基于交换技术的局域网安全研究

交换机是局域网建设的一种常用设备，随着ASIC芯片、网络处理器和光纤的广泛应用，分布式交换技术与三层交换技术的飞速发展，局域网交换技术已成为园区网、城域网的主流技术，交换机也由网络边缘应用逐步走向网络中心应用，交换机提供了丰富的安全措施保障局域网安全，本文介绍了利用交换机实现局域网安全的几种交换机安全技术与实现方法，对于提高局域网的安全性、可靠性有很好的应用价值．     

程控交换仿真实验系统的设计

本文根据程控交换技术,设计了一个程控交换仿真系统,该仿真系统的目的是通过普通的芯片来仿真实现程控交换机的主要功能。该系统包括了硬件和软件两部分,硬件电路采用单片机为核心来构成控制系统,还包含了接口电路和交换网络等各个部分,实现了仿真程控交换机各部分功能的目的。在硬件电路的基础之上,设计了程控交换仿真系统的软件部分,实现了自动局内的呼叫处理功能。     

基于通用交换接口(CSIX)的交换机SOC设计

通用交换接口(CSIX)协议是一种适用于通用交换机设计的接口协议.提出一种可扩展的交换机系统芯片(SOC)设计方案,它是以Cross-bar无阻塞交换结构为核心,结合CSIX接口的特点来实现高速可扩展的通用数据包交换芯片设计.并对其关键部分如收发模块,它的HDL语言设计实现方案进行了重点阐述,利用FPGA设计实现整个系统模块功能,兑现一款8×8的32bits数据线接口的SOC芯片.经测试,该FPGA兑现的SOC芯片可达单片Gbps的数据交换能力.     

CENTREX的创建

Centrex是一种集中交换业务,又称虚拟交换机,是数字程控交换机所具有的一种功能,是当今电话通信中最新应用技术。Centrex意思是在用户端不装任何小交换机,而由数字程控交换机直接向这个企业提供所有电话,可做到虽无小交换机,但这个用户的所有电话都可享有小交换机的基本功能,就像象这台小交换机集中到局用交换机中来了,故称为集中小交换机业务。本文介绍了Centrex基本业务功能、Centrex的特点以及Centrex的创建？     

数字程控交换机模块间信息传输的设计与实现

在分析数字程控交换机常用信息传输方式优缺点的基础上，提出了采用分布式组网方式实现ＪＳＵ２０００－０５数字程控交换机模块间信息传输的方法．系统采用该方式后，效率提高、可靠性增强，具有硬件结构统一、软件编程简单、实用性广泛等优点。     

浅谈宽带交换机

以上海贝尔公司生产的宽带交换机为例,阐述了宽带交换机在窄带交换机上的实现,介绍了S12P3S交换原理、实际应用以及SDH功能在网络中的应用。     

基于CPLD 的时隙交换控制器EDA设计及仿真

本设计借助EDA设计软件“ispEXPERT Ver 7.0 for Lattice”，使用VHDL语言，用一片CPLD大规模集成电路芯片实现了小型程控交换机时隙交换控制电路。     

数字用户环路设备的实现

为使远距离用户可接入交换机,笔者研制了数字用户环路设备.该设备采用8086CPU作控制系统,用户电路和复用电路都采用MITEL公司生产的集成芯片,这使系统控制信号的输出与输入变得极为方便,也便于系统功能的进一步提高(如加入交换功能).该设备体积小,性能稳定,安装方便,具有实用价值.     

七号信令系统第2级功能的实现

介绍了七号信令的第２级——信令链路的功能和过程，以及基于ＤＥＳ－３数字程控交换机上配置的七号信令系统的第２级功能硬件、软件设计及实现，并在Ｈ省实现了ＤＥＳ－３数字程控交换机七号信令系统与Ｓ１２４０七号信令系统的对接。运行结果表明，第２级链路功能部分运行稳定，故障率低，错误信号单元数小于１０－６，达到了设计要求     

CIPT－2000型C5端局数字程控交换机──软件结构的设计与实现

为了适应农村通讯网发展的需要，本文开发了一种中小容量的数字程控Ｃ５局用交换机，在介绍几种交换软件结构的基础上，提出了一种以层次结构为基础的五级管理的交换软件结构。该方法可使软件运行效率较高，便于系统调试和维护。该结构已在ＣＩＰＴ－２０００程控交换机上实现。并给出了系统实现流程图。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the