舰船间激光通信系统视轴捕获技术

空间激光通信逐渐成为舰船间通信新型手段,但捕跟问题是舰船间激光通信最大的难点,阐述了舰船间激光通信捕获特点,分析了舰船间激光通信捕获系统的组成、工作原理和捕获策略,并着重研究捕获概率和捕获时间的影响因素,通过理论建模分析,优化捕获系统中的参数,包括捕获概率、捕获不确定区域,以及捕获时间等.结合具体使用器件对捕获系统参数进行了设计,并通过野外舰船间试验对其进行测试,实验结果测试捕获概率优于98%,不确定区域大小为26mrad,捕获时间优于30s.     

年最大值抽样估算的暴雨频率设计值的低估问题探讨

由年最大值抽样(AMS)和年超大值抽样(AES)的基本理论及重现期(RP)的定义可知,AMS并不符合以"事件"为基础的重现期的定义.以美国西南半干旱区1 438个雨量站和太湖流域96个雨量站的降雨资料为例,通过经验频率与超过概率的比较,发现AMS估算的暴雨频率设计值偏小,尤其是对常遇频率降雨设计值的影响更加显著.美国的降雨量资料站点多、系列长,实际资料验证与理论分析一致.通过对太湖流域AMS资料的分布形态进行分析的结果表明:太湖流域的站点不多,资料长度不够,且大部分站点在雨量大值区数据稀少,使得频率直方图不连续,是造成我国太湖流域的资料验证效果不理想的可能原因.     

遮光罩对GEO对地激光通信系统可通率影响

地球同步卫星(GEO)对地激光通信系统具有通信速率高、保密性好等优势。但系统的光学天线暴露在星体外部,太阳照射对可通率影响严重。针对某GEO对地激光通信系统,不同长度遮光罩对太阳规避造成的可通率及比刚度影响的分析,证明增加遮光罩长度系统可通率提升效果明显。对现有遮光罩形式进行了分析与总结,简述工程中遮光罩长度的确定与限定条件,为优化设计GEO激光通信系统遮光罩及提高系统可通率提供技术基础。     

两状态LMS信道中LMS系统的近似中断性能研究

针对通用的两状态陆地移动卫星(LMS)信道模型中,每一状态的Loo分布包含无限范围内的积分且不存在闭合形式,导致性能估计难以实现的问题,基于两状态信道模型给出等增益合并分集LMS系统中断概率的闭式解。利用Taylor级数展开法将包络的概率密度函数(PDF)近似为Rice分布PDF的加权和,利用Beaulieu序列法推导独立信道随机变量和的累积分布函数和二阶矩,得出系统中断概率的闭式解。仿真结果表明,近似中断概率与理论值十分一致,具有精确性、灵活性、复杂度低的优点。     

Probability-based location anonymity algorithm

As one of the most effective location privacy preservation technologies, the k-anonymity model provides safeguards for location privacy of the mobile client against vulnerabilities for abuse by constructing an anonymous area of k users including the protected one. However, most existing k-anonymity models only utilize the users who are sending requests at recent time. If there are not enough requesting users, the generated anonymous area of the k-anonymity model will be larger than expected. In this paper, a Probability-based Location Anonymity (PLA) algorithm is proposed for protecting location privacy of the mobile users in a road network. The PLA model takes advantage of the historical path track of the users who are not sending the request currently, and then computes the probability into the anonymous section so that it can greatly reduce the size of the anonymous area. Experimental results show that the PLA algorithm is superior to the k-anonymity and it increases its anonymous efficiency enormously.     

Probabilistic analysis of random contact force between geomembrane and granular material

A probabilistic method based on principle of maximum entropy was employed to analyze the randomness of contact force between geomembrane and granular material. The contact force distribution is exponential according to the proposed method and the grain size is the most important factor that affects the distribution of contact force. The proposed method is then verified by a series of laboratory experiments using glass beads and cobbles as granular material and a very thin pressure, indicating that film is firstly used in these experiments which give a reliable method to measure the contact force at each contact point.     

Methodology for estimating probability of dynamical system’s failure for concrete gravity dam简

Methodology for the reliability analysis of hydraulic gravity dam is the key technology in current hydropower construction.Reliability analysis for the dynamical dam safety should be divided into two phases：failure mode identification and the calculation of the failure probability.Both of them are studied based on the mathematical statistics and structure reliability theory considering two kinds of uncertainty characters（earthquake variability and material randomness）.Firstly,failure mode identification method is established based on the dynamical limit state system and verified through example of Koyna Dam so that the statistical law of progressive failure process in dam body are revealed; Secondly,for the calculation of the failure probability,mathematical model and formula are established according to the characteristics of gravity dam,which include three levels,that is element failure,path failure and system failure.A case study is presented to show the practical application of theoretical method and results of these methods.     

无线自组织量子通信网络的Grover路由算法研究

介绍了无线量子通信网络的发展和无线量子通信网络中的路由算法.路由度量基于相邻节点间的纠缠量子对数目.结合Grover量子搜索算法,在限定跳数内搜索路由度量最大的路径作为目标解径,以避免量子信道因纠缠量子对的消耗而断开.路径搜索成功后,节点采用两端逼近的方法建立起量子信道,实现从源节点到目的节点的量子态的传递.采用Grover算法的路由搜索保证了成功率,降低了量子通信网络的网络计算量,使路由搜索快速收敛.     

门级电路可靠性评估方法比较

针对软差错影响下的电路可靠性问题,选取了TP算法、EPP方法和PTM方法 3种门级电路可靠性评估方法,分别介绍其原理,并结合实验指出了它们的功能、适用范围以及复杂度.     

可靠度理论在降雨入渗边坡工程中的应用——以元磨高速K253+(400~560)边坡为例

边坡工程是岩土领域研究的热点和难点,边坡工程的状态涉及众多参数,具有不确定性,可靠度理论能利用数学方法将边坡工程中随机不确定的参数与工程的安全性有机联系。以元磨高速公路K253+(400~560)段为例,通过Bishop法,运用极限平衡理论建立极限状态模型,进而推导极限状态方程;并利用Geo-studio对不同时段中边坡的降雨入渗情况进行分析,选取最不利状态为风险评价对象进行可靠度分析,验证JC法在边坡工程风险评价方法的可行性;同时对影响可靠度指标的变量进行敏感性分析,建议在此类地层相似的边坡加固方面,应该以主要提高土层整体的内摩擦角为主,在此基础上采取提高边坡岩土的黏聚力的治理措施更为有效。