电子计算机英语论文
Security of Computer Network System
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计算机网络安全浅析
摘要：针对计算机网络系统存在的安全性和可靠性问题，本文从网络安全的重要性、理论基础、具备功能以及解决措施等方面提出一些见解，并且进行了详细阐述，以使广大用户在计算机网络方面增强安全防范意识。
关键词：计算机网络虚拟专用网技术加密技术防火墙
引言：随着计算机网络技术的发展，网络的安全性和可靠性已成为不同使用层次的用户共同关心的问题。人们都希望自己的网络系统能够更加可靠地运行，不受外来入侵者干扰和破坏。所以解决好网络的安全性和可靠性问题，是保证网络正常运行的前提和保障。
一、网络安全的重要性。在信息化飞速发展的今天，计算机网络得到了广泛应用，但随着网络之间的信息传输量的急剧增长，一些机构和部门在得益于网络加快业务运作的同时，其上网的数据也遭到了不同程度的攻击和破坏。攻击者可以窃听网络上的信息，窃取用户的口令、数据库的信息；还可以篡改数据库内容，伪造用户身份，否认自己的签名。更有甚者，攻击者可以删除数据库内容，摧毁网络节点，释放计算机病毒等等。这致使数据的安全性和自身的利益受到了严重的威胁。
根据美国FBI（美国联邦调查局）的调查，美国每年因为网络安全造成的经济损失超过170亿美元。75%的公司报告财政损失是由于计算机系统的安全问题造成的。超过50%的安全威胁来自内部。而仅有59%的损失可以定量估算。在中国，针对银行、证券等金融领域的计算机系统的安全问题所造成的经济损失金额已高达数亿元，针对其他行业的网络安全威胁也时有发生。
由此可见，无论是有意的攻击，还是无意的误操作，都将会给系统带来不可估量的损失。所以，计算机网络必须有足够强的安全措施。无论是在局域网还是在广域网中，网络的安全措施应是能全方位地针对各种不同的威胁和脆弱性，这样才能确保网络信息的保密性、完整性和可用性。
二、网络安全的理论基础。国际标准化组织（ISO）曾建议计算机安全的定义为：“计算机系统要保护其硬件、数据不被偶然或故意地泄露、更改和破坏。”为了帮助计算机用户区
分和解决计算机网络安全问题，美国国防部公布了“桔皮书”（orange book，正式名称为“可信计算机系统标准评估准则”），对多用户计算机系统安全级别的划分进行了规定。
桔皮书将计算机安全由低到高分为四类七级：D1、C1、C2、B1、B2、B3、A1。其中D1级是不具备最低安全限度的等级，C1和C2级是具备最低安全限度的等级，B1和B2级是具有中等安全保护能力的等级，B3和A1属于最高安全等级。
在网络的具体设计过程中，应根据网络总体规划中提出的各项技术规范、设备类型、性能要求以及经费等，综合考虑来确定一个比较合理、性能较高的网络安全级别，从而实现网络的安全性和可靠性。
三、网络安全应具备的功能。为了能更好地适应信息技术的发展，计算机网络应用系统必须具备以下功能：
（1）访问控制：通过对特定网段、服务建立的访问控制体系，将绝大多数攻击阻止在到达攻击目标之前。
（2）检查安全漏洞：通过对安全漏洞的周期检查，即使攻击可到达攻击目标，也可使绝大多数攻击无效。
（3）攻击监控：通过对特定网段、服务建立的攻击监控体系，可实时检测出绝大多数攻击，并采取响应的行动（如断开网络连接、记录攻击过程、跟踪攻击源等）。
（4）加密通讯：主动地加密通讯，可使攻击者不能了解、修改敏感信息。
（5）认证：良好的认证体系可防止攻击者假冒合法用户。
（6）备份和恢复：良好的备份和恢复机制，可在攻击造成损失时，尽快地恢复数据和系统服务。
（7）多层防御：攻击者在突破第一道防线后，延缓或阻断其到达攻击目标。
（8）设立安全监控中心：为信息系统提供安全体系管理、监控、保护及紧急情况服务。
四、网络系统安全综合解决措施。要想实现网络安全功能，应对网络系统进行全方位防范，从而制定出比较合理的网络安全体系结构。下面就网络系统的安全问题，提出一些防范措施。
物理安全可以分为两个方面：一是人为对网络的损害；二是网络对使用者的危害。最常见的是施工人员由于对地下电缆不了解，从而造成电缆的破坏，这种情况可通过立标志牌加以防范；未采用结构化布线的网络经常会出现使用者对电缆的损坏，这就需要尽量采用结构化布线来安装网络；人为或自然灾害的影响，需在规划设计时加以考虑。
访问控制安全，访问控制识别并验证用户，将用户限制在已授权的活动和资源范围之内。网络的访问控制安全可以从以下几个方面考虑。
（1）口令：网络安全系统的最外层防线就是网络用户的登录，在注册过程中，系统会检查用户的登录名和口令的合法性，只有合法的用户才可以进入系统。
（2）网络资源属主、属性和访问权限：网络资源主要包括共享文件、共享打印机、网络通信设备等网络用户都有可以使用的资源。资源属主体现了不同用户对资源的从属关系，如建立者、修改者和同组成员等。资源属性表示了资源本身的存取特性，如可被谁读、写或执行等。访问权限主要体现在用户对网络资源的可用程度上。利用指定网络资源的属主、属性和访问权限可以有效地在应用级控制网络系统的安全性。
（3）网络安全监视：网络监视通称为“网管”，它的作用主要是对整个网络的运行进行动态地监视并及时处理各种事件。通过网络监视可以简单明了地找出并解决网络上的安全问题，如定位网络故障点、捉住IP盗用者、控制网络访问范围等。
（4）审计和跟踪：网络的审计和跟踪包括对网络资源的使用、网络故障、系统记帐等方面的记录和分析。一般由两部分组成：一是记录事件，即将各类事件统统记录到文件中；二是对记录进行分析和统计，从而找出问题所在。
数据传输安全，传输安全要求保护网络上被传输的信息，以防止被动地和主动地侵犯。对数据传输安全可以采取如下措施：
（1）加密与数字签名：数字签名是数据的接收者用来证实数据的发送者确实无误的一种方法，它主要通过加密算法和证实协议而实现。
（2）防火墙：防火墙（Firewall）是Internet上广泛应用的一种安全措施，它可以设置在不同网络或网络安全域之间的一系列部件的组合。它能通过监测、限制、更改跨越防火墙的数据流，尽可能地检测网络内外信息、结构和运行状况，以此来实现网络的安全保护。
（3）User Name/Password认证：该种认证方式是最常用的一种认证方式，用于操作系统登录、telnet（远程登录）、rlogin（远程登录）等，但此种认证方式过程不加密，即password 容易被监听和解密。
（4）使用摘要算法的认证：Radius（远程拨号认证协议）、OSPF（开放路由协议）、SNMP Security Protocol等均使用共享的Security Key（密钥），加上摘要算法（MD5）进行认证，但摘要算法是一个不可逆的过程，因此，在认证过程中，由摘要信息不能计算出共享的security key，所以敏感信息不能在网络上传输。市场上主要采用的摘要算法主要有MD5和SHA-1。
（5）基于PKI的认证：使用PKI（公开密钥体系）进行认证和加密。该种方法安全程度较高，综合采用了摘要算法、不对称加密、对称加密、数字签名等技术，很好地将安全性和高效性结合起来。这种认证方法目前应用在电子邮件、应用服务器访问、客户认证、防火墙认证等领域。该种认证方法安全程度很高，但是涉及到比较繁重的证书管理任务。
（6）虚拟专用网络（VPN）技术：VPN技术主要提供在公网上的安全的双向通讯，采用透明的加密方案以保证数据的完整性和保密性。
总结：综上所述，对于计算机网络传输的安全问题，我们必须要做到以下几点。第一，应严格限制上网用户所访问的系统信息和资源，这一功能可通过在访问服务器上设置NetScreen 防火墙来实现。第二，应加强对上网用户的身份认证，使用RADIUS等专用身份验证服务器。一方面，可以实现对上网用户帐号的统一管理；另一方面，在身份验证过程中采用加密的手段，避免用户口令泄露的可能性。第三，在数据传输过程中采用加密技术，防止数据被非法窃取。一种方法是使用PGP for Business Security对数据加密。另一种方法是采用NetScreen 防火墙所提供的VPN技术。VPN在提供网间数据加密的同时，也提供了针对单机用户的加密客户端软件，即采用软件加密的技术来保证数据传输的安全性。
参考文献：
[1] 蔡皖东，计算机网络技术.西安电子科技大学出版，1988。
[2] 杜飞龙，Internet原理与应用，人民邮电出版社，1997。
[3] 胡道元，信息网络系统集成技术，清华大学出版社，1995。
