Noise Reduction Methods for Weighing Lysimeters

Mechanical vibration of the grass and crop weighing lysimeters, located at the University of California West Side Field Research and Extension Station at Five Points, Calif. generated noise in lysimeter mass measurements and reduced the quality of evapotranspiration (ET) data. The estimated power spectral density (PSD) for grass lysimeter mass data acquired at 1.3?ms intervals contained a large peak at 11?Hz. Crop lysimeter data produced similar peaks at frequencies greater than 1?Hz. An effective method for eliminating this noise source is arithmetic averaging of the data, which should be acquired sufficiently rapidly to avoid aliasing. The PSD also increased with decreasing frequency in the range 1.0–0.1?Hz. This noise was addressed by Savitsky–Golay (SG) filtering using 7-, 11-, and 15-point filters. Each filter was applied to the same data set consisting of 2,560 measurements taken during a 1-min interval every 10?min over a 26.3-h period. Noise reduction factors, defined as the ratio of standard deviation of filtered lysimeter mass to standard deviation of unfiltered mean values of lysimeter mass for subsequences of the same data, were 0.90, 0.88, and 0.86 for the 7-, 11-, and 15-point filters, respectively. For the daytime data only, the factors were 0.88, 0.85, and 0.83. The SG filters were more effective during daytime when most of the lysimeter ET occurs. These methods are simple enough to be programmed into commercially available dataloggers for real time filtering. Hourly averages of the standard deviations of lysimeter mass measurements bear a distinct nonlinear relationship to hourly mean wind speed confirming earlier suppositions that wind loading causes noise in counterbalanced weighing lysimeters.     

Measurement system for wind turbines noises assessment based on LabVIEW

An automatic measurement platform based on powerful LabVIEW is designed and implemented for noise assessment of Wind Turbine Generator Systems (WTGS). The measurement method of IEC 61400-11 standard is set-up in order to ensure the consistency and accuracy of noises assessment. Firstly, the techniques of measuring wind speed, calculating apparent sound power at integer wind speed, identifying tonality and audibility at integer wind speed recommended in IEC 61400-11, are described briefly. And then, the measurement system is designed using LabVIEW development system with one PCMCIA card and one USB card inserted into a laptop. The whole system architecture with the hardware configures and software function modules, is introduced in detail. Finally, this system is applied to do noises assessing for GOLDWIND 77/1500 wind turbine and the results have been recognized by the authoritative agency of MEASNET. Benefiting from the module design of sub-virtual instrument in LabVIEW, this system has the characteristics of perfect functions, friendly using interface, high integration, low cost and great practicality. It has wide foreground for noises assessment of WTGS.     

基于模式化方法的二值图像降噪

目前二值图像的降噪已有很多算法,在很多领域有应用,但是还存在一些问题,如降噪后造成图像质量下降。在这种情况下,文章提出了一种新的基于模式化方法的二值图像去噪声算法。通过分析二值图像噪声的微观结构,用行程匹配法提取出二值图像中的图段,然后根据图段参数判定噪声并进行清除。实验结果显示该方法降噪效果较好,具有一定的实际意义。     

基于小波变换的信号去噪研究

介绍了小波变换理论,系统地研究了小波变换在信号处理尤其是信号滤波去噪方面的应用。根据不同类型的噪音．给出了基于不同小波变换的滤波算法并且对基于小波变换的滤波原理进行了分析。     

一种提高分类精度的支持向量机NDR-SVM

提出基于近邻域比率的支持向量机NDR-SVM.该算法对每个训练样本构造一个近邻域,在此邻域中计算与中心同类的样本占邻域中总样本的比率;根据比率与剔除闲值的大小关系决定邻域中心的取舍,并将所保留的样本带入SVM分类.通过修剪训练集,该算法减弱了噪声对SVM泛化能力的影响.实验结果表明,与已有算法相比,NDR-SVM具有更高的分类精度,大大提高了训练速度.     

High visibility or quiet operation?: A statistical inference model of the wiper operation quality by the dual-code theory

The motor industry has assured drivers that it will continually provide quality vehicles without compromising safety and comfort. In this sense, the quality of a product always needs to be determined by what the customer actually perceives, which has not been the case in the domain of wiper operation quality.     

油井干扰特征分析及其野外压制方法

东营凹陷开发程度较高,油井密布,工业设施多,影响了地震资料的信噪比和分辨率。本文调查了油井干扰产生机制及传播途径,分析了表层对油井噪声的衰减程度,对比了不同方法对油井噪声的压制效果。得出了避开油井干扰与压制油井干扰相结合的降噪方法。     

静电悬浮加速度计与真空有关的噪声分析

从麦克斯韦速率分布函数和克努曾的"吸附层"假说出发,推导出静电悬浮加速度计核心部分因辐射计效应和残余气体平衡态阻尼引入的加速度热噪声表达式。指出辐射计效应是加速度计噪声的一个重要来源,气体阻尼的影响相对较小;加速度计长期保持优良的高真空是控制这两项噪声水平的必要措施;认为出气效应比辐射计效应大一到两个数量级是错误的。     

某型汽车电动玻璃升降器异响分析及结构改进

通过对某款量产车型升降器异响的分析和结构改进,提出升降器部件设计时需要与玻璃部件设计充分沟通,才能避免出现系统问题的解决方法.     

Predictive cloud control for multiagent systems with stochastic event-triggered schedule

This paper addresses a predictive cloud control problem for a linear multiagent system with random network delays and noises. To reduce communication cost, a stochastic event-triggered schedule is introduced to decide whether current measurements need to be transmitted. An optimal state estimation algorithm is designed to compensate random network delays in the feedback channel. Subsequently, a predictive cloud control scheme is proposed for the multiagent system to achieve both stability and consensus. Simultaneously, random network delays in the forward channel is compensated actively. Sufficient and necessary conditions of stability and consensus for the closed-loop multiagent system are derived. Finally, a numerical example is provided to verify correctness and effectiveness of the proposed methods.