• Journal of the Korean Chemical Society
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• v.24 no.2
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• pp.115-120
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• 1980

A kinetic study of the methanolysis of t-butylbromide and benzoylchloride in methanol-acetonitrile mixtures is reported. First order rate constants for the methanolysis of t-butyl bromide show maximum at $X_{MeOH}$=0.75∼0.9 and 25∼$50^{\circ}C$. Apparent second order rate constants for the methanolysis of benzoylchloride also show maximum at $X_{MeOH}$= 0.6∼0.95 and 12∼$26^{\circ}C$. The maximum rate is ascribed to the solvent structure change; the addition of acetonitrile to methanol perturbs the methanol structure increasing the free methanol molecules available to stabilize the transition state for the methanolysis of t-butylbromide and benzoylchloride. It has been shown that methanol acts as nucleophilic and electrophilic catalyst upon methanolysis of t-butylbromide and as electrophilic catalyst upon methanolysis of benzoylchloride.

• Journal of Climate Change Research
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• v.1 no.1
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• pp.31-50
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• 2010

The Arctic climate change for the Last Glacial Maximum(LGM) occurred at 21,000 years ago (21ka) was investigated using simulation results of atmosphere-ocean coupled models from the second phase of the Paleoclimate Modelling Intercomparison Program(PMIP2). In the analysis, we used seven models, the NCAR CCSM of USA, ECHAM3-MPIOM of German Max-Planxk Institute, HadCM3M2 of UK Met Office, IPSL-CM4 of France Laplace Institute, CNRM-CM3 of France Meteorological Institute, MIROC3.2 of Japan CCSR at University of Tokyo, and FGOALS of China Institute of Atmospheric Physics. All the seven models reproduces the Arctic climate features found in the present climate at 0ka(pre-industrial time) in a reasonable degree in comparison to observations. During the LGM, the atmospheric $CO_2$ concentration and other greenhouse gases were reduced, the ice sheets were expanded over North America and northern Europe, the sea level was lowered by about 120m, and orbital parameters were slightly different. These boundary conditions were implemented to simulated LGM climate. With the implemented LGM conditions, the biggest temperature reduction by more than $24^{\circ}C$ is found over North America and northern Europe owing to ice albedo feedback and the change in lapse rate by high elevation. Besides, the expansion of ice sheets leads to the marked temperature reduction by more then $10^{\circ}C$ over the Arctic Ocean. The temperature reduction in northern winter is larger than in summer around the Arctic and the annual mean temperature is reduced by about $14^{\circ}C$. Compared to low mid-latitudes, the temperature reduction is much larger in high northern altitudes in the LGM. This results mirror the larger warming around the Artic in recent century. We could draw some information for the future under global warming from the knowledge of the LGM.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.341-345
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• 2018