[4] 杨明福，计算机网络，电子工业出版社，1998.5。
[5] 袁保宗，因特网及其应用，吉林大学出版社，2000。
[6] 隋红建等，计算机网络与通信，北京大学出版社,，1996。
[7] 周明天等，TCP/IP网络原理与应用，清华大学出版社，1993。
[8] 计算机学报，1998-2001。
[9] 网络报，1997-2001。
Security of Computer Network System
Abstract: This paper discussed the secure and dependable problem about the computer network system. On some aspects: the importance of network security, basic theory, function, and the method of solving a problem, etc. Good views for solving the problem are put forward. It strengthens people’s consciousness on network security.
Key words: Computer network Virtual private network Encryption techniques Firewall Introduction:Along with the computer network technology development, the network security and the reliability have become the question of common interest by all users. The people all hoped their own network system can move reliably, not external intruder disturbance and destruction. Therefore solves the network security and the reliable problem carefully, is a guarantee the network normal operation’s premise and safeguard.
First, the importance of the network security. With the informationization developing fast today, the computer network obtained the widespread application, but along with the network information transmission capacity growing faster, some organizations and departments benefit the speedup with the service operation in the network, while, the data has also suffered to extent attack and destruction. The aggressor may intercept the information in the network, steals the user’s password, the database information; also may tamper with the database content, the forge user’s status, denies own signature. And what is more, the aggressor may delete t he database content, the destroy node, releases computer virus and so on. This cause data security and own benefit have received the serious threat.
According to American FBI (US Federal Bureau of Investigation) investigation, the network security creates the economic loss surpasses 17,000,000,000 dollars every year.75% corporation report finance loss is because the computer system security problem creates. More than 50% safe threat come from inside. But only 59% loss could be possible estimate. In China, the economic loss amount in view of financial domain and the bank, negotiable securities computer system security problems creates has reached as high as several hundred million Yuan, also sometimes occurs in view of other profession network security threat.
Thus it can be seen, regardless of is the mean attack, or unconscious disoperation, will all be able to bring the inestimable loss to the system. Therefore, the computer network must have the enough strong security measure. Regardless of is in the local area network or in WAN, the network security measure should be Omni-directional in view of each kind of different threat and the vulnerability, so that it can guarantee the network information’s secrecy, the integrity and the usability.
Second, network security rationale. International Standardization Organization (ISO) once suggested the computer security the definition was: “The computer system must protect its hardware, the data not accidentally or reveals intentionally, the change and the destruction.” In order to help the computer user discrimination and the solution computer network security problem, the American Department of Defense announced “the orange peel book” (orange book, official name is “credible computer system standard appraisal criterion”), has carried on the stipulation to the multiuser computer system security rank division.
