In this study, we proposed a drone structure that is safer than the conventional propeller guard structure and that can reduce drone size as compared with conventional drones. This is achieved by making the rotating blade regions overlap by setting a height difference on adjacent rotor blades. We showed that drones with the proposed structure that have four, six, or eight rotors (quadcopters, hexacopters, or octocopters) can achieve size reductions of about 27%, 46%, or 54%, respectively, as compared with drones with a conventional structure. To evaluate the proposed method, an actual drone was manufactured, and its propulsion capability and control performance were evaluated in an indoor experiment. The results confirm that the performance of the experimental drone was almost equivalent to that of a conventional drone. In addition, we constructed several of the newly proposed drones, built their coordinated flight control units, and conducted demonstration experiments in an outdoor environment, suggesting a framework for high-precision measurement using drones. The results show that the proposed drone structure can reduce the size of the airframe while also reducing the risks associated with the rotor blades. These new drones could be used to eliminate bottlenecks in breeding measurement using drones

This study captures the structural transformation in crop composition in Chumphon Province in southern Thailand at the macro (province) and micro (farm household/plot) levels. Based on the decomposition of crop production value growth into the effects of price, productivity, area reallocation between crops, and enlargement of the total area, production at the province level has been found to be driven by price and productivity effects for the past two decades. This raises the question of how farmers obtain crop price or technical information for crop choice decisions. In our original survey, farm or plot-level crop diversification was studied in villages where coffee production was historically active. We found that the capacity for diversification differs according to farm scale, and information use regarding crop price or farming practices is highly dependent on informal social networks. Furthermore, the role of social relationships in information sharing on price and farming practices of a specific crop is important even for farmers who do not produce that crop, suggesting that social relationships are the effective channel for the promotion of crop diversification and sustainable farming practices