Structural,electrical, and linear/nonlinear optical characteristics of thermally evaporated molybdenum oxide thin films

Homogeneous thin films of Molybdenum oxide (MoO₃) were grown on quartz and glass substrates using the thermal evaporation method. XRD results showed that the MoO₃ powder has a polycrystalline structure with an orthorhombic crystal system whereas the MoO₃ thin films have amorphous nature. SEM images showed that the MoO₃ thin films have a nearly uniform surfaces with worm-like shape grains. The film thickness influences on the linear and nonlinear optical characteristics of MoO₃ thin films that were examined using spectrophotometric measurements and from which, the linear optical constants of the MoO₃ thin films were estimated. The electronic transition type was determined as a direct allowed one. The values of the optical band gap were obtained to be in the range of 3.88–3.72 eV. The dispersion parameters, third-order nonlinear optical susceptibility, and the nonlinear refractive index of the MoO₃ thin films were determined and interpreted in the light of the single oscillator model. The temperature dependence of the DC electrical conductivity and the corresponding conduction mechanism for the MoO₃ films were investigated at temperatures ranging from 303 to 463 K.     

基于单片机C8051F500的无刷直流电机控制研究

永磁无刷直流电机是近些年发展起来的一种新型电机,具有效率高、调速性能好、启动转矩大等诸多优点,在运动控制领域中的应用日趋广泛。基于电机专用控制芯片MC33035,采用单片机C8051F500为主控芯片,设计一款无刷直流电机智能控制器,实现对无刷直流电机启动停止、正反转、调速、转速显示等控制。通过简要介绍无刷直流电机工作原理,使用MATLAB/Simulink对控制系统进行建模仿真,对无刷直流电机控制系统进行软、硬件设计。实验结果表明,该控制系统运行稳定,抗干扰性强,具有良好的市场应用价值。     

Refinement of primary carbides in AISI DC 53 cold work tool steel by thin section copper permanent mould casting and water atomization

In this study, as alternative methods to conventional production methods involving thin section copper permanent mould casting (fast solidification) and water atomization (rapid solidification) of AISI DC 53 cold work tool steel have been investigated. Thin slabs obtained by copper mould casting was homogenized at 1150 °C for one hour and then hot rolling was be applied. After hot rolling, conventional heat treatment have been applied to thin slabs. The same heat treatment procedure have been performed for a commercially available AISI DC 53 which is manufactured by thick section ingot casting and rolling. In order to investigate also the effect of rapid solidification on AISI DC 53 tool steel, steel powder was produced by water atomization technique. Experiments have revealed that thin steel slabs in permanent copper mould and rapidly solidified tool steel powder by water atomization have a more refined primary M₇C₃ carbides than commercially available steel.     

Effects of temperature on creepage discharge characteristics in oil-impregnated pressboard insulation under combined AC–DC voltage

Due to the complexity of the valve side winding voltage of the converter transformer, the insulation characteristics of the oil-impregnated pressboard (OIP) of the converter transformer are different from those of the traditional AC transformer. The study on effect of temperature on the creeping discharge characteristics of OIP under combined AC–DC voltage is seriously inadequate. Therefore, this paper investigates the characteristics of OIP creepage discharge under combined AC–DC voltage and discusses the influence of temperature on creepage discharge characteristics under different temperatures from 70°C to 110 °C. The experimental results show that the partial discharge inception voltage and flashover voltage decrease with increasing temperature. The times of low amplitude discharge (LAD) decrease and amplitude of LAD increases. Simultaneously, the times of high amplitude discharge (HAD) gradually increase at each stage of creepage discharge with higher temperature. The analysis indicates that the charge carriers easily accumulate and quickly migrate directional movement along the electric field ahead of discharging. The residual charge carriers are more easily dissipated after discharging. The ‘hump’ region of LAD moves to the direction of higher discharge magnitude. The interval time between two continuous discharges is shortened obviously. The concentration of HAD accelerates the development of OIP insulation creepage discharge. The temperature had an accelerating effect on the development of discharge in the OIP under applying voltage.     

