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Sol-Gel법에 의해 제조된 Zirconia 나노분말의 결정상과 기공특성
정철원,박시현,송기창,이해형,오상천,동진근,차영엽,변태강 한국화학공학회 2002 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.40 No.6
Sol-Gel법에 의해 출발물질로 zirconium-n-butoxide(ZNB)와 yttrium nitrate를 사용하여 yttria-stabilized zirconia(YSZ) 나노분말을 제조하였다. 또한 ZNB의 가수분해 동안 첨가된 물량의 변화가 얻어진 YSZ 나노분말의 결정상과 기공특성에 미치는 영향을 조사하였다. 하소온도 변화에 따른 결정상 변화는 첨가된 물량에 관계없이 동일한 양상을 보였다. 즉, 100℃에서 건조된 분말은 모두 비정질상이었으며, 400℃에서 입방정상의 결정구조로 전환되었고, 1,000℃에서 정방정상과 단사정상이 나타나 1,400℃까지 정방정상과 단사정상이 공존하는 결정구조를 보였다. ZNB의 가수분해 중 물의 양이 비교적 적게 첨가된 경우로(H_2O/ZNB=20이하) 제조된 분말은 mesopore의 기공분포를 보인 반면, 물의 양이 비교적 많이 첨가된 경우에서는 (H_2O/ZNB=50이상) micropore의 기공분포를 보였다. Yttria-stabilized zirconia(YSZ) nanopowders were prepared by sol-gel method using zirconium-n-butoxide(ZNB) and yttrium nitrate as precursors. In addition, the effect of water content added during the hydrolysis reaction of ZNB was investigated on the phase composition and pore structure of the product powders. The phase composition of YSZ nanopowders with calcination temperatures showed the same trend, irrespective of H_2O amounts added during the hydrolysis reaction of ZNB. All powders dried at 100℃ were amorphous and transformed to cubic phase at 400℃, which converted to tetragonal phase at 1,000℃. Monoclinic phase also appeared at 1,000℃. The powders showed the mixture of tetragonal and monoclinic phases from 1,000℃ to 1,400℃. The pore size distributions of the dried powders prepared with small amounts of water(less than or equal to H_2O/ZNB=20) showed mesopores, while those prepared with large amounts of water(greater than or equal to H_2O/ZNB=50) exhibited micropores.
Gang Zhang,Chang Ho Ra,Hua-Min Li,Tian-zi Shen,Byung-ki Cheong,Won Jong Yoo IEEE 2010 IEEE transactions on electron devices Vol.57 No.11
<P>This paper proposes a modified engineered-potentialwell (MW) for NAND flash memory application. The MW was formed by using a transitional SiO<SUB>2</SUB>/SiO<SUB>x</SUB>,Na-TiO<SUB>x</SUB>,N<SUB>y</SUB> tunnel barrier, a trap-rich TiO<SUB>2</SUB> trapping layer, and an abrupt SiO<SUB>2</SUB> block barrier. The transitional tunnel barrier shrinks to enhance the tunneling of carriers during programming/erasing (P/E) and extends to suppress charge loss during data retention. Deep-level transient spectroscopy suggests that this tunnel barrier has few shallow traps after a N<SUB>2</SUB> + O<SUB>2</SUB> thermal treatment, and the TiO<SUB>2</SUB> trapping layer has deep electron traps. With the variable tunnel barrier and deep electron traps, the MW device showed promising performance in fast programming (<; μs) at low-voltage operation (7-10 MV/cm), good P/E endurance (> 10<SUP>6</SUP> P/E cycles), large threshold voltage window (ΔV<SUB>th</SUB> =M> V), as well as improved data retention at 125 °C.</P>
정강원,Cheong, Gang-Won 한국현미경학회 2000 Applied microscopy Vol.30 No.3
전자현미경을 이용한 단백질 구조분석은 약 30여년간 발전되어 왔다. Bacteriorhodopsin과 porin 등의 near atomic resolution의 구조분석은 전자현미경의 발전과 진행을 보여주는 하나의 예로 설명될 수 있다. 전자현미경을 이용한 거대분자의 3차원 구조를 규명하기 위해 필요한 기본과정 즉, 시료준비, 자료수집과 자료처리 등에 대하여 토론하였다. Electron microscopy has used for analysing the structure of protein over 30 years. Bacteriohodopsin and porins are used as examples to illustrate the progress that has recently been made in attaining resolutions which hitherto were regarded as exclusive to the realm of x-ray crystallography. To determine a protein structure used by electron microscopy, one must pass through a number of basic steps including preparation of specimen , data acquisition and data processing.
Effect of processing parameters on the quality of fresh-cut button mushroom(Agaricus bisporus)
Ji Gang Kim,Ji Weon Choi,Seung Yu Kim,Seung Ryoung Cheong,Won-Sik Kong 한국버섯학회 2010 한국버섯학회지 Vol.8 No.4
This study was conducted to investigate optimum processing procedure of fresh-cut button mushrooms. The experiments were done with different processing parameters including washing method, washing time, sanitation, and cutting time. Fresh mushrooms were washed by swirling water (SW), lift type-immersion washing (LIW), or combined LIW and water spray (LI+WS). Mushroom samples were washed by LIW for 0, 1, 3, and 5 minutes separately. Mushrooms were sanitized with 0, 50, or 100 ㎕L-1 chlorine solution (pH 7) for 60 seconds. Mushrooms were sliced at different times (before washing, after washing, or after drying). The combined washing treatment, LIW+WS was effective in maintaining better appearance and higher Lightness color value among treatments. Optimum washing time to remove foreign materials and maintain color was 3 minutes when mushrooms were washed by LIW. Samples sanitized with 50 ㎕L-1 chlorine reduced initial aerobic bacterial population and had only slight residual chlorine odor. Fresh-cut mushrooms sliced after washing had the lowest loss among samples. The optimized washing, sanitation, and cutting time parameters can be used for sequential processing of fresh-cut button mushrooms.
$Ca^{2+}-ATPase$ 3차원 결정의 Lamellar면 구조분석
정강원,Cheong, Gang-Won 한국현미경학회 1997 Applied microscopy Vol.27 No.2
Cylinder-like crystals of $Ca^{2+}-ATPase$ provide views parallel to the lamellar plane, from which parameters of lamellar stacking can be directly measured. These parameters were measured using different preparation methods. Assuming that molecular packing is the same, data from lamellar plane could supplement those obtained by tilting large, thin plate-like crystals. However, base on data obtained .by electron microscopy and x-ray powder patterns, the plate-like crystal may have another scheme for stacking the lamellar. The projection map (h, 0, 1) from cylinder-like crystals using cryoelectron microscopy suggest the lamellar spacing can be variable.
강종호(Gang, Jong-Ho),이청원(Lee, Cheong-Won) 대한교통학회 2006 대한교통학회 학술대회지 Vol.53 No.-
대기오염 중 자동차에서 배출되는 오염물질이 차지하는 비중이 ’92년 60.8%에서 ’99년 85.2%로 점차 증가하고 있는 현실을 반영하여 자동차 배기가스 인한 대기오염문제는 최근 몇년 동안 교통 및 환경분야에서 중요한 연구과제로 주목 받고 있다. 본 연구에서는 교풍환경관련분야의 국내외 최근 논문 100여편을 복합적으로 분석하여 이 분야의 연구동향 및 시사점을 제시함을 연구목적으로 한다. 본 연구의 결과는 향후 우리나라의 교통환경관련연구의 방향을 보다 합리적으로 설정하고 교통환경정책 및 교통관리전략의 수립에 중요한 지표가 될 것이다.