自适应字典压缩算法中的误码传播分析

在分析LZ77算法编译码原理的基础上,讨论了输入误码对译码字典和解压数据的影响,研究了误码传播问题。指出这些工作为消除误码传播、保证数据完整性具有重要意义。     

基于条件独立测试的链图结构学习算法

链图是贝叶斯网络和马尔科夫网络的自然推广,具有较强的表达能力.但目前关于链图结构学习算法的研究较少.本文基于贝叶斯网络结构学习的Grow-Shrink算法思想,提出一种链图等价类结构学习算法.该算法首先利用网络中结点的局部邻域信息,学习结点的邻接结点恢复网络骨架;然后根据链图复合体有向边的特点,利用条件独立测试确定网络的复合体有向边,从而恢复链图结构.理论分析和实验结果表明了该算法的正确性和有效性.     

Modeling the Sojourn Time of Items for In-Networ Cache Based on LRU Policy

To reduce network redundancy, in- network caching is considered in many future Internet architectures, such as Information Centric Networking. In in-network caching system, the item sojourn time of LRU （Least Recently Used） replacement policy is an important issue for two reasons： firstly, LRU is one of the most common used cache policy; secondly, item sojourn time is positively correlated to the hit probability, so this metric parameter could be useful to design the caching system. However, to the best of our knowledge, the sojourn time hasn＇t been studied theoretically so far. In this paper, we first model the LRU cache policy by Markov chain. Then an approximate closed- form expression of the item expectation sojourn time is provided through the theory of stochastic service system, which is a function of the item request rates and cache size. Finally, extensive simulation results are illustrated to show that the expression is a good approximation of the item sojourn time.     

基于混合方式的贝叶斯网弧定向算法

 贝叶斯网是不确定知识表示及推理的主要方法之一,BNs结构中的因果关系在知识建模中起到十分关键的作用,因此确定BNs中弧的方向是一重要问题.目前已有的方法存在以下问题:(1)算法计算复杂性高;(2)将统计不可分的弧定向,可能与领域知识不符.本文提出一种结合条件独立测试和打分搜索的BNs弧定向方法.该方法仅执行零阶和一阶条件独立测试,执行次数为多项式级;打分搜索可分解为局部子图的搜索,提高了算法的效率.算法输出结果为最大链图,该图仅对统计可分的弧进行定向,对统计不可分的弧保留无向的特性.这种结果更准确的表现了数据中蕴含的因果关系,便于结合领域知识进行建模.     

长春和新乡雨衰时间序列的马尔科夫链模拟

基于马尔科夫理论建立的N阶马尔科夫链模型,模拟了长春和新乡地区的降雨衰减时间序列,比较了长春和新乡地区单个模拟和实测雨衰时间序列的概率分布;分别统计了长春和新乡地区50组模拟雨衰时间序列的百分概率分布,并与国际电信联盟无线电通信研究组(ITU-R)提供的卫星轨道位置为92°E、频率为12.5 GHz在线极化情况下长春和新乡雨区不同降雨衰减值下的时间百分概率进行了比较,一致性很好,从而验证了N阶马尔可夫链模型在中国部分地区的可用性。模拟结果对我国在Ku及以上频段通信卫星的抗衰落技术的发展具有重要的应用价值。     

分布式环境下基于马尔科夫链的图流三角近似计算

图三角数量的计算是计算网络聚集系数和传递性的重要步骤.大数据背景下,以采样为策略的近似计算成为图三角计算的主要方法,然而此类方法面临时空消耗和计算错误性两大难题.本文提出了一种针对图流的基于马尔科夫链的图三角近似计算算法,该算法以窗口作为图流处理单位,将马尔科夫链与采样相结合,保证降低错误率的同时实现动态适应内存空间的变化.实验显示,相较其他三角形近似计算算法,该算法在错误率上降低2~4倍,时间消耗上也有很大改进.     

Total Sensitivity Index Calculation of Tool Requirement Model via Error Propagation Equation

A new and convenient method is presented to calculate the total sensitivity indices defined by variance-based sensitivity analysis. By decomposing the output variance using error propagation equations, this method can transform the ＂double-loop＂ sampling procedure into ＂single-loop＂ one and obviously reduce the computation cost of analysis. In contrast with Sobors and Fourier amplitude sensitivity test （FAST） method, which is limited in non-correlated variables, the new approach is suitable for correlated input variables. An application in semiconductor assembling and test manufacturing （ATM） factory indicates that this approach has a good performance in additive model and simple non-additive model.     

