水平轴风力机桨叶计算模态分析

用有限元分析的方法对水平轴风力机的浆叶进行了计算模态分析和研究,通过对300W浆叶的模态计算分析结果与实验模态结果加以对比和验证,得到了在低阶条件下合理的浆叶模态计算模型,探讨了以有限元为基础的计算模态分析在选择不同的计算模型时对计算结果的影响,最后对600kw浆叶进行了模态计算,其结果与采用“Bladed for Windows”软件的计算结果作了比较,得到了满意的一致结果。     

波分复用无源光接入网生存性机制的分析与设计

在介绍波分复用无源光接入网(WDMPON)的基础上,对WDMPON的生存性机制进行了分析,设计完成了两个具体可行的WDMPON系统保护方案。     

The cyclic oxidation behavior of the single crystal TMS‐82+ superalloy in humidified air

The cyclic oxidation behavior of a single crystal Ni‐based superalloy TMS‐82+ was studied at 800 and 900 °C for 200 h in water vapor (air plus 15% H₂O). Regardless of the exposure temperature, time‐dependence of the growth rate of the scale for the superalloy was fitted by a subparabolic relationship. The oxidation rate was enhanced with increase in exposure temperature, which was evidenced by a higher mass gain and thicker scale. The oxides on the specimen at 800 °C consisted of (Ni,Co)O, CrTaO₄, AlTaO₄, Cr₂O₃, and θ‐Al₂O₃, whereas for the specimen exposed at 900 °C, spinels of NiCr₂O₄ and (Ni,Co)Al₂O₄ as well as α‐Al₂O₃ were observed. An innermost dense α‐Al₂O₃ layer was responsible for a stable growth rate of the scale after the initial rapid oxidation.     

Tuning the de/hydriding thermodynamics and kinetics of Mg by mechanical alloying with Sn and Zn

Mg₉₅Sn₃Zn₂ alloy was prepared by mechanical alloying. The phase constituents and phase transition were analyzed by X-ray diffraction (XRD) method. The microstructure was characterized by scanning electron microscope (SEM). The hydrogen storage properties were evaluated in detail by the measurements of isothermal hydrogen absorption and desorption, and pressure-composition isotherms (PCI) using the Sieverts method. The addition of Zn benefits to extend the solubility of Sn in the Mg lattice, as a result supersaturated Mg(Sn, Zn) ternary solid solution was synthesized by mechanical alloying, which decomposed to MgH₂, Sn and MgZn₂ in the hydrogenating process. The in situ formed nanostructure Mg₂Sn and MgZn₂ have positive effects on the hydrogen absorption and desorption of Mg. Mg₉₅Sn₃Zn₂ alloy showed significantly improved kinetics with lowered hydrogen absorption and desorption activation energies of 38.1 kJ/mol and 86.6 kJ/mol respectively, and exhibited a reduced dehydriding enthalpy of 67.0 ± 1.9 kJ/(mol·H₂).     

The Improvement of Oxidation Resistance of a Re-Based Diffusion Barrier/Ni�CAl Coating on the Single-Crystal Ni-Based TMS-82+ Superalloy

Oxidation behavior of a Re-based diffusion barrier/Ni?CAl coated single-crystal (SC) Ni-based TMS-82+ superalloy was studied to compare with those of the base and Ni?CAl coated superalloys under cyclic air at 1150 °C for 200 h. The base superalloy showed a negative mass gain due to extensive oxide spallation, and the Ni?CAl coated superalloy without the diffusion barrier started to spall slightly after about 90 h. The oxidation resistance of the Ni?CAl coated superalloy with the Re-based diffusion barrier was greatly improved due to the formation of a dense ??-Al₂O₃ layer in the scale. The Re-based alloy was an effective diffusion barrier layer against inward diffusion of Al and outward diffusion of alloying elements in the alloy substrate due to the reduced thickness of interdiffusion zone with small amount of detrimental precipitates and higher content of Al in the Ni?CAl coating that supplied enough Al for formation of the ??-Al₂O₃ layer.     

