一种跨平台即时通信系统实现方案

即时通信系统在社交软件中应用广泛,特别是在移动互联网时代,随着移动终端设备的多样化,即时通信系统在移动平台扮演着重要的角色.基于这种背景,介绍利用HTTP协议、XMPP协议和SSH、DWR、ExtJS等框架,研究包括支持Android、iOS和网页浏览器多平台的即时通信系统的实现,给出了一套跨平台即时通信系统的设计方案.最后,通过大量实验表明,利用该方案实现的系统在可靠性和性能上都比较理想.     

基于Winsock技术P2P与C／S混合模式的EIM系统的研究与实现

针对于目前市面上流行的即时通信软件不适合于企业内部即时通讯的问题,提出了基于Winsock技术P2P与C/S混合模式来实现企业的即时通信,这种通信系统既能实现企业用户间的点对点通讯,又能实现企业内部安全与监督管理.     

校园视频点播网站的设计与开发

主要讨论了采用Windows Media来实现基于校园网络的视频点播网站。首先，在分析当前常用流媒体软件的基础上，采用Windows流媒体系统包括编码平台和服务器平台来设计并实现流媒体的平台建设。随后．详细介绍在这些平台上制作和发布流程的基本流程。最后，采用基于ASP的Web数据库网站实现了对流媒体的管理。     

基于Jabber的图书馆即时通信系统设计

自"智慧图书馆"概念提出以来,越来越多的计算机新技术被应用到图书馆服务当中,其中即时通信技术作为个性化服务的手段,被许多图书馆广泛使用,取得不错效果。该文为解决读者与图书馆之间的即时通信问题,设计了一种基于Jabber的图书馆即时通信系统。该文首先概述了图书馆即时通信系统以及它的优势,继而分析了图书馆即时通信系统的功能需求,在此基础上介绍了系统的设计与实现,包括服务器端搭建与客户端搭建,最后对系统进行了测试,基本符合设计要求。     

P2P流媒体测量平台的设计与实现

P2P流媒体技术已经成为互联网中的主要应用,为了保障和优化流媒体系统的服务质量,基于LStream P2P流媒体直播系统,设计并实现了一个分布式、可扩展的P2P流媒体测量平台.采用被动测量的方法实时监控系统关键节点的性能参数信息,同时根据系统记录的节点活动信息,统计、分析用户的网络行为,使管理人员能及时对系统进行实时监...     

P2P流媒体系统多点下载技术的实现研究

P2P的多点文件下载技术已经比较成熟,但一般的P2P下载技术不适宜流媒体数据的即时播放.利用已经比较成熟的P2P多点下载技术,通过技术改进,尤其是修改其片段选择法,为流媒体系统的实现提出了基本思路,从而可以较少的代价实现流媒体应用.     

WebSocket服务器推送技术的研究

采用传统的＂请求—应答＂模式,使用户从互联网中得到有用的数据信息非常困难,如果互联网可以主动将有用的信息发送到客户端,将会跟用户带来很大的帮助。笔者提出了一种服务器推送方案,该方案使用了基于WebSocket协议的服务器推送技术,还利用了复杂事件处理技术对数据进行快速处理。这种方案可以运用到即时通信系统、股票交易系统、即时订票系统、监控系统等多种实时系统中。     

接触网应急指挥抢修系统的设计与实现

该文基于第三代通信技术(3G),设计了应用于供电段接触网抢修现场的无线应急视频指挥系统.首先对视频监控系统和铁路应急通信的发展过程、现状和系统结构等做了详细的介绍,分析了第三代通信技术三种制式和两种视频算法的优缺点,确定了本系统采用联通WCDMA和H.264标准,并按照所选技术方案对现场的无线局域网的传输性能、丢包率和延时率等进行了仿真分析.其次,根据现场实际需求,分别对监控指挥中心和现场的网络结构和设备做了详细的分析和设计,重点对流媒体服务器、存储服务器、现场3G视频服务器、管理服务器的原理和功能做了详尽的分析、设计和实现,并设计实现了系统WEB监控和手机监控的软件,包括系统数据库设计、监控软件的编写等.     

流媒体技术及其数字化应用的研究

随着计算机多媒体技术和网络技术的飞速发展及人们对信息大量需求，基于网络的分布式流媒体通信系统得到广泛应用，如远程教育、远程医疗、在线游戏等。本文对流媒体通信技术作了较为详细的介绍，包括流式传输方式、视频服务器硬件平台、流媒体传输网络协议、流媒体通信技术发展现状、流媒体在3G中的主要应用等，并针对流媒体通信目前所存在的问题对流媒体通信技术的发展方向作了一定得探讨。     

即时通信系统的安全目标

即时通信系娆(IMS,Instant Messaging System),也叫做在场与即时通信系统(presence and Instant Messaging System),它有两个基本的特征,一是用户之间可以订阅彼此的在场信息(presence information),这样当其状态发生变化(如由"在线"变为"离开")时系统会通知对方;二是用户之间可以实时地交换消息.本文分析即时通信系统在互联网中所面临的安全威胁,最后,给出即时通信系统所应该具备的安全目标.     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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.     

Jane Eyre——A Feminist In The 19th Century

In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.     

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-