• Proceedings of the KSR Conference
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• 2003.10c
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• pp.275-280
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• 2003

The Korean high speed train is designed to run at very high speed such as 350km/h. At this time, ballast in roadbed is dispersed by high speed air flow and this hits the substructure of the train. It becomes the factor of damaging the train. To investigate the main factor and possibility of ballast dispersion, the substructure flow is measured by Kiel-Probe Array System at G7 train experiment. And the wind tunnel experiment is performed with ballast in our research. Also CFD analysis is performed by assuming that the flow field is 2D and using simple shaped cross-tie and flat substructure of the train. By comparing the experimental results and CFD analysis, the accuracy of the analysis is checked. They will become the basic research data for the analysis and optimization of train substructure to prevent the ballast dispersion.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.495-502
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• 2000

For the tunnel design of the first class on new Seoul-Chunchon railway, we investigated for train speeds to run through tunnels without ear-discomfort of passenger in cabin by application of numerical analysis. Also we analyzed the effect of the wind speed induced by train in tunnel that is very harmful to the workers on railroad and the effect of the air-pressure fluctuations which get the fatigue to the tunnel lining and the car body.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1718-1723
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• 2015

The diameter of the rotor of 2MW wind turbine is being developed by a number of companies with more than 80m, reliability and economic efficiency of the wind power generator has been improved. The need for large-scale wind turbine with excellent economy has been attracting attention because the new orders and the location of the wind turbine market has reached a limit. Technology development for enlargement of wind turbine is possible not only the improvement of energy efficiency but also reduce the construction costs per unit capacity. However, mechanical gearboxes used in wind generators have problems of wear, damage, need for lubrication oil and maintenance. Therefore, we want to configure the gearbox of a large-scale wind turbine using a magnetic gear in order to solve these problems of mechanical gearbox.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.3
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• pp.244-252
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• 2012

Recently, the speed of a train has been increased. So the trains are being exposed to wind more severely than before. Because of the operation of high speed trains and lightweight of the train, risks of train derailment have being increased. In this study, aerodynamic effects of a newly designed high speed train, HEMU-400x, are evaluated. For aerodynamic effect evaluation, analysis method is selected by examining the safety standards for high speed train. The condition of aerodynamic effects is selected by adverse effect conditions. In order to calculate $C_s$ coefficients, numerical analysis is conducted. Using $C_s$ coefficients, the side force is calculated. Through dynamics analysis, derailment and wheel unloading are obtained. Using these results, derailment evaluation is performed.

• 한국전산유체공학회:학술대회논문집
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• 2005.04a
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• pp.104-108
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• 2005

The Korean high speed train runs at 300 km/h, ballast-flying phenomenon often happens by strong train-wind. It is important to consider the prevention of ballast-flying phenomenon, because the train under-body and fares or walker around a rail might be damaged. In this study, Numerical analysis of the flow field of under-body of train and study of heighter-effect were conducted to decrease the speed of under-body. The shape of under-body was simplified for convenience of meshing and analysis. According to results of Taguchi's design by orthogonal arrays, a height of tie is dominant in the flow field, so if the heighter is installed on tie, the speed of under-body might be decreased. The result of this study is useful to build a new high-speed-line.

• International Journal of High-Rise Buildings
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• v.2 no.2
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• pp.115-121
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• 2013

The ventilation performance of a street in Bangkok, Thailand, was investigated by performing measurements and conducting a CFD analysis. We focused on a street that was covered by an elevated train station. It was shown that the ventilation efficiency varied drastically depending on the angle between the street and the wind direction. When the wind direction was parallel to the street, the elevated structure had a negative influence, which created higher pollutant concentrations than in locations without elevated structures. However, when the wind direction was perpendicular to the street, the pollutant concentrations in the two situations were similar. Using a CFD analysis and ventilation performance indexes, it was shown that the elevated structure directed the wind flow and enhanced the ventilation efficiency, which positively affected ventilation performance. These kinds of knowledge can lead us to optimize city planning including high-rise buildings with high ventilation efficiency.

• Wind and Structures
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• v.27 no.4
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• pp.255-267
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• 2018

This paper investigated the wind-snow flow around the bogie region of a high-speed train under crosswinds using a coupled numerical method of the unsteady Realizable $k-{\varepsilon}$ turbulence model and discrete phase model (DPM). The flow features around the bogie region were discussed and the influence of bogie fairing height on the snow accumulation on the bogie was also analyzed. Here the high-speed train was running at a speed of 200 km/h in a natural environment with the crosswind speed of 15 m/s. The mesh resolution and methodology for CFD analysis were validated against wind tunnel experiments. The results show that large negative pressure occurs locally on the bottom of wheels, electric motors, gear covers, while the positive pressure occurs locally on those windward surfaces. The airflow travels through the complex bogie and flows towards the rear bogie plate, causing a backflow in the upper space of the bogie region. The snow particles mainly accumulate on the wheels, electric motors, windward sides of gear covers, side fairings and back plate of the bogie. Longer side fairings increase the snow accumulation on the bogie, especially on the back plate, side fairings and brake clamps. However, the fairing height shows little impact on snow accumulation on the upper region of the bogie. Compared to short side fairings, a full length side fairing model contributes to more than two times of snow accumulation on the brake clamps, and more than 20% on the whole bogie.

• Journal of Power Electronics
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• v.8 no.4
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• pp.345-353
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• 2008

In this paper, a novel loss minimization of an induction generator in wind energy generation systems is presented. The proposed algorithm is based on the flux level reduction, for which the generator d-axis current reference is estimated using support vector regression (SVR). Wind speed is employed as an input of the SVR and the samples of the generator d-axis current reference are used as output to train the SVR algorithm off-line. Data samples for wind speed and d-axis current are collected for the training process, which plots a relation of input and output. The predicted off-line function and the instantaneous wind speed are then used to determine the d-axis current reference. It is shown that the effect of loss minimization is more significant at low wind speed and the loss reduction is about to 40% at 4[m/s] wind speed. The validity of the proposed scheme has been verified by experimental results.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.732-737
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• 2009

Wind tunnel testing on the real-scale pantograph for high-speed train has been conducted to investigate the aerodynamic characteristic of the pantograph at high-speed. The mid-scale subsonic wind tunnel of Korea Airforce Acamedy with 3.5m width, 2.45m height, and 8.8m length test section has been employed. The test model has been supported above 50cm height from the bottom of test section using vertical strut to eliminate the boundary layer generated from the bottom of the test section. The height of the pantograph has been varied in three cases, in both of the normal running and reverse running modes. The resultant lift forces of the pantograph to catenary system in all the cases have been measured and the relation between the test conditions and the lift forces have been extensively analyzed.

• Journal of Convergence for Information Technology
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• v.12 no.2
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• pp.142-148
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• 2022

In this paper, the weight reduction design of the yaw gearbox for wind turbine was performed through the finite element analysis method, and the stability was checked by performing the critical speed analysis. The weight reduction product can improve engine efficiency, save parts materials, and earn economic benefits. The yaw gearbox is lightweighted with the goal of achieving a safety rate of 1.3 or higher for wind turbine as indicated by IEC61400-1. In order to reduce the weight of the carrier, a topology optimization method was performed. The safety factor was verified by performing finite element analysis on the carrier. In addition, the housing and carrier were modeled using the finite element method, and the gear train was modeled using MASTA. For the yaw gearbox, the housing and carrier FE model and the gear train model were connected by the partial structural synthesis method to perform the rotational vibration analysis. Vibration excitation sources are mass unbalance and gear mesh frrequemcy, and as a result of the critical speed analysis, it was found that there was no resonance within the operating speed range.