能扩展人们感觉器官的能力,并用来完成信息获取和收集的技术是().A. 计算机技术B. 通信技术C. 控制技术D. 传感技术

混合学习的一般模式包括（）阶段。A. 协作拓展学习B. 面对面的学习C. 形成产品D. 基于Web自主学习

Computer Viruses Any computer connected to the Internet faces a daunting range of electronic threats. Perhaps the biggest single threat to any computer is the humble software bug. Seemingly harmless programming errors can be exploited to force entry into a computer and also provide the weak spots that allow computer worms and viruses to spread. Many software bugs will simply cause a computer to crash. But an expert programmer can sometimes figure out how to make a computer malfunction in a creative way, so that it provides access to secure parts of a system, or shares protected data. When a software weakness is revealed, it is often a race against the clock to apply the correct software patch before an attacker can convert the bug into an "exploit" that can be used to cause major damage. A computer virus is a program that spreads between computers by hiding itself within a seemingly innocent-document or application. A worm, on the other hand, is a program that replicates (复制) and travels without "infecting" anything else on a system. Many modern specimens of malevolent (恶意的) code, however, use a mixture of tricks to cheat their way onto computer systems, blurring the line between worms and viruses. The terms are now often used interchangeably. The first worms appeared in the 1970s and spread slowly between computers connected to the same network. They simply displayed an annoying message on the screen of each infected machine. The first computer virus, called Elk Cloner, was written in 1982 and infected computers via floppy disks.Trojans and Zombies But viruses and worms no longer just provide a way for ill willed hackers to gain bad reputation. Today’s viral code can contaminate computers at lightning speed, spreading via e-mail, peer-to-peer file-sharing networks and even instant messaging programs. The most successful ones cause serious damage, forcing companies around the globe to close down while infected computers are cleaned up. A string of recent specimens have been designed to snatch passwords or credit card information and install programs that can be used to remotely control infected machines. These programs are known as Trojan horses. There is evidence that virus writers can earn large amounts of money by leasing access to networks of compromised computers--often referred to as "botnets". These groups of remote controlled "zombies" have been used to extort money from websites, by threatening to crash them with a denial-of-service (Dos) attack. This involves overloading a server with bogus page requests, so that real messages cannot get through. Spammers have also begun using botnets to forward unwanted bulk e-mail advertising, or spare, through scores of zombie PCs. This makes it far more difficult for spam hunters to block the messages at source and catch the criminals. Once considered a fairly minor problem, spam is rapidly spiraling out of control, and much more than half of all e-mail messages are now thought to consist of unwanted advertising messages. To combat computer scientists’ best efforts to stem the tide of junk e-mail, the spammers have had to become more cunning and sophisticated. More recently, spim (spam by instant messenger) and spit (spam by Internet telephony) have joined the fray. Spam’s more sinister cousin is the phishing e-mail. This is a con trick that arrives as an e-mail and tries to trick a recipient into handing over money or sensitive personal information like their bank account details or a username and password. The simplest phishing tricks try to cheat a target into sending money as part of a get-rich-quick scheme. But phishing tricksters are also getting more devious and recent scams pose as customer service e-mails and send users to false banking or commercial websites where they are invited to "re-enter" their account information. Some genuine sites have even proven vulnerable to software glitches that can be exploited to capture information from regular users. Phishing is especially threatening because it can be used to steal a person’s digital identity.Spyware Along with spam and phishing, spyware represents the third of an unhappy trinity of Internet pests. These threatening and secret programs typically find their way onto a computer system alongside another, often free, software application, although some can also exploit software bugs to get onto a machine. The programs are used to serve up unwanted adverts, change system settings and gather information on a user’s online behavior for marketing purposes. The term "computer hacker" was first coined in the 1960s and originally meant someone capable of developing an ingenious solution to a programming problem. But the phrase has since fallen into disrepute, entering the popular vocabulary as a term for a programmer with criminal intent. The earliest "criminal" hackers were in fact relatively harmless, interested in testing the boundaries of their knowledge and their ability to get around security measures. They mainly performed innocuous pranks, for example employing low-tech tricks to get free calls through the US phone networks. There are many tools in the modem hacking kit, including network scanners, packet sniffers, root kits and decompilers. But "social engineering"--for example, putting a particularly enticing message in an e-mail header to encourage people to open it--and even search engines can also be useful weapons for the hacker. As the number of computers networks has grown, so have the possibilities for more serious misuse. And, as money increasingly becomes a digital commodity, the world has seen the emergence of serious computer criminals. Criminal gangs have also started to get in on the action, attracted by the huge quantities of money now spent online every day. There is evidence that unscrupulous experts can also earn serious money from crime business group by breaking into computer systems, writing viruses and creating phishing scams. And it is not just ordinary desktop computers that are under threat. Governments, banks and critical infrastructure can also be brought to a standstill by an expert armed only with a laptop computer and a net connection. The biggest new target for computer hackers is the mobile device. Virus writers are already experimenting with code designed for smart phones and experts predict more may be on the way, while hackers are also looking at ways to crack handheld devices. While the Interact has transformed global communication beyond recognition, the arms race between those intent on harnessing its power for criminal purposes and those tasked with preventing them has only just begun.Which of the following is NOT true according to the text A. The first worms appeared in 1970, much earlier than the first computer virus.B. The first worms simply displayed an annoying message on the screen of each infected machine.C. The first computer virus was written in 1982 and infected computers via floppy disks.D. The first worms spread slowly between computers connected to the same network.

