本讲主要内容： 置换密码（列置换密码和周期置换密码） 代换密码（单表代换密码、多表代换密码和维尔姆密码） 典型传统密码的分析（统计分析法和明文-密文对分析法）

Objectives Students will be able to: 1. understand the main idea(cloning is a two- edged sword) and structure of the text; 2. appreciate the writing strategies employed by the author, 3. master the key language points and grammatical structures in the text;

Students will be able to: 1. understand the main idea and structure of the text; 2. appreciate how the repeated use of clues helps weave a piece of narration together; 3. grasp the key language points and grammatical structure in the text

Students will be able to 1. understand the main idea and the structure of the text. 2 earn to memorize words in association 3. grasp the key language points and grammatical structures in the text 4. conduct a series of reading, listening speaking and writing activities related to the theme of the unit

At least 90 percent of UFO sightings can be identified as conventional objects, although time-consuming investigations are often necessary for such identification. The objects most often mistaken for UFOs are bright planets and stars aircraft, birds, balloons kites aerial flares, peculiar clouds, meteors and satellites. The remaining sightings most likely can be attributed to other mistaken sightings or to inaccurate reporting hoaxes or delusions although to disprove all claims made about UFOs is impossible

And so even though we face the difficulties of today and tomorrow, I still hay a dream. It is a dream deeply rooted in American dream. I have dream that one day this nation will rise up and live out the true meaning of

1. grasp the main idea( tolerance for solitude and energy made it possible for the writer s family to enjoy their pleasant but sometimes harsh country life.) 2. appreciate the various techniques employed by the writer comparison and contrast, topic sentences followed by detail sentences

grasp the main idea(we should adopt a sensible environmentalism) and the structure of the text(each part containing a contrast) 2)appreciate the various argumentative skills employed in the text 3master the key language points and grammatical structures in the text

Pm Going to Buy the Brooklyn Bridge Teaching Objectives grasp the main idea(the belief in superwomen encourages average women to achieve their goals)and the structure of the text 2) appreciate how the author achieves coherence for her essay 3master the key language points and grammatical structures in the text

文章从众多自由度系统的特定时空尺度大气现象与观测事实密切结合的角 度,对大气科学中非线性与复杂性研究的进展进行了评述,依次讨论了从确定论走向 不确定、混沌中的有序和全球变化等,并就该领域存在的问题和发展前景进行了探讨