机械密封的密封原理是什么？

[单选题]Passage1Laziness is a sin，everyone knows that. We have probably all had lectures pointing out that laziness is immoral, that it is wasteful, and that lazy people will never amount to anything in life. But laziness can be more harmful than that, and it is often caused by more complex reasons than simple wish to avoid work. Some people who appear to be lazy are suffering from much more serious problems. They may be so distrustful of their fellow workers that they are unable to join in any group task for fear of ridicule or fear of having their ideas stolen. These people who seem lazy may be paralyzed by a fear of failure that prevents fruitful work. Or other sorts of fantasies may prevent work; some people are so busy planning, sometimes planning great deals or fantastic achievements that they are unable to deal with whatever "lesser" work is on hand. Still other people are not avoiding work; strictly speaking, they are merely procrastinating-rescheduling their day.Laziness can actually be helpful. Like procrastinators, some people may look lazy when they are really thinking, planning, contemplating, researching. We should all remember that great scientific discoveries occurred by chance. Newton wasn't working in the orchard when the apple hit him and he devised the theory of gravity. All of us would like to have someone "lazy"were caused by the worker's taking time to check each step of his work and to do his job right. And sometimes, being lazy that is, taking time off for a rest is good for the overworked students or executive.Taking a rest can be particularly helpful to the athlete who is trying too hard or the doctor who's simply working himself overtime too many evenings at the clinic. So be careful when you' re tempted to call someone lazy. That person may be thinking, resting, and planning his or her next book.Which of the following conclusions does the passage support?

[单选题]下列各项中，属于会计凭证的是（）

[问答题]我善养吾浩然之气。

[填空题]混凝土出搅拌机后，经过 （） 、 （） 和 （） 后的温度，称为浇筑温度

[多选题]以下关于绘图区的描述正确的是（）

[多选题]患者，男，59岁。5年前开始自觉右上肢动作不如从前灵活，有僵硬感并伴不自主抖动，情绪紧张时症状加重，睡眠时症状消失，1年后左上肢亦出现类似症状，并逐渐出现起身落座动作困难，行走时前冲，易跌倒，步态幅度小，转身困难，近一年来记忆力明显减退，情绪低落。查体：神清，面具脸，面部油脂分泌较多，伸舌居中，鼻唇沟等对，四肢肌张力齿轮样增高，腱反射双侧正常，四肢肌力均正常，双手放置时呈搓丸样，不自主震颤，无明显共济失调。双侧病理征（-），交谈时语音低沉，写字时可见字越写越小。CT示双侧基底节有腔隙性低密度影。提高该患者的记忆力训练方法包括（）。

[名词解释题]污染物转化

[单选题]中运量城市轨道交通系统是指高峰时段单向运输能力达到（）

[单选题]基因的遗传信息需要依靠（）进行繁衍和延续。

[单选题]甲公司20×7年7月1日自母公司（丁公司）取得乙公司60%股权，当日，乙公司个别财务报表中净资产账面价值为3200万元。该股权系丁公司于20×6年6月自公开市场购入，丁公司在购入乙公司60%股权时确认了800万元商誉。20×7年7月1日，按丁公司取得该股权时乙公司可辨认净资产公允价值为基础持续计算的乙公司可辨认净资产价值为4800万元。为进行该项交易，甲公司支付有关审计等中介机构费用120万元。不考虑其他因素，甲公司应确认对乙公司股权投资的初始投资成本是（　）。

[问答题]什么是机械密封及机械密封的组成？

[单选题]机械密封是（）用动密封。

[单选题]机械密封也叫（）密封。

[填空题]机械密封较之填料密封具有密封性能（）使用寿命（）功率消耗（）等优点

[单选题]环水泵外接管采用机械密封胶密封，其余采用密封垫和“O”形密封圈，填料采用.()

[判断题]毡圈密封、唇形密封圈密封、机械密封都是接触式密封。

[填空题]离心泵的机械密封需要使用密封水，一般密封水的压力应该高于介质（）。

[单选题]（）机械密封是将机械密封的传动加荷装置置于工作介质内。

[问答题]什么是机械密封，机械密封的工作原理是什么？机械密封的用途是什么？

[多选题]采用机械密封时，（）是静密封。