问题 问答题 简答题

要分析钢中碳化物成分和基体中碳含量,应选用哪种电子探针仪?为什么?

答案

参考答案:

分析钢中碳化物成分可用能谱仪;分析基体中碳含量可用波谱仪,这是因为与波谱仪相比,能谱仪具有以下优点:能谱仪探测X射线的效率高。其灵敏度比波谱仪高约一个数量级。在同一时间对分析点内所有元素X射线光子的能量进行测定和计数,在几分钟内可得到定性分析结果,而波谱仪只能逐个测量每种元素特征波长。结构简单,稳定性和重现性都很好(因为无机械传动)不必聚焦,对样品表面无特殊要求,适于粗糙表面分析。

与波谱仪相比能谱仪具有以下缺点和不足:分辨率低:Si(Li)检测器分辨率约为160eV;波谱仪分辨率为5-10eV能谱仪中因Si(Li)检测器的铍窗口限制了超轻元素的测量,因此它只能分析原子序数大于11的元素;而波谱仪可测定原子序数从4到92间的所有元素。能谱仪的Si(Li)探头必须保持在低温态,因此必须时时用液氮冷却

阅读理解

The managing editor is usually the person in charge of the day-to-day editorial process of a newspaper. He or she makes sure that the newspaper comes out on time each day and that costs are kept within a budget. He or she is usually responsible for hiring and firing newsroom staff, and serves as the spokesperson for the newspaper. The managing editor may also be involved in story, photo and graphics selection, assignments, laying out pages, and editing copy and writing headlines. 

The news editor is in charge of the news pages of the newspaper. He or she makes decisions on which stories are used and which are not. The news editor and his or her assistants also lay out pages of the paper.

The copy editor edits wire and local stories and writes headlines. The copy editor is often the last person to see a story before it actually appears in print.

The city editor makes sure that the news in the city is covered and that as many local stories as possible get into each edition. The city editor monitors the local general assignment, beat and specialty reporters.

The state editor supervises reporters who cover communities and areas outside the city but still within the circulation (流通) area of the newspaper.

The national editor supervises reporters in bureaus in cities outside the circulation area of the newspaper. Most newspapers rely on the wire services for national news, but some have correspondents(通信员) who work in other cities and report to the national editor.

小题1:If you want to apply for a job in a newspaper newsroom, you are likely to be interviewed by _____.

A.the news editor

B.the national editor

C.the state editor

D.the managing editor小题2:From the passage, we can learn that _________.

A.the managing editor is mainly responsible for laying out pages of the paper

B.the news editor determines which stories are used

C.the copy editor is often the first person to see the story

D.the state editor supervises the local general assignment, beat and specialty reporters小题3:The national news is mostly sent to the national editor by all of the following ways EXCEPT _____.

A.by e-mail

B.by fax

C.by letter

D.by telephone小题4:The underlined word “supervises” in the last paragraph can be replaced by ________.

A.is in favor of

B.is in honor of

C. is in charge of

D.is in need of小题5:What is mainly discussed in this passage?

A.How newspapers are made.

B.People in a newspaper newsroom.

C.How news is collected and edited.

D.People in charge of the newspaper industry.

单项选择题