The orange peel book from low to high divides into the computer security four kinds of seven levels: D1, C1, C2, B1, B2, B3, A1.Above all,D1 level does not have the lowest safety margin
rank, C1 and the C2 level has the lowest safety margin rank, B1 and the B2 level has the medium safekeeping of security ability rank, B3 and A1 belongs to the highest security rating.
In the network concrete design process, it should act according to each technology standard, the equipment type, the performance requirement as well as the funds which in the network overall plan proposed and so on, the overall evaluation determines one quite reasonably, the performance high network security rank, thus realization network security and reliability.
Third, the network security should have function. In order to adapt the information technology development well, the computer network application system must have following function:
(1)Access control: Through to the specific webpage, the service establishment access
control system, in arrives the overwhelming majority attack impediment in front of
the attack goal.
(2)Inspects the security loophole: Through to security loophole cyclical inspection, even if
attacks may get the attack goal, also may cause the overwhelming majority attack to
be invalid.
(3)Attack monitoring: Through to specific webpage, service establishment attack
monitoring system, but real-time examines the overwhelming majority attack, and
adopts the response the motion (for example separation network connection,
recording attack process, pursuit attack source and so on).
(4)Encryption communication: Encrypts on own initiative the communication, may enable
the aggressor to understand, the revision sensitive information.
(5)Authentication: The good authentication system may prevent the aggressor pretends the
validated user.
(6)Backup and restoration: The good backup and restores the mechanism, may causes the
losses when the attack, as soon as possible restores the data and the system service.
(7)Multi-layered defense: The aggressor after breaks through the first defense line delays or
blocks it to reach the attack goal.
(8)Sets up the safe monitoring center: Provides the security system management, the
monitoring, the protection and the emergency case service for the information
system.
Fourth, the network system safety comprehensive solution measures. If want to realize the network security function, we should carry on the Omni-directional guarding to the network system, and thus formulate the quite reasonable network security architecture. Below on the network system security problem, proposes some guard measure.
Physics safe may divide into two aspects: One is the artificial harm to the network; the other is the network to the users. Most common thing is the constructor who did not understand to the buried cable clearly, thus lead to the destruction of electric cable, this kind of situation may through standing symbolized the sign guards against; Has not used the structurized wiring the network to be able to appear the user frequently to the electric cable damage, this needs to use the structurized wiring to install the network as far as possible; Artificial or natural disaster influence, when to consider the plan.
The access control security, the access control distinguishes and confirms the user, limits the user in the already activity and the resources scope which is authorized. The network access control safe may consider from following several aspects.
(1)password: The network security system most outer layer defense line is network user's
registering, in the registration process, the system would inspect the user to register
the name and the password validity, only then the legitimate user can enter the system.
(2)The network resources’ host, the attribute and the visit jurisdiction: The network
resources mainly include the resources which shared files, the shared printer, network
users and so on, that all the network users can use. The resources were the host to
manifest the different user to the resources subordinate relations, such as builder,
modifier and group member and so on. The resources attribute expressed itself deposit
and withdrawal characteristics, as can read by who, write or the execution and so on.
The visit jurisdiction mainly manifests in the user to the network resources available
degree in using assigns the network resources to be the host, the attribute and the
visit jurisdiction may effectively in the application cascade control network system
security.
(3)Network security surveillance: The network surveillance is generally called for “the
network management”, its function mainly is carries on the dynamic surveillance to
the entire network movement and handles each kind of event promptly. May
understand simply through the network surveillance discovers and solves in the
network security problem, such as the localization network fault point, seizes the IP
embezzler, the control network visit scope and so on.
(4)Audit and track: Network audit and track which is including the network aspect,
resources use, network breakdown and system keeping. It composed generally by two
parts: One, the recording event, soon each kind of event entirely records in the
document; Two, carries on the analysis and the statistics to the recording, thus
discovers the question to be at.
The data transmission security, the transmission safety requirements protect the information which is transmitting, prevented passively and encroaches on own initiative. We may take the following measure to the data transmission:
(1)Encryption and digital signature: The digital signature which is the data receiver
confirms the data transmission truly and unmistakable, it mainly realizes through the
encryption algorithm and the confirmation agreement.
(2)Firewall: Firewall is a security measure which is widespread use on the Internet, it may
establish in different network or between a series of part combination. It can through
the monitor, the limit, the change surmounts the firewall’s data stream, it examines
the information inside and outside as far as possible, so that realizes the network
safekeeping of security.
(3)User Name/Password Authentication: This authentication is the most commonly used, it
uses in the operating system registering, telnet (long-distance registers) rlogin
(long-distance registers) and so on, but this kind of authentication way process does
not encrypt, namely password is monitored easily and deciphered.
(4)Use abstract algorithm authentication: Radius (long-distance digit dialing authentication
agreement), OSPF (opening route agreement), SNMP Security Protocol and so on,
these all use sharing Security Key (key), in addition the abstract algorithm (MD5)
carries on the authentication, but the abstract algorithm is an irreversible process,
therefore, in the authentication process, cannot calculate sharing by the abstract
information security key, therefore the sensitive information cannot transmit in the
network. In the market mainly uses the abstract algorithm mainly has MD5 and
SHA-1.
(5)Based on PKI authentication: Uses PKI (public key system) to carry on the
authentication and the encryption. This method safety rate is high, the synthesis used
the abstract algorithm, has encrypted asymmetrically, symmetrical technologies and
so on encryption, digital signature, well security and highly effective union. This
authentication method applies at present in the email, the application server visit, the
customer authentication, the firewall Domains and so on authentication. This kind of
authentication method safety rate is very high, but involves to the quite arduous
certificate management duty.
