孔隙水压力静力触探动态贯入过程的有限元模拟

孔隙水压力静力触探作为一种新型的土体勘测技术已被广泛应用,但是,其机理的研究尚存在很大的不足。笔者系统分析了孔压触探的贯入特征,提出了“孔隙水压力体积基准值”的概念,借此推导出用土体体积变形量计算超孔隙水压力的公式。在此基础上,用轴对称有限单元法模拟探头的动态贯入过程,揭示应力－应变的变化特征,寻找超孔隙水压力生成与消散的规律,对孔压触探的机理进行了研究。     

LiBr溶液从低浓度到高浓度的分子动力学模拟

在 L i Br与水的物质量比分别为 1∶ 64、1∶ 32、1∶ 16、1∶ 8、1∶ 4和 1∶ 3的情况下 ,对 L i Br溶液从低温到高温的分子动力学模拟进行了研究。随浓度增加 ,锂离子的水合数量呈减少趋势但同时又从 L i+- Br-接触离子对的数量增加中得到补偿 ,而 L i离子的第一配位壳层的配位数量保持不变。在高浓度 Li Br溶液中 ,Br- O之间的距离有所增加 ,Br-- O的径向分布的形状更趋于非对称 ,从而很好地确定了 Br离子水合壳层 L i+- Br-接触离子对可以在更稀的溶液中产生 ,但随浓度增加而增加。L i+- Br-距离明显短于溶液中 Li离子与 Br离子的离子半径之和 ,也短于 L i Br晶体中两者离子半径之和。高浓度溶液中水分子的结构几乎被破坏 ,水分子间的氢键明显增加 ,但没有消失。对 L i+、Br-和水的扩数系数计算值与实验值进行了比较     

岩石矿物组份质量转移的模糊聚类定量计算

本文根据岩石矿物组份质量分数值的定和特性 ,提出定量计算组份质量转移的新方法。该方法运用模糊动态聚类分析技术 ,通过计算复原定和差并判定差值类型 ,辅以相应的判别参数 ,逐步从中筛选出真恒量组份 ,再利用真恒量组份定值系数 ,计算出变组岩石矿物各组份的真实质量分数值和转移量值。笔者将该方法称为真恒量组份定值法 (TCF法 )。     

鲁东造山带榴辉岩变质作用特征及其动力学机制

岩相学研究表明,广泛发育鲁东造山逞中的榴辉岩可以划分为四种类型：第一类为含柯石英及其假象榴辉岩;么二类为含蓝晶石 、黝帘石及多硅白云母等榴辉岩;第三类为石榴石－绿辉石－石英组合榴辉岩;第四类为（角闪石）石榴石－辉及有关岩石（非典型“榴辉岩”）。这四类榴辉岩峰期前进变质矿物共生组合及Ｐ－Ｔ条件估算结果均显示它们应属于高温与超高压变质作用产物,其变质作用ＰＴｔ轨迹表现为顺时针演化趋势,反映出板块俯冲碰     

Pre‐ and post‐test mathematical modelling of a plan‐asymmetric reinforced concrete frame building

Pre‐ and post‐test analyses of the structural response of a three‐storey asymmetric reinforced concrete frame building were performed, aimed at supporting test preparation and performance as well as studying mathematical modelling. The building was designed for gravity loads only. Full‐scale pseudo‐dynamic tests were performed in the ELSA laboratory in Ispra. In the paper the results of initial parametric studies, of the blind pre‐test predictions, and of the post‐test analysis are summarized. In all studies a simple mathematical model, with one‐component member models with concentrated plasticity was employed. The pre‐test analyses were performed using the CANNY program. After the test results became available, the mathematical model was improved using an approach based on a displacement‐controlled analysis. Basically, the same mathematical model was used as in pre‐test analyses, except that the values of some of the parameters were changed. The OpenSees program was employed. Fair agreement between the test and numerical results was obtained. The results prove that relatively simple mathematical models are able to adequately simulate the detailed seismic response of reinforced concrete frame structures to a known ground motion, provided that the input parameters are properly determined. Copyright © 2006 John Wiley & Sons, Ltd.     

