冻土路基表面的融化指数与冻结指数

在冻土层之上筑路，由于会改变地-气界面的热物理特性，进而影响冻土层的热力→动力稳定性，故而修筑一定高度的路基成为保护冻土层所采取的一种常规措施．在修筑路基之后，与路基边坡的朝向有关的热效应是冻土路基工程保护措施必须考虑的问题．在数理分析与数值模拟分析的基础上，给出了可根据气温的年最大和最小月平均值计算路基表面的融化指数与冻结指数以及有关热状况参数的方法，并以青藏铁路北麓河段2002年为例进行了计算分析．实例分析表明，即便是没有修筑道路，北麓河地区的冻土也已经处于临界状态；路基相对的两个坡面，由于朝向不同会造成温度分布的强非均匀性，其中南和偏南方向与北和偏北方向的路基坡面热状况差异最大，有必要对路基相对的两个坡面采用不同的防护措施，一方面改善就地取土修筑路基对其下伏冻土层的直接不良影响，同时也尽可能减小路基表面温度分布的非均匀性，以避免纵向裂缝的发生。     

The colonization of periphytic diatom species on artificial substrates in the Ashar canal, Basrah, Iraq

Studies have been conducted between March 1993 and March 1994 in the Ashar canal, a backwater of the Shatt al-Arab River, Iraq. Using artificial substrates, the colonization and development of seventy-five diatom species belonging to twenty genera could be revealed. Taxa apportionment varied seasonally as well as within each season. A few species have been found during all experiments. These are Amphora ovalis, Bacillaria paradoxa, Cocconeis placentula var. euglypta, Cyclotella meneghiniana, Cymbella ventricosa, Navicula tripunctata var. schizonemoides, Rhoicosphenia curvata, and Synedra ulna. The occurrence of B. paradoxa in Experiment 1 (March-April 1993) and Experiment 4 (end of January to beginning of March 1994) was higher than 50%. Similarity of species increased towards the end of each season, and the communities from experiments 1 and 4 were more similar than others. The experiments also suggest that week 4 represents the equilibrium phase while week 6 reflects the increase in biological interactions. The results could also indicate the sequence of primary colonizers and the community development towards the equilibrium.     

A neural network approach for structural identification and diagnosis of a building from seismic response data

This work presents a novel procedure for identifying the dynamic characteristics of a building and diagnosing whether the building has been damaged by earthquakes, using a back‐propagation neural network approach. The dynamic characteristics are directly evaluated from the weighting matrices of the neural network trained by observed acceleration responses and input base excitations. Whether the building is damaged under a large earthquake is assessed by comparing the modal parameters and responses for this large earthquake with those for a small earthquake that has not caused this building any damage. The feasibility of the approach is demonstrated through processing the dynamic responses of a five‐storey steel frame, subjected to different strengths of the Kobe earthquake, in shaking table tests. Copyright © 2002 John Wiley & Sons, Ltd.     

System identification of the Vincent Thomas suspension bridge using earthquake records

