EMD样本熵在滚动轴承信号复杂性度量中的应用

针对常用的傅里叶变换、小波变换等在分析滚动轴承信号时存在难以度量复杂性的局限,采用经验模态分解(EMD)结合样本熵来改进。通过对不同故障程度的滚动轴承信号应用样本熵和EMD样本熵的实际效果进行比较,同时对EMD样本熵大的分量进行包络谱分析。结果发现:样本熵值过于接近不易区分,而EMD样本熵值差别明显准确性更高,并且其变化趋势与信号随故障变化的趋势一致,包络谱中存在故障频率及其倍频。该方法可用于轴承运行状态监测和预判。     

Relative entropy as a measure of the degree of mixing in noisy systems

A new concept of the relative metric entropy is introduced that makes possible quantitative evaluation of the chaotic mixing in a dynamical system under the action of an external noise. It is shown that, in the absence of noise, the relative metric entropy represents an estimate from below for the Kolmogorov entropy of the given dynamical system.     

基于自适应谐波小波和能量熵的转子系统故障诊断研究

针对转子系统非平稳振动时故障特征难以准确提取的问题,提出一种基于自适应谐波小波和能量熵的转子系统故障诊断方法。首先,采用连续谐波小波方法分解转子信号,克服二进制谐波小波包分解不能任意选取感兴趣频段的缺限,同时在分解过程中通过时间尺度变换的方式消除信号采集过程中不同转速及采样频率的影响;然后,通过设定合理的分解参数,提取出表征转子系统的故障特征信息并构建故障模式矩阵,得到转子系统早期局部碰摩、全周碰摩、油膜涡动和油膜振荡等4种工况下的能量熵值;最后,将特征向量输入支持向量机(support vector machine,SVM)判断出转子系统的故障类型。试验结果表明:该方法可以有效用于转子系统的故障诊断。     

Estimating the effects of ADC parameters on the statistical characteristics of the signal from a simulated optoelectronic system

An effective model is proposed for evaluating the effects of analog-to-digital converter (ADC) errors on the value distribution in the output sequence for any distribution of the input, together with a method of estimating ADC performance for statistical studies on signals. __________ Translated from Izmeritel’naya Tekhnika, No. 8, pp. 12–15, August, 2007.     

Generalized K entropy and Gibbs entropy of a system of point vortices

A generalization of the Kolmogorov-Sinay entropy (K entropy) is proposed and applied to a polygonal system of point vortices. It is demonstrated that the generalized K entropy (GK entropy) not only characterizes the local instability and mixing in a dynamical system, but also describes its structural rearrangements, in particular, a transition of the vortex system from one stationary state to another according to some scenario of vortex combination. The Gibbs entropy is constructed, its relation to the GK entropy is established, and it is demonstrated that both describe the transition of a dynamical system to equilibrium.     

Use of a Spectralon panel to measure the downwelling irradiance signal: case studies and recommendations

Field determinations of the remote sensing reflectance signal are necessary to validate ocean color satellite sensors. The measurement of the above-water downwelling irradiance signal Ed(0+) is commonly made with a reference plaque of a known reflectance. The radiance reflected by the plaque (L(dspec)) can be used to determine Ed(0+) if the plaque is assumed to be near Lambertian. To test this assumption, basic experiments were conducted on a boat under changing sky conditions (clear, cloudy, covered) and with different configurations for simultaneous measurements of L(dspec) and Ed(0+). For all measurement configurations, results were satisfactory under a clear sky. Under cloudy or covered skies, shadow effects on the plaque induced errors up to 100% in the determination of Ed(0+). An appropriate measurement configuration was defined, which enabled Ed(0+) to be determined with an accuracy of better than +/- 15% regardless of the sky conditions.     

