• 한국식물학회:학술대회논문집
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• 한국식물학회 1999년도 Proceedings of the 17th Symposium on Plant Biology Environmental Stress and Photosynthesis
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• pp.83-90
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• 1999

Electron crystallography of two-dimensional crystalsand electron cryo-microscopy is becoming an established method for determining the structure and function of a variety of membrane proteins that are providing difficult to crystallize in three dimension. In this study this technique has been used to investigate the structure of a ~160 kDa reaction centre sub-core complex of photosystem II. Photosystem II is a photosynthetic membrane protein consisting of more than 25 subunits. It uses solar energy to split water releasing molecular oxygen into the atmosphere and creates electrochemical potential across the thylakoid membrane, which is eventually utilized to generate ATP and NADPH. Images were taken using Philips CM200 field emission gun electron microscope with an acceleration voltage of 200kW at liquid nitrogen temperature. In total, 79 images recorded dat tilt angles ranging from 0 to 67 degree yielded amplitudes and phases for a three-dimensional map with an in-plant resolution of 6$\AA$ and 11.4$\AA$ in the third dimension shows at least 23 transmembrane helices resolved in a monomeric complex, of which 18 were able to be assigned to the D1, D2, CP47 , and cytochrome b559 alfa beta-subunits with their associated pigments that ae active in electron transport (Rhee, 1998, Ph.D.thesis). The D1/D2 heterodimer is located in the central position within the complex and its helical scalffold is remarkably similar to that of the reaction centres not only in purple bacteria but also in plant photosystem I (PSI) , indicating a common evoluationary origin of all types of reaction centre in photosynthetic organism known today 9RHee et al. 1998). The structural homology is now extended to the inner antenna subunit, ascribed to CP47 in our map, where the 6 transmembrane helices show a striking structural similarity to the corresponding helices of the PSI reaction centre proteins. The overall arrangement of the chlorophylls in the D1 /D2 heterodimer, and in particular the distance between the central pair, is ocnsistent with the weak exciton coupling of P680 that distinguishes this reaction centre from bacterial counterpart. The map in most progress towards high resolution structure will be presented and discussed.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.12-19
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• 2006

It is positively necessary to study on the stiffness of a 13degree-type impact tester in order to improve the fracture prediction of impact testing in wheels using FE(finite-element) analysis. The 13degree-type impact tester consists of an impact striker, a wheel fixer, a steel plate, and four cylindrical rubbers. Important parts of the tester are the steel plate and four cylindrical rubbers which play a role of absorbing impact energy during impact testing. Because of these buffers, the RF(reaction force) variation of the lower part in the 13degree-type impact tester showed the tendency like a damped harmony oscillation during impact testing. In order to investigate the stiffness of a 13degree-type impact tester, this work measured each stiffness of a steel plate and cylindrical rubbers. The stiffness of a cylindrical rubber was measured using a compressive tester. On the other hand, the stiffness of a steel plate was predicted by simulating experimental method using FE analysis.

• Composites Research
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• 제27권3호
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• pp.90-95
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• 2014

복합재료의 경화 시 발생하는 수축 변형률은 복합재료 구조물 내에 잔류응력을 발생시키며 이러한 잔류응력은 spring-in, spring-out, warpage와 같은 구조물 변형의 원인이 된다. 본 연구에서는 Hexcel사의 "Hexply M21EV/34%/UD268NFS/IMA-12K" prepreg를 사용하였다. 시험편의 경화에 따른 cure shrinkage 변화를 DSC(differential scanning calorimetry)와 TMA(thermomechanical analyzer)를 이용하여 측정하였다. 수지의 수축률은 $140{\sim}240^{\circ}C$ 구간에서 $20^{\circ}C$ 간격으로 질소 분위기에서 측정하였다. 경화도는 dynamic과 isothermal DSC scanning을 통하여 측정된 반응열을 이용하여 산출하였으며, DSC 시험은 Argon 분위기에서 수행하였다. 시험결과, 열경화성 수지는 27~80% 경화도에서 급격한 수축이 일어났으며, 경화온도가 높을수록 더 낮은 경화도에서 수축이 시작되는 것을 알 수 있었다.

• 공업화학
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• 제5권3호
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• pp.524-536
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• 1994

