• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.359-360
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• 2006

Magnetic Flux Leakage (MFL) methods are widely employed for the non-destructive testing of gas pipelines. In the application of MFL pipeline inspection technology, corrosion anomalies are detected and identified via their leakage filed due to changes in wall thickness. This paper presents discrete cosine transform (DCT) based MFL signal analysis for defect feature extraction of natural gas pipelines. The original MFL signals are transformed into new ones based on the analysis. The usefulness of the approach has been shown by the experimental results.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2003.12a
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• pp.182-185
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• 2003

We have suggested an equivalent circuit model for switching performance of bipolar spin transistor composed of a nonmagnetic metal film (N) sandwiched between two ferromagnetic metal films (F1 and F2). The 'ON' or 'OFF' operation of this equivalent circuit model is simulated by depending on the orientation of the magnetization of F1 and F2 rather than the strength of the external magnetic filed. Changing the coupling coefficient, turn number of two inductances, (L1:L2) like a transformer, and parallel variable resistance R4 connected to L2 at the collector region, we can explain the magnetic characteristics and the dependence of magneto resistance ratio on the orientation of spin-polarized electrons.

• Journal of the Korean institute of surface engineering
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• v.23 no.4
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• pp.218-224
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• 1990

Silicon nitride thin(SiNx) is deposited onto 3 inch silicon wafor using ECR plasma apparatus. For the two different plasma extraction windows size, the thin films which were deposited by changing the SiH4/N2 gas fole at at 1.5mTorr without substrate heating are analyzed through the XPS and wlliposometer measurements. The very uniform and good quality silicon nitride thin film were obtained with the analyzed results of the deposited films, and particularly, ion temperature perpendicular to the magnetic filed was nearly same as the neutral gas temperature. The large amount of plasma loss in the transport process following magnetic field lines could be seen from the plasma emission intensity measurements.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.63-69
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• 2012

This paper presents an analysis on the induction heating of ring flange for wind farm. Ring flange is used for the connection of poles when building a column of wind power plant. Heat treatment of ring flange with the diameter of ${\O}1,000mm$ has been considered. For analysis on the induction heating, FEA is used. Firstly, electromagnetic filed analysis was performed to get the induction current distribution on the steel, After that, heat transfer analysis was performed using the magnetic filed analysis results. for more precise analysis, some measurement for permeability has been performed and the measurement data was used during the analysis. From the analysis, we get the temperature distribution on the ring flange.

• Journal of Korean Elementary Science Education
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• v.26 no.4
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• pp.440-448
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• 2007

The purpose of this study is to examine elementary students' conceptions of magnetic fields around various magnets by drawing tasks. A total of 105 elementary students from the 3rd and 6th grade levels were asked to draw how iron filings would arrange around magnets. We classified their drawings of magnetic field lines with some criteria to identify conceptions of magnetic forces and checked them through interviewing about their representative drawing. Through analyzing drawings, we discovered that 40% of elementary students drew the correct arrangement of iron filings around a bar magnet. In the case of two bar magnets in opposite directions, 33% of them drew correct patterns of iron dust and around two magnets in the same direction only 20% did well. Only 2.9% and 7.6% of students presented the correct drawings of magnetic fields near a disc and a horseshoe magnet. While 3rd grade students were supposed to be poor in drawings of magnetic fields around a loose and a dense coil which was not learned about, only 31% and 23% of 6th grade students who have just studied electromagnetism properly drew patterns of iron dust. This shows that only one quarter of students understood the magnetic filed lines even after instruction of electromagnetism. Many of 6th grade students learned a solenoid becomes just as a permanent magnet, but very few of them correctly drew a magnetic field line could distinguish between the iron dust around a loose and dense coil. After interviewing students, it is found that students consider magnetic forces to be existed only in parts of magnet because many of them drew magnetic field line of a specific areas around magnets. Students had misconceptions that magnetic forces exist only on the poles not in the middle around a horseshoe magnet. Also the disc-shape magnet made students to reveal various types of misconceptions: N- and S-poles are mixed in a whole magnet and right part of a disc-shape magnet is N-pole, left part is S-pole. Students who had not studied magnetic fields of around a magnet and electromagnets could not draw the correct patterns of iron dust suggest that it is indispensable for students to teach how patterns of iron filings would represent a visual image of magnetic fields in order to understand magnetic fields.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.58.2-58.2
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• 2015

We investigate the decaying incompressible MHD turbulence by including the effect of the expansion and contraction of background medium. In such an environment, incompressible MHD turbulence has two kinds of time scale. One is the eddy turn-over time (teddy), the other is the expansion/contraction time (texp-cntr). The turbulence is expected to behave differently according to the relationship between the two time scales. For instance, for teddy < texp-cntr, the turbulence would be decay more or less as in a static medium. On the other hand, for teddy > texp-cntr, the effects of expansion and contraction would be dominant. We examine the properties of turbulence in these two regime cases. Based on it, we derive a scaling for the time evolution of flow velocity and magnetic field. (i) In the decay effect dominant case, the velocity and magnetic field scale as $\sqrt{{\rho}v}{\sim}a^{-3}$, $b{\sim}a^{-2.5}$(expanding media) and $\sqrt{{\rho}v}{\sim}a^{-2}$, $b{\sim}a^{-1.5}$(contracting media). The total energy and residual spectra follow the $E^T_k{\sim}k^{-5/3}$, $E^R_k{\sim}k^{-7.3}$ in the inertial range. (ii) In the expanding and contracting dominant case, the velocity and magnetic field scale as $\sqrt{{\rho}v}{\sim}a^{-2.5}$, $b{\sim}a^{-2}$ (expanding/contracting media). The Kinetic and magnetic energy spectra follow the $E^K_k{\sim}a^{-5}$, $E^M_k{\sim}a^{-4}$. We have confirmed that scaling of velocity and magnetic filed is almost the same from the analytic estimates and computational models

