• Proceedings of the Korean Environmental Sciences Society Conference
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• 2008.11a
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• pp.503-506
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• 2008

질소제거 능력이 있는 Pseudomonas aeruginosa을 고분자물질인 PEG 에 포괄고정화하였으며 제조된 고정화 미생물을 이용하여 질소제거에 미치는 C/N비, 농도, 충진율, 탄소별 제거율을 검토한 결과 다음과 같은 결론을 얻었다. 1) C/N비 10이상이면 NH$_4$-N 와 NO$_3$-N의 동시 제거가 가능하였으며 2) 탄소 원으로는 glucose를 사용하였을 때 NH$_4$-N 와 NO$_3$-N의 동시 제거가 가능하였으나 methanol은 탄소원으로 사용할 수 없었다. 3) 저농도의 NO$_3$-N(50 mg/L)는 완전히 제거 가능하였으나 NH$_5$-N인 경우에는 초기 NH$_4$-N 100 mg/L에서 60%정도만 제거되었다. 4) 연속처리 결과 NH$_4$-N는 HRT 변동에도 불구하고 유출수 농도 변화가 거의 없었으나, 오히려 C/N비를 증가시키면 NH$_4$-N 제거 효율이 높았고, NO$_3$-N인 경우도 마찬가지로 C/N비를 증가시키면 NO$_3$-N 제거 효율이 높았다.

• The Korean Journal of Ecology
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• v.26 no.6
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• pp.321-326
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• 2003

This study was conducted to investigate and effects of shading treatment on photosynthetic activity of Acanthopanax senticosus. We investigated plant growth, light response curve and A-Ci curve to photosynthesis of A. senticosus at 55%, 75%, and 90% shading treatment. As results, the ratio of above-ground/under-ground biomass was increased at 75% shaded condition and showed highest dry biomass. Under shaded conditions, plants had lower chlorophyll a+b content and a/b ratio and also showed thinner leave. But shaded plants showed higher leaf area and higher total leaf area per a plant. This apparently indicates adapted responses to shaded treatment. Effects of shading treatments on photosynthetic activity were higher in apparent quantum yield, carboxylation efficiency, re-phosphrylation but lower in light compensation point. These results suggested that higher photosynthesis rates in shaded treatments were due to activated carboxylation efficiency. Shading treatment had lower water use efficiency thatn controls but still higher than other tree species.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.3
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• pp.220-226
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• 2005

We investigated the effect of $O_3$ on the photosynthetic characteristics of oriental plane (Platanus orientalis L.) that is used as a side tree or ornamental tree in Korea. Two-year-old oriental plane seedlings were transplanted to pots and transferred into a closed $O_3$ chamber, Photosynthetic pigment content and photosynthetic characteristics of leaves were measured every three weeks during 100 ppb $O_3$ fumigation. There was no visible foliar injury by $O_3$ exposure and the content of photosynthetic pigments did not show significant differences between control and $O_3$-treated seedlings. But photosynthetic rate, stomatal conductance, and water use efficiency in leaves of $O_3$-treated seedlings were reduced after six weeks of ozone fumigation. In addition, reduction of carboxylation efficiency and photochemical efficiency was observed in leaves of $O_3$-treated seedlings after three weeks and six weeks. In accordance with our results, carboxylation efficiency, the most sensitive parameter to $O_3$ stress, was considered to be a suitable indicator of $O_3$ sensitivity.

• Resources Recycling
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• v.30 no.1
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• pp.77-82
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• 2021

Reduction of CO2 emissions is an important issue in the steel industry, and the research on carbon materials that can partially replace cokes is necessary to reduce CO2 emissions. Meanwhile, the biomass fuel contains some fixed carbon, and the carbon content in the biomass can be increased by torrefaction. As one of the biomass fuels, coffee grounds contains about 55 mass% of carbon, and its about 270,000 tons are landfilled and incinerated annually in Korea. In addition, research on the recycling process due to the increase in annual coffee consumption is required. In this study, the effect of temperature on the concentration of fixed carbon in coffee grounds was investigated during torrefaction. Moreover, the effects of mixing ratio of torrefied coffee grounds with cokes on the carbon concentration and dissolution efficiency in the metal sample were investigated.

