• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.22-28
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• 1992

Barium ferrite thin films were reactively deposited with Fe and BaO composite targets by a facing tergects sputtering unit. When thermally oxidized silicon wafers were used as substrates, minimum substrate heating of $750^{\circ}C$ was necessary for the perfect c-axis alignment in barium ferrite films. To lower the critical substrate temperature for the good c-axis alignment, such seed layers as ZnO, ${\alpha}-Fe_{2}O_{3}$ and ${\gamma}-Fe_{2}O_{3}$ were tested. The excellent c-axis algnment of BaM was obtained at a substrate temperature of $600^{\circ}C$ on ZnO seed layer whose (002) plane was parallel to the substrate surface. The magnetic properties of the BaM film showed saturation magnetization of 295 emu/cc, perpendicular coercivity of 1.7 kOe and squareness of 0.75. Optimum deposition rate of $230\;{\AA}/min$ was obtained with the composite target and this was 5 to 20 times higher than those of other investigators with oxide targets.

• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.11-15
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• 2000

13Cr-1.5Nb-Fe alloy powder prepared by water atomizing method is reduced with flowing hydrogen gas. The characteristics of a reduced alloy powder is investigated and magnetic cores formed by using the reduction power sintered in the vacuum of ∼10$\^$-5/ Torr. In order to study on the magnetic cores permeability and power loss in alternating magnetic field are also measured. The result of particle size distribution shows the paticle size is 70 ㎛ at volume fraction of 50 %. The saturation magnetization of the reduced alloy powder is 160 emu/g. The relative peak permeability (H$\_$a/=5Oe) of a magnetic core is 400 and the power loss (B$\_$m/=80G) 0.12 mW/cc at sintering temperature of 1,200 $\^{C}$, 10 ton/㎠ forming pressure, and 1 kHz.

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.241-245
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• 2013

In the case of the existing train control system, the driver monitors the condition of the vehicle through a composite controller device that displays various information on a screen in the vehicle. However, when problems arise such as car trouble, it is difficult for the drivers to take action immediately. In addition, maintenance personnel have to manually save data one by one after storing the vehicle to analyze control information of the main devices such as the brake controller and auxiliary power. To improve these points, a system that sends and receives all information in real time should be established by installing a sensor communication network and a surveillance system. This study attempts to improve the safety and maintenance of rail vehicles by suggesting a standardized method for train control and surveillance system.

• Current Applied Physics
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• v.18 no.11
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• pp.1248-1254
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• 2018

Magnetization versus temperature and magnetic-field measurements, M(T, $H_a$), have been carried out to study the magnetic and critical properties of polycrystalline $La_{1-x}Ba_xCoO_3$ (x = 0.3 and 0.5) cobaltites. These compounds with the density of ${\sim}6.2g/cm^3$ crystallized in the $R{\bar{3}}c$ rhombohedral and $Pm{\bar{3}}m$ cubic structures, respectively. With an applied field $H_a=200Oe$, M(T) data have revealed that the samples with x = 0.3 and 0.5 exhibit the ferromagnetic-paramagnetic (FM-PM) phase transition at the Curie temperature points $T_C=202$ and 157 K, respectively. At 4.2 K, the saturation magnetization ($M_{sat}$) decreases from 35.9 emu/g for x = 0.3-26.1 emu/g for x = 0.5. Particularly, the critical-behavior analyses in the vicinity of $T_C$ reveal all samples undergoing a second-order phase transition, with critical exponent values (${\beta}=0.328$ and ${\gamma}=1.251$ for x = 0.3, and ${\beta}=0.331$ and ${\gamma}=1.246$ for x = 0.5) close to those expected for the 3D Ising model. This proves short-range magnetic order existing in $La_{1-x}Ba_xCoO_3$. We believe that magnetic inhomogeneities due to the mixture of hole-rich FM regions (confined in the trivalent-cobalt hole-poor anti-FM matrix) and uniaxial anisotropy prevent long-range order in $La_{1-x}Ba_xCoO_3$.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.4
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• pp.47-53
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• 2011

The Electric Multiple Unit (EMU) has many types of door system such as sliding door, plug door etc.al. according to customer's requirements. The sliding door is widely used in Korea but has weak point in the noise problem. In the low operation speed, the noise coming from outer side of the EMU is not an important factor. As the speed is higher than before, noise is increased and make a problem. The main cause of noise is the imperfect air tightness in the EMU. The plug door system has advantages for the noise reduction characteristic in the high speed area. We have been developing electric plug-in door. The door is controlled by Door Control Unit(DCU) following the order of Automatic Train Protection (ATP) that is a kind of train signalling system. DCU has to simultaneously open and close the doors and the operation of it is related to the passengers safety. So DCU is a safety device that is important to reliability and safety. DCU is composed of several devices of control, motor driving, Input/Output, communication and power. In this paper, we will describe the functions, characteristic, requirement, subsystem and test results of DCU used for the electric plug-in door.

• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.303-305
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• 1999

Ultrafine cobalt ferrite particles have been synthesized using a microemulsion method. All peaks of X-ray diffranction patterns are fairly broad but correspond to a cubic spinel structure with the lattice constant 8.39$\AA$. The coercivity measureed at 5K is 15.1 kOe. The maximal magnetization measured at 5 and 300 K are 13.2 and 10.7 emu/g, respectively. The particles behave ferrimagnetically at 5 K but superparamagnetically at 300K. Superparamagnetic behavior of the particles at room temperature was confirmed by the conincidence of the M vs. H/T at different temperatures and the Mossbauer spectrum.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1257-1259
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• 2001

In this paper, the diagnosis method for AC traction motor is to reduce their maintenance loads. We tried to apply this method to maintenance of traction motor in railway vehicle. Sample coils for stator of traction motor were tested by accelerative thermal degradation which composed of heat, vibration, moisture, and overvoltage applying. Reliability and expected life were evaluated on the insulation system for 200 class traction motor.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.492-494
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• 1999

To improve safety operation of urban transit, compatible design of signaling system is most important factor at future train operation and management. Therefore, signaling system should be designed compatible transport demand of target year. In addition, signaling system should be designed improved train safety, based fail-safe principle. Most of all, to solve passenger concentration, high density and to improve efficiency of train operation. Headway improvement of train is most important. Train organization length of new urban transit as light rail is generally shorter than EMU. Therefore, to increase passenger service and operation efficiency, minimum headway of one minute in this system should be important required.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.495-497
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• 1999

The TPS accepts as input, vehicle parameters. control parameters. station parameters and right-of-war profile. Outputs of TPS program include velocity elapsed time and power profiles. This paper represents how to develop the TPS program. The TPS program simulates the operation of a single train under the input conditions.

• Proceedings of the KIEE Conference
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• summer
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• pp.1460-1462
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• 2004

기존노선을 이용한 고속화 신기술 개발사업 과제를 수행하여 중장거리 및 도시간의 교통해소를 위해 중고속 철도차량을 개발하여 최고속도 180km/h의 속도로 운행할수 있는 차량의 개발에 있어 핵심 전장품인 열차제어진단장치를 국산화하여 수입대처효과 및 기술개발에 기여하고 있다.