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Obtaining Drinking Water from Air Humidity Not a plant to be seen, the desert ground is too 51 . But the air contains water, and research scientists have found a 52 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 desert1 in Israel2, for example, annual average relative air humidity is 64 percent -- 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 such as thermal 53 collectors and photovoltaic cells, which makes this method completely energy-autonomous. It will therefore function in regions 54 there is no electrical infrastructure," says Siegfried Egner, head of the research team. The principle of the 55 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 into a tank a few meters 56 the ground in which a vacuum prevails4. Energy from solar collectors heats up the brine, which is diluted by the water it has 57 . Because of the vacuum, the boiling point of the liquid is 58 than it would be under normal atmospheric pressure. This effect is known from the mountains: as the atmospheric pressure 59 is lower than in the valley, water boils at temperatures 60 below 100oC. 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 continuously produces the vacuum and so a vacuum pump is not needed. The reconcentrated5 brine runs down the tower surface 61 to absorb moisture from the air. "The concept is suitable for various water 62 . Single-person units and plants 63 water to entire hotels are conceivable," says Egner. Prototypes have been built for both system components— air moisture absorption and vacuum evaporation —and the research scientists have already 64 their interplay on a laboratory scale. In a further step the researchers intend to develop a demonstration 65 .
Cu的原子数分数为2%的Al-Cu合金先从520℃快速冷却至27℃，并保温3h后，形成平均间距为1.5×10-6cm的G.P.区。已知在027℃时，Cu在Al中的扩散系数D=2.3×10-25cm2/s，假定过程为扩散控制，试估计该合金的空位形成能及淬火空位浓度。
The Atmosphere 1 The atmosphere is a mixture of several gases. There are about ten chemical elements which remain permanently in gaseous form in the atmosphere under all natural conditions. Of these permanent gases, oxygen makes up about 21 percent and nitrogen about 78 percent. Several other gases, such as argon, carbon dioxide, hydrogen, neon, krypton and xenon, comprise the remaining one percent of the volume of the dry air. The amount of water vapor and its variations in amount and distribution is of extraordinary importance in weather changes. Atmospheric gases hold in suspension great quantities of dust, pollen, smoke and other impurities which are always present in considerable, but variable amounts. 2 The atmosphere has no definite upper limits but gradually thins until it becomes imperceptible. Until recently it was assumed that the air above the first few miles gradually grew thinner and colder at a constant rate. It was also assumed that upper air had little influence on weather changes. Recently studies of the upper atmosphere, currently being conducted by earth satellites and missile probing, have shown these assumptions to be incorrect. The atmosphere has three well-defined strata. 3 The layer of the air next to the earth, which extends upward for about ten miles, is known as the troposphere. On the whole, it makes up about 75 percent of all the weight of the atmosphere, because most of the solar radiation is absorbed by the earth’s surface which warms the air immediately surrounding it. A steady decrease of temperature with the increasing elevation is a mot striking characteristic. The upper layers are colder because of their greater distance from the earth’s surface and rapid radiation of heat into space. The temperatures within the troposphere decrease about 3.5 degrees per 1000 feet increase in altitude. Within the troposphere, winds and air currents distribute heat and moisture. Strong winds, called jet streams are located at the upper levels of the troposphere. These jet streams are both complex and widespread in occurrence. They normally show a wave shaped pattern and move from west to east at velocities of 150 mph, but velocities as 400 mph have been noted. The influences of changing locations and strengths of jet streams upon weather conditions and patterns are no doubt considerable. Current intensive research may eventually reveal their true significance. 4 Above the troposphere to a height of about 50 miles is a zone called the stratosphere. The stratosphere is separated from the troposphere by a zone of uniform temperatures called the tropopause. Within the lower portions of the stratosphere is a layer of ozone gases which filter out most of the ultraviolet rays from the sun. The ozone layer varies with air pressure. If this zone were not there, the full blast of the sun’s ultraviolet light would burn our skins, blind our eyes and eventually result in our destruction. Within the stratosphere, the temperature and atmospheric composition are relatively uniform. 5 The layer upward of about 50 miles is the most fascinating but the least known of the three strata. It is called the ionosphere because it consists of electrically charges particles called ions, thrown from the sun. The northern lights ( aurora borealis ) originate within this highly charged portion of the atmosphere. Its effect upon weather conditions, if any, is as yet unknown.
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