Nonlinear Inverse Scattering Methods for Large Objects

WPC 2 R B J Z X 编号|X X 6 X @ K X @ QMS JetScript QMSJETSC.PRS X @ 啊啊啊 }X @T ? x x x X 6 X @ K X @ 不 R H H H H 6 X @ K h @ 2 u 6~ ; ) ! t - S ：t @ ，` ; & % t：u 2 4英寸 u$ u 不 3 y u O 不 2 9302145 Chew在保华五年资助计划的前期支持下，研究人员在逆散射和前向散射理论方面取得了重大进展。 提出了一种新的非线性逆散射方法来处理散射体内部的多重散射效应。 玻恩迭代法（BIM）和扭曲玻恩迭代法（DBIM）的发展，证明了反演的对象与对比度高达10：1，并表现出超分辨率的顺序为0.1波长。 另一种新的技术称为局部形状函数（LSF）方法被开发用于对金属散射体进行逆散射，其中先前的方法由于极强的非线性而未能产生收敛解。 最近，人们发现，LSF方法也可以用于反演介质散射和绕过10：1的对比度限制。由于需要反演非常大的散射体，因此对快速前向散射求解器进行了研究。 这些快速算法精确地解决了散射问题，并通过利用散射计算中的固有冗余来节省计算。 第一个算法（RTMA）解决了 ? 0 散射问题适用于所有入射源）（N 2.5 通过利用波动现象的平移性质进行操作。 下一个算法（RATMA）利用了聚合 ? 时间复杂度为O（N） 2 ）算法。 新算法（NEPAL）使用曲面等效原理， ? 一个O（N 1.5 ）算法，该算法适合于并行处理。目前的建议是继续发展新的非线性逆散射理论。 我们计划离开玻恩型方法，并利用新的方法参数化的散射对象，以实现最佳的重建。 我们将使用我们在快速前向散射求解器方面的进展作为构建模块，以加快反演并解决更大的物体。 还将研究解决大型物体，特别是埋在缓慢变化的不均匀背景中的物体的其他方法。 最后，我们希望开发新的实验装置，可以实现高保真度的测量，使这些新的逆方法的全部潜力，可以在一个实际的系统中实现。

WPC 2 R B J Z X Courier #| x x 6 X @ K X @ QMS JetScript QMSJETSC.PRS x @ h h h h }X @T ? x x x x 6 X @ K X @ T R & H H H H 6 X @ K h @ 2 u 6~ ; ) ! t - S :t @ ,` ; & % t : u 2 4 " u$ u t 3 y u O t 2 9302145 Chew The previous support period under the 5 year PYI grant enabled the investigator to make significant progress in both inverse and forward scattering theory. New non linear inverse scattering methods were developed to account for multiple scattering effects within the scattering object. The Born iterative method (BIM) and distorted Born iterative method (DBIM) were developed that demonstrated the inversion of objects with contrasts as great as 10:1 and exhibited super resolution on the order of 0.1 wavelengths. Another new technique known as the local shape function (LSF) method was developed to perform inverse scattering on metallic scatters where previous methods failed to produce a convergent solution due to extremely strong nonlinearities. Recently it was found that the LSF method could also be used for the inversion of dielectric scatters and bypass the 10:1 contrast limitation. The need to invert very large scattering objects stimulated research in fast forward scattering solvers. These fast algorithms solve the scattering problem exactly and achieve computational savings by exploiting inherent redundancies in the scattering calculations. The first of these algorithms (RTMA) solved the ? 0 scattering problem valid for all incidence sources in )(N 2.5 ) operations by exploiting translational properties of wave phenomenon. T he next algorithm (RATMA) exploited an aggregation ? property resulting in an O(N 2 ) algorithm. The new algorithm (NEPAL) instead uses the surface equivalence principle resulting in ? an O(N 1.5 ) algorithm that is amenable to parallel processing. The current proposal is to continue progress in developing new nonlinear inverse scattering theories. We plan to move away for the Born type methods and exploit new ways of parameterizing the scattering object in order to achieve the best possible reconstruction. We will use our progress in fast forward scattering solvers as building blocks to speed up the inversion and solve much larger objects. Other means of solving large objects, particularly objects buried in a slowly varying inhomogeneous background would be investigated as well. Finally, we wish to develop new experimental apparatus that can achieve high fidelity measurements so that the full potential of these new inverse methods could be achieved in a practical system.