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- 저자 : Junpeng Yang (검색결과 5 건)
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Junpeng Yang,Qi Cai,Yongchang Liu,Chong Li,Zongqing Ma,Huijun Li 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
The W-modifi ed Ti 2 AlNb-based alloys synthesized at 1100 °C by spark plasma sintering were solution treated at 1300 °Cfor 4 h and then aged at 800–1000 °C for 1 h. The phase composition, microstructure evolution, and microhardness of theaged alloys are investigated in this study. A signifi cant enhancement of hardness, ~ 750 HV, is obtained in the alloy aged at900 °C, while that of the one without W addition is only ~ 470 HV. The hardness is also higher than that of common β-Ti andTi–6Al–4V alloys. As the ageing temperature increases, the B2/O structure evolves from B2 + O colonies to Widmannstättenstructure, followed by a “disordering to ordering” procedure. This process also involves the variation of the angle betweenadjacent O phase from 90° to 60°. Specifi cally, a herringbone Widmannstätten B2 + O structure is constructed in the alloysaged in the α 2 + B2 + O phase region, which is related to the diff usion of W and the substitution of W for Nb in the latticeof B2 or O.
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Ma, Junpeng,Fan, Jingbiao,Chen, Shang,Yang, Xinyue,Hui, Kwun Nam,Zhang, Hongwen,Bielawski, Christopher W.,Geng, Jianxin American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.14
<P>Lithium-sulfur (Li-S) batteries have received significant attention due to the high theoretical specific capacity of sulfur (1675 mA h g<SUP>-1</SUP>). However, the practical applications are often handicapped by sluggish electrochemical kinetics and the “shuttle effect” of electrochemical intermediate polysulfides. Herein, we propose an in-situ copolymerization strategy for covalently confining a sulfur-containing copolymer onto reduced graphene oxide (RGO) to overcome the aforementioned challenges. The copolymerization was performed by heating elemental sulfur and isopropenylphenyl-functionalized RGO to afford a sulfur-containing copolymer, that is, RGO-<I>g</I>-poly(S-<I>r</I>-IDBI), which is featured by a high sulfur content and uniform distribution of the poly(S-<I>r</I>-IDBI) on RGO sheets. The covalent confinement of poly(S-<I>r</I>-IDBI) onto RGO sheets not only enhances the Li<SUP>+</SUP> diffusion coefficients by nearly 1 order of magnitude, but also improves the mechanical properties of the cathodes and suppresses the shuttle effect of polysulfides. As a result, the RGO-<I>g</I>-poly(S-<I>r</I>-IDBI) cathode exhibits an enhanced sulfur utilization rate (10% higher than that of an elemental sulfur cathode at 0.1C), an improved rate capacity (688 mA h g<SUP>-1</SUP> for the RGO-<I>g</I>-poly(S-<I>r</I>-IDBI) cathode vs 400 mA h g<SUP>-1</SUP> for an elemental sulfur cathode at 1C), and a high cycling stability (a capacity decay of 0.021% per cycle, less than one-tenth of that measured for an elemental sulfur cathode).</P> [FIG OMISSION]</BR>
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Jin Xianjian,Wang Zhaoran,Yang Junpeng,Xu Liwei,Yin Guodong 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.5
Lightweight electric vehicles (LEVs) possess great advantages in the viewpoint of fuel consumption, environment protection and traffic mobility. However, due to the drastic reduction of vehicle weights and body size, the effects of payload parameter variation in LEV control and estimation system become much more pronounced and have to be systematically analysed. This paper proposes a novel payload parameter sensitivity analysis to provide quantitative insight into the sensitivity of payload parameter on the LEV system responses and state estimation. The analysis-oriented LEV dynamic model considering payload parameter variations is developed. Then, the trajectory sensitivity index of the influential parameters is defined and derived with the perturbation approach, the median method is used to improve the calculation accuracy for the trajectory sensitivity of payload parameter. Finally, the extended Kalman filter is designed to show the effect and importance of the sensitive payload parameters on the observation accuracy, the payload parameter variations along with fundamental state estimation such as vehicle sideslip angle, longitudinal velocity and vehicle roll angle are analysed. Simulation results with Matlab/Simulink-Carsim® show that the proposed method can accurately describe the relationship between the vehicle payload parameters and system state estimation, which is helpful to design and evaluate LEV controller and observer performances.
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Jun Peng,Qian Wang,Jin Wang,Jun Yang,Taijun Jiang,Guangsheng Zeng 한국고분자학회 2022 Macromolecular Research Vol.30 No.11
Cardo containing phenoxy and -CF3 derivate diamine was synthesized, and further it was polymerized with 3,3',4,4'-biphenyl tetracarboxylic dianhydride to prepare polyetherimide containing Cardo group. The transmittance of the prepared polymer increased from 82% to 88% and the dielectric constant decreased from 2.91 to 2.83 with a slight decline in thermal and mechanical performance when -CF3 was introduced. The molecular simulation in terms of charge distribution, electric potential energy, chain stiffness and aggregation state revealed that -CF3 could restrain charge transfer and decrease the unit dipole moment and polarization for its larger volume. The optical and dielectric performance was significantly enhanced, but the thermal and mechanical performance decreased slightly when the -CF3 group was introduced. The glass transition temperature of the polymer declined from 329℃ to 311℃. The investigation conducted in this paper can offer valuable reference to the optimization and development of synthesis and comprehensive performance of polyimide.
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