• Journal of Power System Engineering
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• v.19 no.5
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• pp.80-85
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• 2015

The unsteady-state, incompressible and three-dimensional large eddy simulation(LES) was carried out to analyze the structure of turbulent flow fields according to the operating loads of three-dimensional small-size axial fan(SSAF). LES shows the best prediction performance in comparison with any other Reynolds averaged Navier-Stokes(RANS) method because static pressure coefficients analysed by LES show a little bit larger than measurements including all flow coefficients. Also, it can be known that the wake of SSAF is divided into from axial flow to radial flow before and behind stall region according to the increase of static pressure through LES analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.365-370
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• 1998

In this study, the method of analysis which is developed for calculating dynamic train loads and ground vibration by Shin-Chu Yang is verified comparing measurements of real structure. The results of analysis are agreed well with measurements of ground and structural vibration induced by passing train. The vibration level of analyzed results which is more than that of measured gives conservative result. To analyze frequency characteristics, the analyzed results are applied to the ISO environmental vibration regulation and reveal the possibility of application in analysis of frequency characteristics.

• KSTLE International Journal
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• v.2 no.1
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• pp.75-79
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• 2001

This paper is a report on the parametric study of the friction characteristics on the direct acting type OHC valve train system. The numerical simulation was performed by using the IV-TAP. Dynamic analysis by using the lumped mass method was previously performed to define the acting load. The friction characteristics were analyzed by using the partial asperity contact model. The effects of operating conditions and major design parameters on the total driving torque were investigated. From the analytical prediction, it is found that valve spring stillness, surface roughness, and base circle radius are the main factors to reduce the frictional loss on the valve train system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2001.05a
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• pp.131-135
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• 2001

Evaluation of microstructural changes during open die forging of heavy ingots is important for process control. The objective of the control of forging parameters, such as shape of the dies, reduction, temperature and sequence of passes, is to maximize the forging effects md to minimize inhomogeneities of mechanical properties. The hot working die steel is produced by using the multistage open die forging. The structure is altered during forging by subsequent processes of plastic deformation, recrystallization and grain growth. A numerical analysis using an rigid visco-plastic finite element model was performed to predict microstructural evolution of hot working die steel.

• Journal of the Korean Society of Safety
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• v.8 no.3
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• pp.3-12
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• 1993

In reciprocating internal combustion engine, engine performance Is greatly affected by volumetric efficiency. For gas flow, the dynamic effects caused by the pressure pulsation have influence on the volumetric efficiency and correlate to the configuration and pipe length of intake-exhaust system. In this study, the analytic investigation of the unstudy flow In exhaust pipe has been carried out by using the method of characteristics to predict volumetric efficiency. In conculusion, it is possible to take account of the exhaust pipe tuning effect in predicting the engine performance, by the analytic solution of the unsteady flow in the pipes, and comparision of prediction with experimental datas show a good agreement on the pressure varision in the exhaust pipe which has Influence on the volumetric efficiency and performance of engine.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.339-341
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• 2006

This paper presents a new method on controller design of brushless dc motors. In such drives the current ripples are generated by motor inductance in stator windings and the back EMF. To suppress the current ripples the current controller is generally used. To minimize the size and the cost of the drives it is desirable to control motors without the current controller and the current sensing circuits. To estimate the motor current it is modeled by a neural network that is configured as an output-error dynamic system. The identified model is essentially a one step ahead prediction structure in which fast inputs and outputs are used to calculate the current output. Using the model, effective estimator to compensate the effects of disturbance has been designed. The effectiveness of the proposed current estimator is verified through experiments.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.469-475
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• 2004

The vibration on building structures due to exciting vibration forces has been studied only for the vibration level on existing buildings. Recently, several researches have been performed on the prediction of vertical vibration on structures by using an analytical method. However, these studies have been focused on mainly the vibration analysis through analytical modeling of structures. This study aims to investigate the dynamic characteristics of vertical vibration transfer from lower stories to upper ones on the Rahmen building structures due to traffic loads. In order to examine the characteristics of vertical vibration transfer, the mode analysis and the impact experiment were conducted several times on one building structures. The results of this study suggest that the characteristics of vertical vibration transfer are different in terms of the type of trains.

• Journal of Ocean Engineering and Technology
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• v.7 no.2
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• pp.141-149
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• 1993

삼 자유도를 가진 부유물체의 동적 응답을 이론적으로 연구하였다. 평면내 방향 운동모우드에 대한 지배방정식을 선형화한 후, 그들의 조화해를 평명밖 방향 운동모우드의 방정식과 연성시켰다. 그렇게 해서 주어지는 방정식은 시간에 따라 변화하는 계수를 가진 형태로서, 평면밖 방향의 운동만을 보일 것으로 예측되는 부유물체가 평면밖 방향의 운동을 보일 수도 있음을 밝혔다. 동역학적 불안정성과 그 결과로 나타나는 평면밖 방향의 대진폭 운동을 보이고 있다. 본 결과는 주기적으로 동요하는 부유물체가 서로 연성된 운동을 하는 현상으로도 해석할 수 있다.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.6
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• pp.608-611
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• 2012

This paper focuses on attitude stabilization performance improvement of the quadrotor flying robot. First, the dynamic model of quadrotor flying robot was estimated through PEM (Prediction Error Method) using experimental input/output data. And attitude stabilization performance was improved by increasing the generation frequency of PWM signal from 50 Hz to 500 Hz. Also, the controller is implemented using a standard PID (Proportional-Integral-Derivative) controller augmented with feedback on angular acceleration, allowed the gains to be significantly increased, yielding higher bandwidth. Improved attitude stabilization performance is verified by experiment.

• Journal of Welding and Joining
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• v.15 no.3
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• pp.118-127
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• 1997

With the trend towards welding automation and robotization, mathematical models for studying the influence of various variables on the weld bead geometry in gas metal arc (GMA) welding process are required. Partial penetration, single-pass bead-on-plate welds using the GMA welding process were fabricated in 12mm mild steel plates employed four different process variables. Experimental results has been designed to investigate the analytical and empirical formulae, and develop mathematical equations for understanding the relationship between process variables and weld bead geometry. The relationships can be usefully employed not only for open loop process control, but also for adaptive control provided that dynamic sensing of process output is performed.