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Block Incremental Dense Tucker Decomposition with Application to Spatial and Temporal Analysis of Air Quality Data

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Computer Modeling in Engineering & Sciences 2024年第4期139卷 319-336页

作者： SangSeok lee HaeWon Moon lee Sael Department of Artificial Intelligence Ajou UniversitySuwon-si16499Korea Department of Software and Computer Engineering Ajou UniversitySuwon-si16499Korea

How can we efficiently store and mine dynamically generated dense tensors for modeling the behavior of multidimensional dynamic data?Much of the multidimensional dynamic data in the real world is generated in the form of time-growing *** example,air quality tensor data consists of multiple sensory values gathered from wide locations for a long *** data,accumulated over time,is redundant and consumes a lot ofmemory in its raw *** need a way to efficiently store dynamically generated tensor data that increase over time and to model their behavior on demand between arbitrary time *** this end,we propose a Block IncrementalDense Tucker Decomposition(BID-Tucker)method for efficient storage and on-demand modeling ofmultidimensional spatiotemporal *** that tensors come in unit blocks where only the time domain changes,our proposed BID-Tucker first slices the blocks into matrices and decomposes them via singular value decomposition(SVD).The SVDs of the time×space sliced matrices are stored instead of the raw tensor blocks to save *** modeling from data is required at particular time blocks,the SVDs of corresponding time blocks are retrieved and incremented to be used for Tucker *** factor matrices and core tensor of the decomposed results can then be used for further data *** compared our proposed BID-Tucker with D-Tucker,which our method extends,and vanilla Tucker *** show that our BID-Tucker is faster than both D-Tucker and vanilla Tucker decomposition and uses less memory for storage with a comparable reconstruction *** applied our proposed BID-Tucker to model the spatial and temporal trends of air quality data collected in South Korea from 2018 to *** were able to model the spatial and temporal air quality *** were also able to verify unusual events,such as chronic ozone alerts and large fire events.

关键词： Dynamic decomposition tucker tensor tensor factorization spatiotemporal data tensor analysis air quality

Joint member angle limits of composite beams and CFT square columns

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Journal of Central South University 2013年第1期20卷 199-206页

作者： lee Seung-Jo lee Kang-Guk Department of Architecture Chosun College of Science & Technology Research Center for Urban Affair Kyungil University

This work aims to understand the relationship between the member angle limit and the energy ratio for 24 test samples of composite beams and CFT square steel tube columns. This work also compares the formula applicability for member angle limit with the previous test result to provide the basic data for the design of composite beam-CFT column. The evaluation of the member angle limit was performed with concrete compressive strength (fC =22.16 MPa, 30.49 MPa), breadth-to-thickness ratio (B/t=25.0, 33.3, 43.5), and axial capacity ratio (N/N0=0, 0.3, 0.4, 0.5) as the main variables of the test samples. For the relationship between the member angle limit (Ru) and the energy ratio (ES/EC ), the test result shows that the energy ratio becomes lower as the axial capacity ratio and the breadth-to-thickness ratio increase. The energy ratio is lower for the Type B test sample compared with that of Types A and C. For the formula suggested by SATO, the test samples are distributed evenly for comparison between test values and the member angle limit; however, other formulas indicate a deviation. Specifically, for the comparison between R u,cal and R u (Test), Maeda's formula shows severe deviation.

关键词： square steel tube axial capacity ratio member angle limit breadth-to-thickness ratio

Landau damping of twisted waves in Cairns distribution with anisotropic temperature

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Plasma Science and Technology 2021年第8期23卷 18-28页

作者： Sunggeun lee Hankwon LIM School of Energy and Chemical Engineering UNIST50UNIST-gilEonyang-eupUlju-gunUlsan 44919Republic of Korea

The consideration of orbital angular momentum of an electric field(twisted mode)is applied to the kinetic theory of *** linearized Vlasov–Poisson equation is solved for the anisotropic thermal distributed bi-Maxwellian and Cairns distributions of electrons to obtain the damping rates of twisted *** dispersion relation and Landau damping of Langmuir twisted modes are *** presence of twisted modes opens up two more possibilities in Landau damping and dispersion *** may generate a mixture with ion sound *** seems to play the role of a control parameter of Landau damping.

