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Full-Text Articles in Physics

Modeling Of Micromagnetic Barkhausen Activity Using A Stochastic Process Extension To The Theory Of Hysteresis, David C. Jiles, Levent B. Sipahi, G. Williams May 1993

Modeling Of Micromagnetic Barkhausen Activity Using A Stochastic Process Extension To The Theory Of Hysteresis, David C. Jiles, Levent B. Sipahi, G. Williams

Materials Science and Engineering Publications

Recent work by Bertotti [IEEE Trans. Magn. MAG‐24, 621 (1988)] and others has shown that it is possible to model the micromagnetic Barkhausen discontinuities at the coercive point using a two‐parameter stochastic model. However, the present formulation of the model is restricted to limited regions of the hysteresis curve over which dM/dH is approximately constant and whendH/dt is held at a constant rate. A natural extension of this model is to take the basic result, in which the level of Barkhausen activity in one time period is related to the activity in the previous time ...


Comprehensive Analysis Of Barkhausen Emission Spectra Using Pulse Height Analysis, Frequency Spectrum, And Pulse Wave Form Analysis, Levent B. Sipahi, David C. Jiles, D. Chandler May 1993

Comprehensive Analysis Of Barkhausen Emission Spectra Using Pulse Height Analysis, Frequency Spectrum, And Pulse Wave Form Analysis, Levent B. Sipahi, David C. Jiles, D. Chandler

Materials Science and Engineering Publications

The dependence of magnetic Barkhausen emissions (MBE) upon both field excitation and detection frequencies and excitation wave form was studied in order to investigate two of several crucial factors which affect the emissions. Sinusoidal, triangular, and square wave forms were used to generate the MBE and the pulse height spectra, frequency spectra, and pulse wave forms of these signals were analyzed. The frequency spectra of sinusoidal and triangular alternating field excitations showed similar behavior but the spectrum under square wave excitation was different due to the existence of high frequency components during square wave switching. As yet, no common standard ...


General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart Jan 1993

General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart

Review of Progress in Quantitative Nondestructive Evaluation

This paper presents an approach to automated flaw detection (AFD) in an arbitrary X-ray image. The intensities in the digitized radiographic image are modeled as piecewise-smooth surface functions corrupted by noise and flaws. It has been observed that radiographs generated for NDE purposes containing flaws also have a combination of three unwanted features; background trends, geometrical structures, and noise. These features inhibit the performance of automated flaw detection algorithms. The proposed general processing scheme reduces the unwanted features in such a way that candidate flaws within the image can be identified. The proposed scheme is robust and is applicable to ...


Experiments With Double Microwave Apertures, John Basart, Zhong Zhang Jan 1993

Experiments With Double Microwave Apertures, John Basart, Zhong Zhang

Review of Progress in Quantitative Nondestructive Evaluation

One of the significant characterizations of microwave imaging is the spatial resolution. The relative long wavelength of microwaves as compared to ultrasonic waves and x-rays necessarily means that aperture arrays (real-time or synthetic) are required for high-resolution microwave imaging. Certain limitations on resolution apply regardless of how the array is realized. Types of antenna arrays fall into two broad categories: Phased arrays which are usually operated in real time by scanning a beam past an object, and aperture synthesis in which data are collected with one or more antennas and later processed to produce an image. In NDE we are ...