• 생태와환경
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• 제37권2호통권107호
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• pp.193-204
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• 2004

경기도 화성시 서해안 하구역에 조성된 간척 인공호인 화옹호에서 식물플랑크톤의 군집 변화와 종조성, 이에 영향을 미치는 요인을 평가하고자 2002년 6월에서 11월까지 호내 3개 정점과 호외 1개 정점에서 월별 조사 분석을 실시하였다. 조사기간 동안 4개 정점에서 관찰된 식물플랑크톤은 총 5강 8목 26과 63속 192종이었으며, 식물플랑크톤의 총 밀도는 각 정점의 표층에서 24${\sim}$1,882cells $mL^{-1}$로 시기와 정점에 따라 변화의 폭이 컸다. 식물플랑크톤의 총밀도는 염분도, pH, BOD, COD, SS, TN 및 TP등과 유의한 상관관계가 있는 것으로 나타났다. 규조류의 밀도와 관계가 있는 요인은 염분, SS, BOD, COD 및 TN으로 나타났다. 다소 지역적인 차이는 있으나 거리에 따른 농도 구배가 엽록소-a, 총인 및 총질소 모두에서 똑같이 나타남으로써 선행강우로 인한 영양염의 유입이 안정된 시기에 식물플랑크톤의 발달로 나타났다고 추정되었다. 화옹호 태동기의 식물플랑크톤 군집구조는 해양성 조류, 특히 규조류에 의해 좌우되고 있으며, 이들의 시 ${\cdot}$ 공간적 변이에 영향을 미치는 요인으로는 염분도, 강우사상, 영양염 등이 중요한 것으로 나타났다. 본 연구의결과로 판단할 매 화옹호의 현재 환경은 해수의 교환, 희석(강우사상)과 하천으로부터 유입되는 외부기원 영양염에 의해 크게 영향을 받는 상태로 평가된다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권5호
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• pp.49-55
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• 2012

A 1.28 L-batch reactor and continuous-flow stirred tank reactor (CFSTR) fed with formate and trichloroethene (TCE) were operated for 120 days and 56 days, respectively, to study the effect of formate as electron donor on anaerobic reductive dechlorination (ARD) of TCE to cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethylene (ETH). In batch reactor, injected 60 ${\mu}mol$ TCE was completely degraded in the presence of 20% hydrogen gas ($H_2$) in less than 8 days by anaerobic dechlorination mixed-culture (300 mg-soluble protein), Evanite Culture with ability to completely degrade tetrachloroethene (PCE) and -TCE to ETH under anaerobic conditions. Once the formate was used as electron donor instead of hydrogen gas in batch or chemostat system, the TCE-dechlorination rate decreased and acetate production rate increased. It indicates that the concentration of hydrogen produced in both systems is possibly more close to threshold for homoacetogenesis process. Soluble protein concentration of Evanite culture during the batch test increased from 300 mg to 688 mg for 120 days. Through the protein monitoring, we confirmed an increase of microbial population during the reactor operation. In CFSTR test, TCE was fed continuously at 9.9 ppm (75.38 ${\mu}mol/L$) and the influent formate feed concentration increased stepwise from 1.3 mmol/L to 14.3 mmol/L. Injected TCE was accumulated at 18 days of HRT, but TCE was completely degraded at 36 days of HRT without accumulation of the injected-TCE during the left of experiment period, getting $H_2$ from fermentative hydrogen production of injected formate. Although c-DCE was also accumulated for 23 days after beginning of CFSTR operation, it reached steady-state in the presence of excessive formate. We also evaluated microbial dynamic of the culture at different chemical state in the reactor by DGGE (denaturing gradient gel electrophoresis).

• Investigative Magnetic Resonance Imaging
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• 제21권3호
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• pp.171-176
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• 2017

Purpose: To compare different MR sequences for quantification of gadolinium concentration. Materials and Methods: Gadolinium contrast agents were diluted into 36 different concentrations. They were scanned using gradient echo (GRE) and ultrashort echo time (UTE) and R1, $R2^*$ and phase values were estimated from collected data. For analysis, ROI masks were made for each concentration and then ROI value was measured by mean and standard deviation from the estimated quantitative maps. Correlation analysis was performed and correlation coefficient was calculated. Results: Using GRE sequence, R1 showed a strong linear correlation at concentrations of 10 mM or less, and $R2^*$ showed a strong linear correlation between 10 to 100 mM. The phase of GRE generally exhibited a negative linear relationship for concentrations of 100 mM or less. In the case of UTE, the phase had a strong negative linear relationship at concentrations 100 mM or above. Conclusion: R1, which was calculated by conventional GRE, showed a high performance of quantification for lower concentrations, with a correlation coefficient of 0.966 (10 mM or less). $R2^*$ showed stronger potential for higher concentrations with a correlation coefficient of 0.984 (10 to 100 mM), and UTE phase showed potential for even higher concentrations with a correlation coefficient of 0.992 (100 mM or above).

