利用J-A模型求解磁滞回线时，使用龙格库塔四阶方法求解微分方程的代码，并可以将求解结果直接绘制成磁滞回线图像-When the J-A model is used to solve the hysteresis loop, the Runge-Kutta fourth-order method is used to solve the differential equation code, and the solution result can be directly drawn as the

绘制磁滞回线，模拟磁滞回线产生的过程，便于理论分析建模(Drawing hysteresis loops to simulate the process of hysteresis loops is convenient for theoretical analysis and modeling.)