• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.37.2-37.2
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• 2009

In this study, we present a new empirical forecasting method of solar proton events based on flare parameters. For this we used NOAA solar energetic particle (SEP) events from 1976 to 2006 and their associated X-ray flare data. As a result, we found that about only 3.5% (1.9% for M-class and 21.3% for X-class) of the flares are associated with the proton events. It is also found that this fraction strongly depends on longitude; for example, the fraction for $30W^{\circ}$ < L < $90W^{\circ}$ is about three times larger than that for $30^{\circ}E$ < L < $90^{\circ}E$. The occurrence probability of solar proton events for flares with long duration (> 0.3 hours) is about 2 (X-class flare) to 7 (M-class flare) times larger than that for flares with short duration (< 0.3 hours). The relationship between X-ray flare peak flux and proton peak flux as well as its correlation coefficient are strongly dependent on longitude. Using these results for prediction of proton flux, we divided the data into 6 subgroups depending on two parameters: (1) 3 longitude ranges (east, center, and west) and (2) flare impulsive times (long and short). For each subgroup, we make a linear regression between the X-ray flare peak flux and the corresponding proton peak flux. The result shows that the proton flux in the eastern region is much better correlated with the X-ray flux than that in the western region.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.930-932
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• 2001

This paper is proposed the modeling and computational methods for estimating the steady and dynamic characteristics of a transverse flux type SRM. Prediction of the steady and dynamic characteristics state of a switched reluctance motor (SRM) drive can be quite involved because of complex interdependent influences between motor parameters and excitation. To obtain characteristics parameters of the transverse flux type SRM which is considered the magnetic non-linearity phenomena, the magnetic equivalent parameters of SRM are computed by the finite element method as functions of the input current and angular displacement. Dynamic characteristics of the designed transverse flux type SRM is simulated and estimated by Matlab/simlunk.

• Journal of computational fluids engineering
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• v.7 no.4
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• pp.8-18
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• 2002

The primary objective of the present study is evaluation of the k-ε-vv-f turbulence model for prediction of natural convection in a rectangular cavity. As a comparative study, the two-layer k-ε model is also considered. Both models, with and without algebraic heat flux model, are applied to the analysis of natural convection in a rectangular cavity. The performances of turbulence models are investigated through comparison with available experimental data. The predicted results of vertical velocity component, turbulent heat fluxes, turbulent shear stress, local Nusselt number and wall shear stress are compared with experimental data. It is shown that, among the turbulence models considered in the present study, the k-ε-vv-f model with an algebraic heat flux model predicts best the vertical mean velocity and velocity fluctuation, and the inclusion of algebraic heat flux model slightly improves the accuracy of results.

• Journal of computational fluids engineering
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• v.11 no.1 s.32
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• pp.36-42
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• 2006

The existing numerical approximations of convection flux, especially the spatial higher-order difference schemes, in unstructured cell-centered finite volume methods are examined in detail with each other and evaluated with respect to the accuracy through their application to a 2-D benchmark problem. Six higher-order schemes are examined, which include two second-order upwind schemes, two central difference schemes and two hybrid schemes. It is found that the 2nd-order upwind scheme by Mathur and Murthy(1997) and the central difference scheme by Demirdzic and Muzaferija(1995) have more accurate prediction performance than the other higher-order schemes used in unstructured cell-centered finite volume methods.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.376-378
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• 1999

In order to design the current carrying conductor for GIS, it is important to predict temperature-rise when rated current flows. This paper deals with the coupling of Flux2D and analytic method to calculate the heat transfer coefficient. Heat transfer by conduction and convection is considered between the current carrying conductor and $SF_6$ gas. The result shows reasonable temperature distribution.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.1
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• pp.34-40
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• 2012

Flux linkage of phase windings or phase inductance is an important parameter in determining the behavior of a switched reluctance motor (SRM) [1-8]. Therefore, the accurate prediction of inductance at aligned and unaligned rotor positions makes a significant contribution to the design of an SRM and its analytical approach is not straightforward due to nonlinear flux distribution. Although several different approaches using a finite element analysis (FEA) or curve-fitting tool have been employed to compute phase inductance [2-5], they are not suitable for a simple design procedure because the FEA necessitates a large amount of time in both modeling and solving with complexity for every motor design, and the curve-fitting requires the data of flux linkage from either an experimental test or an FEA simulation. In this paper, phase inductance at aligned and unaligned rotor positions is estimated by means of numerical method and magnetic equivalent circuit as well, and the proposed approach is analytically verified in terms of the accuracy of estimated inductance compared to inductance computed by an FEA simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.368-377
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• 2004

A mathematical model was developed for the prediction of the average temperature and RDT(RM Delivery temperature) in a roughing mill. The model consisted of three parts as follows (1) The intermediate numerical model calculated the deformation and heat transfer phenomena in the rolling: region by steady state FEM and the heat transfer phenomena in the interpass region by unsteady state FEM (2) The Off-line prediction model was derived from non-linear regression analysis based on the results of intermediate numerical model considering the various rolling conditions, (3) Using the heat flux in rolling region, temperature profile along thickness direction was calculated. For validation of the presented model, the rolling force per pass and RDT measued in on-line process was compared with those of model and the results showed close agreement with the existing data. In order to demonstrate the effectiveness of the proposed model, the various rolling conditions was tested.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.102-111
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• 2016

In this paper a computation of turbulent natural convection in enclosures with the elliptic-blending based differential and algebraic flux models is presented. The primary emphasis of the study is placed on an investigation of accuracy of the treatment of turbulent heat fluxes with the elliptic-blending second-moment closure for the turbulent natural convection flows. The turbulent heat fluxes in this study are treated by the elliptic-blending based algebraic and differential flux models. The previous turbulence model constants are adjusted to produce accurate solutions. The proposed models are applied to the prediction of turbulent natural convections in a 1:5 rectangular cavity and in a square cavity with conducting top and bottom walls, which are commonly used for validation of the turbulence models. The relative performance between the algebraic and differential flux model is examined through comparing with experimental data. It is shown that both the elliptic-blending based models predict well the mean velocity and temperature, thereby the wall shear stress and Nusselt number. It is also shown that the elliptic-blending based algebraic flux model produces solutions which are as accurate as those by the differential flux model.

• Atmosphere
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• v.29 no.5
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• pp.567-583
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• 2019

In this study, the high-resolution numerical simulations considering detailed anthropogenic heat, albedo, emission and roughness length are analyzed by using single layer Urban Canopy Model (UCM) in Weather Research Forecast (WRF). For this, improved urban parameter data for Seoul Metropolitan Area (SMA) was collected from global data. And then the parameters were applied to WRF-UCM model after it was processed into 2-dimensional topographical data. The 6 experiments were simulated by using the model with each parameter and verified against observation from Automated Weather Station (AWS) and flux tower for the temperature and sensible heat flux. The data for sensible heat flux of flux towers on Jungnang and Bucheon, the temperature of AWS on Jungnang, Gangnam, Bucheon and Neonggok were used as verification data. In the case of summer, the improvement of simulation by using detailed anthropogenic heat was higher than the other experiments in sensible flux simulation. The results of winter case show improved in all simulations using each advanced parameters in temperature and sensible heat flux simulation. Improvement of urban parameters in this study are possible to reflect the heat characteristics of urban area. Especially, detailed application of anthropogenic heat contributed to the enhancement of predicted value for sensible heat flux and temperature.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.590-590
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• 2003