• Journal of Electrochemical Science and Technology
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• v.8 no.3
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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 $H_2SO_4$.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.502-514
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• 1998

The purpose of this study is to observe the corrosion characteristcs of four dental amalgams(CAULK FINE CUT, CAULK SPHERICAL, DISPERSALLOY, TYTIN) and to determine a function of chloride concentration through the anodic polarization curve obtained by using a potentiostat. After each amalgam alloy and Hg being triturated, the triturated mass was inserted into the cylinderical metal mold, and condensed by hydrolic pressure. Each specimen was removed from the metal mold. 24 hours after condensation, specimens were polished with the emery paper and stored at room temperature for 6 months. The anodic polarization curves were employed to compare the corrosion behaviours of the amalgam m KCl and KCl-NaCl solution, which had chlonde concentration of 0.4 g/l, 0.8 g/l, 1.2 gil, and 1.6 gil at $37^{\circ}C$ with 3-electrode potentiostat. After the immersion of specimen in electrolyte for 1 hour, the potential scan was begun. The potential scan range was - 1500mV ~+800mV(vs. S.C.E.) in the working electrode and the scan rate was 50mV/sec. The results were as follows, 1. The corrosion potential. the potential of anodic current peak, and transpassive potential in the solution of high chloride concentration shifted to more cathodic direction than those in the solution of low concentration, and the current density in the solution of high chloride concentration was higher than that in the solution of low concentration. 2. The corrosion potential, the potential of anodic current peak, and transpassive potential for CAULK FINE CUT amalgam were the most cathodic among the others, and the current density were the highest among the others. 3. In the solution of low chloride concentration, the corrosion potential, the potential of anodic current peak, and transpassive potential for DISPERSALLOY were the most anodic among the others, however in the solution of high chloride concentration, those for TYTIN were the most anodic among the others. 4. The anodic polarization curve for CAULK SPHERICAL was similar to that for high copper amalgams.

• Journal of Environmental Science International
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• v.28 no.3
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• pp.291-301
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• 2019

This study was conducted to investigate the effect of salt concentration and turbidity on the inactivation of Artemia sp. by electrolysis, UV photolysis, electrolysis+UV process to treat ballast water in the presence of brackish water or muddy water caused by rainfall. The inactivation at different salt concentrations (30 g/L and 3 g/L) and turbidity levels (0, 156, 779 NTU) was compared. A decrease in salt concentration reduced RNO (OH radical generation index) degradation and TRO (Total Residual Oxidant) production, indicating that a longer electrolysis time is required to achieve a 100% inactivation rate in electrolysis process. In the UV process, the higher turbidity results in lower UV transmittance and lower inactivation efficiency of Artemia sp. Higher the turbidity resulted in lower ultraviolet transmittance in the UV process and lower inactivation efficiency of Artemia sp. A UV exposure time of over 30 seconds was required for 100% inactivation. Factors affecting inactivation efficiency of Artemia sp. in low salt concentration are in the order: electrolysis+UV > electrolysis > UV process. In the case of electrolysis+UV process, TRO is lower than the electrolysis process, but RNO is more decomposed, indicating that the OH radical has a greater effect on the inactivation effect. In low salt concentrations and high turbidity conditions, factors affecting Artemia sp. inactivation were in the order electrolysis > electrolysis+UV > UV process. When the salt concentration is low and the turbidity is high, the electrolysis process is affected by the salt concentration and the UV process is affected by turbidity. Therefore, the synergy due to the combination of the electrolysis process and the UV process was small, and the inactivation was lower than that of the single electrolysis process only affected by the salt concentration.

