• Macromolecular Research
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• v.15 no.4
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• pp.285-290
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• 2007

Ag nanoparticles were distributed onto polystyrene nanoparticle (PS-Ag) beads using two synthetic methodologies. In the first methodology, polystyrene (PS) beads were prepared via emulsion polymerization, with Ag nanoparticles subsequently loaded onto the surface of the PS beads. The polymerization of styrene was radiolytically induced in an ethanol (EtOH)/water medium, generating PS beads. Subsequently, Ag nanoparticles were loaded onto the PS beads via the reduction of Ag ions. The results from the morphological studies, using field emission transmission electron microscopy (FE-TEM), reveal the PS particles were spherical and nanosized, and the average size of the PS spherical particles decreased with increasing volume % of water in the polymerization medium. The size of the PS spherical particles increases with increasing radiation dose for the polymerization. Also, the amount of Ag nanoparticle loading could be increased by increasing the irradiation dose for the reduction of the Ag ions. In the second methodology, the polymerization of styrene and reduction of Ag ions were simultaneously performed by irradiating a solution containing styrene and Ag ions in an EtOH/water medium. Interestingly, the Ag nanoparticles were preferentially homogeneously distributed within the PS particles (not on the surface of the PS particles). Thus, Ag nanoparticles were distributed onto the surface of the PS particles using the first approach, but into the PS clusters of the particles via the second. The antimicrobial efficiency of a cloth coated with the Ag-PS composite nanoparticles was tested against bacteria, such as Staphylococcus aureus and Klebsiella pneumoniase, for 100 water washing cycles.

• Journal of Korean Society on Water Environment
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• v.21 no.5
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• pp.458-463
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• 2005

Considering the characteristics of a filtration bio-reactor equipped with a mesh filter module which can effectively maintain high concentration of biomass and enhanced solid-liquid separation performance, the hybrid process of filtration bio-reactor combined with coagulation was investigated to get improved filtration characteristics as well as water quality in this work. Two bio-reactors (Run-1 & Run-2) were operated under the following conditions: working volume of 25 L, continuous loading of a synthetic wastewater (BOD: 200 mg/L, T-N: 50 mg/L, T-P: 5 mg/L), where an appropriate amount of alum ($Al_2(SO_4)_3{\cdot}18H_2O$) was added once a day into the reactor (Run-2). In the system without using a alum (Run-1), the clogging of mesh filter module was observed two times through 85 days of whole operation. Meanwhile, the filter module did not clog even at higher MLSS concentration (6,000~12,000 mg/L) and the stable filtration (0.7 mid) was continued in the case of using a alum. Due to the stable formation of cake layers, BOD and SS were shown below 6 and 3 mg/L, respectively. T-P and pH of the effluent were changed because of the intermittent addition of the alum. In the case of Al/P=2.5, the average T-P removal efficiency per day was 85.2% and the average T-P concentration of the effluent was 0.3 mg/L. However, the removal efficiency of phosphate was influenced by pH in the reactor.

• Journal of Korean Society on Water Environment
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• v.21 no.5
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• pp.464-469
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• 2005

In the nonwoven fabric filter bioreactor (NFBR), both the construction and the operation costs could be saved because a high concentration of microorganism can be maintained in the reactor as in the membrane bioreactor. However, the NFBR process has been investigated only under aerobic and/or anoxic conditions, In this research, a basic anaerobic treatment experiment was performed at $35^{\circ}C$ by feeding an airtight NFBR with a concentrated synthetic organic wastewater. The organic loading rate (OLR) of the NFBR was increased stepwise from $0.25kg\;COD/m^3-day$ to $0.77kg\;COD/m^3-day$ by gradually decreasing the hydraulic retention time from 20 days to 13 days. The results of the research showed that the best COD removal efficiency achieved at the OLR of $0.67kg\;COD/m^3-day$ with a value of 99.3%. The methane content of the produced gas was highest with a value of 61.2% at the OLR of $0.33g\;COD/m^3-day$. The highest methane production rate was $0.89g\;COD/m^3-day$ at the same OLR. The operation was terminated at the OLR of $0.77kg\;COD/m^3-day$ because of the deterioration in COD removal efficiency, gas production rate, and the methane content of the gas. Further researches are recommended for the NFBR to be employed for anaerobic treatment of organic wastewaters.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.45-53
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• 1987

The purpose of this research was to study the kinetics of a packed bed aerobic biofilm process. Experiments were carried out by feeding an aerated packed bed reactor with a synthetic wastewater. The reactor packed with glass beads as media had a nominal hydraulic detention time of 5 hours. The flow pattern in the reactor was determined by a tracer test using a NaCl solution to be a completely-mixed type. The results of the research showed that the F/M ratio in the reactor was almost constant since the the biomass increased due to the growth of biofilm as the volumetric organic loading increased. It was also proved theoretically and experimentally that packed bed aerobic biofilm process could be analyzed by the kinetics of completely-mixed activated sludge process with sludge recycle.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.207-214
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• 2003

Removal efficiency of methyl iodide at high temperature process by TEDA-impregnated activated carbon used for radioiodine retention in nuclear facility was experimentally compared with that of silver ion-exchanged synthetic zeolite(AgX), In temperature ranges of$30^{\circ}C$ to $400^{\circ}C$, adsorption capacity of un-impregnated carbon was sharply decreased, but TEDA-impregnated carbon showed similar values of adsorption capacity of AgX even around $100^{\circ}C$. Especially, loading amount of methyl iodide on TEDA carbon up to$250^{\circ}C$ represented higher values compared to un-impregnated carbon. Breakthrough curves of methyl iodide in fixed bed packed with AgX and TEDA-impregnated carbon at high temperature was compared. Removal mechanism of methyl iodide on AgX was proposed, based on analysis of by-product gas generated from adsorption reaction.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.138-145
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• 2011

