Enhanced electrochemical performance of solution impregnated La0.8Sr0.2Co0.8Ni0.2O3−δ cathode for intermediate temperature solid oxide fuel cells

Solution impregnated La_0.8Sr_0.2Co_0.8Ni_0.2O₃ + Gd-doped CeO₂ (LSCN + GDC) cathodes for intermediate temperature solid oxide fuel cells (IT-SOFC) are prepared and their electrochemical properties are evaluated and compared with the conventional LSCN cathodes. The results indicate that the cathode performance can be enhanced by the presence of the nanosized microstructure produced with the solution impregnation method. It is determined that the amount of LSCN loading in the LSCN + GDC composite cathode needs to be higher than 35 wt% in order to achieve a performance superior to that of the conventional LSCN cathode. The optimum amount of LSCN loading is in the range of 45-55 wt% with an activation energy near 1.32 eV for oxygen reduction. At temperatures between 600 and 750 °C, the polarization resistance of the 55 wt% LSCN loaded LSCN + GDC cathode is in the range of 1.07 and 0.08 Ω cm², which is only about one half of that for the conventional cathode.     

High-quality hexagonal ZnO crystals grown by chemical vapor deposition

High-quality zinc oxide (ZnO) crystals were grown on a (0001) sapphire substrate by chemical vapor deposition at 830 °C under atmospheric pressure. The hexagonal crystals had an average diameter of about 150 μm, and a thickness of about 15 μm, as observed under a polarizing microscope. The large (0002) facet was flat, regular, and neat. In the X-ray diffraction pattern, strong (0002) and weak (0004) peaks indicate that the crystals had a wurtzite structure. The crystalline quality was characterized by Raman scattering, and the E₂(high), E₂(low), and A_l(LO) modes confirm the high quality of the ZnO crystals. Photoluminescence (PL) spectra of the crystals had a strong and sharp ultraviolet emission peak at 379 nm. The PL mechanism was also discussed.     

Pseudo-plastic moment resistance of continuous beams with cold-formed sigma sections at internal supports: An experimental study

Most thin-walled sections exhibit elastic-softening moment-rotation characteristics in bending, and therefore the elastic analysis/design method is usually recommended for continuous beams with this type of section. A more economical design approach, the pseudo-plastic design method, has been proposed to allow for the development of moment redistribution in the system. To facilitate this design method, pseudo-plastic moment resistance (PPMR) at the internal supports is required. This paper reports an experimental study of the structural performance of continuous beams with cold-formed sigma sections near the internal supports, based on which the PPMR was derived. To this end, only the part of the beam carrying a hogging moment near one of the internal supports was specifically studied. It was represented with a simply supported beam subjected to a central point load. The simple supports were placed at inflexion points and the concentrated load was a representation of the reaction. Research results include the behaviours of initial buckling, post-buckling and post-failure of sigma beams near the internal supports, the ultimate moment resistance under combined bending and shear, and the moment-rotation relationship. Four typical localised collapse patterns have been established and defined. The results of ultimate moment resistance obtained were compared with the theoretical predictions by using two codified methods, namely, the effective width method (EWM) and the direct strength method (DSM). Lastly, a semi-empirical approach has been proposed to find the pseudo-plastic moment resistance at the internal supports.     

Adaptive ANFIS-based filter for active control of sinusoidal primary noise in nonlinear path

Linear active noise control (ANC) system is promising in suppressing broadband and narrowband noise in a linear acoustic site.However,in some situations,the acoustic systems are nonlinear which make the primary noise being nonlinear distortion at the canceling point,and the linear ANC system maybe can not work well for these cases.This paper presents an adaptive network-based fuzzy inference system (ANFIS)-based nonlinear filter for active noise control,which is expected to be successfully applied to situations with nonlinear distortion.In the proposed adaptive control algorithm,the parameters are updated by gradient descent method.In the simulations,the secondary-path FIR model coefficients are estimated in advance by off-line system identification method,and one case for sinusoidal primary noise with nonlinear distortion is presented,which verifies the effectiveness of the proposed system in suppressing sinusoidal noise generated by rotating machines,e.g.,engines in vehicles.     

Numerical simulation of temperature rise within hydrogen vehicle cylinder during refueling

Basing on the Spallart-Allmaras turbulence model and the real gas equation of state, a numerical model is proposed in this paper to study the mechanism of temperature rise within hydrogen vehicle cylinder during refueling. The model is validated by comparing calculated results with experimental data. With the validated model, the effect of mass filling rate, initial pressure within cylinder and ambient temperature on the maximum temperature rise during refueling are investigated. The study shows that the maximum temperature rise increases with the growth in mass filling rate and ambient temperature, while it descends as the initial pressure increases. Finally, an empirical formula is obtained by fitting numerical results and effective methods for temperature control is given.     

西安古城墙连接段工程设计探讨

概要介绍了西安古城墙的历史背景及连接段工程在设计中所采用的几项技术措施,对结构分析也作了简要论述。最后,针对工程在实施中的具体情况指出了存在的不足,并明确了在运营过程中需要继续解决的问题。     

Impedance monitoring of cell adhesion and growth on mesoporous membrane

We present a microdevice configuration for impedance monitoring of adherent cells cultured on the surface of mesoporous membranes. The device fabrication was based on a 3 layer PDMS process which allows easy integration of microelectrodes in close proximity to cultured cells. The measurements were performed with HeLa cells on 30 nm diameter membranes of polycarbonate and embedded Pt and Ag/AgCl electrodes. As expected, the impedance of the cell-membrane assembly changes rapidly during the first 30 min due to cell adhesion and it continuously increases until cell confluence at day 5. This membrane based device configuration should be useful for accurate and real-time monitoring in cell adhesion, growth and migration studies.     

城市河道游憩空间规划建设探讨——以安康市汉滨区汉江为例

随着我国城市化水平的提高以及新型城镇化战略的提出,建设友好的城镇人居环境将是今后城镇建设的重点内容。文章以安康市汉滨区汉江河道游憩空间规划建设为例,分析了城市河道游憩空间的开发的内容和规划设计。     

应用格罗布斯准则判定测量结果中的粗大误差

使用格罗布斯准则判定检测结果中粗大误差是一种简单、实用的方法;在实际检测过程中较其它判定准则效果好;在机械产品的检定过程中有一定的应用价值。     

虚拟装配技术在交互式电子手册中的应用

为了提高装备保障和装备教学的效率,减少真实装备的损耗,以某型装备的维护为背景,利用可视化仿真技术实现了虚拟装配通用平台;该方法采用VS2005为主要开发工具,实现了虚拟环境的建立;然后根据装备的具体操作流程设定对应的逻辑关系,保证了虚拟装配的过程符合实际的装备特性,并在实际的运行环境中进行了流程优化,该平台在具体装备的维护过程中为用户提供了一个生动的交互式虚拟操作环境,实现了在虚拟环境中进行各种操作,同时也为后续的装备保障和装备运行仿真提供了技术基础.