问题 问答题 简答题

润滑油有哪些功用?润滑油SAE5W-40和SAE10W-30有什么不同?

答案

参考答案:

润滑油有如下功用1润滑润滑油在运动零件的所有摩擦表面之间形成连续的油膜,以减小零件之间的摩擦。2冷却润滑油在流经零件工作表面时,可以降低零件的温度。3清洗润滑油可以带走摩擦表面产生的金属碎末及冲洗掉沉积在气缸活塞活塞环及其他零件上的积碳。

4密封附着在气缸壁活塞集活塞环上的油膜,可以起到密封防漏的作用。5防锈润滑油油防止零件发生秀浊的作用SAE10W-30在低温下时,其粘度与SAE10W一样。而在高温下,其粘度又和SAE30相同

阅读理解

Losing weight comes with a lot of health benefits—including making your brain sharper.

Yes, it turns out that overweight may damage cognitive functions (认知功能) such as memory and attention. There have been few studies of overweight and cognitive functioning, possibly because it is generally believed that it is not a primary risk cause for poor cognitive performance. Losing weight, therefore, may help improve these mental functions, according to a new research led by John Gunstad, assistant professor of psychology at Kent State University.

Growing evidence suggests that being fat is linked to cognitive deficits (缺陷). So Gunstad and his team guessed that losing weight might improve mental function. For their study, they measured memory and attention in a group of 150 overweight participants, some of whom had some kind of operation for weight loss and some did not. All of the volunteers completed mental skills tests to assess their abilities of memory and attention at the beginning of the study, and again 12 weeks later. To begin with, about 24% of the patients showed damaged learning and 23% showed signs of poor memory when tested. At the end of the study, those who had lost weight after operation improved their scores into the average or above average range for cognitive functions. Scores for the volunteers who didn’t lose weight dropped even further.

The study helped Gunstad to find out whether losing weight had any effect on mental function. Now that he’s seen the positive effect that weight loss can have on memory and attention, he says he will next study those who choose to lose weight by the traditional way—eating healthier and getting more active. He expects that losing weight in this way will have a similarly positive effect on the brain. “If we can improve the condition with operations, then we can probably produce the same change with behavioral weight loss as well,” he says.

小题1:There is less research on overweight and cognitive functions because researchers _____.

A.believe overweight only affects our body

B.have focused on ways to sharpen people’s mind

C.do not consider overweight a main cause for low cognitive ability

D.are clear about the relation between weight and mental functions小题2:The result of Gunstad’s study shows that ______.

A.losing weight has little effect on people’s memory

B.losing weight can improve people’s mental functions

C.overweight people are likely to have psychology problems

D.overweight people’s abilities of concentration differ greatly小题3:What is Gunstad planning to prove next in his research?

A.Slim people are smarter than overweight people.

B.Healthy diet is better than exercise in losing weight.

C.Traditional ways of losing weight are better than operation.

D.Overweight people will get smarter by taking more exercise.小题4:Which of the following is the best title for th e text?

A.Body Weight and Health

B.Losing Weight by Operation

C.Ways to Improve Mental Functions

D.Losing Weight to S harpen Your MindD

单项选择题