• 대한기계학회논문집B
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• 제24권3호
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• pp.390-401
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• 2000

In this study, numerical calculation is carried out to investigate the influence of injection timing, fuel amount, intake $O_2$ concentration, and EGR on Nitric Oxide(NO) formation using a two-zone model in a diesel engine. Results can be summarized as follows. The NO formation is very sensitive to the burned gas temperature, so multi-zone model must be applied to combustion process to predict the burned gas temperature exactly. Since the burned gas temperature increases rapidly during the premixed combustion, most NO is formed within 20 crank angle degrees after ignition. As the injection timing is retarded, the combustion occurs later in the expansion process which causes the decrease of burned gas temperature and, as a result, NO formation decrease. The increase of fuel amount results in the increase of earlier formation of NO in the engine. As the intake $O_2$ concentration increases, the maximum pressure and burned gas temperature increase due to activate combustion. And, [O] mole fraction of equilibrium combustion products also increase. Therefore NO exponentially increases. If exhaust gas is recirculated, the burned gas temperature decreases which results in NO decrease. If exhaust gas is cooled, more NO can be decreased.

• 한국자동차공학회논문집
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• 제20권1호
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• pp.88-94
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• 2012

One of the effective ways to reduce both $NO_x$ and PM at the same time in a diesel CI engine is to operate the engine in low temperature combustion (LTC) regimes. In general, two strategies are used to realize the LTC operation-dilution controlled LTC and late injection LTC - and in this study, the former approach was used. In the dilution controlled regime, LTC is achieved by supplying a large amount of EGR to the cylinder. The significant EGR gas increases the heat capacity of in-cylinder charge mixture while decreasing oxygen concentration of the charge, activating low temperature oxidation reaction and lowering PM and $NO_x$ emissions. However, use of high EGR levels also deteriorates combustion efficiency and engine power output. Therefore, it is widely considered to use increased intake pressure as a way to resolve this issue. In this study, the effects of intake pressure variations on performance and emission characteristics of a single cylinder diesel engine operated in LTC regimes were examined. LTC operation was achieved in less than 8% $O_2$ concentration and thus a simultaneous reduction of both PM and $NO_x$ emission was confirmed. As intake pressure increased, combustion efficiency was improved so that THC and CO emissions were decreased. A shift of the peak Soot location was also observed to lower $O_2$ concentration while $NO_x$ levels were kept nearly zero. In addition, an elevation of intake pressure enhanced engine power output as well as indicated thermal efficiency in LTC regimes. All these results suggested that LTC operation range can be extended and emissions can be further reduced by adjusting intake pressure.

• Asian-Australasian Journal of Animal Sciences
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• 제27권1호
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• pp.46-54
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• 2014

This study was conducted to investigate the effects of eucalyptus (E. Camaldulensis) crude oils (EuO) supplementation on voluntary feed intake and rumen fermentation characteristics in swamp buffaloes. Four rumen fistulated swamp buffaloes, body weight (BW) of $420{\pm}15.0$ kg, were randomly assigned according to a $2{\times}2$ factorial arrangement in a $4{\times}4$ Latin square design. The dietary treatments were untreated rice straw (RS) without EuO (T1) and with EuO (T2) supplementation, and 3% urea-treated rice straw (UTRS) without EuO (T3) and with EuO (T4) supplementation. The EuO was supplemented at 2 mL/h/d in respective treatment. Experimental animals were kept in individual pens and concentrate mixture was offered at 3 g/kg BW while roughage was fed ad libitum. Total dry matter and roughage intake, and apparent digestibilites of organic matter and neutral detergent fiber were improved (p<0.01) by UTRS. There was no effect of EuO supplementation on feed intake and nutrient digestibility. Ruminal pH and temperature were not (p>0.05) affected by either roughage sources or EuO supplementation. However, buffaloes fed UTRS had higher ruminal ammonia nitrogen and blood urea nitrogen as compared with RS. Total volatile fatty acid and butyrate proportion were similar among treatments, whereas acetate was decreased and propionate molar proportion was increased by EuO supplementation. Feeding UTRS resulted in lower acetate and higher propionate concentration compared to RS. Moreover, supplementation of EuO reduced methane production especially in UTRS treatment. Protozoa populations were reduced by EuO supplementation while fungi zoospores remained the same. Total, amylolytic and cellulolytic bacterial populations were increased (p<0.01) by UTRS; However, EuO supplementation did not affect viable bacteria. Nitrogen intake and in feces were found higher in buffaloes fed UTRS. A positive nitrogen balance (absorption and retention) was in buffaloes fed UTRS. Supplementation of EuO did not affect nitrogen utilization. Both allantoin excretion and absorption and microbial nitrogen supply were increased by UTRS whereas efficiency of microbial protein synthesis was similar in all treatments. Findings of present study suggested that EuO could be used as a feed additive to modify the rumen fermentation in reducing methane production both in RS and UTRS. Feeding UTRS could improve feed intake and efficiency of rumen fermentation in swamp buffaloes. However, more research is warranted to determine the effect of EuO supplementation in production animals.

