We review the space mapping (SM) technique and the SM-based surrogate (modeling) concept and their applications in engineering design optimization. The aim of SM is to achieve a satisfactory solution with a minimal nu...
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We review the space mapping (SM) technique and the SM-based surrogate (modeling) concept and their applications in engineering design optimization. The aim of SM is to achieve a satisfactory solution with a minimal number of computationally expensive "fine" model evaluations. SM procedures iteratively update and optimize surrogates based on a fast physically-based "coarse" model. Parameter extraction is an essential SM subproblem. It is used to align the surrogate (enhanced coarse model) with the fine model. Novel physical illustrations are presented, including the cheese cutting problem and wedge cutting problem. Significant practical applications are reviewed.
The packing of uniform fine spherical particles ranging from 1 to 1000 μm has been simulated by means of discrete particle simulation. The packing structure is analyzed, facilitated by the well established Voronoi te...
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The packing of uniform fine spherical particles ranging from 1 to 1000 μm has been simulated by means of discrete particle simulation. The packing structure is analyzed, facilitated by the well established Voronoi tessellation. The topological and metric properties of Voronoi polyhedra are quantified as a function of particle size and packing density. The results show that as particle size or packing density decreases, (i) the average face number of Voronoi polyhedra decreases, and the distributions of face number and edge number become broader and more asymmetric; (ii) the average perimeter and area of polyhedra increase, and the distributions of polyhedron surface area and volume become more flat and can be described by the log-normal distribution. The topological and metric properties depicted for the packing of fine particles differ either quantitatively or qualitatively from those reported in the literature although they all can be related to packing density. In particular, our results show that the average sphericity coefficient of Voronoi polyhedra varies with packing density, and although Aboav-Weaire’s law is generally applicable, Lewis’s law is not valid when packing density is low, which are contrary to the previous findings for other packing systems.
This paper presents an averaging method to link discrete to continuum variables of granular materials. Compared to the other methods proposed in the literature, it has advantages of being applicable to all flow regime...
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This paper presents an averaging method to link discrete to continuum variables of granular materials. Compared to the other methods proposed in the literature, it has advantages of being applicable to all flow regimes, and to granular flows with or without the effect of physical boundaries. Its application is demonstrated in the determination of the macroscopic properties such as mass density, velocity, stress, and couple stress distributions of a hopper flow, where the discrete results are generated by means of discrete particle simulation. While highlighting the need for considering properly the effect of physical boundaries, the results indicate that the proposed method is an effective way to determine the flow properties of granular materials.
This paper describes the implementation of transmission-line matrix (TLM) method algorithms on a massively parallel computer (DECmpp 12000), the technique of distributed computing in the UNIX environment, and the comb...
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This paper describes the implementation of transmission-line matrix (TLM) method algorithms on a massively parallel computer (DECmpp 12000), the technique of distributed computing in the UNIX environment, and the combination of TLM analysis with Prony's method as well as with autoregressive moving average (ARMA) digital signal processing for electromagnetic field modelling. By combining these advanced computation techniques, typical electromagnetic field modelling of microwave structures by TLM analysis can be accelerated by a few orders of magnitude.
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