• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.3
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• pp.69-75
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• 2013

During the magnetic abrasive polishing of a curved surface, the improvement in surface roughness varies with the maximum value and distribution of magnetic flux density. Thus, in this study, the magnetic flux density on the curved surface was simulated according to curvature radii of magnetic tool. As a result of the simulation, the 14.5mm of the magnetic tool had a higher maximum magnetic flux density and it showed a large weighted magnetic flux density. The weighted magnetic flux density means the highest value for the magnetic flux density in the curvature of the magnetic tool. From the experimental verification, the better improvement in surface roughness was observed on wider area at the 14.5mm radius of the magnetic tool than other radii.

• KSTLE International Journal
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• v.2 no.2
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• pp.114-119
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• 2001

The distribution of magnetic flux density of electro-magnetic chucks may clarify the clamping characteristics, which is strongly related to the machining efficiency and machining accuracy in surface grinding machine. Therefore the distribution of the normal and the tangential components of magnetic flux density have been analyzed theoretically. It appears that the normal component of magnetic flux density increases and the tangential component of magnetic flux density increases as the ratio of the separator width to the pitch, e/p decreases. The results seem to increase the stability and uniformity of normal component of magnetic flux density for the decreased e/p.

• Journal of Welding and Joining
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• v.22 no.6
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• pp.50-56
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• 2004

MlAB(magnetically impelled arc butt) welding is a sort of pressure welding method by melting two pipe sections with high speed rotating arc and upsetting two pipes in the axial direction. The electro-magnetic force, the driving force of the arc rotation, is generated by interaction of arc current and magnetic field induced from the magnetic flux generator in the welding system. In this study, an openable coil system for the generation of magnetic flux and a 3-dimensional numerical model for analyzing the electro-magnetic field were proposed. Through the fundamental numerical analyses, a magnetic concentrator was adopted for smoothing the magnetic flux density distribution in the circumferential direction. And then a series of numerical analysis were performed for investigating the effect of system parameters on the magnetic flux density distribution in the interested welding area.. Numerical quantitative analyses showed that magnetic flux density distribution generated from the proposed coil system is mainly dependent on the exciting current in the coil and the position of coil or concentrator from the pipe outer surface. And the gap between pipe ends and arc current are also considered as important factors on arc rotating behavior.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.2
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• pp.109-115
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• 2004

This paper deals with the behaviors of magnetic flux density near down-conductors by lightning currents. The background on the principle of magnetic flux density measurements using the RL self-integrating magnetic field sensor was described. The magnetic flux density measuring device consisting of RL self-integrating magnetic field sensor and differential amplifier was designed and fabricated. The frequency bandwidth of the magnetic flux density measuring system ranges from 200 Hz to 300 KHz and the response sensitivity was 0.126 $\mu$T/㎷ The distributions of the magnetic flux density near down-conductors due to impulse currents with various rise times were analyzed as a parameter of the bonding conditions and materials of conductor and wiring conduits. The magnetic flux density due to impulse currents was inversely proportional to the distance between the down-conductor and measuring point. The amplitude of the magnetic flux density for PVC Pipe with down-conductor was 72 $\mu$T/㎷ at the distance of 1m and was higher than for steel conduits and coaxial cable. Finally the magnetic flux density is increased with increasing the di/dt it and oscillation frequency of lightning currents in this experimental ranges.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.1
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• pp.37-41
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• 2017

In this paper, the fault current limiting characteristics of the flux-lock type SFCL (superconducting fault current limiter) using magnetic application circuit were analyzed. The flux-lock type SFCL has the structure to install the magnetic application circuit, which can increase the resistance of HTSC ($high-T_C$ superconducting element comprising) the SFCL. To analyze the fault current limiting effect of the flux-lock type SFCL through the magnetic flux application circuit, the flux-lock type SFCL either with the magnetic flux circuit or without the magnetic flux circuit was constructed and the fault current limiting characteristics of the SFCL were compared each other through the short-circuit tests.

