煤岩的显微构造特征及其与瓦斯突出的关系——以南桐鱼田堡煤矿为例

煤瓦斯突出与煤岩显微结构构造密切相关。除部分显微结构构造与成煤阶段的环境等有关外,大部分都是构造变形的结果。因此,我们从构造变形类型和特点来划分煤岩显徽构造类型,既简便又利于应用。根据四川南桐鱼田堡煤矿4号及6号煤层的扫描电子显微镜研究,可将煤岩划分成5类:非构造煤、微裂隙煤、微劈理煤、碎裂构造煤和糜棱构造煤。文中详述了各类煤的特点,指出它们所代表的构造意义,并讨论了它们与瓦斯突出的关系。还特别提出糜棱构造煤的一系列塑性变形特征。得出结论:若其他条件均具备,有糜棱构造煤产出的地段,就可能是瓦斯突出最危险的部位。此外,根据观察煤瓦斯突出后的煤岩显微构造变化,提出有关瓦斯突出的过程,并探讨了煤瓦斯突出机理。在瓦斯突出过程中,已经历过塑性变形的煤岩又叠加了脆性变形,因而发生大量煤“粉尘”随突出而抛出。     

瓦斯突出地球物理场的响应特征

研究了瓦斯突出地球物理场的电磁波和弹性波响应特征,其响应是构成瓦斯突出地球物理场的介质条件所表现出来的。关键层应力墙瓦斯突出机理认为,瓦斯突出煤层由关键层和伴随层构成。关键层和伴随层在空间的分布规律和相互作用体现在物理场的差异上,把关键层（或瓦斯突出煤体）作为地球物理场中的异常体进行研究是可以利用地球物理方法识别的。突出地球物理场响应特征的研究为从地球物理研究瓦斯突出预测理论和方法提供了科学思路。     

用陕西天文台流星雷达监测人为空间碎片可能性的分析

本文分析了利用中国科学院陕西天文台的流星雷达进行人为空间碎片监测的可能性．详细计算了到达接收机的回波的信噪比Ｓ／Ｎ依赖于目标散射横截面。和高度距离Ｒ的关系。理论计算表明，利用陕西天文台的流星雷达完全有可能监测在２００ｋｍ至１２００ｋｍ的高度范围内，半径大于０．５ｍ的人为空间碎片．     

流星雨摄影观测记录的罕见现象

2001年狮子座流星雨,是几百年来难得有机会在中国观测到的一场流星暴。在我们收集到的照相观测资料中,发现了一些特殊的、还未引起广泛注意的流星现象。"蛇行"的流星以及螺旋形并带有辐条结构的流星余迹,早在我国古代记录中就可以找到印证。现代的照相技术,不仅直观地显示了文字难以描述的颜色、形态和变化,而且提供了可永久性进行测量的记录。其中包括罕见的对流星余迹的双站观测资料。用常规的"高空风作用"难以解释这些观测现象。它们可能反映了流星带电体与地球磁场的相互作用。     

The Phanerozoic Reconstitution of Indian Shield as the Aftermath of Break-up of the Gondwanaland

The Indian crust, generally regarded as a stable continental lithosphere, experienced significant tectono-thermal reconstitution during the Phanerozoic. The earliest Phanerozoic tectonic process, which grossly changed the geological and geophysical character of the Precambrian crust, was during the Jurassic when this crustal block broke up from the Gondwana Supercontinent. There were two earlier abortive attempts to fragment the supercontinent in the Palaeozoic. Different types of geological processes were associated with these aborted events. The first was the intrusion of anorogenic alkali granites during the Early Palaeozoic (at 500±50 Ma), while the second was linked with formation of the Gondwana rift basins during Late Palaeozoic. The tectonic history of the Indian Shield subsequent to its separation from the Gondwanaland at around 165 Ma is a complex account of its northward journey, which was culminated with its collision with the northern continental blocks producing the mighty Himalayas in the process. Considerable reconstitution of the Indian Shield took place due to magma underplating when this lithospheric block passed over the four mantle plumes. While the underplating events grossly changed the geophysical character of the Indian Shield in isolated patches, the propagation of the underplated materials was assisted by the deep crustal fractures (geomorphologically expressed as lineaments), which formed during the break-up of the Gondwanaland. Several of these deep fractures evolved through the reactivation of the pre-existing (Precambrian) tectonic grains, while some others developed as new fractures in response to either the extensional stresses generated during the supercontinental break-up or the plume-lithosphere reactions. Significant geomorphological changes occurred in peninsular India subsequent to the continental collision. Most of these changes were brought about by the movements along the lineaments, which fragmented the Indian Shield into a number of rigid crustal blocks. The present day seismic behaviour of the Indian Shield is a reflection of movements of the rigid crustal blocks relative to each other. An interesting feature of the Phanerozoic geological history of the Indian Shield is the evolution of a number of sedimentary basins under different tectono-thermal regimes.     