(6)Hypothesized private network (VPN) technology: The VPN technology mainly provides
on the public network the security bidirectional communication uses the transparent
decipherment scheme to guarantee the data the integrity and the secrecy. Summary:Generally speaking, the security problem which transmits regarding the computer network, we must have to achieve following points. First, we should strictly limit the system information and the resources which the surfer user visits; this function may through the visit on the server to establish the Net Screen firewall to realize. Second, we should strengthen to the user's status authentication, and we can use RADIUS which is the special-purpose identification authentication server. At the same time, it may realize to manage the user’s account; On the other hand, uses the encryption in the identification authentication process the method, avoids the user password revelation the possibility. Third, uses the encryption technology in the data transmission process, prevented the data illegal is stolen. One method is uses PGP for Business Security to encrypt to the data. Another method uses the VPN technology which the Net Screen firewall provides.VPN while provides between the net data encryption, also has provided in view of the single plane user's encryption client side software, and namely uses the software encryption the technology to guarantee the data transmission the security.
Reference:
[1] Cai Wandong, Computer network technology. Xian University press, 1988.
[2] Du Feilong, Internet principle and application, people's posts and telecommunications press, 1997.
[3] Hu Daoyuan, Information network system integration technology, the Qinghua University press, 1995.
[4] Yang mingfu, Computer network, electronics industry press, 1998.5.
[5] Yuan Baozong, Internet and application, Jilin University press, 2000.
[6] Sui Hongjian and so on, Computer network and correspondence, Beijing University press, 1996.
[7] Zhou tianming and so on, TCP/IP network theorem and application, Qinghua University press, 1993.
[8] Chinese Journal of Computers, 1998-2001.
[9] Network newspaper, 1997-2001.
稀疏表示计算机视觉和模式识别 从抽象技术的现象已经可以开始看到稀疏信号在电脑视觉产生重大影响，通常在非传统的应用场合的目标不仅是要获得一个紧凑的高保真度表示的观察信号，而且要提取语义信息。非常规词典在字典的选择中扮演了重要的角色，衔接的差距或学习、训练样本同来获得自己提供钥匙，解出结果和附加语义意义信号稀疏表示。理解这种非传统的良好性能要求词典把新的算法和分析技术。本文强调了一些典型例子：稀疏信号的表现如何互动的和扩展计算机视觉领域，并提出了许多未解的问题为了进一步研究。 稀疏表现已经被证明具有非常强大的工具，获取、表示、压缩高维信号的功能。它的成功主要是基于这个事实，即重要类型的信号(如声音和图像，稀疏表示很自然地就固定基地或串连这样的基地。此外，高效、大概有效算法说明基于凸优化一书提供了计算这样的陈述。 虽然这些应用在经典信号处理的铺垫下,已经可以在电脑视觉上形成一个我们经常更感兴趣的内容或语义，而不是一种紧凑、高保真的表示。一个人可能会理所当然地知道是否可以有用稀疏表示为视觉任务。答案很大程度上是积极的：在过去的几年里，变化和延伸的最小化已应用于许多视觉任务。 稀疏表示的能力是揭示出语义信息，大部分来自于一个简单但重要的性质数据：虽然照片所展示的图像是在非常高自然的空间，在许多同类应用中图像属于次级结构。也就是说他们在接近低维子空间或层次。如果发现一个收集的样本分布，我们理应期望一个典型的样品有一个稀疏表示理论的基础。 然而，想要成功地把稀疏表示应用于电脑视觉，我们通常是必须面对的一个额外的问题，如何正确选择依据。这里的数据选择不同于在信号处理的传统设置，基于指定的环境具有良好的性能可以被假定。在电脑视觉方面，我们经常要学习样本图像的任务词典，我们不得不用一个连贯的思想来贯穿工作。因此，我们需要扩展现有的理论和稀疏表示算法新情况。 自动人像识别仍然是最具有挑战性的应用领域和计算机视觉的难题。在理论基础实验上，稀疏表示在近期获得了显著的进展。 该方法的核心是选择一个明智的字典作为代表，用来测试信号稀疏线性组合信号。我们首先要简单的了解令人诧异的人脸识别途径是有效的解决办法。反过来，人脸识别实例在稀疏表示光曝光之前揭示了新的理论现象。 之前稀疏表示的部分用机器检查并且应用，在一个完全词典里组成的语义信息本身产生的样品。对于许多数据不是简单的应用，这是合乎情理的词典，使用一个紧凑的数据得到优化目标函数的一些任务。本节概述学习方法那种词典，以及这些方法应用在计算机视觉和图像处理。 通过近年来我们对稀疏编码和优化的应用的理解和启发，如面部识别一节描述的例子，我们提出通过稀疏数据编码构造，利用它建立了受欢迎的机器学习任务。在一个图的数据推导出研究学报。2009年3月5乘编码每个数据稀疏表示的剩余的样本，并自动选择最为有效的邻居为每个数据。通过minimization稀疏表示的计算自然的性能满足净水剂结构。此外，我们将会看到描述之间的关系进行了实证minimization线性数据的性能，可以显著提高现有的基于图论学习算法可行性。 摘自：期刊IEEE的论文- PIEEE ，第一卷
1.英语学术论文的语言风格特点就（知人方能论世） 为什么我们会读不懂SCI上面的文章呢？ 第一，由于SCI里面出现的专业词汇一般都是出现在特定领域，一类是一词对应于一意，另外一类则是一词多义。 其次，名词化结构则是另外另外一个普遍出现的现象，可以看到，复合名词，加前缀和后缀，以及省略现象可谓是漫山遍野，因为文体要求行文简洁、表达客观、内容确切、信息量大、强调存在的事实，一般文章不会夹杂着太多主观看法。 最后，大量使用长句和定语从句SCI论文发表中大量使用长句和定语从句，在论证上起到连接信息和强调信息的作用。广泛使用被动语态SCI论文发表中侧重叙事推理，强调客观准确，第一、二人称使用过多，会造成主观臆断的印象。因此尽量使用第三人称叙述，采用被动语态。名词作定语和缩写词使用频繁SCI论文发表中要求结构紧凑、行文简炼，缩写词和名词作定语的频繁使用，增大了信息密度，简化了句型。 如果我们能逆向思维，转换个角度去看文章，如果你要发表一篇SCI论文，你会怎么去构造你的行为，你如何组织你文章的逻辑，特别是用词方面，口语和一些狸语在一般
情况不应该出现在文章中。还有些中式英语也会极大地影响我们的阅读，例如说足球比赛，可不是我们想象中的football match （之前有次演讲说，英语里面不能有2个名词的情况，在此就举了个例子bicycle man），而应该做football play亦作soccer play。 2.翻译是一门艺术，从某种意义上来讲是没有标准答案的。 这里本人想要想要阐述这样一种观点，翻译是一个不断精进的过程，翻译最初的目的即是为了实现语言之间的一个互相沟通，然而不同的人对一句话，应该会有着不同的理解。这也就有了译者极大的自由发挥性，但是译者必须准确理解原文的基础之上的。 有三个字可以高度概括翻译的精髓“信，达，雅”，想必大家都应该听过。”“信”指意义不背原文,即是译文要准确,不歪曲,不遗漏,也不要随意增减意思；同样可以举个例子？This is a pan in my hand （请问如何翻译呢？） “达”指不拘泥于原文形式,译文通顺明白;这里就涉及到一个直译和意译的关系啦，否则就会出现像bicycle
