فهرست مطالب

بین المللی محاسبات و مدل سازی ریاضی - سال ششم شماره 3 (Summer 2016)

مجله بین المللی محاسبات و مدل سازی ریاضی
سال ششم شماره 3 (Summer 2016)

  • تاریخ انتشار: 1395/04/23
  • تعداد عناوین: 7
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  • Amit Sharma Page 189
    The present paper deals with a toxin producing phytoplankton (TPP)-zooplankton interaction in spatial environment in the context of phytoplankton bloom. In the absence of diffusion the stability of the given system in terms of co-existence and hopf bifurcation has been discussed. After that TPP zooplankton interaction is considered in spatiotemporal domain by assuming self diffusion in both population. It has been obtained that in the presence of diffusion given system becomes unstable (Turing instability) under certain conditions. Moreover, by applying the normal form theory and the center manifold reduction for partial differential equations (PDEs), the explicit algorithm determining the direction of Hopf bifurcations and the stability of bifurcating periodic solutions is derived. Finally, numerical simulations supporting the theoretical analysis are also included.
    Keywords: Toxin producing phytoplankton, Zooplankton, Hopf Bifurcation, Turing instability, Normal Form, Center manifold theorem
  • Somayeh Keikha, Javan, Mohsen Rostamy Malkhalifeh Page 199
    Data envelopment analysis (DEA) is a non-parametric technique for evaluation of relative efficiency of decision making units described by multiple inputs and outputs. It is based on solving linear programming problems. Since 1978 when basic DEA model was introduced many its modifications were formulated. Among them are two or multi-stage models with serial or parallel structure often called network DEA models that are widely discussed in professional community in the last years. The exact known inputs and outputs are required in these DEA models. However, in the real world, the concern is systems with interval (bounded) data. When we incorporate such interval data into multi-stage DEA models, the resulting DEA model becomes a non-linear programming problem. In this study, we suggest an approach to measure the efficiency of series and parallel systems with interval data that preserves the linearity of DEA model. Also, the interval DEA models are proposed to measure the lower and upper bounds of the efficiency of each DMU with interval data.
    Keywords: DEA, Network DEA, Interval Data, divisional efficiency, overall efficiency
  • Fereshte Sotoude, Ahmad Pourdarvish Heydari Page 211
    The analysis of cross-correlations is extensively applied for understanding of interconnections in stock markets. Variety of methods are used in order to search stock cross-correlations including the Random Matrix Theory (RMT), the Principal Component Analysis (PCA) and the Hierachical ýStructures.ý
    In ýthis worký, we analyze cross-crrelations between price fluctuations of 20 ýcompany ýstocksýý of Iran by using RMT. We find the eigenvalues and eigenvectors of the matrices of the cross-correlations related to ýtheýse stocks.ýýý
    The results show some eigenvalues do not fall within the bounds of RMT eigenvalues, that indicate the correlations of ýý stocks in usual and critical flucatutions.
    Keywords: Random Matrix Theory, Cross, Correlation, Eigenvalue, eigenvector
  • Mostafa Nouri, Khosrow Maleknejad Page 221
    This article proposes a direct method for solving three types of integral equations with time delay. By using operational matrix of integration, integral equations can be reduced to a linear lower triangular system which can be directly solved by forward substitution. Numerical examples shows that the proposed scheme have a suitable degree of accuracy.
    Keywords: Block pulse functions, Operational matrix, Integral equations with time delay, Delay operational matrix.Block pulse functions, Operational matrix, Integral equations with time delay, Delay operational matrix
  • M. Reza Tanhayi Page 233
    In this paper, we study the Casimir effect of a scalar field with Dirichlet boundary condition in some certain topologies. By numerical analysis we show that Casimir energy is a shape-dependent quantity. We also obtain the phase transition in different topologies in which the Casimir force changes from attractive to repulsive or vice versa. eararqr
    Keywords: Casimir eect, Dirichlet boundary condition, Numerical analysis
  • Mohammad Rahimian, Esmaiel Keshavarz, Hamid Hassasi Page 243
    In most of the real-life applications we deal with the problem of transporting some special fruits, as banana, which has particular production and distribution processes. In this paper we restrict our attention to formulating and solving a new bi-criterion problem on a network in which in addition to minimizing the traversing costs, admissibility of the quality level of fruits is a main objective. However, the fruits are possibly stored at some intermediate node for practical purposes. We call the new model the best shipping pattern problem with intermediate storage. Here, it is assumed that both arc costs and times are crisp numbers. The main contribution of this model is an actual interpretation of the given fuzzy trapezoidal number, as the quality of delivered commodities. Since the presented problem has a fuzzy structure, the Bellman and Zadeh's max-min criterion can be used to treat it as a crisp single-objective problem, which is easily solvable. An illustrative example is solved, to explain the presented details.
    Keywords: multiple criterion optimization, best shipping pattern, fuzzy number, Bellman, Zadeh's principle
  • Salah El Ouadih Page 253
    In this paper, using a generalized translation operator, we prove the
    estimates for the generalized Fourier-Bessel transform in the space L2 on certain
    classes of functions.
    Keywords: singular dierential operator, generalized Fourier, Bessel transform, generalized translation operatorsingular dierential operator, generalized Fourier, Bessel transform, generalized translation operator