• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.58-66
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• 2013

This study investigated quality properties of alkali activated cement free mortar using industrial by-product such as cement kiln dust(CKD), silica fume(SF) and quartz sand powder(SP) to compare with previous research about blast furnace slag(BS) and fly ash(FA). The results were as following. All materials were effective to increase compressive strength, however they showed different tendency on flowability. CKD and SP increased flowability, but on the other hand SF did not because it's blain was great difference with other materials. Flowability and compressive strength were related with grading distributions of binders because CKD, SP and SF which had small particle size filled up BS and FA. Application of industrial by-products with various grading distributions could be effective for the high early strength and flowability of alkali activated cement free mortar using BS.

• Journal of Navigation and Port Research
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• v.34 no.5
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• pp.331-336
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• 2010

The free surface influenced the wake behind a circular cylinder and its effects were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured in this paper. The measured results has been compared with each other to investigate the flow characteristics of the circular cylinder's 2-dimensional section at $Re=1.0{\times}10^3$ using 2-frame grey level cross correlation PIV method. The flow around the circular cylinder with free surface affected the wake structure. Especially, in case of d=1.0D, the boundary layer was measured in the whole area. The separation point and boundary layer of the circular cylinder could be controlled by the water depth.

• Resources Recycling
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• v.7 no.4
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• pp.35-42
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• 1998

Surface mount technology is the biggest theme in the area of deιIronic component. To miniatunze an electronic component, s such as ferrite chip inductor, the cer뼈lic wet process for green-sheet lamination and/or screen printing method through a s solvent medium system is widely used. The preparation and characterization of NiCuZn Ferrite (NCZF) shurry and the green s sheet using the water mixed binder system has been studied. The 21 vol% of NCZF slurry was prepared by a ball milling. The p polyacrylic vinyl copolymer (Mw; 60,000) was used as a binder. Th$\xi$ mixture of distilled water, isopropyl alcohol (IPA) and 2l butoxy ethanol was used as a dispersion medium. The water content of medium varied from about 40% to 80%. As the results. Thc disp$\xi$rston stability of the NCZF slurry was attributed to the free polymer rather than the electrostatic force of the particle. T The viscosity of the NCZF slurry was greatly depended on the ratio of water content in the medium.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.3
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• pp.317-349
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• 1993

This study investigated the effect of filler particle size and weight% on mechanical properties of dental core porcelain. In alumina, variation in particle size and weight% and in zirconia, variation in weight%, all specimens were tested three-point bending strength, transmittance, thermal expansion coefficient, porosity and shrinkage and observed with SEM and analysed with X-ray diffractometer. In order to develop shrink-free porcelain, after firing alumina only, glass wasinfiltrated. And aluminum was added to alumina with the expanding character of aluminum oxidize into alumina, and was followed by second firing of glass infiltration procedure. Then mechanical properties were observed. The results of this study were obtained as follows. 1. The bending strength of zirconia was higher than that of alumina, and $5{\mu}m$ alumina had highest strength in variation of particle size of alumina. Except for $5{\mu}m$ alumina, increased with weight%, bending strength increased up to 80% and decreased at 90%. In case of glass infiltration, bending strength was slight higher than 80% and 90% of $5{\mu}m$ alumina. 2. Transmittance increased with increase of shrinkage, decrease of porosity, and with increase of filler size and had no direct correlation with weight%. 3. Thermal expansion coefficient of alumina group was $7.42\sim8.64\times10^{-6}/^{\circ}C$ and that of zirconia group was $9.83\sim12.11\times10^{-6}/^{\circ}C$ and the latter was higher than the former. 4. In x-ray diffraction analysis, alumina group and zirconia group increased $Al_2O_3$ peak and $t-ZrO_2$ peak with increase of weight%. The second phase(cristobalite peak) was observed in zirconia 40% group. 5. Porosity of zirconia was lower than that of alumina and $5{\mu}m$ alumina group had many pores with SEM. In case of low filler content, fracture occurred in glass and high filler content, in glass and filler. In case of aluminum addition to alumina, small oxidised aluminum was observed. 6. Zirconia group had high shrinkage than alumina group, and mixed group of alumina group had high shrinkage. In case of glass infiltration, shrinkage decreased and aluminum addition to alumina group was almost shrink-free.

• Journal of the Korea Computer Graphics Society
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• v.18 no.3
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• pp.17-27
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• 2012

In this paper, we describe a case study of the film 'Sector 7' which was produced by technologies applied fluid simulation. For the CG scenes in the movie which include highly detailed fluid motions, we used smoothed particle hydrodynamics(SPH) technique to express subtle movements of seawater from a crashed huge tank, and used hybrid simulation method of particles and levelsets to describe bursting water from a submarine's broken canopy. We also used detonation shock dynamics(DSD) technique for detailed flame simulations to produce a burning monster, the film"s main character. At this point, the divergence-free vortex particle method was applied to conserve the incompressible property of fluids. In addition, we used an upsampling method to achieve more efficient video production. Consequently, we could produce the high-quality visual effects by using the domestic technologies.

