• 대한치과기공학회지
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• 제26권1호
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• pp.89-96
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• 2004

Hydroxyapatite powder were synthesized by precipitation method, varying pH, and reaction temperature. The powders were heated at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$ for fabrication of dental prosthesis. The results are as follows: Synthesized powder showed the smallest particle in size, under the conditions of pH 11 and reaction temperature 37$^{\circ}{\cdots}$. The hydroxyapatite was partially converted to $\alpha,\;\beta$-TCP at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$. Mechanical strength of sample was affected by such powder preparation conditions as pH and reaction temperature and sintering temperature. The mechanical strength of sample prepared under the same conditions was increased with increasing pH, reaction temperature and sintering temperature.

• 한국환경농학회지
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• 제35권2호
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• pp.128-136
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• 2016

BACKGROUND: Hydrothermal carbonization reaction is the thermo-chemical energy conversion technology for producing the solid fuel of high carbon density from organic wastes. The hydrothermal carbonization reaction is accompanied by the thermal hydrolysis reaction which converse particulate organic matters to soluble forms (hydro-thermal hydrolysate). Recently, hydrothermal carbonization is adopted as a pre-treatment technology to improve anaerobic digestion efficiency. This research was carried out to assess the effects of hydro-thermal reaction temperature on the methane potential and anaerobic biodegradability in the thermal hydrolysate of organic sludge generating from the wastewater treatment plant of poultry slaughterhouse .METHODS AND RESULTS: Wastewater treatment sludge cake of poultry slaughterhouse was treated in the different hydro-thermal reaction temperature of 170, 180, 190, 200, and 220℃. Theoretical and experimental methane potential for each hydro-thermal hydrolysate were measured. Then, the organic substance fractions of hydro-thermal hydrolysate were characterized by the optimization of the parallel first order kinetics model. The increase of hydro-thermal reaction temperature from 170℃ to 220℃ caused the enhancement of hydrolysis efficiency. And the methane potential showed the maximum value of 0.381 Nm³ kg^-1-VS_added in the hydro-thermal reaction temperature of 190℃. Biodegradable volatile solid(VSB) content have accounted for 66.41% in 170℃, 72.70% in 180℃, 79.78% in 190℃, 67.05% in 200℃, and 70.31% in 220℃, respectively. The persistent VS content increased with hydro-thermal reaction temperature, which occupied 0.18% for 170℃, 2.96% for 180℃, 6.32% for 190℃, 17.52% for 200℃, and 20.55% for 220℃.CONCLUSION: Biodegradable volatile solid showed the highest amount in the hydro-thermal reaction temperature of 190℃, and then, the optimum hydro-thermal reaction temperature for organic sludge was assessed as 190℃ in the aspect of the methane production. The rise of hydro-thermal reaction temperature caused increase of persistent organic matter content.

• 생명과학회지
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• 제5권4호
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• pp.155-161
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• 1995

The effects of substrate concentration, enzyme concentration, reaction temperature, and water content were investigated in intramolecular esterification. This study used cyclohexane as organic solvent, power lipase as enzyme, and benzyl alcohol and octanoic acid as substrate. The initial reaction rate was found to be proportional to enzyme concentration; followed Michaelis-Menten equation for octanoic acid; and was inhibited by benzyl alcohol . The observed initial reaction rate first increased, then decreased with increasing reaction temperature, giving rise to the maximum rate at 20$\circ$. The drop in the reaction rate at higher temperature was to partition equilibrium change of substrate between organic solvent and hydration layer of enzyme molecule in addition to the deactivation by enzyme denaturation. Water layer surrounding enzyme molecule seemed to activate in organic solvent and the realistic reaction was done in the water layer. In the enzymatic reaction in organic solvent, the initial reaction rate was influenced by partition quilibrium of substrate, so the optimum condition of substrate concentration, enzyme concentration, reaction temperature, and water content would give a good design tool.

