Optimal design of passive energy dissipation systems based on H∞ and H2 performances

Passive energy dissipation devices (EDDs), such as viscous dampers, viscoelastic dampers, etc., have been used to effectively reduce the dynamic response of civil infrastructures, such as buildings and bridges, subject to earthquakes and strong winds. The design of these passive energy dissipation devices (EDDs) involves the determination of the optimal locations and the corresponding capacities. In this paper, we present two optimal design methodologies for passive EDDs based on active control theories, including H_∞ and H₂ performances, respectively. The optimal design methodologies presented are capable of determining the optimal locations and the corresponding capacities of EDDs. Emphasis is placed on the application of linear matrix inequality (LMI) for the effective design of passive EDDs using the popular MATLAB toolboxes. One important advantage of the proposed approaches is that the computation of the structural response is not needed in the design process. The proposed optimal design methodologies have been applied to: (i) a 10‐storey building and a 24‐storey building both subject to earthquake excitations, and (ii) a 76‐storey wind‐excited benchmark building, to demonstrate the advantages of the proposed design methodologies over the conventional equal capacity design. Copyright © 2002 John Wiley & Sons, Ltd.     

冻融作用对地气系统能量交换的影响分析

通过对温度波在地层内传播过程问题的分析研究, 讨论土在冻结和融化过程对地气系统能量交换的影响, 并以亚粘土为例应用近似方法计算了在冻结和融化过程地气系统能量交换和地温变化特征, 同时将相同条件下发生冻融作用与不发生冻融作用情况地气系统热交换量进行了比较. 结果表明, 冻融作用使地气系统热交换加强, 同时吸热和放热的过程也发生了改变.     

深切怀念我们的导师-李连捷院士

李连捷院士是杰出的土壤地理学家、我国土壤学的创始人之一，也是土壤地质学派的创史人。他有关土壤发生的地学基础背景的正确而鲜明的学术思想引导着土壤地理和土壤资源的研究、土地资源开发和研究生培养工作。他一方面不断学习国际上在这方面的学术发展动向及前沿；另一方面紧密结合中国发展的生产实际。他在20世纪50-60年代以综合考察，70年代以后以扎根基点的形式发展土壤科学、培养研究生。他一生刚正不阿、高风亮节，实为一代宗师。     

纤维素接枝丙烯酰胺/高岭土高吸水性复合材料研究

在高岭土的存在下，以N，N－亚甲基双丙烯酰胺作交联剂，以硝酸铈铵为引发剂微晶纤维素与丙烯酰胺进行接枝共聚反应，合成接枝纤维素／高岭土高吸水性复合材料。研究了纤维素与单体的配比、高岭土添加量、交联剂用量、引发剂用量及反应温度对吸水率的影响。用红外光谱表征复合材料的结构，用电子显微镜观察复合材料的表面与界面。结果表明，高岭土在接枝聚合物中能较好分散，复合材料吸水率达1166，对生理盐水溶液的吸水率达86。     

深海热泉生物——人类的基因资源宝库

广泛存在于大洋之中的深海热泉生物群落依靠化学自营维持生存与繁衍，构成了独特的生态系统，是对光合作用生态系统理论的一个挑战和补充，在生物学上有着重要的研究意义，对于揭示生命的起源与拓展生命的生存空间有着重要的学术价值，而且还孕育着广泛而重要的应用价值和商业前景，具体体现在新型医药开发、基因疗法、工业应用以及环境保护等方面。深海热泉生物将是人类最重要的基因资源宝库。     

A multi-scale study on land use and land cover quality change: The case of the Yellow River Delta in China

This paper presents a case study of the Yellow River Delta in China, to trace land use and land cover changes during the past 20 years, with an emphasis on land quality changes. Three sets of data are used in this case study: remote sensing data derived from satellite images; crop yield data from statistics; and soil data collected by the researchers in the field. Our study reveals that at the regional scale, LUCC has taken place in a positive direction: vegetation cover has been expanding and crop yields per hectare have been on rise. However, while the overall eco-environment has improved, the improvement is uneven across the Delta region. At local levels, some areas show signs of increased salinization and declining organic content. Both natural forces and human activities are responsible for the LUCC, but human activities play a more important role. While some impacts of human activities are positive, the damages are often long-lasting and irreversible. We also conclude that it is necessary to use both macro data (such as remote sensing data) and micro data (data collected in the field) to study land quality change. The former are efficient in examining land quality changes at the regional scale, the latter can serve to verify ground patterns revealed from macro data and help to identify local variations, so as to get a comprehensive understanding of LUCC and promote sustainable land use and land management. This revised version was published online in July 2006 with corrections to the Cover Date.     

