题目内容
气压试验前，应对管道及管路附件的耐压强度进行验算，验算时采用的安全系数不得小于()。
查看答案
搜索结果不匹配？点我反馈
更多问题
某建设项目的现金流量见下表，己知基准折现率为10%，则该项目的动态投资回收期为()年。
某项目现金流量表的数据如下表所示，该项目静态投资回收期为()年。
Recent stories in the newspapers and magazines suggest that teaching and research contra diet each other that research plays too prominent a part in academic promotions, and that teaching is badly under-emphasized. There is an element of truth in these statements, but they also ignore deeper and more important relationships.
Research experience is an essential element of hiring and promotion at the research university because it is the emphasis on research that distinguishes such a university from an arts college. Some professors, however, neglect teaching for research, and that presents a problem.
Most research universities reward outstanding teaching, but the greatest recognition is usually given for achievements in research. Part of the reason is the difficulty of judging teaching. A highly responsible and tough professor is usually appreciated by top students who want to be challenged, but disliked by those whose records are less impressive. The mild professor gets overall ratings that are usually high, but there is a sense of disappointment on the part of the best students, exactly those for whom the system should present the greatest challenges. Thus, a university trying to promote professors primarily on the basis of teaching qualities would have to confront this confusion.
As modern science moves faster, two forces are exerted on professors: one is the time needed to keep up with the profession; the other is the time needed to teach. The training of new scientists requires outstanding teaching at the research university as well as the arts college. Although scientists are usually "made" in the elementary schools, scientists can be "lost" by poor teaching at the college and graduate school levels. The solution is not to separate teaching and research, but to recognize that the combination is difficult but vital. The title of professor should be given only to those who profess, and it is perhaps time for universities to reserve it for those willing to be an earnest part of the community of scholars. Professors unwilling to teach can be called "distinguished research investigators," or something else.
The pace of modern science makes it increasingly difficult to be a great researcher and great teacher. Yet many are described in just those terms. Those who say we can separate teaching and research simple do not understand the system, but those who say the problem will disappear are not fulfilling their responsibilities.
What idea does the author want to convey in the first paragraph？
Scientists have been taking a closer look at the lighting in our homes, offices and vehicles, and they're seeing a possible way to improve health.
Engineer E. Fred Schubert is talking about a new era of "smart" light sources. "We are looking at lighting systems that provide more than lighting," he says.
He's talking about light-emitting diodes(二极管),or LEDs. Most people know them as being quite small, like the lights that form. numbers on digital clocks. But recent technological advances have made them much more powerful, able to illuminate swimming pools and serve as traffic signals, for example.
Meanwhile, the lighting in offices and schools could be improved to help people stay healthy and productive, by acting on their internal body clocks. The 24-hour internal body clock is best known for governing cycles of alertness and sleep, and for producing jet lag(飞行时差) when people travel across time zones. Lights cues, especially blue light, help keep the clock on its daily cycle. We're pretty much blue-sky detectors. Our clocks count on bright days and dark nights.
But that's not necessarily what modern life delivers. During the winter in the northeast of America, for example, a person can commute roundtrip in the dark and sit all day in electric light that's fine for vision, but may be too dim to stimulate the body clock. That's called biological darkness.
How that affects people has been hard to document in the general population, but studies suggest such possibilities as seasonal depression, fatigue, sleep disturbances and maybe even cancer, especially breast cancer. Some studies suggest reduced productivity on the job. To counter that, architects and lighting engineers might someday take body clocks into account when they design lighting schemes. They may be encouraged to take steps like providing plenty of natural Night through windows and skylights, and installing bright blue LEDs near computer screens to give a dose of clock-adjusting light.
In the following places, where can we not find the LEDs？
微信支付 
支付宝支付