• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.65-70
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• 2010

AC traction power supply system has adopted autotransformer (AT) feeding method. This system has an advantage as long feeding distance. However, the countermeasure for voltage drop should be considered, because load capacity grows larger and headway grows shorter in recent electric railway system. This paper proposes the improved system configuration to enhance voltage drop in ac railway system without additional power electronic device. That is to increase turn ratio between contact wire and rail of AT. By modifying turn ratio of AT at SSP or SP, collecting voltage on train will be enhanced.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1297-1302
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• 2004

In DC power distribution system for urban rail transits potential relay, 64P, is used to detect the ground faults. The problem with this 64P is that though it detects the ground fault it cannot identify the faulted region. Therefore the faulted region cannot be isolated properly. It could results in power loss of the trains on the healthy regions and the safety of the passengers in the trains could be affected adversely. A new ground fault protective relaying scheme that can identify the faulted region is presented in this paper. The new concept uses the current differential scheme and the permissive scheme to identify the faulted region correctly. A device with similar characteristic to the arrestor is adapted to use the current relay for the ground fault detection. The role of the device is to block the ground leakage current in normal operating condition and enable the ground fault current to flow in ground fault condition. The algorithm of the new relay and the effect of the newly adapted device in the new relaying scheme are discussed.

• Journal of Oral Medicine and Pain
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• v.37 no.4
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• pp.205-211
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• 2012

A 35 year-old female presented with the complaint of sudden occurrence of bite change and concurrent opening limitation, as well as pain in the right temporomandibular joint (TMJ) during mouth opening. From her history it was revealed that she had simple clicking of right TMJ for several years before onset of these symptoms, and that the clicking sound subsided recently after development of opening limitation. On clinical examination, anterior open bite, midline shift of the mandible to right, and premature contacts on left posterior teeth were observed. Maximum mouth opening and lateral movement to left were also restricted. On magnetic resonance images, the right TMJ showed anterior disc displacement without reduction and the posterior joint space is greatly collapsed by retrusion of the condyle. It was thought that the sudden occurrence of occlusal change would be resulted from abrupt displacement of the mandible associated with development of the anterior disc displacement without reduction. The stabilization appliance traction therapy was performed initially for first 3 months along with physical and pharmacologic therapy. However, the anterior open bite and opening limitation didn't resolve and the position of mandible still remained altered. So the stabilization appliance was changed to intermaxillary traction device. Then the mandible returned progressively to normal position and the occlusion became more stable and comfortable. After 5 months of intermaxillary traction therapy, the anterior open bite was dissolved completely and the occlusion became stabilized satisfactorily along with recovery of normal mouth opening range. On post-treatment magnetic resonance image, remodeling of condylar head was observed.

• Tribology and Lubricants
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• v.20 no.5
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• pp.225-230
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• 2004

Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the tribological characteristics of a certain lubricant, it is also important to get the information of traction behaviors as well. In this work, we developed a device for measuring the friction force of ehl contact condition as well as the film thickness. To verify the validity of the measuring system, the friction forces and film thicknesses under ehl condition are simultaneously measured with the variations of additive ratios of viscosity index improvers which cause non-linear tendencies of film thickness to contact velocity.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.31-35
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• 2001

IGCTs have established themselves as the power semiconductor of choice at medium voltage levels within the last few years because of their low conduction and switching losses. The trade-off between these losses can be adjusted by various lifetime control techniques and the growing demand for these devices is driving the need for standard types to cover such applications as Static Circuit Breakers (low on-state) and Medium Voltage Drives (low switching losses). The additional demands of Traction (low operating temperatures) and Current Source Inverters (symmetric blocking) would normally result in conflicting demands on the semiconductor. This paper will outline how a range of power devices can meet these needs with a limited number of wafers and gate units. Some of the key differences between IGCTs and IGBTs will be explained and the outlook for device improvements will be discussed.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.218-226
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• 2002

This study was carried out to develop continuously variable-speed transmission(CVT) fur an agricultural tractor. The full-toroidal variator mechanism with flour discs and six rollers was utilized as a device fur changing speed ratio continuously. In system layout design, the sizes of the roller cylinders and the end-load cylinder, which were critical factors for controlling the variator, were designed. The planetary gear unit and six pairs of the gear assemblies were designed to establish the maximum speed of the vehicle at 30 ㎞/hr. In addition, the hydraulic clutch, the silent chain, the hydraulic manifold and the electronic controller were designed. Based on the design, a prototype CVT was developed and tested. Test results show that the CVT developed in this study could successfully provide variable speed of the tractor.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.267-271
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• 2002

Most studies of elsatohydrodynamic lubrication are oriented only to the measurement of film thickness itself with optical interferometer. In order to exactly investigate the characteristics of a certain lubricant, it is also important to get the information of traction force as well. In this work, we developed the device for measuring friction force of ehl contact condition together with the film thickness. To verify the validity of the measuring system, the friction force and film thickness under ehl condition are measured with the variation of additive ratios of viscosity index Improvers.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.298-302
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• 2004

In this paper, AC electric vehicle propulsion system(Converter/Inverter) using high power semiconductor, UM(Intelligent Power module) is proposed. 2-Parallel operation of two PWM converter is adopted for increasing capacity of system and the VVVF inverter control is used a mixed control algorithm, where the vector control strategy at low speed region and slip-frequency control strategy at high speed region. The proposed propulsion system is verified by experimental results with a 1,350kW converter and 1,100kVA inverter with four 210kW traction motors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.1000-1003
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• 2014

The primary purpose of this study is to observe the dynamic behavior within a vehicle on chassis dynamometer throughout cleat impact testing with two different constraining setups (Tie-down strap and one point fixation). Throughout this empirical experiment, no outstanding dynamic behavior characteristics are observed between two setups and thus, the performance of the one point fixation device is validated. Neither the interior noise nor acceleration at driver seat rail and knuckle is heavily influenced by two different constraining methods. However, one point fixation is far more advantageous considering its shorter set up time and its capability of measuring traction force with its built in force sensor.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.553-558
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• 2002

The harmonics in railway high voltage system is due to common use of 3 phase incoming bus and doing the power converter for traction system on the electric car(or electric locomotive). This paper, we analyze the harmonics mechanism and characteristics of railway high voltage system, also we analyze the problem according to the actual measurement about influence of harmonicsontherailwayhighvoltagesystem. And we proved the countermeasure device(passive filter or L-C filter) of harmonics applies in the field. The test result, we have know that the filter is not fit. Consequently, The countermeasure of harmonics for the railway high voltage system be able to resolve by another filter.