Theoretical and applied problems of Physics and Mathematics
http://old.bulletin.kpi.ua/en/taxonomy/term/57/all
enRank One Strong Singular Perturbation by Nonsymmetric Potential
http://old.bulletin.kpi.ua/en/node/2632
<p>For a rank one strong singular perturbation of a self-adjoint operator by nonsymmetric potential, we present a construction and investigated the corresponding eigenvalue problem.</p>
Dudkin М.E.Krein’s formulaoperator spectrumself-adjoint operatorsingular perturbationTheoretical and applied problems of Physics and MathematicsVdovenko T.I.Thu, 04 Dec 2014 12:42:23 +0000admin.bulletin2632 at http://old.bulletin.kpi.uaBehavior of Surface Spin Waves at Reflection from Uniaxial Multilayer Ferromagnet
http://old.bulletin.kpi.ua/en/node/2698
<p>The purpose of this article is to review the reflective properties of multilayer ferromagnet for surface spin waves. It was calculated the reflection coefficient of surface spin waves from multilayer ferromagnet with uniaxial magnetic anisotropy in non-ideal boundary conditions at the interface between layers. The problem is solved in the exchange approximation. Graphics shows us the dependence of the reflection coefficient on the frequency, of the external magnetic field, the exchange interaction constant and uniaxial magnetic anisotropy.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2698" target="_blank">read more</a></p>Andriievska O.M.exchange interaction constantmultilayer ferromagnetreflection coefficientReshetnyak S.A.surface spin waveTheoretical and applied problems of Physics and Mathematicsuniaxial magnetic anisotropyFri, 19 Dec 2014 11:10:11 +0000admin.bulletin2698 at http://old.bulletin.kpi.uaSound Generation by Taylor and Scully Vortexes and the Blade of the Varying Cross Section
http://old.bulletin.kpi.ua/en/node/2695
<p>A problem of the blade vortex interaction noise (BVI) generation has been solved for incoming flux and Taylor, Scully vortexes. Solution for this problem is a closed system of the aeroacoustical equations, which is based on perfect compressible gas model. A behavior of the generated noise has been studied for the different flow velocities and blade thicknesses. Results of the calculations show existence of the two frank regions of the sound existence on the blade shape. The first of it is more resistant for the parameters changing. The second one is a flow region of the instability.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2695" target="_blank">read more</a></p>BVI Taylor and Scully vortexes interactionFELLukianov Petro V.Scullysound generationTheoretical and applied problems of Physics and MathematicsFri, 19 Dec 2014 10:35:40 +0000admin.bulletin2695 at http://old.bulletin.kpi.uaInertial Stability as a Result of the Relation Between Transport and Relative Fluid Rotations
http://old.bulletin.kpi.ua/en/node/2692
<p>The aim of the paper is fluid inertial stability nature determination through the representation of potential (non-rotational) motion as the compensation of two rotations, transport one and relative one. Theoretical methods are used. It is based on well-known description of fluid motion as a sum of three types (Cauchy–Helmholz theorem), but uses theoretical mechanics approach. The motion is considered as a sum of transport and relative ones. Thransport angular velocity corresponds to macroscopic motion, while relative one is caused by fluid parcel deformation.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2692" target="_blank">read more</a></p>IMEinertial stabilityLukianov P.V.potential (non-rotational) motionTheoretical and applied problems of Physics and MathematicsFri, 19 Dec 2014 10:27:17 +0000admin.bulletin2692 at http://old.bulletin.kpi.uaDefinition Peculiarities of Energy of Vacancy Formation In 4d-Transition Metals from First Principles
http://old.bulletin.kpi.ua/en/node/2689
<p>In this paper a study of the temperature dependence of the vacancy formation energy in bulk fcc 4d-transition metals Ag and Pd using DFT was presented. Peculiarity of this work is the use of experimental values of the lattice parameters for the respective temperatures. This paper discusses the various contributions to the vacancy formation energy and shows that they can play an important role. It was shown that thermal excitation has a significant impact on the vacancy formation energy at high temperatures. The possibility of the existence of the compensation effect, i.e.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2689" target="_blank">read more</a></p>density functional theoryelectronic thermal exitationthe energy of formation of vacanciesthe first principlesTheoretical and applied problems of Physics and Mathematicsvibration energyZamulko S.O.Thu, 18 Dec 2014 16:13:38 +0000admin.bulletin2689 at http://old.bulletin.kpi.uaPropagation of Spin Wave Through the Anisotropic Boundary of Two Uniaxial Ferromagnets in an External Magnetic Field
