• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.289-292
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• 1999

The charateristic of hydration reaction was studied in CaO-Al2O3-SiO2 system glass. As a result, the rate of heat liberation curves of synthestized glass becomes fixed after having increased by degrees. And it is decreasing after having increased suddenly. It was found that the total heat liberation with hydration for synthesized glass has a close relationship with the formation amount of ettringite.

• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.76-87
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• 1998

This study was carried out to investigate the effect of on temperature control from actuating method, recycling ratio and the position (top, middle and bottom) of set and controlled temperature within the reactor in adiabatic ebullated recycling condition, when the disturbance was occurred. Estimation of the solution were performed numerically using the finite difference method. It was assumed that the reaction is in constant with heat of reaction and the physical properties(density, heat capacity and viscosity, etc) of the reactants are same condition within the reactor.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.1
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• pp.25-33
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• 1990

Recently developed austempered ductile irons(A.D.I.) have good mechanical properties. However it is still needed to examine the relationships between microstructures related to banitic reaction and the mechanical properties. From the mechanical tests such as impact test, hardness test, tensile test, and the microstructure observations, we concluded that the good mechanical properties of A.D.I. came from the fine banitic ferrite structure formed during the first stage of the austempering reaction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.1
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• pp.60-68
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• 2009

The steam reformer for hydrogen production from methane is studied by a numerical method. Langmuir- Hinshelwood model is incorporated for catalytic surface reactions, and the pseudo-homogeneous model is used to take into account local equilibrium phenomena between a catalyst and bulk gas. Dominant chemical reactions are Steam Reforming (SR) reaction, Water-Gas Shift (WGS) reaction, and Direct Steam Reforming (DSR) reaction. The numerical results are validated with experimental results at the same operating conditions. Using the validated code, parametric study has been numerically performed in view of the steam reformer performance. As increasing a wall temperature, the fuel conversion increases due to the high heat transfer rate. When Steam to Carbon Ratio (SCR) increases, the concentration of carbon monoxide decreases since WGS reaction becomes more active. When increasing Gas Hourly Space Velocity (GHSV), the fuel conversion decreases due to the heat transfer limitation and the low residence time. The reactor shape effects are also investigated. The length and radius of cylindrical reactors are changed at the same catalyst volume. The longer steam reformer is, the better steam reformer performs. However, system energy efficiency decreases due to the large pressure drop.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.481-486
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• 2021

In a hypersonic vehicle to solve the heat problem generated during flight, a cooling technology is being developed which uses the endothermic effect that appears during the decomposition reaction of the mounted fuel. In this study, the decomposition reaction of n-dodecane fuel was performed using HZSM-5 as a catalyst, and the catalyst was coated on metal foam to maximize the endothermic effect of the catalytic decomposition reaction and suppress coke formation. The reactor was a stainless steel flow reactor with a outer diameter of 1.27 cm, and the reaction temperature was 550 ℃, the reaction pressure was 4 MPa, and the flow rate was 12 ml per minute. As a result of the catalytic decomposition reaction using a catalyst coated with HZSM-5 on the metal foam, the heat sink was 2887 kJ/kg as a maximum, the gas phase conversion rate was 34%, and the amount of coke produced on the metal foam decreased by about 56% as the catalyst was coated compared to the uncoated catalyst.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.20 no.3
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• pp.203-224
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• 2016

The heat and mass transfer characteristics of the unsteady hydromagnetic natural convection flow with Hall current and Soret effect of an incompressible, viscous, electrically conducting, heat absorbing and optically thin radiating fluid flow past a suddenly started vertical infinite plate through fluid saturated porous medium in a rotating environment are taken into account in this paper. Derivations of exact analytical solutions are aimed under different physical properties. The velocity, concentration and temperature profiles, Sherwood number and Nusselt number are easily examined and discussed via the closed forms obtained. Soret effect and permeability parameter tends to accelerate primary and secondary fluid velocities whereas hall current, radiation and heat absorption have reverse effect on it. Radiation and heat absorption have tendency to enhance rate of heat transfer at the plate. The results obtained here may be further used to verify the validity of obtained numerical solutions for more complicated transient free convection fluid flow problems.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.2
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• pp.149-154
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• 1995

The alloying of 6.5wt % Silicon in iron decreases the magnetization and the anisotropy and minimizes the iron loss noticeably. But it is very difficult to make thin sheets because of its poor ductility which is due to an ordering reaction (body centered cubic to CsCI type crystal structure). However the ordering reaction can be suppressed by rapid solidification method. The cooling rate of rapidly solidified Fe-6.5wt % Si alloy is about $10^3K/s$ and rapidly solidified structure are fine structure, cellular structure, dendrite and equiaxed grain from surface. The precipitates of $DO_3$ Phase emerges on $B_2$ matrix and the coercive force was 0.51 Oe (50cycle, 15KGauss) in Fe-6.5wt% Si alloy which was processed by heat treatment of $1150^{\circ}C$ for 1hr in high vacuum.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.265-285
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• 1999

