IPSEC、NAT及其和平共处的一点思考

本文根据RFC1826，1827，2402，2406，2409，2663，2709，2993，3022等，首先分别介绍了IPSEC和NAT的基本原理和工作方式。然后。作者试图说明两者同时使用会出现的矛盾，并根据RFC3102—3105提出关于两者和平共处的一点思考和初步方案。     

SARS相关冠状病毒与其他已知冠状病毒的膜蛋白的多序列联配

1　Introduction　SARSisthefirstnewlyidentifiedseriousinfectiousdiseasethathumanbeingisfacingatthebeginningofthe 2 1stcentury .Ithasbeen primarilyrecognizedthatavariantofvirusfromthecoronavirusfamilymightbethecandidatepathogenofSARS ,asreportedbyWHO (WorldHealthOrganization)onApril 2 9,2 0 0 3(http ://www .who .int/csr/sarscountry/en) .　Coronaviruseswerefirstisolatedfromchickensin1937.Therearenowapproximately 15speciesinthisfamily.Coronavirusparticlesareirregularlyshaped ,roundabout 6 0 …     

1995年与2000年小学专任教师学历比较

专任教师学历合格教师比例其中大专及以上学历比例2 0 0 0年 (人 ) 比 1995年增减 (% ) 2 0 0 0年 (% ) 比 1995年增减(百分点 ) 2 0 0 0年 (% ) 比 1995年增减(百分点 )合计 5 860 316　　　 3.4 6　　 96 86　　 8 0 1　　 2 0 0 4　　 14 4 2北京 5 80 0 2 - 4.8898 193 30 37 182 7 2 8天津 4 6697 - 9.15 98.4 63.5 5 2 9.17 17 68河北 32 95 2 5 2 1.9899 5 93 94 2 2 2 2 16 2 6山西 180 362 4 .95 98 895 4 319 4 2 13 33内蒙古 12 92 4 2 - 15 .7895 92 13 2 7 2 1 2 615 0 9辽宁 185 884 - 6.5 98 112 97 2 6 84 18 80吉林…     

互联网IPv6过渡问题描述草案

2007年7月底,国际互联网标准化组织IETF在美国阿灵顿召开会议,宣布了中国的第四个IETF标准——RFC4925,这是由清华大学牵头的中国大陆第一个非中文相关的国际标准。CERNET2在"互联网IPv6过渡问题"中,提出的4over6的机制,得到了国际公认。2005年起,CERNET专家就出任IETF有关IPv4到IPv6过渡技术工作组Softwires的技术顾问,直接参与互联网标准的起草和制定工作。RFC4925的主要作者为CERNET专家委员会委员、清华大学李星教授。     

IVI在CNGI-CERNET2上的部署

拥有足够地址空间的IPv6协议作为下一代互联网协议,早在1998年就有了相应的RFC（RFC 2460）,却没有在十多年的发展中得到大规模的应用。目前作为解决IPv4协议地址空间不足的惟一的替代协议,人们越来越认识到必须向IPv6过渡,IPv6网络的大规模部署势在必行。     

2003年中考数学模拟试题

一、选择题 (将下列各题中惟一正确的答案的序号填入题后括号内 ,每小题 3分 ,共 3 6分 )1. 16的平方根是 (　　 ) .A .± 4　　B .± 2　　C .4　　D .22 .长江三峡工程电站的总装机容量是 182 0 0 0 0 0千瓦 ,如果用科学记数法表示应记作 (　　 ) .A .0 182× 10 8千瓦　　　B .18 2× 10 6千瓦C .1 82× 10 6千瓦　　D .1 82× 10 7千瓦3 .下列计算中正确的是 (　　 ) .A .(3xy) 3 =9x3 y3 　　B .2a2 ·(-3a3 ) =-6a6C .(-2 ) -2 =14 D .(-a3 ) 2 ÷ (-a2 ) 3 =14 .下列方程中 ,有正实数根的是 (　　 ) .A .3x + 1=0　　　　　B …     

1995年与2000年小学规模比较

招生数在校生数学龄儿童入学率2 0 0 0年(人 )比 1995年增减 (% ) 2 0 0 0年 (人 ) 比 1995年增减 (% ) 2 0 0 0年 (% ) 比 1995年增减(百分点 )合计 194 6465 3　 - 2 3 12 130 132 5 48　　 - 1 38　 99 11　 0 96北京 92 0 0 2 - 45 5 374 310 9- 2 6 2 399 95 0 0 2天津 10 0 4 5 3- 32 5 5 71714 6- 18 92 99 990 33河北 10 70 5 13- 34 1681372 68- 4 4 2 99 87 0 77山西 63194 2 - 1 70 34 360 4 45 0 699 74 0 4 3内蒙古 32 70 2 1- 2 7 682 0 15 0 76- 14 0 0 99 4 7 0 68辽宁 5 0 890 7 - 2 7 6634 4 4 172 - 8 2 0 99…     

