布什行政当局将古巴裔美国人前往古巴旅游的次数从每年一次削减为每三年一次，并且不遗余力地强化一项禁令，即禁止其他美国人前往古巴旅游。
George Bush's administration has cut family visits by Cuban-Americans, from once a year to once every three years, and has been zealous in enforcing a ban on travel to the island by other Americans.
参与者被随机地指定做一种每年一次共三次的影像学检查——低剂量螺旋CT或标准X射线胸透。
Participants were randomly assigned to receive three annual screenings with either the low-dose spiral CT or the standard chest X-ray.
在每年的十月至十一月间，当哈德逊湾上第一次结冰的时候，有约一千只世界上最大型的陆地食肉动物迁徙到这个“北极熊的首都”。
More than a thousand of the world’s largest land carnivores migrate through the “polar bear capital of the world” during October and November, when the first ice forms on the edge of Hudson Bay.
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