, would have been far less effective. 50. These particular muscles are difficult to control, and few people can do it （六）完形填空 Obtaining Drinking Water from Air Humidity Not a plant to be seen．the desert ground is too dry．But the air contains water，and research scientists have found a 1 way of obtaining drinking water from air humidity．The system is based completely on renewable energy and is therefore autonomous． Cracks permeate the dried-out desert ground and the landscape bears testimony to the lack of water．But even here，where there are no lakes，rivers or groundwater，considerable quantities of water are stored in the air．In the Negev desertl in Israel，for example，annual average relative air humidity is 64 percent一in every cubic meter of air there are 11.5 milliliters of water． German research scientists have found a way of converting this air humidity autonomously into drinkable water．“The process we have developed is based exclusively on renewable energy sources 2 such as thermal solar collectors and photovoltaic cells， 3 which makes this method completely energy-autonomous．It will 4 therefore function in regions where there is no electrical infrastructure．”says Siegfried Egner，head of the research team．The principle of the 5 process is as follows3：hygroscopic brine—saline solution which absorbs moisture—runs down a tower-shaped unit and absorbs water from the air．It is then sucked 6 into a tank a few meters off the ground in which a vacuum prevails4．Energy from solar collectors 7 heats up the brine，which is diluted by the water it has 8 absorbed ． Because of the vacuum，the boiling point of the liquid is lower than it would be under 9 normal atmospheric pressure．This effect is known from the mountains：as the atmospheric pressure there is lower than in the valley，water boils at temperatures distinctly below 100℃．The evaporated，non-saline water is condensed and runs down through a completely filled tube in a controlled manner．The gravity of this water column 10 continuously produces the vacuum and so a vacuum pump is not needed．The reconcentrated3 brine 11 runs down the tower surface again to absorb moisture from the air． “The concept is suitable for various water 12 users ．Single-person units and plants supplying water to entire hotels are conceivable，”says Egner．Prototypes have been built for 13 both system components—air moisture absorption and vacuum evaporation—and the research scientists have already 14tested their interplay on a laboratory scale．In a further 15 step the researchers intend to develop a demonstrmion facility．