基于样本熵快速算法的心音信号动力学分析

为了准确刻画冠状动脉狭窄引起的血流动力学状态改变,提出了一种基于样本熵快速算法的舒张期心音分析方法。首先利用小波变换去除心音中的呼吸干扰,然后采用改进的香农能量算法自动分割出舒张期段,最后对分割出的舒张期心音用快速算法估计样本熵。对25例健康人和25例冠心病人的分析结果显示,冠心病人和健康人在舒张期心音的样本熵值上具有显著性差异。利用该方法检测冠状动脉狭窄,敏感性为80%,特异性为84%。     

Mapping the interdisciplinarity in information behavior research: a quantitative study using diversity measure and co-occurrence analysis

Scientometrics - Information behavior research is an interdisciplinary field in essence due to the investigation of interdisciplinary in previous work. To track the changes in interdisciplinarity...     

Development of the step complexity measure for emergency operating procedures using entropy concepts

For a nuclear power plant (NPP), symptom-based emergency operating procedures (EOPs) have been adopted to enhance the safety of NPPs through reduction of operators’ workload under emergency conditions. Symptom-based EOPs, however, could place a workload on operators because they have to not only identify related symptoms, but also understand the context of steps that should be carried out. Therefore, many qualitative checklists are suggested to ensure the appropriateness of steps included in EOPs. However, since these qualitative evaluations have some drawbacks, a quantitative measure that can roughly estimate the complexity of EOP steps is imperative to compensate for them.In this paper, a method to evaluate the complexity of an EOP step is developed based on entropy measures that have been used in software engineering. Based on these, step complexity (SC) measure that can evaluate SC from various viewpoints (such as the amount of information/operators’ actions included in each EOP step, and the logic structure of each EOP step) was developed.To verify the suitableness of the SC measure, estimated SC values are compared with subjective task load scores obtained from the NASA-TLX (task load index) method and step performance time obtained from a full scope simulator. From these comparisons, it was observed that estimated SC values generally agree with the NASA-TLX scores and step performance time data. Thus, it could be concluded that the developed SC measure would be considered for evaluating SC of an EOP step.     

基于分数阶功率谱熵的未知水声脉冲信号检测方法

水声侦察的核心问题是在无先验知识条件下捕获其他平台发射的脉冲信号,单频(Continuous Wave,CW)信号和调频(Frequency Modulation,FM)信号是常用的水声探测脉冲.功率谱熵算法能有效检测低信噪比的CW信号,但对FM信号性能不佳,分数阶傅里叶变换(Fractional Fourier Tr...     

Relative measure index: a metric to measure the quality of journals

Journal impact factors (JIF) have been an accepted indicator of ranking journals. However, there has been increasing arguments against the fairness of using the JIF as the sole ranking criteria. This resulted in the creation of many other quality metric indices such as the h-index, g-index, immediacy index, Citation Half-Life, as well as SCIMago journal rank (SJR) to name a few. All these metrics have their merits, but none include any great degree of normalization in their computations. Every citation and every publication is taken as having the same importance and therefore weight. The wealth of available data results in multiple different rankings and indexes existing. This paper proposes the use of statistical standard scores or z-scores. The calculation of the z-scores can be performed to normalize the impact factors given to different journals, the average of z-scores can be used across various criteria to create a unified relative measurement (RM) index score. We use the 2008 JCR provided by Thompson Reuters to demonstrate the differences in rankings that would be affected if the RM-index was adopted discuss the fairness that this index would provide to the journal quality ranking.     

Dither signal effects on the resolution of nonlinear quantizers

The consequences of dithering on nonlinear quantizers are analyzed. A model of the nonlinear quantizer is considered, and a model of the same quantizer with dither is proposed. By means of this approach, relationships are given for the total quantization error in the case of discrete binary, uniform, and Gaussian dither signals     

A quantitative measure of the degree of fibrillation of short reinforcing fibres

The degree of fibrillation of a reinforcing fibre can be viewed as the extent to which the fibre has partially been split longitudinally into thinner fibrils. Fibrillation provides larger surface area and is advantageous because it improves matrix-to-fibre coupling, oil absorption, thickening characteristics, and softness of the fibre. Fibrillation also allows for low bulk density and assists the mat-making capability of the fibre. A general means for quantifying the degree of fibrillation of a fibre is proposed. Taking the squared ratio of the fibre surface area determined by the BET method to that determined by measuring a sampling of many particles in a scanning electron micrograph, the technique for which is described herein, one has a quantitative, relatively simple method for calculating the degree of fibrillation. Results for calcium sodium metaphosphate fibre, a new inorganic fibre developed by Monsanto [1], milled glass fibre, and wollastonite fibre are reported and compared. Benefits of fibrillation are discussed.     

