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Rigid reflections and Kac-Moody algebras

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Science China Mathematics 2019年第7期62卷 1317-1330页

作者： kyu-Hwan lee kyungyong lee Department of Mathematics University of Connecticut Storrs CT 06269 USA Department of Mathematics University of Nebraska-Lincoln Lincoln NE 68588 USA Korea Institute for Advanced Study Seoul 02455 Republic of Korea

Given any Coxeter group, we define rigid reflections and rigid roots using non-self-intersecting curves on a Riemann surface with labeled curves. When the Coxeter group arises from an acyclic quiver, they are related to the rigid representations of the quiver. For a family of rank 3 Coxeter groups, we show that there is a surjective map from the set of reduced positive roots of a rank 2 Kac-Moody algebra onto the set of rigid reflections. We conjecture that this map is bijective.

关键词： Coxeter groups rigid reflections rigid roots non-self-crossing curves Kac-Moody algebras

Response of phenology- and yield-related traits of maize to elevated temperature in a temperate region

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The Crop Journal 2017年第4期5卷 305-316页

作者： Dana Shim kyu-Jong lee Byun-Woo lee Department of Plant Science Seoul National University Seoul 151-921 Republic of Korea Research Institute for Agriculture and Life Sciences Seoul National University Seoul 151-921 Republic of Korea

Extreme high temperatures detrimental to maize production are projected to occur more frequently with future climate *** and yield-related traits were investigated under several levels of elevated temperature in two early-maturing hybrid cultivars:Junda 6(grown in northeastern China)and Chalok 1(grown in South Korea).They were cultivated in plastic houses in Suwon,Korea(37.27°N,126.99°E)held at target temperatures of ambient(AT),AT+1.5°C,AT+3°C,and AT+5°C at one sowing date in 2013 and three different sowing dates in *** and reproductive growth durations showed variation depending on sowing date,experimental year,and *** duration tended to decrease,but not necessarily,with temperature elevation,but somewhat increased again above a certain *** temperature-dependent variation was greater during grain filling than in the vegetative period before *** temperature showed no significant effects on duration or peak dates of silking and anthesis,and thus on anthesis–silking *** yield tended to decrease with temperature elevation above ambient,showing a sharper linear decrease with mean growing season temperature increase in Junda 6 than in Chalok *** decrease in kernel number accounted for a much greater contribution to the yield reductions due to temperature elevation than did the decrease in individual kernel weight in both *** harvestable kernel weight was not significantly affected by temperature elevation *** number showed a linear decrease with mean growth temperature from early ear formation to early grain-filling stage,with Junda 6 showing a much severer decrease than Chalok *** number reduction due to temperature elevation was attributable more to the decrease in differentiated ovule number than to the decrease in kernel set in Chalok 1,but largely to the decrease of kernel set in Junda 6.

关键词： Maize Elevated temperature Phenology Yield Yield-related traits

A Simple Embedding Method for the Laplace-Beltrami Eigenvalue Problem onImplicit Surfaces

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Communications on Applied Mathematics and Computation 2024年第2期6卷 1189-1216页

作者： Young kyu lee Shingyu Leung Department of Mathematics The Hong Kong University of Science and TechnologyClear Water BayHong KongChina

We propose a simple embedding method for computing the eigenvalues and eigenfunctions of the Laplace-Beltrami operator on implicit *** approach follows an embedding approach for solving the surface eikonal *** replace the differential operator on the interface with a typical Cartesian differential operator in the surface *** proposed algorithm is easy to implement and *** will give some two-and three-dimensional numerical examples to demonstrate the effectiveness of our proposed approach.

