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알루미나이드 확산코팅된 스테인레스 합금의 내산화 및 내삭마 특성
황철홍,이효민,오정석,황동현,황유석,이종원,최정묵,박준식,Hwang, Cheol Hong,Lee, Hyo Min,Oh, Jeong Seok,Hwang, Dong Hyeon,Hwang, Yu Seok,Lee, Jong Won,Choi, Jeong Mook,Park, Joon Sik 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.5
Stainless steel, a type of steel used for high-temperature parts, may cause damage when exposed to high temperatures, requiring additional coatings. In particular, the Cr<sub>2</sub>O<sub>3</sub> product layer is unstable at 1000℃ and higher temperatures; therefore, it is necessary to improve the oxidation resistance. In this study, an aluminide (Fe<sub>2</sub>Al<sub>5</sub> and FeAl<sub>3</sub>) coating layer was formed on the surface of STS 630 specimens through Al diffusion coatings from 500℃ to 700℃ for up to 25 h. Because the coating layers of Fe<sub>2</sub>Al<sub>5</sub> and FeAl<sub>3</sub> could not withstand temperatures above 1200℃, an Al<sub>2</sub>O<sub>3</sub> coating layer is deposited on the surface through static oxidation treatment at 500℃ for 10 h. To confirm the ablation resistance of the resulting coating layer, dynamic flame exposure tests were conducted at 1350℃ for 5-15 min. Excellent oxidation resistance is observed in the coated base material beneath the aluminide layer. The conditions of the flame tests and coating are discussed in terms of microstructural variations.
Microfluidic generation of Prussian blue-laden magnetic micro-adsorbents for cesium removal
Kang, Sung-Min,Rethinasabapathy, Muruganantham,Hwang, Seung Kuy,Lee, Go-Woon,Jang, Sung-Chan,Kwak, Cheol Hwan,Choe, Sang-Rak,Huh, Yun Suk Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.341 No.-
<P><B>Abstract</B></P> <P>Here, we designed and synthesized a recoverable multifunctional adsorbent using a microfluidic reaction system and evaluated the removal performance of the smart adsorbent toward radioactive cesium as a model sample. Prussian blue-laden magnetic micro-adsorbents (PB-MNPs-MAs) with uniform morphology and monodispersity were generated via two-step sequential procedures using a glass capillary microfluidic system, followed by chemical co-precipitation with a high production rate. The cesium removal efficacy of the PB-MNPs-MAs was analyzed based on Langmuir and Freundlich isotherms by controlling adsorption parameters such as adsorbent size, initial cesium concentration, and contact time. The adsorption isotherm of the PB-MNPs-MAs was better fitted to the Langmuir model with a maximum cesium adsorption capacity of 58.73 mg g<SUP>−1</SUP>, which was 40% higher than that of macro-adsorbents in a dynamic magnetic field. This result can be attributed to their large specific area, which increased the kinetic rate of cesium adsorption and achieved saturation within 20 min. Additionally, the PB-MNPs-MAs were recovered from wastewater within 5 s under a static magnetic field, indicating their great potential for magnetic actuation. We believe that our PB-MNPs-MAs can encapsulate nano-functional adsorbents and prevent actuation, making them promising for environmental remediation and especially for removal of radionuclides.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PB-MNPs-MAs were generated in microfluidic device using chemical co-precipitation. </LI> <LI> The prepared PB-MNPs-MAs are monodispersed with uniform morphology. </LI> <LI> PB-MNPs-MAs exhibited high Cs adsorption capacity (58.73 mg g<SUP>−1</SUP>). </LI> <LI> 100% recovery of PB-MNPs-MAs is possible under static magnetic field after Cs adsorption. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
HFCVD법을 이용하여 제작한 n-형 다이아몬드 박막의 특성 연구
김병규,황윤식,권민철,김용,이재열,박홍준 동아대학교 기초과학연구소 2000 基礎科學硏究論文集 Vol.17 No.1
HFCVD법으로 암모니아 가스를 사용하여 n-형 도핑된 다이아몬드 박막을 제작하여, 기판온도와 암모니아 가스 첨가비에 따른 박막의 morphology의 변화를 조사하였다. 증착된 시료에 대한 SEM, Raman, XRD를 이용하여 박막의 특성을 분석하고, 도핑에 따른 전계방출 특성을 측정하였다. 양질의 n-형 도핑된 다이아몬드 박막을 증착시키기 위해 기판온도와 암모니아 첨가비에 따른 최적의 증착조건을 찾을 수 있었다. We fabricate n-doped diamond thin films by hot filament chemical vapor deposition method(HFCVD) using ammonia as a doping gas and investigate the effect of the substrate temperature and the ammonia gas ratio upon the diamond film morphology. The SEM, Raman spectroscopy, and the XRD analysis are executed to characterize film morphology. Field emission property of the film is measured also. We find optimum conditions of the substrate temperature and the ammonia gas ratio to deposit high quality n-doped diamond thin films.
