[判断题]火灾危险是指消防系统中存在可能造成人员伤害、财产损失、作业环-我要搜题网

[判断题]和谐型电力机车正常运行时，辅助变流器1工作在CVCF方式，辅助变流器2工作在VVVF方式，分别为机车辅助电动机供电。
A.正确
B.错误

[单选题]表面粗糙度代号中的数字及符号方向应与标注尺寸( )。
A.没规定
B.成一定角度
C.相反
D.必须一致

[简答题]公安消防机构对不合格工程的复验要求？

[多项选择]蓄电池电压过低，所造成现象是（）。
A. 起动发电机转速低
B. 起机时电压表指针急剧下降
C. 柴油机起不了机
D. 起机后不能发电

[不定项选择题]共用题干 Late-Night Drinking
Coffee lovers beware .Having a quick"pick-me-up"cup of coffee late in the day will play havoc with your sleep.As well as being a stimulant,caffeine interrupts the flow of melatonin,the brain hormone that sends people into a sleep.
Melatonin levels normally start to rise about two hours before bedtime.Levels then peak be-tween 2 a.m.and 4 a. m.,before falling again."It's the neurohormone that controls our sleep and tells our body when to sleep and when to wake,"says Maurice Ohayon of the Stanford Sleep Epidemiology Research Center at Stanford University in California. But researchers in Israel have found that caffeinated coffee halves the body's levels of this sleep hormone.
Lotan Shilo and a team at the Sapir Medical Center in Tel Aviv University found that six vol- unteers slept less well after a cup of caffeinated coffee than after drinking the same amount of de-caf（脱因咖啡）.On average , subjects slept 336 minutes per night after drinking caffeinated cof-fee,compared with 415 minutes after decaf. They also took half an hour to drop off-twice as long as usual-and jigged around in bed twice as much.
In the second phase of the experiment,the researchers woke the volunteers every three hours and asked them to give a urine sample,Shilo measured concentrations of a breakdown product of melatonin .The results suggest that melatonin concentrations in caffeine drinkers were half those in decaf drinkers.In a paper accepted for publication in Sleep Medicine,the researchers suggest that caffeine blocks production of the enzyme that drives melatonin production.
Because it can take many hours to eliminate caffeine from the body,Ohayon recommends that coffee lovers switch to decaf after lunch. Which of the following tells us how caffeine affects sleep?
A.Caffeine blocks production of the enzyme that stops melatonin production.
B.Caffeine interrupts the flow of the hormone that prevents people from sleeping.
C.Caffeine halves the body's levels of sleep hormone.
D.Caffeine stays in the body for many hours.

[判断题]火灾危险是指消防系统中存在可能造成人员伤害、财产损失、作业环境破坏勤或其他损失的根源或状态，如危险环境、危险条件、危险状态等。A.正确B.错误

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[判断题]火灾危险是指消防系统中存在可能造成人员伤害、财产损失、作业环境破坏勤或其他损失的根源或状态，如危险环境、危险条件、危险状态等。
A.正确
B.错误