• Bulletin of the Korean Chemical Society
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• 제20권1호
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• pp.89-94
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• 1999

Carbon dioxide reforming of methane on Ni/γ-Al2O3 catalyst was studied. A new 10 wt% Ni/γ-Al2O3 catalyst prepared by the liquid phase oxidation method (L10O) exhibited much higher activity as well as resistances to both sintering and coke formation during the reaction than the catalyst prepared by the conventional impregnation method (D10). The electrically strong attractive interaction between nickel and support during the liquid phase oxidation process and the resultant high nickel dispersion made the L10 have superior activity and stability to the D10. To elucidate the results, the experiments with nickel catalysts on the other supports as well as 7-AI203 were performed. The effect of sodium as a promoter was also studied.

• Corrosion Science and Technology
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• 제20권4호
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• pp.196-203
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• 2021

To improve corrosion resistance and reduce the hydrogen uptake of 22MnB5, up to 5% Mg was added to the AlSi coating of 22MnB5. After hot-stamping and electrocoating were done on the metallic-coated specimen, the surface characteristics of the steel, hydrogen uptake content, and corrosion resistance were examined by transmittance electron microscopy, thermal desorption spectrometry, cyclic corrosion testing, and electrochemical impedance spectroscopy. Mg was investigated as MgO on the surface layer after hot-stamping while it existed as Mg₂Si before hot-stamping. The total hydrogen content of 22MnB5 was decreased along with the Mg content. However, there was no difference at 0.2 wt% or more. When a small amount of Mg was added, the coating corrosion resistance was decreased, but when it was added at around 1.0 wt%, the greatest corrosion resistance increase was seen. However, when 3 wt% or more was added excessively, the corrosion resistance was decreased. MgO on the surface was considered to suppress H uptake by the AlSi melting solution and increase the barrier effect of the coating.

• Journal of Oral Medicine and Pain
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• 제8권1호
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• pp.69-76
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• 1983

Background variables in 203 patients with TMJ pain dysfunction showing no bony change, ranging from 11 to 76 of age, were studied by use of the modified form of self-administered questionnaires deviced by Carlsson et al intended to give a review of the patient's history. All the patients were identified in the Dept. of Oral Diagnosis and Oral Diagnosis and Oral Medicine, Seoul National University Hospital, during the period from Feb. 1983 to Nov. 1983. The questions concerning general somatic and psychic health, educational and social condition were dealt with in this article. The obtained results were as follows : 1. The main symptoms reported by 203 patients were difficulties in opening the mouth wide(74.4%), clicking of TMJ(70.9%), chewing difficulties(69.0%), and pain on movement of mandible(57.6%) 2. The most fequently reported medical symptoms or histories were stomach disease (21.2%), insominia(15.3%), ENT disease(13.8%) and skin disease (12.8%) 3. Seventy-eight percent of the patients denied having had a nervous or psychic disorders while 4% were currently under treatment for such disorders. 4. Eleven percent of 203 patients with TMJ dysfunction thought their family situation was distressing(8.4%) or very troublesome(3.4%).

• 분석과학
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• 제5권2호
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• pp.203-211
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• 1992

Ni-36.5at.%Al 합금에서 결정립계에서의 scavenging 원소로 알려진 V를 첨가하여 이 합금의 파괴거동 및 마르텐사이트 미세조직에 미치는 V의 영향에 대해 조사하였다. 시편의 파단면은 주사전자현미경으로 관찰하였고 EDX spectrometer를 사용하여 파단면의 조성을 분석하였으며 투과전자현미경으로 마르텐사이트 내부조직의 변화에 대해 조사하였다. V의 첨가로 입계파괴에서 입내파괴로 파괴 모드의 변화를 나타내었으며 EDX spectrometer로 분석한 결과 입내에 비해 입계에 Al의 함량이 상대적으로 증가되는 양상을 보여 주었다. Ni-36.5at.%Al 합금의 경우 마르텐사이트 플레이트는 내부쌍정으로 이루어져 있으나 V의 첨가에 따라 twinned 마르텐사이트 조직은 사라지며 stacking fault와 고밀도의 전위를 가진 modulated 조직이 점차 지배적으로 형성되는 것이 관찰되었다. Stacking fault를 분석한 결과 Al과 V의 치환에 따른 extrinsic fault였으며 high-energy 상태인 이 stacking fault가 있는 부위에 유해 원소인 S가 편석됨으로써 결정립계에서의 파괴를 줄일 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제18권2호
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• pp.203-208
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• 1997

A series of MgO-SiO2 catalysts were prepared by coprecipitation from the mixed solution of magnesium chloride and sodium silicate. Some of the sample were modified with 1 N H2SO4 and used as modified catalysts. The addition of MgO to SiO2 caused the increase of acidity and the shift of O-H and Si-O stretching bands of the silanol group to a lower frequency in proportion to the MgO content. The acid structure of MgO-SiO2 agreed with that proposed by Tanabe et al.. Catalytic activity for 2-propanol dehydration increased in relation to the increase of acidity and band shift to a lower frequency.

