• 한국환경과학회지
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• 제29권2호
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• pp.123-132
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• 2020

Seasonal changes in the CO₂ fixation rate and water-use efficiency in the leaves of six evergreen and two deciduous broad-leaved tree species on Jeju Island, Korea, were measured using a portable photosynthesis analyzer, to identify which species are most efficient in taking up CO₂ from the air. The CO₂ fixation rate was high in the deciduous species in spring and summer and decreased in fall, whereas it was high in the evergreen species in summer and fall and decreased in winter. The rate remained high in the deciduous tree Prunus yedoensis from spring to fall (> 7.1 μmol CO₂/m₂/s) and in two evergreen trees, Castanopsis cuspidata var. sieboldii and Cinnamomum camphora, in summer and fall (7.0 9.9 μmol CO₂/㎡/s). Therefore, these tree species fix atmospheric CO₂ effectively. The water-use efficiency was higher in evergreen species than in deciduous species regardless of the season. Exceptionally, it was high in the deciduous species Zelkova serrata in spring and summer (> 100 μmol CO₂/mol H₂O), suggesting that Z. serrata is a useful tree for dry conditions due to its tolerance of water stress. The regressions of the CO₂ fixation rate versus the evaporation rate and stomatal conductance were linear and non-linear, respectively. This suggests that the stomatal activity of leaves plays an important part in CO₂ fixation of plants. In conclusion, C. cuspidata var. sieboldii, C. camphora, and P. yedoensis should be planted along roads or in urban spaces for the greening of cities and mitigation of CO₂ concentrations in the air.

• Journal of Forest and Environmental Science
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• 제23권1호
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• pp.29-33
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• 2007

이 연구는 음나무의 생장에 대한 생리 생태적 특성을 측정하여 조림목의 적지환경을 구명하고자 하는 일련의 연구이다. 본 측정에서는 잎의 기공증산속도의 일변화, 수분이용효율의 일변화, 수분포텐셜의 일변화, 그리고 세포간극의 $CO_2$ 농도 일변화 등을 측정, 고찰하였다. 그 결과를 요약하면 다음과 같다. 1) 기공증산속도의 일변화는 오전 10시경이 가장 높았으며, 16시를 기점으로 기공증산속도는 빠르게 감소하였다. 2) 수분이용효율의 일변화는 오전 8시경에 최대치를 보였고, 그 후 수분포텐셜의 감소와 함께 정오까지 빠르게 감소하였다가 회복한 후 17시 이후부터는 급격한 감소를 보였다. 3) 세포간극의 $CO_2$ 농도($C_i/C_a$ 비율)의 일변화는 오전 9시까지 빠르게 감소하였고, 그 후 16시까지는 큰 변화 없이 안정한 값을 유지하였으며, 16시 이후부터는 다시 빠르게 증가하였다. $C_i/C_a$ 비율의 일변화는 수분포텐셜의 일변화와 거의 유사한 경향을 보였다. 결과적으로 산지에 식재된 음나무 잎의 기공증산, 수분이용효율, 수분포텐셜이 높은 오전에 가장 증가하고, 오후부터 급격한 감소를 나타냈다.

• 한국세라믹학회지
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• 제54권3호
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• pp.205-210
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• 2017

In this study, we examined the photo-degradation efficiency of $CoSe_2$-Graphene-$TiO_2$ ($CoSe_2-G-TiO_2$) nanocomposites under visible light irradiation using rhodamine B (RhB) as standard dye. $CoSe_2-G-TiO_2$ nanocomposites were synthesized by ultrasonication and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopic analysis and UV-Vis absorbance spectra analysis. Our results show that the $CoSe_2-G-TiO_2$ nanocomposite exhibited significant photo degradation efficiency compared to pure $TiO_2$ and $CoSe_2-G$, approximately 85.2% of the rhodamine (Rh B) degraded after 2.5 h. It is concluded that the $CoSe_2-G-TiO_2$ nanocomposite is a promising candidate for use in dye pollutants.

• Transactions on Electrical and Electronic Materials
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• 제13권2호
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• pp.60-63
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• 2012

Enhancement of efficiency and luminance of organic light-emitting diodes was investigated by the introduction of a lithium carbonate ($Li_2CO_3$) electron-injection layer. Electron-injection layer is used in organic light-emitting diodes to inject electrons efficiently between a cathode and an organic layer. A device structure of ITO/TPD (40 nm)/$Alq_3$ (60 nm)/$Li_2CO_3$ (x nm)/Al (100 nm) was manufactured by thermal evaporation, where the thickness of $Li_2CO_3$ layer was varied from 0 to 3.3 nm. Current density-luminance-voltage characteristics of the device were measured and analyzed. When the thickness of $Li_2CO_3$ layer is 0.7 nm, the current efficiency and luminance of the device at 8.0 V are improved by a factor of about 18 and 3,000 compared to the ones without the $Li_2CO_3$ layer, respectively. The enhancement of efficiency and luminance of the device with an insertion of $Li_2CO_3$ electron-injection layer is thought to be due to the lowering of an electron barrier height at the interface region between the cathode and the emissive layer. This is judged from an analysis of current density-voltage characteristics with a Fowler-Nordheim tunneling conduction mechanism model. In a study of lifetime of the device that depends on the thickness of $Li_2CO_3$ layer, the optimum thickness of $Li_2CO_3$ layer was obtained to be 1.1 nm. It is thought that an improvement in the lifetime is due to the prevention of moisture and oxygen by $Li_2CO_3$ layer. Thus, from the efficiency and lifetime of the device, we have obtained the optimum thickness of $Li_2CO_3$ layer to be about 1.0 nm.

