Pub Date : 2012-01-01DOI: 10.1590/S1807-03022012000100002
M. Bortoloti, J. K. Filho
In this work, a consistent stabilized mixed finite element formulation for incompressible pseudoplastic fluid flows governed by the Sisko constitutive equation is mathematically analysed. This formulation is constructed by adding least-squares of the governing equations and of the incompressibility constraint, with discontinuous pressure approximations, allowing the use of same order interpolations for the velocity and the pressure. Numerical results are presented to confirm the mathematical stability analysis. Mathematical subject classification: Primary: 65M60; Secondary: 65N30.
{"title":"A stabilized finite element method to pseudoplastic flow governed by the Sisko relation","authors":"M. Bortoloti, J. K. Filho","doi":"10.1590/S1807-03022012000100002","DOIUrl":"https://doi.org/10.1590/S1807-03022012000100002","url":null,"abstract":"In this work, a consistent stabilized mixed finite element formulation for incompressible pseudoplastic fluid flows governed by the Sisko constitutive equation is mathematically analysed. This formulation is constructed by adding least-squares of the governing equations and of the incompressibility constraint, with discontinuous pressure approximations, allowing the use of same order interpolations for the velocity and the pressure. Numerical results are presented to confirm the mathematical stability analysis. Mathematical subject classification: Primary: 65M60; Secondary: 65N30.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"58 1","pages":"19-35"},"PeriodicalIF":2.6,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85885410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-01-01DOI: 10.1590/S1807-03022012000100007
Z. Avazzadeh, M. Heydari
In this paper, an efficient method is presented for solving two dimensional Fredholm and Volterra integral equations of the second kind. Chebyshev polynomials are applied to approximate a solution for these integral equations. This method transforms the integral equation to algebraic equations with unknown Chebyshev coefficients. The high accuracy of this method is verified through some numerical examples. Mathematical subject classification: 65R20, 41A50, 41A55, 65M70.
{"title":"Chebyshev polynomials for solving two dimensional linear and nonlinear integral equations of the second kind","authors":"Z. Avazzadeh, M. Heydari","doi":"10.1590/S1807-03022012000100007","DOIUrl":"https://doi.org/10.1590/S1807-03022012000100007","url":null,"abstract":"In this paper, an efficient method is presented for solving two dimensional Fredholm and Volterra integral equations of the second kind. Chebyshev polynomials are applied to approximate a solution for these integral equations. This method transforms the integral equation to algebraic equations with unknown Chebyshev coefficients. The high accuracy of this method is verified through some numerical examples. Mathematical subject classification: 65R20, 41A50, 41A55, 65M70.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"1 1","pages":"127-142"},"PeriodicalIF":2.6,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89595684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-01-01DOI: 10.1590/S1807-03022012000100003
V. Costanza, M. I. Troparevsky, P. Rivadeneira
An iterative method based on Picard's approach to ODEs' initial-value problems is proposed to solve first-order quasilinear PDEs with matrix-valued unknowns, in particular, the recently discovered variational PDEs for the missing boundary values in Hamilton equations of optimal control. As illustrations the iterative numerical solutions are checked against the analytical solutions to some examples arising from optimal control problems for nonlinear systems and regular Lagrangians in finite dimension, and against the numerical solution obtained through standard mathematical software. An application to the (n + 1)-dimensional variational PDEs associated with the n-dimensional finite-horizon time-variant linear-quadratic problem is discussed, due to the key role the LQR plays in two-degrees-of freedom control strategies for nonlinear systems with generalized costs. Mathematical subject classification: Primary: 35F30; Secondary: 93C10.