생체적합성이 좋은 천연고분자인 chitosan에 수용성의 비닐계 단량체인 polyethyleneglycol monomethacrylate series를 그라프트중합시켜 그 반응조건과 물성을 검토하였다. 그라프트중합은 ethylene oxide 부가몰수에 따라 PE-90, PE-200, PE-350의 세 가지 단량체에 ceric ammonium nitrate(CAN)를 개시제로 사용하였으며, 중합에서 개시제의 농도, 단량체의 농도, 반응온도, 반응시간이 총전환율, 그라프트율, 그라프트효율에 미치는 영향을 조사하여 최적조건을 규명하였다. 반응은 개시제농도 $4{\sim}5{\times}10^{-3}M$, 단량체농도 0.5~0.6M, 반응시간 2~3시간, 반응온도 $40^{\circ}C$에서 최고의 그라프트율과 총전환율을 나타냈다. 합성한 공중합체의 열적 성질, 용해성 및 점성도를 검토한 결과 고농도의 개시제를 사용하면 그라프트 중합체는 chitosan의 특성을 급격히 감소시켰다. 고유점성도의 경우, chitosan-g-PE-90이 2.81dl/g, chitosan-g-PE-200이 3.01dl/g, chitosan-g-PE-350이 4.93d1/g으로 증가하는 경향이 나타났다. 공중합체를 막으로 성형하여 그라프트율과 polyethyleneglycol monomethacrylates의 ethylene oxide 부가몰수에 따른 공중합체의 기계적 물성과 함수율을 측정하였다. 가교화 공중합체막은 150분 이내에 함수율이 평형에 이르렀다. 공중합체의 물성은 그라프트율과 ethylene oxide 부가몰수의 영향을 받았으며 chitosan의 기계적 물성과 함수율이 공중합체에서 증가되었음을 확인하였으며 그라프트율이 증가함에 따라 vitamin $B_{12}$의 투과량도 증가하였다.

• Journal of Electrochemical Science and Technology
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• 제1권1호
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• pp.19-24
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• 2010

Alloying degree is an important structural factor of PtRu catalysts for direct methanol fuel cells (DMFC). In this work, carbon supported PtRu catalysts were synthesized by reduction method using anhydrous ethanol as a solvent and $NaBH_4$ as a reducing agent. Using anhydrous ethanol as a solvent resulted in high alloying degree and good dispersion. The morphological structure and crystallanity of synthesized catalysts were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM). CO stripping and methanol oxidation reaction were measured. Due to high alloying degree catalyst prepared in anhydrous ethanol, exhibited low onset potential for methanol oxidation and negative peak shift of CO oxidation than commercial sample. Consequently, samples, applying ethanol as a solvent, exhibited not only enhanced CO oxidation, but also increased methanol oxidation reaction (MOR) activity compared with commercial PtRu/C (40 wt%, E-tek) and 40 wt% PtRu/C prepared in water solution.

• 자원환경지질
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• 제42권5호
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• pp.395-401
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• 2009

스멕타이트-일라이트 (SI)의 전이 반응은 쇄설성 퇴적암 지역에 흔히 볼 수 있는 광물 반응이다. 지난 40여년 동안 SI 전이 반응의 중요성에 대한 논문들이 많이 출간되었는데 이는 스멕타이트가 일라이트로 변하는 정도 즉 "illitization" 이 석유의 개발, 퇴적물의 화학적 변화 및 물리적 성질변화 에 많은 연계성이 있기 때문이다. 기존의 S-I 상전이에 대한 메커니즘 연구에서는 layer-by-layer reaction 에 의한 solid state 반응 혹은 dissolution/precipitation 반응으로 집약되지만 박테리아 반응의 역할을 전혀 고려하지 않았다. 무산소 환경에서 박테리아와 점토광물의 반응에 대한 연구, 특히 스멕타이트와 철 환원 박테리아의 반응 작용에 대한 연구에서는 철 환원 박테리아가 스멕타이트 구조 속에 있는 철을 환원시켜 에너지를 얻는다고 밝혀졌다. 최근 발표된 논문들은 미생물의 철 환원 작용에 의하여 S-I 상전이가 일어날 수 있다고 보고되었는데, 이는 기존의 상전이에 대한 개념에 즉 고온, 고압, 오랜 시간이 S-I 전이의 필수 조건이라는 일반적인 해석에 반하는 것으로 새로운 연구 분야의 가능성을 시사하고 있다. 현재까지 발표된 논문에 의하면 박테리아가 S-I 반응을 촉진지킴으로 고온, 고압, 혹은 상당시간의 속성작용이 전제조건으로 작용하지 않을 수 있다는 가능성을 시사한다. 하지만 박테리아가 철을 환원함과 동시에 스멕타이트를 일라이트로 전이시킴에 있어서의 메커니즘에 대한 이해는 아직 미비하다. 따라서 이 논문에서는 현재까지 밝혀진 SI 반응을 살펴보고, 미생물 광물간의 반응작용에 있어서 연구 방법을 소개함을 목적으로 한다.

