198,791 research outputs found
Previsión social
No full textFil: Grippo, Atilio. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Buenos Aires, Argentina.Fil: Unsain, Alejandro M.. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Buenos Aires, Argentina
On the convergence of the block nonlinear Gauss-Seidel method under convex constraints
No full textWe give new convergence results for the block Gauss–Seidel method for problems where the feasible set is the Cartesian product of m closed convex sets, under the assumption that the sequence generated by the method has limit points. We show that the method is globally convergent for m=2 and that for m>2 convergence can be established both when the objective function f is componentwise strictly quasiconvex with respect to m−2 components and when f is pseudoconvex. Finally, we consider a proximal point modification of the method and we state convergence results without any convexity assumption on the objective functio
Nonmonotone derivative-free methods for nonlinear equations
No full textIn this paper we study nonmonotone globalization techniques, in connection with iterative derivative-free methods for solving a system of nonlinear equations in several variables. First we define and analyze a class of nonmonotone derivative-free linesearch techniques for unconstrained minimization of differentiable functions. Then we introduce a globalization scheme, which combines nonmonotone watchdog rules and nonmonotone linesearches, and we study the application of this scheme to some recent extensions of the Barzilai-Borwein gradient method and to hybrid stabilization algorithms employing linesearches along coordinate directions. Numerical results on a set of standard test problems show that the proposed techniques can be of value in the solution of large-dimensional systems of equations
Nonmonotone globalization of inexact difference/ Newton-iterative methods for nonlinear equations
No full textAccettato in forma rivista e ridotta su Optimization Methods and Softwar
Introduction to Methods for Nonlinear Optimization
No full textThis book has two main objectives:
• to provide a concise introduction to nonlinear optimization methods, which can be used as a textbook at a graduate or upper undergraduate level;
• to collect and organize selected important topics on optimization algorithms, not easily found in textbooks, which can provide material for advanced courses or can serve as a reference text for self-study and research.
The basic material on unconstrained and constrained optimization is organized into two blocks of chapters:
• basic theory and optimality conditions
• unconstrained and constrained algorithms.
These topics are treated in short chapters that contain the most important results in theory and algorithms, in a way that, in the authors’ experience, is suitable for introductory courses.
A third block of chapters addresses methods that are of increasing interest for solving difficult optimization problems. Difficulty can be typically due to the high nonlinearity of the objective function, ill-conditioning of the Hessian matrix, lack of information on first-order derivatives, the need to solve large-scale problems.
In the book various key subjects are addressed, including: exact penalty functions and exact augmented Lagrangian functions, non monotone methods, decomposition algorithms, derivative free methods for nonlinear equations and optimization problems.
The appendices at the end of the book offer a review of the essential mathematical background, including an introduction to convex analysis that can make part of an introductory course
RELAP5 simulations of the PASI experiment on Containment Wall Condensation
No full textDuring a Design Basis Accident (DBA) or Beyond Design Basis Accident (BDBA) scenario, concerning a Loss Of Coolant Accident (LOCA), the heat extraction from the containment is related to the steam condensation on the cold surfaces, thermosiphon cooling loop and through the connection to the water tank. For these reasons the presence of a Containment Wall Condenser (CWC) as passive system integrated in the plant design, increase the safety margin in accidental scenarios. Within the framework of the EU2020 PASTELS (Passive Systems: Simulating the Thermal-hydraulics with ExperimentaL Studies) project, a series of test comprising the natural circulation phenomena in a low pressure open loop CWC has been performed. The PASI facility, developed by LUT University, has been used in order to identify the physical phenomena and investigate upon the mechanisms to assure the preservation of the safety function of the entire system and further, to support the system codes validation. As partner of the project, ENEA developed the RELAP5/mod3.3 input deck and performed the whole PASI test matrix, to verify the capability of the code to simulate complex loop component, e.g. the sparger, and related thermohydraulic phenomena such as the water flashing and geysering inside the open loop. In the present paper will be shown the post-test calculations performed with RELAP5 of test 1 (quasi-static test) and test 5-10 (reproducing the drain and refill phase of the water storage tank)
Trattato di diritto privato. Le garanzie personali- la fideiussione in generale
No full textCaratteristiche e funzioni delle garanzie. Peculiarità delle garanzie personali. Disciplina codicistica. La fideiussione
Il reclamo contro i provvedimenti del giudice delegato, dalle dichiarazioni di incostituzionalità alla riforma
No full textIl contributo è stato pubblicato negli scritti in onore di Modestino Acone nella SEZIONE VIII
riguardante L’ESECUZIONE CONCORSUALE
Nonmonotone globalization techniques for the Barzilai-Borwein gradient method
No full textIn this paper we propose new globalization strategies for the Barzilai and Borwein gradient method, based on suitable relaxations of the monotonicity requirements. In particular, we define a class of algorithms that combine nonmonotone watchdog techniques with nonmonotone linesearch rules and we prove the global convergence of these schemes. Then we perform an extensive computational study, which shows the effectiveness of the proposed approach in the solution of large dimensional unconstrained optimization problems
Nonmonotone globalization of the finite-difference Newton-GMRES method for nonlinear equations
No full textIn this paper, we study nonmonotone globalization strategies, in connection with the finite-difference inexact Newton-GMRES method for nonlinear equations. We first define a globalization algorithm that combines nonmonotone watchdog rules and nonmonotone derivative-free linesearches related to a merit function, and prove its global convergence under the assumption that the Jacobian is nonsingular and that the iterations of the GMRES subspace method can be completed at each step. Then we introduce a hybrid stabilization scheme employing occasional line searches along positive bases, and establish global convergence towards a solution of the system, under the less demanding condition that the Jacobian is nonsingular at stationary points of the merit function. Through a set of numerical examples, we show that the proposed techniques may constitute useful options to be added in solvers for nonlinear systems of equations. © 2010 Taylor & Francis
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