• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.475-482
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• 2001

Stadium stand could be led to significant dynamic response due to rhythmical activities of spectator. The dynamic loads induced by spectators movements are considered as static loads in design standard of many countries but these loads have dynamic characteristics. So, it is desirable to apply measured dynamic loads created by spectator activities and to analyze the dynamic behavior of stadium system. The precise investigation of the dynamic loads on stadium structures and the accurate analysis of dynamic behavior of stadium systems are demanded for effective design. As the floor mesh of stadium stand is refined, the number of nodes increase in numerical analysis. So it is difficult to analyze entire stadium structures and much more computer memory are necessary for vibration analysis of stadium system. In this study, the various dynamic loads induced by spectator movements are measured and analyzed. And new modeling method that reduce the nodal points of stadium systems are introduced. Vibration analysis of stadium system is executed to inspect the accuracy and the efficiency of proposed method in this paper.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.343-350
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• 2001

The box system, composed only of reinforced concrete walls and slabs, are adopted by many high-rise apartment buildings recently constructed in Korea. In the buildings, one or more relatively large openings are cut in a shear wall for functional reasons. The openings influence the internal stress of the shear wall and also the structural behavior. Therefore, it is necessary to use subdivided plate elements for accurate analysis of the box system with openings. But it would cost tremendous amount of analysis time and computer memory if the shear wall is subdivided into a finer mesh in the analysis of high-rise buildings. So, it is difficult to apply this modeling method to practical procedure. In this study, an efficient method is proposed for the efficient and accurate analysis of shear wall with openings. The proposed method used the super element and matrix condensations, fictitious beam technique.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.771-776
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• 2007

Widespread propagation of failure can be triggered by localized damage to a structure because of fires, impact and explosion etc. In this paper, the progressive collapse analysis program is developed to automatically check the failed members and construct the modified structural model at each step. OpenSees, that is widely used in many research groups, was used for the developed progressive collapse analysis control program. The control program developed in this study automatically computes the damage indices of all the structural members and performance a progressive collapse analysis after the first failed member is selected. Using the developed program, we compared the progressive collapse behaviors of the example structures considering dynamic effects or not, and the difference of progressive collapse mechanism according to the modeling method of the failed members.

• Journal of computational fluids engineering
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• v.10 no.4 s.31
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• pp.24-31
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• 2005

A dynamic simulation on the missile staging system is conducted with numerical techniques. Both Euler equations and Navier-Stokes equations are numerically solved respectively. The dynamic simulation of two moving bodies is fully integrated into the computational fluid dynamics solution procedure. The Chimera grid scheme is applied in this simulation for unsteady supersonic flow analysis with dynamic modeling. The objective of the study is to investigate the problem pertaining to possible unstability in missile staging. In addition, the computational comparison between in viscid and viscid flow solvers is also performed in this study.

• Journal of computational fluids engineering
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• v.12 no.3
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• pp.20-28
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• 2007

A fast and robust method of grid generation to multiple functions has been developed for flow analysis in three dimensional space. It is based on the Non-Uniform Rational B-Spline(NURBS) of an approximation method. Many of NURBS intrinsic properties are introduced and much more easily understood. The grid generation method, details of numerical implementation. examples of application, and potential extensions of the current method are illustrated in this paper. The object of this study is to develop the surface grid generation and the grid cluster techniques capable of resolving complex flows with shock waves, expansion waves, shear layers. The knot insert method of Non-Uniform Rational B-Spline seems well worked. In addition, NURBS has been widely utilized to generate grids in the computational fluid dynamics community. Computational examples associated with practical configurations have shown the utilization of the algorithm.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.302-307
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• 2008

The development technology for the helicopter is improved by the increasing of computing power and advanced test facilities. The increasing efficiency of fuel consuming by the developing of improved lift-to-drag rotor system is the major issue, the noise reduction for ecology(civil area) and increase of survivability to reduce noise detection(battlefield) also are important. This investigation shows the classification of helicopter external noise and requirements, the noise flight test methods, the numerical modeling method for aero-acoustic of rotor blade and the result of CAA(Computational Aero-Acoustic) for main rotor blade.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.302-307
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• 2008

