谈供水旧管网改造

通过对供水管网的管道建设年代、材质类型、管道破损情况等进行分析研究,较全面地总结了供水管网的现状及存在的问题,并论述了管网更新改造的具体方法,以达到优化管网系统的目的。     

Catalyzed synthesis of rhombohedral boron nitride in sodium chloride molten salt

Although a variety of methodologies/techniques have been used to prepare h-BN powders with different sizes and purities, only a few methods are reported to synthesize r-BN. In this work, highly crystalline r-BN with a purity of 94 wt% was successfully synthesized in sodium chloride molten salt using Na₂B₄O₇ and Mg powders as starting materials at 1000 °C in nitrogen atmosphere. The sodium (Na) produced by the reaction of Mg and Na₂B₄O₇ has a positive effect on the formation r-BN in the molten salt. The effect of Na as a crystallization promoter to produce crystallized r-BN was demonstrated by heating a mixture of t-BN and Na at 800–1200 °C. The formation, dissolution and evaporation of Na in the melt was discussed. The influence of synthesis temperature on the phase composition and morphology of the final products in the melt was also investigated. The possible formation mechanism of r-BN is proposed.     

溢流式球磨机进料部空心轴衬套的改造

溢流式球磨机是选矿分厂矿石细碎的主要设备,其进料部空心轴衬套多次出现固定螺栓断裂、衬套外窜,导致润滑油污染。分析引起衬套损坏的原因,介绍所采取的对策,即改变衬套的部分材质、增加内六方螺栓固定连接等。改造后空心轴衬套运行效果较好,泄漏率大大降低。     

烷基化废硫酸再生工艺技术对比

通过对产品指标、尾气排放达标情况、投资、检修、长周期运行情况的对比,论述了国内、国际烷基化废硫酸再生技术的优缺点。     

基于视觉技术的圆环外观缺陷检测算法研究

针对圆环外观缺陷检测问题,在利用视觉技术的基础上,提出了一种基于极坐标变换的视觉检测算法。分析了圆环外观存在缺陷的种类问题,采用极坐标变换和插值算法将圆环区域转换成矩形区域;在矩形区域内提取圆环亚像素边缘进行圆环宽度测量,获取圆环矩形区域内上下边缘坐标数组并计算其纵坐标平均值,搜索可疑缺陷处;计算了最大最小宽度,并与标准圆环宽度进行对比来判断圆环缺陷的种类,然后依据缺陷处纵坐标判断缺陷位置。利用Halcon软件实现了该算法,实验结果表明:该算法能精确测量圆环宽度和实现圆环外观缺陷检测。     

基于SimulationX的电控变速液压系统仿真研究

传统的工程机械变速系统不利于减轻驾驶员劳动强度、提高操作舒适性,而电控变速系统则能很好地解决这一问题。描述了电控变速系统的原理,应用SimulationX软件对该系统压力变化进行仿真分析,总结出影响因素和规律,为系统设计提供理论依据。     

碳纤维蜂窝夹层结构二次曲面产品定位加工技术

Ka频段通信卫星天线反射器产品通常是由内面板、蜂窝芯子和外面板胶粘剂固化成型的碳纤维蜂窝夹层结构,内面板形成的反射面为满足一定精度要求的二次曲面。由于反射器本身特征无法作为准确基准进行找正,且在工装上的安装位姿不确定性,因此反射器在固化成型后的数控加工过程中无法直接获取定位基准。针对反射面的三坐标测量机检测数据,采用基于曲面最佳拟合数据调整理论模型位姿的方法,解决了碳纤维蜂窝夹层结构二次曲面产品加工基准的精确获取难题,并在数控程序编制中提出"虚拟理论曲面位姿"方法,对已有的数控程序操作进行重用,大幅提高了反射器产品批量研制的数控编程效率。     

Frequency weighting filter design for automotive ride comfort evaluation

Few study gives guidance to design weighting filters according to the frequency weighting factors,and the additional evaluation method of automotive ride comfort is not made good use of in some countries.Based on the regularities of the weighting factors,a method is proposed and the vertical and horizontal weighting filters are developed.The whole frequency range is divided several times into two parts with respective regularity.For each division,a parallel filter constituted by a low-and a high-pass filter with the same cutoff frequency and the quality factor is utilized to achieve section factors.The cascading of these parallel filters obtains entire factors.These filters own a high order.But,low order filters are preferred in some applications.The bilinear transformation method and the least P-norm optimal infinite impulse response(IIR) filter design method are employed to develop low order filters to approximate the weightings in the standard.In addition,with the window method,the linear phase finite impulse response(FIR) filter is designed to keep the signal from distorting and to obtain the staircase weighting.For the same case,the traditional method produces 0.330 7 m · s~(–2) weighted root mean square(r.m.s.) acceleration and the filtering method gives 0.311 9 m · s~(–2) r.m.s.The fourth order filter for approximation of vertical weighting obtains 0.313 9 m · s~(–2) r.m.s.Crest factors of the acceleration signal weighted by the weighting filter and the fourth order filter are 3.002 7 and 3.011 1,respectively.This paper proposes several methods to design frequency weighting filters for automotive ride comfort evaluation,and these developed weighting filters are effective.     

形变和冷却对B1500HS硼钢马氏体相变的影响

利用Gleeble-1500D热模拟试验机,以恒定的应变速率将在900℃奥氏体化的B1500HS硼钢试样分别压缩10%、20%、30%、40%,然后分别以50℃/s、40℃/s、25℃/s的速度对试样进行冷却。研究形变量及冷却速度对B1500HS硼钢的马氏体相变温度、微观组织、显微硬度和残余奥氏体等方面的影响规律。结果表明:相同冷却速度下,马氏体相变开始温度和相变终止温度均随着形变量的增加逐渐升高。随着形变量的增加,马氏体组织越来越细小,而且薄片状马氏体越来越少,板条状马氏体越来越多。形变量和冷却速度的增大,均使B1500HS试样中的残余奥氏体量减小。形变导致B1500HS硼钢的连续冷却转变图左移,避免未变形B1500HS钢试样生成贝氏体组织的临界冷却速度约为25℃/s。当冷却速度为25℃/s时,试样的变形程度达到30%时,微观组织中开始出现贝氏体。     

一种应力诱发相变的超弹性NiTi记忆合金本构模型

采用隐式应力积分塑性理论,建立一个能够考虑超弹性Ni Ti合金相变行为的本构模型。该模型利用VonMises等效应力面构建记忆合金的相变面,描述记忆合金在力载荷驱动下的相变行为,并通过试验进行验证。研究表明,所建立模型能很好描述温度相关应力所引起马氏体的相变行为,同时对马氏体的逆相变行为也能进行合理地描述。