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191.
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The law of the sea has always been open to the charge of being a ‘covenant without a sword’ and its effectiveness when challenged by the perceived national security of a superpower is questionable. Attempts to limit and control antisubmarine warfare (ASW) have demonstrated that neither superpower is prepared to risk its second-strike capability for what may be an illusory legal protection. This article reviews developments relevant to ASW in the law of the sea and describes the significance of ASW to the superpowers' strategic objectives. The authors conclude by stressing the urgent need for effective arms control. 相似文献
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194.
毕思文 《地质灾害与环境保护》2003,14(3):82-86
数字工程是信息化、数字化的虚拟工程。笔者从数字工程提出的背景和研究意义入手,构建了数字工程基础理论框架。首先介绍了数字工程的研究方法,内容包括研究思路、基本概念、研究对象、数字工程的特征、研究任务和数字工程方法论等。然后,阐述数字工程基础理论,内容有:数字工程的连续动态系统和离散动态系统,数字工程的随机性、自组织、简单巨系统和数字工程的复杂巨系统。 相似文献
195.
数字城市若干理论问题探讨 总被引:25,自引:3,他引:22
该文从城市与区域信息化,数字城市工程建设的角度,结合数字城市工程实践,综合城市建设领域,3S领域,测绘科学领域,计算机科学领域专家学者对数字城市的研究成果,对数字城市的基本概念,数字城市的理论框架,数字城市的工程框架等理论问题,进行了初步的研究,提出了数字城市的基本理论框架。 相似文献
196.
大型油田GIS软件工程项目的组织与管理 总被引:1,自引:0,他引:1
本文以“大庆油田地面建设信息系统”为例 ,阐述开发一个成功的 GIS软件工程需要确立的主导原则(即领导重视、用户配合、双方参与、资质审查 )。在项目管理的组织上 ,需要甲方成立行政领导小组、技术管理小组和项目开发小组 3个具体的组织来保证项目的顺利实施 ;同时在项目的实施过程中 ,应采用共建共管、集中实施的机制。 相似文献
197.
福建省地震重点视防御区城市防震减灾体系工程以中国地震局关于建立健全地震监测预报、震灾预防和紧急救援三大体系为主要目标 ,以国家和福建省确定的地震重点监视防御区为主要目标区 ,尤以切实加强重点监视防御内城市的防震减灾措施 ,强化城市对地震灾害的综合防御能力为主要建设内容。该项目得到中国地震局、福建省委、省政府和有关地市大力支持 ,已列为福建省“十五”重点项目 ,省委、省政府为民办实事重点项目 相似文献
198.
Limitations associated with deterministic methods to quantify demands and develop rational acceptance criteria have led to the emergence of probabilistic procedures in performance‐based seismic engineering. The Pacific Earthquake Engineering Research performance‐based methodology is one such approach. In this paper, the impact of certain modelling decisions made at different stages of the evaluation process on the performance assessment of a typical multi‐bent viaduct is examined. Modelling, in the context of this paper, covers hazard modelling, structural modelling and loss modelling. The specific application considered in this study is a section of an existing viaduct in California: the I‐880 interstate highway. Several simulation models of the viaduct are developed, a series of nonlinear time‐history analyses are carried out to predict demands, measures of damage are evaluated and the probability of closure of the viaduct is estimated using the specified hazard for the site. It is concluded that the methodology offers several advantages over existing deterministic performance‐based procedures. Results of the investigation indicate that the assessment methodology is particularly sensitive to the reliability of decisions made by bridge inspectors following a seismic event, and to the dispersion in the demand estimation, which in turn is influenced by several factors including soil–structure interaction effects and ground motion scaling procedures. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
199.
Approximate incremental dynamic analysis using the modal pushover analysis procedure 总被引:2,自引:0,他引:2
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. 相似文献
200.