Measuring distribution performance? Benchmarking warrants your attention

Identifying, designing, and measuring performance metrics is critical to securing customer value, but can be a difficult task. This article examines the use of benchmarks based on publicly available performance data to set challenging, yet fair, metrics and targets.     

Pulvermetallurgische Erzeugung von SiC‐ und Al2O3‐verstärkten Al‐Cu‐Legierungen

Powder metallurgical fabrication of SiC and Al₂O₃ reinforced Al‐Cu alloys Based on metallographic studies the states of composite powder formation during high‐energy ball milling will be discussed. Spherical powder of aluminium alloy AA2017 was used as feedstock material for the matrix. SiC and Al₂O₃ powders of submicron and micron grain size (<2 μm) were chosen as reinforcement particles with contents of 5 and 15 vol.‐% respectively. The milling duration amounted to a maximum of 4 hours. The abrasion of the surface of the steel balls, the rotor and the vessel is indicated by the content of ferrous particles in the powder. High‐energy ball milling leads to satisfying particle dispersion for both types of reinforcement particles. Further improvements are intended. The microstructure of compact material obtained by hot isostatic pressing and extrusion was studied in detail by scanning and transmission electron microscopy. For both types of reinforcement the microstructure of composites is similar. The microporosity is low. The interface between reinforcement particles and matrix is free of brittle phases and microcracks. In the case of SiC reinforcement particles, a small interface interaction is detectable which implies a good embedding of reinforcement particles. High‐energy ball milling under air‐atmosphere leads to the formation of the spinel phase MgAl₂O₄ during the subsequent powder‐metallurgical processing. Because of the size, rate and dispersion of the spinel particles, an additional reinforcement effect is expected.     

面向进制转换和克隆进化的帝国竞争改进算法

帝国竞争算法(imperialist competitive algorithm,ICA)是一种被广泛应用于求解各类理论与实践问题的随机搜索智能优化算法,但它收敛过快的特性令其容易在求解复杂问题时陷入局部最优,故对ICA进行有针对性的改进十分必要.引入二进制转换和克隆进化机制,为算法的进化种群提供新的上升通道和进化模式...     

车用压缩天然气新标准GB 18047-2017解读

从技术要求和试验方法的变化两个角度对GB 18047-2017《车用压缩天然气》新标准进行了详细解读,并指出新标准中待完善之处。新标准中车用压缩天然气的检验项目没有发生太大的变化,只有部分项目的技术要求发生了变化。其中,总硫(以硫计)的技术要求上限值由200mg/m3降低到100mg/m~3。在水含量/水露点方面,首次以"水的质量浓度"代替"水露点"衡量环境温度不低于基准分界点时车用压缩天然气中的含水状态。新标准丰富和扩充了各项目的试验方法,方法的选择性增多,但同时也对各项目的仲裁试验方法进行了规定。另外,高位发热量下限值不符合实际情况,建议适当提高高位发热量的标准,并在车用压缩天然气技术指标中新增"液态烃含量/烃露点"检测项目。