• Title/Summary/Keyword: Oscillating magnetic fields

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Cyclotron Resonance Line Widths in Wurtzite ZnO Structure under Circularly Oscillating Fields

  • Park, Jung-Il
    • Journal of the Korean Magnetic Resonance Society
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    • v.25 no.4
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    • pp.51-57
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    • 2021
  • We study optical quantum transition line widths in relation to magnetic field dependence properties of the electrons confined in an infinite square well potential system between z = 0 and z = Lz in the z - direction. We consider two systems-one is subject to right circularly oscillating external fields and the other is subject to left circularly oscillatory external fields. Our results indicate that the line widths of right circularly oscillating external fields is larger than the line widths of left, while the opposite result is obtained for the line widths.

NUMERICAL SOLUTION OF AN INTEGRO-DIFFERENTIAL EQUATION ARISING IN OSCILLATING MAGNETIC FIELDS

  • PARAND, KOUROSH;DELKHOSH, MEHDI
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.20 no.3
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    • pp.261-275
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    • 2016
  • In this paper, an integro-differential equation which arises in oscillating magnetic fields is studied. The generalized fractional order Chebyshev orthogonal functions (GFCF) collocation method used for solving this integral equation. The GFCF collocation method can be used in applied physics, applied mathematics, and engineering applications. The results of applying this procedure to the integro-differential equation with time-periodic coefficients show the high accuracy, simplicity, and efficiency of this method. The present method is converging and the error decreases with increasing collocation points.

A Numerical Study on the Impinging Jet Flow Characteristics in the Presence of Applied Magnetic Fields (자기장이 인가된 충돌제트의 유동 특성에 관한 수치적 연구)

  • Lee Hyun Goo;Yoon Hyun Sik;Hong Seung Do;Ha Man Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.5 s.236
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    • pp.537-544
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    • 2005
  • The present study numerically investigates two-dimensional fluid flow in the confined jet flow in the presence of applied magnetic field. Numerical simulations to calculate the fluid flow and heat transfer in the confined jet are performed for different Reynolds numbers in the absence and presence of magnetic fields in the range of $0{\le}N{\le}0.05$, where N is the Stuart number (interaction parameter) which is the ratio of electromagnetic force to inertia force. The present study reports the detailed information of flow in the channel at different Stuart numbers. As the intensity of applied magnetic fields increases, the vortex shedding formed in the channel becomes weaker and the oscillating amplitude of impinging jet decreases. The flow fields become the steady state if the Stuart number is greater than a critical value. Thus the pressure coefficients at the stagnation point also vary as a function of Stuart number.

A Numerical Study on the Heat Transfer Characteristics of Impinging Jet Flow in the Presence of Applied Magnetic Fields (자기장이 인가된 충돌제트의 열전달 특성에 관한 수치적 연구)

  • Lee Hyun Goo;Yoon Hyun Sik;Hong Seung Do;Ha Man Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.29 no.6 s.237
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    • pp.653-661
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    • 2005
  • The present study numerically investigates two-dimensional fluid flow and heat transfer ir the confined jet flow in the presence of applied magnetic field. For the purpose of controlling vortex shedding and heat transfer, numerical simulations to calculate the fluid flow and heat transfer in the confined jet are performed for different Reynolds numbers in the absence and presence of magnetic fields and for different Prandtl numbers of 0.02 (liquid metal), 0.7 (air) and 7 (water) in the range of $0{\le}N{\le}0.05$, where N is the Stuart number (interaction parameter) which is the ratio of electromagnetic force to inertia force. The present study reports the detailed information of flow and thermal quantities in the channel at different Stuart numbers. As the intensity of applied magnetic fields increases, the vortex shedding formed in the channel becomes weaker and the oscillating amplitude of impinging jet decreases. The flow and thermal fields become the steady state if the Stuart number is greater than the critical value. Thus the Nusselt number at the stagnation point representing the heat transfer characteristics also vary as a function of Stuart number.

