• 한국안전학회지
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• 제31권5호
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• pp.1-6
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• 2016

The performance of a set of low-cost optical components used for measuring the optical density of PM particles was evaluated in the present study. To this end, the set of low-cost optical components was replaced with that of general optical components used to measure the PM optical density under identical experimental conditions. The optical densities measured from the set of general optical components were then compared to those obtained from the set of low-cost optical components. While the optical density is measured, another key parameter, the dimensionless extinction constant of PM particles (which is needed to optically measure the PM concentration) was also determined in the present study. The experimental results indicate that the optical density and PM concentration measurements performed by low-cost optical components are feasible, producing trackable variations in the OD and concentrations compared to values obtained from the set of general optical components.

• Applied Science and Convergence Technology
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• 제23권1호
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• pp.27-33
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• 2014

We have studied photovoltaic characteristics of single-junction GaAs solar cells with/without an $MgF_2/ZnS$ anti-reflective coating (ARC) illuminated by low-density concentration (<10 suns). By the ARC deposition, the short-circuit current density ($J_{SC}$) and the fill factor (FF) are increased by $5mA/cm^2$ and 5% at a standard illumination (1 sun), respectively, and the resulted conversion efficiency is enhanced by 45%. In contrast with the cell with no ARC showing a rapid degradation with increasing concentration power, the efficiency of ARC-deposited cell remains almost constant as ($17.7{\pm}0.3$)% regardless of the concentration. It informs that ARC treatment is very effective in GaAs concentrator solar cells.

• Journal of Electrochemical Science and Technology
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• 제8권3호
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• pp.197-205
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• 2017

Lead dioxide thin films were electrodeposited on nickel substrate from acidic lead nitrate solution. Current efficiency and thickness measurements, cyclic voltammetry, AFM, SEM, and X-ray diffraction experiments were conducted on $PbO_2$ surface to elucidate the effect of lead nitrate concentration, current density, temperature on the morphology, chemical behavior, and crystal structure. Experimental results showed that deposition efficiency was affected by the current density and solution concentration. The film thickness was independent of current density when deposition from high $Pb(NO_3)_2$ concentration, while it decreased for low concentration and high current density deposition. On the other hand, deposition temperature had negative effect on current efficiency more for lower current density deposition. Cyclic voltammetric study revealed that comparatively more ${\beta}-PbO_2$ produced compact deposits when deposition was carried out from high $Pb(NO_3)_2$ concentration. Such compact films gave lower charge discharge current density during cycling. SEM and AFM studies showed that deposition of regular-size sharp-edge grains occurred for all deposition conditions. The grain size for high temperature and low concentration $Pb(NO_3)_2$ deposition was bigger than from low temperature and high concentration deposition conditions. While cycling converted all grains into loosely adhered flappy deposit with numerous pores. X-ray diffraction measurement indicates that high concentration, high temperature, and high current density favored ${\beta}-PbO_2$ deposition while ${\alpha}-PbO_2$ converted to ${\beta}-PbO_2$ together with some unconverted $PbSO_4$ during cycling in $H_2SO_4$.

• 한국응용과학기술학회지
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• 제28권4호
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• pp.386-392
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• 2011

We are crystallized to the linear low density polyethylene(LLDPE) particles by a thermally induced phase separation(TIPS). TIPS process based on the phase separation mechanism was performed for the LLDPE system which undergoes liquid-solid phase separation. The linear low density polyethylene particle formation occurred by the nucleation and growth mechanism in the metastable region. Although the growth rates depended on the experimental conditions such as the polymer concentration and temperature, the particles were larger when the polymer concentration was higher or temperature was higher. The particles were observed by SEM. The LLDPE particle size distribution became broader when the polymer concentration was higher.

• Ocean and Polar Research
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• 제42권4호
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• pp.271-281
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• 2020

We investigated mesozooplankton in the Yellow Sea in spring to understand its community structure and relationship with environmental factors. Total mesozooplankton density ranged from 1,542 to 7,367 ind. m-3 and the biomass ranged from 3 to 42 mg C m-3. The total density and biomass had a positive relationship with chlorophyll-a (chl-a) concentration. The mesozooplankton community was divided into two groups at 125.5 E by cluster analysis: one was an inshore group and the other was an offshore group. The inshore group of mesozooplankton was of high density but low diversity, while the offshore group was of high diversity but low density. Copepod Acartia hongi and its copepodites were the most abundant species, comprising 27.8% of the total mesozooplankton density. A. hongi was especially abundant at the inshore, serving as the indicator species of the inshore group. Redundancy analysis found a positive relationship between the density of A. hongi and chl-a concentration. Oithona similis and Centropages abdominalis were 2nd and 3rd dominant species comprising 9 and 7% of the total density, respectively. The density of O. similis was positively related to water depth, but C. abdominalis was related to chl-a concentration. Chl-a concentration seems to influence significantly the mesozooplankton community structure in the Yellow Sea in spring, rather than water temperature or salinity.

