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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Magnetics
Journal Basic Information
Journal DOI :
The Korean Magnetics Society
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Volume & Issues
Volume 17, Issue 4 - Dec 2012
Volume 17, Issue 3 - Sep 2012
Volume 17, Issue 2 - Jun 2012
Volume 17, Issue 1 - Mar 2012
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Ab initio Study for Electronic Property and Ferromagnetism of (Cu, N, or F)-codoped ZnO
Kang, Byung-Sub ; Chae, Kwang-Pyo ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 163~167
DOI : 10.4283/JMAG.2012.17.3.163
The effects on the ferromagnetism of the O or Zn defect in Cu-doped ZnO with the concentration of 2.77-8.33% have been investigated by the first-principles calculations. The Cu doping in ZnO was calculated to be a kind of p-type ferromagnetic half-metals. When the Zn vacancy exists in Cu-doped ZnO, the Cu magnetic moment increases, while for the O vacancy it is reduced. It is noticeable that the ferromagnetic state was originated from the hybridized O(2p)-Cu(3d)-O(2p) chain formed through the p-d coupling. The carrier-mediated ferromagnetism by nitrogen or fluorine does not depend on their concentration.
Irreversibility and Thermoremanent Magnetization in Y
Ismail, Agustina ; Yansen, W. ; Rajagukguk, R. ; Kwon, Y.M. ; Kim, J. ; Lee, B.W. ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 168~171
DOI : 10.4283/JMAG.2012.17.3.168
Irreversible magnetization between the zero-field-cooled (ZFC) and field-cooled (FC) states in
(x=0 and 0.2) was investigated.
have a hexagonal structure and the lattice parameter a decreases from 7.4408
while c increases from 12.2244
, respectively. An anomaly is observed at around 74 K in ZFC and FC magnetization measurements for
, whereas in
are split at low temperature, indicating glass-like behavior.
The Low-Radiation Dosimetry Application of "tris" Lyoluminescence using Electron Paramagnetic Resonance at Low Temperature
Son, Phil-Kook ; Choi, Suk-Won ; Kim, Sung-Soo ; Gwag, Jin-Seog ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 172~175
DOI : 10.4283/JMAG.2012.17.3.172
We present a method for detecting very weak radiation by analyzing the inner structure of irradiated tris (lyoluminescence) materials using electron paramagnetic resonance (EPR) at low temperature. Organic materials have been looked into for use in emergency dosimetry of inhabitants around radiation accidents. However, this technology has never been applied to imperceptible radiation doses (< 0.5 Gy) because there is no proper method for detecting the change of inner structure of the subject bombed by very weak radiation at room temperature. Our results show that tris materials can be applied as a radiation detectors of very small radiation doses below 0.05 Gray, if EPR is used at low temperature (130 K
270 K). The EPR signal intensity from the irradiated-tris sample had barely faded at all after 1 year.
Electrical Transport and Magnetoresistance of La
(x = 0, 0.1, 0.2, 0.3, 0.4) Composites
Gencer, H. ; Pektas, M. ; Babur, Y. ; Kolat, V.S. ; Izgi, T. ; Atalay, S. ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 176~184
DOI : 10.4283/JMAG.2012.17.3.176
The structural, magnetic and magnetotransport properties of
(x = 0, 0.1, 0.2, 0.3 and 0.4) composites were investigated systematically. X-ray and EDX analysis indicated that Ag is not substituted into the main
phase and remains an additive to the second phase at the grain boundary. The Curie temperature first decreased from 269 K for x = 0 to 257 K for x = 0.1 and then remained nearly unchanged with increasing Ag content. For the x > 0.1 samples, a second transition temperature (
) was observed in the resistance curves. At temperatures below 150 K, a significant enhancement in MR was observed while high temperature MR decreased with increasing Ag content. The maximum MR was observed to be 55% in the x = 0.4 sample at 10 K and a 6T magnetic field, this value is larger than that of pure
(53% at 265 K and 6 T). In addition, at low fields (H < 1T), a sharp increase in the MR was observed.
Coercivity of Near Single Domain Size Nd
Kwon, H.W. ; Yu, J.H. ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 185~189
DOI : 10.4283/JMAG.2012.17.3.185
The coercivity of near single domain size
-type particles prepared by ball milling of HDDR-treated
alloy was investigated. The feasibility of a surface nitrogenation for improving the coercivity stability of the fine
-type particles was also studied. The near single domain size
-type particles had a high coercivity of over 9 kOe. However, the coercivity radically deteriorated as the temperature increased in air (< 2 kOe at
). This coercivity reduction was attributed to the soft magnetic phases,
, which formed on the surface of the fine particle due to oxidation. Surface nitrogenation of the fine particles significantly improved the stability of their coercivity. The improvement in coercivity stability was attributed to the formation of a thin nitrogenated layer on the surface of the fine
-type particles, which enhanced the anisotropy field and gave improved resistance to oxidation (dissociation).
