• Fire Science and Engineering
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• v.22 no.4
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• pp.85-94
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• 2008

The purpose of this study is to obtain the fundamental fire resistance performance of engineered cementitious composites (ECC) under fire temperature in order to use the fire protection material in high-strength concrete structures. The present study conducted the experiment to simulate fire temperature by employing of ECC and investigated experimentally the explosion and cracks in heated surface of these ECC. In the experimental studies, 5 HSC specimens are being exposed to fire, in order to exami ne the influence of vari ous parameters (such as depth of layer=20, 30, 40 mm; construction method=lining and repairing type) on the fire performance of HSC structures. Employed temperature curve were ISO 834 criterion (3 hr), which are severe in various criterion of fire temperature in building structures. The numerical regressive analysis and proposed equation to calculate ambient temperature distribution is carried out and verified against the experimental data. By the use of proposed equation, the HSC members subjected to fire loads were designed and discussed.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.240-247
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• 2015

Zeolite A was prepared from coal fly ash upon NaOH fusion treatment, followed by hydrothermal treatment. The effects of treatment conditions such as NaOH/ash ratio, fusion temperature, the amount of sodium aluminate added, hydrothermal treatment temperature and time on the type and the crystallinity of zeolites were investigated. The optimal NaOH/ash weight ratio and fusion temperature to produce high crystalline zeolite A were 1.2 and $550^{\circ}C$, respectively. The dissolution of $Si^{4+}$ and $Al^{3+}$ from the fused fly ash was not affected by stirring time. The type of synthetic zeolites was found to be dependent on the amount of sodium aluminate added. The low amount of sodium aluminate favored zeolite X, while a single phase zeolite A was produced by increasing the amount sodium aluminate. Zeolite A was transformed into hydroxysodalite with increasing hydrothermal treatment time and temperature. A high crystalline zeolite A could be obtained by decreasing the temperature increasing time up to the reaction temperature.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.6
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• pp.240-243
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• 2006

The significant color enhancement in low quality Australian natural sapphire has been achieved by a hydrothermal method. The optimal conditions for the color enhancement of Australian natural sapphire were as follows; hydrothermal reaction temperature: $320{\sim}350^{\circ}C$, duration : 3 days, hydrothermal solvent: 2 M NaOH solution. After the hydrothermal treatment, Australian natural sapphires of transparent colors were obtained, and their grades were found to be improved from commercial to middle/top grade by value chart analysis.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.4 no.2
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• pp.139-147
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• 1994

Orthophosphate crystals were grown by the hydrothermal method and the properties of grown crystals were investigated by means of X-ray diffraction. Vickers hardness tester, etc. The starting powders of $AIPO_4 and GaPO_4 $were prepared as a single phase by the solid state reaction of stoichiometric mixture of $AI_2O_3 or Ga_2O_3$ and $NH_4H_2PO_4$ and the subsequently by the hydrothermal treatment. The hydrothermal conditions for high growth rates of the orthophosphate crystals are as follows: $AlPO_4$ crystal; temperature ranges, between $170$~$200^{\circ}C$; temperatures difference, $15$~$20^{\circ}C;$, hydrothermal solvent, 4m HCl, $GaPO_4 crystal; temperature ranges, between $210 and 240^{\circ}C;$; temperature difference, $25$~$30^{\circ}C; $, hydrothermal solvent, 4m HCl. Morphologies of grown crystals tended to be bounded by (1010), (1011) and (0111) faces at low temperatures, and grew with well developed (0001) faces by increasing the growth temperature. On the other hand, the properties of orthophosphate crystals $(AlPO_4/GaPO_4)$ were as follows: lattice parameters (nm); a=0.494, c=1.094/a=0.490, c=1.105, density (gcm-3); 2.62/3.56, Vickers hardness (Nm^2); $1.02{\times}10^1^0/7.06{\times}10^9$, refractive indices; $ne=1.529{\pm}0.003, no=1.519{\pm}0.003/ne=1.611{\pm}0.006, no=1.599{\pm}0.006, birefringence; {\pm}0.01/{\pm}0.012$, dielectric constant (Fm-1); 6/7.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.1
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• pp.12-17
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• 1993

