• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.1-6
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• 2000

Amorphous Fe$_{79.7}$Si$_{9.3}$B$_{9.7}$Ni$_{1.4}$ ribbon alloys were fabricated by a single roll method. To enhance D. C. bias properties, the magnetic and micro-structural changes have been investigated as the variation of annealing time and condition. The D. C. bias properties were found to be directly related to micro-structural changes. Primary ${\alpha}$-Fe dendrites with 200∼300 nm showed the best D. C. bias properties, which resulted from the magnetic domain wall pinning effect. Due to the differences of cooling rate, the growth shape and distribution of the dendrites is divided into two areas.

• Nano
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• v.13 no.12
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• pp.1850142.1-1850142.9
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• 2018

Modified titanate nanotubes (TNT) were tested for their adsorption of methylene blue (MB) from water solutions. They were obtained from the $TiO_2$ nanopowder using a standard alkaline hydrothermal method but in the stage of acid washing, when the titanate flakes begin to roll into nanotubes, magnetite nanoparticles were added. The $Fe_3O_4$ magnetic nanoparticles with diameter of around 2 nm and 12 nm were used in the tests. Significantly stronger adsorption of MB was observed when smaller nanoparticles were used compared to using larger nanoparticles and compared to the case of unmodified nanotubes. It was shown that the increased adsorption of MB is associated with a more negative value of ${\zeta}$-potential for titanates modified by the ultra-small nanoparticles. In the adsorption experiment, pH 7 was selected. These results may prove to be of great importance in the case of potential applications corresponding to the use of such material for wastewater purification.

• Geophysics and Geophysical Exploration
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• v.14 no.4
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• pp.298-304
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• 2011

We conducted magnetic survey using IBRV (Ice Breaker Research Vessel) ARAON of KORDI (Korea Ocean Research and Development Institute), ROV (Remotely Operated Vehicle) of Oceaneering Co. and three components vector magnetometer, at Apr., 2011 in the western slope of the caldera of TA25 seamount, the Lau Basin, the southwestern Pacific. The depth ranges of the survey area are from about 900 m to 1200 m, below sea level. For the deep sea magnetic survey, we made the nation's first small deep sea three components magnetometer of Korea. The magnetometer sensor and the data logger was attached with the upper part and lower part of ROV, respectively. ROV followed the planning tracks at 25 ~ 30 m above seafloor using the altimeter and USBL (Ultra Short Base Line) of ROV. The three components magnetometer measured the X (North), Y (East) and Z (Vertical) vector components of the magnetic field of the survey area. A motion sensor provided us the data of pitch, roll, yaw of ROV for the motion correction of the magnetic data. The data of the magnetometer sensor and the motion sensor were recorded on a notebook through the optical cable of ROV and the network of ARON. The precision positions of magnetic data were merged by the post-processing of USBL data of ROV. The obtained three components magnetic data are entirely utilized by finding possible hydrothermal vents of the survey area.

• Korean Journal of Materials Research
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• v.3 no.2
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• pp.175-184
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• 1993

Abstract Co-and/or AI-added Nd-Fe-B-based magnetic alloys were fabricated by using vacuum induction melting frunace, and melt-spun ribbons were made of the magnetic alloys with single roll rapid quenching method. The variation of magnetic properties of the melt-spun ribbons as a function of Cuwheel velocity (Vs) were investigated. Bonded magnets were made of the optimally quenched ribbon fragments, and the magnetic properties of the melt-spun ribbons and the bonded magnets were studied, relating to the microstructure and crystalline structure. Cu-wheel surface velocity had a strong effect on the magnetic properties of the melt-spun ribbons, and the maximum properties were obtained around Vs =20m/sec. The optimally quenched ribbon had a cellura-type microstructure, in which fine N$d_2$F$e_14$B grains were surrounded by thin Nd-rich phase. In case of a 2.1at% AI-added melt-spun ribbon, the magnetic properties were as follows: iHc, Br, and (BH)max were 15.5KOe, 7.8KG and 8.5MGOe respectively. And resin bonded magnets were fabricated by mixing optimally quenched ribbon fragments with 2.5wt % polyamide resin, compacting and binding at room temperature. The iHc, Br and (BH)max of bonded magnet were lO.2KOe, 4.4KG and 3.3MGOe respectively. And hot-pressed magnets were made by pressing the overquenched ribbons at high temperature. The magnetic properties of hot-pressed magnets were better than those of bonded magnets, and when the holding time was 8 minutes, the iHc, Br, and (BH)max of the hot-pressed magnet were 1O.8KOe, 7.3KG and 8.0MGOe respectively. Domain structure was mainly maze pattern, which means that the easy magnetization axis could be aligned, and the domain width of the hot-pressed magnets was smaller than that of bonded magnets.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.3
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• pp.360-366
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• 2018

In shipyards hull forming is performed by the line heating method using a gas torch and by cold treatment using a roll-press. However, this forming process has some issues, such as difficulties in controlling and accurately estimating the amount of the heat input, as well as a harsh working environment due to exposure to loud noises and air pollution. The induction heating method, which is introduced in this paper, exhibits good control and allows for the estimation of precise heat input. Also, workers can carry out the induction heating in a comfortable working environment. In this research, the induction heating simulation, which consists of electro-magnetic, heat transfer and thermal elasto-plastic analysis, was developed and modified through induction heating experiments. Finally, the effective heating coil was designed for the automatic hull forming system based on the results of induction heating simulation. For the purposes of a future study, if an algorithm to obtain optimal working conditions is developed, automatic systems for hull forming can then be constructed.

