Equation level matching: An extension of the method of matched asymptotic expansion for problems of wave propagation

We introduce an alternative to the method of matched asymptotic expansions. In the "traditional" implementation, approximate solutions, valid in different (but overlapping) regions are matched by using "intermediate" variables. Here we propose to match at the level of the equations involved, via a "uniform expansion" whose equations enfold those of the approximations to be matched. This has the advantage that one does not need to explicitly solve the asymptotic equations to do the matching, which can be quite impossible for some problems. In addition, it allows matching to proceed in certain wave situations where the traditional approach fails because the time behaviors differ (e.g., one of the expansions does not include dissipation). On the other hand, this approach does not provide the fairly explicit approximations resulting from standard matching. In fact, this is not even its aim, which to produce the "simplest" set of equations that capture the behavior

Simple Viscous Flows: from Boundary Layers to the Renormalization Group

The seemingly simple problem of determining the drag on a body moving through a very viscous fluid has, for over 150 years, been a source of theoretical confusion, mathematical paradoxes, and experimental artifacts, primarily arising from the complex boundary layer structure of the flow near the body and at infinity. We review the extensive experimental and theoretical literature on this problem, with special emphasis on the logical relationship between different approaches. The survey begins with the developments of matched asymptotic expansions, and concludes with a discussion of perturbative renormalization group techniques, adapted from quantum field theory to differential equations. The renormalization group calculations lead to a new prediction for the drag coefficient, one which can both reproduce and surpass the results of matched asymptotics

Information Technologies for Assessing the Quality of IT-specialties Graduates' Training of University by Means of Fuzzy Logic and Neural Networks

The information technologies for assessing the quality of IT-specialties graduates' training of university by means of fuzzy logic and neural networks are developed in the article. It makes possible taking into account a wide set of estimation and output parameters, influence of the external and internal factors and allows to simplify the assessing process by means of modern mathematical apparatuses of artificial intelligence

Application of harmonic wavelets to processing oscillating hydroacoustic signals

The paper is devoted to the application of specific functions called harmonic wavelets, which are aimed at processing a wide range of oscillating hydroacoustic signals including multiharmonic and transient signals. We provide basics of the harmonic wavelet transform and a two-stage algorithm for computing wavelet coefficients based on the discrete Fourier transform. We introduce a special efficiency factor of applying these wavelets to oscillating hydroacoustic signals. Application of harmonic wavelets is efficient for processing oscillating hydroacoustic signals since harmonic wavelets have similarities with these types of signals. In many cases the best basis is the basis that has high correlation with the investigated signals since signal representation in such a basis will require a small number of components. We devote special attention to a very important practical task - denoising of oscillating signals using special statistical criteria and wavelet-based thresholding

Information Technologies for Assessing the Quality of IT-specialties Graduates\u27 Training of University by Means of Fuzzy Logic and Neural Networks

The information technologies for assessing the quality of IT-specialties graduates\u27 training of university by means of fuzzy logic and neural networks are developed in the article. It makes possible taking into account a wide set of estimation and output parameters, influence of the external and internal factors and allows to simplify the assessing process by means of modern mathematical apparatuses of artificial intelligence

Применение метформина – целевая метаболическая терапия в онкологии

It is well known that metformin is widely used for the treatment of type II diabetes mellitus. However, in numerous epidemiological studies it was shown that patients taking metformin were less likely to have cancer of different localization and had better survival prognosis. Many researchers consider metformin to be a targeted metabolic drug that has many goals: it acts on mitochondria, affects intracellular signaling, blocks channels, inhibits the formation of endothelial and platelet growth factors, reduces the level of vitamins involved in the synthesis of nucleotides and amino acids, etc. It has also been established that metformin belongs to the group of “metabostemness” drugs, that is, it acts on cancer stem cells, blocking their division. We conducted a survey study that highlights the most important mechanisms and fields of application of metformin. The study of the use of this drug in oncology will make it possible to understand the pathogenetic targets of metabolic therapy and the prevention of cancer. Общеизвестно широкое применение метформина для лечения сахарного диабета II типа. Однако в многочисленных эпидемиологических исследованиях было показано, что больные, принимавшие метформин, реже болели раком различной локализации и имели лучший прогноз по выживаемости. Многие исследователи считают метформин таргетным метаболическим препаратом, который имеет множество целей: действует на митохондрии, влияет на внутриклеточный сигналинг, блокирует каналы, тормозит образование эндотелиального и тромбоцитарного факторов роста, снижает уровень витаминов, вовлеченных в синтез нуклеотидов и аминокислот и пр. Также установлено, что метформин относится к группе «метабостемных» препаратов, то есть действует на раковые стволовые клетки, блокируя их деление. Нами проведено обзорное исследование, которое освещает важнейшие механизмы и области применения метформина. Изучение применения данного препарата в онкологии позволит понять патогенетические мишени метаболической терапии и профилактики онкопатологий.

A separation of electrons and protons in the GAMMA-400 gamma-ray telescope

The GAMMA-400 gamma-ray telescope is intended to measure the fluxes of gamma rays and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV. Such measurements concern with the following scientific goals: search for signatures of dark matter, investigation of gamma-ray point and extended sources, studies of the energy spectra of Galactic and extragalactic diffuse emission, studies of gamma-ray bursts and gamma-ray emission from the active Sun, as well as high-precision measurements of spectra of high-energy electrons and positrons, protons, and nuclei up to the knee. The main components of cosmic rays are protons and helium nuclei, whereas the part of lepton component in the total flux is ~10E-3 for high energies. In present paper, the capability of the GAMMA-400 gamma-ray telescope to distinguish electrons and positrons from protons in cosmic rays is investigated. The individual contribution to the proton rejection is studied for each detector system of the GAMMA-400 gamma-ray telescope. Using combined information from all detector systems allow us to provide the proton rejection from electrons with a factor of ~4x10E5 for vertical incident particles and ~3x10E5 for particles with initial inclination of 30 degrees. The calculations were performed for the electron energy range from 50 GeV to 1 TeV.Comment: 19 pages, 10 figures, submitted to Advances and Space Researc