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Bouraou N., Klofa I., Zhukovskii Y., Kulish E. Theoretical bases of vibration diagnostics of anchor against landslide constructions

Monday, 25 July 2011 09:00 administrator
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The given work is devoted to development of theoretical bases of a new vibrating diagnostics method and evaluation a current condition of the anchor. The research of the pulse response of the anchor against landslide construction is a basis of vibrating diagnostics of a tension condition an anchor, detection of feature of abatement of a tightness, and definition of character of its dependence on a changing stretching force. The elastic body with the distributed parameters (a string) is used as the diagnostic model of the tense and fixed core of an anchor. Dependences of own frequencies changing of the pulse response of an anchor on a tightness changing at deformations and displacement of a place of fastening of an anchor are defined. The discrete model of an anchor against landslide construction is developed and researched for definition of dependences between parameters of an anchor condition and vibrating characteristics of a retaining wall, which is accessible to carrying out of measurements.
Keywords: sliding processes, anchor against landslide constructions, tension of anchors, vibrating diagnostics.

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Bouraou N., Protasov A., Sopilka Yu., Zazhitsky O., Decision making of aircraft engine blades condition based on bispectral analysis of the vibroacoustical signal

Friday, 22 July 2011 17:42 administrator
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In this paper the simulation of vibroacoustical signals radiated by the engine turbine at the stationary vibration excitation is carried out for situations when all turbine blades have no defects and one blade has a small fatigue crack. Bispectral analysis is used for diagnostic information processing. It demonstrates that appearance and evolution of the fatigue crack in a blade change intensity of global and local extremums of bispectral modules. The results of bispectral processing and Probability Neural Network (PNN) are used to recognize of the turbine blades condition. The efficiency factor is used for precision analysis.

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Last Updated on Friday, 22 July 2011 17:47
 

Bouraou N., Sopilka I. Vibroacoustical diagnosis of the crack-like damages of aircraft engine blades at the steady-state and non-steady-state modes

Monday, 25 July 2011 08:50 administrator
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The work is devoted to condition monitoring and vibroacoustical diagnosis of the crack-like damages of the gas-turbine engines (GTE) blades at the steady-state and non-steady-state modes of GTE. The developed diagnostic model of GTE is presented and the influence of damage on the measured vibro- and acoustical signals at the steady-state and non-steady-state modes of GTE is determined. The application of the following signal processing methods: Polyspectral (Higher-Order Spectral) analysis, Wavelet-transformation and dimensionless characteristics of the vibroacoustical signals is proved. The efficiency of signal processing methods is demonstrated by the results of numerical simulations of the turbine stage at the steady-state and non-steadystate modes of vibration excitation. The fault features are detected and investigated.
Keywords: gas-turbine engine, crack-like damage, vibroacoustical diagnosis, signal processing

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Bouraou N., Tyapchenko A. Statistical Characterization of Estimates of Relative Crack Dimensions Based on the Method of Higher Harmonics

Monday, 25 July 2011 08:58 administrator
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Fatigue cracks are diagnosed and characterized using a vector of parameters composed of the ratios between spectral amplitudes of the higher and fundamental harmonics in inherent acoustic modes of an object. Using the method of maximal likelihood, we have obtained estimates of the relative crack dimensions and analyzed their statistical characteristics depending on the composition of the parameter vector and noise intensity in measurements.

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Bouraou N., Zsukovskij Y., Kulish E., Ryzshij M. Information and measuring system for monitoring of buildings and constructions under the influence of micro-seismic oscillations

Monday, 25 July 2011 08:53 administrator
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The work is devoted to problem solution of the gas-turbine engines (GTE) blades condition monitoring and diagnosis of the crack-like damages at the steady-state and non-steady-state modes of GTE. It is based on the development of theoretical basis of the vibroacoustical diagnosis methods, the application of the modern signal processing methods and new information technique for decision making. The application of the following signal processing methods: Wavelettransformation and dimensionless characteristics of the vibroacoustical signals is proved. The neuron networks are used for decision making about blades condition by the above mentioned features application. Classification of turbine blade condition was carried out using a two-layer Probability Neural Network (PNN).
Keywords: blade, crack-like damages, vibroacoustical condition monitoring, neuron networks

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Chernyshov A., Felde Ch., Bogatyryova H., Polyanskii P. Scattering-induced spectral changes