• 한국환경과학회지
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• 제15권7호
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

• 한국재료학회지
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• 제24권1호
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• pp.25-32
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• 2014

In this study, nano-sized cobalt oxide powder with an average particle size below 50 nm was prepared from a cobalt chloride solution by the spray pyrolysis process. The influences of reaction temperature on the properties of the generated powder were examined. The average particle size of the particles formed based on the spray pyrolysis process at a reaction temperature of $700^{\circ}C$ is roughly 20 nm. Moreover, most of these particles cannot appear with an independent type, thereby coexisting in a droplet type. When the reaction temperature increases to $800^{\circ}C$, the average particle size not only increases to roughly 40 nm but also shows a more dense structure while the ratio of particles which shows a polygonal form significantly increases. As the reaction temperature increases to $900^{\circ}C$, the distribution of the particles is from roughly 70 nm to 100 nm, while most of the particle surface is more intricately close and forms a polygonal shape. When the reaction temperature increases to $1000^{\circ}C$, the particle size distribution of the powder shows an existing form from 80 nm to at least 150 nm in an uneven form. As the reaction temperature increases, the XRD peak intensity gradually increases, yet the specific surface area gradually decreases.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.833-841
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• 2021

During the postulated severe accident of nuclear reactor, eutectic reaction leads to low-temperature melting of fuel cladding and early failure of core structure. In order to model eutectic melting with the moving particle semi-implicit (MPS) method, the eutectic reaction model is developed to simulate the eutectic reaction phenomenon. The coupling of mass diffusion and phase diagram is applied to calculate the eutectic reaction with the uniform temperature. A heat transfer formula is proposed based on the phase diagram to handle the heat release or absorption during the process of eutectic reaction, and it can combine with mass diffusion and phase diagram to describe the eutectic reaction with temperature variation. The heat transfer formula is verified by the one-dimensional melting simulations and the predicted interface position agrees well with the theoretical solution. In order to verify the eutectic reaction models, the eutectic reaction of uranium and iron in two semi-infinite domains is simulated, and the profile of solid thickness decrease over time follows the parabolic law. The modified MPS method is applied to calculate Transient Reactor Test Facility (TREAT) experiment, the penetration rate in the simulations are agreeable with the experiment results. In addition, a hypothetical case based on the TREAT experiment is also conducted to validate the eutectic reaction with temperature variation, the results present continuity with the simulations of TREAT experiment. Thus the improved method is proved to be capable of simulating the eutectic reaction in the severe accident.

• 패션비즈니스
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• 제3권1호
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• pp.125-137
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• 1999

The present study aims to reveal the sweating reaction of male adults, focused on athletes. With six subjects (3 athletes and 3 non-athletes) in two different conditions of ambient temperature (I : $25\pm1.0^{\circ}C$, II : $29.5\pm1.0^{\circ}C$), their total sweat rate, local sweat rate, skin temperature, physiological reaction (rectal temperature, blood pressure, and pulse rate), and psychological reaction (thermal, moisture, comfort, and perceptive sweat sensations) were measured. The comparison gave the following results: Total sweating rate was greater in non-athletes, while the two groups had more perspiration in ambience II. Local sweating rate in both ambiences was the greatest in the central breast area (athletes) and the infrascapular area (non-athletes). The mean skin temperature had more changes of increase and decrease in athletes. As to physiological reaction, non-athletes had lower rectal temperature and blood pressure as well as higher pulse rate. As for psychological reaction in Ambience II, the 4 sensations were mostly 'hot', 'humid', 'uncomfortable', and 'sweaty'.

• 통합자연과학논문집
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• 제2권3호
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• pp.219-223
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• 2009

Easy and simple synthesis of CdSe nanocrystals was achieved through sol-gel process. CdSe nanocrystals were synthesized from the reaction of cadmium oxide and selenium in the prescence of trioctylphosphine oxide, tributylphosphine, octadecene, octadecylamine, and stearic acid. The effect of reaction temperature for the determination of size of CdSe nanocrystals was investigated after the addition of selenium. The reaction temperature for the growth of CdSe nanocrystals was increased by every $20^{\circ}C$ from 170 to 190, 210, 230, 250, 270, and $290^{\circ}C$. When the reaction temperature was higher, the absorption wavelength in the absorption spectrum was increased which indicated that the size of CdSe nanocrystals was increased. The emission wavelength in the photoluminescence spectrum was increased from 438 to 489, 542, 591, 643, 692, and 745 nm, as the size of CdSe nanocrystals was increased. The control of the reaction temperature illustrated that the color tuning of emission wavelength were successfully obtained.

