A Wigner spectral analyzer for nonstationary signals

The authors present computational algorithms for the design of an innovative spectral analyzer using the Wigner distribution. This spectral analyzer uses advanced digital signal-processing chips with associated hardware and software. Algorithms for the kernel generation, kernel transformation, and discrete Hilbert transform are discussed. Design strategies are focused on achieving high time-frequency resolution, precision, flexibility, and computational efficiency. Experiments show that spectral analysis using the Wigner distribution yields significantly improved results for nonstationary signals     

A method for simulation and analysis of a multiparameter model of signals of electromagnetic systems for nondestructive testing

We describe a method for the construction of a nonlinear multiparameter model of signals of primary eddy-current probes of systems for electromagnetic nondestructive inspection by approximating solutions of direct problems by many-dimensional polynomials. To determine typical features of response surfaces and choose proper specimens for the adjustment of devices used for nondestructive inspection, we analyze multiparameter models of signals of systems designed for nondestructive inspection. Karpenko Physicomechanical Institute. Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 5, pp. 77–81, September–October, 1996.     

Digital parametric spectrum analyzer for periodic signals using a short sampling period

A parametric method is proposed for estimating the spectra of periodic signals from a short sample (between two and five periods) and a parametric spectrum analyzer is described whose construction is based on a personal computer with a built-in analog-digital converter. The results of processing real periodic signals are presented. Translated from Izmeritel'naya Tekhnika, No. 2, pp. 16–18, February, 1996.     

基于小波变换的心电信号数据处理

本文主要介绍在心电信号（ECG）中干扰的来源和传统的消噪方法。在阐述小波变换理论的基础上,对样条函数的构造原理进行了分析,并选取三阶样条小波为心电信号分析时所用的小波,对所记录的心电信号数据进行了处理。     

Effective spectral method for testing diode modulation meters

Conclusions The error in testing and calibrating modulation meters at high modulating frequencies (up to 500 kHz) by the suggested method does not exceed 2%.By the suggested method it is possible to evaluate the error of calibrating by means of a pulsating signal fed to the input of the diode detector. The pulsating signal method provides a small calibration error at modulating frequencies up to 20 kHz, but it has a considerable error at modulating frequencies in the radio range.     

Blind multiridge detection for automatic nondestructive testing using ultrasonic signals

Ultrasonic imaging has been a significant means for nondestructive testing (NDT). Recently the NDT techniques via the ultrasonic instrumentation have shown the striking capability of the quality control for the material fabrication industry. To the best of our knowledge, all existing signal processing methods require either the a priori information of the ultrasonic signature signals or the manual segmentation operation to achieve the reliable parameters that characterize the corresponding mechanical properties. In this paper, we first provide a general mathematical model for the ultrasonic signals collected by the pulse-echo sensors, then design a totally blind novel signal processing NDT technique relying on neither a priori signal information nor any manual effort. Based on the automatic selection of optimal frame sizes using a proposed new criterion in our scheme, the signature signal can be blindly extracted for further robust multiridge detection. The detected ridge information can be used to estimate the transmission and attenuation coefficients associated with any arbitrary material sample for the fabrication quality control.     

桥梁动力测试信号的自适应分解与重构

针对桥梁结构动力测试信号噪声水平高、难以分离结构有效信号的特点,在总体平均经验模态分解方法和主成分分析的基础上,建立了自适应分解与重构方法。对经验模态分解结果的模态混叠现象进行深入分析,利用白噪声概率密度函数的均匀性对模态混叠模式一进行了改进,基于相关性分析改进了模态混叠模式二,改进后的分解方法在计算效率和分解精度上均有较大提升;随后对所有分解获得的固有模态函数进行多尺度主成分分析,实现降噪和选择并重构测试信号。分别用模拟信号和实际桥梁测试信号对所提方法的有效性进行了验证。结果表明:改进后的信号自适应分解和重构方法能在降噪的同时,有效地提取桥梁结构信息,可用于实际桥梁结构的动力测试分析中。     

Computer simulation of tensile testing

A brief overview of the molecular dynamics method, with emphasis on the work of Parrinello and Rahman, is presented. Molecular dynamics is a method for studying classical statistical mechanics of well-defined systems through a numerical solution of Newton’s equations. A set ofN particles with coordinatesr _i (i=1, …,N) and confined in a cell are allowed to interact through a potential. The bulk is usually simulated by periodically repeating the cell in space. Newton’s equations are then solved numerically and the statistical averages of dynamical properties are calculated as temporal averages over the trajectory of the phase space. This method has already been used to simulate a liquid. Now, based on a Lagrangian formulation, it is possible to study systems under the most general conditions of externally applied stress. Unlike the earlier calculations, in this procedure, shape and size are governed by equations of motion obtained from the Lagrangian. Thus it allows us to study structural transformations which may be brought about by an interplay of external and internal stresses. By applying this technique to a single crystal of Ni, Parrinello and Rahman observe that the stress-strain relations obtained confirm with reported results. Under compressive loading it is found that Ni shows a bifurcation in its stress-strain relation and the system changes from cubic to hexagonal close packing. Such a transformation could perhaps be observed under extreme conditions of shock. Finally the scope of computer simulation is highlighted and the limitations of employing such a method are pointed out. only summary of the talk     

Transmission line model for simulation of guided-wave defect signals in piping

A simple transmission line model for analytically simulating the guided-wave signal reflected from a volumetric defect of arbitrary shape in piping is described. In the model, the guided-wave interaction with a defect is treated as the one-dimensional problem of plane wave reflection from a boundary of multilayered media of different acoustic impedances in a transmission line. Results of simulation show good qualitative agreement with experimentally measured signals.     

应用多种高精度测量机制的电参量分析仪研制

针对计量测试过程中高精度电参量分析的需求,该文提出多种改善分析测量精度的测量机制,包括高精度交流电压采样分压器、高精度改进型双级交流电流互感器、利用DDS实现准同步采样原理进行信号频率跟踪实现同步采样以及非整周期傅里叶补偿谐波算法。并将这些测量方法应用到分析仪的研制设计中,实现电参数测试准确度优于0.01%、谐波分析准确度优于0.02%的高精度电参量分析仪。     

Preservation of diagnostic information in synthesis of ECG signals for a standard lead system from signals measured by an orthogonal frank system: Minnesota code criteria

We show that using the three best known matrices for synthesis of ECG signals and their diagnostic interpretation in terms of the Minnesota code unfortunately cannot be considered valid. Translated from Izmeritel'naya Tekhnika, No. 4, pp. 68–71, April, 1997.     

液体流量计在线检定实验研究与数值模拟

根据计算流体力学原理（CFD）,对不同的管道条件进行数值模拟,分析管道内流场分布情况,并通过实流试验和CFD数值模拟试验的结果比较,讨论了影响在线流量计检定结果的因素。将CFD技术应用到现场在线流量计检定,能够优化检定结果,保证数据的可靠性,从而更好解决一部分不能离线检定的流量计的量值溯源问题。