{"title":"Numerical solution of the variational PDEs arising in optimal control theory","authors":"V. Costanza, M. I. Troparevsky, P. Rivadeneira","doi":"10.1590/S1807-03022012000100003","DOIUrl":"https://doi.org/10.1590/S1807-03022012000100003","url":null,"abstract":"An iterative method based on Picard's approach to ODEs' initial-value problems is proposed to solve first-order quasilinear PDEs with matrix-valued unknowns, in particular, the recently discovered variational PDEs for the missing boundary values in Hamilton equations of optimal control. As illustrations the iterative numerical solutions are checked against the analytical solutions to some examples arising from optimal control problems for nonlinear systems and regular Lagrangians in finite dimension, and against the numerical solution obtained through standard mathematical software. An application to the (n + 1)-dimensional variational PDEs associated with the n-dimensional finite-horizon time-variant linear-quadratic problem is discussed, due to the key role the LQR plays in two-degrees-of freedom control strategies for nonlinear systems with generalized costs. Mathematical subject classification: Primary: 35F30; Secondary: 93C10.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"57 1","pages":"37-58"},"PeriodicalIF":2.6,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90018351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-01-01DOI: 10.1590/S1807-03022012000100009
Rajesh Kumar, T. Kansal
In the present article, we construct the fundamental solution of system of differential equations in the theory of micropolar thermoelastic diffusion with voids in case of steady oscillations in terms of elementary functions. Some basic properties of the fundamental solution are also established. Some special cases are also discussed. Mathematical subject classification: 74Bxx, 74Fxx, 74Hxx.
{"title":"Fundamental solution in the theory of micropolar thermoelastic diffusion with voids","authors":"Rajesh Kumar, T. Kansal","doi":"10.1590/S1807-03022012000100009","DOIUrl":"https://doi.org/10.1590/S1807-03022012000100009","url":null,"abstract":"In the present article, we construct the fundamental solution of system of differential equations in the theory of micropolar thermoelastic diffusion with voids in case of steady oscillations in terms of elementary functions. Some basic properties of the fundamental solution are also established. Some special cases are also discussed. Mathematical subject classification: 74Bxx, 74Fxx, 74Hxx.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"67 1","pages":"169-189"},"PeriodicalIF":2.6,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84068601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-01-01DOI: 10.1590/S1807-03022012000100005
Chao-Ping Chen, C. Mortici
Let ψ denote the psi (or digamma) function. We determine the values of theparameters p, q and r such that ψ(n) ≈ ln(n + p) - is the best approximations. Also, we present closer bounds for psi function, which sharpens some known results due to Muqattash and Yahdi, Qi and Guo, and Mortici. Mathematical subject classification: 33B15, 26D15.
{"title":"Sharpness of Muqattash-Yahdi problem","authors":"Chao-Ping Chen, C. Mortici","doi":"10.1590/S1807-03022012000100005","DOIUrl":"https://doi.org/10.1590/S1807-03022012000100005","url":null,"abstract":"Let ψ denote the psi (or digamma) function. We determine the values of theparameters p, q and r such that ψ(n) ≈ ln(n + p) - is the best approximations. Also, we present closer bounds for psi function, which sharpens some known results due to Muqattash and Yahdi, Qi and Guo, and Mortici. Mathematical subject classification: 33B15, 26D15.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"2 1","pages":"85-93"},"PeriodicalIF":2.6,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78839936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-01-01DOI: 10.1590/S1807-03022012000200004
Shivendra G. Tewari
Calcium plays a significant role in a number of cellular processes, like muscle contraction, gene expression, synaptic plasticity, signal transduction, but the significance of calcium oscillations (CaOs) is not yet completely understood in most of the cell types. It is a widely accepted fact that CaOs are a frequency encoded signal that allows a cell to use calcium as a second messenger while avoiding its toxic effects. These intracellular CaOs are primarily driven by some agonist-dependent pathways or fluctuations in membrane potential. The present mathematical model is of the latter type. The model incorporates expression for all major intracellular ionic species and membrane proteins. Especially, it integrates the coupling effect of sodium pump and Na+ / Ca2+ exchanger over CaOs. By varying sodium pump current, it is found that, sodium pump is a key player in modulating intracellular CaOs. The model predicts that the sodium pump can play a decisive role in regulating intercellular cell signaling process. The present study forms the basis for sodium pump controlled intercellular signaling process and requires further experimental verification. Mathematical subject classification: 34M10, 92C20.
