• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2227-2238
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• 2000

The interfacial features of suspension system made of $CaCO_3$ particles have been investigated for the purpose of designing its effective treatment process. For the examination of variation of electrokinetic potential as a function of pH. the value of potential was observed to shift in the negative direction, which was thought to be due to the adsorption of hydroxide ion on the particle surface. Adsorption of surfactant on suspended particles resulted in the change of surface charge and shift in electrokinetic potential, which was dependent upon the sign of head charge and concentration of surfactant. Addition of inorganic salts affected stability of suspension greatly and sedimentation rate of suspension was influenced by the electric valence and amount of ions produced by dissolution of inorganic coagulants. DLVO theory made it possible to construct a energy profile diagram and a close correlation was found between experimental result and theoretically derived consequences. Non-specific adsorption of indifferent electrolyte resulted in the compression of electrical double layer and specific adsorption induced the shift of IEP and PZC in the opposite direction.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.486-491
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• 2014

In this paper, the adsorption behavior and kinetic characteristics of cibacron brilliant red 3B-A from aqueous solution using granular activated carbon were investigated. The effect of various parameters such as adsorbent dose, pH, initial concentration, contact time and temperature on the adsorption system were studied. Base on the estimated Langmuir constant ($R_L$) and Freundlich constant (1/n), This process could be employed as effective treatment method. From the Temkin constant (B) and Dubinin-Radushkevich constant (E), This adsorption process is physical adsorption. From kinetic experiments, the adsorption process followed the pseudo second order model with good correlation. Base on the Gibbs free energy and enthalpy, the adsorption of cibacron brilliant red 3B-A onto granular activated carbon was physisorption and endothermic in nature.

• Journal of the Korean Society of Groundwater Environment
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• v.1 no.1
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• pp.6-9
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• 1994

Previously reported Ar/N$_2$ratios in groundwater have been measured by single ion monitoring (Barnes et al., 1975; Vogel et al., 1981; Mariotti et al., 1988). The detector geometry and flared flight tube in VG Optima isotopic ratio mass spectrometer appeared to be fortuitously aligned for the simultaneous measurement of Ar/N$_2$ratios. Method development included mechanical adjustments to optimize the mass spectrometer for Ar/N$_2$ratio measurements followed by development of a preparation system for the extraction of air-saturated water samples. Samples containing known Ar/N$_2$ratios were used to assess accuracy and precision, and to test the applicability of methods for measurements of aqueous Ar/N$_2$ratios. The results indicated that the prepared air-saturated water samples were almost identical to the predicted Ar/N$_2$ratios (p ＜0.001). Groundwater samples were collected from on-going research sites, Shelton and Grand Island, Nebraska. Samples from the Grand Island sludge injection site form a lower boundary for worldwide reported Ar/N$_2$ratios. These lower Ar/N$_2$ratios can be explained by the production of nitrogen gas from this site, where denitrification was reported previously.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.1.1-1.1
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• 2011

Printed electronics based on the direct writing of solution processable functional materials have been of paramount interest and importance. In this talk, the synthesis of printable inorganic functional materials (conductors and semiconductors) for thin-film transistors (TFTs) and photovoltaic devices, device fabrication based on a printing technique, and specific characteristics of devices are presented. For printable conductor materials, Ag ink is designed to achieve the long-term dispersion stability and good adhesion property on a glass substrate, and Cu ink is sophisticatedly formulated to endow the oxidation stability in air and even aqueous solvent system. The both inks were successfully printed onto either polymer or glass substrate, exhibiting the superior conductivity comparable to that of bulk one. In addition, the organic thin-film transistor based on the printed metal source/drain electrode exhibits the electrical performance comparable to that of a transistor based on a vacuum deposited Au electrode. For printable amorphous oxide semiconductors (AOSs), I introduce the noble ways to resolve the critical problems, a high processing temperature above $400^{\circ}C$ and low mobility of AOSs annealed at a low temperature below $400^{\circ}C$. The dependency of TFT performances on the chemical structure of AOSs is compared and contrasted to clarify which factor should be considered to realize the low temperature annealed, high performance AOSs. For photovoltaic application, CI(G)S nanoparticle ink for solution processable high performance solar cells is presented. By overcoming the critical drawbacks of conventional solution processed CI(G)S absorber layers, the device quality dense CI(G)S layer is obtained, affording 7.3% efficiency CI(G)S photovoltaic device.

• Journal of dental hygiene science
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• v.18 no.1
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• pp.42-49
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• 2018

The computer-aided design/computer-aided manufacturing (CAD/CAM) system was introduced to shorten the production time of all-ceramic restorations and the number of patient visits. Among these types of ceramic for dental CAD/CAM, they have been processed into inlay, onlay, and crown shapes using leucite-reinforced glass-ceramics to improve strength. The purpose of this study was to observe the mechanical properties and microstructure of leucite-reinforced glass-ceramics for dental CAD/CAM. Two types of leucite-reinforced glass-ceramic blocks (IPS Empress CAD, Rosetta BM) were prepared with diameter of 13 mm and thickness of 1 mm. Biaxial flexural testing was conducted using a piston-on-three-ball method at a crosshead speed of 0.5 mm/min. Weibull statistics were used for the analysis of biaxial flexural strength. Fracture toughness was obtained using an indentation fracture method. Specimens were observed by field emission scanning electron microscopy to examine the microstructure of the leucite crystalline phase after acid etching with 0.5% hydrofluoric acid aqueous solution for 1 minute. The results of strength testing showed that IPS Empress CAD had a mean value of $158.1{\pm}8.6MPa$ and Rosetta BM of $172.3{\pm}8.3MPa$. The fracture toughness results showed that IPS Empress CAD had a mean value of $1.28{\pm}0.19MPa{\cdot}m^{1/2}$ and Rosetta BM of $1.38{\pm}0.12MPa{\cdot}m^{1/2}$. The Rosetta BM sample exhibited higher strength and fracture toughness. Moreover, the crystalline phase size and ratio were increased in the Rosetta BM sample. The above results are expected to elucidate the basic mechanical properties and crystal structure characteristics of IPS Empress CAD and Rosetta BM. Additionally, they will help develop leucite-reinforced glass-ceramic materials for CAD/CAM.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.277-283
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• 2004

