• 한국자동차공학회논문집
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• 제12권2호
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• pp.17-23
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyze the heat quantity of homogeneous charge methane-air mixture under various initial pressures, excess air ratios and ignition times. As the overall pressure increase, the values of maximum combustion pressure, maximum heat release rate and cumulative heat release have been increased. But it is not very meaningful to compare with some values such as maximum combustion pressure, maximum heat release rate and cumulative heat release for different overall pressure due to the different heat energy of supplied fuel. So the each value is needed to be compared with normalized value, which is divided by the entered fuel energy. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. As the overall pressure increase, the CHR ratios and the UHC ratios have been decreased, while the HL ratios have been increased. The CHR ratio of 300 ms has the higher value than that of 10000ms, and the HL ratios of 300 ms have a lower value.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.141-144
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• 2006

In this study, the friction and wear characteristics of pure epoxy and silica-filled epoxy resin composites with average silica particle diameter of $6-33{\mu}m$ were investigated at ambient temperature by pin-on-disc friction test. The cumulative wear volume, friction coefficient and wear rate of these materials against SiC abrasive paper were determined experimentally. The cumulative wear volume tended to increase nonlinearly with increase of sliding distance and depended on diameter of the silica particle for all these composites. The sliding wear tests of the materials demonstrated that the friction coefficient and the wear rate of silica filled epoxy composites were lower than those of the pure epoxy. silica filled epoxy.

• 수산해양기술연구
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• 제50권2호
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• pp.162-168
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• 2014

The friction and wear characteristics of the rubber matrix composites filled with nano sized silica particles were investigated at ambient temperature by pin-on-disc friction test. The volume fraction of silica particles was 19%. The cumulative wear volume and wear rate of these materials on counterpart roughness were determined experimentally. The major failure mechanisms were lapping layers, deformation of matrix, ploughing, debonding of particles, fracture of particles and microcracking by scanning electric microscopy photograph of the tested surface. The cumulative wear volume showed a tendency to increase with increase of sliding distance. The wear rate of these composites tested indicated low value as increasing the sliding distance.

• 수산해양기술연구
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• 제44권3호
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• pp.250-256
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• 2008

Generally the side plate materials of FRP ship are composed of glass fiber and unsaturated polyester resin composites(GFRP composites). In this study, the effect of applied load and sliding speed on friction and wear characteristics of these materials were investigated at ambient temperature by pin-on-disc friction test. The cumulative wear volume, friction coefficient and wear rate of these materials for SiC abrasive paper were determined experimentally. The cumulative wear volume showed a tendency to increase nonlinearly with increase of sliding distance and was dependent on applied load and sliding speed for these composites. The friction coefficient of GFRP composites was increased as applied load increased at same sliding speed in wear test. It was verified by SEM photograph of worn surface that major failure mechanisms were microfracture, deformation of resin, cutting and cracking.

• 한국해양공학회지
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• 제22권6호
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• pp.35-40
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• 2008

The effect of counterpart roughness on abrasive wear characteristics of side plate materials of FRP ship, which were composed of glass fiber and unsaturated polyester resin composites, were investigated at ambient temperature by pin-an-disc friction test. The friction coefficient, wear rate and cumulative wear volume of these materials against SiC abrasive paper were determined experimentally. The wear rate of these materials decreased rapidly with sliding distance and then maintained a constant value. It was increased as counterpart roughness was rougher in a wear test. The cumulative wear volume tended to increase nonlinearly with sliding distance and depended on applied load and sliding speed for these composites. It could be verified by SEM photograph of fracture surface that major failure mechanisms were overlapping layers, microcutting, deformation of resin, delamination, and cracking.

• Asian-Australasian Journal of Animal Sciences
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• 제16권8호
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• pp.1151-1157
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• 2003

The surfactant Tween 80 was evaluated for its ability to influence cumulative gas production, cellulose digestion, and enzyme activities by mixed ruminal microorganisms grown on barley grain or Orchardgrass hay. The addition of Tween 80 at a level of 0.10% significantly (p<0.05) decreased the cumulative gas production rate from both barley grain or Orchardgrass hay substrates. However, 0.05% Tween 80 did not affect gas production rates compared to the control treatment. The addition of 0.05% Tween 80 to cultures growing on barley grain resulted in a significant increase in cellulase (90.01%), xylanase (90.73%) and amylase (487.25%) activities after 30 h incubation. Cultures utilizing Orchardgrass hay had a significant increase in cellulase (124.43%), xylanase (108.86%) and amylase (271.22%) activities after 72 h incubation. These increases in activities were also observed with cultures supplemented with 0.10% Tween 80 throughout all the incubation times tested. These results indicated that the addition of 0.05% Tween 80 could greatly stimulate the release of some of key enzymes without decreasing cell growth rate in contrast to trends reported with aerobic microorganism. Our data indicates potential uses of the surfactant Tween 80 as a feed additive for ruminant animals.

