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Full-Text Articles in Engineering

Eddy Current Automatic Flaw Detection System For Heat Exchanger Tubes In Steam Generators , Sheng-Fa Chuang Jan 1997

Eddy Current Automatic Flaw Detection System For Heat Exchanger Tubes In Steam Generators , Sheng-Fa Chuang

Retrospective Theses and Dissertations

In this dissertation we present an automatic flaw detection system for heat exchanger tubes in steam generators. The system utilizes two well-known techniques, wavelets and fuzzy logic, to automatically detect the flaws in tubing data. The analysis of eddy current inspection data is a difficult task which requires intensive labor by experienced human analysts. To aid the analysts, an accurate and consistent automatic data analysis package was developed. The software development is divided into three parts: data preprocessing, wavelet analysis, and a fuzzy inference system. The data preprocessing procedure is used to set up a signal analysis standard for different ...


Adaptive Iir Filtering Using The Homotopy Continuation Method , Sangmin Bae Jan 1997

Adaptive Iir Filtering Using The Homotopy Continuation Method , Sangmin Bae

Retrospective Theses and Dissertations

The objective of this study is to develop an algorithmic approach for solving problems associated with the convergence to the local minima in adaptive IIR filtering. The approach is based on a numerical method called the homotopy continuation method;The homotopy continuation method is a "solution exhaustive method" for calculating all solutions of a set of nonlinear equations. The globally optimum filter coefficients correspond to the solutions with minimum mean square error. In order to apply the technique to the adaptive IIR filtering problem, the homotopy continuation method is modified to handle a set of nonlinear polynomials with time-varying coefficients ...


Nde Data Fusion Using Morphological Approaches , Young-Won Song Jan 1997

Nde Data Fusion Using Morphological Approaches , Young-Won Song

Retrospective Theses and Dissertations

The objective of most data fusion algorithms is to combine information made available by various sensors synergistically in order to enhance the overall level of information. Since information obtained from data sources such as sensors is often incomplete or imprecise in nature, the application of data fusion techniques has evoked interest in a number of fields ranging from robotics to nondestructive evaluation (NDE). In NDE applications, such techniques can be used to integrate and fuse data obtained using multiple inspection modalities to produce a more comprehensive picture of the condition of the test specimen. As an example, ultrasonic and eddy ...


Advanced Eddy-Current Methods For Quantitative Nde , Cheng-Chi Tai Jan 1997

Advanced Eddy-Current Methods For Quantitative Nde , Cheng-Chi Tai

Retrospective Theses and Dissertations

The objectives of this dissertation were to devise and develop advanced eddy-current methods for quantitative NDE. The techniques used include time-domain methods (pulsed eddy current), frequency-domain methods (swept-frequency eddy current), and the photoinductive imaging method that combines eddy-current and laser-based thermal-wave techniques. We first developed theoretical models to predict the pulsed eddy current signal and showed this technique can be used to characterize metallic coatings on metal substrates. A feature-based rapid inversion method was developed to determine the conductivity and thickness of the coating simultaneously. In the second work, we studied the fundamentals of eddy current interactions with magnetic metals ...


Signal Processing And Image Restoration Techniques For Two-Dimensional Eddy Current Nondestructive Evaluation , Bing Wang Jan 1997

Signal Processing And Image Restoration Techniques For Two-Dimensional Eddy Current Nondestructive Evaluation , Bing Wang

Retrospective Theses and Dissertations

This dissertation presents a comprehensive study on the forward modeling methods, signal processing techniques, and image restoration techniques for two-dimensional eddy current nondestructive evaluation. The basic physical forward method adopted in this study is the volume integral method. We have applied this model to the eddy current modeling problem for half space geometry and thin plate geometry. To reduce the computational complexity of the volume integral method, we have developed a wavelet expansion method which utilizes the multiresolution compression capability of the wavelet basis to greatly reduce the amount of computation with small loss in accuracy. To further improve the ...


Diffraction-Corrected Synthetic Aperture Focusing For Spherical Ultrasonic Radiators , Wassef Munther Masri Jan 1997

Diffraction-Corrected Synthetic Aperture Focusing For Spherical Ultrasonic Radiators , Wassef Munther Masri

Retrospective Theses and Dissertations

Synthetic Aperture Focusing Techniques (SAFT) represent a special class of beam-steering algorithms. They are employed to improve the signal-to-noise ratio (SNR) and resolution of ultrasonic images. Such techniques have traditionally been implemented assuming a geometrical model that neglects the effects of diffraction. This dissertation accounts for diffraction effects by using an analytical model based on the Rayleigh-Sommerfeld formula. The model has been extended to characterize the acoustic fields in an immersed solid; a case frequently encountered in scanning acoustic microscopy applications. The results are then verified by comparing them with results obtained using a finite element model;The analytical model ...