• The Journal of Asian Finance, Economics and Business
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• 제2권3호
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• pp.41-46
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• 2015

Energy saving in the transport sector in the framework of the annual growth of energy consumption, the degree of negative impact on the environment and the amount of harmful emissions are becoming increasingly important. The article considers the world tendencies of energy consumption in transportation sector and emphasizes its dependency from oil. Also article describes the dynamics of energy use and CO₂ emissions from transport of city Almaty. In conclusion authors identify a number of problems in the transport sector, which hinder the implementation of energy efficiency measures and measures to reduce CO₂ emissions.

• 한국작물학회지
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• 제55권3호
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• pp.268-274
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• 2010

The aim of our study was to investigate the interactive effects of container size and nutrient supply on plant growth, chlorophyll synthesis, transpiration, $CO_2$ assimilation, water use efficiency (WUE), and nutrient uptake of vinca plant (Catharanthus roseus). A complete experiment utilizing four concentrations of fertilizer and three volumes of containers was conducted. As the container size was increased, the plant height, leaf area, and dry weight of vinca significantly increased regardless of fertilizer level. The leaf area and dry weight of vinca were highly sensitive to the container size. However, the chlorophyll contents of vinca 20 days after the transplant significantly increased with decreasing container sizes and increasing fertilizer concentrations. Significant differences in transpiration and $CO_2$ assimilation occurred with the use of differentfertilizer solutions, but the highest values for transpiration and $CO_2$ assimilation were in plants grown in the 15 cm-diameter containers. The highest water use efficiency was observed in the plants grown in 10 cm-containers with 4 dS/m of fertilizer, and there were no significant differences in WUE values among container sizes with fertilizer concentrations of 0, 1, or 2 dS/m. No significant difference in nutrient uptake was observed among the fertilizer levels or among the container sizes. However, at a fertilizer concentration of 4 dS/m, the uptake of several nutrients, including N, P, K, Ca, Mg, B and Fe, was higher in small containers than in larger ones.

• 한국산학기술학회논문지
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• 제14권7호
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• pp.3508-3517
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• 2013

지구(district)는 도시를 형성하는 기본 단위로 모든 도시활동이 시작되는 장소이다. 따라서 본 연구에서는 지구단위에서의 교통과 토지이용패턴의 결합 형태에 따른 270개의 시나리오를 가정하고 $CO_2$ 배출량을 분석한 후 $CO_2$ 배출량을 최소화하는 토지이용-교통모형을 작성하고자 하였다. 그 결과 균등 또는 외곽을 고밀도로 개발하는 토지이용패턴이 지구의 중간부나 1개 중앙존만을 개발하는 것보다 $CO_2$ 배출량 감소에 유리한 것으로 파악되었다. $CO_2$ 배출량 감소에 가장 영향을 많이 주는 것은 교통수요관리정책으로, 특히 개발밀도가 높은 상태일수록 $CO_2$를 감소시키기 위해서 교통수요관리는 필수적인 것으로 판단되었다. 고밀개발이 아닌 경우에 주어진 가상 네트워크에서는 2차로도로에 차량통행금지를 시키고 보행자도로로 전환시킬 경우 $CO_2$ 배출량을 감소시킬 수 있음을 알게 되었다. 한편, 제시된 토지이용-교통 회귀모델은 지구설계시 $CO_2$ 배출량을 줄이기 위한 최적대안 선정시 도움을 줄 수 있을 것으로 사료된다.

• 한국정밀공학회지
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• 제25권9호
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• pp.109-115
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• 2008

The cleaning process of contaminant particles adhering to the microchips, integrated circuits (ICs) or the like is essential in modern microelectronics industry. In the cleaning process particularly working with the application of inert gases, the removal of contaminant particles of submicron scale is very difficult because the particles are prone to reside inside the boundary layer of the working fluid, The use of cryogenic $CO_2$ cleaning method is increasing rapidly as an alternative to solve this problem. In contrast to the merits of high efficiency of this process in the removal of minute particles compared to the others, even fundamental parametric studies for the optimal process design in this cleaning process are hardly done up to date, In this study, we attempted to measure the cleaning efficiency with the variations of some principal parameters such as mass flow rate, injection distance and angle, and tried to draw out optimal cleaning conditions by measuring and evaluating an effective cleaning width called $d_{50}$.

• 한국응용과학기술학회지
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• 제31권3호
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• pp.466-471
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• 2014

It is important to develop the smart ventilation system in order to minimize a building energy consumption using ventilation. In this study, We evaluated the efficiency of the smart ventilation system being developed at the nursery. To evaluate the energy savings and carbon dioxide removal efficiency, two kinds of experimental conditions were compared. First, air conditioner and Smart HVAC system were operated. Second, air conditioner was operating and external air was put into the inside by rate of air circulation. It was more effective when working with air conditioning and ventilation system at the same time. If the Smart HVAC system is applied in a multi-use facility, indoor air quality will be comfortable and the social cost will be reduced.

• 한국응용과학기술학회지
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• 제32권2호
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• pp.296-301
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• 2015

The experiment was performed for in order to remove NOx which is generated in the Ship's engine. it was performed test in order to remove NOx which is generated in the Ship's engine. It was used as the oxidizing agent sodium chlorite. Use the oxidizer is nitrogen monoxide was oxidized to nitrogen dioxide. and was tested pH adjustment to increase the efficiency of oxidizing. An aqueous solution of sodium hydroxide was used for the nitrogen dioxide absorbent. Low concentration of the solution, it showed a high efficiency. improves the absorption efficiency by add additives.