• Wind and Structures
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• v.32 no.5
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• pp.453-469
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• 2021

Snow accumulation on the road frequently induces a big traffic problem in the cold snowy region. Accurate prediction on snow distribution is fundamental for solving drifting snow disasters on roads. The present study adopts the transient method to simulate the wind-induced snow distribution on embankment based on the mixture multiphase model and dynamic mesh technique. The simulation and field measurement are compared to confirm the applicability of the simulation. Furthermore, the process of snow accumulation is revealed. The effects of friction velocity and snow concentration on snow accumulation are analyzed to clarify its mechanism. The results show that the simulation agrees well with the field measurement in trends. Moreover, the snow accumulation on the embankment can be approximately divided into three stages with time, the snow firstly deposited on the windward side, then, accumulation occurs on the leeward side which induced by the wake vortex, finally, the snow distribution reaches an equilibrium state with the slope of approximately 7°. The friction velocity and duration have a significant influence on the snow accumulation, and the vortex scale directly affected the snow deposition range on the embankment leeward side.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.64-74
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• 1997

The purpose of this study is to analyze hydraulic characteristics of surface irrigation in a paddy field of direct seeding culture. Field experiment was performed in the paddy field of ridge direct dry seeding. Simulation by a numerical model was also accomplished with the data obtained from the field experiment. The model was developed by one dimensional zero-inertia equation and finite difference method. From the result of the field observation, the furrows of the experimental field were found to have various geometric characteristics. Advance distance and time were measured both in the field and by the model simulation for various furrow lengths and irrigation discharges. Roughness coefficients of each furrow were also estimated by the model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.57-60
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• 2003

This paper explained electric field distribution's characteristics of dielectric pellets with a shape of ball to voltage. When discharge gap of electrode and input voltage are each 20[mm], 10000[V], the electric field simulation results of dielectric pellets with a shape of ball with relative dielectric constant of several kind measured stronger electric field near electric pellets with a shape of ball of ${\phi}5$[mm] than $1{\phi}$[mm] and $3.33{\phi}$[mm] at atmosphere. And the maximum electric field of dielectric pellets with a shape of ball over ${\phi}5$[mm] increased about 5[%] to maximum electric field of electric pellets with a shape of ball ${\phi}5$[mm]. And the result of simulation, when relative dielectric constant of dielectric pellets with a shape of ball is 100, it measured about 90[%] of maximum electric field of dielectric pellets with a shape of ball with relative dielectric constant over 1000.

• Journal of Magnetics
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• v.22 no.2
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• pp.326-332
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• 2017

The effects of exposure to an extremely low-frequency magnetic field (25 Hz 20G) on animal cells have been studied. In some reports, stimulation was performed for fixed frequency and variations in magnitude; however, animal-cell experiments have established that both parameters play an important role. The present work undertook the modeling, simulation, and development of a uniform-magnetic-field generation system with variable frequency and stimulation intensity (0-60 Hz, 1-25G) for experimentation with cell cultures in situ. The results showed a coefficient of variation less than 1 % of the magnetic-field dispersion at the working volume, which is consistent with the corresponding simulation results demonstrating a uniform magnetic field. On the other hand, long-term tests during the characterization process indicated that increments of only $0.4^{\circ}C$ in the working volume temperature will not be an interfering factor when experiments are carried out in in situ cell cultures.

• Membrane Journal
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• v.27 no.4
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• pp.358-366
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• 2017

The most important factor in the performances of polymer electrolyte membranes for fuel cells is how fast hydrogen ions can be transported along the water channel formed inside the electrolyte membrane. Since the morphology of the water channel and the diffusivity of the protons are very important factors for the proton transport behavior, various molecular dynamics simulation studies are being carried out to clarify this. The force-field is an important variable parameterizing the movement and interaction of each atom in molecular dynamics simulation. In this study, proton diffusivities of the 3D models of polymer electrolyte membranes were calculated in order to analyze the effects of various types of force-fields on the molecular simulation. It has been found that the charge value determining the non-bonding interaction plays a very important role in the formation of the water channel morphology, and the COMPASS force-field can calculate the accurate proton diffusion behavior. Accordingly, for molecular dynamics simulation of polymer electrolyte membranes, the proper selection of the force-field is very important due to its great effect on the proton diffusion as well as the final molecular structure.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.49.2-49.2
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• 2010