• The Korean Journal of Physiology
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• 제18권1호
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• pp.1-8
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• 1984

In order to determine the extent of the placental transfer of Lithium ion, pregnant rabbits at $27{\sim}29$ days of gestation, which has hemochorial placenta similar to the human placenta, received 2 mM/Kg of $Li^+$ in the form of LiCl intravenously. Maternal arterial blood, placental sinus blood, fetal blood, amniotic fluid and maternal urine were drawn two hours after the single dose of LiCl. Concentrations of $Li^+$, $Na^+$, $K^+$ and osmolarity were measured in plasma of collected bloods, amniotic fluid and urine. Followings are the results obtained. 1) Evident level of $Li^+$ was detected in fetal blood, although fetal plasma concentration of $Li^+$ found to be almost one third of maternal plasma. 2) Plasma concentration of $Li^+$ in placental sinus blood was higher than that in fetal plasma but lower than that in maternal plasma. It means that downward concentration gradient of $Li^+$ from mother to fetus was still remarkable two hours after the injection. 3) Significant level of $Li^+$ was also detected in amniotic fluid. It seemed likely that $Li^+$, at least in part, excreted by the fetal urinary tract. 4) There were no differences in $Na^+$ and osmolar concentration between fetal and maternal blood. 5) From above results, it was concluded that $Li^+$ may transfer across the placenta but limited passage capacity through placental barrier for $Li^+$ is significant, beacause net transfer assumed to be going on even at two hours, at which time maternal equlibrium has been reached.

• The Korean Journal of Ecology
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• 제24권1호
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• pp.19-26
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• 2001

대형조선소가 위치한 옥포만내 퇴적물, 해수, 참굴(Crassostrea gigas) 중의tributyltin(TBT)과 triphenyltin(TPhT), 그리고 분해산물의 농도를 분석하였다. 퇴적물과 참굴 내 TBT 농도는 각각 5~2,650 ng/g, 387~l,190ng/g dry wt.(as Sn)으로 검출되었다. 해수 중의 TBT 화합물은 19~84 ng/ $\ell$ 농도범위를 나타내었다. 조선소 내 dry-dock에 인접한 정점에서 최고값을 보이며, 조선소로부터 거리가 멀어질수록 감소하는 농토분포를 나타내었다. 이는 조선소가 옥포만내 주 오염원임을 의미한다. 퇴적물 중의 TBT 화합물의 구성비는 약 57%로 dibu-tyltin(DBT)와 monobutyltin(MBT)보다 높게 나타났다 만을 가로지르는 방파제를 경계로 하여 부틸주석 화합물(butyltin)의 농도가 급격하게 감소하여, 방파제가 옥포만 내 유기주석 화합물의 분포에 영향을 미치고 있음을 나타내었다. 페닐주석화합물은 참굴 중 nd-52 ng/g으로 검출되었으며, 퇴적물과 해수의 전 정점에서 검출한계 이하의 값을 보였다. 참굴 중의 TBT 농도는 대조구인 해금강의 시료보다 높은 값을 보였고, 생물농축계수(biological concentration factor, BCF)는 1.1$\times$$10^4$의 값을 보였다.

• 한국수자원학회논문집
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• 제32권2호
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• pp.99-110
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• 1999

모멘트법은 Lagrangian 벙법으로서 격자요소 내에서의 농도의 공간분포에 대한 0차, 1차, 2차 모멘트를 고려한고 각 모멘트의 보존성을 유지하면서 농도분포의 이송을 계산하는 방법이다. 따라 각 격자요소에서의 0차 모멘트, 즉 평균농도 뿐만 아니라 1차 및 2차 모멘트 값의 합리적인 초기 설정이 요구된다. 본 연구에서는 각 모멘트들의 초기값 설정방법을 검토하고, 기존 모멘트법의 Couuant 수에 대한 제약조건을 극복하기 위하여 모멘트법을 개선하였다. 모멘트법에 의한 모의 결과를 유용한 Eulerian 및 Lagrangian 기법에 의한 모의 결과와 비교 검토하여 모한 해석결과를 발생시키는 기법이며, 본 연구에서 제시한 Courant 수 제약조건의 극복에 관한 연구는 성공적으로 이루어진 것으로 나타났다. 한편, 모멘트법은 농도가 전체 계산영역의 일부에 분포하는 2차원 영역에서의 이송 모의시 계산시간에 있어서 매우 효율적인 것으로 나타났다.