The Vincent Thomas Bridge in the Los Angeles metropolitan area, is a critical artery for commercial traffic flow in and out of the Los Angeles Harbor, and is at risk in the seismically active Southern California region, particularly because it straddles the Palos Verdes fault zone. A combination of linear and non‐linear system identification techniques is employed to obtain a complete reduced‐order, multi‐input–multi‐output (MIMO) dynamic model of the Vincent Thomas Bridge based on the dynamic response of the structure to the 1987 Whittier and 1994 Northridge earthquakes. Starting with the available acceleration measurements (which consists of 15 accelerometers on the bridge structure and 10 accelerometers at various locations on its base), an efficient least‐squares‐based time‐domain identification procedure is applied to the data set to develop a reduced‐order, equivalent linear, multi‐degree‐of‐freedom model. Although not the main focus of this study, the linear system identification method is also combined with a non‐parametric identification technique, to generate a reduced‐order non‐linear mathematical model suitable for use in subsequent studies to predict, with good fidelity, the total response of the bridge under arbitrary dynamic environments. Results of this study yield measurements of the equivalent linear modal properties (frequencies, mode shapes and non‐proportional damping) as well as quantitative measures of the extent and nature of non‐linear interaction forces arising from strong ground shaking. It is shown that, for the particular subset of observations used in the identification procedure, the apparent non‐linearities in the system restoring forces are quite significant, and they contribute substantially to the improved fidelity of the model. Also shown is the potential of the identification technique under discussion to detect slight changes in the structure's influence coefficients, which may be indicators of damage and degradation in the structure being monitored. Difficulties associated with accurately estimating damping for lightly damped long‐span structures from their earthquake response are discussed. The technical issues raised in this paper indicate the need for added spatial resolution in sensor instrumentation to obtain identified mathematical models of structural systems with the broadest range of validity. Copyright © 2003 John Wiley & Sons, Ltd.     

高分辨率卫星影像中阴影的自动提取与处理

高分辨率卫星遥感影像开创了许多新的应用领域，但影像中的阴影是一个必须解决的问题。一方面，它给象影像分类这样的一些应用带来了很大麻烦，另一方面，它提供了物体的高度信息。本文利用纹理分析的方法，通过共生矩阵和相应指数的计算，对高分辨率卫影像中阴影的自动提取与处理作了一个尝试并给出了一些结果。     

基于信息块法的矢量符号库的建立和符号化实现

基于试验成果，详细介绍了基于信息块法的矢量地图符号库的建立和空间信息的符号化。     

基于新型机载多角度传感器AMTIS的LAI反演

以实地测量数据为先验知识,利用AMTIS数据对顺义地区的一块小麦地进行了叶面积指数(LAI)反演实验研究,并用实地LAI数据进行了验证。通过利用实测数据作为模型参数,以及对干湿土壤分类和匹配表的调整,使反演结果和反演速度得到了提高。     

应用RMi法估算岩体变形模量

RMR法与Q法是国内外八、九十年代岩体质量和参数估算的常用方法,然而RMR法和Q法对质量较差的岩体不太实用,而RMi法是一种既适用于软岩又适用于硬岩的岩体质量评价和参数估算方法。本文在介绍RMi法基本原理的基础上,对贵州省鱼简河水库坝基岩体变形模量进行确定。     

Reliability based risk index for the design of reinforced earth structures

The design methods currently used for earth reinforcement are mostly based on deterministic properties of both the soil and the construction materials used. Nowadays, however, the general trend is designing at a specific degree of reliability. This is even more true where the raw data such as soil properties exhibit significant variation. Deterministic solutions, in this case, may not suffice. Therefore, this paper will attempt to use probabilistic formulations thereby modifying the existing design procedure of reinforced earth retaining walls to account for uncertainties and variabilities. Through a first order Taylor's series expansion about the mean, the mean and variance of the strip reinforcing components, namely width and length, are derived in terms of the variations in the soil properties. Design charts that enable estimation of both mean and variance are developed to avoid extensive partial differentiation involved in the computations. Using appropriate probability distributions along with the mean and variance, the final design outputs are determined for a selected failure probability by introducing what is refered to as 'risk index'. The results indicate that the risk index increases with an increase in the coefficient of variations and a decrease in failure probability. Furthermore, it is shown that in some cases, depending on the variabilities of the soil properties, the classical design technique produced a relatively high failure probability. This revised version was published online in July 2006 with corrections to the Cover Date.     

广西异常暴雨天气事件之异常指数初探

对广西异常暴雨天气事件之“异常指数”的设置进行了初步探讨，提出暴雨天气事件中过程日最大暴雨范围，过程持续时间，过程强降雨，特强降雨发生范围等四项异常分指数，然后统计同一过程分指数之和，得总指数，在此基础上分别选出了4－10月各月广西异常暴雨天气事件。