关键词： Landau damping Cairns distribution function anisotropic

Development of analysis model for geometric error in turning processes

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Journal of Central South University 2011年第3期18卷 711-717页

作者： lee Mun-jae lee Choon-man Department of Mechanical Design and Manufacturing Engineering Changwon National University

A finite element model was established for analyzing the geometric errors in turning operations and a two-step analyzing process was proposed. In the first analyzing step, the cutting force and the cutting heat for the cutting conditions were obtained using the AdvantEdge. Also, the deformation of a workpiece was estimated in the second step using the ANSYS. The deformation was analyzed for a 150 mm-long workpiece at three different measuring points, such as 10, 70 and 130 mm from a reference point, and the amounts of the deformation were compared through experiments. /n the results of the comparison and analysis, the values obtained from these comparison and analysis represent similar tendencies. Also, it is verified that their geometric errors increase with the increase in temperature. In addition, regarding the factors that affect the deformation of a workpiecc, it can be seen that the geometric error in the lathe is about 15%, the error caused by the cutting force is about 10%, and the deformation caused by the heat is about 75%.

关键词： geometric error machining accuracy finite element analysis turning cutting force, cutting temperature

Reversible faradaic reactions involving redox mediators and oxygen-containing groups on carbon fiber electrode for high-performance flexible fibrous supercapacitors

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Journal of Energy Chemistry 2022年第5期31卷 1-11页

作者： Soobeom lee Geon-Hyoung An Department of Energy Engineering Gyeongsang National UniversityJinju 52849Republic of Korea Future Convergence Technology Research Institute Gyeongsang National UniversityJinju 52849Republic of Korea

Flexible fibrous supercapacitors(FFS)are taking account of as the energy storage devices for wearable electronics owing to their high power density,high safety,long cycle life,and simple manufacturing ***,FFSs have the disadvantage of low specific capacitance that results from the electrochemical characteristics of the electrical double layer on the carbon fiber *** this study,for the first time,an FFS comprising surface-activated carbon fibers as an electrode/current collector and a redox additive gel polymer electrolyte(FFS-SARE)was fabricated for use as a wearable energy storage *** FFS-SARE showed outstanding electrochemical performance,namely,high specific capacitances of 891 and 399 mF cm^(-2) at current densities of 70.0 and 400 μA cm^(-2),respectively,and remarkable ultrafast cycling stability over 5000 cycles with 92%capacitance retention at a current density of 400.0 μA cm^(-2).Moreover,they exhibited mechanical flexibility and had high feasibility,and they showed good energy storage performance that renders them suitable for use in wearable electronic textiles.

关键词： Interface engineering Fibrous supercapacitor Redox additive gel polymer electrolyte Porous structure

Regulating interfacial stability of SiO_(x) anode with fluoride-abundant solid–electrolyte interphase by fluorine-functionalized additive

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Rare Metals 2024年第2期43卷 671-681页

作者： Subin lee Taeeun Yim Advanced Batteries Laboratory Department of ChemistryIncheon National UniversityIncheon22012Republic of Korea Research Institute of Basic Sciences College of Natural ScienceIncheon National UniversityIncheon22012Republic of Korea

Silicon oxide(SiO_(x))has received remarkable attention as a next-generation battery material;however,the sudden decrease in the cycling retention constitutes a significant challenge in facilitating its ***(2,2,2-trifluoroethyl)phosphite(TTFP),which can control parasitic reactions such as the pulverization of SiO_(x)anode materials and electrolyte decomposition,has been proposed to improve the lifespan of the *** electrochemical reduction of TTFP results in solid-electrolyte interphase(SEI)layers that are mainly composed of LiF,which occur at a higher potential than the working potential of the SiO_(x)anode and carbonate-based *** electrolyte with TTFP exhibited a substantial improvement in cycling retention after 100 cycles,whereas the standard electrolyte showed acutely decreased *** thickness of the SiO_(x)anode with TTFP also changed only slightly without any considerable delamination spots,whereas the SiO_(x)anode without TTFP was prominently deformed by an enormous volume expansion with several internal *** cycled SiO_(x)anode with TTFP exhibited less increase in resistance after cycling than that in the absence of TTFP,in addition to fewer decomposition adducts in corresponding X-ray photoelectron spectroscopy(XPS)analyses between the cycled SiO_(x)*** results demonstrate that TTFP formed SEI layers at the SiO_(x)interface,which substantially reduced the pulverization of the SiO_(x)anode materials;in addition,electrolyte decomposition at the interface decreased,which led to improved cycling retention.