• 대한예방한의학회지
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• 제4권2호
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• pp.242-257
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• 2000

This study was to investigate the metal accumulation from Ohjeoksan-Decoction to rat brain(Sprague Dawley). 1. In Control group, each metal concentration was within 26.65mg/kg. and in each experimental groups, was within 28.39mg/kg. And there were no significant metal concentration between control and experimental groups. Exceptionally, Cr and Ni level of control group was lower than experimental groups significantly. (p<0.05) and Cr and Ni level of experimental I group was lower than other experimental groups too. (p<0.05). But, Pb level of control group was higher than experimental groups significantly (p<0.05) Pb level of experimental I group was higher than other experimental groups(p<0.01) 2. In non-hazardous, hazardous and total metal concentration, there was no increase tendency in brain according to the high dose of OD(Ohjeoksan-Decoction) intake. Reversely, in experimental groups, hazardous metal concentration was decrease by high OD intake. (P<0.05) 3. Correlation among each metal in brain was various in each groups Briefly under the intake of Ohjeoksan-Decoction, that if very busy herb prescription , this study was defined within safety in brain metal level by P.O. during 10 days. But, there should be a more research about Pb increase by high dose OD intake

• 한국자동차공학회논문집
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• 제5권1호
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• pp.15-26
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• 1997

The present study is mainly motivated to numerically simulate the autoignition and combustion process of a diesel spray in RCM and effects of design parameters on combustion and engine performance in the DI diesel engine using EGR. In case of the burning spray in RCM, special emphasis is given to the autoignition process coupled with the fluid mechanics and chemical reaction. Computations are carried out for a wide range of operating condition in terms of temperature, concentration of oxygen and carbon dioxide of the intake gas in the DI diesel engine. Numerical results indicate that the mixing process along the edges of spray jet has a crucial role for autoignition and combustion process. Temperature and concentration of O2 and CO2 of intake gas significantly influence the combustion characteristics and engine performance in the diesel/EGR environment.

• 동의생리병리학회지
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• 제16권5호
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• pp.967-975
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• 2002

This study was to investigate the metal accumulation from Ohjeoksan-Decoction to rat brain(Sprague Dawley). 1. In Control group, each metal concentration was within 26.65mg/kg, and in each experimental groups, was within 28.39mg/kg. And, there were no significant metal concentration between control and experimental groups. Exceptionally, Cr and Ni level of control group was lower than experimental groups significantly. (p<0.05) and Cr and Ni level of experimental I group was lower than other experimental groups too.(p<0.05). But, Pb level of control group was higher than experimental groups significantly.(p<0.05) Pb level of experimental I group was higher than other experimental groups(p<0.01). 2. In non-hazardous, hazardous and total metal concentration, there was no increase tendency in brain according to the high dose of OD(Ohjeoksan-Decoction) intake. Reversely, in experimental groups, hazardous metal concentration was decrease by high OD intake.(p<0.05). 3. Correlation among each metal in brain was various in each groups. Briefly under the intake of Ohjeoksan-Decoction, that is very busy herb prescription, this study was defined within safety in brain metal level by P.O. during 10 days. But, there should be a more research about Pb increase by high dose OD intake

• 한국자동차공학회논문집
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• 제2권6호
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• pp.76-86
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• 1994

Combustion of diesel engine depends on the mixing of air and evaporating fuel during ignition delay greatly. Variation of air-fuel mixing rate and ignition delay for engine operating condition causes difference of combustion, performance and exhaust emissions. This study is investigated in a turbocharged diesel engine of IDI swirl chamber type. In the results, As injection timing is advanced until $12.6^{\circ}$ BTC, ignition delay decreases. NOx concentration and smoke level in exhaust gas increases for advanced injection timing Ignition delay, combustion period, pressure rise rate and exhaust gas temperature are increased with increasing engine speed. And ignition delay at high load is more decreased than that at low load. Ignition delay and combustion period are decreased with increasing intake pressure. Power increases, temperature and CO, NOx concentration in exhaust gas decreases as intake pressure increases. With increasing load, ignition delay is decreased and combustion period, motoring pressure are increased.