Combination of Dependent Realizations Within the Gradual Deformation Method

Gradual deformation is a parameterization method that reduces considerably the unknown parameter space of stochastic models. This method can be used in an iterative optimization procedure for constraining stochastic simulations to data that are complex, nonanalytical functions of the simulated variables. This method is based on the fact that linear combinations of multi-Gaussian random functions remain multi-Gaussian random functions. During the past few years, we developed the gradual deformation method by combining independent realizations. This paper investigates another alternative: the combination of dependent realizations. One of our motivations for combining dependent realizations was to improve the numerical stability of the gradual deformation method. Because of limitations both in the size of simulation grids and in the precision of simulation algorithms, numerical realizations of a stochastic model are never perfectly independent. It was shown that the accumulation of very small dependence between realizations might result in significant structural drift from the initial stochastic model. From the combination of random functions whose covariance and cross-covariance are proportional to each other, we derived a new formulation of the gradual deformation method that can explicitly take into account the numerical dependence between realizations. This new formulation allows us to reduce the structural deterioration during the iterative optimization. The problem of combining dependent realizations also arises when deforming conditional realizations of a stochastic model. As opposed to the combination of independent realizations, combining conditional realizations avoids the additional conditioning step during the optimization process. However, this procedure is limited to global deformations with fixed structural parameters.     

Factorial and indicator kriging methods using a geographic information system to delineate spatial variation and pollution sources of soil heavy metals

This study uses factorial and indicator kriging methods with a geographic information system (GIS), to overlay and delineate the variation and pollution sources of soil heavy metals in fields in the north of Changhua County, Taiwan. Accordingly, the spatial variation and pollution probability patterns of soil cadmium, chromium and copper are estimated to support further environmental monitoring, remediation and planning. The overlay maps of industrial plants, irrigation channels and kriging estimates, constitute a GIS. This reveals that the short- and long-range variations and soil pollution by Cd, Cr and Cu strongly corresponded to the locations of irrigation systems and industrial plants in the area of study. The maps also verify most locations of suspected pollution sources from the GIS database. Moreover, the probability spatial patterns estimated by indicator kriging, based on the pollution thresholds of Cd, Cr and Cu, were also highly correlated with irrigation channels and industrial plants. The GIS, with factorial and indicator kriging under different combinations of variations and pollution probabilities of soil Cd, Cr and Cu, provide alternative scenarios for delineating the areas that contain high variation and high pollution probability of these heavy metals, to enable decision makers to identify pollution sources, and to further investigate and remedy soil pollution.     

Dissolved and particulate trace metals and their partitioning in a hypoxic estuary: The Tanshui Estuary in Northern Taiwan

The distribution and partitioning of trace metals (Co, Cu, Fe, Mn, Ni, and Zn) between dissolved and particulate phases were studied in the Tanshui Estuary. The upper reach of the estuary is hypoxic and heavily polluted due to domestic and industrial discharges. The concentration ranges of dissolved and leachable particulate trace metals in the Tanshui Estuary were: Co: 0.3–6.1 nM, 1.8–18.6 mg kg⁻¹; Cu: 5–53 nM, 22–500 mg kg⁻¹; Fe: 388–3,364 nM, 1.08–6.67%; Mn: 57–2,914 nM, 209–1,169 mg kg⁻¹; Ni: 7–310 nM, 6–108 mg kg⁻¹; and Zn: 12–176 nM, 62–1,316 mg kg⁻¹; respectively. The dissolved concentrations of the metals were 2–35 times higher than the average values of the world river water. The distributions of dissolved and particulate studied metals, except Mn, in the estuary showed scattering, which could be attributed to the discharges from many industrial wastewater disposal works located in the upper tributaries. The daily input of dissolved metals from the disposal works to the Tanshui Estuary ranged from 0.1–0.4 tons. Dissolved Mn was nearly conservative in the region with salinity higher than 10 psu, while particulate Mn decreased in the region with salinity of 10–15 psu. The concentration increased significantly seawards, corresponding with the distribution of dissolved oxygen. The distribution coefficient (K_D) for Mn in the lower estuary was nearly three orders of magnitude higher than in the upper estuary. This phenomenon may be attributed to the diffusion of Mn from the anoxic sediment in the upper estuary and gradual oxidation into particulate Mn in the middle and lower estuary as the estuarine water became more oxygenated. The distribution coefficient for Cu decreased with increasing salinity. The percentages of trace metals bound by suspended particulate matter decreased in the following order: Fe>Zn, Cu>Co>Mn>Ni.     

四川江油-北川地区下石炭统灰岩的古地磁研究

对采于四川北部江油 北川地区 (31.4°N ,10 4 .3°E)下石炭统 39个采点的 334块灰岩标本进行了较为系统的古地磁学研究 ,结果表明 ,标本中剩磁方向具有明显的双分量特征 ,低温 (10 0～ 30 0℃ )分量在地理坐标系下与现代地磁场方向基本一致 ,且不能通过褶皱检验 ,应是现代地磁场的重磁化 ,中温 (30 0～ 4 80℃ )反极性分量在地层坐标系中具有高负倾角的特征 ,其形成可能与早侏罗世岩层的褶皱弯曲有关 .