• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.425-428
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• 2006

In order to estimate the reduction of laodbearing capacity, followed by the attributive change of heat while high strength concrete structure is revealed on fire it is necessary to evaluate, it is necessary to evaluate the property of material under high temperature such as thermal conductivity, specific heat, compressive strength, modulus of rigidity and diminution figure. Therefore, this study is for the purpose of presenting evaluation data for the analysis of thermal behavior about the high strength concrete material under high temperature, through the experiment by manufacturing concrete(40, 50, 60, 80, 100 MPa) commonly used in the construction field. As a result of the study, in the case of physical attribute, it demonstrates a greater fluctuation of change than the one of 30 MPa concrete. In case of specific heat, the high strength concrete, shown the serious diminution between $500{\sim}600^{\circ}C$, presents the thermal change area corresponding to the change of high strength concrete. In compressive strength, regardless of intensity of concrete, all of them show the first intensity loss between normal temperature and $100^{\circ}C$, the dramatic loss beyond $400^{\circ}C$. The concrete weighing above 50 MPa shows a twice lower dramatic intensity loss than the one weighing $30{\sim}40MPa$. The concrete ranging from $60{\sim}80MPa$, shows the biggest diminution of modulus of elasticity under $400^{\circ}C$, which implies the structural unstability of temperature.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.69-69
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• 2017

Flame arrestor as end of line flame arrester for endurance burning prevents a light-back at deflagration and stabilized burning (during and after endurance burning) of potentially explosive vapor-air and gas-air mixtures at the end of vent pipes. In a flame arrestor, spring is an important part. The spring load as well as the spring's elasticity determine when the hood is opened. In addition, the spring have to work in high temperature condition due to gas burning. Therefore, it is necessary to analyze mechanical load and elasticity of spring when gas is burned. Based on the dynamic calculation on working process of a specific flame arrestor, analysis of spring is taken. A three dimensional model for spring burned in flame arrestor by using CFD simulation. Results of the CFD analysis are input in FEM simulation to analyze structure of the spring. The simulation results can predict and estimate the spring's load and elasticity at variation of the spring's deflection. Moreover, the obtained result can provide makers with references to optimize design of spring as well as flame arrestor.

• Structural Engineering and Mechanics
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• v.56 no.1
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• pp.137-156
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• 2015

In this paper, an analytical solution of displacement, strain and stress field for rotating thick-walled cylinder made of functionally graded material subjected to the uniform external magnetic field and thermal field in plane strain state has been studied. Stress, strain and displacement field as a function of radial coordinates considering magneto-thermo-elasticity are derived analytically. According to the Maxwell electro-dynamic equations, Lorentz force in term of displacement is obtained in cylindrical coordinates. Also, symmetric temperature distribution along the thickness of hollow cylinder is obtained by solving Fourier heat transfer equation in cylindrical coordinates. Using equation of equilibrium and thermo-mechanical constitutive equations associated with Lorentz force, a second-order inhomogeneous differential equation in term of displacement is obtained and will be solved analytically. Except Poisson's ratio, other mechanical properties such as elasticity modulus, density, magnetic permeability coefficient, heat conduction coefficient and thermal expansion coefficient are assumed to vary through the thickness according to a power law. In results analysis, non-homogeneity parameter has been chosen arbitrary and inner and outer surface of cylinder are assumed to be rich metal and rich ceramic, respectively. The effect of rotation, thermal, magnetic field and non-homogeneity parameter of functionally graded material which indicates percentages of cylinder's constituents are studied on displacement, Von Mises equivalent stress and Von Mises equivalent strain fields.

• Advances in nano research
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• v.14 no.5
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• pp.475-493
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• 2023

In the context of nonclassical nonlocal strain gradient elasticity, this article studies the free and forced responses of functionally graded material (FGM) porous nanoplates exposed to thermal and magnetic fields under a moving load. The developed mathematical model includes shear deformation, size-scale, miscorstructure influences in the framework of higher order shear deformation theory (HSDT) and nonlocal strain gradient theory (NSGT), respectively. To explore the porosity effect, the study considers four different porosity models across the thickness: uniform, symmetrical, asymmetric bottom, and asymmetric top distributions. The system of quations of motion of the FGM porous nanoplate, including the effects of thermal load, Lorentz force, due to the magnetic field and moving load, are derived using the Hamilton's principle, and then solved analytically by employing the Navier method. For the free and forced responses of the nanoplate, the effects of nonlocal elasticity, strain gradient elasticity, temperature rise, magnetic field intensity, porosity volume fraction, and porosity distribution are analyzed. It is found that the forced vibrations of FGM porous nanoplates under thermal and live loads can be damped by applying a directed magnetic field.

• Advances in concrete construction
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• v.10 no.6
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• pp.489-498
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• 2020

This paper investigates mechanical properties of roller compacted concrete (RCC) involving reclaimed asphalt pavement (RAP). In this way, a set of 276 cylindrical RCC specimens were prepared with different RAP sizes (i.e., fine, coarse & total) at various ratios (i.e., 10%, 20%, and 40%). Results reveal that incorporation of RAP decreases unconfined compressive strength (UCS), modulus of elasticity (E), and indirect tensile (IDT) strength of RCC. For each RAP size, a regression model was used to maximize RAP content while satisfying the UCS lower limit (27.6 Mpa) mentioned by ACI as a minimum requirement for RCC used in pavement construction. Moreover, UCS of RAP incorporated mixes, dissimilar to that of control mixes, was found to be sensitive and insensitive to the testing temperature and curing time after 7 days, respectively. The results also demonstrate that the higher amounts of RAP, the more flexibility in RCC is. This issue was also proved by the results of modulus of elasticity test. In addition, the toughness index (TI) shows that increase in RAP content leads to up to 43% increase in energy absorbance capacity of RCC.

