Search results for " optimization"

Notice of Violation of IEEE Publication Principles: Robust Delay-Dependent $H_{\infty}$ Control of Uncertain Time-Delay Systems With Mixed Neutral, D…

2011

The problem of robust mode-dependent delayed state feedback H∞ control is investigated for a class of uncertain time-delay systems with Markovian switching parameters and mixed discrete, neutral, and distributed delays. Based on the Lyapunov-Krasovskii functional theory, new required sufficient conditions are established in terms of delay-dependent linear matrix inequalities for the stochastic stability and stabilization of the considered system using some free matrices. The desired control is derived based on a convex optimization method such that the resulting closed-loop system is stochastically stable and satisfies a prescribed level of H∞ performance, simultaneously. Finally, two numer…

Fractional visco-elastic Timoshenko beam from elastic Euler-Bernoulli beam

2014

The Euler–Bernoulli beam theory is well established in such a way that engineers are very confident with the determination of the stress field or deflections of the elastic beam based on this theory. In contrast, Timoshenko theory is not so much used by engineers. However, in some cases, Euler–Bernoulli theory, which neglects the effect of transversal shear deformation, yields unacceptable results. For instance, when dealing with visco-elastic behavior, shear deformations play a fundamental role. Recent studies on the response evaluation of a visco-elastic Euler–Bernoulli beam under quasi-static and dynamic loads have been stressed that for better capturing of the visco-elastic behavior, a …

Influence of the evolutionary optimization parameters on the optimal topology

2016

Topological optimization can be considered as one of the most general types of structural optimization. Between all known topological optimization techniques, the Evolutionary Structural Optimization represents one of the most efficient and easy to implement approaches. Evolutionary topological optimization is based on a heuristic general principle which states that, by gradually removing portions of inefficient material from an assigned domain, the resulting structure will evolve towards an optimal configuration. Usually, the initial continuum domain is divided into finite elements that may or may not be removed according to the chosen efficiency criteria and other parameters like the spee…

THE TOPOLOGY OPTIMIZATION IN THE PRODUCT DESIGN PROCESS

2009

The design process represents, already for a long time now, a very interesting research field for the scientific community that has tried, through its own activity of research and development, to make it faster, more reliable and efficient. Thanks to this continuous development, during the last years, the product design process has suffered a remarkable improvement, both regarding the methodological aspect, become mostly structured, objective and rational, and as regards the helping tools for the design like, for example, the software CAD, FEM, CFD, that have been improved in their efficiency and functionality. In this context, the development of more and more reliable and simple to use met…

TOPOLOGY OPTIMIZATION OF A CONNECTING ROD FOR AN INTERNAL COMBUSTION ENGINE

2009

The topology optimization of a structure is a process that allows to establish if in a point of an assigned domain there should be some material. No assumption is made with regard to the number and the distribution of the contours and the final topology, that can be very different compared to that one initially hypothesized. In this paper a study related to the topology optimization of a connecting rod for an internal combustion engine is presented. The used technique for the optimization is the density (or distribution of material) method. The developed application, besides giving an innovative solution of the topology of the connecting rod with a lower mass in comparison with the initial …

Sustainability and tourist flow networks: a mean field bi-level optimization approach

The widespread acknowledgement of tourism as a strategic pillar for economic growth and development has boosted competitiveness among tourist destinations. This concept has been greatly emphasized during the current COVID-19 pandemic crisis. Nevertheless, the massive presence of tourists imposes the challenge of adopting sustainable tourism practices to balance economic prosperity opportunities with potential threats to the environment and local communities. There are many definitions for sustainability, but the most effective one is ``the capacity to endure'' [Emel et al, 1997]: from an economic perspective this leads to find an equilibrium between short and long-term objectives so that to…

CLUSTERING TOURIST LOCAL SYSTEMS BY VERTEX PARTITIONING AND LOCAL SEARCH

2014

Nonostante l’industria del turismo venga riconosciuta come un settore trainante per l’intera economia di un Paese, a tutt’oggi si registra una mancanza di criteri e metodologie ai fini della localizzazione, promozione e gestione di un Sistema Turistico Locale (STL). A tal fine, nel presente lavoro viene proposto un approccio di tipo quantitativo al problema sia della localizzazione che del dimensionamento ottimale di un STL tenendo conto di criteri e/o vincoli di natura geografica, economica e demografica. Il problema di ottimizzazione è rappresentato su grafo ed è risolto ricorrendo all’algoritmo di ricerca locale di Threshold Accepting (TA). Despite the importance of tourism as a leading …

The Role of Covariance Matrix Forecasting Method in the Performance of Minimum-Variance Portfolios

2014

Providing a more accurate covariance matrix forecast can substantially improve the performance of optimized portfolios. Using out-of-sample tests, in this paper, we evaluate alternative covariance matrix forecasting methods by looking at (1) their forecast accuracy, (2) their ability to track the volatility of the minimum-variance portfolio, and (3) their ability to keep the volatility of the minimum-variance portfolio at a target level. We find large differences between the methods. Our results suggest that shrinkage of the sample covariance matrix improves neither the forecast accuracy nor the performance of minimum-variance portfolios. In contrast, switching from the sample covariance ma…

The Best Hedging Strategy in the Presence of Transaction Costs

2009

Considerable theoretical work has been devoted to the problem of option pricing and hedging with transaction costs. A variety of methods have been suggested and are currently being used for dynamic hedging of options in the presence of transaction costs. However, very little was done on the subject of an empirical comparison of different methods for option hedging with transaction costs. In a few existing studies the different methods are compared by studying their empirical performances in hedging only a plain-vanilla short call option. The reader is tempted to assume that the ranking of the different methods for hedging any kind of option remains the same as that for a vanilla call. The …

Option Pricing and Hedging in the Presence of Transaction Costs and Nonlinear Partial Differential Equations

2008

In the presence of transaction costs the perfect option replication is impossible which invalidates the celebrated Black and Scholes (1973) model. In this chapter we consider some approaches to option pricing and hedging in the presence of transaction costs. The distinguishing feature of all these approaches is that the solution for the option price and hedging strategy is given by a nonlinear partial differential equation (PDE). We start with a review of the Leland (1985) approach which yields a nonlinear parabolic PDE for the option price, one of the first such in finance. Since the Leland's approach to option pricing has been criticized on different grounds, we present a justification of…