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An unstructured finite-volume time-domain method (UFVTDM) is developed to solve two-dimensional transient heat conduction in multilayer functionally graded materials (FGMs). A four-node quadrilateral grid and a three-node triangular grid are employed to deal with mixed-grid problems. The accuracy of the method is improved by treating the quadrilateral grid as a bilinear element with consideration of both the linear term and the constant term. The improvement is validated to be vital to avoid violent numerical oscillation when applying the method to heat point-source problems. The accuracy and capability of the UFVTDM are validated by numerical tests.

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In this study, a finite volume method for the steady thermoelastic analysis of the functionally graded materials is presented. The method is validated in a benchmark case from the published paper. By incorporating the variation of material properties in the discretization process, the method is able to avoid discontinuous distributions of stresses. Two different formulations for the calculation of variable gradients are assessed. The numerical results show that the least square method achieves better performances than the Gaussian method but least square method costs slightly more iteration and computer memory under different mesh types. Then the method is applied to analyze thermoelastic problems of the functionally graded circular rotating disk under different conditions. The effects of thickness, material properties, reference temperature and temperature difference between the inner and outer surfaces on the thermoelastic performance of the disk have been studied.

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State-of-charge (SOC) prediction is an important part of the battery management system (BMS) in electric vehicles. Since external factors (voltage, current, temperature, arrangement of the battery, etc.) impact SOC prediction differently, the SOC is difficult to model. In this paper, we apply principal component analysis (PCA) to analyze the contribution of various external factors and propose a new SOC prediction method based on an improved support vector machine for regression (SVR) with data classification and training set size optimization. Three groups of simulation experiments with different inputs based on the original SVR algorithm are conducted in the software ADVISOR, and the simulation results show that the input of three features of the battery (current, voltage and temperature) can satisfy the SOC prediction accuracy. The improved SVR algorithm is then applied to the simulation experiment of the three input features. The proposed method is demonstrated to be faster and more accurate than the original SVR algorithm through a comparison of the simulation results. INDEX TERMS State-of-charge (SOC) , principal component analysis (PCA) , support vector machine for regression (SVR) , battery management system (BMS), electric vehicles.

A time-domain finite volume approach is presented for predicting the transmission loss of muffler including thermal effects with non-uniform sound speed field and density field, in which the acoustic wave equation in heterogeneous media is solved by using unstructured finite volume method with the temperature field specified or solved by some commercial code. An improved time-domain impulse method based on the absorbing boundary condition is applied to predict the acoustic attenuation characteristics of mufflers. The approach is validated by numerical simulations of a simple expansion chamber muffler and a complex muffler with five chambers. The predicted results agree well with the corresponding experimental ones and numerical ones obtained by finite element method with commercial code SYSNOISE. The results of both mufflers under different thermal conditions indicate that the temperature distribution has a significant influence on transmission loss. According to the analysis of a complex muffler with ideal medium, it is shown that the variation of working conditions can obviously affect density and sound speed distributions but have little influence on transmission loss. On the other hand, the obtained transmission loss with the solved temperature field deviates much from the one with specified uniform temperature field.