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2005 year, number 4

Sampling functions in periodical signal reconstruction. The variance of a trigonometric interpolation error

V.M. Efimov and A.L. Reznik
Pages: 3-13

Abstract >>
Relationships are obtained for sampling functions when the periodical signal and its derivatives are uniformly sampled. Expressions for the variance of error in reconstructing such a signal at any frequency with the use of the obtained relationships are considered.

Blurred gray-scale image restoration based on hierarchical Gibbs model

V.N. Vasyukov and D.V. Goleshchikhin
Pages: 14-21

Abstract >>
A method for gray-scale image restoration is proposed. It is supposed that the image is linearly blurred and observed in additive Gaussian noise. The image is considered as a realization of a Gibbs random field described by the Gauss-Markov autoregressive model. Increasing restoration quality is attained by introducing to the Gibbs model a hidden level containing borders between areas with a relatively slowly changing brightness. Results of applying the approach to real image recovering are presented.

Detection of objects with the unknown area against background

A.P. Trifonov and Yu.N. Pribytkov
Pages: 22-35

Abstract >>
An algorithm for detecting a Gaussian image with the unknown area against Gaussian background in the presence of spatial noise is synthesized for the applicative model of interaction between the image and the background. The algorithm characteristics are found. The influence of the difference between statistical characteristics of the back-ground and the image on the detection efficiency is analyzed.

Distortion correction of delta-modulated signals by adaptive walsh filters

V.S. Khandetsky, V.A. Pashchenko, and N.A. Matveyeva
Dnepropetrovsk, Ukraine
Pages: 36-49

Abstract >>
Transfer and pulse-response characteristics of Walsh filters are found to insure detecting (for four noise immunity levels) the distortion syndrome of a short sliding sample containing the typical fragment of the delta-modulated measuring pulse envelope in order to decode the sample by a one-step threshold procedure. The proposed algorithm of distortion correction with adapting to noise intensity possesses linear computation complexity and is adequate to the architecture of modern digital signal processors.

Development of an objective method for measuring optical characteristics of the eye

G.A. Lenkova and M.M. Myznik
Pages: 50-61

Abstract >>
Standard methods for controlling visual functions in the acuity of vision and contrast sensitivity of the eye are subjective because the measurement results depend on patient

Algorithm for locating a mobile radiation source in a bistatic dynamic angle-finder system

Yu.B. Popov, V.A. Kurakov, and K.Yu. Khabarova
Pages: 62-68

Abstract >>
An algorithm for estimating the current coordinates and movement parameters of the source of radiation (optical, acoustic, or radio) by mobile spaced angle-finders is considered. The algorithm is based on Kalman filter theory with the use of a linear dynamic model of relative displacement of objects in the Cartesian coordinate system. The equations of observation are also presented in the linear form. This is achieved by introducing the procedure of nonlinear transformation of the current measurements prior to filtering. Results of model research of the algorithm are discussed. Plots are presented to estimate the accuracy of finding the range, velocity, and heading of the radiation source for different bearing measurement errors.

Analysis of optical triangulation systems for measuring mirror surface profiles

S.V. Mikhlyaev
Pages: 69-80

Abstract >>
Two basic schemes of laser triangulation sensors used for sensing a mirror surface are analyzed: the first one uses sensors with the photo-registration plane tilted to the optic axis according to the Scheimpflug principle, and the other uses sensors with the plane that is orthogonal to the optic axis. The measurement errors are estimated. Comparative analysis of metrological characteristics of the schemes is presented. The conditions of Scheimpflug principle applicability are determined. It is shown that for a certain ratio of parameters of the optical system to probing light beam, the scheme with an orthogonal registration plane can ensure a smaller level of measurement errors than the scheme with a tilted output plane, despite the presence of defocusing. This advantage remains valid only at small surface tilts. Peculiarities of sensing a nonstationary surface by the triangulation systems are considered.

The distribution of term frequency in texts

E.L. Kuleshov, V.V. Krysanov, and K. Kakusho
Vladivostok, Russia
Pages: 81-90

Abstract >>
A new mathematical model of distribution of term frequency in texts such as English, Russian texts, and English hypertexts is proposed. A frequency distribution generalizing the Pareto distribution is derived. An algorithm for estimating the model parameters is presented. It is shown that the proposed distribution is far superior to the Pareto distribution since it ensures better agreement with empirical data.

The logical structure-rearrangeable system in process control problems

S.V. Shidlovskiy
Pages: 91-98

Abstract >>
Application of multifunctional logical modules to constructing structure-re-arrangeable systems is discussed. The presented quasi-isotropic environment based on logical modules is able to choose the best control algorithm from the given class for both the objects with a delay and without it.

Analysis of factors producing an effect on estimation of instantaneous analytical signal frequency

G.A. Kashcheeva
Pages: 99-111

Abstract >>
Factors producing an effect on estimation of the instantaneous analytical signal frequency determined according to the proposed algorithm is analyzed using harmonic quadrature signals as an example. It is shown that joint effect of several factors can lead to substantial deviations of the instantaneous frequency from its nominal value. However, the frequency averaged over a period is equal to the nominal one. This opens considerable promise for using the algorithm to measure the instantaneous velocity and other movement parameters.