• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.613-616
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• 1997

MDO(Multidisciplinary Design Optimization) methodology is an emerging new technology to solve a complicate structural analysis and design problem with a number of design variables and constraints. In this paper MDO methodology is adopted through the use of computer aided engineering(CAE) system. And this paper treats the structural design problem of RIROB(Reactor Inspection Robot) through the application of MDO methodology. In a MDO methodology application to the structural design of RIBOS, kinetodynamic analysis is done using a simple fluiddynamic analysis model for the warter flow over the sensor support surface instead of difficult fluid dynamic analysis. Simultaneously the structural static analysis is done to obtain the optimum structural condition. The minimum thickness (0.8cm) of the RIROB housing is obtained for the safe design of RIROB. The kinetodynamic analysis of RIROB. The kinetodynamic analysis of RIROB is done using ADAMS and the static structural analysis of RIROB is done using NISA.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.7
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• pp.113-122
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• 2002

Control system modeling and optimal bending filter design for KSR-III (Korea Sounding Rocket III) are performed. Rigid rocket dynamics, aerodynamics, sloshing, structural bending, actuator dynamics, sensor dynamics and on-board computer characteristics are considered for control system modeling. Compensation for time-varying control system parameters is conducted by gain-scheduling. A filter to stabilize bending mode is designed using parameter optimization technique. Resultant attitude control system can satisfy required frequency domain stability margin.

• Journal of Information Technology Services
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• v.10 no.2
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• pp.75-94
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• 2011

The industrial ecosystem around the Internet services has been evolving since the Internet was first introduced. The Net Neutrality issue best represents the process of the evolution and presents an inevitable challenge that the industry should overcome. This paper deals with this structural change with the Two-Sided Market framework and provides a System Dynamics(SD) model to evaluate the economic implications of the net neutrality policy. In particular, our approach analyzes the policy impacts when two competing platforms (network providers) play a role of the platform in a typical two-sided market, which connects Content Providers(CPs) with users. Previous studies show that the indirect network externality between these two markets makes the entire system tip to one platform. When the multi-homing in the CP market is allowed as in our model, however, their argument may lose its validity. To examine the system behavior, conducted here is SD simulations of our model. The simulation results show that co-existence of the competing platforms persists with the network effects over a certain threshold. The net neutrality policy seems to lower the threshold based on our experimental outcomes.

• Journal of the Korean Ceramic Society
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• v.53 no.3
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• pp.295-300
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• 2016

To investigate the thermal conductivity and the structural properties of naturally cooled excimer-laser annealed Si, molecular-dynamics (MD) simulations have been performed. The thermal conductivity of crystalline Si (c-Si) was measured by direct method at 1000 K. Steady-state heat flow was measured using a stationary temperature profile; significant deviations from Fourier's law were not observed. Reliable processes for measuring the thermal conductivity of c-Si were presented. A natural cooling process to admit heat flow from molten Si (l-Si) to c-Si was performed using an MD cell with a size of $48.9{\times}48.9{\times}97.8{\AA}^3$. During the cooling process, the temperature of the bottom $10{\AA}$ of the MD cell was controlled at 300 K. The results suggest that the natural cooling system described the static structural property of amorphous Si (a-Si) well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.602-606
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• 2011

In this study, operational vibration experiment and analysis have been conducted for the 4-blade small vertical-axis wind turbine (VAWT) including the effect of tower elastic behavior. Computational structural dynamics analysis method is applied to obtain Campbell diagram for the VAWT with elastic tower. An open type wind-tunnel is used to change and keep the wind velocity during the ground test. Equivalent reduced elastic tower is supported to the VAWT so that the elastic stiffness effect of the tower can be reflected to the present vibration experiment. Various excitation sources with aerodynamic forces are considered and the dominant operating vibration phenomena are physically investigated in detail.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.993-998
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• 1988

Adaptive control system has evolved as an attempt to avoid degradation of the dynamic performance of a control system when environmental variations occurs. While the feedback control system is oriented toward the elimination of the effect of state perturbations, the adaptive control system is oriented toward the elimination of the effect of structural perturbation, upon the performances of the control system. The model reference adaptive controller is utilized in velocity loop controller for positioning and tracking is designed based on the linear decoupled dynamics.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.63-68
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• 2006

This paper proposes a fast Fourier transform(FFT)-based spectral analysis method(SAM) for the dynamic responses of the linear discrete dynamic models with non-proportional damping. The SAM was developed by using discrete Fourier transform(DFT)-theory. To verify the proposed SAM, a three-DOF system with non-proportional viscous damping is considered as an illustrative example. The present SAM is evaluated by comparing the dynamic responses obtained by SAM with those obtained by Runge-Kutta method.

• Tribology and Lubricants
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• v.30 no.1
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• pp.64-70
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• 2014

This paper presents a numerical model for investigating the structural dynamics response of a rigid rotor supported on deep-groove ball bearings. The numerical model was used to investigate the influence of race waviness on the dynamic characteristics of a rotor ball bearing system, which is very important from a design viewpoint. The forth-order Runge-Kutta numerical integration technique was applied to determine the time displacement response, Poincare map, and frequency spectra. The analysis demonstrated that the model can be used as a tool for predicting the nonlinear dynamic behavior of a rotor ball bearing system under different operating conditions. The results of this study may help further understanding of the nonlinear dynamics of a rotor bearing system.

• Korean System Dynamics Review
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• v.9 no.1
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• pp.5-31
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• 2008

Korean administrative jurisdiction has changed from separation to integration system, without definite raison d'etre from the effectiveness dimension. It partially comes from the fact that the top priority of most existing documents has given to the behavioral patterns of key variables during specific time periods. As an alternative approach, this study focuses on dynamic analysis on the long-term structural patterns related to urban-rural integration issues. Specifically, it pays attention to unique experiences between two neighboring administrative authorities, namely Cheongju and Cheongwon, all of which have repeated exceptional confrontations between pros and cons over almost two decades. From the theoretical perspectives, this observes structural similarities and differences between separation and integration approaches and compares individual feedback loops in order to examine urban-rural integration effectiveness. Structurally, if the integrated local authority adopts systematic management and balanced territorial development principles, it would gain the highest positive effect of urban-rural integration. After scenario buildings, it analyzes administrative integration dynamics between Cheongju and Cheongwon, highlighting geo-political conditions, key issues, and implementation plans between two administrative authorities. It expects that the integrated jurisdiction as a whole would increase the urban attractiveness as it can facilitate territorial development plans from macro-level. Furthermore, if the integrated authority keeps balanced territorial principles, which would be well reflected in the mutual agreement between two administrative units, it would also guarantee the increased urban attractiveness in the integrated jurisdiction. Nonetheless, compared to Cheongwon, which might be wider open to the location of NIMBY facilities, it would be more difficult for Cheongju to pay attention to territorial development confined to its original jurisdiction in the short run.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1489-1495
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• 2012

In this study, we perform the structural analysis of a floating offshore wind turbine tower by considering the dynamic response of the floating platform. A multibody system consisting of three blades, a hub, a nacelle, the platform, and the tower is used to model the floating wind turbine. The blades and the tower are modeled as flexible bodies using three-dimensional beam elements. The aerodynamic force on the blades is calculated by the Blade Element Momentum (BEM) theory with hub rotation. The hydrostatic, hydrodynamic, and mooring forces are considered for the platform. The structural dynamic responses of the tower are simulated by numerically solving the equations of motion. From the simulation results, the time history of the internal forces at the nodes, such as the bending moment and stress, are obtained. In conclusion, the internal forces are compared with those obtained from static analysis to assess the effects of wave loads on the structural stability of the tower.