一种基于rsync的改进文件同步算法

rsync算法是一种快速有效的文件同步算法,ARsync(AdvancedRemote sync)算法是对rsync的改进,在文件的同步过程中采用对同步过程分步并行化,并在计算步骤中采用流水线方法,充分利用现代计算机的多核处理机架构.在同步校验码计算方面,ARsync针对文件类型和文件结构特点,使用多粒度文件分块的方法,减小校验码总大小.ARsync将整个文件夹作为同步工作单元,采取打包压缩校验码信息的方式,使用一次完整连接来完成对整个文件夹的同步.     

基于Rsync算法的预测性改进

rsync算法在远程文件同步中扮演着一个非常重要的角色,它以开源、差异传输、网络负载低等特性被应用在众多领域。文章首先介绍了rsync算法原理,然后分析了rsync算法中的弱滚动校验,创新性地提出了一种预测性算法来改进效率,最后列举了rsync算法的实际应用领域。     

rsync——远程文件同步备份

在维护文件服务和数据服务的过程中，经常需要在各服务期间同步文件，我们发现了一个非常好用的工具，那就是rsync。     

文件同步系统的研究和实现

当前文件同步技术主要基于文件内容切分和滑动块切分。为进一步提升文件同步过程中的网络带宽利用率,文中提出了一种新的文件同步方法。该方法有效结合rsync算法查找粒度精细和基于文件内容切分方法的额外开销较小的特点,并借鉴重复数据删除技术中的文件分割点的选择策略,能够在网络数据传输量的性能上有所提升。     

基于ZigBee的无线传感器网络中时间同步的算法

在HRTS（Hierarchy Referencing Time Synchronization Protocol）算法的基础上提出了一种分层的时间同步算法。这种算法主要通过层次划分和点与点之间的时间同步来实现全网的时间同步。实验结果表明,在基于ZigBee协议的无线传感器网络中实际产生的时间同步误差可以达到10ms左右。     

基于TDMA机制的工业无线网时间同步算法的改进与实现

基于TDMA机制的MAC层接入协议在工业控制网络的实时性保证方面具有极大的优势。然而要保证该机制微秒级的时隙调度,网络中所有的节点必须保持时间同步的高精度。针对现有的一些同步算法并不能完全满足这种高精度时间同步要求的问题,在传统的时间同步算法基础上,添加时钟漂移预测与补偿机制,改进得到一种具有同步精度高、能量消耗低等优点的同步算法--ITR(Improved Wireless Sensor Networks Time Synchronization Algorithm Based On TPSN and RBS),并在RouterBOARD493G路由节点上进行实验测试。实验结果表明ITR同步算法的平均同步误差比传统同步算法降低了约52%。     

双机热备环境下数据同步的研究

针对VPN设备在双机热备环境下需要将主备机数据进行同步的实际需求,研究了rsync与inotify相结合的同步方式,以保障数据信息的同步。实际运行中当主设备发生故障时网络通信能够正常进行。     

自适应高效无线传感器网络时间同步优化算法

针对无线传感器网络全网多跳自适应时间同步效率低的问题,在接收端与接收端同步模型基础上,该文提出一种自适应高效无线传感器网络时间同步优化算法(AEO)。首先,双节点同步时,从节点接收来自参考节点的同步消息并进行确认,在同步周期结束后通过拟合估计和数据更新完成时间修正,构建交互参数同步包,并与主节点进行信息交换完成同步过程。其次,全网同步时,建立Voronoi多边形拓扑结构,认定拓扑结构中参考节点和邻域节点身份(ID),参考节点覆盖区域间通过邻域节点交换同步信息,实现自适应多区域节点联合时间同步。仿真结果表明该算法在双节点时间同步中能够保证同步误差较小,网络能耗较低;同时,Voronoi拓扑相较于其他典型拓扑,在连通效率和收敛时间方面均有所改进。     

基于TDMA的工业无线网时间同步算法改进与实现

基于TDMA机制的MAC层接入协议在工业控制网络的实时性保证方面具有极大的优势.然而要保证该机制微秒级的时隙调度,网络中所有的节点必须保持时间同步的高精度.针对现有的一些同步算法并不能完全满足这种高精度时间同步要求的问题,在传统的时间同步算法基础上,添加时钟漂移预测与补偿机制,改进得到一种具有同步精度高、能量消耗低等优点的同步算法——ITR(Improved Wireless Sensor Networks Time Synchronization Algorithm Based OnTPSN andRBS),并在RouterBOARD493G路由节点上进行实验测试.实验结果表明ITR同步算法的平均同步误差比传统同步算法降低了约52％.     

