面向智能电网的云计算技术研究

对面向智能电网的云计算技术进行了研究。首先,引入了云计算的基本概念,分析了它的关键特征。其次,将云计算和智能电网技术进行了融合,提出了智能云的概念。随后,深入研究了智能云的构建、资源管理和安全策略问题。最后,给出了结论和未来的研究工作。     

工作流中TBAC权限控制模型的扩展与UML描述

本文首先分析了现实工作流授权所需要满足的一些特征。并提出基于任务的访问控制模型。然后通过分析,在此模型基础上进行了扩展,引入了上下文的概念。能够有效的管理和跟踪工作流的具体任务。针对模型的每一个过程进行了详细的设计和分析,给出了具体的实施办法。并且通过UML进行了有效的描述。     

无线互联 纺织未来

因特网的发展引起了新的产业革命,变革了经济的运行模式,刺激了广大企业的创新意识,促进了教育的普及和提高,大大改变发展中国家的工业化模式,甚至会改变国家之间的力量对比。不仅如此,互联网还造就了崭新的一代群体。就像60年代电视改变了人们的娱乐方式,造就了“电视一代”;80年代电脑改变了人们的工作方式,促成了“电脑一代”一样,九十年代Internet改变了人们获取信息的方式,诞生了“网络一代”。互联网对人类社会的影响是深刻而长远的,即给人们带来挑战,更给人们带来机遇。     

专家控制系统研究进展

回顾了专家控制的起源及其作为一门学科的定位。在阐述专家控制系统基本结构的基础上,介绍了专家控制系统的工作原理。对目前专家控制研究热点进行了总结,比较了各研究方向的优劣,并分别给出了近几年来在各领域成功应用的例子。最后对各研究方向存在的关键问题及难点进行了归纳,提出了对应的研究策略,为下一步的研究指出了基本方向。     

基于μPSD3200的甲烷检测仪的研究与实现

论述了热载体催化元件检测法的原理,提出了对电桥电源和电桥输出电压同步测量的改进方案,有效地提高了测量精度。应用μPSD3200的CPLD功能,实现了软硬件结合的SPI接口方法,提高了MCU运行效率。提出了矿井“黑匣子”,给出了一种硬件控制的安全存取数据的方法,增强了仪表的抗干扰能力。     

计算机多媒体辅助教学网站的开发

该文分析了基于ASP的Web远程考试系统的发展要求。分析了Web下考试系统的基本原理,结合系统需求,给出了系统架构。对于系统的数据库设计给出了详细的表,最后对关键代码进行了分析。     

变频调速在发电厂的应用

介绍了变频调速在发电厂的应用。发电厂引进的变频调速电动机代替滑差调速的电动机后产生了巨大效益,不仅保证了电动机的安全稳定运行,而且也减轻了运行人员的劳动强度,改善了工作环境。调速系统改造完成后至今,没有一个电机被烧毁的现象发生,即延长了电机的使用寿命,保证了正常的生产。并用具体的计算数据证明了它的节能效果。同时叙述了变频器类型和容量的选择,指出了维护电动机运行应注意的几个方面。     

视觉增强环境中图像校正算法的研究

文章研究了在视觉增强环境下的校正问题。建立了在视觉增强环境中校正的模型,研究了算法并提出了解决边缘校正问题的方法。利用边缘检测的方法替代了人工干预的方法,避免了在校正过程中人的参与,减少了人为因素导致的误差,实现了自动校正(SelfCalibration)。     

基于ACIS平台的大型三维CAD系统的设计与开发

该文介绍了一个基于ACIS平台的大型三维CAD系统的设计、开发与应用。分别介绍了该系统的交互系统、造型系统和渲染系统的设计与实现。设计了一个栈式命令处理系统，便于实现异常复杂的用户交互命令。简要介绍了特征造型功能在ACIS平台上的实现。在ACIS框架上自选算法，重新设计了渲染引擎，扩展了渲染数据结构和功能，克服了ACIS提供的渲染引擎的局限性，得到了独特的渲染效果。最后介绍了本系统的应用情况。     

