Quantification of grain boundary defect chemistry in a mixed proton-electron conducting oxide composite

Dual phase oxide membranes have shown promising hydrogen permeation fluxes in syngas applications due to their high mixed proton electron conduction (MPEC). However, the conductivity of grain boundaries can be many orders of magnitude lower than that of the bulk and so limits the total conductivity and hydrogen permeation. In this study, the three-dimensional nanoscale oxygen and cation distributions around grain and phase boundaries in a BaCe_0.8Y_0.2O_3-δ-Ce_0.8Y_0.2O_2-δ (BCY-YDC) membrane were quantified by atom probe tomography (APT) and related to average grain boundary conductivity measured by electrochemical impedance spectroscopy (EIS). Segregation varied among the general high-angle grain boundaries analyzed, but no trend from orientation analysis was determined. Correlative APT and electron energy loss spectroscopy (EELS) of one YDC grain boundary revealed composition and cerium valence information, respectively, allowing for the determination of vacancies at the grain boundary. While a specific MPEC membrane is characterized, the results are relevant to proton and electron conduction in a number of technologically important ceramics.     

低压环境下航空电缆材料燃烧特性的研究

在高高原实验室(61 kPa、4 290 m)和广汉实验室(96 kPa、520 m),分别开展常低压条件下FXL型航空电缆的对比燃烧实验。通过热辐射加热箱、烟密度及成分测试仪和氧指数仪等设备,测量点燃时间、烟密度、质量损失速率和CO、CO2及O2等浓度变化。实验结果表明:在96 kPa和61 kPa两种实验环境下,低压下最小点燃时间及温度的数值更大,两者的温度和时间差分别为15℃和4.8 s;烟密度曲线快速升高后趋于平衡,61 kPa条件下的发烟量小于96 kPa;O2体积浓度随着加热时间先下降后升高,而CO2的变化趋势相反。在61 kPa条件下,CO曲线会出现双峰现象且更明显;随着氧浓度增加,质量损失速率加快且呈线性关系;压力因素对燃烧影响减弱且燃烧持续时间差值变小。研究结果揭示了低压环境对航空电缆的燃烧影响,为增强航空安全提供参考。     

Multi objective optimization of a tri-reforming process with the maximization of H2 production and minimization of CO2 emission & power loss

In this study, the process optimization of a tri-reformer reactor is conducted for the synthesis of hydrogen gas from natural gas using multi-objective optimization (MOO) approach. Specifically, four MOO problems are solved using three objective functions, namely maximization of H₂, minimization of CO₂, and minimization of power loss. It should be noticed that the power loss is an important economic factor due the large pressure drop and flowrates in packed bed reactors. However, it has not been used as an objective function for the optimization based design and/or operation of fixed bed reactor for reforming process to the best of authors’ knowledge. Three of the four MOO problems are 2-objective in nature with all the permutation and combination of the three objectives. The fourth MOO problem is solved considering all the three objectives, simultaneously. For all the MOO problems, feed conditions of O₂, H₂O, and Temperature are considered as the optimization variables. The results obtained with 3 objective functions are observed to be superior to the ones obtained from 2 objective problems.     

A simple improvement of a tip loss model for actuator disc simulations

The loading of a wind turbine decreases towards the blade tip because of the velocities induced by the tip vortex. This tip loss effect has to be taken into account when performing actuator disc simulations, where the single blades of the turbine are not modeled. A widely used method applies a factor on the axial and tangential loading of the turbine. This factor decreases when approaching the blade tip. It has been shown that the factor should be different for the axial and tangential loading of the turbine to model the rotation of the resulting force vector at the airfoil sections caused by the induced velocity. The present article contains the derivation of a simple correction for the tangential load factor that takes this rotation into account. The correction does not need any additional curve fitting but just depends on the local airfoil characteristics and angle of attack. Actuator disc computations with the modified tip loss correction show improved agreement with results from actuator line, free wake lifting line, and blade element momentum simulations.     

入口弯管对矿用轴流通风机气动性能影响的数值研究

以某大型矿用低压轴流式通风机为研究对象, 采用气体动力学性能试验和数值模拟的方法研究了不同入口弯管对风机性能的影响, 重点分析了入口弯管引起的叶轮内部流动特征和损失分布的变化规律。研究结果表明, 风机入口采用弯管连接缩短了进口管道的轴向长度, 节省了地下空间, 但同时来流的均匀性受到影响。弯管内气流速度梯度较大, 管道内侧易发生流动分离, 产生回流区, 增大了流体流动时的能量损失, 风机的整体性能下降。弯管与叶轮入口之间的连接长度会影响内部流场, 当附加直管段较长时, 来流均匀性得到提高, 风机性能有所改善。     

Grain boundary engineering that induces ultrahigh permittivity and decreased dielectric loss in CdCu3Ti4O12 ceramics

Dielectric materials with ultrahigh permittivity are attracting attention due to the increasing demand for these types of materials for microelectronics and energy storage applications. In this work, we successfully synthesized Zn-doped CdCu₃Ti₄O₁₂ (CdCTO) ceramics with low dielectric loss and large permittivity via an ordinary mixed-oxide technique. Remarkably, at a Zn doping level of 0.10, a CdCu_2.9Zn_0.1Ti₄O₁₂ ceramic exhibited both decreased dielectric loss tangent of ~0.058 and large dielectric permittivity > 4.0 × 10⁴, as well as a good frequency stability over a wide frequency range from 40 Hz to 10⁶ Hz. The high dielectric performance was attributed to the enhanced grain boundary resistance and internal barrier layer capacitor (IBLC) effect due to the fine and uniform grains that formed upon Zn doping. The findings reported in this work provide valuable insights into how to simultaneously realize a low dielectric loss and high permittivity in CdCTO and other related dielectric ceramics.     

A simple and effective design strategy to increase power conversion efficiency of linear charge pumps

This paper introduces a simple design strategy to increase the power efficiency of linear charge pumps. The technique exploits a voltage amplitude of the clock signal lower than the supply voltage to reduce the power conversion losses. The nominal output voltage is maintained unaltered by increasing the number of stages.     

立井井筒安全智能巡检机器人系统的研究

煤矿立井井筒作为矿井通往地面的主要进出口,其周围环境的安全状况以及井筒自身施工质量必须予以足够的重视。为了实时监测记录井筒环境参数、及时对井壁裂纹等状态进行评估和预警,设计了一套立井井筒安全智能巡检机器人系统。以STM32F103ZD为主控制核心,并将提升罐笼作为移动平台,通过高清摄像头和传感器等采集信息,经过WiFi无线传输至上位机,方便工作人员实时查看井筒环境状况以及相关设备运行情况,提高建设期及服役期井筒的安全保障能力。     

水煤浆管道输送摩阻损失研究

以十二醇醚为分散剂,进行了水煤浆管道输送实验研究,分析了分散剂浓度和煤浆浓度变化对煤浆摩阻损失的影响。煤浆管道输送数据分析及理论计算结果表明: 分散剂浓度越大,煤浆摩阻损失值越小; 水煤浆浓度越大,摩阻损失值越大。实验数据拟合结果表明有效黏度与平均切变率成线性关系,从理论上给出了煤浆摩阻损失的计算公式,计算值与实测值偏差不大于18%。