• Ocean and Polar Research
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• 제33권1호
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• pp.21-34
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• 2011

We determined potential meso-scale benthic-pelagic ecosystem coupling in the north equatorial Pacific by comparing surface chl-a concentration with sediment bacterial abundance and adenosine triphosphate (ATP) concentration (indication of active biomass). Water and sediment samples were latitudinally collected between 5 and $11^{\circ}N$ along $131.5^{\circ}W$. Physical water properties of this area are characterized with three major currents: North Equatorial Current (NEC), North Equatorial Count Current (NECC), and South Equatorial Current (SEC). The divergence and convergence of the surface water occur at the boundaries where these currents anti-flow. This low latitude area ($5{\sim}7^{\circ}N$) appears to show high pelagic productivity (mean phytoplankton biomass=$1266.0\;mgC\;m^{-2}$) due to the supplement of high nutrients from nutrient-enriched deep-water via vertical mixing. But the high latitude area ($9{\sim}11^{\circ}N$) with the strong stratification exhibits low surface productivity (mean phytoplankton biomass=$603.1\;mgC\;m^{-2}$). Bacterial cell number (BCN) and ATP appeared to be the highest at the superficial layer and reduced with depth of sediment. Latitudinally, sediment BCN from low latitude ($5{\sim}7^{\circ}N$) was $9.8{\times}10^8\;cells\;cm^{-2}$, which appeared to be 3-times higher than that from high latitude ($9{\sim}11^{\circ}N$; $2.9{\times}10^8\;cells\;cm^{-2}$). Furthermore, sedimentary ATP at the low latitude ($56.2\;ng\;cm^{-2}$) appeared to be much higher than that of the high latitude ($3.3\;ng\;cm^{-2}$). According to regression analysis of these data, more than 85% of the spatial variation of benthic microbial biomass was significantly explained by the phytoplankton biomass in surface water. Therefore, the results of this study suggest that benthic productivity in this area is strongly coupled with pelagic productivity.

• 전기화학회지
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• 제26권2호
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• pp.19-34
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• 2023

Due to the intermittency of renewable energy sources, a need to store and transport energy will increase. Hydrogen production through water electrolysis will provide an excellent way to supplement the intermittency of renewable energy sources. While alkaline water electrolysis is currently the most mature technology, it has drawbacks of low current density, large footprint, gas crossover, etc. The PEM water electrolysis has potential to replace the alkaline electrolysis. However, expensive catalyst material used in the PEM electrolysis has been the bottleneck of widespread use. In this review, we have reviewed recent efforts to reduce catalyst loading in PEM water electrolysis. In core-shell nanostructures, the precious metal catalyst forms a shell while heteroatoms form a core. In this way, the catalyst loading can be significantly reduced while maintaining the catalytic activity. In another approach, a corrosion-resistant support is utilized, which provides a stable platform to impregnate precious metal catalyst.

• 한국농공학회지
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• 제39권3호
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• pp.115-127
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• 1997

Nonpoint source (NPS) pollution from small watersheds has recently been brought into attention as a potential pollutant to streams and tnbutaries, as majority of them are experiencing water quality degradation. This necessiates the quantification of NPS loadings from agricultural and forested lands. And this study attempts to quantify daily loadings from forested and farm lands using hydrologic and water quality monitoring. The hydrologic monitoring program consists of five water level gauging stations along creeks and stream at the Banweol reservoir watershed having 1220 hectare in size. Water sam pies were taken and analyzeel periodically at the streamf low gaging sites and tributaries. Soil samples were also taken and the chemical constitutes analyzed. The primary results indicate that the major sources of pollution were small villages and dairy farms on the watersheds, constituting two-third of total nutrient loadings to the reservoir. However, the loadings from paddies and upland areas may cause a problem to the water quality of the reservoir and stream as the measured levels of total nitrogen and phosporus are not low enough to ignore. Further studies are needed to quantify the effects of landuses and treatments at a watershed scale.