한국인 알코올 의존 환자에서 알코올 대사 효소 유전자형 빈도의 남녀 차이
김성곤,김철민,이덕기,황인복,이현숙,김성연,전은숙,송영상,박제민,최병무,김명정 大韓神經精神醫學會 2005 신경정신의학 Vol.44 No.2
Objectives : There are a number of preceding epidemiological studies reporting gender differences in the genetic etiology of alcohol dependence. The author investigated gender difference in the frequencies of ADH2 and ALDH2 genoypes between the patients with alcohol dependence and normal control. Methods : The subjects were 141 alcohol dependent patients (104 males, 37 females) and 138 normal control (79 males, 59 females). The frequencies of 1/1 and 1/2+2/2 (2+ afterward) genotypes for ADH2 and ALDH2 were investigated in male and female between alcohol dependence and normal control group. DNA was extracted from WBC in peripheral venous blood and PCR-RFLP method was used out for genotyping. Results : First, the frequency of ADH2 1/1 genotype was significantly higher in alcohol dependent patients than normal control in both genders. Second, while there was no gender difference in the frequency of ADH2 1/1 genotype in normal controls, in the patient group however, the frequency was significantly higher in females than males. Third, in male subjects with alcohol dependence, the frequency of ALDH2 1/1 genotype was significantly higher than in male normal control subjects. On the other hand, in female subjects with alcohol dependence, the frequency of ALDH2 2+ genotype was significantly higher than in female normal control subjects. Conclusion : These results suggest that while the risk of alcohol dependence is predominantly affected by ALDH2 1/1 geno-type in male, the female ADH2 1/1 genotype is mainly associated with the risk of alcohol dependence. This means that there are gender differences in the genetic etiology of alcohol dependence.
Kwon, Keon Woo,Choi, Sung Sik,Lee, Sang Ho,Kim, Byungkyu,Lee, Se Na,Park, Min Cheol,Kim, Pilnam,Hwang, Se Yon,Suh, Kahp Y. GENERAL AND APPLIED CHEMISTRY JOURNALS 2007 LAB ON A CHIP Vol.7 No.11
<P>A label-free microfluidic method for separation and enrichment of human breast cancer cells is presented using cell adhesion as a physical marker. To maximize the adhesion difference between normal epithelial and cancer cells, flat or nanostructured polymer surfaces (400 nm pillars, 400 nm perpendicular, or 400 nm parallel lines) were constructed on the bottom of polydimethylsiloxane (PDMS) microfluidic channels in a parallel fashion using a UV-assisted capillary moulding technique. The adhesion of human breast epithelial cells (MCF10A) and cancer cells (MCF7) on each channel was independently measured based on detachment assays where the adherent cells were counted with increasing flow rate after a pre-culture for a period of time (<I>e.g.</I>, one, two, and four hours). It was found that MCF10A cells showed higher adhesion than MCF7 cells regardless of culture time and surface nanotopography at all flow rates, resulting in label-free separation and enrichment of cancer cells. For the cell types used in our study, an optimum separation was found for 2 hours pre-culture on the 400 nm perpendicular line pattern followed by flow-induced detachment at a flow rate of 200 µl min<SUP>−1</SUP>. The fraction of MCF7 cells was increased from 0.36 ± 0.04 to 0.83 ± 0.04 under these optimized conditions.</P> <P>Graphic Abstract</P><P>A label-free microfluidic cell separation and enrichment device is presented here by using cell adhesion as a physical marker. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b710054j'> </P>
Lee, Young Hwan,Kim, Han Joon,Moon, Taehwan,Kim, Keum Do,Hyun, Seung Dam,Park, Hyeon Woo,Lee, Yong Bin,Park, Min Hyuk,Hwang, Cheol Seong IOP Pub 2017 Nanotechnology Vol.28 No.30
