• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.425-431
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• 2013

Nowadays, high speed train has settled down as a fast and convenient environment-friendly transportation and it's need is gradually increasing. However increased train speed leads to increased aerodynamic noise, which causes critically affects comfortability of passengers. Especially, the pantograph of high speed train is protruded out of train body, which is the main factor for increased aerodynamic noise. Since aerodynamic noise caused pantograph should be measured in high speed, it is difficult to measure it and to analysis aerodynamic noise characteristics due to the various types of pantograph. In this research, aerodynamic noise of pantograph is predicted by CFD (Computational Fluid Dynamic) and FW-H (Ffowcs Williams-Hawkings) equation. Also, Wind tunnel test results and numerical simulation results were compared. As a result, Simulation results predicting sound pressure level is very similar with wind tunnel test result. To analyze contribution of the pantograph to the noise of high-speed train, simulation results compared with measurement results of exterior noise. The simulation reuslts found that pantograph is a dominant noise source of high-speed trains's exterior noise in low frequency section. This dominant noise was come out from vortex shedding of the panhead in the pantograph. This research will be utilized for reduce sound pressure level of pantograph.

• International Journal of Railway
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• 제6권4호
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• pp.160-168
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• 2013

A spiral lattice girder-reinforced Bi-block sleeper which has enhanced durability against increasingly growing impact force and vibration by wheel load and improved structural performance while train runs at 350km/h high speed is hereby proposed. The section of a spiral lattice girder has stable and superior structural performance thanks to its confinement effect. To compare and analyze the structural performance of spiral lattice girder-reinforced bi-block sleeper, strain and stress distribution were evaluated after applying same load condition as existing triangular lattice girder-reinforced biblock sleeper, and to compare the structural performance of triangular lattice girder and spiral lattice girder, structural analysis of lattice girder was performed separately. As a result, a spiral lattice girder proved to have had superior structural characteristics to bi-block sleeper, and furthermore as a result of evaluating the fastener interface and constructibility with shape-improved lattice girder, no interference with existing railroad structure was found and in terms of cost efficiency, a spiral lattice girder appeared to be superior to existing lattice girder.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제65권8호
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• pp.1450-1456
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• 2016

In this paper, we have checked a method of performance evaluation for electronic pedal, which is a core technology of HBD for detecting the axle temperature of high-speed train. As it is practically impossible to conduct train speed test of 500 km/h, we utilize a high speed rotor for evaluating high speed performance of the electronic pedal instead. According to this method, we found that the measurement results by the velocity measuring instrument is similar with the ones from this research through the high speed rotor. In conclusion, it will be possible to conduct reliability evaluation for high speed performance for Beacon, Balise and RFID, which are utilized for transmitting vital information of train control systems through using the rotor.

• Proceedings of the KIPE Conference
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.518-521
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• 1999

This paper describes high speed squirrel cage induction motor drives without speed sensors using neural network based on Kalman filter Learning. High speed motors are receiving inverasing attentions in various applications, because of advantages of high speed, small size and light weight with same power level. Larning rate by Kalman filtering is time varying, convergence time fast, effect of initial weight between neurons is small.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1078-1083
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• 2000

A high speed rotor balancing machine was developed, which is capable of balancing a flexible rotor in high speed. The machine is largely consisted of vacuum chamber, oil supply system and vacuum pump system. And, in order to investigate performances of the machine, various tests were carried. After high speed rotor balancing of gas turbine engine rotor using influence coefficient method, the flexible engine rotor passed smoothly through its critical speed.

• Proceedings of the KSR Conference
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.376-384
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• 1999

In this paper, we introduce the on-line test plan of high speed rail development, which will be carried out at the test section of Seoul-Pusan high speed line from May to October, 2002. The test items are decided focused on the verification of the perofrmace and acquirement of the technical data of the high speed rail system development. The running time and distance of the train are calculated for several limited maximum speed cases. The detailed test scenario shall be developed according to the process of development and design of the system.

• The Transactions of the Korean Institute of Power Electronics
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• 제14권2호
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• pp.112-119
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• 2009

This paper presents a PLL(Phase Lock Loop) approach for effective speed and torque control of high speed miniature BLDCM(Brushless DC Motor) using hall sensor. The proposed speed control method based on PLL uses only a phase shift between reference pulse signal according to speed reference and actual pulse signal from hall sensor. It doesn't use any speed calculation, and calculates a direct current reference from phase shift. The current reference is changed to reduce the phase shift between reference and actual pulse. So the actual speed can keep the reference speed. The proposed control scheme is very simple but effective speed control is possible. In order to obtain a smooth torque production, the reference current is changed using acceleration and deceleration slope. The proposed control scheme is verified by experimental results of the 50W, 40,000[rpm] high speed miniature BLDCM.

• Journal of the Korean Society for Precision Engineering
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• 제17권4호
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• pp.48-68
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• 2000

The high-speed machining technology of difficult-to-cut material is needed to achieve the high-efficiency of die manufacturing. The high-speed machining is applied in automobile, airplane and electricityㆍelectro industry etc, because it can improve machining efficiency and productivity with high speed, high power and high rotation. In this study, high speed machinability, tool wear characteristics and its monitoring, characteristics of damaged layer, machinability of difficult-to-cut material, characteristics of a free curved surface and method of CAD/CAM system were introduced to acquire the shortening of machining time, the improvement of machining efficiency and the high quality of machined surface. Therefore, we establish the stabilization condition of difficult-to-cut material machining and present the optimal cutting condition for high-efficiency cutting.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.454-459
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• 2003

The paper will present chip formation mechanism and surface integrity generation mechanism based on the systematical experimental tests. Some basic factors such as the end milling cutter tooth number, cutting forces, cutting temperature, cutting vibration, the chip status, the surface roughness, the hardness distribution and the metallographic texture of the machined surface layer are involved. the chip formation mechanism is typical thermal plastic shear localization at high cutting speed with less number og shear ribbons and bigger shear angle than at low speed, which means lack of chip deformation. The high cutting speed with much more cutting teeth will be beneficial to the reduction of cutting forces, enlarge machining stability region, depression of temperature increment, auti-fatigability as well as surface roughness. The burrs always exists both at low cutting speed and at high cutting speed. So the deburr process should be arranged for milling titanium alloy in any case.

• Journal of the Korean Society of Marine Environment & Safety
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• 제5권1호
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• pp.1-8
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• 1999

During the last 10 years, the various type of high speed craft have been greatly developed, and since around of 1990 the large size of high speed passenger and/or cargo vessels are also introduced and took into the service in the various routes over the world. In a marine traffic way some bridge need to build across a rivers, cannals or a waterways. This one will be an obstruction and potential risk of collision in the way of high speed craft. Accordingly some of collision accident have been reported, which were caused by a lost control, wind and hydrodynamic forces, fog or human errors. In this paper a high speed craft having 40 m length is assumed to be collided with a circular type of bridge piers at right angle. The mode of deformation, penetration depth of collapse, impact forces, reduction of speed, loss of kinetic energy, and influence of scantlings, etc. have been calculated in each speed with a time variation to find a maximum values within a limit, and are graphically presented.