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고체산화물 연료전지용 (Ca,Sr)도핑된 LaCrO<sub>3</sub>계 세라믹 연결재 코팅층의 특성 연구
이길용,백동현,송락현,Lee, Gil-Yong,Peck, Dong-Hyun,Song, Rak-Hyun 한국전기화학회 2005 한국전기화학회지 Vol.8 No.4
본 연구는 Pechini법을 이용하여 Ca과 Sr이 도핑된 $LaCrO_3$계의 $La_{0.6}Ca_{0.41}CrO_3$ (LCC41), $La_{0.8}Sr_{0.05}Ca_{0.15}CrO_3$, (LSCC), $La_{0.75}Ca_{0.27}CrO_3$ (LCC27) 분말들을 제조하여, 분말의 소결 특성 및 코팅층의 특성을 조사하였다. 제조된 LCC41, LSCC, LCC27 분말은 각각 0.6, 0.9, $1.5{\mu}m$의 평균 입자크기를 가졌으며, LCC41의 경우 $1400^{\circ}C$에서 98% 이상의 소결 밀도를 나타내었다. 연료극 지지체상의 LSCC 코팅은 LCC41층에 있는 Ca의 이동을 어느 정도 억제하는 역할을 하는 것으로 나타났다. 대기 용사 코팅된 LCC27은 치밀한 코팅막을 형성하였으며, 이 코팅층 위에 LCC41을 습식 코팅할 경우 더욱 치밀하고 높은 전기전도도를 갖는 코팅막을 얻을 수 있었다. 용사코팅된 LCC27, 습식 코팅된 LCC41는 높은 전기전도도를 나타내었으나, LSCC의 경우 낮은 소결성으로 인해 전기전도도가 작게 나타났다. Using Pechini method, we synthesized the $La_{0.6}Ca_{0.41}CrO_3$ (LCC41) and $La_{0.8}Sr_{0.05}Ca_{0.15}CrO_3$ (LSCC) powders for slurry dip coating, and $La_{0.75}Ca_{0.27}CrO_3$ (LCC27) powder for air plasma spray coating. The sintering property of the powders and their coating properties were investigated. The average particle sizes of the LCC41, LSCC, LCC27 were 0.6, 0.9, $1.5{\mu}m$, respectively. The relative density of LCC41 bulk was to be found about 98%. The LSCC coating on anode support prevented Ca migration of the coated LCC41 on the anode some or less, which was confirmed from EDS result. The air plasma spray-coated LCC27 with the dip-coated LCC41 were more dense and showed better electrical conductivity than those of the air plasma spray-coated LCC27 and the dip-coated LSCC and LSCC41. The LCC41 and LCC27 showed good electrical conductivities, but the LSCC had a poor electrical conductivity probably due to low sinterability
사이프러스 에센셜 오일의 흡입이 전임상 실험동물의 손상된 학습능력과 기억력에 미치는 영향
이길용 ( Gil-yong Lee ),이찬 ( Chan Lee ),백정인 ( Jeong-in Baek ),배근영 ( Keunyoung Bae ),박찬익 ( Chan-ik Park ),장정희 ( Jung-hee Jang ) 대한본초학회 2020 大韓本草學會誌 Vol.35 No.5
Objectives : Increasing evidence supports the biological and pharmacological activities of essential oils on the central nervous system such as pain, anxiety, attention, arousal, relaxation, sedation and learning and memory. The purpose of present work is to investigate the protective effect and molecular mechanism of cypress essential oil (CEO) against scopolamine (SCO)-induced cognitive impairments in C57BL/6 mice. Methods : A series of behavior tests such as Morris water maze, passive avoidance, and fear conditioning tests were conducted to monitor learning and memory functions. Immunoblotting and RT-PCR were also performed in the hippocampal tissue to determine the underlying mechanism of CEO. Results : SCO induced cognitive impairments as assessed by decreased step-through latency in passive avoidance test, relatively low freezing time in fear conditioning test, and increased time spent to find the hidden platform in Morris water maze test. Conversely, CEO inhalation significantly reversed the SCO-induced cognitive impairments in C57BL/6 mice comparable to control levels. To elucidate the molecular mechanisms of memory enhancing effect of CEO we have examined the expression of brain-derived neurotrophic factor (BDNF) in the hippocampus. CEO effectively elevated the protein as well as mRNA expression of BDNF via activation of cAMP response element binding protein (CREB). Conclusions : Our findings suggest that CEO inhalation effectively restored the SCO-impaired cognitive functions in C56BL/6 mice. This learning and memory enhancing effect of CEO was partly mediated by up-regulation of BDNF via activation of CREB.
