• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.439-441
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• 2003

In this study the formula of electro magnetic fields under 3-phase power lines with vertical or horizontal line-configurations were deduced and the effect of the earth was considered in the formula. Using the formula the electric field and the magnetic flux density under distribution and transmission lines constucted currently in our country were calculated and the components of each field were investigated with horizontal distance from tower and height above the earth.

• Geophysics and Geophysical Exploration
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• v.25 no.2
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• pp.85-92
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• 2022

An elongated object in one direction can be approximated as a line segment. Here, the closed-form expressions of a line segment's vector magnetic and magnetic gradient tensor are required to interpret responses by a line segment. Therefore, the analytical expressions of the vector magnetic and magnetic gradient tensor are derived. The vector magnetic is converted from the existing gravity gradient tensor using Poisson's relation where the gravity gradient tensor caused by a line segment can be transformed into a vector magnetic. Then, the magnetic gradient tensor is derived by differentiating the vector magnetic with respect to each axis in the Cartesian coordinate system. The synthetic total magnetic data simulated by an iron pile on boreholes are inverted by a nonlinear inversion process so that the physical parameters of the iron pile, including the beginning point, the length, orientation, and magnetization vector are successfully estimated.

• Journal of Magnetics
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• v.21 no.4
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• pp.503-508
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• 2016

The roll- and pitch-induced eddy currents create a magnetic field that contributes to the total magnetic signature of naval vessels. The magnetic signature is of concern, as it exposes the ship to the threat of modern influence mines. It is estimated that the eddy current is the second most important source contributing to a ship's underwater magnetic field following the ferromagnetic effect. In the present paper, the finite element (FE) method is used to predict the eddy current signature of a real ship. The FE model is validated using the measurements of the Canadian research vessel CFAV QUEST at the Earth's Field Simulator (EFS) in Schirnau, Germany. Modeling and validation of the eddy current magnetic signature for a real ship represents a novelty in the field. It is shown that the characteristics of this signature depend on frequency. Based on these results, a ship's degaussing system could be improved to cancel both the ferromagnetic and the eddy current contribution to the magnetic signature simultaneously, reducing the susceptibility to sea mines.

• Journal of the Korean Institute of Navigation
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• v.12 no.2
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• pp.23-32
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• 1988

This paper offers a method of magnetic compass adjustment for the vessel alongside the wharf using newly designed magnetic north former, which makes the same magnetic field-change as the turning vessel does. The characteristics of the magnetic north former was examined by observing the deviation curves of the magnetic compass installed on the compass deviascop at laboratory. The magnetic north former consists of A and B arms which hold the permanent bar magnets at the both ends of each arm. The arm is to rotae in the horizontal plane about the vertical axis fixed at the center boss of the magnetic compass and it is to compensate the horizontal plane about the vertical axis fixed at the center boss of the magnetic compass and it is to compensate the horizontal component of the earth's field. The B arm makes the artificial magnetic north around the magnetic compass for every ship's heading. The results of investigation are summarized as follows ; 1. The observation and correction of magnetic compass deviation can be done without swinging the ship, of the effect of D coefficient is negligible. 2. The residual deviation curve of the magnetic compass depends on the accuracy of deduced value of ship's multplier($\lambda$). 3. The errors due to the inaccuracy of deduced value of ship's multiplier change in the same way as the B and C coefficient do.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.180.2-180.2
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• 2007

• The Bulletin of The Korean Astronomical Society
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• v.17
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• pp.7.2-7.2
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• 1992

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.90-90
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• 2013

Since discovery, NdFeB permanent magnet has replaced application of the conventional magnets rapidly because of its superior physical and mechanical properties. With increasing consumption of power combined with energy resource depletion, energy efficiency is becoming more and more inportant. According to recent reports, almost almost half of the electric power is consumed by motor, and NdFeB magnets which are the core component of the motor play a key role on improving energy efficiency of the devices. In parallel with finding alternatives energy resources, research works improving energy efficiecy have been conducted world wide. Althogh NdFeB magnets usage have been expanded to various applications, key materials such as Nd and Dy, resouces lean heavily on specific area, China. Magnetic industry revently experienced skyrocketing price fluctuatioin of rare earth at around 2008. Chineses government's regulations worsened the situation and arose a necessity to develop methods to minimize rare earth use. In this presentation, POSCO's recent research works on rare earth reduction is presented including novel powder alloying method using nitrate precursors. Also, future R&D plans for rare earth free magnets is briefly introduced as well.

• Publications of The Korean Astronomical Society
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• v.14 no.2
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• pp.83-89
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• 1999

The Earth is exposed to constant outflow of the solar wind from the outer layers of the Sun, and violent transient events taking place from active regions increase the energy flux of both radiation and particles leaving the Sun. Thus the space surrounding the Earth is a highly dynamic environment that responds sensitively to changes in radiation, particles and magnetic field arriving from the Sun. Nowadays, it becomes increasingly important to understand how the physical system of Earth-space works and how the space around the Earth connects to interplanetary space. In the present paper we describe how explosive solar events, such as CME(Coronal Mass Ejection) and flares affect the Earth-space environment and how the space weather reacts to them. Practical consequences are presented to demonstrate why a broader view of Earth's environment is greatly needed to cope with modern day's inhabitation problem in a rapidly developing space age.

• Journal of the Korean Society of Marine Environment & Safety
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• v.11 no.1 s.22
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• pp.29-37
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• 2005

The design and development if Resonant-type Magnetometer(RM) using isotropic magnetic with high permeability is described in this paper. At first, the relationship between the inductance L if the coil winding on a magnetic material and the permeability u(H) appearing in the magnetic material with isotropic and high permeability is defined as a background theory. Then the circuit if RM, which is to obtain the values if L as the change qf frequency is implemented using simple Schmitt Trigger Circuit Through the swinging tests, which is to evaluate the measurement ability if RM, the measurement possibility for the component of earth field was confined.

• Journal of the Korean Magnetics Society
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• v.13 no.6
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• pp.251-256
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• 2003

We have developed the quality analysis system for magnetic field effect of cathode-ray tube that is used a monitor, TV and medical appliance. We designed and constructed the large 3-axis square coil (2 m length) system for the generation of 3-component magnetic field using power supply, magnetometer and computer below 0.2 mT range. The coil constant is 30.31 ${\mu}$T, 29.73 ${\mu}$T and 30.51 ${\mu}$T for the X, Y and Z axis square coil respectively. The magnetic field resolution was 0.01 T. The uniformity of magnetic field was measured within 1 ％ in the range of 12 cm.