• Journal of Environmental Science International
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• v.20 no.8
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• pp.963-975
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• 2011

For this research, they were monitored $CO_2$ flux and environmental factors ($CO_2$ concentration, soil temperature, soil moisture, soil organic carbon, soil pH, soil Eh) in foreshore, paddy field and woods sites at the winter season (January 2009) and the summer season (September 2009). Seasonal and spatial variations for monitored data were analyzed, and linear regression functions of $CO_2$ flux as environmental factors were estimated. $CO_2$ fluxes averaged between surface and atmosphere monitored in foreshore and paddy field at the winter season were shown $-8\;mgCO_2m^{-2}hr^{-1}$ and $-25\;mgCO_2m^{-2}hr^{-1}$, respectively. $CO_2$ fluxes averaged between surface and atmosphere monitored in foreshore and paddy field at the summer season were shown $47\;mgCO_2m^{-2}hr^{-1}$ and $117\;mgCO_2m^{-2}hr^{-1}$, respectively. Thus, $CO_2$ was sunk from atmosphere to surface at the winter season and it was emitted from surface to atmosphere at the summer season. $CO_2$ fluxes in woods site were emitted $145\;mgCO_2m^{-2}hr^{-1}$ at the winter season and $279\;mgCO_2m^{-2}hr^{-1}$ at the summer season.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.104.1-104.1
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• 2011

We present a catalog of infrared supernova remnants (SNRs) in the Large Magellanic Cloud (LMC). We have searched the Spitzer archival data for infrared counterparts to all 45 known SNRs in the LMC, and identified 21 which is 47% of the known SNRs. Seven of them are newly detected: SNR 0450-70.9, SNR in N4, N103B, DEM L241, DEM L249, DEM L316A, and DEM L316B. All newly discovered SNRs show emission at several IRAC 3.4, 4.5, 5.8, and 8.0 micron bands and/or MIPS 24 and 70 micron bands. Most SNRs show shell structures. We derive infrared fluxes of these newly detected SNRs. The catalog contains general information of each SNR such as location, age, and SN type together with AKARI and/or Spitzer fluxes. For the entire SNR sample, we examine their infrared colors and the possible correlation of the infrared fluxes with the fluxes at other wavelengths. For the newly detected SNRs except the SNR in N4, we also performed follow-up imaging observations of [Fe II] 1.644 micron line using IRIS2 mounted on the Anglo Australian Telescope. Three out of six SNRs show [Fe II] emission corresponding to their infrared shells. [Fe II] knots are also detected in N103B which show good spatial correlation to infrared emission seen at Spitzer images as well as knotty $H{\alpha}$ emission. We investigate the characteristics and origin of the infrared emission in individual SNRs, and discuss the environmental and evolutionary effects.

• Korean Journal of Materials Research
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• v.13 no.4
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• pp.239-245
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• 2003

In order to explore the possibility to extract precious metals from PCB(Printed Circuit Board) scrap by gravity separation, a high temperature melting process was adopted, from the recycling view point, to investigate the influence of viscosity on A1$_2$$O_3$-CaO$-SiO_2$ slag system composed of PCB scrap. For optimizing the pre-treatment process of PCB scrap, an experimental condition for the complete calcination and oxidation of organic materials in PCB scrap was established and a quantitative analysis of oxidized PCB scrap was also carrie out. It was found that 6 hours were enough for the complete oxidation of PCB scrap at 1273 K in an atmosphere condition. A slag, l5wt%$A1_2$$O_3$-45wt%CaO-40wt%SiO$_2$, was chosen as a basic slag composition which is determined based on the quantitative analysis of PCB scrap. Viscosities were measured in slag systems both made from pure fluxes and from PCB scrap with additional fluxes. Slag viscosities composed of pure fluxes were measured to be 5.29 poise and 30.52 poise at temperatures of 1773 and 1573 K, whereas that of PCB scrap with additional fluxes were 3.37 poise and 69.89 poise, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.8
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• pp.612-620
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• 2008

New alternative refrigerants have been developed due to the ozone layer depletion and global warming. For this reason, carbon dioxide is believed to be a promising refrigerant for use in air conditioners and heat pumps. Evaporative heat transfer characteristics and pressure drop of $CO_2$ with outer diameter of 5 mm in inclined ($45^{\circ}$) smooth and micro-fin tubes have been investigated by the experiments with respect to several test conditions such as mass fluxes, heat fluxes, evaporation temperatures in this study. The inclined ($45^{\circ}$) smooth and micro-fin tubes with length of 1.44 m were installed to measure the evaporative heat transfer coefficients of $CO_2$ and heat was supplied to the refrigerant by direct heating method where the test tube was uniformly heated by electricity. The tests were conducted at mass fluxes from 212 to $656\;kg/m^2s$, heat fluxes from 15 to $60\;kW/m^2$ and evaporation temperatures from -10 to $20^{\circ}C$. The heat transfer coefficients of $CO_2$ are slightly increased with increasing mass flux, and the heat transfer characteristics in the inclined ($45^{\circ}$) tubes are enhanced about $5{\sim}10%$ compared with those in horizontal or vertical tubes.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1291-1302
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• 2016

