• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.5.1-5.1
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• 2010

One of the most important environmental problems is global warming. Global warming is caused by increase in the amounts of water vapor, methane, carbon dioxide and other gases being released into the atmosphere as a result of the burning of fossil fuels. It has thus become important to reduce fossil fuel use. Environmentally friendly preparation of functional materials has, therefore, attracted much interest for environmental problems. Furthermore, nature mimetic processes are recently been of great interest as environmentally friendly one. There have been many studies on fabrication of various functional nanocrystals. Among various nanocrystal fabrication techniques, flux growth is an environmentally friendly, very convenient process and can produce functional nanocrystals at temperatures below the melting points of the solutes. Furthermore, this technique is suitable for the synthesis of crystals having an enhedral habit. In flux growth, the constituents of the materials to be crystallized are dissolved in a suitable flux (solvent) and crystal growth occurs as the solution becomes critically supersaturated. The supersaturation is attained by cooling the solution, by evaporation of the solvent or by a transport process in which the solute is made to flow from a hotter to a cooler region. Many kinds of oxide nanocrystals have been grown in our laboratory. For example, zero- (e.g., particle), one- (e.g., whisker and tube) and two-dimensional (e.g., sheet) nanocrystals were successfully grown by flux method. Our flux-growth technique has some industrial and ecological merits because the nanocrystal fabrication temperatures are far below their melting points and because the used reagents are less harmless to human being and the environment.

• 한국수자원학회논문집
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• 제56권11호
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• pp.721-728
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• 2023

농업적 가뭄이 발생하면 토양의 수분이 감소하여 식생의 광합성 및 성장을 저해한다. 광합성을 통해 대기 중의 이산화탄소가 흡수되며 산소 생산량이 증가하는데, 이러한 광합성에 부정적인 영향이 생긴다면 대기 중의 이산화탄소 농도가 증가한다. 본 연구에서는 다중분광광학센서인 MODerate resolution Imaging Spectroradiometer (MODIS) 산출물을 이용하여 토양수분, 식생 활력 및 대기 중의 이산화탄소 농도 간의 관계를 분석하였다. 토양수분의 경우, 기존의 마이크로웨이브 센서는 낮은 공간 해상도로 제공되는 특징으로 인해 소규모 연구 지역 분석에 한계가 있어서 상대적으로 고해상도인 광학센서를 이용한 토양수분 산정 방법을 적용하였다. 또한, MODIS 총일차생산량(Gross Primary Productivity, GPP) 산출물을 이용하여 식생의 호흡과의 관계식을 이용하여 이산화탄소 플럭스를 계산하였다. 원격탐사 기반의 토양수분, 식생지수와 이산화탄소 플럭스를 국내의 극한 가뭄 발생시기인 2014년과 2015년도에 대하여 지점 관측 자료인 플럭스타워 값과 비교 분석하였다. 분석한 결과 토양수분과 식생지수 사이에는 한 달의 지체시간, 식생지수와 이산화탄소 플럭스 사이에는 2주 지체시간이 발생했을 때, 상관성이 높게 나타났다.

• Membrane and Water Treatment
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• 제6권1호
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• pp.1-13
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• 2015

The modification of ultrafiltration membranes with carbon nanotube (CNT) buckypaper on fouling control was investigated. Two types of commercially available flat-sheet membranes were used: PS35 and PES900C/D (PES) (the PS35 membranes were hydrophilic with a molecular weight cutoff of 20 kDa, and the PES membranes were hydrophobic with a molecular weight cutoff of 20 kDa). The CNT buckypaper modified ultrafiltration membranes were prepared by filtering a CNT suspension through the flat-sheet membrane in a dead-end ultrafiltration unit. After modification, the pure water flux of PES was significantly increased, while the pure water flux of PS35 was decreased. The properties of the CNT modified membranes were also investigated. Considering the antifouling properties, pure water flux of the modified membrane, and the stability of CNT buckypaper layer on the membrane surface, ethanol solution with a concentration of 50 wt.%, multi-walled carbon nanotubes (MWCNTs) with a larger diameter (30-50 nm), and the CNT loading with $7.5g/m^2$ was selected. The CNT buckypaper on the surface of ultrafiltration membranes can trap the pollutants in sewage effluent and prevent them reaching the surface of virgin membranes. Water quality analysis showed that the effluent quality of the modified membrane was obviously improved. The removal efficiency of humic acid and protein-like matters by the modified membrane was significant. These results indicate the potential application of the CNT buckypaper layer modified membranes in the field of wastewater reclaim.

