基于LS-SVM逆系统的无轴承异步电机解耦控制

无轴承异步电机具有非线性、多变量和强耦合的特点,要实现电机稳定悬浮和旋转运行,必须对其进行非线性动态解耦控制。为了克服逆系统方法精确建模难的局限性,采用基于最小二乘支持向量机(LS-SVM)α阶逆系统方法对无轴承异步电机进行动态解耦控制的研究。首先利用最小二乘支持向量机辨识出无轴承异步电机的逆模型,然后将它串联在原系统前,将无轴承异步电机解耦成四个独立的伪线性子系统-2个径向位移子系统、一个速度子系统和一个磁链子系统。为保证鲁棒性能,最后对解耦后的系统采用非线性内模控制策略。研究表明,LS-SVMα阶逆系统方法能够实现无轴承异步电机径向悬浮力和旋转力之间的动态解耦控制,控制系统具有良好的静态和动态性能。     

辐照改性聚丙烯拉伸流变行为及其挤出发泡的研究

通过在线形聚丙烯中加入双官能团丙烯酸酯类单体,经小剂量γ射线高能辐照,制备了高熔体强度聚丙烯,研究了其拉伸流变行为及其在挤出发泡方面的应用。Rheotens拉伸流变测试表明,辐照改性后由于形成了长支化分子结构,聚丙烯的熔体强度、拉伸黏度显著提高,具有明显的应变硬化特征。实验表明,ZnO可明显降低AC发泡剂分解温度,缓和分解放热;在辐照改性制备的高熔体强度聚丙烯中加入AC／ZnO复合发泡剂,可挤出发泡得到泡孔尺寸较为均一、分布均匀、具有闭孔结构的发泡材料。     

Chemical analysis of volatiles emitted by Pinus svlvestris after induction by insect oviposition

Gas chromatography – mass spectrometry analyses of the headspace volatiles of Scots pine (Pinus sylvestris) induced by egg deposition of the sawfly Diprion pini were conducted. The odor blend of systemically oviposition-induced pine twigs, attractive for the eulophid egg parasitoid Chrysonotomyia ruforum, was compared to volatiles released by damaged pine twigs (control) that are not attractive for the parasitoid. The mechanical damage inflicted to the control twigs mimicked the damage by a sawfly female prior to egg deposition. The odor blend released by oviposition-induced pine twigs consisted of numerous mono- and sesquiterpenes, which all were also present in the headspace of the artificially damaged control twigs. A quantitative comparison of the volatiles from oviposition-induced twigs and controls revealed that only the amounts of (E)--farnesene were significantly higher in the volatile blend of the oviposition-induced twigs. Volatiles from pine twigs treated with jasmonic acid (JA) also attract the egg parasitoid. No qualitative differences were detected when comparing the composition of the headspace of JA-treated pine twigs with the volatile blend of untreated control twigs. JA-treated pine twigs released significantly higher amounts of (E)--farnesene. However, the JA treatment induced a significant increase of the amount of further terpenoid components. The release of terpenoids by pine after wounding, egg deposition, and JA treatment is discussed with special respect to (E)--farnesene.     

冶金过程对齿轮钢窄淬透性的影响与控制

采用电炉炼钢短流程生产20CrMnTiH工艺,对影响淬透性的冶金因素进行分析,发现工艺过程对化学成份控制精度的影响因素并进行研究优化,建立电炉短流程生产齿轮钢20CrMnTiH子钢号工艺模型,加强从加料到精炼全过程控制,确保产品成份。     

Dynamic equivalent method of interconnected power systems with consideration of motor loads

The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus...     

Cycling hardening and serration yielding of Fe-Ni-Cr alloy at high temperature under out-phase TMF

Behaviour of hardening and serration yield of a Fe-Ni-Cr alloy under isothermal cycling (ISC) and out-phase TMF was studied on the basis of varied hysteresis loops. Cycling hardening and serrated yielding for ISC depend on the temperature and the total strain range, stronger hardening with serrated yielding at higher strain range under ISC at 600 °C, but no hardening and serrated yielding occurred under ISC at 800 °C. Stronger hardening with stress serration occurred at the thermal path going to the lowest temperature, no stress serration occurred at the highest temperature under the out-phase. The hardening also depends on the total strain range, higher total strain range with lower cycling temperature resulted in a stronger hardening and remarkable serration yielding behavior. Weaker hardening without serrated yielding occurred at near 800 °C may due to an obvious cycling stress drop under out-phase TMF. Change in the shape of the hysteresis loops also expresses the degree of the damage of the tested alloy under out-phase and ISC.     

Numerical analysis on Joule heating of double-loop channel induction furnaces

In order to investigate Joule heating power, a three-dimensional finite element model (FEM) was developed to predict Joule heating power in the channels of double-loop inductor. The simulated results were compared with experimental data from low load trials for a 400 kW inductor. The results, such as power factor and Joule heating power, show reasonable correlation with experimental data, and Joule heating rate reaches the maximum at the corners and the minimum at the centre of the cross-section area. With increasing relative permeability of iron core, length of coils, current frequency and resistivity of metal melt, the power factor and Joule heating power change. It is concluded that current frequency, the resistivity and length of the coil play a critical role in determining the power factor and Joule heating power, whereas relative permeability of the magnetic core shows no significant influence on them.     

Experimental study on Ti+Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the ferrite region

A Ti+Nb bearing ultra-low carbon bake hardening sheet steel hot-rolled in the conventional austenite region and in the ferrite region with lubrication was experimentally studied.Subsequent cold rolling and continuous annealing processes were also conducted.The results show that microstructures of ultra-low carbon bake hardening hot strips at room temperature are basically irregular polygonal ferrites.The yield strength,ultimate tensile strength,n value,and r value of the No.2 specimen hot-rolled in the ferr...     

高压输变电工程的电磁辐射及其环境影响评价

介绍高压输变电工程产生的电磁环境与人类健康关系以及国内外的相关标准,通过监测实例说明已运行的500 kV变电站和线路的电磁辐射均符合相关标准的要求,同时提出了环境影响评价工作的问题和建议.     

基于小生境遗传算法的YKK系列高压电机优化设计

为了使YKK系列电机最终实现高效节能的目的,并且满足生产实际中所提出的各种约束要求,引入了小生境遗传算法进行电机的优化设计.针对中型高压电机定子成型线圈的结构以及三圆尺寸相对固定的实际情况,对小生境遗传算法进行相应的改进,有效地避免了优化算法易于局部收敛的问题.结果表明:与初始方案相比较,电机的设计结果满足了高效电机所提出的技术指标.并且电机的体积得到了缩小,节约了电机的有效材料.证明了改进的小生境遗传算法的可行性及优越性,并具有工程实用价值.