Experimental Study on Phase Transformation Between MgB2 and MgB4

Using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential scanning calorimetry (DSC), we have investigated the reaction between MgB₄ and Mg in its solid, liquid, and gas physical states. The XRD results indicate that the reaction of MgB₄+Mg=2MgB₂ always occurs independently of the different states of Mg. DSC measurements show that the solid–solid reaction MgB₄( s )+Mg( s )=2MgB₂( s ), the Mg melting Mg( s )→Mg( l ), and the Mg volatilization occur in turn with increasing temperature for mixed (MgB₄+Mg) powder with a nominal stoichiometry of MgB₂. SEM observations indicate that the resulting synthesized MgB₂ samples, obtained from the MgB₄+Mg mixtures, have a denser microstructure than those obtained directly from Mg+B mixtures. On the basis of XRD, DSC, and SEM results, a kinetic model for the reaction between MgB₄ and Mg is proposed.     

仿射变换在压缩感知跟踪中的应用

针对跟踪中目标尺度变化和旋转问题,将仿射变换和应用到压缩感知跟踪中.首先,以上一帧的跟踪结果为均值,以一定的标准差按照高斯分布,随机生成不同尺度和旋转角度的候选框;然后,通过仿射变换将其转换至直角坐标系中,通过多尺度滤波得到目标在不同尺度下的高维特征向量,采用压缩矩阵将高维特征向量降维至低维空间;最后,将低维特征向量通过贝叶斯分类器选取具有最大响应的候选位置作为目标的跟踪位置.在此基础上分别提取正负样本来更新分类器参数,从而实现持续稳定的跟踪.实验结果表明,该算法能够较好地解决压缩感知跟踪中的目标旋转和尺度变化问题.     

碘化钛的电子束熔炼提纯效果分析

通过对碘化钛电子束熔炼提纯效果分析，提出合理、经济的高纯钛制取工艺路线。     

Zirconium Alloys for Orthopaedic and Dental Applications

Zirconium alloys for biomedical applications are receiving increasing attention due to their two unique properties: 1) the formation of an intrinsic bone‐like apatite layer on their surfaces in body environments, and 2) better compatibility with magnetic resonance imaging (MRI) diagnostics due to their low magnetic susceptibility, as well as their overall excellent biocompatibility, mechanical properties, and bio‐corrosion resistance. In particular, since both of the MRI quality and speed depend on magnetic field strength, there is a compelling drive for use of high magnetic field strength (>3 Tesla) MRI systems. This paper provides a comprehensive review of the characteristics of commercially pure (CP) Zr and Zr‐based alloys as orthopaedic and dental implant materials. These include their 1) phase transformations; 2) unique properties including corrosion resistance, biocompatibility, magnetic susceptibility, shape memory effect, and super‐elasticity; 3) mechanical properties; 4) current orthopaedic and dental applications; and 5) the d‐electron theory for Zr alloy design and novel Zr‐alloys. The mechanical properties of Zr‐based bulk metallic glasses (BMGs) and their application as implant materials are also assessed. Future directions for extending the use of Zr‐alloys as orthopaedic and dental implants are discussed.

     

Effect of synthesis temperature on density and microstructure of MgB2 superconductor at ambient pressure

The experimental thermodynamic of MgB₂ synthesis process and phase compositions have been investigated by diffraction thermal analysis (DTA) technology and X-ray diffraction. The fabrication of MgB₂ bulks and superconducting properties at the temperatures range from 600 to 800°C were reported. And microstructure of MgB₂ bulks were observed by scanning electron microscope (SEM). A method was developed to determine the porosity of MgB₂ and the highest density can be obtained in MgB₂ prepared at 650°C at ambient pressure. It is found that the vapor pressure of Mg increases remarkably at high temperature, leading to the high porosity in MgB₂ samples. MgB₂ bulk with good superconducting property and fine microstructure was synthesized at 750°C.     

面向切屑形成过程的瞬时滚削力模型研究

建立滚齿加工的时变滚削力模型是优化滚齿加工工艺参数、减少滚削力波动、提高加工精度的前提,面向滚齿切屑形成过程建立时变滚削力模型是提高建模精度的最直接的物理方法。针对干切滚齿的切屑形成过程,建立滚刀前刀面运动模型,利用MATLAB生成刀齿运动轨迹的动态链接库。基于SolidWorks进行三维布尔运算,提取未变形切屑几何特征,开发切屑几何模型动态链接库。通过C#调用MATLAB和SolidWorks动态链接库,实现三维运动仿真,进而构建多齿瞬时滚削力模型。通过YK3216CNC滚齿机进行样件加工,结合HNC-SSTT软件进行全行程电流检测,间接测量瞬时滚削力。仿真加工的瞬时滚削力与实测滚削力变化趋势基本一致,表明该模型合理、有效。     

铜合金的 Gleeble热模拟试验探讨

铜合金由于延展性好、耐磨损、导热性和导电性高等特点,广泛应用于电力、机械制造、化工、汽车、电气仪表和建筑等各个行业领域。但是在新型铜合金材料研发过程中,铜合金的 Gleeble热模拟试验由于电偶焊接难、加热不稳定、均温区难以确定,导致试验失败率高,数据不准确,分析难度大等问题。使用 Gleeble3800系统,系统地研究 Cu-Cr-Zr合金的 Gleeble热模拟试验。通过多种手段解决了以上问题,试验成功率达到 90%以上,大大提高了试验效率。铜合金拉伸试验结果显示,高温条件下样品整体都会发生拉伸变形,但是主要变形集中在中间 6mm的均温区域,中间 6mm的变形量大约在 90%～110%左右。     

高层建筑灭火弹电磁弹射系统研发

分析高层建筑灭火弹设备的现状,指出存在的问题,提出利用电磁力发射灭火弹。介绍了灭火弹电磁弹射原理、设备总体组成和工作过程。利用ANSYS Electronics 仿真软件对电磁力进行了仿真。电磁弹射系统的研发弥补了现有灭火弹设备在高层建筑灭火方面的不足,为高层建筑快速灭火救援提供了一种新的解决方案。     

煤矿综采工作面高效服务云管控平台

针对目前煤矿综采工作面远程监测监控系统存在信息孤岛、不利于煤矿智能管控的问题,提出了煤矿综采工作面高效服务云管控平台和多个煤矿综采高效服务云平台的设计思路。综采工作面高效服务云管控平台主要包括智能服务云平台系统、专家智能决策管控系统、设备工况数据交互系统、台账仓储交互系统、大数据决策平台管控系统、设备故障诊断数据交互系统、人员管理交互系统和安全监测监控系统等。在煤矿开展了试验验证,结果表明:该平台在PC端或手机移动终端实现了对综采工作面设备的实时监测、多个综采工作面人员高效协同管理和基于大数据的分析决策等功能,对煤矿安全、高效生产具有重要意义。