• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.3
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• pp.277-291
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• 2020

Shield TBM is a tunnelling method that has a wider range of applications in the poor ground condition compared to conventional tunnels (Drill and Blast). Currently, a 13.3 m large-diameter slurry shield TBM is preparing for construction to pass under the Han River. Shield TBM is divided into slurry and EPB shield TBM, and management items during construction are different depending on each characteristic. In this paper, the equipment type, origin, application case and trouble case were analyzed for slurry shield TBM, which is mainly constructed in soft ground. In addition, 2D and 3D model tests were conducted on the condition of soil depth for the possibility of slurry leakage into front of the equipment, with appropriate chamber pressure. Based on this paper, it proposed to provide basic and reference data for proper excavation surface pressure and chamber pressure during construction of slurry shield TBM under soft ground conditions, and proposed measures to minimize stability and environmental decline due to slurry ejection.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.57-58
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• 2006

In MIM (metal insulator metal) capacitor, Ru (ruthenium) has been suggested as new bottom electrode due to its excellent electrical performance, a low leakage of current and compatibility to the high dielectric constant materials. In this case of Ru bottom electrode, CMP (chemical mechanical planarization) process was needed m order to planarize and isolate the bottom electrode. In this study, the effect of chemical A on polishing and etching behavior was investigated as functions of chemical A concentration, abrasive particle and pressure. Chemical A was used as oxidant and etchant. The thickness of passivation layer on the treated Ru surface increased with the increase of chemical A concentration. The etch rate and removal rate of Ru were increased by the addition of chemical A. The removal rate was highest m slurry of pH 9 with the addition of 0.1 M chemical A and 2 wt% alumina at 4 psi. The maximum removal rate is about 80 nm/min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.595-597
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• 2000

Poymeric insulators using in an heavy contamination area are easily attached to contaminants such as salt and by-products of industrial processes. To understand its effect on contaminants adhered to these insulators, we manufactured slurry mixed by some kaolin and salt as artificial contaminated solution. And then put samples in its slurry, for about one minute. And these samples are dried in natural condition for 6 days. We measured the degree of contaminant, AC leakage current for these contaminated samples.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.340-345
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• 2001

Because they have superior insulating properties and lower in price than their ceramic equivalents, polymeric insulators have been used in outdoor insulators. But polymeric insulators mainly using in an heavy contamination area of outdoor could be easily attached to contaminants such as salt and by-products of industrial processes. To understand its effect on contaminants adhered to these insulators, we dismounted polymeric insulators adhered contaminant in the field, and evaluated its electrical characteristics, CA, and ESDD. We also manufactured slurry mixed by some kaolin and salt for the artificial contamination test and measured the degree of contaminant, AC leakage current for these contaminated samples. Consequently, the adhered contaminants to its surface is likely to be affected the performance of insulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.117-117
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• 2008

In MIM capacitor, poly-Si bottom electrode is replaced with metal bottom electrode. Noble metals can be used as bottom electrodes of capacitors because they have high work function and remain conductive in highly oxidizing conditions. In addition, they are chemically very stable. Among novel metals, Ru (ruthenium) has been suggested as an alternative bottom electrode due to its excellent electrical performance, including a low leakage of current and compatibility to high dielectric constant materials. Chemical mechanical planarization (CMP) process has been suggested to planarize and isolate the bottom electrode. Even though there is a great need for development of Ru CMP slurry, few studies have been carried out due to noble properties of Ru against chemicals. In the organic chemistry literature, periodate ion ($IO_4^-$) is a well-known oxidant. It has been reported that sodium periodate ($NaIO_4$) can form $RuO_4$ from hydrated ruthenic oxide ($RuO_2{\cdot}nH_2O$). $NaIO_4$ exist as various species in an aqueous solution as a function of pH. Also, the removal mechanism of Ru depends on solution of pH. In this research, the static etch rate, passivation film thickness and wettability were measured as a function of slurry pH. The electrochemical analysis was investigated as a function of pH. To evaluate the effect of pH on polishing behavior, removal rate was investigated as a function of pH by using patterned and unpatterned wafers.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.2
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• pp.204-211
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• 2006

The electrolyte in the solid oxide fuel cell must be dense enough to avoid gas leakage and thin enough to reduce the ohmic resistance. In order to manufacture the thin and dense electrolyte layer, 8 mol% $Y_2O_3$ stabilized-$ZrO_2$ (8YSZ) electrolyte layers were coated on the porous tubular substrate by the novel vacuum slurry dip-coating process. The effects of the slurry concentration, presintering temperature, and vacuum pressure on the thickness and the gas permeability of the coated electrolyte layers have been examined in the vacuum slurry coating process. The vacuum-coated electrolyte layers showed very low gas permeabilities and had thin thicknesses. The single cell with the vacuum-coated electrolyte layer indicated a good performance of $495\;mW/cm^2$, 0.7 V at $700^{\circ}C$. The experimental results show that the vacuum dip-coating process is an effective method to fabricate dense thin film on the porous tubular substrate.

