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.

Active Disturbance Rejection Position Control for a Magnetic Rodless Pneumatic Cylinder

Abstract: This paper presents an active disturbance rejection position control scheme for a magnetic rodless cylinder in servo systems without pressure states. It is very hard to achieve precise position control of magnetic rodless cylinders due to nonlinearity from large friction force and hysteresis. In this paper, the overshoot, which has a negative influence on position control, is effectively reduced by using a tracking differentiator. Furthermore, the nonlinearity is estimated by a designed extended-state observer. In addition, the self-stable region theory is used to prove the convergence of the extended-state observer. Finally, both control precision and response speed are guaranteed via a nonlinear error feedback controller in the pneumatic system. Experimental results show that the steady-state error within 0.05 mm is achieved for a step signal.

Top-Down Strategy to Synthesize Mesoporous Dual Carbon Armored MnO Nanoparticles for Lithium-Ion Battery Anodes

Abstract: To overcome inferior rate capability and cycle stability of MnO-based materials as a lithium-ion battery anode associated with the pulverization and gradual aggregation during the conversion process, we constructed robust mesoporous N-doped carbon (N–C) protected MnO nanoparticles on reduced graphene oxide (rGO) (MnO@N–C/rGO) by a simple top-down incorporation strategy. Such dual carbon protection endows MnO@N–C/rGO with excellent structural stability and enhanced charge transfer kinetics. At 100 mA g–1, it exhibits superior rate capability as high as 864.7 mAh g–1, undergoing the deep charge/discharge for 70 cycles and outstanding cyclic stability (after 1300 cyclic tests at 2000 mA g–1; 425.0 mAh g–1 remains, accompanying merely 0.004% capacity decay per cycle). This facile method provides a novel strategy for synthesis of porous electrodes by making use of highly insulating materials.

Enabling immobilization and conversion of polysulfides through a nitrogen-doped carbon nanotubes/ultrathin MoS2 nanosheet core–shell architecture for lithium–sulfur batteries

Abstract: Lithium–sulfur batteries are widely considered as promising next generation energy storage devices due to their high energy density and low cost. However, the shuttle effect and sluggish kinetics of polysulfide conversion are still key challenges for practical application. Herein, we designed hierarchical nitrogen-doped carbon nanotubes/ultrathin molybdenum disulfide nanosheets in a core–shell architecture (denoted as NC@MoS2) to alleviate the shuttle effect and propel redox reaction kinetics, thereby improving the electrochemical performance of lithium–sulfur batteries. Both experimental investigations and theoretical studies reveal that MoS2 nanosheets can chemically immobilize lithium polysulfides and catalyze the conversion of polysulfides. Moreover, this unique core–shell architecture could facilitate rapid electrical transport and favorable electrolyte infiltration. We have demonstrated that the obtained S–NC@MoS2 cathodes exhibit excellent rate capability (516 mA h g−1 at 5C) and superior cycle stability (only 0.049% capacity decay per cycle up to 1000 cycles at 2C). Remarkably, the composite cathode with a high sulfur loading of 3.6 mg cm−2 still maintains high rate capability and stable cycling performance over 300 cycles. This work offers a new strategy to develop high-performance lithium–sulfur batteries through the exploration of two-dimensional mediator catalysts.

Effects of high pressure torsion on microstructures and properties of an Al0.1CoCrFeNi high-entropy alloy

Abstract: High pressure torsion (HPT) under a pressure of 6 GPa through 1 and 2 revolutions have been used to follow the evolution of microstructures and properties in an Al0.1CoCrFeNi high-entropy alloy (HEA). The plastic-deformation mechanisms of the HEA include dislocation slip at low strains and twinning at high strains at room temperature. The planar dislocation slip on the normal face-centered-cubic slip system, {111}〈110〉, and nanoscaled deformation twins with a thickness from several nanometers to 40 nm, accompanied with some secondary twins. The hardness of the Al0.1CoCrFeNi HEA increases from 135 Hv at hot-isostatic pressed (HIPed) state to about 482 Hv after HPT processing. The HEAs have a relatively high initial hardness and high work hardening, compared with traditional alloys. The creep resistance of the HEA processed by HPT was determined by a nanoindentation technique. The strain rate sensitivity, m, increases with the decreasing of grain size, for smaller activation volume and the dominant deformation mechanism changing from the dislocation slip to grain-boundary slide. The present results give the plastic-deformation mechanism and mechanical properties evolution of single-phase HEA processed by HPT at room temperature.