尼泊尔波迪科西水利枢纽三维渗流分析     

王恩志  鲁岐峰  杨太华 《工程地质学报》2000,8(4):471-474

针对尼泊尔波迪科西水电工程首部枢纽布置和软土坝基的岩性条件和渗透特征 ,通过对混凝土防渗墙深度、灌浆帷幕长度、混凝土渗透性、地基渗透性的敏感性分析 ,确定出防渗墙和防渗帷幕的优化方案 ,并对三种库水位工况下的三维渗流场进行了详细的计算分析 ,为工程优化设计提供依据.  相似文献   

洞庭湖区洪灾形成机制及其防洪减灾对策     

林彰平  许林书 《热带地理》2000,20(4):265-268

通过对洞庭湖自然灾害系统进行分析,指出长江流域洪水是湖区主要的致灾因子,尖湖关系失调的孕灾环境是形成洪灾的根本原因,承文体的变化总体上不利于防洪减灾,提出了根治洞庭湖区洪灾的“蓄”、“泄”目标时序化的治水策略及相应的对策体系。  相似文献   

5—（偶氮苯）—8—（4—硝基—1—重氮苯）—氨基喹啉与钯的显色反应及应用   总被引：10，自引：1，他引：9  

黄章杰  赵建为 《岩矿测试》1999,20(2):117-119

在弱碱性介质中,乳化剂－ＯＰ存在下,５－（偶氮苯）－８－（４－硝基－１－重氮苯）－氨基喹啉（ＰＡＮＰＡＱ）与钯发生显色反应,生成ｎＰＡＮＰＡＱ∶ｎＰｄ（Ⅱ）＝２∶１的蓝色络合物,最大吸收峰位于６４０ｎｍ,摩尔吸光系数为１．０８×１０５Ｌ·ｍｏｌ－１·ｃｍ－１,钯的质量浓度在０～６００μｇ／Ｌ符合比尔定律。所考查的５４种共存离子,对测定Ｐｄ（Ⅱ）基本无影响。方法已用于钯催化剂中Ｐｄ（Ⅱ）的测定,结果与原子吸收法相符,５次测定的ＲＳＤ在１．３％～１．５％。  相似文献   

Cation ordering in BaAl2Ge2O8-feldspar: implications for the phase transition in anorthite     

T. Malcherek  M. A. Carpenter  H. Kroll  E. K. H. Salje 《Physics and Chemistry of Minerals》1999,26(4):354-366

BaAl₂Ge₂O₈-Feldspar undergoes an order-disorder phase transition I2/c↔C2/m at T _tr ≈1690 K. The thermodynamics of the Al,Ge cation ordering process is described in terms of the compressible Ising model in mean field approximation. The mean field potential predicts a first order character of the phase transition. This is compared to antiferromagnetic ordering in a two-dimensional square Ising model with NN-pair interactions and four-spin interactions on alternating squares. Calculated order parameters and short range ordering are in good agreement with the corresponding properties observed in BaAl₂Ge₂O₈-feldspar by means of X-ray diffraction, hard mode infrared spectroscopy and TEM. Using known calorimetric data a similar model is postulated for Al,Si ordering in anorthite, CaAl₂Si₂O₈, for which the derived potential describes a transition with slightly stronger first order character at T _tr ≈1928 K. Received: 30 January 1998 / Revised, accepted: 29 August 1998  相似文献   

基于Landsat-8数据对甘肃省金塔县主要农作物分类     

石莹  穆岑  田艳君  黄月如  郭润潇  孙晓雪 《测绘与空间地理信息》2022,(2):74-78,81

近年来,随着经济社会发展和人类活动加剧,水资源短缺、生态环境恶化、自然灾害频发等问题对于农作物的生长具有较大影响,因此准确地提取农作物显得尤为重要.本文基于2016年Landsat-8 OLI全生育期的时序遥感影像数据,融合金塔县农作物的物候特征和地表纹理特性,提取主要农作物小麦、玉米、棉花和甜菜的时间序列NDVI曲线...  相似文献   

河北省地震局邯郸中心台远程监控系统     

张小涛  吴鹏  闫俊岗  张磊  贾华 《地震地磁观测与研究》2018,39(4):213-217

根据河北省地震局邯郸中心台监控需求,提出一种基于STM8的台站远程监控系统,对控制单元、电源模块、视频监控模块、仪器远程控制模块等进行说明,介绍软件设计与人机交互界面。在邯郸中心台远程监控中实际应用,认为此系统可提高台站维护效率,保障观测数据的连续可靠具有较高的应用价值。  相似文献   

Simplified procedure for the estimation of local inelastic deformation demands for seismic performance assessment of buildings          下载免费PDF全文

