Linear bipolar OTAs employing exponential‐law circuits

This paper presents design of linear bipolar OTAs, which are composed of two function blocks; one is an exponential‐law circuit and the other is a core cell. Multi‐tanh cells are employed as the core cell. This kind of OTA has lower power dissipation relatively to the conventional multi‐tanh cell. According as the order of the multi‐tanh core cell becomes higher, the number of circuit realization for the core cell increases. For example, we have two OTAs for the core circuit of an emitter‐coupled pair and four OTAs for the doublet core cell. Thus, we consider the generalized OTAs for an arbitrary order n of the core cell and obtain a formula to give the realization number of the linear OTAs for n. According to the formula, there must be eight OTAs in the case of n=3. All of the eight OTAs are examined. Analysis and simulation results show that the OTAs have advantage in their characteristics, such as linear input range, power dissipation, noise, and frequency response. Copyright 2004 John Wiley & Sons, Ltd.     

柔性石墨板的氢气透过率研究

对于聚合物电解质膜燃料电池双极板,阻气性是其重要属性.为了方便测量柔性石墨板样品的阻气性能,自制了气体透过性测量装置,并利用此装置研究了柔性石墨双极板的密度对其阻气性的影响.     

基于IGBT的直流混合型固态断路器及其换流过程

分析和比较了各种固态断路器的优、缺点,提出了适用于直流电力系统的基于IGBT的混合型固态断路器.通过搭建的固态断路器试验平台,进行了直流短路电流分断试验,并理论分析了影响其换流时间的电路参数.与机械断路器分断短路电流实验结果的对比表明,该断路器能有效分断直流短路电流并且有分断时间快、限流能力强、无电弧等优点.     

碳纤维增强酚醛树脂/石墨复合材料双极板的性能

研究了碳纤维表面处理方法及其含量对碳纤维增强酚醛树脂／石墨复合材料导电性能与力学性能的影响。结果表明：空气氧化处理碳纤维表面形成微孔和刻蚀沟槽，容易形成应力集中，复合材料的强度不高；空气加液相氧化处理填充了碳纤维表面的微裂纹，对复合材料有一定的补强作用；液相氧化处理有利于提高碳纤维表面活性以及碳纤维的均匀分散性，使材料表现出较好的力学性能与导电性能；随碳纤维含量增多，材料电导率变小，材料强度开始增大，达到最大值后材料强度下降。对碳纤维进行液相氧化处理，碳纤维含量在3％～4％时复合材料的力学性能与导电性能最好。     

DN-YOLOv5的金属双极板表面缺陷检测算法

为解决氢燃料电池中金属双极板表面缺陷尺寸小，缺陷对比不明显、种类多造成的难以检测，易误检漏检以及缺陷检测模型复杂度太大难以部署等问题，提出一种改进版的金属双极板缺陷检测算法DN-YOLOv5,来探究缺陷检测在冲压成形的金属双极板视觉检测工作台场景下进行快速精准检测的可行性，从而实现智能检测，提升检测效率。本研究着重于修改YOLOv5主干网络Backbone部分，添加网络中模块数量，加入NAM注意力机制和使用深度可分离卷积模块来替代原来CSP/CBS主干网络卷积模块，并引入SIoU对损失函数重新进行了定义，极大的提升了主干网络的轻量化程度。结果表明，本算法的map@0.5可达0.988,每秒检测传输帧率为9.98,模型参数量降低了52.13%,在测试集75张缺陷图像中真检率达到了99.74%。该方法在保证模型较高检测率的同时，显著降低了模型复杂度和参数计算量。此外，该算法结合新的检测尺度设计特征融合网络，提升网络的小目标、多目标检测能力。该算法具有良好的稳定性和鲁棒性，综合性能较好，满足部署移动端场景进行缺陷检测的轻量化需求。     

氢燃料电池中钛双极板研究进展

钛及钛合金密度低、比强度高且在酸性环境中耐蚀性优异,在氢燃料电池双极板中具有较高的应用价值。回顾了近年来氢燃料电池用钛双极板的研究进展,详述了钛双极板表面改性技术的研究成果,包括掺杂合金元素、钛表面涂覆金属基涂层(贵金属、金属碳/氮化物等)和碳基涂层(石墨、无定型碳等)。涂层结构组织的复合化和纳米化,有利于提升钛双极板的耐蚀性、导电性和疏水性,其对于提升氢燃料电池的性能及保证其运行的稳定性和耐久性具有重要作用。     

The effect of Cr doped in amorphous carbon films on electrical conductivity: Characterization and mechanism

Metallic bipolar plates (BPPs) are prospective candidates for BPPs in PEMFCs due to their lower cost and higher power density than traditional graphite. Coatings are used to enhance the electrical conductivity and anti-corrsive quality of BPPs, and amorphous carbon (a-C) films have attracted broad attentions from both industry and academia. In this study chromium was incorporated into a-C to further enhance conductivity. A series of Cr-doped a-C films (a-C:Cr) with different doping contents were prepared by CFUBMSIP. Moreover, Microstructure analyses and composition characterizations were performed to explore the mechanism. The results show that Cr decreases the interfacial resistance with satisfying the anti-corrosive behavior. XRD patterns indicate that Cr will form chromium carbide phase and pure metal phase. Moreover, TEM results also show that Cr atoms bond with C atoms. SEM photographs show that Cr atoms refine the grain size and compact the film all the same. C 1s spectrum of XPS shows that C-sp²/C-sp³ increases first and then decreases, reaching the maximum level of 1.708 at Cr_0.205, indicating the resistance drops first and then increases. In addition, Cr doping will also bring changes in nano-hardness and surface roughness.     

Mechanism of anomalous recovery in advanced SiGe bipolar transistors after low dose rate irradiation for very high total doses

The possible physical mechanism of the anomalous recovery effect in SiGe bipolar transistors is described. The qualitative analysis of saturated oxide trapped charge and interface trap densities at very high total doses as a function of dose rate affords an explain of decreasing excess base current and increasing current gain during further low dose rate irradiation.     

High‐performance porous lead/graphite composite electrode for bipolar lead‐acid batteries

In general, thicker active material bipolar electrode's specific capacity and cycle life are very poor owing to its low bonding strength between the active material and the substrate and the diffusion rate of the sulfuric acid electrolyte inside the active material. In this paper, we synthesize a novel attached and porous lead/graphite composite electrode for bipolar lead‐acid battery and can effectively solve these problems. The graphite/polytetrafluoroethylene emulsion is employed to improve the bonding strength and conductivity and the porous can provide electrolyte diffusion channels. The specific capacities of 2‐mm thick positive active material at 0.25, 0.5, 1 and 2 C can attain 75.99, 58.98, 47.97, and 33.36 mAh·g^?1. The discharge voltage platform is also relatively high and no rapid decline with increasing discharge rate. Furthermore, after 80 cycles, the specific capacity does not drop evidently. Copyright © 2017 John Wiley & Sons, Ltd.