• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1310-1313
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• 1997

Application of eddy current sensing principle for the non-contact estimation of very low concentration of electrolytic solution is presented in this paper. for this application, a new, simple, low-cost, low-power structure for the eddy current sensor is proposed. By measuring the eddy current produced in the conducting electrolytic solution, the concentration is estimated. Therefore, the unknown concentration can be estimated comparing with the database which is prepared as the relation between the change in inductance and various concentrations of electrolytic solution. The concentration, as low as l ppm of the solutioin can be detected by this sensor. It was tested on various low concentration solutions of NaCl. It shows distinct response for various concentrations.

• 한국재료학회지
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• 제32권4호
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• pp.230-236
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• 2022

The formation behavior of a passive state film on the surface of STS304 in electrolytic solution was analyzed to determine its metallic ion composition. The properties of passive state films vary depending on the Fe and Cr ions in the electrolytic solution. It was observed that the passive state film surface became flat and glossy as the concentration of Fe and Cr ions in the electrolytic solution increased. The corrosion resistance property of the passive state film was proportional to the amount of Fe and Cr in the electrolytic solution. An initial passive state film with high Fe concentration was formed on the surface of STS304 during early electrolytic polishing. Osmotic pressure of Fe ions occurs between the passive state film and electrolytic solution due to the Fe ion concentration gradient. The Fe in the passive state film is dissolved into the electrolyte, and Cr fills up the Fe ion vacancies. As a result, a good corrosion-resistant floating film was formed. The more Fe ions in the electrolytic solution, the faster the film is formed, and as a result, a flat passive state film containing a large amount of Cr can be formed.

• 한국염색가공학회지
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• 제16권4호
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• pp.10-18
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• 2004

In this work, Aqueous sericin solution was prepared by degumming process with electrolytic reduction water. Then, the microfiltration and ultrafiltration systems were applied to the concentration of aqueous sericin solution. The objective of this study was to select the optimum operating condition among the different pressure. The permeate flux and rejection ratio were observed with time, pressure, flow rate and concentration. and, the wastewater and permeated water quality values such as pH, BOD, COD, and NH levels were measured. In order to see the influence of electrolytic reduction water, the flux of pure water and electrolytic reduction water by PVDF22(MF) and PS100(UF) membrane was measured. In microfiltration system, the relative flux reduction decreased rapidly to 0.02 in the 30min, as the concentration polarization and gel layer formation were increased. and then the sericin concentration rejection ratio was 40%. In ultrafiltration system, the permeate flux decreased with time and concentration, and increased with the operating pressure and flow rate. Optimal condition in PS100 membrane system for sericin concentration was operating pressure 1.464kgf/$cm^24, operating flow rate $7\ell/min at\; 40^{\circ}C$. At that time, sericin concentration rejection ratio was 83% respectably. The sericin solution was concentrated from 0.1wt% solution to 0.2 wt % solution during about 2 hrs by the UF filteration membrane system.

• 한국표면공학회지
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• 제49권2호
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• pp.119-124
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• 2016

Plasma electrolytic oxidation (PEO) is a promising coating process to produce ceramic oxide on valve metals such as Al, Mg and Ti. The PEO coating is carried out with a dilute alkaline electrolyte solution using a similar technique to conventional anodizing. The coating process involves multiple process parameters which can influence the surface properties of the resultant coating, including power mode, electrolyte solution, substrate, and process time. In this study, ceramic oxide coatings were prepared on commercial Al alloy in electrolytes with different KOH concentrations (0.5 ~ 4 g/L) by plasma electrolytic oxidation. Microstructural and electrochemical characterization were conducted to investigate the effects of electrolyte concentration on the microstructure and electrochemical characteristics of PEO coating. It was revealed that KOH concentration exert a great influence not only on voltage-time responses during PEO process but also on surface morphology of the coating. In the voltage-time response, the dielectric breakdown voltage tended to decrease with increasing KOH concentration, possibly due to difference in solution conductivity. The surface morphology was pancake-like with lower KOH concentration, while a mixed form of reticulate and pancake structures was observed for higher KOH concentration. The KOH concentration was found to have little effect on the electrochemical characteristics of coating, although PEO treatment improved the corrosion resistance of the substrate material significantly.

• 해양환경안전학회지
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• 제3권2호
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• pp.69-76
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• 1997

Each factor for the most effective electrolytic reaction in treating shipboard sewage was enhanced by means of batch electrolyitc reactor using DSA electrode. The effective clearance was 6mm and pH was 5-6. In such case, more than 20% of sea water concentration was needed to attain 90% of COD removal rate. The suspended solids was effectively removed by electro-floatation in proportion as charged current density. The nitrogen and posporous were effectively removed in the electrolytic device when mixed seawater.

