The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell. Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz equation governing the acoustic pressure. Reasonably good agreement is obtained between theoretical results and experimental data. However, it was anticipated that loss mechanisms other than viscous and thermal boundary losses occur and should be included. Nevertheless, the feasibility to use FEM together with the derived boundary conditions to simulate the photoacoustic signal was demonstrated and good agreement with experiments for the actual resonance frequency and the quality factor of the cell was obtained despite its complicated geometry.
African dung beetle Scarabaeus galenus can use its front legs for multiple purposes that include walking, manipulating or forming a dung ball, and also transporting it. Its multifunctional legs have not been thoroughly investigated or even used as inspiration for robot leg design. Thus, in this paper, we present the development of real robot legs based on the front leg of the beetle. Each robot leg consists of three main segments which were built using 3D printing. The segments were combined with in total four active joints (i.e., 4 degrees of freedom) in order to mimic the leg movements of the beetle for locomotion as well as object manipulation and transportation. Kinematics analysis of the leg was also performed to identify its workspace. The leg movements of the beetle, during walking as well as manipulating and transporting a dung ball, were observed and reproduced on the robot leg. The results show that the robot leg is able to perform all the movements with trajectories comparable to the beetle leg. To this end, the study contributes not only novel multifunctional robot legs but also the methodologies for both bio-inspired leg design and leg movement generation.
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