Prediction of the Supersonic Flow Base Pressure by Axisymmetric ‎Direct Numerical Simulation

Axisymmetric direct numerical simulation (DNS) has been carried out to predict supersonic base flow behavior. Substantially fine grid has been used to perform calculations for the flow with Reynolds number up to 106. Optimal grid resolution was established through test calculations for affordable run time and solution convergence determined by the vorticity value. Numerical scheme provides fourth-order approximation for dissipative, fifth-order for convective and second-order for unsteady terms of conservation equations. Reynolds Averaged Navier-Stokes (RANS) approach has been employed to obtain input flow profiles for DNS calculations. Series of calculations have been carried out for Mach number 1.5 with Reynolds numbers 104, 105, 106 and for Mach number 2.46 with Reynolds number 1.65×106. It has been found that local base pressure coefficient calculated by DNS is a bit overestimated in a zone close to symmetry axis in comparison with experiment while integrated base drag coefficient shows good agreement with experimental data and noticeably better than one obtained by RANS approach

Homopolymer tract length dependent enrichments in functional regions of 27 eukaryotes and their novel dependence on the organism DNA (G+C)% composition

BACKGROUND: DNA homopolymer tracts, poly(dA).poly(dT) and poly(dG).poly(dC), are the simplest of simple sequence repeats. Homopolymer tracts have been systematically examined in the coding, intron and flanking regions of a limited number of eukaryotes. As the number of DNA sequences publicly available increases, the representation (over and under) of homopolymer tracts of different lengths in these regions of different genomes can be compared. RESULTS: We carried out a survey of the extent of homopolymer tract over-representation (enrichment) and over-proportional length distribution (above expected length) primarily in the single gene documents, but including some whole chromosomes of 27 eukaryotics across the (G+C)% composition range from 20 – 60%. A total of 5.2 × 10(7 )bases from 15,560 cleaned (redundancy removed) sequence documents were analyzed. Calculated frequencies of non-overlapping long homopolymer tracts were found over-represented in non-coding sequences of eukaryotes. Long poly(dA).poly(dT) tracts demonstrated an exponential increase with tract length compared to predicted frequencies. A novel negative slope was observed for all eukaryotes between their (G+C)% composition and the threshold length N where poly(dA).poly(dT) tracts exhibited over-representation and a corresponding positive slope was observed for poly(dG).poly(dC) tracts. Tract size thresholds where over-representation of tracts in different eukaryotes began to occur was between 4 – 11 bp depending upon the organism (G+C)% composition. The higher the GC%, the lower the threshold N value was for poly(dA).poly(dT) tracts, meaning that the over-representation happens at relatively lower tract length in more GC-rich surrounding sequence. We also observed a novel relationship between the highest over-representations, as well as lengths of homopolymer tracts in excess of their random occurrence expected maximum lengths. CONCLUSIONS: We discuss how our novel tract over-representation observations can be accounted for by a few models. A likely model for poly(dA).poly(dT) tract over-representation involves the known insertion into genomes of DNA synthesized from retroviral mRNAs containing 3' polyA tails. A proposed model that can account for a number of our observed results, concerns the origin of the isochore nature of eukaryotic genomes via a non-equilibrium GC% dependent mutation rate mechanism. Our data also suggest that tract lengthening via slip strand replication is not governed by a simple thermodynamic loop energy model

The structure of poly(dA):poly(dT) in a condensed state and in solution.

New X-ray and energetically optimal models of poly(dA):poly(dT) with the hydration spine in the minor groove have been compared with the NMR data in solution (Behling, R.W. and Kearns, D.R. (1986) Biochemistry 25, 3335-3346). These models have been refined to achieve a better fit with the NMR data. The obtained results suggest that the poly(dA):poly(dT) structure in a condensed state is similar to that in solution. The proposed conformations of poly(dA):poly(dT), unlike the classic B form, satisfy virtually all geometrical requirements which follow from the NMR data. Thus, the X-ray and energetically optimal poly(dA):poly(dT) structures (or those with slight modifications) can be considered as credible models of the poly(dA):poly(dT) double helix in solution. One of the features distinguishing these models from the classic B form is a narrowed minor groove

Algorithm of recognition of images of structures with use single-vane attributes and methods of neural networks

В статье рассматривается алгоритм распознавания текстур, основанный на использовании моментных признаков, способа выбора участков изображения при извлечении признаков, применения методов системного анализа для принятия решений, параллельной нейросетевой архитектуры.Розглядається алгоритм розпізнавання текстур, заснований на використанні моментних ознак, способу вибору ділянок зображення при витягу ознак, застосування методів системного аналізу для прийняття рішень, паралельної нейромережевої архітектури.In clause the algorithm of recognition of the structures, based on use single-vane attributes, a way of a choice of sites of the image is considered at extraction of attributes, applications of methods of the system analysis for the decision-making, parallel neuronet architecture

RESEARCH OF INCREASING THE ACCURACY OF UNGUIDED AVIATION WEAPONS BY TAKING INTO ACCOUNT IN AIMING SYSTEMS THE DISTURBING ACTION OF THE HELICOPTER MAIN ROTOR JET

Работа посвящена разработке алгоритма учета в прицельных системах возмущающего действия струи несущего винта вертолета с целью повышения точности применения неуправляемых авиационных средств поражения (снарядов и ракет).  Представлены математические модели воздушной струи несущего винта вертолета, расчета траектории движения снарядов и ракет с учетом влияния струи несущего винта. С помощью разработанного программного комплекса моделирования и визуализации стрельбы с подвижного носителя проведены исследования влияния воздушной струи несущего винта на отклонение траекторий ракет. На основе базы данных вычислительных экспериментов построены аппроксимирующие модели, позволяющие учесть влияние струи несущего винта в прицельных системах вертолета.The work is devoted to development the algorithm for accounting in aiming systems of the disturbing action of a helicopter main rotor jet in order to improve the accuracy of the use of unguided aviation weapons (projectiles and rockets). Mathematical models of the helicopter main rotor jet, calculation of the trajectory of projectiles and rockets, taking into account the influence of the main rotor jet, are presented. With the help of the developed software complex for modeling and visualization of shooting from a moving carrier, studies of the influence of the main rotor jet on the deviation of rocket trajectories were carried out. On the basis of a database of computational experiments, approximating models have been built that allow taking into account the influence of the main rotor jet in the helicopter aiming systems.Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта № 20-01-00072