• 천문학회보
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• 제39권2호
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• pp.58.2-58.2
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• 2014

We present the results of the KVN observations of central galaxies in cool-core and non cool-core clusters. The goal is to study how cooling environments affect the AGN activities in the core where their host galaxies are embedded. From the HIghest FLUx Galaxy Cluster Sample (HIFLUGCS), we have selected 19 radio bright AGNs located in the center of clusters with various cooling timescale. In our pilot study, we have obtained 22 and 43 GHz fluxes and morphologies of the sample using the Korean VLBI network. We find that 22/43 GHz fluxes do not strongly depend on the presence of a cool gas flow. However, an intriguing fact is that most AGNs in the cool-core clusters show the hint of a pc-scale jet component while the ones in the non cool-core clusters do not. Based on these results, we discuss the role of cooling flows in the central cluster AGNs and their co-evolution.

• 멤브레인
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• 제21권3호
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• pp.290-298
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• 2011

팔라듐이 코팅된 $V_{53}Ti_{26}Ni_{21}$ 합금 분리막을 통해 수소 투과시 혼합가스의 영향에 대해 알아보았다. 순수 수소, 수소, 이산화탄소 및 일산화탄소의 혼합가스를 공급가스로 주입할 때, $450^{\circ}C$, 1-3 bar의 압력에서 팔라듐이 코팅된 $V_{53}Ti_{26}Ni_{21}$ 합금 분리막의 수소 투과 실험을 수행하였다. 수소만을 공급한 투과 실험에서 팔라듐 코팅된 $V_{53}Ti_{26}Ni_{21}$ 합금 분리막(두께: 0.5 mm)의 수소 투과량은 3 bar, $450^{\circ}C$ 조건에서 $5.36mL/min/cm^2$였다. 또한 수소/이산화탄소, 수소/일산화탄소 및 수소/이산화탄소/일산화탄소를 공급한 투과실험에서 $V_{53}Ti_{26}Ni_{21}$ 합금 분리막의 수소 투과량은 각각 4.46, 5.20, $3.91mL/min/cm^2$였다. 따라서, 수소/이산화탄소, 수소/일산화탄소 및 수소/이산화탄소/일산화탄소 혼합가스를 각각 공급할 때 투과량은 온도와 압력에 상관없이 수소 분압 감소만큼 감소하였고 모든 경우 Sievert 법칙을 잘 만족시켰다. 투과 후 분리막의 XRD 결과로부터 $V_{53}Ti_{26}Ni_{21}$ 합금 분리막은 여러 혼합가스에 대해 안정성과 내구성이 우수하다는 것을 알 수 있었다.

• Ocean and Polar Research
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• 제24권2호
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• pp.123-134
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• 2002

Seasonal variations of settling particles and metal fluxes were monitored at a nearshore site of Marian Cove, King Geroge Island, Antarctica from 28th February 1998 to 22nd January 2000. Near-bottom sediment traps were deployed at 30m water depth of the cove, and sampling bottles were recovered every month by SCUBA divers. Total particulate flux and metal concentrations were determined from the samples. Total particulate flux showed a distinct seasonality, high in austral summer and low in austral winter: the highest flux $(21.97g\;m^{-2}d^{-1})$ was found in February of 1999, and the lowest $(2.47g\;m^{-2}d^{-1})$ in September of 1998, when sea surface was frozen completely. Lithogenic particle flux accounted for 90% of the total flux, and showed a significantly negative correlation with the thickness of snow accumulation around the study site. It was suggested that the most of the lithogenic particles trapped in the bottles was transported by melt water stream from the surrounding land. Fluxes of Al, Fe, Ti, Mn, Zn, Cii, Co, Ni, Cr, Cd, and Pb showed similar seasonal variations with the total flux, and their averaged fluxes were 34000, 9000,960, 180, 13.8, 17.6, 3.0,2.1, 5.4, 0.02, and $1.5nmol\;m^{-2}d^{-1}$ respectively. Among the metals, Cu and Cd showed the most noticeable seasonal patterns. The Cd flux correlated positively with the fluxes of biogenic components while the Cu flux correlated with both the lithogenic and biogenic particle fluxes. The Cu flux peak in the late summer is likely related to a substantial amount of inflow of ice melt water laden with Cu-enriched lithogenic particles. On the other hands, the Cd flux peak in the early spring may be associated with the unusually early occurred phytoplankton bloom.

