过盈连接装配,当过盈量及配合尺寸较小时,在常温下一般采用()装配。
A、压入法
B、热胀法
C、冷缩法
D、温差法
参考答案:A
(9分)实验是学习化学的重要手段,通过实验可以培养实践能力和创新精神。
(一)实验室制取气体是初中一类重要的实验,结合下列仪器或装置图回答有关问题:
装置I 装置Ⅱ 装置Ⅲ
(1)装置I是用高锰酸钾制氧气,反应的化学方程式为_________________________,表明氧气已经收满的实验现象是 。
(2)某同学用装置Ⅱ制取并收集二氧化碳,用燃着的木条放在集气瓶口验满,始终未发现火焰熄灭,原因是______________________________________________。
(3)用装置Ⅲ进行二氧化锰和双氧水制取氧气的实验时,若反应速率过快,可以采取的处理方法是 。
(4)我们已经学过实验室制取O2、CO2、H2三种气体的反应原理及制取、收集方法。请你归纳出制取这三种气体时反应的共同点_______(填选项序号)。
A.需要加热
B.需使用催化剂
C.没有气体参加反应
D.生成的气体只有一种(二)选用下列装置测定水的元素组成,请回答问题:
(5)为准确测定水的组成并防止杂质、空气等干扰,导管口的正确连接顺序为:
③→___→____→____→____→①→②→⑧→⑨→⑩。
(6)若测得A装置中样品在实验后减少了6.4克,E装置质量增加了7.2克,F装置增加了0.1克,据此可求出水中H、O元素质量比为(只写计算式)____________。
(7)实验结束后,若A处仍有黑色固体,这对实验结果的影响是________________(填“氧的质量偏大”、“氢的质量偏大”、“无影响”)。
At a basic level, cloud computing is simply a means of delivering IT resources as ().Almost all IT resources can be delivered as a cloud service: applications, compute power, storage capacity, networking,programming tools,even communication services and collaboration ()。
Cloud computing began as large-scale Internet service providers such as Google,Amazon,and others built out their infrastructure. An architecture emerged: massively scaled, () distributed system resources,abstracted as virtual IT services and managed as continuously configured, pooled resources. In this architecture, the data is mostly resident on ()“somewhere on the Intemet”and the application runs on both the "cloud servers”and the user’s browser.
Both clouds and grids are built to scale horizontally very efficiently. Both are built to withstand failures of () elements or nodes. Both are charged on a per-use basis. But while grids typically process batch jobs, with a defined start and end point, cloud services can be continuous. What’s more, clouds expand the types ofresources available —— file storage, databases, and Web services —— and extend the applicability to Web and enterprise applications.
At a basic level, cloud computing is simply a means of delivering IT resources as ().
A.hardware
B.computers
C.services
D.software