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The rheological behavior of wood plastic composites' (WPCs') melts is closely associated with extrusion processability, especially in highly filled systems. This study investigated the extrusion processibility and the effects of test conditions and typical WPC additives on the torque rheological behavior of wood flour/high-density polyethylene (WF/HDPE) mixing melts compounded using a twin-screw extruder. Both equilibrium melt temperature (Te) and equilibrium torque (Ma) at steady state increased with WF content. Addition of 2% lubricant TPW604 based on the total weight of WF and HDPE matrix resulted in a decrease in measured Te and Ma, showing a reduction in shear heating in mixing chamber. Adding 4% maleic anhydride grafted polyethylene (MAPE) as compatibilizer resulted in an increase in measured Te and Ma. In this study, adding lubricant TPW604 and/or compatibilizer MAPE can improve the extrusion processability of highly filled WF/HDPE melts. For a WPC system with preset compositions, its Ma value can be used to evaluate its extrusion processability. The results provide both knowledge about the compounding procedure and practical methods for evaluating the effectiveness of WPC additives, the flow performance, and extrusion processability of highly filled WPC melts. [ABSTRACT FROM AUTHOR]

We measured the force of free pulling water striders, using a hair attached to their backs and a 3D strain gauge force sensor. We showed the repeatability and accuracy of this method. The error of the method was estimated by comparing the projected angles of the force vector on each plane derived from the force data, with those angles derived from video recordings, and was estimated as 12.4%. Females on average were stronger (1.32 mN) than males (0.87 mN), however the ratio of force/weight was not significantly different. Compared with other lighter species, A. paludum seems to be stronger, but the force/weight ratio is actually lower as expected. A. paludum applies about 0.30–0.40 mN/cm with its mid-legs, thus avoiding penetrating the surface tension while propelling itself rapidly over the water. [ABSTRACT FROM AUTHOR]

Gravitational forces can induce deviations in body posture from desired configurations in multi-legged arboreal robot locomotion with low leg stiffness, affecting the contact angle between the swing leg's end-effector and the climbing surface during the gait cycle. The relationship between desired and actual foot positions is investigated here in a leg-stiffness-enhanced model under external forces, focusing on the challenge of unreliable end-effector attachment on climbing surfaces in such robots. Inspired by the difference in ceiling attachment postures of dead and living geckos, feedforward compensation of the stance phase legs is the key to solving this problem. A feedforward gravity compensation (FGC) strategy, complemented by leg coordination, is proposed to correct gravity-influenced body posture and improve adhesion stability by reducing body inclination. The efficacy of this strategy is validated using a quadrupedal climbing robot, EF-I, as the experimental platform. Experimental validation on an inverted surface (ceiling walking) highlights the benefits of the FGC strategy, demonstrating its role in enhancing stability and ensuring reliable end-effector attachment without external assistance. In the experiment, robots without FGC only completed 3 out of 10 trials, while robots with FGC achieved a 100% success rate in the same trials. The speed was substantially greater with FGC, achieving 9.2 mm s -1 in the trot gait. This underscores the proposed potential of the FGC strategy in overcoming the challenges associated with inconsistent end-effector attachment in robots with low leg stiffness, thereby facilitating stable locomotion even at an inverted body attitude., (Creative Commons Attribution license.)