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11.
黄河内蒙古不同河型段对洪水过程的响应特征   总被引:7,自引:0,他引:7  
黄河内蒙古河段的河道淤积近年来有所加重,一些人寄望于人造洪峰冲沙来降低河床。本文根据典型年份的最大洪水的流量—水位过程线变化特征,揭示黄河内蒙古不同河型段对这些洪水的响应机制,得出黄河内蒙古河段洪水的流量—水位过程线类型有线形、顺时针环线、逆时针环线3类单一关系和线形+逆时针环线、逆时针环线+线形、"8"字形+线形、嵌套状逆时针环线以及交叉线形5类复合关系。这些关系总体上可以反映洪水过程中河床是侵蚀还是沉积、何时侵蚀何时沉积、以及冲淤是否具有反复性。黄河内蒙古冲积性河段的河道对同一次洪水过程的响应沿程表现出分化现象,其中辫状河段以河床侵蚀下降为特征,弯曲河段以河床明显沉积升高为特征,而顺直河段以少量沉积或冲淤平衡为特征。不同河型段的河道对洪水的响应趋势与洪水动能的沿程减小相适应,洪峰含沙量沿程减小是该趋势的具体体现。人造洪峰冲沙难以逆转上述淤积趋势,对防治洪灾帮助有限。  相似文献   
12.
Earthquake codes have been revised and updated depending on the improvements in the representation of ground motions, soils and structures. These revisions have been more frequently seen in recent years. One of the key changes in earthquake codes has been performed on the design spectra. In this paper, the design spectra recommended by Turkish Earthquake Code and three other well known codes (Uniform Building Code, Eurocode 8, and International Building Code) are considered for comparison. The main purpose of this study is to investigate the differences caused by the use of different codes in the dynamic analysis and seismic verification of given types of buildings located at code defined different sites. The differences in expressions and some important points for elastic and inelastic spectra defined by the codes are briefly illustrated in tables and figures. Periods, base shears, lateral displacements and interstory drifts for the analyzed buildings located at code defined ground type are comparatively presented.  相似文献   
13.
The paper provides state-of-the-art information on the following aspects of seismic analysis and design of spread footings supporting bridge piers: (1) obtaining the dynamic stiffness (“springs” and “dashpots”) of the foundation; (2) computing the kinematic response; (3) determining the conditions under which foundation–soil compliance must be incorporated in dynamic structural analysis; (4) assessing the importance of properly modeling the effect of embedment; (5) elucidating the conditions under which the effect of radiation damping is significant; (6) comparing the relative importance between kinematic and inertial response. The paper compiles an extensive set of graphs and tables for stiffness and damping in all modes of vibration (swaying, rocking, torsion), for a variety of soil conditions and foundation geometries. Simplified expressions for computing kinematic response (both in translation and rotation) are provided. Special issues such as presence of rock at shallow depths, the contribution of foundation sidewalls, soil inhomogeneity and inelasticity, are also discussed. The paper concludes with parametric studies on the seismic response of bridge bents on embedded footings in layered soil. Results are presented (in frequency and time domains) for accelerations and displacements of bridge and footing, while potential errors from some frequently employed simplifications are illustrated.  相似文献   
14.
The paper presents the prediction of total energy production and consumption in all provinces and autonomous regions as well as determination of the variation of gravity center of the energy production, consumption and total discharge of industrial waste water, gas and residue of China via the energy and environmental quality data from 1978 to 2009 in China by use of GM(1,1) model and gravity center model, based on which the paper also analyzes the dynamic variation in regional difference in energy production, consumption and environmental quality and their relationship. The results are shown as follows. 1) The gravity center of energy production is gradually moving southwestward and the entire movement track approxi-mates to linear variation, indicating that the difference of energy production between the east and west, south and north is narrowing to a certain extent, with the difference between the east and the west narrowing faster than that between the south and the north. 2) The gravity center of energy consumption is moving southwestward with perceptible fluctuation, of which the gravity center position from 2000 to 2005 was relatively stable, with slight annual position variation, indicating that the growth rates of all provinces and autonomous regions are basically the same. 3) The gravity center of the total discharge of industrial waste water, gas and residue is characterized by fluctuation in longitude and latitude to a certain degree. But, it shows a southwestward trend on the whole. 4) There are common ground and discrepancy in the variation track of the gravity center of the energy production & consumption of China, and the comparative analysis of the gravity center of them and that of total discharge of industrial waste water, gas and residue shows that the environmental quality level is closely associated with the energy production and consumption (especially the energy consumption), indicating that the environment cost in economy of energy is higher in China.  相似文献   
15.
