单片机控制IGBT逆变埋弧焊机的研制

针对IGBT逆变埋弧焊机设计了基于单片机80C196KC的控制系统,介绍了系统的软、硬件组成和控制原理.焊接电源采用PWM控制技术,通过电流反馈PI控制算法调节电源输出外特性.送丝及行走小车调速系统采用MOSFET型开关电源,采用电弧电压反馈PI算法,实现了送丝速度的闭环控制.研制的焊机具有参数预置、数字显示和自动引弧收弧等功能.试验结果表明,样机性能稳定,工作可靠,达到了设计要求.     

基于数据仓库技术的SDN企业实施MC的技术集成框架

论述了企业实施大规模定制(MC)所必需的基于数据仓库技术的其他相关技术和以SDN为主导的先进管理理念,提出了基于数据仓库技术的SDN企业实施MC的技术集成框架,并详细阐述了该方案的运作过程,为企业实施MC提供参考模型.     

MONTE CARLO SIMULATION OF TRIBLOCK COPOLYMER/HOMOPOLYMER BLEND FILMS

The morphologies of triblock copolymer/homopolymer blend films, ABA/A and ABA/B,confined between two neutral hard walls were studied via Monte Carlo (MC) simulation on a simple cubic lattice. The effects of ψh (the volume fraction of homopolymer) and Mn/Mb (the molecular weight of homopolymer in relation to that of the corresponding blocks in the copolymer) on the morphologies were investigated in detail.     

POLYCAPROLACTAM MODIFIED BY POLYBENZIMIDAZOLE

Three polycaprolactam samples modified by 0.05—0.50% polybenzimidazole (PBI) by weight were prepared. Their structure and mechanical properties were characterized by means of FT-IR, SEM, DTA, density tensile, impact and viscoelastic method. PBI delayed the superimposed polymerization-crystallization process of the activated anionic polymerization of caprolactam. The monomer casting (MC) nylons modified by PBI had lower crystallinities, lower T_g and more nearly perfect spherulites than MC nylon itself, and showed a typical toughening effect.     

Absorbed weak polyelectrolytes: Impact of confinement,topology, and chemically specific interactions on ionization,conformation free energy,counterion condensation,and absorption equilibrium

Absorption of weak polyelectrolytes impacts on properties such as ionization, conformations, and counterion (CI) condensation that are important in several areas of applied and fundamental science. We used a weak polyelectrolyte model and Monte Carlo simulations to investigate how the mentioned properties depend on pH or the size of a spherical cavity (SC) permeable to CIs but not to polyelectrolytes; the latter have either linear or starlike topologies and may be allowed to form charged hydrogen bonds (c? H‐bonds) between ionized and neutral monomers. Average ionization decreases upon increasing the number of arms at a constant number of monomers; it instead increases with the arm length in large SC due to CI screening. The way SC size, c? H‐bonds, and pH values interrelate to define ionization is instead more complicate due to arm pairing or clustering when c? H‐bonds are possible. These induce oscillations in the arm local ionization and impact on both monomer and CI distributions in the complete simulation cell in a way that also depends on polymer topology. The impact of ionization on the confinement free energy is also estimated; this highlighted that c? H‐bonding may enhance absorption compared with neutral chains. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 491–510     

基于MC9S12XS128的自动电阻测试仪设计

本文以飞思卡尔公司的16位微处理器MC9S12XS128为控制芯片,用4×4矩阵键盘作为人与系统对话设备,用自带汉字库的带背光的12864LCD为显示器,设计了自动电阻测试仪。测试仪实现了100Ω、1KΩ、10KΩ、10MΩ四档位的精确测量,且在各档位间能实现自动切换;同时具有电阻筛选功能;测试仪还设计了自动测量电位器阻值随旋转角度变化的装置,能动态显示电位器阻值随旋转角度变化的曲线。系统性能稳定,测量精度高,具有相应的灵活性和实用性。     

加速度传感器在模型火箭定高分离中的应用

模型火箭定高分离是航天模型比赛的重要比赛项目之一,其难点在于高度的精确控制。为了使模型火箭能在设定高度分离,系统采用飞思卡尔MC9S08AW60单片机和集成3轴加速度传感器MMA7455模块,通过SPI数据传输协议将加速度传感器测得值传至单片机进行变加速度的二次积分运算求得高度值。实验测试结果表明,能完成对模型火箭高度的测定与其在定高分离的功能,其定高精度指标符合模型火箭定高分离系统的应用要求。     

基于贝叶斯理论的ATS测量不确定度评定

从自动测试系统(ATS)的组成机理出发,提出一种ATS测量不确定度评定方法。其基本过程是首先基于测量信号路径,建立相应的测量链;其次,计算各个传递单元的不确定度,静态测量、动态测量分别选用贝叶斯信息融合法和贝叶斯预测法进行评定;最后,利用蒙特卡罗(MC)法计算各链的合成不确定度。通过某ATS中具体的测量链作为实例,重点分析了动态测量不确定度评定过程中遇到的不同情况及解决办法。实验表明,较其它常用评定方法,该法评定ATS静态测量得到的结果更接近理论值,不确定度变化小,评定动态测量得到结果更符合ATS动态特性且精确度高。     

MR Study of Water Distribution in a Beech (Fagus sylvatica) Branch Using Relaxometry Methods

Wood is a widely used material because it is environmentally sustainable, renewable and relatively inexpensive. Due to the hygroscopic nature of wood, its physical and mechanical properties as well as the susceptibility to fungal decay are strongly influenced by its moisture content, constantly changing in the course of everyday use. Therefore, the understanding of the water state (free or bound) and its distribution at different moisture contents is of great importance. In this study, changes of the water state and its distribution in a beech sample while drying from the green (fresh cut) to the absolutely dry state were monitored by 1D and 2D ¹H NMR relaxometry as well as by spatial mapping of the relaxation times T₁ and T₂. The relaxometry results are consistent with the model of homogeneously emptying pores in the bioporous system with connected pores. This was also confirmed by the relaxation time mapping results which revealed the moisture transport in the course of drying from an axially oriented early- and latewood system to radial rays through which it evaporates from the branch. The results of this study confirmed that MRI is an efficient tool to study the pathways of water transport in wood in the course of drying and is capable of determining the state of water and its distribution in wood.     

低温等离子体放电的数值模型

综述了迄今为止各种分析低温等离子体放电物理过程的数值模型,以帮助我们从数值模型出发理解许多至今仍无法解释的现象,同时也为低温等离子体在等离子体处理技术、气体激光等工业应用以及在微电子、材料制备、环保、航空航天、军事等领域的应用提供了研究方法.