[八年级英语作文 my dream]Everyone has a dream. Now I want to say something about my dream. What is my dream? I often ask myself. In my mind, everyone shall have his own dream. I think t...+阅读

噪音污染 We know the sounds of cities are loud enough to cause great harm to people's hearing in the U. S. One person out of twenty has got some hearing loss. And all over the world the situation is getting worse and worse all the time since the noise increases with the population. With the development of machines, noise has also increased greatly in the 20th century. We live surrounded by loud planes, trucks and electric tools. TV sets and radios add up to 90 or J00 decibels, a certain unit used to measure the loudness of sound. A normal dialogue reaches 55 decibels; a plane goes to 100, and an ordinary train, reaching the station, can be twice as loud as the loudest plane. Disco music reaches about 118. At decibels the ear stops hearing sound, and pain starts. How terrible if things go on like this！ 电脑病毒 Computer Virus A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user. The original may modify the copies or the copies may modify themselves, as occurs in a metamorphic virus. A virus can only spread from one computer to another when its host is taken to the uninfected computer, for instance by a user sending it over a network or carrying it on a removable medium such as a floppy disk, CD, or USB drive. Additionally, viruses can spread to other computers by infecting files on a network file system or a file system that is accessed by another computer. Viruses are sometimes confused with computer worms and Trojan horses. A worm, however, can spread itself to other computers without needing to be transferred as part of a host. A Trojan horse is a file that appears harmless until executed. In contrast to viruses, Trojan horses do not insert their code into other computer files. Many personal computers are now connected to the Internet and to local-area networks, facilitating their spread. Today's viruses may also take advantage of network services such as the World Wide Web, e-mail, and file sharing systems to spread, blurring the line between viruses and worms. Furthermore, some sources use an alternative terminology in which a virus is any form of self-replicating malware. The term comes from the term virus in biology. A computer virus reproduces by making (possibly modified) copies of itself in the computer's memory, storage, or over a network. This is similar to the way a biological virus works. Some viruses are programmed to damage the computer by damaging programs, deleting files, or reformatting the hard disk. Others are not designed to do any damage, but simply replicate themselves and perhaps make their presence known by presenting text, video, or audio messages. Even these benign viruses can create problems for the computer user. They typically take up computer memory used by legitimate programs. As a result, they often cause erratic behavior and can result in system crashes. In addition, many viruses are bug-ridden, and these bugs may lead to system crashes and data loss. There are many viruses operating in the general Internet today, and new ones are discovered every day.

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