This paper presents a new and efficient scheme to determine the optimal neutron source position in a model near-equilibrium pressurized water reactor, which is based on the OPR1000 Hanul Unit 3 Cycle 7 configuration. The proposed scheme particularly assigns importance of source positions according to the local adjoint flux distribution. In this research, detailed pin-by-pin reactor adjoint fluxes are determined by using the Monte Carlo KENO-VI code from solutions of the reactor homogeneous critical adjoint transport equations. The adjoint fluxes at each allowable source position are subsequently ranked to yield four candidate positions with the four highest adjoint fluxes. The study next simulates ex-core detector responses using the Monte Carlo MAVRIC code by assuming a neutron source is installed in one of the four candidate positions. The calculation is repeated for all positions. These detector responses are later converted into an inverse count rate ratio curve for each candidate source position. The study confirms that the optimal source position is the one with very high adjoint fluxes and detector responses, which is interestingly the original source position in the OPR1000 core, as it yields an inverse count rate ratio curve closest to the traditional 1/M line. The current work also clearly demonstrates that the proposed adjoint flux-based approach can be used to efficiently determine the optimal geometry for a neutron source and a detector in a modern pressurized water reactor core.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.11
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• pp.613-625
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• 2017

For two agricultural reservoirs that are rented for fishing spots, benthic nutrient fluxes experiment were performed two times with two sediments from fishing-effective zone and one sediment from fishing-ineffective zone using laboratory core incubation in oxic and anoxic conditions. During benthic nutrient fluxes experiment, the changes in DO, EC, pH, and ORP in the supernatant were not significantly different between fishing-effective zone and fishing-ineffective zone, and were similar to the sediment-hypolimnetic diffused boundary layer in agricultural reservoir. Except for $NO_3{^-}-N$, more benthic nutrient fluxes of $NH_4{^+}-N$, T-P, and $PO{_4}^{3-}-P$ from sediment to hypolimnetic was measured in anoxic than in oxic conditions (p<0.05). As the DO concentration in hypolimnetic decreases, the microorganism-mediated ammonification is promoted, the nitrification is suppressed, and finally the $NH_4{^+}-N$ diffuses out from sediment to hypolimnetic. Also, the diffusion of T-P and $PO{_4}^{3-}-P$ from sediments to hypolimnetic is accelerated through the dissociation of the phosphorus bound to both organic matters and metal hydroxides. The difference in the benthic nutrient diffusive fluxes between fishing-effective zone and fishing-ineffective zone was not statistically significant (p>0.05). Therefore, it was found that fishing activities did not increase the benthic nutrient diffusive fluxes to a statistically significant level. Due to the short fishing activities of 10 years and the rate-limited diffusion of the laboratory core incubation, the contribution of fishing activities on sediment pollution is estimated to be low. No significant correlation was found between the total amount of nutrients in sediment and the benthic nutrient diffusive fluxes in both aerobic and anaerobic conditions. Therefore, nutrients input from various nonpoint sources of watersheds are considered to be a more dominant factor rather than fishing activities in water quality deterioration, and both aeration and water circulation in hypolimnetic were required to suppress the anoxic environment in agricultural reservoirs.

• 한국해양학회지
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• v.30 no.2
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• pp.91-115
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• 1995

