• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.184-192
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• 2015

Characteristics of Char-$CO_2$ gasification for petroleum coke, biomass and mixed fuels were compared in the temperature range of $1,100{\sim}1,400^{\circ}C$ using TGA (Thermogravimetric analyzer). Kinetic constants with respect to reaction temperature were determined by using different gas-solid reaction models. Also activation energy (Ea) and pre-exponential factors ($K_0$) in each models were calculated by using Arrhenius equation and then were compared with experimental values to determine reaction rate equation for char-$CO_2$ gasification. Reaction time for $CO_2$ gasification decreased with an increase of reaction temperature. Also, the activation energy of $CO_2$ gasification reaction for mixture with petroleum coke and biomass decreased with increasing biomass contents. This indicates that mixing with biomass could bring synergy effects on $CO_2$ gasification reaction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.9
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• pp.853-860
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• 2017

To evaluate the effects of mode II on the crack initiation and propagation stages, the effects in the fatigue threshold region under a mixed-mode I+II loading state was experimentally investigated. In the case of mixed-mode I + II, during the crack initiation stage, as the loading application angle (${\theta}$) increased, cracks occurred in the lower load owing to the effects of mode II, while the crack propagation rate decreased. The effects of mode II were experimentally investigated in the crack propagation stage by means of multilevel loading direction variation. Following mixed-mode I+II ($0^{\circ}{\rightarrow}{\theta}{\rightarrow}60^{\circ}$), as the load application angle increased, the fatigue crack propagation rate decreased, as did the fatigue crack propagation rate, which occurred later. Following mixed-mode I + II in case of(${\theta}{\geq}75^{\circ}$), the fatigue crack propagation rate was found to increase, while the fatigue life decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.65-65
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• 2009

본 연구에서는 ICP 식각장치 및 $Cl_2$/Ar 플라즈마에 의한 $Ba_2Ti_9O_{20}$(BTO) 박막의 식각 특성을 고찰하였다. XPS 분석 장치를 이용하여 식각 표면 반응을 조사하였으며, 공정 변수 ($Cl_2$/Ar 가스 혼합비, 소스파워, 챔버 압력, 바이어스 파워)에 따라 플라즈마 특성 변화를 Langmuir probe measuring system을 이용하여 추출하였다. $Cl_2$/Ar 가스에서 Ar 가스의 혼합비가 증가함에 따라 BTO 박막의 식각 속도는 감소하였으며, $Cl_2$ 가스만을 사용하는 경우, 31.7 nm/min 으로 가장 높은 식각 속도를 보였다. Ar 가스의 혼합비에 따른 BTO박막의 식각속도 변화는 Langmuir probe 특성과 XPS 분석결과로부터 플라즈마 내에 형성되는 Cl radical density와 밀접한 관련이 있는 것으로 판단할 수 있다.

• Journal of the Korean Chemical Society
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• v.20 no.5
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• pp.333-339
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• 1976

The rates of solvolysis for 2-thenoyl chloride have been measured in aqueous acetone and aqueous ethanol at various temperatures ranging from 20 to $40^{circ}C$. The activation parameters and the Grundwald-Winstein's slope are determined by the analysis of solvolysis rates. The results indicated that the reaction rates of solvolysis are considerably slower than those of the reaction for benzoyl chloride due to the electron donating effect of thiophene nucleus. The results also showed that the reaction proceeds with the $S_N1$ mechanism in water-rich solvents whereas the $S_N2$ character increases with the decrease of water content, and overall reaction is subject to entropy control.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.198-204
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• 2004

Using liquefied natural gas as a fuel, water, natural gas and liquefied natural gas-cooled firing tests were conducted. With the viewpoint of characteristic velocity, and specific impulse, the effect of OF mixture ratio and fuel inlet temperature into a combustion chamber were analyzed. OF mixture ratio and fuel inlet temperature into a combustion chamber have great influence on the performance. Characteristic velocity and theoretical specific impulse attain the maximum value at 0.72~0.75 and 0.75 of OF mixture ratio, respectively. Engine performance has a tendency to increase, proportional to fuel inlet temperature into a combustion chamber affected by the regenerative cooling.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.274-277
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• 2004

Fuel/air mixing in air turbo ramjet(ATR) combustor is a significant parameter of combustion stability and efficiency. In this study, fuel distribution in the ATR model combustor was measured to compare the degree of mixing with respect to the velocity ratio$(r=v_a/v_f)$ between fuel gas and air. Planar laser-induced fluorescence(PLIF) and image processing method were used to obtain two dimensional fuel distribution. Fuel mixing went bad with approaching to r=1.

• Journal of the Korea Institute of Building Construction
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• v.23 no.1
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• pp.35-43
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• 2023

In this study, the mechanical properties of concrete mixed with non-sintered hwangto(NHT) as an alternate material for cement were evaluated, and the compressive strength prediction equation of concrete based on ultrasonic pulse velocity analysis was proposed. Cement replacement rates for mixed NHT were set to 0, 15, and 30%, and design compressive strength was set to 30 and 45MPa to evaluate the effect on the amount of cement and NHT powder. The mechanical properties items analyzed were compressive strength, ultrasonic pulse velocity, and elastic modulus, and were measured on days 1, 3, 7, and 28. As the replacement rate of NHT increased, the mechanical properties tended to decrease. In addition, as a result of analyzing the correlation between compressive strength and ultrasonic pulse velocity, the correlation coefficient(R²) showed a high relationship(R²=0.95) on concrete mixed with NHT.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.591-594
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• 2008

지구 온난화 문제의 심각성이 대두되면서 이산화탄소 저감 기술에 대한 관심이 증폭되고 있다. 가장 이상적인 방법은 탄소가 포함되지 않은 청정 재생 에너지원이지만, 에너지 공급 규모 면에서 보면 근미래에도 화석 연료가 에너지 수요에 대한 주요 공급원으로 남아있을 것이라는 의견이 지배적이다. 많은 화석 연료 중 천연가스는 탄소 배출량이 가장 적은 청정 연료로 지난 10년간 수요가 폭발적으로 증가해왔다. 이를 고려해볼 때 탄소 배출량이 적은 천연가스를 생산하면서 이산화탄소를 격리 시킬 수 있는 기술은 매우 매력적이다. 본 연구에서는 심해저의 메탄 하이드레이트로 부터 천연가스를 생산하는 기술로서 이산화탄소와 질소의 혼합 가스를 사용하는 기술 개발의 일환으로 혼합 가스에 의한 메탄 하이드레이트 해리 속도를 $^{13}C$ NMR을 이용해 측정한 결과를 제시하고자 한다.

• The Journal of Information Technology
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• v.4 no.4
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• pp.51-63
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• 2001

Residue Number System has carry free operation and parallelism each modulus, So it is used for special purpose processor such as Digital Signal Processing and Neuron Processor. Magnitude comparison and sign detection are in need of Mixed Radix Conversion, and these operations are impediment to improve the operation speed. So in this Paper, MRC(Mixed Radix Converter) is designed using modified partitioned residue to speed up the operation of MRC, so it has progressed maximum twice operation time but increased the size of converter comparison to other converter.

• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.156-161
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• 2003

In this study, a hybrid navigation system with a low-cost GPS Receiver plus Gyro and Odometer is developed and tested. This hybrid navigation system adopted a modified coupling method which can be distinguished from tightly coupled method or loosely coupled method, so that GPS receivers or Gyros or Odometers can be chosen arbitrary. Comparing to the existing hybrid navigation system, the test results show that this navigation system enhances the accuracy and is robust against the multipath error. It is also proven that this system has an advantage of acquiring GIS data for post processing.