• Journal of Photoscience
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• 제5권4호
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• pp.169-174
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• 1998

Photosynthetic responses to dehydration were examined by the simulataneous measurement of O2 evolution and chlorophyll (Chl) fluorescence in green pepper leaves. Dehydration was induced by immersing the plant roots directly in the Hoagland solution containing varying concentration (2-30%) of polyethylene glycol(PEG-6000) . Water potential of the leaf was decreased time-and concentation -dependently by PEG-treatment. The decrease in water potential of leaf was correlated with the decrease in both the maximal photosynthesis (Pmax) and quantum yield of O2 evolution, but Pmax dropped more rapidly than quantum yield at all water deficit conditions tested. However, Chl fluorescence parameters were not affected much. Dehydration did not change the initial fluorescence (Fo) and maximum photochemical efficiency(Fv/Fm) of photosystem(PS) II. Both the photochemical quenching (qP) and non-photochemical quenching(NPQ) were not changed by dehydration under low PFR(50 $\mu$mols m-2s-1 ). In contrast, under high PFR(270$\mu$mols m-2s-1)qP was slightly decreased while NPQ was greatly increased. The fast induction kinetics of Chl fluroecence showed no change in Chl fluorescence pattern by dehydration at high PFR (640 $\mu$mols m-2s-1 ), but exhibited a significant drop in peak level(Fp)at low PRFR (70$\mu$mols m-2s-1 ). PS I oxidation and reduction kinetics revealed normal reduction but delayed oxidation to P-700+, suggesting no lesionin electron flow from PSII to PSI , but impaired electron transport to NADP+,These results suggest that water stress caused by PEG-treatment results in the reduction of photosynthesis, promarily due to the reducted electron trasport from PSI to NADP+ or hampered subsequent steps involving Calvin Cycle.

• 한국토양비료학회지
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• 제37권2호
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• pp.91-96
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• 2004

집약적인 시설재배 농업에서 화학비료와 퇴비의 연용과 과다한 사용은 용탈현상이 제한되어 있는 시설재배 토양의 염류집적현상을 쉽게 유발시키고 있다. 토양중의 염류집적에 따른 수분 흡수의 어려움을 극복하기 위하여 식물은 여러 가지의 무기 및 유기용질을 체내에 축적하는데, 특히 토양 중에 그 함량이 높아 쉽게 이용할 수 있는 $NO_3$를 삼투압 조절물질로 흡수 축적하는 것으로 결론지을 수 있다. 안전농산물의 생산 측면에서 특히 시설재배 신선야채류의 $NO_3$ 축적을 줄이기 위한 노력이 요구되고 있으며, 이를 이해서는 과다한 시비의 지양과 광조건의 개선이 필요하며 이에 더하여 토양 염류집적을 줄일 수 있는 토양 관리 및 시비 방법들이 심각하게 고려되어야 할 것이다.

• Journal of Advanced Marine Engineering and Technology
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• 제31권7호
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• pp.823-832
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• 2007

This paper presents the static characteristics of EGR-WI combined system. The water injection system was statically characterized by recording the engine exhaust outlet $NO_x$ emissions for comparison with baseline $NO_x$ emissions. Effects of the water injection system on CO and HC emissions and fuel consumption were examined. The research engine used for these experiments was a 103 kW turbocharged, intercooled, 2.5 L VM Motori CIDI engine equipped with a cooled EGR system. Water injection in the intake system demonstrated the potential for significant reductions in engine outlet $NO_x$ emissions. The system has reduced engine outlet $NO_x$ emissions by 40-50%, but caused significant increases in CO and HC emissions, particularly at low loads. Fuel consumption effects were minimal.

• The Korean Journal of Ecology
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• 제17권3호
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• pp.241-249
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• 1994