• 부동산연구
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• 제28권1호
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• pp.115-130
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• 2018

본 연구에서는 주택연금 해지비율이 높아져 가는 추세에 따라 주택연금 해지에 영향을 미치는 요인을 좀 더 세분화하여 알아보고자 한다. 또한, 담보주택 가격대별로 해지사유와 해지비율을 비교하기 위해 가격구간별 모형을 구성하여 가입자입장에서 담보주택 가격대별로 주택연금 계약 해지에 영향을 미치는 요인에 있어서의 차이를 확인한다. 실증분석 결과, 가입 시의 담보주택가격의 초과누적상승률이 클수록, 월지급금액이 클수록, 월지급금과 최소노후생활비와의 차이가 클수록, 전월 순인구이동률과 대출금누계가 적을수록, 주택연금 계약을 해지할 확률이 높은 것으로 나타났다. 특히 담보주택의 가격구간대별 주택연금 계약 해지비율의 차이가 커 각 구간대별로 주택연금 계약 해지에 영향을 미치는 요인이 다를 것이며, 이를 확인하고자 담보주택가격구간대별 모형을 구성하여 분석하였다. 분석 결과, 주택연금 가입 고령층의 60%가 가입담보주택의 평균 가격 보다 낮은 가격 수준으로 가입되어 있으며, 각 구간마다 주택연금 계약 해지에 영향을 미치는 요인과 유의미함이 다르다는 사실을 확인하였다. 이에 주택연금 계약 해지율을 증가시키는 리스크에 대한 관리를 적절히 한다면, 사회 전체적으로 주택연금이 확대되어 고령자의 노후소득 확보와 생활의 안정을 제고하고 인구고령화의 충격을 완화해 나갈 수 있는 의미있는 수단이 될 수 있을 것이다.

• Asian-Australasian Journal of Animal Sciences
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• 제13권11호
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• pp.1536-1541
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• 2000

The present study was carried out to measure changes of feed intake and thirst level caused by water deprivation in goats fed on dry feed and to elucidate the relationship between those two parameters. Water deprivation significantly (p<0.01) decreased cumulative feed intake and rate of eating at 30, 60, 90 and 120 min, respectively, after feed presentation. Cumulative feed intake, after completion of 2 h feeding, was reduced by about 20, 21 and 64 % due to water deprivation during feeding for 2 h (WD2), for 22 h (WD22) and for 46 h (WD46), respectively, compared to free access to water (FAW). Compared to the FAW, WD2, WD22 and WD46 increased thirst level by about 5, 5 and 9 times, respectively. Mean thirst level (X, g/30 min) was negatively correlated with cumulative feed intake (Y, g DM) after completion of 2h feeding (Y=1302-0.2 X, $r^2=0.97$, p<0.05). Water deprivation depressed plasma volume and there was a significant positive regression between plasma volume (X, ml) and cumulative feed intake (Y, g DM) after completion of 2h feeding (Y=-1003+0.6 X, $r^2=0.99$, p<0.01). Mean plasma osmolality (X, mOsmol/l) correlated significantly and negatively with cumulative feed intake (Y, g DM) after completion of 2h feeding (Y=27004-84.9 X, $r^2=0.95$, p<0.05). In conclusion, a decrease of feed intake during water deprivation is mainly due to an increase of thirst level quantitatively, and the act of feeding itself induces thirst more than the length of water-deprivation periods in goats fed on dry feeds. The present findings suggest that plasma osmolality and plasma volume which affect thirst level are involved in the decrease of feed intake in water-deprived goats.

• 한국토양비료학회지
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• 제50권6호
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• pp.574-587
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• 2017

Excessive application of nitrogen (N) fertilizer to support switchgrass growth for bioenergy production may cause adverse environmental effects. The objective of this study was to determine optimum N application rate to increase biomass yield of switchgrass and to reduce adverse environmental effects related to N. Switchgrass was planted in May 2008 and biomass yield, N uses of switchgrass, nitrate ($NO_3$) leaching, and nitrous oxide ($N_2O$) emission were evaluated from 2010 through 2011. Total N removal significantly increased with N rate despite the fact that yield did not increased with above $56kg\;N\;ha^{-1}$ of N rate. Apparent nitrogen recoveries were 4.81 and 5.48% at 56 and $112kg\;N\;ha^{-1}$ of N rate, respectively. Nitrogen use efficiency decreased into half with increasing N rate from 56 to $112kg\;N\;ha^{-1}$. Nitrate leaching and $N_2O$ emission were related to N use of switchgrass. There was no significant difference of cumulative $NO_3$ leaching between 0 and $56kg\;N\;ha^{-1}$ but, it significantly increased at $112kg\;N\;ha^{-1}$. There was no significant difference of cumulative $N_2O$ emission among N rates in crest, but it significantly increased at $112kg\;N\;ha^{-1}$ in toe. Excessive N application rate (above $56kg\;N\;ha^{-1}$) beyond plant requirement could accelerate $NO_3$ leaching and $N_2O$ emission in switchgrass field. Overall, $56kg\;N\;ha^{-1}$ might be optimum N application rate in reducing economic waste on N fertilizer and adverse environmental impacts.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.560-570
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• 2006

This paper proposes a selectively cumulative sum (S-CUSUM) control chart with variable sampling intervals (VSI) for detecting shifts in the process mean. The basic idea of the VSI S-CUSUM chart is to adjust sampling intervals and to accumulate previous samples selectively in order to increase the sensitivity. The VSI S-CUSUM chart employs a threshold limit to determine whether to increase sampling rate as well as to accumulate previous samples or not. If a standardized control statistic falls outside the threshold limit, the next sample is taken with higher sampling rate and is accumulated to calculate the next control statistic. If the control statistic falls within the threshold limit, the next sample is taken with lower sampling rate and only the sample is used to get the control statistic. The VSI S-CUSUM chart produces an 'out-of-control' signal either when any control statistic falls outside the control limit or when L-consecutive control statistics fall outside the threshold limit. The number L is a decision variable and is called a 'control length'. A Markov chain model is employed to describe the VSI S-CUSUM sampling process. Some useful formulae related to the steady state average time-to signal (ATS) for an in-control state and out-of-control state are derived in closed forms. A statistical design procedure for the VSI S-CUSUM chart is proposed. Comparative studies show that the proposed VSI S-CUSUM chart is uniformly superior to the VSI CUSUM chart or to the Exponentially Weighted Moving Average (EWMA) chart with respect to the ATS performance.