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Ji‑Eun Ahn,Young‑Kyun Kim,Sang‑Hoon Yoon,Kee‑Ahn Lee 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
An equiatomic CoCrFeMnNi high entropy alloy (HEA) coating layer was prepared via a cold spray (CS) process. In orderto control the microstructure and nano-indentation properties of the CS HEA, heat treatments were employed. CS HEAcoating layer showed a heterogeneous microstructure where ultra-fine grains were formed at the particle interfaces, whilecoarse grains were formed inside the particles. Furthermore, deformation twins (DTs) were also formed inside the particlesdue to severe plastic deformation (SPD) in each particle generated during the CS deposition. For the 550 °C heat treatment(HT), fine Cr-rich precipitates were additionally formed at the grain boundary and particle boundary. By contrast, recrystallizationoccurred during 850 °C HT, while the size of the Cr-rich precipitate increased. The nano-indentation hardness ofthe CS HEA coating layer was 10.9 GPa, which was ~ 3 times higher than that of the conventional cast HEA. The superiorhardness of the CS HEA might has been enabled due to the combination of the high dislocation density, DTs, and ultra-finegrains. Based on the results above, the strategy to control the microstructure and mechanical properties through HT of theequiatomic CoCrFeMnNi HEA coating layer prepared via the CS process has been discussed.
기계적합화법으로 제조된 TiNi 분말의 방전플라즈마 소결에 관한 연구
김윤호,강지훈,김지순,안인섭,권영순 울산대학교 1999 공학연구논문집 Vol.30 No.2
기계적합금화법(MA)에 의해 제조된 TiNi 분말을 사용하여 방전플라즈마 소결법(SPS)으로 소결체를 제조하고 치밀화 거동을 조사하기 위하여 미세조직의 관찰 및 상분석을 행하였다. SPS법으로 소결체를 제조한 결과, 통상적인 소결법으로 소결체를 제조하였을 때 보다, 낮은 온도와 짧은 시간의 유지시간에서 이론 밀도의 99% 가까운 소결체 밀도를 얻을 수 있었고, 소결체의 상은 B2구조의 cubic과 2차상으로 Ti₂Ni가 존재함을 확인하였다. Mechanically-alloyed TiNi powders were densified by Spark-Plasma Sintering(SPS) method. The densififcation behavior was investigated throgh the microstructural observation, the phase analysis and the measurement of change in devsity, linear shrinkage and densification rate as a function of temperature. Sintered body with close to 99% relative density was obtained at lower sintering temperature for shorter holding time in comparison to the conventional sintering methods. TiNi with B2 structure was confirmed as the major phase and Ti₂Ni as the second phase.
문창기,박상준,조민구,김영중,김소연,김윤권,정준오,안석진,김은실,서승오,김지훈,최원제,이윤영,박형기,최규영,김현근 대한감염학회 2006 감염과 화학요법 Vol.38 No.6
Background: The purpose of this study was to document the incidence and clinical characteristics of patients with tuberculosis (TB) in combat and auxiliary police, living in a group, in Korea where the incidence rate of active TB in a general population is higher than in Western countries. Materials and Methods:We retrospectively reviewed the medical records of all tuberculosis patients diagnosed at National Police Hospital from January 2002 through December 2004. Results:In 2002-2004, a total of 156 cases of tuberculosis were identified with the mean (Standard deviation) age of 20.6 (±1.0) years. Of these, 134 (85.9%) patients were registered as new cases, 11 (7.1%) as relapse, 2 (1.3%) as failure, 5 (3.1%) as treatment-after-default cases whereas 4 (2.6 %) patients were not included in any categories. Average annual new TB rate and smear-positive TB rate were 86.5/10^(5) and 17.4/10^(5) person-years, respectively. In 12 of 31 smear-positive cases, time from onset of symptoms to diagnosis was more than 30 days. Two multidrug-resistance TB cases were identified and two suspected outbreak episodes of TB had occurred during 3 years. Conclusion:There was no statistically significant difference in the incidence rate of new cases of TB between the general population aged 20 to 29 years and combat and auxiliary police in Korea. 