问题 多项选择题

MRI设备配套保障系统的冷水机组的主要作用是()。

A.冷却匀场线圈

B.冷却冷头氦压缩机

C.冷却梯度系统

D.冷却射频系统

E.冷却磁体线圈

答案

参考答案:B, C

解析:

MRI设备的冷水机组是为了确保MRI设备冷头及梯度系统的正常运转所配置的。MRI设备的冷头是通过氦压缩机制冷,氦压缩机采用水冷却方式,它的散热器被冷水管包绕,产生的热量最终由冷水机组提供的循环冷水冷却;梯度系统中梯度放大器及梯度线圈中产生大量的热量,这些热量也是通过冷水机组的冷水冷却。

单项选择题
单项选择题

Halfway through " The Rebel Sell," the authors pause to make fun of" free-range" chicken. Paying over the odds to ensure that dinner was not, in a previous life, confined to tiny cages is all well and good. But"a free-range chicken is about as plausible as a sun-loving earthworm" : given a choice, chickens prefer to curl up in a nice dark corner of the barn. Only about 15% of "free-range" chickens actually use the space available to them.

This is just one case in which Joseph Heath, who teaches philosophy at the University of Toronto, and Andrew Potter, a journalist and researcher based in Montreal, find fault with well-meaning but, in their view, ultimately naive consumers who hope to distance themselves from consumerism by buying their shoes from Mother Jones magazine instead of Nike. Mr Heath and Mr Potter argue that" the counterculture, "in all its attempts to be subversive, has done nothing more than create new segments of the market, and thus ends up feeding the very monster of consumerism and conformity it hopes to destroy. In the process ,they cover Marx, Freud, the experiments on obedience of Stanley Milgram, the films "Pleasantville"," The Matrix" and "American Beauty", 15th-century table manners, Norman Mailer, the Unabomber, real-estate prices in central Toronto (more than once), the voluntary-simplicity movement and the world’s funniest joke.

Why range so widely The authors’ beef is with a very small group: left-wing activists who eschew smaller, potentially useful campaigns in favor of grand statements about the hopelessness of consumer culture and the dangers of "selling out". Instead of encouraging useful activities, such as pushing for new legislation, would-be leftists are left to participate in unstructured, pointless demonstrations against "globalization," or buy fair-trade coffee and free-range chicken, which only substitutes snobbery for activism. Two authors of books that railed against brands, Naomi Klein ( "No Logo") and Alissa Quart ("Branded"), come in for special derision for diagnosing the problems of consumerism but refusing to offer practical solutions.

Anticipating criticism, perhaps, Messrs Heath and Potter make sure to put forth a few of their own solutions, such as the 35-hour working week and school uniforms (to keep teenagers from competing with each other to wear ever-more-expensive clothes). Increasing consumption, they argue throughout, is not imposed upon stupid workers by overbearing companies, but arises as a result of a cultural "arms race": each person buys more to keep his standard of living high relative to his neighbors’. Imposing some restrictions, such as a shorter working week, might not stop the arms race, but it would at least curb its most offensive excesses. (This assumes one finds excess consumption offensive; even the authors do not seem entirely sure. )

But on the way to such modest suggestions, the authors want to criticise every aspect of the counterculture, from its disdain for homogenisation, franchises and brands to its political offshoots. As a result, the book wanders: chapters on uniforms and on the search for "cool" could have been cut. Moreover, the authors make the mistake of assuming that the consumers they sympathise with--the ones who buy brands and live in tract houses--know enough to separate themselves from their purchases, whereas the free-trade-coffee buyers swallow the brand messages whole, as it were.

Still, it would be a shame if the book’s ramblings kept it from getting read. When it focuses on explaining how the counterculture grew out of post-World War Ⅱ critiques of modern society, "The Rebel Sell" is a lively read, with enough humour to keep the more theoretical stretches of its argument interesting. At the very least, it puts its finger on a trend: there will be plenty of future critics of capitalism lining up for their free-range chicken.

The word "eschew" (paragraph 3)is closest in meaning to()

A. organize

B. favor

C. shun

D. encourage