DSpace Collection: Preprints
http://hdl.handle.net/10525/3204
The Collection's search engineSearch the Channelsearch
http://sci-gems.math.bas.bg/jspui/simple-search
Oscillations in an Age-Dependent Model with a Dominant Age Class
http://hdl.handle.net/10525/3310
Title: Oscillations in an Age-Dependent Model with a Dominant Age Class<br/><br/>Authors: Kostova, Tanya V.<br/><br/>Abstract: We consider an age-structured model of population dynamics with vital rates depending on the size of a certain age class, the so called dominant age group. We introduce the notion of “totally oscillatory solutions” of an age-dependent model. These are solutions whose total population size oscillates. We demonstrate that the dominant age-dependent model admits totally oscillatory solutions. Numerical examples illustrate the theory.<br/><br/>Description: [Kostova Tanya V.; Костова Таня В.]Wed, 01 Mar 1995 00:00:00 GMTDiscrete Distributions Related to Success Runs of Length к in a Multi-State Markov Chain
http://hdl.handle.net/10525/3309
Title: Discrete Distributions Related to Success Runs of Length к in a Multi-State Markov Chain<br/><br/>Authors: Kolev, Nikolai; Minkova, Leda<br/><br/>Description: [Kolev Nikolai; Колев Николай]; [Minkova Leda; Минкова Леда]Wed, 01 Feb 1995 00:00:00 GMTOn Certain Systems of Generators of Infinite Symmetric and Alternating Groups
http://hdl.handle.net/10525/3307
Title: On Certain Systems of Generators of Infinite Symmetric and Alternating Groups<br/><br/>Authors: Iliev, Valentin Vankov<br/><br/>Description: [Iliev Valentin Vankov; Илиев Валентин Ванков]Wed, 01 Feb 1995 00:00:00 GMTOn the Black Body Oscillator Equation
http://hdl.handle.net/10525/3306
Title: On the Black Body Oscillator Equation<br/><br/>Authors: Angelov, Vasil G.<br/><br/>Abstract: The paper is concerned with the oscillator equation assigned to the black body. A new form of the Lorentz radiation term is derived. It corresponds to the original physical assumptions due to Dirac. This leads to a nonlinear functional differential equation of neutral type. By means of a fixed point theorem an existence result has been proved. As a consequence the ultra-violet catastrophe disappears.<br/><br/>Description: [Angelov Vasil G.; Ангелов Васил Г.]Sun, 01 Jan 1995 00:00:00 GMTA Block - Matrix Iterative Numerical Method for Coupled Solving 2D Navier-Stokes Equations
http://hdl.handle.net/10525/3305
Title: A Block - Matrix Iterative Numerical Method for Coupled Solving 2D Navier-Stokes Equations<br/><br/>Authors: Iliev, Oleg P.; Makarov, Mikhail M.<br/><br/>Abstract: An algorithm for coupled solving 2D Navier - Stokes equations in the stream function φ - vorticity ω variables is presented. Lid driven cavity flow is computed as a test example. Implicit difference schemes on uniform grids are used for discretizing the unsteady Navier - Stokes equations. An iterative method, similar to the BLOCK-ORTHOMIN(К) method, is used for solving block-matrix set of linear algebraic equations at each time step . The non-symmetric block is reversed on each block-iteration by using approximate factorization - OR- THOMIN(1) iterative method. The difference Laplace operator is reversed by means of a direct method. The comparison of the results, provided by coupled solving Navier-Stokes equations with those provided by decoupled (consecutive) solving the equations for ω and φ demonstrate the advantages of the suggested computing technique.<br/><br/>Description: [Iliev Oleg P.; Илиев Олег П.]; [Makarov Mikhail M.; Макаров Михаил М.]Tue, 13 Dec 1994 00:00:00 GMTBartlett's formulae - closed forms and recurrent equations
http://hdl.handle.net/10525/3304