• Korean Chemical Engineering Research
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• 제56권5호
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• pp.738-751
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• 2018

The effect of the reaction temperature and reaction time on the thermal oxidative purification quality of detonation nanodiamond (NDsoot) was investigated in a gas-solid fluidized bed reactor of a $0.10m-ID{\times}1.0m$-high stainless steel column with zirconia beads ($d_{SV}=99.2{\mu}m$). The carbon conversion increased with increasing the reaction temperature; however, when the reaction temperature was greater than 773 K, the carbon conversion did not increase. The content of $sp^3$-hybridized carbon at the reaction temperature of 703 K barely changed when the reaction time was more than 30 minutes, but at 773 K, the content decreased as preferred. At 703 K, the purification quality increased with the increasing reaction time; however, at 773 K, the purification quality increased up to 30 minutes and then decreased rapidly.

• 펄프종이기술
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• 제33권3호
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• pp.84-99
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• 2001

This study was carried out to acquire basic data necessary for the use of rice-straw chemical pulp. It investigated the proper bleaching conditions when rice-straw chemical pulp(alkaline sulfite-${Na_2}{S_2}{O_4}$) was bleached using the various kinds of bleaching agents by the two-stages bleaching methods. And, physical properties of pulps bleached with eight kinds of two-stages bleaching methods were tested. The results of this study were as follow; 1. The first-stage bleaching was conducted under the proper conditions with chlorine(C). And then, the proper conditions related to the calcium chlorite(H), hydrogen peroxide(P) and sodium hydrosulfite(Y) bleaching as the second-stage bleaching were investigated. The proper conditions of CH stage were determined to be 0.3% concentration of calcium chlorite, $30^{\circ}C$ of reaction temperature and 20min. of reaction time. For CP stage, the proper conditions of concentration of hydrogen peroxide, reaction temperature and reaction time were 1.5%, $60^{\circ}C$ and 90min., respectively. And for CY stage, the proper conditions were 0.5% concentration of sodium hydrosulfite, $40^{\circ}C$ of reaction temperature and 90min. of reaction time. 2. The first-stage bleaching was conducted under the proper conditions with chlorine dioxide(D). And then, the proper conditions related to the calcium chlorite(H), hydrogen peroxide(P) and sodium hydrosulfite(Y) bleaching as the second-stage bleaching were investigated. The proper conditions of DH stage were determined to be 0.5% concentration of calcium chlorite, $25^{\circ}C$ of reaction temperature and 5min. of reaction time. For DP stage, the proper conditions of concentration of hydrogen peroxide, reaction temperature and reaction time were 1.0%, $70^{\circ}C$ and 90min., respectively. And for DY stage, the proper conditions were 0.3% concentration of sodium hydrosulfite, $50^{\circ}C$ of reaction temperature and 20min. of reaction time. 3. The first-stage bleaching was conducted under the proper conditions with calcium chlorite(H). kAnd then, the proper conditions related to the hydrogen peroxide(P) and sodium hydrosulfite(Y) bleaching as the second-stage bleaching were investigated. The proper conditions of HP stage were determined to be 0.3% concentration of hydrogen peroxide, $30^{\circ}C$ of reaction temperature and 60min. of reaction time. For HY stage, the proper conditions of concentration of sodium hydrosulfite, reaction temperature and reaction time were 2.5%, $60^{\circ}C$ and 30min., respectively. 4. When the rice-straw chemical pulps were bleached with eight kinds of two-stages bleaching methods in the proper conditions mentioned above, respectively, the final brightnesses after CH, CP, CY, DH, DP, DY, HP, and HY bleachings were 62.0, 74.3, 61.4, 58.9, 66.9, 62.9, 50.4 and 60.1, respectively. And strengthes of pulps bleached with DP and DH methods were comparatively higher than those of pulps bleached with other bleaching methods.