问题 问答题 简答题

热态启动对冲转时参数如何规定?

答案

参考答案:

机侧过热蒸汽温度高于汽轮机高压内缸上缸内壁温度50-100℃,再热蒸汽温度高于中压上缸内壁温度30-50℃,并至少具有50℃以上的过热度时,汽轮机即可冲转。

选择题
单项选择题

A total of 4.6 million digital televisions have been sold, and the sales of HDTV sets have quadrupled since last year. Consumers have bought HDTVs to play their DVDs and to have clearer pictures and wide screens. Only a small percentage of the people who have purchased HDTVs, however, have actually hooked their TVs up to receive high-definition television digital signals. Perhaps television viewers are having trouble keeping up with the changes in technology. Even the manufacturers of HDTVs, like Mitsubishi, Thomson Multimedia, Sony, and Samsung seem to have a tough time learning how to make their sets work with the various digital TV formats because little standardization has been required or implemented in the industry.

Some of the HDTVs weigh over 200 lbs., and a variety of retailers offer a delivery service to the buyer’s home to help install the heavy sets. This is known as a white-glove service and usually comes with an extra fee. After HDTV purchasers get their sets home and hook them up, they will still need to work to get the digital signals to their systems. Most of the industry’s cable providers do not yet offer high~definition programing, and only about 15% of commercial television stations have switched over to even the lowest improved digital pictures. Worse yet, viewers may need to install antenna before they can even get the digital signals to their new HDTV sets. Another frustration for home-theater seekers is that the current HDTV sets allow owners only to watch high-definition programs, not to record them.

According to the passage, which of the following offers most of the HDTV programmes so far().

A. Retailer delivery services.

B. Cable providers.

C. Commercial television stations.

D. HDTV set manufacturers.