• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.98-102
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• 2010

Magnolia kobus leaf extract was used for the synthesis of bimetallic Au core-Ag shell nanoparticles. Gold seeds and silver shells were formed by first treating aqueous solution of $HAuCl_4$ and then $AgNO_3$ with the plant leaf extract as reducing agent. UV-visible spectroscopy was monitored as a function of reaction time to follow the formation of bimetallic nanoparticles. The synthesized bimetallic nanoparticles were characterized with transmission electron microscopy(TEM), energy dispersive X-ray spectroscopy(EDS), and X-ray photoelectron spectroscopy(XPS). TEM images showed that the bimetallic nanoparticles are a mixture of plate(triangles, pentagons, and hexagons) and spherical structures. The atomic Ag contents of the bimetallic Au/Ag nanoparticles determined from EDS and XPS analysis were 34 and 65 wt%, respectively, suggesting the formation of bimetallic Au core-Ag shell nanostructure. This core-shell type nanostructure is expected to have potential for application in surface enhanced Raman spectroscopy and in the sensitive detection of biomolecules.

• Journal of the Korean Electrochemical Society
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• v.15 no.4
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• pp.236-241
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• 2012

It is widely recognized that it is hard to prepare hydrophilic graphite nanoparticles because of their high crystallinity and inert characteristics. In this study, we successfully synthesized the hydrophilic graphite nanoparticles by using liquid phase pulsed laser ablation method which has been actively employed for the thin film deposition up to now. The obtained hydrophilic graphite showed an ultra-high dispersion stability in water, because the hydrophilic functional groups like carboxyl and carbonyl group was simultaneously introduced onto the graphite surface with the nanoparticle formation, as confirmed by FT-IR and zeta potential measurements. Finally, a markedly enhanced gas sensing ability for acetone was shown in comparison with the conventional carbon black for the carbon polymer composite sensor with polyethyleneglycol (PEG).

• Journal of Hydrogen and New Energy
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• v.31 no.5
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• pp.489-497
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• 2020

The Li-ion battery is considered to be one of the potential power sources for electric vehicles. In fact, the efficiency, reliability, and cycle life of Li-ion batteries are highly influenced by their thermal conditions. Therefore, a novel thermal management system is highly required to simultaneously achieve high performance and long life of the battery pack. Basically, thermal modeling is a key issue for the novel thermal management of Li-ion battery systems. In this paper, as a basic study for battery thermal modeling, temperature distributions inside the simple Li-ion battery pack (comprises of nine 18650 Li-ion batteries) under a 1C discharging condition were investigated using measurement and computational fluid dynamics (CFD) simulation approaches. The heat flux boundary conditions of battery cells for the CFD thermal analysis of battery pack were provided by the measurement of single battery cell temperature. The temperature distribution inside the battery pack were compared at six monitoring locations. Results show that the accurate estimation of heat flux at the surface of single cylindrical battery is paramount to the prediction of temperature distributions inside the Li-ion battery under various discharging conditions (C-rates). It is considered that the research approach for the estimation of temperature distribution used in this study can be used as a basic tool to understand the thermal behavior of Li-ion battery pack for the construction of effective battery thermal management systems.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.753-760
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• 2007

For protection of the cylinder wall of the ball mill for grinding raw ore. the inner side of the cylinder is covered with rubber liner. The rubber is easily worn down because the rubber relatively soft compared with raw ore. So the rubber liner in the ball mill cylinder must be replaced almost every year and the cost for replacing rubber liner formidable. In this paper, for reducing or excluding the cost of replacing rubber liner the basalt liner is designed. The basalt materials are generally harder than raw ore and the basalt liner in the ball mill does not wear down and so it can be used almost permanently. The concave surfaces are made on the liner of the ball mill and the liner in the cylinder wall plays also the role of raising the steel balls mixed in the raw ore. The section profiles of the concave surface have an important effect on the performance of the ball mill. The deep concave grooves raise the steel balls to high levels and give the large potential energy to the steel balls impacting to the raw ore. But if the concave grooves are too deep. the steel balls raised too high by the concave grooves fly along the parabolic path and reach to the other side of cylinder wall and so the steel balls do not play the roles of grinding the raw ore. The forces acting to a steel ball in a concave groove of the cylinder liner are also analyzed in this paper. The formulas calculating the height and the impact point of the steel ball are introduced and presented. Based to these formulas, the optimum section profiles of the basalt liner are presented.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.4
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• pp.341-348
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• 2005

Bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste because of its low permeability, high sorption capacity, self sealing characteristics, and durability in nature. In this study, the potential for separation of bentonite particles caused by the groundwater erosion was studied experimentally for a Korean Ca-bentonite under the relevant repository conditions. Results showed that bentonite particles can be generated at the bentonite/granite interface and mobilized by the water flow although the intrusion of bentonite into fracture by swelling pressure was observed to be small. Different processes of mobilization of theses colloids from the compacted bentonite block have been identified in this study. The concentration of particles eluted in water was increased as the flow rate increased. Thus the result reveals that the erosion of the bentonite surface due to the groundwater flow together with intrusion processes is the main mechanism that can mobilize bentonite colloids in the fracture of the granite.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.409-409
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• 2011

