A new spatial coherence model and analytical coefficients for multi-support response spectrum combination   总被引：1，自引：0，他引：1  

王君杰  陈虎 《地震工程与工程振动(英文版)》2007,6(3):225-235

In this paper, a new spatial coherence model of seismic ground motions is proposed by a fi tting procedure. The analytical expressions of modal combination (correlation) coeffi cients of structural response are developed for multi-support seismic excitations. The coeffi cients from both the numerical integration and analytical solutions are compared to verify the accuracy of the solutions. It is shown that the analytical expressions of numerical modal combination coeffi cients are of high accuracy. The results of random responses of an example bridge show that the analytical modal combination coeff icients developed in this paper are accurate enough to meet the requirements needed in practice. In addition, the computational effi ciency of the analytical solutions of the modal combination coeff icients is demonstrated by the response computation of the example bridge. It is found that the time required for the structural response analysis by using the analytical modal combination coeffi cients is less than 1/20 of that using numerical integral methods.  相似文献   

Late Quaternary clay minerals off Middle Vietnam in the western South China Sea: Implications for source analysis and East Asian monsoon evolution     

Christophe COLIN 《中国科学D辑(英文版)》2007,50(11):1674-1684

High-resolution clay mineral records combined with oxygen isotopic stratigraphy over the past 450 ka during late Quaternary from Core MD05-2901 off Middle Vietnam in the western South China Sea are re-ported to reconstruct a history of East Asian monsoon evolution. Variations in Illite, chlorite, and kaolinite contents indicate a strong glacial-interglacial cyclicity, while changes in smectite content present a higher frequency cyclicity. The provenance analysis indicates a mixture of individual clay minerals from various sources surrounding the South China Sea. Smectite derived mainly from the Sunda shelf and its major source area of the Indonesian islands. Illite and chlorite originated mainly from the Mekong and Red rivers. Kaolinite was provided mainly by the Pearl River. Spectral analysis of the kaolin-ite/(illite chlorite) ratio displays a strong eccentricity period of 100 ka, implying the ice sheet-forced win-ter monsoon evolution; whereas higher frequency changes in the smectite content show an ice sheet-forced obliquity period of 41 ka, and precession periods of 23 and 19 ka and a semi-precession period of 13 ka as well, implying the tropical-forced summer monsoon evolution. The winter monsoon evolution is generally in coherence with the glacial-interglacial cyclicity, with intensified winter monsoon winds during glacials and weakened winter monsoon winds during interglacials; whereas the summer monsoon evolution provides an almost linear response to the summer insolation of low latitude in the Northern Hemisphere, with strengthened summer monsoon during higher insolation and weakened summer monsoon during lower insolation. The result suggests that the high-latitude ice sheet and low-latitude tropical factor could drive the late Quaternary evolution of East Asian winter and summer monsoons, respectively, implying their diplex and self-contained forcing mechanism.  相似文献   

工程勘察信息系统的简单实现     

胡展飞  杨震 《上海国土资源》2002,(1):36-39

随着城市建设的迅速发展，各个勘察单位积累了大量的工程资料，怎样有效的保持和利用这些资料成了一个迫切的问题。文章根据个人开发工程勘察信息系统的经历，介绍了利用VB6、Server和Matlab开发工程勘察信息系统的步骤和方法。  相似文献   

黑色电气石矿物组成与红外辐射特性的关系   总被引：4，自引：0，他引：4  

杨如增  徐礼新  杨满珍  姚桂田 《上海国土资源》2002,(1):61-64

作者对产自云南马关－麻粟坡矿带、广西钟山八步矿区的黑色电气石进行了矿物组成及化学成分的分析测试。实验表明，不同矿点黑色电气石的矿物组成和化学成分存在明显差异，化学成分对红外辐射特性存在一定影响，氧化镁含量较高的镁电气石具有高的红外法向比辐射率。论文对电气石的化学成分与成因的相互关系进行了讨论，为合理选矿，有效利用黑色电气石资源提供了实践和理论依据。  相似文献   

南海北部1987～1988年颗粒物质和硅藻通量的季节性变化:季风气候与 El Nino的响应   总被引：2，自引：0，他引：2       下载免费PDF全文

郑玉龙  王汝建  郑连福  陈荣华  陈建芳 《第四纪研究》2001,21(4):359-365

南海北部1987年9月～1988年10月沉积物捕获器中颗粒物质和硅藻通量的季节性变化受到季风气候的控制.颗粒物质与硅藻在东北和西南季风盛行期增加,在季风转变期减少.浅层和深层的颗粒总通量、蛋白石通量、碳酸钙通量、蛋白石/颗粒总通量比值、碳酸钙/颗粒总通量比值、有机碳/磷的比值以及浅层硅藻Thalassionema nitzschioides、Coscinodiscus excentricus、Coscinodiscus nodulifer、Nitzschia marina和Rhizosolenia bergonii的通量在东北季风期间明显地增加了,这些变化可能与1987年～1988年发生的EINino事件相关.  相似文献   

