Wenjie Yu, Xunbo Li, Hang Yang, Bo Huang

Intelligent Automation & Soft Computing, Vol.24, No.2, pp. 367-376, 2018, DOI:10.1080/10798587.2017.1294873

Abstract This paper studies how to deploy relay nodes into traditional wireless sensor networks with constraint aiming to simultaneously optimize two important factors; average energy consumption and average network reliability. We consider tackling this multi-objective (MO) optimization problem with three metaheuristics, which employ greatly different evolutional strategies, and aim at an in-depth analysis of different performances of these metaheuristics to our problem. For this purpose, a statistical procedure is employed to analyse the results for confidence, in consideration of two MO quality metrics; hypervolume and coverage of two sets. After comprehensive analysis of the results, it is concluded that NSGA-II provides… More >

Haitao Luo¹, Jia Fu¹, Rong Chen¹, Peng Wang²

Intelligent Automation & Soft Computing, Vol.25, No.4, pp. 855-864, 2019, DOI:10.31209/2019.100000089

Abstract Space payloads which installed on spacecraft such as satellites and airships are usually experienced random vibrations and low-frequency sinusoidal vibrations during launching. In this paper, a space payload cabinet is introduced, and the damping design is carried out by applying constrained viscoelastic damping layer to the surfaces of the cabinet to ensure that the space payloads can withstand the above-mentioned mechanical environmental conditions. A reliable connection between the space payload cabinet and the shaking table is achieved through the vibration test fixture. The basic requirements for the function and design of the vibration test fixture are presented. A method for… More >

Davide Piovesan^{1, *}, Roberto Bortoletto²

CMES-Computer Modeling in Engineering & Sciences, Vol.123, No.1, pp. 23-47, 2020, DOI:10.32604/cmes.2020.09231

Abstract Exoskeletons are designed to control the forces exerted during the physical coupling between the human and the machine. Since the human is an active system, the control of an exoskeleton requires coordinated action between the machine and the load so to obtain a reciprocal adaptation. Humans in the control loop can be modeled as active mechanical loads whose stiffness is continuously changing. The direct measurement of human stiffness is difficult to obtain in real-time, thus posing a significant limitation to the design of wearable robotics controllers. Electromyographic (EMG) recordings can provide an indirect estimation of human muscle force and stiffness,… More >

Reham Reda^{1, *}

FDMP-Fluid Dynamics & Materials Processing, Vol.15, No.3, pp. 171-185, 2019, DOI:10.32604/fdmp.2019.03923

Abstract Constrained groove pressing (CGP) is a severe plastic deformation (SPD) technique used as a strengthening method for sheet metal. In the current work, an optimal/cost-saving design for CGP dies was attained using the stress analysis tool in SolidWorks Simulation Xpress wizard. This study examined low-cost and widely industrially applied aluminium materials, i.e., pure 1050 Al and 5052 Al alloy. Each material was subjected to three passes of the CGP process using a 150 tons capacity press. For both materials, inter-pass annealing treatment was undertaken before the third pass. The effect of the number of CGP passes on the microstructure and… More >

Peng Ni¹, Homer Walker¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.7, No.1, pp. 43-50, 2008, DOI:10.3970/icces.2008.007.043

Abstract One of the fundamental problems in electronic structure calculations is to determine the electron density associated with the minimum total energy of a molecular or bulk system. The total energy minimization problem is often formulated as a nonlinear eigenvalue problem. The most widely used algorithm for solving this type of problem is the self-consistent field (SCF) iteration accelerated by Direct Inversion on the Iterative Subspace (SCF-DIIS), in which a linearly constrained least-squares problem is embedded. We will examine and compare the numerical stability of three different ways to solve this least-squares problem. More >

B. Amaziane¹, A. Naji², D. Ouazar³, A. H.-D. Cheng⁴

CMC-Computers, Materials & Continua, Vol.2, No.2, pp. 85-96, 2005, DOI:10.3970/cmc.2005.002.085

Abstract In this paper the optimization of groundwater pumping in coastal aquifers under the threat of saltwater intrusion is investigated. The aquifer is inhomogeneous and contains several hydraulic conductivities zones. The aquifer data such as the hydraulic conductivities are uncertain, but with their expected mean and standard deviation values given. A stochastic boundary element method based on the perturbation technique is employed as the simulation tool. The stochastic optimization is handled by the chance-constrained programming. Genetic algorithm is selected as the optimization tool. Numerical examples of deterministic and stochastic problems are provided to demonstrate the feasibility of the proposed schemes. More >

Jean-Philippe Jehl¹, Richard Kouitat Njiwa²

CMES-Computer Modeling in Engineering & Sciences, Vol.102, No.5, pp. 345-358, 2014, DOI:10.3970/cmes.2014.102.345

Abstract Extended continuum mechanical approaches are now becoming increasingly popular for modeling various types of microstructured materials such as foams and porous solids. The potential advantages of the microcontinuum approach are currently being investigated in the field of biomechanical modeling. In this field, conducting a numerical investigation of the material response is evidently of paramount importance. This study sought to investigate the potential of the (constrained) microstretch modeling method. The problem’s field equations have been solved by applying a numerical approach combining the conventional isotropic boundary elements method with local radial point interpolation. Our resulting numerical examples demonstrated that the model… More >

Haitao Liao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.95, No.3, pp. 207-234, 2013, DOI:10.3970/cmes.2013.095.207

Abstract The constrained optimization multi-dimensional harmonic balance method for calculating the quasi-periodic solutions of nonlinear systems is presented. The problem of determining the worst quasi-periodic response is transformed into a nonlinear optimization problem with nonlinear equality constraints. The general nonlinear equality constraints are built using a set of nonlinear algebraic equations which is derived using the multi-dimensional harmonic balance method. The Multi- Start algorithm is adopted to solve the resulting constrained maximization problem. Finally, the validity of the proposed method is demonstrated with a Duffing oscillator and numerical case studies for problems with uncertainties are performed on a nonlinear two-degree of… More >

C. Jeong¹, L.F. Kallivokas²

CMES-Computer Modeling in Engineering & Sciences, Vol.35, No.1, pp. 49-72, 2008, DOI:10.3970/cmes.2008.035.049

Abstract We discuss the inverse scattering problem of identifying the shape and location of a rigid scatterer fully buried in a homogeneous halfplane, when illuminated by surficial (line) wave sources generating SH waves. To this end, we consider the full-waveform response of the coupled host-obstacle system in the frequency domain, and employ the apparatus of partial-differential-equation-constrained optimization, augmented with total differentiation for tracking shape evolutions across inversion iterations, and specialized continuation schemes in lieu of formal regularization. We report numerical results that provide evidence of algorithmic robustness for detecting a variety of shapes, including elliptically- and kite-shaped obstacles. More >

S.Y. Wang^1,2, K.M. Lim^2,3, B.C. Khoo^2,3, M.Y. Wang⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.18, No.3, pp. 155-182, 2007, DOI:10.3970/cmes.2007.018.155

Abstract In this paper, a geometric deformation constrained level set method is presented as an effective approach for structural shape and topology optimization. A level set method is used to capture the motion of the free boundary of a structure. Furthermore, the geometric deformation of the free boundary is constrained to preserve the structural connectivity and/or topology during the level set evolution. An image-processing-based structural connectivity and topology preserving approach is proposed. A connected components labeling technique based on the 4-neighborhood connectivity measure and a binary image is used for the present region identification. The corresponding binary image after an exploratory… More >