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151.
152.
众多城市坐落于沉积河谷之中,沉积河谷-密集建筑群间的地震动力相互作用规律尚不明确。采用间接边界元方法(IBEM),对在平面SV波入射下,沉积河谷-建筑群之间的地震相互作用进行二维模拟计算和参数分析。研究结果表明:沉积河谷-建筑群间存在着显著而复杂的地震动力相互作用;较浅沉积河谷中建筑群地震响应呈现强弱交替变换特征;入射波角度、沉积河谷的材料、几何特征是影响沉积河谷-建筑群整体地震响应规律的关键因素。总体上看,建筑群对浅沉积河谷地震动响应有较大的降幅效应,特别是高频波入射下最大降幅近50%。实际河谷地震放大效应评估需考虑密集建筑群的影响,而位于地震波聚焦位置的建筑物需适当提高设防标准。 相似文献
153.
ZHU XinyanGONG JianyaZHANG XiaodongXIONG Hanjiang ZHU Xinyan Professor National Laboratory for Information Engineering in Surveying Mapping Remote Sensing WTUSM Luoyu Road Wuhan China 《地球空间信息科学学报》1999,2(1):49-54
Spatial data, including geometrical data, attribute data, image data and DEM data, are huge in volume and relations among them are complex. How to effectively organize and manage those data is an important problem in GIS. Several problems about space data organization and management in GeoStar which is a basic GIS software made in China are discussed in this paper. The paper emphasizes on object model of spatial vector, data organization, data management and how to realize the goal, and the like. 相似文献
154.
Indirect Effects of Epibiosis on Host Mortality: Seastar Predation on Differently Fouled Mussels 总被引:5,自引:0,他引:5
In situ experiments were run with the seastar Asterias rubens to investigate the influence of epibiosis on predation preferences. Mussels ( Mytilus edulis ) monospecifically fouled by different epibiont species (the barnacle Balanus improvisus , the red filamentous alga Ceramium strictum , the sponge Halichondria panicea and the hydrozoan Laomedea flexuosa ) and macroscopically clean mussels were exposed and seastar predation was monitored by SCUBA. Asterias rubens preferred macroscopical unfouled mussels as prey. Fouling generally reduced predation pressure on the mussel hosts (associational resistance). Barnacles protected mussels less efficiently than hydrozoans or algae.
We hypothesize that in top-down controlled communities this influence of epibiosis on predation pressure should affect mussel community patterns. A survey of natural mussel-epibiont distribution in the presence or absence of A. rubens showed that the prevalence of differently fouled mussels differed between predation-exposed and predation-protected habitats. Natural mussel-epibiont associations reflected the preferential predation of the major local predators. Additionally, higher epibiotic diversity and evenness could be observed at locations accessible to benthic predators as compared with habitats protected from predation.
As blue mussels and seastars are important structuring and controlling elements in the shallow water community of Kiel Fjord, major consequences of epibiosis on the entire system are discussed. 相似文献
We hypothesize that in top-down controlled communities this influence of epibiosis on predation pressure should affect mussel community patterns. A survey of natural mussel-epibiont distribution in the presence or absence of A. rubens showed that the prevalence of differently fouled mussels differed between predation-exposed and predation-protected habitats. Natural mussel-epibiont associations reflected the preferential predation of the major local predators. Additionally, higher epibiotic diversity and evenness could be observed at locations accessible to benthic predators as compared with habitats protected from predation.
As blue mussels and seastars are important structuring and controlling elements in the shallow water community of Kiel Fjord, major consequences of epibiosis on the entire system are discussed. 相似文献
155.
From the point of view of urban consumption behavior, urban fresh water consumption could be classified as three types, namely,
direct, indirect and induced water consumption. A calculation approach of urban fresh water consumption was presented based
on the theory of urban basic material consumption and the input-output method, which was utilized to calculate urban fresh
water consumption of China, and to analyze its structural change and causes. The results show that the total urban fresh water
consumption increased 561.7×109m3, and the proportion to the total national fresh water resources increased by 20 percentage points from 1952 to 2005. The
proportion of direct and induced water consumption had been continuously rising, and it increased by 15 and 35 percentage
points separately from 1952 to 2005, while the proportion of indirect water consumption decreased by 50 percentage points.
Urban indirect water consumption was mainly related to urban grain, beef and mutton consumption, and urban induced water consumption
had a close relationship with the amount of carbon emission per capita. Finally, some countermeasures were put forward to
realize sustainable utilization of urban fresh water resources in China.
Foundation item: Under the auspices of Key Project of National Natural Science Foundation of China (No. 40535026) 相似文献
156.
环境背景数据的分类编码与应用 总被引:1,自引:0,他引:1
以环境背景数据为研究对象,通过对语义时间、存储格式、记载介质、负责机构、专题信息等属性特征的分析,提出完整的环境背景数据概念;强调环境背景数据的分类编码,应侧重环境背景数据的发现,并着重讨论分类编码的贯彻实施应以元数据为标准载体,在统一的环境背景数据分类编码无法确定时,利用核心元数据中的关键字字段实现分类编码的间接引用,确保元数据标准对不同系列分类编码的兼容并包。 相似文献
157.
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159.
A variationally coupled BEM–FEM is developed which can be used to analyse dynamic response, including free-surface sloshing motion, of 3-D rectangular liquid storage tanks subjected to horizontal ground excitation. The tank structure is modelled by the finite element method and the fluid region by the indirect boundary element method. By minimizing a single Lagrange function defined for the entire system, the governing equation with symmetric coefficient matrices is obtained. To verify the newly developed method, the analysis results are compared with the shaking-table test data of a 3-D rectangular tank model and with the solutions by the direct BEM–FEM. Analytical studies are conducted on the dynamic behaviour of 3-D rectangular tanks using the method developed. In particular, the characteristics of the sloshing response, the effect of the rigidity of adjacent walls on the dynamic response of the tanks and the orthogonal effects are investigated. © 1998 John Wiley & Sons, Ltd. 相似文献
160.
在水力因素多变的长江下游感潮河段建立ADCP在线测流系统实时采集指标流速,可选用合适的方法推求断面平均流速,从而实现流量的实时报汛和整编。多元线性回归分析和BP神经网络具有原理明晰、实现便捷等特点,为比较以上两种方法在断面平均流速计算中的优劣,以南京水文实验站2014年以来实测数据为例,分析不同情况下两种模型的拟合精度和预测精度。结果表明,两种模型均具有较好的有效性、精确性和稳定性,且拟合精度与模型选用的监测指标有关;对于只采用单一指标流速而言,BP神经网络模型的结果明显优于多元线性回归模型。同时,两种模型都能较好的预测断面平均流速,其中BP神经网络适应更好。 相似文献