数字式电能表电压采样误差的理论分析与仿真

证明了整周期采样无原理性误差,推导了非整周期采样的误差公式,仿真实验反映了电压频率、采样点数和采样起始角与相对误差的关系.在论文实验条件下:频率变化0.1Hz时误差变化约0.1％,采样点数与误差为反比关系,起始角与误差近似为余弦关系.结论同样适用于电流有效值的计量.     

A chemometric approach for the quantification of free fatty acids in cottonseed oil by Fourier transform infrared spectroscopy

The aim of this study was to quantify free fatty acid in cottonseed oil (Gossypium) variety by a chemometric approach using Fourier transform infrared spectroscopy. Calibration standards were prepared by gravimetrical mixing of oleic acid (0.1–40 g/100 g) in neutralized cottonseed oil containing <0.1% free fatty acids. Fourier transform infrared technique coupled with partial least square and principle component regression models were used to develop calibrations in the specific absorption region of carbonyl between 1690–1727 cm^?1. On the basis of regression coefficient and evaluated free fatty acids results with comparison to titration method, partial least square was found to be more accurate than principle component regression calibration model. All the analyzed cottonseed oil varieties showed high content of free fatty acids in the range of 17.1–38.5%. The results of the present study indicated that Fourier transform infrared method in combination with partial least square or principle component regression could be used as a greener alternative to the standard titration method.     

交流弧焊电源的动向

本文综述了新近发展的手工电弧焊(MMA)、钨极惰性气体保护焊(TIG)和埋弧焊(SAW)中使用的交流弧焊电源。其原理、结构、功能、效果、计算方法和数据。由于电子技术的发展及其在焊接设计中的应用,冲击了老产品的杂繁结构,促使新、老产品向着物美价廉的方向发展。     

机动目标跟踪的完全最小二乘法输入估计

针对最小二乘法对目标机动进行估计时忽略系数矩阵偏差的问题,采用完全最小二乘法,同时考虑测量数据偏差和系数矩阵偏差对目标机动估计的影响,给出了机动目标跟踪中基于完全最小二乘法的输入估计方法。根据卡尔曼滤波器的一致性条件判断目标是否发生机动,使用完全最小二乘法估计出目标所发生的机动大小,并用目标机动的估计值对跟踪算法进行了补偿。仿真结果表明,基于完全最小二乘法的输入估计方法的跟踪效果要优于基于最小二乘法的输入估计方法。     

基于DNA遗传优化的正交小波常模盲均衡算法

在上行多用户中继网络中,针对中继协作波束成形与多天线基站联合优化的问题,本文提出了两种不同的但是具有一定相关性的设计方法。在第一种方法中,考虑在接收端SINR约束的情况下,使中继节点总功率最小化;在第二种方法中,研究在中继节点满足一定功率约束的情况下,使接收端SINR最大化。研究发现,基站线性接收器的最优权值矩阵决定于中继节点加权向量,进而可将多变量优化的复杂问题转化为单一变量优化问题。原问题进而可转化为半正定规划问题,可以用内点法方便的解决。仿真结果表明,与通过迭代运用凸优化求多向量的方法相比,该方法性能更优。     

最小二乘支持向量机在电梯故障诊断中的应用(英文)

针对电梯故障诊断中特征提取困难和故障样本数量少问题,提出了应用小波包分解和最小支持向量机( LS-SVM) 相结合进行电梯急停智能故障诊断的方法。借助小波包分解,该方法首先提取电梯轿厢振动信号作为特征向量,然后利用 LS-SVM 分类模型对故障进行辨识。实验证明,小波包与 LS-SVM 相融合的故障诊断与识别技术可发挥两者的优势,该方法对电梯急停故障的诊断具有较好的诊断效果。     

