岩土工程可靠度分析中方差折减函数确定的一般规律     

闫澍旺  郭林坪  曹永华 《岩土力学》2014,35(8):2286-2292

将可靠度理论应用于岩土工程稳定性分析过程中,即使是已证明安全的工程所得到的边坡或地基的失效概率通常较大,导致这一现象的原因是估算的方差偏大。计算土性指标的试验数据仅表征了该试验点的特征,而不是空间平均特征。在随机场理论应用于岩土工程可靠度分析的过程中,方差折减函数是将点特性过渡为空间平均特性的必要参数。首次对闫澍旺等提出的完全不相关距离理论中完全不相关距离的确定方法进行改进,不但理论上有所突破,而且计算方法更为简洁。对折减函数值的确定过程进行了分析,得到了用完全不相关距离方法确定折减函数的一般规律。  相似文献   

基于最多叶子生成树的中国航空网络轴辐结构构建     

徐敏政  许珺  陈娱 《地理学报》2014,69(12):1847-1857

航空网络的轴辐 (Hub-Spoke) 结构是实现规模经济发展的重要交通运输网络结构,本文为此提出了一种全新的航空网络轴辐结构构建方法。该方法从图论和地理学的角度出发,引入地理距离约束,改进了传统的最多叶子生成树 (Maximum Leaf Spanning Tree) 算法,直接从现有的中国航空网络中抽取树形轴辐结构形成航空支线网络,然后选取支线网络中度前10的节点作为航空枢纽点,并将枢纽点之间在原图中的航线抽取为航空干线网络,最后将支线网络和干线网络合并形成中国航空网络的轴辐结构。在与相关研究的对比分析中,本文方法虽是从图论角度出发,但构建的中国航空轴辐结构符合实际地理环境,划分支线网络距离阈值的选择更加客观合理,所选的航空枢纽点地理意义更为明显,干支线网络的覆盖度更为全面。  相似文献   

城市人居环境的失配度——以辽宁省14 个市为例   总被引：3，自引：0，他引：3  

李雪铭  田深圳  杨俊  张峰  孔凡强 《地理研究》2014,33(4):687-697

提出并运用城市人居环境失配度,将生态学的健康距离模型引入到城市人居环境科学,实证研究2005-2011 年辽宁省14 个市城市人居环境失配度的时空演变趋势、五大系统之间的失配关系以及造成失配的内部作用机理。结果表明：① 时空特征,时间上呈现出上升趋势且具有明显的阶段性和极值分布性特征;空间上呈现出区域差异性和“中部凸起,两翼凹陷”的方向性递减趋势;演变态势上具有较为特殊的非均衡变动性特征。② 五大系统失配关系分析,无论是单一系统本身还是多系统之间综合健康距离的变化都能作用于城市人居环境失配度,导致其数值增减,进而反映出城市人居环境的优劣变化。③ 人居环境失配度作用机理分析,政府宏观调控、经济发展方式以及城市基础设施的同步性和匹配性是城市人居环境失配度变化的内部驱动机理。  相似文献   

The P-wave velocity structure of the lithosphere of the North China Craton——Results from the Wendeng-Alxa Left Banner deep seismic sounding profile   总被引：3，自引：0，他引：3  

ShuaiJun Wang  FuYun Wang  JianShi Zhang  ShiXu Jia  ChengKe Zhang  JinRen Zhao  BaoFeng Liu 《中国科学:地球科学(英文版)》2014,57(9):2053-2063

For the first time on the Chinese mainland, long-range wide-angle seismic reflection/refraction profiling technology has been applied to seismic wave phases from different depths and with different attributes within the various blocks of the North China Craton to characterize the structure of the crust and upper mantle lithosphere. By comparative analysis of the seismic wave phase characteristics in each block across a 1500-km-long east-west profile, we have identified conventional Pg, Pci, PmP and Pn phases in the crust, made a clear contrast between PL1 and PL2 waves belonging to two groups of lithospheric-scale phases, and produced a model of crust-mantle velocity structures and tectonic characteristics after one- and two-dimensional calculations and processing. The results show that the thickness of the crust and lithosphere gradually deepens from east to west along the profile. However, at the reflection/refraction interface, seismic waves in each group show obvious localized changes in each block. Also, the depth to the crystalline basement changes greatly, from as much as 7.8 km in the North China fault basin to only about 2 km beneath the Jiaodong Peninsula and Taihang-Lüliang area. The Moho morphology as a whole ranges from shallow in the east to deep in the west, with the deepest point in the Ordos Block at 47 km; in contrast, the North China Plain Block is uplifting. The L1 interface of the lithosphere is observed only to the west of Taihang Mountains, at a relatively slowly changing depth of about 80 km. The L2 interface varies from 75 to 160 km and shows a sharp deepening to the west of Taihang Mountains, forming a mutation belt.  相似文献   

一种可存储路径的三维非均质空间最短距离场生成算法   总被引：1，自引：0，他引：1  

王丽芳  吴湘滨  张宝一  李小丽  杨莉 《吉林大学学报(地球科学版)》2015,45(4):1257-1268

针对成矿定量预测强调三维空间信息综合研究的特殊需求和地质要素定量表达难、深层次信息挖掘难等关键问题,笔者提出了一种基于三维非均质地质空间的最短距离场算法,并且可回溯出目标体元到源体元的最短路径.应用该方法实现了对某铜矿区三维地质实体模型深层次和组合信息的挖掘,在反映断层对地质空间分划作用的基础上,建立了侵入岩体的最短距离场,可用于对侵入岩体热力场和围岩蚀变等问题的分析.  相似文献   

