ANN inverse analysis based on stochastic small-sample training set simulation

A new approach of inverse analysis is proposed to obtain parameters of a computational model in order to achieve the best agreement with experimental data. The inverse analysis is based on the coupling of a stochastic simulation and an artificial neural network (ANN). The identification parameters play the role of basic random variables with a scatter reflecting the physical range of potential values. A novelty of the approach is the utilization of the efficient small-sample simulation method Latin Hypercube Sampling (LHS) used for the stochastic preparation of the training set utilized in training the artificial neural network. Once the network has been trained, it represents an approximation consequently utilized to solve the key task: To provide the best possible set of model parameters for the given experimental data. The efficiency of the approach is shown using numerical examples from civil engineering computational mechanics.     

A heat mixed variational theorem for thermoelastic multilayered composites

This paper presents for thermoelastic media the analogue of the Reissner’s mixed variational theorem (RMVT), initially developed for elastic media, by adding the transverse thermal field–temperature increment relation as a constraint via a Lagrange multiplier. The latter is shown to be the transverse (normal) heat flux, which continuity at the laminated composite interfaces can now be fulfilled in a natural way as is the case for transverse stresses in the RMVT. Hence, the resulting new heat mixed variational theorem (HMVT) will be well suited for modelling thermoelastic layered composites. Mixed coupled thermoelastic constitutive equations to be used in conjunction with the HMVT are also presented. Finally, discussions are made on the application of the HMVT to the quasi-static and steady-state classical cases leading to uncoupled heat transfer and thermal-stress analyses.     

Application of aeroelastic modes on nonlinear supersonic panel flutter at elevated temperatures

This paper shows that the use of aeroelastic modes, instead of the traditional in vacuo natural modes, can reduce drastically the number of coupled nonlinear modal equations for the large amplitude nonlinear panel flutter analysis at an arbitrary yawed supersonic flow angle and elevated temperatures. All four types of panel behavior can be predicted and they are flat and stable, aerothermally buckled but dynamically stable, limit cycle oscillations, and chaos.     

A continuum-based modeling of MEMS devices for estimating their resonant frequencies

A continuum-based modeling of coupled electrostatics-structure interactions is presented for the frequency computations of MEMS devices. The present general formulation of electrostatics accounting for free space is validated first by specializing it to one-dimensional uniform motion of conducting surfaces and comparing the resulting electrostatics to conventional lumped models. The general coupled electrostatics-structure interactions are then applied for the prediction of resonant frequencies of MEMS devices due to bias-voltage changes and temperature variations. Comparisons of predicted resonant frequencies obtained by the present coupled electrostatics-structure interaction models with experimental results available in the literature demonstrate that the proposed continuum-based interaction modeling yields high-confidence predictions of resonant frequencies of MEMS devices.     

Similarity coefficient methods applied to the cell formation problem: a comparative investigation

Although many similarity coefficients have been proposed, very few comparative studies have been done to evaluate the performance of various similarity coefficients. In this paper, we compare the performance of 20 well-known similarity coefficients. Two hundred and fourteen numerical cell formation problems, which are selected from the literature or generated deliberately, are used for the comparative study. Nine performance measures are used for evaluating the goodness of cell formation solutions. Two characteristics, discriminability and stability of the similarity coefficients are tested under different data conditions. From the results, three similarity coefficients are found to be more discriminable. Jaccard is found to be the most stable similarity coefficient. Four similarity coefficients are not recommendable due to their poor performances.     

Pool boiling of saturated FC-72 on nano-porous surface

Pool boiling heat transfer from nano-porous surface immersed in a saturated FC-72 dielectric fluid has been experimentally studied at atmospheric pressure (101 kPa). The data obtained from nano-porous surface (Anodisc 25) of thickness about 70 μm made from aluminum oxide (Al₂O₃) obtained from Whatman, were compared to that of a plain surface (aluminum) of thickness about 105 μm. From the experimental data obtained it was evident that there is a reduction of about 30% in the incipient superheat for the applied power for nano-porous surface over plain surface. SEM photographs of the nano-porous coating were taken for determining the size of the pores.