• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.25-33
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• 2018

Renewable energy has been of interests in the area of modern alternative fuels. Biogas is produced in waste landfill sites through anaerobic digestion processes, including hydrolysis, acidogenesis, organic acid fermentation (acetogenesis), and methane fermentation (methanogenesis). High contents of fine dust and moisture limited its utilization for direct combustion, town gas and vehicle fuel. Thus, this study proposed a new design for a cooling device using a centrifugal cyclone for simultaneous removal of fine dust and moisture as a pretreatment in the purification processes. A heat exchanger and an ID fan, which are installed inside and outside of the cyclone, in order to cool the humid gas below the freezing point and form a foggy mist. Such an atmosphere enhanced to capture fine dust as recirculating the cold mist flow. The water removal rate was 80.8% at a relative humidity of 95%, and the particle removal efficiency was 98.3% for $2.5{\mu}m$. Simultaneous removal efficiency was 70.8% and 99.6% for particle and moisture respectively.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.6
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• pp.581-589
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• 2005

Recently, membrane processes have been replacing the conventional processes for waste water treatment to produce better quality of effluent and to meet more stringent regulations because of water shortage. However, using membrane processes for water treatment has confronted with fouling and difficulty in treating dissolved organic pollutants. In this study, membrane process equipped with crossflow microfiltration is combined with coagulation process using alum and PAC to improve permeability and treatment efficiency. The effects of coagulant dosage and optimum membrane operating conditions were investigated from measurement of permeate flow, cumulative volume, total resistance, particle size, dissolved organic pollutant, dissolved aluminium and quality of effluent. Characteristic of PAC coagulation was compared with that of alum coagulation. PAC coagulation reduced membrane fouling because of forming larger particle size and increased permeate velocity and cumulative volume. Less dissolved organic pollutants and dissolved aluminum made decreasing-rate of permeate velocity being lowered. At using $0.2\;{\mu}m$ membrane, cake filtration observed. At using $0.45\;{\mu}m$ membrane, there was floc breakage due to shear stress occurred born circulating operation. It made floc size smaller than membrane pore size, which subsequently to decrease permeate velocity and to increase total resistance. The optimum coagulation dosage was $300{\pm}50\;mg/L$ for both alum and PAC. PAC coagulation was more efficiently used with $0.2\;{\mu}m$ membrane, and the highest permeate flux was in using $0.45\;{\mu}m$membrane. The greatest efficiency of treatment was as follows; turbidity 99.8%, SS 99.9%, $BOD_5$ 94.4%, $COD_{Cr}$ 95.4%, T-N 54.3%, T-P 99.8%.

• The Korean Journal of Malacology
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• v.30 no.1
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• pp.9-15
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• 2014

This study is aimed at figuring out the reasons of the mass mortality of abalone and the increase in its mortality rate in the sea cage. The study suggests that lack seawater circulation in an abalone aquaculture cage is an important culprit for it. We analyzed the current distribution around a 1/20 scaled-down abalone unit cage of 4 rows and 10 columns by fluid flow visualization technique (PIV : Particle Image Velocimetry). The speed of current in the model cage definitely slowed down in the first column of a unit cage. We also observed currents going down to the bottom of a water tank from the unit cages placed in the middle. The speed of wakes behind inside the row in the middle was slower than that outside the row. Water velocity inside and outside a real abalone cage at Nowha Island adjacent to Wan Island was measured to verify results from the tank test. The speed of current in front of the cage by 2 m was 0.11 m/sec while it was only 0.0009 m/sec inside the cage. It had similar findings with those of a tank test.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.434-435
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• 2012

