Influence of silicon on the growth of barrier-type anodic films on titanium

Amorphous anodic titania, stabilised by incorporation of silicon species, is shown to grow to high voltages on sputter-deposited, single-phase Ti-Si alloys during anodizing at a constant current density in ammonium pentaborate electrolyte. The films comprise two main layers, with silicon species confined to the inner layers. An amorphous-to-crystalline transition occurs at ∼60 V on the Ti-6 at.% Si alloy, while the transition is suppressed to voltages above 140 V on alloys with 12 and 26 at.% silicon. The crystalline oxide, nucleated at a depth of ∼40% of the film thickness, is associated with the presence of a precursor of crystalline oxide in the pre-existing air-formed oxide. The modified structure of the air-formed oxide due to increased incorporation of silicon species suppresses the amorphous-to-crystalline transition until the onset of dielectric breakdown. The transport numbers of cations and anions during growth of the anodic oxides are independent of the concentration of silicon species in the inner layer, despite the marked change in the field strength.     

基于新型正序故障分量综合阻抗的有源配电网纵联保护

分布式电源接入配电网改变了传统配电网的拓扑结构,使故障特性发生了改变,常规的配电网电流保护将失去选择性。针对该问题,提出一种基于新型正序故障分量综合阻抗的有源配电网纵联保护方法。对不同类型分布式电源接入的线路发生区/内外故障时的正序故障电压、电流故障特征进行分析。利用区段两端电压、电流正序故障分量,构造两侧的线路推算阻抗,将它们相减后得到新型的综合阻抗。将综合阻抗与线路阻抗之比作为阻抗系数,进而构造区、内外短路故障的保护判据。通过大量仿真验证了所提保护算法的有效性,其能够准确地检测出短路故障,不受故障类型、故障位置、分布式电源类型、渗透率、分布式电源退出的影响,具有较强的抗过渡电阻能力,且灵敏度较高。     

Electrochemical properties of titanium arsenate membrane

Membrane potential is a measurable and reliable parameter to characterize the charge property of membrane. Membrane potentials have been measured across polystyrene based titanium arsenate membrane separating various 1:1 electrolytes at different concentrations. Membrane potential data have been used to calculate transference number of ions, mobility, distribution coefficient, charge effectiveness, permselectivity and also to derive the thermodynamically fixed charge density which is an important characteristic governing the membrane phenomena by utilizing the generally accepted theories for the salt concentration dependence of uni-univalent potentials, proposed by Teorell-Meyer-Sievers and Kobatake method and these are compared in order to obtain a relationship for the theoretical data of uni-univalent potentials. The good agreement between the theoretical and the experimental data of uni-univalent potentials proves the applicability of the relationship derived to the membrane system. Kobatake's equation was used under two limiting conditions, namely in the concentration range and in the dilute range. The two limiting forms of Kobatake's equation gave identical values of θ for the membrane taken in this investigation. Membrane is negatively charged (cation selective) and the selectivity increases with dilution. The structure of the membrane was observed with the aid of a scanning electron microscope. The order of fixed charge density for electrolytes used is found to be KCl > NaCl > LiCl.     

Numerical solutions of two dimensional Sobolev and generalized Benjamin–Bona–Mahony–Burgers equations via Haar wavelets

This work addresses, numerical method based on Haar wavelets and finite differences to solve two dimensional linear, nonlinear Sobolev and non-linear generalized Benjamin–Bona–Mahony–Burgers (NGBBMB) equations. The temporal part is discretized using finite differences while spatial part is approximated by two dimensional Haar wavelets. With this strategy, computing solution of two dimensional PDEs reduces to computing solution of linear system of algebraic equations. Collocation approach is then applied to determine the wavelet coefficients from linear system. This paper shows that two dimensional Haar wavelets are suitable and effective for two dimensional linear and non-linear PDEs. For validation of the proposed scheme different problems have been solved and error norms $L_{\infty },L_2$ are computed. Computation verifies that current scheme has good outcome.     

Synthesis of yttrium and cerium doped ZnO nanoparticles as highly inexpensive and stable photocatalysts for hydrogen evolution

Yttrium and cerium co-doped ZnO nanoparticles were synthesized by combustion route and characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),UV-visible diffuse reflectance spectroscopy(UV-vis DRS),photoluminescence(PL)and electrochemical impedance spectroscopy(EIS)techniques.The introduction of yttrium ions has efficiently increased the relative percentage of Ce³⁺ions in ZnO.Yttrium and cerium co-doped ZnO shows efficient photo activity for hydrogen evolution(10.61 mmol/((g·h))higher than previously reported optimal value for rare earth codoped ZnO photocatalysts.This remarkably increased hydrogen evolution can be ascribed to the synergy between electronic anchoring effect of Y³⁺/Y²⁺and Ce⁴⁺/Ce³⁺redox couples.This report presents new idea for the synthesis of efficient photocatalyst using economical route and ion anchoring effect.The hydrogen evolution was also tested using Na₂S and Na₂SO₃as electron donors under visible light illumination.The synthesized photocatalysts also exhibit high stability.