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Revisiting the Climatology of Atmospheric Blocking in the Northern Hemisphere

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Advances in Atmospheric Sciences 2013年第2期30卷 397-410页

作者： ho nam cheung 周文 Hing Yim MOK Man Chi WU Yaping SHAO City University of hong Kong Shenzhen Research Institute Guy Carpenter Asia-Pacific Climate Impact Centre School of Energy and Environment City University of Hong Kong hong Kong Observatory Institute for Geophysics and Meteorology University of Cologne

In addition to the occurrence of atmospheric blocking, the climatology of the characteristics of blocking events, including duration, intensity, and extension, in four seasons over the Northern Hemisphere was analyzed for the period 1950-2009. The seasonality and spatial variations of these characteristics were studied according to their longitudinal distributions. In general, there were sharp discrepancies in the blocking characteristics between winter and summer, and these differences were more prominent over the Atlantic and Pacific Oceans. The blocking not only occurred more frequently but also underwent stronger amplification in winter; likewise, the blocking occurred less frequently and underwent weaker amplification in summer. There are very strong interrelationships among different blocking characteristics, suggesting that they are supported by similar physical factors. In addition, the relationship between blocking over different regions and East Asian circulation was examined. Ural-Siberia is a major blocking formation region in all seasons that may exert a downstream impact on East Asia. The impact is generally weak in summer, which is due to its lower intensity and smaller duration. however, the extratropical circulation over East Asia in summer can be disturbed persistently by the frequent occurrence of blocking over the Asian continent or the Western Pacific. In particular, the blocking frequency over the Western Pacific significantly increased during the study period. This climatological information provides a background for studying the impact of blocking on East Asian circulation under both present and future climate conditions.

关键词： atmospheric blocking climatology seasonality East Asian circulation

Mixed diversity of shifting IOD and El Ni?o dominates the location of Maritime Continent autumn drought

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National Science Review 2020年第7期7卷 1150-1153页

作者： Chundi Hu Tao Lian ho-nam cheung Shaobo Qiao Zhenning Li Kaiqiang Deng Song Yang Dake Chen School of Atmospheric Sciences and Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies Sun Yat-sen University State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography Ministry of Natural Resources Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) and Key Laboratory of Tropical Atmosphere-Ocean System (Sun Yat-sen University) Ministry of Education Institute of Environment Energy and Sustainability The Chinese University of Hong Kong Department of Earth Science University of Gothenburg Institute of Earth Climate and Environment System Sun Yat-sen University

The Maritime Continent is a huge heat source region over the Indo-Pacific warm pool and it plays a key role in global weather/climate variations. The locations of Maritime Continent autumn droughts, linked to frequent... 详细信息

关键词： Drought

Shear deformable finite beam elements for composite box beams

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Acta Mechanica Sinica 2014年第2期30卷 223-240页

作者： nam-Il Kim Dong-ho Choi Department of Architectural Engineering Sejong University Department of Civil and Environmental Engineering Hanyang University

The shear deformable thin-walled composite beams with closed cross-sections have been developed for coupled flexural, torsional, and buckling analyses. A theoretical model applicable to the thin-walled laminated composite box beams is presented by taking into account all the structural couplings coming from the material anisotropy and the shear deformation effects. The current composite beam includes the transverse shear and the restrained warping induced shear deformation by using the first-order shear deformation beam theory. Seven governing equations are derived for the coupled axial-flexural-torsional-shearing buckling based on the principle of minimum total potential energy. Based on the present analytical model, three different types of finite composite beam elements, namely, linear, quadratic and cubic elements are developed to analyze the flexural, torsional, and buckling problems. In order to demonstrate the accuracy and superiority of the beam theory and the finite beam elements developed by this study,numerical solutions are presented and compared with the results obtained by other researchers and the detailed threedimensional analysis results using the shell elements of ABAQUS. Especially, the influences of the modulus ratio and the simplified assumptions in stress-strain relations on the deflection, twisting angle, and critical buckling loads of composite box beams are investigated.

关键词： Thin-walled Composite box beam Deflection Twisting angle Buckling load Shear deformation

Comparative Study of Transfer Learning Models for Retinal Disease Diagnosis from Fundus Images

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Computers, Materials & Continua 2022年第3期70卷 5821-5834页

作者： Kuntha Pin Jee ho Chang Yunyoung nam Department of ICT Convergence Soonchunhyang UniversityAsan31538Korea Department of Ophthalmology Soonchunhyang University Bucheon HospitalSoonchunhyang University College of MedicineBucheon420-767Korea Department of Computer Science and Engineering Soonchunhyang UniversityAsan31538Korea

