The evolution and morphological stability of a spherical crystal

The growth model of a spherical crystal in the undercooled melt including the surface energy, interfacial kinetics and convective flow is established. The effect of the convective flow induced by a small far field flow on the evolution and morphological stability of the interface of the spherical crystal is studied. The interface shape of the spherical crystal, which is affected by the far field flow, and the dispersion relation of the growth rate of amplitude of the perturbed interface are derived. It is shown that the convection induced by the far field flow makes the interface of the growing spherical crystal further grow in the upstream direction of the far field flow and inhibit growth in the downstream direction; the interface of the decaying spherical crystal further decays in the upstream direction and inhibits decay in the downstream direction. The theoretical result suggests that both the growth of the sphere in the upstream direction and the decay of the sphere in the downstream direction make the spherical crystal tend to evolve into an oval; the morphological stability of the interface depends on a certain radius R _c such that the spherical crystal is unstable when its radius is greater than R _c and stable when its radius is less than R _c . The surface energy and interfacial kinetics have strong stabilizing effects on the growth of the spherical crystal. In the meantime interfacial kinetics is a table factor of the interface when the interface of the sphere is growing; it is an unstable factor of the interface when the interface is decaying. Supported by the National Basic Research Program of China (Grant No. 2006CB605205), the National Natural Science Foundation of China (Grant Nos. 10672019 and 10572062), and the Science and Technology Foundation of Shanghai (Grant No. 055207081)     

原位复合反应制成TiB对提高管道耐磨性的研究

将自蔓延和离心铸造的方法相结合,制备了原位TiB晶须增强钛基复合材料;采用扫描电子显微镜分析了复合材料的显微组织,结合磨损表面、剖面显微组织.分析探讨了复合材料表面的磨损机制;评价了复合材料的耐磨性能.结果表明：TiB晶须尺寸细小、长径比大、在基体中分布均匀;与基体合金相比,钛基复合材料的耐磨性能显著提高,这是由于TiB晶须具有增强作用和承载作用所致.     

基于信息熵的模糊随机桁架结构动力特性分析

考虑桁架结构同时具有模糊性和随机性，利用模糊熵和概率熵的概念，将结构的随机性和模糊性统一为结构的模糊性，将模糊随机结构转化为纯粹的模糊结构。利用模糊因子法和区间运算推导出结构固有频率的主值和最大、最小值的计算表达式。通过算例，分析结构物理参数和几何尺寸的模糊随机性对结构固有频率的影响，获得了一些有意义的结论。     

铂、铱金火花塞自动焊接设备

介绍了一种铂、铱金火花塞自动焊接设备，该设备用于将细小的铂、铱金丝焊接在火花塞的点火端上，全自动、焊接质量稳定可靠。     

The off-state gate isolation technique to improve ASET tolerance in differential analog design

A novel off-state gate RHBD technique to mitigate the single-event transient(SET)in the differential data path of analog circuit is demonstrated in this paper.Simulation results present that this off-state gate technique could exploit charge sharing in differential circuits and reduce differential mode voltage perturbation effectively.It is indicated that this technique is more effective to mitigate SET than the differential charge cancellation(DCC)technique with less penalty.     

浅谈影响子午胎动平衡的因素及其改进措施

子午胎动平衡指标是评价子午胎使用性能和品质的重要指标,也是衡量现代轮胎企业技术质量基础管理水平高低的重要标志之一。在子午胎的制造过程中影响动平衡的因素很多,贯穿于整个生产过程。本文结合自身体会,就影响子午胎动平衡的因素进行分析并提出改进措施。     

广义均值移动跟踪算法

CAMSHIFT算法和Comaniciu/Meer算法是均值移动在视频目标跟踪中最为常用的两个基本算法.本文对Bradski和Comaniciu/Meer等人的工作加以推广,给出了广义均值移动跟踪算法.论文采用一个一般形式的相似性度量函数,并推导了其相应的像素权值计算和搜索窗口位置更新公式.新算法基于搜索窗内各像素权值的零阶矩来计算更新其搜索窗口尺寸.然后证明现有的两种基本算法都可以归纳到广义均值移动跟踪算法的统一框架中.对多段视频序列的跟踪实验分析比较了统一框架中3种均值移动算法的跟踪性能.     

圆锥破碎机液压系统动态仿真研究

根据功率键合图得出了圆锥破碎机液压系统的数学模型（非线性状态方程）,然后给出了仿真模型,并介绍了如何用MATLAB/Simulink软件包对该液压系统的动态特性进行仿真,同时讨论了如何通过改变参数来确定影响该系统特性的主要因素.     

PLC在过程控制系统实验装置中的应用

本文介绍了西门子PLC混合网络在过程控制实验装置中的应用。控制系统在逻辑结构上分为两层：现场设备层和网络控制层，PROFIBUS用于现场设备层，网络控制层采用工业以太网。文章对控制系统的设计思想、系统结构、组态方法进行详细的分析和论述。     

铸造镁合金成形工艺现状与发展趋势

本文综述了以压铸为代表的铸造镁合金主要加工方法的现状,并对与铸造镁合金成形工艺相关的研究课题和发展趋势作了简要的论述.