基于决策树算法的AMT挂挡过程冗余控制研究

为了对AMT系统挂挡过程进行良好的冗余控制,针对挂挡位移传感器失效状况,提出了一种基于CART决策树算法的挂挡时间预测模型.模型建立过程中,选取挂挡阶段的气压p、变速器输入轴转速n₁、变速器输出轴转速n₂和同步器的同步速差Δn作为特征值变量,选取挂挡时间作为预测值.通过交叉验证,对原始决策树进行修剪,得到最优决策树模型.在使用测试集进行模型验证时,在预测误差不超过50 ms的情况下,对挂挡时间的预测具有90%以上的准确率.台架及实车试验表明,在挂挡位移传感器失效的情况下,基于该算法的电磁阀控制策略可以完成正常的换挡操作,通过实际传动比和控制策略预测得到的理论传动比的对比发现,预测的换挡点时刻的判断误差在50 ms以内.      

基于动态双重前缀的模糊相似性连接算法

针对相似性连接问题, 提出了动态双重前缀的模糊相似性连接算法.与之前的算法不同的是,本文采用双重前缀,即在查找候选以及构建索引时使用不同的前缀来提高过滤效率,并在此基础上进行了优化.首先通过取各个前缀生成的候选集合的交集来缩小候选集合;其次提出最大区分任选前缀,利用此前缀进行预验证来减少最终进入到验证过程的候选对,以此来减少连接时间.并且在三个真实数据集上进行实验,将本文算法与Silkmoth算法以及MF-Join算法进行比较,结果表明所提算法可以生成更小的候选集集合并且需要更少的连接时间.     

Phase evolution process and hydrogen storage performances of V72Ti18Cr10 alloy prepared by Co-precipitation-reduction method

The V₇₂Ti₁₈Cr₁₀ alloy was prepared by a co-precipitation-reduction method in order to consume less energy during whole-life alloy manufacturing, and the phase evolution process in hydrogenation/dehydrogenation process was investigated. The structure refinement analysis of the alloy contented with 1 ?wt% hydrogen after hydrogenation shows that BCC phase, BCC-hydride phase and FCC phase coexisted, but little BCT phase was found. It indicates that the phase evolution process during hydrogenation was BCC→ BCC-hydride→ FCC, nevertheless the formation of BCT phase was restrained. The limited particle sizes of the alloy in the range of 0.1–5 ?μm and fewer defects than the normal alloy ingot contributed to the suppression of BCT formation. The annealed alloy, which had similar particle sizes with the unannealed alloy, has less unevenness of the compositions than the unannealed alloy, and the annealed alloy showed flatter plateau in the hydrogenation PCT (pressure-composition-temperature) curves. However, the BCT phase in the annealed alloy appeared in its dehydrogenation process owing to the produced defects during the following dehydrogenation and the hydrogenation process. The alloy with the limited particle sizes even in the range from 0.1 ?μm to 5 ?μm could not prevent the generation of BCT phase in the dehydrogenation process.     

Microstructure evolution of Ti–6Al–4V under cold rolling + low temperature nitriding process

A new nitriding process modifying both the surface and the matrix is proposed to improve the poor wear resistance and low hardness of the titanium alloy surface. The treatment of solid solution treatment, cold rolling and low temperature nitriding was used for surface modification. The results showed that the microstructure of the Ti–6Al–4V(TC4) titanium alloy sample changed from the original α+β phase to the residual α phase, metastable β phase and martensite α′ phase after solution treatment. The results of cold rolling experiments indicated that with the increase of rolling amount, many defects generated, and the grains were first elongated and then partially broken. During the process of low-temperature nitriding the recrystallization occurred, which effectively avoided the problem of coarse matrix structure. It has been found that after low-temperature nitriding, thin strip-like α-phase with dispersed distribution, which is a typical aging structure, formed. The XRD test results indicate that steady state nitrides Ti₂N formed on the surface of the sample, but the content of Ti₂N was relatively low. Based on the morphology of content of the surface and cross-section it is believed that a special type of nitriding layerformed after low-temperature nitriding. The mechanical performance test results indicate that the wear resistance and hardness of the alloy increased significantly.     

新型零售网络中多业态组合选址问题

针对新型零售网络中超市多业态组合选址问题进行研究,提出了地理信息系统与模糊层次分析相结合的方法。该方法首先在一个区域内若干个超市可供建设点中选出一定数量的备选建设点,再考虑超市的数量、业态、覆盖范围等要求,以总成本最小为目标函数建立数学模型,运用Matlab求解出最优的选址结果。最后,结合实际案例对该综合选址方法进行有效应用。     

爆炸荷载作用下单层钢结构厂房易损性综合评估

单层钢结构厂房普遍应用于重型机械制造、冶金等重工业及军事工业,战略意义重要,常为敌方空中打击的首选目标。为评估单层钢结构厂房在常规武器爆炸荷载作用下的易损性,在分析单层钢结构厂房易损性表征内涵的基础上,提出单层钢结构厂房易损性表征指标体系,包括外部钢结构易损性表征指标和内部空间易损性表征指标,并给出易损性表征指标的量化方法。基于层次分析和模糊数学综合评判方法,建立因素集、定义评判集、确定权重集、构建易损性隶属度函数,并逐层进行模糊综合分析,最终应用加权平均法得到综合评判结果。算例表明,厂房几何中心综合易损性表征指标高于几何边角综合易损性表征指标,但子项钢结构的易损性表征指标较后者略低,算例结果可作为单层钢结构厂房防护的参考,两级表征指标体系可作为单层钢结构厂房易损性评估的参考。     

FOX-7/HMX混合炸药烤燃试验的数值计算

为研究FOX-7/HMX混合炸药的热响应特性,基于热爆炸理论中的热平衡原理,以McGuire-Tarver三步反应模型及成核和生长反应模型分别描述HMX和FOX-7的化学反应过程,建立了FOX-7/HMX混合炸药烤燃过程的计算模型.将建立的计算模型以用户自编函数的方式添加到Fluent软件中,对混合炸药的烤燃过程进行了...     

借助Projector辅助软件的图形思维分析

针对工程制图教学中学生普遍存在的图形思维的困难,提出以立体投影、组合体投影内容为重点,借助于专门针对投影制图的Projector投影工具软件进行图形思维过程推导与分析的教学方法,该方法弥补了多媒体课件交互性与实时性差的缺憾,而且简便易行,有利于提高二维图形与三维形体互逆的图形思维能力.     

烧结过程控制专家系统(Ⅲ)——透气性中心控制策略和烧结终点预报策略

为了克服烧结过程因机理复杂、影响因素多且相关性高而难以准确控制的困难,提出了烧结过程状态控制以透气性为中心的控制策略,研究了透气性的判断方法和实现此策略的控制原则和方法;同时,为了解决烧结过程控制的长时滞问题,提出了烧结终点的预报策略,研究了烧结终点的预报方法．     

铝酸钠溶液分解过程的红外光谱研究

本文用红外光谱方法跟踪了铝酸钠溶液的分解过程,提出了铝酸钠溶液分解过程中含铝阴离子的转变方式,探讨了分解反应机理。