• Asian-Australasian Journal of Animal Sciences
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• 제19권3호
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• pp.412-417
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• 2006

This study evaluated the effectiveness of different arsenical sources on inducing fatty liver, on changes in lipid metabolism and on liver function in mule ducks. Sixty twelve-week-old mule ducks were selected and randomly divided into five treatments, including the control group and four different arsenical sources; Roxarsone (300 mg/kg), arsanilic acid, $As_2O_5$ or $As_2O_3$, containing 85.2 mg/kg arsenic were included in the basal diet. The ducks were fed the medicated basal diet for 3 weeks followed by a one-week drug withdrawal. The results showed Roxarsone treatment decreased body weight, feed intake, liver weight and abdominal fat weight (p<0.05), while it increased the relative liver weight (p<0.05) during medication period ($3^{rd}$ week). The $As_2O_5$ treatment decreased abdominal fat weight and relative abdominal fat weight when compared to the control (p<0.05). Only Roxarsone among the treatment groups increased feed intake, liver weight and relative liver weight, while the $As_2O_3$ group showed the lightest liver weight and relative liver weight among treatment groups during the withdrawal period ($4^{th}$ week). The Roxarsone group decreased (p<0.05) NADP-malic dehydrogenase (MDH) and acetyl-CoA carboxylase (ACC) activities and increased (p<0.05) cholesterol concentration during the medication period, and elevated the MDH and ACC activities during the withdrawal period. All four arsenical treatment groups showed lymphocytic infiltration in liver tissue, while the Roxarsone and $As_2O_3$ treatments showed an increase in aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities (p<0.05). During the withdrawal period, arsenical treatments resulted in liver vacuoles. However, the arsenicals differed in effectiveness and mechanisms of inducing fat vacuoles.

• 해양환경안전학회지
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• 제21권2호
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• pp.188-193
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• 2015

일반적으로 선박용 디젤엔진의 아산화질소($N_2O$)배출률은 이산화황($SO_2$)배출률과 밀접한 상관성을 갖고 있고, 선박에서 사용되는 연료의 다양성은 $N_2O$배출특성에 영향을 미친다고 받아들여져 왔다. 최근의 연구보고에 의하면 연료 연소에서 발생한 충분한 일산화질소(NO)가 존재할 경우, 배기의 $SO_2$배출률이 $N_2O$생성에 미치는 영향은 NO의 영향보다 막대하게 크다. 그러므로 $SO_2$성분으로부터 기인하는 $N_2O$생성은 NOx저감을 위한 배기가스 재순환(EGR) 시스템에서 중요한 인자로 작용한다. 본 실험적인 연구의 목적은 $SO_2$유량 증가를 갖는 디젤엔진의 흡기가 배기의 $N_2O$배출률에 미치는 영향에 대하여 조사하는 것이다. 실험에 사용된 테스트 엔진은 2600rpm에서 12kW의 출력을 갖는 4행정 직접분사식 디젤엔진이고, 운전조건은 75% 부하에서 실시되었다. 0.499%($m^3/m^3$)의 $SO_2$표준가스는 흡기의 $SO_2$농도를 변화시키기 위해 사용되었다. 결과적으로 황 성분을 포함하지 않는 연료는 $SO_2$를 배출시키지 않았고, 흡기 중에 $SO_2$표준가스의 증가에 따른 배기의 $SO_2$배출률은 $SO_2$흡입률과 비교하여 거의 같은 비율이었다. 또한, 흡기의 $SO_2$유량 상승은 $N_2O$배출률을 상승시켜 배기 중의 $N_2O$는 흡기의 $SO_2$혼합기에 의해 생성되었다. 결국 황 성분을 함유한 연료는 연소 중에 $SO_2$를 형성하고 배기 중의 $N_2O$는 연소실에 존재하는 NO와 $SO_2$의 반응에 의해 발생된다고 할 수 있다.

• Asian-Australasian Journal of Animal Sciences
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• 제26권3호
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• pp.416-422
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• 2013

This experiment was conducted to evaluate the effects of dietary olive oil on growth performance, carcass parameters, serum characteristics, and fatty acid composition of breast and drumstick meat in broiler chickens. A total of 480 broilers were randomly allotted into three dietary treatments, including T (basal diet, 5% tallow), O1 (2% olive oil+3% tallow), and O2 (5% olive oil). During d 0 to 21, broilers fed the diet supplemented with 5% olive oil showed lower (p<0.05) body weight gain (BWG) and feed intake (FI) compared with those fed the T diet. Serum triglyceride concentration was reduced (p<0.05), while high density lipoprotein (HDL)-cholesterol concentration was increased (p<0.05) in the O2 treatment group compared with the T and O1 treatment groups. The addition of olive oil to the diets induced a reduction (p<0.05) in the total saturated fatty acid (SFA) contents in breast and drumstick meat, and increased (p<0.05) the total unsaturated fatty acid (USFA) contents and USFA/SFA ratios. In conclusion, a diet with 5% olive oil could decrease BWG and FI of broilers during the starter period (wk 0 to 3), and cause an increase in the serum HDL-cholesterol level, while decreasing the serum triglyceride concentration. Furthermore, USFA level and USFA/SFA ratios in breast and drumstick meat were increased by dietary supplementation of 2 or 5% olive oil.