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Iwasawa Theory of Quadratic Twists of X0（49）

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Acta Mathematica sinica,English series 2018年第1期34卷 19-28页

作者： Junhwa choi John COATEs Department of Mathematics POSTECH Emmanuel College Cambridge University

The field K ---- Q（x/-AT） is the only imaginary quadratic field with class number 1, in which the prime 2 splits, and we fix one of the primes p of K lying above 2. The modular elliptic curve X0 （49） has complex multiplication by the maximal order O of K, and we let E be the twist of Xo （49） by the quadratic extension K（v/M）/K, where M is any square free element of O with M -- i mod 4 and （M, 7） = 1. In the present note, we use surprisingly simple algebraic arguments to prove a sharp estimate for the rank of the MordeII-Weil group modulo torsion of E over the field F∞=k（Ep∞ ）, where Epic denotes the group of p∞-division points on E. Moreover, writing B for the twist of X0（49） by K（C/ET）/K, our Iwasawa-theoretic arguments also show that the weak form of the conjecture of Birch and swinnerton-Dyer implies the non-vanishing at s =1 of the complex L-series of B over every finite layer of the unique Z2-extension of K unramified outside p. We hope to give a proof of this last non-vanishing assertion in a subsequent paper.

关键词： Birch-swinnerton-Dyer conjecture elliptic curves Iwasawa theory

The geometry of the moduli space of one-dimensional sheaves

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science China Mathematics 2015年第3期58卷 487-500页

作者： choi Jinwon CHUNG Kiryong school of Mathematics Korea Institute for Advanced Study

Let Md be the moduli space of stable sheaves on P2with Hilbert polynomial dm+*** this paper,we determine the effective and the nef cone of the space Md by natural geometric *** idea is to use the wall-crossing on the space of Bridgeland stability conditions and to compute the intersection numbers of divisors with curves by using the Grothendieck-Riemann-Roch *** also present the stable base locus decomposition of the space *** a byproduct,we obtain the Betti numbers of the moduli spaces,which confirm the prediction in physics.

关键词： effective cone nef cone birational morphism determinant line bundle Bridgeland wall-crossing

Effect of pre-strain on microstructural evolution during thermal exposure of single crystal superalloy CMsX-4

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Transactions of Nonferrous Metals society of China 2011年第6期21卷 1291-1296页

作者： B.G.choi C.y.JO I.s.KIM s.M.sEO H.M.KIM High Temperature Materials Group Korea Institute of Materials Science

Compressive and tensile pre-strains at room temperature were induced in the second generation single crystal superalloy CMsX-4 fully heat *** compressive and tensile pre-strain generated shear bands in the single crystal *** exposure for 10 h at 950 ℃ on the pre-strained single crystal CMsX-4 developed preferential coarsening of γ＇ particles along the shear bands.γ＇ particles on the shear band gradually invaded γ ***,the γ channels along the shear band ***-like particles appeared at the expense of γ channel ***,thermal exposure for 10 h of the normal single crystal CMsX-4 did not develop TCP precipitation or preferential coarsening of γ＇ *** exposure for 100 h of pre-strained CMsX-4 developed preferential coarsening of γ＇ and TCP phase particles along the shear bands as well as coarsening of γ＇ particles in the matrix.

关键词： pre-strain microstructural evolution superalloy CMsX-4

searching for Bacterial Biofilm in Recurrent Cholangitis in Primary sclerosing Cholangitis:A Case Presentation and Introduction of an Unexplored Disease Mechanism

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Journal of Clinical and Translational Hepatology 2018年第1期6卷 114-118页

作者： Alyssa y. choi Florencia Jalikis Maria Westerhoff sarag Boukhar Elinor Pulcini Chris Damman Lei yu Department of Internal Medicine University of WashingtonSeattleWashingtonUSA Department of Pathology University of WashingtonSeattleWashingtonUSA Department of Pathology University of IowaIowa CityIowaUSA Center for Biofilm Engineering Montana State UniversityBozemanMontanaUSA Division of Gastroenterology University of WashingtonSeattleWashingtonUSA