方钢管约束钢筋混凝土轴压短柱试验研究与分析

进行了20个方钢管约束钢筋混凝土短柱的轴压力学性能试验研究,试验的主要参数为钢管宽厚比(50,70和100)和混凝土强度(C50,C80)。试验结果表明：方钢管约束钢筋混凝土柱中被分隔钢管的高度对其轴压承载力和延性无明显影响。随钢管宽厚比增大和混凝土强度的提高,轴压短柱的延性降低。采用弹塑性应力分析方法对钢管进行了全过程应力分析,分析结果表明,方钢管约束钢筋混凝土轴压短柱的峰值荷载点并不对应钢管的屈服点,钢管在轴压短柱达到峰值荷载后屈服。根据试验结果和钢管的应力分析结果,建立了方钢管约束钢筋混凝土短柱的轴压承载力计算式,试验结果与计算结果吻合良好。并提出了设计建议。图8表2参12     

压电超精密定位台的动态迟滞建模研究

为了提高压电超精密定位台的建模精度,采用Backlash-Like迟滞非线性模型来描述压电超精密定位台的迟滞特性,采用基于遗传因子的递推最小二乘法来辨识Backlash-Like模型的参数,并结合压电超精密定位台的动态特性,建立了压电超精密定位台的二阶动态迟滞模型。通过实验得到,对比Backlash-Like模型,动态迟滞模型在频率为30和40 Hz时,最大输出位移误差由1.21和1.39μm下降到0.32和0.44μm,且最大相对误差分别仅为3.5%和4.4%,平均位移误差由0.53和0.76μm下降到0.17和0.21μm,平均相对误差由1.93%和3.38%下降到1.11%和1.37%。实验结果验证了提出的动态迟滞模型,既能减小了因压电超精密定位台的动态特性而引起的系统误差,又能很好地模拟其迟滞特性与动态特性,并且避免了不同频率下的模型参数反复辨识问题,提高了压电超精密定位台在高频、快速、大行程定位中的精度。该方法简单且适应性强,易于工程实现。     

考虑电压暂降非线性分布的配网故障区段定位

提出一种新的配网故障区段定位方法,根据电压暂降在线路呈非线性分布的特性,仅用单端测量采集到的电压暂降特征进行故障区段定位。对某配电网进行故障模拟分析,建立节点电压暂降数据库和电压暂分布函数降数据库,当实际短路故障发生时,将监测点采集的电压暂降与数据库中的电压暂降数据进行匹配,搜索出所有可能故障区段,计算故障点电压暂降与可能故障区段的电压暂降分布函数的离差,并认为离差最小对应的区段为最有可能故障区段。通过对一个11 kV典型配电网进行单相接地短路故障仿真,结果验证了所提方法的有效性和准确性。     

混响室频率搅拌技术研究（英文）

The radio frequency(RF)modes of reverberation chamber(RC) in different frequency ranges are calculated to develop frequency-stirring techniques for RCs.An experimental system is built with a two-port vector network analyzer,of which one port is connected to a transmitting antenna located in a corner of a RC,and the other port is connected to a receiving antenna located in the working area of the RC.The parameter S21 is obtained in eight different locations of the receiving antenna for discussing the number of RF modes and the stirring bandwidth.It is found that the lowest useable frequency of a RC is determined by the RC’s dimension:the larger the dimension is,the lower the lowest useable frequency is.S21 at the lowest useable frequency is about-20 dB,and it is more stable than that at lower frequencies when the frequency increases.Increasing the bandwidth would result in a smoother dependence of S21 on frequency,which shows that frequency stirring is effective.In a RC with frequency stirring,the standard deviations of three individual field components and the total field are within the specified tolerance,i.e.the electric field distribution is uniform.Meanwhile,the electric field’s magnitude is characterized by the Chi-distribution with two degrees of freedom or the Rayleigh distribution,and the square of the magnitude is characterized by the Chi-square distribution with two degrees of freedom or the exponential distribution.Therefore,both good uniformity and good behavior of the electric field can be obtained if the RF modes in the RC are sufficient.