• Microbiology and Biotechnology Letters
• /
• v.14 no.2
• /
• pp.169-174
• /
• 1986

Cytosine deaminase was partialy purified about 10 fold from the ceil-free extract of Aspergillus fumigatus. The partialy purified enzyme was relatively stable in a pH 5.5 to 8.0, but thermo-unstable. The enzyme activity was found in a pH optimum of 7.0 and temperature optimum of 30 to 35$^{\circ}C$. The activation energy calculated to be 13,240 cal/mol. The apparent Michaelis constants Km for cytosine was found to be 1.53 mM and the molecular weight was determined to be approximately 32,000. The enzyme was strongly inhibited by 0.1 mM of Hg$^^{2+}$, Pb$^{2+}$, Cd$^{2+}$ and Fe$^{2+}$, furthermore inhibited by 1mM of ATP, UTP, o-phenanthroline and p-chloromercuribenzoate.

• Applied Biological Chemistry
• /
• v.30 no.3
• /
• pp.278-284
• /
• 1987

As a basic research for inhibition of enzymatic browning of apples during dehydration or processing, polyphenol oxidase was extracted from Fuji apples to investigate heat inactivation, chemical inhibition and other properties. Polyphenol oxidase showed the highest activity at $20^{\circ}C$ and pH 5.5 with catechol as substrate, and the Michaelis constant of 0.14 M under the same condition of substrate and pH. The thermal inactivation followed pseudo first-order kinetics to have activation energy of 23.0 kcal/mol and z value of $19.7^{\circ}C$. As for substrate specificity the polyphenol oxidase showed high affinity toward the o-diphenolic compounds, particularly chlorogenic acid. Neither the m- and p-dihydroxy phenols nor monophenols were attacked. Browning by polyphenol oxidase was completely inhibited at the concentrations of 10mM for potassiummetasulfite and thiourea and 1mM for L-cysteine, ascorbic acid and sodium diethyldithiocarbamate.

• Journal of the Korean Society of Safety
• /
• v.25 no.3
• /
• pp.53-60
• /
• 2010

LPG(Liquefied Petroleum Gas) vehicles in metropolitan area are being applied to improve air quality and have been proven effective for the reduction of air pollutant. In addition, LPG demand is growing rapidly as an environmentally friendly energy source and its gas station is also increasing every year. Consequently, this study tries to find out the influence of flame caused by the VCE(Vapor Cloud Explosion) in filling station on the adjacent combustibles and people by simulating relevant quantity of TNT. In addition, the damage estimation was conducted by using API regulations. If the scale of the radiation heat is known by calculating the distance of flame influence from the explosion site, the damage from the site can be easily estimated. And the accident damage was estimated by applying the influence on the adjacent structures and people into the PROBIT model. According to the probit analyze, the spot which is 30m away from the flame has 100% of the damage probability by the first-degree burn, 99.2% of the damage probability by the second-degree burn and 93.4% of the death probability by the fire.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.7
• /
• pp.258-264
• /
• 2018

This paper presents application of a differential search (DS) meta-heuristic optimization algorithm for optimal operation of a micro grid system. The DS algorithm simulates the Brownian-like random-walk movement used by an organism to migrate. The micro grid system consists of a wind turbine, a diesel generator, a fuel cell, and a photovoltaic system. The wind turbine generator is modeled by considering the characteristics of variable output. Optimization is aimed at minimizing the cost function of the system, including fuel costs and maximizing fuel efficiency to generate electric power. The simulation was applied to a micro grid system only. This study applies the DS algorithm with excellence and efficiency in terms of coding simplicity, fast convergence speed, and accuracy in the optimal operation of micro grids based on renewable energy resources, and we compared its optimum value to other algorithms to prove its superiority.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.2
• /
• pp.449-454
• /
• 2010

In this paper, flow characteristics of R600a in an adiabatic capillary tube were investigated employing the homogeneous flow model. The model is based on fundamental equations of mass, energy and momentum which are solved simultaneously. Two friction factors(Churchill) and viscosity(McAdams) are comparatively used to investigate the flow characteristics. Thermodynamic and transport properties of R600a are calculated employing EES property code. Flow characteristics analysis of R600a in an adiabatic capillary tube is presented to offer the basic design data for the operating parameters. The operating parameters considered in this study include condensation temperature, evaporation temperature, subcooling degree and inner diameter tube of the adiabatic capillary tube. The main results were summarized as follows: condensation and evaporation temperature, inlet subcooling degree and inner diameter tube of an adiabatic capillary tube using R600a have an effect on length of an adiabatic capillary tube. The length of an adiabatic capillary tube using R600a is expressed to the correlation shown in Eq. (15).

