变约 meaning in English

alter an agreement

We discuss the effect on the focusing of the probe beams for the five initial parameters : the amplitude of the pump beam , the separation between the pump and the probe beam centers , the wavelength ratio of the pump and the probe beams and the ratio of the initial beam widths at the directions of x and y . our numerical results show that , more the amplitude of the pump beam , the wavelength ratio of the pump and the probe beams and the ratio of the initial beam widths at the direction of y , more the probe focus ; the separation between the pump and the probe beam centers and the ratio of the initial beam widths at the direction of x have optimum values , respectively
研究了泵浦光束输入振幅、泵浦光束-信号光束初始偏移、泵浦光束-信号光束波长比和泵浦光束-信号光束x 、 y方向的初始束宽比五个参量对信号光束聚焦程度的影响。数值模拟结果表明，泵浦光束输入振幅越大、泵浦光束-信号光束波长比越大、 y方向束宽比越大，信号光束聚焦程度越大；泵浦光束-信号光束初始偏移和x方向初始束宽比都存在一个最佳值，使得光束聚焦达到最佳效果，有趣的是这两个最佳值的比值基本保持不变约为0 . 4 0 . 6 。