基于Boost电路的蓄电池容量检测装置设计

介绍了改进型的Boost电路结构,给出了能够适应多种蓄电池的通用型容量检测装置的设计方法。阐述了放电电阻的优化设计方法,给出了设计准则。解决了被放电蓄电池涵盖范围广和误接自保护的问题。实验结果验证了设计的正确性。     

具有多重签名功能的文件签名管理系统

本文介绍了一个利用公开密钥数字签名技术开发的文件签名管理系统。本系统能够对任意格式的电子文件进行不限次数的签名及其认证,在签名时还可以附上任意格式的意见文件,对于原文及意见文件可以调用原生成软件进行浏览。     

File migration and file replication: a symbiotic relationship

Much of the past research on file migration and file replication has examined these two resource management strategies in isolation or in an environment where they do not work together. We establish through simulation that these two strategies can be utilized simultaneously to potentially provide significant performance benefits over a system without file migration or replication. File replication can be viewed as a natural extension to file migration, and thus, we derive a dynamic file replication policy based on an established file migration heuristic: a file is migrated (or replicated) whenever a reduction in total mean response time of the file requests currently in the affected storage sites can be achieved. Through our performance model, we use simulation to establish the conditions under which our file migration/replication policies are beneficial in a distributed file system     

基于智能卡的一种文件加密方案

在FreeBsd系统中,有一种对文件的保护机制,称为Disk Partitions Encryption(磁盘分区加密),对所有放在被设置为加密分区上的文件,将会被自动加密,用户不会有丝毫察觉,但文件是以加密的方式保存在磁盘上的。当用户在此分区上打开文件时,如果用户的权限满足,文件自动解密后被打开,对用户来说做到完全透明。当磁盘不慎丢失或者被偷窃,此加密分区上的数据也不会泄漏。该文就阐述如何通过一个加密Agent和一个解密Agent,在基于智能卡的基础上在Windows系统上模拟一个如同FreeBsd一样的分区保护系统,用户可以把需要加密的文件拖入到设定的加密分区或者加密文件夹中,文件将被自动加密,用户也可以在此文件夹或者分区中任意打开,阅读以及修改此文件,当保存的时候文件将被自动加密。     

Analysis of Long Term File Reference Patterns for Application to File Migration Algorithms

In most large computer installations files are moved between on-line disk and mass storage (tape, integrated mass storage device) either automatically by the system and/or at the direction of the user. In this paper we present and analyze long term file reference data in order to develop a basis for the construction of algorithms for file migration. Specifically, we examine the use of the on-line user (primarily text editor) data sets at the Stanford Linear Accelerator Center (SLAC) computer installation through the analysis of 13 months of file reference data. We find that most files are used very few times. Of those that are used sufficiently frequently that their reference patterns may be examined, we find that: 1) about a third show declining rates of reference during their lifetime, 2) of the remainder, very few (about 5 percent) show correlated interreference intervals, and 3) interreference intervals (in days) appear to be more skewed than would occur with the Bernoulli process. Thus, about two-thirds of all suffi1ciently active files appear to be referenced as a renewal process with a skewed interreference distribution. A large number of other file reference statistics (file lifetimes, interference distributions, moments, means, number of uses/ file, file sizes, file rates of reference, etc.) are computed and presented. Throughout, statistical tests are described and explained. The results of our analysis of file reference patterns are applied in a companion paper to the development and comparative evaluation of file migration algorithms.     