토픽 모델링을 활용한 ‘4차 산업혁명 시대 교육’ 동향 분석 : 2018-2020년 교육부 문서와 종합일간지 비교 분석
이길용(Lee, Gil-yong),홍후조(Hong, Hoo Jo) 한국교육학회 2021 敎育學硏究 Vol.59 No.2
본 연구는 2018년 1월부터 2020년 12월까지 4차 산업혁명 시대 교육과 관련된 정부 차원의 교육부 문서와 민간 차원의 일간지 기사를 수집 및 비교 분석하여 키워드 및 주제의 변화 흐름을 살피고 향후 발전 방향과 교육적 시사점을 도출하고자 하였다. 교육부 문서는 교육부 홈페이지의 뉴스·홍보란의 게시물과 교육부가 발간한 월간지가 포함되며, 일간지 기사는 국내 전국단위 11개 종합일간지 기사가 대상이다. 웹크롤링을 이용하여 자료를 수집한 후, 통계 프로그램 ‘R’을 통해 키워드 분석과 토픽 모델링, 감성분석을 수행하였다. 분석 결과, 교육부 문서에서는 기술교육, 중·고교교육, 대학교육이 강조되었는데, 기술교육의 경우 이후 진로·직업 교육으로 확장되는 모습을 보였다. 중·고교교육의 경우 학생 맞춤형 교육과 거점형 고등학교를 강조하는 모습이 나타났으며, 대학교육에서는 대학, 기업, 사회 등의 교육의 주체간 다각도의 협력이 강조되었다. 반면 일간지 기사에서는 기술교육 중에서도 인공지능에 대한 관심이 꾸준히 높았다. 중·고교교육에서는 대학수학능력시험 과목의 변화가 주로 다루어졌으며, 진로교육이나 정부와 정치권의 4차 산업혁명 교육 관련 정책이 폭넓게 다루어졌다. 끝으로, 정부 차원에서는 4차 산업혁명 시대 교육에 대해 긍정어가 차지하는 비율이 높아지는 데 반해 민간 차원에서는 부정어가 차지하는 비율이 높아졌다. This study aims to examine the trend in changes in keywords and topics of the 4th Industrial Revolution as it pertains to education between 2018 and 2020, and to derive future development directions and educational implications. For the public sector, posts on the Ministry of Education s website and its monthly magazine have been targeted. For the private sector, articles from eleven comprehensive daily newspapers nationwide are targeted. After collecting data through web crawling, keyword analysis, topic modeling, and sentiment analysis were performed using R. As a result, technical education, middle and high school education, and university education were found to be emphasized in the Ministry of Education s documents. Technical education showed an extension to career and vocational education. In the case of middle and high school education, the emphasis was on student-specific education and on the strategic location of high schools. In university education, cooperation through subjects such as universities, companies, and society were emphasized. On the other hand, in daily newspapers, interest in AI was steadily high. In middle and high school education, major changes in the subjects on the College Scholastic Ability Test were dealt with, and career education and government policies, and political circles were dealt with broadly. Finally, the proportion of positive words in the public sector increased, while the proportion of negative words in private sector increased.
이길용(Gil-Yong Lee),장희도(Hee-Doh Jang),장지욱(Jee-Uk Chang),한동철(Dong-Chul Han) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
The vibration isolator using negative stiffness mechanism(NSM) which shows very low natural frequency could be designed by applying axial compressive forces to the beam-column springs. In this paper the design specifications of NSM passive vibration isolator are investigated. A commercial NSM vibration isolator has little damping, so the constrained layer damping(CLD) with viscoelastic materials which could give effective damping characteristic to the system is suggested. The beam-column springs show structural damping characteristics depending on the mechanical properties and the geometries of the added viscoelastic materials. The design specifications of the beam-column springs with built-in viscoelastic materials are considered by analytical and experimental approaches. And then also its validity is considered by applying it to the 1 DOF passive vibration isolator.
Gil Yong Lee(이길용),Phill-Seung Lee(이필승),Yong-Hwa Park(박용화) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
In structural dynamics, the harmonic balance method (HBM) has been widely applied to obtain the frequency response of many mechanical systems in the presence of nonlinearities. It approximates the periodic solution utilizing a truncated Fourier series, resulting in a set of nonlinear algebraic equations in the frequency domain. However, one still difficulty in the HBM is that dimension of the nonlinear equations is the product of number of degrees of freedoms and harmonics , so the computational cost of the continuation over the frequency range can be easily burdensome . In this work , we present the proper generalized decomposition -based harmonic balance method (PGD-HBM) for the efficient numerical continuation of the nonlinear frequency response. The PGD-HBM utilizes the low-dimensional subspace of the HBM, constructing the HBM response as a separated representation of the spatial and temporal components . The updated progressive Galerkin scheme is adopted to obtain a set of components . During the continuation , the spatial modes obtained at the previous computation are used as a reduced basis. Through numerical studies, it is demonstrated that the PGD-HBM not only provides significant computational savings compared to the HBM, but also maintains accuracy.