The purposes of this investigation were to observe the reaction kinetics of five commercial dual cured resin cements (Bistite, Dual, Scotchbond, Duolink and Duo) when cured under varying thicknesses of porcelain inlays by chemical or light activation and to evaluate the effect of the porcelain disc on the rate of polymerization of dual cured resin cement during light exposure by using thermal analysis. Thermogravimetric analysis(TGA) was used to evaluate the weight change as a function of temperature during a thermal program from $25{\sim}800^{\circ}C$ at rate of $10^{\circ}C$/min and to measure inorganic filler weight %. Differential scanning calorimetry(DSC) was used to evaluate the heat of cure(${\Delta}H$), maximum rate of heat output and peak heat flow time in dual cured resin cement systems when the polymerization reaction occured by chemical cure only or by light exposure through 0mm, 1mm, 2mm and 4mm thickness of porcelain discs. In 4mm thickness of porcelain disc, the exposure time was varied from 40s to 60s to investigate the effect of the exposure time on polymerization reaction. To investigate the effect on the setting of dual cured resin cements of absorption of polymerizing light by porcelain materials used as inlays and onlays, the change of the intensity of the light attenuated by 1mm, 2mm and 4mm thickness of porcelain discs was measured using curing radiometer. The results were as follows 1. The heat of cure of resin cements was 34~60J/gm and significant differences were observed between brands (P<0.001). Inverse relationship was present between the heat of reaction and filler weight % the heat of cure decreased with increasing filler content (R=-0.967). The heat of reaction by light cure was greater than by chemical cure in Bistite, Scotchbond and Duolink(P<0.05), but there was no statistically significant difference in Dual and Duo(P>0.05). 2. The polymerization rate of chemical cure and light cure of five commercially available dual cured resin cements was found to vary greatly with brand. Setting time based on peak heat flow time was shortest in Duo during chemical cure, and shortest in Dual during light cure. Cure speed by light exposure was 5~20 times faster than by chemical cure in dual cured resin cements. The dual cured resin cements differed markedly in the ratio of light and chemical activated catalysts. 3. The peak heat flow time increased by 1.51, 1.87, and 3.24 times as light cure was done through 1mm, 2mm and 4mm thick porcelain discs. Exposure times recommended by the manufacturers were insufficient to compensate for the attenuation of light by the 4mm thick porcelain disc. 4. A strong inverse relationship was observed between peak heat flow and peak time in chemical cure(R=0.951), and a strong positive correlations hip was observed between peak heat flow and the heat of cure in light cure(R=0.928). There was no correlationship present between filler weight % or heat of cure and peak time. 5. The thermal decomposition of resin cements occured primarily between $300^{\circ}C$ and $480^{\circ}C$ with maximum decomposition rates at $335^{\circ}C$ and $440^{\circ}C$.

• Journal of Ginseng Research
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• v.35 no.1
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• pp.60-68
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• 2011

The chemical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity changes of ginsenoside $Rb_1$-glycine and ginsenoside $Rg_1$-glycine mixtures by Maillard reaction were investigated to identify the role of Maillard reaction in the increased antioxidant activity of ginseng by heat-processing. The DPPH radical scavenging activity of $Rg_1$-glycine mixture was more strongly increased by heat-processing than that of $Rb_1$-glycine mixture. From the analyses of ginsenosides, $Rb_1$ was gradually changed into 20(S)-$Rg_3$, 20(R)-$Rg_3$, $Rk_1$ and $Rg_5$ by heat-processing. $Rg_1$ was gradually changed into 20(S)-$Rh_1$, 20(R)-$Rh_1$, $Rk_3$ and $Rh_4$ by heat-processing. However, the generation of these less-polar ginsenosides was not related to the increased DPPH radical scavenging activity of $Rb_1$-glycine and $Rg_1$-glycine mixtures because their DPPH radical scavenging activities were already significantly increased when dried at $50^{\circ}C$, which temperature induce no structural changes of ginsenosides. In the comparison of browning compound levels of $Rg_1$-glycine and $Rb_1$-glycine mixtures, the extents of Maillard reaction were positively correlated with their increased free radical scavenging activities. Based on the chemical and DPPH radical scavenging activity changes of $Rg_1$-glycine and $Rb_1$-glycine mixtures by heat-processing, we clearly identified that the increased free radical scavenging activity of ginsenoside is mediated by the Maillard reaction between sugar moiety of ginsenoside and amino acid.

• Journal of Photoscience
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• v.5 no.4
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• pp.157-162
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• 1998

The effect of heat treatment in the light on the subsequent CO2 fixation was studied with isolated spinach chloroplasts to define the role of light during heat stress. The degree of inhibition in CO2 fixation after heat treatment at 35$^{\circ}C$ under full light intensity (600W/$m^2$) was same as that in the dark. However, heat treatment of isolated chloroplasts in the light manifested thylakoidal damage, which did not occur in the dark. Under weak light (10~30 W/$m^2$ ) where no thylakoidal damage occurred, the inhibition was substantially alleviated , showing protective effect of light . The inhibition caused by heat treatment in the dark or light is prevented by the addition of a few combined compounds to the medium prior to treatment. Fructose-1-6- bisphosphate(with aldolase)and ribose-5-phosphate, known to be effective combined with oxaloacetate in preventing inhibition after heat treatment in the dark were equally effective in the light even without oxaloacetate. Addition of sugar phosphate reduced the Mehler reaction, which may occur in fast rae under high light. However, the addition of bicarbnate and catalase that would remove Mehler reaction did not provide any protection, indicating that protective role of sugar phosphate is elsewhere. Furghermore, in whole plants rapid recovery from heat stress was observed in the light. The apparently lesser or equal inhibition in spite of additional thylakoidal damage under heat stres in the light and less requirement for the protection against heat treatment suggest that the inhibitory effect of heat stress is alleviated by light treatment.