OFDM系统中的同步技术

文中在分析无线信道模型的基础上,综述了目前对无线通信中OFDM的同步技术研究方面所获得的主要成果,包括符号同步,载波同步和采样率同步的各种算法,并对这些算法进行了比较分析。这对于OFDM技术在无线信道的应用研究,具有一定的借鉴意义。     

Pushing Dependent Data in Clients–Providers–Servers Systems

In satellite and wireless networks and in advanced traffic information systems in which the up-link bandwidth is very limited, a server broadcasts data files in a round-robin manner. The data files are provided by different providers and are accessed by many clients. The providers are independent and therefore files may share information. The clients who access these files may have different patterns of access. Some clients may wish to access more than one file at a time in any order, some clients may access one file out of of several files, and some clients may wish to access a second file only after accessing another file. The goal of the server is to order the files in a way that minimizes the access time of the clients given some a-priori knowledge of their access patterns. This paper introduces a clients–providers–servers model that better represents certain environments than the traditional clients–servers model. Then, we show that a random order of the data files performs well, independent of the specific access pattern. Our main technical contribution is de-randomizing the procedure that is based on selecting a random order. The resulting algorithm is a polynomial-time deterministic algorithm that finds an order with the same performance bounds as those of the random order.     

Adaptive Data Wiping Scheme with Adjustable Parameters for Ext4 File System

Data wiping is a useful technology which can prevent possible data recovery in a file system. But the growth of the amount of data usually leads to a decline in wiping efficiency. In order to make improvement, a novel data wiping scheme for Ext4 file system DWSE is pro-posed. It includes two proposed algorithms for wiping files and free space adaptively. According to a rate of rest blocks which is specified by users, the file wiping algorithm WFile tries to clean part of a selected file for saving time. The free space wiping algorithm WFree tries to speed up the process of cleaning dirty blocks by employing a random sampling and hypothesis testing method with two adjustable rates which represent status and content of a block group. A journal cleaning algorithm CleanJ is also proposed which tries to clean old records by creating and deleting tempo-rary files for preventing data recovery from a journal file. With the help of parameters, users can wipe their data in a balanced way between security and efficiency. Several ex-periments are performed on our scheme. The experimental results show that our scheme can wipe files and free space in different security and efficiency with different parame-ters. Our scheme can achieve higher security and efficiency than other two data wiping schemes.     

应用PSpice中的vector文件实现SOC系统协同仿真

随着近年来电子学系统SOC设计的飞速发展，电子系统越来越复杂，基于系统验证的协同仿真技术也显得更为重要。一般说来要搭建系统协同仿真平台都相对费时费力，因此本文提出一个比较简单的方法，用以实现SOC协同仿真。本文提出使用电子电路仿真工具OrCAD／PSpice中的仿真数据输出文件vector，可以极其精确的对数模混合电路的仿真结果进行记录，并为其他仿真器所调用。本文详细介绍了vector文件的特性和两种生成方式，并使用具体示例阐述了如何使用他来实现系统协同仿真。     

一种新的基于不等式的碎片文件分割技术

Fragmented File carving is an important technique in Digital Forensics to recover files from their fragments in the absence of file system allocation information. In this paper, the fragmented file carving problem is formulated as a graph theoretic problem. Using this model, we describe two algorithms, “Best Path Search” and “High Fragmentation Path Search”, to perform file reconstruction and recovery. The best path search algorithm is a deterministic technique to recover the best file construction path. We show that this technique is more efficient and accurate than existing brute force techniques. In addition, a test was carried out to recover 10 files from their scattered fragments. The best path search algorithm was able to successfully recover all of them back to their original state. The high fragmentation path search technique involves a trade-off between the final score of the constructed path of the file and the file recovery time to allow a faster recovery process for highly fragmented files. Analysis shows that the accurate eliminations of paths have an accuracy of up to greater than 85%.     

