• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1374-1378
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• 2005

Appropriate upward force is crucial for the pantograph on high speed train to collect current from the catenery system without separation. However, at high speed, large aerodynamic lifting force is generated by the contact plate and the arms of pantograph, which may cause wear of the contact wire. In this study, to confirm the interface performance of the pantograph on Korea High Speed Train, a method to measure the contact force of the pantograph was proposed and the related measurement system was developed. The forces acting on the pantograph were clarified and a procedure to calculate the aerodynamic lifting force was proposed. A special device was invented and applied to measure the lifting force. Measured contact forces were displayed by the developed system and evaluated according to the criteria. Countermeasures were also taken to reduce the contact force based on the results.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.679-686
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• 2013

The reduction unit is one of the most important components in railway cars, due to the transmission of torque from the motor to the wheels. Faulty reduction gears in high-speed trains result from excessive wear on the gear or damage to the gear. These types of gear defects have a significant effect on high-speed rail operation and safety; thus, a diagnosis system for the reduction unit is needed. Vibration diagnosis technology is one of the most effective diagnostics. In this paper, the vibration parameters of a reduction unit were evaluated during a driving-gear test and a full-vehicle test, using kurtosis and the crest factor. These tests were performed under normal operating conditions; a specimen tester was used to diagnose problems in defective gears.

• Journal of Power Electronics
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• v.1 no.2
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• pp.78-87
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• 2001

A new high-power step-up based on the two-module parallel-input (PISO) modular dual inductor-fed push-pull converter is proposed. The proposed converter is operated at a constant duty cycle and employs and auxiliary circuit to control the output voltage with a phase-shift between two modules. It shows a high efficiency due to the greatly reduced switch turn-off stress. It also shows a high and linear voltage conversion ratio, low current stress in the output capacitor, and fast control-to-output dynamics. The operation principles and the mathematical models of the proposed converter are presented. Features of the proposed converter are discussed in comparison with the two-module PISO modular dual inductor-fed push-pull converter. Also, experimental results from a 50kHz, 800W, 350 Vdc prototype with an input voltage range of 20-32 Vdc are provided to confirm the validity of the proposed converter. The new converter compares favorably with the conventional counterpart, and is considered well siuted to high-power step-up applications.

• Korean Journal of Metals and Materials
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• v.46 no.10
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• pp.627-633
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• 2008

The austenitic Fe-Mn alloys have received considerable attention as a possible candidate for the automotive structural materials due to their high strength and high formability with high elongation. This research investigates the effect of alloying elements on the phase transformation, deformation behavior and mechanical properties in high Mn steels for the development of a high strength high ductility steel. The mechanical stability of austenitic phases is very important for high ductility and it depends largely on the composition of carbon, manganese and aluminum. The dominant deformation mode shifts from TRIP to TWIP mode as the amount of C, Mn and Al is increased. Especially, even a small amount of Al addition facilitates significantly TWIP deformation due to the increase of stacking fault energy in Fe-Mn alloys, this leads to increase the ductility and also decrease the crack sensitivity.

• International Journal of High-Rise Buildings
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• v.4 no.1
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• pp.75-83
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• 2015

In the present study, the preliminary results of a large-scale seismic response analysis of a super-high-rise steel frame considering soil-structure interaction are presented. A seismic response analysis under the excitation of the JR Takatori record of the 1995 Hyogoken-Nanbu earthquake is conducted. Precise meshes of a 31-story super-high-rise steel frame and a soil region, which are constructed completely of hexahedral elements, are generated and combined. The parallel large-scale simulation is performed using K computer, which is one of the fastest supercomputers in the world. The results are visualized using an offline rendering code implemented on K computer, and the feasibility of using a very fine mesh of solid elements is investigated. The computation performance of the analysis code on K computer is also presented.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.231-233
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• 2009

The plating equipment, water treatment system, electrolysis facility, etc need the high current and high power rectifier for their original purposes. So the paper investigates the applicable types of rectifiers and carries out their comparisons, and also suggest the practical design guidelines for a suitable candidate rectifier for low voltage high current high power applications.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2189-2191
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• 1999

To improve the reliability of the klystron-modulator systems, the stable operations of the thyratron an important factor of the system are required. The thyratron always has a possibility of self-fire according to the conditions of the applied high voltage and this induces the system fault. Therefore a command charging method was introduced to reduce the applied tim8 of the high voltage into the thyratron. The high voltage switch used in the command charging method is the SCR (1.6 kV, 50A) and consists of 10 SCRs in series to discharge 10 kV. A pulse transformer was used to apply the trigger pulse. The objectives of this research are the fabrication of the semiconductor switch and the study of the experimental result of the operation characteristics of the high voltage semiconductor switch.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.3079-3081
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• 2009

• Structural Engineering and Mechanics
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• v.76 no.2
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• pp.207-222
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• 2020

Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train subjected to fluctuating crosswind. To ensure the safe operation in metro lines in mountain cities, running safety of the metro train over the high-pier bridge under crosswind is analyzed in this paper. Firstly, the dynamic model of the wind-train-bridge (WTB) system is built, in which the speed-up effect of crosswind is fully considered. On the basis of time domain analysis, the basic characteristics of the WTB system with high-pier are analyzed. Afterwards, the dynamic responses varies with train speed and wind speed are calculated, and the safety zone of metro train over a high-pier bridge subjected to fluctuating crosswind in mountain city is determined. The results indicate that, fluctuating crosswind triggers drastic vibration to the metro train and high-pier bridges, which in turn causes running instability of the train. For this reason, the corresponding safety zone for metro train running on the high-pier is proposed, and the metro traffic on the high-pier bridge should be closed as the mean wind speed of standard height reaches 9 m/s (15.6 m/s for the train).

• Journal of Industrial Technology
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• v.37 no.1
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• pp.32-36
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• 2017

In this study, as part of a research on the development of economical high-performance concrete with high strength and high quality, the physical properties of high-performance concrete were analyzed by substituting a certain amount of low-cost domestic silica fume exempted from the re-importation type distribution structure of the domestic production and the existing high-priced silica fume distribution structure. Performing tests to identify the physical properties of the fresh and hardened concrete and durability analogy of the concrete which use low-cost domestic silica fume and imported silica fume, the chloride ion penetration resistance test result showed that the strength difference between the low-cost silica fume and the imported silica fume is not big but the strength of the low-cost silica fume was measured higher than the imported silica fume. The chloride ion penetration resistance of all variables was measured as "very low". Since the low-cost domestic silica fume can be used as a high-performance admixture of concrete, the results suggest that it is possible to produce a more economical high-performance concrete.