年代，除70年代外，不断增多。     

兰坪坳陷油气组群特征及其成因

兰坪坳陷的油气主要见于金顶矿区的下含矿层，储层主要为上三叠统三合洞组的灰岩和角砾状灰岩。油气地球化学特征表明有机母源输入是多源的，沉积成烃水体介质以还原性占优势．具有较高盐度，有机质热演化处于成熟一高成熟阶段．生物降解改造较为强烈。根据原油的母源贡献、生物降解、环境介质条件等特征，将兰坪坳陷原油划分为3类组群。     

长江中下游地区地下水中Mn元素的背景特征及其形成

该文论述了长江中下游地区地下水锰元素的背景特征及其与地下水的含水介质成分、上覆岩土性质、氧化还原环境、地下水的迳流条件、地下水及土壤酸碱度的关系.研究结果表明,长江中下游地区地下水中Mn元素含量,在区域上分布特点为江汉平原东部区〉长江三角洲南部区〉鄱阳湖区.     

载荷试验确定基床系数修正方法的讨论

Winkler地基模型是目前工程界应用最广的一种地基模型，但对其关键参数——基床系数k的确定，许多文献的表述并不一致。该文在大量试验资料的基础上，通过对该问题的深入研究，阐明了通过载荷试验确定基床系数修正方法的有关概念。对于砂性土地基，载荷板试验得出的基准基床系数仅需要进行基础大小修正，而对于粘性土地基，则需要进行基础大小和基础形状两项修正。     

河流调整中的熵、熵产生和能耗率的变化

河流是一个真正的开放系统,而不是孤立系统或封闭系统。运用经典热力学和非平衡态热力学基本原理,分析研究了河流调整中的熵、熵产生和能耗率的变化。指出:熵和熵产生是两个不同的概念;最小熵产生原理等价于最小能耗率原理;冲积河流在调整过程中遵循最小熵产生原理或最小能耗率原理,而不是最大熵原理。     

我国主要金矿类型中黄铁矿"电子-空穴心"特征及影响因素

通过对我国主要金矿类型中黄铁矿导电类型的分析表明，黄铁矿“电子。空穴心”与金矿床的成因类型具有密切的联系，华北地台太古代变基性火山岩中的金矿床(绿岩带型)、热水淋滤型(卡林型)金矿床，黄铁矿多为单一的“电子心”型导电。大多数产于中生代岩体中的中深脉状金矿、火山次火山岩中的金矿床，黄铁矿为“电子心”、“空穴心”混合型导电，个别的为单一的“空穴心”导电。黄铁矿的“电子．空穴心”受杂质成分As、Co、Nl在成矿背景中的丰度，进入黄铁矿品格中的替代能力的差异、补偿类质同象现象、成矿时温度以及．f(S2)等多种因素的耦合制约。