Cryptocurrencies, FOREX and stocks: portfolio diversification and the Russia-Ukraine war

The aim of this study is to investigate how the Russia-Ukraine war could affect the diversification benefits between stock index, FOREX and cryptocurrencies. The wavelet coherence is used to examine the difference in co-movement between assets during normal and war periods and dynamic conditional correlation (DCC) is used to examine the correlation between cryptocurrencies and other assets to examine its diversification properties during war periods. Wavelet coherence results indicates that not all asset’s correlation would increase during war and international portfolio diversification benefits still exist in a globalised and integrated economy. Contagion effect is found to increase for some assets during war period. Also, the DCC proves that not all cryptocurrencies act as effective diversifiers for FOREX and stock market. However, cryptocurrencies are found to be a more effective diversifier for FOREX when compared to stock

Numerical computation for the impact of pantograph angles on the near-field and far-field aerodynamic noises of pantographs

Pantographs are an important part of power supply systems of high-speed trains, whose good working performance is a guarantee for the steady power supply and safety operation of high-speed trains. The aerodynamic drag of pantographs will have negative impacts on the running of high-speed trains. In the meanwhile, the disturbance effect of pantographs on airflow will cause large aerodynamic noises when a high-speed train runs at a high speed. Therefore, this paper conducted a numerical simulation for the flow field and aerodynamic noises of pantographs on the symmetrical plane, compared simulation results with experimental one, verified the correctness of the numerical simulation model, and further studied the impact of pantograph angles on radiation noises. When pantographs were working, cylindrical rods which were vertical to the direction of airflows had a more obvious disturbance effect on airflows and caused a larger range of vortex shedding. Shedding vortexes were mainly distributed at the pantograph head, hinge joints between upper and lower arms, and rear bases. Near-field aerodynamic noises on the longitudinal symmetrical plane of pantographs were distributed at the lower arm, middle hinge joints and bases. The maximum appeared at the middle hinge joints. The intensity of vortexes at the middle hinge joints, lower arms and bases when the pantograph angle was 60° was more than that at other pantograph angles. In this case, the near-field aerodynamic noise of pantographs was more than that of other pantograph angles. In addition, radiation noises of observation points of pantographs in all directions presented an obvious linear relationship. The far-field radiation noise of pantographs was gradually decreased with the increased distance from pantographs. In addition, the far-field radiation noises of pantographs on the same vertical plane had the intensity with the same level