Approximate incremental dynamic analysis using the modal pushover analysis procedure

Incremental dynamic analysis (IDA)—a procedure developed for accurate estimation of seismic demand and capacity of structures—requires non‐linear response history analysis of the structure for an ensemble of ground motions, each scaled to many intensity levels, selected to cover the entire range of structural response—all the way from elastic behaviour to global dynamic instability. Recognizing that IDA of practical structures is computationally extremely demanding, an approximate procedure based on the modal pushover analysis procedure is developed. Presented are the IDA curves and limit state capacities for the SAC‐Los Angeles 3‐, 9‐, and 20‐storey buildings computed by the exact and approximate procedures for an ensemble of 20 ground motions. These results demonstrate that the MPA‐based approximate procedure reduces the computational effort by a factor of 30 (for the 9‐storey building), at the same time providing results to a useful degree of accuracy over the entire range of responses—all the way from elastic behaviour to global dynamic instability—provided a proper hysteretic model is selected for modal SDF systems. The accuracy of the approximate procedure does not deteriorate for 9‐ and 20‐storey buildings, although their dynamics is more complex, involving several ‘modes’ of vibration. For all three buildings, the accuracy of the MPA‐based approximate procedure is also satisfactory for estimating the structural capacities for the limit states of immediate occupancy, collapse prevention, and global dynamic instability. Copyright © 2006 John Wiley & Sons, Ltd.     

Seasonal dynamics of soil CO_2 effluxes with responses to environmental factors in lower subtropical forests of China

Seasonal metrics and environmental responses to forestry soil surface CO2 emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatograph techniques among three types of lower subtropical forests. Results showed that annual CO2 effluxes (S L) reached 3942.20, 3422.36 and 2163.02 CO2 g·m-2·a-1, respectively in the monsoon evergreen broadleaf forest, mixed broadleaf-coniferous forest and coniferous forest. All the three types of forests revealed the same characteristics of seasonal changes with the CO2 effluxes peaking throughout June to August. During this peaking period, the effluxes were 35.9%, 38.1% and 40.2% of the total annual effluxes, respectively. The CO2 emission process responding to the environmental factors displayed significantly different patterns in forestry soils of the three types of forests. The coniferous forest (CF) was more sensitive to temperature than the other two types. The Q10 values were higher, along with greater seasonal variations of the CO2 efflux, indicating that the structurally unique forestry ecosystem has disadvantage against interferences. All the three types of forestry CO2 effluxes showed significant correlation with the soil temperature (Ts), soil water content (Ms) and air pressure (Pa). However, stepwise regression analysis indicated no significant correlation between air pressure and the soil CO2 efflux. With an empirical model to measure soil temperature and water content in 5 cm beneath the soil surface, the CO2 effluxes accounting for 75.7%, 77.8% and 86.5% of the efflux variability respectively in soils of BF, MF and PF were calculated. This model can be better used to evaluate the CO2 emission of soils under water stress and arid or semi-arid conditions.     

时态GIS的空间实体关联技术应用研究

在自然界中大多数现实世界的实体都是动态的,地图上的公路、铁路、居民地等只是相对于一个很短的时间里是静态的,经过一个长的时间这些实体都将发生改变。本文根据不同时态地理实体的各种特征比较,将两个时态的数据进行关联,建立几何、位置和属性的变化模型,将这个动态的过程表现出来。试验表明,本文的算法是有效的。     

基于Socket通信的WebGIS实时监测系统

在W ebG IS实时监测系统中,针对客户端采用实时刷新页面来更新信息方式的不足,本文提出应用Socket通信技术实现W ebG IS实时监测系统的设计思想和实现方法。首先,在分析Socket通信的原理和基本过程的基础上,给出了系统体系结构,然后讨论了其核心设计与系统实现,最后给出实例说明在W ebG IS实时监测系统中应用Socket通信技术可有效降低数据传输量,提高系统实时响应速度。     

一种中分辨率遥感影像道路的快速搜索算法

基于动态规划的思想,提出了一种用于中等分辨率遥感影像的道路搜索算法,利用线段代价最小规则进行道路线段跟踪,实验结果表明算法相对简单、快速有效、抗噪性能好。