Search results for "optimization"
showing 10 items of 2824 documents
A semi-Lagrangian AMR scheme for 2D transport problems in conservation form
2013
In this paper, we construct a semi-Lagrangian (SL) Adaptive-Mesh-Refinement (AMR) solver for 1D and 2D transport problems in conservation form. First, we describe the a-la-Harten AMR framework: the adaptation process selects a hierarchical set of grids with different resolutions depending on the features of the integrand function, using as criteria the point value prediction via interpolation from coarser meshes, and the appearance of large gradients. We integrate in time by reconstructing at the feet of the characteristics through the Point-Value Weighted Essentially Non-Oscillatory (PV-WENO) interpolator. We propose, then, an extension to the 2D setting by making the time integration dime…
Partial differential equations governed by accretive operators
2012
The theory of nonlinear semigroups in Banach spaces generated by accretive operators has been very useful in the study of many nonlinear partial differential equations Such a theory is fundamentally based in the Crandall-Liggett Theorem and in the contributions of Ph. Benilan. In this paper, after outlining some of the main points of this theory, we present some of the applications to some nonlinear partial differential equations that appear in different fields of Science.
Stability and Finiteness Properties of Medial Axis and Skeleton
2004
The medial axis is a geometric object associated with any bounded open set in \Bbb R^n which has various applications in computer science. We study it from a mathematical point of view. We give some results about its geometrical structure when the open set is subanalytic and we prove that it is stable under C2-perturbations when the open set is bounded by a hypersurface with positive local feature size.
Some common fixed point results for weakly compatible mappings in cone metric type space
2013
In this paper we consider cone metric type spaces which are introduced as a generalization of symmetric and metric spaces by Khamsi and Hussain in 2010. Then we prove several common fixed point for weakly compatible mappings in cone metric type spaces. All results are proved in the settings of a solid cone, without the assumption of continuity of the mappings.
Weak A-frames and weak A-semi-frames
2021
After reviewing the interplay between frames and lower semi-frames, we introduce the notion of lower semi-frame controlled by a densely defined operator $A$ or, for short, a weak lower $A$-semi-frame and we study its properties. In particular, we compare it with that of lower atomic systems, introduced in (GB). We discuss duality properties and we suggest several possible definitions for weak $A$-upper semi-frames. Concrete examples are presented.
A fast hierarchical dual boundary element method for three-dimensional elastodynamic crack problems
2010
In this work a fast solver for large-scale three-dimensional elastodynamic crack problems is presented, implemented, and tested. The dual boundary element method in the Laplace transform domain is used for the accurate dynamic analysis of cracked bodies. The fast solution procedure is based on the use of hierarchical matrices for the representation of the collocation matrix for each computed value of the Laplace parameter. An ACA (adaptive cross approximation) algorithm is used for the population of the low rank blocks and its performance at varying Laplace parameters is investigated. A preconditioned GMRES is used for the solution of the resulting algebraic system of equations. The precond…
Designing the internal reinforcements of a sailing boat using a topology optimization approach
2022
In naval design it is common practice to define an internal regular web frame made of longitudinal elements and transversal sections with the purpose of giving stiffness to the whole structure and, at the same time, promoting lightness. In this work, FEM simulation and Topology Optimization (TO) tools are implemented to present a different approach in placing the reinforcements inside the hull of a sailing dinghy. The methodology proposed in this paper considers as a starting point the volume inside the hull and the deck completely filled with material and the result after the simulations is a free form shape of the sailboat reinforcements. The TO procedure is based on two different input F…
A Computationally Inexpensive Approach in Multiobjective Heat Exchanger Network Synthesis
2010
We consider a heat exchanger network synthesis problem formulated as a multiobjective optimization problem. The Pareto front of this problem is approximated with a new approximation approach and the preferred point on the approximation is found with the interactive multiobjective optimization method NIMBUS. Using the approximation makes the solution process computationally inexpensive. Finally, the preferred outcome on the Pareto front approximation is projected on the actual Pareto front. peerReviewed
Modelling Airlines Competition on Fares and Frequencies of Service by Bi-level Optimization
2011
Abstract The research aims to understand how airlines make operative decisions on fares and frequencies of service in a competitive envi-ronment. A game approach has been developed to model the airlines’ choices in a duopolistic market. In particular, the short haul market for intercity linkages has been investigated. In this segment the air mode is in competition with other ground modes (i.e. road and high speed rail). A bi-level optimization program has been realized. The variables of model are: fares and frequencies of airlines.
A fuzzy programming method for optimization of autonomous logistics objects
2013
Recently several studies have explored the realization of autonomous control in production and logistic operations. In doing so, it has been tried to transmit the merit of decision-making from central controllers with offline decisions to decentralized controllers with local and real-time decision makings. However, this mission has still some drawbacks in practice. Lack of global optimization is one of them, i.e., the lost chain between the autonomous decentralized decisions at operational level and the centralized mathematical optimization with offline manner at tactical and strategic levels. This distinction can be reasonably solved by considering fuzzy parameters in mathematical programm…