MCU White Noise Generator Based on Random Rearrangements of Pseudo-random Sequence

针对当前白噪声发生器生成的白噪声不白,即功率谱分布范围窄和能量分布不均匀的问题,以AT89C516单片机和DAC0832数/模转换芯片为硬件平台设计白噪声发生器,该发生器通过对存储于程序存储空间的伪随机序列片段的随机重排拓宽噪声的频谱范围,增强其随机性,以获得理想的白噪声.试验结果表明,该噪声发生器生成的白噪声性能良好.     

一种基于以太网通信的新型频谱分析仪及其化工设备监测应用

根据化工机械设备的测控和信号处理要求,用以太网通讯对接的两台PC机为硬件平台,以虚拟仪器图形化开发软件LabVIEW为开发平台,设计了一套多功能信号频谱分析仪。在1台PC机上开发了任意信号发生器虚拟仪器（virtual instrument,VI）模块,在另1台PC机上开发了频谱分析仪VI模块。任意信号发生器VI模块生成2路可叠加白噪声的波形信号。频谱分析仪VI模块通过以太网采集任意信号发生器VI模块输出的带噪声的波形信号,对其进行低通滤波、加窗平滑处理,完成波形信号的幅值谱和相位谱分析。在某化工试验车间的化工设备运行稳定性监测应用试验结果表明,该频谱分析仪的各项性能良好。     

基于MATLAB的伪随机信号选频滤波器设计

频率域电磁法的关键在于向地下供入不同频率的电流,以获得不同深度的电磁响应。中南大学的何继善院士提出了以伪随机信号为激励信号的广域电磁法[1],伪随机信号可以同时测量多个深度的地电信息,但实测数据中存在以工频、低频干扰为主的噪声信号。为了减小噪声影响,本文分析了伪随机信号和干扰信号的频谱特征,以MATLAB为平台,设计了FIR选频滤波器,并进行了仿真模拟,已验证所设计滤波器的去噪效果。     

基于LabVIEW新型虚拟函数信号发生器的开发

介绍一种自行开发的基于LabVIEW虚拟函数信号发生器。与传统函数信号发生器相比,该仪器不但界面友好,而且功能强大、操作简便。它不但可以产生正弦波、三角波、方波、锯齿波,而且还可以产生白噪声及多频波。输出波形频率范围更宽,具有相关参数的调整与同步显示及其幅度频谱分析功能。实现对输出信号的高速离散采样数据的本地存储,以便本地调用和远程传输。     

基于近似最小一乘准则的Hammerstein-Wiener模型随机梯度辨识

基于最小一乘准则和随机梯度算法原理,针对受尖峰噪声影响的非线性Hammerstein-Wiener模型,提出基于最小一乘准则的随机梯度算法。为解决最小一乘准则函数不可微的问题,该算法引入确定性可导函数近似代替残差绝对值。仿真实验表明:基于最小一乘准则的随机梯度算法对于非线性Hammerstein-Wiener模型可以有效地辨识出模型参数,同时抑制尖峰噪声对辨识结果的影响,具有更高的辨识精度、更快的收敛速度和良好的鲁棒性。     

路径长度受限的随机需求VRP的模型和算法

路径长度受限的随机需求VRP在生产、生活中有着广泛的应用。给出了路径长度受限的随机需求VRP问题的线性整数规划模型,在不允许部分服务和仅能服务失败一次的策略下设计了一个启发式算法。该算法以离散优化中广泛应用的扫描算法为基础生成服务的一个初始可行方案,然后利用模拟退火算法改进得到近似最优解。对需求为二项分布的50个结点、1个服务中心的问题进行了数值试验,数值结果表明该算法对求解路径长度受限的随机需求VRP是有效的。     

采用核主元成分分析和随机森林的电梯故障诊断

针对传统分析方法不能显著反映电梯急停故障特征样本的不明显及非线性属性等问题,采用核主元成分分析与随机森林相结合应用于电梯急停故障诊断。诊断结果表明,核主元成分分析能够有效选择特征样本,随机森林对噪声具有较好的容忍度和很高的评估准确率,该方法能够有效地识别电梯轿厢急停故障。     

随机地质建模技术方法简介

随机建模是指以已知的信息为基础,以随机函数为理论,应用随机模拟方法,产生可选的、等概率的储层模型方法。该方法承认控制点以外的储层参数具有一定的不确定性,即具有一定的随机性。Deautch等根据模拟单元的特征,将随机模型分为基于目标的随机模型和基于象元的随机模型。     

滴流床中液体流动的随机模型

本文以状态离散、时间离散的齐次Markov过程描述滴流床内液体的滴流与脉动流流动,提出了可直接计算任一床层高度上液体的流率分布和极限流率分布的方法和计算式。推导出了随机堆积球型颗粒床层中液体流动的转移概率矩阵。计算结果表明,本文模型计算值与实验值吻合较好。     

气流式雾化过程的有限随机分裂模型

滴径分布是描述喷嘴雾化性能的一个重要指标.从液滴分裂的自相似性出发,提出了描述气流式雾化过程的液滴有限随机分裂模型.实验和模拟计算结果表明,该模型能较好地模拟三通道喷嘴气流式雾化过程的平均滴径和滴径分布的非线性关系.     