All solid-state thin film lithium batteries have many applications in miniaturized devices because of lightweight, long-life, low self-discharge and high energy density. The research of cathode materials for thin film lithium batteries that provide high energy density at fast discharge rates is important to meet the demands for high-power applications. Among cathode materials, lithium manganese oxide materials as spinel-based compounds have been reported to possess specific advantages of high electrochemical potential, high abundant, low cost, and low toxicity. However, the lithium manganese oxide has problem of capacity fade which caused by dissolution of Mn ions during intercalation reaction and phase instability. For this problem, many studies on effect of various transition metals have been reported. In the preliminary study, the Sn-substituted LiMn2O4 thin films prepared by pulsed laser deposition have shown the improvement in discharge capacity and cycleability. In this study, the thin films of LiMn2O4 and LiSn0.0125Mn1.975O4 prepared by RF magnetron sputtering were studied with effect of deposition parameters on the phase, surface morphology and electrochemical property. And, all solid-state thin film batteries comprised of a lithium anode, lithium phosphorus oxy-nitride (LiPON) solid electrolyte and LiMn2O4-based cathode were fabricated, and the electrochemical property was investigated.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.2
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• pp.103-111
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• 2014

The wave power, extracted from a circular array of small power buoys, is investigated under the potential theory. It is assumed that the buoy's radius, the draft, and the separation distance are much smaller than the water depth, the wave length, and the radius of a circular deployment area. The boundary value problem involving the macro-scale boundary condition on the mean surface covered by buoys is solved using the eigenfunction expansion method. The capture width, which is defined as the ratio of the extracted power to the wave power per unit length of the incident wave crest, is assessed for various combinations of packing ratio, radius of a circular array, and PTO damping coefficient. It is found that the circular array deployment is more effective in the viewpoint of efficiency than the single large buoy of the same total displaced volume.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.4
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• pp.242-251
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• 2020

In this study, the extraction efficiency and reflection coefficient by a two-dimensional OWC (Oscillating Water Column) WEC (wave energy converter) installed in front of a seawall was investigated for regular/irregular waves. The matched eigenfunction expansion method (MEEM) based on the linear potential theory was applied as an analytical tool. The diffraction problem by the incident wave in the open-chamber and the radiation problem by the oscillating pressure in the closed-chamber were solved to obtain the volume fluxes at the internal free-surface. Applying the volume fluxes into the continuity equation for the airflow in a chamber, we got the oscillating air pressure. The maximum extracted power and corresponding reflection coefficient were determined at the optimal turbine coefficient that maximizes the extracted power. OWC device designed for a high extracted efficiency simultaneously contributes to reduce reflected waves.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2841-2848
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• 2010

Quasiclassical trajectory (QCT) method has been used to investigate stereodynamics information of the reaction $O(^1D)+H_2{\rightarrow}\;OH$+H on the DK (Dobbyn and Knowles) potential energy surface (PES) at a collision energy of 23.06 kcal/mol, with the initial quantum state of reactant $H_2$ being set for v = 0 (vibration quantum number) and j = 0-5 (rotation quantum number). The PDDCSs (polarization dependent differential cross sections) and the distributions of P($\theta_r$), P($\phi_r$), P($\theta_r$, $\phi_r$) have been presented in this work. The results demonstrate that the products are both forward and backward scattered. As j increases, the backward scattering becomes weaker while the forward scattering becomes slightly stronger. The distribution of P($\theta_r$) indicates that the product rotational angular momentum j' tends to align along the direction perpendicular to the reagent relative velocity vector k, but this kind of product alignment is found to be rather insensitive to j. Furthermore, the distribution of P($\phi_r$) indicates that the rotational angular momentum vector of the OH product is preferentially oriented along the positive direction of y-axis, and such product orientation becomes stronger with increasing j.

• Nuclear Engineering and Technology
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• v.50 no.2
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• pp.229-236
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• 2018

Accident-tolerant fuels (ATFs) are currently of high interest to researchers in the nuclear industry and in governmental and international organizations. One widely studied accident-tolerant fuel concept is multilayer cladding (also known as coated cladding). This concept is based on a traditional Zr-based alloy (Zircaloy-4, M5, E110, ZIRLO etc.) serving as a substrate. Different protective materials are applied to the substrate surface by various techniques, thus enhancing the accident tolerance of the fuel. This study focuses on the results of testing of Zircaloy-4 coated with pure chromium metal using the cold spray (CS) technique. In comparison with other deposition methods, e.g., Physical vapor deposition (PVD), laser coating, or Chemical vapor deposition techniques (CVD), the CS technique is more cost efficient due to lower energy consumption and high deposition rates, making it more suitable for industry-scale production. The Cr-coated samples were tested at different conditions ($500^{\circ}C$ steam, $1200^{\circ}C$ steam, and Pressurized water reactor (PWR) pressurization test) and were precharacterized and postcharacterized by various techniques, such as scanning electron microscopy, Energy-dispersive X-ray spectroscopy (EDX), or nanoindentation; results are discussed. Results of the steady-state fuel performance simulations using the Bison code predicted the concept's feasibility. It is concluded that CS Cr coating has high potential benefits but requires further optimization and out-of-pile and in-pile testing.