A fuel-cell/battery hybrid DC backup power system via a new high step-up three port converter

In this paper, a fuel-cell (FC)/battery hybrid direct-current (DC) backup power system is proposed for high step-up applications. This system is composed of a newly developed non-isolated three-port converter, which achieves a high voltage gain by taking the advantage of a quasi Z-source network and an energy transfer capacitor. After analyzing the converter, a comprehensive comparison study and a design procedure are provided. Moreover, the controllers regulating the source power levels while smoothing the FC power profile according to the proposed energy management strategy (EMS) are designed based on the developed small-signal model of the proposed converter. Both hardware and controller design procedures are validated through the PSIM model of the whole system. As a result, it is shown that the proposed system can effectively couple FC and battery while transferring their energies to a high voltage DC bus according to the offered EMS.     

Conductive and flexible multi-walled carbon nanotube/polydimethylsiloxane composites made with naphthalene/toluene mixture

Conventional conductive materials face challenges when utilizing them for flexible and wearable electronics and soft robotics. Carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites are a promising alternative to the conventional hard conductors because they are light and can realize large deformation. To date, well dispersion of CNTs into PDMS to increase conductivity while maintaining flexibility remains challenging. We aimed at developing highly electrically conductive and flexible multi-walled carbon nanotube/PDMS (MWCNT/PDMS) composites. To this end, we proposed a method to enhance the dispersion of MWCNTs into PDMS using naphthalene and toluene. Our results showed that the addition of naphthalene and toluene into the composites improved dispersion of the MWCNTs and increased the direct current (DC) electrical conductivity. We also found that the morphology of primary aggregates of the MWCNTs influenced the DC electrical conductivity of the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48167.     

航空直流接触器电寿命预测研究

设计了适用于航空直流接触器的电寿命试验平台，并建立了电寿命预测模型。研究时选用释放时间、释放电压作为特征参数，试验数据利用小波分析的方法进行了去噪处理，分别基于BP神经网络建立了单参数和双参数的预测模型，并验证了预测效果。试验结果表明：预测模型具有良好的预测效果。所做研究是对航空直流接触器寿命预测工作进行的初步探索，同时也可以为部队航空直流接触器的维护工作提供一些参考，从而提高飞机电气系统的可靠性，保障飞行任务的顺利实施。     

基于ＰＩＤ控制算法的直流微网容错控制方法研究

构建直流微网容错控制对象模型，调节直流微电网的输出回路参数；以输出功率、直流微网的 参考电压、弱电网下系统惯性响应特征等为约束参量，构建直流微网容错控制目标函数，在不同电网强度下 进行直流微网容错控制的参数自整定性调节，采用无功环比例积分控制方法进行直流微网容错寻优分析， 建立模糊 ＰＩＤ控制模型，采用变结构的模糊 ＰＩＤ控制方法进行直流微网容错控制过程中的自适应加权学习 和误差反馈调节，实现直流微网容错控制改进设计。仿真结果表明，采用该方法进行直流微网控制的容错 性能较好，输出稳定性较强，具有较好的直流微网输出增益。     

Robust constrained stabilization of boost DC–DC converters through bifurcation analysis

This paper proposes a new methodology for designing robust affine state-feedback control laws, so that wide-range safe and efficient operation of switched-mode DC–DC boost converters is guaranteed. Several undesirable nonlinear phenomena such as unstable attractors and subharmonic oscillations are avoided through bifurcation analysis based on the bilinear averaged model of the converter. The control design procedure also relies on constrained stabilization principles and the generation of safety domains using piecewise linear Lyapunov functions, so that robustness to supply voltage and output load variations is ensured, while input saturation is avoided and additional state constraints are also respected. The technique has been numerically and experimentally validated.