• Journal of the Korean Society for Railway
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• v.3 no.3
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• pp.131-138
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• 2000

The design of current collection system of high speed train requires the fundamental understandings for the dynamic characteristics of catenary system and pantograph. The stiffness of catenary system of high speed train has the varying characteristics for the change of contact point with pantograph, since the supporting pole and hanger make the different boundary conditions for the up-down stiffness of a trolley wire. The variation of stiffness results in Mathiue equation, which characterizes the stability of the system. However, the two-term variation of the stiffness due to span length and hanger distance cannot be solved analytically. In this paper, the stiffness variations are calculated and the physical reasoning of linear model and one term Mathieu equation are reviewed. And the numerical analysis for the two-term variation of the stiffness is done for the several design parameters of pantograph.

• The Journal of the Acoustical Society of Korea
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• v.25 no.8
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• pp.356-361
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• 2006

We present the performance of differential space-time block decoders. which does not require the channel state information. We suggest the structure of the multiple blocks differential space time decoders. which does not require the channel state information, and analyze the Performances. In quasi-static flat fading channels. the Performance of multiple blocks differential detection (MD-STC) outperforms that of 2 blocks(D-STC) by 1.5dB. But in the time-selective fading channels due to Doppler frequency $(f_d)$, the performance of MD-STC degrades as the vehicular speed is greater than 200km/hr in 802.16e systems, where the data transmission rate is 144kbps.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.71-77
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• 2002

We consider the simultaneous slewing and vibration suppression control problem of an idealized structural model which has a rigid hub with two cantilevered flexible appendages and finite tip masses. The finite clement method(FEM) is used to obtain linear finite dimensional equations of motion for the model. In the linear quadratic regulator(LQR) problem, a simple method is introduced to provide a physically meaningful performance index for space structure models. This method gives us a mathematically minor but physically important modification of the usual energy type performance index. A numerical procedure to solve a time-variant LQR problem with inequality control constraints is presented using the method of particular solutions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1210-1215
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• 2000

Investigation is performed on the stability of general form of dynamic system under colored noise random disturbance whose damping and stiffness are varying in irregular manner along time, which is a preliminary result in the course of research on the characteristic and the control of the stochastic system. Adopted physical model is airfoil under random atmospheric disturbance, which becomes a "time-varying system" whose the governing equation is derived via F-P-K approach in stochastic sense. Control performance and effect of 'Heo-stochastic controller for colored noise' is studied. Also stochastic feature of flutter boundary is discussed as well.