类透镜介质中的传导模及与激光束的耦合     

翁兴涛 《武汉大学学报(信息科学版)》1994,(4)

从求解柱坐标内亥姆霍兹方程出发，导出了类透镜介质传导模的特征参量、场分布状态及传播常数，求出了入射激光束和导模之间的耦合系数，并讨论了它们的物理意义．  相似文献   

傅利叶重建法的数值模拟研究     

王亚秀 《内陆地震》1994,8(4):310-314

运用ＣＴ技术中的傅利叶重建法，根据任意所给的两个初始速度模型，用几组平行射线束进行扫描，采集走时数据，并利用走时数据反演速度图象．反演结果与初始模型比较两者基本相符合。由此证明，傅利叶重建法在一定条件下可以用来反演地壳速度结构，并可得到较好的结果．这种方法是ＣＴ技术应用于地学研究的一种新的尝试．  相似文献   

Bacterial contribution to sedimentary organic matter; a comparative study of lipid moieties in bacteria and Recent sediments     

H. Goossens  W. Irene  C. Rijpstra  R.R. Düren  J.W. De Leeuw  P.A. Schenck 《Organic Geochemistry》1986,10(4-6)

A systematic study of the lipid composition of thirteen bacterial species and three Recent sediments (methanogenic sediment, cyanobacterial mat and evaporative gypsum crust) was undertaken in an attempt to recognize bacterial organic matter in sediments. A sequential method, which distinguishes between three different modes of occurrence of lipid moieties (free, OH⁻- and H⁺-labile), was applied. The acid-labile fractions are discussed.The three main groups of bacteria, archaebacteria, gram-positive eubacteria and gram-negative eubacteria, are easily distinguished. Methanogenic and extremely halophilic archaebacteria are characterized by the presence of diphytanyl glyceryl ether and the absence of fatty acids. The gram-positive eubacteria contain primarily iso- and anteiso-branched fatty acids whereas the gram-negative bacteria and sediments are dominated by β- and α-hydroxy fatty acids. A wide variety of H⁺-labile hydroxy fatty acids was observed which included several, as yet unknown, structures.β-Hydroxy fatty acids in this H⁺-labile mode of occurrence are exclusively present in bacteria. Their distribution patterns in sediments are considered “fingerprints” of past and present bacterial populations. The specific differences in β -hydroxy fatty acid compositions observed in the different bacteria and the three sediments investigated, suggest that amide-linked β-hydroxy fatty acid patterns are useful as markers of bacterial populations and therefore of environmental conditions.  相似文献   

安徽沙溪斑岩铜矿床中伴生金的赋存状态     

季汝清  周文雅  张仕兰 《岩石矿物学杂志》1987,6(1):64-71

矿体赋存于燕山早期形成的石英闪长斑岩及闪长玢岩中。矿石的主要金属矿物有:黄铜矿、黄铁矿、斑铜矿、自然金、银金矿等。黄铁矿、黄铜矿是金的主要载体矿物。通过矿相鉴定、单矿物化学研究、物相分析,电子探针分析、透射电镜分析等,查明了金的赋存状态。显微金呈包体状态包含于黄铜矿之中,粒径为5—20微米。次显微佥呈球状、链状及不规则状分布于黄铁矿晶体边缘及微裂隙中。经探针分析,金的成色为790—850,平均成色为815。经物相分析,金的矿物量为85%—95%,表明金是以矿物态存在。我国玉龙、德兴、多宝山等地的斑岩铜矿都有不同程度金的显示,查明金的富集规律及赋存状态,对于综合开发斑岩铜矿,提高矿床利用价值将会开拓新的前景。  相似文献   

结构平稳随机地震反应时域分析:方法   总被引：3，自引：3，他引：3  

李鸿晶  孙广俊 《地震工程与工程振动》2005,25(4):31-36

给出了三种常用的随机地震地面运动过程模型,即理想白噪声模型、金井清模型、改进金井清模型的相关函数表达式.引入状态向量,在状态空间中建立地震地面运动激励下的结构振动方程,并求解出结构的复模态特性和复模态反应.利用复模态叠加法推导出线性时不变多自由度体系在这三种随机地震动激励下的平稳协方差反应的解析式,可在时域内直接计算结构随机反应的统计特征.该方法物理概念清晰,结论简便明确,可作为实际工程结构平稳随机地震反应的实用分析方法.  相似文献   

