• 한국환경과학회지
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• 제8권2호
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• pp.145-150
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• 1999

To estimate the thermal effect of the vegetation canopy on the surface sublayer environment numerically, we used the combined model of Pielke's1) single layer model for vegetation and Deardorff's2) Force restore method(FRM) for soil layer. Application of present combined model to three surface conditions, ie., unsaturated bare soil, saturated bare soil and saturated vegetation canopy, showed followings; The diurnal temperature range of saturated vegetation canopy is only 20K, while saturated bare soil and unsaturated bare soil surface are 30K, 35K, respectively. The maximum temperature of vegetation canopy occurs at noon, about 2 hours earlier than that of the non-vegetation cases. The peak latent heat fluxes of vegetation canopy is simulated as a 600Wm-2 at 1300 LST. They have higher values during afternoon than beforenoon. Furthermore, the energy redistribution ratios to latent heat fluxes also increased in the late afternoon. Therefore, oasis effect driving from the vegetation canopy is reinforced during late afternoon compared with the non-vegetated conditions.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권2호
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• pp.117-125
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• 2000

A series of simulations were carried out to test the accuracy of a CFD (Computational Fluid Dynamics) model for flow and dispersion problems around buildings. The basic equations involved are Reynolds-averaged Navier-Stokes equations. Two different cases were selected to estimate the accuracy of a CFD model. Case 1 adopted Euler equations, which are obtained by neglecting the viscous fluxes, which can be closed by the $textsc{k}$-$\varepsilon$model for a turbulent close problem. The results of both cases were compared with wind tunnel data. The results for Case 2 were closer to the wind both cases were compared with wind tunnel data. The results for Case 2 were closer to the wind tunnel data than Case 1. Accordingly, this indicates that the inclusion of viscous fluxes in a CFD model is required for the simulation of flow and 야spersion around buildings.

• 천문학회보
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• 제38권2호
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• pp.70.1-70.1
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• 2013

We present long-term optical to NIR data of the tidal disruption object, Swift J1644+57. The data were obtained with CQUEAN, UKIRT WFCAM observations. We analyze the morphology of the host galaxy of this object and decompose the bulge component using high resolution HST WFC3 images. We conclude that the host galaxy is bulge dominant. We also estimate the multi-band fluxes of the host galaxy through the light curves based on the long-term observational data. We fit the SED models to the multi-band fluxes of the host galaxy and determine its stellar mass. Finally, we estimate the mass of the central super massive black hole which is thought to be the main role of the tidal disruption event. The estimated stellar mass and black hole mass are $10^{9.1}M_{\odot}$, $10^{6.8}M_{\odot}$ respectively. We compare our results to other results that have studied before.

• 천문학논총
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• 제32권1호
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• pp.49-53
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• 2017

The point sources in the Bright Source Catalogue of the AKARI Far-Infrared Surveyor (FIS) were classified based on their FIR and mid-IR fluxes and colours into young stellar object (YSO) and extragalactic source types using a Quadratic Discriminant Analysis method (QDA) and Support Vector Machines (SVM). The reliability of the selection of YSO candidates is high, and the number of known YSO candidates were increased significantly, that we demonstrate in the case of the nearby open cluster IC348. Our results show that we can separate galactic and extragalactic AKARI point sources in the multidimensioal space of FIR fluxes and colours with high reliability, however, differentiating among the extragalactic sub-types needs further information.

• 대한기계학회논문집
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• 제17권8호
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• pp.2069-2078
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• 1993

The buoyancy-driven turbulent thermal convection is predicted using an anisotropic hybrid turbulence model, which is incorporated with a low Reynolds k-.epsilon. turbulence model and an anisotropic buoyant part of algebraic stress model(ASM). The numerical predictions are compared with the Davidson's model,(1) the full ASM and the experimental results of Cheesewright et al.(2) All the models are shown to predict good agreements with the experiments for the averaged turbulence quantities. It is found that the effect of an anisotropic part on the Reynolds stress and the turbulent heat fluxes is substantial. In this study, the present hybrid model gives a fairly reasonable prediction in terms of the computational accuracy, convergence and stability. The contribution of an anisotropic buoyant part to turbulent heat fluxes are also scrutinized over the range of Rayleigh numbers $(4.79{\times}10^{10}{\le}Ra{\le}7.46{\times}10^{10}).$

