问题 问答题 简答题

与正常停机相比,事故停机过程有何特点?一般事故停机与紧急事故停机有何差异?

答案

参考答案:

事故停机过程的特点是:主汽门和调节阀迅速关闭,负荷瞬间降到零,机组与电网解列,进入惰走阶段。一般事故停机与紧急事故停机的差异在于:打闸停机后,要不要立即破坏凝汽器的真空。

一般事故,允许机组继续转动,不需立即破坏凝汽器真空。按正常停机的惰走过程,适时停主抽气器,转速降到零时,凝汽器真空也降至零,停止向轴封供汽,投入盘车装置进行盘车。而紧急事故停机打闸停机后,要立即破坏凝汽器的真空,以增加转子的摩擦鼓风作用,使转速迅速降至零。

选择题
写作题

第三节:读写任务(共1小题,满分25分)

【阅读材料】                           

Billy and his part-time job

Billy is 14 years old and in his the ninth grade. He has a part-time job which gets him up every morning at 5 o’clock. He is a newspaper delivery boy.

In the winter it is still dark when he gets up, but during the rest of the year it is light. Bill must deliver the newspapers to the houses of the people on his route in all kinds of weather. He tries to put each paper on the porch where it will be protected from wind and rain of snow. All his customers think he does a good job.

Billy earns about $ 70 per month, and he is earning some of the money to go to college. He spends the rest on records and clothes. Once a month, he has to collect money from his customers. Since many of them work during the day, Billy has to collect the money in the evening. Sometimes, when Billy is ill, his brother has to deliver the newspapers. Once, his father has to help.

Billy has 70 customers now, but he hops to get more soon. Some day, if he gets more customers, Billy might win a prize for being an outstanding newspaper boy. He wants to win a trip to Europe, but he will still be happy if he only wins a new bicycle.

【写作任务】                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     

概括短文内容,30词左右。

就“学生是否该做兼职”发表看法,包括以下内容要点。120词左右。

(1). 列举现实生活中学生做兼职的情况。

(2). 分析学生做兼职的原因:

a). 兼职可以帮助解决贫困家庭孩子经济问题。

b). 可以丰富学生的社会经验。

c). 可以学以致用。

3. 你对兼职的看法,并说明理由。

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