A new method for non‐stationary random critical excitation     

Izuru Takewaki 《地震工程与结构动力学》2001,30(4):519-535

Since earthquake ground motions are very uncertain even with the present knowledge, it is desirable to develop a robust structural design method taking into account these uncertainties. Critical excitation approaches are promising and a new non‐stationary random critical excitation method is proposed. In contrast to the conventional critical excitation methods, a stochastic response index is treated as the objective function to be maximized. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. It is shown that the original idea for stationary random inputs can be utilized effectively in the procedure for finding a critical excitation for non‐stationary random inputs. The key for finding the new non‐stationary random critical excitation is the exchange of the order of the double maximization procedures with respect to time and to the power spectral density function. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

ANALYSES OF THE DYNAMIC EFFECTS ON WINTER CIRCULATION OF THE TWO MAIN MOUNTAINS IN THE NORTHERN HEMISPHERE--Ⅰ.RELATIONSHIP AMONG GENERAL CIRCULATION, TELECONNECTION AND STATIONARY WAVES          下载免费PDF全文

Zou Xiaolei  Ye Duzheng  Wu Guoxiong 《Acta Meteorologica Sinica》1992,6(4):395-407

The distribution of troughs and ridges of geopotential height,the teleconnection patterns and the propagation patterns of stationary waves are the main features of the January mean geopotential height field at 500hPa.Data analyses and numerical experiments indicate that these three characteristics are associated to one another and closely related to the mechanical forcing of the Rocky Mountains and Tibetan Plateau.There exists a prominent negative correlation in the intensity variation between the American trough and the Asian trough at high and middle latitudes.Such negative correlation,in connection with the interannual variation of the intensity of the jets in front of the two troughs,leads to the existence of similar teleconnection patterns in North America and East Asia.On the other hand,the different propagation behaviour of quasi-stationary waves downstream of the two main mountains results in a fundamental difference in the distribution of correlation chains in North America and East Asia.  相似文献   

应用声学多普勒流速仪进行冰期流量测验的比测研究     

原金勇李嘉伟  陈耀祖 《水文》2005,25(5):43-47

水利部松辽委黑龙江水文水资源勘测局、黑龙江省水文局和美国SonTek／YSI水文仪器公司合作，在黑龙江黑河地段的卡伦山水文站进行了冰期流量、流速和水深的比测研究。比测研究采用了SonTek／YSI的1．5MHz河猫Mini—ADP进行实测，并与先期采用机械式旋杯流速仪的实测资料进行比对。比测研究的目的是通过声学多普勒定点测流技术与标准的机械流速仪测量技术进行对比，验证声学多普勒剖面流速仪定点流量测量的精度，推广应用声学多普勒测流技术在封冰期测流的方法。  相似文献   

半承压含水层按稳定流承压含水层求参数的讨论     

刘新才 《新疆地质》1989,(1)

用稳定流承压含水层公式对半承压含水层求参数时,计算出的导水系数“T”比非稳定流计算出的要大,影响半径R与经验系数相比普通偏小.用水位恢复法计算也同样.原因在于半承压含水层中地下水受潜水垂向越流补给及水平径向补给,因而用稳定流承压含水层法计算时,或者修改公式,或者用非稳定流计算.  相似文献   

一类反应扩散方程组正平衡解的存在性与唯一性     

蒋飞达  李刚 《南京气象学院学报》2007,30(5):687-693

利用锥映射不动点指数计算方法,结合极值原理、解耦方法得到了一类反应扩散方程组正平衡解的存在性和唯一性.分析过程表明,对此类微分方程组的解耦方法类似于代数方程中的消元法.  相似文献   

风云静止与极轨卫星产品在湖北暴雨监测和预报方法中的应用研究     

徐双柱  吴涛  张萍萍  王继竹  董良鹏 《气象》2015,41(9):1159-1165

根据2010—2014年风云2号(FY 2)和风云3号(FY 3)气象卫星资料,结合雷达资料、常规观测资料和数值预报产品等,利用多阈值法、面积重叠法进行了湖北省暴雨云团的识别跟踪方法研究;利用配料法进行了湖北省6 h暴雨短时预报方法研究。建立了以网页形式的风云系列卫星资料的暴雨监测预报业务系统,定量监测和预预暴雨的发生、发展。2014年应用检验结果表明,该系统对于湖北省暴雨的监测和预报有指导作用。  相似文献   

Energy distribution of a stationary beam of light     

Ragab?M.?GadEmail author 《Astrophysics and Space Science》2005,295(4):451-458

Aguirregabiria et al. showed that Einstein, Landau and Lifshitz, Papapetrou, and Weinberg energy-momentum complexes coincide for all Kerr-Schild metric. Bringely used their general expression of the Kerr-Schild class and found energy and momentum densities for the Bonnor metric. In this paper the latter results are obtained without using Aguirregabiria et al results. This also supports Aguirregabiria et al results as well as Cooperstock hypothesis. We obtain further the energy distribution of the space-time under consideration.  相似文献   

Diel patterns in pelagic fish behaviour and distribution observed from a stationary, bottom-mounted, and upward-facing transducer   总被引：1，自引：1，他引：1  

Axenrot  Thomas; Didrikas  Tomas; Danielsson  Charlotte; Hansson  Sture 《ICES Journal of Marine Science》2004,61(7):1100-1104

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Application of Random Process in Soil Profile Modeling     

Yan Shuwang  Jia Xiaoli  Deng Weidong Professor  Dept. of Hydraulic Eng.  Tianjin University  Tianjin Graduate student  Dept. of Hydraulic Eng.  Tianjin University  Tianjin Senior Engineer  Chongqing Institute of Highway Science 《中国海洋工程》1994,(4)

When using the random process in soil profile modeling, the stationary and ergodicity of thesoil properties in the profile must be tested. This paper describes a procedure for stationary and ergodicity testing. Numerical examples were given for demonstration. A log-cosine function is suggested to simulate the correlation function, which has been proved to be good for soil profile modeling.  相似文献   

Stochastic analysis of the linear equivalent response of bridge piers with aseismic devices     

Luisa Carlotta Pagnini  Giovanni Solari 《地震工程与结构动力学》1999,28(5):543-560

The dynamic response of bridge piers with aseismic devices to earthquake excitation is evaluated by the stochastic equivalent linearization technique. The seismic acceleration is schematized through a Gaussian stationary random process. The pier is considered linear elastic, the span is idealized as a rigid mass, the restoring force of the device is represented through a non-linear differential model. The study of the complex modes of the linearized system gives an interpretation of the mechanical behaviour, leads to a formally elementary solution and highlights some phenomena which are typical of the hysteretic systems, particularly of those marked by weak hardening. Even though the solution is limited to the stationary field, it brings out several noteworthy considerations about the effective non stationary behaviour of the structure. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献