• Fire Science and Engineering
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• v.16 no.2
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• pp.8-13
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• 2002

Induction heating is widely used in today's industry, in operations such as metal hardening, pre-heating for forging operations, melting or cooking. In this paper, the magneto-thermal analysis of an induction heating jar(IH-JAR) was presented as an efficient design. The magnetic field intensity inside the axisymmetric shaped cooker was analyzed using three-dimensional axisymmetric finite element method(FLUX2D) and the effectual heat source was obtained by ohmic losses from eddy currents induced in the jar. The heat was calculated using the heat source and heating equation. Also, it was presented the temperature characteristics of the IH-JAR according to time and relative permeability in stainless parts and in aluminum parts.

• Journal of Aerospace System Engineering
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• v.9 no.2
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• pp.57-62
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• 2015

The satellite orbit is continuously changing due to space environment. Especially for low earth orbit, atmospheric drag plays an important role in the orbit altitude decay. Recently, solar activities are expected to be high, and relevant events are occurring frequently. In this paper, analysis on the impact of geomagnetic storm on LEO satellite orbit is presented. For this, real flight data of KOMPSAT-2, KOMPSAT-3, and KOMPSAT-5 are analyzed by using the daily decay rate of mean altitude is calculated from the orbit determination. In addition, the relationship between the solar flux and geomagnetic index, which are the metrics for solar activities, is statistically analyzed with respect to the altitude decay. The accuracy of orbit prediction with both the fixed drag coefficient and estimated one is examined with the precise orbit data as a reference. The main results shows that the improved accuracy can be achieved in case of using estimated drag coefficient.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.77-82
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• 2006

Evaluation of the elliptic blending turbulence model (EBM) together with the two-layer model, shear stress transport (SST) model and elliptic relaxation model (V2-F) is performed for a better prediction of natural convection and thermal stratification. For a natural convection problem the models are applied to the prediction of a natural convection in a rectangular cavity and the computed results are compared with the experimental data. It is shown that the elliptic blending model predicts as good as or better than the existing second moment differential stress and flux model for the mean velocity and turbulent quantities. For thermal stratification problem the models are applied to the thermal stratification in the upper plenum of liquid metal reactor. In this analysis there exist much differences between the turbulence models in predicting the temporal variation of temperature. The V2-F model and EBM better predict the steep gradient of temperature at the interface of thermal stratification, and the V2-F model and EBM predict properly the oscillation of temperature. The two-layer model and SST model fail to predict the temporal oscillation of temperature.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.35-46
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• 1988

The prediction of clad surface temperatures is important to the design and the safety anlaysis of nuclear reactor. The accurate prediction requires the detailed knowledge of the flow structure and heat transfer, which is complicate due to anisotropic turbulent phenomena. A two-equation model including anisotropic eddy viscosity model is applied to forecast the velocity distribution. And the temperature field is calculated with uniform wall heat flux. The Galerkin's weighted residual finite element method has been used to calculate the turbulent quantities right up to the wall. The numerical results show good agreement with available data and that turbulence anisotropy strongly affects on the mean flow and thus the temperature field. And Nu-P/D correlation is established for sodium coolant in close-packed equilateral triangular bundle in the P/D range of 1.05 to 1.30.

• Atmosphere
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• v.24 no.4
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• pp.471-479
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• 2014

A road surface temperature prediction model (UM-Road) using input data of the Unified Model (UM) output and road physical properties is developed and verified with the use of the observed data at road weather information system. The UM outputs of air temperature, relative humidity, wind speed, downward shortwave radiation, net longwave radiation, precipitation and the road properties such as slope angles, albedo, thermal conductivity, heat capacity at maximum 7 depth are used. The net radiation is computed by a surface radiation energy balance, the ground heat flux at surface is estimated by a surface energy balance based on the Monin-Obukhov similarity, the ground heat transfer process is applied to predict the road surface temperature. If the observed road surface temperature exists, the simulated road surface temperature is corrected by mean bias during the last 24 hours. The developed UM-Road is verified using the observed data at road side for the period from 21 to 31 March 2013. It is found that the UM-Road simulates the diurnal trend and peak values of road surface temperature very well and the 50% (90%) of temperature difference lies within ${\pm}1.5^{\circ}C$ (${\pm}2.5^{\circ}C$) except for precipitation case.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.3
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• pp.104-112
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• 1997

