更多"Ultroviolet light has long been use"的相关试题:
[填空题]Ultroviolet light has long been used in water-treatment plants to help with virus killing. As long as the water is clear enough not to absorb the rays, (36) it to a discharge lamp will destroy the DNA of viruses and (37) that could otherwise cause illness when (38) . Now a group of researchers have developed an industrial-scale solar-driven purification system that removes not only bugs but also chemical (39)
The first of their (40) has been built as demonstration project. The researchers wanted to clean the water that they use to cool their (41) engines. This cooling water (42) gets contaminated both with rocket fuel and with (43) produced by the burning of the fuel.
The trick the researchers use to boost the cleansing action of ultraviolet is to add a light-activated catalyst(催化剂) to the waste water. (44) . After a complex series of reactions, water gets pure enough to be
[单项选择]How long has the magazine been on saleHow long has the magazine been on sale
A. for one year
B. for eighteen months
C. for two years
[单项选择]Stamp collection has long been recognized as having an educational value. There is every reason to encourage young people to take an interest in them, thereby ( ) to their knowledge of geography and history.
A. to add
B. adding
C. added
D. adds
[单项选择]Which of the following has been used only recently to advertise vacancies
A. Newspapers.
B. Recruitment agencies.
C. Internet.
[单项选择]Archaeology has long been an accepted tool for studying prehistoric cultures. Relatively recently the same techniques have been systematically applied to studies of the more immediate past. This has been called "historical archaeology," a term that is used in the United States to refer to any archaeological investigation into North American sites that postdate the arrival of Europeans.
Back in the 1930’s and 1940’s, when building restoration was popular, historical archaeology Was primarily a tool of architectural reconstruction. The role of archaeologists was to find the foundations of historic buildings and then take a back seat to architects.
The mania for reconstruction had largely subsided by the 1950’s and 1960’s. Most people entering historical archaeology during this period came out of university anthropology departments, where they had studied prehistoric cultures. They were, by training, social scientists, not historians, and their work tended to reflect this bias.
A. Why historical archaeology was first developed.
B. How the methods and purpose of historical archaeology have changed.
C. The contributions architects make to historical archaeology.
D. The attitude, of professional archaeologists toward historical archaeology.
[单项选择]It has long been the subject of speculation among the police and criminologists: what would happen if all the officers who now spend so much of their time taking statements, profiling criminals and moving pieces of paper around were suddenly put on the streets Crime figures released by London’s Metropolitan Police this week provide the best answer yet.
Following the bombings of July 7th and 21st, thousands of police officers materialised on London’s pavements, many of them sporting brightly coloured jackets. Drawn from all over the city, they were assigned to guard potential targets such as railway stations. The police presence was especially heavy in the bombed boroughs: Camden (which was struck three times), Hammersnrith and Fulham, Lamheth, Tower Hamlets, Westminster and the City of London.
The show of force did not just scare off terrorists. There was less crime in July than in May or June, which As unusual: the warmer month tends to bring out criminal tendencies, as wind
A. consent
B. ambivalent
C. denial
D. approval