全文索引技术(full-text index technique)作为提高全文检索时空效率的有效方式之一,近年来得到了广泛而深入的研究.根据全文索引实现技术的不同,将其分为三大类:索引技术、压缩与索引混合技术以及自索引技术(self-index technique).从...全文索引技术(full-text index technique)作为提高全文检索时空效率的有效方式之一,近年来得到了广泛而深入的研究.根据全文索引实现技术的不同,将其分为三大类:索引技术、压缩与索引混合技术以及自索引技术(self-index technique).从上述分类角度综述了全文索引时空效率方法中具有代表性的一些方法和技术:倒排文件、签名文件、后缀树与后缀数组、基于这3种索引的压缩技术、基于倒排文件的自索引与基于后缀数组的自索引的基本原理、所面临的问题及进展,并对这些技术的时空性能进行了详细的分析和比较,分析了各种技术的适应环境及优劣.最后总结了上述技术的特点,指出了存在的问题以及未来的研究方向.展开更多
There are three major research hotspots in efficient visualization techniques of high resolution remotely sensed data in network environment: the data organiza-tion and access in disk storage,the image data stitching ...There are three major research hotspots in efficient visualization techniques of high resolution remotely sensed data in network environment: the data organiza-tion and access in disk storage,the image data stitching and fitting methods,and the network transfers and access. In this paper a new method of "Big File" organi-zation for improving the storage access efficiency of high resolution remote data is presented; a "virtual data source" concept is introduced to solve the stitching problem of remotely sensed data from different sources with different resolutions; a remotely sensed data access engine design based on ATL technique is discussed to process the network transfers and access of remotely sensed data. All these techniques have been adopted in a prototype of digital China named "ChinaStar".展开更多
Protecting the security of sensitive information has become a matter of great concern to everyone. Data hiding technique solves the problem to some extent, but still, some shortcomings remain for researching. To impro...Protecting the security of sensitive information has become a matter of great concern to everyone. Data hiding technique solves the problem to some extent, but still, some shortcomings remain for researching. To improve the capability of hiding huge data file in disk with high efficiency. In this paper, we propose a novel approach called CryptFS, which is achieved by utilizing the file access mechanism and modifying the cluster chain structure to hide data. CryptFS can quickly hide data file with G bytes size in less than 0.1s. The time used for hiding and recovering data is irrelevant to the size of data file, and the reliability of the hidden file is high, which will not be overlaid by new created file and disk defragment.展开更多
在航天器上采用FLASH设备作为存储介质,需要采用文件系统来管理存储设备.在航天嵌入式系统中,数据存储的规模越来越大,进行采集任务产生的数据量将达到TB级别.出于安全性的考虑,航天器嵌入式系统内存容量受限,并且实时性要求极高.普通...在航天器上采用FLASH设备作为存储介质,需要采用文件系统来管理存储设备.在航天嵌入式系统中,数据存储的规模越来越大,进行采集任务产生的数据量将达到TB级别.出于安全性的考虑,航天器嵌入式系统内存容量受限,并且实时性要求极高.普通嵌入式系统在内存容量和实时性的要求同航天嵌入式系统相差较多,因此不适用于航天嵌入式系统.本文针对航天器系统资源受限的特殊需求,对嵌入式系统中常用的YAFFS2文件系统中存在的内存中文件索引结构占用空间随文件数据量线性增长的问题,提出基于二元组索引的低内存开销快速文件管理(Low Overhead and Fast File Management based on Binary group,BLOF)方法,通过基于B+树引入二元组链表结构对连续FLASH页进行统一索引,并依据索引结构设计文件读、文件写操作算法,具有文件系统内存占用小,读写文件速度快的特点.实验结果表明,BLOF相比于YAFFS2索引方法,对任意数据量的文件:1)当文件数据所在闪存页达到平均6个页以上连续时,BLOF方法内存占用低于YAFFS2方法,最高节省55.55%;2)在文件规模大于512KB时,BLOF方法的文件读写时间始终小于YAFFS2的文件读写时间,并且YAFFS2文件写时间和BLOF写时间之差随文件大小呈线性增长趋势.BLOF方法更适合于文件数据量大且存储在大量连续页的情境下.展开更多
文摘全文索引技术(full-text index technique)作为提高全文检索时空效率的有效方式之一,近年来得到了广泛而深入的研究.根据全文索引实现技术的不同,将其分为三大类:索引技术、压缩与索引混合技术以及自索引技术(self-index technique).从上述分类角度综述了全文索引时空效率方法中具有代表性的一些方法和技术:倒排文件、签名文件、后缀树与后缀数组、基于这3种索引的压缩技术、基于倒排文件的自索引与基于后缀数组的自索引的基本原理、所面临的问题及进展,并对这些技术的时空性能进行了详细的分析和比较,分析了各种技术的适应环境及优劣.最后总结了上述技术的特点,指出了存在的问题以及未来的研究方向.