砂土的抗剪强度与干密度的曲线拟合     

龚平玲  邓飞 《矿产与地质》2005,19(2):207-208

利用曲线拟合的最小二乘法原理，确定砂土在某垂直压力下的抗剪强度与干密度的关系，并绘制曲线图，可避免人工处理数据的随意性，减小了误差。  相似文献   

基于集群理论的产业规划模式探析   总被引：1，自引：0，他引：1  

赵西君  吴殿廷  何燕  宋金平 《世界地理研究》2007,16(3):59-64,105

传统产业规划在信息网络时代正受到诸多挑战，地方化、信息化正成为地区产业发展的重要驱动力量，在此思路上，本文试图构建一种新型的产业规划模式——集群理论下的产业规划模式。文章首先分析了传统产业规划的概念、基础理论及其存在问题，在此基础上引入了集群理论并梳理了其理论要点，同时借鉴国外集群创导理论和一些具体规划范式构建了基于集群理论的产业规划的一般模式，并对该模式实施的误区及其与传统产业规划的区别联系进行了分析，最后提出了模式实施的相关保障措施。  相似文献   

Time–frequency representation of earthquake accelerograms and inelastic structural response records using the adaptive chirplet decomposition and empirical mode decomposition     

P.D. Spanos  A. Giaralis  N.P. Politis 《Soil Dynamics and Earthquake Engineering》2007,27(7):675-689

In this paper, the adaptive chirplet decomposition combined with the Wigner-Ville transform and the empirical mode decomposition combined with the Hilbert transform are employed to process various non-stationary signals (strong ground motions and structural responses). The efficacy of these two adaptive techniques for capturing the temporal evolution of the frequency content of specific seismic signals is assessed. In this respect, two near-field and two far-field seismic accelerograms are analyzed. Further, a similar analysis is performed for records pertaining to the response of a 20-story steel frame benchmark building excited by one of the four accelerograms scaled by appropriate factors to simulate undamaged and severely damaged conditions for the structure. It is shown that the derived joint time–frequency representations of the response time histories capture quite effectively the influence of non-linearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event; in this context, tracing the mean instantaneous frequency of records of critical structural responses is adopted.The study suggests, overall, that the aforementioned techniques are quite viable tools for detecting and monitoring damage to constructed facilities exposed to seismic excitations.  相似文献   

A contribution to seismic shear design of R/C walls in dual structures     

Andreas J. Kappos  P. Antoniadis 《Bulletin of Earthquake Engineering》2007,5(3):443-466

The paper focuses on the seismic response of walls in dual (frame + wall) structures, with particular emphasis on shear behaviour. Although dual structures are widely used in earthquake-resistant medium-rise and high-rise buildings, the provisions of modern seismic codes regarding design of walls for shear are not fully satisfactory, particularly in the (common) case that walls of substantially different length form part of the same structure. Relevant provisions of the leading seismic codes are first summarised and their limitations discussed. Then an extensive parametric study is presented, involving two multistorey dual systems, one with identical walls, and one with walls with unequal length, designed to the provisions of Eurocode 8 for two different ductility classes (H and M). The walls of the same structures are also designed to other methods such as those used in New Zealand and Greece. The resulting different designs are then assessed by subjecting the structures to a suite of strong ground motions, carrying out inelastic time history analysis, and comparing the results against design action effects. It is found that although modern code procedures generally lead to satisfactory performance (differences among them do exist), the design of walls seems to be less appropriate in the case of unequal length walls. For this case a modified procedure is proposed, consisting of an additional factor to account for the relative contribution of walls of the same length to the total base and an improved envelope of wall shears along the height; this improved method seems to work better than the other procedures evaluated herein, but further calibration is clearly required.  相似文献   

在浏览器中平滑调用MICAPS系统   总被引：5，自引：0，他引：5       下载免费PDF全文

董良淼  李宇中 《气象》2001,27(3):30-32

介绍了通过安装，配置Web服务器软件并编写CGI程序实现在浏览器中平滑调用MICAPS系统的方法，指出融合因特网技术是进行新一代MICAPS系统和天气预报业务平台设计开发的必同之路。  相似文献