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。     

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。     

发挥多媒体技术的优势,营造轻松的学习氛围

小学语文教学应用于多媒体技术,实现二者的整合,营造了宽松的学习环境,突出了学生的主体地位,激发了学生的创新意识。多媒体技术的应用为小学语文教学改革带来了机遇与挑战,为学生提供了全面的感性材料,活跃了教学气氛,激发了学习欲望。多媒体技术与小学语文教学有机结合,形成了一种全新的学习方式。本文试就发挥多媒体技术的优势,营造轻松的学习氛围进行了阐述。     

降落伞投放实验仿真系统的研究与实现

该文介绍了某型降落伞投放实验仿真系统的组成、功能、设计思想和实现的方法。首先讨论了仿真系统的建模，提出了系统的功能并给出了整个系统的数据流图。接着介绍了伞系统的建模方法，重点讨论了主伞衣的模型和降落过程的实现。然后介绍了投放环境的仿真方法，讨论了天空、地形以及飞机的建模方法。最后给出了一个利用Open GL实现该系统的方法，并显示了系统的运行情况。该系统能真实反映降落伞的整个投放过程。     

一种新的表格框架生成算法及其实现

本文首先分析了现有的两大类表格框架生成算法，指出了它们存在的缺点。然后提出了一种新的表格框架生成算法，这种新算法既吸取了现有表格框架生成算法的优点，又克服了其缺点。同时，对表格进行了分析和归纳，提出了五种表元。由此五种表元可以拼接成所有表格。从而提高了表格生成的效率，扩大了表格的适应能力和通用性。最后，给出了新算法实现的关键子程序。     

产品经理就是总经理

2006年,傅盛从雅虎出来,重新加入了老东家周鸿神的奇虎公司。此时的奇虎公司创立时间还不长,却已经有了一张未来的蓝图。在当时3721担任了三年产品经理的傅盛,带着三个人开始了360安全卫士的产品之路。现在,360安全卫士已经成为了家喻户晓、耳熟能详的安全软件了,而傅盛却改变了自己的人生轨迹,加盟经纬中国成为了一名投资人。     

OpenGL在航天员舱外活动仿真中的应用

简要阐述了进行航天员EVA(ExtraVehicularActivity)仿真的必要性和实现步骤。介绍了OpenGL的基本概念。在详细阐述了Kane方法、反向运动学以及反向动力学的基础上,给出了具体的实现仿真的算法。选取STS-63飞行中的航天员操纵大质量载荷为仿真对象,在做了适当简化的基础上,得到了7节段6自由度的航天员人体模型。对模型进行了求解,用OpenGL根据结果实现了EVA的动画显示。对求解结果和动画序列进行了分析,得出了结论。     

天下视频Flash 制作下载转换通

宽带流行了,播客兴起了,FLV吃香了,菜鸟也坐不住了,迅即抱回了DV,开通了播客。历经N天修炼,Flash视频终于成为菜鸟的拿手好菜之一。播客的兴起,使得Flash视频(FLV)格式大行其道。究其原因,不外乎FLV视频避免了不安装特定视频插件就     

求解约束网络图的逆向推理方法

本文研究了几何约束网络的求解问题。首先,介绍了常用的几何推理方法,指出了存在的问题。然后,提出了求解约束网络图的一种新方法——逆向推理方法,阐明了基本思想,并给出了应用实例。逆向推理方法继承了几何推理方法的优点,克服了其不足。     

数据交换研究

随着信息技术的不断发展,数据交换逐渐成为实现信息共享与高效利用的关键技术之一。归纳了数据交换技术发展过程及其主要研究方向,分析了典型的数据交换概念。通过总结数据交换领域的研究状况,归纳出了两种数据交换模式,探讨了现有的数据交换系统存在的不足之处。在分析了策略的优点后,提出了策略驱动的数据交换机制的想法。作为总结给出了数据交换领域的发展趋势。     

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。     

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.     

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 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.