• 한국미생물·생명공학회지
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• 제20권3호
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• pp.348-354
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• 1992

SUC2 유전자를 가진 재조합 Saccharomyces cerevisiae의 invertase 생산성을 향상시키기 위하여 균체 생육과 유전자 발현에 미치는 아미노산과 용존산소 농도의 영향을 연구하였다. 균체 생육과 invertase 발현에 적합한 leucine과 histidine의 최적 첨가량은 탄소원인 포도당에 대한 비율로서 나타내어 0.03g/g glucose와 0.04g/g glucose였다. 회분배양에서는 통기량이 적을수록 invertase 비활성이 증가하였다. 희석율 0.09h에서 용존산소농도를 조절한 연속배양에서는 요존산소농도가 감소함에 따라 유전자 발현이 잘되어 5 포화 이하일때 invertase 비활성이 급격히 증가하여 통기를 하지 않은 조건에서 125.54KU/g cell의 최고 비활성을 얻었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2192-2197
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• 2008

An experimental study was performed to investigate the effects of configuration of burner and air excess ratio on CO & NOx emission characteristics of the cooktop burners which are used extensively. In this study, the combustion characteristics were investigated with the variation of design factor of cooktop burners. The results showed that as the thermal input increases, flammable region go narrower. With the increase of loading height from the cap to grate, the CO emission decrease owing to the reduction of quenching by flame impingement on the load. Additionally, the CO emission increase with angle of main slot, however the NO emission is almost unaffected.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3102-3107
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• 2008

This paper was focused on the particulate matter (PM) on the gasoline and bio ethanol. Bio ethanol as a clean fuel is considered one of the alternative fuels that decreased the PM emission from the vehicle. Particle formation in SI engine was depended on the fuel and engine operating condition. In this paper, Particle number concentration behaviors were analyzed by DMS500 (Differential Mobility Spectrometer) and CPC (Condensation Particle Counter) instrument which was recommended by PMP (Particle Measurement Programme). Particle emissions were measured with various engine operating variables such as air excess ratio ($\lambda$), spark timing and intake valve opening (IVO) at part load condition. In vehicle test, the number of particulate matter was analyzed with golden particle measurement system, which was consist of CVS (Constant Volume Sampler), particle number counter and particle number diluter.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.521-529
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• 2012

Since the energy demand for refrigeration and air-conditioning has greatly increased all over the world, thermally activated refrigeration cycle has attracted much attention. This study carries out a performance analysis of a vapor compression cycle (VCC) driven by organic Rankine cycle (ORC) utilizing low-temperature heat source in the form of sensible heat. The ORC is assumed to produce minimum net work which is required to drive the VCC without generating an excess electricity. Effects of important system parameters such as turbine inlet pressure, condensing temperature, and evaporating temperature on the system variables such as mass flow ratio, net work production, and coefficient of performance (COP) are thoroughly investigated. The effect of choice of working fluid on COP is also considered. Results show that net work production and COP increase with increasing turbine inlet pressure or decreasing condensing temperature. Out of the five kinds of organic fluids considered $C_4H_{10}$ gives a relatively high COP in the range of low turbine inlet pressure.

• International Journal of Automotive Technology
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• 제4권3호
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• pp.109-117
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• 2003

The analysis and evaluation of the transient performance by the transient response specifications under various acceleration speeds and types based on driver's typical acceleration habit are implemented by the experimental study to provide the appropriate direction for the transient control in a gasoline engine. The concept of the transient response specifications which consist of delay time, rising time, maximum overshoot and settling time, and the analysis method using them are introduced to evaluate the characteristics of the transient performance quantitatively. Furthermore four acceleration speeds and four acceleration types are set respectively to realize the various transient states which are similar to the real drive. Several performance parameters in terms of engine speed, manifold absolute pressure, fuel injection duration and air excess ratio are measured simultaneously during the various acceleration using a throttle actuator controlled by a PC. The transient response specifications characterized well the transient performance for the various acceleration speed and types quantitatively. Delay and rising time with increment of the acceleration speed became shorter, but settling time did longer. Intensified acceleration type appeared to be the most economical in view of fuel consumption, and linear acceleration type was found to have the least harmful emission concentration.