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.979-985
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• 2020

A wide range of techniques have been developed to separate X or Y- chromosome-bearing sperm. In particular, bovine semen sex-sorted by using flow cytometry based on differences in the amount of DNA between X and Y chromosome bearing sperm is used in dairy farms. The first piglets were produced using sex-sorted sperm 30 years ago. However, sexed sperm have not been commercially available in pigs because the flow cytometry technique is not capable of sorting the high number of sperm required for porcine artificial insemination (AI), and the prolonged exposure to an electrical filed might damage to the DNA in sperm. The purpose of this study was to evaluate a boar sperm sorting method based on magnetic nanoparticles. A flow cytometer assay verified the efficacy of the magnetic nanoparticles (> 90% of sex-sorted sperm). In addition, a duplex polymerase chain reaction (PCR) assay using sex chromosome specific genes including SRY (sex-determining region Y; male), ZFY (zinc finger protein Y-linked; male), and ZFX (zinc finger protein X-linked; female) showed that in vitro fertilized porcine embryos by X and Y-chromosome bearing sperm were 100% female (40/40) and 72% female (35/48), respectively, at 8-cell or morula stages, suggesting that the sex-sorted sperm were fertile. In conclusion, our findings suggest that the sex-sorted method based on magnetic nanoparticles can be utilized for porcine sex-sorted AI.

• Progress in Medical Physics
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• v.13 no.4
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• pp.195-201
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• 2002

Several investigators have presented the effects of external magnetic fields on the dose distributions for clinical electron and photon beams. We focus the low energy electron beam with more lateral scatter In this study we calculated the beam profiles for an clinical electron beam of 6 MeV with longitudinal magnetic fields of 0.5 T-3.0 T using a Monte Carlo code. The principle of dose enhancements in the penumbra region is to deflect the laterally scattered electrons from its initial direction by the skewness of the laterally scattered electrons along the direction of magnetic field lines due to Lorentz force under longitudinal magnetic field. To discuss the dose enhancement effect on the penumbra area from the calculated results, we introduced the simple term of penumbra reduction ratio (PRR), which is defined as the percentage difference between the penumbra with and without magnetic field at the same depth. We found that the average PRR are 33%, and 49% over the depths of 1.5 cm, 2.0 cm, and 2.4 cm for the magnetic fields of 2.0 T and 3.0 T respectively. For the case of 0.5 T and 1.0 T the effects of magnetic filed were not observed significantly. In order to obtain the dose enhancement effects by the external magnetic field, we think that its strength should be more than 2 T approximately. We expect that the PRR would be saturated to 50-60% with magnetic fields of 3 T-5 T As a result of these calculations we found that the penumbra widths can be reduced with increased magnetic fields. This Penumbra reduction is explained as a result of electron lateral spread outside the geometrical edges of the beam in a longitudinal magnetic field. This means that the electron therapy benefits from the external magnetic fields.

• Korean Journal of Materials Research
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• v.3 no.4
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• pp.327-335
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• 1993

Using a RF cylindrical magnetron operated with two electromagnets having a Helmholz configuration, RF magnetron plasma properties and characteristics of reactive ion ething of Si were investigated as a function of applied magnetic field strengths using 3mTorr $CF_4/H_2$ and $CHF_3$. Also, I-V characteristics of Schottky diodes, which were made of silicons etched under different applied magnetic field strengths and gas environments, were measured to investigate the degree of radiation damage during the reactive ion etching. As the magnetic field strent;th increased, ion densities and radical densities of the plasmas were increased linearly, however, the dc self-bias voltages induced on the powered electrode, where the specimen are located, were decreased exponentially. Maximum etch rates, which were 5 times faster than that etched without applied magnetic filed, were obtained using near lOOGauss, and, under these conditions, little or no radiation damages on the etched silicons were found.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.343-345
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• 1998

By computer simulation, the pattern of magnetic field distribution on the Nb-foil of a rotating flux type superconducting power supply has been calculated. Using the results, the current pumping rate has been calculated and compared with the results obtained by the experiment. The experiment has been executed with small-size flux-rump in the environment of LN2 and LHe in order to compare the pattern of magnetic filed in the superconducting state and in the normal state. Five hall-sensor was located on the center, right side, left-side, upper side, lower side of the Nb-foil in order to obtain more accurate pattern of the magnetic field generated by rotating pole. In the simulation, the effects of the excitation-magnet and the iron core located at the inner-side and circumference of the magnet have been considered. By comparing the data from the experiment and the results from the simulation, the size of normal spot estimated. At the same time, by calculating the linkage flux, the current-pumping-rate has been obtained. Consequently, the results obtained from experiment and simulation coincided as expected.