• Journal of Mechanical Science and Technology
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• 제17권3호
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• pp.440-448
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• 2003

In the present paper, numerical simulations of buoyant plume dispersion in a neutral and stable atmospheric boundary layer have been carride out. A Lagrangian Stochastic Model (LSM) with a Non-Linear Eddy Viscosity Model (NLEVM) for turbulence is used to generate a Reynolds stress field as an input condition of dispersion simulation. A modified plume-rise equation is included in dispersion simulation in order to consider momentum effect in an initial stage of plume rise resulting in an improved prediction by comparing with the experimental data. The LSM is validated by comparing with the prediction of an Eulerian Dispersion Model (EDM) and by the measured results of vertical profiles of mean concentration in the downstream of an elevated source in an atmospheric boundary layer. The LSM predicts accurate results especially in the vicinity of the source where the EDM underestimates the peak concentration by 40% due to inherent limitations of gradient diffusion theory. As a verification study, the LSM simulation of buoyant plume dispersions under a neutral and stable atmospheric condition is compared with a wind-tunnel experiment, which shows good qualitative agreements.

• 한국환경보건학회지
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• 제34권5호
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• pp.387-394
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• 2008

The toxicity of methyl tert-butyl ether (MTBE), tert-butyl alcohol (TBA) and formaldehyde (FA) on the indigenous microbial community in forest soil was studied. MTBE, TBA and FA with different concentrations were added into microcosms containing forest soil samples. After 10 and 30 days, total viable cell number and dehydrogenase activity in the microcosms were evaluated. Bacterial communities in the microcosms were also analyzed using a denaturing gradient gel electrophoresis (DGGE). Dehydrogenase activity and total viable cell number were decreased according to the increase of MTBE, TBA and FA concentrations (P<0.05). FA toxicity was the highest, but TBA toxicity was the lowest. The results of principal component analysis using DGGE fingerprints showed that the microbial communities contaminated MTBE, TBA and FA were grouped by exposure time not exposure concentration. Dominant species in the microcosms were as follows: Photobacterium damselae sub sp. and Bacillus sp. KAR28 for MTBE; Mycobacterium sp. and Uncultured Clostridium sp. for TBA; and Uncultured Paenibacillaceae bacterium and Anxynobacillus, Flavithermus for FA.

• 한국막학회:학술대회논문집
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• 한국막학회 1995년도 제3회 심포지움 (분리막 연구의 최신동향)
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• pp.57-71
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• 1995

A simple mathematical model for gacilitated mass transport with a fixed site carrier membrane was derived by assuming an instantaneous, microscopic concentration (activity) fluctuation, The concentration fluctuation, developed due to reversible chemical reaction between carrier and solute, could acuse the higher chemical potential gradient and the facilitated transport. For mathematical formulation, an analogy was employed between the mass transfer for the facilitated transport with fixed site carrier membrane and the electron transfer in a parallel resistor-capacitor (RC) circuit. For the single RC model, it was assumed that a single capacitor represented the total carrier and a solute could not inter-diffuse between matrix and carrier, allowing only two diffusional pathways, This assumption was relaxed by adopting a serial combination of the parallel RC circuit. Here, a solute diffuses in two elements (matrix or carrier) can exchange its pathway, exhibiting four diffusional pathways. The current models were examined against experimental data and the agreement was exceptional.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.342-354
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• 2013

The aim of this work is to investigate and study the quantum effects in the modeling of nanoscale symmetric double-gate InAlAs/InGaAs/InP HEMT (High Electron Mobility Transistor). In order to do so, the carrier concentration in InGaAs channel at gate lengths ($L_g$) 100 nm and 50 nm, are modelled by a density gradient model or quantum moments model. The simulated results obtained from the quantum moments model are compared with the available experimental results to show the accuracy and also with a semi-classical model to show the need for quantum modeling. Quantum modeling shows major variation in electron concentration profiles and affects the device characteristics. The two triangular quantum wells predicted by the semi-classical model seem to vanish in the quantum model as bulk inversion takes place. The quantum effects thus become essential to incorporate in nanoscale heterostructure device modeling.