• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.321-327
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• 2019

The purpose of this study is paper is to improve the flow performance and to reduce the aerodynamic noise of air discharge system consisting of a centrifugal fan, ducts and a housing for the clothes dryer. Using computational fluid dynamics and acoustic analogy based on FW-H (Ffowcs-Williams and Hawkings) Eq., air flow field and acoustic fields of the air discharge system are investigated. To optimize aerodynamic performance and aerodynamic noise, the response surface method is employed. The two factors central composite design using the inflow and outflow angles of fan blades is adopted. The devised optimum design shows the reduction of turbulent kinetic energy in the ducts and the housing of the system, and as a result, the improved flow rate and reduce noise is confirmed. Finally, the experment using the proto-type manufactured usign the optimum design shows the increase of flow rate by 4.2 %.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.315-319
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• 2018

Fenton reaction is widely used as a out of cell method for evaluating the membrane electrochemical durability of Proton Exchange Fuel Cell (PEMFC). In this study, we investigated the factors affecting the Fenton reaction. In order to estimate the degree of the reaction, it is necessary to analyze the radicals as a product in the Fenton reaction. However, since the radicals are difficult to analyze, the degree of the reaction was measured by analyzing the concentration of hydrogen peroxide. The activation energy was calculated from the rate of hydrogen peroxide change with temperature. The activation energy was 24.9 kJ/mol at 180 min. The Fenton reaction rate was affected by the iron ion concentration. At $80^{\circ}C$, 200 rpm, and $Fe^{2+}$ 80 ppm, the concentration of hydrogen peroxide was decreased more than 20% even for 1 hour, which shows that frequent solution replacement increases the membrane degradation rate.

• Journal of the Korean Chemical Society
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• v.53 no.6
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• pp.635-639
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• 2009

Experimental work was carried out to study the combustion kinetics of the Indian coal-char in the varying mixture of carbon dioxide-oxygen ($CO_2-O_2$). The coal sample was pulverized and sieved to less than 58 microns and charred using volatile furnace by passing the nitrogen gas. The experiments were carried out using the Thermo Gravimetric Analyzer (TGA-50) at CPRI, Bangalore, different proportions of ($CO_2-O_2$) gas was allowed in to the TGA-50 (80-20, 60-40, 40-60, 20-80) mole basis were used to study the combustion kinetics of coal Isothermally, kinetic parameters like Activation energy (E) and the pre-exponential factors (A) are calculated using the unification approach and modified Arrhenius equation.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.1
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• pp.15-25
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• 2020

Biogas production potential was experimentally estimated for mono- and co-digestion of cow manure and waste grass. The two organic wastes were mixed at five different ratios (100:0, 75:25, 50:50, 25:75, 0:100) on the volatile solids basis, and were assessed using biochemical methane potential (BMP) test. Thee reaction temperatures, 25℃, 30℃ and 35℃, were applied as well, resulting in 15 different combinations for the test. The results showed that both higher temperature and waste grass mixing ratio resulted in higher methane yield and maximum methane production rate. Based on the experimental results, a theoretical farm- or community-scale (240 or 2400 ㎥) anaerobic digester was designed to evaluate the energy balance associated with mono- and co-digestion of the wastes at different temperatures. Although the energy production increased as the temperature and the waste grass mixing ratio increased, the net energy gain, energy production subtracted by energy consumption for heating and maintenance, was estimated to be the highest at 30℃, followed by at 35℃ and 25℃. Therefore, it is advised that both the experimental methane production and the detailed design parameters must be considered for the optimization of the net energy gain from these wastes.

• Korean Journal of Microbiology
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• v.45 no.1
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• pp.10-16
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• 2009

A diverse range of stresses such as heat, cold, salt, ethanol, oxygen starvation or nutrient starvation induces same stress-responsive proteins. This general stress response enhances bacterial survival significantly. In Bacillus subtilis and closely related Gram-positive bacteria Listeria monocytogenes, the general stress response is controlled by the alternative transcription factor ${\sigma}^B$. The activity of ${\sigma}^B$ is regulated post-translationally by a signal transduction network that has been extensively studied in B. subtilis, and serve as a model for L. monocytogenes. The proposed model of L. monocytogenes signal transduction network is similar to that of B. subtilis, but the energy stress pathway is missing. More than 150 general stress proteins belong to ${\sigma}^B$ regulon of B. subtilis and L. monocytogenes. In both bacteria, ${\sigma}^B$ function is primarily important for resistance to diverse stresses. In addition, ${\sigma}^B$ function contributes to the control of important virulence genes in food-borne pathogen L. monocytogenes. Therefore, understanding of the general stress response is important not only for bacterial physiology, but also for pathogenicity.

