17（）

A. so that
B. for that
C. in that
D. except that

9-12

4-8

10-15

20-28

20-30

To live in the Untied States today is to gain an appreciation for Dahrendorf’ s assertion that social change exists everywhere. Technology, the application of knowledge for practical ends, is a major source of social change.

Yet we would do well to remind ourselves that technology is a human creation; it does not exist naturally. A spear or a robot is as much a cultural as a physical object. Until humans use a spear to hunt game or a robot to produce machine parts, neither is much more than a solid mass of matter. For a bird looking for an object on which to rest, a spear or robot serves the purpose equally well. The explosion of the Challenger space shuttle(挑战者号航天飞机) and the Russian nuclear accident at Chernobyl drive home the human quality of technology; they provide cases in which well-planned systems suddenly went haywire(变得混乱)and there was no ready hand to set them right. Since technology is a human creation, we are responsible for what is done with it. Pessimists worry that we will use our technology eventually to blow our world and ourselves to pieces. But they have been saying this for decades, and so far we have managed to survive and even flourish. Whether we will continue to do so in the years ahead remains uncertain. Clearly, the impact of technology on our lives deserves a closer examination.

Few technological developments have had a greater impact on our lives than the computer revolution. Scientists and engineers have designed specialized machines that can do the tasks that once only people could do. There are those who assert that the switch to an informationbased economy is in the same camp as other great historical milestones, particularly the Industrial Revolution. Yet when we ask why the Industrial Revolution was a revolution, we find that it was not the machines. The primary reason why it was a revolutionary is that it led to great social change. It gave rise to mass production and, through mass production, to a society in which wealth was not confined to the few.

In somewhat similar fashion, computers promise to revolutionize the structure of American life, particularly as they free the human mind and open new possibilities in knowledge and communication. The industrial Revolution supplemented and replaced the muscles of humans and animals by mechanical methods. The computer extends this development to supplement and replace some aspects of the mind of human beings by electronic methods. It is the capacity of the computer for solving problems and making decisions that represents its greatest potential and that poses the greatest difficulties in predicting the impact on society.

Norwalk-like viruses caused horrors among people.

Norwalk-like viruses can be eliminated by CDC.

Norwalk-like viruses casually appear on vessels.

Norwalk-like viruses co-exist with gastrointestinal illness.

The "MyDoom" virus could presage a generation of computer attacks by organised gangs aiming to extract ransoms from online businesses, experts said yesterday.

The warning came as the website run by SCO, a company that sells Unix computer software, in effect disappeared from the web under a blizzard of automated attacks from PCs infected by the virus, which first appeared a week ago.

The "MyDoom-A" version of the virus is reckoned to be the worst to have hit the internet, in terms of the speed of its spread, with millions of PCs worldwide believed to be infected. Such "zombie" machines begin to send out hundreds of copies of the virus every hour to almost any e-mail address in their files.

On Sunday they began sending automated queries to SCO’s website, an attack that will continue until 12 February. The attack is the web equivalent of ringing the company’s doorbell and running away a million times a second, leaving its computers unable to deal with standard requests to view its pages.

"You have to wonder about the time limit," said Graham Cluley, senior technology consultant at the antivirus company Sophos. "Someone could go to SCO after the 12th and say, ’If you don’t want this to happen again, here are our demands’." Raimund Genes, European president of the security software firm Trend Micro, said: "Such a programme could take out any major website on the internet. It’s not terrorism, but it is somebody who is obviously upset with SCO"

SCO has earned the enmity of computer users through a lawsuit it has filed against IBM. SCO claims ownership of computer code it says IBM put into the free operating system Linux, and is demanding licence fees and damages of $1bn.

Mr. Cluley said: "It might be that whoever is behind this will say to SCO, ’if you don’t want the next one to target you, drop the lawsuit’." SCO has offered $250,000 (￡140,000) for information leading to the arrest of the person or people who wrote and distributed MyDoom.

Nell Barrett, of the security company Information Risk Management, said, "I would give a lot of credence to the idea of gangs using viruses to extort money. It’s hard for law enforcement to track them down, because they’re using machines owned by innocent people."

A second variant of MyDoom will start attacking part of Microsoft’s website later today. The antivirus company MessageLabs said it had blocked more than 16 million copies of the virus in transit over the net so far. But millions more will have reached their targets.

某单跨预应力钢筋混凝土屋面简支梁，混凝土强度等级为C40，计算跨度L₀=17.7m，要求使用阶段不出现裂缝。

当超过梁高的错层部分面积大于该楼层总面积的30%时，属于平面不规则

顶层及其他楼层局部收进的水平尺寸大于相邻下一层的25%时，属于竖向不规则

抗侧力结构的层间受剪承载力小于相邻上一层的80%时，属于竖向不规则

平面不规则或竖向不规则的建筑结构，均应采用空间结构计算模型