As one of the basic inventory cost models, the （Q, τ）inventory cost model of dual suppliers with random procurement lead time is mostly formulated by using the concepts of ＂effective lead time＂ and ＂lead time de...As one of the basic inventory cost models, the （Q, τ）inventory cost model of dual suppliers with random procurement lead time is mostly formulated by using the concepts of ＂effective lead time＂ and ＂lead time demand＂, which may lead to an imprecise inventory cost. Through the real-time statistic of the inventory quantities, this paper considers the precise （Q, τ） inventory cost model of dual supplier procurement by using an infinitesimal dividing method. The traditional modeling method of the inventory cost for dual supplier procurement includes complex procedures. To reduce the complexity effectively, the presented method investigates the statistics properties in real-time of the inventory quantities with the application of the infinitesimal dividing method. It is proved that the optimal holding and shortage costs of dual supplier procurement are less than those of single supplier procurement respectively. With the assumption that both suppliers have the same distribution of lead times, the convexity of the cost function per unit time is proved. So the optimal solution can be easily obtained by applying the classical convex optimization methods. The numerical examples are given to verify the main conclusions.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
基金supported by the National High Technology Research and Development Program of China(863 Program)(2007AA04Z102)the National Natural Science Foundation of China(6087407160574077).
文摘As one of the basic inventory cost models, the （Q, τ）inventory cost model of dual suppliers with random procurement lead time is mostly formulated by using the concepts of ＂effective lead time＂ and ＂lead time demand＂, which may lead to an imprecise inventory cost. Through the real-time statistic of the inventory quantities, this paper considers the precise （Q, τ） inventory cost model of dual supplier procurement by using an infinitesimal dividing method. The traditional modeling method of the inventory cost for dual supplier procurement includes complex procedures. To reduce the complexity effectively, the presented method investigates the statistics properties in real-time of the inventory quantities with the application of the infinitesimal dividing method. It is proved that the optimal holding and shortage costs of dual supplier procurement are less than those of single supplier procurement respectively. With the assumption that both suppliers have the same distribution of lead times, the convexity of the cost function per unit time is proved. So the optimal solution can be easily obtained by applying the classical convex optimization methods. The numerical examples are given to verify the main conclusions.
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。