Comparative Analysis on Magnetic Field and Inductances of Slotless Permanent Magnet Machine with Two Types of Winding based on Analytical Method
Jang, Seok-Myeong ; Kim, Jeong-Man ; Jeong, Jae-Hoon ; Han, Cheol ; Ahn, Ji-Hun ; Chang, Duk-Jin ; Park, Hyun-Jun ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 190~195
DOI : 10.4283/JMAG.2012.17.3.190
This paper presents an analytical approach to the magnetic field and the inductances of slotless permanent magnet machines with two types of winding. On the basis of a magnetic vector potential and a two-dimensional polar system, analytical solutions for flux density due to a permanent magnet and current are obtained. In addition, self and mutual inductances are obtained using the energy relationship. The analytical results are extensively validated by the nonlinear finite element method and by experimental results.
Calculation of Winding Inductances for a Single-Phase Brushless DC Machine
Joo, Dae-Suk ; Woo, Kyung-Il ; Kim, Dae-Kyong ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 196~199
DOI : 10.4283/JMAG.2012.17.3.196
This paper presents the analytical calculation of winding inductance for a single-phase brushless DC machine based on the magnetic circuit concept. The machine is used in the low power range of applications, such as ventilation fans, due to its simplicity and low cost. Since flux linkage is proportional to inductance, the calculation of winding inductance is of central importance. By comparison with experimental and analytical values, it is shown that proposed analytical expression is able to effectively predict the winding inductance of single-phase brushless DC machines at the design stage.
A Simplified Torque Ripple Reduction using the Current Shaping of the Flux Switched Reluctance Motor
Lee, Heon-Hyeong ; Wang, Qi ; Kim, Se-Joo ; Choi, Woong-Chul ; Lee, Geun-Ho ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 200~205
DOI : 10.4283/JMAG.2012.17.3.200
Recently, applications of the reluctance torque motor have been quite limited due to their inherent limitation of noise and vibration and thus, researches on the reluctance motor have been limited as well. However, with the tremendous increase in the cost of rare earth material magnets, studies of the reluctance torque motor are being conducted more and more. In principle, reluctance torque is generated when the inductance is changed. Therefore, in order to generate continuous torque in the switched reluctance motor, it is necessary to figure out the exact inductance level corresponding to the rotor position and the current level to be applied in that rotor position, respectively. If the current level or the rotor position is not accurately determined, then the generated reluctance torque becomes unstable and undesirable torque ripples prevail to eventually cause noise and vibrations. In this research, a flux switched reluctance motor (FSRM), which is classified into the switched reluctance motor (SRM), was studied. A methodology using the current shaping control according to the rotor position was proposed. Based on the proposed methodology, the optimal current waveform and the torque distribution function for the FSRM to minimize torque ripple was established and demonstrated in this paper.
Nondestructive Evaluation for Remanent Life of 1Cr-0.5Mo Steel by Reversible Permeability
Ryu, Kwon-Sang ; Lee, Yun-Hee ; Park, Jong-Seo ; Baek, Un-Bong ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 206~209
DOI : 10.4283/JMAG.2012.17.3.206
Peak interval for reversible permeability is presented for nondestructively evaluating the remanent life of 1Cr-0.5Mo steel. The method to measure the peak interval of reversible permeability is based on the value of reversible permeability is the same as the differential value of the hysteresis loop. The measurement principle is based on the first harmonics voltage induced in a sensing coil using a lock-in amplifier tuned to a frequency of the exciting voltage. Results obtained for the peak interval of reversible permeability and Rockwell hardness on the aged samples decrease as aging time and the Larson-Miller parameter increase. We could estimate the remanent life of 1Cr-0.5Mo steel by using the relationship between the peak interval of reversible permeability and the Larson-Miller parameter, nondestructively.
Metallic Crack Detections by Planar Inductive Coil Sensor Under AC and DC Magnetic Fields
Lee, Joon-Sik ; Nam, Baek-Il ; Kim, Ki-Hyeon ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 210~213
DOI : 10.4283/JMAG.2012.17.3.210
To detect the surface and the opposite side cracks on iron specimen under AC and DC magnetic fields, the planar inductive coil sensors were employed. When the induced signals were measured, the planar inductive coil sensor and the magnetic field source were lifted off about 2 mm from the top surface of the specimen. AC magnetic fields and DC magnetic fields were applied to the specimens by single straight Cu coil and NdFeB permanent magnet, respectively. The detected signals at crack positions were good coincidence with those of the simulation results.