球面小波分析技术及在全球重力模型中的应用     

许惠平  刘万崧  R.H.N.Haagmans  A.J.Th.deBrnoue 《物探与化探》2001,25(1):8-13

在介绍球面小波理论的基础上,推导和比较了几种球面小波,分析了最新地球重力模型-EGM96,以此为依据,把球面小波多分辨分析用于计算全球自由空气异常及重力大地水准面,并对处理结果做出解释。  相似文献   

Transition of Quaternary glacial cyclicity in deep-sea records at Nansha, the South China Sea     

WANG Pinxian  TIAN Jun  CHENG Xinrong 《中国科学D辑(英文版)》2001,44(10):926-933

High-resolution oxygen isotope records over the last 2249 ka (MIS 1–86) have been obtained from cores of the upper section (105.08 m) at ODP Site 1143 (water depth of 2772 m) drilled in the Nansha area, southern South China Sea. The sampling resolution is at about 2 ka intervals, resulting in one of the best oxygen isotope records over the global ocean. The oxygen isotope curves, displaying details in the Pleistocene glacial cycles, have revealed a nearly 300 ka long stage of transition from a predominant 40 ka to 100 ka periodicity. Therefore, the “Mid-Pleistocene Revolution” should be considered as a process of transition rather than an abrupt change. Within the 100 ka glacial cycles, the changes in tropical sea surface water were found to lead those in high-latitude ice sheet. Our comparisons show that the ice sheet expansion and the glacial stage extension in the Northern Hemisphere with the 100 ka cycles must have been driven not by ice sheet itself, but by processes outside the high latitudes of the Northern Hemisphere.  相似文献   

An abrupt cooling event early in the last interglacial in the northern South China Sea     

TU Xia  ZHENG Fan  Wang Jiliang  CAI Huimei  WANG Pinxian  C.Bühring  M.Sarnthein 《中国科学D辑(英文版)》2001,44(10):865-870

The high-resolution quantitative analysis of the planktonic foraminifera and the δ¹⁸O records of the section between 96.49– 137.6 mcd at ODP Site 1144 on the continental slope of northern South China Sea reveals an abrupt cooling event of sea surface temperature (SST) during the last interglacial (MIS 5.5, i.e. 5e). The dropping range of the winter SST may come to 7.5°C corresponding to 1.2‰ of the δ¹⁸O value of sea surface water. This event is comparable with those discovered in the west Europe and the northern Atlantic Ocean, but expressed in a more intensive way. It is inferred that this event may have been induced by middle- to low-latitude processes rather than by polar ice sheet change. Since the Kuroshio-index speciesPulleniatina obliquiloculata displayed the most distinct change at the event, it may also be related to the paleoceanographic change of the low-latitude area in the western Pacific Ocean. This event can be considered as one of “Younger Dryas-style coolings” and is indicative of climate variability of the last interglacial stage.  相似文献   

Earth’s density flattening and hypothesis of latitudinal normal density     

Hao Xiaoguang  Xu Houze  LIU Dajie 《中国科学D辑(英文版)》2001,44(8):673-679

In this paper, the definition of latitudinal density and density flattening of the level ellipsoid is given, and integral formulas of latitudinal density for pole gravity and equator gravity are derived. According to the pole gravity condition and equator gravity condition for the level ellipsoid, latitudinal density distribution function of the level ellipsoid is obtained. It is proved mathematically that latitudinal density of the earth’s equator is larger than that of the pole, the earth’s density flattening calculated preliminarily is 1/322, and hypothesis of the earth’s latitudinal normal density is further proposed, so that theoretical preparation for studying the forming cause of the earth gravity in problems such as continent drift, mantle convection, and submarine extension is made well.  相似文献   

Evolution of planktonic foraminifera and thermocline in the southern South China Sea since 12 Ma (ODP-184, Site 1143)     

Ll Baohua  JlAN Zhimin 《中国科学D辑(英文版)》2001,44(10):889-896

Down-core variation in planktonic foraminifera (PF) at Site 1143 (ODP 184) has disclosed the evolution of upper water-column structure over the last 12 Ma in the southern South China Sea. In the early Late Miocene (∽10.6–7.8 Ma), there existed a lower percentage of total deep-dwelling species, reflecting a water thermocline deeper than that in the Middle Miocene, which resulted from the closure of Indonesian seaway and relevant intensification of the equatorial warm current. After the increase in deep-dwelling PF and the rising of thermocline during the late Late Miocene (7.6–6.4 Ma), the total deep-dwelling species decreased gradually from late Late Miocene (6.4 Ma) to the Pliocene, implying the deepening of water thermocline. The evolution of thermocline depth in the southern South China Sea reflected by the PF at Site 1143 might be a good indicator of the change of west Pacific “warm pool”.  相似文献