20 research outputs found

    Stable Numerical Solutions Preserving Qualitative Properties of Nonlocal Biological Dynamic Problems

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    [EN] This paper deals with solving numerically partial integrodifferential equations appearing in biological dynamics models when nonlocal interaction phenomenon is considered. An explicit finite difference scheme is proposed to get a numerical solution preserving qualitative properties of the solution. Gauss quadrature rules are used for the computation of the integral part of the equation taking advantage of its accuracy and low computational cost. Numerical analysis including consistency, stability, and positivity is included as well as numerical examples illustrating the efficiency of the proposed method.This work has been partially supported by the Ministerio de Economía y Competitividad Spanish grant MTM2017-89664-P.Piqueras-García, MÁ.; Company Rossi, R.; Jódar Sánchez, LA. (2019). Stable Numerical Solutions Preserving Qualitative Properties of Nonlocal Biological Dynamic Problems. Abstract and Applied Analysis. 2019:1-7. https://doi.org/10.1155/2019/5787329S172019Ahlin, A. C. (1962). On Error Bounds for Gaussian Cubature. SIAM Review, 4(1), 25-39. doi:10.1137/1004004Aronson, D. ., & Weinberger, H. . (1978). Multidimensional nonlinear diffusion arising in population genetics. Advances in Mathematics, 30(1), 33-76. doi:10.1016/0001-8708(78)90130-5Berestycki, H., Nadin, G., Perthame, B., & Ryzhik, L. (2009). The non-local Fisher–KPP equation: travelling waves and steady states. Nonlinearity, 22(12), 2813-2844. doi:10.1088/0951-7715/22/12/002Edelman, G. M., & Gally, J. A. (2001). Degeneracy and complexity in biological systems. Proceedings of the National Academy of Sciences, 98(24), 13763-13768. doi:10.1073/pnas.231499798Fakhar-Izadi, F., & Dehghan, M. (2012). An efficient pseudo-spectral Legendre-Galerkin method for solving a nonlinear partial integro-differential equation arising in population dynamics. Mathematical Methods in the Applied Sciences, 36(12), 1485-1511. doi:10.1002/mma.2698FISHER, R. A. (1937). THE WAVE OF ADVANCE OF ADVANTAGEOUS GENES. Annals of Eugenics, 7(4), 355-369. doi:10.1111/j.1469-1809.1937.tb02153.xFurter, J., & Grinfeld, M. (1989). Local vs. non-local interactions in population dynamics. Journal of Mathematical Biology, 27(1), 65-80. doi:10.1007/bf00276081Genieys, S., Volpert, V., & Auger, P. (2006). Pattern and Waves for a Model in Population Dynamics with Nonlocal Consumption of Resources. Mathematical Modelling of Natural Phenomena, 1(1), 63-80. doi:10.1051/mmnp:2006004Genieys, S., Bessonov, N., & Volpert, V. (2009). Mathematical model of evolutionary branching. Mathematical and Computer Modelling, 49(11-12), 2109-2115. doi:10.1016/j.mcm.2008.07.018Hamel, F., & Ryzhik, L. (2014). On the nonlocal Fisher–KPP equation: steady states, spreading speed and global bounds. Nonlinearity, 27(11), 2735-2753. doi:10.1088/0951-7715/27/11/2735Shivanian, E. (2013). Analysis of meshless local radial point interpolation (MLRPI) on a nonlinear partial integro-differential equation arising in population dynamics. Engineering Analysis with Boundary Elements, 37(12), 1693-1702. doi:10.1016/j.enganabound.2013.10.002Tian, C., Ling, Z., & Zhang, L. (2017). Nonlocal interaction driven pattern formation in a prey–predator model. Applied Mathematics and Computation, 308, 73-83. doi:10.1016/j.amc.2017.03.017Apreutesei, N., Bessonov, N., Volpert, V., … Vougalter, V. (2010). Spatial structures and generalized travelling waves for an integro-differential equation. Discrete & Continuous Dynamical Systems - B, 13(3), 537-557. doi:10.3934/dcdsb.2010.13.537Weinberger, H. F. (2002). On spreading speeds and traveling waves for growth and migration models in a periodic habitat. Journal of Mathematical Biology, 45(6), 511-548. doi:10.1007/s00285-002-0169-3Weinberger, H. F., Lewis, M. A., & Li, B. (2007). Anomalous spreading speeds of cooperative recursion systems. Journal of Mathematical Biology, 55(2), 207-222. doi:10.1007/s00285-007-0078-

    Finite Element Method for the One-Dimensional Telegraph Equation

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    A linear telegraph equation with periodic boundary conditions is chosen for a modelproblem in this paper. The model problem is used in order to be illustrated a new finite elementmethod for solving hyperbolic boundary value problems. There are various weak forms of thetelegraph equation that have been in use up to now. An original weak problem related to theproblem of interest is obtained. A detailed multigrid algorithm describing the essence of theconsidered method is developed. Numerical simulations including smoothing of an errorfunction and a graph of an approximate solution are demonstrated. An approximate asymptoticrate of convergence is calculated by applying three successive triangulations and cubic trialfunctions

