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排序方式: 共有2887条查询结果,搜索用时 15 毫秒
1.
Lu Sun 《国际地质力学数值与分析法杂志》2003,27(1):69-84
A closed‐form deflection response of a beam rest is presented in this paper using the integral transform method. The theory of linear partial differential equations is used to represent the deflection of beam subjected to a moving harmonic line load in integration form. The solution is finally carried out using the inverse Fourier transform. To evaluate the integration analytically, poles of the integrand are identified with the help of algebraic equation theory. Residue theorem is then utilized to represent the integration as a contour integral in the complex plane. Closed‐form deflections and numerical results are provided for different combinations of load frequency and velocity. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
2.
E. Tóth F. Deak C. S. Gyurkócza Z. S. Kasztovszky R. Kuczi G. Marx B. Nagy S. Oberstedt L. Sajó-Bohus C. S. Sükösd G. Toth N. Vajda 《Environmental Geology》1997,31(1-2):123-127
A steady radon exhalation is assumed in most publications. In a village of North-East Hungary, however, high radon concentrations
have been measured, differing strongly in neighbouring houses and varying in time, due to the interplay of geochemical phenomena.
Received: 20 November 1995 · Accepted: 18 June 1996 相似文献
3.
分离入射波与反射波的解析方法 总被引:5,自引:0,他引:5
提出了一种新的分离入射波和反射波的解析方法(AM)。利用两点处的 波高信息,运用Hilbert变换得到波浪信号在复域内的解析表达式,不需要计算合成波高和相位差即可实现信号的分离。根据分离结果,可以精确地估计入射波与反射波的幅值以及反射系数等参数,能够获得入射波与反射波之间的相位信息,并且可方便地用于不规则波的分离。文中通过数值模拟与物理模型实验对AM法进行了检验,所得的结果与实际值非常吻合。 相似文献
4.
L. G. Kodosky 《Environmental Geology》1994,23(1):65-72
Analysis of 153 residential air radon (Rn-222) screening measurements from southeast Michigan indicates that basements host Rn levels two to three times higher than upper-level rooms. Compared to unfinished basements, finished (e.g., paneled walls, tiled floors) basements apparently reduce indoor air Rn levels while partially finished basements may not. Factor analysis of residence questionnaire data explains 59 percent of the Rn data variance. The volume of pathways (e.g., foundation cracks/holes, uncapped sumps) allowing Rn seepage into the dwelling controls the largest portion, 23 percent, of the explained data variance. The residence water source explains 11 percent of the Rn data variance. Groundwater Rn levels contribute to the air Rn data variability, but the study data cannot quantitatively assess this contribution. Seven percent of the Rn data variance is likely controlled by house depressurization facilitated by residence structural properties. Residences with foundation cracks or poorly sealed joints and low-volume indoor-outdoor air exchange are more prone to this effect. Eighteen percent of the explained Rn data variance correlates with the residence's primary heat source. Evidently, operating combustion sources also induce house depressurization and allow Rn to be drawn into the house through entry paths. Twenty-four percent of the analyses equal or exceed 4 pCi/1 Rn. In residences occupied 5 years by the same individuals, 17 percent of the Rn data are 4 pCi/l; here the arithmetic mean air Rn level is 8.3 pCi/l and the average occupancy period 17.4 years. 相似文献
5.
The seismic hazard assessment of the Dead Sea rift, Jordan 总被引:1,自引:0,他引:1
Abdallah S. Al-Zoubi Z.S.H. Abu-Hamatteh Amrat Abdealkaderer 《Journal of African Earth Sciences》2006,45(4-5):489-501
The Dead Sea fault system and its branching faults represent one of the most tectonically active regions in the Middle East. The aim of this study is to highlight the degree of hazards related to the earthquake activities associated with the Dead Sea rift, in terms of speculating the possible future earthquakes. The present investigation mainly is based on available data and vertical crustal modeling of Jordan and the Dead Sea model for the Dead Sea basin with particular emphasis of the recent earthquake activities, which occurred on December 31st, 2003 (Mc = 3.7), February 11th, 2004 (strongest Mc = 4.9 R), and March 15th, 2004 (Mc = 4). The present research examines the location of the strong events and correlates them with the various tectonic elements in the area. The source mechanism of the main shock and the aftershock events is also examined. The analyses were based on the available short period seismogram data, which was recorded at the Natural Resources Authority of Jordan, Seismological Observatory. The seismic energy appears to have migrated from the south to the north during the period from December 31st up to March 12th, where the released seismic energy showed a migration character to the southern block of the eastern side of the Dead Sea, which led the seismic event to occur on March 15th. 相似文献
6.
7.
A bivariate meta-Gaussian density for use in hydrology 总被引:3,自引:0,他引:3
K. S. Kelly R. Krzysztofowicz 《Stochastic Environmental Research and Risk Assessment (SERRA)》1997,11(1):17-31
Convenient bivariate densities found in the literature are often unsuitable for modeling hydrologic variates. They either
constrain the range of association between variates, or fix the form of the marginal distributions. The bivariate meta-Gaussian
density is constructed by embedding the normal quantile transform of each variate into the Gaussian law. The density can represent
a full range of association between variates and admits arbitrarily specified marginal distributions. Modeling and estimation
can be decomposed into i) independent analyses of the marginal distributions, and ii) investigation of the dependence structure.
Both statistical and judgmental estimation procedures are possible. Some comparisons to recent applications of bivariate densities
in the hydrologic literature motivate and illustrate the model. 相似文献
8.
Introduction With the development of the seismological observation technique and deep-going of seismicdata application fields, especially the digitization of data in earthquake station networks, theimprovement of the precision, the data quantity increases as geometric order, which bringdifficulty to saving and transfering these data. To keep all information, seismic data, like medicalimages, should be compressed without error in many applications. In generally, traditionalcompression meth… 相似文献
9.
10.
基于二维小波变换的FMI图象分割 总被引:1,自引:0,他引:1
为了从FMI资料中定量提取参数,一个重要的步骤是从实际FMI资料中分离出反映溶孔、溶洞、裂缝的子图像。本文给出的方法,考虑图像像元邻域的特征,应用二维小波变换求出目标与背景边缘的点集,按这个边缘点集的坐标点所对应的原图像像素灰度值的平均值作为分割阈值进行图像分割。实际资料处理表明,应用这种方法可以从实际的FMI资料中准确地分割出孔洞、裂缝的子图像并且可以按深度段连续自动处理,为后续定量计算参数奠定了良好基础。 相似文献