问题 填空题

计算机硬件故障通常是由元器件失效引起的,元器件可靠性分为3个阶段:①器件处于不稳定期,失效率较高;②器件进入正常工作期,失效率最低,基本保持常数;③元器件开始老化,失效率又重新提高(“浴盆模型”)。
因此计算机系统的可靠性指标也相当重要,计算机的可靠性用 (4) 来度量,可维护性用 (5) 来度量,可用性用 (6) 来衡量。
常见的三种计算机可靠性数学模型为:①串联系统可靠性模型;②并联系统可靠性模型;③ (7)

答案

参考答案:MTTF/(MTTF+MTTR)×100%

单项选择题
单项选择题

Many parents complain that their teenage children are rebelling. They greet their children’s teenage with needless dread. While teenagers may assault us with heavy-metal music, wear strange clothes, have strange hair styles, and spend all their time dating or meeting friends, such behavior scarcely adds up to full-scale revolt.

Take a good look at the present rebellion. It seems that teenagers are all taking the same way of showing that they disagree with their parents. Instead of striking out boldly on their wings, most of them are clutching at one another’s hands for reassurance. Their reason for thinking or acting in thus-and-such a way is that the crowd is doing it. It has become harder and harder for a teenager to stand up against the popularity wave and to go his or her own way. They have come out of their cocoon—into a larger cocoon.

Teenage rebellion, according to psychologist Laurence Steinberg, coauthor of You and Your Adolescent, has been greatly overstated. Many other psychologists agree. The idea that teenagers inevitably rebel is a myth that has the potential for great family harm. This notion can damage communication during this critical time for parents to influence youngsters.

Still adolescence is often a trying time of transition for child and parent. Teenagers need to establish themselves as individuals—in their own minds and in the eyes of others. This search isn’t about rebellion: it’s about becoming a person of one’s own. " Teenagers ought to be growing away from their parents and learning to stand on their own two feet, " says Steinberg.

Here is one way parents can help: don’t stereotype. " Parents who expect teenage rebellion may actually stir it up, " says Kenneth I. Howard, a member of a research team that collected survey data on more than 20,000 teenagers over a 28-year period.

Howard cautions parents not to resort to suppression at the first sight of adolescent independence, fearful that giving in even slightly now means drugs cannot be far behind. When parents overreact, teenagers assert themselves more, parents clamp down harder, and a full-scale blowup results.

In fact, psychologists say that there is no inevitable pattern to teenage behavior, and no such creature as a typical teenager. Your teenager is now larger, per, older and smarter than before, with an additional supply of hormone raging through the bloodstream. But he or she is still the same human being you have lived with since birth. Given a chance, your son or daughter will continue to behave in ways you have established.

Overstating teenage rebellion will lead to the following consequences EXCEPT()

A.it can do harm to the family

B. it can damage parents’ influence

C. it can prevent teenagers from being individuals

D. it can impair teenagers’ ability to make correct judgment