• Journal of the Mineralogical Society of Korea
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• v.26 no.1
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• pp.1-8
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• 2013

This study was carried out to test the possibility of using an environmentally friendly method of leaching silver concentrate from the Samjo mine. The Samjo mine ore contained minerals such as pyrite, chalcopyrite, galena, arsenopyrite, and sphalerite. The concentrate samples tested with the thiourea solution were roasted at $750^{\circ}C$. The results of different experimental conditions showed that the highest silver leaching rate was obtained when the concentration of thiourea was at 0.8 g with ferric sulfate at 0.425 g and the leaching temperature at $60^{\circ}C$. The Ag leaching rate obtained was 91.5% at a pulp density of 10%. However, in the XRD analysis, peaks of pyrite, galena, and hematite were still found in the leached solid residues in which the Ag leaching rate was the highest. it is expected that the unrecovered silver in the solid residue can be lost.

• Fashion & Textile Research Journal
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• v.13 no.2
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• pp.263-268
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• 2011

One-step reduction/dyeing method was applied for ramie dyeing with natural indigo powder. The effect of reduction/dyeing conditions including the pH of bath, dye temperature and time, and concentration of indigo powder and reduction agent on dye uptake and color properties were investigated. Regardless of addition of alkali, the dyed fabrics appeared in the PB Munsell color range(${\lambda}_{max}$: 660 nm) and the dye uptake was much higher with no addition of sodium hydroxide. Dyeing was carried out through the use of only sodium hydrosulfite in the bath. The maximum dye uptake was obtained at 60 for 30min. Saturated dye uptake was obtained at 2 g/L of sodium hydrosulfite concentration up to 2 g/ L of indigo powder. Whereas, at higher indigo powder concentration (4 g/L), more than 3 g/L of reducing agent concentration was required for obtaining the saturated dye uptake. Color reproducibility was reliable with color difference in the range of 0.03~0.16. Regardless of color strength, fastness to rubbing was acceptable with a 3/4~4/5. Fastness to washing, dry cleaning, and light of samples with low color strength were poor. Whereas, fastness to washing, dry cleaning, and light of samples with high color strength were very good.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3125-3134
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• 2010

Three-way catalyst durability in the Korea requires 5 years/80,000km in 1988 but require 10 years/120,000km after 2002. Domestic three-way catalyst satisfies exhaust gas conversion efficiency or pressure drop etc. but don't satisfy thermal durability. Three-way catalyst maintains high temperature in interior domain but maintain low temperature on outside surface. This study evaluated thermal durability of three-way catalyst by thermal flow and structure analysis and the procedure is as followings. Thermal flow parameters ranges were determined by vehicle test and basic thermal flow analysis. Response surface for rear catalyst temperature was constructed using the design of experiment (DOE) for thermal flow parameters. Thermal flow parameters for rear catalyst temperature in vehicles examination were predicted by desirability function. Temperature distribution of three-way catalyst was estimated by thermal flow analysis for predicted thermal flow parameters.

• Progress in Superconductivity and Cryogenics
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• v.13 no.1
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• pp.6-11
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• 2011

The $BaHfO_3$ (BHO) buffer layer on the IBAD MgO template was turned to be effective for a successful fabrication of $GdBa_2Cu_3O_{7-{\delta}}$ (GdBCO) films with high critical current density ($J_c$). Both the BHO buffer layers and GdBCO films were prepared by pulsed laser deposition (PLD). The effects of the PLD conditions, including substrate temperature ($T_s$), oxygen partial pressure ($PO_2$), and deposition time on the in-plane texture, surface roughness, and microstructures of the BHO buffer layers on the IBAD MgO template were systematically studied for processing optimization. The c-axis oriented growth of BHO layers was insensitive to the deposition temperature and the film thickness, while the in-plane texture and surface roughness of those were improved with increasing $T_s$ from 700 to $800^{\circ}C$. On the optimally processed BHO buffer layer, the highest $J_c$ value (77 K, self-field) of 3.68 $MA/cm^2$ could be obtained from GdBCO film deposited at $780^{\circ}C$, representing that BHO is a strong candidate for the buffer layer on the IBAD MgO template.

• YAKHAK HOEJI
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• v.40 no.2
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• pp.155-162
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• 1996

Hyperkeratinization is a dermatologic disorder, which is due to the increase of corneocyte cohesion force. Glycolic acid, an alpha hydroxy acid(AHA), has been used to breakdown the hyperkeratinization processes. However, it has a problem of skin irritation when applied topically, due to the strong acidity especially in high concentration. A molecular optimization of glycolic acid has been tried to reduce the skin irritation by the way of prodrug formation. Ethyl glycolate was synthesized by the esterification of glycolic acid with ethanol in acidic conditions in the presence of sulfuric acid, and examined under the spectroscopic trials, such as UV, IR, $^1H$-NMR, and GC-MS. The physicochemical and biopharmaceutical properties of the prodrug were also evaluated. Through the toxicological tests of both skin irritation and eye mucous irritation, it has been proved that ethyl glycolate was less irritant than glycolic acid, since the pH value of synthetic prodrug was higher than that of glycolic acid. In the penetration test through nude mouse skin by diffusion cell, ethyl glycolate was continuously hydrolyzed to glycolic acid, which was assayed form the receptor compartment. It was obtained that the penetrated amount of ethyl glycolate was five times higher than that of glycolic acid. These results suggest that ethyl glycolate might be a successful prodrug of glycolic acid to reduce the skin irritation and to increase the skin penetration as well.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.101-109
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• 1990

