This study presents an analysis of the effect of the concentrated mass on the acoustic power and the resonant frequencies of a vibrating thin circular plate. The fluid-structure interactions and the acoustic wave radiation effect have been included. The eigenfunction expansion has been used to express the transverse displacement of the plate. The appropriate number of modes is determined approximately to achieve physically correct results. Then highly accurate results are obtained numerically. The radiated acoustic power has been used to determine the resonant frequencies. The introducing of the concentrated mass is justified by modelling the added mass of the moving component of the exciter.

In this paper, we propose a multi-layer micro-perforated panel structure based on a curled space for broadband sound absorption at low frequencies, which increases the number of perforated panel layers in a limited space using a curled space. The absorption coefficients of the structure under plane wave conditions were calculated using the transfer matrix method and the finite element method. It is demonstrated that the multilayer micro-perforated panel structure can ensure high absorption (consistently over 90%) in the frequency range of 400~5000 Hz. The sound absorption mechanism of the multi-layer micro-perforated panel structure is investigated by using the acoustic impedance along with the reflection coefficient of the complex frequency surface. In addition, we also discuss the effects of the micro-perforated panel parameters on the structural sound absorption coefficient. The results show that the proposed multi-layer micro-perforated panel structure provides an excellent solution for sound absorption in a limited space.

In this investigation the surface of an aluminized sample of plain carbon steel was melted and alloyed using a tingsten inert gas (TIG) welding process to produce iron-aluminide intermetallic phases on the surface. The produced coating was then characterized by SEM and EDS and its high-temperature properties in O2 + 1%SO2 gas were examined. The results showed that the Fe3Al coating produced could protect the substrate as it was subjected to the corroding gases at 700oC due to the formation of an alumina layer between the substrate and an outer layer of Fe2O3. At 900oC, the coating could only protect the substrate for 64 h. The lack of further protection at this temperature is attributed to the decrease in the protective properties of alumina with an increase in its temperature and the lack of presence of enough Al atoms in the coating for the repair of the defects formed in the alumina layer.

Alginate – chitosan – alginate multilayer hydrogel encapsulation systems were investigated for

encapsulation of chondrocytes. Hydrogel is crosslinked due to ionic interaction between cationic

chitosan and anionic alginate, and additionally by calcium ions. Two types of chitosan with

molecular weight were investigated. Cells were encapsulated in two shape microcapsules, microbeads with diameter size 300 – 400 and 500 - 600 µm and fibres with diameter 500 - 600 µm. The

work provides a detailed examination of the impact of the microencapsulation process on the growth

of cells. The viability of chondrocytes can be influenced by the size of produced microcapsules,

while the shape of microcapsules has no important significance on cell viability. The applied

encapsulation methods do not contain harmful stages and create conducive conditions for cell

growth. A possible application area of the developed system is dressing and regeneration of

damaged joint cartilage.