NURBS curve equation has three kinds of the equivalence form, i. e. rational fraction, rational base function and homogeneous coordinate.
NURBS曲线方程具有三种等价形式：有理分式表示、有理基函数表示和齐次坐标表示。
2
A method for calculation the economic results of the preconcentration using magnetic-pulley separator is recommended and a simple and rational calculation equation is deduced from the method.
本文提出了一种计算磁滑轮预选经济效益的方法，并导出了简单而又合理的计算公式。
3
Based on the new method, the paper discusses an inverse mapping of rational parameter surface, also, the implicit equation of the parametric equation is obtained.