• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.605-616
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• 2013

An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In the present paper, characteristics of rail vibration and radiated sound power from concrete slab tracks for domestic high speed train(KTX) is investigated by means of a numerical method. The waveguide finite element and boundary element are combined and applied for this analysis. The concrete slab track is modelled simply with a rail and rail pad regarding the concrete slab as a rigid ground. The wave types which contribute significantly to the rail vibration and radiated noise are identified in terms of the mobility and decay rates. In addition, the effect of the rail pad stiffness on the radiated power is examined for two different rail pad stiffnesses.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.249-260
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• 2014

When a train enters the tunnel at high speed, the pressure wave occurs. When this pressure wave reaches at the exit of tunnel, some are either emitted to the outside or reflected in tunnel by the form of expansion wave. The wave emitted to the outside forms the impulsive pressure wave. This wave is called 'Micro Pressure Wave'. The micro pressure wave generates noise and vibration around a exit portal of tunnel. When it becomes worse, it causes anxiety for residents and damage to windows. Thus, it requires a counterplan and prediction about the micro pressure wave for high speed railway construction. In this paper, the effects of train head nose and tunnel portal shape were investigated by model test, measurement for the micro pressure wave at the operating tunnel as well as numerical analysis for the gradient of pressure wave in the tunnel. As results, a method for predicting the intensity of the micro pressure wave is suggested and then the intensity of the micro pressure wave is analyzed by the tunnel length and the cross-sectional area.

• 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.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2464-2472
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• 2011

Train runs on high speed and the concrete track is constructed. Rail fastening device needs to reduce elasticity, transferred load, noise, and vibration etc. Consequently, low elastic pad has a great impact of the durability and stability of the track. In this study, discussed in previous studies, static numerical analysis and real scale repeated loading test, followed by dynamic response analysis were implemented. The most distinctive characteristics of the model proposed is to simulate the real wheel behavior on rail. And the main analysis object is to evaluate and compare the deformation characteristics of the transition track while load reduction effect of transfer on roadbed assessed by various low elastic pad.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.652-657
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• 2004

Korean High Speed Train (KHST) designed to operate at 350km/h has been tested on KyungBu high speed line since it was developed in 2002. The specification of the interior noise level for high speed train in Korea has been adopted through the contract between KHRC and Korea TGV consortium, not a national specification. But it can not be adopted to KHST designed at 350km/h because this has involved up to 300Km/h. Therefor, in this paper, the interior noise level at 350km/h are predicted in passenger car using the results at 300Km/h and these results show that the KHST's interior noise levels are good up to 300Km/h but need to be reduced at 350Km/h in the view point of limit value at 300Km/h of the contract between KHRC and Korea TGV consortium. Also it proposed to make a national specification for the interior noise level to evaluate it in detail at 350Km/h.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1095-1104
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• 1997

When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. For the purpose of the impulsive noise reduction, the present study investigated the effect of a vertical bleed duct on the compression wave propagating into a model tunnel. Numerical results were obtained using a Piecewise Linear Method and testified by experiment of shock tube with an open end. The results showed that the vertical bleed duct reduces the maximum pressure gradient of compression wave front by about 30 percent, compared with the straight tunnel without the bleed duct. As the width of the vertical bleed duct becomes larger, reduction of the impulsive noise is expected to be greater. However the impulsive noise is independent of the height of the vertical bleed duct.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4036-4043
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• 1996

When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. In the purpose of the impulsive noise reduction, the present study tested the effect of porous walls on the compression wave propagating into a model tunnel. Experimental results were obtained using a shock tube with an open end. The results showed that the cavity/porous wall is very effective for the compression wave with a large nonlinear effect. The porosity of 30% is most effective for attenuation and pressure gradient reduction of the compression wave front. Also the impulsive noise reduction increases with increasing the length and height of the cavity, compared with the tunnel equivalent diameter.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.409-417
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• 2009

This paper is focused on a relationship between the noise and vibration of a wheelset and the railway irregularity of a high speed railway using a time-varying frequency transform for a preliminary research of the railway condition monitoring by an in-service high-speed railway vehicle. Generally, the monitoring has been performed by a special railway inspection vehicle or industrial engineers for railway maintenance. However, they have been limited at night due to the in-service high-speed railway vehicles, and too slow to monitor all of the section. To solve this problem, the monitoring should be performed by an in-service high-speed railway vehicle. For the research, the noise and vibration of a wheelset are utilized, because they are closely related to the railway condition. They are measured by using some microphones and accelerometers, and stored in an on-board data acquisition system. The signals are post-processed by a time-varying frequency analysis and compared with the result of a railway geometry and profile measurement system. From the comparison, it is able to observe the relationship between the noise and vibration of a wheelset and the irregularity of a high-speed railway. Also, some distinct frequency components are observed, which are not observed in the railway geometry and profile.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.454-459
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• 2013

Pressure waves are generated and propagate in a tunnel when train enters tunnel high speed. A compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as an expansion wave. An expansion wave due to the entry of the train tail propagates along the tunnel and is reflected at tunnel exit as a compression wave. These pressure waves are repeatedly propagated and reflected at the tunnel entrance and exit. Severe pressure changes causes ear-discomfort for passengers in the cabin and micro pressure waves around the tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnels qualitatively and quantitatively, because pressure change rate is considered as one of the major design parameters for optimal tunnel cross sectional area and repeated fatigue force on car body. In this study, we developed a characteristics method based on a fixed mesh system and boundary conditions for crossing trains and analyzed this system using an X-t diagram. The results of the simulation show that offsetting of pressure waves occurs for special entry conditions of a crossing train.

• Journal of the Korean Society for Railway
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• v.15 no.5
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• pp.436-441
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• 2012

Pressure waves are generated and propagate in tunnel when train enters a tunnel with high speed. Compression wave due to the entry of train head propagates along the tunnel and is reflected at tunnel exit as expansion wave. While expansion wave due to the entry of train tail propagates along the tunnel and is reflected at tunnel exit as compression wave. These pressure waves are repeatedly propagated and reflected at tunnel entrance and exit. Severe pressure change per second causes ear-discomfort for passengers in cabin and micro pressure wave around tunnel exit. It is necessary to analyze the transient pressure phenomena in tunnel qualitatively and quantitatively, because pressure change rate is considered as one of major design parameters for an optimal tunnel cross sectional area and the repeated fatigue force on car body. In this study, we developed the characteristics method analysis based on fixed mesh system and compared with the results of real train test. The results of simulation agreed with that of experiment.