• Journal of The Korean Astronomical Society
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• v.47 no.3
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• pp.105-113
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• 2014

We apply differential affine velocity estimator (DAVE) to the Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager (HMI) 12-min line-of-sight magnetograms, and separately calculate the injected magnetic helicity for the leading and the following polarities of nine emerging bipolar active regions (ARs). Comparing magnetic helicity flux of the leading polarity with the following polarity, we find that six ARs studied in this paper have the following polarity that injected more magnetic helicity flux than that of the leading polarity. We also measure the mean area of each polarity in all the nine ARs, and find that the compact polarity tend to possess more magnetic helicity flux than the fragmented one. Our results confirm the previous studies on asymmetry of magnetic helicity that emerging bipolar ARs have a polarity preference in injecting magnetic helicity. Based on the changes of unsigned magnetic flux, we divide the emergence process into two evolutionary stages: (1) an increasing stage before the peak flux and (2) a constant or decreasing stage after the peak flux. Obvious changes on magnetic helicity flux can be seen during transition from one stage to another. Seven ARs have one or both polarity that changed the sign of magnetic helicity flux. Additionally, the prevailing polarity of the two ARs, which injects more magnetic helicity, changes form the following polarity to the leading one.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.42-49
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• 2005

Our purpose is to develop a precision magnetic displacement sensor that has sub-micron resolution and small size probe. To achieve this, we first have tried to establish mathematical models of a magnetic sensor in this paper. The inductance model that presents basic measuring principle of a magnetic sensor is based on equivalent magnetic circuit method. Especially we have concentrated on modeling of magnetic flux leakage and magnetic flux fringing. The induced model is verified by experimental results. The model, including the magnetic flux leakage and flux fringing effects, is in good agreement with the experimental data. Subsequently, based on the augmented model, we will design magnetic sensor probe in order to obtain high performances and to scale down the probe.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.2
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• pp.29-35
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• 1992

The distribution of magnetic flux density of electro-magnetic chucks may clarify the clamping characteristics which are strongly related to the machining efficiency and machining accuracy in a surface grinder. Therefore the distribution of the normal and the tangential components of magnetic flux density has been analyzed theoretically. It appears that the normal and the tangential components of magnetic flux density increase as the ratio of the separator width to the pitch e/p decreases. The results seem to increase the uniformity and stability of normal component of magnetic flux density for the decreased e/p.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.58.2-58.2
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• 2018

Theoretically, the magnetic helicity transport flux through the solar surface into the upper atmosphere can be estimated indefinitely precisely by magnetic field footpoint tracking if the observational resolution is infinitely fine, even with magnetic flux emergence or submergence. In reality, the temporal and spatial resolutions of observations are limited. When magnetic flux emerging or submerging, the footpoint velocity goes to infinity and the normal magnetic field vanishes at the polarity inversion line. A finite observational resolution thus generates a blackout area in helicity flux estimation near the polarity inversion line. It is questioned how much magnetic helicity is underestimated with a footpoint tracking method due to the absence of information in the blackout area. We adopt the analytical models of Gold-Hoyle and Lundquist force-free flux ropes and let them emerging from below the solar surface. The observation and the helicity integration can start at different emerging stages of the flux rope, i.e., the photospheric plane initially cuts the flux rope at different levels. We calculate the magnetic helicity of the flux rope below the photospheric level, which is eventually to emerge, except the helicity hidden in the region to be swept by the blackout area with different widths. Our calculation suggests that the error in the integrated helicity flux estimate is about half of the real value or even larger when small scale magnetic structures emerge into the solar atmosphere.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.73-81
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• 2001

The MIAB welding uses a rotating arc as its heat source and is known as an efficient method fur pipe butt welding. The arc is rotated around the weld line by the electro-magnetic force resulting from the interaction of arc current and magnetic field. The electro-magnetic force is affected by magnetic flux density, arc current, and arc length. Especially, the magnetic flux density is an important factor on arc rotation and weld quality. This paper presents a 2D finite element model for the analysis of magnetic flux density in the actual welding conditions. The magnetic flux density is mainly dependent on gap between two pipes, the position of coil from gap center, exciting current, and relative permeability. Thus, the relations between magnetic flux density and main factors were investigated through experiment and analysis. Experiments were performed for the steel pipes(48.1mm O.D and 2.0mm thickness). The analysis results of magnetic flux density reveal that it increases with increasing exciting current, increasing relative permeability, decreasing distance from gap center to coil, and decreasing gap size. It is considered that the results of this study can be used as important data on the design of coil system and MIAB welding system.