Highly elastic cobweb-like SiO/CNF composites with reconstructed heterostructure for high-efficient lithium storage

The silicon-based materials are promising candidates for lithium-ion batteries owing to their high energy density. However, achieving long lifespan under realistic conditions remains a challenge because of the volume expansion and low conductivity. In this work, the highly elastic cobweb-like composite materials consisted by SiO and nanofibers are designed and fabricated for high-efficient lithium storage by ball-milling & electrostatic spinning method. The reconstructed heterostructure and highly elastic nanofibers can simultaneously increase the conductivity and inhibit the “expansion effect” of silicon-based materials. The constructed electrode of n-SiO/CNF delivers an initial capacity of 1700 mAh/g, and maintains the capacities over 1000 mAh/g after 100 cycles at the current density of 500 mA/g. Meanwhile, this electrode can give an initial coulombic efficiency over 85% and maintains at 98% in the following charge/discharge processes. Furthermore, it exhibits efficient long-term electrochemical performance, maintaining the capacity at about 1000 mAh/g at a high current density of 1000 mA/g after 1000 cycles. This work could provide a promising strategy for enhancing the performance of silicon-based composite materials for practical application in lithium-ion batteries.     

氮化铂在高压下的相变及弹性性质的第一原理计算

用PBE形式下的广义梯度近似（GGA）赝势平面波方法研究了氮化铂的结构相变以及弹性性质,计算了氮化铂的氯化钠（B1）、氯化铯（B2）、闪锌矿（B3）、纤维矿（B4）等四种结构并应用高压下的焓与压强的关系,得出在常温常压下B4结构是最稳定的结构,这与Yu 等人得的结果一致,且 B4→B1及B1→B2的相变压强分别发生在36.7 GPa和 185.4 GPa,同时,研究了B4结构在高压的弹性性质,发现弹性常数、体模量、剪切模量、压缩波速、剪切波速以及德拜温度均随着压强的增大而单调增大     

Light-Driven Crawling of Molecular Crystals by Phase-Dependent Transient Elastic Lattice Deformation

The light-driven crawling of a molecular crystal that can form three phases, (α, β, and γ) is presented. Laser irradiation of the molecular crystal can generate phase-dependent transient elastic lattice deformation. The resulting elastic lattice deformation that follows scanning irradiation of a laser can actuate the different phases of molecular crystal to move with different velocity and direction. Because the γ phase has a large Young's modulus (ca. 26 GPa), a force of 0.1 μN can be generated under one laser spot. The generated force is sufficient to actuate the γ-formed molecular crystals in a wide dimensional range to move longitudinally at a velocity of about 60 μm min⁻¹, which is two orders of magnitude faster than the α and β phases.     

Anisotropic Poisson Effect and Deformation-Induced Fluorescence Change of Elastic 9,10-Dibromoanthracene Single Crystals

Elastic organic crystals have attracted considerable attention as next-generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10-dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c-axes) of the crystal are contracted upon elongation along the long axis (a-axis). Moreover, we found that the Poisson's ratios along the b-axis and c-axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c-axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.     

Anisotropic Poisson Effect and Deformation‐Induced Fluorescence Change of Elastic 9,10‐Dibromoanthracene Single Crystals

Elastic organic crystals have attracted considerable attention as next‐generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10‐dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c‐axes) of the crystal are contracted upon elongation along the long axis (a‐axis). Moreover, we found that the Poisson's ratios along the b‐axis and c‐axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c‐axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.     

Contact vibration analysis of the functionally graded material coated half-space under a rigid spherical punch

This paper studies the contact vibration problem of an elastic half-space coated with functionally graded materials (FGMs) subject to a rigid spherical punch. A static force superimposing a dynamic time-harmonic force acts on the rigid spherical punch. Firstly, we give the static contact problem of FGMs by a least-square fitting approach. Next, the dynamic contact pressure is solved by employing the perturbation method. Lastly, the dynamic contact stiffness with different dynamic contact displacement conditions is derived for the FGM coated half-space. The effects of the gradient index, coating thickness, internal friction, and punch radius on the dynamic contact stiffness factor are discussed in detail.     

时滞效应对弹性地基上梁主共振响应影响分析

本文研究了弹性地基上梁主共振响应的时滞效应．基于Hamilton原理,建立了时滞影响下弹性地基上梁的非线性运动微分方程,采用多尺度法,求得了时滞效应下主共振响应调制方程以及稳定性条件．通过数值算例,分析了时滞和调谐参数影响下主共振响应的峰值及幅频响应特性．结果表明,地基反力中的时滞效应对主共振响应影响较大,会导致共振域偏移,在一定区间内,响应幅值随时滞变化先减小再增大,呈现出周期性,并导致幅频曲线弯曲程度增大．     

Load’s temporal characteristics for annulling forced vibrations of linear elastic plates

We consider trapezoidal load-time pulses with linearly increasing and affinely decreasing durations equal to integer multiples of the time period of the first bending mode of vibration of a linearly elastic structure. For arbitrary spatial distributions of loads applied to monolithic and laminated orthotropic plates, it is shown through numerical solutions that plates’ vibrations become miniscule after the load is removed. This phenomenon is independent of the dwell time (i.e., the time duration between the rising and the falling portions) during which the load is kept constant. The primary reason for this response is that for such time-dependent loads, nearly all of plate’s strain energy is concentrated in deformations corresponding to the fundamental bending mode of vibration. Thus plate’s deformations can be studied by taking the mode shape of the 1st bending mode as the basis function and reducing the problem to that of solving a single second-order ordinary differential equation. We have verified this postulate by comparing strain energies computed from the 3-dimensional deformations of different plate geometries and boundary conditions with those determined by using the single degree of freedom (DoF) model. Thus for trapezoidal time-dependent loads applied on plates, the 1 DoF model provides reasonably accurate results and saves considerable computational effort.     

Identification of functionally key residues in maltose transporter with an elastic network model-based thermodynamic method

Periplasmic binding protein-dependent maltose transport system (MBP-MalFGK₂) of Escherichia coli, an important member of the Adenosine triphosphate-binding cassette transporter superfamily, is in charge of the transportation of maltoses across cellular membrane. Studies have shown that this transport processes are activated by the binding of maltose and are accompanied by large-scale cooperative movements between different domains which are mediated by a network of important residues related to signal transduction and allosteric regulation. In this paper, the functionally crucial residues and long-range allosteric pathway of the regulation of the system by substrate were identified by utilising a coarse-grained thermodynamic method proposed by our group. The residues whose perturbations markedly change the binding free energy between maltoses and MBP-MalFGK₂ were considered to be key residues. In result, the key residues in 62 clusters distributed in different subdomains were identified successfully, and the results from our calculation are highly consistent with experimental and theoretical observations. Furthermore, we explored the long-range cooperation within the transporter. These studies will help us better understand the physical mechanism of the effects of the maltose on MBP-MalFGK₂ by long-range allosteric modulation.