Home – Home – Jornals – Avtometriya 2011 number 4

This paper reviews the experimental work conducted at the physicochemical workstation of the Novosibirsk free electron laser (FEL) since 2005 on developing methods for studying the fractional composition of nanoobjects of different nature. It has been found that the submillimeter radiation of the FEL leads to soft ablation of biological macromolecules. Furthermore, the molecules are transferred to the aerosol phase separately, each type of molecules forms its own fraction of aerosol nanoparticles without destruction and denaturation, and their sizes correlate with molecular weight. It is suggested that submillimeter laser ablation can be used to determine the sizes of nanoobjects of different origin. The paper discusses the results of experiments with mineral clusters, nanopowders, synthetic and biological polymers carried out using traditional methods of investigation of the fractional composition of nanoscale materials (atomic force microscopy, scanning electron microscopy, dynamic light scattering, and x-ray diffractometry) and using the new method-the analysis of the aerosol products of submillimeter laser ablation. It is shown that submillimeter laser ablation with the subsequent registration of aerosol products by modern equipment is a versatile, simple, fast, and accurate method which can complement the above-mentioned methods.

Characteristics of a system of polarization-optical detection of a pulsed terahertz spectrometer in nonlinear crystals of zinc telluride (ZnTe) are considered. The influence of the ZnTe crystal thickness (0.5, 1, and 2 mm) on the detection system sensitivity is studied experimentally; a comparison with model calculations is performed. The effect of the time step and the interval of scanning of the terahertz pulse on the spectral resolution and range of the spectrometer is demonstrated experimentally and theoretically. Terahertz transmission spectra of typical container materials are measured.

Pulsed generation of terahertz radiation in GaAs, InAs, and InSb semiconductors under the action of femtosecond laser radiation at the wavelength of 775 nm is studied. The generation efficiency is shown to increase by a factor of 2.7 if InAs is placed into a magnetic field of 0.8 T. An increase in the generation efficiency by the mechanism of optical rectification in InAs samples with the 〈111〉 orientation is demonstrated.

The rate of data transfer through an optical communication channel with a photon counter based on an avalanche photodiode being used as a detector in this channel is studied. The rate of data transfer through the optical channel is found as a function of the reverse bias voltage of the photodiode, the optical signal power, and the threshold level of detection.

This paper considers the results of using a two-mirror multiple-beam reflection interferometer (RI) which has a response function in reflection similar to the response function of a Fabry-Perot interferometer in transmission. The two-mirror cavity of the RI included two flat mirrors, one of which was highly reflective, and the other had an asymmetric coefficient of reflection from different sides. The light reflected from the RI was brought to an optical fiber through a collimator lens. The optical fiber, collimator, and RI constituted an integrated fiber RI, which was first used for continuous tuning of the wavelength of an erbium ring fiber laser with a continuous generation in the spectral range 1520-1566 nm.

This paper analyzes the effect of changes in the key parameters of an algorithm for identifying cracks in images of rolls of continuous casting machines. The effects of the background threshold of binary conversion and the filter kernel size on the total error of calculations of geometric characteristics of cracks are considered. The range of crack lengths for which the developed algorithm is suitable is calculated based on experimental data.

New nonparametric statistics and a criterion (test) based on them are proposed to check the hypothesis of homogeneity of three and two samples, where one sample contains an even number of elements and, hence, can be divided into two samples, against an alternative hypothesis, which implies that random values of one sample are stochastically greater than random values of two other samples. The test is mainly sensitive to shifts of distributions and is more powerful than the Wilcoxon-Mann-Whitney and Whitney tests, at least for problems with samples from exponential and uniform distributions.

An effective algorithm of predicting the trend (deterministic basis) m(t) of a steady (in a wide sense) random process X(t) is proposed. The initial information about the random process X(t) is limited to the assumption that its mean value (mathematical expectation) is equal to zero. The interval [0, T] of observation of the trend sum m(t) and the sample x(t) of the random process X(t) is assumed to be finite. Construction of a prediction estimate μ(T + τ), where τ is the prediction interval, ensures automatic allowance for statistical characteristics of the random process X(t).

Based on an analysis of asymptotic properties of a family of nonparametric decision functions in the pattern recognition problem, a method for synthesizing the structure of this family is proposed.

This paper considers the problem of reducing the computation time in the formation of a single image based on its individual fragments using the sliding window method. A payoff function is obtained. Numerical simulation helped demonstrating the effect of the measurement error and the window size on the accuracy of determination of the shift coordinates of the fragments. The choice of the form of the functional and the window size is substantiated.

Improved algorithms for calculating oil saturation based on the cross-plot method are considered. Oil saturation is determined by comparing analytical parameters obtained by well logging and the corresponding parameters of physical reservoir models that are specifically created at metrological centers. The application of cluster analysis to this problem are discussed. Testing was performed on real data.

This paper considers retrial queueing (RQ) systems with Poisson (elementary) and Markovmodulated Poisson processes. The study is performed by the method of asymptotic cumulants using the theory of vector characteristic functions and the matrix form of equations, which makes it possible to obtain asymptotic results for the whole class of models. The analysis of a single-line RQ system performed revealed the range of applicability of asymptotic results for prelimit situations.

A scanning tunneling microscope equipped with an attachment for high-resolution tunneling spectroscopy is described. The electronic unit of the microscope provides advance of the needle, scanning, and measurement of the tunneling current, and has means for coupling with a tunnel current spectrometer. The spectrometer uses a modulation procedure for measuring the second derivative of the volt-ampere characteristic of the tunneling gap and has a sensitivity of up to 0.25 pA for a modulating signal amplitude of 2 mV.