膜电极结构对质子交换膜燃料电池性能的影响

膜电极(MEA)作为质子交换膜燃料电池(PEMFC)的核心组件之一，其结构和组成对电池的性能有着重要的影响。提高膜电极性能的一个重要的指导思想是在催化粒子的周围形成良好的质子、电子和气体通道。以此为主线，从电极制备工艺的发展历程，Nafion的使用与质子通道的改进、电子通道的改进、阴极催化等几个方面详细地总结和讨论了近年来MEA的研究状况，并在此基础上对MEA的进一步研究提出了若干建议。     

基于离散单元法的锥形双螺杆输送及混合机理分析

锥形双螺杆挤出机结构模型与其他普通螺杆挤出机相差很大且构成独特,近年来在聚合物加工行业中发挥了很大的作用。设计螺槽深度与螺杆半径比为1∶2、2∶5、1∶3的三种锥形双螺杆挤出机,通过离散单元法模拟了锥形双螺杆挤出机挤出LDPE、HDPE两种颗粒的过程,分析了锥形双螺杆挤出机螺槽内颗粒速度的变化,同时在不同参数下对三种锥形双螺杆挤出机的输送效率进行了比较。利用EDEM软件对LDPE和HDPE颗粒进行离散元分析,得出不同时刻两种颗粒在三种锥形双螺杆挤出机内的混合情况。结果表明,螺槽深度与螺杆半径比为1∶2的锥形双螺杆挤出机的混合效率优于螺槽深度与螺杆半径比为2∶5、1∶3的锥形双螺杆挤出机。     

青藏铁路无人值守车站战时运用研究

为提高青藏铁路战时运输投送保障能力,分析无人值守车站布局、设施设备配置、能力生成等战时运用的可行性;确定无人值守车站选定条件、开设时机和组织流程;基于无人值守车站多处于无人区、距离生活聚集区较远,指出必须统筹生活保障、卫勤保障、通信保障、装备保障和公路运输车辆保障事宜,着力解决战时装卸载能力与部队铁路输送需求之间突出的矛盾与问题.     

Fabrication and characterization of PFSI/ePTFE composite proton exchange membranes of polymer electrolyte fuel cells

PFSI/ePTFE composite proton exchange membranes were fabricated by impregnating perfluorosulfonic acid resin (PFSI resin, Nafion) into chemically modified expanded PTFE (ePTFE) matrix. Chemical modification of sodium-naphthalene treatment and N-methylol acrylamide (NMA) grafting decreased the contact angle of the as-received ePTFE from 125 ± 0.5° to 67 ± 0.5°, effectively converting the as-received hydrophobic ePTFE to a hydrophilic ePTFE matrix. The composite membrane fabricated with the hydrophilic ePTFE have higher impregnated PFSI loading, much lower porosity and better PTFE/PFSI interface contact, as compared to the composite membranes with the as-received ePTFE. This leads to much lower gas permeability and significantly improves the durability under an accelerated dry/wet cycle test. The fuel cell made from the PFSI/ePTFE composite membranes with hydrophilic ePTFE showed superior performance as compared to that with the composite membrane made from the as-received ePTFE and Nafion 211 membrane.     

计算机虚拟仿真在机器人教学中的应用

为解决机器人实验教学问题，本文在VisualC 6．0平台上，基于OpenGL，开发了机器人图形仿真系统。对机器人进行了三维实体几何造型，并实现了其空间运动仿真，可再现机器人运动全过程，实现机器人的示教仿真。该机器人仿真系统大大的方便了机器人教学。     

基于多特征融合的无监督真值发现方法

真值发现是数据集成领域具有挑战性的研究热点之一。传统的方法利用数据源与观测值之间的交互关系推断真值,缺乏足够的特征信息;基于深度学习的方法可以有效地进行特征抽取,但其性能依赖于大量手工标注,而在实际应用中很难获取到大量高质量的真值标签。为克服以上问题,本文提出一种基于多特征融合的无监督真值发现方法（Unsupervised truth discovery method based on multi-feature fusion, MFOTD）。首先,利用集成学习无监督标注“真值”标签;然后,分别使用预训练模型 Bert和独热编码获取观测值的语义特征和交互特征;最后,融合观测值多种特征并使用其“真值”标签构建初始训练集,通过自训练方式训练真值预测模型。在两个真实数据集上的实验结果表明,与已有方法相比,本文所提出的方法具有更高的真值发现准确性。     

多AUV虚拟仿真测试平台实时仿真技术研究

为了对多AUV系统的体系结构、协调控制策略等进行演示和验证,文中基于实时网络提出了一种新型的多AUV虚拟仿真测试平台;在此基础上,研究了该虚拟仿真测试平台实时仿真技术方案的结构与组成,并对其实时网络通讯方法,仿真计算机的实时仿真方法等关键技术进行了详细的说明,最终给出了多AUV协同航行的实时仿真视图;试验结果表明该技术方案工作可靠、使用方便、易于开发与维护,完全能够满足多AUV虚拟仿真测试平台进行仿真测试的需要.     

Periodic Nafion-silica-heteropolyacids electrolyte t for PEM fuel cell operated near 200 °C

Periodic ordered Nafion-silica-heteropolyacids electrolyte is synthesized through a facile multiphase self-assembly between the positively charged silica, negatively charged HPW acids (H₃PW₁₂O₄₀) and Nafion ionomers. The results exhibit uniform nanoarrays with long-range order of the electrolyte. The well-ordered proton conducting sites make the proton move through the membrane freely with low humidity dependence of proton transportation through the electrolyte. The Nafion-Silica-HPW electrolyte displays desirable conductivity at both low and elevated temperature. The proton conductivity of Nafion-Silica-HPW electrolyte at absolutely dry condition of 200 °C is 0.044 Scm⁻¹. At low temperature of 75 °C, the proton conductivities of the electrolyte were 0.029 Scm⁻¹ and 0.093 Scm⁻¹ at absolute dry (0 RH%) and full humidifying condition (100 RH%), respectively.     

老年医院护理单元的设计策略探索

随着中国人口老龄化速度的加快,截至2020年,65岁以上老年人口比例增至11.7％.老龄人口的递增,促使老年医院在各地不断涌现.其中,护理单元作为老年医院的康复核心,患者停留时间长,医疗任务重,须进行高标准设计.本文分析、总结了老年医护单元的设计模式,以期对相关研究有所启发.     

Hydrogen crossover through perfluorosulfonic acid membranes with variable side chains and its influence in fuel cell lifetime

In this study, hydrogen crossover in long side chain Nafion 211 membrane and short side chain Aquivion membrane is studied under different conditions. It is found that both temperature and relative humidity significantly influence the hydrogen crossover in the polymer electrode membranes (PEMs). The difference in hydrogen crossover behavior between Nafion 211 membrane and Aquivion membrane is revealed. The influence of hydrogen crossover on the fuel cell lifetime is also investigated under open circuit voltage (OCV). It is proved hydrogen crossover in the PEM would lead to possible degradation of the PEM and the decrease of electro-chemical surface area in the catalyst of the single cell. Single cell assembled with Aquivion membrane shows slower OCV and ECSA decay compared to the Nafion 211 single cell. Our results suggest that the PEM fuel cell lifetime is closely related to the hydrogen crossover in the PEM. The current study also highlights the possibility of improving the fuel cell durability by rational design of the PEM morphology.