• 한국자기학회지
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• 제9권6호
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• pp.291-295
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• 1999

IrMn을 반강자성체로 사용하고 순수한 Al을 자연산화시켜서 제작한 Al203를 절연층으로 사용한 spin-valve 형태의 NiFe/Co/Al2O3/Co/IrMn 터널링 접합의 자기저항효과를 조사하였다. IrMn의 두께가 약 100$\AA$이상일 경우 강자성체와의 교환상호작용이 발생하기 때문에 NiFe(183$\AA$)/Co(17$\AA$)/Al-oxide(16$\AA$)IrMn(100$\AA$) 터널링 접합에서 자기저항효과가 관찰되며 TMR비(%)는 $\pm$20 Oe의 인가자장에서 10% 이상의 값을 갖는다. 하부 자성층인 NiFe/Co의 길이방향으로 수행한 자장 중 열처리에 의해 저항은 다소 감소하고 TMR비(%)는 열처리온도에 따라 증가하여 20$0^{\circ}C$에서 23%의 최대값을 갖는다. 자성층의 폭을 변호시켜 접합면적을 달리한 시료의 TMR비(%)는 접합면적이 증가할수록 증가하고 저항은 감소한다.

• 한국분말재료학회지
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• 제15권3호
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• pp.196-203
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• 2008

The densification behavior of Al-20Si-5.5Fe-1.2Mg-0.5Mn powders was investigated through micro-structure analysis of sintered specimens. The specimens sintered in vacuum or in high purity (99.999%) nitrogen showed porous near-surface microstructures. The densification of near-surface part was enhanced by means of ultra-high purity (99.9999%) nitrogen atmosphere. The relationship between slow densification and oxide surfaces of Al alloy powders was discussed. And the effects of Mg addition, nitrogen gas, and humidity on densification were discussed. In addition, the rapid growth of primary Si crystals above the critical temperature was reported.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2002년도 추계학술대회 논문집
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• pp.202-203
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• 2002

황사는 아시아 대륙의 중심부에 위치한 건조지대와 황토지대의 작은 모래나 황토가 공중에 부유하거나 상층 바람을 타고 멀리 수송되어 다시 지면 가까이 낙하하는 현상을 말한다(오성남 등, 1999). 최근 황사가 빈번하게 발생됨에 따라 황사에 대한 관심이 고조되고 있으며, 국내에서도 1990년대 초부터 황사에 대한 연구가 활발하게 수행되고 있다(배귀남 등, 2002b; Chun et al., 2001; 오성남 등, 1999). 본 연구에서는 2002년 봄철에 발생된 황사기간 동안 측정한 에어로졸의 농도 및 크기분포 특성을 고찰하였다. (중략)

• 한국세라믹학회지
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• 제39권2호
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• pp.199-203
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• 2002

소결 분위기가 금속입자분산 세라믹스기 복합체의 미세 조직 및 물성에 미치는 영향에 대하여 조사하고자 화학적 방법으로 합성한 $Al_2O_3$/Fe-Ni 나노복합분말을 수소 및 아르곤 가스 분위기, 또한 소결온도 등으로 제어하여 열간가압 소결하였다. 수소분위기에서 소결한 복합체는 아르곤분위기의 경우보다 반응상 $FeAl_2O_4$의 형성이 억제되었으며, 증가된 파괴강도 및 인성 값을 나타내었다. 또한, 소결 온도를 낮추었을 경우 기지상 및 금속 분산상의 미세화와 향상된 기계적 성질을 얻을 수 있었다. 소결 조건에 따른 기계적 특성의 변화는 주로 반응상의 형성과 관련된 미세조직 특성에 의존하는 것으로 해석하였다.

• 한국수정란이식학회지
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• 제27권4호
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• pp.193-203
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• 2012

The development of embryos reconstructed by nuclear transfer is dependent upon numerous factors including the type of recipient cell, method of enucleation, the type of donor cell, method of reconstruction, activation, the cell cycle stage of both the donor nucleus and the recipient cytoplasm and the method of culture of the reconstructed embryos. Many of these points which have been reviewed extensively elsewhere (Sun and Moor, 1995; Colman, 1999; Oback and Wells, 2002; Renard et al., 2002; Galli et al., 2003b), here we will concentrate on main area, the production of suitable cytoplast and nuclear donor, nuclear-cytoplasmic coordination, oocyte activation, culture of reconstructed embryos, and the effects that this may have on development.