Empirical relationships between natural vibration period and height of buildings in Singapore          下载免费PDF全文

Tso‐Chien Pan  Key Seng Goh  Kusnowidjaja Megawati 《地震工程与结构动力学》2014,43(3):449-465

Singapore is a classic case of a modern metropolis with low hazard but high exposure to the seismicity in Sumatra. Because of land shortage, more than 80% of the population lives in high‐rise residential buildings. As part of the efforts to assess the seismic performance of buildings in Singapore subjected to long‐distance Sumatran earthquakes, relationships between the natural vibration period and height of high‐rise public residential buildings in Singapore are derived empirically by conducting ambient vibration tests on 116 buildings. The measured buildings have a height ranging from 4 to 30 stories. The aspect ratio of buildings in plan is found to be insignificant in affecting the natural vibration period of the first mode of the buildings. The period‐height relationships are derived using regression analysis considering the site properties of a building. It is concluded that the vibration periods estimated from the proposed period‐height relationship for buildings located at soft‐soil site are about 40% longer than the vibration periods estimated for buildings located at firm‐soil site. Measurements are also conducted to study the influence of buildings on the measured frequency of the surrounding soil. For this purpose, two buildings with 25 and 30 stories located at firm‐soil site and soft‐soil site, respectively, are selected. It is found that the distance of building influence on the measured frequency of the surrounding soil may reach up to one building height for a firm‐soil site and two building heights for a soft‐soil site. Additional data of natural vibration periods of 19 instrumented residential buildings, which have height ranging from 9 to 30 stories, were obtained from the building response recorded during the September 30, 2009 Sumatran earthquake event. The natural vibration periods of these buildings are compared with those estimated using the proposed period‐height relationships, and the absolute differences are found to be less than 12%. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Helioseismic Travel-Time Definitions and Sensitivity to Horizontal Flows Obtained from Simulations of Solar Convection     

Sébastien Couvidat  Aaron C. Birch 《Solar physics》2009,257(2):217-235

We study the sensitivity of wave travel times to steady and spatially homogeneous horizontal flows added to a realistic simulation of the solar convection performed by Robert F. Stein, Ake Nordlund, Dali Georgobiani, and David Benson. Three commonly used definitions of travel times are compared. We show that the relationship between travel-time difference and flow amplitude exhibits a non-linearity depending on the travel distance, the travel-time definition considered, and the details of the time – distance analysis (in particular, the impact of the phase-speed filter width). For times measured using a Gabor wavelet fit, the travel-time differences become nonlinear in the flow strength for flows of about 300 m s⁻¹, and this non-linearity reaches almost 60% at 1200 m s⁻¹ (relative difference between actual travel time and expected time for a linear behavior). We show that for travel distances greater than about 17 Mm, the ray approximation predicts the sensitivity of travel-time shifts to uniform flows. For smaller distances, the ray approximation can be inaccurate by more than a factor of three.  相似文献   

Consistently large cosmic flows on scales of  100 h⁻¹ Mpc : a challenge for the standard ΛCDM cosmology     

Richard Watkins  Hume A. Feldman  Michael J. Hudson 《Monthly notices of the Royal Astronomical Society》2009,392(2):743-756

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Characteristics of triggered lightning during Shandong artificial triggering lightning experiment (SHATLE)   总被引：1，自引：0，他引：1  

Xiushu Qie  Yang Zhao  Qilin Zhang  Jing Yang  Guili Feng  Xiangzhen Kong  Yunjun Zhou  Tinglong Zhang  Guangshu Zhang  Tong Zhang  Dongfang Wang  Haihua Cui  Zhongkuo Zhao  Shujun Wu 《Atmospheric Research》2009,91(2-4):310-315

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A ＂Dressed＂ Ensemble Kalman Filter Using the Hybrid Coordinate Ocean Model in the Pacific   总被引：1，自引：0，他引：1  

万莉颖  朱江  王辉  闫长香 《大气科学进展》2009,26(5):1042-1052

The computational cost required by the Ensemble Kalman Filter (EnKF) is much larger than that of some simpler assimilation schemes, such as Optimal Interpolation (OI) or three-dimension variational assimilation (3DVAR). Ensemble optimal interpolation (EnOI), a crudely simplified implementation of EnKF, is sometimes used as a substitute in some oceanic applications and requires much less computational time than EnKF. In this paper, to compromise between computational cost and dynamic covariance, we use the idea of ``dressing' a small size dynamical ensemble with a larger number of static ensembles in order to form an approximate dynamic covariance. The term ``dressing' means that a dynamical ensemble seed from model runs is perturbed by adding the anomalies of some static ensembles. This dressing EnKF (DrEnKF for short) scheme is tested in assimilation of real altimetry data in the Pacific using the HYbrid Coordinate Ocean Model (HYCOM) over a four-year period. Ten dynamical ensemble seeds are each dressed by 10 static ensemble members selected from a 100-member static ensemble. Results are compared to two EnKF assimilation runs that use 10 and 100 dynamical ensemble members. Both temperature and salinity fields from the DrEnKF and the EnKF are compared to observations from Argo floats and an OI SST dataset. The results show that the DrEnKF and the 100-member EnKF yield similar root mean square errors (RMSE) at every model level. Error covariance matrices from the DrEnKF and the 100-member EnKF are also compared and show good agreement.  相似文献