Yanshan University

About: Yanshan University is a education organization based out in Qinhuangdao, China. It is known for research contribution in the topics: Microstructure & Control theory. The organization has 19544 authors who have published 16904 publications receiving 184378 citations. The organization is also known as: Yānshān dàxué.

Decoupling the Voltage Hysteresis of Li-Rich Cathodes: Electrochemical Monitoring, Modulation Anionic Redox Chemistry and Theoretical Verifying

Abstract: Cathodes in lithium-ion batteries with anionic redox can deliver extraordinarily high specific capacities but also present many issues such as oxygen release, voltage hysteresis, and sluggish kinetics. Identifying problems and developing solutions for these materials are vital for creating high-energy lithium-ion batteries. Herein, the electrochemical and structural monitoring is conducted on lithium-rich cathodes to directly probe the formation processes of larger voltage hysteresis. These results indicate that the charge-compensation properties, structural evolution, and transition metal (TM) ions migration vary from oxidation to reduction process. This leads to huge differences in charge and discharge voltage profile. Meanwhile, the anionic redox processes display a slow kinetics process with large hysteresis (≈0.5 V), compared to fast cationic redox processes without any hysteresis. More importantly, a simple yet effective strategy has been proposed where fine-modulating local oxygen environment by the lithium/oxygen (Li/O) ratio tunes the anionic redox chemistry. This effectively improves its electrochemical properties, including the operating voltage and kinetics. This is also verified by theoretical calculations that adjusting anionic redox chemistry by the Li/O ratio shifts the TM 3d—O 2p bands and the non-bonding O 2p band to a lower energy level, resulting in a higher redox reaction potential.

New crystal structure and discharge efficiency of poly(vinylidene fluoride-hexafluoropropylene)/poly(methyl methacrylate) blend films

Abstract: A series of PMMA/poly(vinylidene fluoride-hexafluoropropylene) [P(VDF-HFP)] blend films were prepared with a solution blending process to improve discharge efficiency. The crystal structure and properties of the PMMA/P(VDF-HFP) blend films were carefully studied. The results show that the crystallinity, the dielectric constant and the loss of the polymer blend films decreased, while melting temperature increased with the increase in PMMA content. The XRD results demonstrate the existence of a γ-2b phase. It is believed that the phase transition of the P(VDF-HFP) crystals from α to γ-2b contributes to the increase in melting temperature. The energy loss of P(VDF-HFP) reduced significantly with the addition of PMMA. The blend film with 10% PMMA showed the best discharge efficiency with a value above 80% in 300 MV m−1. This increase in discharge efficiency is thought to result mainly from the formation of γ crystals.

MPC-Based Cooperative Control Strategy of Path Planning and Trajectory Tracking for Intelligent Vehicles

Abstract: In this paper, we propose a progressive model predictive control scheme (PMPCS) by considering the cooperative control of local planning and path tracking for intelligent vehicles. An improved particle swarm optimization (IPSO) based model predictive control (MPC) method is developed to solve the planning and tracking problem. With the PMPCS, the total computational burden can be reduced sharply because of the seamless connection and mutual promotion between the optimization of two layers. Besides we also propose a novel planning algorithm, which can take traffic lights and overtaking time constraint into account. To solve these problems, we first combine model predictive control with artificial potential field (APF) to get a collision-free path by treating the time-varying safety constraints as the scope of the repulsive force and an asymmetrical lane potential field function. Furthermore, the pseudo velocity planning method is adopted to take traffic lights into account in the planning module. Simulation results show the reliability of the proposed algorithm and the advantages of the scheme compared with general hierarchical algorithm.

A novel process to obtain ultrafine-grained low carbon steel with bimodal grain size distribution for potentially improving ductility

Abstract: A novel process to obtain ultrafine-grained low carbon steel with bimodal grain size distribution was developed for potentially improving the ductility of ultrafine-grained steels. In this process, a low carbon steel with dual-phase starting microstructure composed of martensite and ferrite obtained by predeformation intercritical quenching was compressively deformed at room temperature and annealed at moderate temperatures. Results show that the ultrafine-grained ferrite with bimodal grain size distribution and dispersive nanoscale carbide particles was achieved.