Takéhiko Nakama¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.4, pp. 233-242, 2009, DOI:10.3970/icces.2009.009.233

Abstract Random noise perturbs objective functions in a variety of practical optimization problems, and genetic algorithms (GAs) have been widely proposed as an effective optimization tool for dealing with noisy objective functions. In this paper, we investigate GAs applied to objective functions that are perturbed by multiple sources of additive and multiplicative noise that each take on finitely many values. We reveal the convergence properties of GAs by constructing and analyzing a Markov chain that explicitly models the evolution of the algorithms in noisy environments. Our analysis shows that this Markov chain is indecomposable; it has only one positive recurrent communication… More >

R.M.A. Marretta¹, C. Orlando¹, M. Carley²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.4, pp. 225-232, 2009, DOI:10.3970/icces.2009.009.225

Abstract A propeller low noise design procedure based on boundary integral equation is presented. The aerodynamic field is computed via a potential-based boundary element method for lifting body while the aeroacoustic emitted field is calculated on the basis of the Ffowcs Williams-Hawkings equation. Families of airfoils sections are aerodynamically processed to select the ones that meet the requested performance. Successively, the airfoil sections characterized by the lowest noise emission, among the previously selected ones, are chosen to built the propeller blade. Eventually the whole propeller aeroacoustic performances are analyzed. More >

Keerasut Suttanarak¹, Nirut Naksuk², Jarruwat Charoensuk¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 87-88, 2009, DOI:10.3970/icces.2009.010.087

Abstract The water management in Proton Exchange Membrane (PEMFC) is crucial in operating PEMFC system concerning water balance between electrode and membrane. Improper cell humidification might lead to drying or flooding of the electrodes, which degrades cell performance. In this research, effects of gas humidification are studied to aid a system designer in achieving the optimal condition of fuel cell system. The investigation takes into account the conservation of mass, momentum, energy and species as well as the water transport equations including electro-osmotic drag and back diffusion through numerical simulation. More >

Chih-Chang Chang, Ruey-Jen Yang¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 77-86, 2009, DOI:10.3970/icces.2009.010.077

Abstract This paper presents a theoretical investigation into chaotic mixing in low Reynolds number electro-osmotic flows. In this mixing system, the primary flow is the plug-like electro-osmotic flow contributed by the permanent surface charge at the wall, and the secondary electro-osmotic flows (or electro-osmotic recirculating rolls) contributed by the field-effect-induced surface charge act as the perturbed flow. By time-periodic switching two different secondary electro-osmotic flows, it makes streamlines to cross at successive intervals and results in chaotic mixing. Dynamic system techniques such as Poincaré map and finite-time Lyapunov exponent analyses are employed to describe the behaviors of particle motion in this… More >

T. Tsutsui¹, H. Obiya¹, K. Ijima¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 71-76, 2009, DOI:10.3970/icces.2009.010.071

Abstract This study shows an algorithm, which solves the contact phenomenon without friction with large deformation for plane frame structures. Particularly, the study mentions about a technique for the case when contact node slide to the next-door element from edge of the contact element. The technique is to use the re-division and uniting of the element, in order to avoid the computational unstable territory around the edge of the contact element. Furthermore the authors consider about unstable territory of the contact point by some numerical examples. More >

Tae Soo Kim¹, Pa Ul Mun¹, Myung Kuk Lee¹, Jae Soo Kim^1,2

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 65-70, 2009, DOI:10.3970/icces.2009.010.065

Abstract This article has no abstract. More >

Hong-Ching Her¹, Jin H. Huang¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 55-56, 2009, DOI:10.3970/icces.2009.010.055

Abstract To play melodious sound, a microspeaker in a cellular phone needs to generate wide, smooth sound-pressure-level distribution over the mid-frequency spectrum, ranging from 600 Hz to 10 kHz. In this paper, parametric study is carried out to investigate the effect of various design parameters on the sound-pressure-level distribution. The electro-mechano-acoustical analogous approach is applied to simulate the sound-pressure-level. Also, experiments are conducted for verifications. Discussions about each role of the design parameters are addressed to improve the overall sound-pressure-level performance over the mid-frequency spectrum. More >

Dongwoo Sohn¹, Jae Hyuk Lim², Young-Sam Cho³, Seyoung Im¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 53-54, 2009, DOI:10.3970/icces.2009.010.053

Abstract A novel multiscale finite element (FE) scheme is proposed for a simulation of crack propagation in the heterogeneous media including randomly distributed microstructures, such as voids, rigid fibers. A fine scale mesh is employed to capture the singularity of the crack tip and the effect of microstructures at the vicinity of crack tip. On the other hand, a region far from the crack tip is composed of coarse scale mesh, wherein the effect of the microstructures is averaged through the homogenization theory. An interface between the fine scale mesh and the coarse scale mesh is connected by variable-node finite elements… More >

Youngmin Lee, Jae Shin Park, Seyoung Im

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 51-52, 2009, DOI:10.3970/icces.2009.010.051

Abstract We study energetics and mobility of dislocations in silicon crystal in atomistic scale. The electronic structure of silicon affects its dynamics, so that it is analyzed with tight-binding method for high accuracy, emerged as a useful method for studying structural and dynamical properties of covalent systems. The tight biding potential used for silicon crystalline is the one of GSP known as a transferable potential. Due to the nature of rare events, the analysis is executed by action-derived molecular dynamics (ADMD) calculations. The changes of the system energy due to dislocation glide are explored with a view to finding the Peierls… More >

S. M. Beden¹, S. Abdullah¹, A. K. Ariffin¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.10, No.2, pp. 41-50, 2009, DOI:10.3970/icces.2009.010.041

Abstract Fatigue crack growth as consequence of service loads depends on many different contributing factors. This paper describes the fatigue crack growth behavior of metallic materials under cyclic loading towards standardizing the fatigue crack studies on metallic materials. For the simulation purpose, three points bend (TPB) with span to width ratio 8:1 and compact tension (CT) specimens geometry were used. There are many factors affecting the fatigue crack growth in structures, such as fatigue crack growth model, stress ratio, aspect ratio and type of geometry. The behavior of such cases is shown using different fatigue crack models (Paris, Forman and Austen).… More >