多路输出反激式开关电源的反馈环路设计

在分析反激式开关电源控制框图的基础上,得到了功率级电路的传递函数。为避免连续电流模式的右半平面零点影响,设计了基于TL431和光耦TLP781的反馈补偿网络。应用Matlab提供的伯德图分析工具,对反馈网络传递函数进行分析,优化了补偿网络的电路参数。最后通过实验证明设计的反馈网络具有良好的稳定性和动态响应特性。     

机载相干MIMO雷达杂波自由度估计研究

针对任意发射波形合成结构影响下的机载相干MIMO雷达杂波自由度的估计问题。论文提出了一种机载相干MIMO雷达杂波自由度估计的构造法,该方法利用发射波形合成结构直接构造等效矩阵代替杂波协方差矩阵进行求秩。通过递推分解等效矩阵,提出并证明了一种杂波自由度快速估计准则,建立了机载相干MIMO雷达发射波形合成结构、阵列稀布构型与杂波自由度之间的定量关系。研究表明:该方法和准则能够准确预测任意发射波形合成结构下的机载MIMO雷达的杂波特征谱结构。该理论既保证了降秩STAP算法性能的最优又具有较小的计算量,并为最优发射波形合成方案和MIMO STAP算法的设计提供了依据。     

The effects of Nafion ionomer content in PEMFC MEAs prepared by a catalyst-coated membrane (CCM) spraying method

We analyzed the effects of ionomer content on the proton exchange membrane fuel cell (PEMFC) performance of membrane electrode assemblies (MEAs) fabricated by a catalyst-coated membrane (CCM) spraying method in partially humidified atmospheric air and hydrogen. When high loading Pt/C catalysts (45.5 wt.%) were used, we observed that catalytic activity was not directly proportional to electrochemical active surface area (EAS). This suggests that ionic conductivity through ionomers in catalyst layers is also an important factor affecting MEA performance. In addition, the effects of mass transport were experimentally evaluated by manipulating the air stoichiometry ratio at the cathodes. MEA performance was more sensitive to flow rates under conditions of higher ionomer content. Due to the combined effect of EAS, ionic conductivity, and mass transfer characteristics (all of which varied according to the ionomer content), an MEA with 30 wt.% ionomer content at the cathode (25 wt.% at the anode) was shown to yield the best performance.     

宽板连铸结晶器设计若干技术问题分析

结合国内涟源钢铁公司和伊朗穆巴拉克宽板连铸结晶器设计技术特点和工艺要求,详细提出宽板结晶器主要部件在设计过程需要优化和改进的要点,为后来宽板连铸项目的结晶器设计、优化提供更好的基础和思路。     

连铸辊缝仪测量原理及测量图形分析

使用连铸辊缝仪能有效检测连铸机设备状况,确保设备辊列精度处于受控状态,也是检测钢坯质量、探测缺陷的重要环节。根据宝钢罗泾炼钢厂连铸机辊缝仪测量原理及使用情况,结合现场管理实绩,分析设备功能精度管理中辊缝仪测量数据超标现象;以及通过对辊缝测量图形的分析,研究设备冷热态变化、离线对中等因素可能对辊缝开口度超标及弧度偏大的影响。     

开关电源数字均值电流控制技术研究

以连续导电模式(CCM)的Buck变换器为例,详细介绍了数字均值电流控制技术,着重推导后缘、前缘、三角后缘及三角前缘调制DAC控制Buck变换器的占空比算法.证明了双缘调制方式的数字均值电流控制具有优异的负载瞬态特性.     

反激型光伏微型逆变器不同工作模式的分析与比较

反激型光伏并网微型逆变器工作模式有不连续导通模式（DCM）和连续导通模式（CCM）两种。在工作原理的基础上,文中通过对这两种工作模式的分析和研究,推导了两种模式下逆变器主要参数的计算公式,从不同方面对两种模式的优缺点进行了对比分析,并得出相应结论,为根据设计要求合理选择逆变器的工作模式提供了理论依据。     

小方坯连铸机结晶器振动装置设计及特点

小方坯连铸机结晶器振动装置采用半板簧结构,双偏心驱动,内弧侧布置,设有弹簧过载保护装置,集合了仿弧精度高、结构简单、重量轻诸多优点。通过ADAMS机械系统动力学仿真分析软件创建振动系统虚拟样机模型,用其求解器对系统进行运动学分析,然后进行设计优化,获得高仿弧精度的结晶器振动装置的结构位置关系。最后对振动装置进行动态静力学分析,计算驱动力矩,为电机的选取和强度校核提供了依据。     

LED低压驱动电源——DC/DC降压变换器（上）

详细分析了DC/DC降压变换器驱动LED电路的工作原理,并推导了输出电压与输入电压的关系和电路参数选择依据的公式;给出一种DC/DC降压变换器芯片实例及其实用电路。     

Performance improvement by a glue-functioned Nafion layer coating on gas diffusion electrodes in PEM fuel cells

To reduce the performance difference of membrane electrode assembles (MEAs) between catalyst coated membrane (CCM) and gas diffusion electrode (GDE) methods, this study presents a novel structure of a glue-functioned Nafion layer coating on the catalyst layer of GDEs to enhance performance. The process of hot pressing is omitted from the membrane electrode assembly (MEA) fabrication in this study. In exploring the effect of the glue-functioned Nafion layer, five MEAs are compared, including one made by the CCM method and four by the GDE method. Loadings of 0, 0.1, 0.3 and 0.5 mg cm⁻² of glue-functioned Nafion layer are coated on the surface of the catalyst layer at room temperature with a condensed Nafion solution (20 wt%). The performance of the 0.3 mg cm⁻² Nafion layer coating improves 55% compared with that without an extra Nafion layer for the peak power density, and the performance difference reduces from 61.2% to 39.4% when compared with the one using the CCM method. However, the performance of the 0.5 mg cm⁻² Nafion layer coating is almost the same as without the Nafion layer. This indicates that increased Nafion cannot guarantee higher performance.