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In recent years, the need for reliable signal transmission in forested areas has increasingly grown, and the past few decades have witnessed significant developments in related research. With the emergence of smart forestry and precision forestry, understanding the science behind enhancing signal reliability in forests—specifically, studying the patterns and models of radio wave attenuation in these environments—has become crucial. To this end, we conducted a comprehensive review based on bibliometrics to summarize and construct the existing academic literature, revealing current research trends and hotspots. Utilizing bibliometric techniques, we analyzed the literature on radio wave attenuation in forests to summarize and evaluate previous studies. Our analysis indicates that empirical models (67%), hybrid models (21%), and equivalent models (12%) are the three main research clusters in this field. We observed that studies on radio attenuation are more prevalent in urban and artificial forests, while there is a scarcity of research in complex conditions like tropical rainforests and extreme weather; studies are more focused on UHF, VHF, and SHF frequency bands, with lesser attention given to other bands. Previous research has not adequately considered the impact of seasonal factors on signal attenuation patterns nor the influence of forest working environments. [ABSTRACT FROM AUTHOR]

Sapindus mukorossi seeds are commonly drilled and processed into Buddha beads and other craft products. To improve the machining qualities of the micro-drilling of S. mukorossi seeds, the effects of drilling parameters (feed rate, drilling speed, and drill diameter) on the drilling force, hole diameter and hole morphology were found. The mechanism behind these changes was further analyzed. The drilling parameters and machining process for the micro-drilling of S. mukorossi seeds were optimized. Results indicated that each drilling parameter influenced the drilling force and hole-machining quality by affecting the amount of cutting, the working conditions of the drill bit, chip formation, and the generation of drilling heat. Moreover, the feed rate and drill diameter were the main factors that influenced the drilling force, and the drilling speed played a leading role that influenced hole-machining quality. Interestingly, for the drilling of S. mukorossi seeds, a feed rate of 0.03 mm/r, a drilling speed of 6 m/min, and a drill-bit diameter of 0.9 or 1.5 mm resulted in a hole with high accuracy, good hole morphology, and minimal wear on the drill bit. This study facilitates the selection of suitable drilling parameters and processing technology for the micro-drilling of S. mukorossi seeds to improve processing accuracies and qualities, and provides a theoretical basis for the improvement of related drilling processing equipment. [ABSTRACT FROM AUTHOR]

In light of limitations in the performance of thermoelectric materials, this study proposes a two-stage thermoelectric generator (TEG) system integrated with phase change materials (PCMs). Three sets of experiments were designed to investigate the factors influencing the proposed TEG-PCM system. Two of them examined the effects of different heat sink configurations on the heat generated with and without paraffin wax as the PCM. The third experiment investigated the thermoelectric performance of the proposed system using a single-cavity heat sink with different PCMs. The results show that the heat source had a greater influence on the performance of the system than the thermal resistance of the heat sink. The PCM reduced the second-stage voltage, but it lasted for a long time. The configuration of the heat sink had a greater influence on the second-stage voltage (U2) than the first-stage voltage (U1). Although the mean value of U1 for the four-cavity configuration without PCM was slightly larger than that of the single-cavity configuration by 10 mV, the maximum value of U2 for the latter was larger than that of the former by 60 mV. The single-cavity configuration is thus more suitable for the two-stage TEG system. Under a 10 W power supply, the properties of different PCMs significantly influenced the duration of voltage in each stage while U1 was maintained at 600 mV. The results show that the factors considered here influenced the performance of the two-stage TEG-PCM system in the order of heat source > thermal resistance of the heat sink > type of PCM. [ABSTRACT FROM AUTHOR]