To fabricate green sheet of transparent dielectric for PDP front panel, dispersion of transparent dielectric slurry, density, and mechanical properties of green sheets have been investigated as a function of amount and composition of organic additives. Measurements of sedimentation and viscosity were employed to determine a proper dispersant and its amount for a well dispersed transparent dielectric powders in non-aqueous system. Green sheets, having various ratios of transparent dielectric powders to transparent dielectric powders＋ binder＋plasticizer and binder to binder＋plasticizer, were fabricated. All the tape casting slurries showed shear thinning effect, that is, the apparent viscosity decreased with the increase of shear rate. It was found that the amount and composition of organic additives were main variables to affect densities and mechanical properties of transparent dielectric green sheets for PDP.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.795-798
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• 2003

Toxic organics are of great environmental concern primarily because they are toxic to mammals and birds, and are relatively soluble in water to contaminate surface water and groundwater. In this study, the decomposition of phenol, a widely used organic, in aqueous solutions by Boron doped diamond(BDD) electrode was examined. Thin, Boron-doped conducting diamond films are expected to be excellent electrodes for industrial electrolysis. Boron-doped diamond (BDD) were used as anode for generating ozone gas by electrolysis of acid solution. In this work. we have studied ozone generating system using BDD electrode. In order to determine the ozone generation properties of diamond electrode, experimental conditions, electrolyte concentration, temperature, flow rate and reaction time were varied diversely. As a result, we could confirm that ozone gas was generated successfully and the performance of diamond electrode was stable for electrolyte while $PbO_2$ electrode was disintegrated. Actually we are found that ozone amount increased by lowering the temperature of electrolyte. Decomposition of phenol concentration in the reaction solution by photolytic ozonation( $UV/O_3$) was analyzed by HPLC epuipped with a UV detector.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.416-422
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• 2017

PURPOSE. To investigate the effect of reducing tooth preparation and ceramic thickness on fracture resistance of lithium disilicate crowns. MATERIALS AND METHODS. Specimen preparation included a standard complete crown preparation of a typodont mandibular left first molar with an occlusal reduction of 2 mm, proximal/axial wall reduction of 1.5 mm, and 1.0 mm deep chamfer (Group A). Another typodont mandibular first molar was prepared with less tooth reduction: 1 mm occlusal and proximal/axial wall reduction and 0.8 mm chamfer (Group B). Twenty crowns were milled from each preparation corresponding to control group (n=5) and conditioned group of simultaneous thermal and mechanical loading in aqueous environment (n=15). All crowns were then loaded until fracture to determine the fracture load. RESULTS. The mean (SD) fracture load values (in Newton) for Group A were 2340 (83) and 2149 (649), and for Group B, 1752 (134) and 1054 (249) without and with fatigue, respectively. Reducing tooth preparation thickness significantly decreased fracture load of the crowns at baseline and after fatigue application. After fatigue, the mean fracture load statistically significantly decreased (P<.001) in Group B; however, it was not affected (P>.05) in Group A. CONCLUSION. Reducing the amount of tooth preparation by 0.5 mm on the occlusal and proximal/axial wall with a 0.8 mm chamfer significantly reduced fracture load of the restoration. Tooth reduction required for lithium disilicate crowns is a crucial factor for a long-term successful application of this all-ceramic system.

• Journal of the Korean Chemical Society
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• v.22 no.5
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• pp.320-325
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• 1978

In order to elucidate the mechanism associated with the solvent extraction of uranium(VI) using DEPA and DPPA as extractant the uranium(VI) complexes formed during the solvent extraction were isolated and characterized by means of IR, NMR, chemical analysis and molecular weight determination. It has been found that uranium(VI) replaces the acidic hydrogen ions of the extractants DEPA and DPPA to form chelated polynuclear complexes, the molecular weight of U(VI)-DEPA complex being $2.1{\times}10^4$. The isolated U(VI)-DEPA complex has been found to be the same chemical species as is formed during the solvent extraction process. In case of DEPA the distribution coefficient of uranium is the largest of the pure aqueous uranium solution and is increasing for the acidic solutions in the order of $H_3PO_4.

• Journal of the Korean Chemical Society
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• v.32 no.5
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• pp.458-463
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• 1988

The solubility parameter theory for retention behaviors of phenols in a reversed phase liquid chromatography can be applied to limited ranges of the aqueous solvent system. The many examples of the exception to this theory were found to show no agreement with the retention behavior of phenols. Therefore, a new solute-solvent interaction parameter, ${\delta}_{im}$ is added to the Schoenmakers equation of the solubility parameter theory in LC to approach the equation to the real one. The new solute-solvent interaction pararneter, ${\delta}_{im}$ depends on the kinds of solvent, the solvent composition and the structure of solutes. The parameter, ${\delta}_{im}$ has the linear relationship with the solubility parameter of mobile phase, ${\delta}_{im}$. The prediction of retention behavior by this modified equation turns out to be greater than the previous one.