    Semi-Infinite Structure Analysis with Bimodular Materials with Infinite Element

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    The modulus of elasticity of some materials changes under tensile and compressive states is simulated by constructing a typical material nonlinearity in a numerical analysis in this paper. The meshless Finite Block Method (FBM) has been developed to deal with 3D semi-infinite structures in the bimodular materials in this paper. The Lagrange polynomial interpolation is utilized to construct the meshless shape function with the mapping technique to transform the irregular finite domain or semi-infinite physical solids into a normalized domain. A shear modulus strategy is developed to present the nonlinear characteristics of bimodular material. In order to verify the efficiency and accuracy of FBM, the numerical results are compared with both analytical and numerical solutions provided by Finite Element Method (FEM) in four examples

    Solving Inverse Conductivity Problems In Doubly Connected Domains By the Homogenization Functions of Two Parameters

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    In the paper, we make the first attempt to derive a family of two-parameter homogenization functions in the doubly connected domain, which is then applied as the bases of trial solutions for the inverse conductivity problems. The expansion coefficients are obtained by imposing an extra boundary condition on the inner boundary, which results in a linear system for the interpolation of the solution in a weighted Sobolev space. Then, we retrieve the spatial- or temperature-dependent conductivity function by solving a linear system, which is obtained from the collocation method applied to the nonlinear elliptic equation after inserting the solution. Although the required data are quite economical, very accurate solutions of the space-dependent and temperature-dependent conductivity functions, the Robin coefficient function and also the source function are available. It is significant that the nonlinear inverse problems can be solved directly without iterations and solving nonlinear equations. The proposed method can achieve accurate results with high efficiency even for large noise being imposed on the input data

    Sub-daily precipitation returns levels in ungauged locations: Added value of combining observations with convection permitting simulations

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    Extreme rainfall events trigger natural hazards, including floods and debris flows, posing serious threats to society and the economy. Accurately quantifying extreme rainfall return levels in ungauged locations is crucial for improving flood protection infrastructure and mitigating water-related risks. This paper quantifies the added value of combining rainfall observations with Convection Permitting Model (CPM) simulations to estimate sub-daily extreme rainfall return levels in ungauged locations. We assess the performance of CPM-informed estimates of extreme return level against a traditional interpolation techniques. We find that kriging methods with external drift outperform inverse distance weighting for both traditional and CPM-informed approaches. We then assess the effectiveness of the two methods under different scenarios of station density. At the highest station density (1/196 km2), traditional interpolation methods outperform the CPM-informed method for durations under 6 h. The performance becomes comparable between 6 and 24 h. For lower station densities (1/400 and 1/800 km2), the CPM-informed method outperforms the traditional method, with average reductions in fractional standard error of 24 %, 13 %, and 8 % for return periods of 2, 10 and 50 years, respectively for a rain gauge density of 1/800 km2, and 16 %, 8 %, and 3 % for density of 1/400 km2. Information from CPM simulations can thus be useful for estimating sub-daily extreme rainfall events in ungauged sites, particularly in data-scarce areas in which the density of rain gauges is low

    An interactive meshless cutting model for nonlinear viscoelastic soft tissue in surgical simulators

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    In this paper, we present a novel interactive cutting simulation model for soft tissue based on the meshless framework. Unlike most existing methods that consider the cutting process of soft tissue in an over simplified manner, the presented model is able to simulate the complete cutting process that includes three stages: deformation before cutting open (DBCO), cutting open (CO), and deformation after cutting open (DACO). To characterize the complicated physical and mechanical properties of soft tissue, both nonlinearity and viscoelasticity were incorporated into the equations governing the motion of soft tissue. A line contact model was used for simulating the cutting process after analyzing the two major types of surgical instruments, i.e., scalpel and electrostick. The cutting speed and angle were taken into account in order to improve haptic rendering. Biomechanical tests and simulation experiments verified the validity of the introduced model. Specifically, the displacement vs. cutting force curves can be divided into three segments corresponding to the three stages of the cutting process. The results were also applied in a liver cutting simulating system and satisfactory visual effect and haptic feedback were achieved

    A Meshless LBIE/LRBF Method for Solving the Nonlinear Fisher Equation: Application to Bone Healing

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    A simple Local Boundary Integral Equation (LBIE) method for solving the Fisher nonlinear transient diffusion equation in two dimensions (2D) is reported. The method utilizes, for its meshless implementation, randomly distributed nodal points in the interior domain and nodal points corresponding to a Boundary Element Method (BEM) mesh, at the global boundary. The interpolation of the interior and boundary potentials is accomplished using a Local Radial Basis Functions (LRBF) scheme. At the nodes of global boundary the potentials and their fluxes are treated as independent variables. On the local boundaries, potential fluxes are avoided by using the Laplacian companion solution. Potential gradients are accurately evaluated without RBFs via a LBIE, valid for gradient of potentials. Nonlinearity is treated using the Newton-Raphson scheme. The accuracy of the proposed methodology is demonstrated through representative numerical examples. Fisher equation is solved here via the LBIE/LRBF method in order to predict cell proliferation during bone healing. Cell concentrations and their gradients are numerically evaluated in a 2D model of fractured bone. The results are demonstrated and discussed
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