天文学家们过去一直感到奇怪,为什么只有土星有光环.Astronomers used to ask why only Saturn has rings.“土星族”飞行器可以分为三类或三组.The Saturn family of launch vehicles falls into three types or groups.数值例子大多数取自“土星V”飞行器的研究.Numerical examples are mostly taken ...
to optimize the allocation of resources优化资源配置...Malthus's theories about the ineluctable tendency of populations to exceed resources.马尔萨斯的人口增长会不可避免地超出资源承载限度的理论The management team meets several times a week to juggle...