• Journal of Mechanical Science and Technology
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• v.19 no.4
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• pp.976-984
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• 2005

This paper presents the analysis results of dynamics in the billiards game within the frame­work of rigid-body mechanics and a numerical simulation program. The friction exists between the ball and the table bed as well as between the ball and the rail. There are three parts in the dynamic behavior of the ball on the table bed; motion of the ball on the table bed, collision between balls, and collision between the ball and the cushion. During the development of the simulation program, the dynamics problems such as rolling motion and three-dimensional frictional impact motion have been analyzed in detail. The theoretical issues are implemented into a viable graphic simulation program and its efficacy is demonstrated through the experi­mental validation of the billiards game. The resulting analysis results are verified quantitatively and qualitatively using high-speed video camera. Through the experimental tests, it was found that the physical parameters such as coefficients of restitution and friction vary according to the motion variables and corresponding empirical formulations were developed. The simulation and experimental results agree well.

• Korean System Dynamics Review
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• v.2 no.1
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• pp.93-112
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• 2001

Inter-Organizational Cooperation is the most common and important strategy in modern public and privet sectors managerial activities. In this paper the concepts of inter-organizational cooperation means not selfish cooperation as in the game circumstance and theory, but general collaborative action between organizations, they have share same goal. The achievement level of jointed-goal of inter-organization is depended upon the performance of cooperation, which resulted from the conditions and circumstances of cooperation. This paper analyses the effect of inter-organizational cooperation on achievement level of the jointed goal between two organizations with computer simulation model of the system dynamics approach. In the computer simulation model, three factors, goal perception, communication, and control, are considered as a key conditions of cooperation, which impact on the performance of cooperation. Simulation model was constructed with focus on the dynamic interactions between these three factors and the achievement level of jointed-goal. Consequently, the results found in this paper may provide further grounds for reducing the time delay that included in the conditions of cooperation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.237-244
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• 2007

In order to obtain mechanical properties of CNT/Polymer nano-composites, molecular dynamics simulation is performed. Overall system was modeled as a flexible unit cell in which carbon nanotubes are embedded into a polyethylene matrix for N $\sigma$ T ensemble simulation. COMPASS force field was chosen to describe inter and intra molecular potential and bulk effect was achieved via periodic boundary conditions. In CNT-polymer interface, only Lennard-Jones non-bond potential was considered. Using Parrinello-Rahman fluctuation method, mechanical properties of orthotropic nano-composites under various temperatures were successfully obtained. Also, we investigated thermal behavior of the short CNT reinforced nanocomposites system with predicting glass transition temperature.

• Advances in concrete construction
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• v.4 no.4
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• pp.305-317
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• 2016

Porous materials such as concrete could be subjected to aggressive ions transport. Durability of cement paste is extremely depended on water and ions penetration into its interior sections. These ions transport could lead different damages depending on reactivity of ions, their concentrations and diffusion coefficients. In this paper, chloride diffusion process in cement hydrates is simulated at atomistic scale using molecular dynamics. Most important phase of cement hydrates is calcium silicate hydrate (C-S-H). Tobermorite, one of the most famous crystal analogues of C-S-H, is used as substrate in the simulation model. To conduct simulation, a nanopore is considered in the middle of simulation cell to place water molecules and aggressive ions. Different chloride salts are considered in models to find out which one is better for calculation of the transport properties. Diffusion coefficients of water molecules and chloride ions are calculated and validated with existing analytical and experimental works. There are relatively good agreements among simulation outputs and experimental results.

• Journal of the Korean Society of Safety
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• v.28 no.1
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• pp.57-62
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• 2013

Aerodynamic characteristics of cross section shape is an important parameter for the wind response and structural stability of long span bridges. Numerical simulation methods have been introduced to estimate the aerodynamic characteristics for more detailed flow analysis and cost saving in place of existing wind tunnel experiment. In this study, the computational fluid dynamics(CFD) simulation and large eddy simulation( LES) technique were used to estimate lift, drag and moment coefficients of four cross sections. The Strouhal numbers were also determined by the fast Fourier transform of time series of the lift coefficient. The values from simulations and references were in a good agreement with average difference of 16.7% in coefficients and 8.5% in the Strouhal numbers. The success of the simulations is expected to attribute to the practical use of numerical estimation in construction engineering and wind load analysis.

