In this paper, by defining new state vectors and developing new transfer matrices of various elements mov- ing in space, the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to stud...In this paper, by defining new state vectors and developing new transfer matrices of various elements mov- ing in space, the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to study the dynamics of multibody system with flexible beams moving in space. Formulations and numerical example of a rigid- flexible-body three pendulums system moving in space are given to validate the method. Using the new method to study the dynamics of multi-rigid-flexible-body system mov- ing in space, the global dynamics equations of system are not needed, the orders of involved matrices of the system are very low and the computational speed is high, irrespec- tive of the size of the system. The new method is simple, straightforward, practical, and provides a powerful tool for multi-rigid-flexible-body system dynamics.展开更多
为解决当前S盒加密算法主要是借助固定S盒进行像素扩散,且S盒的生成与明文无关,导致其安全性不佳的不足,提出一种基于线性Diophantus模型与循环移位动态S盒的图像加密算法。从Logistic映射迭代生成的混沌数组中选择两个元素,计算Diophan...为解决当前S盒加密算法主要是借助固定S盒进行像素扩散,且S盒的生成与明文无关,导致其安全性不佳的不足,提出一种基于线性Diophantus模型与循环移位动态S盒的图像加密算法。从Logistic映射迭代生成的混沌数组中选择两个元素,计算Diophantus模型的系数,获取两个解集合,定义位置排序法,形成置乱密钥;借助外部密钥,生成2DLogistic映射的初始条件,输出随机整数序列,基于等尺度变换,拓展2D Arnold映射,形成矩形变换机制,获取系数矩阵;基于有限域理论,设计循环移位动态S盒,构建像素扩散模型;利用改进的引力模型,定义密文深度增强机制,优化密文的NPCR(number of pixels change rate)与UACI(unified average changed intensity)值。实验结果表明,与基于固定S盒的加密技术相比,所提算法的安全性与加密效率更高。展开更多
增量型电场积分方程(augmented eletric field integral equation,AEFIE)是一种新的全波分析方法,主要是用来解决大型复杂电磁学问题。AEFIE采用了分离电荷和电流的思想,对电场积分方程进行改革,使其成为低频问题的一种解法,此时积分方...增量型电场积分方程(augmented eletric field integral equation,AEFIE)是一种新的全波分析方法,主要是用来解决大型复杂电磁学问题。AEFIE采用了分离电荷和电流的思想,对电场积分方程进行改革,使其成为低频问题的一种解法,此时积分方程的矢量位和标量位被分离,然后使用合适的频率归一化因子使它们趋于平衡,从而解决EFIE(electric field integral equation)方法中的低频崩溃问题。通过AEFIE方法分析电小尺寸的微带结构,为了能够有效地解决未知量过大的问题,利用远场相互作用形成的子矩阵块具有低秩特性,引入了矩阵分解与奇异值分解算法(matrix decomposition algoithm and singular value decomposition,MDA-SVD),节省了计算时间和内存需求。数值结果表明该方法的有效性和精确性。展开更多
基金supported by the Natural Science Foundation of China Government (10902051)the Natural Science Foundation of Jiangsu Province (BK2008046)the German Science Foundation
文摘In this paper, by defining new state vectors and developing new transfer matrices of various elements mov- ing in space, the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to study the dynamics of multibody system with flexible beams moving in space. Formulations and numerical example of a rigid- flexible-body three pendulums system moving in space are given to validate the method. Using the new method to study the dynamics of multi-rigid-flexible-body system mov- ing in space, the global dynamics equations of system are not needed, the orders of involved matrices of the system are very low and the computational speed is high, irrespec- tive of the size of the system. The new method is simple, straightforward, practical, and provides a powerful tool for multi-rigid-flexible-body system dynamics.
文摘为解决当前S盒加密算法主要是借助固定S盒进行像素扩散,且S盒的生成与明文无关,导致其安全性不佳的不足,提出一种基于线性Diophantus模型与循环移位动态S盒的图像加密算法。从Logistic映射迭代生成的混沌数组中选择两个元素,计算Diophantus模型的系数,获取两个解集合,定义位置排序法,形成置乱密钥;借助外部密钥,生成2DLogistic映射的初始条件,输出随机整数序列,基于等尺度变换,拓展2D Arnold映射,形成矩形变换机制,获取系数矩阵;基于有限域理论,设计循环移位动态S盒,构建像素扩散模型;利用改进的引力模型,定义密文深度增强机制,优化密文的NPCR(number of pixels change rate)与UACI(unified average changed intensity)值。实验结果表明,与基于固定S盒的加密技术相比,所提算法的安全性与加密效率更高。
文摘增量型电场积分方程(augmented eletric field integral equation,AEFIE)是一种新的全波分析方法,主要是用来解决大型复杂电磁学问题。AEFIE采用了分离电荷和电流的思想,对电场积分方程进行改革,使其成为低频问题的一种解法,此时积分方程的矢量位和标量位被分离,然后使用合适的频率归一化因子使它们趋于平衡,从而解决EFIE(electric field integral equation)方法中的低频崩溃问题。通过AEFIE方法分析电小尺寸的微带结构,为了能够有效地解决未知量过大的问题,利用远场相互作用形成的子矩阵块具有低秩特性,引入了矩阵分解与奇异值分解算法(matrix decomposition algoithm and singular value decomposition,MDA-SVD),节省了计算时间和内存需求。数值结果表明该方法的有效性和精确性。
