单级离心泵壳的作用是什么？

既用治热病神昏、癫痫痰闭证，又用治肝胆湿热黄疸证的药物是（）。

A.姜黄

B.茵陈

C.黄连

D.郁金

E.栀子

在下列说法中，不是影响设备购买的主要因素是( )。

A．设备的购置价格
B．设备的年运转费用
C．保险费
D．折旧费

Astronaut Jim Voss has enjoyed many memorable moments in his career, including three space flights and one space walk. But he recalls with special fondness a decidedly earthbound experience in the summer of 1980, when he participated in the NASA-AS-EE Summer Faculty Fellowship Program. Voss, then a science teacher at West Point, was assigned to the Marshall Space Flight Center’s propulsion lab in Alabama to analyze why a hydraulic fuel pump seal on the space shuttle was working so well when previous seals had failed. It was a seemingly tiny problem among the vast complexities of running the space program. Yet it was important to NASA because any crack in the seals could have led to destructive results for the astronauts who relied on them.

"I worked a bit with NASA engineers," says Voss, "but I did it mostly by analysis. I used a handheld calculator, not a computer, to do a thermodynamic analysis. "At the end of the summer, he, like the other NASA-ASEE fellows working at Marshall, summarized his findings in a formal presentation and detailed paper. It was a valuable moment for Voss because the ASEE program gave him added understanding of NASA, deepened his desire to fly in space, and intensified his application for astronaut status.

It was not an easy process. Voss was actually passed over when he first applied for the astronaut program in 1978. Over the next nine years he reapplied repeatedly, and was finally accepted in 1987. Since then he has participated in three space missions. The 50-year-old Army officer, who lives in Houston, is now in training for a four-month mission as a crew member on the International Space Station starting in July 2000.

Voss says the ASEE program is wonderful for all involved. "It brings in people from the academic world and gives NASA a special property for a particular period of time. It brings some fresh eyes and fresh ideas to NASA, and establishes link with our colleges and universities," Voss explains. "There’s an exchange of information and an exchange of perspectives that is very important."

For the academic side, Voss says, the ASEE program also "brings institutions of higher learning more insight into new technology. We give them an opportunity to work on real-world problems and take it back to the classroom. \

How many flights will Voss have finished if his four-month mission starting in July 2000 ends up successfully ？（）

A. Three

B. Two

C. Four

D. five

手动变速器互锁装置是作用是防止手动变速器同时挂进两个档。

“轮机”一词的含义是怎样演变的？