• Journal of Ocean Engineering and Technology
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• v.36 no.4
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• pp.217-231
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• 2022

Reinforced polyurethane foam (R-PUF), a material for liquefied natural gas cargo containment systems, is expected to have different mechanical properties depending on its stacking position of foaming as the glass fiber reinforcement of R-PUF sinks inside R-PUF under the influence of gravity. In addition, since R-PUF is not a homogeneous material, it is also expected that the coordinate direction within this material has a great correlation with the mechanical properties. So, this study was conducted to confirm this correlation with the one between the mechanical properties and the stacking position. In particular, in this study, R-PUF of 3 different densities (130, 170, and 210 kg/m³) was used, and tensile, compression, and shear tests of this material were performed under 5 temperatures. As a result of the tests, it was confirmed that the strength and modulus of elasticity of the material increased as the temperature decreased. Specifically, the strength and modulus of elasticity in the Z direction, which was the lamination direction, tended to be lower than those in the other directions. Finally, the strength and elastic modulus of different specimens of the material found at the bottom of their lamination compared to the specimens with these properties found at positions other than their lamination bottom were evaluated. Further analysis confirmed that as the temperature decreased, hardening of R-PUF occurred, indicating that the strength and modulus of elasticity increased. On the other hand, as the density of R-PUF increased, a sharp increase in strength and elastic modulus of R-PUF was observed.

• The Korea Journal of Herbology
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• v.39 no.3
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• pp.1-9
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• 2024

Objectives : The purpose of this study was to find out the efficacy of placenta on the skin by comparing the difference effect between only MTS (microneedle therapy system) and the placenta extract application after MTS treatment. Methods : The present author performed once a week and total 4 times of MTS treatment. The treatment time took about 5~10 minutes and the depth of the needle was adjusted according to the participant's skin condition. One week after each treatment, the change of skin condition was measured. Two weeks after the end of the clinical trial, the skin condition was checked again. Results : In the case of moisture and elasticity, significant increases were observed in both the experimental and control groups. In the experimental group, skin temperature significantly decreased one week after the second treatment, and pore size significantly increased one week after the third treatment. In the case of skin tone, there was a significant temporary decrease after the first treatment in the control group, and in the experimental group, the skin tone showed a total decrease. Conclusion : When placenta extract was applied after MTS, skin temperature decreased and pores enlarged in the second and third treatments, and side effects such as rash and itchiness appeared. The final result showed a significant increase in skin moisture and elasticity. When animal-based ingredients containing high fat content are applied to the skin, the effect on the skin is good, but hypersensitivity reactions may occur, so use them with caution.

• Korean journal of food and cookery science
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• v.15 no.1
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• pp.50-54
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• 1999

The persimmon puree was hydrolyzed with commercial polysaccharide hydrolyzing enzymes, Viscozyme and Celluclast and jam was prepared with the enzyme treated persimmon juice by addition of pectin. The textural characteristics of the jam were studied for the effects of pectin addition and storage temperature. When the persimmon jam was prepared with the enzyme treated juice with addition of pectin(2.2∼3.0%), the hardness of the go] was stabilized at the addition level of more than 2.8% as measured by %sag. The hardness, cohesiveness, adhesiveness, and gumminess were also significantly increased as the amount of pectin addition increased, whereas the cohesiveness and elasticity did not change significantly. The gel prepared with the puree hydrolyzed with Celluclast generally showed higher hardness, gumminess and adhesiveness and less cohesiveness and elasticity than those treated with Viscozyme. Higher temperature (17$^{\circ}C$) caused a significant decrease in most of the textural properties except elasticity. Results of sensory test showed the orange colors was much improved by the Celluclast treatment, while other characteristics such as total acceptability and texture were not significantly different.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.672-675
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• 2004

The objective of this study was to understand the effect of hwangtoh and slag on various properties of concrete. Main variables were replacement level of admixtures, hwangtoh and slag, and curing temperature. Test results indicated that the compressive strength of concrete replaced by either hwangtoh and slag was significantly influenced by curing temperature. The elasticity modulus and compressive peak strain of concrete showed a small increase with increasing hwangtoh replacement.

• Journal of the Korean Graphic Arts Communication Society
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• v.18 no.1
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• pp.157-166
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• 2000

UV-curable resins have adventages of quick set, space saving, clean environment, and efficient use of energy. The polymerization induced phase separation has been studied to solve the problem in UV-curing of thick films and develop the new functional materials. On the exposure to UV irradiation, the dynamic elasticity properties were mesured for mixtures of alkyd resin and UV-cruable monomers which have different molecular structures and molecular weights. The curing rate increases with increasing temperature and UV intensity. In addition, The gel point is strongly influenced by temperature and UV intensity