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Full-Text Articles in Physics

Self-Enhancement Of Dynamic Gratings In Photogalvanic Crystals, Nickolai Kukhtarev, Sergei F. Lyuksyutov, Preben Buchhave, Tatiana Kukhtareva, K. Sayano, Partha P. Banerjee Nov 1998

Self-Enhancement Of Dynamic Gratings In Photogalvanic Crystals, Nickolai Kukhtarev, Sergei F. Lyuksyutov, Preben Buchhave, Tatiana Kukhtareva, K. Sayano, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

We have developed a compact closed-form solution of the band transport model for high-contrast gratings in photogalvanic crystals. Our solution predicts the effect of the photoconductivity and the electric field grating enhancement due to the photogalvanic effect. We predict a pronounced dependence of the steady-state photogalvanic current on the contrast of the interference pattern and an increase of holographic storage time due to the enhancement of the photoconductivity grating contrast. In the high contrast limit and a large photogalvanic effect the refractive index grating will be shifted from the position of the intensity modulation pattern, contrary to the usually adopted ...


Experimental Investigations Of Wavelength And Angular Errors In Holographic Gratings With Non-Bragg-Matched Read Beams, Monish Ranjan Chatterjee, Vivek Ray Jul 1998

Experimental Investigations Of Wavelength And Angular Errors In Holographic Gratings With Non-Bragg-Matched Read Beams, Monish Ranjan Chatterjee, Vivek Ray

Electrical and Computer Engineering Faculty Publications

Perfect Bragg matching is generally desirable for accurate optical interconnections with holographic gratings. In reality, however, gratings may be illuminated by READ beams with non-Bragg-matched angles, or wavelengths, or both. In such cases, the scattered beams are generally misdirected, and may suffer loss of efficiency and possibly more serious errors such as crosstalk noise or missed connections. A conventional wave-vector triad method of analyzing the scattered beam errors leads readily to near-Bragg estimates of the output angular misalignment. However, the READ wave-vector triads appear to indicate a possible wavelength shift in the output beam even with a Bragg-matched READ wavelength ...


Finite Element Analysis Of The Influence Of A Fatigue Crack On Magnetic Properties Of Steel, Y. Shi, David C. Jiles Jun 1998

Finite Element Analysis Of The Influence Of A Fatigue Crack On Magnetic Properties Of Steel, Y. Shi, David C. Jiles

Center for Nondestructive Evaluation Publications

Fatigue can affect the magnetic properties of materials due to microstructural changes. Previous investigations have shown that several structure sensitive magnetic properties, such as coercivityHc and remanenceBr, changed systematically as a result of fatigue. When approaching failure the accumulated changes in microstructure resulted in the occurrence of fatigue cracks and the magnetic properties showed dramatic changes which mainly resulted from the geometrical changes in samples due to the cracks. It was found that the remanenceBr followed the changes in stress, while the coercivityHc sometimes showed different trends. In this article the influence of the size and the position of a ...


Domain-Wall Motion In Random Potential And Hysteresis Modeling, M. Pasquale, V. Basso, G. Bertotti, David C. Jiles, Y. Bi Jun 1998

Domain-Wall Motion In Random Potential And Hysteresis Modeling, M. Pasquale, V. Basso, G. Bertotti, David C. Jiles, Y. Bi

Ames Laboratory Publications

Two different approaches to hysteresis modeling are compared using a common ground based on energy relations, defined in terms of dissipated and stored energy. Using the Preisach model and assuming that magnetization is mainly due to domain-wall motion, one can derive the expression of magnetization along a major loop typical of the Jiles–Atherton model and then extend its validity to cases where mean-field effects and reversible contributions are present.


Attitude Measurement, Mark A. Stedham, Partha P. Banerjee, Seiji Nishifuji, Shogo Tanaka Jan 1998

Attitude Measurement, Mark A. Stedham, Partha P. Banerjee, Seiji Nishifuji, Shogo Tanaka

Electrical and Computer Engineering Faculty Publications

In many practical situations, it is important to determine and measure the attitude of a particular vehicle, such as a ship, an airplane, a piece of mechanical equipment such as a, crane lifter, or a spacecraft. For this reason, many attitude sensors have been developed with advanced computer and semiconductor technologies. This section first introduces the various attitude sensors with an explanation of their operating principles and then presents several methodologies for attitude measurement and determination, including ships and crane lifters, aircraft, and spacecraft applications.


Measurements And Modeling Of The Effects Of An Orthogonal Bias Field On Properties Of Isotropic Magnetic Materials , Ying Bi Jan 1998

Measurements And Modeling Of The Effects Of An Orthogonal Bias Field On Properties Of Isotropic Magnetic Materials , Ying Bi

Retrospective Theses and Dissertations

The effects of the orthogonal bias field were investigated systematically in this study. The measurements on various magnetic materials under different experimental conditions showed that the orthogonal bias field rotated the hysteresis loop reducing permeability and reduced its enclosed area. As a result, permeability, hysteresis loss, coercivity and remanence decreased with increasing orthogonal bias field. The experimental results indicated that the orthogonal field reduced hysteresis loss by increasing the component of reversible domain rotation magnetization;In the present study, the Jiles-Atherton model has been expanded to include the effect of an orthogonal bias field. Based on the experimental observation, a ...