NUMERICAL MODELLING OF METHANE GAS MIGRATION IN DRY COAL SEAMS

This paper presents the development of a mathematical model for methane gas migration in coal seams. The major focus of this model is the coupling between the gas flow and deformation of solid coal. The effect of diffusion of adsorbed methane gas from the solid matrix to the voids has been taken into account. The adsorption of gas in the coal seam causes a two-phase state of gas flow. The governing equation for the two-phase gas flow is a non-linear partial differential equation with non-linear boundary conditions. A finite element model has been developed for simulation of the distribution of pressure and concentration of methane gas due to gas migration in coal seams.     

The Canadian Meteor Orbit Radar: system overview and preliminary results

This paper describes the Canadian Meteor Orbit Radar (CMOR) that has been in operation since late 2001. CMOR is a 3 station meteor radar operating at a frequency of 29.85 MHz near Tavistock, Ont. To avoid bias against fragmenting meteoroids that is inherent in the traditional multi-station method of Gill and Davies (Mon. Not. R Astron. Soc. 116 (1955) 105), we use a completely geometrical method similar to that used in the AMOR system (Quart. J. R. Astron. Soc. 35 (1994) 293) based on the interferometric determination of the echo directions and the time delays of echoes from two remote stations to obtain the trajectories and speeds of meteoroids. We describe the hardware and some of the software and present some preliminary results that provide a good indication of present capabilities of the system. Typically, we can measure 1500 individual trajectories, and hence orbits, per day with a mean accuracy of 6° in direction and about 10% in speed. A small subset of these for which it is possible to measure the speeds using Hocking's (Radio. Sci. 35 (2000) 1205) method yield speeds with a precision of about 5%. The purpose of this paper is to show that the radiants and speeds necessary for the computation of orbits are well measured rather than to discuss any orbital surveys.     

Study of the fast X-ray transient XTE J1901+014 based on INTEGRAL,RXTE, and ROSAT data

The source XTE J1901+014 discovered by the RXTE observatory during an intense outburst of hard radiation and classified as a fast X-ray transient is studied. The source’s spectral characteristics in the quiescent state have been investigated for the first time both in the soft X-ray energy range (3–20 keV) based on ROSAT and RXTE data and in the hard energy range (>20 keV) based on INTEGRAL data. A timing analysis of the source’s properties has revealed weak nonperiodic bursts of activity on time scales of several tens of seconds and two intense (～0.5–1 Crab) outbursts more than several hundred seconds in duration. Certain assumptions about the nature of the object under study are made.     

Probabilities of Perception and Population Index in Visual Observations of Meteor Showers

Earth, Moon, and Planets -     

Swelling-induced volumetric strains internal to a stressed coal associated with CO2 sorption

It is generally accepted that typical coalbed gases (methane and carbon dioxide) are sorbed (both adsorbed and absorbed) in the coal matrix causing it to swell and resulting in local stress and strain variations in a coalbed confined under overburden pressure. The swelling, interactions of gases within the coal matrix and the resultant changes in the permeability, sorption, gas flow mechanics in the reservoir, and stress state of the coal can impact a number of reservoir-related factors. These include effective production of coalbed methane, degasification of future mining areas by drilling horizontal and vertical degasification wells, injection of CO₂ as an enhanced coalbed methane recovery technique, and concurrent CO₂ sequestration. Such information can also provide an understanding of the mechanisms behind gas outbursts in underground coal mines.The spatio-temporal volumetric strains in a consolidated Pittsburgh seam coal sample were evaluated while both confining pressure and carbon dioxide (CO₂) pore pressure were increased to keep a constant positive effective stress on the sample. The changes internal to the sample were evaluated by maps of density and atomic number determined by dual-energy X-ray computed tomography (X-ray CT). Early-time images, as soon as CO₂ was introduced, were also used to calculate the macroporosity in the coal sample. Scanning electron microscopy (SEM) and photographic images of the polished section of the coal sample at X-ray CT image location were used to identify the microlithotypes and microstructures.The CO₂ sorption-associated swelling and volumetric strains in consolidated coal under constant effective stress are heterogeneous processes depending on the lithotypes present. In the time scale of the experiment, vitrite showed the highest degree of swelling due to dissolution of CO₂, while the clay (kaolinite) and inertite region was compressed in response. The volumetric strains associated with swelling and compression were between ± 15% depending on the location. Although the effective stress on the sample was constant, it varied within the sample as a result of the internal stresses created by gas sorption-related structural changes. SEM images and porosity calculations revealed that the kaolinite and inertite bearing layer was highly porous, which enabled the fastest CO₂ uptake and the highest degree of compression.