• 한국환경보건학회지
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• 제47권4호
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• pp.366-377
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• 2021

Background: Polycyclic aromatic hydrocarbons (PAHs) are generated in petrochemical complexes, can spread to residential areas and affect the health of residents. Although harmful PAHs are mainly present in particle phase, gas phase PAHs can generate stronger toxic substances through photochemical reaction. Therefore, the risk assessment for PAHs around the petrochemical complex should consider both particle and gas phase concentrations. Objectives: This study aimed to investigate the concentration characteristics of particle and gas phase PAHs by season in residential areas around petrochemical complexes, and to assess the risk of PAHs. Methods: Samples were collected for 7 days by seasons in 2014~2015 using a high volume air sampler. Particle and gas phase PAHs were sampled using quartz filter and polyurethane foam, respectively, analyzed by GC-MS. Chronic toxicity and probabilistic risk assessment were performed on 14 PAHs. For chronic toxicity risk assessment, inhalation unit risk was used. Monte-Carlo simulation was performed for probabilistic risk assessment using the mean and standard deviation of measured PAHs. Results: The concentration of particle total PAHs was highest in autumn. The gas phase concentration was highest in autumn. The average gas phase distribution ratio of low molecular weight PAHs composed of 2~3 benzene rings was 85%. The average of the medium molecular weight composed of 4 benzene rings was 53%, and the average of the high molecular weight composed of 5 or more benzene rings was 9%. In the chronic toxicity risk assessment, 7 of the 14 PAHs exceeded the excess carcinogenic risk of 1.00×10^-6. In the Monte-Carlo simulation, Benzo[a]pyrene had the highest probability of exceeding 1.00×10^-6, which was 100%. Conclusions: The concentration of PAHs in the residential area around the petrochemical complex exceeded the standard, and the excess carcinogenic risk was evaluated to be high. Therefore, it is necessary to manage the air environment around the petrochemical complex.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.860-865
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• 2012

바이오매스 합성가스는 저열량 가스이지만 유류를 대체하기 위한 목적으로 공업로, 보일러 등에서 혼소방법으로 이용되고 있다. 혼소버너의 기본구조는 오일버너를 중심부로 하고 저열량 가스 연료를 그 주위로 공급하는 형태로 설계되었다. 본 연구에서는 가스의 균일분산 방법과 가스노즐 각도를 변화시키는 방법을 적용하여 세 종류의 버너를 설계하였다. 연소공기량 증가에 따라 CO 발생량이 감소하였으며, 혼소조건에서 화염으로부터 잔염 발생 원인은 오일버너로부터 미립화 불량인 것으로 나타났다. 혼소조건에서는 가스와 오일연료에 대한 과잉공기 요구량이 서로 다르기 때문에 적절하게 연소공기량을 맞추기가 어려웠지만, 과잉산소 4.7~8.2% 범위에서 안정적인 연소조건 유지가 가능하였다. 본 연구를 통하여 합성가스와 유류의 혼소 이용은 합성가스 성분이 오일보다 연소속도가 빠르게 이루어져 오일버너 미립화를 촉진시켜주고, 오일 단독연소조건보다 CO 배출 농도를 낮게 유지할 수 있음을 알 수 있었다.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.86-92
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• 2003

