信元网络交换机简介

信元网络交换机简介●付杰伟王宏图１正则信元交换信元网是通过高速信元交换机将高速数据链路互连而构成的网络互连环境，数据链路仅仅传递信元，这些信元通常捆绑为ＳＯＮＥＴ帧格式，交换机的工作是为信元在各链路之间选择路由。信元交换机有许多设计和制造方法，每种方...     

一种新的高性能ATM共享存储交换单元

ATM交换单元中．可选用三种基本排队策略一输入捧队、输出捧队和共享存贮捧队。根据平均信元时延、吞吐量和信元丢失概率性能．最佳的排队策略是共享存储捧队。由于传统的共享存储交换单元必须缓冲经过交换单元的所有信元，因此交换单元的吞吐量和信元丢失概率性能仍不理想，特别是对于大规模交换单元情况更是如此。本文提出了一种新的高性能共享存储交换单元，称为阻塞信元共享存储（BCSM)交换单元。顾名思义，BCSM仅仅缓冲交换单元输入端口的阻塞信元，而不必缓冲经过交换单元的所有信元。均匀业务下的分析结果证明，BCSM交换单元比一般共享存贮交换单元具有更好的性能。     

高速路由器的公平排队仿真模型的研究与实现

在当今高速路由器／交换机中，为提高传输效率．通常采用基于固定长度信元的定长交换技术。本文主要对基于固定长度的信元排队的WFQ(Weighted Fair Queueing)进行了建模和仿真研究，详细分析了模型的各个组成部分。利用信元定长的特点，使用了固定时间驱动的方式实现了该模型。最后比较了的FIFO(First In First Out)和WFQ的公平性。仿真结果表明，基于信元排队的WFQ适用于高速路由器／交换机中。     

两级Hash算法在网络处理器上实现多连接包分类

随着网络技术的高速增长,包分类技术的关键性日益凸显.由于网络处理器具有灵活编程和高速处理的能力,已成为当今网络中数据处理的有效解决方案.该研究用微码实现了二次Hash算法,解决了IXP2400网络处理器数据包信息存储空间有限和访问及时性相互制约的问题,在Intel的仿真环境Workbench下验证完成多个连接的ATM信元的同时分类重组实验,为高速数据流的线速处理提供了借鉴.     

一种利用ABR业务支持多媒体传输的机制

ＡＴＭ是一种基于信元交换，宫接的高速技术，其特点就是能够传送任何业务，不管这些业务有什么样的特征、。多媒体是使用ＡＴＭ提供的高速宽带业务的重要应用，利用可用比特率业务传输多媒体通讯 ，可以在保证较高的服务质量同时还能获得较高的网络带宽的利用率。     

在B—ISDN网中重发方式的选择

本文着重研究在ＩＳＤＮ网中用重发恢复丢失信元的方案。当检测到一帧内有信元丢失时，可以采用信元重发方式或帧重发方式。在信元丢失率较低时，帧重发带宽利率较高，当信元丢失率较高时，马尔可夫模型表明信元丢失集中在少数帧内，因此，选用帧发是合理的。     

高速ATM中CRC算法与信元定界的FPGA实现

在通信领域循环冗余码CRC得到了广泛的应用。为解决高速ATM中信头误码差错控制和信元定界问题,通过对循环冗余校验原理的分析,采用递推的方法得出了一种高效的CRC算法。该算法能检测到多个bit错误,并能纠正单bit的错误。相对于一般的按位串行计算或者查表并行计算的方法,这种算法运算速度快且不需要额外的空间存储余数表,提高了高速链路上数据吞吐率。数据之间逻辑关系简单,十分便于采用FPGA实现。     

B—ISDN网的重发方式选择

着重研究在Ｂ－ＩＳＤＮ ＡＴＭ网中用重发丢失信元的方案。当检测到有丢失信元时，可以采用信元重发或帧重发方式，在信元丢失率低时，帧重发带宽利用率较高；当信元丢失度较高时，马尔可夫链模型表明信元丢失集中在当烽帧内。因此，选用帧重发是合理的。     

B—ISDN网的重发方式选择

着重研究在Ｂ—ＩＳＤＮＡＴＭ网中用重发恢复丢失信元的方案。当检测到有丢失信元时，可以采用信元重发或帧重发方式。在信元丢失率低时，帧重发带宽利用率较高；当信元丢失率较高时，马尔可夫链模型表明信元丢失集中在少数帧内。因此，选用帧重发是合理的。     

以太网流量的自相似性

以太网ＬＡＮ流量在统计上是自相似的，通常使用的流量模型都不能俘获这一分形（ｆｒａｃｔａｌ）特性，这类特性对于基于信元的高速网络的设计、控制和分析都具有重要的意义。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.