Inverse Problems, Layer Stripping and the Riesz Transform

主要研究人员和合作者针对无损分层介质(一维Helmholtz方程)发展了一种数学上严格且高度稳定的逆散射算法，该算法成功地处理了高噪声水平的实验遥感数据。该方法是一种基于非线性Riesz变换的剥层方法，而不是迹公式。它的特点是一个非线性Plcherel等式和一些非线性Payley-Weiner定理。与Riesz变换一起，即使在存在强烈多次反射的情况下，这些方法也允许我们开发出相当完整的傅立叶分析。在这个项目中，我们计划研究将这些方法扩展到更复杂的(例如，有损和非分层)介质。有关更详细的概述，请参见www.math.washington.edu/~Sylvest/。科学的根本任务是探索我们周围的世界。实现这一目标最有效的方法是以波的形式将能量引导到一个物体上，并在波与该物体相互作用后观察它们。例如，传统的照片是通过将光波从闪光灯引导到研究对象并将反射波形成的图像记录在胶片上产生的。虽然这样的实验结果很容易被人类科学家理解(我们可以只看图片)，但使用更深入研究介质的波(如微波、X射线和一些声波)进行的类似实验的结果没有直接意义。深入到介质中的波使我们有机会看到表面下的情况。然而，我们得到的图片是一堆顶部表面及其下面的不同层的图像，所有这些图像都叠加在同一张“照片”上。此外，还有更多由层间内部反射(多次反射)形成的重叠图像。这个项目继续开发一种数学方法，将一张由一叠叠加图像组成的“微波照片”变成一堆单独的照片，每一张照片都包含介质的单层图像。从这些单独的照片中，我们看到了潜在媒介的真实结构。

The principal investigator and collaborators have developed a mathematically rigorous and highly stable inverse scattering algorithm for a lossless stratified medium (1-D Helmholtz Equation), which has successfully treated experimental remote sensing data with high noise levels. The method is a layer stripping method, based on a nonlinear Riesz transform, rather than a trace formula. It features a nonlinear Plancherel equality and some nonlinear Payley-Weiner theorems. Together with the Riesz transform, these allow us to develop a rather complete Fourier analysis, even in the presence of strong multiple reflections. In this project, we plan to investigate the extensions of these methods to more complicated (e.g. lossy and non-stratified) media. For a more detailed overview, see "www.math.washington.edu/~sylvest/".The fundamental task of science is to probe the world around us. The most powerful method for accomplishing this goal is to direct energy, in the form of waves, at an object and to observe the waves after they have interacted with that object. For example, a conventional photograph is produced by directing light waves from the flash bulb to the object under study and recording the image formed by the reflected waves on film.While the results of such an experiment can be readily understood by the human scientist (we can just look at the picture), results of analogous experiments using waves which penetrate more deeply into the medium under study (e.g. microwaves, X-rays, and some sound waves) are less directly meaningful.A wave which penetrates deeply into a medium gives us the opportunity to see below the surface. However, the picture we obtain is a stack of images of the top surface and the various layers below it, all superimposed on the same "photograph". In addition, there are even more superimposed images, formed from internal reflections between layers (multiple reflections).This project continues development of a mathematical method for turning a "microwave photograph", made up of a stack of superimposed images, into a stack of individual photographs, each containing the image of a single layer of the medium. From these individual photographs, we see the true structure of the underlying medium.