Line heating process has been used in forming hull surfaces long before and it has depended on skillful workers. As the reduction of production cost is major concern of shipbuilding companies, line heating work must be improved for higher productivity. In this paper, as the first step to automatic hull forming, a method is proposed to predict deformations due to line heating. It includes a simplified thermal elasto-plastic analysis to increase computing efficiency and to do real time visualization of deformed shapes. For the prediction of deformation, a method to estimate heat flux of the torch is also introduced. Predicted deformations for line heated plates show good agreement with experimental results. The proposed method can be used in control and simulation of line heating process with ease.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.93-103
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• 1998

The nucleate boiling heat transfer experiments are performed using a ternary refrigerant R407C which is a candidate of alternatives of HCFC 22. The boiling phenomena of R-32, R-125 and R-134a which are the constituent refrigerants of R407C are also investigated. The nucleate boiling heat transfer coefficients of R407C are less than those of HCFC 22 which have the similar physical and transport properties. In our experimental pressure range, which is similar to the operational pressure of air conditioning system, the deterioration of boiling heat transfer coefficients of mixture refrigerant R407C does not appear for moderate wall superheat region. Since nucleate boiling heat transfer coefficients cannot be obtained from ideal mixing law of mixture, Thome's method was used to predict. To account for the heat flux effect and system pressure in Thome's method, the correcting factor, a(P.L1T), was introduced and obtained from experiments for ternary refrigerant R407C.

• Journal of Integrative Natural Science
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• v.2 no.2
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• pp.101-130
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• 2009

In recent years, South Korea has often witnessed damages by gusts caused by thunderstorms in summer. The Korea Meteorological Administration defines that a gust happens when the maximum instantaneous wind velocity is 10m/s or more and draws up hourly observation reports. When a cumulonimbus develops due to an ascending current and reaches the height of 12~16 km, the temperature of the cloud top drops and a lightening happens, which causes a gust accompanied by a thunderstorm and further regional meteorological damage. It's difficult to predict a regional gust with the mesoscale prediction model at the administration. Thus this study set out to analyze the damage cases by a gust accompanied by a thunderstorm and to make a contribution to the prediction and understanding of a gust by a thunderstorm. A gust by a thunderstorm happens where potential equivalent temperature converges or is higher than the surrounding areas. The convergence area of potential equivalent temperature matches the track of thunderstorm cells. The Kimje gust took place where high potential equivalent temperature converged, and the Jangsu gust did as the area of high potential equivalent temperature approached. There should be a good amount of vapor supply with the moisture flux converging at the bottom layer in order to bring instability. In addition, it should collide into a dry and cold atmosphere at 700 hPa. The moving track at the center of the low dew point spread corresponds to that of a gust.

• Journal of Environmental Impact Assessment
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• v.21 no.1
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• pp.105-117
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• 2012

Future climate according to land-use change was simulated by regional climate model. The goal of study was to predict the distribution of meteorological elements using the Weather Research & Forecasting Model (WRF). The KME (Korea Ministry of Environment) medium-category land-use classification was used as dominant vegetation types. Meteorological modeling requires higher and more sophisticated land-use and initialization data. The WRF model simulations with HyTAG land-use indicated certain change in potential vegetation distribution in the future (2086-2088). Compared to the past (1986-1988) distribution, coniferous forest area was decreased in metropolitan and areas with complex terrain. The research shows a possibility to simulate regional climate with high resolution. As a result, the future climate was predicted to $4.5^{\circ}$ which was $0.5^{\circ}$ higher than prediction by Meteorological Administration. To improve future prediction of regional area, regional climate model with HyTAG as well as high resolution initial values such as urban growth and CO2 flux simulation would be desirable.

• Atmosphere
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• v.32 no.1
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• pp.17-25
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• 2022

As climate change due to global warming continues to be accelerated, various extreme events become more intense, more likely to occur and longer-lasting on a much larger scale. Recent studies show that global warming acts as the primary driver of extreme events and that heat-related extreme events should be attributed to anthropogenic global warming. Among them, both terrestrial and marine heat waves are great concerns for human beings as well as ecosystems. Taking place around the world, one of those events appeared over East Sea in July 2021 with record-breaking high temperature. Meanwhile, climate condition around East Sea was favorable for anomalous warming with less total cloud cover, more incoming solar radiation, and shorter period of Changma rainfall. According to the results of wave activity flux analysis, highly activated meridional mode of teleconnection that links western North Pacific to East Asia caused localized warming over East Sea to become stronger.