Optimal distribution of linear control intensity over the frequency range

In this paper, a control strategy for structural systems is proposed and developed in the frequency domain. The algorithm is substantially based on a linear derivative feedback and a convolution of the control parameter, whose distribution in the frequency field is chosen in such a manner as to comply with the requirements of an ad hoc formulated constrained optimum problem, with the response data monitored until the instant of control action application. Some numerical testing is carried out by referring to given recorded accelerograms, showing a good performance of the proposed approach. Copyright © 2002 John Wiley & Sons, Ltd.     

Disjunctive Kriging with Hard and Imprecise Data

This paper presents a methodology for assessing local probability distributions by disjunctive kriging when the available data set contains some imprecise measurements, like noisy or soft information or interval constraints. The basic idea consists in replacing the set of imprecise data by a set of pseudohard data simulated from their posterior distribution; an iterative algorithm based on the Gibbs sampler is proposed to achieve such a simulation step. The whole procedure is repeated many times and the final result is the average of the disjunctive kriging estimates computed from each simulated data set. Being data-independent, the kriging weights need to be calculated only once, which enables fast computing. The simulation procedure requires encoding each datum as a pre-posterior distribution and assuming a Markov property to allow the updating of pre-posterior distributions into posterior ones. Although it suffers some imperfections, disjunctive kriging turns out to be a much more flexible approach than conditional expectation, because of the vast class of models that allows its computation, namely isofactorial models.     

科学计算可视化技术的研究与应用

本文介绍了科学计算可视化技术的发展和应用情况，论述了这一新技术的特点及其在油气藏描述，工程设计ＣＡＤ等学科的应用和发展趋势。阐述了目前国际国内计算机图形学领域具体的研究方向和方法及图形软件、图形硬件的发展概况。     

洪泛平原农村居民地空间分布特征定量研究及应用探讨

通过对影响居民地空间分布因素的分析,探讨了洪泛平原农村居民地空间分布特征;利用地理信息系统技术对不同高程带内居民地分布规模、等级和空间分布密度作了定量研究,得到了居民地空间分布密度和人口空间分布密度参数;并结合洪灾淹没区居民地损失的估算,对研究结果的应用作了探讨。     

CLIMATIC RECORDS FROM ANNUAL LAYERS AND STABLE ISOTOPES OF A STALAGMITE IN BEIJING OVER THE LAST 2300 YEARS

Ｉ.ＩｎｔｒｏｄｕｃｔｉｏｎＳｔａｌａｇｍｉｔｅｓｈａｖｅｂｅｅｎａｐｐｌｉｅｄｔｏｕｓｅａｓｈｉｇｈｒｅｓｏｌｕｔｉｏｎｐａｌｅｏｃｌｉｍａｔｉｃｉｎｄｉｃａｔｏｒｓｓｉｎｃｅｔｈｅａｎｎｕａｌｇｒｏｗｔｈｂａｎｄｉｎｇｗａｓｒｅｃｏｇｎｉｚｅｄｉｎｓｔａｌａｇｍｉｔｅｓ[1,2].Ａｎｎｕａｌｇｒｏｗｔｈｂａｎｄｉｎｇｃａｎｂｅｍａｎｉｆｅｓｔｅｄｉｎｓｅｖｅｒａｌｍａｎｎｅｒｓｄｅｆｉｎｅｄｂｙ1)ａｌｔｅｒｎａｔｉｎｇｆｌｕｏｒｅｓｃｅｎｔａｎｄｎｏｎ-ｆｌｕｏｒｅｓｃｅｎｔｃａｌｃｉｔｅ[3,4];2)…     

An application of factor analysis for the study of the hydrogeological conditions in Plio-Pleistocene aquifers of NW Achaia (NW peloponnesus, Greece)