名词解释 （共4题，20.0分）21. (5.0分) 数据电文

数据库中事务的特点数据库事务(Database Transaction)，是指作为单个逻辑工作单元执行的一系列操作。事务处理可以确保除非事务性单元内的所有操作都成功完成，否则不会永久更新面向数据的资源。通过将一组相关操作组合为一个要么全部成功要么全部失败的单元，可以简化错误恢复并使________更加可靠。一个逻辑工作单元要成为事务，必须满足所谓的ACID（原子性[1][1][1]、一致性、隔离性[2][2][2]和持久性）属性。原子性（atomic）（atomicity)事务必须是原子工作单元；对于其________，要么全都执行，要么全都不执行。通常，与某个事务关联的操作具有共同的目标，并且是相互依赖的。如果系统只执行这些操作的一个子集，则可能会破坏事务的总体目标。原子性消除了系统处理操作子集的可能性。一致性（consistent）(consistency)事务在完成时，必须使所有的数据都保持一致状态。在相关数据库中，所有规则都必须应用于事务的修改，以保持所有数据的完整性。事务结束时，所有的内部________（如B树[3][3][3]索引或双向链表[4][4][4]）都必须是正确的。某些维护一致性的责任由________开发人员承担，他们必须确保应用程序已强制所有已知的完整性约束[5][5][5]。例如，当开发用于转帐的应用程序时，应避免在转帐过程中任意移动小数点。隔离性（insulation）(isolation)由并发事务所作的修改必须与任何其它并发事务所作的修改隔离。事务查看数据时数据所处的状态，要么是另一并发事务修改它之前的状态，要么是另一事务修改它之后的状态，事务不会查看中间状态的数据。这称为隔离性，因为它能够重新装载起始数据，并且重播一系列事务，以使数据结束时的状态与原始事务执行的状态相同。当事务可序列化[6][6][6]时将获得最高的________。在此级别上，从一组可并行执行的事务获得的结果与通过连续运行每个事务所获得的结果相同。由于高度隔离会限制可并行执行的事务数，所以一些应用程序降低隔离级别以换取更大的吞吐量。防止数据丢失C/S又称Client/Server或客户/服务器模式。服务器通常采用高性能的PC、工作站或小型机，并采用大型数据库系统，如Oracle、Sybase、Informix或SQL Server。客户端需要安装专用的客户端软件。B/S是Brower/Server的缩写，客户机上只要安装一个浏览器（Browser），如Netscape Navigator或Internet Explorer，服务器安装Oracle、Sybase、Informix或SQL Server等数据库。浏览器通过Web Server同数据库进行数据交互。C/S的优点是能充分发挥客户端PC的处理能力，很多工作可以在客户端处理后再提交给服务器。对应的优点就是客户端响应速度快。缺点主要有以下几个：只适用于局域网[7][7][7]。而随着互联网的飞速发展，移动办公和分布式办公越来越普及，这需要我们的系统具有扩展性。这种方式远程访问[8][8][8]需要专门的技术，同时要对系统进行专门的设计来处理分布式的数据。客户端需要安装专用的客户端软件。首先涉及到安装的工作量，其次任何一台电脑出问题，如病毒、硬件损坏，都需要进行安装或维护。特别是有很多分部或专卖店的情况，不是工作量的问题，而是路程的问题。还有，系统软件升级时，每一台客户机需要重新安装，其维护和升级成本非常高。对客户端的操作系统一般也会有限制。