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.

Immobilizing Polysulfides with MXene-Functionalized Separators for Stable Lithium-Sulfur Batteries.

Abstract: Lithium-sulfur batteries have attracted increasing attention as one of the most promising candidates for next-generation energy storage systems. However, the poor cycling performance and the low utilization of sulfur greatly hinder its practical applications. Here we report the improved performance of lithium-sulfur batteries by coating Ti3C2Tx MXene nanosheets (where T stands for the surface termination, such as -O, -OH, and/or -F) on commercial "Celgard" membrane. In favor of the ultrathin two-dimensional structure, the Ti3C2Tx MXene can form a uniform coating layer with a minimum mass loading of 0.1 mg cm-2 and a thickness of only 522 nm. Owing to the improved electric conductivity and the effective trapping of polysulfides, the lithium-sulfur batteries with MXene-functionalized separators exhibit superior performance including high specific capacities and cycling stability.

Type synthesis of 3R2T 5-DOF parallel mechanisms using the Lie group of displacements

Abstract: The use of lower mobility parallel manipulators with less than six degrees of freedom (DOFs) has drawn a lot of interest in the area of parallel robots In this paper, the type synthesis of 3R2T 5-DOF parallel mechanisms (PMs) is performed systematically using the Lie group of displacements, where R denotes a rotational DOF, and T denotes a translational DOF First, some necessary theoretical fundamentals about the displacement group are recalled Then, a general approach is proposed for the type synthesis of 3R2T 5-DOF PMs The limb kinematic chains, which produce the desired displacement manifolds, are synthesized and enumerated Structural conditions, which guarantee that the intersection of the displacement manifolds generated by the limb is the desired 5-DOF manifold, are presented An exhaustive enumeration of 3R2T 5-DOF symmetrical PMs is obtained Finally, an input selection method is proposed

Novel Superhard Carbon: C-Centered Orthorhombic C 8

Abstract: A novel carbon allotrope of C-centered orthorhombic ${\mathrm{C}}_{8}$ ($\mathrm{Cco}\mathrm{\text{\ensuremath{-}}}{\mathrm{C}}_{8}$) is predicted by using a recently developed particle-swarm optimization method on structural search. $\mathrm{Cco}\mathrm{\text{\ensuremath{-}}}{\mathrm{C}}_{8}$ adopts a $s{p}^{3}$ three-dimensional bonding network that can be viewed as interconnected $(2,2)$ carbon nanotubes through 4- and 6-member rings and is energetically more favorable than earlier proposed carbon polymorphs (e.g., $M$ carbon, $\mathrm{bct}\mathrm{\text{\ensuremath{-}}}{\mathrm{C}}_{4}$, $W$ carbon, and chiral ${\mathrm{C}}_{6}$) over a wide range of pressures studied (0--100 GPa). The simulated x-ray diffraction pattern, density, and bulk modulus of $\mathrm{Cco}\mathrm{\text{\ensuremath{-}}}{\mathrm{C}}_{8}$ are in good accordance with the experimental data on structurally undetermined superhard carbon recovered from cold compression of carbon nanotube bundles. The simulated hardness of $\mathrm{Cco}\mathrm{\text{\ensuremath{-}}}{\mathrm{C}}_{8}$ can reach a remarkably high value of 95.1 GPa, such that it is capable of cracking diamond.

Novel Bimorphological Anisotropic Bulk Nanocomposite Materials with High Energy Products.

Abstract: Nanostructuring of magnetically hard and soft materials is fascinating for exploring next-generation ultrastrong permanent magnets with less expensive rare-earth elements. However, the resulting hard/soft nanocomposites often exhibit random crystallographic orientations and monomorphological equiaxed grains, leading to inferior magnetic performances compared to corresponding pure rare-earth magnets. This study describes the first fabrication of a novel bimorphological anisotropic bulk nanocomposite using a multistep deformation approach, which consists of oriented hard-phase SmCo rod-shaped grains and soft-phase Fe(Co) equiaxed grains with a high fraction (≈28 wt%) and small size (≈10 nm). The nanocomposite exhibits a record-high energy product (28 MGOe) for this class of bulk materials with less rare-earth elements and outperforms, for the first time, the corresponding pure rare-earth magnet with 58% enhancement in energy product. These findings open up the door to moving from a pure permanent-magnet system to a stronger nanocomposite system at lower costs.

Dynamic Phasors-Based Modeling and Stability Analysis of Droop-Controlled Inverters for Microgrid Applications

Abstract: System modeling and stability analysis is one of the most important issues of inverter-dominated microgrids. It is useful to determine the system stability and optimize the control parameters. The complete small signal models for the inverter-dominated microgrids have been developed, which are very accurate and could be found in literature. However, the modeling procedure will become very complex when the number of inverters in microgrid is large. One possible solution is to use the reduced-order small signal models for the inverter-dominated microgrids. Unfortunately, the reduced-order small signal models fail to predict the system instabilities. In order to solve the problem, a new modeling approach for inverter-dominated microgrids by using dynamic phasors is presented in this paper. Our findings indicate that the proposed dynamic phasor model is able to predict accurately the stability margins of the system, while the conventional reduced-order small signal model fails. In addition, the virtual ${\boldsymbol{\omega }}$ -E frame power control method, which deals with the power coupling caused by the line impedance X/R characteristic, has also been chosen as an application example of the proposed modeling technique.