新疆冰雹天气过程的基本特征   总被引：5，自引：0，他引：5  

王旭  马禹 《沙漠与绿洲气象(新疆气象)》2002,25(1):10-11,14

通过对新疆39a冰雹天气资料的普查，得到76次系统性冰雹天气过程和1279次局地冰雹天气过程，局地冰雹天气的发生远远多于系统性雹天气。冰雹天气过程与地形密切相关，主要发生在山区，冰雹天气以1天为主，多发生于夏季，系统性冰雹天气均由中尺度高压造成。  相似文献   

台风活动对副热带高压位置和强度的影响   总被引：9，自引：7，他引：9  

李春虎  黄福均  罗哲贤 《高原气象》2002,21(6):576-582

利用一个浅水模式，实施了6组时间积分为4－5个模式日的试验，研究了台风对副热带高压中心位置及强度的影响。结果表明：台风和副热带高压的相互作用可以使高压中心位置西移,强度增加。据此讨论了台风活动和西北地区东部干旱之间统计联系的可能机制。  相似文献   

CLIMATOLOGICAL CHARACTERISTICS FOR THE ONSET OF ASIAN SUMMER MONSOON AS REVEALED BY HIRS-Tb12 AND DROUGHT AND FLOODS IN EASTERN CHINA     

施宁  蒋尚城  严明良 《热带气象学报(英文版)》2002,8(2):141-149

As shown in comparison and study of the HIRS-Tb12 data and conventional data, temperature, humidity and vertical motion are structured differently in the Southern and Northern Hemispheres, which are well depicted with the HIRS-Tb12 data. When high pressures rapidly decrease over the regions of South China Sea and Arabian Sea with the HIRS-Tb12 less than 200 W/m2, monsoons will set off in the South China Sea, Arabian Sea and Bay of Bengal, respectively. From a year of significant drought to one of significant floods, the trend of evolution is significantly different in the downdraft areas of the subtropical highs between the two hemispheres.  相似文献   

1999年杭嘉湖平原一次连续暴雨过程诊断分析   总被引：1，自引：1，他引：1       下载免费PDF全文

郭可义  盛文斌 《应用气象学报》2002,13(6):696-703

用新的曲面拟合法(NMOCSF)对江淮和杭嘉湖平原一次连续暴雨过程作物理诊断，结合天气形势讨论了准静止华北高压的形成及其对江淮和杭嘉湖平原连续暴雨的贡献。指出，当江淮和杭嘉湖平原处在梅雨期时，应特别注意华北高压的强度和位置，一旦构成阻塞形势，就极可能发生大范围、持续性的强降水过程。  相似文献   

赣北中元古界双桥山群低变质强变形行为与格林威尔期造山作用   总被引：4，自引：1，他引：4  

秦松贤  章泽军  张志  赵温霞  蔡雄飞  顾延生 《地质科技情报》2002,21(2):8-12

广泛分布于赣北地区的中元古界双桥山群，以低级区域变质作用、强烈构造变形、具陆内造山带构造变形特征；其成果系在华夏古陆与扬子古陆的碰撞拼接过程中，其应力向陆内传递的结果；时间大致在1100－800Ma，与全球格林威尔期造山作用相当。  相似文献   

新疆西天山高硫化型京希-伊尔曼德金矿床的识别标志及其找矿意义   总被引：3，自引：0，他引：3  

肖龙  王方正  张桂林  付民禄  Begg Graham  Hayward Nick 《地质科技情报》2002,21(3):74-78

经过详细的野外地质勘查、热液蚀变及蚀变矿物学研究，流体包裹体和同位素研究，首次将西天山京希－伊尔曼德金矿床确定为高硫化型浅成低温热液金矿床。该矿床的主要识别标志为：发育以多孔状石英为特征的硅化蚀变带和高级泥化蚀变带；成矿流体性质为低盐度[W(NaCl)为0.3-4.2%]、低pH值（3－4）和高氧化态；氧同位素δ（^18O)为1.7 ‰-4.3‰,δ(D)为－60‰--80‰。金主要富集在高级泥化带和中心硅化蚀变带内。系统研究和总结了成矿地质－地球化学制约因素以及区域、靶区和勘探区尺度的找矿标志。  相似文献   

Tests on low‐ductility RC frames under high‐ and low‐frequency excitations     

Ser‐Tong Quek  Chengmei Bian  Xilin Lu  Wensheng Lu  Haibei Xiong 《地震工程与结构动力学》2002,31(2):459-474

