• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.730-734
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• 2019

Thermophoresis is a transport phenomenon of particles driven by a temperature gradient of a medium. In this paper, we discuss the thermophoresis of particles in microfluidic channels. In a non-fluidic, stagnant channel, the thermophoretic transport of micro-particles was found to be larger in proportion to the voltage applied to the platinum wire heat source installed in the channel. The variation of the temperature around the platinum wire depending on the voltage was estimated, by using the Callendar-van Dusen equation. The thermophoretic behavior of nano-particles in the same system was observed, which is similar to that of the microparticles. Finally, we fabricated a Y-shaped microfluidic channel with a platinum wire heat source installed in the channel, to realize the thermophoretic phenomenon of the particles in the suspension flowing through the channel. It is shown that the flow of the suspension can be controlled based on the thermophoretic principle.

• Journal of Microbiology and Biotechnology
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• v.29 no.9
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• pp.1383-1390
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• 2019

In this study, we expressed cotA laccase from Bacillus subtilis on the surface of B. subtilis spores for efficient decolorization of synthetic dyes. The cotE, cotG, and cotY genes were used as anchoring motifs for efficient spore surface display of cotA laccase. Moreover, a $His_6$ tag was inserted at the C-terminal end of cotA for the immunological detection of the expressed fusion protein. Appropriate expression of the CotE-CotA (74 kDa), CotG-CotA (76 kDa), and CotY-CotA (73 kDa) fusion proteins was confirmed by western blot. We verified the surface expression of each fusion protein on B. subtilis spore by flow cytometry. The decoloration rates of Acid Green 25 (anthraquinone dye) for the recombinant DB104 (pSDJH-EA), DB104 (pSDJH-GA), DB104 (pSDJH-YA), and the control DB104 spores were 48.75%, 16.12%, 21.10%, and 9.96%, respectively. DB104 (pSDJH-EA) showed the highest decolorization of Acid Green 25 and was subsequently tested on other synthetic dyes with different structures. The decolorization rates of the DB104 (pSDJH-EA) spore for Acid Red 18 (azo dye) and indigo carmine (indigo dye) were 18.58% and 43.20%, respectively. The optimum temperature for the decolorization of Acid Green 25 by the DB104 (pSDJH-EA) spore was found to be $50^{\circ}C$. Upon treatment with known laccase inhibitors, including EDTA, SDS, and $NaN_3$, the decolorization rate of Acid Green 25 by the DB104 (pSDJH-EA) spore decreased by 23%, 80%, and 36%, respectively.

• Journal of Wetlands Research
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• v.22 no.1
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• pp.49-58
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• 2020

The excessive use of fertilizer and compost in agricultural land increases the accumulation of nutrients in soil. The surplus nutrients in soil transported through surface and sub-surface flow can lead to water pollution problems and algal bloom. Moreover, nutrient accumulation and continuous crop cultivation changes the physical structure of the soil, which increases the potential of nutrient. The cultivation in the Daecheong Lake reservoir area may have a direct effect on the lake's water quality due to leaching and releasing of nutrients when water level rises. This research was carried out to analyze the physical and chemical properties of soil in the agricultural areas surrounding Daecheong Dam reservoir to provide basic data available for the establishment of Daecheong Lake water quality management measures. The soil of the Daecheong Lake reservoir was classified as sandy Loam, where surplus nutrients can be transported. Chemical compositions in the soil were found to be significantly affected by use of different fertilizer amounts. Nutrient outflow occurred during spring rainfall events from the rice paddy fields, whereas excess nutrients from summer to fall seasons originated from dry paddy fields. Nutrient outflow from dry paddy fields is mainly from sub-surface flow. Organic agricultural wastes from agricultural land and excessive vegetation inside the river was also evaluated to contribute to the increase in organic matter and nutrients of the river. The results can be used to select the priority management area designation and management techniques in the Daecheong Lake for water quality improvement.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.740-745
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• 2015

This study investigated the effect of different collection methods on physical properties of pectin hydrogels in microfluidic synthetic approach. The pectin hydrogels were simply produced by the incorporation of calcium ions dissolved in continuous mineral oil. Then, different collection methods, pipetting, tubing, and settling, for harvesting pectin hydrogels were applied. The settling method showed most uniform and monodispersed hydrogels. In the case of settling, a coefficient of variation was 3.46 which was lower than pipetting method (18.60) and tubing method (14.76). Under the settling method, we could control the size of hydrogels, ranging from $30{\mu}m$ to $180{\mu}m$, by simple manipulation of the viscosity of pectin and volumetric flow rate of dispersed and continuous phase. Finally, according to the characteristics of simple encapsulation of biological materials, we envision that the pectin hydrogels can be applied to drug delivery, food, and biocompatible materials.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.107-116
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• 2017

When drilling operation is being performed, many physical and chemical changes are occurred near wellbore. To handle various changes of well condition and keep drilling process safe, additives of bulk, such as bentonite for increasing density of drilling mud, barite for increasing viscosity of drilling mud, polymer for chemical control, or surfactant, are added into drilling mud through a mud shear mixer. Because the achievement of the required material property through mud mixing system is essential to stabilize drilling system, it is of importance to analyze multi-phase flow during mud mixing process, which is directly related to increase mixing performance of the system and guarantee the safety of the whole drilling system. In this study, a series of liquid-solid flow simulation based on a computational fluid dynamics (CFD) are performed with comparing to solid concentration in experiment by Gilles et al. [2004] to understand the characteristics of liquid-solid mixing in a mud shear mixer. And then, the simulation-based design of shear mixer are carried out to improve mixing performance in a mud handling system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.722-727
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• 2016

