中国大陆及华北地区地震资料的小波分析

基于地震活动为多尺度多活动这一观点，运用小波变换方法，以不同的小波尺度分析了中国大陆1900～2001年和华北地区1500～2001年M≥5地震的本尼奥夫应变资料，得到了各种层次地震活跃期和平静期，分析结果可信而又符合实际。对历史地震研究和地震危险性预测具有一定的参考价值。     

某些微量元素与人体健康的关系

人类是大自然的产物,是由多种元素组成的生命体,同时又是各种化学反应密切配合的体系。人体与外界环境存在着物质和能量的交换。人类生存需要各种常量元素和微量元素,维持人体正常机能所必需的Fe,Cu,Zn,Sr,F,I,Se,Si等微量元素,无论缺乏或过量都会导致人体产生疾病;而Cd等无生物功能作用的微量元素,对人体只能有毒害作用。     

基于树的多关键词搜索算法在网络监控系统中的应用

介绍了基于树的多关键词快速文本搜索算法，并针对该算法在实际应用中的问题提出了改进措施，在不增加预处理时间和内存空间消耗的前提下有效避免搜索中漏搜和多搜，无损于该算法的高效性。     

三维地震勘探在构造复杂区的应用

三维地震勘探通过炮点与检波点的灵活组合,适合于复杂地表条件下地震勘探,从原理上也更加符合地质体的三维空间特性,有利于构造复杂的研究与探测.本文介绍的查庄煤矿就是利用三维地震勘探方法成功解决复杂构造问题的典型实例之一.     

Nearly simultaneous observations of the conjugate polar cusp regions

The first simultaneous (within 6 min) observations of the low altitude polar cusp regions in the conjugate hemispheres are reported here based on two events detected by the DMSP-F2 and F4 satellites within the same geomagnetic local time sector. It is found that the electron spectra in the cusp are identical in the opposing hemispheres. In one case the observed latitudinal location and extent of the cusps are the same at the two hemispheres. However, in the other case the location of the equatorward boundary of the cusp regions differs by about 2° with drastically different spatial features. It is also found that in one of the events the plasma sheet electron precipitation regions overlap with the cusp regions at lower latitude in both hemispheres. The poleward boundary of these overlapping regions is located at the same latitude on either hemisphere, suggesting that this is the latitude of the last closed field line and that the cusp electrons are present on both closed and open magnetic field lines.     

Intensity distribution of dayside polar soft electron precipitation and the IMF

The influence of the B_z and B_y polarity of the IMF on the location of the dayside regions of precipitating, low energy electrons recorded by the DMSP F-2 satellite, is investigated. The average differential electron flux was determined for 2 months during local summer. It is found that the spatial distributions are similar for electrons in the range from 50 to 183 eV. The region of maximum intensity for K_p? 2+ over the Southern Hemisphere is located on the opposite side of noon from the Northern Hemisphere. The current intensity carried by precipitating electrons in the cusp region agrees with that measured by the TRIAD magnetometer. When the IMF is northward a marked asymmetry of the low energy electron precipitation between positive and negative B_y cases is observed. For positive B_y the maximum electron flux occurs between 0800 and 1200 M.L.T.and ?76 and ?83° M.L.A.T.and for negativeB_ythe region occurs between 1200 and 1500 M.L.T. and ?79 and ?82° M.LAT. The dynamical variations associated with substorm activity when the IMF is southward obscure the expected B_y effect.     

农田生态系统中重金属的积累积循环

本文通过对北京东郊高碑店地区污染农田的调查研究,探讨了重金属在农田生态系统中的积累和循环,计算出重金属在区域环境中的输入输出量,说明本区仍处于重金属积累状态,为防治农田环境污染,提出了停止施用污水处理厂的晾干污泥,减少灌溉污水中的重金属含量等保护性措施。     

在"98.7"武汉强暴雨过程中不同尺度波动的作用及其相干性

以Morlet复数小波函数分析方法等为基础,研究了1998年7月下旬长江中下游强暴雨过程中不同尺度波动的作用,同时用交叉谱研究了不同尺度波动的相干性。结果表明,这次强暴雨过程是一次中-β尺度能量积累与释放的过程,在2h左右的较短时周期波动中,中-α尺度对中-β尺度产生一定的干涉效应。     

绿洲边缘夏季小气候特征及地表辐射与能量平衡特征分析

利用“绿洲系统能量与水分循环过程观测试验”加强期(IOP)在甘肃省酒泉市金塔绿洲观测的资料,分析了夏季金塔绿洲边缘的小气候特征及地表辐射收支和地表能量平衡特征。作为绿洲沙漠相互作用的界面,在白天绿洲边缘的垂直运动仍然是以上升气流为主,并且其小气候主要受土壤湿度的影响。中午前后绿洲边缘的总辐射最大值在1000W.m-2左右,净辐射>700W.m-2;在白天,仅有个别天数的感热通量超过100W.m-2,最大值仅为150W.m-2左右。在整个观测期,有超过70%的天数出现负感热通量。而Bowen比在±10-1量级,地表能量不平衡的差额较大,约28%。     

Spatial heterogeneity of the driving forces of cropland change in China

Along with the increasing problems of rapid popu-lation increase, resources scarcity and environment deterioration, the interaction between human devel-opment and natural environment changes, especially the Land-Use/Land-Cover, LUCC issue is becoming a frontier and hot field[1], in which investigation on the mechanisms of land use change is one of the three core issues. Deficient natural resources, in particular the shortage of cropland resource in China, are the important constraints to Ch…