Valery Pickalov | Siberian Branch of the Russian Academy of Sciences (original) (raw)

Papers by Valery Pickalov

Plasma Physics Reports, 2006

The interaction of an expanding laser plasma with a uniform external magnetic field is studied ov... more The interaction of an expanding laser plasma with a uniform external magnetic field is studied over a wide range of the experimental parameters (for a plasma energy of up to 300 J and a magnetic induction of up to 8 kG). By analyzing the data from these and other experiments, as well as the results of simulations with the use a two-fluid Hall plasma model, it was found for the first time that the flute instability of the plasma boundary play a decisive role in the process of the plasma cloud expansion. It is shown that, when the ion Larmor radius is sufficiently large, this instability can significantly affect the maximum radius of the diamagnetic cavity of the plasma cloud and the deceleration of its front by the magnetic field. A physical model based on the Hall effect is proposed to explain such influence. The model adequately describes data from one-dimensional simulations, as well as from experiments with quasi-spherical laser plasma clouds. The results obtained can be helpful in interpreting the data from active magnetospheric experiments with barium plasma clouds (such as AMPTE) and analyzing the plasma dynamics in future ICF reactors and magnetic propulsion systems for direct conversion of fusion energy into electric one.

(Published in Russian) The problems of few-view tomography require sophisticated iterative algori... more (Published in Russian) The problems of few-view tomography require sophisticated iterative algorithms which employ a priori information on an unknown object. One of the well-developed algorithms for parallel tomography is the Gerchberg-Papoulis algorithm, which alternately iterates images in Fourier space and in image space. The application of this algorithm in the case of fan-beam tomography is blocked by the lack of the corresponding central slice theorem that connects 1D Fourier coefficients of projections with the Fourier coefficients of a 2D image. In this paper, we formulate the central slice theorem for the case of fan-beam tomography. The use of this modified theorem is illustrated by several numerical examples. Keywords: fan-beam, tomography, Gerchberg-Papoulis algorithm, central slice theorem

Advanced Microscopy Techniques IV; and Neurophotonics II, 2015

ABSTRACT The lateral shearing phase shifting interference microscopy with low coherent illuminati... more ABSTRACT The lateral shearing phase shifting interference microscopy with low coherent illumination for tomography of living cells has been proposed. To create projections of a sample at different angles the angular scanning of the probe beam was used. The experimental results of erythrocyte tomogram reconstruction are presented.

Для решения задач двумерной томографии высокого разрешения для выделенных областей (Region of Int... more Для решения задач двумерной томографии высокого разрешения для выделенных областей (Region of Interest, ROI) разработан многосеточный алгоритм MG-ART (Multigrid ART), который осуществляет томографическую реконструкцию за несколько итераций во вложенных областях. В настоящей статье изучены: скорость сходимости алгоритма, достигаемая точность реконструкции и достигаемая экономия времени счета. Область применения разработанного многосеточного алгебраического алгоритма веерной томографии относится, в первую очередь, к сложным геометриям регистрации проекционных данных, как это имеет место, например, в экспериментах по сейсмической томографии или в задачах промышленной томографии с ограниченным углом обзора. Работа проводилась при частичной поддержке Междисциплинарного интеграционного проекта СО РАН № 14 "Обратные задачи и их приложения: теория, алгоритмы, программы" (2012-2014 гг.).

Spectrochimica Acta Part B: Atomic Spectroscopy, 1984

The analytical possibilities with a two-jet plasmatron with non-consumable electrodes have been i... more The analytical possibilities with a two-jet plasmatron with non-consumable electrodes have been investigated. Large amounts of easily ionised additives present in the plasma enhance atom line intensities of trace elements, the effect being greater the lower the ion&lion potential of the element but the effect on ion line intensities is not significant. The temperature of the plasma is only slightly affected by the ionisation potential of the substance introduced into the plasma.

Plasma Physics and Controlled Fusion, 1998

A method is presented to obtain tomographic inversions of line-integrated measurements in magneti... more A method is presented to obtain tomographic inversions of line-integrated measurements in magnetized plasmas, both for the cases of scalar and vector fields. For the Hamiltonian flow of the magnetic field in tokamaks the vector tomographic problem can be reduced to a scalar one. In many fusion experiments the amount of measured data is insufficient to allow an inversion without further assumptions. We present a variational method, where such assumptions can easily be implemented by the use of constraints. We outline the procedures using the example of obtaining the function on tokamaks from Faraday rotation measurements.