脱硫石膏轻质底层粉刷砂浆施工应用技术研究

以脱硫建筑石膏主要胶凝材料,配合轻骨料以及外加剂配制而成的脱硫石膏轻质底层粉刷砂浆,代替传统水泥砂浆或混合砂浆,兼具墙体的找平层和保温层,同时具有防火、吸声、调节空气湿度等功能。采用机械喷涂技术,可解决石膏砂浆的施工难度问题,且施工速度提高三倍。同时解决脱硫废渣的处置问题,符合循环经济和节能环保要求。     

广域网数据库查询系统及其实现

文章提出了架构于各个数据库查询系统之上的全局数据库查询系统———广域网数据库查询系统,分析了广域网数据库查询系统的基本框架,并给出了一个应用实例。     

Effects of graphite addition and air exposure on ball-milled Mg–Al alloys for hydrogen storage

Magnesium hydride (MgH₂) is a promising candidate as a hydrogen storage material. However, its hydrogenation kinetics and thermodynamic stability still have room for improvement. Alloying Mg with Al has been shown to reduce the heat of hydrogenation and improve air resistance, whereas graphite helps accelerating hydrogenation kinetics in pure Mg. In this study, the effects of simultaneous Al alloying and graphite addition on the kinetics and air-exposure resistance were investigated on the Mg₆₀Al₄₀ system. The alloys were pulverized through high-energy ball milling (hereinafter HEBM). We tested different conditions of milling energy, added graphite contents, and air exposure times. Structural characterization was conducted via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). H₂ absorption and desorption properties were obtained through volumetry in a Sieverts-type apparatus and Differential Scanning Calorimetry (DSC). The desorption activation energies were calculated using DSC curves through Kissinger analysis. Mg₆₀Al₄₀ with 10 wt% graphite addition showed fast activation kinetics, even after 2 years of air exposure. Graphite addition provided a catalytic effect on ball-milled Mg–Al alloys by improving both absorption and desorption kinetics and lowering the activation energy for desorption from 189 kJ/mol to 134 kJ/mol. The fast kinetics, reduced heat of reaction, and improved air resistance of these materials make them interesting candidates for potential application in hydride-based hydrogen storage tanks.     

Hydrogenation of Pd/Mg films: A quantitative assessment of transport coefficients

Due to increasing energy demands, interest in hydrogen storage is substantial. Magnesium is one of the most attractive systems, yet, development for practical application remains challenging. By combination of X-ray diffraction, electron microscopy and in-situ measurements of resistivity we determine the diffusion coefficient of hydrogen in MgH₂ at technically relevant pressure (20 bar). Pd coated thin films of well-defined thickness enable a quantitative evaluation of the hydrogenation rate. From this, we detect linear to parabolic kinetic transition and obtain the diffusion coefficient of hydrogen in MgH₂. Measurements at different temperatures (RT-300 °C) demonstrate an Arrhenius behaviour with an activation energy E_a = 28.1 kJ mol⁻¹. This low value and the transformation into a nanocrystalline microstructure upon hydrogenation indicate grain boundary diffusion as the essential mechanism. In completion, the interface Pd/Mg is studied. Mg₅Pd₂ and Mg₆Pd form at elevated temperatures required for dehydrogenation. These phases affect, but do not prevent, further hydrogen loading.     

运动测量误差对带状SAR成像影响的定量分析

定量分析运动测量误差对成像的影响是实际机载SAR系统设计中的重要问题。本导出了沿方位向及瞄准线同时存在恒定位置误差和恒定速度误差,以及同时存在恒定位置误差、恒定速度误差及恒定加速度两种情况下,SAR回波信号压缩波形主瓣偏移、二次相位误差、三次相位误差及四次相位误差的解析式。对4个点目标得到的方位像仿真结果和利用中解析式计算结果一致,证明了推导的正确性。