• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.2 s.245
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• pp.101-109
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• 2006

The narrow band-averaged transmissivity of $CO_2-H_2O$ mixtures is expressed by multiplying the transmissivities of $CO_2\;and\;H_2O$. Applying the multiplication property of narrow band transmissivities for gas mixtures of $CO_2-H_2O$ of the narrow band based WSGGM (weighted sum of gray gases model), the number of gray gases, required for accurate representation of the absorption characteristics by using the narrow band based WSGGM, is significantly increased. To reduce the computational loads by reducing the number of gray gases, we propose a gray gas regrouping process where the gray gases used for .the WSGGM are regrouped into a specified number of groups according to the magnitudes of absorption coefficients. To evaluate the proposed WSGGM for gas mixtures, the radiative transfer problems through 3-dimensional gas media are considered. The radiative source terms and the radiative heat fluxes obtained by using the proposed method are fairly well compared to previous results obtained by using the SNB model and other models. The regrouping technique results in an excellent computational efficiency with minor loss of accuracy.

• Nuclear Engineering and Technology
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• v.40 no.2
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• pp.155-162
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• 2008

Heat transfer experiments in an annulus passage were performed using SPHINX(Supercritical Pressure Heat Transfer Investigation for NeXt Generation), which was constructed at KAERI(Korea Atomic Energy Research Institute), to investigate the heat transfer behaviors of supercritical $CO_{2}$. $CO_{2}$ was selected as the working fluid to utilize its low critical pressure and temperature when compared with water. The mass flux was in the range of 400 to 1200 $kg/m^{2}s$ and the heat flux was chosen at rates up to 150 $kW/m^{2}$. The selected pressures were 7.75 and 8.12 MPa. At lower mass fluxes, heat transfer deterioration occurs if the heat flux increases beyond a certain value. Comparison with the tube test results showed that the degree of heat transfer deterioration in the heat flux was smaller than that in the tube. In addition, the Nusselt number correlation for a normal heat transfer mode is presented.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.6
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• pp.506-513
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• 2004

Spirulina produces $\gamma$-linolenic acid (GLA), an important pharmaceutical substance, in a relatively low level compared with fungi and plants, prompting more research to improve its GLA yield. In this study, metabolic flux analysis was applied to determine the cellular metabolic flux distributions in the GLA synthetic pathways of two Spiru/ina strains, wild type BP and a high­GLA producing mutant Z19/2. Simplified pathways involving the GLA synthesis of S. platensis formulated comprise of photosynthesis, gluconeogenesis, the pentose phosphate pathway, the anaplerotic pathway, the tricarboxylic cycle, the GLA synthesis pathway, and the biomass syn­thesis pathway. A stoichiometric model reflecting these pathways contains 17 intermediates and 22 reactions. Three fluxes - the bicarbonate (C-source) uptake rate, the specific growth rate, and the GLA synthesis rate - were measured and the remaining fluxes were calculated using lin­ear optimization. The calculation showed that the flux through the reaction converting acetyl­CoA into malonyl-CoA in the mutant strain was nearly three times higher than that in the wild­type strain. This finding implies that this reaction is rate controlling. This suggestion was sup­ported by experiments, in which the stimulating factors for this reaction $(NADPH\;and\;MgCl_{2})$ were added into the culture medium, resulting in an increased GLA-synthesis rate in the wild type strain.

• Journal of The Korean Astronomical Society
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• v.27 no.1
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• pp.81-102
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• 1994

