• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
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• pp.883-887
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• 1998

Hydration is the main reason for the growth of the material properties. A exact parameter to control the chemical and physical process is not the time, but the degree of hydration. Therefore, it is reasonable that development all material properties should be formulated in terms of degree of hydration. Mathematical formulation of degree of hydration is based on combination of reaction rate functions. The effect of moisture conditions as well as temperature on the rate of reaction is considered in the degree of hydration model. This effect is subdivided into two contributions: water shortage and water distribution. The former is associated with the effect of on the progress of hydration. The water needed for progress of hydration do not exist and there is not enough space for the reaction products to form. The latter is associated with the effect of free capillary water distribution in the pore system. Physically absorption layer does not contribute to progress of hydration and only free water is available for further hydration.

• 대한기계학회논문집B
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• 제28권1호
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• pp.9-15
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• 2004

$CO_2$ is a well-known green house gas as well as the major source of global warming. Many researchers have studied to reduce $CO_2$ emission in combustion processes. Among the method for reducing $CO_2$ emission, oxygen-enriched combustion has been proposed. Because its adiabatic flame temperature is relatively too high, existing facilities must be changed or the flame temperature in the combustion zone should be reduced. The combustion characteristics, composition in the flame zone, temperature profile and emission gases were investigated experimentally for the various oxygen-enriched ratios(OER) by the addition of $CO_2$, under constant $O_2$ flow rate. Results showed that the reaction zone was quenched and broadened as the addition of $CO_2$ was increased. The emission of NOx in flue gas was decreased as decreasing temperature in reaction zone. It was also shown that the reaction was delayed by the cooling effect. As the addition of $CO_2$ was increased, the composition of CO in the flame zone was increased due to the increase of reaction rate by increasing mixing effect of oxidant/fuel at OER=0％, but the composition of CO was decreased by quenching effect at OER=50％ and 100％.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.61-65
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• 2008

This study, having combined and displaced blast furnace slag("BS" hereinafter) known as admixture material that delays hydration reaction with coarse particle cement("CC" hereinafter) collected in particle classification method during ordinary portland cement("OPC" hereinafter), reviewed the hydration heat characteristics affecting the concrete. To reduce hydration heat, the study plain-mixed which used 100% OPC for W/B 50% level 1, displaced CC at level 3 of 25%, 50% and 75% for OPC, and by displacing BS with admixture material at level 5 of 0%, 20%, 40%, 60% and 80% for cement(OPC+CC), experimented totally 16 batches. As a result of experiment, in the case of flow, the more CC displacement rate increased, the more it tended to decrease, and the more BS displacement rate increased, the more it decreased. Also, as for simple adiabatic temperature rise by the CC and BS displacement rates, it decreased as displacement rate increased, and particularly in the case of displaced BS of 80%, It showed temperature reduction effect of about 63% companing with plain. Compressive strength decreased in proportion to displacement rate, however strength reduction increment was shown to decrease with age progress.

• 폴리머
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• 제39권2호
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• pp.210-218
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• 2015

본 연구에서는 아민계 젤화 촉매 dimethylcyclohexyl amine(DMCHA)과 칼륨계 젤화 촉매 potassium octoate(PO)가 경질 폴리우레탄 발포체의 반응거동에 미치는 영향에 대해 연구하였다. Polymeric 4,4'-diphenyl methane diisocyanate, 폴리에스터 폴리올, 실리콘 유화제, 발포제 그리고 젤화 촉매를 사용하여 경질 폴리우레탄 발포체를 제조하였다. DMCHA 촉매의 함량이 0에서 2.0 g으로 증가함에 따라 반응 시간이 약 330초에서 약 35초로 감소하였고, 발열 반응으로 최대 반응온도는 약 217에서 약 $234^{\circ}C$로 증가하였다. PO 촉매의 함량이 0에서 2.5 g으로 증가할수록 반응 시간은 약 79초에서 약 38초로 감소함을 보였고, 특히 젤 타임, 택 프리 타임의 단축에 기여하였으며, 최대 반응온도가 약 182에서 약 $271^{\circ}C$로 증가하였다. 단열 온도 상승법을 이용하여 전환율을 구하였고, 반응식의 상수들을 계산하였다. 반응속도상수 $k_0$는 DMCHA 촉매의 양이 증가할수록 큰 값을 갖는 것을 확인하였고, PO 촉매의 경우 촉매량 증가와 큰 관계없이 유사한 값을 나타냈다.

• 대한기계학회논문집
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• 제12권5호
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• pp.1113-1120
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• 1988

본 연구에서는 4종류의 실험 모델을 채택하여 연소 반응용다공성 블럭(combu- stive reacting porous block)내의 화염대 위치와 화염의 온도 분포, 화염이 안정화 되는 범위를 고찰하여 내부 열재순환 효과를 규명하고 예열용 다공성 블럭(preheating porous block)과 복사 차폐용 다공성 블럭(radiative insulating porous block)의 효 과에 대한 연구와 초희박 혼합기나 저 발열량 연료의 연소 가능성을 제시하고 수치 계 산에 필요한 자료를 제시하는 것이다.