우리나라는 전 국토의 70%가 산지이고 하천경사가 다른 나라에 비해 상대적으로 급하여 홍수 관리에 매우 불리한 조건을 가지고 있으며, 특히 홍수기간의 집중호우 및 돌발홍수는 인명과 재산의 막대한 피해를 입히고 있다. 최근은 기후변화로 인하여 극심한 홍수, 가뭄 등 재해의 발생빈도가 증가하는 추세로 기후변화의 영향을 최소화할 수 있는 수재해 방재관리가 필요한 상황이다. 중 대하천의 경우에는 비교적 수재해 방재관리가 잘 이루어지고 있으나, 소하천(일부 중하천 포함)의 경우에는 취약한 구조를 보이고 있다. 특히 홍수기간(7월~9월)의 인명과 재산의 피해는 주로 소하천 위주로 발생하고 있으며, 사전 사후의 체계적인 대응이 이루어지지 못하고 있다. 수재해 방재관리를 위해서는 일차적으로 수문자료의 획득에 있으며, 그 이후 해당 유역에 적합한 수재해 대응을 위한 체계적인 방법론과 방재시스템 개발 운영이 수반되어야 안전한 방재관리를 할 수 있다. 따라서 수재해 방재관리 체계를 구축하기 위해서는 중 소규모 유역 단위를 대상으로 지속적이고 신뢰성 있는 자료의 획득과 축적이 중요하므로 중 소규모 유역 단위의 대표성 있는 시험유역의 운영은 매우 의미가 있다고 볼 수 있다. 본 논문에서는 한국건설기술연구원에서 운영하는 차탄천 유역(유역면적 $190.64km^2$, 유로경사 0.96%, 경기도 연천군 소재)의 신뢰성 높은 2017년 관측자료를 이용하여 강우특성, 유출특성, 증발산량 등 수문특성을 분석하였으며, 과거 관측결과와 비교하였다. 강우특성 분석으로는 호우사상 분리, 주요 호우사상 분석, 지속기간별 최대강우량, 시간분포 등이 있다. 2017년은 2016년보다 최대 강우지속기간과 평균 강우지속기간은 크게, 최대 강우강도는 작게, 평균 강우강도는 크게 나타나는 호우의 특징을 보이고 있다. 2017년의 하천유출률은 강우량 대비 53.1%(장진교, 유역출구)와 60.4%(보막교, 중간소유역)로 과거 5년간의 평균 유출률인 장진교(52.4%)와 4년간의 평균유출률인 보막교(58.8%)와 비슷한 값을 보인다. 강우유출특성 분석결과 연간 강우량은 다소 적었지만, 평균 강우강도의 증가에 기인하여 2017년의 연간 하천유출량은 2016년보다 장진교는 약 39.5%의 증가와 보막교는 약 2.9% 감소가 하였다. 수문학적 동질성 갖는 유역에서 하천유출량의 차이는 강우량 발생 시기(2016년의 경우는 10월에 215.7mm의 강우량 발생)와 토지이용(중 하류부 농경지 발달)의 차이에 기인한다고 볼 수 있다. 그리고 2017년의 증발산량은 강우량 대비 장진교는 38.4%, 보막교 35.1%로 2016년 장진교의 50.1%보다는 감소하고, 보막교의 35.4%와는 비슷한 값을 보인다. 온도, 습도, 풍속, 일조시간에 영향을 받는 증발산량은 2016년 대비 기온(일최고/일최저)의 감소(90.6%) 습도(일최대/일평균/일최저)의 감소(98.5%), 일평균 풍속의 감소(54.7%)에 기인하여 적은 증발산량을 보이는 것으로 분석되었다. 이와 같이 산정된 수문자료는 수재해 방재를 위한 기초자료로 매우 유용하게 활용되므로 지속적인 시험유역의 운영은 매우 필요하다.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.879-884
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• 2012

In this present study, Aspergillus niger NRRL 567 was cultivated on an inert support material and the effects of various fermentation parameters including temperature, nutrient solution pH, inoculation level, and moisture content were observed and optimized by one-factor-at-a-time (OFAT) and response surface methodology (RSM), sequentially. It was found that the incubation temperature of $30^{\circ}C$ with 75% moisture content, nutrient solution pH of 7.1 and inoculation level of $4.0{\times}10^6$ spores/ml were the most favorable. Again, fermentation parameters were optimized using RSM. The determined optimum condition is $26.5^{\circ}C$, pH 9.9, 75.1%, and $6.0{\times}10^6$ spores/ml. Under this optimized condition, A. niger NRRL 567 produced 118.8 g citric acid/kg dry peat moss at 72 hr. Maximum citric acid production of optimized condition by RSM represented a 1.6-fold increase compared to that obtained from control experiment.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.315-319
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• 2016

This study examined the optimization of hot-water extraction conditions for maximizing the total polyphenol compounds (TPC) extracted from amaranth leaf. The effects of three independent variables, including extraction temperature, extraction time and ethanol concentration on TPC were investigated using central composite design (CCD). The concentration of TPC increased with increased levels of extraction temperature and time. The extraction temperature and the ethanol concentration showed the significant effect on TPC production (p<0.05). The predicted values at the optimized condition were acceptable when compared to the experimental values ($R^2=0.9566$). The optimum extraction conditions were as follows: temperature of $90.1^{\circ}C$, time of 50 min and ethanol concentration of 61.6% (v/v) for the maximum TPC of 12.6 mg GAE/g DM.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.659-672
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• 1997

