搅拌摩擦加工制备纳米RE/Al2O3增强铝基复合材料

铝基复合材料因其优异的物理性能及机械性能已得到广泛应用.文中通过在2219-O铝合金内部添加不同比例的RE/Al₂O₃纳米粉末,利用搅拌摩擦加工技术,制备铝基复合材料.并对搅拌区进行金相、拉伸、硬度、SEM,EDS和XRD等试验.结果表明,搅拌区金属在搅拌头强烈的搅拌摩擦作用下发生显著的塑性变形和连续动态再结晶,形成细小的等轴晶粒,并具有明显的洋葱环组织.复合材料的抗拉强度为母材的163%、屈服强度为母材的195%,同时硬度也明显增加.但是不同稀土比例对金属基复合材料的组织形貌和力学性能影响不大.大块复合材料制备过程粉末添加及隧道型缺陷的控制是关键.     

激光测量点云的数据处理方法研究

激光测量技术具有高分辨率、快速、非接触和数字化的特点,其应用日益广泛。基于激光测量的散乱点云,研究测量点云的数据处理方法。在分析通常的数据处理流程与方法的基础上,重点研究了如何应用数据的虚拟切割技术和测量点云的虚拟投影技术。点云虚拟切割技术主要包括径向/轴向切割技术、柱面切割技术与指定切割半径处的轴向截面切割技术。点云虚拟投影技术主要包括规则特征投影技术和轴向旋转投影技术。基于点云的虚拟投影,阐述了零件的参数提取策略。通过基于激光测量的零件数字化检测的实践表明所提出的点云数据处理方法与策略是行之有效的。     

低碳高强度高塑性锚杆用钢的试验研究

研究了等温淬火的等温温度和等温时间对低碳Si-Mn系TR IP钢力学性能的影响。试验用钢经810℃两相区加热,保温50 m in,在380℃盐浴中等温淬火20 m in,得到贝氏体＋铁素体＋残留奥氏体的三相组织,具有较高的抗拉强度（Rm=843 MPa）和良好的塑性（A5=31%）。     

JB/T 4730-2005《承压设备无损检测》答疑--超声检测部分(Ⅰ)

1 一般要求中．探伤仪工作频率由原来的1～ 5 MHz改为0．5～10 MHz．主要考虑哪些因素？     

Exergetic analysis of fuel cell micropowerplants fed by methanol

In the present study, a hydrogen polymer electrolyte fuel cell (PEFC) micropowerplant in combination with a steam reformer fed by methanol and a direct methanol fuel cell (DMFC) micropowerplant are analyzed numerically regarding their exergetic efficiency. The effects of concentration and activation overpotentials, and ohmic resistance on the efficiency are considered in quasi-two-dimensional fuel cell models. The influence of significant operational parameters on the exergetic efficiency is examined numerically. Experimental results are conducted for the steam reformer. This work shows the importance of an exergy analysis of the fuel cell as part of an entire thermodynamic system generating electric power and compares PEFC and DMFC micropowerplants exergetically.     

Effect of cooling rate on the electrochemical properties of solid-state synthesized spinel LiMn2O4

LiMn₂O₄ samples were prepared by solid-state reaction with different cooling rates (0.5, 1, 3, 5 °C min^− 1, and quenching) from Li₂CO₃ and electrolytic MnO₂. X-ray diffraction patterns of the prepared samples are identified as the spinel structure with a space group of Fd3¯m. The lattice parameters increase gradually as the cooling rates rise. The quickly cooled samples show better capacity properties at high current densities and a capacity fade when cycling at lower current density. Varieties of electrochemical methods were introduced to investigate the electrochemical properties of spinel LiMn₂O₄.     

Low operational temperature Li–CFx batteries using cathodes containing sub-fluorinated graphitic materials

Commercial lithium/polycarbon monofluoride batteries [Li–(CF)_n] are typically current-limited and are therefore not implemented in high-rate or low-temperature applications. Recent results suggest, however, that CF-based cathodes that use sub-fluorinated CF_x (SFCF_x) active materials in a thin electrode form factor are able to support very high currents (up to 5 C) while still providing a significant fraction of their specific capacity. In this work, the low temperature efficacy of these materials is examined in a −40 °C environment. CF_0.54 and CF_0.65 powders were characterized using X-ray diffraction, scanning electron microscopy, and X-ray energy dispersive spectroscopy. These materials were then implemented in a spray-deposited electrode using a 1-mil (∼25 μm) aluminum foil current collector and PVDF as a binder. Electrochemical tests showed that these materials were able to deliver specific capacity values up to five times greater than commercial CF_1.08 powder inserted into identically fabricated test cells tested at −40 °C. Testing also indicated that a room-temperature pre-discharge step was necessary to condition the electrode materials before exposure to the low-temperature test environment.     

基于神经网络的出入境货物宏观质量指数研究

以检验检疫情况统计数据为基础,运用感知器神经网络理论,对货物的宏观质量指标及其评价方法进行了研究。该方法为出入境货物的检验检疫宏观监控提供了决策依据。     

货物配装模型与算法研究

货物合理配装在物流配送中发挥着重要作用,影响货物配装的因素有很多,诸多因素影响的是货物的配装优先级。以配装优先级为基础,提出了基于优先级理论的货物配装模型和求解算法。算例分析验证了所提方法的有效性。     

空穴载流子在多晶p-ZnO薄膜中的输运特性研究

利用变温霍尔测量技术,研究了空穴载流子在Li和N双受主掺杂的p型ZnO多晶薄膜中的输运特性。实验结果和理论模型的比较研究表明：当温度在85～140K时,空穴载流子主要受晶界散射;当温度在140-300K时,空穴载流子主要受晶格振动散射、位错散射和电离杂质散射的共同作用。