未分类题

在现代通信技术中，数字信号可以进行数字传输，也可以进行模拟传输。实现数字信号转变成模拟信号的技术称为
A．调制 B．解调 C．编码 D．解码

A.调制
B.解调
C.编码
D.解码

【参考答案】

A
在信号的变换中，将数字信号转变成适合模拟信道传输的模拟信号称为调制，反之称为解调。将模拟信号采样并转变成数字......

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单项选择题

Year after year a dedicated Swedish chemist worked to find a substance which, when【C1】______nitroglycerine (硝化甘油), would make explosives safer to handle【C2】______weakening their force. He had a personal【C3】______scientific reason to pursue his search, because his【C4】______brother had been killed when a can of nitroglycerine【C5】______exploded. The oily liquid had been 【C6】______for so many disasters that its【C7】______ had finally been outlawed by many countries. While【C8】______a new formula one morning, the doctor broke a test tube and gashed (划开) his finger. He was daubing (涂搽) the【C9】______with collodion (火棉胶), a coating solution of gun-cotton dissolved in ether-alcohol (乙醚),【C10】______the idea struck him —mix collodion with the nitroglycerine!【C11】______was the answer. The new mixture,【C12】______blasting gelatine (爆胶), was not only【C13】______safe to handle as dynamite, but it was also one-and-a-half times more powerful! In fact, so powerful 【C14】______ that it paved the way for a whole new【C15】______in construction and engineering. Mines were【C16】______, roads were built, and canals were cut at a speed once【C17】______impossible. It had another use, also —death and destruction in warfare. Its inventor had believed that the power of his new【C18】______ would so awe the military mind that it would actually be a deterrent (威慑物) to war.【C19】______it became a weapon that brought death to millions of soldiers and【C20】______.【C1】A．mixing withB．mixed withC．was mixing withD．was mixed with

A.
B.【C19】______it
C.
【C1】
A．mixing
D.mixed
E.was
F.was

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