We have decomposed the 11-cm radio continuum emission of the W51 complex into thermal and non-thermal components. The distribution of the thermal emission has been determined by analyzing HI, CO, and IRAS $60-{\mu}m$ data. We have found a good correlation between the 11-cm thermal continuum and the 60- 11m emissions, which is used to obtain the thermal and non-thermal 11-cm continuum maps of the W51 complex. Most of the thermal continuum is emanating from the compact H II regions and their low-density ionized envelopes in W51A and W51B. All the H II regions, except G49.1-0.4 in W51B, have associated molecular clumps. The thermal radio continuum fluxes of the compact H II regions are proportional to the CO fluxes of molecular clumps. This is consistent with the previous results that the total mass of stars in an H II region is proportional to the mass of the associated molecular clump. According to our result, there are three non-thermal continuum sources in W51: G49.4-0.4 in W51A, a weak source close to G49.2-0.3 in W51B, and the shell source W51C. The non-thermal flux of G49.5-0.4 at 11-cm is $\~28 Jy$, which is $\~25\%$ of its total 11-cm flux. The radio continuum spectrum between 0.15 and 300 GHz also suggests an excess emission over thermal free-free emission. We show that the excess emission can be described as a non-thermal emission with a spectral index ${\alpha}{\simeq}-1.0 (S_v{\propto}V^a)$ attenuated by thermal free-free absorptions at low-frequencies. The non-thermal source close to G49.2-0.3 is weak $(\~9 Jy)$. The nature of the source is not known and the reality of the non-thermal emission needs to be confirmed. The non~thermal shell source W51C has a 11-cm flux of $\~130Jy$ and a spectral index ${\alpha}{\simeq}-0.26$.

• Atmosphere
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• v.23 no.3
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• pp.307-320
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• 2013

We performed comprehensive quality control for eddy-covariance measurements from 3 farmland sites and 1 industrial site adjacent to Nakdong river. The quality control program is based on Foken and Wichura (1996) and Vicker and Mahrt (1997) and we added criteria for trend and standard deviation for scalar variables and modified criteria for non-stationarity condition of Foken and Wichura (1996) to consider random error of fluxes. The classification of data quality is designed for the raw data and the processed flux data, separately. Use of added criteria efficiently reduces the number of outlier for water vapor and $CO_2$ fluxes and use of modified criteria for non-stationarity reduces the number of outlier for scalar fluxes and increases the number of data with accepted quality for further work. Energy balance ratio is higher in farmlands than industrial site, which is due to neglect of heat storage term in industrial site. Among farmland sites, C4 site shows higher energy balance ratio than other sites. This is due to more homogeneous surface of C4 site than other farmland sites. However, energy balance ratio is very low or even negative at night. Mismatch between the flux footprint and the other energy component footprint over the heterogeneous surface is main cause for energy imbalance at night. Other possible causes are also discussed.

• Bulletin of the Korean Chemical Society
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• v.26 no.8
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• pp.1260-1264
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• 2005

Three new quaternary tantalum thiophosphates, $K_{0.18}TaPS_6,\;K_{0.28}TaPS_6,\;and\;Rb_{0.09}TaPS_6$ have been synthesized by using reactive alkali metal halide fluxes and structurally characterized by single crystal X-ray diffraction techniques. The crystal structures of $K_{0.18}TaPS_6,\;K_{0.28}TaPS_6,\;and\;Rb_{0.09}TaPS_6$ contain 3-dimensional open framework anions, $[TaPS_6]^{x-}$(x = 0.09, 0.18, 0.28) with the empty channel which disordered alkali metal cations, $K^+\;and\;Rb^+$ are located in. Crystal data: $K_{0.18}TaPS_6$, tetragonal, space group$I4_1$/acd (no. 142), a=15.874(3) $\AA$, c=13.146(4) $\AA$, V=3312.7(12) ${\AA}^3$, K, Z=16, R1=0.0545. Crystal data: $K_{0.28}TaPS_6$, tetragonal, space group $I4_1$/acd (no. 142), a=15.880(2) $\AA$, c=13.134(3) $\AA$, V=3312.1(10) ${\AA}^3$, Z=16, R1=0.0562. Crystal data: $Rb_{0.09}TaPS_6$, tetragonal, space group I41/acd (no. 142), a=15.893(3) $\AA$, c=13.163(4) $\AA$, V=3324.7(15) ${\AA}^3$, Z=16, R1=0.0432.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.284-289
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• 2003

