Envíos recientes

  • Convergent and asymptotic methods for second-order difference equations with a large parameter 

    Ferreira, Chelo; López García, José Luis; Pérez Sinusía, Ester (Springer, 2018)   Artículo / Artikulua
    We consider the second-order linear difference equation y(n+2)−2ay(n+1)−Λ2y(n)=g(n)y(n)+f(n)y(n+1) , where Λ is a large complex parameter, a≥0 and g and f are sequences of complex numbers. Two methods are proposed to find ...
  • The asymptotic expansion of the swallowtail integral in the highly oscillatory region 

    Ferreira, Chelo; López García, José Luis; Pérez Sinusía, Ester (Elsevier, 2018)   Artículo / Artikulua
    The mathematical models of many short wavelength phenomena, specially wave propagation and optical diffraction, contain, as a basic ingredient, oscillatory integrals with several nearly coincident stationary phase or saddle ...
  • Uniform convergent expansions of the Gauss hypergeometric function in terms of elementary functions 

    Ferreira, Chelo; López García, José Luis; Pérez Sinusía, Ester (Taylor & Francis, 2018)   Artículo / Artikulua
    We consider the hypergeometric function 2F1(a, b; c; z) for z ∈ C \ [1,∞). For Ra ≥ 0, we derive a convergent expansion of 2F1(a, b; c; z) in terms of the function (1 − z)−a and of rational functions of z that is uniformly ...
  • Uniform representation of the incomplete beta function in terms of elementary functions 

    Ferreira, Chelo; López García, José Luis; Pérez Sinusía, Ester (Kent State UniversityJohann Radon Institute (RICAM), 2018)   Artículo / Artikulua  OpenAccess
    We consider the incomplete beta function Bz(a, b) in the maximum domain of analyticity of its three variables: a, b, z ∈ C, −a /∈ N, z /∈ [1, ∞). For <b ≤ 1 we derive a convergent expansion of z−aBz(a, b) in terms of the ...
  • Asymptotic and convergent expansions for solutions of third-order linear differential equations with a large parameter 

    Ferreira, Chelo; López García, José Luis; Pérez Sinusía, Ester (Shanghai Normal UniversityWilmington Scientific Publisher, 2018)   Artículo / Artikulua  OpenAccess
    In previous papers [6–8,10], we derived convergent and asymptotic expansions of solutions of second order linear differential equations with a large parameter. In those papers we generalized and developed special cases not ...
  • The use of two-point Taylor expansions in singular one-dimensional boundary value problems I 

    Ferreira, Chelo; López García, José Luis; Pérez Sinusía, Ester (Elsevier, 2018)   Artículo / Artikulua
    We consider the second-order linear differential equation (x + 1)y′′ + f(x)y′ + g(x)y = h(x) in the interval (−1, 1) with initial conditions or boundary conditions (Dirichlet, Neumann or mixed Dirichlet-Neumann). The ...
  • Convergent expansions of the incomplete gamma functions in terms of elementary functions 

    Bujanda Cirauqui, Blanca Upna; López García, José Luis; Pagola Martínez, Pedro Jesús (World Scientific Publishing, 2017)   Artículo / Artikulua  OpenAccess
    We consider the incomplete gamma function γ(a,z) for Ra>0 and z∈C. We derive several convergent expansions of z−aγ(a,z) in terms of exponentials and rational functions of z that hold uniformly in z with Rz bounded from ...
  • A simplification of the stationary phase method: application to the Anger and Weber functions 

    López García, José Luis (Kent State UniversityJohann Radon Institute (RICAM), 2017)   Artículo / Artikulua  OpenAccess
    The main difficulty in the practical use of the stationary phase method in asymptotic expansions of integrals is originated by a change of variables. The coefficients of the asymptotic expansion are the coefficients of the ...
  • Analytic formulas for the evaluation of the Pearcey integral 

    López García, José Luis; Pagola Martínez, Pedro Jesús (American Mathematical Society, 2017)   Artículo / Artikulua  OpenAccess
    We can find in the literature several convergent and/or asymptotic expansions of the Pearcey integral P(x, y) in different regions of the complex variables x and y, but they do not cover the whole complex x and y planes. The ...
  • Convergent expansions of the Bessel functions in terms of elementary functions 

    López García, José Luis; Pagola Martínez, Pedro Jesús (Springer US, 2018)   Artículo / Artikulua  OpenAccess
    We consider the Bessel functions Jν (z) and Yν (z) for ν > −1/2 and z ≥ 0. We derive a convergent expansion of Jν (z) in terms of the derivatives of (sin z)/z, and a convergent expansion of Yν (z) in terms of derivatives ...
  • Orthogonal basis with a conicoid first mode for shape specification of optical surfaces 

