3D meshless FEM-BEM model for prediction of sound fields in cabins due to external sound disturbances

The Finite Element Method (FEM) and Boundary Element Method (BEM) are widely applied to predict the sound pressure level (SPL) in enclosed spaces for low frequency problems. However, a single method usually cannot fulfill the task for predicting the internal SPL in enclosures including objects in the interior due to external disturbances. Moreover, these methods have some disadvantages such as complex pre-processing, time-consuming and inevitable pollution effects. Based on these drawbacks, this paper attempts to combine the Meshless Method (MM), acoustical FEM and BEM into a hybrid method which can be applied to predict the SPL in an enclosed environment with external sound sources. Firstly, the hybrid theory for the acoustic problem and its implementation are illustrated. Next, numerical simulations and experiments are conducted to validate the peak value, SPL and computing efficiency using this method. Comparative results obtained from the proposed method, FEM and BEM using SYSNOISE are shown to be in agreement, and the proposed method is more efficient. Experimental results show that the average relative error of SPL in each location is less than 5.26 %. It is corroborated that the proposed method is applicable to the prediction of the internal SPL with the case of exterior sound sources existed

A study on compressive anisotropy and nonassociated flow plasticity of the AZ31 Magnesium Alloy in hot rolling

Effect of anisotropy in compression is studied on hot rolling of AZ31 magnesium alloy with a three-dimensional constitutive model based on the quadratic Hill48 yield criterion and nonassociated flow rule (non-AFR). The constitutive model is characterized by compressive tests of AZ31 billets since plastic deformations of materials are mostly caused by compression during rolling processes. The characterized plasticity model is implemented into ABAQUS/Explicit as a user-defined material subroutine (VUMAT) based on semi-implicit backward Euler\u27s method. The subroutine is employed to simulate square-bar rolling processes. The simulation results are compared with rolled specimens and those predicted by the von Mises and the Hill48 yield function under AFR. Moreover, strip rolling is also simulated for AZ31 with the Hill48 yield function under non-AFR. The strip rolling simulation demonstrates that the lateral spread generated by the non-AFR model is in good agreement with experimental data. These comparisons between simulation and experiments validate that the proposed Hill48 yield function under non-AFR provides satisfactory description of plastic deformation behavior in hot rolling for AZ31 alloys in case that the anisotropic parameters in the Hill48 yield function and the non-associated flow rule are calibrated by the compressive experimental results

Influence and Estimation of Geopolitical Risk on FDI in Eastern European Economies

In the current complex international situation, especially underthe influence of the Russian-Ukrainian conflict, the inflow of FDI in Eastern European countries is seriously affected by geopoliticalrisks. However, there is a lack of research on this subject in Eastern Europe. Based on FDI inflow data in Eastern European countries and the political risk ratings of the ICRG from 2009 to 2020, this paper investigates the effect of geopolitical risks on FDI inflow to Eastern Europe using simple linear regression. It has been found that geopolitical risks have a significant negative impact on FDI inflows in Eastern European countries. However, further studies have found that signing RTAs can help alleviate this negative effect; actively carrying out bilateral trade or investment agreements is conducive to the development of FDI in host countrie