• 설비공학논문집
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• 제21권1호
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• pp.16-22
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• 2009

In order to investigate $CO_2$ heat transfer coefficient and pressure drop by PAG oil concentration during $CO_2$ evaporation, the experiment on evaporation heat transfer characteristics in a mini-channels were performed. The experimental apparatus consisted of a test section, a DC power supply, a heater, a chiller, a mass flow meter, a pump and a measurement system. Experiment was conducted for various mass fluxes($300{\sim}800kg/m^{2}s$), heat fluxes($10{\sim}40kW/m^2$) saturation temperatures($-5{\sim}5^{\circ}C$), and PAG oil concentration(0, 3, 5wt%). The variation of the heat transfer coefficient was different according to the oil concentration. With the increase of the oil concentration, the evaporation heat transfer coefficient decreased and the delay of dryout by oil addition was found. Pressure drop increased with the increase of the oil concentration and heat flux, and the decrease of saturation temperature.

• 천문학회보
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• 제38권1호
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• pp.51.2-51.2
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• 2013

We present observational results of CO outflows towards 24 embedded young stellar objects (YSOs), which are selected from the targets of the Herschel key program, "Dust, Ice, and Gas in Time" (DIGIT). Molecular outflow activity, which is believed to have strong dependence on accretion process, is the most powerful in the early embedded phase of star formation and declines as the central protostars evolve to the main sequence stage. In order to study the relation between the CO outflows observed in low J transitions and the properties of protostars, we mapped the CO outflows of the selected targets in J=1-0 and J=2-1 with the 14-m TRAO telescope and the 6-m SRAO telescope, respectively. We also compare the CO outflow momentum fluxes with the FIR molecular line luminosities of CO, $H_2O$, OH, and OI, which were detected by the Herschel-PACS observations.

• 대한기계학회논문집B
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• 제38권7호
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• pp.607-618
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• 2014

초임계 $CO_2$의 수직상향유동에서의 난류열전달에 관한 실험적연구가 내경 4.5 mm의 원형관에서 수행되었다. 실험범위는 유체평균온도 $29-115^{\circ}C$, 압력 74.6 - 102.6 bar, 국부 벽면 열유속 $38-234kW/m^2$ 그리고 질량유속 $208-874kg/m^2s$였다. 중간정도의 벽면 열유속 및 낮은 질량유속에서 벽면온도는 확연한 최대점을 나타냈다. 열전달에 대한 부력 및 유동가속의 영향을 살펴보기 위하여 실험 및 참조상관식(Kranoshchekov and Protopopov)에서 획득된 Nusselt 수의 비를 부력 및 유동가속을 나타내는 변수인 $Bo^*$ 및 $q^+$를 이용하여 분석하였다. 이 분석을 통해 유동가속 변수인 $q^+$는 실험에서의 열전달 현상을 적절히 표현할 수 있는 변수라는 것을 확인할 수 있었다. 마지막으로 초임계 유체의 수직상향 유동에서의 새로운 열전달 상관식이 개발되었으며, 이 상관식은 ${\pm}30%$의 오차범위에서 실험데이터를 잘 예측하였다.