• 대한본초학회지
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• 제21권2호
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• pp.63-75
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• 2006

Objectives : We investigated the effects of Liriopis Tuber on the nervous protection. Methods : We measured the reaction behavior with EPM(Elevated Plus Maxe) and MWM(Morris Water Maze) after applying restraint stress to rats. Also, the degrees of AchE generation were measured with immunohistochemical method in the regions of hippocampus, and the degree of TH generation in the regions of VTA and LC, respectively. Results : 1. As the results of measuring how long EPM which reflects anxiety reaction stayed in the open arm, there was the trend which can suppress anxiety reaction in the MMD+stress group(Liriopis Tuber+stress) but no statistical significance. The counting results how many EPM passed between opened and closed arm showed suppression trend against a physical activity in the saline+stress group but there was no statistical significance. 2. According to the result of MWM, the saline+stress group showed the learning retardation which means increased time arriving at goal compared to ti1e normal group at the second and third day of measurement. On the contrary, a learning retardation was significantly decreased in the MMD+stress group. Among the probe trial test a memory loss occurred in the saline+stress group, meanwhile memory ability was notably increased in the saline-stress group. 3. The degree of TH generation was investigated at the VTA and LC respectively after test animals treated with drug. In the saline+stress group, TH-immunoreactive cells were significantly increased, and these stress-induced TH increases were suppressed in the saline+stress group at the VTA region. However, the saline+stress group did not show any significant difference. 4. the degree of AchE generation was investigated at the CA3 of hippocampus. The saline+stress group showed that AchE-immunoreactive cells were significantly decreased. Those stress-induced reductions of AchE cells were meaningfully recovered in the saline+stress group. Although the cells showed recovery trend in the region of CA1 of hippocampus, statistical significance was not observed. Conclusion : The results of our study indicate that Liriopis Tuber can improve spatial memory ability of rats applied a restraint stress. This improvement of the spatial memory ability is considered to have an efficacy of nervous protection that Liriopis Tuber suppresses the generation of AchE in the hippocampus region and enhances the generation of TH in the VTA.

• 청정기술
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• 제25권2호
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• pp.107-113
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• 2019

2단 유동층 염화로에서 일메나이트광의 선택염화반응과 이산화티탄의 탄소염화반응의 염화도를 예측하기 위해서 shrinking core 모델과 유출률 및 입자파손을 고려한 수치 모델을 개발하였다. 입자분포를 고려하여 입자별 물질 수지와 염화반응을 반영할 수 있는 유동층 염화 반응 해석이 가능하다. 유동층 염화로의 실험값과 비교하여 약 6% 오차율의 정확성을 보였다. 입자 크기에 따라서는 입자 크기가 작을수록 염화도의 변화가 더 크게 나타났으며 염화도 1의 값에 도달하는 반응시간 차이가 약 100 min 정도로 나타났다. 온도의 변화($800{\sim}1000^{\circ}C$)에 대한 염화도의 변화는 염화도 0.9에 도달하는 반응시간이 약 10 min 차이로 크게 나타나지 않았다. 1단계 선택염화공정에서 일메나이트광의 질량감소율은 180 min 경과 시에 이론값인 0.4735 값에 근접하고, Fe 성분의 염화도는 $FeCl_2$ 또는 $FeCl_3$로 변환되어 180 min 경과 시에는 거의 1의 값을 보인다. 2단계 탄소염화공정에서 $TiO_2$의 염화도는 180 min 경과 시 0.98에 근접하고, 질량분율은 0.02에 도달하여 $TiCl_4$로 변환되는 것으로 나타났다. 1단계 선택염화공정에서 $TiO_2$는 180 min 경과 시에 98%까지 생성되었다가 연속적인 2단계 탄소염화공정에서 추가로 90 min 경과 시(총 경과 시간 270 min)에 99% $TiCl_4$로 전환되는 것으로 나타나고, 질량감소율도 99% 이상 감소하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.53-58
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• 2000

During the curing process of thick glass/epoxy laminates, a substantial amount of temperature lag and overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites. Also, it requires a longer time for full and uniform consolidation. In this work, temperature, degree of cure and consolidation of a 20mm thick unidirectional glass/epoxy laminate were investigated using an experiment and a 3-dimentional numerical analysis considering the exothermic reaction. From the experimental and numerical results, it was found that the experimentally obtained temperature profile agreed well with the numerical one and the cure cycle recommended by the prepreg manufacturer should be modified to prevent a temperature overshoot and to obtain full consolidation.

• 대한치과마취과학회지
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• 제12권3호
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• pp.151-155
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• 2012

A vasovagal reaction is defined as the 'development of hypotension and bradycardia associated with the typical clinical manifestations of pallor, sweating and weakness'. The most profound degree of vasovagal reaction results in fainting or syncope. Incidence of vasovagal reactions in the local anesthetic department of a dental hospital is around 2%. The pathophysiology of the hypotension/bradycardia reflex responsible for vasovagal syncope is not completely understood. Central as well as peripheral mechanisms have been implicated in its pathogenesis: however their relative contribution is not fully elucidated. Recently, trigeminocardiac reflex, previously known as oculocardiac reflex, may serve as syncope. The management of vasovagal syncope is evolving. Non-pharmacological treatment options are a fundamental first step of all treatment pathways. In this article, we would like to review new mechanism of vasovagal syncope and hope to be of help to manage the syncopal patients.