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Biblioteca Digital do IPB (53.442 recursos)

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DEMAT - Publicações Indexadas em Actas/Proceedings

Mostrando recursos 1 - 17 de 17

  1. Multistart hooke and jeeves filter method for mixed variable optimization

    Fernandes, Florbela P.; Costa, M. Fernanda P.; Fernandes, Edite M.G.P.; Rocha, Ana Maria A. C.
    In this study, we propose an extended version of the Hooke and Jeeves algorithm that uses a simple heuristic to handle integer and/or binary variables and a filter set methodology to handle constraints. This proposal is integrated into a multistart method as a local solver and it is repeatedly called in order to compute different optimal solutions. Then, the best of all stored optimal solutions is selected as the global optimum. The performance of the new method is tested on benchmark problems. Its effectiveness is emphasized by a comparison with other well-known stochastic solvers.

  2. Mathematical model of feet temperature

    Bento, David; Pereira, Ana I.; Monteiro, Fernando C.
    In this work it is consider the problem of finding the best approximation to characterize the feet temperature distribution. For this study it was consider the nonlinear least squares technique, combined with penalty method, to identify the function that approximate better the data obtained through thermographic images. The preliminary results indicate that the best function approximation is based on trigonometric sums.

  3. PSSA : parallel stretched simulated annealing

    Ribeiro, Tiago; Rufino, José; Pereira, Ana I.
    We consider the problem of finding all the global (and some local) minimizers of a given nonlinear optimization function (a class of problems also known as multi-local programming problems), using a novel approach based on Parallel Computing. The approach, named Parallel Stretched Simulated Annealing (PSSA), combines simulated annealing with stretching function technique, in a parallel execution environment. Our PSSA software allows to increase the resolution of the search domains (thus facilitating the discovery of new solutions) while keeping the search time bounded. The software was tested with a set of well known problems and some numerical results are presented.

  4. A comparison between a manual and automatic method to characterize red blood cell trajectories

    Pinto, Diana; Gayubo, Fernando; Pereira, Ana I.; Lima, R.
    The current study proposes an automatic method for the segmentation and tracking of red blood cells (RBCs) flowing through a 100 u m glass capillary. The measurements obtained with the proposed automatic method are compared with a manual tracking method using nonlinear optimization techniques.

  5. Liquid phase stability via global optimization

    Rodrigues, Vânia; Pereira, Ana I.; Ferreira, Olga; Pinho, Simão
    In this work, the Penalty Stretched Simulated Annealing Method and the Multilocal Branch and Bound method were applied to identify the stationary points of the tangent plane distance function defined for the Gibbs energy. The classic excess Gibbs energy Non Random Two Liquid model was used for these studies in several multicomponent mixtures, for which specific numerical difficulties were shown. The preliminary results obtained by applying the methodology developed in this work were satisfactory.

  6. Numerical experiments with nonconvex MINLP problems

    Fernandes, Florbela P.; Costa, Maria F.P.; Fernandes, Edite M.G.P.
    We present a methodology to solve nonconvex Mixed-Integer Nonlinear Programming problems, that combines the Branch-and-Bound and simulated annealing type methods, which was implemented in MATLAB. A set of benchmark functions with simple bounds and different dimensions was used to analyze its practical behaviour. We exhibit computational results showing the good performance of the method.

  7. Red blood cells motion in a glass microchannel

    Pinho, Diana; Pereira, Ana I.; Lima, R.
    The motion of the red blood cells (RBCs) flowing in microvessels and microchannels depend on several effects, such as hematocrit (Hct), geometry, and temperature. According to our knowledge, the effect of the temperature on RBC motion was never investigated at a microscale level. Hence, the aim of the present work is to determine the effect of the temperature on the RBC’s trajectories and to investigate the best approximation of the trajectories through a nonlinear optimization. In vitro human blood was pumped through a 100 mm circular microchannel and by using a confocal micro- PTV system the RBC’s trajectories were measured at different temperatures, i.e., 25◦C...

  8. O software open source como instrumento pedagógico: aplicação prática à econometria e à matemática

    Nunes, Alcina; Balsa, Carlos
    Nowadays, the software open source represents an important teaching resource. However, it is not sufficiently explored in the university teaching methodologies. In subjects with a very specific goal, applied contents and attended by a small number of students, the commercial software is still preferred to the software open source. Aware of this reality, the present paper presents a reflection about the use of software open source in Econometrics and Applied Mathematics. The adoption of two different software programmes – Gretl and Octave – allows presenting a comprehensive set of pedagogical, economical and technical advantages and some observed practical limitations. In practice, the...