• Environmental Engineering Research
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• v.19 no.2
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• pp.165-174
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• 2014

A model combining multi-dimensional discretized population balance equations with a computational fluid dynamics simulation (CFD-DPBE model) was developed and applied to simulate turbulent flocculation and sedimentation processes in sediment retention basins. Computation fluid dynamics and the discretized population balance equations were solved to generate steady state flow field data and simulate flocculation and sedimentation processes in a sequential manner. Up-to-date numerical algorithms, such as operator splitting and LeVeque flux-corrected upwind schemes, were applied to cope with the computational demands caused by complexity and nonlinearity of the population balance equations and the instability caused by advection-dominated transport. In a modeling and simulation study with a two-dimensional simplified pond system, applicability of the CFD-DPBE model was demonstrated by tracking mass balances and floc size evolutions and by examining particle/floc size and solid concentration distributions. Thus, the CFD-DPBE model may be used as a valuable simulation tool for natural and engineered flocculation and sedimentation systems as well as for flocculant-aided sediment retention ponds.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.139-147
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• 1995

The mechanism of the ionized cluster beam deposition has been studied using Molecular Dynamics Simulation. The Embedded Atom Method(EAM) potential were used in the simulation. The impact of a Au95-cluster on Au(100) substrate was studied for the impact energies 0.15-10eV/atom. The dependency of the impact energy of cluster beam was observed. For the cluster energy impact of 10eV per atom, the defects on surface were created and the cluster embedded into substrate as an amorphous state. For the energy of 0.5eV per atom, the defect free homoepitaxial growth was observed and atomic scale nucleation was formated, which are in good agreement with experiment. Thus molecular dynamics simulation is very useful to study the mechanism of the ionized cluster beam deposition.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.409-414
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• 2007

Nowadays, with the advancement of computational mechanics, and vehicle dynamics simulation linked up with virtual testing laboratory(VTL) and virtual proving ground(VPG) technologies has become a useful method for analyzing numerous driving performances and diverse noise/vibration characteristics. In this paper, the analytical vehicle model based on multi-body dynamics theory was developed to investigate the vibration characteristics according to various road conditions. For the purpose, the whole vehicle parameters, each vehicle's part parameter, and part connecting elements such as spring, damper, and bush were measured by an experiment. Also, the vehicle dynamics model, which includes the front suspension, rear suspension, steering, front wheel, rear wheel, and body subsystems has been constructed for computer simulation. With the developed vehicle dynamics model, three forces and three moments measured at each wheel center were applied to evaluate and analyze dynamics and vibration characteristics for miscellaneous road conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.1
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• pp.60-67
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• 2005

Generally. in the molecular dynamics simulations. the Verlet neighboring list algorithm is used for the reduction of a simulation time On the other hand. the application of the Verlet neighboring list forces the time evolution of a simulation system to follow an unrealistic path in a phase space. In equilibrium state, it does not matter with the simulation results because the individual molecule's motion is originally random and any effect due to a small deviation from a real time evolution can be completely ignored. However, if an unsteady state is involved. such a deviation may significantly affect to the results. That is, there is a Possibility that the simulation results Provide ones with any misleading data In this study we evaluated the effect due to the Verlet neighboring list in performing the simulation of a non-equilibrium state and suggested the method to avoid it.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.11
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• pp.1617-1624
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• 2013

This paper analyzes the relation between fire shutters and fire spread by conducting fire simulation on inner space with fire shutters. Using Fire Dynamics Simulator (FDS), a commercial fire simulation software, the simulation is done on an ideal inner robby, where fire size and the open/close of fire shutters are varied. Our simulation environment can derive significant fire parameters such as temperature variation of fire room walls and entrances of refuge stairs, variation of carbon dioxide, and soot spread. According to the simulation results, temperature and carbon dioxide distribution in refuge stairs have little dependence on vent open or close, but the part close of fire shutters blocks soot inflow to refuge stairs.