In this study, we attempted to reduce the generation of waste acids in the electropolishing process by improving the current efficiency. The optimum conditions of the electropolishing process when using the round bus bar were determined by the Taguchi method. The current density, polishing time, electrolyte temperature and flow rate were selected as the control factors for the current efficiency in the electropolishing process. An orthogonal array was created by considering three levels for each factor and experiments were carried out. The larger-the-better SN ratios were calculated by the Taguchi method. The current density was the most important factor affecting the current efficiency and the polishing time was the least important one. The optimum conditions to minimize the generation of waste acids were a current density of $45A/dm^2$, polishing time of 4 min, electrolyte temperature of $65^{\circ}C$ and flow rate of 7 L/min. The results of the ANOVA confirmed that the effects of the current density, electrolyte temperature and flow rate are significant at the 95% confidence level. The increase in the contact area and contact force afforded by using the round bus bar improved the current efficiency which, in turn, reduced the amount of waste acids generated. Further research is planned to investigate the effect of the type of bus bar on the current efficiency.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1438-1439
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• 2006

$Ge_{2}Sb_{2}Te_5$(GST) thin film at present is a promising candidate for a phase change random access memory (PCRAM) based on the difference in resistivity between the crystalline and amorphous phase. PCRAM is an easy to manufacture, low cost storage technology with a high storage density. Therefore today several major chip in manufacturers are investigating this data storage technique. Recently, A. Pirovano et al. showed that PCRAM can be safely scaled down to the 65 nm technology node. G. T Jeonget al. suggested that physical limit of PRAM scaling will be around 10 nm node. Etching process of GST thin ra films below 100 nm range becomes more challenging. However, not much information is available in this area. In this work, we report on a parametric study of ICP etching of GST thin films in $Cl_2$/Ar chemistry. The etching characteristics of $Ge_{2}Sb_{2}Te_5$ thin films were investigated using an inductively coupled plasma (ICP) of $Cl_2$/Ar gas mixture. The etch rate of the GST films increased with increasing $Cl_2$ flow rate, source and bias powers, and pressure. The selectivity of GST over the $SiO_2$ films was higher than 10:1. X-ray photoelectron spectroscopy(XPS) was performed to examine the chemical species present in the etched surface of GST thin films. XPS results showed that the etch rate-determining element among the Ge, Sb, and Te was Te in the $Cl_2$/Ar plasma.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.98-105
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• 1999

In the present study, buoyant force and its stabilizing effects in an electrostatic field were examined systematically in order to reduce the effect of natural convection with thermal stratification in a horizontal fluid-saturated porous layer. The correlation of ionic mass transport induced by double-diffusive convection in a horizontal porous layer has been derived theoretically. And the theoretical model was examined by electrochemical experiments. The theoretical correlation for mass transport which is satisfying Forchheimer's flow equation and based on the micro-turbulence model is derived as a function of soltual Darcy-Rayleigh number, thermal Darcy-Rayleigh number and Lewis number. In the experiment, the mass transport of copper ions in $CuSO_4-H_2SO_4$ solution is measured by electrochemical technique. By assembling theoretical correlation and experimental results, the mass transport correlation induced by double-diffusive convection is proposed as $$Sh=\frac{0.03054(Rs_D-LeRa_D)^{1/2}}{1-3.8788(Rs_D-LeRa_D)^{-1/10}}$$ The present correlation looks flirty reasonable with comparing experimental results, and very promising for the applications of its prototype into various systems involving heat transfer as well as mass transfer, in order to control the effects of natural convection effectively.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.389-396
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• 2018

The Kori-1 Nuclear Power Plant (NPP), WH 2-Loop Pressurized Water Reactor (PWR) operated for approximately 40 years in Korea, was permanently ceased on June 18, 2017. To reduce worker exposure to radiation by reducing the dose rate in the system before starting main decommissioning activities, the permanently ceased Kori-1 NPP will be subjected to full system decontamination. Generally, the range of system decontamination includes Reactor Pressure Vessels (RPV), Pressurizer (PZR), Steam Generators (SG), Chemical & Volume Control System (CVCS), Residual Heat Removal System (RHRS), and Reactor Coolant System (RCS) piping. In order to decontaminate these systems and equipment in an effective manner, it is necessary to evaluate the influence of the flow characteristics in the RCS during the decontamination period. There are various methods of providing circulating flow rate to the system decontamination. In this paper, the flow characteristics in Kori-1 NPP reactor coolant according to RHR pump operation were evaluated. The evaluation results showed that system decontamination using an RHR pump was not effective at decontamination due first to impurities deposited in piping and equipment, and second to the extreme flow unbalance in the RCS caused deposition of impurities.

• Journal of Radiation Industry
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• v.18 no.3
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• pp.235-240
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• 2024

Electron beam technology has recently attracted attention as one of the powerful air pollution control methods. In this study, methyl mercaptan decomposition by electron beam in a continuous gas flow system was studied. To this, the effect of gas flowrate, which is one of important operating variables in the continuous gas flow electron beam process, on methyl mercaptan treatment efficiency was studied. In particular, the treatment efficiency and the reaction kinetics of methyl mercaptan decomposition were compared when calculated based on the absorbed dose and when calculated based on the current intensity of electron beam. When based on the electron beam absorbed dose, the treatment efficiency and 1st-order reaction constant increased as the gas flowrate was increased, contrary to the trends in general chemical reactions. However, when based on the current intensity, the treatment efficiency and 1st-order reaction constant increased as the gas flowrate was decreased, which can be theoretically explained. This is due to the fact that the current intensity increased as the gas flowrate was increased, resulting in improved the electron beam treatment efficiency. In conclusion, it is necessary to consider not only the absorbed dose but also the current intensity of electron beam in order to explain the results of reaction efficiencies and kinetics in the continuous flow electron beam gas treatment process.