1,721,267 research outputs found
Magnetization reversal mechanism switching between domain wall displacement and coherent rotation: theory and observation
No full textA new torque magnetometric method for measuring M-H hysteresis loops of small magnetic anisotropy materials
No full textParameter robust control design using bimatrix co-evolution algorithms
No full textThe parameter robust controller design problem is often expressed as a game between the controller and uncertain parameters. The game is expressed as a constrained minimax problem if design requirements are treated as the constraints, but the saddle-point solution of the constrained minimax problem is difficult to obtain by using conventional methods. This paper proposes a new method of designing parameter robust controllers by introducing a bimatrix co-evolution algorithm which solves the constrained minimax problem. The proposed algorithm approximates the problem as a bimatrix game between two groups having independent fitness measures and finds the saddle-point solution through successive bimatrix games. The resulting controller guarantees robustness against bounded parameter uncertainties and satisfies the design requirements. The performance of the proposed algorithm is verified by its application to a satellite attitude control problem
EFFECTS OF PD PREDEPOSITION LAYER ON MAGNETIC-PROPERTIES IN COMPOSITIONALLY MODULATED CO/PD MULTILAYERS
No full textWe have investigated the effects of Pd predeposition layer on magnetic properties in compositionally modulated Co/Pd multilayers. The samples were prepared at the Ar sputtering pressure of 10 mTorr by dc magnetron sputtering. The thickness of the Pd predeposition layer was varied from 0 to 1000 angstrom with a 100 angstrom interval. It was observed that the magnetic properties of the saturation magnetization, the perpendicular anisotropy energy, and the coercivity remained relatively constant until the thickness of the predeposition layer was up to 600 angstrom. However, those were rapidly increased with the predeposition-layer thickness when the thickness was thicker than 600 angstrom. The results were caused by a change in the microstructure of the multilayers deposited on different predeposition-layer thicknesses.This work was supported in part by the Korea Science
and Engineering Foundat.ion
Two-stage active noise control with online secondary-path filter based on an adapted scheduled-stepsize NLMS algorithm
No full textA two-stage active noise control (ANC) system is proposed for non-stationary environments: a secondary-path filtering (SPF) stage and a control filtering (CF) stage. The secondary-path filter is roughly trained as quickly as possible in the SPF stage. Based on the trained secondary-path filter, the control filter is trained to minimize the residual errors sensed by an error microphone in the CF stage. A stage-switching algorithm is designed to exchange between the SPF stage and the CF stage based only on signals from the error microphone, which moves the CF stage to the SPF stage whenever the residual errors reach up to a certain level in which the control filter cannot suppress the residual errors mainly caused by the change of the secondary path. To train the secondary-path filter and the control filter quickly and robustly, a scheduled-stepsize normalized least mean square (NLMS) algorithm is adapted to handle not only measurement noises but also disturbances mutually generated between the training of the secondary-path filter and that of the control filter. Since the adapted scheduled-stepsize NLMS algorithm presets the optimal stepsizes for each iteration, the proposed ANC system trains quickly the filters without the additional computations and reduces the residual errors over other ANC systems. (C) 2019 Elsevier Ltd. All rights reserved.11Nsciescopu
New measurement techniques to determine magnetization and coercivity using a torque magnetometer
No full textWe have developed new techniques to measure the magnetization and the coercivity of a uniaxial magnetic material using a torque magnetometer. The magnetization could be measured from the linear dependence at the low-field regime in a plot of the torque versus the applied magnetic field, where the direction of the applied field. was perpendicular to the uniaxial orientation. The coercivity could be obtained by taking the value of the applied field where the torque is zero, when the direction of the applied field was (180+delta) degrees from the uniaxial orientation. The techniques were applied to determine the magnetizations and the coercivities of several Co/Pd multilayer thin films. The results were confirmed to be similar within a 2% difference to those obtained by a vibrating sample magnetometer
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