Wavenumber of the guided wave supported by a thin resistive layer in marine controlled‐source electromagnetics

This paper discusses the asymptotic behaviour of the electromagnetic fields received on the sea‐bed (target response), as well as the fields distributed inside a thin resistive target, generated by a horizontal electric dipole above the sea‐bed in marine controlled‐source electromagnetics for hydrocarbon exploration. It is found that the guided wave supported by a thin resistive target can be expressed as a single‐mode exponential function. A simple closed‐form expression is derived to relate the single‐mode wavenumber of the guided wave to the model parameters: the resistivity and thickness of the target layer, the sea‐bed resistivity and the frequency. When the air‐wave is removed, the guided wave is dominant among the fields received on the sea‐bed at far offset. Hence the wavenumber of the guided wave can be calculated from the fields measured on the sea‐bed. The closed‐form expression can then be used to invert the target property from the calculated wavenumber and hence, can be considered as a hydrocarbon indicator.     

Horizontal distribution and transport processes of bloom-forming Microcystis in a large shallow lake (Taihu, China)

The horizontal distribution of bloom-forming Microcystis in a specific lake area and the transport of Microcystis by wind-driven lake currents between Meiliang Bay and the open water of Taihu Lake were measured during continuous field observations from August 21 to 25, 2006. During the observations, the horizontal distributions of Microcystis, represented by Chlorophyll a, showed a clear concentration toward downwind lake areas. According to the lake currents and the Chl a concentrations on the boundary line between the Meiliang Bay and the open water, the transported Chl a was less than 2% of the total weight of Chl a in Meiliang Bay on August 22, 24 and 25. The results suggest that the horizontal distribution of the bloom-forming Microcystis was strongly affected by the wind conditions, and the wind-driven Microcystis accumulation was mainly determined by surface drift; the transport of Microcystis by lake currents was much less important in this large, shallow lake.     

Study of roof stability of the end of working face in upward longwall top coal

Low recovery of longwall top coal caving (LTCC) remains one of the most difficult engineering problems in this mining method and impedes its application. The top coal left in the gob at face end accounts for a large portion of the total coal loss, and the instability of the leftover triangle coal at face end has long been a threat to the safety of miners and the mining equipment. In this paper, based on the engineering background of Ruilong mine, we explore the stability of the roof at the end of the face by using theoretical analysis, numerical simulation, and field measurement. Results reveal that in the inclined longwall top coal caving face, the immediate roof forms an “arch” structure, and the basic roof forms a “masonry beam” structure after the roof collapses; working resistance of the support calculated by the method of ultimate bearing capacity was adequate to meet the requirement of roof load; roof load of coal pillar was related to the length of key block and fracture position; and increasing the size of coal pillar could ensure the stability of both coal pillar and roof.     

Cryptic diversity of marine gastropod Monodonta labio (Trochidae): did the early Pleistocene glacial isolation and sea surface temperature gradient jointly drive diversification of sister species and/or subspecies in the Northwestern Pacific?

Formation of glacial refugia during the Pleistocene climatic oscillations has been put forward to elucidate the diversification of marine organisms in the north‐western Pacific. The marine gastropod Monodonta labio is one of the most common species in the Northwestern Pacific and possibly possesses cryptic diversity. Here, we investigate the phylogeographic pattern of this species to test the potential mechanisms driving its diversification in the Northwestern Pacific. Genetic information for two mitochondrial genes (Cytochrome oxidase subunit I and 16S rDNA) and one nuclear gene (internal transcribed spacer 1) was acquired to detect genetic structuring and to reconstruct the gastropod's phylogenetic history. Our results revealed that M. labio is comprised of five main clades, and divergence time estimates place their cladogenesis as corresponding to the initiation (c. 2.5 mya) and intensification (c. 0.9 mya) of large‐scale Northern Hemisphere ice sheets. The early and middle Pleistocene divergence times are consistent with the emergence times of the Dongshan land bridge, which would seperate the ancient East China Sea and the ancient South China Sea forming two potential refugia. In addition, the deep trough in the Qiongzhou Strait would possibly act as another potential refugium with the uplift of the Qiongzhou Strait at mid‐Pleistocene. This study suggests that the current genetic architecture of M. labio is probably correlated with glacial isolation and sea surface temperature gradient. We also put forward the possibility that these factors were probably an important driver for the diversification of sister species or subspecies of other taxa in the Northwestern Pacific.     

主成分分法在天体物理中的应用

主成分分析法是从观测数据中获取主要信息的一种多种变量统计方法，它用数目少得多的新主代会原有观测量，以寻找原观测量之间的相互关系，且不损失原始数据的主要信息，尤其是对于大样本，多参量情况，该方法更为简捷而有效，目前，主成分分析法被广泛应用于三体物诸多研究领域中,介绍了主成分分法的原理和它在天体物理和它在天体物理中的广泛应用。     

利用3-D AVO分析识别陆相薄互层砂岩气藏和深层火成岩

大庆地区陆相砂泥岩薄互层AVO特性不明显,甚至 没有显示。本文以松辽盆地北部三肇地区为例详 细描述了3-D AVO分析方法及其在该区的应用效 果。通过对该区AVO数据的特殊处理和解释,并应 用有关的测井曲线指导AVO正演,在升81井扶余 油层得到了明显的砂岩气藏AVO响应,查明扶余油 层砂岩气藏存在着"振幅随炮检距增加而增大"这 一AVO异常特征。同时在三肇地区应用3-D AVO分 析技术首次发现了深层火山岩,查明了火山岩的 空间展布形态,其喷发的通道位于断裂的交叉处, 这与地球动力学和大地构造物理学的观点相吻合。     

金龙山地区斜坡滑动优势面分析

据优势面分析原理和方法,对金龙山地区斜坡各种结构面所作的优势面分析结果显示:浅层强风化岩体中顺坡向剪切裂隙,是控制浅层顺层滑坡发生发展的滑动优势面;深层弱风化岩体中粘土岩风化软弱夹层、斜坡上段拉张裂隙与斜坡下段顺坡向剪切裂隙三者相组合,是控制深层顺层滑坡发生的滑动优势面。当地受滑动优势面控制的滑坡变形破坏模式有:浅层为蠕滑—拉裂,深层为滑移—弯曲。     

移动GIS关键技术及其应用

随着移动通讯技术、无线互联技术和各种移动终端技术的发展，传统的GIS发展正在逐渐向移动GIS发展。本文首先分析了移动GIS体系的组成结构和系统原理，接着论述了移动GIS系统的关键技术。最后本文分析了LBS与移动GIS的关系，并指出LBS是移动GIS最有前景的应用之一。     

2003年11月6日大同市异常暴雪成因初探

2003年11月6日大同市产生暴雪天气过程,此次暴雪主要是由高空强冷气旋、低气切变线和地面倒槽前部强盛的偏东暖湿气流的共同影响所引发的。通过分析论述,进一步揭示出大同市暴雪发生的环流背景和水汽辐合区,为今后的暴雪预报总结出一些关键着眼点。     

Classification and Extraction of Urban Land-Use Information from High-Resolution Image Based on Object Multi-features

INTRODUCTIONWith the rapid development of industrialization,urbanization,andinformation technology ,as well asthe practice of “digital city”and “digital earth”( Gore , 1998) , many administrators and decision-makers are realizing the i mportance of high-resolution i mage information to urban planning andmanagement . Especially in recent years , with thefast development of remote sensing technology ,remote sensing data can be obtained that are complementaryin spatial andti me resolution…