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案例二[背景材料]某住宅楼是一幢地上6层、地下1层的砖混结构住宅，总建筑面积3200m2。在现浇顶层一间屋面的混凝土施工过程中出现坍塌事故，坍塌物将与之垂直对应的下面各层预应力空心板砸穿，10名施工人员与4辆手推车、模板及支架、混凝土一起落入地下室，造成2人死亡、3人重伤、经济损失26万元人民币的事故。从施工事故现场调查得知，屋面现浇混凝土模板采用300mm×1200mm×55mm和300mm×1500mm×55mm定型钢模，分三段支承在平放的50mm×100mm方木龙骨上，龙骨下为间距800mm均匀支撑的4根直径100mm圆木立杆，这4根圆木立杆顺向支承在作为第6层楼面的3块独立的预应力空心板上，并且这些预应力空心板的板缝灌混凝土浇筑仅4天，其下面也没有任何支撑措施，从而造成这些预应力空心板超载。施工单位未对模板支撑系统进行过计算也无施工方案，监理方也未提出异议，便允许施工单位进行施工。出事故时监理人员未在场。[问题] 请简要分析本次事故发生的原因。
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What does the man like doing
Person who is invited to one’s home.
(77) Heredity (遗传) is not the only thing that influences our color. Where we live and how we live after we are born are important too. For instance, our genes influence how fat or thin we are. But our weight depends mainly upon how much we eat and how much exercise we get. In the same way, our skin color depends to a large extent upon how much sunshine we get.When summer arrives and light-colored people go to the beaches, some will tan dark-ly, some will tan lightly and few will not tan at all. Each one has inherited a different abili-ty to tan, but the differences do not appear until the conditions are right. An outdoor man will soon become pale if he changes to an indoor job, while a desk clerk will take on tan after a short vacation in the sun.Sometimes people decide that being tanned is better than being pale. Sometimes they decide the opposite.Centuries ago, most of the people in Europe were peasants and they had to work in the fields all day. Noblemen, on the other hand, did not have to work. They stayed indoors and remained pale. You could always tell a nobleman from a peasant because a peasant had a tan. As a result, a skin so pale that veins (血管) were showed was considered a mark of great beauty.During the Industrial Revolution things changed. Farmers left their fields and went to work in factories, minesand mills. Working for long hours in dimly-lit factories and mines made theirskins pale. (78) Wealthy people, however, could afford to travel to sunny countries. They had the leisure to lie around on the beaches and get tan. Having a tan became a sign of wealth.In Western Europe and North America pale skin is no longer desirable. Instead of bleaching themselves white with lemon juice, many women spend their time under a sun-lamp. The desire for a quick tan has led to the invention of pills and lotions (涂剂) that darken the skin artificially without exposure to sunlight. These pills and lotions can be bought by anyone at any drugstore. A rich man can spend hundreds of dollars on a vacation in the sunny West Indies and get his suntan there. But his lowest-paid clerk can have what looks like the same tan out of a bottle for a few cents. Pills and lotions have been invented in Western Europe and North America ______.
Heredity(遗传)is not the only thing that influences our color．
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