Natural fibres are attractive as the raw material for developing sound absorber, as they are green, eco-friendly, and health friendly. In this paper, pineapple leaf fibre/epoxy composite is considered in sound absorber development where several values of mechanical pressures were introduced during the fabrication of absorber composite. The results show that the composite can absorb incoming sound wave, where sound absorption coefficients α _n > 0.5 are pronounced at mid and high frequencies. It is also found that 23.15 kN/m^2 mechanical pressure in composite fabrication is preferred, while higher pressure leads to solid panel rather than sound absorber so that the absorption capability reduces. To extend the absorption towards lower frequency, the composite absorber requires thickness higher than 3 cm, while a thinner absorber is only effective at 1 kHz and above. Additionally, it is confirmed that the Delany-Bazley formulation fails to predict associated absorption behavior of pineapple leaf fibre-based absorber. Meanwhile, a modified Delany-Bazley model discussed in this paper is more useful. It is expected that the model can assist further development of the pineapple leaf composite sound absorber.

In this paper, the dynamics of an acoustic bubble with a constant charge in compressible liquid are investigated numerically, which is based on the Gilmore-NASG model to estimate the radial oscillations. The cavitation effects are enhanced due to the presence of the charge on the bubble surface. The obtained results from the present model are compared with that calculated by the previous model within a wide range of parameters (e.g., charge, acoustic pressure amplitude, ultrasound frequency, and liquid temperature). The similar influences of these parameters on bubble collapse intensity can be observed from both models. Since the present model fully considers the compressibility of gas and liquid, it can be applied to a wider parameter range and leads to the larger predicted values. The research in this paper can provide important insights about the effects of charge on bubble dynamics and the acoustic cavitation applications (e.g., sonochemistry, water treatment, and food industry).

The galvanostatic method used in previous measurements of the chemical diffusion coefficient in the Al-rich aluminium-lithium alloys has given a numerical values of the above coefficient at four imposed temperatures. This directly measured values of diffusion coefficient is compared with the value obtained indirectly from the measurement of the Li-solute redistribution within the Al-3.5Li alloy solidified directionally in the Bridgman system. The adequate theoretical considerations dealing with the description of solute redistribution in eutectic system has been made to calculate the value of back-diffusion parameter for the performed 2D experiment. The definition of back-diffusion parameter has been rearranged to calculate the numerical value of the diffusion coefficient in the solid. It has been shown that back-diffusion parameter plays essential role in the model of solute redistribution which is discussed from the viewpoint of the application of current model for redistribution to calculation of the solidification path.

W XVII wieku funkcjonowały w Anglii dwa typy przestrzeni publicznych: skwery typu piazza, pozbawione kompozycji roślinnych oraz ogrodzone zielone place o charakterze ogrodowym, przeznaczone dla mieszkańców domów zlokalizowanych w pobliżu. Angielskie ogrody publiczne prezentowały typ wysokiej klasy przestrzeni miejskiej, który z czasem stał się popularny w wielu miastach europejskich. Celem artykułu jest określenie znaczenia tych założeń w krajobrazie zurbanizowanym, w tym wskazanie funkcji, jakie współcześnie pełnią one w tkance urbanistycznej miast.