M. Zaouche, A. Beloula, R. Louali¹, S. Bouaziz², M. Hamerlain³

CMES-Computer Modeling in Engineering & Sciences, Vol.104, No.3, pp. 159-184, 2015, DOI:10.3970/cmes.2015.104.159

Abstract Safety automation of complex mobile systems is a current topic issue in industry and research laboratories, especially in aeronautics. The dynamic models of these systems are nonlinear, Multi-Input Multi-Output (MIMO) and tightly coupled. The nonlinearity resides in the dynamic equations and also in the aerodynamic coefficients’ variability.
This paper is devoted to developing the piloting law based on the combination of the robust differentiator with a dynamic adaptation of the gains and the robust controller via second order sliding mode, by using an aircraft in virtual simulated environments.
To deal with the design of an autopilot controller, we propose… More >

É. Budyn¹, A. Bilagi², V. Subramanian³, A.A. Espinoza Orías⁴, N. Inoue⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.98, No.3, pp. 341-374, 2014, DOI:10.32604/cmes.2014.098.341

Abstract Focal damage such as cartilaginous defects, erosions, micro-fractures, Schmorl nodes and thinning in the human vertebral endplate are thought to contribute to intervertebral disc degeneration by compromising the nutrition transport between the vertebral bone marrow and the disc nucleus pulposus. However, microfractures in the endplate are currently not detectable by conventional clinical radiographic methods. Nonetheless high quality visualisation of the human endplate is possible by means of advanced light microscopy and appropriate staining. The objective of this study focuses on efficient and inexpensive multi-scale protocols to prepare the surfaces of human endplate specimens for morphometric characterisations at the tissue and… More >

Jia Dongyao^1,2, Zhu Huaihua¹, Ai Yanke¹, Zou Shengxiong¹

CMES-Computer Modeling in Engineering & Sciences, Vol.103, No.6, pp. 411-427, 2014, DOI:10.3970/cmes.2014.103.411

Abstract The existing study on the image segmentation methods based on the image of vehicle lights is insufficient both at home and abroad, and its segmentation efficiency and accuracy is low as well. On the basis of the analysis of the regional characteristics of vehicle lights and a level set model, an image segmentation method for complex vehicle lights based on adaptive significance level set contour model is proposed in this paper. Adaptive positioning algorithm of the significant initial contour curve based on two-dimensional convex hull is designed to obtain the initial position of evolution curve, thus the adaptive ability of… More >

N Pimprikar¹, J Teresa², D Roy^1,3, R M Vasu⁴, K Rajan⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.92, No.1, pp. 33-61, 2013, DOI:10.3970/cmes.2013.092.033

Abstract Nearly pollution-free solutions of the Helmholtz equation for k-values corresponding to visible light are demonstrated and verified through experimentally measured forward scattered intensity from an optical fiber. Numerically accurate solutions are, in particular, obtained through a novel reformulation of the H1 optimal Petrov-Galerkin weak form of the Helmholtz equation. Specifically, within a globally smooth polynomial reproducing framework, the compact and smooth test functions are so designed that their normal derivatives are zero everywhere on the local boundaries of their compact supports. This circumvents the need for a priori knowledge of the true solution on the support boundary and relieves the… More >

K. Lee¹, C.T. Wu², G.V. Clarke³, S.W. Lee⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.1, pp. 109-130, 2008, DOI:10.3970/cmes.2008.033.109

Abstract A geometrically nonlinear finite element analysis of a low areal density composite space reflector is conducted under static conditions and the results are compared with independently carried out experimental data. The finite element analysis is based on an assumed strain formulation of a geometrically nonlinear nine-node solid shell element. Numerical results are in good agreement with experimental data. This demonstrates the effectiveness of the present solid shell element approach when applied to the analysis of highly flexible space structures. The results of numerical analysis and the experimental data reported in the present paper provide a benchmark for future investigations on… More >

