A probabilistic framework for durability assessment of concrete structures in marine environments was proposed in terms of reliability and sensitivity analysis, which takes into account the uncertainties under the env...A probabilistic framework for durability assessment of concrete structures in marine environments was proposed in terms of reliability and sensitivity analysis, which takes into account the uncertainties under the environmental,material, structural and executional conditions. A time-dependent probabilistic model of chloride ingress was established first to consider the variations in various governing parameters, such as the chloride concentration,chloride diffusion coefficient, and age factor. Then the Nataf transformation was adopted to transform the nonnormal random variables from the original physical space into the independent standard Normal space. After that the durability limit state function and its gradient vector with respect to the original physical parameters were derived analytically, based on which the first-order reliability method was adopted to analyze the time-dependent reliability and parametric sensitivity of concrete structures in marine environments. The accuracy of the proposed method was verified by comparing with the second-order reliability method and the Monte Carlo simulation. Finally, the influences of environmental conditions, material properties, structural parameters and execution conditions on the time-dependent reliability of concrete structures in marine environments were also investigated. The proposed probabilistic framework can be implemented in the decision-making algorithm for the maintenance and repair of deteriorating concrete structures in marine environments.展开更多
针对BYOD(bring your own device)、移动云计算等兼具强安全性、高开放性需求的新型应用场景,提出了一种移动嵌入式平台敏感应用防护方案.为满足强安全性需求,方案基于ARM TrustZone硬件隔离技术构建可信执行环境,即使在整个操作系统内...针对BYOD(bring your own device)、移动云计算等兼具强安全性、高开放性需求的新型应用场景,提出了一种移动嵌入式平台敏感应用防护方案.为满足强安全性需求,方案基于ARM TrustZone硬件隔离技术构建可信执行环境,即使在整个操作系统内核被攻破的情况下仍能保证敏感应用的安全.为满足高开放性需求,方案实现了传统TrustZone安全方案不具备的两大优势.首先,将TrustZone保护域扩展至普通世界,安全世界不再实现具体的敏感应用,而只实现一个轻量级监控模块用以监控普通世界内核的行为.因此整个系统可信计算基不随敏感应用数量的增加而增大,减少了其可攻击面和潜在漏洞。其次,监控模块确保内核为这些敏感应用提供安全的系统服务,从而为满足开放性需求提供关键功能支持,例如提供标准系统调用接口、敏感应用动态部署和加载等.最后,方案提出了内核主动证明机制,要求内核主动提供关键信息协助监控模块验证其自身行为,有效提高了系统运行效率.在真实设备上实现了原型系统,实验结果证明了该方案的安全性和较为理想的运行效率.展开更多
基金financially supported by National Natural Science Foundation of China(Grant Nos.51168003,51368006 and51478125)the Major Project of Guangxi Natural Science Foundation(Grant No.2012GXNSFEA053002)+1 种基金Program for Distinguished Scholars and High-Level Innovative Research Team of Guangxi Higher Education(Grant No.GJR-2013-38)the Guangxi Science and Technology Development Program(Grant No.1377001-11)
文摘A probabilistic framework for durability assessment of concrete structures in marine environments was proposed in terms of reliability and sensitivity analysis, which takes into account the uncertainties under the environmental,material, structural and executional conditions. A time-dependent probabilistic model of chloride ingress was established first to consider the variations in various governing parameters, such as the chloride concentration,chloride diffusion coefficient, and age factor. Then the Nataf transformation was adopted to transform the nonnormal random variables from the original physical space into the independent standard Normal space. After that the durability limit state function and its gradient vector with respect to the original physical parameters were derived analytically, based on which the first-order reliability method was adopted to analyze the time-dependent reliability and parametric sensitivity of concrete structures in marine environments. The accuracy of the proposed method was verified by comparing with the second-order reliability method and the Monte Carlo simulation. Finally, the influences of environmental conditions, material properties, structural parameters and execution conditions on the time-dependent reliability of concrete structures in marine environments were also investigated. The proposed probabilistic framework can be implemented in the decision-making algorithm for the maintenance and repair of deteriorating concrete structures in marine environments.
文摘针对BYOD(bring your own device)、移动云计算等兼具强安全性、高开放性需求的新型应用场景,提出了一种移动嵌入式平台敏感应用防护方案.为满足强安全性需求,方案基于ARM TrustZone硬件隔离技术构建可信执行环境,即使在整个操作系统内核被攻破的情况下仍能保证敏感应用的安全.为满足高开放性需求,方案实现了传统TrustZone安全方案不具备的两大优势.首先,将TrustZone保护域扩展至普通世界,安全世界不再实现具体的敏感应用,而只实现一个轻量级监控模块用以监控普通世界内核的行为.因此整个系统可信计算基不随敏感应用数量的增加而增大,减少了其可攻击面和潜在漏洞。其次,监控模块确保内核为这些敏感应用提供安全的系统服务,从而为满足开放性需求提供关键功能支持,例如提供标准系统调用接口、敏感应用动态部署和加载等.最后,方案提出了内核主动证明机制,要求内核主动提供关键信息协助监控模块验证其自身行为,有效提高了系统运行效率.在真实设备上实现了原型系统,实验结果证明了该方案的安全性和较为理想的运行效率.
