针对目前基于LWE (Learn With Errors)构造的全同态加密方案普遍需要高斯函数抽样以及公钥尺寸过大等问题,本文采用高效的LWR (Learning With Rounding)替换传统的LWE方案,提出了多用户云环境中提供端到端数据保护的基于密钥策略–属性...针对目前基于LWE (Learn With Errors)构造的全同态加密方案普遍需要高斯函数抽样以及公钥尺寸过大等问题,本文采用高效的LWR (Learning With Rounding)替换传统的LWE方案,提出了多用户云环境中提供端到端数据保护的基于密钥策略–属性的全同态加密(LWR-ABFHE)方案。本文提出的LWR-ABFHE方案能够在对加密数据进行细粒度访问的同时执行同态计算,并且在不牺牲同态加密的计算能力情况下,达到在一组授权属性上处理单调访问结构的效果。本文在LWR假设下,证明了LWR-ABFHE方案在选择明文攻击下的安全性。展开更多
针对目前基于LWE(Learn With Errors)构造全同态加密方案普遍需要高斯函数抽样、公钥尺寸过大等问题,提出利用高效的LWR(Learning With Rounding)替换传统的LWE,构造基于LWR(Learning With Rounding)的身份基全同态加密方案,对方案的安...针对目前基于LWE(Learn With Errors)构造全同态加密方案普遍需要高斯函数抽样、公钥尺寸过大等问题,提出利用高效的LWR(Learning With Rounding)替换传统的LWE,构造基于LWR(Learning With Rounding)的身份基全同态加密方案,对方案的安全性进行严格证明。LWR问题是LWE问题的变体,消除了LWE问题利用高斯函数抽样生成噪声的过程,具有更高的计算效率以及更小公钥和密文尺寸。展开更多
在设计阶段考虑环境对疲劳的影响是第三代核电站一回路主设备设计的关键技术之一,本文介绍了ASME规范Code Case N-792对轻水堆(LWR)一级承压设备考虑环境影响疲劳时的环境影响疲劳修正系数(Fen)和应变速率ε'的计算方法。建立反应...在设计阶段考虑环境对疲劳的影响是第三代核电站一回路主设备设计的关键技术之一,本文介绍了ASME规范Code Case N-792对轻水堆(LWR)一级承压设备考虑环境影响疲劳时的环境影响疲劳修正系数(Fen)和应变速率ε'的计算方法。建立反应堆压力容器接管的轴对称模型,并根据Code Case N-792的要求对一回路主设备反应堆压力容器接管进行考虑环境影响的疲劳计算,计算时分别采用简化法和详细积分法。对不考虑环境影响的ASME第III卷的疲劳计算结果和Code Case N-792的疲劳计算结果进行对比和探讨。当考虑环境影响后,SCL1截面的疲劳寿命缩短为空气状态下的1/3,SCL2截面的疲劳寿命减少了3/5。展开更多
In this paper,we develop a stochastic LWR model based on the influences of the driver's individual property on his/her perceived density and speed deviation.The numerical results show that the driver's individ...In this paper,we develop a stochastic LWR model based on the influences of the driver's individual property on his/her perceived density and speed deviation.The numerical results show that the driver's individual property has great effects on traffic flow only when the initial density is moderate,i.e.,at this time,oscillating traffic flow will occur and the oscillating phenomena in the traffic system consisting of the conservative and aggressive drivers is more serious than that in the traffic system consisting of the conservative(aggressive) drivers.展开更多
In-Vessel Retention (IVR) is one of the existing strategies of severe accident management of LWR, which intends to stabilize and isolate corium & fission products inside the reactor pressure vessel (RPV) and prima...In-Vessel Retention (IVR) is one of the existing strategies of severe accident management of LWR, which intends to stabilize and isolate corium & fission products inside the reactor pressure vessel (RPV) and primary containment structure. Since it has become an important safety objective for nuclear reactors, it is therefore needed to model and evaluate relevant phenomena of IVR strategy in assessing safety of nuclear power reactors. One of the relevant phenomena during accident progression in the oxidic pool is non-uniform high heat generation occurring at large scale. Consequently, direct experimental studies at these scales are not possible. The role computer codes and models are therefore important in order to transpose experimental results to reactor safety applications. In this paper, the state-of-the-art ANSYS FLUENT CFD code is used to simulate Non-uniform heat generation in the lower plenum by the application of Cartridge heating under severe accident conditions to derive the basic accident scenario. However, very few studies have been performed to simulate non-uniform decay heat generation by Cartridge heaters in a pool corresponding lower plenum of power reactor. The current investigation focuses on non-uniform heating in the fluid domain by Cartridge heaters, which has been done using ANSYS FLUENT CFD code by K-epsilon model. The computed results are based on qualitative assessment in the form of temperature and velocity contour and quantitative assessment in terms of temperature and heat flux distribution to assess the impact of heating method on natural convective fluid flow and heat transfer.展开更多