Fine-grained management of I/O optimizations based on workload characteristics

With the advent of new computing paradigms, parallel file systems serve not only traditional scientific computing applications but also non-scientific computing applications, such as financial computing, business, and public administration. Parallel file systems provide storage services for multiple applications. As a result, various requirements need to be met. However, parallel file systems usually provide a unified storage solution, which cannot meet specific application needs. In this paper, an extended file handle scheme is proposed to deal with this problem. The original file handle is extended to record I/O optimization information, which allows file systems to specify optimizations for a file or directory based on workload characteristics. Therefore, fine-grained management of I/O optimizations can be achieved. On the basis of the extended file handle scheme, data prefetching and small file optimization mechanisms are proposed for parallel file systems. The experimental results show that the proposed approach improves the aggregate throughput of the overall system by up to 189.75%.     

基于特征标识的文件类型识别与匹配

不同类型文件的识别与匹配是计算机文件系统中一个重要问题,一般分为特征标识(魔数)和后缀名两种方式,其中后者是被广泛接受的一种方式.然而在使用过程中,经常遇见文件名被篡改或损坏、文件后缀名缺失而无法被系统自动识别的情况,此时无法正常打开、浏览或编辑文件.文件头的特征标识将文件特征信息存储于文件数据内部,不容易被修改或损坏...     

内存映射文件在提取有限元模态结果中的应用

对于有限元分析软件导出的大型结果文件,在使用常规的文件操作函数处理时,容易导致计算机速度缓慢甚至失去响应。针对这个问题,提出了一种基于内存映射文件读写数据的方法。该方法通过建立磁盘文件与进程地址的关联,直接访问磁盘文件,提取相关结果信息。当文件过大时,采用了分段映射的技术,逐段进行处理,并对两种不同的分段方式进行了比较。测试结果表明,比起传统的文件读写方法,该方法可以大大提高文件读取的速度,有效适应巨型文本文件的读取需求。     

Short communication dmert crash resistant file systems

DMERT (Duplex, Multi-Environment, Real Time) is a real-time operating system that supports reliable telecommunications applications. Although DMERT file systems are based on UNIX^TM file systems, which suffer robustness drawbacks, DMERT file systems do not suffer these drawbacks. The DMERT file manager uses synchronous writes and file system audits to manage crash resistant file systems. The performance penalty for this crash resistance is minimal. This note describes DMERT's crash resistance policy and shows how UNIX and UNIX-like file systems can be made crash resistant without sacrificing performance.     

A cached WORM file system

This paper describes a general-purpose file system that uses a write-once-read-many (WORM) optical disk accessed via a magnetic disk cache. The cache enables blocks to be modified a number of times before they are written to the WORM and increases performance. Snapshots of the file system can be made at any time without limiting the users' access to files. These snapshots reside entirely on the WORM, are accessible to the user via a second read-only file system, do not contain multiple copies of unchanged data, and can be used to rebuild the file system in the event that the disk cache is destroyed. The file system has been implemented as part of Plan 9, an experimental operating system under development at AT&T Bell Laboratories.     

A unified framework for designing high performance in-memory and hybrid memory file systems

The emerging non-volatile memory technologies provide a new choice for storing persistent data in memory. Therefore, file system structure needs re-studying and re-designing. Our goal is to design a framework that gives high-performance in-memory file accesses and allows a file whose data can be stored across memory and block device. This paper presents a novel unified framework for in-memory and hybrid memory file systems based on the concept that each file has a contiguous “File Virtual Address Space”. Within this framework, the file access for in-memory data can be efficiently handled by address translation hardware and the virtual address space of file. The file accesses for data in block devices are handled by a dedicated page fault handler for file system. A file system called Hybrid Memory File System (HMFS) is implemented based on this framework. Experimental results show that the throughput of HMFS approaches the memory bus bandwidth in best cases. Compared with in-memory file systems, HMFS reaches 5 times, 2.1 times, and 1.6 times faster than EXT4 on Ramdisk, RAMFS, and PMFS, respectively. Compared with EXT4 on SSD and EXT4 using page cache, HMFS also achieves 100 times and tens of times performance improvement, respectively.