Preparation of Al2O3-mullite thermal insulation materials with AlF3 and SiC as aids by microwave sintering

Al₂O₃-mullite composites were prepared under the synergy effect of AlF₃ and SiC aids by microwave heating. The phase composition, microstructure, porosity, flexural strength, thermal shock resistance, and thermal conductivity were investigated. The XRD results revealed that the content of mullite phase steadily increased with the increasing of AlF₃ content. The microstructure showed that the lower content (≤1 wt%) of AlF₃ led to the formation of granular mullite and the higher content (≥3 wt%) of AlF₃ led to the formation of mullite whiskers, which could form an interlocking structure. In addition, the SiC hot spots can also promote the generation of mullite whiskers by microwave sintering. The thermal shock resistance was significantly improved by the interlocking structure of mullite whiskers. The residual rate of flexural strength of the composite with 3 wt% AlF₃ was 86%. The composite with 3 wt% AlF₃ additives got its optimized thermal conductivity from 30°C to 950°C, the value was between 0.819 and 1.021 W/(mK), which possess excellent thermal insulation performance.     

基于断裂力学的钢丝缠绕胶管疲劳寿命分析

建立钢丝缠绕胶管的三维有限元模型,基于橡胶材料疲劳裂纹扩展理论,选取钢丝缠绕角度、钢丝层间距、钢丝层数、钢丝直径4个结构参数,采用正交试验法,以橡胶材料疲劳寿命为依据,分析在交变负荷下胶管的疲劳寿命和最大轴向位移。结果表明:钢丝层间距对胶管疲劳寿命的影响最大,其次是钢丝缠绕角度,再次是钢丝层数,最小是钢丝直径;钢丝层数对胶管最大轴向位移的影响最大,其次是钢丝缠绕角度,再次是钢丝层间距,最小是钢丝直径。     

面向踝部康复的广义球面并联机构型综合

针对现有踝关节康复机器人难以充分拟合踝关节复杂运动，人机相容性较差的问题，提出一系列与踝关节实际骨结构匹配程度更高的串联等效拟合模型。为满足踝关节串联等效拟合模型对康复机器人机构本体的功能需求，给出一种具有串联等效拟合模型的广义球面并联机构型综合方法。首先枚举出广义球面机构的基本构件及运动副，并依此构造出广义球面支链。继而基于螺旋理论分析单支链以及多支链组合对动平台的约束性能，给出支链的组合条件与原则，阐明不同支链在机构中作用的异同，并依此归纳出位置支链和姿态支链两类广义球面基本支链。最后基于基本支链的约束特性，根据支链组合条件，综合出一系列适用于踝关节康复机器人本体研究的广义球面并联机构，并通过螺旋理论证明其与踝关节串联等效拟合模型的自由度数及性质具有一致性，为此类康复机器人本体设计提供理论依据。     

一种新型高杆灯灯盘挂接装置模型的设计与实验研究

高杆灯是由钢制柱型灯杆和大功率组合式灯架构成的新型照明装置。文中对高杆灯顶部灯盘的挂接进行研究,设计了一套挂接和脱卸方便,电极对接可靠的灯盘挂接装置模型,以指导实际产品的设计制作。通过改变挂接方式与挂接装置结构,借助SolidWorks软件进行三维模型结构设计,加工装配得到挂接装置实物模型。整套机构模型利用单片机控制,引导灯盘挂接顺利完成。     

防振条约束失效对蒸汽发生器传热管面内流弹失稳的影响研究

根据防振条布置以及面内支承连续失效个数，将防振条面内约束失效分析划分为多种工况，分析了不同工况下面内约束失效对传热管面内模态的影响，采用各位置阻尼在振型函数上进行加权平均的方法计算了各阶模态的阻尼比，进而研究了防振条面内不同约束对传热管面内流弹失稳的影响。分析结果表明，随着面内支承连续失效位置的增多，弯管段面内首阶模态频率不断降低，出现在弯管段的振型越加明显；弯管段面内首阶模态不一定是最大流弹失稳比值出现的模态，最大流弹失稳比值出现模态的振型几乎都出现在弯管段；随着面内支承连续失效位置的增多，面内流弹失稳比值不断增大，当连续3个及以上防振条面内约束失效时，将出现流弹失稳现象。     

Exploratory study of betavoltaic battery using ZnO as the energy converting material

Third-generation-semiconductor zinc oxide is utilized as an energy converting material in a betavoltaic battery, where 0.06 Ci~(63) Ni and 8 Ci~(147) Pm are used as the beta sources. Based on a Monte Carlo simulation, the full scales of the devices are derived as 17 and 118 lm,respectively, for both sources. The influences of semiconductor doping concentrations on the electrical properties of the devices are analyzed. For a typical doping concentration N_A= 10~(17) cm~(-3), N_D= 10~(16) cm~(-3), the conversion efficiencies are 7.177% and 1.658%, respectively, using63 Ni and147 Pm sources. The calculation results of energy deposition in materials for the two sources show that the doping concentrations drop to 1 × 10~(13)–5×10~(14) cm~(-3) and 1 × 10~(12)–5×10~(13), and accordingly, the energy conversion efficiencies rise to 14.212% and 18.359%, respectively.     

Anchoring single Pt atoms on hollow Ag3VO4 spheres for improved activity towards photocatalytic H2 evolution reaction

The high cost of noble metal catalysts has been a great bottleneck for the catalyst industry. Using the noble metal at a single-atom level for catalytic applications could dramatically decrease the cost. The impacts of single Pt atoms on the photocatalytic performance of Ag₃VO₄ have been investigated and reported. In this report, single Pt atoms were anchored on the surface of Ag₃VO₄ (AVO) as a cocatalyst, and the resultant composite photocatalyst has been studied for photocatalytic H₂ production from water driven by visible light. The as-prepared AVO particles are hollow nanospheres in the monoclinic phase with a bandgap of 2.20 eV. The light absorption edge of AVO/Pt is slightly red-shifted compared to that of the pristine AVO, indicating more visible light absorption of AVO/Pt. The XPS peaks of Ag, V, and Pt exhibit a significant shift after AVO and Pt get into contact, suggesting the strong interaction between the surface Ag and V atoms, and single Pt atoms. After 3-h illumination, the photocatalytic H₂ evolution amount from AVO/Pt is improved up to 1400 μmol, which is 2.8 times that on the bare AVO. Such efficient photocatalytic H₂ evolution on AVO/Pt is still maintained after five reaction cycles. The better photocatalytic performance of AVO/Pt has been attributed to the more efficient visible light utilization and the lower interfacial charge transfer resistance, as demonstrated in the DRS and EIS spectra. The presence of the surface Pt atoms also leads to a higher amount of reactive radicals, which could efficiently promote the surface redox reactions.     

变邻域量子烟花算法求解CVRP

针对带容量约束的车辆路径问题，提出一种融合量子进化算法和变邻域优化策略的变邻域量子烟花算法。该算法采用等分随机键与最大位置法结合的实数编码方式，通过量子旋转门和非门变异提高算法全局搜索能力，同时运用结合2-Opt的变邻域优化策略加强局部搜索能力。选取17个基准算例进行参数实验和对比实验，实验结果表明，相对于对比算法，所提出的算法具有较好的寻优能力和收敛速度。