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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

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

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

Experimental Investigation and Numerical Analysis to Develop Low-Energy Large-Midwater Trawls

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China Ocean Engineering 2017年第6期31卷 700-708页

作者： Jihoon lee Taeho KIM Chun-Woo lee Subong PARK Division of Marine Technology Chonnam National University Yeosu 550-749 Korea Division of Marine Production System Management Pukyong National University Busan 608-737 Korea Department of Fisheries Physics Pukyong National University Busan 608-737 Korea

Fuel consumption in fisheries is a primary concern because of its effects on the environment and the costs incurred by fishermen. Many studies have been conducted to reduce the fuel consumption in fishing operations. Fuel consumption due to fishing gear during a fishing operation is generally related to the hydrodynamic resistance on the gear. This means that fuel consumption is proportional to the drag created by the towing speed. Based on numerical methods, this study suggests a new approach to reduce fuel consumption in fisheries. The results of the simulation are in good agreement with those of model experiments. The total as well as partial resistance forces on the gear are calculated by simulation. The simulation results suggest improved materials and gear structure for reducing the hydrodynamic forces on the gear while maintaining gear performance. The method for assessing the gear performance involves measuring the height and width of the net mouth. Furthermore, this study investigates the efficiency of a low-energy trawl from an economic point of view. The findings of this study will be useful in reducing greenhouse gas （GHG） emissions in fishing operations, and thereby contribute toward lowering fishing costs by saving fuel.

关键词： low-energy fishing gear numerical methods greenhouse gasesemission hydrodynamic resistance fuelconsumption

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

A numerical study of turbulent combustion characteristics in a combustion chamber of a scramjet engine

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Science China(Technological Sciences) 2010年第8期53卷 2111-2121页

作者： lee ChunHian School of Aeronautical Sciences and Engineering Beihang University

3D numerical simulation of flow fields in a combustion chamber of a scramjet engine using an SST turbulence model with an explicit compressibility correction was performed and the results were compared to the experimental *** characteristics of the turbulent combustion flow fields were analyzed via the numerical results and *** order to identify the mechanisms of turbulent combustion in supersonic flows,the evolutions of governing dimensionless parameters in the flow fields were investigated based on the theory of combustion and the available numerical *** was found that the supersonic combustion takes place in the region of fully developed turbulence and that the strongest effects of turbulence and combustion processes appear in the vicinity of the *** unsteady effects and the local flame extinction phenomenon induced by turbulent flows were found to be negligibly small,and the steady flamelet approximation will hold for practical applications.

关键词： scramjet turbulent combustion flamelet approximation numerical simulation

Characterization of the three-dimensional supersonic flow for the MHD generator

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Science China(Physics,Mechanics & Astronomy) 2009年第4期52卷 534-545页

作者： lee ChunHian National Laboratory for Computational Fluid Dynamics Beihang University

A numerical procedure based on a five-wave MHD model associated with non-ideal,low magnetic Reynolds number MHD flows was developed in the present study for analyzing the flow fields in the MHD generator of a MHD bypass scramjet. The numerical procedure is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations,in conjunction with an SOR method for solving the elliptic equation governing the electrical potential. It was found that a separation would take place near the downstream edge of the second electrode,where the local adverse pressure gradient is large,and the core of the flow field is characterized as a 2-D flow due to the Hartmann effects along the direction of the magnetic field. The electric current lines would be increasingly distorted as the magnetic interactive parameter increases,and even induce an eddy current. Induced eddy current was also found in the different cross-sections along the axial direction,all of these would definitely deteriorate the performance of the MHD generator. The cross-sectional M-shape velocity profile found along the axial direction between the insulating walls is responsible for the formation of the vortex flow at the corner of the insulator cross-section,which,in turn,induces the corner eddy current at the corner. A numerical parametric study was also performed,and the computed performance parameters for the MHD generator suggest that,in order to enhance the performance of MHD generator,the magnetic interaction parameter should be elevated.

关键词： MHD generator entropy conditioned scheme SOR numerical simulation