Estimation of Concentration of Particles in Polymerizing Fluid during Centrifugal Casting of Functionally Graded Polymer Composites

The concentration of uniformly distributed particles in a fluid changes with time in the direction of gravitational or centrifugal force to form a concentration gradient. The change in the concentration is an outcome of velocity variation of particles in a fluid. A modified equation for terminal velocity, v _m of particles in polymerizing-fluid under centrifugal force is proposed to estimate the changes in the volume fraction of particles in the graded composites. The proposed equation introduces the effect of cure kinetics of polymer and its effect on particle movement in the model that was based on the modified Stoke’s law, considering the parameters related to particle hindrance, centrifugal force, particle dimensions, viscosity variation etc. The model predictions of concentration changes at the different locations of samples were compared with calcium carbonate filled polysulphide-modified-epoxy graded composites prepared by centrifugal casting.. The effect of particle size, delayed curing rate of matrix were explored. The simulated results are in good agreement with those of experiments.     

基于Cortex M3的铝型材生产全自动牵引切割系统的研究与设计

分析了铝型材生产中对牵引切割的技术要求,建立了双牵引机运动模型,并根据该模型设计了一种基于Cortex M3的无双线牵引机控制系统,设计了硬件电路,编写相应的控制程序及设计了无线通信协议,使该系统具有良好的兼容性。该系统完全实现了双牵引机运动模型,并在某铝材生产厂家运行测试。试验证明,该系统完全符合厂家的要求,而且价格低廉,结构简单,性能稳定,具有良好的应用前景。     

塑料挤出成型模具流道优化设计

本文依据流变学理论，采用优化方法进行挤出成型模具（即机头）流道设计，探讨了建立流道优化数学模型的有关问题。     

国内外聚氯乙烯塑料门窗的现状及展望

介绍了未增塑聚氯乙烯塑料门窗的导热系数低、防水、防潮等特点,利用PVC型材作门窗是节约建筑材料的一条重要途径.重点阐述了国内外聚氯乙烯塑料门窗的生产、使用情况及国内产品存在的缺陷,另外还论述了国内塑料门窗的发展趋势,对PVC塑料门窗在国内的发展应用有促进作用.     

异型材口模挤出三维流动计算机模拟系统

建立了异型材口模挤出三维流动计算机模拟系统的基本框架，介绍了其结构和功能，该系统主要包括前置处理，有限元分析和后置处理三大模块，有限元分析模块又包括对口模内幂律流动的分析模块，粘弹性PTT流体流动的分析模块以及粘弹性PTTI充体三维挤出胀大的分析模块，后置处理主要包括速度场和应力场的后置处理。该系统目前只是一个雏形，经过不断发展和完善，有望成为异型材口模挤出过程模拟的通用分析软件。     

基于模态Petri网的行为有效区间寻找最优路径的方法

为满足客户需求,在行为约束下的业务流程中寻找行为执行的最优路径具有一定的实际意义。已有的研究是建立在静态分析基础上,通过优化算法或是行为分析来寻找最优执行路径,忽略了行为约束条件对执行行为有效性的影响,所得结果具有一定的局限性。文中在已有方法的基础上,利用Petri网行为轮廓序关系描述约束条件并确定行为有效区间,提出了基于模态Petri网分支有效区间的业务流程最优路径选择方法。该方法以行为有效区间替代已有的固定值方法,以便更好地描述业务流程的行为约束以及约束下的有效行为。通过一个具体的业务流程分析实例分析了该方法的有效性。     

水化放热曲线在研究铝酸钙水泥和浇注料中的应用

为了预测水泥或浇注料的凝结性和强度发展趋势,取1500g按一定程序搅拌好的水泥胶砂或浇注料,迅速倒入模具中,振动10s后置入j-型热电偶,由计算机绘制出其水化放热曲线。浇注料的水化放热曲线形貌不仅能反映水泥的矿物组成和反应活性,而且能反映浇注料中其他原材料(如骨料、氧化铝或二氧化硅微粉和外加剂等)和作业环境对水泥及浇注料的影响,为此可用于水泥与浇注料流变特性的研究和控制,同时也为浇注料用原材料的甄选提供了一种有用的工具。     

冷桥用PA66挤出异型条专用料研究

介绍采用双螺杆挤出机生产冷桥用PA66挤出异型条专用料的配方及工艺。该专用料以PA66为主体原料，经玻纤，改性剂，滑石粉共混改性制成。分析了几种改性材料对冷桥用PA66挤出异型条专用料性能的影响，并探讨了PA66自身性能对专用料性能的影响。该专用料经有关厂家使用，其性能达到使用要求。     

Near Wall Studies of Pulp Suspension Flow Using LDA

A detailed study of the flow behaviour in the near wall region of pulp suspensions up to 4.7% have been performed using Laser Doppler Anemometry (LDA) in pipe flow. Axial mean velocity profiles show a distinct plug flow and an increase of the plug region as the flow rate decreases and fibre concentration increases. An attempt is made to relate the LDA data‐rate to fibre concentration, which indicates a dilution region at 1‐2 mm from the wall that is larger than the annulus region. The dilution region increases with increasing flow rate, decreasing concentration and when using longer pulp fibres.     

Confocal Raman study of poly(ethylene terephthalate) fibres dyed in supercritical carbon dioxide: dye diffusion and polymer morphology

Confocal Raman microscopy (CRM) has been used to extract dye diffusion data from poly(ethylene terephthalate) (PET) fibres dyed with Disperse Yellow 23 under supercritical CO₂ conditions. Spectral information as a function of depth was measured in a non-destructive manner using dry and oil objectives in confocal Raman mode. Mapping along the radius of the fibre cross-section was performed and compared to the data from the confocal measurements. A significant dye concentration gradient has been observed along the line normal to the fibre surface which the data from the oil confocal measurements accurately describes to a depth of 45 μm. The effect of the supercritical CO₂ dyeing process on the fibre morphology has also been evaluated using CRM.