• The Korean Journal of Ecology
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• v.27 no.3
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• pp.147-153
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• 2004

The objective of this study was to understand differences among three half-sib families of Betula schmidtii seedlings in the effect of three Cd levels on growth and photosynthesis. One-year-old seedlings of B. schmidtii were treated with 0, 0.4 and 0.8 mM CdSO$_4$ㆍ8/3$H_2O$ for two months. Growth and physiological responses to Cd treatment levels of three families determined using dry weight, relative height growth rate(RHGR), apparent quantum yield and carboxylation efficiency. The B. schmidtii seedlings exposed to 0.4 and 0.8 mM Cd showed statisticall significant decrease in dry weight and RHGR relative to controls. In addition, the growth inhibition of B. schmidtii seedlings was accompanied by a significant decrease in net photosynthesis measured as $CO_2$ assimilation. Apparent quantum yield and carboxylation efficiency were also affected by Cd treatment, undergoing a significant and progressive reduction with increasing Cd concentrations in all families. We also found significant difference among three families of B. schmidtii in growth, biomass and photosynthesis when exposed to Cd stress. Therefore the present study showed that the difference in Cd tolerance among families might be attributed to genetic factor in response to Cd stress.

• Korean Journal of Agricultural and Forest Meteorology
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• v.12 no.3
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• pp.173-182
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• 2010

This study was conducted to investigate ozone sensitivity of physiological indicators and the difference in ozone tolerance of 8 families of Sophora japonica seedlings on the basis of the standardized physiological indicators. After ozone treatment, photosynthetic parameters, photosynthetic pigments and malondialdehyde (MDA) content, and antioxidative enzyme activities were analyzed from the leaves of S. japonica seedlings. Ozone tolerance indices among 8 families were calculated with the standardized physiological parameters. In addition, the reduction of carboxylation efficiency and apparent quantum yield were observed in the leaves of seven families, except for family No. 6 and 7, respectively. The apparent quantum yield varied from -27% to -61% of the control seedlings. Photosynthetic pigment content differed significantly among 8 families, but was not affected significantly by ozone treatment. Superoxide dismutase (SOD) activity increased from 7% to 64% after ozone exposure, and significant difference existed among 8 families. Ascorbate-peroxidase (APX) activity of 8 families increased by ozone treatment, and the activity of family No. 7 showed the highest increase (218%) in comparison to their respective control plants. On the basis of the standardized indices, family No. 6 showed the lowest tolerance by indicating higher reduction of both photosynthetic parameters and pigment content and lower increase of antioxidative enzyme activities. On the contrary, family No. 7 showed the highest tolerance as indicated by lower reduction of photosynthetic parameters, higher amounts of photosynthetic pigments, and higher enzyme activity.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.262-267
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• 2016

In this study, we present an excellent approach for easily and uniformly immobilizing Pt, Au and bimetallic PtAu nanoparticles (NPs) on a multi-walled carbon nanotube (MWNT)-coated layer through dry plasma reduction. The NPs are stably and uniformly immobilized on the surface of MWNTs and the nanohybrid materials are applied to counter electrode (CE) of dye-sensitized solar cells (DSCs). The electrochemical properties of CEs are examined through cyclic voltammogram, electrochemical impedance spectroscopy, and Tafel measurements. As a result, both electrochemical catalytic activity and electrical conductivity are highest for PtAu/MWNT electrode. The DSC employing PtAu/MWNT CE exhibits power conversion efficiency of 7.9%. The efficiency is better than those of devices with MWNT (2.6%), AuNP/MWNT (2.7%) and PtNP/MWNT (7.5%) CEs.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.1
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• pp.22-28
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• 2014

This study was conducted to investigate the photosynthetic characters of Populus alba${\times}$glandulosa cuttings in response to elevated $CO_2$ concentration and air temperature for selecting tree species adaptive to climate change. The cuttings were grown in environment controlled growth chambers with two combinations of $CO_2$ concentration and air temperature conditions: (i) $22^{\circ}C$ + $CO_2$ 380 ${\mu}mol$ $mol^{-1}$ (control) and (ii) $27^{\circ}C$ + $CO_2$ 770 ${\mu}mol$ $mol^{-1}$ (elevated) for almost three months. The cuttings under the elevated treatment showed reduced tree height and photosynthetic pigment contents such as chlorophyll and carotenoid. In particular, the elevated treatment resulted in a marked reduction in the chlorophyll a closely associated with $CO_2$ fixative reaction system. Different levels of reduction in photosynthetic characters were found under the elevated treatment. A decrease was noted in photochemical reaction system parameters: net apparent quantum yield (7%) and photosynthetic electron transport rate (14%). Moreover, a significant reduction was obvious in $CO_2$ fixative reaction system parameters: carboxylation efficiency (52%) and ribulose-1,5-bisphosphate(RuBP) regeneration rate (24%). These results suggest that the low level of photosynthetic capacity may be attributed to the decreased $CO_2$ fixative reaction system rather than photochemical reaction system.

