改进的遗传算法在同步器优化中的应用

汽车同步器是自动变速器的重要组成部分.对同步器的模拟优化能为同步器的设计生产提供重要的参考.为了获得一个较好的优化效果,提出了一种改进的遗传算法.通过对遗传算法选择过程的标准进行了改进,结合适应度函数与染色体之间差异,形成一种新的适应度函数.该函数同时考虑了选择压力和物种多样性.通过对函数中两个常量的调整,可以使算法在不同情况下可以有不同的偏重.引入两种典型测试函数的分别从高纬度变量和低纬度变量进行试验,分析改进算法中两个影响因子的作用.并与几类遗传算法进行比较,结果表明该改进的遗传算法能更快更稳定的找到较优的解.最后将改进选择策略结合自适应遗传算法对同步器进行优化,证明了该选择策略具有良好的鲁棒性和实效性.     

某取排水车180°铰接式弯管优化分析

为了解决新型铰接式弯管的变形问题,利用ANSYS软件对铰接式弯管进行建模和流固耦合分析,发现原始弯管两侧中部内凹、弯径增大、最大应力超过许用应力,据此提出了导流器错位排布方案.结果 表明:采用方案三错位排布导流器方案、将导流器间距设为70 mm时得到最优方案,优化后的弯管4最大应力由178.12 MPa降低到92.4 MPa、降低了52％,弯管12最大应力由289.52 MPa降低到135.4 MPa、降低了47％,取得了较好的优化效果,为180°弯管导流器设计提供了一种新方案.     

氧化装置卧螺离心机故障停机的原因浅析

针对乌鲁木齐石化公司氧化装置卧式螺旋离心机的故障停车原因进行了分析及总结,明确了该项工作实施的实际效果及其重大意义.     

基于MF-DCCA 的呼吸道疾病与大气污染物相关性分析

针对呼吸道系统疾病与大气 PM2:5、 SO2 浓度序列的相关性特征, 应用多重分形消除趋势波动分析法 (MF-DCCA), 对张家界市永定区呼吸道系统疾病患病人数与大气 PM2:5、 SO2 浓度序列进行了研究。结果发现该地区 呼吸道系统疾病患病人数与大气 PM2:5、 SO2 浓度的相关性具有长期持续特征和多重分形特征。随后对它们相关性 多重分形特征的动力来源进行了分析, 通过随机重排和相位随机处理, 结果表明在不同时间尺度上的长期持续性影响 是其主要动力来源。进一步研究发现该地区呼吸道系统疾病与大气 PM2:5、 SO2 浓度序列的相关性在四个季节均具 有长期持续性的多重分形特征, 且夏季多重分形特征相对强于其他季节。     

基于卓越工程师教育的频率特性分析课堂教学研究

频率特性分析在工程应用中具有重要的作用,在电路分析、模拟电子技术、信号与系统、自动控制理论等相关课程中都涉及到相关章节内容,在不同课程中如何根据工程应用和学生学习阶段把握具体的讲解内容和讲解方式非常重要。本文从频率特性的求解方法和具体物理意义角度开展在不同课程中讲解的方法,从时域和频域角度分别讨论其物理意义和具体的分析方法。通过渐进深化的教学过程和教学方法不断提高学生的知识掌握和应用技能,提高学生的工程意识、工程素质和工程创新能力,强化学生对于频率特性课程知识的综合应用能力。     

4,6-二氯嘧啶合成工艺研究

4,6-二氯嘧啶是一种重要的化工中间体.研究了反应温度、溶剂种类、催化剂种类、催化剂用量和反应物投料配比在4,6-二氯嘧啶合成过程中对反应的影响.结果 表明,在以邻硝基甲苯为溶剂,苄基三乙基氯化铵为催化剂,且催化剂用量为4,6-二羟基嘧啶质量的2％,n(4,6-二羟基嘧啶):n(三光气)=1∶0.8,反应温度为100～110℃的最佳条件下,产品收率可以达到93.4％.     

