• Journal of Korea Foundry Society
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• v.18 no.5
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• pp.481-487
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• 1998

Shell sand is widely used to make a complex shape castings due to its good collapsibility. When molten metal is poured into the mold, various gases are generated by the thermal decomposition of binder in the shell core. Casting defects such as blow hole and blister come from these gases. If it is possible to predict the evolution of gas quantitatively, it may provide effective solutions for minimizing the casting defects. To examine the gas evolution by shell core quantitatively, casting experiment and calculation were carried out. Gas pressure and gas volume evolved by shell core were measured in the experiment, and temperature distribution in the shell core was obtained by heat transfer analysis. From the result above, prediction on the gas volume evolved during pouring was tried. As forming pressure of the shell core increased and forming temperature decreased, the gas evolution increased. There was a close relationship between the calculated gas volume evolved and the measured one.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.87-92
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• 2002

At present, the polymer-modified mortars are used as high-performance as well as multi-functional materials in the construction industry. The purpose of this study is to synthesize polymer to modify in cement mortars and make test samples to understand pore size distribution. This paper deals with the effect of monomer ratio on the typical properties of polymer-modified mortars using Methylmethacrylate-Butyl Acrylate(MMA/BA) latexes synthesized through emulsion polymerization. From the results, we knew that the pore volume of polymer-modified mortars using Methylmethacrylate-Butyl Acrylate latexes at bound MMA contents of 70 and 60 percent is 7.5-75cm$^3$/g and the fine pore volume is increased with an increase in the polymer-cement ratio. The total pore volume of polymer-modified mortars using MMA/BA latexes is linearly reduced with an increase in the bound MMA content and increased in the polymer-cement ratio.

• Journal of Environmental Impact Assessment
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• v.16 no.5
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• pp.341-350
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• 2007

Lake Youngrang is a lagoon whose effluent flows into the East Sea. Because two resort towns and two golf courses are situated at the lake basin, many tourists visit this area. Stormwater runoff surveys were carried out for the eight storm events from 2004 to 2005 in the eutrophic lake watershed to give a basic data for the diffuse pollution control of the lake. Dimensionless mass-volume curves indicating the distribution of pollutant mass vs. volume were used to analyze the first flush phenomenon. The mass-volume curves were fitted with a power function and polynomial equation curves. The regression analysis showed that the polynomial equation curves were better than the power function in representing the tendency of the first flush, and second degree polynomial equation curves indicated the strength of the first flush effectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.1
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• pp.100-108
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• 1999

Variable air volume(VAV) system designed for improving interior environmental control has steadily evolved over the last 20 years. Major advantage of VAV system is that VAV technology allows a single system to provide simultaneous heating and cooling without a seasonal changeover. Research is carried out in order to study the influence on the energy consumption and ventilation performance of two kinds of office building with a mixing ventilation system. Data required for performance evaluation in these building is obtained from the central monitoring station and by measurement.

• Korean Journal of Computational Design and Engineering
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• v.14 no.5
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• pp.346-354
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• 2009

BRDF (bidirectional reflectance distribution function) is critical in realistic simulation of material appearances since it models the directional characteristics of reflection of light. Although many BRDF models have been proposed so far, it is still not easy to find one specific model that could represent all the reflection properties of real materials such as generalized diffusion, off-specular reflection, Fresnel effect, and back scattering. In this paper, we compare three BRDF models including B-spline volume BRDF (BVB), Cook-Torrance, and Lafortune in their ability to represent the measured BRDF data for physically-based rendering. We show that B-spline volume BRDF surpass the others in quality of data fitting and rendering, especially for materials without specular reflections.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.265-272
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• 2000

This study introduces the current theory of the SWCC and tries to verify the theory by performing laboratory tests for the local soils of Korea. First, the SWCCs of Poi-dong soil and Shinnae-dong soil, the most typical weathered residual soils in Korea, were experimentally obtained and the results were compared among others. Second, a SWCC model for deformable soils was proposed. For deformable soils, which show huge volume change during desaturation, the volume change behavior should be considered, and the SWCC should be expressed as a function of void ratio as well as suction.