While the usage of digital ocular fundus image has been widespread in ophthalmology practice,the interpretation of the image has been still on the hands of the ophthalmologists which are quite *** explored a robust deep learning system that detects three major ocular diseases:diabetic retinopathy(DR),glaucoma(GLC),and age-related macular degeneration(AMD).The proposed method is composed of two ***,an initial quality evaluation in the classification system is proposed to filter out poorquality images to enhance its performance,a technique that has not been explored ***,the transfer learning technique is used with various convolutional neural networks(CNN)models that automatically learn a thousand features in the digital retinal image,and are based on those features for diagnosing eye *** performance of many models is conducted to find the optimal model which fits with fundus *** the different CNN models,DenseNet-201 outperforms others with an area under the receiver operating characteristic curve of ***,the corresponding specificities for healthy,DR,GLC,andAMDpatients are found to be 89.52%,96.69%,89.58%,and 100%,*** results demonstrate that the proposed method can reduce the time-consumption by automatically diagnosing multiple eye diseases using computer-aided assistance tools.

关键词： Multiclass classification deep neural networks glaucoma agerelated macular degeneration diabetic retinopathy transfer learning quality evaluation

Polygonal multi-polymorphed Li4Ti5Oi2@rutile TiO2 as anodes in lithium-ion batteries

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Nano Research 2019年第4期12卷 897-904页

作者： Chang Hyun Hwang Hee-eun Kim Inho nam Jin ho Bang Department ofBionano Technology Hanyang University 55 Hanyangdaehak-ro Sangnok-gu Ansan Gyeonggi-do 15588 Republic of Korea School of Chemical Engineering & Materials Science Chung-Ang University 84 Heukseok-ro Dongjak-gu Seoul 06974 Republic of Korea Department of Chemical and Molecular Engineering Hanyang University 55 Hanyangdaehak-ro Sangnok-gu Ansan Gyeonggi-do 15588 Republic of Korea

Li4Ti50i2 (LTO) has attracted considerable attention in lithium-ion battery (LIB) applications because of its favorable characteristics as an anode material. Despite its promise, the widespread use of LTO is still limited primarily due to its intrinsically poor electric and ionic con ductivities and high surface reactivity. To address these issues, we desig ned polyg onal nano architectures composed of various Li-Ti oxide crystal polymorphs by a facile synthesis route. Depending on the pH condition, this synthesis approach yields multi-polymorphed Li-Ti oxides where the interior is dominantly composed of a Li-rich phase and the exterior is a Li-deficient (or Li-free) phase. As one of these variations, a polygonal LTO-rutile TiO2 structure is formed. The rutile TiO2 on the surface of this LTO composite significantly improves the kinetics of Li^+ insertion/extraction because the channel along the o-axis in TQ2 provides a Li^+ highway due to the significantly low energy barrier for Li^+ diffusion. Moreover, the presenee of rutile TiO2, which is less reactive with a carbonate-based electrolyte, ensures Iong-term stability by suppress)ng the undesirable interfacial reaction on LTO.

关键词： micro-polygon structure Li-Ti oxide multi-polymorphs Li4Ti5Oi2@ rutile TiO2 anode lithium-ion batteries

A simple fabricated thickness-based stiffness gradient for cell studies

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Science Bulletin 2017年第3期62卷 222-228页

作者： Yiwei Shu ho nam Chan Dongshi Guan hongkai Wu Lan Ma Division of Life Science & Health Graduate School at Shenzhen Tsinghua University Shenzhen 518055 China Department of Chemistry The Hong Kong University of Science and Technology Hong Kong China Department of Physics The Hong Kong University of Science and Technology Hong Kong China

In this work, we developed a simple method to fabricate a thickness-based continuous stiffness gradient for biological studies. It was made by glass slides, polydimethylsiloxane （PDMS） pre-polymer, spacer and clips only, without any sophisticated equipment. It is easy to fabricate in any general biological and pharmaceutical laboratories. The stiffness gradient was characterized in terms of apparent Young＇s modulus by atomic force microscopy （AFM） and the Young＇s modulus along the gradient was found to be 8.5- 120 kPa, which is within the physiological relevant range. HeLa-C3 ceils were cultured on the gradient to study their morphological behavior according to the substrate stiffness. Furthermore, the drug efficiency of etoposide, an anti-cancer drug, was studied along the substrate stiffness gradient. It was found that HeLa-C3 cells cultured on the soft region of the gradient （8.5-11 kPa） are more sensitive to etoposide. We believe the proposed device could promote cell investigations and drug screenings on a substrate with comparable stiffness to the native tissue.