http://old.bulletin.kpi.ua/en/node/2686
<p>This paper represents the investigation of the reflection of bulk spin waves at the interface of two uniaxial ferromagnetic media that propagate at an angle to the interface and their penetration from one ferromagnetic medium to another one. Thereby, the interaction similar to the interaction of two antiferromagnets is taken into account at the boundary interface between two media in an external constant uniform magnetic field. The problem is solved in the formalism of spin density based on equations of Landau–Lifshitz in the absence of dissipation in the system.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2686" target="_blank">read more</a></p>ferromagnetFPMGorobets O.Yu.Gorobets Yu.I.Landau–Lifshitz equationRospotniuk T.Yu.Rospotnyuk V.P.spin wavesthe boundary conditions for the magnetizationthe surface magnetic anisotropyTheoretical and applied problems of Physics and MathematicsTue, 16 Dec 2014 12:21:49 +0000admin.bulletin2686 at http://old.bulletin.kpi.uaDistribution of the Antiferromagnetism Vector for an Isolated Antidot and a System of Remote Antidots in Antiferromagnets
http://old.bulletin.kpi.ua/en/node/2683
<p>In the paper, an antiferromagnetism vector distribution in an antiferromagnetic film composed of an uniaxial or isotropic two-sublattice antiferromagnet with a set system of circular antidots is investigated. For such a system, the Landau-Lifshitz equation is written and its solution is obtained.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2683" target="_blank">read more</a></p>antidotantiferromagnetantiferromagnetic vectorGorobets O.Yu.Gorobets Yu.I.Kulish V.V.Theoretical and applied problems of Physics and Mathematicsthin magnetic filmTue, 16 Dec 2014 12:11:38 +0000admin.bulletin2683 at http://old.bulletin.kpi.uaSolution of the Linear Boundary–Value Problem without Initial Conditions for the Second Order Hyperbolic Equation
http://old.bulletin.kpi.ua/en/node/2680
boundary value problem without initial conditionsFPMhyperbolic equation of the second orderKhoma-Mohylska S.G.operatorsolutionTheoretical and applied problems of Physics and MathematicsTue, 16 Dec 2014 11:54:51 +0000admin.bulletin2680 at http://old.bulletin.kpi.uaSymmetry Analysis of a Class of (2+1)-Dimensional Linear Ultra-Parabolic Equations
http://old.bulletin.kpi.ua/en/node/2677
<p>In this paper, a class of (2+1)-dimensional linear ultra-parabolic equations of the second order is investigated by using the methods of group analysis of differential equations. The class under study generalizes a number of the classical equations of mathematical physics such as the free Kramers equation, the linear Kolmogorov equation etc. The classification of the symmetry properties of equations from the class is carried out by using the well-known Lie–Ovsiannikov algorithm.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2677" target="_blank">read more</a></p>equivalence transformationFPMKopas I.M.Kovalenko S.S.Lie symmetrylinear ultra-parabolic equationmaximal algebra of invarianceStogniy V.I.Theoretical and applied problems of Physics and MathematicsTue, 16 Dec 2014 11:00:53 +0000admin.bulletin2677 at http://old.bulletin.kpi.uaMinimal Systems of Generators and Relations and Properties of Wreath Products of Perfect Groups
http://old.bulletin.kpi.ua/en/node/2674
<p>Generators and defining relations for wreath products of perfect group which is two generating and alternating groups (m 2 times) are given. System of generators of metaperfect groups are found. Generators and defining relations for wreath products of 2-generating perfect groups were found, including alternating groups, i.e. (m 2 time). Systems of generators for metaperfect groups were investigated. A constructive proof of the minimality found system of generators was presented. It is shown that metaperfect group is not locally finite group.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2674" target="_blank">read more</a></p>FPMmetaperfect groupminimal system of generatorsSkuratovsky R.V.Theoretical and applied problems of Physics and Mathematicswreath productTue, 16 Dec 2014 10:52:10 +0000admin.bulletin2674 at http://old.bulletin.kpi.uaComplex-Valued Functions with Nondegenerate Groups of Regular Points
http://old.bulletin.kpi.ua/en/node/2671