关键词： Laplace-Beltrami operator Level set method Implicit representation Eigenvalues Numerical PDEs

Effect of CaO composition on oxidation and burning behaviors of AM50 Mg alloy

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Transactions of Nonferrous Metals Society of China 2011年第A1期21卷 23-27页

作者： Jin-kyu lee Shae K.KIM Advanced Material Division Korea Institute of Industrial Technology 7-47 Songdo-Dong Yeonsu-Gu Incheon 406-840 Korea

Oxidation and burning behaviors were studied for CaO added AM50 Mg composites which were manufactured by conventional melting and casting processes without SF6 protective gas. CaO added AM50 Mg composites show the stable oxidation resistance, while AMS0 Mg alloys show the poor oxidation resistance. The effects of CaO addition on the burning resistance under ambient, nitrogen and dry air atmospheres were examined for CaO added AM50 Mg composites. With increasing CaO addition, the burning temperature increases under ambient, nitrogen and dry air atmospheres. The burning temperatures of small test specimen under all conditions greatly increase even by 0.3% CaO （mass fraction） addition into AM50 Mg alloys.

关键词： Mg alloy CaO oxidation behavior burning behavior

FEA technique of hot plate forming process using cell-typed die with cooling device

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中国有色金属学会会刊：英文版 2012年第S3期22卷 831-837页

作者： Jung-Min lee In-kyu lee kyung-Hun lee Dae-Soon KIM Byung-Min KIM Dongnam Regional Division Korea Institute of Industrial Technology School of Mechanical Engineering Pusan National University Industrial Technology Division Hyundai Heavy Industries

Hot plate forming using a cell-typed die is a process for forming a large thick plate with a spherical shape for the manufacture of a large spherical LNG ***-typed upper and lower dies made of a framework of steel plates fitted to make a grid pattern are used in this process,and an air-cooling device is separately installed inside the lower die.A finite element analysis (FEA) technique was developed,which included hot forming,air flow,cooling and thermal deformation analysis for the hot plate forming process using the cell-typed ***,the convective and interface heat transfer coefficients were used to reproduce analytically the effects of the cooling device in the hot plate forming analysis.A small-scale model test of the process was conducted to verify the FEA *** analysis results show that the curvature of the final plate agrees well with that of the designed experiment within a maximum relative error of 0.03% at the corner of the plate.

关键词： cell-typed die hot plate forming spherical LNG tank heat transfer coefficient

Electron beam deposition and characterization of thin film Ti-Ni for shape memory applications

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Rare Metals 2006年第Z2期25卷 237-242页

作者： NOH Hae-Yong JEE Kwang-Koo lee kyu-Hwan lee Young-Kook Department of Metallurgical System Yonsei University Seoul 120-749 KoreaAdvanced Materials Research Center Division of Materials Korea Institute of Science and Technology Cheongryang Seoul 130-650 Korea Advanced Materials Research Center Division of Materials Korea Institute of Science and Technology Cheongryang Seoul 130-650 Korea Department of Metallurgical System Yonsei University Seoul 120-749 Korea

Thin film of Ti-Ni alloy has a potential to perform the microactuation functions required in the microelectromechanical system (MEMS). It is essential, however, to have good uniformity in both chemical composition and thickness to realize its full potential as an active component of MEMS devices. Electron beam evaporation technique was employed in this study to fabricate the thin films of Ti-Ni alloy on different substrates. The targets used for the evaporation were first prepared by electron beam melting. The uniformity of composition and microstructure of the thin films were characterized by electron probe microanalysis (EPMA), Auger electron spectroscopy (AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). The mechanical property of the thin films was evaluated by the nano-indentation test. The martensitic transformation temperature was measured by differential scanning calorimetry (DSC). It is confirmed that the chemical composition of deposited thin films is identical to that of the target materials. Furthermore, results from depth profiling of the chemical composition variation reveal that the electron beam evaporation process yields better compositional homogeneity than other conventional methods such as sputtering and thermal evaporation. Microstructural observation by TEM shows that nanometer size precipitates are preferentially distributed along the grain boundaries of a few micron size grains. The hardness and elastic modulus of thin films decreases with an increase in Ti contents.