• Journal of the Korean Electrochemical Society
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• v.16 no.1
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• pp.30-38
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• 2013

In this study, a catalyst slurry was prepared with a Pt/C catalyst, Nafion ionomer solution as a binder, an ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate), deionized water and ethanol as a solvent for the application to polymer electrolyte fuel cells (PEFCs) at high-temperatures. The effect of the IL in the electrode of each design was investigated by performing a cyclic voltammetry (CV) measurement. Electrodes with different IL distributions inside and on the surface of the catalyst electrode were examined. During the CV test, the electrochemical surface area (ESA) obtained for the Pt/C electrode without ILs gradually decreased owing to three mechanisms: Pt dissolution/redeposition, carbon corrosion, and place exchange. As the IL content increased in the electrode, an ESA decrement was observed because ILs leaked from the Nafion polymer in the electrode. In addition, the CVs under conditions simulating leakage of ILs from the electrode and electrolyte were evaluated. When the ILs leaked from the electrode, minor significant changes in the CV were observed. On the other hand, when the leakage of ILs originated from the electrolyte, the CVs showed different features. It was also observed that the ESA decreased significantly. Thus, leakage of ILs from the polymer electrolyte caused a performance loss for the PEFCs by reducing the ESA. As a result, greater entrapment stability of ILs in the polymer matrix is needed to improve electrode performance.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.95-103
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• 2015

In this study, the causes and countermeasures for the leakage of a sea dyke under construction are analyzed. In general, the seabed ground is clearly divided from the embankment but a lot of parts show abnormal zones with low resistivity from the results of electric resistivity survey. Hence the causes of the leakage are considered as following: three-dimensional shear strain behavior, irregular compulsory replacement of the soft seabed ground with low strength and quality deterioration of the waterproof sheets during the closing process. The improvement method is determined by considering the constructability in the seawater and its velocity condition, durability, economic feasibility, similar application cases and so on. Consequently, a combination of low slump mortar and slurry grouting and injection method is selected as an optimum combination. Mixing ratio and improvement pattern are determined after drilling investigation and pilot test. The improvement boundary is separated into general and intense leakage area. The construction is performed with each pattern and the improvement effects are confirmed. The confirmed effects with various tests after completion show tolerable ranges for all of the established standards. Finally, various issues such as prediction of length of the waterproof sheet, installation of it against seawater velocity, etc. should be considered when sea dykes are designed or executed around the western sea which has high tide difference.

• KSBB Journal
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• v.14 no.1
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• pp.114-118
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• 1999

In order to use a polysaccharide, curdlan, as a concrete admixture, we first developed a pilot-scale fermentation process for the mass production of curdlan. We also examined the rheological properties of curdlan, and tested how well the curdlan obtained in this work increased the segregational resistance of the cement slurry. Fermentation was performed in a 300-liter fermenter equipped with 3 disk-turbine impellers. Since curdlan production is stimulated under nitrogen-limiting conditions, the culture pH was shifted from the optimal pH for cell growth (pH 7.0) to the optimal pH for curdlan production (pH 5.5) at the onset of ammonium exhaustion. We obtained a curdlan production of 65 g/L in 120 hr batch cultivation of Agrobacterium species. The insoluble curdlan at the final stage of fermentation was readily harvested by centrifugation together with the cells. The freeze-dried sample contained 78% (w/w) of curdlan. The solubility and viscosity of the curdlan increased with the increase of the solution pH, which enhances the viscosity of concrete since the pH of concrete is extremely high (pH 13.0). Test results of the curdlan as a concrete admixture with cement slurry demonstrated that it prohibits the leakage of water. In conclusion, this work certifies and enlarges curdlan's industrial potential as a concrete admixture.

• Restorative Dentistry and Endodontics
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• v.14 no.2
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• pp.38-48
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• 1989

The purpose of this study was to investigate the proper consistency of root canal sealer needed in obtaining an efficient canal obturation in injection-thermoplasticized low-temperature ($70^{\circ}C$) gutta-percha method. The sealer was made by incorporating zinc oxide powder into $0.5m{\ell}$ of eugenol and then the $0.5m{\ell}$ of mixture slurry was placed between two flat glass plates. The consistency was determined by measuring the degree of spread of the slurry at loading the 120gm of weight from the top plate. The sealer was prepared according to P/L ratio corresponding to the acquired consistency of 65.45mm, 46.80mm, 28.95mm and 22.60mm. The distal roots were obtained by cutting off from 125 extracted human lower molars and the root canals were prepared by using step-back method. The prepared canals were coated with the sealers on their walls and obturated by using the injection-thermoplasticized low-temperature ($70^{\circ}C$) gutta-percha method. All specimens were immersed in 2% methylene blue dye solution for 48 hours at $37^{\circ}C$. Calipers was used to measured the dye penetration into the root canals from apical constrictions. The results were as follows : The canals obturated without sealer showed significantly more leakage than the canals obturated with sealer. Within the consistency from 65.45mm to 22.60mm, the sealer of 65.45mm appeared significantly better than that of 28.95mm and 22.60mm in the canals obturated by injection-thermoplasticized gutta-percha method, and better than that of 46.80mm without statistical significance.