    Ferreira, Chelo; López García, José Luis; Navarro, Rafael; Pérez Sinusía, Ester (Optical Society of America, 2016)   Artículo / Artikulua  OpenAccess
    A rigorous and powerful theoretical framework is proposed to obtain systems of orthogonal functions (or shape modes) to represent optical surfaces. The method is general so it can be applied to different initial shapes and ...
  • The Pearcey integral in the highly oscillatory region 

    López García, José Luis; Pagola Martínez, Pedro Jesús (Elsevier, 2016)   Artículo / Artikulua  OpenAccess
    We consider the Pearcey integral P(x, y) for large values of |y| and bounded values of |x|. The integrand of the Pearcey integral oscillates wildly in this region and the asymptotic saddle point analysis is complicated. ...
  • Zernike-like systems in polygons and polygonal facets 

    Ferreira, Chelo; López García, José Luis; Navarro, Rafael; Pérez Sinusía, Ester (Optical Society of America, 2015)   Artículo / Artikulua  OpenAccess
    Zernike polynomials are commonly used to represent the wavefront phase on circular optical apertures, since they form a complete and orthonormal basis on the unit disk. In [Diaz et all, 2014] we introduced a new Zernike ...
  • On a modifcation of Olver's method: a special case 

    Ferreira, Chelo; López García, José Luis; Pérez Sinusía, Ester (Springer US, 2016)   Artículo / Artikulua  OpenAccess
    We consider the asymptotic method designed by Olver (Asymptotics and special functions. Academic Press, New York, 1974) for linear differential equations of the second order containing a large (asymptotic) parameter : xm ...
  • Convergent and asymptotic expansions of the Pearcey integral 

    López García, José Luis; Pagola Martínez, Pedro Jesús (Elsevier, 2015)   Artículo / Artikulua  OpenAccess
    We consider the Pearcey integral P(x; y) for large values of |x|, x, y ∈ C. We can find in the literature several convergent or asymptotic expansions in terms of elementary and special functions, with different levels of ...
  • A mixed-FEM and BEM coupling for the approximation of the scattering of thermal waves in locally non-homogeneous media 

    Rapún Araiz, María Luisa; Sayas, Francisco Javier (EDP Sciences, 2006)   Artículo / Artikulua  OpenAccess
    This paper proposes and analyzes a BEM-FEM scheme to approximate a time-harmonic diffusion problem in the plane with non-constant coefficients in a bounded area. The model is set as a Helmholtz transmission problem with ...
  • Formulas for the amplitude of the van der Pol limit cycle through the homotopy analysis method 

    López García, José Luis; Abbasbandy, S.; López Ruiz, R. (Hindawi / Wiley, 2009)   Artículo / Artikulua  OpenAccess
    The limit cycle of the van der Pol oscillator, x¨+ε(x2−1)x˙+x=0, is studied in the plane (x,x˙) by applying the homotopy analysis method. A recursive set of formulas that approximate the amplitude and form of this limit ...
  • Implementation and operational analysis of an interactive intensive care unit within a smart health context 

    López Iturri, Peio Upna; Aguirre Gallego, Erik Upna; Trigo Vilaseca, Jesús Daniel; Astrain Escola, José Javier Upna; Azpilicueta Fernández de las Heras, Leyre Upna; Serrano Arriezu, Luis Javier Upna; Villadangos Alonso, Jesús Upna; Falcone Lanas, Francisco Javier Upna (MDPI, 2018)   Artículo / Artikulua  OpenAccess
    In the context of hospital management and operation, Intensive Care Units (ICU) are one of the most challenging in terms of time responsiveness and criticality, in which adequate resource management and signal processing ...
  • Analysis of radio wave propagation for ISM 2.4 GHz wireless sensor networks in inhomogeneous vegetation environments 

    Azpilicueta Fernández de las Heras, Leyre Upna; López Iturri, Peio Upna; Aguirre Gallego, Erik Upna; Mateo Zozaya, Ignacio; Astrain Escola, José Javier Upna; Villadangos Alonso, Jesús Upna; Falcone Lanas, Francisco Javier Upna (MDPI, 2014)   Artículo / Artikulua  OpenAccess
    The use of wireless networks has experienced exponential growth due to the improvements in terms of battery life and low consumption of the devices. However, it is compulsory to conduct previous radio propagation analysis ...
  • Design and performance analysis of wireless body area networks in complex indoor e-Health hospital environments for patient remote monitoring 

    Aguirre Gallego, Erik Upna; López Iturri, Peio Upna; Azpilicueta Fernández de las Heras, Leyre Upna; Rivarés Garasa, Carmen; Astrain Escola, José Javier Upna; Villadangos Alonso, Jesús Upna; Falcone Lanas, Francisco Javier Upna (SAGE, 2016)   Artículo / Artikulua  OpenAccess
    In this article, the design and performance analysis of wireless body area network–based systems for the transmission of medical information readable in an android-based application deployed within complex indoor e-Health ...

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