基于极点配置的逆变器双环控制方案

介绍一种基于极点配置的逆变器瞬时电压电流PI控制器的设计方法,建立系统模型,为了提高逆变器输出波形的精度,提出了一种基于极点配置的PI双环和重复控制的复合控制方案。该复合控制方案克服了PI双闭环控制方案带整流性负载时输出电压质量不高的缺点,也解决了嵌入式重复控制方案应用在逆变系统中对逆变器谐振峰值不可控的问题。仿真表明,所设计的复合控制方案提高了逆变电源带整流性负载时的输出电压质量,该方案既保持了重复控制良好的稳态特性,也明显改善了系统的动态性能。     

Experimental study on the optimization of heat and mass transfer of industrial drying of the TiO2 bulb by infrared radiation

The characteristics of radiation and drying properties of TiO₂ bulb in the fixed bed with infrared radiation have been studied in this paper, and the experiments on drying dynamics has been analysed also. The optimization of heat and mass transfer data has been determined, which could provide the scientific basis for engineering design.     

微生物中的烷基硫酸酯酶在生物转化中的应用研究进展

在工业生物技术中,大多数催化生产非天然化合物的水解酶对于对映异构体都有一定的偏爱性,如羧酸酯水解酶、脂肪酶以及蛋白酶,但它们在催化过程中不能改变底物的立体化学结构,而烷基硫酸酯酶可以通过倒置或保留底物构型来改变底物的立体化学。所以硫酸酯酶可催化外消旋体发生对映体汇聚过程,将外消旋硫酸酯水解成单一立体构型仲醇,且理论产率为100%。这对于传统的动力学拆分而言,是一个很大的进步。因为在动力学拆分中,要产生2种构型产物,产率分别都为50%。     

辊弯二次成形介绍

本文简介了从日本引进的辊弯成形机组的设备，工艺及产品，对辊弯二次成形方式的特点进行分析及论述，同时介绍东洋异型管开发新产品的实践。     

啮合型异向旋转双螺杆挤出机熔体输送流场及特性的近似解析解

从简化的物理模型和数学模型出发,参照流速分布数值计算结果所反映出的规律性,求出了C形小室内熔体流速分布的近似解析解,并由此导出了熔体输送段中产生的轴向力、扭矩、功耗和比功耗的计算公式。与数值计算得出的结果相比,这些公式由于具有解析形式,不但能直观地反映上述熔体输送特性参数与其他参数的关系,而且更便于运用。     

EMD-ICA联合降噪在滚动轴承故障诊断中的应用

滚动轴承早期故障信号具有能量小、频带分布宽等特征,易受到其他能量较大的振源信号的干扰,致使传统滤波降噪方法存在很大的局限性。针对这一特点,提出经验模式分解(EMD)和独立分量分析(ICA)相结合的联合降噪新方法。将单通道振动信号进行EMD分解,基于互相关准则对分解后的本征模函数进行重组,构造虚拟噪声通道,并以此作为ICA的输入矩阵,采用FastICA算法实现源信号和噪声信号的分离,从而达到降噪的目的。将该方法应用于滚动轴承故障诊断中,对降噪后的重构信号进行频谱分析,进而判断滚动轴承的运行状态。仿真和试验分析结果表明该方法有效可行。     

Friction and Wear Behaviors of Ni-based Composites Containing Graphite/Ag2MoO4 Lubricants

In order to improve the tribological properties of Ni-based composites, novel adaptive Ni-based composites containing multiple lubricants were prepared via a mechanical alloying and hot-press sintering technique. The phase constituents and microstructure of the composites were characterized and the tribological properties were evaluated from room temperature to 700 °C. The results showed that the Ag₂MoO₄ phase decomposed and new phases of Mo₂C, Ag, and MoO₃ formed in the sintered composites, which can be attributed to the solid state reaction of silver molybdate lubricant during the sintering process. The wear test results indicated that the Ni-based composites containing graphite and silver molybdate lubricants exhibited superior tribological properties at ambient and high temperatures. Subsequently, the Raman results demonstrated that the composition of the tribo-layers on the worn surface of the Ni-based composites was varied with increasing temperature. Combined with the wear test results, it can be proposed that the improvement of tribological properties is due to the synergistic lubricating action of silver molybdate, iron oxide, and nickel oxide. Furthermore, Raman results of the composite containing silver molybdate and silver/molybdenum trioxide lubricants revealed that the silver molybdate lubricant can reproduce easily by the direct reaction between molybdenum trioxide and silver in the agglomerate state.     

950mm冷轧轧机中间辊滚珠轴承失效原因分析

某冷轧厂950mm轧机中间辊用滚珠轴承经短时间使用后发生滚珠断裂。采用化学成分分析、硬度检测和金相检验等方法对断裂的滚珠进行分析。结果表明,该滚珠碳含量偏高,基体中存在碳化物聚集现象,滚珠局部硬度偏低,且非金属夹杂物过多,这些最终导致滚珠在运行过程中发生断裂。     

ICP-OES测白色木器涂料中的砷(As)元素含量

通过对白色木器涂料样品进行微波消解、定容,再使用电感耦合等离子体发射光谱仪(ICP-OES)进行测试而建立了白色木器涂料中砷元素含量的测试方法。重点讨论了微波消解仪和ICP-OES仪器的设置参数,测试的精密度和回收率。该方法的精密度好,回收率高,可用于测试白色木器涂料中的砷元素含量。     

涂料用钛白应用性能评定标准的探讨

通过测定涂料用钛白的油分散性和吸油量,探讨了钛白制造商和涂料制造商对这两项应用性能评定标准的差异性。