In the sentence “In some designs the cylinder oil is timed so that the oil injects only on the piston ring belt.” The "piston ring belt" means _____.
A. piston crown
B. piston ring groove
C. piston skirt
D. piston ring area
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A diesel engine using lube oil with too high a viscosity will exhibit ____.
A. increased starting difficulty in cold weather
B. increased oil consumption
C. thickening at higher operating temperatures
D. minimal friction losses
The ability of lubricating oils to resist viscosity changes during temperature changes is indicated by the _______.
American Petroleum
B. viscosity index number
C. Seconds Saybolt Furol number
D. Seconds Saybolt Universal number
The function of lubricating oil is to ___.
A. reduce friction between moving surfaces
B. provide even distribution of bearing wear
C. reduce the accumulation of harmful detergents
D. maintain a constant oil temperature output at each bearing
某企业拟新建一项目,有两个备选方案技术上可行。甲方案投资5000万元,计算期15年,净现值为200万元;乙方案投资8000万元,计算期20年,净现值为300万元,基准贴现率为10%。则关于两方案比选的方法说法正确的是
A. 甲方案投资少于乙方案,净现值大于零,故甲方案较优
B. 乙方案净现值大于甲方案,且都大于零,故乙方案较优
C. 甲方案计算期较短,说明甲方案的投资回收速度快于乙方案
D. 乙方案净年值大于甲方案,且都大于零,故乙方案较优
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