• 한국환경과학회지
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• 제27권1호
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• pp.47-53
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• 2018

In this study, high-purity silver nanocolloids were synthesized by an electrolytic reaction, and the effect of temperature on the nanocolloid concentration was analyzed by performing the reaction at $70^{\circ}C$ and $90^{\circ}C$. The antibacterial properties of the thus-synthesized silver nanocolloids were also studied. When the synthesis was performed at $90^{\circ}C$, the concentration of silver nanocolloid increased to 14 mg/L after 5 min, 1756 mg/L after 30 min, and 2147 mg/L after 60 min. The concentration of silver nanocolloid synthesized by electrolytic reaction at $70^{\circ}C$ and $90^{\circ}C$ for 60 min was 1,882 mg/L and 2147 mg/L, respectively. The preferred temperature at which the electrolytic synthesis is performed is $70^{\circ}C$ to obtain high concentrations of 1,000 mg/L or more. The antibacterial performance of the thus-synthesized silver nanocolloids was 99.9% for E. coli and 99.5% for Pseudomonas aeruginosa.

• 한국환경보건학회지
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• 제23권3호
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• pp.1-6
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• 1997

This research was conducted in the laboratory to investigate an alternative of Copper(Cu) removal from an heavymetal wastewater using the electrochemical precipitation(ECP) process. The ECP unit consisted of an electrolytic cell made of Titanium plate and Steel plate representing anode and cathode. The DC power source applied to the ECP unit had electrical potential(E) of 50$\pm$ 1V, respectively. The synthetic wastewater used in the experiments contained Cu in the 10 mg/l concentration and the electrode separation were 2, 3, 4 cm and the initial pH were 3, 6, 9, 12, and electrolytic concentration were 0.005, 0.0125, 0.025, 0.0375 mole, and the real heavymetal wastewater used in the experiments. From the experiment for removal efficiency according to pH variation, the low pH area doesn't give the coagulation effect by Ti(OH)$_4$ because process interfere with the coagulation and oxidation reaction, therefore the optimum pH was 4-7. The removal rate was 97.75% after the lapse of 30 minutes when copper concentration and electrolytic concentration were respectively 10 mg/l and 0.025 mole. The removal rate was 96.41% after the lapse of 30minutes when the real heavymetal wastewater used. The optimum consumption of power showed 27KWh/m$^3$ when copper concentration, electrolyte concentration and cell potential were respectively 10 mg/l, 0.025 mole and 50$\pm$ 1 Volt.

• 한국표면공학회지
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• 제49권3호
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• pp.225-230
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• 2016

The present work was conducted to investigate the effects of NaF concentration in phosphate and silicate-containing alkaline electrolyte on the morphology, thickness, surface roughness and hardness of anodic oxide films formed on AZ31 Mg alloy by plasma electrolytic oxidation (PEO) method. The PEO films showed flat surface morphology with pores in the absence of NaF in the electrolyte, but nodular features appeared on the PEO film surface prepared in NaF-containing electrolyte. Numerous pores ranging from 1 to $20{\mu}m$ in size were observed in the PEO films and the size of pores decreased with increasing NaF concentration in the electrolyte. Surface roughness and thickness of PEO films showed increases with increasing NaF concentration. Hardness of the PEO films also increased with increasing NaF concentration. It was noticed that hardness of inner part of the PEO films is lower than that of outer part of them, irrespective of the concentration of NaF. The low hardness of PEO films was explained by the presence of a number of small size pores less than $2{\mu}m$ near the PEO film/substrate interface.

• 한국재료학회지
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• 제32권6호
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• pp.301-306
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• 2022

This study explored the possibility of forming a coating layer containing alginic acid on the surface of a magnesium alloy to be used as a biomaterial. We formed a coating layer on the surface of a magnesium alloy using a plasma electrolytic oxidation process in an electrolytic solution with different amounts of alginic acid (0 g/L ~ 8 g/L). The surface morphology of all samples was observed, and craters and nodules typical of the PEO process were formed. The cross-sectional shape of the samples confirmed that the thickness of the coating layer became thicker as the alginic acid concentration increased. It was confirmed that the thickness and hardness of the sample significantly increase with increasing alginic acid concentration. The porosity of the surface and cross section tended to decrease as the alginic acid concentration increased. The XRD patterns of all samples revealed the formation of MgO, Mg₂SiO₄, and MgF₂ complex phases. Polarization tests were conducted in a Stimulate Body Fluid solution similar to the body's plasma. We found that a high amount of alginic acid concentration in the electrolyte improved the degree of corrosion resistance of the coating layer.

• 환경위생공학
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• 제13권2호
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• pp.139-146
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• 1998

The characteristics of color and COD removal for dyeing-wastewater using electrochemical reaction were investigated. >From the result, the removal efficiency of color and COD were increased with increase of temperature, decrease of electrode distance, increase of electrolyte concentration and increase of potential and these were obtained above 99%, above 75% within 30 min, individually. Cause of higher COD removal efficiency, it is more suitable that dyeing-wastewater is treated by electrolytic treatment prior to biological treatment. It is concluded that the electrolytic treatment of dyeing-wastewater can be used as the effective and economical method in practical treatment.