• KSBB Journal
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• v.22 no.4
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• pp.222-227
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• 2007

Biodiesel (fatty acid methyl esters) have used to as substitutes for petro-diesel by mixed-form with petro-diesel. In several processes of biodiesel production, alkali-catalyst transesterification produced to biodiesel of high contents with short reaction time. In this study, we investigate the optimal condition of alkali-catalyst transesterification of rapeseed oil produced at Jeju island in Korea using response surface methodology. The optimal condition of biodiesel production is reaction temperature 59.7$^{\circ}C$, catalyst amount 1.18%, oil to methanol molar ratio 1:8.75, and reaction time 5.18 min. At that reaction condition, the fatty acid methyl ester contents of product are above 97%. Our results may provide useful information with regard to the development of more economic and efficient biodiesel production system.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.142-146
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• 2008

Titanium silicalite-1 catalyst was prepared using a $SiO_2-TiO_2$ xerogel and applied to allylchloride (ALC) epoxidation by $H_2O_2$ as oxidant in a batch reactor. The reaction temperature was varied from 25 to $55^{\circ}C$, and the concentrations of ALC and $H_2O_2$ were changed from 0.2 to 3 M and from 0.2 to 1.5 M, respectively. The kinetic data obtained were applied to the power rate law, Eley-Rideal, and a Langmuir-Hinshelwood model, and power rate law fits the experimental data best. Activation energy was 27.9 kJ/mol, and the reaction orders with respect to $H_2O_2$ and ALC were determined to be 0.41 and 0.52, respectively.

• Nuclear Engineering and Technology
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• v.26 no.2
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• pp.257-264
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• 1994

Experimental studies hate been peformed to investigate vapor explosion phenomena which may threaten the containment integrity during severe accidents in nuclear power plants. In this study, experimental equipment is constructed for vapor explosion experiments, and the vapor explosion experiments were conducted using water/R22. During the experiments, water/R22 interaction phenomena were observed using the high speed camera, and the explosion pressure and released mechanical energy were measured with pressure transducer and pressure relief tube. And the effects of some important parameters-hot liquid temperature, hot liquid injection velocity, hot liquid injection velocity, hot liquid injection time, and cold liquid depth-were investigated on the vapor explosion. Also, the experiment with grid was conducted to study reactor -vessel-lower-structure effect on fuel/coolant interaction. Water/R22 explosion conversion ratios were measured between 0.5∼1.6%.

• Journal of Energy Engineering
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• v.16 no.4
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• pp.155-163
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• 2007

To insure nuclear reactor safety, the reactivity of control rods should be calculated by measuring the criticality of reactor core and it is regularly performed during the annual physics test period. Also, the core criticality should be monitored during the start-up operation to avoid reactivity induced accidents. Many research works on control rod reactivity measurement and subcriticality measurement have been accomplished throughout the world for decades and recently a new method named "Modified Neutron Source Multiplication Method (MNSM)" was proposed in Japan which is known to be improved overcoming limitations of traditional Neutron Source Multiplication Method (NSM). In this study, MNSM was tested in calculation of subcriticalities and in evaluation of application validity using the educational reactor in Kyung Hee University, AGN-201. For this study, a revised nuclear data library and a neutron transport code system TRANSX - PARTISN were established. Correction factors for various control rod positions were produced using the k-effective values and the corresponding flux distributions and adjoint flux distributions. Experimental values of the core criticality were obtained using the neutron count rates of the BF3 proportional counters. The results showed that the expected reactivity worth of control rods by MNSM agreed well with the theoretical values and the correction factors contributed much for this purpose.

• Resources Recycling
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• v.11 no.6
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• pp.38-46
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• 2002

Fundamental investigations were conducted far the recovery process of waste organic solvent by fractional distillation in the aspects of equilibrium and kinetics. Mixture of toluene and xylene, which were both being used in the largest amount as industrial organic solvent, was taken as the artificial waste organic solvent and their distillation behaviors were studied. The purity of recovered solvent was investigated by Cir Chromatography and shown to be in the range of 94～98%. Based upon equilibrium calculations, the changes in the Gibbs free energy, standard enthalpy, and standard entropy for distillation reaction have been estimated. The standard enthalpy changes for toluene and xylene were shown to be 44.833 and 47.044 kJ $mol^{-1}$ respectively, which were similar to their molar heats of evaporation. The activation energies of distillation fur toluene and xylene obtained from kinetic studies were 3.281 and 2.699 kJ $mol^{-1}$ and they were about one tenths of the standard enthalpy changes of distillation reaction. The highness of the purity of recovered organic solvents suggested the possibility that the recovered waste organic sol-vent could partly replace the original solvent.