竞赛中的三角形更开放

在数学竞赛中 ,常出现一些开放性的问题 ,这些问题涉及知识面广、思想内涵丰富、解题方法灵活、趣味性强 ,充分展现了数学世界的壮丽空间 .本文以竞赛中的三角形为例 ,向你透视这一壮丽空间 .例 1　 (第 16届江苏省初中数学竞赛试题 C)已知三角形每条边长的数值都是 2 0 0 1的质因数 ,那么这样的不同的三角形共有 (　　 )( A) 6个 .　 ( B) 7个 .　 ( C) 8个 .　 ( D) 9个 .解 :2 0 0 1=3× 2 3× 2 9.( 1)当三角形为等边三角形时 ,有 3个 ;( 2 )当三角形为等腰三角形时 ,有 ( 3,2 3,2 3)、( 3,2 9 ,2 9)、( 2 3,2 9,2 9)、( 2 9,2 3,2 3)…     

普通高等学校五年之间招生增长最快的20个专业

序　号专　业　名　称 1999年招生 1995年招生增加数 %0 1计算机科学与技术 110 334 4 6667 63667 136 4 30 2英语 690 684 0 197 2 887171 820 3汉语言文学 72 2 514 3734 2 8517 65 2 10 4法学 4 2 982 1874 62 4 2 3612 9 2 90 5电子科学与技术 34 758110 52 2 370 62 14 50 6工商管理 57134 3354 7 2 3587 70 310 7机械设计制造及其自动化 714 53 4 7953 2 350 0 4 9 0 10 8电子信息工程 3782 0 17772 2 0 0 4 8112 810 9临床医学 584 60 3932 4 191364 8 6610数学与应用数学 4 7834 2 9757 180 77 60 7511建筑学 2 72 3192 4 91798…     

错在哪里？

河北省石家庄市 2 0 0 3年高考模拟试题中有这样一道密码题 :现代社会对破译密码的难度要求越来越高 ,有一种密码把英文的明文 (真实文 )按两个字母一组分组 ,如果最后剩一个字母 ,则任意加一个字母拼成一组 ,例如 :Wish you success分组为 :Wi sh yo usuc ce ss,得到 :2 39,1 98,2 51 5,2 11 9,2 13,35,1 91 9,其中英文的 a,b,c,… ,z的2 6个字母 (不论大小写 )依次对应 1 ,2 ,3,… ,2 6这 2 6个自然数 ,见表 1 .表 1a b c d e f g h i j k l m12 345 6 78910 1112 13n o p q r s t u v w x y z14 15 16 1718192 0 2 12 2 2 32 4 2 5 2 6…     

动态配置OSPF物理接口的支撑算法

根据RFC1583建立物理接口的方法，深入研究OSPF协议的运行状况，在TMS体系结构模型的基础上，提出了一种动态配置OSPF物理接口的支撑算法，算法较为详细地列出了动态处理OSPF的相关事件，并分析了算法的实现效率．     

网页文件上传方法分析与研究

在基于浏览器／服务器的应用环境中，在浏览器中上传各种类型的文件一直是困扰用户的难题之一。在HTTP中上传文件有三种机制：RFC1867，PUT和WebDAV，常采用在RFC1867中引入的一个新类型：File以及ADO Stream对象。文章对上述上传方法及实现原理作一论述，并给出了具体解决实例。     

Effects of memory load on word recognition: Are there dual-routers in Norway?

The release-from-competition (RFC) effect, inwhich a difficult concurrent memory task speedspronunciation of low-frequency irregular wordsbut slows pronunciation of other word types,has been interpreted as strong support for thedual-route approach to word recognition. However, attempts to replicate this effect havenot produced consistent results. Besides,attempts at replication have mostly beenlimited to skilled readers of English. Thepresent research attempted to replicate the RFCeffect with mature normal readers of Norwegianand thus tested the generalizability ofdual-route models to a considerably moreshallow orthography than English. There was noevidence that the RFC effect reliably occurredamong Norwegian readers in this study, not evenamong certain selected readers who were seen ascandidates for possessing a dual-routearchitecture and suffering within thatarchitecture the kind of competition in naminglow-frequency irregular words that RFC issupposed to eliminate. Thus, it was notpossible to extend the applicability of adual-route approach to word recognition to therelatively shallow Norwegian orthography, andthe question of the architectural organizationof Norwegian readers was essentially leftunanswered by our data.     