In order to understand the configuration of magnetic field producing a solar penumbral microjet that was recently discovered by Hinode, we performed a magnetohydrodynamic simulation reproducing a dynamic process of how that configuration is formed in a modeled solar penumbral region. A horizontal magnetic flux tube representing a penumbral filament is placed in a stratified atmosphere containing the background magnetic field that is directed in a relatively vertical direction. Between the flux tube and the background field there forms the intermediate region in which the magnetic field has a transitional configuration, and the simulation shows that in the intermediate region magnetic reconnection occurs to produce a clear jet- like structure as suggested by observations. The result that a continuous distribution of magnetic field in three-dimensional space gives birth to the intermediate region producing a jet presents a new view about the mechanism of a penumbral microjet, compared to a simplistic view that two field lines, one of which represents a penumbral filament and the other the background field, interact together to produce a jet. We also discuss the role of the intermediate region in protecting the structure of a penumbral filament subject to microjets.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2A
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• pp.383-390
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• 2006

In this paper, a stochastic field that is compatible with Monte Carlo simulation is suggested for an expansion-based stochastic analysis scheme of weighted integral method. Through investigation on the way of affection of stochastic field function on the displacement vector in the series expansion scheme, it is noticed that the stochastic field adopted in the weighted integral method is not compatible with that appears in the Monte Carlo simulation. As generally recognized in the field of stochastic mechanics, the response variability is not a linear function of the coefficient of variation of stochastic field but a nonlinear function with increasing variability as the intensity of uncertainty is increased. Employing the stochastic field suggested in this study, the response variability evaluated by means of the weighted integral scheme is reproduced with high precision even for uncertain fields with moderately large coefficient of variation. Besides, despite the fact that only the first-order expansion is employed, an outstanding agreement between the results of expansion-based weighted integral method and Monte Carlo simulation is achieved.

• Journal of Korean Society of societal Security
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• v.4 no.1
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• pp.29-37
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• 2011

Recently, Inhabitants nearby the high embankment road have requested a civil complaint on the environmental deteriorations and economic harms. This study was carried out numerical simulation using the 3-D microclimate model 'Envi-met' in order to investigate the variations of a flow field and a temperature field at the road sections with a high embankment and a bridge. About the simulation of flow field, the wind field has changed due to the disturbance of airflow by a high embankment road considerably. And the wind velocity decreased in the whole of simulation space widely. But, the wind velocity and wind direction sited loose to the section of a bridge, relatively. In the results of a temperature field, the slight variations of temperature field were discovered by the disturb of the mixing flow from a high embankment road. These results indicate that the numerical simulation can provide useful information to minimize the disasters, such as traffic accidents and various microclimatic environments in the transportation projects.

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.913-923
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• 2005

The dynamic mixed model (DMM) combined with a box filter of Zang et. al. (1993) has been generalized for passive scalar transport and applied to large eddy simulation of turbulent channel flows with Prandtl number up to 10. Results from a priori test showed that DMM is capable of predicting both subgrid-scale (SGS) scalar flux and dissipation rather accurately for the Prandtl numbers considered. This would suggest that the favorable feature of DMM, originally developed for the velocity field, works equally well for scalar transport problem. The validity of the DMM has also been tested a posteriori. The results of the large eddy simulation showed that DMM is superior to the dynamic Smagorinsky model in the prediction of scalar field and the model performance of DMM depends to a lesser degree on the ratio of test to grid filter widths, unlike in the a priori test.

• Journal of IKEEE
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• v.5 no.2 s.9
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• pp.121-127
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• 2001

Actual system apparatuses are necessary in order to verify the efficiency and stability of photovoltaic(PV) generation systems considering the size of solar panel, the sort of converter type, and the load conditions and so on. Moreover, it is hardly possible to compare a certain MPPT control scheme with others under the exactly same weather and load conditions as well. For the purpose of solving above mentioned difficulties in a laboratory basis, a transient simulation of PV generation system using real field weather conditions is indispensable. A straightforward simulation scheme with cost effective hardware structures under real weather conditions is proposed in this paper using EMTDC type of transient analysis simulators. Firstly, a solar cell has been modeled with VI characteristic equations, and then the real field data of weather conditions are interfaced to the EMTDC through Fortran program interface method. As a result, the stability and the efficiency analysis of PV generation systems according to various hardware structures and MPPT controls are easily possible under the exactly same weather conditions.