Reliable transmission of consultative committee for space data systems file delivery protocol in deep space communication

In consultative committee for space data systems（CCSDS） file delivery protocol（CFDP） recommendation of reliable transmission,there are no detail transmission procedure and delay calculation of prompted negative acknowledge and asynchronous negative acknowledge models.CFDP is designed to provide data and storage management,story and forward,custody transfer and reliable end-to-end delivery over deep space characterized by huge latency,intermittent link,asymmetric bandwidth and big bit error rate（BER）.Four reliable transmission models are analyzed and an expected file-delivery time is calculated with different trans-mission rates,numbers and sizes of packet data units,BERs and frequencies of external events,etc.By comparison of four CFDP models,the requirement of BER for typical missions in deep space is obtained and rules of choosing CFDP models under different uplink state informations are given,which provides references for protocol models selection,utilization and modification.

Persistent Data Layout in File Systems

Data layout in a file system is the organization of data stored in external storages. The data layout has a huge impact on performance of storage systems. We survey three main kinds of data layout in traditional file systems： in-place update file system, log-structured file system, and copy-on-write file sys- tem. Each file system has its own strengths and weaknesses under different circumstances. We also include a recent us- age of persistent layout in a file system that combines both flash memory and byte- addressable non- volatile memory. With this survey, we conclude that persistent data layout in file systems may evolve dramatically in the era of emerging non-volatile memory.

A Complexity Analysis and Entropy for Different Data Compression Algorithms on Text Files

In this paper, we analyze the complexity and entropy of different methods of data compression algorithms: LZW, Huffman, Fixed-length code (FLC), and Huffman after using Fixed-length code (HFLC). We test those algorithms on different files of different sizes and then conclude that: LZW is the best one in all compression scales that we tested especially on the large files, then Huffman, HFLC, and FLC, respectively. Data compression still is an important topic for research these days, and has many applications and uses needed. Therefore, we suggest continuing searching in this field and trying to combine two techniques in order to reach a best one, or use another source mapping (Hamming) like embedding a linear array into a Hypercube with other good techniques like Huffman and trying to reach good results.

Refreshing File Aggregate of Distributed Data Warehouse in Sets of Electric Apparatus

Integrating heterogeneous data sources is a precondition to share data for enterprises. Highly-efficient data updating can both save system expenses, and offer real-time data. It is one of the hot issues to modify data rapidly in the pre-processing area of the data warehouse. An extract transform loading design is proposed based on a new data algorithm called Diff-Match,which is developed by utilizing mode matching and data-filtering technology. It can accelerate data renewal, filter the heterogeneous data, and seek out different sets of data. Its efficiency has been proved by its successful application in an enterprise of electric apparatus groups.

基于ArcGIS Engine的数据文件到Shapefile转换方法及其实现

地理数据的多源性导致存储格式的多样性,使其难以在同一GIS平台下实现互操作与空间分析,这有碍于信息的共享。为此,以ArcGIS为基础平台,采用ArcGIS Engine组件进行集成二次开发,通过对数据文件进行访问和空间参考的定义、空间与属性信息的转换来实现Excel型数据文件至Shapefile型矢量文件的转换,以初步实现地理信息间的共享与操作,进而给出了直观的、可视化的数据管理与表达。用此方法实现了山西省宁武县煤炭资源的采矿权文件之转换,即Access→Excel→Shapefile文件。结果表明,其不仅体现出了针对初始文件的降维性、无损性以及可视性的转换表达,还可将记录信息重组(分解)为空间信息与属性信息,对于前者,矿权图层可与遥感影像叠合成图;后者(矿种、开采方式等)可与前者实现无缝链接,并可据以获取相应的开发利用现状信息,以便开展资源遥感监测。

基于ECharts Library和File API的本地数据绘图技术

为解决web绘图每次更改图形绘制均需修改代码,且反复修改易造成代码编写错误的弊端,提出一种针对本地TXT文件,利用ECharts Library和File API简化数据处理程序的绘图技术。该绘图技术可以直接对TXT文件进行修改,简单方便,易于操作。

多普勒雷达DATA文件安全模型的设计

从计算机DATA文件安全的内涵出发,针对目前DATA文件面临的安全威胁,分析了影响DATA文件的安全因素,提出了DATA文件安全体系层次结构。重点论述DATA文件层次的安全控制所采取的技术手段和应急措施,在此基础上设计了一种新型DATA文件安全防护模型,使之能够控制DATA文件多层安全,保证DATA文件的安全运行。

基于JavaScript File API的本地数据读取、处理机制改进

随着Web本地数据的日益增多和B/S模式下客户端数据处理的频繁增加,JavaScript的本地数据处理功能也得到拓展和发展。JavaScript File API虽然实现本地数据的可视化,却不能用于实际的计算。因为result数组只是将本地文本数据以单字节的形式保存,在实际过程中result数组并没有实际用途;利用一系列循环迭代算法,在File API基础上进行改进,最终可以实现对本地数据的提取以及预处理,可供以后的实际计算。

对ArcView shapefile dBASE中空间属性数据的双向查询

当先进的空间技术使对空间数据的存储和管理成为可能时,对空间数据的存取、访问和查询已是在所难免的趋势。展示了一个在WindowsCE4.0上开发的应用,它可以对ArcViewshapefile的dBASE文件中空间数据和属性数据进行双向查询。

Building Hot Snapshot Copy Based on Windows File System

This paper describes a method for building hot snapshot copy based on windows-file system （HSCF）. The architecture and running mechanism of HSCF are discussed after giving a comparison with other on-line backup tecbnology. HSCF, based on a file system filter driver, protects computer data and ensures their integrity and consistency with following three steps： access to open files, synchronization and copy on-write. Its strategies for improving system performance are analyzed including priority setting, incremental snapshot and load balance. HSCF is a new kind of snapshot technology to solve the data integrity and consistency problem in online backup, which is different from other storage-level snapshot and Open File Solution.