An efficient and effective region-based image retrieval framework

An image retrieval framework that integrates efficient region-based representation in terms of storage and complexity and effective on-line learning capability is proposed. The framework consists of methods for region-based image representation and comparison, indexing using modified inverted files, relevance feedback, and learning region weighting. By exploiting a vector quantization method, both compact and sparse (vector) region-based image representations are achieved. Using the compact representation, an indexing scheme similar to the inverted file technology and an image similarity measure based on Earth Mover's Distance are presented. Moreover, the vector representation facilitates a weighted query point movement algorithm and the compact representation enables a classification-based algorithm for relevance feedback. Based on users' feedback information, a region weighting strategy is also introduced to optimally weight the regions and enable the system to self-improve. Experimental results on a database of 10,000 general-purposed images demonstrate the efficiency and effectiveness of the proposed framework.     

面向航空电子系统的网络文件系统设计

针对IMA的多个应用模块的文件共享问题,基于具有自主知识产权的机载多分区实时OS平台,提出了一种网络文件系统NFS的设计方案。文中采用网络文件锁,通过对文件的上锁和解锁,实现多个分区互斥访问文件;使用权限验证机制验证用户对文件的访问权限,用户通过验证后方可对文件执行相应的操作;日志文件保存整个NFS的运行情况,用于对NFS性能的分析。文中阐述了NFS客户端、服务器端的设计和网络封装格式,并给出了NFS运行的原理图。     

Using object multiplex technique in data broadcast on digital CATV channel

Data broadcast is a new kind of value-add service of DTV broadcasting and some data broadcast protocols have already been established. However, these protocols only describe the method for locating files in data streams, and a method for distribution of a large collection of files in one or more data streams is not provided. Research on this problem mainly focuses on how to decrease the wait time and some methods of allocating files on multiple streams based on access probability are proposed, but how to assign the file with a reasonable bandwidth is ignored. In this paper, we introduced an object multiplex algorithm to optimize the allocation of objects on a DTV channel. This method assigns different bandwidth statistically to a different object according to its size and access probability. In this method, both download time and wait time are considered. It adopts a modified virtual clock (VC) scheduling algorithm to multiplex files accurately and smoothly.     

Android malware detection method based on SimHash

A new similarity detection scheme based on hierarchical SimHash algorithm was proposed.The scheme extractd contents from different aspects to represent the APK file,then used the improved SimHash to respectively represent the file.The scheme analyzed the APK file by extracting the AndroidManifest.xml file in it,the sum of the Smali code from the decompilation of dex file,instructions extracted in Smali files,Java code set,and instructions extracted in Java code files.Through the study of Voted Perceptron voting algorithm,the scheme used trust weight method,by valuating a trust weight in every layer,then combined all the result with weight in every layer as a resule of scheme,the result can be more reasonable and more convincing.     

一种集群计算并行I/O中启发式文件分类分配策略研究

提出了一种新的应用于集群计算环境的文件分配算法,即启发式文件分类分配算法(Heuristic FileSorted Assignment algorithm,HFSA),它在保证系统负载基本均衡的前提下,按相似的访问服务时间对每个待分配的数据文件进行磁盘分配.具体实现时,首先对待分配文件按它们的服务时间大小进行排序,然后从集群中选择一个结点的磁盘,将有序的若干文件连续地分配到该磁盘上,直接该磁盘达到最大负载时为止.通过对新策略与已有的贪婪文件分配法进行实验比较,结果表明:在访问响应时间方面,系统轻负载时,缩短了20.2%,系统重负载时,缩短了31.6%,并且数据访问的速率越高,由启发式文件分类分配策略所改善的性能就越明显.