作为一种特殊土,盐渍土有着独特的工程性质并由此引发了盐胀、溶陷等工程问题,其发生及发展均与土体含水量密切相关,不同含水量条件下土中的吸力也对土体工程性质有着较大影响。本文选取甘肃酒泉地区的盐渍土,室内利用Ku-pF非饱和导水...作为一种特殊土,盐渍土有着独特的工程性质并由此引发了盐胀、溶陷等工程问题,其发生及发展均与土体含水量密切相关,不同含水量条件下土中的吸力也对土体工程性质有着较大影响。本文选取甘肃酒泉地区的盐渍土,室内利用Ku-pF非饱和导水率仪测试了不同干密度状态下盐渍土试样的土水特征曲线,发现渗透吸力的存在使得盐渍土试样的土水特征曲线转化阶段较一般土平缓,同一含水量条件下土中的吸力较一般土大,土体持水能力有所增强。不同干密度试样土水特征曲线的测试结果表明,干密度增大后土中大孔隙减少,中、小孔隙增多,孔隙连通性变差,导致土样饱和含水量降低,进气值增大,失水速率减慢,土体持水能力有一定增强。对比国内外广泛使用的模型对实测盐渍土土水特征曲线进行拟合,发现Fredlund and Xing模型能较好地反映盐渍土土中吸力与含水量的关系。最后,基于盐渍土的颗粒累积分布曲线及其基本物理指标,依据Fredlund物理-经验预测模型的理论和方法,预测了不同干密度盐渍土的完整土水特征曲线,以期为盐渍土地区土体工程性质的研究和预测提供理论支持和有益参考。展开更多
针对复杂装备故障预测问题,本文提出一种基于故障模式,影响及危害性分析(failure mode,effects and criticality analysis,FMECA)知识的故障预测贝叶斯网络模型(failure prediction BayesiannetWork,FPBN)建模方法.首先,在分析现有FMEC...针对复杂装备故障预测问题,本文提出一种基于故障模式,影响及危害性分析(failure mode,effects and criticality analysis,FMECA)知识的故障预测贝叶斯网络模型(failure prediction BayesiannetWork,FPBN)建模方法.首先,在分析现有FMECA知识所包含故障信息的基础上,提出了基于FMECA单元的FPBN网络结构转化方法和FPBN概率参数计算方法,建立起对应的FPBN单元模型.然后,对复杂装备各组成部分对应的FPBN单元模型进行连接,构建整体系统的FPBN集成模型.最后,根据某机载平视显示器(head up display,HUD)FMECA知识,建立了HUD电子组件的FPBN模型实例.实例分析结果表明,基于FMECA知识建立的FPBN模型具有不确定性表达和定量分析方法的优势,能够准确、有效地进行复杂装备故障预测.展开更多
The Fourth Assessment Report (AR4) of the Intergovernmental Panel of Climate Change (IPCC) concluded that the climate projection using climate models that took account of both human and natural factors provided credib...The Fourth Assessment Report (AR4) of the Intergovernmental Panel of Climate Change (IPCC) concluded that the climate projection using climate models that took account of both human and natural factors provided credible quantitative estimates of future climate change; however, the mismatches between the IPCC AR4 model ensembles and the observations, especially the multi-decadal variability (MDV), have cast shadows on the confidence of the model-based decadal projections of future cli mate. This paper reports an evaluation of many individual runs of AR4 models in the simulation of past global mean tempera ture. We find that most of the individual model runs fail to reproduce the MDV of past climate, which may have led to the overestimation of the projection of global warming for the next 40 years or so. Based on such an evaluation, we propose an al ternative approach, in which the MDV signal is taken into account, to project the global mean temperature for the next 40 years and obtain that the global warming during 2011–2050 could be much smaller than the AR4 projection.展开更多
文摘作为一种特殊土,盐渍土有着独特的工程性质并由此引发了盐胀、溶陷等工程问题,其发生及发展均与土体含水量密切相关,不同含水量条件下土中的吸力也对土体工程性质有着较大影响。本文选取甘肃酒泉地区的盐渍土,室内利用Ku-pF非饱和导水率仪测试了不同干密度状态下盐渍土试样的土水特征曲线,发现渗透吸力的存在使得盐渍土试样的土水特征曲线转化阶段较一般土平缓,同一含水量条件下土中的吸力较一般土大,土体持水能力有所增强。不同干密度试样土水特征曲线的测试结果表明,干密度增大后土中大孔隙减少,中、小孔隙增多,孔隙连通性变差,导致土样饱和含水量降低,进气值增大,失水速率减慢,土体持水能力有一定增强。对比国内外广泛使用的模型对实测盐渍土土水特征曲线进行拟合,发现Fredlund and Xing模型能较好地反映盐渍土土中吸力与含水量的关系。最后,基于盐渍土的颗粒累积分布曲线及其基本物理指标,依据Fredlund物理-经验预测模型的理论和方法,预测了不同干密度盐渍土的完整土水特征曲线,以期为盐渍土地区土体工程性质的研究和预测提供理论支持和有益参考。
文摘针对复杂装备故障预测问题,本文提出一种基于故障模式,影响及危害性分析(failure mode,effects and criticality analysis,FMECA)知识的故障预测贝叶斯网络模型(failure prediction BayesiannetWork,FPBN)建模方法.首先,在分析现有FMECA知识所包含故障信息的基础上,提出了基于FMECA单元的FPBN网络结构转化方法和FPBN概率参数计算方法,建立起对应的FPBN单元模型.然后,对复杂装备各组成部分对应的FPBN单元模型进行连接,构建整体系统的FPBN集成模型.最后,根据某机载平视显示器(head up display,HUD)FMECA知识,建立了HUD电子组件的FPBN模型实例.实例分析结果表明,基于FMECA知识建立的FPBN模型具有不确定性表达和定量分析方法的优势,能够准确、有效地进行复杂装备故障预测.
基金supported by the National Basic Research Program of Chi-na (Grant No. 2011CB952000)the National Natural Science Founda-tion of China (Grant No. 40810059003)+1 种基金Qian Cheng was partly supported by the "Strategic Priority Research Program" of the Chinese Academy of Sciences (Grant No. XDA05090103)Wu Zhaohua was supported by the Natural Science Foundation of USA (Grant No. ATM-0917743)
文摘The Fourth Assessment Report (AR4) of the Intergovernmental Panel of Climate Change (IPCC) concluded that the climate projection using climate models that took account of both human and natural factors provided credible quantitative estimates of future climate change; however, the mismatches between the IPCC AR4 model ensembles and the observations, especially the multi-decadal variability (MDV), have cast shadows on the confidence of the model-based decadal projections of future cli mate. This paper reports an evaluation of many individual runs of AR4 models in the simulation of past global mean tempera ture. We find that most of the individual model runs fail to reproduce the MDV of past climate, which may have led to the overestimation of the projection of global warming for the next 40 years or so. Based on such an evaluation, we propose an al ternative approach, in which the MDV signal is taken into account, to project the global mean temperature for the next 40 years and obtain that the global warming during 2011–2050 could be much smaller than the AR4 projection.