• 한국초전도ㆍ저온공학회논문지
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• 제21권2호
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• pp.36-39
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• 2019

Effects of the spherically shaped Ge and the rod-like carbon-coated Ge on the superconducting properties of $MgB_2$ were investigated. Pure Ge and carbon-coated Ge nano-powders were synthesized under the different amount of $CH_4$ (0 to 5 kPa) by using DC thermal plasma method. When the $CH_4$ was added ~100 nm sized Ge with a spherical shape changed to rod-like morphology with a diameter of ~30-70 nm and a length of ~400-500 nm. Also it was confirmed that thin carbon layers of a few nanometers were formed along the rod length and the agglomerated carbons were found on the edges of rods. Pure spherical Ge and Ge/C rods were mixed and milled with Mg & B precursor to form the doped $MgB_2$ bulk samples by the solid-state reaction method. Almost no change of $T_c$ was noticed for the pure Ge-added $MgB_2$, whereas $T_c$ was found to decrease with the Ge/C-added $MgB_2$ samples. It was found that the pure spherical Ge showed to have a negative effect on the flux pinning of $MgB_2$. However, Ge/C rods can enhance the flux pinning property of $J_c$ due to the coated carbon on Ge rods.

• The Korean Journal of Ecology
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• 제26권5호
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• pp.289-296
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• 2003

The ecological process-based approach provides a detailed assessment of belowground compartment as one of the major compartment of carbon balance. Carbon net balance (NEP: net ecosystem production) in forest ecosystems by ecological process-based approach is determined by the balance between net primary production (NPP) of vegetation and heterotrophic respiration (HR) of soil (NEP=NPP-HR). Respiration due to soil heterotrophs is the difference between total soil respiration (SR) and root respiration (RR) (HR=SR-RR, NEP=NPP-(SR-RR)). If NEP is positive, it is a sink of carbon. This study assessed the forest carbon balance by ecological process-based approach included belowground compartment intensively. The case study in the Takayama Station, cool-temperate deciduous broad-leaved forest was reported. From the result, NEP was estimated approximately 1.2 t C $ha^{-1} yr^{-1}$ in 1996. Therefore, the study area as a whole was estimated to act as a sink of carbon. According to flux tower result, the net uptake rate of carbon was 1.1 t C $ha^{-1} yr^{-1}$.

• 대기
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• 제34권1호
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• pp.69-81
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• 2024

In this paper, Annual flux variations in the Boseong Tall Tower (BTT) from 2016 to 2020 were analyzed using data from three levels (2.5 m, 60 m, and 300 m). BTT was installed in Boseong-gun, Jeollanam-do in February 2014 and continued to conduct energy exchange observations such as CO2, sensible heat, and latent heat using the eddy covariance method until March 2023. The BTT was located in a very flat and uniform paddy field, and flux observations were conducted at four levels: 2.5 m, 60 m, 140 m, and 300 m above ground. Surface energy balance was confirmed from observed data of net radiation flux, soil heat flux, sensible heat flux, and latent heat flux. Additionally, 2.5 m height surface fluxes, which are most influenced by agricultural land, were compared with data from Local Data Assimilation and Prediction System (LDAPS) of the Korea Meteorological Administration to evaluate the accuracy of LDAPS flux data. The correlation coefficient between LDAPS flux data and observed values was 0.95 or higher. Excluding summer latent heat flux data, there was a general tendency for LDAPS data to be higher than observed values. The footprint areas estimated below 60 m height mainly covered agricultural land, and flux observations at 2.5 m and 60 m heights showed typical agricultural characteristics. In contrast, the footprint estimated at 300 m height did not show agricultural characteristics, indicating that observations at this height encompassed a wide range, including mountains, sea, and roads. The analysis results of long-term flux observations can contribute to understanding the energy and carbon dioxide fluxes in agricultural fields. Furthermore, these results can be utilized as essential data for validating and improving numerical models related to such fluxes.

