问题 问答题 简答题

JZ--7型制动机的主要特点有哪些?

答案

参考答案:

(1)即能适用客运机车也能适用货运机车;

(2)它属自动保压形式.在结构上采用橡胶膜板和柱塞结构,因而方便了制动机的使用、维护、

检修和延长了定检期限.

(3)分配阀采用了二压力与三压力混合型式的机构,适用于现代机车制动缸容量的要求,使制动缸压力不随制动缸容积大小变化,不论机车在列车中的联挂位置如何,均能得到相同的制动缸压力,当制动缸漏泄时,能自动补充,具有良好的制动不衰性,施行非常制动后,具有增压作用,并且有阶段缓解和一次缓解作用.

(4)自阀设有二位阀,使列车制动后保压时,能切断或开通制动管的补气性能

(5)为适应长大货物列车的需要,设有过充位,以缩短制动管副风缸的初充气和再充气的时间;

(6)由于增大了向制动管充气和排气的有效面积,因此较旧型制动机具有充气快,排气快的特点.

单项选择题

As Philadelphia grew from a small town into a city in the first half of the eighteenth century, it became an increasingly important marketing center for a vast agricultural hinterland. Market days (1) the crowded city even more crowded, as farmers from within a (2) of 24 or more kilometers brought their sheep, vegetables, cider and other products for direct sale to the (3) . The High Street Market was continuously (4) throughout the period until 1736, (5) it (6) from Front Street to Third. By 1745 New Market was opened on Second Street. The next year the Callow Hill Market began (7) .

Along with market days, the (8) of twice-yearly fairs persisted in Philadelphia (9) after similar trading days had been discontinued in other colonial cities. The (10) provided a means of bringing handmade goods from (11) places to would-be buyers in the city. Linens and stockings from Germantown, (12) , were popular items.

Auctions were another popular (13) of trade. Because of the competition, retail (14) opposed these as well as the fairs. (15) governmental attempts to eradicate fairs and auctions were less than successful, the ordinary (16) of economic development was on the merchants’side, as increasing business specialization became the (17) of the day. Export merchants became differentiated from their importing counterparts, and specialty shops began to appear (18) general stores selling a variety of goods.

One of the reasons Philadelphia’s merchants prospered was because the surrounding area was undergoing tremendous economic and demographic growth. They did their business, (19) , in the capital city of the province, (20) to not only the governor and his circle, but citizens from all over the colony.

4()

A.envisioned

B.endangered

C.enriched

D.enlarged

应用设计题