关键词： Lithium-ion batteries(LIBs) Silicon oxide anode Electrolyte Additive Solid-electrolyte interphases(SEI) Tris(2,2,2-trifluoroethyl)phosphite

Preparation of Polyester Polyol from Epoxidized Palm Olein

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Chinese Journal of Chemistry 2011年第4期29卷 840-846页

作者： lee, Choy Sin lee, Song Cang Pharmaceutical Chemistry Department International Medical University No 126 Jalan 19/155B Bukit Jalil 57000 KL Malaysia Biomedical Engineering Department Faculty of Engineering University of Malaya 50603 KL Malaysia

In this work, polyester polyols with high weight average molecular weight （Mw）（Mw= 10000-15000） were prepared from epoxidized palm olein （EPOo） and a series of dicarboxylic acids （C6-C12） at elevated temperature under non-catalyzed condition. The optimal reaction conditions were determined as 180 ℃ for 4 h. Longer carbon chain length of dicarboxylic acids was more reactive when reacted with EPOo. The physical appearance of the product was observed as liquid at room temperature. This palm oil-based polyester polyol is proposed as starting material for flexible polyurethane. For reaction monitoring purposes, FTIR was used while 1H NMR analysis was carried out to characterize the important functional groups of the products. The effects of reaction time and temperature on the Mw of the reaction mixture were also studied by GPC.

关键词： dicarboxylic acids epoxidized palm olein polyester poyol

Effects of surface roughness on bending properties of rolled AZ31 alloy

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Journal of Magnesium and Alloys 2023年第4期11卷 1224-1235页

作者： Gyo Myeong lee Jong Un lee Sung Hyuk Park School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea

This study investigated the effects of mechanical-polishing-induced surface roughness and the direction of polishing lines on the bending properties of a rolled AZ31 *** this end,three-point bending tests were performed on one sample without polishing lines(SS sample)and two samples with polishing lines—one in which the polishing lines were parallel to the rolling direction(RS-RD sample)and the other in which they were parallel to the transverse direction(RS-TD sample).In all three samples,macrocracks were formed in the width direction on the outer surface,where tensile stress was predominantly generated in the longitudinal ***,the macrocracks formed in the SS sample were curved because of the merging of uniformly formed fine microcracks,whereas those formed in the RS-TD sample were linear owing to the formation of relatively coarse microcracks along the polishing *** bendability of the samples was in the order of SS>RS-RD>RS-TD,and their limiting bending depths were 4.8,4.6,and 4.4 mm,*** the presence of mechanical-polishing-induced surface roughness,polishing lines perpendicular to the direction of the major stress(i.e.,tensile stress along the longitudinal direction)resulted in a greater degree of stress concentration on the outer surface of the bending *** higher stress concentration promoted the formation of undesirable{10–11}contraction and{10–11}–{10–12}double twins—which typically act as crack initiation sites—and thereby facilitated crack generation and ***,the surface roughness caused premature fracture during bending deformation,which,in turn,caused deterioration of the bendability of the rolled Mg alloy.

关键词： AZ31 alloy Bending Surface roughness Stress concentration Crack

A Favré averaged transition prediction model for hypersonic flows

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Science China(Technological Sciences) 2010年第8期53卷 2049-2056页

作者： lee ChunHian School of Aeronautical Sciences and Engineering Beijing University of Aeronautics and Astronautics

Transition prediction is crucial for aerothermodynamic and thermal protection system design of hypersonic *** compressible form of laminar kinetic energy equation is derived based on Favréaverage formality in the present paper.A closure of the equation is deduced and simplified under certain hypotheses and scaling analysis.A laminar-to-turbulent transition prediction procedure is proposed for high Mach number flows based on the modeled Favré-averaged laminar kinetic energy equation,in conjunction with the Favré-averaged Navier-Stokes *** proposed model,with and without associated explicit compressibility terms,is then applied to simulate flows over flared-cones with a free-stream Mach number of 5.91,and the onset locations of the boundary layer transition under different wall conditions are *** computed onset locations are compared with those obtained by the model based on a compressibility correction deduced from the reference-temperature concept,together with experimental *** is revealed that the present model gives a more favorable transition prediction for hypersonic flows.

关键词： transition prediction laminar fluctuation hypersonic compressibility