배경 : 국내 결핵의 발생은 감소 추세에 있으나 여전히 후진국형 발생양상을 보이고 있다. 특히 집단생활을 하는 젊은이들에서 발생하는 결핵의 유행이 간헐적으로 알려지고 있어 우려를 낳고 있다. 이에 저자들은 최근 전경대원의 결핵 발병 양상에 대해 알아보고자 본 연구를 시행하였다. 재료 및 방법 : 2002년 1월부터 2004년 12월까지 3년간 경찰병원에서 결핵 진료를 받은 전경대원의 의무기록을 후향적으로 분석하여 연도별 결핵 신환발생률, 도말양성결핵 신환율, 진단 지연, 집단발병, 다제내성결핵을 조사하였다. 결과 : 연도별 결핵 신환자 수(10만명당 발생추정치)는 2002년 50명(83.6명), 2003년 42명(83.7명), 2004년 42명(93.5명)이었고 도말양성 폐결핵 신환자 수는 2002년 10명(16.7명), 2003년 11명(21.9명), 2004년 6명(13.4명)이었다. 3년간 도말양성 폐결핵 환자는 31명이 있었고 그 중 12명은 호흡기 증상 발생 30일이 지나서 진단을 받았다. 다제내성 결핵은 2명이 있었으며 결핵의 집단발병이 의심되는 사례는 2차례 있었다. 결론 : 전경대원과 20-29세 연령군 일반인의 결핵 신환발생률, 도말양성 폐결핵 발생률의 통계적으로 유의한 차이는 없었다.
Ahn, Ji-Hoon,Lee, Myoung-Jae,Heo, Hoseok,Sung, Ji Ho,Kim, Kyungwook,Hwang, Hyein,Jo, Moon-Ho American Chemical Society 2015 Nano letters Vol.15 No.6
<P>van der Waals layered materials have large crystal anisotropy and crystallize spontaneously into two-dimensional (2D) morphologies. Two-dimensional materials with hexagonal lattices are emerging 2D confined electronic systems at the limit of one or three atom thickness. Often these 2D lattices also form orthorhombic symmetries, but these materials have not been extensively investigated, mainly due to thermodynamic instability during crystal growth. Here, we show controlled polymorphic growth of 2D tin-sulfide crystals of either hexagonal SnS<SUB>2</SUB> or orthorhombic SnS. Addition of H<SUB>2</SUB> during the growth reaction enables selective determination of either <I>n</I>-type SnS<SUB>2</SUB> or <I>p</I>-type SnS 2D crystal of dissimilar energy band gap of 2.77 eV (SnS<SUB>2</SUB>) or 1.26 eV (SnS) as a final product. Based on this synthetic 2D polymorphism of <I>p</I>–<I>n</I> crystals, we also demonstrate <I>p</I>–<I>n</I> heterojunctions for rectifiers and photovoltaic cells, and complementary inverters.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-6/acs.nanolett.5b00079/production/images/medium/nl-2015-00079a_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5b00079'>ACS Electronic Supporting Info</A></P>
Ahn, Ji Young,Kim, Whi Dong,Kim, Jae Hyun,Kim, Ji Hoon,Lee, Jae Keun,Kim, Jong Man,Kim, Soo H. Hindawi Limited 2011 Journal of nanomaterials Vol.2011 No.-
<P>We demonstrate a simple and viable method for controlling the energy release rate and pressurization rate of nanoenergetic materials by controlling the relative elemental compositions of oxidizers. First, bimetallic oxide nanoparticles (NPs) with a homogeneous distribution of two different oxidizer components (CuO and Fe2O3) were generated by a conventional spray pyrolysis method. Next, the Al NPs employed as a fuel were mixed with CuO-Fe2O3bimetallic oxide NPs by an ultrasonication process in ethanol solution. Finally, after the removal of ethanol by a drying process, the NPs were converted into energetic materials (EMs). The effects of the mass fraction of CuO in the CuO-Fe2O3bimetallic oxide NPs on the explosive reactivity of the resulting EMs were examined by using a differential scanning calorimeter and pressure cell tester (PCT) systems. The results clearly indicate that the energy release rate and pressurization rate of EMs increased linearly as the mass fraction of CuO in the CuO-Fe2O3bimetallic oxide NPs increased. This suggests that the precise control of the stoichiometric proportions of the strong oxidizer (CuO) and mild oxidizer (Fe2O3) components in the bimetallic oxide NPs is a key factor in tuning the explosive reactivity of EMs.</P>
