• 한국물환경학회지
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• 제23권5호
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• pp.776-780
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• 2007

A biofilm reactor packed with porous media was investigated for nitrogen removal of synthetic wastewater. The effect of different loading rates on the nitrification was sustained to be steady state with stable efficiency of 50~60% in the range of $0.0083{\sim}0.017gNH_4-N/gMLVSS{\cdot}day$ of F/MN ratio and $1{\sim}2kgNH_4-N/m^3{\cdot}day$ of media volumetric loading rate. However, nitrification efficiency was rapidly decreased to 25~30% as F/MN ratio and media volumetric loading rate were increased to the range of $0.025{\sim}0.034gNH_4-N/gMLVSS{\cdot}day$ and $3{\sim}4kgNH_4-N/m^3{\cdot}day$, respectively. Also the consumption rate of alkalinity was higher under 8 hours of HRT than unter 6 hours of HRT. Accordingly the influent loading rate variation by detention time with influent flow influenced more on the nitrification efficiency than the influent loading rate variation by the influent concentration did. The temperature effect on the nitrification showed 25% higher in summer than in winter as the results reported by other researchers who reported that the nitrification efficiency in biofilm showed 20% increase from 55% to 75% when the temperature was raised from $20^{\circ}C$ to $25^{\circ}C$. Denitrification with sulfur-media showed 90% removal efficiency under steady-state with no effect from the increase of influent concentration and empty bed contact time (EBCT) change such as EBCT was decreased from 8.4 hr to 4.3 hr and $NO_3-N$ loading rate was changed within the range of $0.1{\sim}0.4kgNO^3-N/m^3{\cdot}day$. Accordingly Denitrification with sulfur-media is feasible for post denitrification at the concentration less than $80mgNO^3-N/L$.

• 한국응용과학기술학회지
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• 제28권1호
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• pp.85-94
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• 2011

Expanded graphites were used as anode materials of high power Li-ion secondary battery. The expanded graphite was prepared by mixing the graphite with $HClO_4$ as a intercalation agents and $KMnO_4$ as a oxidizing agents. The physical and electrochemical properties of prepared expanded graphites through the variation of process variables such as contents of intercalation agent and oxidizing agent, and heat treatment temperature were analyzed for determination of optimal conditions as the anode of high power Li-ion secondary battery. After examing the electrochemical properties of expanded graphites at the different preparing conditions, the optimal conditions of expanded graphite were selected as 8 wt.% of oxidizing agent, 400 g of intercalation agent for 20 g of natural graphite, and heat treatment at $1000^{\circ}C$. The sample showed the improved charge/discharge characteristics such as 432 mAh/g of initial reversible capacity, 88% of discharge rate capability at 10 C-rate, and 24 mAh/g of charge capacity at 10 C-rate. However, the expanded graphite had the problems of potential plateaus like natural graphite and lower initial efficiency than the natural graphite.

• Journal of Plant Biology
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• 제28권2호
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• pp.119-126
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• 1985

Sargassum confusum을 대상으로 동해안 오호리 지역에서 1983년 3월 부더 1984년 4월까지 이 종의 생장 및 일차생산력을 조사하였다. S. confusum은 2월에 생장하기 시작하여 여름에 최대생장을 나타낸 후 빠른 속도로 쇠퇴하는 생육주기를 가진다. 생식활동은 6월에 주로 이루어 진다. 이러한 생장양상은 수온과 밀접한 관제를 갖는다. 최대성장율은 5월의 1.3cm/day이며 최대길이는 8월의 120cm이다. 산소명암병법으로 측정된 S. confusum의 일순생산력은 6월에 11.2 gC/dry wt/day이며 이를 기초로 추정한 연생산력은 745 gC/$m^2$/yr이다. 한편 현존량의 변화에만 의존하여 추정된 연생산력은 745 gC/$m^2$/yr로서 탈락에 의한 손실이 약 60%에 달하고 있다.

• Journal of Biosystems Engineering
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• 제34권2호
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• pp.106-113
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• 2009

This study was carried out to test feasibility of a granule fertilizer applicator for rapeseed seeding in paddy fields. The metering plate of a conventional applicator was modified for rapeseed seeding. The modified plate had new three seeding openings with total area of $342mm^2$. Average target discharging rates ranged from 6.3 to 21.0 g/s and correlated with opening areas. Application patterns of the rapeseed seeding showed M-shape. The coefficients of variation of the application showed 70.5% at 0.99 m/s of forwarding speed and 14.3 g/s of a discharge rate, and 77.7% at 1.72 m/s of a forwarding speed and 8.23 g/s of a discharge rate. The coefficients of variation in the direction of transverse of the tractor ranged from 7.3 to 47.7%. In rapeseed seeding tests using the applicator, seed damages rates were less than 15% due to the agitator, the seed hopper and the seeding plate break. Therefore, improvements of the applicator blow heads and seeding equipments were required in order to apply rapeseed efficiently.

