变形监测网的二类优化设计

本文讨论监测网值则阵的构成方法及监测网含准则降的二类设计求解问题。针对监测网具有监测方向性这一特点,通过旋转Q_x的第一主分量来构成监测网的准则阵。在比较几种二类设计计算法的基础上,提出了一种新的算法——逐次旋转法。利用这种算法能获得满意的优化方案。     

关于一般建筑物抗震设防标准问题

工程场地的设计地震动参数,目前多用概率地震危险性分析的方法给出。场地的地震基本烈度以设计基准期T=50年、加速度超越概率P=0.1的标准确定。本文根据广东省数地地震危险性分析结果结合我国常见的砖混结构的地震动参数的优化决策,认为上述标准宜取为T=50年、P=0.05—0.1。     

一个热带气旋移向变化的判据

本文对热带气旋移向突变进行了动力学分析,得到影响路径变化的主要因子,并在此基础上设计了一个诊断气旋移向稳定性的判据,经两百多次计算检验,证实其准确率达84％强。     

Computer Simulation of Coastal Acoustic Tomography by a Two-Dimensional Vortex Model

Computer simulation of coastal acoustic tomography with four, five, seven and nine stations was applied to two-dimensional vortex fields of horizontal domain 5 km × 5 km. Travel time data obtained in reciprocal directions between all pairs of acoustic stations were analyzed to reconstruct the vortex fields by the stochastic inverse method, reduced to the damped least squares method. The weighting factor appearing in the inverse analysis was determined by applying the L-curve method, in which a point making both the size of estimated error ‖y - Ex‖ and solution ‖x‖ as small as possible in a balance is specified as an optimum. The performance of this method was examined using two-dimensional vortex models which have different wavenumber spectra and adding the random error of different levels to the travel time difference data y. This study suggests that in the selection of the optimal weighting factor the horizontal section of the simulated tidal vortex fields can be well reconstructed by the coastal acoustic tomography system composed of five to seven acoustic stations located in the periphery of the vortex fields. This revised version was published online in August 2006 with corrections to the Cover Date.     

地震应急工作遵循的准则及其在地震预报中的实现

阐述了地震应急工作应遵循的准则－“社会满意准则”介绍上海市地震局在１９９６年１１月９日长江口以东海域发生Ｍｓ６．０地震时，迅速作出趋势判断的原始依据，由于当时作的趋势判断符合地震应急的科学性和社会性，因而在稳定性社会秩序，保障经济活动中取得了较好的经济效益，可供有关方面参考。     

Estimation of bearing capacity for multiple footings in sand

In the present study, the effects of multiple-footing configurations in sand on bearing capacity were investigated using field plate load tests and finite element analyses. Both strip and spread footings were considered in the finite element analyses. In each case, different footing distances were applied for the purposes of comparison among all of the results. From these results, it was observed that the load responses of multiple footings are similar to those of the single footing at distances greater than three times the footing width. Design equation and correlation parameters, necessary for quantifying the values of the bearing capacity ratio for the different multiple-footing configuration, were derived. Experimental test results from the literature were selected and used in verifying the proposed method.     

高应力下砂土与钢材界面单剪试验研究

疏排水沉降引起的竖直附加力导致了华东地区多个立井井筒破裂,高应力下土与结构界面剪切特性研究是解决这一工程问题的关键。在自行加工、改造的高应力单剪仪试验系统上进行了一系列单剪试验。试验数据分析表明高应力下砂土同钢材界面剪应力-剪切位移关系可用非线性弹性-理想、塑性本构关系描述;高应力下界面的强度准则符合无粘聚力的莫尔-库仑公式表示。     

农地边际化的表现特征及其诊断标准

本文对农地边际化与边际土地的概念与本质、农地边际化在区域土地利用中的表现特征及其诊断标准进行了理论探讨。农地边际化是一种受社会、经济、政治和环境等因素综合驱动作用的过程,一种在现有的土地利用和社会-经济结构条件下,农地变得不再具有经济生产能力的过程。在农地边际化过程中,农户会有不同的行为响应,从而导致区域土地利用在“集约度、播种面积、用途转移与土地经营制度”等方面发生重大变化;农地利用的“边际收益指标”、“集约度指标”与“播种面积指标”是诊断农地边际化的三大指标。一般而言,如果该农地利用的“边际收益”为负,且在随后的土地利用过程中出现了“集约度下降、播种面积缩小,甚至弃耕撂荒”等变化特征,可以初步判断该农地利用出现了边际化现象。但不同类型农地边际化,其诊断标准也有差异。     

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