• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.2
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• pp.17-24
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• 2012

Tetrahydrotricyclopentadiene(below THTCPD) isomer is a good candidate materials for the high performance liquid fuel component because of its high density and heat of combustion value. The object of this study was to find out the proper reaction condition to improve the fluidity of THTCPD which is solid state at room temperature. Therefore, we have carried out isomerization reactions using aluminum chloride in the varying reaction condition such as reaction temperature and solvents. The results showed that when using aluminum chloride catalyst, THTCPD isomerization reaction was more active in the polar halogenated reaction media such as dichloromethane(methylene chloride: MC), 1,2-dichloroethane(ethylene chloride: EC) and chloroform than in non-polar hydrocarbon media such as n-Hexnae and toluene and was effected by reaction temperature variation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.1
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• pp.132-136
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• 1999

Mechanical alloying (MA) by ball mill of $Fe_{30}Cr_{70}$ elemental powders was carried out under the nitrogen gas atmosphere. Amorphization has been observed in this case, while MA under an inert argon gas atmosphere produces the bcc solid solution. The DSC spectrum for the mechanically alloyed $(Fe_{30}Cr_{70})_{0.85}N_{0.15)$powders exhibits a sharp exothermic peak due to crystallization at about $550^{\circ}C$. Structural transformation from the bcc crystalline to amorphous states was observed through X-ray and neutron diffractions. During amorphization process the octahedral unit, which is typical of a polyhedron formed in any crystal structures, was preferentially destroyed and transformed into the tetrahedral unit. Futhermore, neutron diffraction measurements revealed that a nitrogen atom is situated at a center of the tetrahedron formed by metal atoms.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.127-134
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• 2017

In this study, moist curing equipment was used in the exist gang-form system. By achieving sufficient spray curing, the quality of the concrete was improved and the cracking occurred in building's side wall was decreased. The following results could be made as the conclusion. For the compressive strength, all zones showed the similar results. Comparing with the zone without using moist curing equipment, the zone used moist curing equipment showed higher rebound hardness results. For the cracking, the zone utilized moist curing equipment showed the cracking averaged as 6.6 m and the zone without using moist curing equipment showed the cracking averaged as 10.3m. The effectof reducing cracking by utilizing moist curing equipment is about 36 %. Using moist curing equipment is considered as a good solution to reduce the cracking in the structure. Considering all the factors analysed, using moist curing equipment improved the quality of the concrete and decreased the cracking. When this equipment was used in the construction site, it is expected that the construction periodcan be shrunk and the ratio of defect caused by drying shrinkage can be decreased. In this research conditions, The 0.3mm sized moist curing equipment provided the most desirable results on concrete quality and preventing cracking.

• Journal of the Korean Society of Safety
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• v.22 no.5
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• pp.77-83
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• 2007

This study is conducted on spontaneous ignition temperature and activation energy of Hydroxypropyl Methyl Cellulose(HMC) powder. HMC is a kind of cellulose derivative and used as additives for building material, surface coating, printing ink, adhesives, cosmetics and medical supplies. So this material has been widely used as important additive in the chemical industry fields and a mount of production has increased year by year. Therefore, it is very important to find out the thermal ignition characteristics of its danger and the critical ignition temperature. This study was performed by the Spontaneous Ignition Tester(SIT) and so on. Based on the data of the SIT-II, the critical ignition point of HMC is about $186^{\circ}C$ which is slightly lower than normal cellulose.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1641-1646
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• 2010

Recently, environmental concerns increased, CNG fuel research for the prevention against air pollution is actively. But, the problems of CNG fuel have less output and a shorter charging distance than gasoline. Especially, the causes of the torque and output reduction are the mixed fuel has a combustion timing loss in case of CNG fuel which has a smaller heating value per a unit volume and a slower flame propagation speed than gasoline. In this paper, we design the spark advanced controller in consideration of the spark timing loss. Through the experimental of chassis dynamometer, we show that maximum power and torque have improved compared to that of general CNG bi-fuel system.

