在2002年9月，发现号航天飞机的第二次重大修改(船上监测手册)用于维修和升级的时期做好准备。
In September of 2002, Discovery was ready for its second Orbiter Major Modification (OMM) period for maintenance and upgrades.
设计、材料和制造工艺的改进，意味着今天的汽车安全行驶寿命比以往任何时期都长——尽管车主必须不断的进行维护和维修。
Improvements in design, materials and manufacturing mean that today's vehicles can be operated safely longer than ever, albeit at the cost of continuous maintenance and repair.
基于此规律，有针对性地提出了延缓病害转化的三个关键时期的养护维修对策和实施时机的选择方法。
Based on this rule, it puts forward three keys to delay disease conversion in period of the implementation of conservation measures and the timing of repair options.
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