Microstructure and shear strength of ZrB2SiC/Ti6Al4V joint by TiCuZrNi with Cu foam

In this paper, brazing behaviors between ZrB₂SiC and Ti6Al4V by Cu foam interlayer were studied. The microstructure, formation mechanism, mechanical property and fracture surface of the joints were systematically studied. The results showed that the phases in the joints were α+β-Ti, TiCu, Ti₂Cu, Cu(s, s), TiC, TiB₂ and Ti₃SiC₂. An optimum shear strength reached up to 435??MPa?at a brazing temperature of 910?°C and holding time of 20?min. Such a shear strength was 90?MPa higher than the one without the Cu foam. The obtained high shear strength of joint was discussed from microstructure and residual stress. With the increase of brazing time, Cu(s,s) gradually disappeared and the content of Ti₂Cu intermetallic compound increased, which was harmful for the joint. Furthermore, the residual stress of joint with Cu foam was calculated to be 324?MPa, lower than the one without Cu foam interlayer.     

铜铁试剂—示波计时电位法测天然水/饮用水中的铝含量

铜铁试剂(CUP)—示波计时电位法直接测定天然水和饮用水中的铝含量。在0.5 mol/L(NH_4)_2SO_4-NH_3·H_2O(pH值=5.4)缓冲溶液中,加入铝后,铝—CUP配合物切口电位为-1.20V,切口深度在7.2×10~(-7)～3.2×10~(-5)mol/LAl范围内有线性关系,检测下限为5.8×10~(-7)mol/L。在2.0×10~(-5)mol/L时相对标准偏差为5.1(n=10)。应用该法测定了天然水和饮用水中铝含量,并同ICP/AES所获结果进行了对照。结果基本一致。     

基于XGBoost-LSTM组合模型的光伏发电功率预测

该文提出一种基于极端梯度提升（XGBoost）模型和长短期记忆网络（LSTM）模型的短期光伏发电功率预测组合模型。根据短期光伏发电特性,首先分别建立XGBoost模型和LSTM模型,然后利用XGBoost模型进行初步预测增加特征,并利用误差倒数法将两模型组合起来进行预测。选取2018年光伏电站人工智能运维大数据处理分析大赛的数据集进行实验评估,最终结果表明,该文所构建的XGBoost-LSTM组合模型的均方根误差（RMSE）为0.214,将上述方法与随机森林、GBDT模型和单一的XGBoost模型和LSTM模型相比较,该文提出的方法具有更高的预测精度。     

基于CLSSVM的风电机组齿轮箱故障诊断

针对风电机组齿轮箱传统故障诊断方法以全局误诊断率最小化为目标,忽略了误分类型之间的差别的问题,提出基于代价敏感最小二乘支持向量机(Cost-sensitive Least Squares Support Vector Machine,CLSSVM)的风电机组齿轮箱故障诊断方法。该方法在最小二乘支持向量机原始最优化问题中二次损失函数中嵌入不同样本的误分类代价,建立以误分类代价最小化为目标的CLSSVM故障诊断模型,并同最小二乘支持向量机和代价敏感支持向量机比较。实验结果表明,该方法能提高误分类代价高的故障类样本的诊断正确率,具有代价敏感性,其训练速度也足以满足风电机组齿轮箱故障诊断实时性的需求。     

超环面-CPC组合系统的太阳能聚集特性分析

结合光学软件比较分析了碟式抛物镜、菲涅尔反射镜、超环面聚光镜的聚集辐射性能,重点考察光线入射角度对光斑均匀性、聚光比等性能的影响。优化设计获得一种在聚光比、光斑均匀性、公差容忍度等性能方面都较优异的超环面-CPC组合系统,为太阳能聚集设备的创新设计提供了新思路。     

大颗粒生物质高温热解模型的建立及数值模拟

通过对生物质理化特性和热解机理的深入分析,建立了高温条件下生物质热解模型.耦合生物质热解化学反应动力学方程和传热方程,用四阶龙格库塔法和三角追赶法求解,并将计算结果与文献中的实验数据进行对比.模拟结果表明:在径向位置颗粒中心温度的增加速率比表面的增加速率高;随着颗粒粒径的增加,生物质热解完成所需的时间加长;大分子焦油在1273K以上才开始快速裂解,温度越高裂解速率越快,当温度达到1673K时,大分子焦油几乎裂解完全.     

Experimental investigation on heat transfer characteristics of low mass flux rifled tube with upward flow

An experiment for heat transfer of water flowing in a vertical rifled tube was conducted at subcritical and supercritical pressure. The main purpose is to explore the heat transfer characteristics of the new-type rifled tube at low mass flux. Operating conditions included pressures of 12–30 MPa, mass flux of 232–1200 kg/(m² s), and wall heat fluxes of 133–719 kW/m². The heat transfer performance and wall temperature distribution at various operating conditions were captured in the experiment. In the present paper, the heat transfer mechanism of the rifled tube was analyzed, the effects of pressure, wall heat flux and mass flux on heat transfer were discussed, and corresponding empirical correlations were also presented. The experimental results exhibit that the rifled tube has an obvious enhancement in heat transfer, even at low mass flux. In comparison with a smooth tube, the rifled tube efficiently prevents Departure from Nucleate Boiling (DNB) and delays dryout at subcritical pressure, and also improves the heat transfer of supercritical water remarkably, especially near pseudo-critical point. An increase in pressure or wall heat flux impairs the heat transfer at both subcritical and supercritical pressure, whereas the increasing mass flux has a contrary effect.     

Multi-objective optimization of cassava-based fuel ethanol used as an alternative automotive fuel in Guangxi,China

Multi-objective optimization of net energy, external costs of environment pollutant-emissions, and cost of using cassava-based fuel ethanol as an alternative automotive fuel in Guangxi has been conducted based on its holistic life cycle, from feedstock production to fuel combustion. A new indicator, cost of net energy (CNE), linking net energy-yield, external cost of environment pollutant-emissions, and production cost (the lower the CNE reading, the better the total performance) of ethanol–gasoline blends, is proposed for carrying out multi-objective optimization. On the life-cycle basis, CNE of ethanol–gasoline blends is found to obtain its lowest value, i.e. 0.119  RMB/MJ, when processing fuel during the ethanol conversion stage was natural gas and the ratio of ethanol blended with gasoline was 5%. From the standpoint of the CNE indicator, the most viable implement form of cassava-based fuel ethanol should be used as one of oxygenate additives. The recommended processing fuel during ethanol conversion stage should be natural gas.     

东方超超临界二次再热660MW汽轮机热力设计特点

二次中间再热机组相对一次再热机组经济性提高约1．5％．文章详细论述了东方660MW二次再热超超临界汽轮机的热力设计特点,对促进我国火力发电技术进步和节能减排具有现实意义,为我国大容量燃煤机组发展提供了示范,为更高参数700℃等级燃煤电站的实现具有示范和技术储备的作用。