Timothy Hall,畢業於美國哥倫比亞大學,英語語言學專業碩士。
Arthur H. Milch,美國新澤西學院TESOL專業教育學碩士。
Denise McCormack,美國新澤西學院TESOL專業教育學碩士。
The principles making radio possible were developed throughout the nineteenth century. The first breakthrough was by the British physicist Michael Faraday in 1831. He discovered that when an electric current passes through one wire, it produces a current in another wire even though the wires do not touch each other. In 1864, James Maxwell showed that this current——composed of electromagnetic waves——travels at the speed of light. Heinrich Hertz proved that the waves pass through solid objects. With these discoveries in place, the race was on to develop a system of wireless radio.
Among the contenders was Reginald Fessenden, a Canadian inventor. Fessenden began experimenting with radio detectors in order to explore the possibility of voice transmission. In 1900, he was the first person to transmit his voice, but the sound was unrecognizable because the waves were not continuous. He invented a barreter detector, taking its name from the French word exchanger, to receive AM (amplitude modulated) signals, but it was not sensitive enough. One day in 1901, he accidentally left a filament of wire in acid for too long until only a tip of the wire was in contact with the acid. Fessenden noticed that, with the wire in the acid, the barreter was very sensitive to nearby continuous radio waves.
Fessenden called his invention a liquid barreter, but it became known as an electrolytic detector. The detector consisted of several connected parts forming an electric circuit. A silver-coated platinum wire was dipped into a small platinum cup filled with nitric or sulfuric acid and connected to the ground. A battery was connected between the wire and the acid, prompting a current to flow in the detector. Someone wearing headphones that were hooked up to the detector could hear a hissing noise, which could be adjusted by turning a dial until the hissing noise stopped. At that point, the detector was highly sensitive to incoming radio waves.
……
本係列叢書從托福考試所考查的聽、說、讀、寫四項技能入手,為考生提供詳盡的考試指導,並將各技能分為初、中、高三級,通過獨特的“進階訓練”方式,再輔以大量練習,幫助考生逐步掌握托福實考的技巧,同時切實提高英語實際運用能力,從而在短期內輕鬆取得托福高分。本叢書內容編排由易到難,循序漸進,實戰性強,是不可多得的托福備考資料。
評分2005年9月,美國教育考試服務中心ETS在全球推齣瞭一種全新的綜閤英語測試方法,即能夠反映在一流大專院校教學和校園生活中對語言實際需求的新托福考試,即TOEFL iBT(Internet Based Test)。
評分書本已經收到瞭質量很好啊!
評分給學生買的,學生說不錯,閱讀從初級中級高級練習,循序漸進。
評分這係列的人復習資料還是不錯的,推薦英語基礎弱的人先做這個再刷原題!
評分好,,,,,,,,,,,,,,,,
評分買瞭一個係列很多本,最近一本一本買的……趕緊看啊
評分本係列叢書從托福考試所考查的聽、說、讀、寫四項技能入手,為考生提供詳盡的考試指導,並將各技能分為初、中、高三級,通過獨特的“進階訓練”方式,再輔以大量練習,幫助考生逐步掌握托福實考的技巧,同時切實提高英語實際運用能力,從而在短期內輕鬆取得托福高分。本叢書內容編排由易到難,循序漸進,實戰性強,是不可多得的托福備考資料。
本站所有内容均为互联网搜索引擎提供的公开搜索信息,本站不存储任何数据与内容,任何内容与数据均与本站无关,如有需要请联系相关搜索引擎包括但不限于百度,google,bing,sogou 等
© 2025 book.tinynews.org All Rights Reserved. 静思书屋 版权所有