问答题
汽环有何作用？试述汽环的密封原理？
发布日期：2021-03-23
试题解析
密封
密封，指严密地封闭。语出晋葛洪《抱朴子·金丹》：“又尹子丹法：以云母水和丹，密封致金华池中，一年出，服一刀圭，尽一斤得五百岁。”密封可分为静密封和动密封两大类。密封是防止流体或固体微粒从相邻结合面间泄漏以及防止外界杂质如灰尘与水分等侵入机器设备内部的零部件或措施。 静密封指严密地封闭密封舱密封容器用于密封函件和遗嘱的印章。
- 中文名
- 密封
- 解释
- 严密地封闭
- 分类
- 静密封和动密封
- 外文名
- seal
- 出处
- 《抱朴子·金丹》
- 目的
- 防止流体或固体微粒从相邻结合面间泄漏以及防止外界杂质等侵入
有何
有何，读音yǒu hé，汉语词语，意思是有什么。
- 中文名
- 有何
- 注音
- ㄧㄡˇ ㄏㄜˊ
- 拼音
- yǒu hé
- 释义
- 有什么
原理
原理，现任哈尔滨市南岗区审计局二级调研员。
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The number of speakers of English in Shakespeare’s time is estimated (估计) to have been about five million. Today it is estimated that some 260 million people speak it as a native language, mainly in the United States, Canada, Great Britain, Ireland, South Africa, Australia and New Zealand. In addition to the standard varieties of English found in these areas, there are a great many regional and social varieties of the language as well as various levels of usage that are employed both in its spoken and written forms. In fact, it is impossible to estimate the number of people in the world who have acquired an adequate (足够的) working knowledge of English in addition to their own languages. The purpose for English learning and the situations in which such learning takes place are so varied that it is difficult to explain and still more difficult to judge what forms an adequate working knowledge for each situation. The main reason for the widespread demand for English is its present-day importance as a world language. Besides serving the indefinite needs of its native speakers, English is a language in which some of important works in science, technology, and other fields are being produced, and not always by native speakers. It is widely used for such purposes as meteorological and airport communications, international conferences, and the spread of information over the radio and television networks of many nations. It is a language of wider communication for a number of developing countries, especially former British colonies. Many of these countries have multilingual populations and need a language for internal communication in such matters as government, commerce, industry, law and education as well as for international communication and for entrance to the scientific and technological developments in the West.What forms an adequate working knowledge of English
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