电容滤波直流电源电路谐波产生分析与抑制方法

电容滤波直流电源电路在工作过程中会产生比较严重的谐波电流,这些谐波电流的存在会给后端电路和供电系统带来危害。对此,首先对电容滤波直流电源电路中谐波电流的产生机理进行了分析,然后针对这些谐波电流给出了两种基于LC谐振滤波的谐波抑制方法,并对其抑制性能进行了仿真和实验验证。结果表明,两种LC谐振滤波的谐波抑制方法均可有效降低直流电源电路中谐波电流的占比,并显著提高电源有用输出功率。     

约束电爆过程中石墨的纳米化机制

利用自行研制的约束电爆石墨制备低维纳米碳装置,通过改变初始充电电压与约束管管径进行系列性电爆实验,实验中对气溶胶形式的电爆产物进行原位取样,并进行显微分析.结合电爆产物显微分析结果和约束管中能量密度与电爆产物粒径间的关系,对电爆过程中石墨的纳米化机制进行研究.研究结果表明:电爆过程中约束管内产生的机械压缩波能够对石墨施加瞬间高压使石墨碎化,这一压缩波在传播过程中对已碎化的石墨进行反复冲击与剥离,从而导致石墨颗粒从约束管中喷射而出.在喷射过程中,石墨颗粒之间以及石墨颗粒与约束管壁之间不断发生碰撞,致使石墨颗粒进一步碎化,并形成低维纳米碳.     

空洞缺陷形状对杉木圆盘电阻与应力波断层成像效果的影响

无损检测技术能对木材空洞缺陷进行快速且准确的检测,现存的各种检测技术都有一定的优缺点,因此有必要对它们进行试验和对比。以福建杉木圆盘为对象,研究不同面积、不同轮廓形状的空洞缺陷对电阻和应力波断层成像技术的影响,比较两种检测技术的缺陷图像与实际缺陷图像的差异。结果表明:①电阻和应力波检测技术均能直观显示木材内部缺陷,其检测精度会受到空洞缺陷面积、轮廓形状以及截面积比率影响; ②当空洞实际面积与被测木材截面积比率从4.90%上升到44.05%时,电阻成像系统显示的缺陷图像面积与实际缺陷面积相对误差从34.03%下降到11.69%,应力波成像系统显示缺陷图像面积与实际缺陷面积相对误差从46.41%下降到14.88%; ③缺陷轮廓形状对两种成像均有一定影响。对于电阻成像,近圆形的空洞成像精度低于狭长形的空洞缺陷,在电阻成像中,除了扇形和圆形缺陷外,其余的空洞缺陷形状均不能被明显地检测出,但是应力波成像中,狭长形的扇形缺陷能够比较清晰地被系统显示。研究表明:电阻断层成像法对于空洞缺陷的检测比应力波断层成像法灵敏,且图像检测精度也比应力波断层成像法高; 而对于缺陷轮廓的识别能力,应力波断层成像法要优于电阻断层成像法。     

中国新能源汽车的研发及展望

 近年来中国新能源汽车发展迅速,成为技术创新和产业升级的亮点领域。核心技术的突破带动了产品性能的提升,鼓励政策的实施促进了产业化的进程。本文对国家科技研发计划支持下的新能源汽车技术进步及其产业化进行了总结,展望了未来5年新能源汽车科技研发的重点。     

车用大功率电力电子器件研究进展

 车用电机驱动变流器是电动汽车电机驱动的关键部件,大功率电力电子器件是其核心。对比分析了国内外电动车辆用电机驱动变流器的拓扑结构、变流器控制特点及体积功率密度等关键指标,指出车用电机驱动变流器的技术创新重点在于硅基绝缘栅双极性晶体管(IGBT)芯片及封装技术持续改进碳化硅(SiC)器件的应用。综述了硅基IGBT芯片的演进和IGBT模块封装技术的创新,介绍了碳化硅器件的技术特点。     

纤维增强复合材料在电网中的应用

 纤维增强复合材料具有轻质、高强、耐蚀、绝缘、环保等性能,在电力行业输配电网络中已有广泛应用。综述了纤维增强复合材料在电网中的应用,主要包括复合绝缘子、复合材料杆塔、复合材料电力金具、碳纤维复合材料芯导线及复合材料电力安全工器具等。分析表明,纤维增强复合材料性能优良,能够满足现行环保节能新要求,未来具有巨大发展潜力。     

数字化时代背景下的校园一卡通系统

校园一卡通系统以IC芯片卡为载体,贯穿于整个校园应用管理系统,即凡是有现金、票证或需要识别身份的场合均采用IC卡来完成.以校园一卡通系统为例,详述卡片内部结构,具体的文件类型以及IC卡内各个模块的分工协作.对校园一卡通系统在应用中遇到的实际问题做出分析,并给出了合理的解决方案.     

Ultrasound effects on zinc recovery from EAF dust by sulfuric acid leaching

In this work, an ultrasound-assisted leaching process was studied for the recovery of zinc from electric arc furnace (EAF) dust, in which zinc was mainly present in the form of franklinite (60%). Hydrometallurgy is emerging as a preferred process for the recovery of a variety of metals, and the use of ultrasound could offer advantages over the conventional leaching process, especially for the dissolution of franklinite. Franklinite is a refractory phase that is difficult to leach and represents the main obstacle in conventional hydrometallurgy processing. Atmospheric leaching with different sulfuric acid concentrations (0.2-2.0 M) at two temperatures (323 and 353 K) was performed. The tests were conducted using both conventional and ultrasound-assisted leaching. After the leaching tests, the solid residues were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, whereas the leach liquor was analyzed by inductively coupled plasma spectroscopy (ICP). The use of ultrasound facilitated the dissolution of franklinite at low acid concentrations and resulted in a greater zinc recovery under all of the investigated operating conditions.     

New pyrometallurgical process of EAF dust treatment with CaO addition

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace (EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite (ZnFe₂O₄), which accounts for more than half of total zinc in the EAF dust, into ZnO and Ca₂Fe₂O₅ by CaO addition. The EAF dust was mixed with CaO powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100℃ for a predetermined holding time. All ZnFe₂O₄ was transformed into ZnO and Ca₂Fe₂O₅ at a minimum temperature of 900℃ within 1 h when sufficient CaO to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess CaO beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than ZnFe₂O₄. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100℃ when CaO was added.     

四轮独驱电动汽车复合制动控制策略

伴随汽车的电子化与智能化发展,针对四轮独驱电动汽车驱/制动力独立可控的优势,提出了一种考虑驾驶员制动特性的四轮独驱电动汽车复合制动控制策略。通过应用车辆动力学仿真软件CarSim与MATLAB/Simulink软件建立车体模型、电机模型、电池模型和能量回收控制模型,并合理分配前后轴制动力矩和液压制动与电机制动的比例,通过两种不同循环实验工况对能量回收控制方法进行仿真实验验证。实验结果表明:所提出的复合制动控制策略可以有效分配汽车前后轴制动力矩,保证汽车制动稳定性,并获得较高的能量回收率,提高汽车行驶里程。