Please summarize the words According to 6 the degree of nonlinearity of ISPs can be analyzed 3 29 as follows 1 If $barbarchi cdot barA ll 1$ corresponding to weak scatterers the Taylor terms for $n ge

According to previous research, the degree of nonlinearity of ISPs can be analyzed in different ways. If the scatterers are weak, the Taylor terms for higher orders can be ignored, thereby reducing the problem to a linear one. However, in practice, measured scattered fields are often contaminated with noise, making direct inversion of the linear operator meaningless. In such cases, regularization techniques like Tikhonov regularization are necessary to balance accuracy in data fitting and solution stability. For moderate scatterers, multiple scattering effects inside the scatterers become strong, and low-degree polynomials should be included in the estimation of scattered fields. This turns the problem into a nonlinear optimization task, requiring nonlinear optimization methods. For strong scatterers, multiple scattering effects are intensive, and a higher degree of polynomial or even nonpolynomial relationship exists between the scattered fields and contrast function. In such cases, obtaining a solution is challenging even in the absence of noise