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.12
• /
• pp.6980-6985
• /
• 2014

A micro-conductive pattern was fabricated on an insulating substrate ($SiO_2$) surface using a laser direct writing method. In the LIFT process, when the laser beam irradiates a thin metal film, the photon energy is absorbed by the film and converted to thermal energy, and the thermal decomposition reaction produced by the resulting heat conduction forms a deposit on the substrate. The resistivity of the micro-electrodes deposited through LIFT process with and without polymer coating was measured. The results showed that the electric conductivity of the micro-pattern and micro-structure can be increased approximatly two times when the deposited micropattern is fabricated through a LIFT process with a polymer coating, compared to the case without a polymer coating.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.3
• /
• pp.1600-1604
• /
• 2015

As modern houses are constructed with high-density and high-insulation, there is benefit to reduce energy consumption, but there are many side effects raised from polluted air. To solve the problem, a ventilation system is used to improve a indoor air quality. In this research, we experimentally estimate ventilation performance of HRV(heat recovery ventilator) with heat-pipe according to working fluid filling quantity and ventilation. Heat-pipe used in this study was designated separately to be applied to a ventilation system. The working fluid was R22, which was filled from 40 to 55 (%vol.) by 5(%vol.). Ventilation based on the front velocity was measured from 0.3 m/s to 1.5 m/s by 0.3 m/s intervals. Refrigerant filling quantity with the highest efficiency was found to depend on the ventilation. From this study the optimal refrigerant filling quantity in accordance with the ventilation of the detachable heat pipes was found experimentally.

• Journal of the Korea Computer Industry Society
• /
• v.2 no.3
• /
• pp.369-376
• /
• 2001

The optimization of resonator and laser power supply has been considered to be significant for improving the efficiency of a pulsed Nd:YAG laser system. We have proposed a new method of 3-mesh parallel sequential charge and discharge circuit as a laser power supply; more compact than conventional power supply, competitive in price, easy to control the laser power density according to various material processing, and equipped with the optimum reflectivity of output coupler. In this study, we could find that the maximum laser output was obtained by using 85% of reflectivity in the case of 50[W]-class. In addition using the power supply of new method, it's possible to charge each capacitor bank with a higher energy within the given charging time adopted a new method mentioned above; namely, we can allow each capacitor to have much more charging time and storage energy. So, higher laser output was obtained than conventional power supply.

• 기계와재료
• /
• v.24 no.2
• /
• pp.38-46
• /
• 2012

인구의 증가와 급속한 산업화 그리고 편안함을 추구하고자 하는 문명의 이기로 인한 에너지 사용량 증가는 환경오염을 가속화시키는 문제를 유발하고 있어 전 세계적으로 심각한 사회문제로 대두되고 있다. 이에 반해 삶의 질의 향상에 따라 보다 쾌적한 환경에 대한 욕구와 인식의 변화로 환경보호에 대한 관심이 증가하는 추세이며, 이에 따라 각 국의 환경규제는 날로 강화되고 있다. 이러한 환경문제를 해결하기 위한 국제협력이 활발해지면서 무역과 연계된 국제 환경규제가 가속화되고 있으며, 환경선진국은 이러한 환경규제를 무역장벽으로 이용하고 있어 국가의 대외경쟁력에도 직 간접적으로 영향을 미치고 있다. 환경오염물질 중 질소산화물(NOx), 황산화물(SOx), 일산화탄소(CO), 이산화탄소($CO_2$) 및 휘발성유기화합물(VOCs), 다이옥신 그리고 입자상물질(PM)과 같은 대기오염물질은 대기 중으로 쉽게 확산되는 특성에 의해 인접한 지역까지 영향을 미치기 때문에 국제적인 규제대상의 초점이 되고 있으며, 경제협력개발기구(OECD, Organization for Economic Cooperation and Development), 유엔산하 국제해사기구(IMO, International Maritime Organization) 및 국제연소기구협회(CIMAC, International Council on Combustion engines)등 여러 국제기구를 중심으로 각종 규제수단을 개발하여 적용하고 있다. 특히, 국제해사기구(IMO)에서는 선박에서 발생되는 오염물질 등에 대한 규제강화를 위하여 새로운 국제해양오염방지협약(MARPOL)을 채택, 발효하여 그 규제 범위를 넓혀감에 따라 선박에 대한 각종 환경규제가 대폭 강화되고 있어 친환경 선박 및 관련 기술 개발이 활발히 진행 중에 있다. 이 글에서는 선박에서 배출되는 대기오염물질 중 그 자체로도 인체에 유해하며, 산성비, 광화학스모그 등 다양한 환경문제를 유발시키는 대표적인 물질인 질소산화물(NOx)과 질소산화물 배출규제에 대한 대응기술인 선택적촉매환원법(SCR, Selective Catalytic Reduction)과 SCR 탈질시스템에 사용되는 SCR 촉매에 대해 소개하고자 한다.

• Korean Chemical Engineering Research
• /
• v.48 no.1
• /
• pp.1-9
• /
• 2010

Since carbon dioxide, $CO_2$, was revealed as a major greenhouse gas, techniques for its separation, capture, and storage have received increasing interest in recent years. Aqueous amines are the most widely accepted $CO_2$ absorbents, but they cause the problems such as high regeneration energy, thermal degradation, and loss of absorbents due to their volatility. Ionic liquids having high thermal stability, extremely low vapor pressure, and capability of selectively absorbing specific gases have been proposed as new $CO_2$ capturing solvents which may potentially replace aqueous amines. By reviewing the ionic liquids having capability to absorb $CO_2$ reported in previous papers, we seek to develop a comprehensive understanding on the factors that influence the $CO_2$ solubility in ionic liquids such as their structures, absorption temperature, pressure, water content, etc., and to estimate the potential of ionic liquids as $CO_2$ separating media.