The development technology for the helicopter is improved by the increasing of computing power and advanced test facilities. The increasing efficiency of fuel consuming by the developing of improved lift-to-drag rotor system is the major issue, the noise reduction for ecology(civil area) and increase of survivability to reduce noise detection(battlefield) also are important. This investigation shows the classification of helicopter external noise and requirements, the noise flight test methods, the numerical modeling method for aero-acoustic of rotor blade and the result of CAA(Computational Aero-Acoustic) for main rotor blade.

• Korean Journal of Computational Design and Engineering
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• v.13 no.1
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• pp.36-44
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• 2008

This paper proposes a modeling and simulation process of a panel production line (PPL) in a shipyard. The panel production line is an assembly process to produce a main panel of a flat block and a curved block. In this paper, its activity analysis is carried out using expression of IDEF0, and its process is qualitatively and quantitatively analyzed and modeled by Petri Nets. A commercial discrete event simulation tool, $QUEST^{TM}$, is used for virtual PPL and simulation. The modeling results by Petri Net are mapped to elements of the simulation tool. Finally, an integrated simulation environment of PPL is implemented in order to efficiently utilize the virtual PPL model. With the help of IDEF0 and Petri Nets, we could systematically analyze and describe the PPL process that are characterized as being concurrent, asynchronous, distributed, parallel, nondeterministic, and/or stochastic. Also, the dynamic and concurrent activities of a PPL system were able to be simulated. A timing concept can be included into the Petri nets model to evaluate performance and dependability issues of the system.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.147-153
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• 2004

This paper presents an analytical modeling technique fer representing a hysteretic behavior of a multi-leaf spring used for a large truck. It divides a nonlinear hysteretic curve of the multi-leaf spring into four parts; loading part, unloading part and two transition parts. It provides conditions fur branching to a part of the curve corresponding to a current multi-leaf spring status. This paper also presents a computational modeling technique of the multi-leaf spring. It models the multi-leaf spring with three links and a shackle. It assumes those components as rigid bodies. The links are connected by rotational joints, and have rotational springs at the joints. The spring constants of the rotational springs are computed with a force from the analytical model of the hysteretic curve of the multi-leaf spring. Static and dynamic tests are performed to verify the reliability of the presented techniques. The tests are performed with various amplitudes and excitation frequencies. The hysteretic curves from the tests are compared with those from the simulations. Since th e presented techniques reproduce the hysteretic characteristic of the multi -leaf spring faithfully, they contribute on improving the reliability of the computational model of a large truck.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.889-896
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• 2012

Recent progress in the computational fluid dynamics methods of two- and multiphase phase flows has already started opening up new exciting possibilities for using complete multidimensional models to simulate boiling systems. Combining this new theoretical and computational approach with novel experimental methods should dramatically improve both our understanding of the physics of boiling and the predictive capabilities of models at various scale levels. However, for the multidimensional modeling framework to become an effective predictive tool, it must be complemented with accurate mechanistic closure laws of local boiling mechanisms. Boiling heat transfer has been studied quite extensively before. However, it turns out that the prevailing approach to the analysis of experimental data for both pool boiling and forced-convection boiling has been associated with formulating correlations which normally included several adjustable coefficients rather than based on first principle models of the underlying physical phenomena. One reason for this has been the tendency (driven by practical applications and industrial needs) to formulate single expressions which encompass a broad range of conditions and fluids. This, in turn, makes it difficult to identify various specific factors which can be independently modeled for different situations. The objective of this paper is to present a mechanistic modeling concept for both pool boiling and forced-convection boiling. The proposed approach is based on theoretical first-principle concepts, and uses a minimal number of coefficients which require calibration against experimental data. The proposed models have been validated against experimental data for water and parametrically tested. Model predictions are shown for a broad range of conditions.