Computer Algorithms and Architectures for Three-Dimensional Eddy-Current Nondestructive Evaluation. Volume 2. Chapters 1-5

摘要

This report develops an electromagnetic model for three-dimensional inversion of eddy-current data, an inversion algorithm based on the conjugate gradient technique, and a special purpose computer that we estimate can execute this algorithm in times comparable to high speed main-frames. This computer has a pipe architecture and is designed around our parallel implementation of the inversion algorithm and makes use of high-speed DSP chips. The inversion process achieves a higher performance measure when more than one data set is inverted. The sequential order of the inversion scheme restricts the number of active elements in the pipeline for a single problem. When more than one inversion problem enters the pipe, then more than one element could be active to improve the overall performance of the system. The basic electromagnetic model starts with the integral equations for electromagnetic scattering, which are then discretized by means of the method of moments. This gives us the fundamental inversion model, which is then solved using the conjugate gradient algorithm. In order to accomplish the three-dimensional inversion, we acquire data at a number of frequencies; therefore, our inversion process is called a multifrequency method. The choice of frequencies, and the number of frequencies to be used, depend upon the conductivity of the host material, and the depth resolution sought. (kr)