Air-sea heat fluxes in the East Sea were estimated from the various ship's data observed from 1961 to 1990 and the JMA buoy #6 data from 1976 to 1985. The oceanic heat transport in the sea was also determined from the fluxes above and the heat storage rate of the upper layer of 200m from the sea surface. In winter, The incoming solar radiation is almost balanced with the outgoing longwave radiation. but the sea loses her heat through the sea surface mainly due to the latent and sensible heat fluxes. The spatial variation of the net surface heat flux is about 100 Wm/SUP -2/, and the maximum loss of heat is occurred near the Tsugaru Strait. There are also lots of heat losses in the southern part of the East Sea, Korea Strait and Ulleung Basin. Particularly, the heat strong loss in the south-western part of the sea might be concerned with the formation of her Intermediate Homogeneous Water. In summer, the sea is heated up to about 120∼140 Wm/SUP -2/ sue to strong incoming solar radiation and weak turbulent heat fluxes and her spatial variation is only about 20 Wm/SUP -2/. The oceanic heat flux is positive in the southeasten part f the sea and the magnitude of the flux is larger than that of the net surface heat flux. This shows the importance of the area. In the southwestern part of the sea, however, the oceanic heat flux is negative. This fact implies cold water inflow, the North Korean Cold Water. The sigh of net surface heat flux is changed from negative to positive in March and from positive to negative in September. The heat content in the upper surface 200 m from the sea surface reaches its minimum in March and maximum in October. The annual variation of the net surface heat flux is 580 Wm/SUP -2/ in southwestern part of the sea. The annual mean values of net surface heat fluxes are negative, which mean the net heat transfer from the sea to the atmosphere. The magnitude of the flux is about 130 Wm/SUP -2/ near the Tsugaru Strait. The net surface fluxes in the Korea Strait and the Ulleung Basin are relatively larger than those of the rest areas. The spatial mean values of surface heat fluxes from 35$^{\circ}C$ to 39$^{\circ}$N are 129, -90, -58, and -32 Wm/SUP -2/ for the incoming solar radiation, latent hear flux, outgoing longwave radiation, and sensible heat flux, respectively.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.181-182
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• 2012

Using the AKARI mid-infrared all-sky survey catalogue, we are searching for debris disks which are important objects as an observational clue to on-going planetary system formation. Debris disk candidates are selected through a significant excess of the measured flux over the predicted flux for the stellar photospheric emission at $18{\mu}m$. The fluxes were originally estimated based on the near-infrared spectral energy distributions (SEDs) of central stars constructed from the 2MASS J-, H-, and Ks-band fluxes. However, we found that in many cases the 2MASS photometry has large errors due to saturation in the central part of a star image. Therefore we performed follow-up observations with the IRSF 1.4m near-infrared telescope in South Africa to obtain accurate fluxes in the J-, H-, and Ks-bands. As a result, we have succeeded in improving the SEDs of the central stars. This improvement of the SEDs allows us to make more reliable selection of the candidates.

• Asian Journal of Atmospheric Environment
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• v.10 no.1
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• pp.42-50
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• 2016

This study presents a performance evaluation of four different land surface models (LSM) available in Weather Forecast Research (WRF). The research site was located in Haean Basin in South Korea. The basin is very unique by its geomorphology and topography. For a better representation of the complex terrain in the mesoscale model were used a high resolution topography data with a spatial resolution of 30 meters. Additionally, land-use layer was corrected by ground mapping data-sets. The observation equipments used in the study were an ultrasonic anemometer with a gas analyzer, an automatic weather station and a tethered balloon sonde. The model simulation covers a four-day period during autumn. The result shows significant impact of LSM on meteorological simulation. The best agreement between observation and simulation was found in the case of WRF with Noah LSM (WRF-Noah). The WRF with Rapid Update Cycle LSM (WRF-RUC) has a very good agreement with temperature profiles due to successfully predicted fog which appeared during measurements and affected the radiation budget at the basin floor. The WRF with Pleim and Xiu LSM (WRF-PX) and WRF with Thermal Diffusion LSM (WRF-TD) performed insufficiently for simulation of heat fluxes. Both overestimated the sensible and underestimated the latent heat fluxes during the daytime.

• Ocean Science Journal
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• v.42 no.4
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• pp.241-246
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• 2007

Northern Arabian Sea (NAS) between $17^{\circ}N-20.5^{\circ}N$ and $59^{\circ}E-69^{\circ}E$ was observed by using Argo float daily data fur about 9 months, from April 2002 through December 2002. Results showed that during April - May mixed layer shoaled due to light winds, clear sky and intense solar insolation. Sea surface temperature (SST) rose by $2.3^{\circ}C$ and ocean gained an average of 99.8 $Wm^{-2}$. Mixed layer reached maximum depth of about 71 m during June - September owing to strong winds and cloudy skies. Ocean gained abnormally low $\sim18Wm^{-2}$ and SST dropped by $3.4^{\circ}C$. During the inter monsoon period, October, mixed layer shoaled and maintained a depth of 20 to 30 m. November - December was accompanied by moderate winds, dropping of SST by $1.5^{\circ}C$ and ocean lost an average of 52.5 $Wm^{-2}$. Mixed layer deepened gradually reaching a maximum of 62 m in December. Analysis of surface fluxes and winds suggested that winds and fluxes are the dominating factors causing deepening of mixed layer during summer and winter monsoon periods respectively. Relatively big]h correlation between MLD, net heat flux and wind speed revealed that short term variability of MLD coincided well with short term variability of surface forcing.