• 한국재료학회지
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• 제5권7호
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• pp.869-879
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• 1995

TiAi intermetallic compound has been extensively studied for possible high temperature structural applications because of its high specific strength at high temperature, high creep resistance, and good oxidation resistance at elevated temperatures. In addition to its good properties, an economic manufacturing routes should be developed for this material to be used more extensively. One of the promising route in manufacturing TiAl intermetallics is the Self-propagating High-temperature Synthesis (SHS) method. Thus in this study, an attempt was made to study the mechanism of the SHS process in TiAl synthesis. The composition of the sample was Ti-(45, 50, 53)at% Al and the microstuctures of the products were analyzed using optical microscope and scanning electron microscope. When the phases formed at the main SHS reaction of whicyh combustion temperature is higher than the melting temperature of aluminum were identified as TiAl and Ti$_3$Al ; Ti$_3$Al cores surrounded by TiAl phase. In order to increase the combustion temperature, carbon was added 5 and 10at.%. When the carbon content was 10at.%, the heat of the reaction was large enough to melt the phase formed and that is consistent with the theoretical calculation results of the adiabatic temperature. The combution temperatue, which was measured by a computer data acquisition system, increased with the carbon content. The phases formed from the reaction involving the carbon added were indentified as TiAl and Ti$_2$AlC using XRD. The vickers hardness of the reaction product increased with the carbon content.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.97-102
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• 1997

In this study, a predictive method which was modified from KIshi's model for the temperature development of concrete was developed by using mineral compounds of clinker and pozzolans. Temperature dependent heat generation of reaction was also considered. Specific heat considering the effect of mix proportion and temperature was calculated with experimental data in the literatures. Thermal conductivity considering the effect of mix proportion and temperature was experimentally investigated. Through this research it was found that the developed method considering thermal properties accurately predicted adiabatic temperature rise of concrete without the experiment. It was also found that the thermal conductivity of concrete could be predicted by the volume ratio of each component of mix proportion and was independent of temperature within the normal climatic range.

• 대한기계학회논문집B
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• 제27권6호
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• pp.685-692
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• 2003

A numerical simulation of flame propagation in a micro combustor was carried out. Combustor has a sub -millimeter depth cylindrical internal volume and axisymmetric one-dimensional was used to simplify the geometry. Semi-empirical heat transfer model was used to account for the heat loss to the walls during the flame propagation. A detailed chemical kinetics model of $H_2/Air$ with 10 species and 16 reaction steps was used to calculate the combustion. An operator-splitting PISO scheme that is non-iterative, time-dependent, and implicit was used to solve the system of transport equations. The computation was validated for adiabatic flame propagation and showed good agreement with existing results of adiabatic flame propagation. A full simulation including the heat loss model was carried out and results were compared with measurements made at corresponding test conditions. The heat loss that adds its significance at smaller value of combust or height obviously affected the flame propagation speed as final temperature of the burnt gas inside the combustor. Also, the distribution of gas properties such as temperature and species concentration showed wide variation inside the combustor, which affected the evaluation of total work available of the gases.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.122-128
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• 1999

CARS(Coherent anti-Stokes Raman Spectroscopy) temperature measurement under engine-like condition was validated by measuring unburned gas temperatures of premixed propane-air flame in a constant volume combustion chamber. The measured temperatures were compared with predictions of 2 zone flame propagation model. End-gas temperatures were measured were measured by CARS technique in a conventional 4 cylinder DOHC spark-ignition engine fueled with PRF 80. Cylinder pressure was measured simultaneously with CARS signal and used as a parameter on fitting CARS spectrum to library of theoretical spectra. There was a good agreement between the measured temperature and adiabatic core temperature calculated from measured cylinder pressure. Significant heating by pre-flame reaction in the gas was observed in the late part of compression stroke.

• Korean Chemical Engineering Research
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• 제57권3호
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• pp.420-424
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• 2019

포항산업과학연구원(RIST, Research Institute of Industrial Science & Technology)-고등기술연구원(IAE, Institute for Advanced Engineering)에서 제안한 합성천연가스(Synthetic Natural Gas, SNG) 제조공정(3개의 단열반응기와 1개의 등온반응기로 구성됨)에서, 합성가스와 함께 스팀을 공급함으로써 메탄화반응과 수성가스전환반응을 동시에 반응시켜 촉매층의 온도와 촉매 비활성화를 제어하였다. SNG 공정개발을 위해 본 연구에서는, 포항산업과학연구원에서 제조한 니켈계 촉매를 사용하여 낮은 $H_2/CO$ 비($CO_2$ 22% 포함) 조건에서의 메탄화반응 특성을 평가하였다. 운전조건(1차 단열반응기의 $H_2O/CO$ 비, 4차 등온반응기의 운전온도 범위 등)은 이전의 연구 결과를 반영하였으며, 동일한 조건을 유지하면서 파일럿 규모의 SNG 공정을 운전하였다. 그 결과, 파일럿 규모의 SNG 공정은 안정적으로 운전되었으며, CO 전환율 100%, $CH_4$ 선택도는 96.9% 그리고 $CH_4$ 생산성은 $660ml/g_{cat}{\cdot}h$의 값을 얻었다.