ACCURACY OF LINEAR SPECTRAL ESTIMATES OF BAND-LIMITED SIGNALS

Abstract. We consider the problem of estimating the spectrum of a band-limited signal perturbed by additive white noise. Sharp bounds on the mean square errors of linear spectral estimates are computed and expressed as functions of time-bandwidth products and signal-to-noise power ratios.     

节涌流化床压力波动动力学研究(Ⅱ)模拟与实验

研究了节涌流化床多自由度随机波动模型参数,提出了确定气栓和料栓长度的试差迭代法、床层底部的“白噪声”扰动函数和床层表面的正态扰动函数.模型模拟计算的结果对于节涌流化床波动结构的动力学特征、压力波动的频谱特征和波动的传播与衰减等与实验结果取得了较好的吻合.     

ANALYSIS OF BISTABLE AND OSCILLATING REACTION SYSTEMS IN PRESENCE OF AN EXTERNAL NOISE

The paper analyses a bistable and an oscillatory reaction system in the presence of an external noise. The analysis of a bistable system shows that in the normal way the inclusion of noise destroys all the deterministic solutions. In other words, the stochastic system does not admit any solution. With imposition of certain restraints it is possible, however, to get stochastic solutions in a certain region of parameter space, which in general shrinks with the extent of noise. The modality of diminishing the region of solutions is different for white and nonwhite noise and has been discussed

The paper also evaluates the influence of white and nonwhite noise on the behavior of an oscillating system and illustrates it by considering two case examples. One example indicates the conflicting role of white and nonwhite noise in bringing about the transitions from the oscillatory behavior while the second example shows no influence of white and nonwhite noise on the oscillating solution

The implications of the role of noise in analysing bistable and oscillatory systems is discussed.     

A Simple Test for White Noise in Functional Time Series

We propose a new procedure for white noise testing of a functional time series. Our approach is based on an explicit representation of the L²‐distance between the spectral density operator and its best (L²‐)approximation by a spectral density operator corresponding to a white noise process. The estimation of this distance can be easily accomplished by sums of periodogram kernels, and it is shown that an appropriately standardized version of the estimator is asymptotically normal distributed under the null hypothesis (of functional white noise) and under the alternative. As a consequence, we obtain a very simple test (using the quantiles of the normal distribution) for the hypothesis of a white noise functional process. In particular, the test does not require either the estimation of a long‐run variance (including a fourth order cumulant) or resampling procedures to calculate critical values. Moreover, in contrast to all other methods proposed in the literature, our approach also allows testing for ‘relevant’ deviations from white noise and constructing confidence intervals for a measure that measures the discrepancy of the underlying process from a functional white noise process.     

基于STM32的新型信号发生器设计

给出信号发生器的硬件组成,阐述DDS芯片AD9833的工作原理,SPI通信过程,正弦波、三角波、方波3种信号的软件实现方法。搭建控制平台验证信号发生器的性能,结果表明:该信号发生器信号输出高频噪声少、频率精度高。     

Role of external white and nonwhite poisson noise in the behaviour of chemically reacting systems: The case of single variable multistationary systems

The present paper analyses some common forms of the rate function to assess the influence of white and nonwhite Poisson noise on the behaviour of reacting systems. The results afford a comparison with the corresponding results for the case of Gaussian noise and show the variations between the two types of noise.The first example analysed shows the opposing influences of the intensity of Gaussian and Poisson noise in bringing about a noise-induced transition in the system, while the second shows that the new transitions, not permissible in the case of white Gaussian noise, can be induced due to Poisson noise. The role of time-correlation effects of the two types of noise has also been analysed and discussed.     

A stochastic approach to the analysis of chemically reacting systems—II. Effect of external fluctuations

In this part the dynamic behaviour of an oscillatory reacting system is analysed in the presence of noise. The influence of both white and coloured noises is investigated. The results indicate that the presence of noise generally deforms the oscillatory behaviour and changes in amplitude and time period of oscillations occur. The results also indicate that coloured noise can bring about a change from a unique stable solution to oscillatory behaviour. Such transitions cannot be effected, at least for the case studied, with white noise alone.     

撞击流对火焰稳定性影响的试验研究

研究了射流火焰噪声和撞击式火焰噪声,对比两者以探求撞击流对火焰稳定性的影响。对火焰噪声信号进行频谱分析（FFT）,结果表明,射流火焰噪声包含燃烧噪声和喷流噪声,火焰噪声以燃烧噪声为主,撞击式火焰噪声是主频约420Hz的高频噪声,由燃烧噪声、喷流噪声和撞击区燃烧噪声组成。撞击式火焰噪声频谱图表明,撞击流强化了气化燃烧,有利于火焰的稳定,对气化炉的稳定运行有重大意义。