• Journal of Environmental Science International
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• v.27 no.6
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• pp.349-358
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• 2018

In this study, using coke dust from ironwork, the pulse pressure on a pulse air jet bag filter was investigated considering the influence of the pressure loss due to filtration velocity and pressure intervals. The research on the optimal pulse pressure prediction of a pulse air jet type bag filter using coke dust showed the following results. Pressure loss volatility produced by the pulse pressure under low dust concentration(0.5, $1g/m^3$) and low face velocity(1.25 m/min) was less than $10mmH_2O$. This suggests that the pulse pressure has a low impact on the pressure loss. In contrast, pressure loss volatility under high dust concentration($3g/m^3$) and high face velocity(1.75 m/min) was $25mmH_2O$. Therefore, pulse pressure with high dust concentration and high face velocity has a strong influence on the pressure loss volatility, compared to the condition of low dust concentration and low face velocity. The optimal pulse pressure of inlet dust concentration($0.5g/m^3$) was $6kg/cm^2$ under the same face velocity(1.75 m/min). As concentration increased from 1 to $2g/m^3$, the pulse pressure gradually reached $5kg/cm^2$ thus indicating that the pulse pressure($5kg/cm^2$) is pertinent at a high concentration($3g/m^3$). The pulse intervals: 20, 25 and 30 sec, which are relatively longer than 10 and 15 sec, corresponded to high pressure loss volatility produced by the pulse pressure. Furthermore, low pressure loss volatility was noted at $5kg/cm^2$ of the overall pulse pressure.

• Preventive Nutrition and Food Science
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• v.10 no.3
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• pp.224-230
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• 2005

The effects of low viscosity chitosan on the rheological properties of soymilk using a model system and on tofu qualities were examined. The flow behavior of soy milk with chitosan closed the Newtonian flow and stabilized according to increasing chitosan concentration. The soymilk containing $glucono-\delta-lactone$ exhibited a more pseudoplastic flow behavior compared with that of the control soymilk. The addition of low viscosity chitosan to the tofu preparation did not significantly affect its physicochemical properties. However, the results of the TEM image and instrumental textural properties showed that low viscosity chitosan affected the construction of the tofu structure. Chitosan tofu had low scores across the whole field of appearance in the sensory evaluation, and its overall eating quality was scored significantly lower. These results suggest that the addition of low viscosity chit os an affects the quality of tofu, which changes according to the degree of polymerization and concentration of chitosan.

• Korean Journal of Biological Psychiatry
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• v.3 no.2
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• pp.258-261
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• 1996

Objective : Several studies hove suggested that reduction of cholesterol concentration and low cholesterol level increases suicide, homicide, and depression. The authors sought to determine whether low cholesterol is associated with a history of suicidal attempts among major depression patients. Method : The subjects were 105 patients with major depression, diagnosed according to the DSM-III-R criteria, and 105 age, sex matched healthy controls. Blood was token following overnight fast and serum cholesterol concentration were measured by a enzymatic method Results : The serum cholesterol level was significantly lower in the patients with major depression than in healthy controls($180.4{\pm}43.4mg/dl$ vs $199.7{\pm}35.8mg/dl$). And the serum cholesterol level was significantly lower in major depression patients with suicidal attempt than in major depression patients without suicidal attempt($156.7{\pm}38.2mg/dl$ vs $ 187.8{\pm}42.5mg/dl$) Conclusion : It is hypothesized that low cholesterol level is associated with depression by modifying the serotonin metabolism and the production of interleukin-2, low cholesterol concentration should be further investigated as a potential biological marker of suicidal risk in major depression. Prospective study with serial cholesterol determinations should be done.

• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.57-62
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• 2001

The effect of micro scale turbulence on flame structure and stability were experimentally investigated by changing the area of micro turbulence generator(MTG) and air velocity in terms of low NOx and high efficiency combustion. NOx and CO concentration were also measured for different MTG areas to investigate whether a vane swirler having MTG has a possibility of using as part for low NOx combustor. From the obtained results, it is shown that flame stability region increases and flame size becomes small as MTG area increases since MTG in itself makes small scale recirculation flow and swirler does large scale recirculation one. It is also shown that low NOx concentration(about 20${\sim}$30ppm@$O_2$ 11%) is achieved for all MTG areas without any increase in CO concentration regardless of air velocity range tested in this study when the equivalence ratio is 0.7. The results obtained in this study can give basic guideline for the design of compact low NOx high efficiency combustor using a vane swirler having MTG.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.682-687
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• 2001

This study represents effect of exhaust performance by according to active muffler valve spring. The experimental parameter were divided engine speed and torsion coil spring constant. The sound pressure level was generally low at engine speed 2000-2500rpm but That was showed the lowest at spring constant k=0.75. Flow speed of exhaust gas was showed the fast at spring constant k=0.75 but the low value was showed at k=0.97. It was contained a rather low concentration of carbon monoxide(CO) at engine speed 2000-2500rpm and k=0.81, low concentration of hydrocarbon(HC) at spring constant k=0.81 but that was high at spring constant k=0.97. A conclusion based on FFT analysis was generally low concentration value at k=0.79 and k=0.81. The temperature distributions into the muffler was shown similar conditions. Heat transfer was well spreaded at thermocouple No.8 because valve was opened.

• Korean Journal of Environment and Ecology
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• v.34 no.5
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• pp.466-482
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• 2020

This study used 3D computational fluid dynamics (CFD) in the ENVI-met program to investigate how particulate matters (PM) generated on roads disperse through adjacent urban neighborhoods according to the urban development pattern. An urban area centered on a six-lane road in the vicinity of Miryang City Hall in Gyeongnam Province was selected to simulate the effect of the green space and building height on the PM concentration. The ENVI-met model considered the presence of green space and different building heights (high/low) on both sides of the road to examine the dispersion of PM. The result showed that the area of high-rise buildings and green space had the lowest PM concentration dispersed to the adjacent area, followed by the area of high-rise buildings and no green space. In contrast, the PM concentration remained relatively high for low-rise buildings, regardless of the green space. The reason for the low PM concentration in the area with high-rise buildings was a strong building wind, which caused PM to disperse to the outside, lowering the PM concentration quickly. These results indicate that the PM can disperse faster, and the PM concentration remains low in the urban neighborhood. On the other hand, green space had no significant effect on reducing PM in the urban neighborhood. In particular, when there are low-rise buildings on both sides of the road, the green space has no effect on the PM concentration in the urban neighborhood. Since this study considered only the case of PM emitted from the road, future studies should investigate other factors to figure out the dispersion model of PM and conduct on-site experiments.

• Development and Reproduction
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• v.10 no.2
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• pp.115-125
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• 2006

The present experiment was performed to confirm the effects of selenium on maturation and viability of mouse oocyte. Maturation of oocytes was observed by microscope, Germinal vesicle breakdown(GVBD) and polar body formation(PB) were confirmed at 2.5, 13 hours after in vitro culture. Viability of oocytes was observed by microscope. Normal and abnormal oocytes were distinguished by morphological change in vitro culture for 72 hours. Glutathione(GSH) content of collected oocytes from individual stage also was measured by glutathione assay using spectrophotometer. The results obtained were as follows; The low concentration of selenium($0.005\;{\mu}g/mL{\sim}0.5\;{\mu}g/mL$) increased the maturation rate of germinal vesicle(GV) oocytes to GVBD and PB oocytes. The high concentration of selenium($5\;{\mu}g/mL$) decreased the maturation rate. The low concentration of selenium increased the viability rate of PB oocytes. The high concentration of selenium did not affect the viability rate. The low concentration of selenium increased the GSH content in PB oocytes. The high concentration of selenium decreased GSH content. GSH content in PB oocyte was much higher than that in GVBD oocyte. The results indicate that the low concentration of selenium increases the maturation rate by helping quality elevation of oocyte and minimizing damages of oxidative stress generated from metabolism process. The low concentration of selenium also increases the viability rate by increasing GSH content.