• 한국물환경학회지
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• 제24권5호
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• pp.550-555
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• 2008

This study was conducted to assess the growth characteristics of phytoplankton and to understand seasonal dynamics of phytoplankton in response to limiting nutrients in an agricultural reservoir from November 2002 to December 2003. Marked increase of chl.a concentration observed in July ($99.0{\mu}g/L$) and November ($109.7{\mu}g/L$) after heavy rainfall. TP concentration ranged $48.0{\sim}126.6{\mu}g/L$, and its the temporal variation was similar to that of chl.a concentration. Microcystis spp., dominant phytoplankton species were used for the growth kinetics experiment, except for the season when Aulacoseira spp. (March, April) and Aphanocapsa sp. (May) dominated. In the temperature range between $10{\sim}25^{\circ}C$, the rate of growth increase per $10^{\circ}C$ was almost two folds. The highest maximum growth rate (${\mu}_{max}=1.09day^{-1}$) of phytoplankton observed September, and ${\mu}_{max}$ was lowest ($0.34day^{-1}$) in March when Aulacoseira spp. dominated. The ${\mu}_{max}$ ($0.78{\pm}0.20day^{-1}$) was relatively high in the summer season when water temperature is above $20^{\circ}C$ and cyanobacteria dominated compared to the spring when diatoms dominated ($0.43{\pm}0.08day^{-1}$). The maximum growth rate ($0.55{\pm}0.12day^{-1}$) and the half saturation concentration ($K_s=0.73{\pm}0.15{\mu}M$) of cyanobacteria during winter season (November, December) was higher than those of diatoms. However, the ${\mu}_{max}$ and $K_s$ of cyanobacteria in December was similar to those of diatom, reflecting that diatom cell quota (Mean 48.4 pgP/cell) was greater than cyanobacteria (34.0 pgP/cell) during this time.

• 소성∙가공
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• 제16권5호통권95호
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• pp.354-359
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• 2007

Effects of forging and mechanical properties of 6061 aluminum alloy wheel for automobiles were investigated in the present study. Microstructural and tensile characteristics of automobile wheel after hot forging process using dynamic screw press were analyzed to evaluate effect of metal flow on mechanical properties. The results showed advanced mechanical properties of 6061 alloy wheel because of $Mg_2Si$ precipitation by T6, elongated grain by forging, and work hardening by dense metal flow, etc. Hot compression tests were conducted in order to characterize high temperature compression deformation behaviors and microstructural variation in the range of $300{\sim}450^{\circ}C$, in the strain rate range of $10^{-3}{\sim}10^1\;sec^{-1}$. As strain rate increased, maximum compression stress increased but it was shown the reverse linear relation between temperature and maximum stress irrelevant to strain rate variation. On the other hand, temperature and yield stress didn't have any linear relation and its relation showed big deviation by a function of strain rate and test temperature.

• 한국세라믹학회지
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• 제27권3호
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• pp.401-411
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• 1990

Deposition of diamond films on Si(100) from the mixtures of methane and hydrogen were investigated using hot W filament CVD method. The nucleation density could be increased thousandfold by surface treatment with SiC powder. Upon oxygen addition to the mixture, crystal facets became developed more clearly by selectively removing non-diamond carbons, but the film growth rate generally decreased. However, at a very high methane content(e.g. 10%), a small amount of oxygen addition has resulted in an increase in the film deposition rate presumably by promotion of methane decomposition. When the gas pressure was varied, the growth rate exhibited a maxiumum at around 20torr and the film crystallinity steadily improved with the pressure increase. The observed variation of the growth rate by oxygen addition was discussed in terms of its role in the pyrolysis and the subsequent gas phase reactions.