Observation of Water Level and Temperature Properties by using a Giant Magnetoresistance-Spin Valve Film
Choi, Jong-Gu ; Park, Kwang-Jun ; Lee, Sang-Suk ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 214~218
DOI : 10.4283/JMAG.2012.17.3.214
The water level and temperature properties for the cooling system of potassium titanyl phosphate laser systems were observed. The middle point of the GMR-SV magnetoresistance curve is set in the neighborhood of high magnetic sensitivity (2.8 %/Oe). The experimental results for resistance dependence on water height and temperature showed linear regions with rates of 0.4
, respectively. The proposed results were found to be for adjusting the water level and temperature in the laser cooling system.
Changes in SNR and ADC According to the Increase in b Value in Liver Diffusion-Weighted Images
Cho, Jae-Hwan ; Kim, Ham-Gyum ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 219~224
DOI : 10.4283/JMAG.2012.17.3.219
In the present study, changes in signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) of the diffusion-weighted images in the normal livers were investigated using changes in b values in 1.5 T MR (magnetic resonance) instruments. Respective diffusion-weighted images and ADC map images were obtained from 20 healthy individuals by increasing b values from 50 to 400 and 800
using 1.5T MR scanner between January 2011 and November 2011. At each ADC map image obtained at each b value, ADCs in the right hepatic lobe, spleen and kidney were measured. As a result, ADCs of the right hepatic lobe, spleen and kidney have gradually decreased in the diffusion-weighted images in accordance with the reduced b value. This outcome may be used as preliminary data for applications to various abdominal diseases.
Pulsed Ultrasound and Pulsed Electromagnetic Field in the Treatment of Muscle Contusion in Rats
Cheon, Song-Hee ; Lee, Sun-Min ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 225~228
DOI : 10.4283/JMAG.2012.17.3.225
Muscle contusion usually results from a direct blunt impact and is frequently associated with contact sports. Muscle contusion results from microscopic muscle fiber and capillary disruption causing a microhemorrhage dissecting torn fibers and remaining viable muscle fibers. Recent studies concluded that some physical methods, including pulsed ultrasound (PU) and pulsed electromagnetic field (PEMF) treatment, accelerate and facilitate wound healing, improve scar quality and have beneficial effects on muscle and tendon healing. However, there are few studies on the effects of the early use of physical methods, such as PU and PEMF, on the expression of neurotrophic factors. The objective of this study was to investigate the effects of the early application of PU and PEMF, measured through the expression of BDNF in the muscles (gastrocnemius) and spinal cords of rats after skeletal muscle contusion. In the spinal cords and muscles, there was a significant increase of BDNF expression in the PEMF and PU groups, a greater increase was found in the PEMF group than in the PU group. In conclusion, PEMF is a useful therapeutic method that improves muscle healing after muscle contusion.
A Study on Comparison of Cardiac Ejection Fraction Values Measured in Myocardium SPECT and Cine MRI
Han, Jung-Seok ; Dong, Kyung-Rae ; Park, Yong-Soon ; Chung, Woon-Kwan ; Cho, Jae-Hwan ; Cho, Young-Kuk ;
Journal of Magnetics, volume 17, issue 3, 2012, Pages 229~232
DOI : 10.4283/JMAG.2012.17.3.229
This study examined the correlation between MR cine and myocardium Single-photon emission computed tomography (SPECT) by comparing the measured cardiac ejection fractions. The usefulness of cardiac MRI was also evaluated. Ten patients (8 men, 2 women and average age of 58.6 years), who underwent a myocardium SPECT scan and cardiac cine MRI scan among patients who visited the hospital for the chief complaint of cardiac disorder from June 1, 2010 to February 10, 2011, were enrolled in this study. The cardiac ejection fraction was calculated from the images obtained in both scans. The data was used to examine the correlation. The regression equation the cardiac ejection fraction values of the 10 patients obtained in myocardium SPECT and MRI cine was Y = 1.12X-8.91 (
= 0.78, significance of F = 0.001639, and confidence level of 95%). The results were significant when the cardiac ejection fraction obtained from MRI cine was compared with that obtained from myocardium SPECT. Overall, a cardiac examination using MRI enables an investigation of not only the ejection fraction but also the ED and ES volumes, stroke volume, wall thickness, and wall thickening in a higher spatial resolution despite the examination being conducted once. This examination is believed to be very useful for diagnosing patients with cardiac disease.