Special Issue “Physics and Mechanics of New Materials and Their Applications 2019”

Advanced materials and composites can be applied in a number of ways not only in modern science, techniques and technologies but in everyday life, including in the fields of aviation, medicine, waste reprocessing or the study of the underwater world. Modern scientific achievements have allowed us to deepen our understanding in these areas. Ideas and methods that have been developed to solve emerging problems and tasks are very interesting to scientists and engineers, as well as to the general population, as the final results aim to improve our environment and health.

This Special Issue consists of four papers with promising results which were presented at the 2019 International Conference on “Physics, Mechanics of New Materials and Their Applications” (PHENMA-2019), which took place in Hanoi (Vietnam) on 7–10 November 2019. (https://www.facebook.com/PHENMA2019/, accessed on 26 September 2022). The papers included into this Special Issue have attracted great interest and a sufficient number of citations.

Shevtsov et al. [1] presented a new approach to the modeling of the vacuum infusion process in the manufacturing of 3D composite elements with complex shapes. This approach and the numerical methods used enabled reliable prediction with the required level of accuracy and the elimination of unrecoverable defects of composite structures such as dry spots. The experimental results demonstrated two cases of the formation of dry spots in large Carbon-Fiber-Reinforced Plastic (CFRP) panels during vacuum infusion and analyzed the reasons for their presence. The resin infusion model was formulated as a coupled two-phase (air/resin) media dynamics problem, in which the phase field equation was accepted as the ruling one. With the aim of simplifying the verification of the modeling approach, the heat transfer, the thermal kinetics, the wetting compaction and the change in the dimension effects of the composite elements during the filling and post-filling stages were neglected. The phase field equation was coupled with the Richards equation, describing the fluid motion in unsaturated soils with spatially varied pressure, depending on porosity and saturation. As a result, the resin front motion and the formation of inner and outer dry spots during movement were correctly reconstructed. For the rapid detection of preform zones in which defect formation was suspected, two indicators, which were calculated during process simulation, were proposed and tested in the numerical experiments. In the MATLAB environment using finite element modeling, the times of formation, localization and the dimensions of the arising dry spots were detected. Liu et al. [2] identified the risk factors for complications (such as hyperpigmentation, hypopigmentation and petechiae), which can occur after frequent use of a neodymium-doped yttrium aluminum garnet (Nd-YAG) laser for the removal of pigmented skin patches and the rejuvenation of skin. The paper was devoted to the development of a multivariable logistic regression model with a least absolute shrinkage and selection operator (LASSO) in order to provide valid predictions of the incidence of post-inflammatory hyperpigmentation complication probability (PIHCP). With this aim, 125 female patients undergoing laser toning therapy were examined for post-inflammatory hyperpigmentation (PIH) complications. Factor analysis was performed using 15 potential predictive risk factors of PIH. The LASSO algorithm with cross-validation was used to select the optimal number of predictive risk factors for a multivariate logistic regression PIH complication model. The predictive risk factors were stated as follows: immediate endpoints of laser (IEL), α-hydroxy acid (AHA) peels, Fitzpatrick skin phototype (FSPT), acne and melasma. The overall performance of the LASSO-based PIHCP model was satisfactory based on the AUC, Omnibus, Nagelkerke R² and Hosmer–Lemeshow tests. Yeh et al. [3] investigated the optimal initial moisture content and seeding proportion with mature compost (microbial inoculant) during food waste composting on the basis of six varying moisture contents (42%, 55%, 61%, 66%, 70% and 78%) and four different mature compost seeding amounts (0%, 10%, 20% and 30% w/w). The most effective setups were defined due to their temperature variations during the first four days of composting. The experiments showed that the initial moisture contents of 55–70% and the 20% w/w of mature compost were optimal for effective food waste composting. Then, the optimal compost mixture ratio was used to study the evolution and spatial distribution of the temperature during a 30-day composting period. As a result, the heat, produced during this process, was estimated as 2.99 MJ/kg. Lin et al. [4] proposed a direct-mapping (DM)-based multi-input multi-output (MIMO) filter bank multi-carrier (FBMC) underwater acoustic multimedia communication architecture (UAMCA). The proposed UAMCA included a 2 × 2 DM transmission mechanism, a (2000, 1000) low-density parity-check code encoder, a power assignment mechanism, an object-composition PetriNet mechanism, adaptive binary phase shift keying modulation and four-offset quadrature amplitude modulation methods. The real-time requirements for voice, image and data signals were achieved by using the proposed underwater multimedia transmission power allocation algorithm (UMTPAA). The bit error rates (BERs) of the multimedia signals, data symbol error rates of the data signals, power-saving ratios of the voice, image and data signals, mean square errors of the voice signals, peak signal-to-noise ratios of the image signals for the proposed UAMCA with perfect channel estimation and channel estimation errors of 5%, 10% and 20%, respectively, were explored and demonstrated. It was shown that the proposed 2 × 2 DM-based MIMO-FBMC UAMCA was suitable for low-power and high-speed underwater multimedia sensor networks.

While submissions for this Special Issue are closed, the presented scientific areas, which touch on the fabrication, research and application of advanced materials and composites, continue their steady development, quickly changing modern techniques, technologies and industry.