How to measure the degree of independence of a research system?

The French bibliographic data-base PASCAL is used to study relations between Research Systems in terms of dependance of a periphery upon a Center.The deployment of disciplines, the productivity and the use of mother tongue of 9 developped countries are quantified (on the Life Science file only).This dependance is also quantified by reference to who studies whom, and in which language the results are available. A search in Life Science and Earth Science files by means of subject terms added by PASCAL indexers at input to papers published by 5 developped countries working on fourteen Latino-american and African countries.     

Implementing a videoconferencing system based on a single-chip signal and image processor

This article describes an implementation of a flexible videoconferencing system, the Sony Mini-1000, which is based on the Texas Instruments TMS320C80, a multiprocessor DSP, with software from IAT, Texas Instruments, and Sony. The H.320 videoconferencing standard used in the Mini-1000 is described with emphasis on the H.261 video compression standard. We have heavily used many features of the TMS320C80 including the parallel processors optimized for imaging applications and the transfer controller, which is a powerful memory access engine. Mapping the H.320 standard on the Mini-1000 system, particularly on the TMS320C80, is described in detail. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol 9: 434–441, 1998     

Separation of the informative component from a chaotic signal of a time-delay system

A new method is proposed for determining the parameters of time-delay systems using the observable time series. With this method, it is possible to reveal communications in the case of data transmission based on the nonlinear mixing of the informative signal and a chaotic signal of the time-delay system.     

一种基于奇异谱熵和脉冲响应的结构损伤诊断方法

根据结构振动响应的行为会随结构状况的变化而改变的原理,提出了用奇异谱熵作为指标来评价结构状况的方法.采用脉冲响应序列重构相空间,在相空间中通过奇异值分解得到奇异谱熵,由熵的变化来判断结构损伤的发生.该方法直接利用结构响应,无需建立结构模型,减少了建模误差.为了抑制噪声对诊断结果的影响,引入循环移位树降噪技术进行降噪处理,分析了相空间维数、激励点和测点对奇异谱熵的影响.以ASCE学会提出的基准结构为对象,应用该方法对受脉冲激励的结构进行了损伤分析,结果表明该方法是有效的.     

基于混沌和二维近似熵的滚动轴承故障诊断

针对滚动轴承故障的特征频率处于较低频带,容易被噪声淹没而难于直接检测的问题,提出了在衡量二维时间序列复杂性方面具有普遍意义的二维近似熵,及基于混沌和二维近似熵的滚动轴承故障诊断方法。该方法利用混沌振子对微弱周期信号的敏感性,可以直接检测低频段内滚动轴承微弱的故障特征频率。同时,以二维近似熵作为测度,能够从二维角度全面地量化振子的相变规律,从而客观、准确地识别振子状态并确定故障类型。对滚动轴承内、外圈故障的诊断实例验证了该方法的有效性。     

Evanescent magnetic field effects on entropy generation at the onset of natural convection

This paper numerically investigates the effect of an externally evanescent magnetic field on total entropy generation in a fluid enclosed in a square cavity by using a control volume finite element method to solve the conservation equations at Prandtl number of 0·71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for, fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number varying from 10⁴ to 10⁵. The effects of the Hartman number and the magnetic field inclination angle on the evolution of total entropy generation throughout the transient regime were investigated. Results show that the application of evanescent magnetic field not only suppresses the fluctuation of the total entropy generation in the transient state, but also reduces the gap for magnetic field relaxation time less than 1/10.