Growth runs of KTP single crystals were carried out by the hydrothermal method. KTP powders used for the crystal growth were prepared as a single phase by the solid state reaction of a stoichiometric mixture of $KH_2PO_4 and TiO_2$ at TEX>$800^{\circ}C$ and subsequently by the hydrothermal treatment at $250^{\circ}C$ 4m KF solution. The most effective solvents for the crystal growth of KTP were KF and K $K_2HPO_4$ solutions. Solubilities of KTP in these solutions were positive over the range $350~450^{\circ}C$.Seed crystals of good quality could be obtained by the horizontal temperature gradient method at temperatures over the range 380~430^{\circ}C$ in these solutions. The hydrothermal conditions for the high growth rates of seed crystals are as follows: growth method; vertical temperature gradient method, solvent; 4m KF or $K_2HPO_4$ solution, temperature region; $400~450^{\circ}C$, pressure region; $1000~1500kg/cm^2$, where solubility of KTP was large enough to proceed the growth. Under such conditions, seed crystals of KTP are grown at a rate of approximately 0.06-0.08mm/day in the direction of the c-axis. Morphologies of grown crystals tended to be bounded by (100), (011) and (201) faces.

• Solar Energy
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• v.12 no.1
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• pp.95-102
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• 1992

A small scale solar collector system composed of a Fresnel lens of $0.5m^2$ area as a solar concentrator and a compact fluidized-bed solar receiver was developed. Performance and temperature distribution in the fluidized bed receiver were measured using SiC for particles and air for working fluid. The maximum gas temperature was attained up to 1250K at this moment. In this study, energy efficiency achieved by the present experiment was high for the small scale solar collector system and compact receiver.

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.243-247
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• 2005

본 연구에서는 화력발전소 바닥재를 중금속 흡착제로 활용하기 위한 기초연구로서 수열합성법에 의해 제올라이트를 합성하였다. 화력발전소 바닥재를 분쇄하여 반응온도$(80{\sim}150^{\circ}C)$ 및 NaOH 농도$(1{\sim}5M)$를 변화시키면서 알칼리 수열합성법으로 반응시킨 결과, NaP1, hydrxoy-sodalite, tobermorite 등이 생성되었으며, 양이온 교환 능력이 높은 NaP1은 $120^{\circ}C$ 이하의 온도와 2M 이하의 NaOH 농도에서 주로 합성되었다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.127-128
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• 2021

In this study, a study was conducted to analyze thermal diffusion according to the depth of concrete exposed to high temperatures. For thermal diffusion analysis, a test specimen in which K-type sheath thermocouples were poured in 0, 10, 20, 30, and 40 mm sections was manufactured, and thermal diffusion measurement was performed through one-sided heating for 180 minutes under heating conditions. As a result of the review, it was shown that as the temperature condition increased, the heat diffusion increased as the depth increased.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2004.06a
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• pp.205-208
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• 2004

• Korean Journal of Materials Research
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• v.7 no.4
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• pp.267-275
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• 1997

본 연구에서는 암석폐재를 대상으로 직경이 60mm인 고화체를 얻을 수 있는 수열 hot press 장치를 개발하였고, 고형화를 위한 최적조건을 찾아내는 내용을 다루었다. 이어 고화체의 기계적 성질을 평가하였고, 고화기구와 미시적 파괴거동을 규명하기위하여 SEM관찰 및 음향방출실험을 실시하였다. 고형화를 위한 최적조건은 NaOH용액이 10wt%, 수열온도가 30$0^{\circ}C$이고, 유지시간이 1시간이었다. 또한 수열반응동안에 다양한 제 2화합물들이 생성되었으며, 이들은 고화체의 기계적 성질에 큰 영향을 미쳤다. 아울러 원석의 경우에는 AE Counts가 초기화중에서부터 나타났으나, 고화체는 초기하중에서 전혀 AE Counts가 검출되지 않았다. 이와같은 사실로부터 수열 hot press법에 의해 얻어진 고화체는 원석과는 다르게 암석 입자간의 결합이 보다 치밀하게 이루어지고 있음을 유추할 수 있다.