Inflammation and fibrosis of the bile ducts are the defining pathological characteristics of primary sclerosing cholangitis(PsC).A previously unexplored mechanism for recurrent cholangitis,one of PsC's most common presentations,is bacterial colonization of the biliary epithelium in the form of biofilm,which may confer resistance to antibiotics and host phagocytic *** aim of the current study was to assess whether bacteria could be seen on the liver explant and whether they organized in the form of *** explanted PsC liver from a 60-year-old male who suffered from recurrent cholangitis was formalin-fixed,paraffinembedded and Gram *** specimens were observed under light *** bacteria nor biofilm were *** did not detect bacteria or biofilm in the liver explant of a single PsC patient with recurrent cholangitis using standard light *** suspect this may be in part due to techniques related to tissue preservation and microscopy.

关键词： Primary sclerosing cholangitis Recurrent cholangitis Biofilm

Remote Observations in China’s Ramsar sites: Wetland Dynamics, Anthropogenic Threats, and Implications for sustainable Development Goals

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Journal of Remote sensing 2021年第1期2021卷 319-331页

作者： D.Mao Z.Wang y.Wang C.-y.choi M.Jia M.V.Jackson R.A.Fuller Key Laboratory of Wetland Ecology and Environment Northeast Institute of Geography and AgroecologyChinese Academy of SciencesChangchun 130102China National Earth system science Data Center BeijingChina Department of Natural Resources sciences University of Rhode IslandKingstonRI 02881USA school of Environmental science and Engineering College of EngineeringSouthern University of Science and TechnologyShenzhen 518055China school of Biological sciences The University of QueenslandBrisbaneAustralia

The Ramsar Convention on Wetlands is an international framework through which countries identify and protect important *** Ramsar wetlands are under substantial anthropogenic pressure worldwide,and tracking ecological change relies on multitemporal data ***,we evaluated the spatial extent,temporal change,and anthropogenic threat to Ramsar wetlands at a national scale across China to determine whether their management is currently *** analyzed Landsat data to examine wetland dynamics and anthropogenic threats at the 57 Ramsar wetlands in China between 1980 and *** reveal that Ramsar sites play important roles in preventing wetland loss compared to the dramatic decline of wetlands in the surrounding ***,there are declines in wetland area at 18 Ramsar *** those,six lost a wetland area greater than 100 km^(2),primarily caused by agricultural *** expansion of anthropogenic land covers occurred within 43(75%)Ramsar sites,and anthropogenic threats from land cover change were particularly notable in eastern *** pond expansion and spartina alterniflora invasion were prominent threats to coastal Ramsar *** observations within China’s Ramsar sites,which in management regulations have higher levels of protection than other wetlands,can help track progress towards achieving United Nations sustainable Development Goals(sDGs).The study findings suggest that further and timely actions are required to control the loss and degradation of wetland ecosystems.

关键词： sustainable threat wetland

Laser-assisted deposition of Cu bumps for microelectronic packaging

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中国有色金属学会会刊：英文版 2012年第S3期22卷 683-687页

作者： Won-seok choi Joohan KIM Department of Nano IT Fusion Program Seoul National University of Science and Technology Department of Mechanical and Automotive Engineering Seoul National University of Science and Technology

Cu bump was transferred using a focused laser pulse for microelectronic *** Nd:yAG laser pulse (maximum energy of 500 mJ;wavelength of 1064 nm;fluences of 0.4-2.1 kJ/cm2) was irradiated on a sacrificial absorption layer with copper *** focused laser beam induced plasma between the semi-transparent donor slide and the sacrificial layer,causing a shock *** shock wave pressure pushed the Cu layer and transferred material to deposit a bump on substrate.A beam-shaper was used to produce uniform pressure at the interface to reduce fragmentation of the transferred material on the *** calculated shock wave pressure with respect to laser fluence was 1-3 GPa.A Cu bump of diameter of 200 μm was successfully deposited at laser fluence of 0.6 kJ/cm *** pressure control at the sacrificial layer using a laser pulse was critical to produce a bump with less *** technique can be applied to forming Cu bump for an interconnecting process in electronics.