<P>HfO<SUB>2</SUB>-ZrO<SUB>2</SUB> solid-solution films were prepared by radio frequency sputtering, and the subsequent annealing process was optimized to render enhanced ferroelectric behavior. The target power, working pressure and O<SUB>2</SUB> partial pressure ratios were varied, along with the annealing gas, time and temperature. Then, the film’s structural and electrical properties were carefully scrutinized. Oxygen-deficient conditions were necessary during the sputter deposition to suppress grain growth, while annealing by O<SUB>2</SUB> gas was critical to avoid defects and leakage problems. It is expected that the grain size difference under various deposition conditions combined with the degree of TiN top and bottom electrode oxidation by O<SUB>2</SUB> gas will result in different ferroelectric behaviors. As a result, Hf<SUB>0.5</SUB>Zr<SUB>0.5</SUB>O<SUB>2</SUB> prepared by radio frequency sputtering showed optimized ferroelectricity at 0% of O<SUB>2</SUB> reactive gas, with a doubled remnant polarization value of ∼20 <I>μ</I>C cm<SUP>−2</SUP> at a thickness of 11 nm. Film growth conditions with a high growth rate (4–5 nm min<SUP>−1</SUP>) were favorable for achieving the ferroelectric phase film, which feasibly suppressed both the grain growth and accompanying monoclinic phase formation.</P>
Adaptive Length Block Truncation Coding for LCD Overdrive
Min-Cheol Hwang,Jong-Woo Han,Yeo-Jin Yoon,Jun-Hyung Kim,Sung-Jea Ko 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1
Overdrive technique in liquid-crystal displays (LCD) is important to alleviate the motion blur caused by the slow response time of the liquid-crystal. Since this technique requires the memory storing a previous frame, the amount of the frame data should be decreased to reduce LCD cost as much as possible. To do this end, in this paper, we propose an improved block truncation coding (BTC) which adopts an adaptive length coding according to the pixel variance. In the proposed method, an efficient bit allocation for luminance and chrominance components is further utilized. The experimental results show that the proposed method outperforms the conventional method.
Min Jeong Kim,Young-Mee Lee,Jae Jin Han,Seok Jin Choi,Tae-Yoon Hwang,Min Jeong Kwon,Hyouk-Soo Kwon,Man-Sup Lim,Won Min Hwang,Min Cheol Joo,Jong-Tae Lee,Eunbae B. Yang 한국의학교육학회 2018 Korean journal of medical education Vol.30 No.2
The Korean Association of Medical Colleges (KAMC) developed graduate outcomes based on “The role of Korean doctor, 2014” to serve as guidelines regarding outcome-based education in Korea. The working group in this study analyzed 65 competencies proposed in “The role of Korean doctor, 2014” according to the developmental principle that certain outcomes should be demonstrated at the point of entry into the graduate medical education. We established 34 competencies as “preliminary graduate outcomes” (PGOs). The advisory committee consisted of 11 professors, who reviewed the validity of PGOs. Ultimately, a total of 19 “revised graduate outcomes” (RGOs) were selected. We modified the RGOs based on opinions from medical schools and a public hearing. In November 2017, the KAMC announced the “graduate outcomes for basic medical education,” which serves as a guide for basic medical education for the 40 medical schools throughout Korea. Medical schools can expand the graduate outcomes according to their educational goals and modify them according to their own context. We believe that graduate outcomes can be a starting point for connecting basic medical education to graduate medical education.