Plasma enhanced chemical vapor deposition (PECVD) silicon dioxide thin films have many applications in semiconductor manufacturing such as inter-level dielectric and gate dielectric metal oxide semiconductor field effect transistors (MOSFETs). Fundamental chemical reaction for the formation of SiO2 includes SiH4 and O2, but mixture of SiH4 and N2O is preferable because of lower hydrogen concentration in the deposited film [1]. It is also known that binding energy of N-N is higher than that of N-O, so the particle generation by molecular reaction can be reduced by reducing reactive nitrogen during the deposition process. However, nitrous oxide (N2O) gives rise to nitric oxide (NO) on reaction with oxygen atoms, which in turn reacts with ozone. NO became a greenhouse gas which is naturally occurred regulating of stratospheric ozone. In fact, it takes global warming effect about 300 times higher than carbon dioxide (CO2). Industries regard that N2O is inevitable for their device fabrication; however, it is worthwhile to develop a marginable nitrous oxide free process for university lab classes considering educational and environmental purpose. In this paper, we developed environmental friendly and material cost efficient SiO2 deposition process by substituting N2O with O2 targeting university hands-on laboratory course. Experiment was performed by two level statistical design of experiment (DOE) with three process parameters including RF power, susceptor temperature, and oxygen gas flow. Responses of interests to optimize the process were deposition rate, film uniformity, surface roughness, and electrical dielectric property. We observed some power like particle formation on wafer in some experiment, and we postulate that the thermal and electrical energy to dissociate gas molecule was relatively lower than other runs. However, we were able to find a marginable process region with less than 3% uniformity requirement in our process optimization goal. Surface roughness measured by atomic force microscopy (AFM) presented some evidence of the agglomeration of silane related particles, and the result was still satisfactory for the purpose of this research. This newly developed SiO2 deposition process is currently under verification with repeated experimental run on 4 inches wafer, and it will be adopted to Semiconductor Material and Process course offered in the Department of Electronic Engineering at Myongji University from spring semester in 2012.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.106-110
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• 2006

If drugs are made from nanoparticles, their formulations can be more effective than the conventional ones. Especially, water insoluble drugs having low absorption rates into our body could show improvement in their adsorption and bioavailability by decreasing their particle sizes to nanometers. In this study, polyvinylpyrrolidone (PVP) and various sugars were employed as stabilizers for the nanoparticles of a water insoluble drug, Itraconazole. Nanoparticles were successfully produced by the wet slurry process for five days. Then, spray drying converted the aqueous dispersions into dry powders, and the redispersibility of dried nanoparticles into water was investigated. The effects of temperature, pressure, and flow rate were studied to understand the importance of processing variables on redispersibility. It was found in particle size analysis that nanoparticles containing sugars have better redispersibility than those without sugars. Additionally, the mainly spherical morphology of dried nanoparticles was identified by SEM (Scanning Electron Microscopy) and AFM (Atomic Force Microscopy).

• Clean Technology
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• v.13 no.1 s.36
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• pp.34-45
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• 2007

Phase behavior of the ternary systems of water-insoluble simvastatin drug, which is well known to be effective drugs for hypercholesterolemia therapy, in solvent mixtures of dichloromethane and supercritical carbon dioxide was investigated to present a guideline of establishing operating conditions in the particle formation of the drugs by a supercritical anti-solvent recrystallization process utilizing dichloromethane as a solvent and carbon dioxide as an anti-solvent. The solubilities of simvastatin in the mixtures of dichloromethane and carbon dioxide were determined as functions of temperature, pressure and solvent composition by measuring the cloud points of the ternary mixtures at various conditions using a high-pressure phase equilibrium apparatus equipped with a variable-volume view cell. The solubility of the drug increased as the dichloromethane composition in solution and the system pressure increases at a fixed temperature. A lower solubility of the drug was obtained at a higher temperature. The second half of this work is focused on the particle formation of the simvastatin drug by a supercritical anti-solvent recrystallization process in a cylindrical high-pressure vessel equipped with an impeller. Microparticles of the simvastatin drug were prepared as functions of pressure (8 MPa to 12 MPa), temperature (303.15 K, 313,15 K), feed flow rate of carbon dioxide, and stirring speed (up to 3000 rpm), in order to observe the effect of those process parameters on the size and shape of the drug microparticles recrystallized.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.519-526
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• 2001