Saturday, 23 July 2011 20:45 administrator
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The model of intermediately rough surface as the specific anti-reflection layer is presented for explaining the coloring of the regular component of a white-light beam forward scattered by a colorless glass with such surface. It is shown that this model predicts the sequence of colors of the forward scattered component of a white-light beam that is observed in practice. New experimental arguments supported this approach are provided.
Keywords: induced spectral changes, rough surfaces, anti-reflection coatings

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Chernyshov A., Felde Ch., Bogatyryova H., Polyanskii P., Soskin M. Vector singularities of the combined beams assembled from mutually incoherent orthogonally polarized components

Saturday, 23 July 2011 20:52 administrator
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It is shown that, for an incoherent superposition of the orthogonally polarized laser beams, the vector singularities of a specific type arise at the transversal cross section of a paraxial combined beam instead of common singularities, such as amplitude zeros or optical vortices (inherent in scalar, i.e. homogeneously polarized, fields), and C points, where polarization is circular, and L lines, along which polarization is linear (inherent in completely coherent vector, i.e. inhomogeneously polarized fields). There are U lines (closed or closing at infinity) along which the degree of polarization equals zero and the state of polarization is undetermined, and isolated P points where the degree of polarization equals unity and the state of polarization is determined by the non-vanishing component of the combined beam. U surfaces and P lines correspond to such singularities in three dimensions, by analogy with L surfaces and C lines in three-dimensional completely coherent vector fields. P lines directly reflect the snake-like distortions of a wavefront of the singular component of the combined beam. Crossing of the U line (surface) is accompanied by a step-like change of the state of polarization onto the orthogonal one. U and P singularities are adequately described in terms of the complex degree of polarization with the representation at the Stokes space, namely at and inside of the Poincar´e sphere. The conditions of topological stability of U and P singularities are discussed, as well as the peculiarities of the spatial distribution of the degree of polarization in the closest vicinity to such singularities. Experimental examples of reconstruction of the combined beam’s vector skeleton formed by U and P singularities as the extrema of the complex degree of polarization are given. Comparison with the related investigations is provided.
Keywords: optical singularities, partial polarization, partial coherence, Stokes polarimetry

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Chizh I., Afonchyna N. Eye Refractometry by the Modified Foucault-knife Method

Friday, 27 March 2015 12:04 administrator
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Chizh I., Afonchyna N. Eye Refractometry by the Modified Foucault-knife Method. – Innovations and Technologies News, Nr.3(11), 2011, Latvia.

The modified Foucault-knife method is a new direction in the ophthalmological refractometry for eye ametropy and astigmatism determination. The principal advantages of this method are relative simplicity of hardware and mathematical algorithm and low cost price. It also gives the potential possibility for the reconstruction of the wave aberration function by usage of the isodiopter zones images, video-recorded at the pupil plane.

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Last Updated on Friday, 27 March 2015 12:08
 

Chyzh I., Sokurenko V. Accuracy of modal wave-front estimation from eye transverse aberration measurements

Friday, 22 July 2011 20:36 administrator
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The influence of random errors in measurement of eye transverse aberrations on the accuracy of reconstructing wave aberration as well as ametropia (mean power) and astigmatism parameters is investigated. The dependence of mentioned errors on a ratio between the number of measurement points and the number of polynomial coefficients is found for different pupil location of measurement points. Recommendations are proposed for setting these ratios.
Key words: wave-front deformation, eye transverse aberrations, Zernike polynomials, least-squares technique, astigmatism,
errors.

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Chyzh I., Sokurenko V., Osipova I. Influence of eye micromotions on spatially resolved refractometry

Saturday, 23 July 2011 13:49 administrator
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The influence eye micromotions on the accuracy of estimation of Zernike coefficients from eye transverse aberration measurements was investigated. By computer modeling, the following frequently found eye aberrations have been examined: defocusing, primary astigmatism, spherical aberration of the 3rd and the 5th orders, as well as their combinations. It was determined that the standard deviation of estimated Zernike coefficients is proportional to the standard deviation of angular eye movements. Eye micromotions cause the estimation errors of Zernike coefficients of present aberrations and produce the appearance of Zernike coefficients of aberrations, absent in the eye. When solely defocusing is present, the biggest errors, cased be eye micromotions, are obtained for aberrations like coma and astigmatism. In comparison with other aberrations, spherical aberration of the 3rd and the 5th orders evokes the greatest increase of the standard deviation of other Zernike coefficients.
Key words: eye micromotions, wave-front deformation, eye transverse aberrations, Zernike polynomials, astigmatism, spherical aberration, spatially resolved refractometer.

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