• 한국표면공학회지
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• 제36권5호
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• pp.379-385
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• 2003

The surface morphology, the glossiness and the hardness of Zn-Cr and Zn-Cr-X(X:Co, Mn) alloy electrodeposits were investigated by using chloride bath with EDTA additive and flow cell system. The surface morphology of Zn-Cr alloy and Zn-Cr-Mn alloy changed from fine needle shape crystalline structure to colony structure of fine granular crystallites with increasing current density in the range of 20-100 $A/dm^2$. The surface morphology of Zn-Cr-Co alloy deposited from low Co concentration bath(2.5-10 g/$\ell$) was similar to that of Zn-Cr alloy, while that of Zn-Cr-Co alloy deposited from high cobalt concentration bath was fine granular crystalline structure in the same range of current density. The glossiness of Zn-Cr and Zn-Cr-Mn alloy increased noticeably with increasing current density, while that of Zn-Cr-Mn alloy decreased with increasing Mn concentration of bath in high current density region. The glossiness of Zn-Cr-Co alloy deposited from low Co concentration bath increased with current density while that of the alloy from high Co concentration bath decreased with increasing current density. The hardness of Zn-Cr and Zn-Cr-X alloy increased noticeably with current density.

• Corrosion Science and Technology
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• 제17권4호
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• pp.154-165
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• 2018

During the process of sulfur dioxide removal, flue gas desulfurization equipment provides a serious internal corrosion environment in creating sulfuric acid dew point corrosion. Therefore, the utilities must use the excellent corrosion resistance of steel desulfurization facilities in the atmosphere. Until now, the trend in developing anti-sulfuric acid steels was essentially the addition of Cu, in order to improve the corrosion resistance. The experimental alloy used in this study is Fe-0.03C-1.0Mn-0.3Si-0.15Ni-0.31Cu alloys to which Ru, Zn and Ta were added. In order to investigate the effect of $H_2SO_4$ concentration and the alloying elements, chemical and electrochemical corrosion tests were performed. In a low concentration of $H_2SO_4$ solution, the major factor affecting the corrosion rate of low alloy steels was the exchange current density for $H^+/H_2$ reaction, while in a high concentration of $H_2SO_4$ solution, the major factors were the thin and dense passive film and resulting passivation behavior. The alloying elements reducing the exchange current density in low concentration of $H_2SO_4$, and the alloying elements decreasing the passive current density in high concentration of $H_2SO_4$, together play an important role in determining the corrosion rate of Cu-bearing low alloy steels in a wide range of $H_2SO_4$ solution.

• 자원리싸이클링
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• 제14권1호
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• pp.55-63
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• 2005

This study investigated the electrochemical recovery of palladium in a HCl solution that is used for palladium leaching. The high acidity of HCl solution and the low concentration of Pd ions increased the cathodic overpotential and reduced the limiting current density. Lowering the current density produced dense deposits; however, they were under high tensile stress. Raising the temperature affected both the densification and the stress, which enabled the attainment of dense Pd deposits under low stress. Lowering the current density and raising the temperature up to 70$^{\circ}C$ was recommended for the recovery of palladium as sound bulk Pd deposits. Current efficiency was over 85% at the initial stage of recovery may decrease the current efficiency, since a low Pd ion concentration results in a low limiting current density.

• 생명과학회지
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• 제7권4호
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• pp.289-296
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• 1997

Antioxidative activity of fraction extracted from cultivation of Aspergillus sp. A-5 against oxidation of human low density lipoprotein(LDL) was investigated. Fractions of Aspergillus sp. A-5 cultivation was sucessively purified with ethyl acetate and silica gel column chromatography. The concentration of fraction 4 inhibited Cu$^{2+}$-induced oxidation of LDL almost completely. Band 3 isolated by the further purification of fraction 4 was higher than that of same concentration of $\alpha$-tocopherol, BHA and BHT. The elcetrophoretic mobility of oxidized LDL by addition of Band 3 was faster than that of native LDL, but slower than that of oxidzed LDL. It is concluded that fraction of Aspergillus cultivation contained antioxidants with the capacity to inhibit oxidative modification of LDL.

• 한국표면공학회지
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• 제18권3호
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• pp.105-115
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• 1985

Lead-tin-copper ternary alloy electrodeposition is conducted onto the inner bore surface of plain bearings as an overlay in order to investigate the effect of slot width, current density and fluoboric acid concentration on the uniformity of overlay. The thickness of overlay is analyzed by means of current distribution resulting from the overvoltage of plating bath and the apparent distance between cathode and anode. The result demonstrate that the uniformity of overlay is remarkably dependent of the slot size and current density, but has little bearing on the fluoboric acid concentration over 100g/L. This present study indicates that uniform overlay is obtainable within the tolerable thickness of ${\pm}2{\mu}m$ by using the slot width of 22mm. The surface morphology examination also shows the important role of concentration polarization of the micro-uniformity of overlay. The micro-uniformity has improved at the low concentration polarization which resulted from operating at the low current density and high fluoboric acid concentration. The surface morphology of deposits exhibits the vivid pyramid crystalline in the plating condition of low concentration polarizatio and all deposits have columnar structure parallel to the applied electric field regardless of the electroplating condition used.