Provable security has been widely used for analyzing the security of cryptosystems. Its main idea is to reduce the security to some well-defined computational assumption. The reduction process is called the security p...Provable security has been widely used for analyzing the security of cryptosystems. Its main idea is to reduce the security to some well-defined computational assumption. The reduction process is called the security proof. In this paper, we find a flaw in the security proof of BDOP-PEKS and PEKS-STAT, present a new conclusion for the security of BDOP-PEKS, and give a security proof. The flaw in the security proof of PEKS-STAT can be fixed in the same way. Finally we conclude some steps of security proof, and emphasize that the probability is as important as the construction.展开更多
The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took pl...The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took place to form fine epoxy-rich globules dispersing in the PEK-C matrix, in which the epoxy-rich phase had the absolutely higher volume fraction. The phase structure and the interfacial properties were also studied by means of FTIR, DSC, and DMTA as well. An accompanying mechanical determination revealed that an improved toughness was achieved both in the blend casts and in the carbon fiber composites. A composite structural model was hence suggested.展开更多
基金Supported by the National Natural Science Foundation of China (60473021)
文摘Provable security has been widely used for analyzing the security of cryptosystems. Its main idea is to reduce the security to some well-defined computational assumption. The reduction process is called the security proof. In this paper, we find a flaw in the security proof of BDOP-PEKS and PEKS-STAT, present a new conclusion for the security of BDOP-PEKS, and give a security proof. The flaw in the security proof of PEKS-STAT can be fixed in the same way. Finally we conclude some steps of security proof, and emphasize that the probability is as important as the construction.
文摘为了研究PEK-C膜热解交联过程的反应机理,通过制备PEK-C膜进行热解交联实验来确定该过程的分子结构变化,并以此为基础构建模型并对PEK-C热解交联过程进行分子模拟,通过拟合实验与分子模拟结果来探究反应截断半径、反应温度与交联度间的变化规律.结果表明:交联温度介于643~748 K之间且交联度随温度的升高而增加;截断半径为0.3~0.6 nm且交联度随截断半径的增加而增加;交联反应截断半径随反应温度的增加而增加且二者呈线性关系,热解交联过程最适反应温度为658~743 K.
文摘The morphological structure of various epoxies toughened with a special amorphous thermoplastic PEK-C and their carbon fiber composites were studied by using SEM. For both cases, phase separation and inversion took place to form fine epoxy-rich globules dispersing in the PEK-C matrix, in which the epoxy-rich phase had the absolutely higher volume fraction. The phase structure and the interfacial properties were also studied by means of FTIR, DSC, and DMTA as well. An accompanying mechanical determination revealed that an improved toughness was achieved both in the blend casts and in the carbon fiber composites. A composite structural model was hence suggested.
