Thermally induced mechanical and permeability changes around a nuclear waste repository—a far-field study based on equivalent properties determined by a discrete approach

A numerical investigation is conducted on the impacts of the thermal loading history on the evolution of mechanical response and permeability field of a fractured rock mass containing a hypothetical nuclear waste repository. The geological data are extracted from the site investigation results at Sellafield, England.A combined methodology of discrete and continuum approaches is presented. The results of a series of simulations based on the DFN–DEM (discrete fracture network–distinct element method) approach provide the mechanical and hydraulic properties of fractured rock masses, and their stress-dependencies. These properties are calculated on a representative scale that depends on fracture network characteristics and constitutive models of intact rock and fractures. In the present study, data indicate that the large scale domain can be divided into four regions with different property sets corresponding to the depth. The results derived by the DFN–DEM approach are then passed on to a large-scale analysis of the far-field problem for the equivalent continuum analysis.The large-scale far-field analysis is conducted using a FEM code, ROCMAS for coupled thermo-mechanical process. The results show that the thermal stresses of fractured rock masses vary significantly with mechanical properties determined at the representative scale. Vertical heaving and horizontal tensile displacement are observed above the repository. Observed stress and displacement fields also shows significant dependency on how the mechanical properties are characterized. The permeability changes induced by the thermal loading show that it generally decreases close to the repository. However, change of permeability is small, i.e., a factor of two, and thermally induced dilation of fracture was not observed. Note that the repository excavation effects were not considered in the study.The work presented in this paper is the result of efforts on a benchmark test (BMT2) within the international co-operative projects DECOVALEX III and BENCHPAR.     

A flexible content repository to enable a peer‐to‐peer‐based wiki

Wikis—being major applications of the Web 2.0—are used for a large number of purposes, such as encyclopedias, project documentation, and coordination, both in open communities and in enterprises. At the application level, users are targeted as both consumers and producers of dynamic content. Yet, this kind of peer‐to‐peer (P2P) principle is not used at the technical level being still dominated by traditional client–server architectures. What lacks is a generic platform that combines the scalability of the P2P approach with, for example, a wiki's requirements for consistent content management in a highly concurrent environment. This paper presents a flexible content repository system that is intended to close the gap by using a hybrid P2P overlay to support scalable, fault‐tolerant, consistent, and efficient data operations for the dynamic content of wikis. On the one hand, this paper introduces the generic, overall architecture of the content repository. On the other hand, it describes the major building blocks to enable P2P data management at the system's persistent storage layer, and how these may be used to implement a P2P‐based wiki application: (i) a P2P back‐end administrates a wiki's actual content resources. (ii) On top, P2P service groups act as indexing groups to implement a wiki's search index. Copyright © 2009 John Wiley & Sons, Ltd.     

Web仓储中的单视图一致性

Web仓储系统使用物化视图的方法管理和维护Web数据，它可以给用户的查询和分析带来更快的效率，特别适合联机分析处理(OLAP)和决策支持。Web环境中数据更新非常频繁，为保持系统的时新性(freshness)，需要不断刷新物化视图，在Web视图刷新的过程中，必须保持物化视图与基础数据之间的一致性(称为单视图一致性，SVC)，否则系统中的数据就会产生错误，进而影响用户的正确使用，围绕这种单视图一致性，针对Web环境的特性，给出了相关保持算法，这些算法具有良好的Web环境适应性和伸缩性。     

基于本体的物流行业知识库的研究*

构建了基于本体的物流行业信息化知识库。应用语义Web和Web服务技术研究物流知识资源,设计了物流领域本体,实现了文本摘要、规则抽取、本体整合等关键功能,解决物流系统中语义和重用问题,提高了物流企业的知识共享和协作能力。这不仅为物流行业信息化奠定了坚实基础,而且为知识库的复用创造了条件。     

国内外核废物处置库近场温度场模拟预测

核废物处置后因所含的放射性核素衰变而产生的衰变热通过传导、对流以及辐射等方式从废物体向外传递,从而引起废物罐体、缓冲材料及近场围岩温度升高,导致废物体至近场围岩之间形成温度梯度。温度梯度随着时间的延续而变化,最终会影响地下水系统和核素迁移。本文对一些国家的处置库温度预测模式进行了调研,对源项、处置库模型简化、热传递数学模型和模拟结果做了初步总结,为我国拟建处置库的温度场预测提出了建议。     

一种高效的基于刻面分类的构件检索算法研究

如何从构件库中准确快速找到需要的构件,是每个构件库系统需要解决的一个主要问题。基于树匹配的思想通过研究构件的特点,提出了基于刻面路径匹配的算法,它使用后缀字典排序来提高查询的效率,该算法可以在保持构件查询速度的前提下,有效提高构件的查全率和查准率,实验结果证明了该算法的可行性与有效性。