La0.6Sr0.4Co0.2Fe0.8O3-δ nanofiber cathode for intermediate-temperature solid oxide fuel cells by water-based sol-gel electrospinning: Synthesis and electrochemical behaviour

Water-based sol-gel electrospinning is employed to manufacture perovskite oxide La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) nanofiber cathodes for intermediate-temperature solid oxide fuel cells. LSCF fibrous scaffolds are synthesized through electrospinning of a sol-gel solution employing water as the only solvent. Morphological characterizations demonstrate that the LSCF fibers have highly crystalline structure with uniform elemental distribution. After heat treatment, the average fiber diameter is 250 nm and the porosity of the nanofiber tissue is 37.5 %. The heat treated LSCF nanofibers are applied directly onto a Ce_0.9Gd_0.1O_1.95 (CGO) electrolyte disk to form a symmetrical cell. Electrochemical characterization is carried out through electrochemical impedance spectroscopy (EIS) in the temperature range 550?°C–950?°C, and reproducibility of the electrochemical performance for a series of cells is demonstrated. At 650?°C, the average measured polarization resistance R_p is 1.0 Ω cm². Measured performance decay is 1 % during the first 33?h of operation at 750?°C, followed by an additional 0.7 % over the subsequent 70?h.     

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.     

中国大陆PCB产业自动化的现况与未来

从中国大陆PCB发展的现况分析实行设备自动化连线为企业所创造的价值。设备自动化连线是中国大陆PCB必须面临的改革出路。     

BaxSr（1—x）TiO3多层膜椭偏光谱研究

用溶胶－凝胶技术在Bi(100）衬底上制备了单层和渐变型多层的BaxSr(1-X)TiO3薄膜，其膜层组分分别为：Ba0.7Sr0.3TiO3,Ba0.8Sr0.2TiO,Ba0.9Sr0.1TiO3,BaTiO3，对生长制备出的多层BaxSr(1-X)TiO3薄膜进行了变角度椭偏光谱测量，通过椭偏光谱解谱分析研究，首次得到了BaxSr(1-X)TiO3多层膜结构不同膜层的膜厚和光学常数，其结果显示：椭偏光谱分析得到的不同膜层的膜厚与卢瑟福背向散射测量得到的结果基本相符；渐变型多层膜中BaTiO3薄膜的折射率比单层BaTiO3薄膜折射率大许多，与体BaTiO3的折射率相接近，这说明渐变型多层膜中BaTiO3薄膜的光学性质与体材料的光学性质接近。     

CNC中插补和轴伺服的微机仿真

本文级出了在ＰＣ机上对一个自己开发ＣＮＣ系统插祉和轴伺服控制进行仿真的结果。它包含按插补原理对直线、圆和渐开线的插补以及对轴伺服控制中的位置环和前馈控制的仿真。轴伺服马达通过一个二阶连续系统模型来仿真，最后得出对伺服进行前馈控制补偿可显著改善系统的输出。     

Google Erath在石油勘探中的应用

从网上下载的Google Earth卫星遥感照片更接近实际地形，在石油勘探初期，经常用它对工区进行踏勘和施工设计。文中详细地介绍了利用Google Earth进行施工设计的方法和步骤。     

The geometric nature of plasticity laws

This paper concerns the plasticity constitutive laws in small strain. In the thermodynamic approach developed here, the key concept is that of internal variables. The differential nature of plasticity law has been pointed out for a long time. If we unite the invariance condition of these laws in a state variable transformation, this involves, ultimately, that the natural mathematic frame of plasticity theory is Differential Geometry. The system state is defined as a point of a differentiable manifold. The state variable are the local coordinates of this point in a chart. The internal stresses are the components of a covariant vector of the cotangent bundle to internal state manifold and the elastic domain is a convex part of cotangent vector space. The plastic yield criteria such as von Mises condition define a Riemannian structure over the manifold. The metric element is identified with the internal dissipation element. Constitutive laws link the covariant derivatives of the thermodynamic stress with the state variable. Hardening modulus splits up in two parts, kinematic hardening and metric hardening. This last is defined by Christoffel connection coefficients. Applied to von Mises isotropic yield condition, the metric hardening is identified with isotropic hardening. The Baltov-Sawczuk model is also analysed. The use of appropriate polar coordinates simplifies significantly the computations. Generalization to a significant category of non-differentiable yield criteria, such as Tresca condition, is considered by introducting a metric tensor family. The adaptation of Drucker's postulate to the proposed model requires the introduction of parallel transport of the internal stress covector. Generally, this transport is different over distinctive paths joining two points. This fact expresses internal state manifold curvature. The Riemann-Christoffel tensor is computed for von Mises, Baltov-Sawczuk and Tresca models.