姓名：王雪健学号：201390503 专业：计算机科学与技术3 班学院：信息科学与工程学院 On Information Resources Abstract: With the development of human society, the way people gather information more and more https://www.doczj.com/doc/8b45866.html,rmation resources as a special social resources, With strategic nature, can spread the properties, it can increase the properties and comprehensive quality characteristics. Information resource with great economic and social value, not only is important to take a new road to industrialization led forces, but also changes the mode of production and social progress in an enormous boost. 1 Introductio Information resources, as a special configuration has a special meaning and forms of social resources, their role is with each passing day growing. Information resources are the basic elements of modern social productive forces, while change in the way of social production and people's way of life enhancement, resulting in an invaluable influence and promote the role. At the same time in the modern society, the content of information resources is continuously expanding to include not only the growing number of natural science information resources, but also times of social science information resources. The availability of information resources and use of attention is whether the growth of a country's comprehensive national strength is an important factor, but also the extent a country is an important symbol of
《计算机英语（第4版）》参考译文 第一单元：计算机与计算机科学 课文A：计算机概览 一、引言 计算机是一种电子设备，它能接收一套指令或一个程序，然后通过对数字数据进行运算或对其他形式的信息进行处理来执行该程序。 要不是由于计算机的发展，现代的高科技世界是不可能产生的。不同类型和大小的计算机在整个社会被用于存储和处理各种数据，从保密政府文件、银行交易到私人家庭账目。计算机通过自动化技术开辟了制造业的新纪元，而且它们也增强了现代通信系统的性能。在几乎每一个研究和应用技术领域，从构建宇宙模型到产生明天的气象报告，计算机都是必要的工具，并且它们的应用本身就开辟了人们推测的新领域。数据库服务和计算机网络使各种各样的信息源可供使用。同样的先进技术也使侵犯个人隐私和商业秘密成为可能。计算机犯罪已经成为作为现代技术代价组成部分的许多风险之一。 二、历史 第一台加法机是法国科学家、数学家和哲学家布莱斯?帕斯卡于1642年设计的，它是数字计算机的先驱。这个装置使用了一系列带有10个齿的轮子，每个齿代表从0到9的一个数字。轮子互相连接，从而通过按照正确的齿数向前转动轮子，就可以将数字彼此相加。17世纪70年代，德国哲学家和数学家戈特弗里德?威廉?莱布尼兹对这台机器进行了改良，设计了一台也能做乘法的机器。 法国发明家约瑟夫―玛丽?雅卡尔，在设计自动织机时，使用了穿孔的薄木板来控制复杂图案的编织。在19世纪80年代期间，美国统计学家赫尔曼?何勒里斯，想出了使用类似雅卡尔的木板那样的穿孔卡片来处理数据的主意。通过使用一种将穿孔卡片从电触点上移过的系统，他得以为1890年的美国人口普查汇编统计信息。 1、分析机 也是在19世纪，英国数学家和发明家查尔斯?巴比奇，提出了现代数字计算机的原理。他构想出旨在处理复杂数学题的若干机器，如差分机。许多历史学家认为，巴比奇及其合伙
A Preliminary Analysis of the Scienti?c Production of Latin American Computer Science Research Groups Juan F.Delgado-Garcia,Alberto https://www.doczj.com/doc/8b45866.html,ender and Wagner Meira Jr. Computer Science Department,Federal University of Minas Gerais 31270-901-Belo Horizonte-Brazil {jfdgarcia,laender,meira}@dcc.ufmg.br Abstract.In this paper,we present a preliminary analysis of the sci- enti?c production of Latin American Computer Science research groups. Our analysis is based on data over a period of20years collected from DBLP,and addresses24groups from academic institutions in Argentina, Chile,Colombia,Cuba,Mexico,Peru,Uruguay and Venezuela.Our re- sults show a clear improvement in the publication output of these groups in the last10years,particularly in Argentina,Chile and Mexico. Keywords:Latin America,Computer Science,Scienti?c Production, Coauthorship Analysis,Bibliometrics 1Introduction According to SCIMago Journal and Country Rank(JCR)1,recent years have witnessed a tremendous increase in the scienti?c production in Computer Sci-ence(CS)all over the world.Considering data from2002to2012,for instance,in North America(Canada and USA)the number of publications increased59.73%, in Western Europe(considering only the top-5countries,UK,Germany,France, Italy and Spain)184%,and in Latin American(also considering only the top-5 countries,Brazil,Mexico,Argentina,Chile and Colombia)319%.In other re-gions,countries like Australia,China,Korea,India and Poland have achieved ?gures even higher.Although SCIMago numbers re?ect only publications that appeared in selected journals,they show that CS is a very productive research area with many active research groups spread around the world. In view of this scenario,in this paper we present a preliminary analysis of the scienti?c production of Latin American CS research groups.Our analysis is based on data over a period of20years collected from DBLP2,and addresses 24groups from academic institutions in Argentina,Chile,Colombia,Cuba,Mex-ico,Peru,Uruguay and Venezuela.Despite being the country in Latin America with the highest productivity in the area[4],we have not included Brazil in our analysis for two reasons.First,Brazil is by far the Latin American country 1https://www.doczj.com/doc/8b45866.html,/countryrank.php 2https://www.doczj.com/doc/8b45866.html,rmatik.uni-trier.de/~ley/db
