Microstructure,tribological behavior and magnetic properties of Fe−Ni−TiO2 composite coatings synthesized via pulse frequency variation

The Fe−Ni−TiO₂ nanocomposite coatings were electrodeposited by pulse frequency variation. The results showed that the nanocomposite with a very dense coating surface and a nanocrystalline structure was produced at higher frequencies. By increasing the pulse frequency from 10 to 500 Hz, the iron and TiO₂ nanoparticles contentswere increased in expense of nickel content. XRD patterns showed that by increasing the frequency to 500 Hz, an enhancement ofBCC phase was observed and the grain size of deposits was reduced to 35 nm. The microhardness and the surface roughness were increased to 647 HV and 125 nm at 500 Hz due to the grain size reduction and higher incorporation of TiO₂ nanoparticles into the Fe−Ni matrix (5.13 wt.%). Moreover, the friction coefficient and wear rate values were decreased by increasing the pulse frequency;while the saturation magnetization and coercivity values of the composite deposits were increased.     

基于GA-BP的汽车风振噪声声品质预测模型

目前对于汽车风振噪声的优化研究主要以声压级（Sound pressure level，SPL）作为单一评价指标，既不能全面反映噪声的物理属性，也无法考虑人耳对噪声的主观认知过程。为准确评价风振噪声，引入声品质，运用大涡模拟（Large eddy simulation，LES）对风振噪声进行数值仿真，根据实车道路试验判断仿真的准确性；对仿真结果进行声品质客观评价与主观评价，综合声品质客观评价参数与声品质主观评价试验结果建立BP神经网络预测模型；利用遗传算法（Genetic algorithm，GA），进一步对BP神经网络的结构参数进行优化，建立GA-BP声品质预测模型。研究结果表明，GA-BP声品质预测模型在训练速度和预测精度上都优于BP神经网络预测模型。预测模型基于声品质主客观评价结果，其预测值可以代替传统的声压级评价指标，为风振噪声提供更为准确合理的评价。     

Heat transfer in dusty fluid with suspended hybrid nanoparticles over a melting surface

The melting effect with the magnetic field performs a significant role in various manufacturing and industrial applications, such as welding, casting, magma-solidification, nuclear engineering, and so forth. The present study focuses on the impact of the melting effect and magnetic field with inhomogeneous heat origination and sink. The formulation of the mathematical model is done by considering fluid with hybrid nanoparticles and dust particles in two different phases. We have considered Fe₂SO₄ and Cu as nanoparticles dispersed in the base fluid water along with suspended dust particles. The set of partial differential equations is reduced by using apt similarity variables and boundary conditions to obtain ordinary differential equations. The numerical solution is approximated using MATLAB-bvp4c adopting the shooting technique. The impact of numerous pertinent physical parameters on the velocity and thermal profiles is plotted and deliberated. Furthermore, the rate of heat flow and friction factor is also tabulated and visualized through the graphs. Streamlines are also drawn to know the behavior of the fluid flow. The rise in values of M_E quickly increases the velocity of the fluid motion but declines the thermal gradient and thickness of its related boundary layer. Also, inclining values of Pr enhance the thermal profile due to the impact of melting.     

Effects of direct current magnetic field treatment time on the properties of pork myofibrillar protein

This study investigated the effects of direct current magnetic field (DC-MF) treatment time (1, 3, 5, 8 h) on properties of porcine myofibrillar protein (MP). Gel water-holding capacity increased from 83.40% to 87.20% when DC-MF-treatment time changed from 1-h to 8-h. The 3-h treatment time of DC-MF was found to promote MP unfolding, rearrangement and aggregation, leading to the loss of total sulfhydryl, the increase of reactive sulfhydryl, surface hydrophobicity, turbidity as well as the formation of MP clusters and the greater degree of crosslinking as compared with 0-h treatment, thus a firmer and more ordered MP gel network for trapping more water. However, excessive DC-MF treatment (8-h) weakened DC-MF effect on MP aggregation as well as gel network and texture. This study has shed light on the effects of DC-MF treatment time on MP properties and provides useful information for the application of DC-MF in the food industry.     

