steradian
🇬🇧/stəˈreɪdɪən/ 🇺🇸/stɪˈredin/ 66the angle that, having its vertex in the centre of a sphere, cuts off an area of the surface of the sphere equal to the square of the length of the radius 球面度
noun [专属名词]球面度;立体角;立体弧度;球面角度
The ideal cosine entrance system is required for measuring the total radiation of the solar including the direct radiation.
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