圆型限制性三体问题的动力学特征

禁行域在圆型限制性三体问题中对第三体的运动有极为重要的影响. 利用零速度曲线讨论天体禁行域与系统参数之间的关系. 禁行域与雅可比常数有关，且能影响天体的运动区域和轨道构型. 利用最大李雅普诺夫指数寻找该模型的混沌轨道，给出混沌轨道在不同系统参数下随天体初始位置的分布. 这些分布说明，当第三天体从两主天体连线的中点处释放时，容易产生混沌运动；当质量参量足够小时，体系无法产生混沌现象.     

高熵形状记忆合金的研究进展

高熵形状记忆合金是在等原子比NiTi合金的基础上,结合高熵合金的概念,逐渐发展起来的一种新型高温形状记忆合金。近年来,已开发出了综合性能优异的(TiZrHf)50(NiCoCu)50系和(TiZrHf)50(NiCuPd)50系高熵形状记忆合金,引起了广泛的关注和研究兴趣。本文从物相组成、微观组织、马氏体相变行为、形状记忆效应和超弹性等角度出发,综述了高熵形状记忆合金的研究进展,并对高熵形状记忆合金未来的研究重点进行了展望。     

Thermal transport and chemical conversion in single reacting sorbent particles

The effects of particle size and carbon dioxide concentration on chemical conversion in engineered spherical particles undergoing calcium oxide looping are investigated. Particles are thermochemically cycled in a furnace under different carbon dioxide concentrations. Changes in composition due to chemical reactions are measured using thermogravimetric analysis. Gas composition at the furnace exit is evaluated with mass spectroscopy. A numerical model of thermal transport phenomena developed previously is adapted to match the physical system investigated in the present study. The model is used to elucidate effects of reacting medium characteristics on particle temperature and reaction extent. Experimental and numerical results show that (1) an increase in particle size results in a decrease in carbonation extent, and (2) the carbonation step consists of fast and slow reaction regimes. The reaction rates in the fast and slow carbonation regimes increase with increasing carbon dioxide concentration. The effect of carbon dioxide concentration and the distinction between the fast and slow regimes become more pronounced with increasing particle size.     

Structural dependence of microwave dielectric properties in ilmenite-type Mg(Ti1-xNbx)O3 solid solutions by Rietveld refinement and Raman spectra

Mg(Ti_1-xNb_x)O₃ (x = 0–0.09) ceramics were prepared by the conventional solid-state reaction method. The phase composition, sintering characteristics, microstructure and dielectric properties of Ti⁴⁺ replacement by Nb⁵⁺ in the formed solid solution Mg(Ti_1-xNb_x)O₃ (x = 0–0.09) ceramics were systematically studied. The structural variations and influence of Nb⁵⁺ doping in Mg(Ti_1-xNb_x)O₃ were also systematically investigated by X-ray diffraction and Raman spectroscopy, respectively. X-ray diffraction and its Rietveld refinement results confirmed that Mg(Ti_1-xNb_x)O₃ (x = 0–0.09) ceramics crystallised into an ilmenite-type with R-3 (148) space group. The replacement of the low valence Ti⁴⁺ by the high valence Nb⁵⁺ can improve the dielectric properties of Mg(Ti_1-xNb_x)O₃ (x = 0–0.09). This paper also studied the different sintering temperatures for Mg(Ti_1-xNb_x)O₃ (x = 0–0.09) ceramics. The obtained results proved that 1350 °C is the best sintering temperature. The permittivity and Q × f initially increased and then decreased mainly due to the effects of porosity caused by the sintering temperature and the doping amount of Nb₂O₅, respectively. Furthermore, the increased Q × f is correlated to the increase in Ti–O bond strength as confirmed by Raman spectroscopy, and the electrons generated by the oxygen vacancies will be compensated by Nb⁵⁺ to a certain extent to suppress Ti⁴⁺ to Ti³⁺, which was confirmed by XPS. The increase in τ_f from ?47 ppm/°C to ?40.1 ppm/°C is due to the increment in cell polarisability. Another reason for the increased τ_f is the reduction in the distortion degree of the [TiO₆] octahedral, which was also confirmed by Raman spectroscopy. Mg(Ti_0.95Nb_0.05)O₃ ceramics sintered at 1350 °C for 2 h possessed excellent microwave dielectric properties of ε_r = 18.12, Q × f = 163618 GHz and τ_f = ?40.1 ppm/°C.