<p>Complex-valued functions with nondegenerate groups of regular points are studied in the paper. A class of functions , which takes value on the complex plain and for which the limit exists, and is nonzero and finite for some from subset of positive real numbers is considered. It was received that this subset is multiplicative group, and it is called the group of regular points. Functions with nondegenerate groups of regular points generalize the class of RV functions. The corresponding limit functions are defined for complex-valued functions with nondegenerate groups of regular points.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2671" target="_blank">read more</a></p>FPMgroup of regular pointsORV functionPavlenkov V.V.RV functionTheoretical and applied problems of Physics and MathematicsTue, 09 Dec 2014 15:51:40 +0000admin.bulletin2671 at http://old.bulletin.kpi.uaConsistency of Least Squares Estimator of Linear Regression Parameter in Case of Discrete Tme and Long-Range or Weak Dependent Regressors
http://old.bulletin.kpi.ua/en/node/2668
<p>Linear regression model with discrete time, long-range/weak dependent random noise and time dependent regressors, which are observed with long L range/weak dependent errors, is considered. Parameter estimation of such models is one of the important problems of statistics of random processes. Least squares estimator is chosen for the estimation. The aim of the work is to prove consistency of least squares estimator of such regression model.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2668" target="_blank">read more</a></p>consistencyerrors in regressorsleast square estimatornonlinear regression modeOrlovsky I.V.strong dependenceTheoretical and applied problems of Physics and Mathematicsweak dependenceTue, 09 Dec 2014 15:44:14 +0000admin.bulletin2668 at http://old.bulletin.kpi.uaThe Limit Theorems for Extreme Residuals in Nonlinear Regression Model with Gaussian Stationary Noise
http://old.bulletin.kpi.ua/en/node/2665
<p>In this paper non-linear regression model with Gaussian stationary random noise and continuous time is considered. The behavior of normalized in some way maximum residuals and maximum of residuals absolute values in which its the least squares estimator is substituted instead of unknown parameter of regression function. The convergence of distribution of these normalized maximum to double exponent law is proved which follows from the assumption of random noise normality.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2665" target="_blank">read more</a></p>estimator consistencyFPMIvanov O.V.maximal residualsnonlinear regression modePrihodko V.V.stationary Gaussian noiseTheoretical and applied problems of Physics and Mathematicsvariance and the second spectral moment estimatorsweak convergenceTue, 09 Dec 2014 15:34:37 +0000admin.bulletin2665 at http://old.bulletin.kpi.uaMoments Asymptotic Expansion of the Least Squares Estimator of the Vector-Parameter of Nonlinear Regression with Correlated Observations
http://old.bulletin.kpi.ua/en/node/2662
<p>A nonlinear regression model with continuous time and mean square continuous separable measurable Gaussian stationary random noise with zero mean and integrable covariance function is considered. Parameter estimation in the models of such kind is an important problem of statistics of random processes. In this paper, the first terms of asymptotic expansions of the bias vector and covariance matrix of the least square estimator of nonlinear regression function vector parameter are obtained.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2662" target="_blank">read more</a></p>asymptotic expansionFPMIvanov O.V.least square estimatorMoskvychova K.K.nonlinear regression modestationary Gaussian noiseTheoretical and applied problems of Physics and MathematicsTue, 09 Dec 2014 15:11:09 +0000admin.bulletin2662 at http://old.bulletin.kpi.uaAsymptotic Uniqueness of the Non-Linear Regression Model Parameter with Least Squares Estimator
http://old.bulletin.kpi.ua/en/node/2659
<p>In the paper the nonlinear regression model with continuous time and random noise, which is a local functional of strongly dependent stationary Gaussian random process, is considered. Sufficient conditions of asymptotic uniqueness of the least squares estimator of regression function parameters are obtained. This result is applied to the least squares estimator of amplitude and angular frequencies of harmonic oscillations sum observed on the background of given random noise.</p>
<p><a href="http://old.bulletin.kpi.ua/en/node/2659" target="_blank">read more</a></p>asymptotic uniquenessFPMhidden periodicitiesleast square estimatornonlinear regressionstrong dependenceTheoretical and applied problems of Physics and MathematicsZhurakovskyi B.M.Tue, 09 Dec 2014 14:44:41 +0000admin.bulletin2659 at http://old.bulletin.kpi.ua