Thermal response induced from nonlinear temperature distribution in composite box gilder bridges depends on several variables(environmental conditions, physical and material properties, location and orientation of bridge, and cross-section geometry). In this paper, parametric study are conducted in order to find the effects of variations of seasons, location and orientation of bridge, sectional geometry and some material properties on the axial deformation, curvature and stresses in composite box girder bridge. A two-dimensional transient finite element model to conduct this parametric studies is briefly presented. Firstly, the effects of the parameters on the diurnal variation of curvature are considered, and for the time of maximum curvature, on the distribution of temperature and stresses of composite box girder sectional are considered. Finally, some considerations about the influence of the parameters on the daily maximum values of axial deformation, curvature and stresses are carried out. The influence of thermal effect on structures is important as much as the influence of live or dead load in some cases. In the design of steel composite bridges, the thermal stresses calculated on the supposition that the temperature difference between the concrete slab and steel girder is $10^{\circ}C$ and the temperature distributions are uniform in concrete slab and steel girder can be underestimated.

• Korean Journal of Food Science and Technology
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• v.18 no.5
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• pp.372-375
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• 1986

The temperature dependence of the cooking rate of soybean cotyledon was investigated by cooking samples at $106^{\circ}C-121^{\circ}C$ and by measuring the maximum cutting force. The cooking of soybean followed a first-order reaction and the reaction rate constant was approximately doubled by increase of cooking temperature by 4 or $5^{\circ}C$. The z-value for softening of the soybean, which was calculated from the time-temperature combinations that gave the same degree of cooking, was $13.3^{\circ}C$.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.43-48
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• 2002

In this study, high performance electrode catalyst was developed in fabrication of membrane electrode assembly for PEMFCs(Polymer Electrolyte Membrane Fuel Cells). The I-V characteristics were measured to evaluate the influence of Nafion solution and Pt loading amount in the catalyst composition. The electrode characteristics were also investigated with respect to temperature change. The electrode performance was optimized at Nafion 5 wt% and 0.5 mg Pt/$\textrm{cm}^2$ content. The increase in the concentration of Nafion solution resulted in the decrease in electrode performance. At $80^{\circ}C$ of unit cell, I-V characteristics excelled those obtained at lower temperature. There was no difference in performance at low current density, but the improvement of voltage value in higher temperature could be found at high current density.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1030-1035
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• 2012

In this research, we analysed design and CFD analysis of an inflow radial turbine for OTEC with an output power of 8kW using an working fluid of ammonia. The inflow radial turbine consists of scroll casing, vain nozzle with 18 blade numbers and rotor blade with 13 blade numbers. Mass flow rate, and inlet temperature are 0.5kg/s and $25^{\circ}C$ respectively, and variable rotational speeds were applied between 12,000 and 36,000 with 3,000 rpm intervals. As the results according to the rotational speeds, the designed speed is 24,000 rpm where maximum efficiency exists. The maximum efficiency and output power are 88.66% and 8.52kW, respectively. Through this study, we expect that the analysed results will be used as the design material for the composition of the turbine optimal design parameters corresponding to the target output power under various working material conditions.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.4
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• pp.408-415
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• 1986

This study was conducted to define the effects of light transparent rate of the shading on the photosynthesis ability of the ginseng leaves and their seasonal changes. Regardless the effects of light transparent rate of shading and age of ginseng plant, 10,000 lux was the most adequate light intensity for the maximum photosynthesis of ginseng leaves and seasonal difference was not significant. The ginseng plants which were grown under 10 to 15 percent light transparent shading showed the highest photosynthesis ability. The photosynthesis ability of ginseng leaves was significantly decreased in September than June and the decreasing rate was higher at the ginseng plants planted on back rows than front rows. In June, the ginseng plants grown under 10 to 15 percent light transparent shading showed high respiration amount but in September, those grown under 20 to 25% light transparent shading showed the highest respiration. The amount of chlorophyll of ginseng leaf was significantly decreased by increasing light transparent rate of shading.