Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy

Bucharest, Romania

Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy

Bucharest, Romania

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Jayswal A.,Indian School of Mines | Stancu-Minasian I.M.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy | Choudhury S.,Indian School of Mines
OPSEARCH | Year: 2015

The aim of this paper is to introduce the concept of second-order (F, α, ρ, θ)-convexity for variational problems. An example is constructed to examine the existence of the introduced class of functions, which is more general than previously defined functions. In order to relate the primal variational problem and its second order dual, several duality results, viz., weak, strong and strict converse duality results are established. © 2014, Operational Research Society of India.


Beznea L.,Simion Stoilow Institute of Mathematics of the Romanian Academy | Beznea L.,University of Bucharest | Deaconu M.,French Institute for Research in Computer Science and Automation | Deaconu M.,University of Lorraine | And 4 more authors.
Journal of Statistical Physics | Year: 2016

We give a stochastic model for the fragmentation phase of an avalanche. We construct a fragmentation-branching process related to the avalanches, on the set of all fragmentation sizes introduced by Bertoin. A fractal property of this process is emphasized. We also establish a specific stochastic differential equation of fragmentation. It turns out that specific branching Markov processes on finite configurations of particles with sizes bigger than a strictly positive threshold are convenient for describing the continuous time evolution of the number of the resulting fragments. The results are obtained by combining analytic and probabilistic potential theoretical tools. © 2016, Springer Science+Business Media New York.


Preda V.,University of Bucharest | Preda V.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy | Dedu S.,University of Bucharest | Sheraz M.,Ningbo University
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2016

The aim of this paper is to develop some risk assessment models involving truncated and censored loss random variables. Representation formulas for the second order entropy corresponding to the left truncated or censored from below and right truncated or censored from above random variables are derived. Also, some properties and interpretations of the results are provided.


Beldiman M.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2013

Some types of equilibrium problems and systems of equilibrium problems on cones are studied. For these, we obtain equivalence results and prove, using a fixed - point theorem of Chowdury and Tan, existence results.


Jayswa A.,Birla Institute of Technology | Stancu-Minasian I.M.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2010

We introduce new classes of generalized convex n-set functions that we call d-weak strictly pseudoquasi type-I univex, d-strong pseudo-quasi type-I univex and d-weak strictly pseudo type-I univex functions. We focus on multiobjective subset programming problem. Sufficient optimality conditions are obtained under the assumptions involving such functions. Duality results are also established for Mond-Weir and general Mond-Weir type dual problems in which the functions involved satisfy appropriate generalized d-type-I univexity conditions. The results obtained in this paper present a refinement and improvement of previously known results in the literature.


Marinoschi G.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy | Marinoschi G.,Simion Stoilow Institute of Mathematics of the Romanian Academy
Journal of Biological Dynamics | Year: 2013

We study a model, motivated by a bioremediation process, describing a cross-diffusion movement of a bacteria population b attracted by a chemoattractant signal c, in a nonhomogeneous stratified medium with n layers. We assume that this reaction-diffusion process is characterized by a low rate of degradation and a low diffusion coefficient of the chemoattractant, expressed in the model by a small parameter ε{lunate}. The model consists of n systems of nonlinear parabolic equations with transmission conditions between layers. We prove a global-in-time solution for the asymptotic model setup with respect to the small parameter of the problem, for arbitrarily large initial data. Next, we deal with the control problem focusing mainly on the reduction of the chemoattractant concentration, by acting upon the initial distribution of the bacteria population b0. To this end, we prove the existence of a solution to the control problem and determine the optimality conditions. © 2013 The Author(s). Published by Taylor & Francis.


Ionescu V.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy
Proceedings of the Romanian Academy Series A - Mathematics Physics Technical Sciences Information Science | Year: 2011

We give a new proof concerning the complete positivity of the Boolean product of contractive, completely positive maps between C*-Algebras (see [9]). This is inspired by a technique due to M. Bozejko, M. Leinert and R. Speicher from [6] and uses an extension of a W.L.Paschke and E. Stormer's criterion for the positivity of a matrix over a C*-Algebra[13] [18].


Barbu T.,Romanian Academy of Sciences | Marinoschi G.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy
International Journal of Control | Year: 2016

We propose a technique for image denoising by solving a nonconvex optimal control problem with the state and controller connected on a manifold described by a nonlinear elliptic equation. The existence of a control able to denoise an initial blurred image is proved and the optimality conditions are determined by a passing to the limit technique in an appropriate approximating problem, involving the Legendre–Fenchel relations. An algorithm constructed on the basis of the theoretical results is developed and numerical simulations are provided. © 2016 Informa UK Limited, trading as Taylor & Francis Group


Popescu M.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy
2011 International Conference on Communications, Computing and Control Applications, CCCA 2011 | Year: 2011

We consider the problem of optimum concerning to the minimization quadratic functionals of Bolza type with constraints represented differential systems with parameter. One demonstrates the uniqueness of optimal feedback nonlinear control obtained, by utilizing that the U Hilbert space control domain is rotund. The solution for two point boundary value problem implies the determination of the solution of the system in variations associated to the linearized system. The construction of the solution use of an iterative procedure, yielding the initial value results of the adjoint variable. By presenting the state vectors x X and the control vectors u U in orthonormal basis, one develops a numerical approximation method of the solution to the optimum problem. © 2011 IEEE.


Beldiman M.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy | Boaca I.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy | Marinoschi G.,Institute of Mathematical Statistics and Applied Mathematics of the Romanian Academy | Marinoschi G.,Simion Stoilow Institute of Mathematics of the Romanian Academy
ZAMM Zeitschrift fur Angewandte Mathematik und Mechanik | Year: 2013

We address an optimization problem related to a diffusive flow in a nonhomogeneous porous medium. More exactly, the purpose is to control by a flow parameter an optimal average of the solution in a subset of the domain. The state model is degenerate and ill-posed and this requires to develop a technique of optimization for a singular state system. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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