文摘针对目前基于LWE (Learn With Errors)构造的全同态加密方案普遍需要高斯函数抽样以及公钥尺寸过大等问题,本文采用高效的LWR (Learning With Rounding)替换传统的LWE方案,提出了多用户云环境中提供端到端数据保护的基于密钥策略–属性的全同态加密(LWR-ABFHE)方案。本文提出的LWR-ABFHE方案能够在对加密数据进行细粒度访问的同时执行同态计算,并且在不牺牲同态加密的计算能力情况下,达到在一组授权属性上处理单调访问结构的效果。本文在LWR假设下,证明了LWR-ABFHE方案在选择明文攻击下的安全性。
文摘针对目前基于LWE(Learn With Errors)构造全同态加密方案普遍需要高斯函数抽样、公钥尺寸过大等问题,提出利用高效的LWR(Learning With Rounding)替换传统的LWE,构造基于LWR(Learning With Rounding)的身份基全同态加密方案,对方案的安全性进行严格证明。LWR问题是LWE问题的变体,消除了LWE问题利用高斯函数抽样生成噪声的过程,具有更高的计算效率以及更小公钥和密文尺寸。
文摘在设计阶段考虑环境对疲劳的影响是第三代核电站一回路主设备设计的关键技术之一,本文介绍了ASME规范Code Case N-792对轻水堆(LWR)一级承压设备考虑环境影响疲劳时的环境影响疲劳修正系数(Fen)和应变速率ε'的计算方法。建立反应堆压力容器接管的轴对称模型,并根据Code Case N-792的要求对一回路主设备反应堆压力容器接管进行考虑环境影响的疲劳计算,计算时分别采用简化法和详细积分法。对不考虑环境影响的ASME第III卷的疲劳计算结果和Code Case N-792的疲劳计算结果进行对比和探讨。当考虑环境影响后,SCL1截面的疲劳寿命缩短为空气状态下的1/3,SCL2截面的疲劳寿命减少了3/5。
基金Supported by the National Natural Science Foundation of China under Grant Nos. 70971007 and 71271016
文摘In this paper,we develop a stochastic LWR model based on the influences of the driver's individual property on his/her perceived density and speed deviation.The numerical results show that the driver's individual property has great effects on traffic flow only when the initial density is moderate,i.e.,at this time,oscillating traffic flow will occur and the oscillating phenomena in the traffic system consisting of the conservative and aggressive drivers is more serious than that in the traffic system consisting of the conservative(aggressive) drivers.
文摘In-Vessel Retention (IVR) is one of the existing strategies of severe accident management of LWR, which intends to stabilize and isolate corium & fission products inside the reactor pressure vessel (RPV) and primary containment structure. Since it has become an important safety objective for nuclear reactors, it is therefore needed to model and evaluate relevant phenomena of IVR strategy in assessing safety of nuclear power reactors. One of the relevant phenomena during accident progression in the oxidic pool is non-uniform high heat generation occurring at large scale. Consequently, direct experimental studies at these scales are not possible. The role computer codes and models are therefore important in order to transpose experimental results to reactor safety applications. In this paper, the state-of-the-art ANSYS FLUENT CFD code is used to simulate Non-uniform heat generation in the lower plenum by the application of Cartridge heating under severe accident conditions to derive the basic accident scenario. However, very few studies have been performed to simulate non-uniform decay heat generation by Cartridge heaters in a pool corresponding lower plenum of power reactor. The current investigation focuses on non-uniform heating in the fluid domain by Cartridge heaters, which has been done using ANSYS FLUENT CFD code by K-epsilon model. The computed results are based on qualitative assessment in the form of temperature and velocity contour and quantitative assessment in terms of temperature and heat flux distribution to assess the impact of heating method on natural convective fluid flow and heat transfer.
