• 한국터널지하공간학회 논문집
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• 제14권6호
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• pp.607-616
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• 2012

지속적인 터널 건설의 증가는 터널 내 대기질 관리에 대한 필요성을 점증시키고 있어 측정 및 모델 모사를 통한 터널 내 대기질 거동에 대한 연구를 수행하였다. 남산1호 터널 입구와 출구의 $CO_2$ 농도차는 250 ppm~400 ppm으로 출구쪽이 높았으며 환기를 안 하는 차량 내부의 농도는 외부에 비해 200 ppm~300 ppm 낮게 측정되었다. 교통량이 적을 시 터널 내 유속은 빨라지며 일정한 농도 구배를 나타내고, 교통량이 증가하면 일정치 않은 농도 구배를 나타내는 것으로 나타났다.

• Preventive Nutrition and Food Science
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• 제11권2호
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• pp.120-126
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• 2006

Fish backbone, a major by-product in the fish processing industry, accounts for about 15% of whole fish weight. In this study, recovery of bioavailable calcium from Alaska pollack (Theragra chalcogramma) backbone by-products using enzymatic hydrolysis was investigated. Finely ground fish backbones were hydrolyzed with two proteolytic enzymes (pepsin and protease) to obtain soluble calcium from the by-products. The pepsin digest had a higher degradation efficiency (88%) than protease. Four different concentrations of the fish backbone calcium (100, 250, 500 and 1000 mg/L) prepared by the pepsin digest were treated with $Na_2HPO_4$ at a concentration gradient (0, 1, 2, 4, 8, 10, 15 and 20 mM) to evaluate their solubility, revealing that solubilities of the fish backbone calcium were superior to those of $CaCl_2$ at all the calcium and $Na_2HPO_4$ concentrations. Among the tested concentrations the highest solubility was found in the pepsin digest containing a calcium concentration of 1000 mg/L. Thus, hydrolyzing with pepsin is an effective mode of recovering bioavailable calcium from Alaska pollack fish backbones.

• 한국대기환경학회지
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• 제23권6호
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• pp.734-743
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• 2007

Polyurethane foam-disk passive air samplers (PAS) were deployed in a southern area of Korea for three months. The target compounds were 12 coplanar polychlorinated biphenyls (PCBs). The congener profiles measured in this study were the same as those in ambient air and emission gas from the incinerator. A gradient of the total PCBs in different regions (industrial>residential>rural) was observed, suggesting the industrial complex may be an important source of coplanar PCBs. In general, only gas-phase compounds are mainly sequestrated by PAS. In order to estimate the concentration of particle-phase PCBs, a gas/particle partition model was used. A combined result (gas+particle-phase PCBs) was compared with previous results, indicating that the level of coplanar PCBs in our study area is comparable to those in other urban sites in the world. The validation of this method for estimating the total concentration is required through additional backup studies.

• 농약과학회지
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• 제2권1호
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• pp.1-11
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• 1998

The generally accepted idea for carbohydrate translocation in plants is an osmotic pressure flow hypothesis. According to the hypothesis, a high concentration of carbohydrate in the phloem of carbohydrate synthesis regions (source) causes a water influx into the phloem. The generated osmotic potential in the phloem is responsible for long distance carbohydrate transport through the positive hydrostatic pressure. In regions of carbohydrate utilization and storage (sink), translocated carbohydrates are continuously metabolized and compartmentalized, generating a concentration gradient between source and sinks. In this system, carbohydrates load into the phloem (phloem loading) and unload out of the phloem (phloem unloading). Phloem-mobile herbicides that are applied to plants are also translocated from the source to sinks. However, some experimental results reveal that the patterns of phloem translocation between carbohydrates and herbicides are different. The differences are due, in part, to the physico-chemical properties of herbicides and to the absence/presence of specific carrier(s) in the phloem.

• 생태와환경
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• 제41권spc호
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• pp.1-10
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• 2008

We patterned water quality of agricultural reservoirs according to the differences of six physico-chemical environmental factors (TN, TP, DO, BOD, COD, and SS) using four different ordination methods: Principal Components Analysis (PCA), Detrended Correspondence Analysis (DCA), Nonmetric Multidimensional Scaling (NMS), and Isometric Feature Mapping (Isomap). The data set was obtained from the water quality monitoring networks operated by the Ministry of Agriculture and Forestry and the Ministry of Environments. Chlorophyll-${\alpha}$ displayed the highest correlation with COD, followed by TP, BOD, SS, and TN (p<0.01), while negatively correlated with altitude and bank height of the reservoirs (p<0.01). Although four different ordination methods similarly patterned the reservoirs according to the gradient of nutrient concentration, PCA and NMS appeared to be the most efficient methods to pattern water quality of reservoirs based on the explanation power. Considering variable scores in the ordination map, the concentration of nutrients was positively correlated with Chl-${\alpha}$, while negatively correlated with altitude and bank height. These ordination methods may help to pattern agricultural reservoirs according to their water quality characteristics.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.601-606
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• 2007

