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America is a country on the move. In unheard of numbers, people of all ages are exercising their way to better health. According to the latest figures, 59 percent of American adults exercise regularly-up 12 percent from just two years ago and more than double the figure of 25 years ago. Even non-exercisers believe they would be more attractive and confident if they were more active.It is hard not to get the message. The virtues of physical fitness are shown on magazine covers, postage stamps, and television ads for everything from beauty soaps to travel books. Exercise as a part of daily life did not catch on until the late 1960s when research by military doctors began to show the health benefits of doing regular physical exercises. Growing publicity (宣传) for races held in American cities helped fuel a strong interest in the ancient sport of running. Although running has leveled off in recent years as Americans have discovered equally rewarding--and sometimes safer-forms of exercise, such as walking and swimming, running remains the most popular form of exercise.As the popularity of exercise continues to mount, so does scientific evidence of its health benefits. The key to fitness is exercising the major muscle groups vigorously (强有力地) enough to approximately double the heart rate and keep it doubled for 20 to 30 minutes at a time. Doing such physical exercises three times or more a week will produce considerable improvements in physical health in about three months. A growing interest in sports developed after（）
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Even plants can run a fever, especially when they’re under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away — straight up. A decade ago, adapting the infrared scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers precisely target pesticide spraying rather than rain poison on a whole field, which invariably includes plants that don’t have pest problems.Even better, Paley’s Remote Scanning Services Company could detect crop problems before they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured the heat emitted by crops. The data were transformed into a color-coded map showing where plants were running "fevers". Farmers could then spot-spray, using 50% to 70% less pesticide than they otherwise would.The bad news is that Paley’s company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find. But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. "This technique can be used on 75% of agricultural land in the United States," says George Oerther of Texas A＆M. Ray Jackson, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade. But only If Paley finds the financial backing which he failed to obtain 10 years ago. Plants will emit an increased amount of heat when they are（）
配送服务质量可以用配送时间、配送费用、配送效率来衡量。
可从配送规模和配送服务质量中综合反映出配送的总体需求。
配送消除了交叉输送，完善了运输系统。
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