Water electrolysis using plate electrodes in an electrode-paralleled non-uniform magnetic field

Compared with other ways to produce hydrogen, water electrolysis is the best way to obtain ultra-pure hydrogen, but its low energy efficiency greatly limits its wide application. It was proved that external magnetic field can reduce energy consumption, thereby increase electrolysis efficiency. Most of the researchers are focused on the impact of uniform magnetic field but few on a non-uniform one. To address the industrial operation reality, in our work, water electrolysis was operated using alkaline solution and plate electrodes in a non-uniform Magnetic field. The results show that a rotational flow on the vertical plane was formed by Lorentz force within the entire cell range. Although the entrainment effect of rotating flow made the cell full of microbubbles, the cell voltage was still reduced. By measuring the voltage difference of cathode side and anode side, we think that the bubble layer in the vicinity of the electrode surface matters the most among the sources of electric resistance. And the velocity distribution near the electrode was measured by PIV, it reveals that MHD flow is the dominant effect on the flow field of the cell. The results show that non-uniform magnetic field has potential merit in industrial electrolysis process.     

Study of new flow field geometries to enhance water redistribution and pressure head losses reduction within PEM fuel cell

Efficiency of fuel cell is dependent on reactant distribution, products evacuation, pressure losses and many of these factors is dependent on the design of flow field plate. With an effective design, reactant distribution, pressure drop, and water and heat management can be further improved. In this work, two new designs, as multi-serpentine set-up with additional slots and hybrid geometry, on stainless steel bipolar plates, are presented. Electrical performance, and pressure head losses are analyzed by electrochemical methods such as polarization curve and use of electrochemical noise as a diagnostic tool to further understand the impact of water management on performance. On the one hand, multi-serpentine design shows the best electrical performance with an increase of 0.2 V (66%) at 0.9 A/cm² in comparison of traditional serpentine design. On the other hand, hybrid design reveals the lowest pressure head losses, with a decrease of 2 mbar (about 50%) in comparison of traditional serpentine design, and a higher stability with time that can be useful to downsize compressor and provide lower impact on fuel cell stack durability.     

转底炉处理赤泥工艺技术

为了综合利用氧化铝冶炼产生的赤泥，探索在转底炉中直接还原赤泥、磨矿磁选获得高品位直接还原铁。通过实验室试验摸索了转底炉还原工艺参数，并在转底炉工业试验线进行了工业试验。实验室结果表明，赤泥还原后的直接还原铁(DRI)金属化率可达88.6%，磁选后的铁品位可达82.1%，磁选后的铁回收率可达88.9%。工业试验中，转底炉还原后，产品金属化率平均为69.2%，将还原后的DRI磁选获得高品位的DRI产品，磁选后DRI的铁品位为72.8%，磁选后铁回收率达到了85.2%,初步打通了在转底炉中还原赤泥、磁选的工艺路径。     

磁场环境下铝电解熔融铝液成分激光诱导击穿光谱原位测量分析

铝电解车间具有高温、强磁、多粉尘等环境特点,当前生产过程中熔融原铝的成分检测主要是人工取样然后离线分析,化验过程及结果具有较大的滞后性,故将激光诱导击穿光谱(LIBS)技术应用于铝电解车间铝液成分原位、实时测量具有重要意义。实验采用Nd:YAG脉冲激光器,多通道光纤光谱仪和电感耦合器件(CCD)探测器组成的激光诱导击穿光谱测量系统对电流为400kA电解槽中熔融铝液的主要成分铁、硅进行了探测,对原铝中部分元素的特征谱线进行了归属分析。考察了激光能量在磁场环境下的衰减变化及谱线梯度变迁规律,结果表明,距离电解槽边缘约2m处激光能量衰减达最大。分析了磁场对测试系统的影响,并建立了定标曲线,铁和硅两种元素按照内标法建立的定标曲线拟合度分别为93.50%和97.10%,采用该模型进行了测试实验,并用国标GB/T 7999—2015中光电直读发射光谱(OES)测试的相关指标验证测试结果的重复性与允许差。实验证明,LIBS技术在电解铝行业在线检测方面具有较好的应用前景,但是测试的稳定性与重复性也是面临的一个重要问题。