• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.339-343
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• 2010

A series of $Ce_1Mg_xZr_{1-x}O_2$ (CMZO) mixed metal oxide with different molar ratio were prepared by simple co-precipitation method. The prepared materials were tested for their catalytic activity performance using Knoevenagel condensation of various aromatic aldehydes with barbituric acid under solvent-free condition in microwave. The best catalytic activity was obtained with CMZO (1:0.6:0.4). The synthesized materials were characterized by using XRD, FT-IR, SEM-EDS techniques.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.73-73
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• 2003

나노 크기의 기공이 규칙적으로 배열되어 있는 실리케이트 메조포러스 분말 재료는 넓은 표면적과 화합물에 대한 선택적 흡착 등이 가능하여 많은 연구가 진행퇴고 있다. 최근에는 실리케이트 메조포러스 재료를 박막으로 제조하여 전자소자 혹은 광소자의 제작에 응용하기 위한 연구가 많이 진행되고 있다. 이러한 실리케이트 기공 내부의 표면에 소수성, 극성, 광전자 활성 등, 특정한 기공 표면 특성을 부여하기 위해서 grafting 방법과 co condensation 방법을 이용하고 있다. 특히, co-condensation 방법을 이용하여 tetraalkoxysilane 과 organo-trialkoxysilane을 함께 반응시키는 경우, 유기성분의 양을 더욱 증가시킬 수 있고 물질 내부에 균일한 유기성분의 분포를 얻을 수 있다. 메조포러스 무기 network에 fluorine을 포함하는 그룹이 공유결합으로 결합되어져 있는 물질은 소수성, 흡착성 및 광학적으로 응용 가능성을 가질 것으로 기대된다.

• Ocean Systems Engineering
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• v.2 no.1
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• pp.33-47
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• 2012

This study revealed the behavior of droplets formed through leak process in deep water. There was a threshold depth named the universal attraction depth (UAD). Droplets rose upward in the zone below the UAD called the rising zone, and settled down in the zone above the UAD called the settling zone. Three mass loss modes were identified and formulated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. The first two were active for the settling zone, and all the three were effective for the rising zone. In consequence, the life time of the droplets in the rising zone was far shorter than that of the droplets in the settling zone.

• Journal of Environmental Science International
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• v.16 no.6
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• pp.689-698
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• 2007

Mesoporous silicas for heavy metals adsorption were prepared by co-condensation of surfactant as a template and Ludox HS-40 as a silica precursor. Various mesoporous silicas with the introduction of chelating ligands (mercaptopropyl and aminopropyl groups) were synthesized to remove heavy metal ions from aqueous solutions. The surface modification was conducted with a co-condensation process using the sequential or simultaneous addition of mesoporous silica and high concentration of the organosilane(3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilane). These materials have been characterized by elemental analysis, XRD, SEM and TEM analysis. Adsorbents synthesized with 3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilane shows a high loading capacity for Hg(II), Pb(II), Cd(II) and anion Cr(VI). Especially the one synthesized with a mercaptopropyl function has the highest adsorption capacity for Hg(II) and Cd(II).

• Journal of Power System Engineering
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• v.17 no.3
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• pp.44-49
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• 2013

The refrigerating system are high efficiency and comfortable due to the automation of the system as well as enhance energy saving are contributing to driving system. Previous study the rotational frequency of the compressor was confined to the fixed condition have changed load of evaporator and condenser related about the refrigerator performance characteristic according to the evaporation load and condensation load change tries to be analyze through the experiment. The useful data for the economic driving of the freezing apparatus tries to be drawn. Consequently, it confirmed that refrigerant in the compressor overheated and as the evaporation load increased the specific volume was increased and the coolant circulation rate decreased. In confirmed that condensation load increased the compression ratio and discharge gas temperature increased. It reduced the low-temperature efficiency and condensation calorie and the quality factor was decreased.

• Journal of Powder Materials
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• v.9 no.3
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• pp.174-181
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• 2002

Nanosized tungsten carbide powders were synthesized by the chemical vapor condensation(CVC) process using the pyrolysis of tungsten hexacarbonyl($W(CO)_6$). The effect of CVC parameters on the formation and the microstructural change of as-prepared powders were studied by XRD, BET and TEM. The loosely agglomerated nanosized tungsten-carbide($WC_{1-x}$) particles having the smooth rounded tetragonal shape could be obtained below $1000^{\circ}C$ in argon and air atmosphere respectively. The grain size of powders was decreased from 53 nm to 28 nm with increasing reaction temperature. The increase of particle size with reaction temperature represented that the condensation of precursor vapor dominated the powder formation in CVC reactor. The powder prepared at $1000^{\circ}C$ was consisted of the pure W and cubic tungsten-carbide ($WC_{1-x}$), and their surfaces had irregular shape because the pure W was formed on the $WC_{1-x}$ powders. The $WC_{1-x}$ and W powders having the average particles size of about 5 nm were produced in vacuum.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.44 no.12
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• pp.94-97
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• 2015

• Proceedings of the Korean Vacuum Society Conference
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• 2004.08a
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• pp.180-180
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• 2004

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2812-2822
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• 2023

The supercritical carbon dioxide (sCO₂) Brayton power cycle is more effective than the conventional power cycle and is more widely applicable to heat sources. The inlet working conditions of the compressor have a higher influence on their operating performance because the thermophysical properties of the CO₂ vary dramatically close to the critical point. The flow in the sCO₂ compressor is simulated and the compressor performance is analyzed. The results show that the sCO₂ centrifugal compressor operates outside of its intended parameters due to the change in inlet temperature. The sCO₂ compressor requires more power as the inlet temperature increases. The compressor power is 582 kW when the inlet temperature is at 304 K. But the power is doubled when the inlet temperature increases to 314 K, and the change in the isentropic efficiency is within 5%. The increase in the inlet temperature significantly reduces the risk of condensation in centrifugal compressors. When the heat load of the sCO₂ power system changes, the inlet pressure to the turbine can be kept constant by regulating the rotational speed of compressors. With the increase in rotational speed, the incidence loss and condensation risk increase.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.10a
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• pp.687-688
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• 2005