참나무속 식물 6종류의 잎의 확산저항, 기공밀도, 공변세포의 길이 및 털의 밀도를 측정하여 건조스트레스에 대한 이 식물들의 전략을 주성분분석법으로 분석하였다. 상수리나무, 갈참나무 및 졸참나무의 잎의 확산저항은 다른 3종보다 높은 Ψleaf 또는 낮은 WSD에서 빠르게 상승함으로써 수분 스트레스를 회피하였다. 그러나, 신갈나무와 떡갈나무는 낮은 Ψleaf, 낮은 기공밀도, 작은 기공 크기 및 높은 털밀도로 수분스트레스를 회피하였다. 그러나 신갈나무와 떡갈나무는 낮은 Ψleaf에서 기공 확산저항의 상승을 보였다. 건조스트레스에 대한 조정능과 관련된 15변수의 주성분분석에서 참나무속 식물은 2그룹, 즉 건성생육지종인 굴참나무, 신갈나무 및 떡갈나무와 중성생육지종인 상수리 나무, 갈참나무 및 졸참나무로 구별되었고, 건성생육지종인 굴참나무는 높은 털밀도, 낮은 기공밀도 및 높은 LAR에서 신갈나무 및 떡갈나무와 다시 구별되었다. 이 결과는 자연생육지에서 참나무속 식물의 건조에 대한 전략을 잘 설명하고 있다.

• The Korean Journal of Ecology
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• 제28권4호
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• pp.231-235
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• 2005

상록활엽수의 저온스트레스에 대한 저항성과 내 건성을 파악하고자 대표적인 상록활엽수인 붉가시나무와 구실잣밤나무의 초겨울 비교 수분 관계 특성을 기온 변화와 함께 해석하였다. 10월 이후 강수량과 기온이 급격하게 감소하였으며, 이러한 감소에 대해 붉가시나무와 구실잣밤나무는 세포 내 용질의 양을 증가시켜 삼투 포텐셜을 저하시키는 삼투조절을 행하였다. 그 결과, 두 종 모두 원형질 분리점과 팽윤 상태에서의 삼투 포텐셜은 11월에서 보다 12월에 더욱 낮은 값을 기록하였으며, 이러한 삼투조절 능력은 같은 수분 포텐셜에서도 11월보다 12월에 더욱 높은 팽압을 유지할 수 있게 하였다. 또한, 구실잣밤나무는 이러한 삼투조절 능력에다 붉가시나무에 비해 세포벽 유연성을 높게 가짐으로서 겨울철의 저온 스트레스와 수분 스트레스 하에서 팽압을 유지하는데 기여하고 있는 것을 나타내었다.

• 한국물환경학회지
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• 제30권3호
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• pp.329-339
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• 2014

This study aims to estimate chlorophyll-a concentration in rivers using multi-spectral RapidEye imagery and Spectral Mixture Analysis (SMA) and assess the applicability of SMA for multi-temporal imagery analysis. Comparison between images (acquired on Oct. and Nov., 2013) predicted and ground reference chlorophyll-a concentration showed significant performance statistically with determination coefficients of 0.49 and 0.51, respectively. Two band (Red-RE) model for the October and November 2013 RapidEye images showed low performance with coefficient of determinations ($R^2$) of 0.26 and 0.16, respectively. Also Three band (Red-RE-NIR) model showed different performance with $R^2$ of 0.016 and 0.304, respectively. SMA derived Chlorophyll-a concentrations showed relatively higher accuracy than band ratio models based values. SMA was the most appropriate method to calculate Chlorophyll-a concentration using images which were acquired on period of low Chlorophyll-a concentrations. The results of SMA for multi-temporal imagery showed low performance because of the spatio-temporal variation of each end members. This approach provides the potential of providing a cost effective method of monitoring river water quality and management using multi-spectral imagery. In addition, the calculated Chlorophyll-a concentrations using multi-spectral RapidEye imagery can be applied to water quality modeling, enhancing the predicting accuracy.

• 한국분무공학회지
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• 제18권2호
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• pp.81-86
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• 2013

To comply with the regulation of the reinforcing Clean Air Conservation Act, it is necessary for the semiconductor manufacturers to develop effective low-concentration acid gas abatement system to treat the flue gas. The low-concentration acid gas was found to be harder to deal with than the high-concentration one. In this study, the effect of various potential treatments such as air-assist nozzle spraying, magnetizing the scrubbing water, and adding surfactants to spraying and scrubbing water were investigate through the application of the statistical ANCOVA method, which was proved to be very useful tool when the inlet concentration of acid gas could not be controlled precisely and it affected the removal efficiency of the abatement system.