问题 问答题 简答题

纳米摩擦学

答案

参考答案:

纳米摩擦学,也称为微观摩擦学或分子摩擦学,它是在原子、分子尺度上研究摩擦界面上的行为、损伤及其对策。纳米摩擦学是90年代兴起的纳米技术的重要分支,有着广泛的应用需求。随着精密机械和高新技术装备的发展,特别是纳米科技所推动的新兴学科为纳米摩擦学的产生提供了一种新的研究模式和研究领域,具有广阔的发展前景。然而摩擦学的宏观研究直接面向机械产品性能提高,因而仍然是本学科现阶段主要研究领域。随着纳米摩擦学的深入发展,并实现宏观与微观研究的有机结合,必将促进摩擦学进一步完善,从而更大限度地发挥其在国民经济中的巨大潜力。

单项选择题 案例分析题

The food we eat seems to have profound effects on our health.Although science has made enormous steps in making food more fit to eat ,it has, at the same time,made many foods unfit to eat. Some research has shown that perhaps eighty percent of all human illnesses are related to diet and forty percent of cancer is related to the diet as well,especially cancer of the colon. Different cultures are more likely to cause certain different illnesses because of the food that is characteristic in these cultures. That food is related to illness is nto a new discovery. In 1945, about 35 years ago, government researchers realized that nitrates, commonly used to preserve color in meats,and other food additives,caused cancer. Yet, these carcinogenic additives remain in our food, and it becomes more difficult all the time to know which things on the packaging labels of processed food are helpful or harmful. The additives which we eat are not all so direct. Farmers often give penicillin to beef and living animals, and because of this ,penicillin has been found in the milk of treated cow. Sometimes similar drugs are given to animals not for medical purposes,but for financial reasons. The farmers are simply trying to fatten the animals in order to obtain a higher price on the market. Although the Food and Drug Administration(FDA) has tried repeatedly to control these procedures, the practices continue.

What are nitrates used for?()

A.They preserve flavor in packaged foods.

B.They preserve the color of meats.

C.They are the objects of research.

D.They cause the animals to become fatter.

单项选择题