• Journal of Magnetics
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• v.21 no.3
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• pp.340-347
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• 2016

At the stroke end of an electromagnetic circuit breaker, the high speed of the mover makes a huge impact at the contact point, which induces the rebound problem of the mover that causes a breaker failure. Thus, a speed reduction equipment is required to address such problems. This study suggests to use an electric brake reduces the speed at the end of the stroke. The proposed circuit breaker which adopts the electric brake has a variable speed reduction function such that the continued rebound phenomenon ceases to occur. The electric brake is designed by the Finite Element Method (FEM) and the circuit and motion equations are solved using Time Difference Method (TDM). The comparisons between the simulation and experiments demonstrated the usefulness and validity of this study.

• Korean Journal of Materials Research
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• v.18 no.9
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• pp.492-496
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• 2008

The through-thickness variations of strain and microstructure of high-speed hot rolled 1050 pure aluminum sheet were investigated. The specimens of 1050 aluminum were rolled at temperatures ranging from 410 to $560^{\circ}C$ at a rolling speed of 15 m/s without lubrication and quenched in water at an interval of 30ms after rolling. The redundant shear strain induced by high friction between rolls and the aluminum sheet was increased largely beneath the surface at a rolling reduction above 50%. Recrystallization occurred in the surface regions of the specimen rolled to reduction of 65% at $510^{\circ}C$, while only recovery occurred in the other regions.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.249-253
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• 2016

In this study, a harmonic-pulsation-compensator (HPC) is presented to reduce a periodic speed ripple in IPMSM. A proportional-integral compensator in HPC is proposed instead of the existing integral compensator to reduce the speed ripple more rapidly. A formula to calculate a rotation angle is also proposed, making compensation optimal in sensored and sensorless controls. The validity of the proposed algorithm is verified by experiments.

• Journal of KSNVE
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• v.10 no.4
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• pp.636-641
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• 2000

KHST(Korea High Speed Train) project plans to design and to build an high speed train. There are noise requirements in passenger room for the standing and running condition, which should be reached. Predicted noise calculated for the standing and running TM5(Motorized car) and TT4(Trailer car) train (v=300 km/h and v=350 km/h) to find out critical areas in or around the train. From the estimation in DWA IfS, actions of noise reduction are proposed to reach the requirements. This paper takes the review of the calculated results in DWA IfS to propose a new design of inner wall.

• International Journal of Railway
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• v.4 no.3
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• pp.74-79
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• 2011

Recent years have witnessed speed up of moving vehicles such as high-speed of trains. Increase in speed entails concomitant increase in turbulent air flow which contributes toward increased aerodynamic noise. The proposed method for aerodynamic noise reduction is based on a biomimetic design of owl feather. The five morphological parameters of the owl feather are extracted from close observation, and simulation cases are constructed by applying design of experiments methodology. Swirling strength for each case is obtained through steady-state CFD analysis, and key morphological parameters that affect the turbulence are identified. Large eddy simulations (LES) are then performed on selected cases to predict the air turbulence. Different cases show varying vortex distributions which are expected to lead to varying aerodynamic noise levels.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.867-875
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• 2014

Planing crafts were specifically designed to achieve relatively high speeds on the water. When a planing craft is running at high speed, dynamic pressure on the bottom makes the boat rise on the surface of the water. This reduces the area of the sinking surface of the boat to increase air resistance. Air resistance means the resistance that occurs when the hull and deck house over the surface of the water come in contact with the air current. In this paper, we carried out a CFD numerical analysis to find optimal deck houses that decreased air-resistance on the water when planing crafts are running at high speed. We finally developed the deck house shape of high-speed planing crafts that optimally decreased air resistance.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1148-1153
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• 2008

Noise pollution from a high speed train has been a serious social issue nowadays. Especially when a train speed exceeds 350 km/hr, an aerodynamic noise level has been known to be increased drastically. In this paper, explained were the studies on the noise reduction and engineering approaches to estimate and analyze influences of noise. Based on this study, it is estimated to apply results to development of trains and expected to accomplish futuristic technology by devising noise prediction of high speed EMU and measures to reduce noise on a design phase.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1305-1306
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• 2006

A new material was developed to achieve improvement of heat durability, improvement of wear resistance, stability of friction coefficient and reduction in aggression to counterpart, because it is difficult to maintain braking properties by using currently available materials in the train wagons used for high-speed transportation. As a result, the new material showed a stable wear resistance even in the speed range of 350km/h, where improvement was also confirmed in reduction of aggression to counterpart material by more than approximately 10%. This development was adopted for the brake lining in the Taiwan High Speed Rail project.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.273-279
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• 1998

This study represents the technique about the noise reduction of HVAC equipment for high speed train(HST) operating at 200km/h. HST is different from the low speed train in the various points as well as the speed. Especially, the noise of cabin is closely related to the comfort of passenger and the noise from HVAC is one of main noise source in the cabin. In this study, the noise from HVAC was reduced by 5 dB(A) using the concept of multiple resonator and guide vein. Therefore, the noise of cabin decreased from 60 dB(A) to 55 dB(A) at the center of the cabin.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6C
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• pp.450-456
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• 2005

In this paper, we propose a high-speed turbo decoding algorithm and present results of its implementation. The latency caused by (de)interleaving and iterative decoding in conventional MAP turbo decoder can be dramatically reduced with the proposed scheme. The main cause of the time reduction is to use radix-4, center to top, and parallel decoding algorithm. The reduced latency makes it possible to use turbo decoder as a FEC scheme in the real-time wireless communication services. However the proposed scheme costs slight degradation in BER performance because the effective interleaver size in radix-4 is reduced to an half of that in conventional method. To ensure the time reduction, we implemented the proposed scheme on a FPGA chip and compared with conventional one in terms of decoding speed. The decoding speed of the proposed scheme is faster than conventional one at least by 5 times for a single iteration of turbo decoding.