广义双sine—Gordon方程的新精确解

借助符号计算系统，应用推广的tanh方法，获得了广义双sine—Gordon方程丰富的新精确解。     

A double receding contact axisymmetric problem between a functionally graded layer and a homogeneous substrate

In this paper, the axisymmetric problem of a frictionless double receding contact between a rigid stamp of axisymmetric profile, an elastic functionally graded layer and a homogeneous half space is considered. The graded layer is modelled as a nonhomogeneous medium with an isotropic stress-strain law. Assuming the double contact between the bodies to be frictionless, only compressive normal tractions can be transmitted in each contact area while the rest of the surface is free of tractions. Using an appropriate integral transform, the axisymmetric elasticity equations are converted analytically into a system of singular integral equations where the unknowns are the pressures and the radii of the receding contact area in the two contact zones. The global equilibrium conditions are supplemented to solve the problem. The singular integral equations are solved numerically using orthogonal Chebyshev polynomials. An iterative scheme based on the Newton-Raphson method is employed to obtain the receding contact radii and pressures that satisfy the equilibrium conditions. The main objectives of the paper are to study the effect of the nonhomogeneity parameter, the thickness of the graded layer and the magnitude of the applied load on the contact pressures, the radii of the receding contact zones and the indentation for the case of a spherical rigid punch.     

Fabrication of cobalt aluminum-layered double hydroxide nanosheets/carbon spheres composite as novel electrode material for supercapacitors

A new design route was presented to fabricate cobalt aluminum-layered double hydroxide(CoAl-LDH) thin layers which grow on carbon spheres(CSs) through a growth method. The CoAl-LDH thin layers consist of nanoflakes with a thickness of 20 nm. The galvanostatic charge–discharge test of the CoAl-LDH/CSs composite shows a great specific capacitance of 1198 F/g at 1 A/g (based on the mass of the CoAl-LDH/CSs composite) in 6 mol/L KOH solution, and the composite displays an impressive specific capacitance of 920 F/g even at a high current density of 10 A/g. Moreover, the composite remains a specific capacitance of 928 F/g after 1000 cycles at 2 A/g, and the specific capacitance retention is 84%, indicating that the composite has high specific capacitance, excellent rate capability and good cycling stability in comparison to pristine CoAl-LDH.     

并联双线圈式直流接触器电磁机构合闸动作特性研究

直流接触器是新能源系统以及电动汽车中配置最为广泛的开关电器之一。而直流接触器的动态特性是衡量直流接触器性能的重要指标之一。本文以并联双线圈式直流接触器为研究对象，建立了直流接触器电磁机构的动力学模型，利用基于Adams与Maxwell的联合仿真研究方法对直流接触器的电磁机构进行合闸过程的仿真分析，研究结果表明，机构合闸动作的仿真合闸时间与试验合闸时间相吻合，验证了该仿真方法的正确性；同时研究了弹簧参数和线圈参数等因素对机构合闸运动特性的影响，研究发现在一定范围内弹簧预压力变化对合闸时间影响不大，线圈安匝数增大会导致合闸时间变小，线圈内阻增大会导致合闸时间变大且动触头弹跳更剧烈。本文的仿真方法与结果能为直流接触器电磁机构的改进设计与优化提供一定参考。     

多维重调和方程的基本解及有关边值问题

在广义函数的意义下，利用拉氏方程的基本解讨论了二维、三维双调和方程的基本解，并且进一步给出了ｎ重调和方程的基本解的表达式。最后通过引入格林函数同方程△３△３ｕ＝ｆ（ｘ，ｙ，ｚ）的边值问题的解的积分表达式。     

Frictional Pressure Drop of Air Non‐Newtonian Liquid Flow through Helical Coils in Horizontal Orientation

Investigations have been carried out to evaluate the two‐phase frictional pressure drop for air non‐Newtonian liquid flow through helical coils in horizontal orientation. The experiments performed using 36 different helical coils and 4 different concentrations of sodium salt of carboxymethyl—cellulose (SCMC) as non‐Newtonian liquids. The effects of air and liquid flow rate, coil diameter, helix angle and liquid properties‐ on two‐phase frictional pressure drop have been discussed. An attempt has been made to fit the experimental two‐phase frictional pressure drop data by the Lockhart and Martinelli, Chem. Eng. Prog. 45 , 39–48 (1949) correlation and the modified Lockhart‐Martinelli correlation as presented by different authors. In another approach, friction factor method was adopted to correlate the experimental data by dimensional analysis. The correlation developed predicts the two‐phase frictional pressure drop with acceptable statistical accuracy.     

Synthesis of metatungstate pillared layered double hydroxides with variable layer composition. Effect of the Mg:Al ratio on the microporous structure

A series of layered double hydroxides (LDHs) pillared with the Keggin ion H₂W₁₂O₄₀⁶⁻ has been synthesized with final Mg:Al ratios of 1.75:1, 2.31:1 and 3.51:1 by ion exchange reaction of the LDH-hydroxide and LDH-adipate precursors. In each case, the pillared product was characterized by specific BET N₂ surface areas of more than 110 m² g⁻¹ and micropore volumes in excess of 0.026 ml g⁻¹. The micropore size distribution plots obtained from the argon adsorption isotherms indicate that the micropore diameters become smaller as the surface charge density of the LDH increases. A study was also performed on each of the LDH precursors in order to determine any problematic steps in the overall synthesis. Significant differences were noticed in the POXRD patterns of the LDH-adipate precursor; these are believed to be due to differences in the orientation and degree of order of the adipate anions in the gallery space of the LDH. It was found that adipate anions orientated with the long axis perpendicular to the inorganic layers were easier to exchange than those where the long axis was aligned parallel to the inorganic layers.     

双倾导管被交位置的计算

对加工设计阶段单件图中被交位置的计算提出2种计算方法,即手工计算法和计算机提取数据法,并对这2种方法进行了比较。     

强化汽车齿轮的有效途径：计算顶隙与齿轮弯曲强度

文章提出了计算顶隙的概述一面分析后指出计算隙可以极大地提高齿轮的承载能力，为产品设计人员设计高强度齿轮提供了一种行之有效设计方法。     

Electrocatalysis of gold nanoparticles/layered double hydroxides nanocomposites toward methanol electro-oxidation in alkaline medium

A nanocomposite based on layered double hydroxides (LDHs) and gold nanoparticles (AuNPs) was prepared via hydrothermal treatment followed by a reduction procedure. The AuNPs were obtained in Mg-Al LDHs, and they maintained good stability. The electrocatalytic activities of AuNPs/LDH-modified glassy carbon electrodes for methanol oxidation in alkaline medium were investigated in detail. Under the same conditions, the modified electrode exhibited higher electrocatalytic activity than both the pure AuNPs-modified electrode and LDH-modified electrode. The role of the AuNPs and LDHs in this composite system was explored by cyclic voltammetry and chronoamperometry, respectively. Further studies demonstrated that the promoting effect of LDHs could be due to its strong adsorption and partly to the discharge of OH⁻ during methanol oxidation. This work indicates that LDHs is expected to be a good supporting material in the development of methanol anode catalysts.