{"title":"The sodium pump controls the frequency of action-potential-induced calcium oscillations","authors":"Shivendra G. Tewari","doi":"10.1590/S1807-03022012000200004","DOIUrl":"https://doi.org/10.1590/S1807-03022012000200004","url":null,"abstract":"Calcium plays a significant role in a number of cellular processes, like muscle contraction, gene expression, synaptic plasticity, signal transduction, but the significance of calcium oscillations (CaOs) is not yet completely understood in most of the cell types. It is a widely accepted fact that CaOs are a frequency encoded signal that allows a cell to use calcium as a second messenger while avoiding its toxic effects. These intracellular CaOs are primarily driven by some agonist-dependent pathways or fluctuations in membrane potential. The present mathematical model is of the latter type. The model incorporates expression for all major intracellular ionic species and membrane proteins. Especially, it integrates the coupling effect of sodium pump and Na+ / Ca2+ exchanger over CaOs. By varying sodium pump current, it is found that, sodium pump is a key player in modulating intracellular CaOs. The model predicts that the sodium pump can play a decisive role in regulating intercellular cell signaling process. The present study forms the basis for sodium pump controlled intercellular signaling process and requires further experimental verification. Mathematical subject classification: 34M10, 92C20.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"29 1","pages":"283-304"},"PeriodicalIF":2.6,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73853735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-12-12DOI: 10.1590/S1807-03022011000300002
A. Ghorbani, M. Gachpazan, Jafar Saberi-Nadjafi
The original parametric iteration method (PIM) provides the solution of a nonlinear second order boundary value problem (BVP) as a sequence of iterations. Since the successive iterations of the PIM may be very complex so that the resulting integrals in its iterative relation may not be performed analytically. Also, the implementation of the PIM generally leads to calculation of unneeded terms, which more time is consumed in repeated calculations for series solutions. In order to overcome these difficulties, in this paper, a useful improvement of the PIM is proposed. The implementation of the modified method is demonstrated by solving several nonlinear second order BVPs. The results reveal that the new developed method is a promising analytical tool to solve the nonlinear second order BVPs and more promising because it can further be applied easily to solve nonlinear higher order BVPs with highly accurate. Mathematical subject classification: Primary: 34B15; Secondary: 41A10.
{"title":"A modified parametric iteration method for solving nonlinear second order BVPs","authors":"A. Ghorbani, M. Gachpazan, Jafar Saberi-Nadjafi","doi":"10.1590/S1807-03022011000300002","DOIUrl":"https://doi.org/10.1590/S1807-03022011000300002","url":null,"abstract":"The original parametric iteration method (PIM) provides the solution of a nonlinear second order boundary value problem (BVP) as a sequence of iterations. Since the successive iterations of the PIM may be very complex so that the resulting integrals in its iterative relation may not be performed analytically. Also, the implementation of the PIM generally leads to calculation of unneeded terms, which more time is consumed in repeated calculations for series solutions. In order to overcome these difficulties, in this paper, a useful improvement of the PIM is proposed. The implementation of the modified method is demonstrated by solving several nonlinear second order BVPs. The results reveal that the new developed method is a promising analytical tool to solve the nonlinear second order BVPs and more promising because it can further be applied easily to solve nonlinear higher order BVPs with highly accurate. Mathematical subject classification: Primary: 34B15; Secondary: 41A10.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"66 1","pages":"499-515"},"PeriodicalIF":2.6,"publicationDate":"2011-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86867278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-08-31DOI: 10.1590/S1807-03022011000200006
T. Shah, Atlas Khan, A. A. Andrade
This paper introduces novel constructions of cyclic codes using semigroup rings instead of polynomial rings. These constructions are applied to define and investigate the BCH, alternant, Goppa, and Srivastava codes. This makes it possible to improve several recent results due to Andrade and Palazzo [1].
