中文说明：
matlab画传输线上电压分布曲线图：传输线特性阻抗Z0=50，求线上电压分布，并画出与z 的关系曲线（用matlab 划出曲线图）。
English Description：
Draw the voltage distribution curve of transmission line with Matlab: the characteristic impedance of transmission line is Z0 = 50, calculate the voltage distribution on the line, and draw the relationship curve with Z (draw the curve with Matlab).