关键词： Stiffness gradient Cell analysis PDMS Etoposide

Etching characteristics of thin SiON films using a liquefied perfluorocarbon precursor of C_6F_(12)O with a low global warming potential

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Plasma Science and Technology 2020年第10期22卷 135-144页

作者： Junmyung LEE Yunho nam Jongchan LEE Hyun Woo LEE Kwang-ho KWON Department of Control and Instrumentation Engineering Korea UniversitySejong 30019Republic of Korea Department of Aeronautic Computer Engineering Hanseo UniversitySeosan 31962Republic of Korea

Perfluorocarbon gas is widely used in the semiconductor ***,perfluorocarbon has a negative effect on the global environment owing to its high global warming potential(GWP) *** alternative solution is ***,we evaluated the possibility of replacing conventional perfluorocarbon etching gases such as CHF_3 with C_6F_(12)O,which has a low GWP and is in a liquid state at room *** this study,silicon oxynitride(SiON) films were plasma-etched using inductively coupled CF4+C_6F_(12)O+O_2 mixed ***,the etching characteristics of the film,such as etching rate,etching profile,selectivity over Si,and photoresist,were investigated.A double Langmuir probe was used and optical emission spectroscopy was performed for plasma *** addition,a contact angle goniometer and x-ray photoelectron spectroscope were used to confirm the change in the surface properties of the etched SiON film ***,the etching characteristics of the C_6F_(12)O mixed plasma exhibited a lower etching rate,higher SiON/Si selectivity,lower plasma damage,and more vertical etched profiles than the conventional CHF_3 mixed *** addition,the C_6F_(12)O gas can be recovered in the liquid state,thereby decreasing global *** results confirmed that the C_6F_(12)O precursor can sufficiently replace the conventional etching gas.

关键词： global warming potential perfluorocarbon silicon oxynitride etching characteristics liquid-state perfluorocarbon

Extended X-ray absorption fine structure (EXAFS) of FAPbI_(3) for understanding local structure-stability relation in perovskite solar cells

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Journal of Energy Chemistry 2022年第4期31卷 549-554页

作者： Dong-ho Kang Yong-Jun Park Yun-Sung Jeon nam-Gyu Park School of Chemical Engineering and Center for Antibonding Regulated Crystals Sungkyunkwan UniversitySuwon 16419Korea

Perovskite solar cells (PSCs) employing formamidinium lead iodide (FAPbI_(3)) have shown high ***,operational stability has been issued due to phase instability of α phase FAPbI_(3) at ambient *** precursors in the perovskite precursor solution has been proposed to improve not only power conversion efficiency (PCE) but also device ***,there is a controversial issue on the beneficial effect on PCE and/or stability between excess FAI and excess PbI_(2).We report here extended X-ray absorption fine structure (EXAFS) of FAPbI_(3) to study local structural change and explain the effect of excess precursors on photovoltaic performance and *** films prepared from the precursor solution with excess PbI_(2)shows better stability than those from the one with excess FAI,despite similar PCE.A rapid phase transition from α phase to non-perovskite δ phase is observed from the perovskite film formed by excess ***,the (Pb-I) bond distance evaluated by the Pb L_(III)-edge EXAFS study is increased by excess FAI,which is responsible for the phase transition and poor device *** work can provide important insight into local structure-stability relation in the FAPbI_(3)-based PSCs.

关键词： Extended X-ray absorption fine structure EXAFS Excess precursor Local structure Stability Perovskite solar cells

Spatio-temporal variability in sea surface wind stress near and off the east coast of Korea

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Acta Oceanologica Sinica 2005年第1期24卷 107-114页

作者： nam SungHyun KIM Young ho PARK Kyung-Ae KIM Kuh Ocean Laboratory/RIO School of Earth and Environmental Sciences Seoul National University Seoul 151-742 KoreaOcean Laboratory/RIO School of Earth and Environmental Sciences Seoul National University Seoul 151-742 KoreaOcean Laboratory/RIO School of Earth and Environmental Sciences Seoul National University Seoul 151-742 KoreaOcean Laboratory/RIO School of Earth and Environmental Sciences Seoul National University Seoul 151-742 Korea

Sea surface wind stress variabilities near and off the east coast of Korea, are examined using 7 kinds of wind datasets from measurements at 2 coastal (land) stations and 2 ocean buoys,satellite scatterometer (QuikSCAT), and global reanalyzed products (ECMWF,NOGAPS,and NCEP/NCAR). Temporal variabilities are analyzed at 3 frequency bands; synoptic (2-20 d), intra-seasonal (20-90 d),and seasonal (>90 d).Synoptic and intra-seasonal variations are predominant near and off the Donghae City due to the passage of the mesoscale weather system. Seasonal variation is caused by southeastward wind stress during Asian winter monsoon. The sea surface wind stress from reanalyzed *** and KMA-B measurements off the coast show good agreement in the magnitude and direction,which are strongly aligned with the alongshore *** the land-based sites,wind stresses are much weaker by factors of 3-10 due to the mountainous landmass on the east parts of Korea *** first EOF modes(67%-70%) of wind stresses from reanalyzed and QuikSCAT data have similar structures of the strong southeastward wind stress in winter along the coast but show different curl structures at scales less than 200 km due to the orographic *** second EOF modes (23%-25%) show southwestward wind stress in every September along the east coast of the North Korea

关键词： sea surface wind stress spatio-temporal variability monsoon seasonal intra-seasonal synoptic band orographic effect