The mechanisms of shallow earthquakes and the monitoring of a comprehensive test ban

The ability of seismological criteria to identify earthquakes from underground explosions depends partly on the orientation of the earthquake source. Well-determined double-couple moment tensor solutions for a large number of earthquakes have been published in the Harvard centroid moment tensor (CMT) and United Slates Geological Survey (USGS) catalogues. Statistical analyses of these catalogues indicate that the distribution of the orientation of earthquake mechanisms is not random. The distribution of the T axes shows significant clustering around the downward vertical, indicating that a larger number of earthquake mechanisms radiate compressional P -wave energy to teleseismic distances from near the maximum of the radiation pattern than is predicted if earthquake sources are randomly oriented double couples. The clustered T axes correspond to compressional dip-slip mechanisms, and it is this type of mechanism which is believed to cause both the m _b: M _s (the ratio of body-wave to surface-wave magnitude) and first-motion criteria to misidentify an earthquake as an explosion.     

Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers （ADPs） deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40-80 cm/s at the mooring stations. M2 current is the most dominant primary tidal constituent, while MS4 and M4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.     

2013-06����ƽ��С��Ⱥ���������̽��

2013-06~07??????????3?????????????С??????????п???????У???????????????????????????????????????????????????????????????????????????????????????????????????????????(ETAS???)??????????????????????崥???????????????й???????????????????     

自适应遗传算法配准三维数字样品模型及其CAD模型

通过包围盒的初始匹配和浮点数编码自适应遗传算法的精确匹配,实现了三维数字样品模型及其CAD模型的配准。初始匹配决定精确匹配空间变换参数的范围:精确匹配在搜索变换矩阵的6个变换参数过程中,采用最小二乘方法构造目标函数;遗传算法中引入种群多样性指标;在遗传操作的交叉算子和变异算子中引入该指标,并将该指标用于交叉概率和变异概率两个参数的调整,有效地克服了遗传算法的早收敛问题,实验结果表明该方法较好地解决了三维数字样品模型及其CAD模型的配准问题,且算法稳定,易于实现。     

哈密南部暴雨成因分析

通过对 2 0 0 2年 6月 1 8～ 1 9日哈密南部暴雨的环流背景、物理机制、T2 1 3产品的物理量及卫星云图分析 ,揭示形成暴雨的成因     

社会经济统计数据空间化研究进展

社会经济统计数据通常是以各级行政区为单位的汇总数据,它虽然能反映统计单元之间的差异但却不能反映统计单元内部的异质性,在实际应用中,无法满足统计任意区域内的社会经济数据的需求,而社会经济统计数据空间化则是有效解决该问题的一条重要途径。本文对现有社会经济统计数据的空间化方法、社会经济统计数据空间化过程所依赖的辅助数据、现有主要的社会经济空间化数据产品进行了归纳总结,并从空间化方法的制约因素和改进方向、新型辅助数据的探索和多源辅助数据的综合利用、高时空分辨率和高精度数据产品研发3个方面展望了社会经济统计数据空间化的未来发展趋势。研究结果可为社会经济统计数据空间化方法的选择与改进、辅助数据的选择与综合利用、社会经济空间化数据产品的选择与改进提供参考。     

Improvement in the performance of solar adaptive optics

Adaptive optics （AO）, which provides diffraction limited imaging over a field-of-view （FOV）, is a powerful technique for solar observation. In the tomographic approach, each wavefront sensor （WFS） is looking at a single reference that acts as a guide star. This allows a 3D reconstruction of the distorted wavefront to be made. The correction is applied by one or more deformable mirrors （DMs）. This technique benefits from information about atmospheric turbulence at different layers, which can be used to reconstruct the wavefront extremely well. With the assistance of the MAOS software package, we consider the tomography errors and WFS aliasing errors, and focus on how the performance of a solar telescope （pointing toward zenith） is related to atmospheric anisoplanatism. We theoretically quantify the performance of the to- mographic solar AO system. The results indicate that the tomographic AO system can improve the average Strehl ratio of a solar telescope in a 10＂ - 80＂ diameter FOV by only employing one DM conjugated to the telescope pupil. Furthermore, we discuss the effects of DM conjugate altitude on the correction achievable by the AO system by selecting two atmospheric models that differ mainly in terms of atmospheric prop- erties at ground level, and present the optimum DM conjugate altitudes for different observation sites.     

测角观测误差在初轨确定中的传布

本文用非线性规划方法探讨了初轨确定问题。测角观测误差看作为参数的微摄动,而非线性规划的灵敏性分析模型（ｆｈｐ） 建立在无摄动的情况下。由此,得出了在一阶近似下轨道根数计算值和测角观测误差值间关系的分析表达式。     

基于遥感信息的土地资源可持续利用研究

遥感信息是对自然界的反映，它具有宏观、动态、准确、快速的优点，可以及时提供动态数据。基于遥感信息，对吉林西部土地资源利用状况进行调查，运用主成分分析法，可以不损失或很少损失原有的信息，将原来个数较多而且彼此相关的变量转换为新的个数较少而且彼此独立或不相关的新变量。对土地资源可持续利用进行定量分析研究，指出土地利用中存在的问题，并提出吉林西部土地资源可持续利用发展模式。