可能适应于Win98,但不能用于win2000或Windows XP。或者不适用于微软新的操作系统等等，更不用说Linux、Unix等。B/S最大的优点就是可以在任何地方进行操作而不用安装任何专门的软件。只要有一台能上网的电脑就能使用，客户端零维护。系统的扩展非常容易，只要能上网，再由系统管理员分配一个用户名和密码，就可以使用了。甚至可以在线申请，通过公司内部的安全认证（如CA证书）后，不需要人的参与，系统可以自动分配给用户一个账号进入系统。18：莱布尼茨公式19：洛必达法则20：C语言里面为什么要有Main函数？C程序最大的特点就是所有的程序都是用函数来装配的。main（）称之为________，是所有程序运行的入口。其余函数分为有参或无参两种，均由main（）函数或其它一般________21：数据结构中最小生成树[9][9][9]的应用网络G表示n个________的________网线路22：TCP的拥塞控制[10][10][10]通过限制拥塞扩散和持续时间来减轻拥塞的一组操作拥塞现象是指到达________中某一部分的分组数量过多,使得该部分网络来不及处理,以致引起这部分乃至整个网络性能下降的现象,严重时甚至会导致________业务陷入停顿,即出现________现象。缓冲区预分配[11][11][11]法该法用于________________网中。在建立________时,让呼叫请求分组[12][12][12]途经的________为虚电路[13][13][13]预先分配一个或多个________。若某个________缓冲器已被占满,则呼叫请求分组另择________,或者返回一个"忙"信号给呼叫者。这样,通过途经的各________为每条________开设的永久性________(直到虚电路拆除),就总能有空间来接纳并转送经过的分组。此时的________跟电路[14][14][14]交换很相似。当________收到一个分组并将它转发出去之后,该节点向发送节点返回一个确认信息。该确认一方面表示接收________已正确收到分组,另一方面告诉发送节点,该节点已空出________以备接收下一个分组。上面是"停一等"协议下的情况,若________之间的协议允许多个未处理的分组存在,则为了完全消除拥塞的可能性,每个节点要为每条________保留等价于窗口大小数量的________。这种方法不管有没有通信量,都有可观的资源(线路________或________)被某个连接占有,因此________的有效利用率不高。这种控制方法主要用于要求高带宽和低延迟的场合,例如传送________语音信息的________。分组丢弃法该法不必预先保留________,当________占满时,将到来的分组丢弃。若________提供的是________,则用分组丢弃法来防止拥塞发生不会引起大的影响。但若________提供的是________,则必须在某处保存被丢弃分组的备份,以便拥塞决后能重新传送。有两种决被丢弃分组重发的方法,一种是让发送被丢弃分组的________超时,并重新发送分组直至分组被收到;另一种是让发送被丢弃分组的节点在尝试一定次数后放弃发送,并迫使数据源节点超时而重新开始发送。但是不加分辨地随意丢弃分组也不妥,因为一个包含确认信息的分组可以释放________的缓冲区,若因节点元空余缓冲区来接收含确认信息的分组,这便使节点缓冲区失去了一次释放的机会。