Good evening. Tonight, I can report to the American people and to the world that the United States has conducted an operation that killed Osama bin Laden, the leader of al Qaeda, and a terrorist who’s responsible for the murder of thousands of innocent men, women, and children. 晚上好。今天晚上，我終于能向美國人民和全世界宣布，美國指揮的一項行動已經將基地組 織的頭目，為成千上萬美國無辜的男人女人和兒童的死亡負責的奧薩馬·本·拉登擊斃。 It was nearly 10 years ago that a bright September day was darkened by the worst attack on the American people in our history. The images of 9/11 are seared into our national memory -- hijacked planes cutting through a cloudless September sky; the Twin Towers collapsing to the ground; black smoke billowing up from the Pentagon; the wreckage of Flight 93 in Shanksville, Pennsylvania, where the actions of heroic citizens saved even more heartbreak and destruction. 當年那個陽光明媚的九月被美國有史以來遭受的最慘重的恐怖襲擊遮蔽， 這件事距今就要有 十年了。 911 事件的情景一直留在我們全國人民的記憶中——被劫持的飛機劃過萬里無云的 九月晴空；雙子塔轟然倒塌；五角大樓冒出濃濃黑煙；93 航班上英勇的乘客們為了挽救更 多無辜生命采取行動讓飛機墜毀在賓夕法尼亞。 And ye
W:Well,today we have Professor chen and professor wei in our studio to talk about the Radar technical,good afternoon ,professors.
Radar is a variant of radio technology and has been widely utilized in various areas.we will helps you have a rough idea of what the radar technology is,how it came into being and where it has been applied. We mainly talk about the radar technical overvie:its general principles and the Cavity Magnetron,one of its critical devices,which can create high power high frequency electromagnetic pulses.
W1: Can you tell us the Radar technical’s devolop?
In 1888 Heinrich Hertz showed that the invisible electromagnetic waves radiated by suitable electrical circuits travel with the speed of light, and that they are reflected in a similar way. From time to time in the succeeding decades it was suggested that these properties might be used to detect obstacles to navigation, but the first successful experiments