In this study, an acoustic behaviour of S-polymer gears made of the material combination POM/PA66 was investigated and compared to the standardised involute gears (E-gears). Basic evaluating characteristics included noise during operation, which is of particular significance when noise reduction is expected. The measured signals were analysed in time and frequency domains and the levels of acoustic activity were compared. The experimental results have shown that the sound pressure level of both E- and S-polymer gears are proportional to the torque. However, the comprehensive noise evaluation has shown some advantages of S-polymer gears if compared to the E-polymer gears. In that respect, S-polymer gears were found more appropriate for noise reduction of gear drive systems in the case of normal loading and typical drive speed. Future studies in the operating behaviour of S-polymer gears could also cover noise evaluation using new methods of sound signal analysis at different temperatures of gears.

This paper explains liquefied nitrogen’s cooling ability on a nickel super alloy called Inconel 718. A set of experiments was performed where the Inconel 718 plate was cooled by a moving liquefied nitrogen nozzle with changing the input parameters. Based on the experimental data, the empirical model was designed by an adaptive neuro-fuzzy inference system (ANFIS) and optimized with the particle swarm optimization algorithm (PSO), with the aim to predict the cooling rate (temperature) of the used media. The research has shown that the velocity of the nozzle has a significant impact on its cooling ability, among other factors such as depth and distance. Conducted experimental results were used as a learning set for the ANFIS model’s construction and validated via k-fold cross-validation. Optimization of the ANFIS’s external input parameters was also performed with the particle swarm optimization algorithm. The best results achieved by the optimized ANFIS structure had test root mean squared error ( $test RMSE)=0.2620$ , and $test R^2=0.8585$ , proving the high modeling ability of the proposed method. The completed research contributes to knowledge of the field of defining liquefied nitrogen’s cooling ability, which has an impact on the surface characteristics of the machined parts.