第一单元：计算机与计算机科学 课文A：计算机概览 一、引言 计算机是一种电子设备，它能接收一套指令或一个程序，然后通过对数字数据进行运算 或对其他形式的信息进行处理来执行该程序。 要不是由于计算机的发展，现代的高科技世界是不可能产生的。不同类型和大小的计算 机在整个社会被用于存储和处理各种数据，从保密政府文件、银行交易到私人家庭账目。计 算机通过自动化技术开辟了制造业的新纪元，而且它们也增强了现代通信系统的性能。在几 乎每一个研究和应用技术领域，从构建宇宙模型到产生明天的气象报告，计算机都是必要的 工具，并且它们的应用本身就开辟了人们推测的新领域。数据库服务和计算机网络使各种各 样的信息源可供使用。同样的先进技术也使侵犯个人隐私和商业秘密成为可能。计算机犯罪 已经成为作为现代技术代价组成部分的许多风险之一。 二、历史 第一台加法机是法国科学家、数学家和哲学家布莱斯.帕斯卡于1642年设计的，它是数 字计算机的先驱。这个装置使用了一系列带有10个齿的轮子，每个齿代表从0到9的一个数字。轮子互相连接，从而通过按照正确的齿数向前转动轮子，就可以将数字彼此相加。17世纪70 年代，德国哲学家和数学家戈特弗里德.威廉.莱布尼兹对这台机器进行了改良，设计了一台 也能做乘法的机器。 法国发明家约瑟夫―玛丽.雅卡尔，在设计自动织机时，使用了穿孔的薄木板来控制复 杂图案的编织。在19世纪80年代期间，美国统计学家赫尔曼.何勒里斯，想出了使用类似雅 卡尔的木板那样的穿孔卡片来处理数据的主意。通过使用一种将穿孔卡片从电触点上移过的 系统，他得以为1890年的美国人口普查汇编统计信息。 1、分析机 也是在19世纪，英国数学家和发明家查尔斯.巴比奇，提出了现代数字计算机的原理。 他构想出旨在处理复杂数学题的若干机器，如差分机。许多历史学家认为，巴比奇及其合伙 人，数学家奥古斯塔.埃达.拜伦，是现代数字计算机的真正先驱。巴比奇的设计之一，分析 机，具有现代计算机的许多特征。它有一个以一叠穿孔卡片的形式存在的输入流、一个保存 数据的“仓库”、一个进行算术运算的“工厂”和一个产生永久性纪录的打印机。巴比奇未 能将这个想法付诸实践，尽管在那个时代它在技术上很可能是可行的。 2、早期的计算机 模拟计算机是19世纪末开始制造的。早期型号是靠转动的轴和齿轮来进行计算的。用任 何其他方法都难以计算的方程近似数值，可以用这样的机器来求得。开尔文勋爵制造了一台 机械潮汐预报器，这实际上就是一台专用模拟计算机。第一次和第二次世界大战期间，机械 模拟计算系统，以及后来的电动模拟计算系统，在潜艇上被用作鱼雷航线预测器，在飞机上 被用作轰炸瞄准具的控制器。有人还设计了另一个系统，用于预测密西西比河流域春天的洪 水。 3、电子计算机 第二次世界大战期间，以伦敦北面的布莱切利公园为工作地点的一组科学家和数学家， 制造了最早的全电子数字计算机之一：“巨人”。到1943年12月，这个包含了1500个真空管 的“巨人”开始运转了。它被以艾伦.图灵为首的小组用于破译德国用恩尼格码加密的无线 电报，他们的尝试大部分是成功的。 除此而外，在美国，约翰.阿塔纳索夫和克利福德.贝里早在1939年就在艾奥瓦州立学院
第一单元启动软件项目 第一部分听说 A. 对话：启动软件项目 （Kevin、Sharon和Jason是三名北京航空航天大学软件学院大学二年级学生。今天，在第四个学期末暑假开始之前，他们正在参加一个班会。） 老师：大家早上好。在这个假期中，大家将要完成一个真正的项目作为你们的课程设计，这里有一些题目，每个人可以根据自己的兴趣和经验来选择，并请在下周之内把你的决定提交给我。 Kevin：对不起，老师，请问一下，这个项目是需要每个人单独完成还是几个同学合作完成呢？ 老师：我推荐团队合作，因为这可以让你学习如何与你的同学携手合作，并且作为一名团队成员，怎样互相交流、分享、表达并了解互相的想法。但是每组成员不要超过4个人。 Sharon：我感兴趣的主题是四季酒店管理信息系统，你呢，Kevin？ Kevin：哦，这也正是我的想法，我想我们可以组成一个小组。嗨，Jason，你愿意加入我们吗？ Jason：哦，好的，我非常愿意！ Sharon：好的，现在让我们讨论一下每个人的职责。 Jason：Kevin善于组织并具有丰富的编程经验，因此我认为他可以作为我们的团队组长或是项目经理，负责指导我们的团队和编程实践。 Sharon：我同意。 Kevin：非常感谢你们的信任。好，我一定会尽我所能。关于我们的项目，我觉得除了编码以外还需要构建一个数据库并实现一组用户界面。 Jason：我对数据库比较感兴趣，我愿意负责建立和管理数据库。 Sharon：我喜欢艺术设计，我认为我可以为项目做用户界面设计和文档撰写的工作。Kevin：哦，不错，看来这是一个很棒的团队，它让我感到很有信心！现在让我们根据项目的各个阶段来大致分配一下任务。作为组长，我来负责需求，Jason负责设计，Sharon负责测试。 Jason：接下来，我们将为我们的项目制定一个粗略的进度计划。 Kevin：我们可以根据老师提供的最初的需求文档来设计并完成用户界面操作，与此同时，Jason可以构建数据库，最后我们一起来完成编码。 Sharon：听起来不错！但是，我担心的是，老师所提供的最初的需求文档对我们的设计来说信息可能不全，所以，我们必须先根据这个文档来做我们的需求分析，并完成一个正式的
外文资料 Object landscapes and lifetimes Technically, OOP is just about abstract data typing, inheritance, and polymorphism, but other issues can be at least as important. The remainder of this section will cover these issues. One of the most important factors is the way objects are created and destroyed. Where is the data for an object and how is the lifetime of the object controlled? There are different philosophies at work here. C++ takes the approach that control of efficiency is the most important issue, so it gives the programmer a choice. For maximum run-time speed, the storage and lifetime can be determined while the program is being written, by placing the objects on the stack (these are sometimes called automatic or scoped variables) or in the static storage area. This places a priority on the speed of storage allocation and release, and control of these can be very valuable in some situations. However, you sacrifice flexibility because you must know the exact quantity, lifetime, and type of objects while you're writing the program. If you are trying to solve a more general problem such as computer-aided design, warehouse management, or air-traffic control, this is too restrictive. The second approach is to create objects dynamically in a pool of memory called the heap. In this approach, you don't know until run-time how many objects you need, what their lifetime is, or what their exact type is. Those are determined at the spur of the moment while the program is running. If you need a new object, you simply make it on the heap at the point that you need it. Because the storage is managed dynamically, at run-time, the amount of time required to allocate storage on the heap is significantly longer than the time to create storage on the stack. (Creating storage on the stack is often a single assembly instruction to move the stack pointer down, and another to move it back up.) The dynamic approach makes the generally logical assumption that objects tend to be complicated, so the extra overhead of finding storage and releasing that storage will not have an important impact on the creation of an object. In addition, the greater flexibility is essential to solve the general
