电气化铁路的输电线常用图所示的方式悬挂在钢缆上.钢缆的A端固定在电杆上,B端连接

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问题:

电气化铁路的输电线常用图所示的方式悬挂在钢缆上.钢缆的A端固定在电杆上,B端连接在滑轮组上.滑轮组由a、b、c三个滑轮构成,配重P由多个混凝土圆盘悬挂在一起组成,配重的总重为G,若不计摩擦和滑轮的重量,则以下说法中正确的是(  )

A.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G

B.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为G

C.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G

D.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为G

考点:定滑轮及其工作特点动滑轮及其工作特点
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病程相对较长,中毒症状多不明显,洞壁较厚,多呈偏心空洞,内壁凹凸不平,空洞周围多无炎性浸润。()

A.空洞性肺结核,继发感染

B.支气管肺癌

C.囊肿继发感染

D.肺脓肿

E.细菌性肺炎

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Today’s lecture is about the mass (1) of the world’s population. There are two major (2) why people are moving to cities. The first reason is (3) . People are moving to the cities because that’s where they can find (4) and earn money. The second reason for the move to cities has to do with (5) of life issues: comfort and (6) . Cities often offer better (7) . And then for many, city life is just more (8) . An interesting consequence of urbanization is that the average (9) of people in the countryside is increasing, while that of the cities is (10) .
Three key (11) can be identified in our cities. First of all, they’re getting bigger. Most cities are bigger now than ever before. Cities are also changing shape. They’re getting (12) , because land is getting more and more expensive. (13) have become a symbol of modern cities.
Cities are also changing shape in other ways. The (14) Model and the (15) Nuclei Model are probably more typical of the cities we know today. They show the urban (16) that’s occurring in contemporary cities.
The third change is that our cities are breaking up into (17) communities, often by (18) group or (19) level. This often means that people stay within their community and do not come into contact with others from different (20) .

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以下因素可影响钾在细胞内外分布,除外()

A.糖代谢

B.体液pH

C.脂肪代谢

D.消化功能

E.肾和呼吸功能

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发电机组保护接地应完好有效;排烟管按《汽车加油加气站设计与施工规范》,接出(),并装()。

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稻草绳草把、稻草垫主要作为一次性()使用。

A.苫盖材料

B.加固装置

C.防滑衬垫

D.防磨衬垫

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