The narrow band-averaged transmissivity of $CO_2-H_2O$ mixtures is expressed by multiplying the transmissivities of $CO_2$ and $H_2O$. Applying the multiplication property of narrow band transmissivities for gas mixtures of $CO_2-H_2O$, the number of gray gases, required for accurate representation of the absorption characteristics by using the narrow band based WSGGM, is significantly increased. To reduce the computational loads by reducing the number of gray gases, we propose a gray gas regrouping process where the gray gases used for the WSGGM are regrouped into a specified number of groups according to the magnitudes of absorption coefficients. To evaluate the proposed WSGGM for gas mixtures, the radiative transfer problems through three-dimensional gas media are considered. The radiative source terms and the radiative heat fluxes obtained by using the proposed method are fairly well compared to those obtained by using the SNB model. The regrouping technique results in an excellent computational efficiency with minor loss of accuracy.

• Journal of Korean Society on Water Environment
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• v.29 no.5
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• pp.610-617
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• 2013

Investigating the budgets of alkalinity and dissolved inorganic carbon (DIC) in lake water systems is significant for the examination of the behavior of a lake as a sink or a source with respect to the circulation of inorganic carbon chemistry. Budgets of total alkalinity ($Alk_T$) and DIC in Onondaga Lake, which was polluted by chronic calcium (Ca) loading in spite of the closure of soda ash ($Na_2CO_3$) facility, were determined by the analyses of inorganic carbon chemistry in tributary stream channels linked to the lake. AlkT and DIC fluxes of Onondaga Creek and Ninemile Creek occupied 65% and 54%, respectively, as larger tributary streams in comparison with other tributaries as well as different input sources. Budget calculations indicate that 18% of AlkT and 11% of DIC inputs to Onondaga Lake, respectively, remained immobilized in the Lake. This suggests that Ca chronically leached had been precipitated with inorganic carbon or remineralized by secondary mineral formation during the experimental period. In this study, the assumed mass balance calculation in Onondaga Lake with tributary streams resulted in exhibiting that the lake played a role of the sink for the inorganic carbon cycle.

• The Korean Journal of Ecology
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• v.28 no.2
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• pp.105-112
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• 2005

Environmental factors such as light and low $CO_2$ concentrations trigger events which may result in stomatal opening. Stomatal aperature is largely controlled by the solute contents of guard cells, but not exclusively, by through changes in their content of potassium salts, with $K^+$ balanced either by $Cl^-$ or malate, depending on the species and conditions. However, how these signals are sensed and how they are transduced into driving the ion fluxes that control stomatal movements is not still fully understood. The basic role of stomata is regulating transpiration and photosynthesis. Photosynthesis plays a central role in the physiology of plants and an understanding of its response to light is, therefore, critical to any discussion of how plants sense and respond to light. It had been proposed that the evidences pointed three possible mechanisms for the light response. Firstly, there is a direct response of stomata to light. Secondly. there is an indirect response of stomata to light through the effect of $CO_2$. Lastly, there are some evidences for a third effect of light on stomata. However, attempts to investigate how these three possible mechanisms explained in detail in response to light have not been made. Therefore, this study is examined the differences among these three possible mechanisms.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.707-714
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• 2007

The heat transfer coefficient and Pressure drop during gas cooling process of $CO_2$ (R-744) in inclined helical coil copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver. a variable-speed pump. a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45mm inner diameter. The refrigerant mass fluxes were varied from 200 to $600[kg/m^2s]$ and the inlet Pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in the inclined helical coil tubes increases with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively good agreement with those Predicted by Ito's correlation developed for single-phase in a helical coil tube. The local heat transfer coefficient of $CO_2$ agrees well with the correlation by Pitla et al. However, at the region near pseudo-critical temperature. the experiments indicate higher values than the Pitla et al. correlation. Therefore. various experiments in the inclined helical coil tubes have to be conducted and it is necessary to develop the reliable and accurate prediction determining the heat transfer and pressure drop of $CO_2$ in the inclined helical coil tubes.