计算机专业英语教程课文翻译 Chapter 1 信息技术与第三产业革命 Section B 第三产业革命 第三产业革命是由J.R.概括出来的一种概念和视图，并且在2007年被欧洲议会所认同。纵观历史，经济转变的发生往往伴随着汇聚了新的能源系统的新一代通信技术。这种新的通信方式成为了组织和管理更加复杂的文化的媒介，而这种文化又是由新的能源来源产生的。21世纪，互联网通信技术和可再生能源的结合，带来了第三产业革命。 第三产业革命是以五大支柱为基础的： ·可再生能源的转换。 ·将房屋建筑转变为发电厂。 ·氢能源和其他能源的储存技术。 ·智能电网技术。 ·“轨道的”，电动的、混合动力的、燃料电池为动力的交通运输。 1.五大支柱 ·可再生能源的转换：太阳呢过、风能、氢能、地热能、洋流能?能和生物质能等可再生形式的能量组成了第三产业革命的第一大支柱。虽然这些能源在全球能源结构中只占据了很小的比例，但是它们的增长速度非常之快。这是因为政府把它们当做任务目标，要使这些能源广泛地进入市场和它们不断下降的价格使它们的竞争力不断上升。 ·房屋建筑成为发电厂：新技术的突破，将首次使得这种设想成为可能。我们设计并建造从各种本地的可再生能源中生产所有自身所需能源的房屋，我们能够对房屋建造方式进行重构使房屋变为发电厂。这种商业上和经济上的设想对房地产行业来说是影响深远的。25年内，成千上万的房屋建筑：房子、办公室、商场、工业园区、技术园区，都将会
被建造成发电厂和住宿一体化的形式。这些建筑将能够通过本地所能获得的阳光、风、垃圾、农业和林业废弃物、海浪、抄袭、氢气和地热中收集并产生能量。这些足够的能量将满足人们自身的需求，同时剩余的能量将被相互分享。 ·在每栋建筑物和所有基础设置中部署氢气和其他能源存储技术来存储周期性的能源（其实就是剩余没用到的嘛）。为了能够最大化的利用可再生能源，并且使得成本最小化，必须配备一定的存储方法。这种存储方法，将能够促进这些可再生能源中的（of this energy source根本就是废话~上文有了下文根本不需要有）周期性的剩余能源转化为可靠的资产。电池和一些其他的媒介，与水泵的区别在于，可以提供有限的（能源）存储容量。不过也有一种可得的、广泛的、并且相对高效的存储媒介——氢能。氢能是公认的能够存储各种形式可再生能源的媒介，并且它能够保证在能源生产中稳定和可靠的供应，此外同样重要的是，氢能易于运输。 ·运用互联网技术将每个洲的传输电网转换成一个像互联网一样工作的能源互联电网。这种对世界能源电网的重新配置正在被一些欧洲的能源公司进行试验。它将沿着互联网的线路，使得商业用户和家庭住户能够产生自己所需的能量并相互分享。这种新型的只能电网或者是互联电网，将为电能的产生和传播方式带来革命性的变化。成千万的新的和正在兴起的房屋建筑—房屋、办公室、工厂，将能够转化为或者建设成发电厂。这种发电厂是能够获得当地的可再生能源，如太阳能、风能、地热能、生物能、氢能和海浪能，来产生供应房屋建筑的电能。同时剩余的能量可以通过互联电网与别的用户一起分享。整个过程，就像如今我们通过互联网产生和传播自己的信息给他人一样。 ·略，没啥难度嘛 当这五个支柱汇集到一起，他们组成不可分割的技术平台：一个拥有与它各个组成部分完全不同的属性和功能的应急系统。换言之，每个支柱之间相互协调将会带来一个新的、足
学号09710128 计算机英语论文 书名：计算机网络（第四版） 作者：AndrewS.T anenbaum 出版社：清华大学出版社 出版时间：2004年8月 学生姓名袁璇 班级计算机1班 成绩 指导教师(签字) 电子与信息工程系 2011年10月8日
Uses of Computer Networks Before we start to examine the technical issues in detail, it is worth devoting some time to pointing out why people are interested in computer networks and what they can be used for. After all, if nobody were interested in computer networks, few of them would be built. We will start with traditional uses at companies and for individuals and then move on to recent developments regarding mobile users and home networking. 1．Business Applications Many companies have a substantial number of computers. For a example,a company may have separate computers to monitor production, keep track of inventories, and do the payroll. Initially, each of these computers may have worked in isolation from the others, but at some point, management may have decided to connect them to be able to extract and correlate information about the entire company. Put in slightly more general form, the issue here is resource sharing, and the goal is to make all programs, equipment, and especially data available to anyone on the network without regard to the physical location of the resource and the user. An obvious and widespread example is having a group of office workers share a common printer. None of the individuals really needs a private printer, and a high-volume networked printer is often cheaper, faster, and easier to maintain than a large collection of individual printers. However, probably even more important than sharing physical resources such as printers, scanners, and CD burners, is sharing information. Every large and medium-sized company and many small companies are vitally dependent on computerized information. Most companies have customer records, inventories, accounts receivable, financial statements, tax information, and much more online. If all of its computers went down, a bank could not last more than five minutes. A modern manufacturing plant, with a computer-controlled assembly line, would not last even that long. Even a small travel agency or three-person law firm is now highly dependent on computer networks for allowing employees to access relevant information