MD5的一种新的碰撞攻击

模差分分析是结合整数模减差分和XOR差分而定义的一种新的差分,与单一的模减差分或XOR差分相比,2种差分结合能表达更多的消息,从而可以更有效地分析、破解现有的哈希函数.MD5是哈希函数的一种,对消息的差分分析是对哈希函数实施碰撞攻击的重要手段,从目前已知的基于差分技术的攻击事实看,主要采用的是6比特差分和1比特差分.提...     

Monitoring the market or the salesperson? The value of information in a multilayer supply chain

We study a supply chain in which a manufacturer relies on a salesperson to sell the products to the consumers. The sales outcome is determined by a random market condition and the salesperson's service level, both of which are privately observed by the salesperson. Apart from them, there are two types of resellers: a knowledgeable reseller observes the market condition, whereas a diligent reseller can monitor the service level. While delegating to a reseller enhances information acquisition, it may also result in double marginalization and inefficiency. We identify several operating regimes in which double marginalization can be eliminated via simple contracts and establish the benefit of monitoring the salesperson over monitoring the market. Our dominance result is not prone to our model characteristics regarding the complementarity of market condition and sales effort, the relative importance of adverse selection and moral hazard, and the contract form. We then generalize our model and re‐establish the dominance result in the presence of reseller's risk aversion or private monitoring expertise. We also quantify the performance gaps among different selling schemes under various scenarios. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

Optimization of steerable sensor network for threat detection

A Markov chain approach to detecting a threat in a given surveillance zone by a network of steerable sensors is presented. The network has a finite number of predetermined states, and transition from one state to another follows a Markov chain. Under the assumption that the threat avoids detection, two game theoretic problems for finding an optimal Markov chain (two surveillance strategies) are formulated: the first maximizes the probability of threat detection for two consecutive detection periods, whereas the second minimizes the average time of detection for the worst‐case threat's trajectory. Both problems are reduced to linear programming, and special techniques are suggested to solve them. For a dynamic environment with moving noise sources, the optimal Markov chain changes at each detection period, and the rate of convergence of the Markov chain to its stationary distribution is analyzed. Both surveillance strategies are tested in numerical experiments and compared one with another. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

基于运动相似性的监控轨迹聚合分析

对于监控轨迹序列集,提出一种使用运动特征发现其潜在语义内容的方法.在特征统计估计阶段,将轨迹曲线中的拐点特征加入到核密度估计过程中,得到准确平滑的方向多性态分布;使用隐马尔科夫模型估计轨迹子类中存在的串行或并行空间模式.最后以运动特征分布为基础,提出一种基于运动相似性的轨迹层次聚合模型.实验结果表明,该模型可以有效地分...     

系统动力学的C~4ISR系统信息优势价值链模型仿真

实现信息优势是网络中心战的核心,C4ISR系统是打赢网络中心战、夺取信息优势、决策优势和行动优势的客观基础。从C4ISR系统的工作流程出发,分析了C4ISR系统信息优势价值链,围绕战场态势感知信息优势价值链的生成过程,运用系统动力学方法建立了对抗条件下C4ISR系统信息优势价值链的SD模型,并结合作战背景对试验结果进行了仿真分析,验证了该方法研究复杂军事信息系统的可行性。     

基于Markov决策支持系统的坦克排作战效能预测

分析了Markov模型的一般预测过程,建立了一种基于Markov决策支持系统的作战效能预测分析模型,根据坦克排在担负不同作战任务时的特点,给出了坦克排作战效能预测分析的应用实例,预测分析的结果表明,该模型能够对作战态势做以正确的预测,有利于指挥员更好地进行兵力部署,发挥坦克排作战的最佳效能.     

Outbound supply chain network design with mode selection and lead time considerations

We present a large‐scale network design model for the outbound supply chain of an automotive company that considers transportation mode selection (road vs. rail) and explicitly models the relationship between lead times and the volume of flow through the nodes of the network. We formulate the problem as a nonlinear zero‐one integer program, reformulate it to obtain a linear integer model, and develop a Lagrangian heuristic for its solution that gives near‐optimal results in reasonable time. We also present scenario analyses that examine the behavior of the supply chain under different parameter settings and the performance of the solution procedures under different experimental conditions. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

A produce‐to‐stock system with advance demand information and secondary customers

We consider a manufacturer (i.e., a capacitated supplier) that produces to stock and has two classes of customers. The primary customer places orders at regular intervals of time for a random quantity, while the secondary customers request a single item at random times. At a predetermined time the manufacturer receives advance demand information regarding the order size of the primary customer. If the manufacturer is not able to fill the primary customer's demand, there is a penalty. On the other hand, serving the secondary customers results in additional profit; however, the manufacturer can refuse to serve the secondary customers in order to reserve inventory for the primary customer. We characterize the manufacturer's optimal production and stock reservation policies that maximize the manufacturer's discounted profit and the average profit per unit time. We show that these policies are threshold‐type policies, and these thresholds are monotone with respect to the primary customer's order size. Using a numerical study we provide insights into how the value of information is affected by the relative demand size of the primary and secondary customers. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

专家系统优化排列准则及时间估计模型研究

军用仿真系统中 ,专家系统作为一个决策软件包 ,满足整个软件系统运行的性能需要 ,因此研究专家系统的推理时间是必要的。专家系统的推理时间与其推理模式、知识库结构等因素有关。针对知识库结构 ,利用时间齐次马尔可夫链为专家系统知识库进行建模 ,并给出了相应的时间估计模型及其排列准则 ,从而可以研究专家系统的实时性。     

Repairable consecutive‐k‐out‐of‐n: F system with Markov dependence

In this article, a model for a repairable consecutive‐k‐out‐of‐n: F system with Markov dependence is studied. A binary vector is used to represent the system state. The failure rate of a component in the system depends on the state of the preceding component. The failure risk of a system state is then introduced. On the basis of the failure risk, a priority repair rule is adopted. Then the transition density matrix can be determined, and the analysis of the system reliability can be conducted accordingly. One example each of a linear and a circular system is then studied in detail to explain the model and methodology developed in this paper. © 2000 John Wiley & Sons, Inc. Naval Research Logistics 47: 18–39, 2000