Emerald | Engineering Computations

Neural Network Hysteresis Modeling with an Improved Preisach Model for Piezoelectric Actuator

Weiping Guo, Diantong Liu, Wei Wang — 2012-01-20 00:00:00.0

Abstract

Purpose - A neural network hysteresis model is realized with an improved Preisach model to predict the output of piezoelectric actuator.Design/methodology/approach - Firstly the improved Preisach model is given and analyzed in detail. Secondly a neural network is designed to approximate the hysteresis model that is described by a two-to-one mapping relation for the piezoelectric actuators. Finally some experiments are carried out and the results show the validity for predicting the output of hysteresis in piezoelectric actuators.Findings - This work is supported by Research Award Fund for Outstanding Middle-aged and Young Scientist of Shandong Province (under Grant No.BS2009DX021), a Project of Shandong Province Higher Educational Science and Technology Program (under Grant No.J08LJ16).Originality/value - A neural network hysteresis model is realized with an improved Preisach model to predict the output of piezoelectric actuator.

Design and Optimization of Microstructure of Auxetic Materials

Akbar Javadi, Asaad Faramarzi, Raziyeh Farmani — 2012-03-30 00:00:00.0

Abstract

Purpose - Auxetic materials differ from conventional materials by the manner in which they respond to stretching; they tend to get fatter when stretched, resulting in a negative Poisson’s ratio. This paper presents a numerical methodology for design of microstructure of 2D and 3D auxetic materials with a wide range of different negative Poisson’s ratios.Design/methodology/approach - The proposed methodology is based on a combination of finite element method and a genetic algorithm. The problem is formulated as an optimization problem of finding microstructures with prescribed behavioral requirements. Different microstructures are generated and evolved using the genetic algorithm and the behavior of each microstructure is analyzed using the finite element method to evaluate its fitness in competition with other generated structures.Findings - Numerical examples show that it is possible to design a large number of new auxetic materials, each with a different value of negative Poisson’s ratio.Originality/value - The proposed methodology can be used as an effective method to tailor new materials with prescribed values of negative (or positive) Poisson’s ratio. The methodology can also be used to optimize other material properties.

Application of homotopy perturbation and numerical methods to the magneto-micropolar fluid flow in the presence of radiation

Yasir Khan — 2012-03-30 00:00:00.0

Abstract

Purpose - This paper reports the effect of radiation on flow of a magneto-micropolar fluid past a continuously moving plate with suction and blowing. The governing equations are transformed into dimensionless nonlinear ordinary differential equations by similarity transformation. Analytical technique namely the homotopy perturbation method combining with Pade´ approximants and finite difference method are used to solve dimensionless non-linear ordinary differential equations. The skin friction coefficient and local Nusselt numbers are also calculated. Beside this, the comparison of the analytical solution with numerical solution is illustrated by the graphs for different values of dimensionless pertinent parameters. Design/methodology/approach - This paper reports the effect of radiation on flow of a magneto-micropolar fluid past a continuously moving plate with suction and blowing. The governing equations are transformed into dimensionless nonlinear ordinary differential equations by similarity transformation. Analytical technique namely the homotopy perturbation method combining with Pade´ approximants and finite difference method are used to solve dimensionless non-linear ordinary differential equations. The skin friction coefficient and local Nusselt numbers are also calculated. Beside this, the comparison of the analytical solution with numerical solution is illustrated by the graphs for different values of dimensionless pertinent parameters. Findings - This paper reports the effect of radiation on flow of a magneto-micropolar fluid past a continuously moving plate with suction and blowing. The governing equations are transformed into dimensionless nonlinear ordinary differential equations by similarity transformation. Analytical technique namely the homotopy perturbation method combining with Pade´ approximants and finite difference method are used to solve dimensionless non-linear ordinary differential equations. The skin friction coefficient and local Nusselt numbers are also calculated. Beside this, the comparison of the analytical solution with numerical solution is illustrated by the graphs for different values of dimensionless pertinent parameters. Originality/value - This paper reports the effect of radiation on flow of a magneto-micropolar fluid past a continuously moving plate with suction and blowing. The governing equations are transformed into dimensionless nonlinear ordinary differential equations by similarity transformation. Analytical technique namely the homotopy perturbation method combining with Pade´ approximants and finite difference method are used to solve dimensionless non-linear ordinary differential equations. The skin friction coefficient and local Nusselt numbers are also calculated. Beside this, the comparison of the analytical solution with numerical solution is illustrated by the graphs for different values of dimensionless pertinent parameters.

Experimental Study on Sound Radiation Time-frequency Characteristics of Double Cylindrical Shell Based on EMD

Fang Ji, Xiong-liang Yao, A-man Zhang, Xi Ye — 2012-01-18 00:00:00.0

Abstract

Purpose - Laying the acoustic decoupling material on the surface of underwater structures is an effective noise reduction technology. The underwater sound radiation experiment of finite stiffened double cylindrical shell with separate-sound and decoupled tile is done in order to find out the most effective laying condition.Design/methodology/approach - The segmentation power function interpolation method and vertex extreme value envelope continuation method are introduced into basic theory of EMD. The original measured sound pressure signals are decomposed to Intrinsic Mode Function group through EMD, and the high-frequency components are filtered out. Because the mechanical noise of submarine is mainly at low frequency, the IMFs in low frequency are researched through power spectrum analysis. The noise reduction effects of different separate-sound and decoupled tile laying conditions are compared.Findings - The sound pressure signal components’ amplitudes, periods and phases are obtained through EMD. The test data shows that the double cylindrical shell entirely covered with separate-sound and decoupled tile is the most effective laying conditions in noise reduction.Originality/value - With reference to the case study, this is believed to be the first application of the EMD in sound radiation time-frequency characteristics of double cylindrical shell. The evaluation of separate-sound and decoupled tile laying conditions is of great importance of engineering application.

On the design and implementation of parallel finite element approximate inverses using POSIX threads on multicore systems

2012-03-30 00:00:00.0

Abstract

Purpose - To propose novel parallel computational techniques for the parallelization of explicit finite element generalized approximate inverse methods, based on Portable Operating System Interface for UniX (POSIX) Threads, for multicore systems.Design/methodology/approach - Our main motive for the derivation of the new Parallel Generalized Approximate Inverse Finite Element Matrix algorithmic techniques is that they can be efficiently used in conjunction with explicit preconditioned conjugate gradient - type schemes on multicore systems. The proposed parallelization technique of the Optimized Banded Generalized Approximate Inverse Finite Element Matrix (OBGAIFEM) algorithm is achieved based on the concept of the "fish bone" approach with the use of a thread pool pattern. Theoretical estimates on the computational complexity of the parallel generalized approximate inverse finite element matrix algorithmic techniques are also derived.Findings - Application of the proposed method on a two dimensional boundary value problem is discussed and numerical results are given on a multicore system using POSIX Threads. These results tend to become optimum and are favorably compared to corresponding results from multiprocessor systems as presented in a recent publication, (Gravvanis et al., 2010).Research limitations/implications - Further parallel algorithmic techniques will be investigated in order to improve the speedups and the computational complexity of the parallel explicit finite element generalized approximate inverse preconditioning.Originality/value - The proposed parallel explicit finite element generalized approximate inverse preconditioning, using approximate factorization and approximate inverse algorithms, is an efficient computational method that is valuable for computer scientists and for scientists and engineers in engineering computations.