Magnetic Field Measuring System by using Loop-type Sensor (루우프형 센서를 이용한 자장측정계)

  • Lee, Bok-Hee;Kil, Gyung-Suk;Park, Dong-Hwa
    • Journal of Sensor Science and Technology
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    • v.4 no.2
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    • pp.14-21
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    • 1995
  • This paper deals with the active magnetic field measuring system which can measure the time-varying magnetic fields generated by power installations and lightning discharges. The magnetic field measuring system consists of the loop-type magnetic field sensor and the active integrator operated by a differential amplifier. The theoretical principle and design rule of the time-varying magnetic field measuring device and the calibration apparatus are introduced. From the calibration experiments, the frequency bandwidth of the full measuring system ranges from 270 Hz to about 2.3 MHz and the response sensitivity for magentic field strength is 128 $mV/{\mu}T$, respectively, and the calculated B-field values in the center of the loop-type sensor versus the the applied current made with a region of ${\pm}3\;%$error. The actual survey experiments by using lightning impulse current and oscillating impulse current were performed, the results of comparision between the input current waveforms and the magnetic field waveforms are a good agreement with each others and their deviations are less than 0.5 %.

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Oscillatory Josephson-Vortex Resistance in Stacks of $Bi_{2}Sr_{2}CaCu_{2}O_{8+x}$ Intrinsic Josephson Junctions

  • Choi Jae-Hyun;Bae Myung-Ho;Lee Hu-Jong;Kim Sang-Jae
    • Progress in Superconductivity
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    • v.7 no.1
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    • pp.17-21
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    • 2005
  • We report the oscillation of the Josephson vortex-flow resistance in the rectangular stacks of $Bi_{2}Sr_{2}CaCu_{2}O_{8+x}$(Bi-2212) intrinsic Josephson junctions (IJJs). Apiece of Bi-2212 single crystal containing a few tens of IJJs was sandwiched between two gold electrodes and fabricated into a rectangular shape with the typical lateral size of about $1.5{\times}10\;{\mu}m^2$, using e-beam lithography and focused ion-beam etching techniques. In a tesla-range magnetic field applied in parallel with the junction planes, the oscillation of the Josephson vortex flow resistance was observed at temperatures near 60 K. The oscillation results from the interplay between the triangular Josephson vortex lattice and the potential barrier at the boundary of a single crystal. The oscillatory magnetoresistance for different bias currents, external magnetic fields, and the tilt-angles provides useful information on the dynamics of the coupled Josephson-vortex lattice system.

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Application of a New NDI Method using Magneto-Optical Film for Inspection of Micro-Cracks (미소균열 탐상을 위한 자기광학소자를 이용한 비파괴탐상법의 제안과 적용)

  • Lee, Hyoung-No;Park, Han-Ju;Shoji, Tetsuo
    • Journal of the Korean Society for Nondestructive Testing
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    • v.21 no.2
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    • pp.197-203
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    • 2001
  • Micro-defects induced by design and production failure or working environments are known as the cause of SCC(Stress Corrosion Cracking) in aged structures. Therefore, the evaluation of structural integrity based on micro-cracks is required not only a manufacturing step but also in-service term. So we introduce a new nondestructive inspection method using the magneto-optical film to detect micro-cracks. The method has some advantage such as high testing speed, real time data acquistion and the possibility of remote sensing by using of a magneto-optical film that takes advantage of the change of magnetic domains and domain walls. This paper introduces the concept of the new nondestructive inspection method using the magneto-optical film, also proves the possibility of this method as a remote testing system under oscillating load considering application on real fields by applying the method to four types of specimens.

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The three dimensional measuring system for ELF magnetic fields with the multiturn loop-type sensors (멀티턴 루우프형 센서를 이용한 3차원 ELF 자장측정계)

  • Lee, Bok-Hee;Lee, Jeong-Gee;Kil, Gyung-Suk;Ahn, Chang-Hwan;Park, Dong-Hwa
    • Journal of Sensor Science and Technology
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    • v.5 no.2
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    • pp.29-36
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    • 1996
  • With the three dimensional magnetic field measuring system dealt with in this paper, accurate measurements and analyses of extremely low frequency(ELF) magnetic fields caused by starting and/or operating electric devices and power installations can be conducted. To obtain high performance for lower frequency and spatial components without any distortion, the measuring system is designed as three dimensionally including the multiturn loop-type magnetic field sensors, differential amplifiers and active integrators. As the results of calibration experiments, the frequency response characteristics of the measuring system range from 8[Hz] to about 53[kHz] for each direction of x, y, z axes, and the response sensitivities are 9.54, 9.21, $10.89[mV/{\mu}T]$, respectively. The actual survey experiments by using an oscillating impulse current generator confirm a reliability of the proposed measuring system. Also, through the other experiments by using small-sized induction motors, the magnetic field intensities when starting and steady-state operating mark 15.8, $8.61[{\mu}T]$ as maximum value, respectively. And those intensities decrease steeply according as the measuring distance increases.

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