• 한국환경과학회지
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• 제26권6호
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• pp.729-739
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• 2017

The Weather Research and Forecasting (WRF) model and Vegetation Photosynthesis and Respiration Model (VPRM) were coupled to simulate atmospheric $CO_2$ concentrations. The performance of the WRF-VPRM to simulate regional scale $CO_2$ concentration was estimated over coastal basin areas. Either Hestia 2011(HST) or Vulcan 2002(VUL) anthropogenic $CO_2$ emission data were used in two numerical experiments for the study regions. Simulated meteorological variables were validated with ground and background $CO_2$ measurement data, and the results show that the model captured temporal variations of $CO_2$ concentration on a daily basis. $CO_2$ directional analysis revealed that the dominant $CO_2$ emission sources are located S and SW. The simulated Net Ecosystem Exchange (NEE) agreed relatively well with measured $CO_2$ fluxes at each vegetation class site, showing approximately 40% at max improvement at shrub areas.

• 한국토양비료학회지
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• 제51권1호
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• pp.71-78
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• 2018

This study was conducted to investigate the application effect of liquid fertilizer using pig cadavers on potato and corn cultivations in upland field. Field experiments were designed with control (Cn), liquid fertilizer (LF), inorganic fertilizer (IF), and LF + IF treatments. Crop yields in potato and corn cultivations were higher in the order of $LF+I{\geq_-}IF{\geq_-}LF$ > Cn treatments. The potato and corn yields in LF + IF treatment were 237% and 29% greater than those in Cn treatment, respectively. Following crops harvest, soil status was improved, showing greater soil chemical properties in the LF treated areas compared to those in the Cn treatment. In addition, total $CO_2$ fluxes in LF + IF treatment during potato and corn cultivations were significantly increased compared with Cn and IF treatments. Therefore, these results suggest that LF application was effective on crop cultivation and improvement of soil fertility.

• 대기
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• 제28권2호
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• pp.113-121
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• 2018

In order to monitor greenhouse gases including $CO_2$, various types of surface-, aircraft-, and satellite-based measurement projects have been conducted. These data help understand the variations of greenhouse gases and are used in atmospheric inverse modeling systems to simulate surface fluxes for greenhouse gases. CarbonTracker is a system for estimating surface $CO_2$ flux, using an atmospheric inverse modeling method, based on only surface observation data. Because of the insufficient surface observation data available for accurate estimation of the surface $CO_2$ flux, additional observations would be required. In this study, a system that assimilates aircraft $CO_2$ measurement data in CarbonTracker (CT2013B) is developed, and the estimated results from this data assimilation system are evaluated. The aircraft $CO_2$ measurement data used are obtained from the Comprehensive Observation Network for Trace gases by the Airliner (CONTRAIL) project. The developed system includes the preprocessor of the raw observation data, the observation operator, and the ensemble Kalman filter (EnKF) data assimilation process. After preprocessing the raw data, the modeled value corresponding spatially and temporally to each observation is calculated using the observation operator. These modeled values and observations are then averaged in space and time, and used in the EnKF data assimilation process. The modeled values are much closer to the observations and show smaller biases and root-mean-square errors, after the assimilation of the aircraft $CO_2$ measurement data. This system could also be used to assimilate other aircraft $CO_2$ measurement data in CarbonTracker.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.152-153
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• 2004

The growth rate of atmospheric $CO_2$ undergoes significant interannual variability, largely due to temporal variability of partitioning of $CO_2$ between terrestrial biosphere and ocean. In the present paper, as a follow-up to the work by Lee et al. [1], we estimated the year-to-year variability in net global air-sea $CO_2$ fluxes between 1982 and 2003 from observed changes in wind speed and estimated changes in ${\Delta}pCO_2$ Changes in $pCO_{25W}$ were inferred from global records of sea surface temperature (SST) anomalies and seasonally varying SST dependence of $pCO_{25W}$. The modeled interannual variability of $\pm0.2\;Pg\;C\;yr^{-1}\;(1{\sigma})$ from the present work is significantly smaller than the values deduced from atmospheric observations of $^{1.3}CO_2/CO_2$ in conjunction with different atmospheric transport models, but it is closer to the recent estimates inferred from a 3-D ocean biogeochemical model and atmospheric transport models constrained with extensive observations of atmospheric $CO_2$.