• Journal of Magnetics
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• v.17 no.1
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• pp.1-5
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• 2012

The coercivity of a single 27 nm-spherical barium ferrite (S-BaFe) particle was simulated using three models: 1) Gibbs free energy (GFE), 2) Landau-Lifshitz-Gilbert (LLG), and 3) Stoner-Wohlfarth (S-W). Spherically and hexagonally shaped particles were used in the GFE and LLG simulations to investigate coercivity with the different shape anisotropies. The effect of shape was not included in the S-W model. It was found that the models using a spherical shape resulted in a coercivity higher than the models using the hexagonal shape with both shapes having the same diameter. The coercivity estimated with the S-W model was approximately the same as that for the spherical-shape models, which indicates that spherical shape has no significant effect on the particle's coercivity at nanoscale.

• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.471-479
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• 1994

Al-2%Si-2%Mg alloy containing SiC particle in 20, $70{\mu}m$ were prepared by mean of squeeze casting with various pressure 50, 100, 150 and 220MPa respectively. The specimens were made by casting into $50{\Phi}{\times}100{\ell}$ mold under various squeeze conditions(pressures, pressurizing temperature, particle sizes). Mechanical properties(hardness, tensile strength, elongation and wear characteristics) were evaluated at room temperature with those various fabrication factors. It became feasible to make favorable Al-SiCp composite free from casting defects by the injection of Ar gas during melting and 100MPa pressure squeeze casting. However, pressure of 50MPa was not sufficient to avoid completely porosity formation as a result of precessing and shrinkage during solidification. As the particle size is smaller and the squeeze pressure is higher, the hardness and tensile strength at room temperature are higher. Cell size became smaller gradually with increase of squeeze pressure. With increase of squeeze pressure(MPa), wear behaviors of those composites were changed from adhesive into abrasive wear, and the tendency of above behavior became outstanding with increasing sliding speed. The chemical reaction(4Al＋3SiC${\rightarrow}$$Al_4C_3+3Si$) is more accelerated at interface between SiCp and matrix with increase of squeeze pressure. Therefore $Al_4C_3$ intercompound and Si peak intensity is increased at interface.

• Journal of Industrial Technology
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• v.18
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• pp.249-258
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• 1998

In this paper, we investigated the post-combustion removal of nitrogen oxide($NO_x$) and sulfur oxide($SO_x$) which is based on the gas to particle conversion process by the pulsed corona discharge. Under normal pressure, the pulsed corona discharge produces the energetic free electrons which dissociate gas molecules to form the active radicals. These radicals cause the chemical reactions that convert $SO_x$ and $NO_x$ into acid mists and these mists react with $NH_3$ to form solid particles. Those particles can be removed from the gas stream by conventional devices such as electrostatic precipitator or bag filter. The reactor geometry was coaxial with an inner wire discharge electrode and an outer ground electrode wrapped on a glass tube. The simulated flue gas with $SO_x$ and $NO_x$ was used in the experiment. The corona discharge reactor was more efficient in removing $SO_x$ and $NO_x$ by adding $NH_3$ and $H_2O$ in the gas stream. We also measured the removal efficiency of $SO_x$ and $NO_x$ in a cylinder type corona discharge reactor and obtained more than 90 % of removal efficiency in these experimental conditions. The effects of process variables such as the inlet concentrations of $SO_x$, $NH_3$ and $H_2O$, residence time, pulse frequencies and applied voltages were investigated.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.81-85
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• 2022

Mist-CVD is known to have advantages of low cost and high productivity method since the precursor solution is misting with an ultrasonic generator and reacted on the substrate under vacuum-free conditions of atmospheric pressure. However, since the deposition distribution is not uniform, various efforts have been made to derive optimal conditions by changing the angle of the substrate and the position of the outlet to improve the result of the preceding study. Therefore, in this study, a deposition distribution uniformity model was derived through the shape and position of the substrate support and the conditions of inlet flow rate using the particle tracking method of computational fluid dynamics (CFD). The results of analysis were compared with the previous studies through experiment. It was confirmed that the rate of deposition area was improved from 38.7% to 100%, and the rate of deposition uniformity was 79.07% which was higher than the predicted result of simulation. Particle tracking method can reduce trial and error in experiments and can be considered as a reliable prediction method.

• Journal of the Semiconductor & Display Technology
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• v.21 no.3
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• pp.101-104
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• 2022

Mist-CVD is known to have advantages of low cost and high productivity compared to ALD and PECVD methods. It is capable of reacting to the substrate by misting an aqueous solution using ultrasonic waves under vacuum-free conditions of atmospheric pressure. In particular, Ga₂O₃ is regarded as advanced power semiconductor material because of its high quality of transmittance, and excellent electrical conductivity through N-type doping. In this study, Computational Fluid Dynamics were used to predict the uniformity of the thin film on a large-area substrate. And also the deposition pattern and uniformity were analyzed using the flow velocity and particle tracking method. The uniformity was confirmed by quantifying the deposition cross section with an FIB-SEM, and the consistency of the uniformity prediction was secured through the analysis of the CFD distribution. With the analysis and experimental results, the match rate of deposition area was 80.14% and the match rate of deposition thickness was 55.32%. As the experimental and analysis results were consistent, it was confirmed that it is possible to predict the deposition thickness uniformity of Mist-CVD.