问题 单项选择题

在瓷熔附金属时,其金瓷匹配是十分关键的,其主要涉及的因素包括

烤瓷材料的烧结温度与金属的熔点的关系是

A.两者相同

B.前者低于后者

C.前者高于后者

D.前者明显低于后者

E.前者明显高于后者

答案

参考答案:B

解析:烤瓷合金的熔点应大于烤瓷粉的熔点。国产烤瓷Ni-Cr合金属高熔合金,其熔点约为1320℃。烤瓷粉采用低熔瓷粉,其熔点为871~1065℃。合金熔点必须高于瓷粉的熔点170~270℃,以保证在金属基底上熔瓷时不至引起金属基底熔融或变形。

阅读理解

Cell phones:  is there a cancer link?

Could your cell phone give you cancer? Whether it could or not, some people are worrying about the possibility that phones, power lines and Wi-Fi could be responsible for a range of illnesses, from rashes to brain tumors.

Some say there is evidence to support the growing anxieties. David Carpenter, a professor of environmental health sciences at the university at Albany, in New York, thinks there’s a greater than 95 percent chance that power lines can cause childhood leukemia(白血病). Also there’s a greater than 90 percent chance that cell phones can cause brain tumors. “It’s apparent now that there’s a real risk, ” said Carpenter.

But others believe these concerns are unjustified. Dr Martha Linet, the head of radiation epidemiology(流行病学) at the US National Cancer Institute, has looked at the same research as Carpenter but has reached a different conclusion. “I don’t support warning labels for cell phones, ” said Linet. “We don’t have the evidence that there’s much danger. ”

Studies so far suggest a weak connection between EMFs(电磁场) and illness— so weak that it might not exist at all. A multinational investigation of cell phones and brain cancer, in 13 countries outside the US, has been underway for several years. It’s funded in part by the European Union, in part by a cell phone industry group. The final report should come out later this year, but data so far don’t suggest a strong link between cell phone use and cancer risk.

小题1:From the passage we can learn that some people are worried because _______.

A.they have evidence that the use of cell phones can lead to cancer

B.they make a fuss over cell phone use

C.some experts have given a warning

D.cell phones are responsible for brain tumors小题2:By saying “I don’t support warning labels for cell phones, ” Dr Martha Linet has the idea that _______.

A.the worrying is unnecessary

B.cancer-warning labels should be on cell phones

C.there is a link between cell phones and cancer

D.cell phones have nothing to do with cancer小题3:Which of the following best describes the attitude of the author towards the debate?

A.Optimistic.

B.Objective.

C.Opposite.

D.Casual. ]

多项选择题