凸轮实际工作廓线为什么会出现变尖现象?设计中如何避免?

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问题:

凸轮实际工作廓线为什么会出现变尖现象?设计中如何避免?

考点:机械工程机械原理机械原理题库
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一个两位小数,如果取它的近似值是5.8,这个数最大是______.

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Food sometimes gets poisoned with harmful things. A person who eats such food can get an illness called food poisoning. Food poisoning is usually not serious, but some types are deadly. The symptoms of food poisoning usually begin within hours of eating the poisoned food. Fever is one of the most common symptoms.

Certain microorganisms(微生物)cause most types of food poisoning. Bacteria and other microorganisms can poison eggs, meat, vegetables, and many other foods. After entering the body, these tiny living things release(释放)poisons that make people sick.

Some chemicals can also cause food poisoning. They are often added to food while it is being grown, processed, or prepared. For example, many farmers spray chemicals on crops to kill weeds and insects. Some people may have a bad reaction to those chemicals when they eat the crops.

Some plants and animals contain natural poisons that are harmful to people. These include certain kinds of seafood, grains, nuts, seeds, beans, and mushrooms.

When people handle food properly, the risk of food poisoning is very small. Microorganisms multiply rapidly in dirty places and in warm temperatures. This means that people should never touch food with dirty hands or put food on unwashed surfaces. Food should be kept in a refrigerator to stop microorganisms from growing. Meat needs to be cooked thoroughly to kill any dangerous microorganisms. People should also wash food covered with chemicals before eating it. Finally, people should not eat wild mushrooms or other foods that grow in the wild. Some of these foods may contain natural materials that are poisonous to humans. In addition, some types of fish can be poisonous.

Most people recover from food poisoning after a few days of resting and drinking extra water. If people eat natural poisons, they must go to the hospital right away to have their stomachs emptied.

1. Which of the following statements is NOT true?

A. Food when poisoned can make people sick.

B. Food poisoning means death.

C. Food poisoning comes in varieties.

D. Food poisoning can be serious.

2.We know from the passage that the symptoms of food poisoning__________.

A.are always accompanied by a fever

B.are too common to be noted

C.can be noticed within hours

D.can he ignored

3.Food poisoning can be caused by all the following EXCEPT__________

A.some chemicals

B.low temperatures

C.some tiny living things

D.certain natural materials

4.From Paragraph 5,we can learn that__________

A.mushrooms should not be eaten

B.vegetables are safer than meat and seafood

C.natural poisons are more dangerous than chemicals

D.different types of food should be handled differently

5.It can be inferred from the passage that__________

A.natural materials are safe in food processing

B.chemicals are needed in food processing

C.food poisoning can be kept under control

D.food poisoning is out of control

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代维人员可以随意着装参加代维工作,但必须佩带移动公司颁发的上岗证。()

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单位定期存款的利息计提为按月计提。每月()日终计提应付利息,以原币计提。实际支付存款利息时从计提的原币应付利息中列支。

A.20日

B.21日

C.30日

D.月末

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次氯酸钠用在循环水里起什么作用?

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