首先优化年度检修计划，而月和日运行计划则在年度检修计划的基础上，以系统可靠性和运行费用为目标进行优化。
The annual ms is optimized first, and the monthly and daily operation scheduling problems are then optimized on the annual ms with the aim of minimizing the risk and operation costs.
一种被冰覆盖的绕日运行的小天体，通常有着一个极高度椭圆的轨道，这使其在轨道的一端尽头非常接近太阳，而在轨道另一端尽头却离太阳非常遥远。
A small icy object orbiting the Sun, often in a very highly elliptical orbit which takes it very close to the Sun at one end of its orbit, and very far away from the Sun at the other end of its orbit.
1990年的11月13日，万维网首次运行。
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