Investigation of the two-phase flows of working bodies in an electrogasdynamic expander by using a laser Doppler anemometer

The dependence of the fundamental characteristics of an electrogasdynamic expander on the velocity and mobility of the electrically charged two-phase flow particles is examined. Results are presented of an experimental investigation of the velocity of the condensed two-phase flow particles by using a laser Doppler anemometer.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 2, pp. 258–262, August, 1989.     

Velocity field in a low-turbulence hydrodynamic facility,using a laser-doppler technique

This paper describes a laser-Doppler measurement instrument, and also the technique and the results of an investigation of the velocity field obtained with this instrument in the working section of a hydrodynamic facility.Notation x, y, z coordinate axes - boundary-layer thickness - b working section height - U component of the mean velocity along the x axis - u fluctuating velocity component along the x axis - U velocity in the oncoming flow Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 5, pp. 818–824, November, 1979.     

Analysis of the possibility of using laser Doppler anemometer for the investigation of highly dust-laden flows

The capabilities of laser Doppler anemometer are investigated from the standpoint of measurement of the velocity of particles of a highly concentrated heterogeneous flow. The dependences of the key characteristics of Doppler signal on the mode of flow are analyzed. The parameters of heterogeneous flow, in the case of which a laser Doppler anemometer may be employed, are determined experimentally.     

On finite amplitude waves in heterogeneous elastic solids

The perturbation technique of the ‘stretching of the coordinates’ is used to obtain first and second order perturbation solutions of finite amplitude plane waves which propagate into an elastic half-space whose material property varies in the direction of the propagation. The interaction between nonlinearity and heterogeneity is discussed, and the results are illustrated by means of two examples: the longitudinal waves propagating in an elastic half-space with harmonic heterogeneity; the shear wave in a half-space whose property varies as A[1 + ?(X/L)ⁿ], where A, ? ? 1, L, and n are constants, and X denotes the initial particle position measured normal to the plane boundary.     

Binary square pulse amplitude modulation in generating a set of precision amplitude-modulated signals

Translated from Izmeritel'naya Tekhnika, No. 4, pp. 60–63, April, 1993.     

Some regularities of heterogeneous reactions in laminar flows in channels

A gas-mixture flow in a channel on whose walls heterogeneous reactions take place is considered. Numerical simulation is performed on the basis of equations for a narrow channel. Results of a numerical solution of the equations are interpolated by a relation involving analytically obtained asymptotic formulas. Some regularities are obtained for the problem considered. Russian Scientific Center “Applied Chemistry,” St. Petersburg. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 2, pp. 206–214, March–April, 1996.     

Noise-immune measurement of the amplitude of flat-top pulse signals

A method for making noise-immune measurements of the amplitude of pulse signals is considered. The method is based on multiple delay and parallel integration of the signals. A block diagram of a system for making such measurements is given, and the random error of the measurements is analyzed. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 69–71, June, 1996.     

A study of finite amplitude waves using Bell's parabolic law

It is known that the Karman-Taylor-Rakhmatulin theory of the propagation of finite amplitude waves is applicable when rods of various metals and alloys are subjected to impact loading. Using a generalized parabolic law, we have extended the theory for a three dimensional state of stress. In particular, we consider the effect of lateral inertia on the propagation of large amplitude plane waves in rods. Also the propagation of combined tension-torsion waves in thin walled tubes is discussed. On the basis of this investigation, we can explain some phenomena observed by Bell and others in their experimental studies on the propagation of large amplitude waves in annealed metals and alloys.     

A comparative study of model selection criteria for the number of signals

The performance of six existing model selection criteria is compared, which are commonly used in time series and regression analysis, when they are applied to the problem of the number of signals in the multiple signal classification (MUSIC) method. The five criteria are Akaike Information Criterion (AIC), Hannan and Quinn Criterion, Bayesian Information Criterion (BIC), Corrected AIC (AlCc) and the recently introduced Vector Corrected Kullback Information Criterion (KICvc) and Weighted-Average Information Criterion (WIC). The general form of the above information criteria consists of a log likelihood function expressed in terms of the eigenvalues of the sample covariance matrix and a unique penalty term. In our estimation procedure, the number of signals is obtained by minimising each of the above criteria. Several simulated data sets, including a linear antenna array data set, are adopted for the comparison purpose. The authors show that, in simple MUSIC additive white noise model, for small sample size n, WIC performs nearly as well as AlCc and outperforms other criteria, and for moderately large to large n, WIC performs nearly as well as BIC and outperforms other criteria. Therefore when the authors are not certain of the relative sample size, WIC may be a practical alternative to any criterion. The main purpose is to draw the attention and interests of signal processing researchers to adopt more recent statistical model selection criteria, such as WIC, in general signal processing problems.     