{"title":"Encoding through generalized polynomial codes","authors":"T. Shah, Atlas Khan, A. A. Andrade","doi":"10.1590/S1807-03022011000200006","DOIUrl":"https://doi.org/10.1590/S1807-03022011000200006","url":null,"abstract":"This paper introduces novel constructions of cyclic codes using semigroup rings instead of polynomial rings. These constructions are applied to define and investigate the BCH, alternant, Goppa, and Srivastava codes. This makes it possible to improve several recent results due to Andrade and Palazzo [1].","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"93 1","pages":"349-366"},"PeriodicalIF":2.6,"publicationDate":"2011-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80445613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-07-18DOI: 10.1590/S1807-03022011000200008
Xia Wang, Zhen Guo, Xinyu Song
In this paper, we consider the pest management model with spraying microbial pesticide and releasing the infected pests, and the infected pests have the function similar to the microbial pesticide and can infect the healthy pests, further weaken or disable their prey function till death. By using the Floquet theory for impulsive differential equations, we show that there exists a globally asymptotically stable pest eradication periodic solution when the impulsive period τ τmax. Finally, by means of numerical simulation, we showthatwith the increaseof impulsive period, the system displays complicated behaviors.
{"title":"Dynamical behavior of a pest management model with impulsive effect and nonlinear incidence rate","authors":"Xia Wang, Zhen Guo, Xinyu Song","doi":"10.1590/S1807-03022011000200008","DOIUrl":"https://doi.org/10.1590/S1807-03022011000200008","url":null,"abstract":"In this paper, we consider the pest management model with spraying microbial pesticide and releasing the infected pests, and the infected pests have the function similar to the microbial pesticide and can infect the healthy pests, further weaken or disable their prey function till death. By using the Floquet theory for impulsive differential equations, we show that there exists a globally asymptotically stable pest eradication periodic solution when the impulsive period τ τmax. Finally, by means of numerical simulation, we showthatwith the increaseof impulsive period, the system displays complicated behaviors.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"37 1","pages":"381-398"},"PeriodicalIF":2.6,"publicationDate":"2011-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91101590","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-07-18DOI: 10.1590/S1807-03022011000200009
J. T. Ngnotchouye, M. Herty, S. Steffensen, M. Banda
The treatment of control problems governed by systems of conservation laws poses serious challenges for analysis and numerical simulations. This is due mainly to shock waves that occur in the solution of nonlinear systems of conservation laws. In this article, the problem of the control of Euler flows in gas dynamics is considered. Numerically, two semi-linear approximations of the Euler equations are compared for the purpose of a gradient-based algorithm for optimization. One is the Lattice-Boltzmann method in one spatial dimension and five velocities (D1Q5 model) and the other is the relaxation method. An adjoint method is used. Good results are obtained even in the case where the solution contains discontinuities such as shock waves or contact discontinuities.
{"title":"Relaxation approaches to the optimal control of the Euler equations","authors":"J. T. Ngnotchouye, M. Herty, S. Steffensen, M. Banda","doi":"10.1590/S1807-03022011000200009","DOIUrl":"https://doi.org/10.1590/S1807-03022011000200009","url":null,"abstract":"The treatment of control problems governed by systems of conservation laws poses serious challenges for analysis and numerical simulations. This is due mainly to shock waves that occur in the solution of nonlinear systems of conservation laws. In this article, the problem of the control of Euler flows in gas dynamics is considered. Numerically, two semi-linear approximations of the Euler equations are compared for the purpose of a gradient-based algorithm for optimization. One is the Lattice-Boltzmann method in one spatial dimension and five velocities (D1Q5 model) and the other is the relaxation method. An adjoint method is used. Good results are obtained even in the case where the solution contains discontinuities such as shock waves or contact discontinuities.","PeriodicalId":50649,"journal":{"name":"Computational & Applied Mathematics","volume":"9 1","pages":"399-425"},"PeriodicalIF":2.6,"publicationDate":"2011-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76822981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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