The pfSense is а software system that combines router and firewall in one product

High-frequency wood drying is the modern method used in raw wood drying so that treated wood can be used further in various processes. Such systems are used because of the economy, energy efficiency, obtaining of good mechanical properties of the wood after treatment, as well as reducing time consumption. Therefore, it is extremely important to understand each component of such systems and processes. The mentioned systems are implemented using high-frequency generators based on vacuum tubes (VT). Their development and, in particular, optimization are by far more complex than the transistor systems; therefore, the development is now compelled to rely on computer modelling and simulation. In this research, a high-frequency (HF) generator of 20 kW output power and 1.5–15 MHz adjustable frequency based on VT was produced and then, with the corresponding model for VT itself and the rest of the developed circuit, was followed by computer simulation and real-system measurement. The model parameters were adjusted, which provided additional system optimization. An extra match of the results from the simulation and measurement was obtained; thus, the optimization was performed faster and more precisely. In addition, an easier and quicker way of adjusting parameters of the PID controller using a developed software-based control system was attained. The problems of cooling the VT anode under high DC voltage, as well as temperature measurement in the HF electric field, have been solved.

..most teachers used online learning platforms as well as virtual meetings during the Covid-19 pandemic and they were satisfied.

This paper presents the integration of the 10Rs of the circular economy (CE) strategy with the 7S tools of Lean manufacturing, and lifecycle management of wearable sensors. The presented algorithm, based on CE, and the application of additive manufacturing (AM) in the realization of a modular enclosure from biodegradable polymer material, demonstrate a strategy for the sustainable development of prototypes with low material waste, rapid design changes, ease of disassembly and assembly, reuse, repair, and revitalization. The stated algorithm closes the circle between design, use, maintenance, and end-of-life of a product, incorporating sustainability into everyday engineering decisions through the example of wearable sensors. The electronic enclosure shown in the work is compact; it can be worn around the waist or secured to the head with a flexible tape. The results showed that the 10R/7S connection raises the enterprises' competitiveness through efficient production, extended product life, and reduced waste, while simultaneously addressing challenges such as regulatory observation, affordability, and user feedback after long-term product use. The study confirms a practical methodology for applying CE principles to wearable sensor systems and highlights opportunities for modular improvements, serviceability, and the use of environmentally friendly materials. The work contributes to engineering and product design by gathering sustainable product development and more effective product lifecycle management.