Modeling and optimization of operating parameters for abrasive waterjet turning alumina ceramics using response surface methodology combined with Box–Behnken design

Abrasive waterjet turning is a newly emerging non-traditional technology for machining ceramics. In the present study, an attempt has been made to investigate the effect of operating parameters on depth of penetration and surface roughness (Ra) in turning of alumina ceramics using abrasive waterjet. The quadratic regression models were developed to predict the depth of penetration and Ra by experiments using Response Surface Methodology. The influence of each operating factors has been studied through analysis of variance technique. Key parameters and their interactive effects on depth of penetration and surface roughness have also been presented in graphical contours which are useful for choosing operating parameter preciously. The operating parameters for depth of penetration and surface roughness were simultaneously optimized by RSM with desirability function. The absolute average error between the experimental and predicted values at the optimal combination of parameter settings for depth of penetration and surface roughness were calculated as within 5%. Thus the developed model can be effectively used to predict the depth of penetration and surface roughness in the machining of alumina ceramics.     

Highly dispersed sulfur in ordered mesoporous carbon sphere as a composite cathode for rechargeable polymer Li/S battery

A mesoporous carbon sphere with the uniform channels (OMC) is employed as the conductive matrix in the sulfur cathode for the lithium sulfur battery based on all-solid-state PEO₁₈Li(CF₃SO₂)₂N-10 wt%SiO₂ electrolyte. Cyclic voltammograms (CV) and electrochemical impedance spectrum (EIS) suggest that the electrochemical stability of the S-OMCs is obviously superior to the pristine sulfur cathode. The S-OMCs composite shows excellent cycling performance with a reversible discharge capacity of about 800 mAh g⁻¹ after 25 cycles. This would be attributed to an appropriate conductive structure in which the active sulfur is highly dispersed in and contacted with the OMCs matrix.     

公共自行车租赁系统车辆监管平台的设计与实现

公共自行车租赁系统是在城市交通日益拥挤的环境下,减轻交通压力、缓解交通堵塞的优选解决方案。本文在综合公共自行车系统的自身特点和所存在问题的基础上,提出了一种后台车辆监管平台的设计方案。介绍了公共自行车租赁系统车辆监管平台的整体软件设计方案及功能模块设计。重点阐述了车辆调度模块以及车辆监管平台与租赁站点自助服务终端间数据通信的站点车辆管理模块。测试表明,软件系统运行流畅,与站点自助服务终端通信稳定可靠,实现了平台智能化管理。     

1Cr17Ni2压气机叶片多层膜制备及耐蚀性研究

采用真空电弧离子镀技术在1Cr17Ni2不锈钢基体表面沉积Ti/TiN/Zr/ZrN多层膜,并对膜的形貌、相结构、结合力以及极化曲线和交流阻抗等电化学性能进行分析和测试。结果表明:制备的Ti/TiN/Zr/ZrN膜界面清晰、结构致密、晶粒细小,膜层厚度约为2~3μm,膜层的主要物相为TiN和ZrN两相,以及少量的金属Ti和Zr;膜层与基体结合良好,结合力大于70 N,显微硬度(HV_(0.025))高达29 000 MPa,Ti/TiN/Zr/ZrN多层膜与1Cr17Ni2基材相比,具有更高的极化电位和极化电阻,更低的腐蚀电流密度,更大容抗弧。     

Reducing input/output current ripple for driving converter by multiple technology

To improve the vehicle dynamic performance and ultra-capacitor operating circumstance,this paper studied the multi-current-two-quadrant converter applied to drive high power DC motor in ultra-capacitor electric bus(UCEB).Compared with normal current-two-quadrant converter,the multi-current-two-quadrant converter can reduce the motor armature current ripple and the ultra-capacitor current ripple.Moreover,it improves power capabilities,reliability and fault tolerant capability of driving system.After analyzing the structure and working principle of the multi-current-two-quadrant converter,the expressions of armature current ripple and the quantitative relationships between the ultra-capacitor power loss and duty cycle were derived.The simulation and experimental results showed that the multi-current-two-quadrant converter has great advantages in reducing the armature current ripple and ultra-capacitor power loss,which can improve the vehicle performance and overall efficiency.     

The effect of Bi1.5Zn0.5Nb0.5Ti1.5O7 cover layer on the dielectric and tunable properties of Ba0.6Sr0.4TiO3/Bi1.5Zn0.5Nb0.5Ti1.5O7 bilayered thin films

Bi_1.5Zn_0.5Nb_0.5Ti_1.5O₇ (BZNT) thin films with different thicknesses as cover layers were deposited on the Ba_0.6Sr_0.4TiO₃ (BST) thin films on the Pt/Ti/SiO₂/Si substrates by radio frequency magnetron sputtering method. The microstructure, surface morphology, dielectric and tunable properties of BST/BZNT heterogeneous bilayered films were investigated as a function of the thickness of BZNT films and the effect of BZNT films on the asymmetric electrical properties of BST/BZNT bilayered films was discussed. It was found that BZNT cover layer significantly improved the leakage current and the dielectric loss, and the dielectric constant and tunability of BST/BZNT bilayered thin films simultaneously decreased with the increasing thickness of BZNT films. The BST/BZNT bilayered thin film with a 50 nm BZNT cover layer gave the largest figure of merit (FOM) of 33.48 with the upper tunability of 55.38%. The asymmetric electrical behavior of BST/BZNT bilayered films is probably related to an internal electric field caused by built-in voltages at Pt/BST and BZNT/Au interfaces.