  9. Teaching methodologies and open source software: empirical application to econometrics and mathematics

    Nunes, Alcina; Balsa, Carlos
    Nowadays, the software open source represents an important teaching resource. However, it is not sufficiently explored as an higher education teaching methodology. In subjects with a very specific goal, applied contents and attended by a small number of students, the commercial software is still preferred to the open source software. Aware of this reality, this paper presents a reflection about the use of open source software in Applied Econometrics and Mathematics. The adoption of two different software programmes – Gretl and Octave – allows the discussion about a comprehensive set of pedagogical, economical and technical advantages and some observed practical...

  10. Pinto's golden tilings

    Almeida, João Paulo
    We present an one-to-one correspondence between (i) Pinto's golden tilings; (ii) smooth conjugacy classes of golden di eomorphism of the circle that are xed points of renormalization; (iii) smooth conjugacy classes of Anosov difeo- morphisms, with an invariant measure absolutely continuous with respect to the Lebesgue measure, that are topologically conjugated to the Anosov au- tomorphism G(x; y) = (x + y; x); (iv) solenoid functions. As we will explain, the solenoid functions give a parametrization of the in nite dimensional space consisting of the mathematical objects described in the above equivalences.

  11. Motion of red blood cells in a glass microchannel: a global optimization approach

    Pinho, Diana; Pereira, Ana I.; Lima, R.
    Este artigo também deve ser anexado ao Departamento Tecnologia Mecânica, docente Rui Alberto Madeira Macedo Lima.

  12. Constrained multi-global optimization using a penalty stretched simulated annealing framework

    Pereira, Ana I.; Fernandes, Edite M.G.P.
    This paper presents a new simulated annealing algorithm to solve constrained multi-global optimization problems. To compute all global solutions in a sequential manner, we combine the function stretching technique with the adaptive simulated annealing variant. Constraint-handling is carried out through a nondifferentiable penalty function. To benchmark our penalty stretched simulated annealing algorithm we solve a set of well-known problems. Our preliminary numerical results show that the algorithm is promising.

  13. On a reduction line search filter method for nonlinear semi-infinite programming problems

    Pereira, Ana I.; Fernandes, Edite M.G.P.
    In this paper, a reduction-type method combined with a line search filter method to solve nonlinear semi-infinite programming problems is presented. The algorithm uses the simulated annealing method equipped with a function stretching technique to compute the maximizers of the constraint, and a penalty technique to solve the reduced finite optimization problem. The filter method is used as an alternative to merit functions to guarantee convergence from poor starting points. Preliminary numerical results with a problems test set are shown.

  14. A hyperbolic penalty filter method for semi-infinite programming

    Pereira, Ana I.; Fernandes, Edite M.G.P.
    This paper presents a new reduction-type method for solving semi-infinite programming problems, where the multi-local optimization is carried out with a sequential simulated annealing algorithm, and the finite reduced problem is solved by a penalty technique based on an hyperbolic function. Global convergence is ensured by a line search filter method. Numerical experiments with a set of known problems show that the algorithm is promising.

  15. Numerical experiments with a continuous L-2-exponential merit function for semi-infinite programming

    Pereira, Ana I.; Fernandes, Edite M.G.P.
    Here, we present some numerical experiments with a reduction method for solving nonlinear semi-infinite programming (SIP) problems. The method relies on a line search technique to ensure a sufficient decrease of a L_2-exponential merit function. The proposed merit function is continuous for SIP and improves the algorithm efficiency when compared with other previously tested merit functions. A comparison with other reduction methods is also included.

  16. Overview on mixed integer nonlinear programming problems

    Fernandes, Florbela P.; Costa, Maria F.P.; Fernandes, Edite M.G.P.
    Many optimization problems involve integer and continuous variables that can be modeled as mixed integer nonlinear programming (MINLP) problems. This has led to a wide range of applications, in particular in some engineering areas. Here, we provide a brief overview on MINLP, and present a simple idea for a future nonconvex MINLP solution technique.

  17. Recognition of graphs with convex quadratic stability number

    Pacheco, Maria F.; Cardoso, Domingos M.
    A stable set of a graph is a set of mutually non-adjacent vertices. The determination of a maximum size stable set, which is called maximum stable set, and the determination of its size, which is called stability number, are central combinatorial optimization problems. However, given a nonnegative integer k, to determine if a graph G has a stable set of size k is NP-complete. In this paper we deal with graphs for which the stability number can be determined by solving a convex quadratic programming problem. Such graphs were introduced in [13] and are called graphs with convex-QP stability number....

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