Environmental and energy life cycle analyses of passenger vehicle systems using fossil fuel-derived hydrogen

Hydrogen energy utilization is expected due to its environmental and energy efficiencies. However, many issues remain to be solved in the social implementation of hydrogen energy through water electrolysis. This analyzes and compares the energy consumption and GHG emissions of fossil fuel-derived hydrogen and gasoline energy systems over their entire life cycle. The results demonstrate that for similar vehicle weights, the hydrogen energy system consumes 1.8 MJ/km less energy and emits 0.15 kg-CO 2 eq./km fewer GHG emissions than those of the gasoline energy system. Hydrogen derived from fossil fuels may contribute to future energy systems due to its stable energy supply and economic efficiency. Lowering the power source carbon content also improved the environmental and energy efficiencies of hydrogen energy derived from fossil fuels.     

基于灰色聚类方法的加工中心进给系统可靠性评价

应用MTALAB软件对加工中心进给系统的故障数据进行分析,得到平均首次故障时间(MTTFF)和平均故障间隔时间(MTBF)的点估计值和区间估计值。采用灰色聚类方法划分可靠性指标可拓区间灰数等级,并通过建立白化权函数得到等级区间权重矩阵。再结合构建比较判断矩阵确定的两种可靠性指标权重,最终建立了灰色聚类综合评价模型,对该加工中心进给系统可靠性水平进行评价。     

端承桩承载力不会随时间而增长

强风化岩的力学指标不会随时间而增长，而淤泥层的固结，在端承桩条件下只能引起桩侧负摩擦而使桩的有效承载力略为下降。“解析法推算”所得桩极限荷载，只是预测试桩当时可能达到的极限荷载，而与“时间推移”无关。     

基于QFD电动汽车技术特性重要度的确定方法研究

技术重要度是开展电动汽车综合设计优化的目标函数,提出了一种基于QFD的电动汽车关键技术重要度的综合确定方法。方法分析了电动汽车顾客需求和电动汽车技术指标,基于质量屋建立顾客需求重要度与技术特性重要度耦合模型,应用粗糙数进行顾客需求重要度排序,根据电动汽车市场竞争性评估对其进行修正;应用灰色关联法确定顾客需求与技术特性之间的相关关系,分析电动汽车技术特性自相关关系建立相应的修正决策系统。基于该方法,以本研究院研究车型与市场同类车型进行实例分析,证明了方法的有效性和可行性。     

基于田口试验的高Nb-TiAl合金小孔电火花加工试验研究

采用D703F高速电火花小孔加工机床在高Nb-TiAl合金(Ti-44Al-8.5Nb-0.2Mo-0.2B)板材上加工直径为1mm小孔,运用田口试验法研究电火花加工参数(电流、脉宽和冲液压力)对加工速度和加工质量的影响,并对试验结果进行方差分析和灰关联度分析。结果表明:电流为10 A、脉宽为32μs、冲液压力为3 MPa时加工速度和孔径精度较高,对实现高Nb-TiAl合金的高效率、精密加工具有一定的实用价值。     

基于RPCA的SAR图像纹理特征去噪

合成孔径雷达(SAR)图像具有丰富的纹理信息,这些纹理信息能反映地物空间结构关系。当前纹理特征被广泛应用于SAR图像分类和SAR图像分割中。受成像因素影响,直接采用从SAR图像中提取的纹理特征效果不够好。为避免传统先滤波再提取纹理特征的方法对纹理、边缘信息造成损失,提出了一种先提取SAR图像纹理特征,再利用Robust PCA方法对纹理特征去噪的新方法,最后采用Kmeans聚类方法检验RPCA处理后的纹理特征表达效果。实验结果表明该方法能将聚类正确率从82%提高到84%。     

Modeling and Multiresponse Optimization of the Mechanical Properties of Roselle Fiber-Reinforced Vinyl Ester Composite

In this study, the roselle fiber-reinforced vinyl ester composites were prepared based on Taguchi’s L₂₇ experimental design using hand lay-up technique. A gray-based Taguchi technique was used to optimize the process parameters with mechanical properties (multiple performance characteristics). The results also show that the fiber content is the most significant process parameter which greatly affects the mechanical properties. It was proved that the multiple performance characteristics of the plant-based natural fiber-reinforced polymer composites can be effectively improved by this method. The proposed response surface mathematical models to predict mechanical properties of composite were found statistically valid.     

Sage of Lacock

Abstract

‘The good is oft interred with their bones.’ Much of what has been written of William Henry Fox Talbot has done him meagre justice: criticism for patenting his inventions, accusations that he patented the ideas of others, denigration of the importance of his discoveries. Though acknowledged as a scientist, his place as an artistic worker in the medium he invented has not been appreciated.     

硫对离心铸造汽缸套切削性能的影响

一般来说，硫是有害元素。但对于灰铸铁来讲，含有少量的硫对于石墨的生核和切削性能都有非常重要的影响。在铸造生产过程中通过加入一定量的硫，提高铁液的含硫量，从而使铸件获得更好的切削性能。     

动态测量不确定度贝叶斯评定的改进方法研究

动态测量不确定度的评定一直是比较复杂的问题,到目前为止,国内外有许多学者对这一问题进行了探索与研究,给出了一些评定的方法,但这些方法都存在自身的缺点与不足,还不能给出十分精确的评定结果。因此,通过对现有基于贝叶斯理论的动态测量不确定度评定方法进行分析,用最大熵原理改进其先验分布的选择与计算方法,从而有效提高计算后验分布的精度,最终提高不确定度的计算准确度。