Title: Bartlett's formulae - closed forms and recurrent equations<br/><br/>Authors: Boshnakov, Georgi N.<br/><br/>Abstract: We show that the entries of the asymptotic covariance matrix of the sample autocovariances and autocorrelations of a stationary process can be expressed in terms of the square of its spectral density. This leads to closed form expressions and fast computational algorithms.<br/><br/>Description: [Boshnakov Georgi N.; Бошнаков Георги Н.]Tue, 01 Nov 1994 00:00:00 GMTConditions for Local Integrability of Systems of m Smooth Complex Vector Fields on m+1 Dimensional Real Cartesian Space
http://hdl.handle.net/10525/3303
Title: Conditions for Local Integrability of Systems of m Smooth Complex Vector Fields on m+1 Dimensional Real Cartesian Space<br/><br/>Authors: Apostolova, Lilia N.<br/><br/>Description: [Apostolova Lilia N.; Апостолова Лилия Н.]Tue, 01 Nov 1994 00:00:00 GMTCompact Self-Dual Hermitian Surfaces
http://hdl.handle.net/10525/3302
Title: Compact Self-Dual Hermitian Surfaces<br/><br/>Authors: Apostolov, Vestislav; Davidov, Johann; Muškarov, Oleg<br/><br/>Abstract: Mathematics Subject Classification (1991): 53C55<br/><br/>Description: [Apostolov Vestislav; Апостолов Вестислав]; [Davidov Johann; Давидов Йохан]; [Muškarov Oleg; Mushkarov Oleg; Мушкаров Олег]Tue, 01 Nov 1994 00:00:00 GMTA Refinment of a Local Limit Theorem for a Branching Process Conditioned on the Total Progeny
http://hdl.handle.net/10525/3301
Title: A Refinment of a Local Limit Theorem for a Branching Process Conditioned on the Total Progeny<br/><br/>Authors: Kerbashev, Tzvetozar B.<br/><br/>Description: [Kerbashev Tzvetozar B.; Кербашев Цветозар Б.]Sat, 01 Oct 1994 00:00:00 GMTA Boundary Value Problem with a Finite Number of Impulses
http://hdl.handle.net/10525/3300
Title: A Boundary Value Problem with a Finite Number of Impulses<br/><br/>Authors: Ivanov, R. P.; Kitanov, P. M.<br/><br/>Abstract: This work considers Impulsive differential systems with boundary conditions. The characteristic feature of the impulsive boundary value problems is the unknown impulse moment. The solvability of the differential systems without impulses does not imply solution for the corresponding impulsive problem. Another specialty of the impulsive boundary value problem is that the set of solutions may not be a closed set.The problem is considered as a special logically controlled impulsive boundary value problem.The control may choose to use an optional impulse on the surface S. It is proved that the set of solution of the above mentioned controlled problem with a fixed and finite number of impulses is a closed set. If the boundary conditions describe a compact set then the set of impulsive solutions is a compact set too. The sufficient conditions for the existence of solutions of single impulse linear boundary value problem are presented. An example is considered.AMS (MOS) subject classification: 34A6O.<br/><br/>Description: [Ivanov R. P.; Иванов Р. П.]; [Kitanov P. M.; Китанов П. М.]Thu, 01 Sep 1994 00:00:00 GMTDifferential Inclusions with Upper Semicontinuous Right-Hand Side
http://hdl.handle.net/10525/3299
Title: Differential Inclusions with Upper Semicontinuous Right-Hand Side<br/><br/>Authors: Ivanov, Radostin Petrov<br/><br/>Abstract: An existence theorem is proved for solutions of differential inclusions with an upper semicontinuous and nonconvex right-hand side. The proof is based on an inner and directional continuous parameterization. This parameterization leads to a familie of disturbed differential inclusions. The solution of the starting differential inclusion is obtained as an uniformly limit of the solutions of disturbed systems. Some aspects of the existence of the above mentioned inner parameterization are discussed. A few examples are presented.AMS (MOS) subject classification: 34A60.<br/><br/>Description: [Ivanov Radostin Petrov; Иванов Радостин Петров]Mon, 01 Aug 1994 00:00:00 GMTLimit Theorems for Age-Dependent Branching Processes with State-Dependent Immigration
