摘要：In order to maintain a uniform distribution of pareto-front solutions, a modified NSGA-II algorithm coupled with a dynamic crowding distance(DCD) method is proposed for the multi-objective optimization of a mixed-flow pump impeller. With the pump meridional section fixed, ten variables along the shroud and hub are selected to control the blade load by using a three-dimensional inverse design method. Hydraulic efficiency, along with impeller head, is applied as an optimization objective; and a radial basis neural network(RBNN) is adopted to approximate the objective function with 82 training samples. Local sensitivity analysis shows that decision variables have different impacts on the optimization objectives. Instead of randomly selecting one solution to implement, a technique for ordering preferences by similarity to ideal solution(TOPSIS) is introduced to select the best compromise solution(BCS) from pareto-front sets. The proposed method is applied to optimize the baseline model, i.e. a mixed- flow waterjet pump whose specific speed is 508 min?1?m3s?1?m. The performance of the waterjet pump was experimentally tested. Compared with the baseline model, the optimized impeller has a better hydraulic efficiency of 92% as well as a higher impeller head at the design operation point. Furthermore, the off-design performance is improved with a wider highefficiency operation range. After optimization, velocity gradients on the suction surface are smoother and flow separations are eliminated at the blade inlet part. Thus, the authors believe the proposed method is helpful for optimizing the mixed-flow pumps.

摘要：过渡金属磷化物是电催化设计中的新兴材料,而多元金属磷化物因其能显著提高电催化活性而备受关注.然而,由于不同种类金属前驱物之间水解和缩合速率的差异,当前有关超过两种金属元素和化学计量比精确控制的多元金属磷化物的报道非常少.因此,合理设计多元金属磷化物的组成对提高其催化性能具有重要意义.本工作通过直接磷化二价过渡金属离子氢氧化物的合成策略,制备了能够精确控制化学计量比(x:y:z=(1–10):(1–10):1)的分级结构Co_(x)Ni_(y)Fe_(z)P,其中具有最优组分的Co_(1.3)Ni_(0.5)Fe_(0.2)P在析氧反应(OER)中展示了优异的催化活性和高稳定性.密度泛函理论计算表明,相对于其他组分的过渡金属磷化物,Co_(1.3)Ni_(0.5)Fe_(0.2)P在费米能级附近的态密度明显增加,这可以增强催化剂对OH−的吸附,从而提升OER性能.

摘要：Tire force and moment testing is a valuable way of quantifying the performance of a tire. The data collected from such testing is also used by many researchers for vehicle dynamic simulation studies as well as chassis control system development. Although various studies have claimed correlation between data from rolling road type machines and road testing trailers, the claim only extends for on-road conditions. Many military vehicles as well as agricultural vehicles operate in an environment which requires new levels of tire test data. This paper will discuss the design and testing of a portable trailer tire test rig. This rig was conceived and constructed for use on both on- and off-road driving surfaces and is also fitted for wet-road testing. The rig will eventually be used to collect tire data on various tire sizes both on and off-road on various road surfaces, such as grass, asphalt, concrete, and gravel for varying speeds, pressures, loads, and slip angles. The data will be used to develop a modified Pacejka Magic Formula Tire Model that can be used for conducting simulation in both on and off-road conditions.

摘要：我认为,造船师和轮机师考虑海上环境设计的船舶,它们99.9%的时间在海上渡过.但他们忘了,这些船舶还必须进入河道装卸货物.当某件引起公众高度关注的事故发生,船舶建造者或许会进入公众视线,发现他们犯有疏忽罪,要为建造了动力不足和操纵不良的船舶负责.

摘要：核壳结构合金纳米粒子可在原子水平上对其界面相互作用和表面微结构进行调控,对设计具有高活性和耐久性的电催化剂具有重要意义.本文制备了一系列具有不同界面,以钯合金为内核、单原子铂层为壳的核壳结构催化剂,其中Pd3Fe@Pt1L催化剂展示出最优的氧还原活性和稳定性.理论计算和X射线吸收精细结构研究表明,以Pd3Fe为内核,可以实现对Pt壳层应力和电子效应的双重调控,从而优化其催化过程中含氧中间体的吸附强度,增强其催化性能.