• Structural Engineering and Mechanics
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• v.80 no.5
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• pp.553-562
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• 2021

In this paper, a hybrid scaled boundary finite element and finite volume method (SBFEM-FVM) is proposed for simulating hydraulic-fracture propagation in brittle concrete materials. As a semi-analytical method, the scaled boundary finite element method is introduced for modelling concrete crack propagation under both an external force and water pressure. The finite volume method is employed to model the water within the crack and consider the relationship between the water pressure and the crack opening distance. The cohesive crack model is used to analyse the non-linear fracture process zone. The numerical results are compared with experimental data, indicating that the F-CMOD curves and water pressure changes under different loading conditions are approximately the same. Different types of water pressure distributions are also studied with the proposed coupled model, and the results show that the internal water pressure distribution has an important influence on crack propagation.

• 한국전산유체공학회:학술대회논문집
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• 1997.10a
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• pp.106-112
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• 1997

The effects of radiative heat transfer are investigated in a turbulent combustion flow field with highly non-adiabatic flames. Turbulent combustion is modeled by the $k-{\varepsilon}-g$ model and a one step irreversible reaction scheme for the combustion chemistry. The radiative trasport equation is solved by the finite volume method considering the radiative transfer from $CO_2,\;H_{2}O$ and soot only. Gray gas is assumed to calculate the radiative properties of $CO_2\;and\;H_2O$. A two-equation soot formation model is applied to predict soot volume faction distribution. All equations are solved in a coupled manner and the numerical results are compared with available experimental data.

• Progress in Medical Physics
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• v.29 no.2
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• pp.47-52
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• 2018

To investigate the effect of low magnetic field on dose distribution in SABR plans for liver cancer, we calculated and evaluated the dose distribution to each organ with and without magnetic fields. Ten patients received a 50 Gy dose in five fractions using the $ViewRay^{(R)}$ treatment planning system. For planning target volume (PTV), the results were analyzed in the point minimum ($D_{min}$), maximum ($D_{max}$), mean dose ($D_{mean}$) and volume receiving at least 90% ($V_{90%}$), 95% ($V_{95%}$), and 100% ($V_{100%}$) of the prescription dose, respectively. For organs at risk (OARs), the duodenum and stomach were analyzed with $D_{0.5cc}$ and $D_{2cc}$, and the remained liver except for PTV was analyzed with $D_{mean}$, $D_{max}$, and $D_{min}$. Both inner and outer shells were analyzed with the point $D_{min}$, $D_{max}$, and $D_{mean}$, respectively. For PTV, the maximum change in volume due to the presence or absence of the low magnetic field showed a percentage difference of up to $0.67{\pm}0.60%$. In OAR analysis, there is no significant difference for the magnetic field. In both shell structure analyses, although there are no major changes in dose distribution, the largest value of deviation for $D_{max}$ in the outer shell is $2.12{\pm}2.67Gy$. The effect of low magnetic field on dose distribution by a Co-60 beam was not significantly observed within the body, but the dose deposition was only appreciable outside the body.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.109-122
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• 2018

Domestic LPG meters are being tested for LPG quantification in accordance with the "Measures Act". The LPG meter is re-tested every three years in accordance with the "Enforcement Decree of the Measures Act". The maximum permissible error within the test is within ${\pm}1.0%$, and the tolerance is within ${\pm}1.5%$. For the quantitative measurement of LPG, a hydrometer for LPG, a balance, and a pressure vessel are used. The volume of LPG varies in depending on the temperature and pressure. The current quantitative measurement method of LPG requires the measurement of temperature, pressure and density in order to determine the volume of LPG, respectively, and some equipments are needed accordingly. Coriolis mass flowmeter, on the other hand, measure the mass flow, density and temperature at the same time, and can be converted and calculated to the required values using a computer program, also it is widely applied in the industrial field. In this study, the volume of LPG was measured using a Coriolis mass flowmeter as a basic study of LPG quantitative measurement. In addition, it is shown that it is possible to apply for the LPG quantitative measurement using the Coriolis mass flowmeter by comparing it with the conventional LPG quantitative measurement method.