電子信息科學與技術畢業(yè)論文之外文文獻翻譯 中英文對照

1、畢業(yè)設計說明書英文文獻及中文翻譯學生姓名： 學號： 0705014141 學 院： 信息與通信工程 專 業(yè)： 電子信息科學與技術 指導教師： 李建民 2011 年 6 月中北大學 2011 屆畢業(yè)設計說明書第 2 頁 共 16 頁unit for frequency is the hertz (Hz) ， defined

2、as events or cycles per second. The frequency of electrical signals is often measured in multiples of hertz， including kilohertz (kHz)， megahertz (MHz)， or gigahertz (GHz)， where 1 kHz equals one thousand (103) events pe

3、r second， 1 MHz equals one million (106) events per second， and 1 GHz equals one billion (109) events per second. A device that produces frequency is called an oscillator. The process of setting multiple oscillators to t

4、he same frequency is called synchronization.Of course， the three types of time and frequency information are closely related. As mentioned， the standard unit of time interval is the second. By counting seconds， we can de

5、termine the date and the time-of-day. And by counting events or cycles per second， we can measure frequency. Time interval and frequency can now be measured with less uncertainty and more resolution than any other physic

6、al quantity. Today， the best time and frequency standards can realize the SI second with uncertainties of ≈1×10-15.Physical realizations of the other base SI units have much larger uncertainties.Coordinated Universa

7、l Time (UTC) The world’s major metrology laboratories routinely measure their time and frequency standards and send the measurement data to the Bureau International des Poids et Measures (BIPM) in Sevres， France. The BIP

8、M averages data collected from more than 200 atomic time and frequency standards located at more than 40 laboratories， including the National Institute of Standards and Technology (NIST). As a result of this averaging， t

9、he BIPM generates two time scales， International Atomic Time (TAI)， and Coordinated Universal Time (UTC). These time scales realize the SI second as closely as possible. UTC runs at the same frequency as TAI. However， it