• Bulletin of the Korean Space Science Society
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• 2005.04a
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• pp.129-132
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• 2005

This paper describes BAUSAT-2 orbital thermal analysis and preliminary design of thermal control subsystem. To design thermal control subsystem of HAUSAT-2, we have considered active & passive thermal control method based on basic theory and themal equilibrium equation. Using this result, suitable thermal control method and material have been selected. We have designed thermal control subsystem based on analysis of HAUSAT-2's thermal environments on sun synchronous orbit with altitude 650km, inclination $98^{\circ}$ and thermal distribution and range expectation of each HAUSAT-2's surface. Thermal analysis consists of system level, box level and board level analysis. We have completed system level and box level analysis. Till now, board level analysis of main heat dissipation board in progress. Thermal control subsystem has designed according to thermal analysis result. This design is to maintain all of the HAUSAT-2 components within the allowable temperature limits. In future, STM

• KSBB Journal
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• v.10 no.2
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• pp.149-158
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• 1995

The capacity of inclusion complex formation between ${\alpha}$-, ${\beta}$-, ${\gamma}$-cyclodextrins(CDs) and various compounds, such as pH indicators, biloslalns, glycoside, amino acid, and fatty acids, was compared. Fatty acid was identified as the most suitable ligand for fractionation of CDs in terms of capacity and selectivity. The effects of complex formation conditions, such as, mixing ratio of CD and fatty acid, pH, ionic strength, and temperature, on the capacity of fatty acrid-CD complex was also investigated. The carbon number of fatty acids was identified as the most significant factor determining the capacity and selectivity of inclusion complex formation of CDs. Capric acid(C10) and palmitic acid(C16) showed high specificity for ${\alpha}$- and ${\beta}$-CDs, respectively. Under the optimal conditions, the molar ratio of complex formed was found to be 1.0:2.6 for ${\alpha}$-CD/capric acid and 1.0:1.9 for ${\beta}$-CD/palmitic acid. X-ray diffraction and infrared spectrum of the formed inclusion complex were analyzed. The changes of enthalpy($\Delta$H) of the inclusion complex formation reaction was evaluated by differential scanning calorimetry, showed that the reaction was endothermic.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.203-212
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• 1987

The hydration and strength of concrete are affected by curing conditions, especially curing temperature. In this paper, the hydration temperature of heated curing concrete specimen are measured by thermo-couples instead of conduction calorimeter, and strengths of concrete are tested. The results of this study show that the compressive strengths of concrete are especially dependent on the curing temperature. And the strength results of concrete agree approximately with the results of approach to the hydration process of cement concrete.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.119-125
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• 2004

This paper is described the indirect induction heated boiler system and induction heated hot air producer using the voltage-fed series resonant high-frequency inverter which can operate in the frequency range from 20〔KHz〕 to 50〔KHz〕. A specially designed Induction heater, which is composed of laminated stainless assembly with many tiny holes and interconnected spot welding points between stainless plates, is inserted into the ceramic type vessel with external working coil. This working coil is connected to the resonant inverter. In the induction heater, it's primary heating section creates low-pressure saturated steam and secondary heating section generates heat distribution evaporating fluid from the turbulence fluid which is flowing through the vessel. The operating performances of this unique appliance in next generation and its effectiveness are evaluated and discussed from the practical point of view.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.105-109
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• 2005

We heat treated pure sapphire samples at $1800^{\circ}C{\sim}100$ hours in BeO-${Al_2}{O_3}$ powder by varying BeO contents of $5{\sim}50\;wt%$ in order to quantify the BeO diffusion enhancement for corundum gem stones. We investigated the heat treated samples with visual evaluation, color coordination analysis, and surface roughness measurement. We confirmed that $Be^{2+}$ ions did not lead to orange color but to dark gray. The lightness in CIE Lab index decreased while surface roughness increased rapidly as BeO contents increased. We propose that BeO yellow color enhancement may be feasible only for $Fe^{3+}$ rich blue sapphires and sub-5% BeO content be appropriate to shorten post re- cutting process.