Miguel Araújo  José Miguel Castro 《地震工程与结构动力学》2017,46(3):491-514

The implementation of performance‐based design and assessment procedures in seismic codes leads to the need for an accurate estimation of local component demands. According to Part 3 of Eurocode 8 safety checks should be always conducted in terms of plastic rotations, even when linear elastic methods of analysis are used. This paper demonstrates that linear analysis fails to predict inelastic deformation demands at the member level. Therefore, a simplified procedure that allows for the estimation of beam inelastic deformation demands using linear elastic methods of analysis in a simple and conservative way is presented herein. A number of moment‐resisting steel frames designed according to different criteria and exhibiting different column‐to‐beam strength ratios were analysed and used for the derivation of the proposed procedure. A comparative study between alternative methods of quantifying inelastic deformation demands using linear analysis is also carried out. The results obtained allow concluding about the efficiency and conservativeness of the proposed procedure which makes it attractive to be employed in engineering practice. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Proposal of design rules for ductile X-CBFS in the framework of EUROCODE 8     

Silvia Costanzo  Mario D'Aniello  Raffaele Landolfo 《地震工程与结构动力学》2019,48(1):124-151

Cross concentrically braced frames (X-CBFs) are commonly used as primary seismic resisting system, owing to their large lateral stiffness, simplicity of design, and relatively low constructional cost. Current EN 1998-1 provides design rules theoretically aiming at developing ductile global plastic mechanism, namely enforcing plastic deformations in the diagonal members, while the remaining structural members and connections should elastically behave. However, as widely demonstrated by many existing studies, the design and the corresponding seismic performance of EC8-compliant X-CBFs are generally affected by several criticisms, eg, difficulties in sizing of diagonal members, massive and non-economical structures, and poor seismic behavior. In light of these considerations, the research activity presented in this paper is addressed to revise the design rules and requirements given EN 1998-1 for X-CBFs to simplify the design process and to improve the ductility and the dissipative capacity of this structural system. Hence, design rules are proposed for the next version of EN 1998-1 and numerically validated by means of nonlinear dynamic analyses.  相似文献   

Direct estimation of seismic response in reduced-degree-of-freedom isolation and energy dissipation systems     

Konstantinos I. Gkatzogias  Andreas J. Kappos 《地震工程与结构动力学》2019,48(10):1112-1133

A methodology for the development of design tools for direct estimation of peak inelastic response in reduced-degree-of-freedom (RDOF) isolation and energy dissipation systems is presented. The suggested procedure is an extension of an earlier method addressing purely hysteretic isolation systems. Herein, the dynamic equation of motion is first normalised to reduce the number of design parameters that significantly affect the response. The sensitivity of normalised response quantities to the amplitude of the ground motion is then investigated through extensive parametric nonlinear dynamic analyses of isolated single-degree-of-freedom (SDOF) systems with linear viscous damping using code-based target spectra. Regression analysis is subsequently employed to develop generalised design equations (GDEs) suitable for design. Further investigations are made to address nonlinear viscous damping and the effect of the transverse component of seismic action in two-degree-of freedom (2DOF) systems under bidirectional excitation, making the procedure applicable to common bridge isolation schemes. GDEs constitute an alternative to equivalent linearisation approaches commonly adopted by codes, informing the selection among alternative isolation and energy dissipations schemes without requiring iterative analysis. The approach is incorporated in the Deformation-Based Design methodology for seismically isolated bridges in a forthcoming paper.  相似文献   

基于随机森林模型的太湖水生植被遥感信息提取   总被引：3，自引：1，他引：2  

侍昊  李旭文  牛志春  李继影  李杨  李宁 《湖泊科学》2016,28(3):635-644

水生植被作为太湖湿地的重要组分,其数量和范围变化影响着湖泊生态系统的平衡,故利用遥感技术对水生植被的空间分布开展研究有助于太湖湿地生态系统的保护.以Landsat 8多光谱遥感影像为主要数据源,利用光谱指数和图像变换方法构建多个特征变量,结合随机森林(RF)模型,提取太湖水生植被的空间分布.结果表明:(1)通过对比分析训练样本特征值的平均值、标准差和变异系数,NDVI、NDWIF、SR等指数更易于区分开敞水域和沉水植被、浮叶植被和挺水植被;(2)当设置1000棵分类树和4个分割节点的随机变量时,RF分类模型的袋外误分率小于6%,误分主要受SR、MNDWI和NDVI等特征变量影响;(3)通过验证分析,基于RF模型获得的2014年7月太湖水生植被覆盖面积约为306.0km2,分类精度为88.56%(Kappa系数为0.88),主要分布在湖体的东部和南部,以沉水和浮叶植被为主,两者占水生植被覆盖总面积的84.9%.  相似文献