XIDM: A Common Data Model Based on XML

Integration between file systems and multidatabase systems is a necessary approach to support data sharing from distributed and heterogeneous data sources. We first analyses problems about data integration between file systems and multidatabase systems. Then, A common data model named XIDM(XML\|based Integrating Dada Model), which is XML oriented, is presented. XIDM bases on a series of XML standards, especially XML Schema, and can well describe semistructured data. So XIDM is powerfully practicable and multipurpose.

An Information Hiding Algorithm Based on Bitmap Resource of Portable Executable File

An information hiding algorithm is proposed, which hides information by embedding secret data into the palette of bitmap resources of portable executable （PE） files. This algorithm has higher security than some traditional ones because of integrating secret data and bitmap resources together. Through analyzing the principle of bitmap resources parsing in an operating system and the layer of resource data in PE files, a safe and useful solution is presented to solve two problems that bitmap resources are incorrectly analyzed and other resources data are confused in the process of data embedding. The feasibility and effectiveness of the proposed algorithm are confirmed through computer experiments.

Repeated sending file delivery protocol in satellite networking communication

Satellite networking communications in navigation satellite system and spacebased deep space exploration have the features of a long delay and high bit error rate （BER）. Through analyzing the advantages and disadvantages of the Consulta tive Committee for the Space Data System （CCSDS） file delivery protocol （CFDP）, a new improved repeated sending file delivery protocol （RSFDP） based on the adaptive repeated sending is put forward to build an efficient and reliable file transmission. According to the estimation of the BER of the transmission link, RSFDP repeatedly sends the lost protocol data units （PDUs） at the stage of the retransmission to improve the success rate and reduce time of the retransmission. Theoretical analyses and results of the Opnet simulation indicate that the performance of RSFDP has significant improvement gains over CFDP in the link with a long delay and high BER. The realizing results based on the space borne filed programmable gate array （FPGA） platform show the applicability of the proposed algorithm.

Scalable Distributed File Sharing System: A Robust Strategy for a Reliable Networked Environment in Tertiary Institutions

The bane of achieving a scalable distributed file sharing system is the centralized data system and single server oriented file [sharing] system. In this paper, the solution to the problems in a distributed environment is presented. Thus, inability to upload sizeable files, slow transportation of files, weak security and lack of fault tolerance are the major problems in the existing system. Hence, the utmost need is to build a client-server network that runs on two or more server systems in order to implement scalability, such that when one server is down, the other(s) would still hold up the activities within the network. And to achieve this reliable network environment, LINUX network operating system is recommended among others as a preferred platform for the synchronization of the server systems, such that every user activity like sending of internal memos/mails, publication of academic articles, is replicated;thereby, achieving the proposed result. Hence, Scalable Distributed File Sharing System provides the robustness required to having a reliable intranet.

Migration to Intermediate XML for Electronic Data (MIXED)

MIXED is a digital preservation project. It uses a strategy of converting data to intermediate XML. In this paper we position this strategy with respect to the well-known emulation and migration strategies. Then we detail the MIXED strategy and explain why it is an optimized, economical way of migration. Finally, we describe how DANS is implementing a software tool that can perform the migrations needed for this strategy.

SEQUENTIAL RETRIEVAL OF B-TREES AND A FILE STRUCTURE WITH A DENSE B-TREE INDEX

A simple fast method is given for sequentially retrieving all the records in a B tree. A file structure for database is proposed. The records in its primary data file are sorted according to the key order. A B tree is used as its dense index. It is easy to insert, delete or search a record, and it is also convenient to retrieve records in the sequential order of the keys. The merits and efficiencies of these methods or structures are discussed in detail.

基于文件结构的改进In-Place File Carving方法

针对现有文件雕复方法存在的文件恢复误报率较高的问题,提出基于文件结构的现场文件雕复方法。该方法在传统现场雕复方法的基础上,结合各类型文件的物理结构信息,利用通用框架对文件类型进行识别,并基于文件结构对所得文件进行筛选和恢复。实验结果表明,与现有雕复工具相比,该方法能够有效减少误报率,提升文件恢复效果。

A novel clustering and supervising users' profiles method

To better understand different users' accessing intentions, a novel clustering and supervising method based on accessing path is presented. This method divides users' interest space to express the distribution of users' interests, and directly to instruct the constructing process of web pages indexing for advanced performance.

Reducing Computational and Communication Complexity for Dynamic Provable Data Possession

Nowadays, an increasing number of persons choose to outsource their computing demands and storage demands to the Cloud. In order to ensure the integrity of the data in the untrusted Cloud, especially the dynamic files which can be updated online, we propose an improved dynamic provable data possession model. We use some homomorphic tags to verify the integrity of the file and use some hash values generated by some secret values and tags to prevent replay attack and forgery attack. Compared with previous works, our proposal reduces the computational and communication complexity from O(logn) to O(1). We did some experiments to ensure this improvement and extended the model to file sharing situation.

Shapefile地图与S-57海图集成与显示方法研究

基于通用的GIS地图数据格式Shapefile,实现陆地图与海图的集成。通过分析对比Shapefile文件和S-57标准文件的结构,提出了二者的数据集成与显示方法,设计了它们的空间数据共享模型,结合该模型开发了能同时解译Shapefile和S-57数据并集成显示的GIS组件。研究表明:基于该组件,能实现陆地图和海图的无缝融合,可应用于水陆一体化的GIS信息管理,弥补了以往单一GIS的不足,能很好的满足现代物流信息管理的需求。