The chromatographic behaviors of nucleotides (inosine 5'-monophosphate, uridine 5'-monophosphate, guanosine 5'-monophosphate, and thymine monophosphate disodium salts) on a C18 column were studied with different types of ionic liquids (ILs) as additives for the mobile phase in reversed-phase liquid chromatography (RPLC). Three ILs, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIm][BF4]), and 1-ethyl-3-methylimidazolium methylsulfate ([EMIm][MS]), were used. Eluents were composed of water and methanol (90/10%, vol) with the addition of 0.5-13.0 mM of ILs. The effects of the concentration of ILs on retention and separation were investigated and discussed. The results showed that the addition of ILs affects the retention and resolution of the tested compounds. Use of 13.0 mM of [BMIm][BF4] as the eluent modifier resulted in a baseline separation of nucleotides without requiring gradient elution. This study demonstrates that ILs can be potentially applied as a mobile phase modifier in RPLC.

• 상하수도학회지
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• 제30권5호
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• pp.553-559
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• 2016

There has been increasing global interest in the environmental pollution problems produced by fossil fuel consumption and greenhouse gas emissions. In order to tackle these issues, new renewable energy such as solar, wind, bio gas, fuel cell and pressure retarded osmosis(PRO) have been developed extensively. Among these energy sources, PRO is one of the salinity gradient power generation methods. In PRO, energy is obtained by the osmotic pressure generated from the concentration difference between high and low concentration solutions separated by a semipermeable membrane. The development for high power density PRO membranes is imperative with the purpose of commercialization. This study investigates development of thin film composite PRO membrane and spiral wound module for high power density. Also, the influence of membrane backing layer on power density was identified, and the characteristic factors of PRO membranes was determined. Different backing layers were used to improve power density. As expected, the PRO membrane with more porous backing layer showed higher power density.

• 한국대기환경학회지
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• 제19권3호
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• pp.275-284
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• 2003

The soil -air exchange processes of CH$_4$ were investigated in Hari district of Kang Hwa Island, Korea during the late April 2002. In the course of our field experiments, we measured the concentration, concentration gradients (between two different heights of 1 and 5 m), and the fluxes of CH$_4$ using the surface layer gradient microm-eteorological methods. If the relationships between CH$_4$ fluxes and the relevant environmental parameters are examined, CH$_4$ fluxes were found to be affected most significantly by parameters like wind speed. The results of our study indicate that the study area behaved as a net source of CH$_4$ to the atmosphere with a net daily emission rate of 3.6 mg m￣$^2$ The findings of relatively low exchange rate observed at our study site suggest that the rice paddy area investigated prior to planting period can behave as a moderate source of methane.

• The Korean Journal of Ecology
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• 제26권2호
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• pp.87-89
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• 2003

Although a forest damage of large area due to air pollution has not yet been found in Korea, declines of Korean red pine (Pinus densiflora Sieb. et Zucc.), the most common coniferous species, have been locally reported. To evaluate the effect of air pollution and acid deposition on the forests, SO$_2$ concentration, acid load, soil pH and tree decline were monitored for 13 years from 1988 to 2001 in Namsan, Doowang and Gyebangsan with the gradient of air pollution. During the study period, annual mean SO$_2$ concentration in Namsan, Doowang and Gyebangsan were 14 ppb, 13 ppb and 6 ppb, respectively. Annual mean acid loads in Namsan and Doowang were three to four times more than that in Gyebangsan. As respected, forest surface soils in Namsan and Doowang were acidified to pH 4.1 and 4.3, whereas that in Gyebangsan showed normal value as pH 5.4. On the other hand, decline degrees of Korean red pines in Namsan and Doowang in both 1996 and 2001 were higher than those in Gyebangsan. It is reasonable that the severer tree declines in Namsan and Doowang could be closely related with the higher air pollution, acid load, and the effects (possibly Ca deficit and Al toxicity) of soil acidification.

• 한국결정성장학회지
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• 제2권2호
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• pp.77-82
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• 1992

FZ법에 의한 결정성장에 있어서 용융대는 고액 계면의 장력에 의해 유지되고 상.하부의 고체봉 사이에 위치하고 있다. 따라서, 용융대의 표면에서는 온도와 농도 차이에 의해 표면장력의 구배가 발생하고 있는 marangoni 대류의 구동력으로 작용한다. 본 연구에서 정상상태의 결정성장시는 결정의 가장자리 영역에서의 Solute 농도는 결정내부 보다도 높아지게 되고 전위의 분포도 불규칙하여 지며, void나 기포 침투, Secondary phase의 생성 및 미소균열등의 결함 발생 확률이 계면부근에서 높아지는 결과를 알 수 있었다. 이는 고액성장 계면이 marangoni 대류에 의하여 이 영역에서 온도의 국부적인 변동에 의해 불규칙하여 지게 되기 때문이라 사료된다.