http://hdl.handle.net/10525/3298
Title: Limit Theorems for Age-Dependent Branching Processes with State-Dependent Immigration<br/><br/>Authors: Slavtchova-Bojkova, Maroussia N.; Yanev, Nickolay M.<br/><br/>Abstract: We consider a model of Bellman-Harris branching processes with immigration only in the state zero (BHIO) which permits in addition an immigration component of i.i.d. BHIO processes entering the population at i.i.d. times of an independent renewal process (BHIOR). Asymptotic properties and limit theorems are proved in поп-critical cases.60J80<br/><br/>Description: [Slavtchova-Bojkova Maroussia N.; Славчова-Божкова Маруся Н.]; [Yanev Nickolay M.; Янев Николай М.]Fri, 01 Jul 1994 00:00:00 GMTDensely Two-Valued Metric Projections in Uniformly Convex Banach Spaces
http://hdl.handle.net/10525/3237
Title: Densely Two-Valued Metric Projections in Uniformly Convex Banach Spaces<br/><br/>Authors: Zhivkov, N. V.<br/><br/>Abstract: For every uniformly convex Banach space X with dim X ≥ 2 there is a residual set U in the Hausdorff metric space B(X) of hounded and closed sets in X such that a metric projection generated by a set from U is two-valued and upper semicontinuous on a dense and everywhere continual subset of X.For any two closed and separated subsets M1 and M2 of X the points on the equidistant hypersurface which have best approximations both in M1 and M2 form a dense G𝛿 set in the induced topology.1991 Mathematics Subject Classification. Primary 41A65, 54E52. Secondary 46B20.<br/><br/>Description: [Zhivkov N. V.; Живков Н. В.]Sun, 01 May 1994 00:00:00 GMTKuratowski convergence of the efficient sets in the parametric linear vector semi-infinite optimization
http://hdl.handle.net/10525/3236
Title: Kuratowski convergence of the efficient sets in the parametric linear vector semi-infinite optimization<br/><br/>Authors: Todorov, Maxim Ivanov<br/><br/>Abstract: In the space of whole linear semi-infinite optimization problems we consider the mappings putting into correspondence to each problem the set of efficient and weakly efficient points, respectively. We endow the image space wit Kuratowski convergence and by means of the lower and upper continuity of these mappings we prove generic well-posedness of the vector optimization problems. The connection between the continuity and some properties of the efficient sets is also discussed.<br/><br/>Description: [Todorov Maxim Ivanov; Тодоров Максим Иванов]Mon, 01 Nov 1993 00:00:00 GMTSecond-order subdifferentials of C^1,1 functions and optimality conditions
http://hdl.handle.net/10525/3235
Title: Second-order subdifferentials of C^1,1 functions and optimality conditions<br/><br/>Authors: Georgiev, Pando Gr.; Zlateva, Nadia P.<br/><br/>Abstract: We present second-order subdifferentials of Clarke’s type of C^1,1 functions, defined in separable Banach spaces with separable duals, i.e. of functions whose gradient mapping is locally Lipschitz. One of them is an extension of the generalized Hessian matrix of such functions in R^n, considered by J.B. H.-Urruty, J.J. Strodiot and V.H. Nguyen. Various properties of these subdifferentials are proved. Second order optimality conditions (necessary, sufficient) for constrained minimization problems with C^1,1 data are obtained.<br/><br/>Description: [Georgiev Pando Gr.; Георгиев Пандо Гр.]; [Zlateva Nadia P.; Златева Надя П.]Fri, 01 Oct 1993 00:00:00 GMTRiesz summability of multiple Hermite series
http://hdl.handle.net/10525/3234
Title: Riesz summability of multiple Hermite series<br/><br/>Authors: Karadzhov, G. E.<br/><br/>Description: [Karadzhov G. E.; Karadzhov Georgi Eremiev; Karadžov Georgi; Караджов Георги Е.]Fri, 01 Oct 1993 00:00:00 GMT