发表于2025-02-22
新東方·新托福考試專項進階:高級閱讀 pdf epub mobi txt 電子書 下載 2025
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.
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還不錯吧還好不錯可以用,比較官方權威的參考書
評分閱讀(Reading):有三篇文章
評分新東方的書,品質的保證
評分新東方的書,品質的保證
評分還行吧,質量還不錯,手感也不錯
評分書都是新的,希望自己能好好利用。
評分為瞭自學準備托福考試買的~包裝很好京東快遞優秀~
評分編寫的很好的一部書,難易適中,循序漸進,打摺下來也挺劃算,推薦
評分很不錯,希望有幫助
新東方·新托福考試專項進階:高級閱讀 pdf epub mobi txt 電子書 下載