Readiness of teachers for change in schools

Theorizing on the role of teacher attitudes in change effectiveness, this study examined the predictive value of context (trust), process (social interaction, participative management and knowledge sharing) and outcome (job satisfaction and workload perception) variables for cognitive, emotional and intentional readiness of teachers for change. The study was designed as predictive correlational study. Data were collected from 1649 elementary teachers. Hierarchical linear regression analysis results indicated that background and context variables are weak predictors of readiness for change (RFC), while job outcome and process variables emerged as stronger predictors of RFC. The central role of job satisfaction and trust in predicting RFC suggests that readiness cannot be limited to times of change; rather, it is closely related to total experiences of teachers on their job. As a result, for a more effective management of teachers’ attitudes towards change leadership needs to hold a broader temporal and contextual understanding rather than demonstrating limited interventions during times of change.     

用JAVA语言实现FTP客户端

介绍了实现FTP协议客户端的可扩展算法,用JAVA语言实现FTP服务端及由RFC定义的标准协议。     

Caregivers' readiness for change: predictive validity in a child welfare sample

OBJECTIVE: To assess the predictive validity of continuous measures of problem recognition (PR), intentions to change (ITC), and overall readiness for change (RFC) among primary caregivers who received in-home services following substantiated reports of child abuse or neglect. METHOD: A modified version of the University of Rhode Island Change Assessment scale was included in interviews with a sample of 353 primary caregivers at 4 weeks, 16 weeks, and 1 year after referral for in-home services. Additional data were obtained from administrative records and caseworker surveys. Hierarchical linear and nonlinear models were used to assess relationships between PR, ITC, RFC and changes over time in measures of individual and family functioning (e.g., parenting behaviors, children's behaviors, housing and economic problems, social support, and life events). Bivariate probit regression analysis was used to examine relationships between PR, ITC, RFC and the likelihood of subsequent reports of child maltreatment and out-of-home placements within 1 year after referral. RESULTS: Initial problem recognition and intentions to change predict a few improvements in individual and family functioning, along with significant reductions in the likelihood of additional reports of child maltreatment within 1 year. Initial intentions to change also predict reductions in the substantiation of subsequent reports of maltreatment. An overall measure of readiness for change predicts reductions in the likelihood of out-of-home placement. CONCLUSIONS: Problem recognition and intentions to change predict somewhat different outcomes; hence, there are few advantages of a combined measure of readiness for change. Further inquiry is needed to determine whether and how these associations are mediated by intervention processes or other factors in child welfare services populations.     

EAPS技术中网络自愈时间的关键因素研究

针对以太网交换技术中常用的故障恢复技术--STP和RSTP的缺点,分析了以太网自动保护交换EAPS(Ethernet Automatic Protection Switching)这种新型交换技术在故障恢复方面的特点与优势,并给出了具体实现的实例和实际测试数据.     

移动自组网AODV多路径路由研究

AODV协议是唯一通过IETF批准成为RFC文档的移动自组网按需控制路由协议．分析AODV路由协议工作过程及优缺点，并介绍了几种典型的基于AODV的多路径路由改进协议，最后对这些多路径协议进行优缺点分析及性能比较。     

基于熵理论的真实IPv6地址随机测度分析

IPv6通过EUI-64实现无状态地址自配置的同时也带来用户隐私问题。为此,IETF又引入RFC3041标准以产生有特定时效的无状态随机IPv6地址,提高用户的安全性,但这种无状态随机自配置地址也给IPV6包分类及网络扫描等算法的优化设计带来新的困扰。文章通过熵理论对真实IPv6地址进行随机性分析,并通过逾10万样本数据的随机测度计算后发现:RFC3041产生的IPv6地址具有固定比特恒为0的随机特性。     

IPTV测试仪媒体流传送指标（MDI）监测子系统的FPGA实现

媒体流传送指标（MDI）反映了IP承载网络的传输损伤对IPTV媒体质量的影响．通过研究RFC4445所述的MDI指标测试方法,创新性的提出了在MDI／DF测试中采用微分法即将测试间隔细分为若干微间隔的方法,并在实现的角度对原算法加以改进．在此基础上给出了基于FPGA的MDI指标测试实现方案及仿真结果．该方法不仅减少了计算因子,而且降低了硬件实现复杂度．该方案已应用于lPTV测试仪中,实际测试效果良好．