关键词： electron beam evaporation TiNi SMA thin film martensitic transformation reverse martensitic transformation

Colored ultrathin hybrid photovoltaics with high quantum efficiency

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Light(Science & Applications) 2014年第1期3卷 36-42页

作者： kyu-Tae lee Jae Yong lee Sungyong Seo L Jay Guo Department of Electrical Engineering and Computer Science The University of MichiganAnn ArborMichigan 48109USA

Most current solar panels are fabricated via complex processes using expensive semiconductor materials,and they are rigid and heavy with a dull,black *** a result of their non-aesthetic appearance and weight,they are primarily installed on rooftops to minimize their negative impact on building *** large surfaces and interiors of modern buildings are not efficiently utilized for potential electric power ***,we introduce dual-function solar cells based on ultrathin dopant-free amorphous silicon embedded in an optical cavity that not only efficiently extract the photogenerated carriers but also display distinctive colors with the desired angle-insensitive ***-energy-harvesting colored signage is ***,a cascaded photovoltaics scheme based on tunable spectrum splitting can be employed to increase power efficiency by absorbing a broader band of light *** study pioneers a new approach to architecturally compatible and decorative thin-film photovoltaics.

关键词： color filters nanocavities organic–inorganic nanostructures photovoltaics spectrum splitting

High-performance colorful semitransparent perovskite solar cells with phase-compensated microcavities

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Nano Research 2018年第5期11卷 2553-2561页

作者： kyu-Tae lee Ji-Yun Jang Na Young Ha Soonil lee Hui Joon Park Department of Materials Science and Engineering University of Illinois Urbana Illinois 61801 USA Department of EnergySystems Research Ajou University Suwon 16499 Republic of Korea Department of Electrical and Computer Engineering Ajou University Suwon 16499 Republic of Korea

We demonstrate highly efficient multi-colored semitransparent perovskite solar cells that can create high angular tolerant controllable transmissive colors up to 60~, based on phase-compensated microcavities. The efficiency of the semitransparent colors was improved by impedance matching, which was enabled by placing a dielectric functional layer on top of traditional optical microcavities, with negligible influence on color pureness. The vast majority of the visible part of solar radiation is efficiently utilized for solar energy harvesting, achieving 10.47%, 10.66%, and 11.18% of efficiency for red, green, and blue （RGB） colored solar cells, respective136 while a very small proportion of the visible solar spectrum is used for structural coloration that can be readily tuned by altering the cavity medium thickness. The approach described herein can be suitable for a variety of applications such as display systems with ultra-low power consumption, highly efficient colorful solar panels, low-power wearable electronics, and energy-efficient optoelectronics.

关键词： perovskite solar cells semitransparency color filters optical cavities

IMPROVING THE ENVIRONMENTAL PERFORMANCE OF FISH-FARMING HOUSES:A COMPARATIVE PASSIVE DESIGN STUDY IN SOUTH KOREA

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Journal of Green Building 2020年第2期15卷 71-90页

作者： kyu-In lee Yoon-Boum Cho Hwang Yi Department of Architecture Ajou University206 World cup-roYeongtong-guSuwon-SiGyeonggi-do443-749South Korea

Aquaculture in South Korea largely involves crudely-built plastic fishery houses that consume excessive electricity and produce carbon *** study explores a potential method to make Korean aquaculture more sustainable by suggesting design alternatives that can save energy and *** this end,the authors compare the energy use and indoor environments of three different designs through field *** three designs include(i)a triple-layered plastic screen house(Design 1),(ii)an insulated vault house(Design 2),and(iii)a passive-house design(Design 3),in addition to(iv)a single-layered plastic house(baseline).Our findings indicate that,compared to the baseline,operational electricity was reduced to 57.81% in Design 1,53.92% in Design 2,and 40.59% in Design ***,Designs 2 and 3 were able to mitigate indoor temperature fluctuations in *** 1 showed a relatively unstable temperature distribution during the night but offered better farming conditions than the *** often rose to 100% but did not affect the maintenance of a desirable fish and workplace *** a high concentration of carbon dioxide of up to 3,000 ppm in Designs 1 and 2 was not expected to harm farmers’*** analyses revealed that construction expenses increased to 20.9% in Design 1,135.8% in Design 2,and 73.9% in Design 3 due to large quantities of materials and *** trade-offs with energy saving,the payback period is 7.2 years for Design 1,35.5 years for Design 2,and 17.9 years for Design *** that the lifetime expectancy of Designs 1 and 3 is over two years,the study’s results confirm that Designs 1 and 3 have a comparative advantage in producing sustainable fish-farming houses.

关键词： passive house Building performance fish-farming house aquaculture sustainability