决这个问题的方法可以为每条输入链路[15][15][15]永久地保留一块________,以用于接纳并检测所有进入的分组,对于________信息的分组,在利用了所捎带的确认释放缓冲区后,再将该分组丢弃或将该捎带好消息的分组保存在刚空出的缓冲区中。定额控制法这种方法在________中设置适当数量的称做"许可证"的特殊信息,一部分许可证在通信子网[16][16][16]开始工作前预先以某种策略分配给各个源________,另一部分则在子网开始工作后在网中四处环游。当源________要发送来自源________的分组时,它必须首先拥有许可证,并且每发送一个分组注销一张许可证。目的________方则每收到一个分组并将其递交给目的________后,便生成一张许可证。这样便可确保________中分组数不会超过许可证的数量,从而防止了拥塞的发生。23：面向对象的特点面向对象主要特征：封装性：封装是一种________技术，它体现于类的说明，是对象的重要特性。封装使数据和加工该数据的方法（函数）封装为一个整体，以实现独立性很强的模块，使得用户只能见到对象的外特性（对象能接受哪些消息，具有那些处理能力），而对象的内特性（保存内部状态的私有数据和实现加工能力的________）对用户是隐蔽的。封装的目的在于把对象的设计者和对象者的使用分开，使用者不必知晓行为实现的细节，只须用设计者提供的消息来访问该对象。继承性：继承性是子类[17][17][17]自动共享父类之间数据和方法的机制。它由类的派生功能体现。一个类直接继承其它类的全部描述，同时可修改和扩充。继承具有传递性。继承分为单继承[18][18][18]（一个子类只有一父类）和多重继承（一个类有多个父类）。类的对象是各自封闭的，如果没继承性机制，则类对象________、方法就会出现大量重复。继承不仅支持系统[19][19][19]的可重用性，而且还促进系统的可扩充性。多态性[20][20][20]：对象根据所接收的消息而做出动作。同一消息为不同的对象接受时可产生完全不同的行动，这种现象称为多态性。利用多态性用户可发送一个通用的信息，而将所有的实现细节都留给接受消息的对象自行决定，如是，同一消息即可调用不同的方法。例如：Print消息被发送给一或表时调用的打印方法与将同样的Print消息发送给一正文文件而调用的打印方法会完全不同。多态性的实现受到继承性的支持，利用类继承的层次关系，把具有通用功能的协议存放在类层次中尽可能高的地方，而将实现这一功能的不同方法置于较低层次，这样，在这些低层次上生成的对象就能给通用消息以不同的响应。在OOPL中可通过在________中重定义基类函数（定义为________或虚函数）来实现多态性。24：VC中多态是怎么实现的？我们知道多态性实现的关键是晚绑定（或者称为后期绑定），其实质就是编译器并没有在编译期间指定调用函数的绝对地址[21][21][21]，而是指定了某个类内部该函数的偏移地址。为了实现上面的功能，编译器为我们作了手脚

|2分)以下哪个不属于大数据的来源A. 社交媒体B. 企业数据库C. 物联网设备D. 天气预报数据

robotstudio窗口被意外关闭的话 很难恢复默认界面。(0.5)A. 正确 LiB. 错误

多媒体一词指的是以下哪个？()A. Multi-MediaB. MANC. Multi-MakeD. Make-Media

封装数据时,下面 ()顺序是正确的。A. 数据、帧、包、数据段、比特B. 数据段、数据、包、帧、比特C. 数据、数据段、包、帧、比特D. 数据、数据段、帧、包、比特

结合实际场景，分析APP交互设计中“手势交互”的优势与潜在问题，以及对应的解决策略。