• Journal of Microbiology and Biotechnology
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• 제12권2호
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• pp.258-267
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• 2002

A flux determination methodology has been built which enables to develop constrained stoichiometric relationships and metabolic balances. The analysis differs from those developed for anaerobic growth conditions in that cell mass formation is a significant sink for carbon. When combined with experimental measurements, a determined system of equations results yielded tricarboxylic acid (TCA) cycle and glycolytic fluxes. The methodology was implemented to determine the fluxes of E. coli B/r and K12, and it was found that as the growth rate in a glucose minimal medium increased, the cells became increasing glycolytic and the TCA fluxes either leveled off or declined. The pattern identified for the TCA fluxes corresponded to ${\alpha}$-ketoglutarate dehydrogenase's induction-repression pattern, thereby suggesting that the induction-repression of the enzyme could result in significant flux changes. When the minimum flux solution was contrasted to the glycolytic and TCA fluxes determined, two observations were made. First, the minimum flux could provide the cell's biosynthetic ATP requirements. Second, at a high growth rate in a glucose medium, the excess glycolytic flux exceeded that of the TCA cycle, which appeared to more closely match the biosynthetic needs.

• Membrane and Water Treatment
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• 제12권2호
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• pp.65-73
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• 2021

Sponge ball cleaning can generate an abrasion effect, which leads to an attractive increasing in both permeate flux and membrane rejection. The aim of this study was to investigate the influence of the daily sponge ball cleaning (SBC) on the performance of different UF cross-flow membrane modules integrated with a bioreactor. Two 1"-membrane modules and one 1/2"-membrane module were tested. The parameters measured and controlled are temperature, pH, viscosity, particle size, dissolved organic carbon (DOC), total suspended solids (TSS), and permeate flux. The permeate flux could be improved by 60%, for some modules, after 11 days of daily sponge ball cleaning at a transmembrane pressure of 350 kPa and a flow velocity of 4 m/s. Rejection values of all tested modules were improved by 10%. The highest permeate flux of 195 L/㎡.h was achieved using a 1"-membrane module with the aid of its negatively charged membrane material and the daily sponge ball cleaning. In addition, the enhancement in the permeate flux caused by daily sponge ball cleaning improved the energy specific demand for all tested modules. The negatively charged membrane showed the lowest energy specific demand of 1.31 kWh/㎥ in combination with the highest flux, which is a very competitive result.

• 한국농림기상학회지
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• 제5권2호
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• pp.116-127
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• 2003

태국 북서부의 Tak 지방에 KoFlux(Korean Flux Network) 연구의 일환으로서 플럭스 관측소(Tak flux measurement, TFM site)가 설립되었다. 이곳에서 이산화탄소와 물, 그리고 에너지 플럭스를 관측하기 위해 와 공분산시스템(eddy covariance system)을 적용하였으며 관측된 자료는 실시간 자료 감시 및 모사 시스템(Real time monitoring and simulation system, RTMASS)을 이용하여 처리되어 전송된다. RTMASS는 KoFlux-DIS(Data information system)의 핵심 구조이고 원격지 시스템과 중앙 시스템으로 나누어지며 자료의 수집 및 전송. 자료의 저장 및 처리가 본 시스템의 주된 기능이다. 난류특성과 미기상학적인 분석 자료에 따르면, TM 관측소는 열대 낙엽수림에 대한 다양한 플럭스 및 에너지 수지를 관측하고 분석하는데 적합하다고 할 수 있다.

• 환경위생공학
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• 제12권2호
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• pp.65-74
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• 1997

The purpose of this study was to investigate the removal effect and variation of contaminated water by various water treatment processes using sediment filter, activated carbon, photocatalysis, reverse osmosis, ultra violet sterilizer and ultra filtration. The removal effect of chloride and trace metal was low by activated carbon and ultra filter but high in reverse osmosis. The removal effect of bacteria and E. coli was low by activated carbon and membrane filter system using activated carbon but high in impregnated activated carbon. The removal effect of TCE was low in sand and ultra filter system as compared with activated carbon. Ultra filtration process was effective for purify agricultural water without E.coli. Reverse osmosis was effective to remove heavy metal and activated carbon was effective to remove halogenated organic chemical compound. The flux and the removal effect of COD in spiral wound ultrafilter were higher than the hollow fiber ultrafilter.