• 한국전산유체공학회지
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• 제10권1호
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• pp.99-106
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• 2005

Performance of first, second and third order accurate methods for calculation of in viscid fluxes in fluid flow governing equations are investigated here. For the purpose, an upwind method based on Roe's scheme is used to solve 2-dimensional Euler equations. To increase the accuracy of the method two different schemes are applied. The first one is a second and third order upwind-based algorithm with the MUSCL extrapolation Van Leer (1979), based on primitive variables. The other one is an upwind-based algorithm with the Chakravarthy extrapolation to the fluxes of mass, momentum and energy. The results show that the thickness of shock layer in the third order accuracy is less than its value in second order. Moreover, applying limiter eliminates the oscillations near the shock while increases the thickness of shock layer especially in MUSCL method using Van Albada limiter.

• Journal of Microbiology and Biotechnology
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• 제16권7호
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• pp.1139-1143
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• 2006

Various techniques and strategies have been developed for the identification of intracellular metabolic conditions, and among them, isotope balance-based flux analysis with gas chromatography/mass spectrometry (GC/ MS) has recently become popular. Even though isotope balance-based flux analysis allows a more accurate estimation of intracellular fluxes, its application has been restricted to relatively small metabolic systems because of the limited number of measurable metabolites. In this paper, a strategy for incorporating isotope balance-based flux data obtained for a small network into metabolic flux analysis was examined as a feasible alternative allowing more accurate quantification of intracellular flux distribution in a large metabolic system. To impose GC/MS based data into a large metabolic network and obtain optimum flux distribution profile, data reconciliation procedure was applied. As a result, metabolic flux values of 308 intracellular reactions could be estimated from 29 GC/ MS based fluxes with higher accuracy.

• 한국대기환경학회지
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• 제23권2호
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• pp.242-249
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• 2007

Deposition fluxes of polycyclic aromatic hydrocarbons (PAHs) were measured at the Chonbuk National University located in Jeonju between June and November 2002. Fluxes of gaseous and particulate PAHs were separately obtained using a water surface sampler (WSS) and a dry deposition plate (DDP). Most of PAHs were deposited in the gaseous form since the low molecular weight PAHs dominates in the atmosphere. The deposition velocity of particulate PAHs was higher than that of gaseous PAHs when the molecular weight was low, but substantially decreased as the fine particle fraction increased with molecular weight. The deposition velocity was generally higher at high wind speeds. However, increase in the deposition velocity in unstable atmospheric conditions was also observed for gaseous PAHs of intermediate molecular weight.

• Interaction and multiscale mechanics
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• 제4권3호
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• pp.207-217
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• 2011

International efforts have focused recently on the development of tungsten surfaces that can intercept energetic ionized and neutral atoms, and heat fluxes in the divertor region of magnetic fusion confinement devices. The combination of transient heating and local swelling due to implanted helium and hydrogen atoms has been experimentally shown to lead to severe surface and sub-surface damage. We present here a computational model to determine the relationship between the thermo-mechanical loading conditions, and the onset of damage and failure of tungsten surfaces. The model is based on thermo-elasticity, coupled with a grain boundary damage mode that includes contact cohesive elements for grain boundary sliding and fracture. This mechanics model is also coupled with a transient heat conduction model for temperature distributions following rapid thermal pulses. Results of the computational model are compared to experiments on tungsten bombarded with energetic helium and deuterium particle fluxes.

• 대한기계학회논문집B
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• 제30권11호
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• pp.1035-1042
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• 2006

An experimental investigation was performed to study two-phase pressure drop of deionized water in a microchannel. Measurement and evaluation of two-phase frictional pressure gradient were carried out using a single horizontal rectangular microchanne1 having a hydraulic diameter of $100{\mu}m$. Tests were performed for mass fluxes of 90, 169, and 267 $kg/m^2$s and heat fluxes of 200-700 $kW/m^2$. Test results showed that the measured two-phase frictional pressure gradient increased with the mass flux and vapor quality. Most macro-channel correlations of two-phase frictional pressure gradient did not provide reliable predictions except under certain limited conditions.