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

Investigation of Dynamic Interactions of Solids by Methods of Mathematical Simulations

Алексей Матвеевич Липанов, доктор технических наук, академик, Председатель Президиума, Удмуртский научный центр УрО РАН (г. Ижевск, Российская Федерация), [email protected]. Александр Васильевич Вахрушев, доктор физико-математических наук, профессор, заведующий лабораторией ≪Механика наноструктур≫, Институт механики УрО РАН, заведующий кафедрой ≪Нанотехнологии и микросистемная техника≫, Ижевский государственный технический университет имени М.Т. Калашникова (г. Ижевск, Российская Федерация), [email protected]. Алексей Юрьевич Федотов, кандидат физико-математических наук, доцент, старший научный сотрудник, лаборатория ≪Механика наноструктур≫, Институт механики УрО РАН (г. Ижевск, Российская Федерация), [email protected]. A.M. Lipanov, Udmurt Scientific Center, Ural Branch of RAS, Izhevsk, Russian Federation, [email protected], A.V. Vakhrouchev, Institute of Mechanics, Ural Branch of RAS, Kalashnikov Izhevsk State Technical University, Izhevsk, Russian Federation, [email protected], A.Yu. Fedotov, Institute of Mechanics, Ural Branch of RAS, Izhevsk, Russian Federation, [email protected]Высокоскоростное ударное нагружение твердых тел находит широкое применение в технике, промышленности, военном деле. При рассмотрении данного процесса главной задачей является изучение степени разрушения и фрагментации взаимодействующих твердых тел на основе расчета и анализа напряженно-деформированного состояния. Основными прикладными задачами исследований являются: разрушение и фрагментация преграды, вид разрушения, процессы откольного разрушения, величины перегрузок, интегральные силы сопротивления внедрению, конечные глубины проникновения, скорости при сквозном разрушении твердых тел, исследования влияния армирования на процессы разрушения, конфигурации зоны ударного взаимодействия, движения твердого тела в преграде и запреградном пространстве. Анализ экспериментальных данных показывает, что с изменением параметров ударяющего тела и свойств преграды, существенно меняются механизмы разрушения. Поэтому моделирование данных процессов является весьма актуальной задачей. Моделирование процессов проникновения и разрушения, как правило, выполняется, вследствие их сложности и взаимосвязанности, численными методами, методом конечных элементов и методом гладких (сглаженных) частиц. В работе описывается методология процессов взаимодействия снаряда с преградой. Математическая модель взаимодействия включает в себя законы сохранения массы, импульса и энергии, уравнения состояния вещества, модели напряженно- деформируемых состояний материалов. Численная модель основывается на аппроксимации основных законов сохранения явными уравнениями Эйлера. Взаимодействующие тела рассматриваются как совокупность частиц, обладающих определенными физико-механическими свойствами. Данная модель получила название метода сглаженных частиц SPH (Smoothed Particle Hydrodynamics) и широко используется при интенсивном динамическом нагружении тел, когда имеет место существенное изменение топологии моделируемых объектов. Приводятся результаты моделирования твердых тел. High-speed impact loading of solids is widely used in engineering, industry, military affairs. In considering of this process the main problem is to study the level of destruction and fragmentation of interacting solids based on the calculation and analysis of stress-strain state. The destruction and fragmentation of obstacles, failure mode, the processes of spall fracture, the value of overload, integral resistance force introduction, the final depth of penetration rate in through the destruction of solids, studies of the effect of reinforcing the processes of destruction zone configuration shock interaction, movement solid in the barrier and free space are the main applied objectives of the study. The analysis of experimental data shows that the mechanisms of destruction are significantly change with variation in the parameters of the impacting body and barrier properties. Therefore, the simulation of these processes is a topical problem. The simulation of processes of penetration and destruction is usually performed using numerical methods: finite element method, and the method of smooth (antialiased) particles because of their complexity and interconnectedness. The paper describes the methodology of the processes of dynamic interaction of solids. A mathematical model of the interaction includes the laws of conservation of mass, momentum and energy equations of state, the model of the stress-strain state of the materials. The numerical model is based on an approximation of the fundamental laws of conservation of explicit Euler equations. Interacting bodies are considered as a collection of particles with certain physical and mechanical properties. This model is called a smoothed particle hydrodynamics(SPH) method and is widely used in intensive dynamic loading of bodies, where there is a significant change in the topology of modeled object