Benign Bronchoesophageal Fistula in Adults: Endoscopic Closure as Primary Treatment
( Ji Yong Ahn ),( Hwoon Yong Jung ),( Ji Young Choi ),( Mi Young Kim ),( Jeong Hoon Lee ),( Kwi Sook Choi ),( Do Hoon Kim ),( Kee Don Choi ),( Ho June Song ),( Gin Hyug Lee ),( Jin Ho Kim ) 대한소화기기능성질환·운동학회 2010 Gut and Liver Vol.4 No.4
Background/Aims: Benign bronchoesophageal fistula (BEF) is a rare condition that is usually treated surgically; however, less invasive endoscopy procedures have been attempted to overcome the disadvantages of surgery. The aim of this study was thus to determine the results of endoscopic management as a primary treatment in patients with BEF. Methods: We retrospectively analyzed data from 368 patients with BEF who were treated at a tertiary care, academic medical center between January 2000 and August 2009. Results: Benign causes were found for only 18 of the 368 patients. Of these, seven were treated endoscopically and the others by surgery or other methods. The first endoscopy procedures failed in all seven patients, with second trials of endoscopy performed in four patients at a median of 8 days (range, 3 to 11 days) after the first procedure. The second endoscopic procedure was successful in two out of four patients; one patient showed no recurrence of the fistula, whereas the second patient experienced a recurrence after 24 months. All patients underwent successful surgical procedures after the failure of endoscopic treatment, with no further recurrences. Conclusions: Although we observed a low rate of success for primary endoscopic treatment of benign BEF, the invasive nature of surgery suggests the need for a prospective study with a large number of patients to evaluate the efficacy of less invasive procedures such as endoscopic treatment. (Gut Liver 2010;4:508-513)
( Ji Yong Ahn ),( Jin Seo Lee ),( Gin Hyug Lee ),( Ji Wan Lee ),( Hee Kyong Na ),( Kee Wook Jung ),( Jeong Hoon Lee ),( Do Hoon Kim ),( Kee Don Choi ),( Ho June Song ),( Hwoon-yong Jung ),( Jin-ho Kim 대한간학회 2016 Gut and Liver Vol.10 No.5
Background/Aims: We developed a new endoscopic biopsy training simulator and determined its efficacy for improving the endoscopic biopsy skills of beginners. Methods: This biopsy simulator, which presents seven biopsy sites, was constructed using readily available materials. We enrolled 40 participants: 14 residents, 11 first-year clinical fellows, 10 second-year clinical fellows, and five staff members. We recorded the simulation completion time for all participants, and then simulator performance was assessed via a questionnaire using the 7-point Likert scale. Results: The mean times for completing the five trials were 417.7±138.8, 145.2±31.5, 112.7±21.9, and 90.5±20.0 seconds for the residents, first-year clinical fellows, second-year clinical fellows, and staff members, respectively. Endoscopists with less experience reported that they found this simulator more useful for improving their biopsy technique (6.8±0.4 in the resident group and 5.7±1.0 in the first-year clinical fellow group). The realism score of the simulator for endoscopic handling was 6.4±0.5 in the staff group. Conclusions: This new, easy-to-manufacture endoscopic biopsy simulator is useful for biopsy training for beginner endoscopists and shows good efficacy and realism. (Gut Liver 2016;10:764-772)