江苏淤泥质潮滩对海平面变化的形态响应   总被引:9,自引:0,他引:9  
通过对江苏滨海平原淤泥质潮滩1980年以来19个固定潮滩断面112个测次滩面高程测量的统计分析,探讨典型淤泥质潮滩剖面形态对海平面变化的形态响应过程。结果表明,典型淤涨岸段海平面上升,多年平均潮位线以上滩面仍将淤积加高,但淤高幅度除多年平均高潮线附近滩面相对较大外,其余均较小,表明随海平面上升该滩带总体淤积速率将趋于减小;与此相反,多年平均潮位线以下滩面则趋于蚀低,且侵蚀强度较大,表明该滩带的侵蚀有加剧趋向,最终滩面总体形态将因上带不断淤高和下带不断蚀低而逐渐变陡,剖面上凸形态的曲率不断加大。曲型侵蚀岸段,海平面上升的效应则相反,海平面上升,多年平均潮位线以上滩面强烈蚀低;而多年平均潮位线以下滩面则强烈淤积加高,剖面的上凹形态最终将因上带不断蚀低和下带不断淤高而趋于平直。  相似文献   
16.
朱妮  张艳芳 《干旱区地理》2015,38(4):843-850
基于陕西省1989-2011年能源消费等统计数据,分析能源消费结构、产业结构的演变特征,建立陕西省能源消费结构-产业结构-碳排放强度系统的VAR模型,对该系统的长期和短期动态关系进行实证分析。结果表明:陕西省的发展模式,是能源消费结构长期以高碳能源为主和产业结构长期以高碳产业为主导。能源消费结构与产业结构的变化对陕西省碳排放强度的减小作用初期微弱;从中长期来,两个结构多元化提高的负效应对碳排放强度的增加有长期持久的抑制作用,且能源消费结构演进对碳排放强度的冲击效果始终大于产业结构变化的冲击效果。优化产业结构和调整能源消费结构尤其是提高低碳产业与低碳能源比重是驱动陕西省碳排放强度下降的有效措施。  相似文献   
17.
GM4型磁通门磁力仪性能检验方法   总被引:5,自引:0,他引:5  
目前,磁通门磁力仪广泛应用于观测地球磁场相对变化的仪器。相对于应用,仪器的性能测试不为人们所熟悉。本文针对GM4型磁通门磁力仪的噪声特性,频率特性,线性度,温度特性等关键性能指标的测试依据、测试方法及流程给予详细的阐述。  相似文献   
18.
农用地集约利用程度直接关系到区域土地的可持续利用,与区域社会经济发展密切相关,科学量化评价农用地集约利用变化过程及其与经济增长之间的动态关系,对于农业可持续发展有着重要的意义。利用新疆拜城县1978-2010年时间序列数据,通过构建农用地集约利用评价指标体系,在对原始数据进行标准化的基础上,采用熵值法确定各指标权重,利用多因素综合评分法对历年农用地集约利用水平进行测度与分析,然后利用协整检验、Granger因果检验、脉冲响应函数及方差分解模型考察农用地集约利用指数与农民人均纯收入水平之间的内在联系。研究发现:改革开放以来,拜城县的农用地集约利用水平逐步提高,农用地投入强度、利用程度、产出效率和持续状况对农用地集约利用水平的贡献率呈现出各自的变化特征。农用地集约利用指数是农民人均纯收入水平的格兰杰原因,而农民人均纯收入水平不是农用地集约利用指数的格兰杰原因,脉冲响应和方差分解的结果表明,随着农用地集约利用指数的提高,农民人均纯收入水平将不断加强。  相似文献   
19.
地磁预报地震的方法越来越多,本文应用加卸载响应比方法,分析山西地区2009—2016年观测的加卸载响应比与山西地区4.0级地震之间的对应关系,初步给出适用于山西地区震例特征的磁异常判别指标。  相似文献   
20.
A criterion previously developed by Heredia-Zavoni and Esteva for selecting optimal sensor locations is used to analyse the optimal instrumentation of structures on soft soils. The stochastic response of a linear structural system on a flexible base is formulated for use of the criterion. The case of MDOF shear systems on flexible base, with uncertain lateral stiffness and subjected to random earthquake ground motions, is studied. The optimal location of accelerometers, the reduction of prior uncertainty on the lateral stiffness, the effects of the base flexibility, the relative influence of translation and rocking of the base, and the influence of recording noise are assessed and discussed. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
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