• International Journal of Ocean System Engineering
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• v.2 no.4
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• pp.223-232
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• 2012

For the accurate estimation of the position and orientation of a UUV (unmanned underwater vehicle), a low-cost AHRS (attitude heading reference system) was developed using a low-cost IMU (inertial measurement unit) sensor which provides information on the 3D acceleration, 3D turning rate and 3D earth-magnetic field data in the object coordinate system. The main hardware system is composed of an IMU sensor (ADIS16405) and TMS320F28335, which is coded with an extended kalman filter algorithm with a 50-Hz sampling frequency. Through an experimental gimbal device, good estimation performance for the pitch, roll, and yaw angles of the developed AHRS was verified by comparing to those of a commercial AHRS called the MTi system. The experimental results are here presented and analyzed.

• Aerospace Engineering and Technology
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• v.2 no.1
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• pp.124-132
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• 2003

The function and performance test of the developed sub-system should be conducted before integrating into the total system. For the successful achievement of the flight test, the integration tests of sub-systems must be performed to eliminate and prevent abnormal conditions, which may happen due to ground problems, Electro-Magnetic Interference noises, and so on. This paper describes the certification test procedure and results for the roll axis attitude control system of Korea Sounding Rocket-III.

• Research in Vestibular Science
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• v.17 no.4
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• pp.167-169
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• 2018

Rotatory vertebral artery syndrome (RVAS) is characterized by recurrent attacks of vertigo, nystagmus, and syncope induced by compression of the vertebral artery during head rotation. A 60-year-old man with atlas vertebrae fracture presented recurrent attacks of positional vertigo. Left-beat, upbeat and count clock-wise torsional nystagmus occurred after lying down and bilateral head roll (HR) showing no latency or fatigue. Magnetic resonance imaging revealed foramen magnum stenosis (FMS) and dominancy of right vertebral artery (VA). The flow of the right VA on transcranial Doppler decreased significantly during left HR. The slower the velocity was, the more the nystagmus was aggravated. RVAS can be evoked by FMS causing compression of the VA. And the nystagmus might be aggravated according to the blood flow insufficiency.

• Current Research on Agriculture and Life Sciences
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• v.32 no.3
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• pp.159-163
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• 2014

Agricultural unmanned helicopters have become a new paradigm for aerial application. Yet, such agricultural helicopters require easy and affordable attitude control systems. Therefore, this study presents an affordable attitude measurement system using a DCM (direction cosine matrix) algorithm that would be applied to agricultural unmanned helicopters. An IMU using a low-cost MEMS and an algorithm to estimate the attitude of the helicopter were applied in a gimbals structure to evaluate the accuracy of the attitude measurements. The estimation errors in the attitude were determined in comparison with the true angles determined by absolute position encoders. The DCM algorithm and sensors showed an accuracy of about 1.1% for the roll and pitch angle estimation. However, the accuracy of the yaw angle estimation at 3.7% was relatively larger. Such errors may be due to the magnetic field of the stepping motor and encoder system. Notwithstanding, since the intrinsic behavior of the agricultural helicopter remains steady, the determination of attitude would be reliable and practical.

• Journal of the Korean Magnetics Society
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• v.5 no.1
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• pp.1-7
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• 1995

${(Fe_{0.85}Co_{0.15})}_{75}Al_{7}B_{18-x}Nb_{x}(x=2,\;4\;and\;6\;at%)\;and\;{(Fe_{0.85}Co_{0.15})}_{75}Al_{y}B_{21-y}Nb_{4}(y=3,\;5,\;7,\;9\;at%)$ alloys were prepared by a single-roll quenching method. Microstructure and magnetic properties of the alloys such as saturation magnetization, initial permeability, coercive force and power loss have been investigated as functions of composition and armea1ing temperature. Nanocrystallines are obtained by armealing of as-prepared amorphous alloys in all compositions except the alloy of 9 at% AI. Saturation magnetization increases after armea1ing and, decreases with Nb content. However, AI and B affects the saturation magnetization insignificantly. Initial perrreability of nanocrystallized alloy at 50 kHz is improved roore than twice compared to that of the as-prepared alloy. Coercive force and core loss reach less than half after armea1ing.