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燃油锅炉有机械未完全燃烧热损失吗？

答案

参考答案：

燃料油灰分含量很低，燃烧后的灰分中一般也不含有可燃物，过去曾认为燃油锅炉是不存在机械未完全燃烧热损失的。实际上这是不正确的，燃油炉如果配风工况不好、雾化质量不良，燃烧后的烟气中可能出现未燃尽的炭黑或焦壳。炭黑或焦壳是固体可燃物，所造成的热量损失也是机械未完全燃烧热损失。因此，燃油炉实际上是存在机械未完全燃烧热损失的，有的燃油沪严重时可高达0.5%.

燃油炉机械未完全燃烧热损失，可通过试验测出炭黑浓度并计算出干烟气容积。

单项选择题

Questions 6-10 are based on Passage Two:Passage TwoEducating girls quite possibly yields a higher rate of return than any other investment available in the developing world. Women’s education may be unusual territory for economists, but enhancing women’s contribution to development is actually as much an economic as a social issue. And economics, with its emphasis on incentives, provides guideposts that point to an explanation for why so many girls are deprived of an education.Parents in low-income countries fail to invest in their daughters because they do not expect them to make an economic contribution to the family: girls grow up only to marry into somebody else’s family and bear children. Girls are thus seen as less valuable than boys and kept at home to do housework while their brothers are sent to school- the prophecy becomes self-fulfilling, trapping women in a vicious circle of neglect.An educated mother, on the other hand, has greater earning abilities outside the home and faces an entirely different set of choices. She is likely to have fewer but healthier children and can insist on the development of all her children, ensuring that her daughters are given a fair chance. The education of her daughters then makes it much more likely that the next generation of girls, as well as of boys, will be educated and healthy. The vicious circle is thus transformed into a virtuous circle.Few will dispute that educating women has great social benefits. But it has enormous economic advantages as well. Most obviously, there is the direct effect of education on the wages of female workers. Wages rise by lo t0 20 percent for each additional year of schooling. Such big returns are impressive by the standard of other available investments, but they are just the beginning. Educating women also has a significant impact on health practices, including family planning.

The author argues that educating girls in developing countries is ( ).

A．troublesome

B．labor-saving

C． rewarding

D．expensive
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问答题 简答题

通管体杂物时，是否要戴护目镜？为什么？
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