Diesel particulate filter (DPF) systems are being used to reduce the particulate matter emission of diesel vehicles. The DPF should be regenerated after certain driving hours or distance to eliminate soot in the filter. The most widely used method is active regeneration with oxygen at $550{\sim}650^{\circ}C$. Syngas (synthetic gas) can be used to lower the regeneration temperature of Catalyzed DPF (CDPF). The syngas is formed by fuel reforming process of CPOx (Catalytic Partial Oxidation) at specific engine condition (1500rpm, 2bar) using 1wt.% $Rh/CeO_2-ZrO_2$ catalyst. The oxidation characteristics of PM with syngas supplied to filter were studied using partial flow system that can control temperature and flow rate independently. The filter is coated with washcoat loading of $25g/ft^3$ $Pt/Al_2O_3-CeO_2$, and multi-channel CDPF (MC-CDPF) was used. The filter regeneration experiments were performed to investigate the effect of syngas exothermic reaction on soot oxidation in the filter. For this purpose, before oxidation experiment, PM was collected about 8g/L to the filter at engine condition of 1500rpm, bmep 8bar and flow temperature of $200^{\circ}C$ Various conditions of temperature and concentration of syngas were used for the tests. Regeneration of filter started at 2% $H_2$ and CO concentration respectively and inlet temperature of $260^{\circ}C$. Filter Regeneration occurs more actively as the syngas concentration becomes higher.

• International Commerce and Information Review
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• v.6 no.2
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• pp.361-384
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• 2004

Recently the port logistics service has been recognized as a important function of the international logistics, therefore, a lot of papers have been issued concerning the measurement of the service quality of that. But in spite of variety of papers, we can not find out the papers concerning the model of the synthetic customer satisfaction. And also the most of papers concerning the customer satisfaction of service quality have been focused not by cognitive evaluation of the customer, but by affective response. In this thesis, the authors are postulating the model and hypothesis to achieve the research by using the Gr$\"{o}$nroos's model. In order to research the relationship between the port logistics service quality and the customers satisfaction, we are selecting the shipping companies located in Busan and Kwangyang as purchaser and the loading and unloading companies as supplier, and the questionnaires was performed to them. In the result of the empirical study, the technical quality of the port logistics service are affecting directly on the customer satisfaction, but the functional quality are affecting not directly on the customer satisfaction. And also the customer response(affective response) has been proved that it has been exercised as a intermediate role between the port logistics service quality and the customer satisfaction. Therefore it is proved that the affective response of the customer has been exercised a crucial role in the course of supplying the port logistics service.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.795-796
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• 2010

Interest has been increasing worldwide in Fischer-Tropsch synthesis (F-T) as a method of producing synthetic liquid fuels from biomass. Hydroisomerization of $C_7-C_{15}$ paraffins applies to production of diesel fuel with high cetane number and improved cold flow properties, such as viscosity, pour point and freezing point. The commercial products such as fuel jet produced from F-T synthesis should have low freezing and pour points. In this study, our major aim is to develop a catalyst for hydroisomerization of synthesis-oil for bio-jet fuel. Effects of zeolites and platinum loading on hydroisomerization of dodecane were investigated as a model reaction in a batch reactor.

• Steel and Composite Structures
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• v.20 no.2
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• pp.317-335
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• 2016

Concentrically braced steel frames (CBFs) can be optimised during the seismic design process by using lateral loading distributions derived from the concept of uniform damage distribution. However, it is not known how such structures are affected by uncertainties. This study aims to quantify and manage the effects of structural and ground-motion uncertainty on the seismic performance of optimum and conventionally designed CBFs. Extensive nonlinear dynamic analyses are performed on 5, 10 and 15-storey frames to investigate the effects of storey shear-strength and damping ratio uncertainties by using the Monte Carlo simulation method. For typical uncertainties in conventional steel frames, optimum design frames always exhibit considerably less inter-storey drift and cumulative damage compared to frames designed based on IBC-2012. However, it is noted that optimum structures are in general more sensitive to the random variation of storey shear-strength. It is shown that up to 50% variation in damping ratio does not affect the seismic performance of the optimum design frames compared to their code-based counterparts. Finally, the results indicate that the ground-motion uncertainty can be efficiently managed by optimizing CBFs based on the average of a set of synthetic earthquakes representing a design spectrum. Compared to code-based design structures, CBFs designed with the proposed average patterns exhibit up to 54% less maximum inter-storey drift and 73% less cumulative damage under design earthquakes. It is concluded that the optimisation procedure presented is reliable and should improve the seismic performance of CBFs.

• Journal of Life Science
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• v.9 no.3
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• pp.268-275
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• 1999

Rhodopseudomonas sp. was immobilized in three supports(agar, k-carrageenan, and PVA) in order to remove nitrate in wastewater coming from fish farm. Among them 3% agar was the most suitable support when denitrification rate and bead durability were tested. Optimum bead size was 4mm-diameter when the substrate transfer into the bead and shear stress for bead were considered, and optimum cell loading was 25mg dry $cells/cm^2$gel gel. Ethanol was the best as a carbon source, and optimum C:N ratio, temperature and pH were 1.5:1, $31^{\circ}C$,, and 6, respectively. Under these conditions the maximum denitrification rate in synthetic wastewater was $$345{\MU}{\ell};N_2/Cm^3 gel{\cdot}hr;and that in modified MYC medium was 450{\MU}{\ell}};N_2/Cm^3 gel{\cdot}hr $$.