The friction welding has more technical and economic advantages than the other welding processes. As this welding process has the characteristics such as curtailment of production time, materials, cost reduction, etc., it has been widely used in production of various mechanical components which have complex shapes. So, this paper deals with optimizing the friction welding conditions and analyzing various mechanical properties of the friction welded joints of torsion bar material SUP9A bar to bar. The results obtained are summarized as follows; 1) The quantitative relation between heating time($t_{1}$, sec) and total upset(U, mm)can be obtained. The empirical formula obtained is ; U = 3.29$t_{1}$ + 1.6 2) The tensile strength($\sigma_{t}$, kgf/$mm^{2}$) of friction welding joints as post weld heat treated(PWHT) depends upon heating time($t_{1}$, sec) quantitatively and the empirical formula obtained is ; $\sigma$= -5.1$t_{1}\;^{2}$+44.90$t_{1}$+45.2 3) It is certain that the optimum condition for friction welded joints of SUP9A steel bars of diameter 14.5mm is, considering on various properties such as tensile strength, torsional strength, impact energy and strain of the joints after PWTH ; n = 2000rpm, $P_{1}$=8kgf/$mm^{2}$, $P_{2}$=20kgf/$mm^{2}$, $t_{1}$=4sec, $t_{2}$=3sec 4) The tensile strength, torsional strength and hardness were increased with the increased with the increasing carbon equivalent, but toughness was decreased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.5
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• pp.386-392
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• 2020

In this study, the drift current characteristics of charged particles are analyzed for panels fabricated by varying the waveform biasing of the active particle loading method (APLM), which is a method driven by the electrophoretic principle of loading charged particles into a cell of a barrier rib-type electronic paper. We prepare 3 panels using APLM and 1 panel without APLM. The waveform of APLM uses square wave and ramp wave, and the step voltage wave is applied to the driving voltage. The drift currents measured from the square wave and ramp wave with the same period applied by APLM are 4.872 µC and 5.464 µC, respectively, and the ramp wave is shown to be relatively advantageous for loading charged particles that have a large q/m. The time-current curve results confirm that the abrupt movement of charged particles is occurring. When the step form wave signal with a short time of 1s is first applied, initial large movement of the charged particles is confirmed to occur in all samples, which is understood as the effect of applying the voltage necessary to remove the imaging force. The results of this study are expected to improve the loading of charged particles into the electronic paper cell, driven by the electrophoretic principle and optimization of the driving conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.47-52
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• 2013

The higher energy efficiency for ship and the lower pollution for global environment are required strictly. However the performance of marine diesel engine is gradually deteriorated with time. And also the operation condition is varied with sea conditions. Hence the optimization for operating condition of marine engines is needed for energy saving and environment kindly. In this paper, it was attempted to investigate the influence of aging for marine diesel engine. The deterioration of engine performance is assessed by the calculation results of the simulation program for two-stroke marine diesel engine developed by author which was reported before. And three parameters for deterioration of engine performance were considered such as lower efficiency of turbocharger by fouling, increase of blow-by gas due to wear of cylinder liner and getting worse of combustion by poor injection. By the results, it was shown that the influence of engine performance by aging was relatively not so small - 10.4 bar low in Pmax and 3.2% decrease in Pmi.

• Journal of Korean Society of Transportation
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• v.22 no.4 s.75
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• pp.159-173
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• 2004

This study utilizes the fuzzy logic and genetic algorithm to improve the existing incident detection models by addressing the problems associated with "crisp" thresholds and model transferability (applicability). The model's major components were designed to be a set of the fuzzy inference engines, and for the self-adaptation capability the genetic algorithm was introduced in optimization(or training) of the fuzzy membership functions. This approach is often called "the hybrid of fuzzy-genetic algorithm" The model performance was tested and found to be compatible with that of the existing well-recognized models in terms of performance measures such as detection rate, false alarm rate, and detection time. This study was not an effort for simple improvement of the model performance, but an experimental attempt to incorporate new characteristics essential for the incident detection model to be universally applicable for various roadway and traffic conditions. The study results prove that the initial objective of the study was satisfied, and suggest a direction that the future research work in this area must follow.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.255-260
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• 2004

Recently, the technologies related to the swash plate type oil hydraulic piston pump are requiring extreme technologies to overcome the limit of high efficiency in cope with high speed and pressure, and are devoted to compact the unit, to gain low noise level, and to adopt electronic technologies, and the question regarding to maximize the mechanical efficiency, that is, to minimize the torque loss by minimizing the leakage loss in the relative sliding region but these are in trade-off relation that tribological responding is very difficult. Cylinder block-valve pate in high speed relative sliding motion has the characteristics that should be extremely controlled for the optimization of these leakage loss and mechanical efficiency, and pressure resistance designing of them is important for high pressure performance. But, studies on the stress analysis of these parts have not been performed briskly, so in this paper the stress distribution and the region where the highest displacement appears are described through the static stress analysis using CATIA V5. Through the future studies on these theme, it has the purpose of finding the suitable materials for the other parts as well as cylinder block and valve plate, in cope with high pressure operation through the stress analysis with the most similar conditions for the practical operation.