Timothy Hall,毕业于美国哥伦比亚大学,英语语言学专业硕士。
Arthur H. Milch,美国新泽西学院TESOL专业教育学硕士。
Denise McCormack,美国新泽西学院TESOL专业教育学硕士。
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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京东的包装真的超级放心!一点都没有损坏!以后买书也要认准京东了(?????????)新东方自营店嘻嘻当然放心是正版(?????????)
评分买了一堆,不知道看完要何年何月了,慢慢来吧,我的托福可全靠这一堆了!
评分 评分准备7月份得托福考试,希望做题有用哈
评分运货速度快,东西很好,好评。
评分给学生买的,学生说不错,阅读从初级中级高级练习,循序渐进。
评分仅1988~1989年度,全世界就有56万多人参加了TOEFL考试,全球170多个国家和地区共设立了1700多个TOEFL考试中心。至今为止,美国和加拿大共有2300多所院校规定,凡是外国学生申请到该校入学学习的,必须提供T0EFL,GRE,GMAT或TSE的某一项或两项标准化考试证明,只有达到学校所要求成绩的报考者,才能取得入学和申请奖学金的资格。除了美国、加拿大等大部分国家的高等院校外,欧洲(如英国)、大洋洲(如澳大利亚、新西兰)以及东南亚一些国家和地区也都已承认TOEFL考试成绩。近几年来,国内的联合国驻华机构和外企及合资企业在聘录用职员时,或国际基金组织在测试职员的英语水平时,也都采用TOEFL考试成绩。[2]
评分新东方的,我相信是好的。书的印刷质量不错,送货也快。
评分买了一堆,不知道看完要何年何月了,慢慢来吧,我的托福可全靠这一堆了!
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