问题 单项选择题

Intel 8251A不可以工作在______ ( )

A.同步方式

B.异步方式

C.全双工方式

D.半双工方式

答案

参考答案:D

解析: Intel8251A是通用同步/异步数据接收发送器(USART),广泛应用与微型计算机中作为可编程串行通信接口电路,它可以工作在同步方式、异步方式和全双工方式,不可以工作在半双工方式下。

单项选择题
阅读理解

阅读理解。

      A Battery's Nightmare

      Portable electronics that can be carried about easily are only as good as their batteries (电池) and, let's

face it, batteries aren't very good, especially when compared with, say, petrol, which packs 100 times a

battery's energy into an equal space. That's why a large group of mechanical engineers (centered at the

Massachusetts Institute of Technology, but with partners at other universities and companies) are hard at

work in an effort to replace batteries with a tiny engine that runs on fuel. Imagine a battery-free life! When

the fuel runs out in your mobile phone, you just fill up and go.

     The engine-about the size of a ten-cent coin-starts with a combustion chamber (燃烧室) that burns

hydrogen. Its tiny parts are etched (蚀刻) onto silicon wafers (硅片) in the same manner that computer

parts are etched onto integrated circuits (集成电路). The first engine is made up of five wafers. And since

these wafers could be produced in much the same way as computer chips, they could probably be produced

quite cheaply.

      But the devil in all this nice detail is efficiency. Tiny engine parts don't always behave like the bigger parts

of the first engine. Something between the parts can slow down the works, according to Columbia University

Professor LucFrechette, one of the engine's designers. Extreme heat from the combustion chamber is also a

problem, often leaking to other parts of the engine.

     The scientists' goal is to create an engine that will operate 10 times better than batteries operate. Frechette

says that a complete system, with all parts in place and working, will be set up in the next couple of years,

but commercial models aren't likely until at least the end of the next ten years.

1. According to the passage, the title suggests that ______. [ ]

A. batteries should be greatly improved

B. petrol will be used instead of batteries

C. the time of batteries will be gone forever

D. pollution problems caused by batteries must be solved

2. What's the meaning of the underlined word "devil" in paragraph 3? [ ]

A. Problem

B. Advantage

C. Invention

D. Technique

3. What can we infer from the passage? [ ]

A. The new invention doesn't need any fuel.

B. The new engine has been produced in large quantities.

C. The new invention is much cheaper than the battery.

D. The new engine needs to be improved before it's on sale.