• Computational Structural Engineering
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• v.4 no.1
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• pp.73-82
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• 1991

Recently, the finite element method has been sucessfully extended to treat the rather complex phenomena such as nonlinear buckling problems which are of considerable practical interest. In this study, a finite element program to evaluate the elasto-plastic buckling stress is developed. The Stowell's deformation theory for the plastic buckling of flat plates, which is in good agreement with experimental results, is used to evaluate bending stiffness matrix. A bifurcation analysis is performed to compute the elasto-plastic buckling stress. The subspace iteration method is employed to find the eigenvalues. The results are compared with corresponding exact solutions to the governing equations presented by Stowell and also with experimental data due to Pride. The developed program is applied to obtain elastic and elasto-plastic buckling stresses for various loading cases. The effect of different plate aspect ratio is also investigated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.27-27
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• 2003

최근 탄소나노튜브를 전계방출 표시소자(FED, field omission display)용 에미터 재료로 사용한 캐소드 개발에 대한 연구가 활발히 진행되고 있다. 캐소드전극으로는 투명전도성 반도체 박막인 ITO를 사용하고, 에미터용 재료로는 탄소나노튜브를 사용해서 스크린 인쇄법으로 2극(diode type)형 전계방출 소자용 캐소드를 제작하였다. 본딩재(bonding materials)의 종류와 공정변수를 달리해서 에미터용 탄소나노튜브와 ITO 캐소드 전극 사이의 전기적 접촉방법을 변화시켰을때 탄소나노튜브 캐소드의 전계방출 특성을 체계적으로 연구하였다. 첫째로, 본딩재의 전기전도성 (electrical conductivity)을 변수로 해서 탄소나노튜브 에미터의 전계강화(fold enhancement) 효과를 연구한 결과 본딩재의 구성 성분중 부도체(insulator)의 분율이 높을수록 전계강화 효과가 크게 나타남을 확인하였다. 두 번째로, ITO박막 캐소드전극과 탄소나노튜브 잉크 사이에 중간층(inter layer)을 형성시켜서 중간층이 전계방출 특성에 미치는 영향을 연구하여, 중간층의 존재가 탄소나노튜브의 전계방출 전류의 균일성과 전류밀도의 증가에 기여하는 것을 확인하였다. 본 연구의 결과 전계방출 전류가 안정적이면서 동시에 전계방출 효율이 크게 개선된 탄소나노튜브 캐소드를 제작하는 공정기술이 개발되었다. 개발된 기술은 기존의 방법에 비해서 탄소나노튜브 캐소드의 진공패키징시 아웃개싱(outgassing)의 양도 현격하게 작았으며, 에미터와 캐소드 전극 사이의 본딩력(adhesion)도 우수해서 항후 탄소나노튜브 전계방출 표시소자의 개발에 크게 기여할 것으로 판단된다.luminum 첨가량이 증가함에 따라 세라믹 수율도 증가하였음을 확인하였다. 합성된 aluminum-contained polycarbosilane은 20$0^{\circ}C$에서 1시간 동안 불융화과정을 거쳐 환원 및 진공 분위기에서 고온 열처리하였으며 이로부터 얻어진 시료에 대해 XRD분석을 수행하였다. SEM과 TEM을 이용하여 미세구조를 관찰하였다./100 duty로 구동하였으며, duty비 증가에 따라 pulse의 on-time을 고정하고 frequency를 변화시켰다. dc까지 duty비가 증가됨에 따라 방출전류의 양이 선형적으로 증가하였다. 전압을 일정하게 고정시키고 각 duty비에서 시간에 따라 방출전류를 측정한 결과 duty비가 높을수록 방출전류가 시간에 따라 급격히 감소하였다. 각 duty비에서 방출전류의 양이 1/2로 감소하는 시점을 에미터의 수명으로 볼 때 duty비 대 에미터 수명관계를 구해 높은 duty비에서 전계방출을 시킴으로써 실제의 구동조건인 낮은 duty비에서의 수명을 단시간에 예측할 수 있었다. 단속적으로 일어난 것으로 생각된다.리 폐 관류는 정맥주입 방법에 비해 고농도의 cisplatin 투여로 인한 다른 장기에서의 농도 증가 없이 폐 조직에 약 50배 정도의 고농도 cisplatin을 투여할 수 있었으며, 또한 분리 폐 관류 시 cisplatin에 의한 직접적 폐 독성은 발견되지 않았다이 낮았으나 통계학적 의의는 없었다[10.0%(4/40) : 8.2%(20/244), p>0.05]. 결론: 비디오흉강경술에서 재발을 낮추기 위해 수술시 폐야 전체를 관찰하여 존재하는 폐기포를 놓치지 않는 것이 중요하며, 폐기포를 확인하지 못한