R- andQ-mode factor analysis is applied to 51 groundwater samples collected from wells drilled in the Plio-Pleistocene aquifers of NW Achaia, Greece. The purpose ofR- andQ-mode factor analysis application is to identify (i) the regional groundwater flow pattern, and (ii) the deterioration of groundwater quality. Sixteen hydrogeological parameters are used in order to examine their importance and to provide significant insight into their correlations. In theR-mode factor analysis, a six-factor model is suggested which can explain more than 77.5% of the total variance. The contribution of each factor at every site (factor scores) also is computed. Maps are constructed showing the geographical distribution of the factor scores. From these maps, the high salinity areas are delineated (seawater intrusion, possible appearance of halite layers) and the areas with elevated contribution of karastic-water are defined. Using theQ-mode correspondence analysis the meaning of the electrical conductivity as the most important variable in groundwater quality characterization is demonstrated.     

Texture and mineralogy of sediments from the Ganges-Brahmaputra-Meghna river system in the Bengal Basin, Bangladesh and their environmental implications

 The Bengal basin, Bangladesh, represents one of the most densely populated recent floodplains of the world. The sediment flux through the basin is one of the highest on a global scale. A significant portion of this sediment load find its sink in the basin itself because of its lower elevation and frequent flooding. The textural, mineralogical and chemical nature of the sediments thus have an important bearing on the environmental quality of the basin as well as for the Bay of Bengal. The sediment load of the Ganges-Brahmaputra-Meghna (GBM) river system consists exclusively of fine sand, silt and clay at their lower reaches within the Bengal basin, Bangladesh, and is deposited under uniformly fluctuating, unidirectional energy conditions. The sediments have a close simitarity in grain size with the sediments of the surrounding floodplain. The mineral assemblage is dominated by quartz and feldspars. Illite and kaolinite are the major clay minerals, and occur in almost equal proportion in bed sediments. The heavy mineral assemblage is dominated by unstable minerals which are mostly derived from high-rank metamorphic rocks. The characteristic smaller grain-size, i.e. having large surface-to-mass ratios, and the mineralogy of sediments suggests that they are susceptible to large chemical adsorptive reactions and thus could serve as a potential trap for contaminants. However, the sediments of the GBM river system in the Bengal basin, Bangladesh, shows lower concentration of Pb, Hg and As, and a marginally higher value for Cd as compared to that of standard shale. Considering population density and extensive agricultural practice in the basin, the sediments can in the long run become contaminated. Received: 9 November 1994 · Accepted: 18 June 1996     

Coal-generated oil in Tuha Basin

The Turpan-Harmi (abbreviated to Tuha below) Basin is a typical basin of coal-generated oil accumulation in China. The Middle-Lower Jurassic coal measures are considered the main source beds. Hence, both desmocollinite and suberinite are considered the contributors for coal-generated oil. Principal geochemical features of the crude oil in the Tuha Basin are rich in alkanes (70%—80%), high pristane/phytane ratio (6—8), abundant heavy carbon isotope (δ¹³C PDB= -26%–-23%) and absolute GP sterane predominance. The hydrocarbon generation process from the coal series is characterized by multistages, early generation and early expulsion.     

黄河上游径流预报的灰色拓扑方法

以龙羊峡水库年平均入库流量预报为例，根据灰色系统理论的建模方法，利用龙羊峡水库入库水量代表站唐乃亥水文站的实测径流资料，建立了一个ＧＭ（１，１）拓扑预测模型，用于黄河上游径流的长期预报，并取得了较为满意的结果。     

天山山区近40a年降水变化特征与南、北疆的比较

本文分析了天山山区近40 a来年降水变化的基本特征，并与南疆、北疆进行了比较，所得的主要结果如下：(1)天山山区在年降水量干湿变化阶段上与北疆的相似性强于南疆。(2)年降水量的空间分布的同步变化性以北疆为最好，南疆最差，天山山区居中，而年降水量的空间分布的反向变化性，以天山山区为最大，北疆最小，南疆居中。(3)天山山区与南疆从60年代到90年代，年降水均表现出了持续的增加的趋势，北疆年降水从60年代到90年代，除70年代外，不断增多。