Cepheid variable stars are stars whose brightness changes at regular periods.造父变星是一种光线按规律周期发生变化的恒星.His first great discovery was made when he recognized a Cepheid variable star.他的首次重大发现产生于他认识了一颗造父变星的时候....
我们筑起土坝,防止洪水泛滥.We built banks of earth to hold back the flood waters.在道路、桥头等工程中,公路路堤和桥头土坝等基础刚度较小,与地基刚度相差不大.The rigidity of highway bank and dyke is small compared with the one of highway base....