Finite element optimization of sample geometry for measuring the torsional shear strength of glass/metal joints

Assessment of mechanical properties of glass/metal joints is a challenging process, especially when the application relevant conditions of the joints have to be considered in the test design. In this study, a finite element method (FEM) is implemented to analyze a torsional shear strength test designed for glass-ceramic/steel joints aiming towards solid oxide fuel/electrolysis cells application. Deviations from axial symmetry of the square flanges (ends) of respective hourglass-shaped specimens and also supporting and loading sockets of the test set-up are included in the model to simulate conditions close to reality. Undesirable tensile stress and also shear stress concentration appear at the outer edge of glass-ceramic layers, which are less for the hollow-full specimen. The simulation results show that for a specimen with either 9 mm thick square- or 6 mm thick triangular-flanges, locally enhanced tensile stresses almost disappear, resulting in a symmetric shear stress distribution. The difference between the analytically derived nominal shear strength and the real critical shear stress derived via simulation reduces with decreasing the fracture torque.     

Yolk–shell structured iron carbide/N-doped carbon composite as highly efficient and stable oxygen reduction reaction electrocatalyst

We report a simple route to synthesize iron carbide/carbon yolk–shell composite via a facile two-step process including polymerization of pyrrole using Fe₃O₄ as a sacrificial template to form a Fe₃O₄/polypyrrole composite, followed by annealing at high temperature in N₂ atmosphere. The yolk–shell composite, with iron carbide (Fe_2.5C) embedded in nitrogen-doped carbon layers, shows impressively high catalytic activity and stability for oxygen reduction reaction in alkaline solution. Both the pyridinic-N and graphic-N in the shell of Fe₃O₄–PPy-700, together with the Fe_2.5C confined in carbon layers are believed to be the active sites for the ORR.     

Performance investigation on a novel 3D wave flow channel design for PEMFC

Flow field structure can largely determine the output performance of Polymer electrolyte membrane fuel cell. Excellent channel configuration accelerates electrochemical reactions in the catalytic layer, effectively avoiding flooding on the cathode side. In present study, a three-dimensional, multi-phase model of PEMFC with a 3D wave flow channel is established. CFD method is applied to optimize the geometry constructions of three-dimensional wave flow channels. The results reveal that 3D wave flow channel is overall better than straight channel in promoting reactant gases transport, removing liquid water accumulated in microporous layer and avoiding thermal stress concentration in the membrane. Moreover, results show the optimal flow channel minimum depth and wave length of the 3D wave flow channel are 0.45 mm and 2 mm, respectively. Due to the periodic geometric characteristics of the wave channel, the convective mass transfer is introduced, improving gas flow rate in through-plane direction. Furthermore, when the cell output voltage is 0.4 V, the current density in the novel channel is 23.8% higher than that of conventional channel.     

Fabrication and characterization of In doped Li13.9Sr0.1Zn(GeO4+δ)4 electrolytes for proton-conducting solid oxide fuel cells

Li_13.9Sr_0.1Zn(GeO_4+δ)₄ (LSZG) materials can exhibit proton conduction by Li⁺/H⁺ ion exchange in hydrogen atmosphere. It can be used in solid oxide fuel cells (SOFCs) as an electrolyte. In this study, In³⁺ doped LSZG powders are synthesized by sol-gel method. X-ray diffraction, scanning electron microscopy, thermal gravimetric analyzer, and electrochemical impedance spectroscopy are used to investigate the effects of In doping on LSZG. All Li_13.9-xIn_xSr_0.1Zn(GeO_4+δ)₄ (LISZG, 0 ≤ x ≤ 0.3) ceramics exhibit the same phase with LSZG. The dopant of In promotes the sintering activity and Li⁺/H⁺ ion exchange rate of LSZG. The optimum doping of In is x = 0.2. At 600 °C, Li_13.7In_0.2Sr_0.1Zn(GeO_4+δ)₄ (0.2LISZG) shows a proton conductivity of 0.094 S/cm under 0.9 V direct current bias voltage. In addition, the single cell based on 0.2LISZG electrolyte is prepared, and it has been demonstrated that the practical utilization of 0.2LISZG in IT-SOFCs is feasible.     