The response of low‐ductility reinforced concrete (RC) frames, designed typically for a non‐seismic region, subjected to two frequencies of base excitations is studied. Five half‐scaled, two‐bay, two‐storey, RC frames, each approximately 5 m wide by 3.3 m high, were subjected to both horizontal and/or vertical base excitations with a frequency of 40 Hz as well as a lower frequency of about 4 Hz (close to the fundamental frequency) using a shake table. The imposed acceleration amplitude ranged from 0.2 to 1.2g. The test results showed that the response characteristics of the structures differed under high‐ and low‐frequency excitations. The frames were able to sustain high‐frequency excitations without damage but were inadequate for low‐frequency excitations, even though the frames exhibited some ductility. Linear‐elastic time‐history analysis can predict reasonably well the structural response under high‐frequency excitations. As the frames were not designed for seismic loads, the reinforcement detailing may not have been adequate, based on the crack pattern observed. The effect of vertical excitation can cause significant additional forces in the columns and moment reversals in the beams. The ‘strong‐column, weak‐beam’ approach for lateral load RC frame design is supported by experimental observations. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Pseudodynamic tests on rubber base isolators with numerical substructuring of the superstructure and strain‐rate effect compensation     

F. J. Molina  G. Verzeletti  G. Magonette  Ph. Buchet  V. Renda  M. Geradin  A. Parducci  M. Mezzi  A. Pacchiarotti  L. Federici  S. Mascelloni 《地震工程与结构动力学》2002,31(8):1563-1582

A pseudodynamic testing procedure has been applied by which the seismic response of a base‐isolated building is obtained by using as specimen the isolators, while the superstructure is numerically simulated. The procedure also takes advantage of the continuous pseudodynamic testing capabilities of the ELSA laboratory, which increase the accuracy of the results and reduce the strain‐rate effect of the rubber bearings. A simple proportional correction of the measured forces compensates the remaining strain‐rate effect due to the unrealistic speed of the test. The correction factor is obtained by means of a characterizing test on the specific rubber isolators. The developed method has been successfully applied to the prediction of the seismic response of a base‐isolated four‐storey building submitted to several specified accelerograms. The results for those earthquakes as well as the effects of some changes of the parameters of the system are discussed. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Study on effects of damping in laminated rubber bearings on seismic responses for a ⅛ scale isolated test structure     

Bong Yoo  Yang‐Hann Kim 《地震工程与结构动力学》2002,31(10):1777-1792

The effects of damping in various laminated rubber bearings (LRB) on the seismic response of a ?‐scale isolated test structure are investigated by shaking table tests and seismic response analyses. A series of shaking table tests of the structure were performed for a fixed base design and for a base isolation design. Two different types of LRB were used: natural rubber bearings (NRB) and lead rubber bearings (LLRB). Three different designs for the LLRB were tested; each design had a different diameter of lead plug, and thus, different damping values. Artificial time histories of peak ground acceleration 0.4g were used in both the tests and the analyses. In both shaking table tests and analyses, as expected, the acceleration responses of the seismically isolated test structure were considerably reduced. However, the shear displacement at the isolators was increased. To reduce the shear displacement in the isolators, the diameter of the lead plug in the LLRB had to be enlarged to increase isolator damping by more than 24%. This caused the isolator stiffness to increase, and resulted in amplifying the floor acceleration response spectra of the isolated test structure in the higher frequency ranges with a monotonic reduction of isolator shear displacement. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

末次盛冰期百年尺度气候变化的南京石笋记录   总被引：17，自引：10，他引：17       下载免费PDF全文

汪永进  孔兴功  邵晓华  吴江滢 《第四纪研究》2002,22(3):243-251

据年层计数和TIMSU系测年结果,建立了南京汤山葫芦洞YT石笋年际精度时间标尺(18000～14000aB.P.)。除石笋顶部5mm层段外,高分辨率的^δ18O、灰度和年层厚度3种指标在百年尺度上具有相当一致的对应关系,表明这3种指标对气候因素变化响应比较敏感。综合石笋^δ18O和本区古植被资料,估计末次盛冰期和波令暖期年均温分别达7℃和15℃。石笋揭示的末次盛冰期气候可进一步划分为4个阶段:1)18150～16900aB.P.,年均温和洞穴湿度逐步下降;2)16900～16100aB.P.,年均温和洞穴湿度相对稳定,可进一步划分为3个暖峰和两个冷谷;3)16100～15600aB.P.,年均温快速下降,按氧同位素平衡方程计算,其冷谷可能接近于0℃,但洞穴湿度比前期下降幅度并不大;4)15600～14750aB.P.,年均温和洞穴湿度比较稳定。这种气候演化的阶段性和突变性与北大西洋地区气候记录可以对比,反映极地与东亚季风气候受共同的驱动机制支配。从石笋4种指标(^δ18O、^δ13C、灰度和年层厚度)的功率谱图中识别出不同尺度的太阳活动周期成分,其中80aGleissberg周期特别显著,表明末次盛冰期边界条件下太阳活动仍是短尺度气候变化的主要驱动力。  相似文献