感应加热电源中频率跟踪控制电路的设计与分析

为使感应加热电源中的逆变器始终工作在功率因数接近或等于1的准谐振或谐振状态,设计出一种适合中频感应加热电源的频率跟踪控制电路。控制电路通过压控振荡器和逻辑电路实现了频率跟踪,经过示波器的测试,电路稳定性得到了提高,捕捉速度明显改善。     

Polyaniline nanofiber/carbon film as flexible counter electrodes in platinum-free dye-sensitized solar cells

Efficient transfer of charges from a counter electrode to an electrolyte is a key process during the operation of dye-sensitized solar cells. Here, we develop a flexible counter electrode by electrochemical deposition of polyaniline nanofibers on graphitized polyimide carbon films for use in a tri-iodide reduction. As determined by the electrochemical impedance spectroscopy, the flexible counter electrode exhibited very low charge transfer resistance and series resistance. These results are due to the high electrocatalytic activity of the polyaniline nanofibers and the high conductivity of the flexible graphitized polyimide film. In combination with a dye-sensitized TiO₂ photoelectrode and electrolyte, the photovoltaic device with the polyaniline counter electrode shows an energy conversion efficiency of 6.85% under 1 sun illumination. Short-term stability tests indicate that the photovoltaic device with the polyaniline counter electrode almost maintains its initial performance.     

Electropolymerization of a poly(3,4-ethylenedioxythiophene) and functionalized, multi-walled, carbon nanotubes counter electrode for dye-sensitized solar cells and characterization of its performance

Composite films of poly(3,4-ethylenedioxythiophene) and functionalized, multi-walled, carbon nanotubes (PEDOT–MWCNT) were fabricated by a simple oxidative electropolymerization method. These films were formed on fluorine-doped, tin oxide, glass substrates as counter electrodes (CEs) of platinum-free, dye-sensitized solar cells (DSSCs). The surface morphology, formation mechanism and electrochemical nature of PEDOT–MWCNT films were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and alternating current (AC) impedance spectroscopy. The SEM and AFM images showed that PEDOT–MWCNT films were more porous than PEDOT films. CV and AC impedance spectroscopy revealed that the PEDOT–MWCNT electrode had higher electrocatalytic activity for the I₃⁻/I⁻ redox reaction and a smaller charge transfer resistance than the PEDOT electrodes. The energy conversion efficiency of the DSSC with a PEDOT–MWCNT CE was 13.0% higher than with a PEDOT CE using the same conditions with a ruthenium sensitizer.     

反重力铸造装备技术的应用与发展

本丈介绍了反重力铸造装备技术的分类、应用状况及发展趋势.在反重力铸造装备中,四立柱式装备适用于金属型,具有生产效率高、自动化程度高的特点,而压力罐式装备适合砂型、石膏型、精铸模壳等铸型材料,可用于不同种类大中小型铸件的生产.随着工业控制技术的发展,计算机与PLC技术的应用、数字组合阀的研制以及传统控制技术与模糊控制的有机结合,都使反重力铸造液面加压控制系统在压力控制精度、运行可靠性等方面获得了巨大的发展.     

俄罗斯的城市化演进及发展趋势

在向市场经济转轨过程中,俄罗斯的城市化进程在遵循世界发展普遍规律的同时有着自身发展的独特性。回顾了转型时期俄罗斯城市发展跌宕起伏的发展历程,总结了俄罗斯城市发展具有大城市较少、结构单一的市镇较多、城市化进程中的“伪城市化”现象、城市规模等级体系发育不够完善和城市群发展不成熟、城市空间分布不均衡、城市化地区差异明显等主要特征,最后就俄罗斯的“逆城市化”现象以及未来发展趋势提出了自己的看法。     

基于STM32微处理器的光栅信号处理方法的研究

在三维移动平台运动控制系统中,STM32微处理器作为主控制器实时地处理光栅尺反馈信号和发送相应指令。由于微处理器中计数器的位数和计数方式,不适宜在大行程三维移动平台中应用,针对这一缺陷,给出了扩展计数器位数和辨向的方法,探讨如何选择合理的查询周期,延长光栅尺的测量长度,实现在平台上的应用。实验证明:该方法计数准确、可靠性高,满足光栅尺信号的处理要求。     

西门子802D系统行程润滑功能的实现

利用西门子802D系统的接口信号及参数调节实现对数控车床行程润滑功能的控制,达到机床合理润滑的目的。     

一种任意整数周期的高精度测速系统设计

介绍了一种由89C51单片机与82C53计数器组成的高精度测速系统.通过系统外围电路和控制软件设计,采用单片机在两次中断中开启和停止定时器,实现了对电机转速脉冲信号任意个完整周期的精确测量;克服了82C53计数器由于打入计数初值原因,随机地产生系统少计或多计一个脉冲的情况.最后以Agilent公司生产的高精度信号发生器为基准对该系统进行了速度测量模拟实验,并对实验结果进行了分析.结果证明,该测速系统具有测速精度高,测量范围宽的优点.     

礼品包装设计探析

在现实生活中，以“礼”传“情”，作为礼品的包装就显得尤为重要，且礼品作为特殊性的商品，其包装固然会有它的个性特性，通过对中国古代礼品包装及日本现代礼品包装进行分析探讨，阐述了现代礼品包装设计必须注重的几个方面。