Use of conditioning time to investigate the mechanisms of interactions of selected fatty acids on hematite Part II laboratory investigations

It is the aim of this paper to examine the effects of conditioning time on the flotation of hematite using three technical grade fatty acid reagents as providing additional evidence on their mechanism of interaction with the hematite surface. Various mechanisms have been postulated as occurring as conditioning time is increased. Both physical (e.g. conditioning time and power input) and chemical (nature, dispersion and solubility of the adsorbing species) contribute to the mechanisms of attachment of collector. In this paper, the mechanism of attachment of oleate to hematite can be readily explained by chemisorption, but the mechanism of attachment of lauric acid appears to be physical adsorption at neutral pH. The flotation of hematite with a mixture of tallow-type fatty acids (palmitic, stearic and oleic acids) is very sensitive to conditioning time, and suggests that, even though flotation is very effective at short conditioning times, it is very susceptible to the presence of fines and their associated high surface areas. It is therefore obvious that both the physical and chemical conditions contribute to the mechanisms of adsorption of fatty acids on iron-containing oxide minerals and must be understood in order to optimise the flotation of these minerals in an industrial situation.     

多视点稀疏测量的图像绘制方法

为了减少所需采集的视频数据量, 基于图像绘制(Image-based rendering, IBR) 的前沿方法将稠密视点信息映射成压缩感知框架中的原始信号, 并将稀疏视点图像作为随机测量值, 但低维测量信号由所有稠密视点信息线性组合而成, 而稀疏视点图像仅仅来源于部分视点信息, 导致稀疏视点采集的图像与低维测量信号不一致. 本文提出利用间隔采样矩阵消除测量信号与稀疏视点图像位置之间的差异, 进而通过约束由测量矩阵和基函数构成的传感矩阵尽量满足有限等距性, 使得能够获得原始信号的唯一精确解. 仿真实验结果表明, 相比于前沿方法, 本文提出的方法对于不同复杂程度的场景重建都提高了主客观质量.     

正弦脉宽调制波通用谐波计算与分析方法

针对采样型正弦脉宽调制(SPWM)技术中几种传统实现方法各有优缺点的问题,特别是在谐波含量这一重要指标上的比较,提出了一种谐波通用计算与分析方法,可作为SPWM新技术研究的辅助工具。基于MATLAB数值计算和傅里叶级数,以不对称规则采样法SPWM波的生成及其谐波计算为例,详细分析了脉宽调制(PWM)波的各次谐波和总谐波系数(THD)的计算过程。通过该方法计算对称规则采样法与不对称规则采样法SPWM波的THD值,比较结果验证了该方法的可行性。同时通过以占空比为30%的方波的谐波计算,证明了该方法的通用性。     

基于多变量解耦控制的配电网单相接地故障集成化柔性消弧方法

随着静止无功补偿装置、柔性消弧装置、大功率逆变器等电力电子装备应用逐渐增多,配电网柔性化加快发展,但已有电力电子装备存在功能单一、成本高等问题.基于直流侧并接储能元件的直挂式级联H桥变流器,将多变量解耦控制方法与电流消弧方法相结合,实现柔性电力电子装备输出电流在dq0坐标系下的独立调节,使单套柔性电力电子装备同时集成配电网有功功率、无功功率双向流动控制,以及单相接地故障柔性消弧功能,有效提高电力电子装备的利用效率.理论分析以及功率控制和单相接地故障消弧建模仿真结果验证了所提方法的可行性.     

A dinuclear copper(II) complex and a zigzag chain iron(II) polymer based on the 4-antipyrine derived Schiff base ligands: The hydroxylation and redox occurred under the solvothermal conditions

A new dinuclear copper(II) compound, [Cu₂(L1-O)₂] (1) (L1 = (4E)-4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one), and zigzag chain polymer, {[FeCl₂(L2)]}_n (2) (L2 = 1,5-dimethyl-2-phenyl-4-{[(1E)-pyridine-4-ylmethylene]amino}-1,2-dihydro-3H-pyrazol-3-one), were synthesized by solvothermal reactions and structurally characterized. The methyl group hydroxylation and the redox have been observed in the preparation of 1 and 2, respectively.     

新能源汽车低频振动噪声传递路径模拟方法

针对新能源汽车低频噪声分布规律具有复杂性,造成噪声传递路径模拟难度加大等问题,提出新能源汽车低频振动噪声传递路径模拟方法。定义声阻与声抗以明确材料声学特征,以此为基础建立新能源汽车低频振动方程。分析低频振动噪声传递路径,使用力锤激励法测量传递函数,同时采用悬置刚度方法测量激励力,分析噪声激励响应,并修正噪声响应系数。计算有效点导纳,分别获取每个噪声在对应传递路径上的贡献量,确定噪声分布规律,实现噪声传递路径模拟。仿真结果表明,所提方法噪声估计精准度高,模拟时间短,模拟准确率高,能够为汽车降噪提供重要参考。