Soviet Physics Uspekhi, 1983

Numerical Analysis and Applications, 2011

In this paper, numerical methods for reconstruction of the singular support of a vector field fro... more In this paper, numerical methods for reconstruction of the singular support of a vector field from its known longitudinal and (or) transverse ray transforms are proposed. Apart from a modification for the Vainberg operator, we use integral operators of angular moments and back projections as well as differential operators of tensor analysis for solving the problem. Results of numerical simulation for reconstructing discontinuous vector fields and with discontinuities in the derivatives are presented. Visualization of their singular support is shown.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1998

This paper is devoted to some aspects of the synchrotron radiation usage in the three-dimensional... more This paper is devoted to some aspects of the synchrotron radiation usage in the three-dimensional transmission tomography. The problem connected with the finite probing beam parameters is in the scope. The new method of the projection matrix construction is suggested for its solving with algebraic methods. The Vainberg's method generalization is also considered. The numerical simulations carried out have shown the effectiveness of both the algebraic algorithms and the Vainberg's method for the tomography with finite aperture beams.

Journal of Biological Systems, 2002

formulas that accurately predict the number of distinct protein domains and the number of protein... more formulas that accurately predict the number of distinct protein domains and the number of protein-coding genes for a given organism as functions of the number of non-redundant domain-to-protein links in the proteomes. These functions allows us to predict that there are 42,740, 27,900, and 21,200 protein-coding genes/open reading frames in the human,A. thaliana, and mouse genomes, respectively. We also estimate that there are 5271, 2955, and 4915 distinct protein domains in the human, A. thaliana, and mouse proteomes, respectively, and about 5500 distinct protein domains in the entire "proteome world".

Beiträge aus der Plasmaphysik, 1982

Two methods ace dqcribed to determine local parameters of the unetedy asymmetric plasma.

Beiträge aus der Plasmaphysik, 1984

The paper presents a mathematical description of tomographic algorithms for experimental data red... more The paper presents a mathematical description of tomographic algorithms for experimental data reduction. In a numerical experiment, problems of selection of optimum parameters of a measuring system to attain a prescribed accuracy of the emission coefficient reconstruction were investigated.

Mainly because of the limited set of projections poloidally viewing plasma emission diagnostics t... more Mainly because of the limited set of projections poloidally viewing plasma emission diagnostics together with subsequent tomographic inversion do sometimes lead to non-unique solutions. Usually, we can reliably restore two-dimensional images of three-dimensional objects only, if we use a priori information, i.e. constraints. Additional data from a toroidally viewing system can provide such information. A tangentially viewing camera that gives twodimensional soft X-ray images with a resolution of 100x100 pixels has been installed on TEXTOR-94 in 1999 [1] and will be improved in 2000.

J. Phys. D: Appl. Phys. -1996. -Vol.29. No.12. -P. 3009-3016. , 1996

Most standard tomographic inversion methods require many measurements with a regular coverage of ... more Most standard tomographic inversion methods require many measurements with a regular coverage of the object studied. A new method has been developed to obtain tomographic reconstructions from measurements by systems with a small number of detectors and an irregular coverage. The method reconstructs values on a regular grid in projection space from the measurements on an irregular grid by an iterative interpolation scheme. It applies a priori information and smoothing between the iterations. Furthermore, consistency of the results is obtained by an iteration between projection space and actual space. The tomographic reconstructions required in this iteration are made by a filtered-back-projection (FBP) method for the regular grid. The algorithm has been tested on assumed emission profiles. For a fan-beam system with a limited number of views the method has been compared with an FBP method for fan-beam systems; it was found to perform equally well. The method has also been applied to the visible-light tomography system on the RTP tokamak, which has only 80 channels and a very irregular coverage. Satisfactory results were obtained both for simulations and for reconstructions of actual measurements. The method appears to be a promising new approach to tomographic reconstructions of measurements by systems with irregular coverage and a small number of detectors.

Investigation of structure of supersonic jet exhausted from convergent nozzle with polish inner s... more Investigation of structure of supersonic jet exhausted from convergent nozzle with polish inner surface and with microroughness on the inner nozzle surface is presented. Essential influence of the artificial microroughness on spatial flow structure in the supersonic jet shear layer is shown. Results of the spectral analysis of the stationary distributions in the jet shear layer with use both Fourier and wavelet analyses are presented. Accordance between results of Fourier and wavelet analyses is shown. Possibility existence local laminar flow region near nozzle exit for supersonic underexpanded jet exhaust from convergent axisymmetric nozzle is observed.