双冗余结构路由器故障恢复模型与方案研究

为了提高路由器系统的可用性,系统地分析了双冗余结构路由器的高可用性实现方式,将其故障恢复方式分为协议扩展、状态同步和数据复制,并通过连续时间马尔可夫链(CTMC)对各种方式进行了建模和分析。在理论分析的基础上提出了一种自适应的故障恢复方案(AFM),可根据应用场景动态选择不同的保护和恢复方式,有效地提高了系统的可用性并具有较好的可扩展性,已应用于交换容量为128Gbit/s的高性能路由器系统中。     

Throughput behavior of link adaptive 802.11 DCF with MUD capable access node

Conventional IEEE 802.11 medium access control (MAC) protocol discourages simultaneous transmission to avoid collisions. With fast advances in physical layer technologies, multi-user detection (MUD) capable receivers which can detect multiple frames from different users simultaneously become available. If we are to utilize them in today's wireless LAN, however, it is not entirely clear how we should change the MAC and how much benefit is available and can be obtained by doing so. The primary objective of this paper is to investigate such questions. We approach this objective by developing a new throughput expression for 802.11 distributed coordination function (DCF). The derived expression has been verified in simulation. We show that significant throughput gain can be garnered with slight modification in 802.11 DCF.     

Fast Cross-Platform Binary Code Similarity Detection Framework Based on CFGs Taking Advantage of NLP and Inductive GNN

Cross-platform binary code similarity detection aims at detecting whether two or more pieces of bina-ry code are similar or not.Existing approaches that combine control flow graphs(CFGs)-based function representa-tion and graph convolutional network(GCN)-based similarity analysis are the best-performing ones.Due to a large amount of convolutional computation and the loss of structural information,the use of convolution networks will in-evitably bring problems such as high overhead and sometimes inaccuracy.To address these issues,we propose a fast cross-platform binary code similarity detection framework that takes advantage of natural language processing(NLP)and inductive graph neural network(GNN)for basic blocks embedding and function representation respectively by simulating extracting structural features and temporal features.GNN's node-centric and small batch is a suitable training way for large CFGs,it can greatly reduce computational overhead.Various NLP basic block embedding models and GNNs are evaluated.Experimental results show that the scheme with long short term memory(LSTM)for basic blocks embedding and inductive learning-based GraphSAGE(GAE)for function representation outperforms the state-of-the-art works.In our framework,we can take only 45％overhead.Improve efficiency significantly with a small performance trade-off.     

波动率服从马尔可夫链的期权定价

对服从马尔可夫链的波动率进行分析，通过二叉树方法计算美式期权的价值，避免复杂的随机波动率模型，改进了常数波动率的结果，获得与真实结果比较接近的数值解。     

一种关于PHP源代码安全漏洞的静态检测方法

PHP脚本语言是一种当前比较流行的服务端脚本语言,多用来开发Web应用程序。文中介绍了一种针对PHP的静态缺陷分析方法,能有效检测出PHP中常见安全缺陷,如SQL注入、XSS等,文中给出了对当前比较流行的几个开源PHP工程的检测结果,其中大部分缺陷是可以远程利用的。     

基于IEEE802.15.4协议的延时线问题探讨

IEEE802.15.4协议引入了延时线的概念,给协议带来了一定的影响.通过探讨工作在饱和状态、星形拓扑、信标使能的传感器网络下带时隙的马尔可夫链模型,推导出了该状态下的延时计算公式.仿真表明,延时线对延时的影响可以忽略,主要起节能作用.针对延时线的引入导致接入概率降低的问题,提出了让接入时隙的分布和节点数据长度相关的解决方案.     

Packet prioritization for H.264/AVC video with cyclic intra-refresh line

Insertion of a cyclic intra-refresh line is a lightweight way of mitigating spatio-temporal error propagation in a video stream transmitted over a mobile network. This paper presents low-complexity yet effective prioritization based on slice position within a video frame relative to the cyclic refresh line. Two prioritization schemes are compared. The first is a region-based method, while the second, which is packet-based, improves packet classification. Experimental results indicate that, the packet-based scheme can achieve video quality gains of up to 4 dB, compared to when the scheme is not used. The proposed schemes require no decoder modifications and do not introduce an increase in bitrate or in computational complexity.     

Failure propagation in GMPLS optical rings: CTMC model and performance analysis

Network reliability and resilience has become a key design parameter for network operators and Internet service providers. These often seek ways to have their networks fully operational for at least 99.999% of the time, regardless of the number and type of failures that may occur in their networks.This article presents a continuous-time Markov chain model to characterise the propagation of failures in optical GMPLS rings. Two types of failures are considered depending on whether they affect only the control plane, or both the control and data planes of the node. Additionally, it is assumed that control failures propagate along the ring infecting neighbouring nodes, as stated by the Susceptible-Infected-Disabled (SID) propagation model taken from epidemic-based propagation models. A few numerical examples are performed to demonstrate that the CTMC model provides a set of guidelines for selecting the appropriate repair rates in order to attain specific availability requirements, both in the control plane and the data plane.