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1.
空间激光通信研究现状及发展趋势   总被引:2,自引:0,他引:2  
综述了空间激光通信的技术优势,总结了国外主要空间激光通信系统运行计划和相应的参数指标,重点介绍了空间激光通信技术在美国、欧洲、日本的研究现状,给出了激光通信的关键技术。指出了未来的空间激光通信技术不仅会使通信速率越来越高,其通信模式也会从点对点单一通信模式向中继转发和构建空间激光通信网络方向发展。最后对我国空间激光通信技术的发展作了简要介绍。  相似文献
2.
高能X射线工业CT数据传输系统的设计   总被引:2,自引:1,他引:1       下载免费PDF全文
 针对高能X射线工业CT的特点,开发了基于USB2.0的数据传输系统。该传输系统主要包括USB2.0接口部分和传输控制部分。USB2.0接口部分使用Cypress公司的EZ-USB FX2系列CY7C68013A芯片,配置为从属FIFO接口模式,通过块传输方式将数据传送给上位机。传输控制部分使用Altera公司Cyclone系列EP1C6Q240C8N芯片,定义缓冲区接收来自探测部分的数据,产生逻辑控制信号和时序信号,发送数据到USB的端点缓冲区。测试表明该传输系统易于扩展,占用系统资源少,传输速率高,满足高能X射线工业CT数据传输的要求。  相似文献
3.
新一代高密度数字多用光盘(HD-DVD)研究进展   总被引:1,自引:0,他引:1  
刘波  阮昊  干福熹 《物理》2002,31(12):784-788
文章综述了新一代高密度数字多用光盘的研究进展,介绍了多种新型蓝绿光高密度可录和可擦重写光盘存储材料,讨论了高密度数字多用光盘所面临的问题以及其解决方法,最后提出了中国超高密度光盘存储技术发展的研究思路。  相似文献
4.
We propose and experimentally demonstrate a 2 x 2 imaging multiple-input-multiple-output (MIMO) Ny quist single carrier visible light communication (VLC) system based on spectral efficient 64/32-ary quadrature amplitude modulation, as well as pre- and post-equalizations. Two commercially available red-green- blue light-emitting diodes (LEDs) with 3 dB bandwidth of I0 MHz and two avalanche photodiodes with 3 dB bandwidth of i00 MHz are employed. Due to the limited experiment condition, three different colors/ wavelengths are transmitted separately. The achieved data rates of red, green, and blue LED chips are 1.5 , 1.25, and 1.25 Gb/s, respectively. The resulting bit error ratios are below the 7% pre-forward error correction limit of 3.8 × 10-3 after 75 cm indoor transmission. To the best of our knowledge, this is the first experimental investigation of imaging MIMO system, and it is the highest data rate ever achieved in MIMO VLC system.  相似文献
5.
模式的概念一般有4个基本要素:模式名称(PattemName)、问题(Problem)、解决方案(Solution)、效果(Consequences)。EJB设计模式强调的是怎样用EJB来完成任务,讨论特定于EJB的问题和特定于EJB的复杂实现问题。层间数据传输模式回答了客户端怎样从服务器获得数据并返回的问题。EJB系统中客户层需要一种方法来向服务器来回传输大量数据,数据传输对象模式,它是层间数据传输模式中的一种,它讨论为什么、怎么样和什么时候整理跨越网络的叫做数据传输对象(DTOs)的大量数据。  相似文献
6.
Large distributed systems such as Computational/Data Grids require large amounts of data to be co-located with the computing facilities for processing.From our work develogpin a scalable distributed network cache.we have gained experience with techniques necessary to achieve high data throughput over high bandwidth Wide Area Networks(WAN).In this paper,we discuss several hardware and software dsign techniques,and then describe their application to an implementation of an enhanced FTP protocol called GridFTP,We describe results from the Supercomputing 2000 conference.  相似文献
7.
The necessity to distribute the data over the wide area network( WAN) to the physicists‘home institutes will increase,and the effective utilization of the network becomes crucial,However,networks in the future WAN will typically have a large bandwidth at an order of gigabit per second,with a latency of several hundreds seconds so that the large bandwidth-delay prodeuct extends to tens of megabytes and numerous problems are encountered.such networks are called“long fat networks(LFNs)“ In order to study the data transfer operating on a long fat network,we have built the PC clusters connected with the router which can simulate bandwidth limitations.delays,packet losses,and multipath effects.this router is running on FreeBSD with DUMMYNET kernel option.On these machines we have measured the performance of the bulk data transfter with numerous conditions and studied the effecient transfter methods.  相似文献
8.
The ALICE detector at LHC( CERN),will record raw data at a rate of 1.2 Gigabytes per second.Trying to analyse all this data at CRN will not be feasible.As originally proposed by the MONARC project,dta collected at CERN will be transferred to remote centres to use their computing infrastructure,The remote centres will reconstruct and analyse the events.and make available the results.Therefore high-rate data transfer between computing centres(Tiers)will become of paramount importance.This paper will present several tests that have been made between CERN and remote centres in Padova(Italy),Torino(Italy),Catania(Italy),Lyon(France),Ohio(United States),Warsaw(Poland)and Calcutta( India),These tests consisted,in a first stage,of sending raw data from CERN to the remote centres and back,using a ftp method that allows connections of several streams at the same time.Thanks to these multiple streams,it is possilble to increase the rate at which the data is transferred.While several “multiple stream ftp solutions“ already exist,our method is based on a parallel socket implementation which allows,besides files,also objects(or any large message)to be send in parallel.A prototype will be presented able to manage different transfers.This is the first step of a system to be implemented that will be able to take care of the connections with the remote centres to exchange data and monitor the status of the transfer.  相似文献
9.
The BaBar data acquisition system(DAQ)transports data from the detector front end eletronics to short term disk storage.A monitoring application(VMON)has been developed to monitor the one hundred and ninety computers in the dataflow system.Performance information for each CPU is collected and multicast across the existing data transport network.The packets are currently collected by a single UNIX workstation and archived.A ROOT based GUI provides control and displays the DAQ performance in real time.The same GUI is reused to recover archived VMON data,VMON has been deployed and constantly monitors the BaBar dataflow system.It has been used for diagnostics and provides input to models projecting future performance.The application has no measurable impact on data taking ,responds instantaneously on the human timescale to requests for information display,and uses only 3% of a 300MHz Sun Ultra5 CPU.  相似文献
10.
In the all-optical switches using Mach-Zelmder interferometer side-coupled with a ring resonator, the switching power is quadratically reversely proportional to the resonator finesse in the high-finesse case. In order to enhance the resonator finesse, the loss rate a and the coupler reflectivity r should approach 1, Therefore, we propose a new configuration by inserting an amplifier into the ring to compensate for the losses in the ring and using a pumped nonlinear coupler instead of the ordinary coupler. The resonator finesse can be enhanced dramatically and the minimum switching power can be obtained.  相似文献
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