The effects of methyl isobutyl ketone(MIBK)/ethanol(EtOH) solvent mixtures on the dispension, particle size distribution and rheology of $Al_2$O$_3$/ZrO$_2$ nonaqueous suspensions were investigated by measuring sedimentation density and viscosity. The sedimentation density of $Al_2$O$_3$ and ZrO$_2$ particles increased in MIBK-rich($\geq$60 vol%) solvents with 'Hypermer' KD-1 as a dispersant. The ball-milled suspensions in 80MIBK/20EtOH(vol%) solvent exhibited the narrow and unimodal particle size distribution. Although all Suspensions exhibited the Pseduo-Plastic flow(Shear thinning) the shear thinning behavior was somewhat different depending on the mixture ratio of $Al_2$O$_3$/ZrO$_2$ and MIBK/EtOH. Under a given shear rate( <300 s$^{-1}$ for $Al_2$O$_3$; <3000 s$^{-1}$ for ZrO$_2$) the strongest shear thinning appeared in the $Al_2$O$_3$ and ZrO$_2$ suspensions with pure MIBK solvent. The shear thinning was nearly independable on the mixture ratio of $Al_2$O$_3$/ZrO$_2$ in case of using the identical solvent(80MIBK/20EtOH, vol%).

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.12
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• pp.1753-1757
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• 2012

A new liquid chromatographic tandem mass spectrometric (LC-MS/MS) assay for the quantification of ginsenoside Rb1 in human plasma was developed and validated. The separation was performed on a Agilent C18 column ($4.6mm{\times}150mm$, particle size 5 ${\mu}m$) with a gradient elution of 0.1% formic acid in water and 0.1% formic acid in methanol and a flow rate of 0.9 mL/min. The analyte was determined using electrospray positive ionization mass spectrometry in the multiple reaction monitoring (MRM) mode (m/z 1131.714${\rightarrow}$365.303). Human plasma samples were extracted with acetone : water (50:50) by the liquid-liquid extraction method. The method was linear over the dynamic range of 10~500 ng/mL with a correlation coefficient of r=0.9995. The intra-and inter-day precision over the concentration range of ginsenoside Rb1 was lower than 5.8% (correlation of variance, CV), and the accuracy was between 96.0~104.6%. This LC-MS/MS assay of ginsenoside Rb1 in human plasma is applicable for quantification in a pharmacokinetic study.

• Composites Research
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• v.35 no.6
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• pp.447-455
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• 2022

Currently, the problem of pollution of the marine environment by microplastics is emerging seriously internationally. In this study, to develop a lightweight portable microplastic collection device, the types and number of microplastics in 21 coastal areas nationwide in Korea were investigated. And CFRP (Carbon Fiber Reinforced Plastic), GFRP (Glass Fiber Reinforced Plastic), ABS (Acrylonitrile Butadiene Styrene copolymer) and aluminum were applied for design and analysis of microplastic collection device to have the durability, corrosion resistance and lightweight. As a result of sample collection and classification from the shore, it was confirmed that microplastics were distributed the most in Hamdeok beach, and the polystyrene was found to be mainly distributed microplastics. Particle information through coastal field survey and CFD (Computational Fluid Dynamics) analysis were used to analyze the flow rate and distribution of particles such as sand and impurities, which were applied to the structural analysis of the cyclone device using the finite element method. As a result of structural analysis considering the particle impact inside the cyclone device, the structural safety was examined as remarkable in the order of CFRP, GFRP, aluminum, and ABS. In the view of weight reduction, CFRP could be reduced in weight by 53%, GFRP by 47%, and ABS by 61% compared to aluminum for the cyclone device.

• Journal of Environmental Science International
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• v.10 no.4
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• pp.287-292
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• 2001

A packed bed of volcanic rock was used as deodorizing material to remove hydrogen sulfide($H_2$S) from air in a laboratory-scale column, and was inoculated with Thiobacillus sp. as $H_2S$ oxidizer. The effects of volcanic rock particle size distribution on system pressure drop were examined. Various tests have been conducted to evaluate the effect of $H_2S$ inlet concentration and CBCT(Empty Bed Contact Time) on $H_2S$ elimination. The pressure drop for particles of size range from 5.6 to 10 mm was 14 mm$H_2S$/m at a representative gas velocity of 0.25m/s. Biofilter using scoria and Thiobacillus sp. could get the stable removal efficiencies more than 99.9% under $H_2S$ inlet concentrations in the range from 30 to 1,100ppm at a constant gas flow rate of $15.2{\ell}$/min. $H_2S$ removal efficiencies greater than 99% were observed as long as EBCT was longer than 8sec at the 250ppm of $H_2S$ inlet concentration. When EBCT was reduced to 5.5 sec, $H_2S$ removal efficiency decreased by about 12 percent. The maximum $H_2S$ elimination capacity was determined to be 269g-$H_2S/m^3{\cdot}hr$.