题目内容
同一回路的相线和中性线必须穿在同一进户管内，配电系统如采用TN-C或TN-C-S制，在室外进线处的PEN线或()的PE线均应进行重复接地。
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焊接工程中的焊后气压强度试验以气体为介质进行强度试验，试验压力为设计压力的()倍。
焊接工程中的焊后液压强度试验常用水进行，试验压力为设计压力的()倍。
某企业为扩大生产规模，修建一幢教学大楼，建筑面积为4300m2，类似工程的建筑面积为3200m2，预算成本为826900元，类似工程各种费用占预算成本的权重是：人工费8%、材料费65%、机械费12%、措施费9%、间接费15%、其他费8%；拟建工程地区与类似工程地区造价之间的差异系数为K1=1.03、K2=1.05、K3=0.90、K4=0.96、K5=1
That’s not good enough, however, the same stability that makes CFC so safe in industrial use makes them extremely longlives, some of the CFCs released today will still be in the atmosphere a century from now. Moreover, each atom of chlorine liberated form. a CFC can break up as many as 100,000 molecules of ozone.
For this reason, governments should ensure the careful handling and recycling of the CFC now in use. When plastic-foam burger holders are broken, the CFCs trapped inside escape. Discarded refrigerators re- lease CFCs as well, and, a significant part of the U.S. contribution to CFC emissions comes from draining automobile air conditioners. Such release of CFCs could be prevented if consumers and businesses were offered cash incentives to return brokendown air conditioners and refrigerators to auto and appliance dealers. Then the units could be sent back to the manufacturers so that the CFCs could be reused.
While recycling will help, the only sure way to save the ozone is a complete ban on CFC manufacture, which should be phased out over the next five years. Fortunately, as the Montreal Protocal demonstrates, banning CFCs will be far simpler than reducing other dangerous gases. But a ban could admittedly be economically disruptive to the entire world: the annual market for CFCs is some $ 2.2 billion. The Soviet Union, which is a heavy user of CFCs, will have a particularly tough time phasing out the chemicals. "I agree with the ban in principle, "said Vladimir Sakharov, a member of the Soviet State Committee for Enviromental Protection, "but in practice it will be extremely difficult. Our economy is not flexible as others."
To make the transition easier, chemical companies are working hard to find practical substitutes for CF- Cs. The most promising approach so far is to use CFC family members that are chemically altered to make them less dangerous to the environment. The chlorine - free substitutes is the high cost of making them. It may be that until better manufacturing techniques are developed, consumers will have to pay more for affected products. The prospect is not a pleasant one, it is a small price to pay for curbing tile green house effect and saving the life -preserving ozone layer.
Why should governments ensure tire careful handling and recycling of the CFCs now in use？
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