基金the National Basic Research Program of China ("973") (Grant No. 2005CB321900)the National Natural Science Foundation of China (Grant No. 40701134)
文摘There are three major research hotspots in efficient visualization techniques of high resolution remotely sensed data in network environment: the data organiza-tion and access in disk storage,the image data stitching and fitting methods,and the network transfers and access. In this paper a new method of "Big File" organi-zation for improving the storage access efficiency of high resolution remote data is presented; a "virtual data source" concept is introduced to solve the stitching problem of remotely sensed data from different sources with different resolutions; a remotely sensed data access engine design based on ATL technique is discussed to process the network transfers and access of remotely sensed data. All these techniques have been adopted in a prototype of digital China named "ChinaStar".
基金Supported by the National High Technology Research and Development Program of China (863 Program) (2009AA01Z434)the "Core Electronic Devices, High_End General Chip, and Fundamental Software" Major Project (2013JH00103)
文摘Protecting the security of sensitive information has become a matter of great concern to everyone. Data hiding technique solves the problem to some extent, but still, some shortcomings remain for researching. To improve the capability of hiding huge data file in disk with high efficiency. In this paper, we propose a novel approach called CryptFS, which is achieved by utilizing the file access mechanism and modifying the cluster chain structure to hide data. CryptFS can quickly hide data file with G bytes size in less than 0.1s. The time used for hiding and recovering data is irrelevant to the size of data file, and the reliability of the hidden file is high, which will not be overlaid by new created file and disk defragment.
文摘在航天器上采用FLASH设备作为存储介质,需要采用文件系统来管理存储设备.在航天嵌入式系统中,数据存储的规模越来越大,进行采集任务产生的数据量将达到TB级别.出于安全性的考虑,航天器嵌入式系统内存容量受限,并且实时性要求极高.普通嵌入式系统在内存容量和实时性的要求同航天嵌入式系统相差较多,因此不适用于航天嵌入式系统.本文针对航天器系统资源受限的特殊需求,对嵌入式系统中常用的YAFFS2文件系统中存在的内存中文件索引结构占用空间随文件数据量线性增长的问题,提出基于二元组索引的低内存开销快速文件管理(Low Overhead and Fast File Management based on Binary group,BLOF)方法,通过基于B+树引入二元组链表结构对连续FLASH页进行统一索引,并依据索引结构设计文件读、文件写操作算法,具有文件系统内存占用小,读写文件速度快的特点.实验结果表明,BLOF相比于YAFFS2索引方法,对任意数据量的文件:1)当文件数据所在闪存页达到平均6个页以上连续时,BLOF方法内存占用低于YAFFS2方法,最高节省55.55%;2)在文件规模大于512KB时,BLOF方法的文件读写时间始终小于YAFFS2的文件读写时间,并且YAFFS2文件写时间和BLOF写时间之差随文件大小呈线性增长趋势.BLOF方法更适合于文件数据量大且存储在大量连续页的情境下.