To analyze the characteristics of ozone formation, measurements of the concentrations of individual exhaust hydrocarbon species have been made under various engine operating parameters in a 2-liter 4-cylinder engine for natural gas and LPG. Tests were performed at constant engine speed, 1800 rpm for two compression ratios of 8.6 and 10.6, with various operating parameters, such as excess air ratio of 1.0~1.6, bmep of 250~800 na and spark timing of BTDC 10~$55^{\circ}$. It was found that the natural gas gave the less ozone formation than LPG in various operating conditions. This was accomplished by reducing the emissions of propylene($C_3H_6$), which has relatively high maximum incremental reactivity factor, and propane($C_3H_8$) that originally has large portion of LPG. In addition, the natural gas show lower values in the specific reactivity and brake specific reactivity. Higher compression ratio of the test engine showed higher non methane HC emissions. However, specific reactivity value decreased since fuel species of HC emissions increase. brake specific reactivity showed almost same values under high bmep, over 500kPa for both fuels. This means that the increase of non methane HC emissions and the decrease of specific reactivity with higher bmep affect each other simultaneously. With advanced spark timing, brake specific reactivity values of LPG were increased while those of natural gas showed almost constant values.

• Journal of Trauma and Injury
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• 제28권3호
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• pp.108-114
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• 2015

Purpose: To improve outcome of severe trauma patient, the shortening of transport time is needed. Although helicopter emergency medical services (HEMS) is still a subject of debate, it must also be considered for trauma system. The aim of this study is to assess whether transport method (HEMS versus ground EMS) is associated with outcome among inter-hospital transport. Methods: All trauma patients transported to regional emergency center by either HEMS or ground EMS from September 2011 to September 2014. We have classified patients according to two groups by transport method. Age younger than 15 years and self-discharged patients were excluded. Results: A total of 427 patients were available for analysis during this period. 60 patients were transported by HEMS and 367 patients were transported by ground EMS. HEMS group had higher mortality than ground EMS group (23.3% vs 3.5%; p<0.001), and included more patients with excess mortality ratio adjusted injury severity score (EMR-ISS) above 25 (91.7% vs 48.8%; p<0.001). In the multivariable regression analysis, HEMS was not associated with improved outcome compared with ground EMS, but only EMR-ISS was associated with a mortality of patients (odds ratio, 1.06; 95% confidence interval, 1.04-1.09). Conclusion: In this study, helicopter emergency medical services transport was not associated with a decreased of mortality among the trauma patients who inter-hospital transported to the regional emergency center.

• Journal of Biosystems Engineering
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• 제12권4호
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• pp.31-43
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• 1987

This study was performed to develop a hot water boiler system with small scale automatic rice hull furnace for the multi-purpose use in the farm. For the experiment a prototype hot water boiler system with rice hull furnace was fabricated, which was equipped with automatic hull feeder, igniter and ash removal device. Optimum operational conditions of the prototype: system were analyzed. The results arc summarized as follows. 1. The temperature measured right above the burning surface should be higher than $500^{\circ}C$ combustion. 2. The top zone of the combustion chamber was the most suitable location of the thermocouple to pick up the control temperature for the automatic operation of the rice hull furnace. 3. The content of carbon monoxide in the flue gas was increased with the filling height of burning material but it was less than 0.3 percent in volume in this experiment. When the filling height was expressed as the ratio of rice hull feed rate to the volume of the combustion chamber above the burning surface, the optimum ratio was about $150kg/m^3-h$. 4. The combustion efficiency of the prototype was higher than 95 percent when the feed rate was 1.1 to 2.3 kg/h and moisture content of rice hull was 22.4 percent (w.b.) or less. 5. It was estimated that the optimum operational conditions of the system were 1.3 to 2.0 kg/h in feed rate, 70 to 100 percent in excess air and 500 to $510^{\circ}C$ in control temperature. 6. The efficiency of coil heal exchanger increased with a decrease in feed rate of rice hull. When the rice hull feed rates were 1.1, 1.7 and 2.3 kg/h, the efficiencies of coil heat exchanger were about 34, 30 and 25 percent and heat transfer rates were 5.7, 7.6 and 8.8 MJ/h, respectively. When the flat plate heat exchanger was used in addition to the coil heat exchanger, the efficiency of the heat exchanger system increased to 48 percent.