D.M.S. Albuquerque¹, J.M.C. Pereira¹, J.C.F. Pereira^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.72, No.4, pp. 337-366, 2011, DOI:10.3970/cmes.2011.072.337

Abstract A numerical study of fluid-structure interaction is presented for the analysis of viscous flow over a resonant membrane airfoil in hovering flight. A flexible membrane moving with a prescribed stroke period was naturally excited to enter into 1st, 2nd and 3rd mode of vibration according to the selected membrane tension. The Navier-Stokes equations were discretized on a moving body unstructured grid using the finite volume method. The instantaneous membrane position was predicted by the 1D unsteady membrane equation with input from the acting fluid flow forces. Following initial validation against reported rigid airfoils predictions, the model is applied to the… More >

Yuta Kitamura¹, Noriyuki Miyazaki¹, Takahito Kumazaki², Naoto Nagakura³, Yasuhiro Hashimoto³, Isao Masada³

CMES-Computer Modeling in Engineering & Sciences, Vol.68, No.2, pp. 151-166, 2010, DOI:10.3970/cmes.2010.068.151

Abstract CaF₂ single crystal is used as high performance optical elements. We developed an analysis system for simulating birefringence of CaF₂ single crystal used as a chamber window of a gas laser light source. The analysis system consists of a stress analysis and a birefringence analysis. In the stress analysis, the finite element method was applied to obtain the mechanical stress caused by a window holder and gas pressure. In the birefringence analysis, the photo-elastic effect gives the change of refractive indices, from which the optical path difference and the fast axis are calculated by using the average stress method. The… More >

Che-Wun Hong^1,2, Chia-Yun Tsai¹

CMES-Computer Modeling in Engineering & Sciences, Vol.67, No.2, pp. 79-94, 2010, DOI:10.3970/cmes.2010.067.079

Abstract This paper describes the quantum mechanical simulation on the photonic properties of group-III nitride clusters, whose bulk types are common materials for light emitting diodes (LEDs). In order to emit different colors of light using the same semiconductor materials, it is possible to vary the band gap by controlling the quantum dot sizes or doping a third atom theoretically. Density functional theory (DFT) calculations are performed to analyze a set of binary (GaN)_n (3≤n≤32) and ternary In_xGa_1-xN (0≤x≤0.375) clusters to study their photonic characteristics. The ground state structures are optimized to calculate the binding energies using the time-independent DFT. Then… More >

Mahdi Izadi¹, Mohd Zainal Abidin Ab. Kadir¹

CMES-Computer Modeling in Engineering & Sciences, Vol.67, No.1, pp. 1-12, 2010, DOI:10.3970/cmes.2010.067.001

Abstract Evaluation of electric field due to indirect lightning strike is an interesting subject. Calculation of electric and magnetic fields in time domain with the consideration of ground conductivity effect in the shortest possible time is an important objective. In this paper, using dipole method, Maxwell's equation and Cooray-Rubinstein formula, a new method for calculation of electric field in time domain is proposed. In addition, this proposed algorithm can also be used to evaluate the effect at the far distance cases of observation point from lightning channel. More >

J.M.C.Pereira¹, N.A.R.Maia¹, J.C.F.Pereira¹

CMES-Computer Modeling in Engineering & Sciences, Vol.49, No.2, pp. 113-142, 2009, DOI:10.3970/cmes.2009.049.113

Abstract We present a 2D incompressible Navier-Stokes numerical simulation of a virtual model of an elliptic, or flat plate, foil in hovering flight configuration. Computations obtained with a general purpose solver were validated against reference data on forward flapping flight, normal or dragonfly hovering. The moving mesh technique allows airfoil translation and angular mesh movement accompaining the airfoil stroke motion. Close to the ground the mesh deforms to occupy the narrow computational domain formed between the airfoil and the ground. Computations have been carried out for some parameters, including the distances h between the foil center and the surface, h/c =… More >