• 한국농림기상학회지
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• 제7권1호
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• pp.57-65
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• 2005

토양은 리터의 축적, 분해, 뿌리호흡을 포함하는 토양호흡을 통해 많은 양의 탄소를 저장 또는 방출할 수 있다. 이러한 토양의 주요한 탄소 및 양분의 공급원은 낙엽낙지의 유입과 유입된 낙엽낙지의 분해이며 생태계로 돌아가는 영양의 약 60%가 낙엽에서 유래되는 것으로 알려져 있다. 본 연구의 목적은 천연자연림으로 잘 보존된 경기도 광릉시험림의 온대낙엽활엽수림의 리터 생산량과 분해속도가 토양호흡의 계절적 변 이에 미치는 영향을 파악하고 낙엽층과 토양호흡간의 관련성을 찾아 생태계에서의 탄소순환을 이해하기 위한 것이다. 광릉 낙엽활엽수림에서 2003년 생산된 리터의 총량은 1489 Cm/sup -2/ yr/sup -1/ 이었으며 조사지의 우점종인 졸참나무, 서어나무, 까치박달의 순수 낙엽의 총량은 1189 Cm/sup -2/ yr/sup -1/이었다. 낙엽의 분해율은 조사기간인 1년 동안 졸참나무는 24.2%(k = 0.28), 서어나 무는 25.7％(k = 0.30), 까치박달은 33.0%(k = 0.46)이었 다. AOCC를 이용한 연속적인 토양호흡 측정결과 연간 토양호흡량은 629.69 Cm/sup -2/ yr/sup -1/이었으며 이 중 리터 분해가 차지하는 비율은 약 5％인 309 Cm/sup -2/ yr/sup -1/이었다. 토양호흡의 동절기 최저값은 7.4±1.4g Cm/sup -2/ month/sup -1/ 이었으며 이 시기의 리터 분해속도도 0.8g Cm/sup -2/ month/sup -1/로 최저값을 나타내었다. 하절기에는 토양 호흡과 리터 분해속도 모두 증가하여 111.5 ± 16.2g Cm/sup -2/ month/sup -1/와 11.4g Cm/sup -2/ month/sup -1/로 최고값을 보였다. 토양호흡 중 리터 분해속도가 차지하는 비율은 식물 지하부의 생장이 활발해지는 5-6월에는 4.3%로 감소하였으며 리터의 생산량이 증가하는 11- 12월에는 23.5%로 증가하였다. 회귀분석결과 리터 분해속도와 토양호흡과는 r²= 0.63의 상관관계를 가지고 있었다.

• 공업화학
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• 제10권5호
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• pp.682-689
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• 1999

본 연구는 용융법에 의한 폴리아미드 6,6과 EPM 및 EPM-g-MA와 블렌딩시 탄성 중합체 함유량, 조성비(wt %), 혼합온도, 혼합속도 등의 변화에 따른 이성분 PA 6,6/EPM(or EPM-g-MA) 블렌드물과 삼성분 PA 6,6/EPM/EPM-g-MA 블렌드물을 제조하여 블렌드물 내 탄성 중합체 평균 입자 크기, 입자 형상 및 분포 등의 변화를 분석하고, 이에 따른 블렌드물의 기계적, 열적 특성에 미치는 영향을 고찰하였다. 본 연구결과, 혼합속도 250 rpm하에서 압출기 내 다섯 영역의 온도를 270, 265, 265, 255 및 $255^{\circ}C$로 변화시켜 탄성 중합체의 함유량 변화에 의하여 제조된 이성분 블렌드물중 높은 충격강도는 PA 6,6/EPM-g-MA(70/30) 블렌드물에서 확인되었으며 폴리아미드 6,6의 충격강도에 비하여 25배 증가하였다. 동일한 압출기 내 조건하에서 제조된 삼성분 블렌드물 중 PA 6,6/EPM/EPM-g-MA(70/15/15) 블렌드물 내 탄성 중합체 평균 입자크기는 $0.56{\mu}m$이면서 고른 입자분포를 나타내었으며 충격강도는 제조된 모든 블렌드물 중 가장 높았다. 이러한 블렌드물의 조성비하에서 혼합온도와 혼합속도 변화에 의하여 제조된 블렌드물의 기계적 특성과 블렌드물 내 탄성 중합체 분산정도는 감소하였다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.226-226
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• 2015

The complex climate system regarding human actions is well represented through global climate models (GCMs). The output from GCMs provides useful information about the rate and magnitude of future climate change. Especially, the temperature variable is most reliable among other GCM outputs. However, hydrological variables (e.g. precipitation) from GCM outputs for future climate change contain too high uncertainty to use in practice. Therefore, we propose a method that simulates temperature variable with increasing in a certain level (e.g. 0.5oC or 1.0oC increase) as a global warming scenario from observed data. In addition, a hydrometeorological variable can be simulated employing block-wise sampling technique associated with the temperature simulation. The proposed method was tested for assessing the future change of the seasonal precipitation in South Korea under global warming scenario. The results illustrate that the proposed method is a good alternative to levy the variation of hydrological variables under global warming condition.