关键词： laser induced forward transfer bump deposition Nd:yAG pulsed laser micro system packaging beam shaping

High-Performance Perovskite Quantum Dot solar Cells Enabled by Incorporation with Dimensionally Engineered Organic semiconductor

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Nano-Micro Letters 2022年第12期14卷 272-285页

作者： seyeong Lim Dae Hwan Lee Hyuntae choi yelim choi Dong Geon Lee sung Beom Cho seonkyung Ko Jongmin choi younghoon Kim Taiho Park Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Department of Materials science and Engineering Hanyang UniversitySeoul 04763Republic of Korea Center of Materials Digitalization Korea Institute of Ceramic Engineering and Technology(KICET)Jinju 52851Republic of Korea Department of Materials science and Engineering Ajou UniversitySuwon 16499Republic of Korea Department of Energy science and Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)Daegu 42988Republic of Korea Department of Chemistry Kookmin UniversitySeoul 02707Republic of Korea

Perovskite quantum dots(PQDs)have been considered promising and effective photovoltaic absorber due to their superior optoelectronic properties and inherent material merits combining perovskites and ***,they exhibit low moisture stability at room humidity(20-30%)owing to many surface defect sites generated by inefficient ligand exchange *** surface traps must be re-passivated to improve both charge transport ability and moisture *** address this issue,PQD-organic semiconductor hybrid solar cells with suitable electrical properties and functional groups might dramatically improve the charge extraction and defect *** organic semiconductors are typically low-dimensional(1D and 2D)and prone to excessive self-aggregation,which limits chemical interaction with *** this work,we designed a new 3D star-shaped semiconducting material(star-TrCN)to enhance the compatibility with *** robust bonding with star-TrCN and PQDs is demonstrated by theoretical modeling and experimental *** star-TrCN-PQD hybrid films show improved cubic-phase stability of CsPbI_(3)-PQDs via reduced surface trap states and suppressed moisture *** a result,the resultant devices not only achieve remarkable device stability over 1000 h at 20-30%relative humidity,but also boost power conversion efficiency up to 16.0%via forming a cascade energy band structure.

关键词： CsPbI3 quantum dots star-shaped organic semiconductors Hybrid perovskite quantum dots solar cell stability High-efficiency photovoltaics

Groundwater contamination and natural attenuation capacity at a petroleum spilled facility in Korea

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Journal of Environmental sciences 2011年第10期23卷 1650-1659页

作者： Hyun-Mi choi Jin-yong Lee Department of Geology Kangwon National University

As a remedial option, the natural attenuation capacity of a petroleum contaminated groundwater at a military facility was examined. Hydrogeological conditions, such as high water level, permeable uppermost layer and frequent heavy rainfall, were favorable to natural attenuation at this site. The changes in the concentrations of electron acceptors and donors, as well as the relevant hydrochemical conditions, indicated the occurrence of aerobic respiration, denitrification, iron reduction, manganese reduction and sulfate reduction. The calculated BTEX expressed biodegradation capacity ranged between 20.52 and 33.67 mg/L, which appeared effective for the reduction of the contaminants levels. The contribution of each electron accepting process to the total biodegradation was in the order： denitrification 〉 iron reduction 〉 sulfate reduction 〉 aerobic respiration 〉 manganese reduction. The BTEX and benzene point attenuation rates were 0.0058-0.0064 and 0.0005-0.0032 day-1, respectively, and the remediation time was 0.7-1.2 and 2.5-30 years, respectively. The BTEX and benzene bulk attenuation rates were 8.69 × 10^-4 and 1.05 × 10^-3 day-l, respectively, and the remediation times for BTEX and benzene were 7.2 and 17.5 years, respectively. However, most of the natural attenuation occurring in this site can be attributed to dilution and dispersion. Consequently, the biodegradation and natural attenuation capacities were good enough to lower the contaminants levels, but their rates appeared to be insufficient to reach the remediation goal within a reasonable time frame. Therefore, some active remedial measures would be required.

关键词： petroleum contaminated site BTEX electron acceptor expressed biodegradation capacity natural attenuation

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