and documents instantly. For smaller companies, all the computers are likely to be in a single office or perhaps a single building, but for larger ones, the computers and employees may be scattered over dozens of offices and plants in many countries. Nevertheless, a sales person in New Y ork might sometimes need access to a product inventory database in Singapore. In other words, the mere fact that a user happens to be 15,000 km away from his data should not prevent him from using the data as though they were local. This goal may be summarized by saying that it is an attempt to end the ''tyranny of geography.'' In the simplest of terms, one can imagine a company's information system as consisting of one or more databases and some number of employees who need to access them remotely. In this model, the data are stored on powerful computers called servers. Often these are centrally housed and maintained by a system administrator. In contrast, the employees have simpler machines, called clients, on their desks, with which they access remote data, for example, to include in spreadsheets they are constructing. (Sometimes we will refer to the human user of the client machine as the ''client,'' but it should be clear from the context whether we mean the computer or its user.) The client and server machines are connected by a network, as illustrated in Fig. 1-1. Note that we have shown the network as a simple oval, without any detail. We will use this form when we mean a network in the abstract sense. When more detail is required, it will be provided.
Unit 8 Computer Networking Text 1 令狐文艳 Text 2 Data Communications The end equipmentcan be computers, printers, keyboards, CRTs, and so on.They are either generates the digital information for transmission oruses the received digital data. This equipment generally operates digital information internally in word units. DTE is data terminal equipment. A station controller (STACO)is the corresponding unit at the secondaries. At one time, the DTE was the last piece of equipment that belonged to the subscriber in a data link system. Between the DTEs, first is the modem, and then is the communications equipment. The communication equipment is owned and maintained by Telco. Data communications equipment (DCE) accepts the serial data stream from the DTE. And DCE converts it to some form of analog signal suitable for transmission on voice-grade lines. At the receive end, the DCE performs the reverse function. It converts the received analog signal to a serial digital data stream.
题目：计算机硬件概述（Overview of the computer hardware based） 学院：信息技术学院 班级：XXXXXX 学号：XXXXXXXXXX 姓名：XXXX
A computer is a fast and accurate symbol processing system. It can accept, store, process data and produce output results. A computer can automatically process data without human intervention. However, it must be given a set of instruction to guide it, step by step, through processes. The set of instructions is called a program, The program is stored physically inside the machine, making it a program. All computer systems of interest to us are similar. They contain hardware components for input, central processing unit and output. The system on the small-scale is called a microcomputer or minicomputer. Continuing up the size scale, the mainframe computer is one that may offer a faster processing speed and a greater storage capacity than a typical mini. Finally comes the supercomputer, designed to process complex scientific applications，which is the largest and fastest. Although the capacity of computers' storage locations is varied，every computer stores numbers，letters，and other characters in a coded form. Every character in the storage is represented by a string of 0s and 1s，the only digits founded in the binary numbering system. BCD and ASCII are popular computer codes. So, what part of computer hardware that contains it? Computer hardware has four parts: the central processing unit (CPU) and memory, storage hardware, input hardware, and output hardware. The Central Processing Unit Pronounced as separate letters it is the abbreviation for central processing unit. The CPU is the brains of the computer. Sometimes referred to simply as the central processor, but more commonly called processor, the CPU