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核废料地下处置系统研究的国际合作项目DECOVALEX(development of coupled models and their validation against experiments) 致力于高放射性核废料地质处置系统围岩中多个物理场的耦合过程研究和工程屏障的可行性评估.中国研究小组第一次参加DECOVALEX计划.介绍了其子课题Task_D的情况和阶段性研究结果,包括2种处置方式--瑞士FEBEX和美国Yucca Mountain类型的1×104 a以上的预测模拟及其比较分析.建立一套复杂的非饱和多孔介质中热液力(THM)耦合过程的非等温流动和形变控制方程,涉及到固、液、气三相和四种组分(固体骨架,水,干空气和水蒸汽).其表现为相对独立同时又相互交叠的4类模型(1) 考虑有效应力、热膨胀应力和膨润土的水膨胀应力变形模型;(2) 考虑水与蒸汽在蒸发凝结时物质交换的流动模型;(3) 包含蒸汽/干空气相对运动的蒸汽分子扩散和对流模型;(4) 三相局部非等温过程的热交换模型.在此基础上根据Task_D的设定要求简化为较为实用的方程,并发展了相应的程序对1×106 a THM耦合行为进行了预测模拟,其结果在2005年2月Task_D讨论会和DECOVALEX工作会议与多个国家相互独立的研究结果进行对比,吻合程度很高,这给模型的建立和程序发展都带来了信心. 相似文献
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Since their introduction in 1929, polychlorinated biphenyls (PCBs) have been used in a wide range of applications, mainly in industrialized countries. Although production of PCBs was largely banned in the 1970s, they are still present in various applications as well as in the environment where they remain a potential threat to animal and human health. PCBs were applied in different building materials in Norway in the period between 1950 and 1980. This study attempts to estimate the use for various applications in buildings, and to distinguish between residential and non-residential buildings. The results are combined with a dynamic material flow analysis (MFA) to estimate past and future stocks and flows of building-related PCBs in Norway. Results indicate that PCBs in the building stock peaked around 1980, and have since decreased as PCBs have been banned and efforts made to remove the substance from existing applications. However, considerable amounts remain in the building stock and will be released in smaller amounts for many more decades. While current legislation focuses mainly on the applications with short lifetimes, the handling of building applications with long lifetimes represent the main unresolved challenges of the future. 相似文献
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Vegetation naturally cleanses the atmosphere by absorbing gases and some particulate matter through leaves. Plants have a very large surface area and their leaves function as an efficient pollutant‐trapping device. Some plants have been classified according to their degree of sensitivity and tolerance towards various air pollutants. Sensitive plant species are suggested to act as bio‐indicators. Levels of air pollution tolerance vary from species to species, depending on the capacity of plants to withstand the effect of pollutants without showing any external damage. In this study, the air pollution tolerance index (APTI) of 30 plant species has been evaluated. High values of APTI were recorded in Mangifera indica, Moringa pterydosperma, Cassia renigera and Ailanthus excelsa. The anticipated performance index (API) of 30 plant species has also been evaluated for green belt (GB) development in and around an industrial urban area in India. Using APTI and this performance rating, the most tolerant plants have been identified. 相似文献