问题 问答题 简答题

汽轮机调速系统为什么必须设反馈装置?

答案

参考答案:

在汽轮机的调节系统中,滑阀的位移,使油动机动作。而油动机的动作又反过来影响滑阀的位移,这种作用叫反馈作用。反馈作用是汽轮机自动调节中保持调节动作能稳定下来的一个重要组成部分。如果没有反馈作用,调节系统将无法工作。

单项选择题 A1/A2型题
单项选择题

Don’t have time to read anymore Now you can get free, quick literature via email. More than 100,000 people open their email each day to read a chapter of a book, through Chapter-A-Day, an online book club created two years ago. It’s a free email service that provides a short daily reading for busy people, exposing them to literature they may not find on their own, inspiring some to recommit to the reading habit. About 550 public library systems representing over 3,000 branch libraries already have signed up to offer Chapter-A-Day. Via email, participants get about five minutes’ worth of reading every day. After three chapters are emailed, the installments stop, and those who want to keep reading can borrow the book at their public library or purchase it online. Chapter-A-Day has eight free book clubs, and sells thousands of books each month.

Chapter-A-Day started in 1999 when Suzanne Beecher, a lifelong book lover, realized how many of the women who worked part-time for her software development company didn’t have time in their busy lives to read. She decided to type part of a chapter of a book, and send it to her employees through email. The next day she typed a little more, and continued to send literary installments each day. She says she started getting feedback from the staff about how reading made them feel. "They were interested, and realized that, though they didn’t have time in their busy lives for reading, just reading that little bit each day got them back in the habit." Realizing that many other people could benefit, she decided to take the idea even further and start an email "chapter-a-day" book club to help others ease their way back into daily reading. "Reading makes changes in people’s lives," Beecher says.

Pat Dempsey, a librarian at a public library in Ohio, has found Chapter-A-Day helps her library clients get back in the habit of reading. "It’s a different way to get people hooked on hooks," she says.

The word "installment" in the passage probably means" () ".

A. a library email

B. a rare piece of literature

C. a free novel

D. a part of a book