Measurement of attenuation using a normalized amplitude spectrum

In conventional material evaluation and attenuation measurement, methods employing multiple ultrasonic echoes in the thickness direction of the samples are often used to calculate the reflection and attenuation coefficients. The successive echoes must be well resolved, and there is consequently a minimum thickness of material which can be tested for a given frequency transducer. For thin specimens, a high frequency probe may be used, but this may be problematic for composite laminates since the reflections from the individual plies can cause interference. In this paper, an alternative method based on the amplitude spectrum of the reflections from the specimen is presented. The technique deduces the attenuation coefficients by using the spectral amplitudes at the anti-resonance (or resonance) frequencies of the normalized amplitude spectrum, and has the advantage that it does not require that the successive echoes be separated in time. Measurements made on glass, epoxy, and composite laminate specimens are used to compare our attenuation measurement technique with the standard method.     

Intermittence and structure of the transitional boundary layer at a plate using a laser anemometer

The procedure for investigating the intermittence in a transitional boundary layer using a laser anemometer is described. The distribution of the coefficient of intermittence over the thickness of the boundary layer as a function of the velocity of the oncoming stream is presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 1, pp. 16–20, July, 1982.     

Method of detecting and measuring low amplitude potentials in bioelectric signals

A method is proposed for detecting and measuring the late potentials of the ventricles of the heat (LPV). The method is based on computations of the amplitude, time, and spectral parameters of the signal. Examples are given of the use of the method in patients with or without LPV. Translated from Izmeritel'naya Tekhnika, No. 2, pp. 57–59, February, 1996.     

Laser-mode selection by a combination of biprism-like reflectors with narrow amplitude masks

In recent work the laser mode selectivity induced separately by a biprism-like reflector and by an absorbing strip was investigated by numerical analysis. It was shown that each of these elements in an otherwise conventional resonator was suitable to cause the laser to oscillate preferentially on the first odd mode that contains a line singularity, which is a useful dark beam (i.e., a laser beam with a dark central region) for high-resolution metrological applications. We study the combined effect of these two mode-selecting elements and show that the unified analysis leads to much better performance than could be expected from a simple superposition of the performance with each element alone. The results indicate that the mode selectivity can be enhanced by at least a factor of 3 compared with that of laser resonators with biprism-like reflectors alone. Thus a laser equipped with such a combined element will oscillate on a pure first-order mode with high power efficiency. Moreover, calculations show that the resultant dark beam, focused for metrological applications, has a significantly improved shape compared with the dark beam obtained by external modulation of a fundamental Gaussian beam.     

Estimation of the correlation amplitude of RF signals in small cutaneous vessels

Time domain correlation technique is a widely used method for blood flow velocity measurement. The time shift between a pair of windowed ultrasonic echoes is estimated by searching the temporal position of the maximum of the interpolated normalized correlation function. Between two consecutive echoes, the acoustical footprint of a group of scatterers, which are transported with the flow, moves and is deformed. This implies a decreasing of the amplitude of the normalized correlation coefficient. In the case of microcirculation (low flow rate, low SNR), the amplitude of the correlation peak can be used to detect the presence of blood flow and to discriminate false and true detections (reliability index). We have numerically evaluated the statistical performances of the cross-correlation algorithm used as a correlation peak amplitude estimator in severe conditions (short correlation window length, low SNR). These theoretical results have been compared with in vitro experimentation on a 100-/spl mu/m-diameter microcirculatory phantom and with in vivo experimentation on a 180-/spl mu/m-diameter vessel of a human leg carrying erysipelas.     

Intelligent heating control of a new ice-free anemometer

The wind industry has grown over the years along with the collective desire to produce clean energy. High wind potential sites are often located in northern regions where harsh climatic conditions arise. The performance of anemometers, which provide essential measurements to wind turbine operation and wind resource assessment, is then jeopardized by ice build-up and snow accumulation. These conditions result in the need for heated instruments able to remain ice-free regardless of weather conditions while minimizing energy consumption. The main objective of this work was to develop an intelligent heating control for a new generation of ice-free anemometers. The controller is based on vision recognition of ice build-up on the cups of the anemometer using a neural network. Heating power is applied according to the icing state and the icing history of the instrument. Primary results have shown that, for a completely ice-free performance, the developed controller uses an average of less than two thirds of the energy consumed by common control systems similar to those used by other ice-free anemometers available on the market.     

基于Gabor重构的发动机振声信号阶次分量瞬时幅值的提取

从数值试验中总结了高斯窗STFT幅值谱对阶次分量的分隔能力与连续时间域内高斯窗的时间宽度之间的定量关系,并指出STFT幅值谱的阶次切片做为瞬时幅值估计所存在的问题。论述了Gabor阶次波形重构技术有效的前提条件,并基于确立的高斯窗宽与STFT幅值谱对阶次分量的分隔能力之间的关系,提出了一种改进的Gabor阶次波形重构流程,该流程摒弃了试凑分析参数的模式。仿真表明重构的阶次波形经Hilbert变换得到的包络可以做为瞬时幅值的有效估计。