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Radiative cooling, which normally requires relatively high infrared (IR) emissivity, is one of the insects' effective thermoregulatory strategies to maintain their appropriate body temperature. Recently, the physical correlation between the delicate biological microstructures and IR emissivity for thermal radiation draws increased attention. Here, a scent patch region on the hindwing of Rapala dioetas butterfly is found to exhibit enhanced IR emissivity compared with the non-scent patch regions. A series of optical simulations are conducted to differentiate the effect of biological structures and material composition on the high IR emissivity. Besides the intrinsic IR absorption (emission) of chitin (the main composition of butterfly wings), the hierarchical microstructures of the scent patch scale further improve the IR absorption (emission) through the increased inner surface area and multi-scattering effect. This enhancement of IR emissivity enables the butterfly to efficiently radiate heat from the scent patch region to the environment with a limited volume of chitin. This study of the correlation between IR emissivity and microstructural designs may offer additional pathways to engineer bioinspired materials and systems for radiative cooling applications. [ABSTRACT FROM AUTHOR]

Heating with the wave in the ion cyclotron range of frequencies (ICRF) has been used in the development of high-performance H-mode operations in EAST. A different ion cyclotron resonance heating scenario in three-ion component plasma with real experimental parameters on EAST was investigated using a numerical tool. Excellent radio frequency wave absorption was found with an extremely low 3He concentration (0.1%–0.4%) in D-H-(3He) plasma, by adjusting the plasma composition appropriately in our simulation. In this case, the 3He fundamental resonance layer is located between the two ion–ion hybrid resonance-cutoff pairs in close proximity, and therefore E + of the wave was considerably enhanced near the 3He fundamental resonance layer. The minority 3He tail was estimated to be superenergetic (∼1 MeV) because of the high power carried by each resonant 3He ion. The potential of the three-ion ICRF heating means on EAST was shown, and the scenarios investigated are particularly promising for fast particle generation schemes. [ABSTRACT FROM AUTHOR]

When a liquid droplet is placed on a sufficiently hot surface, it will be levitated by the vapor cushion between the droplet and the hot surface due to the Leidenfrost effect. Such Leidenfrost-based levitation can greatly reduce friction and thus offers a promising approach for low-friction devices. In this work, we demonstrated a self-propelled rotational Leidenfrost rotor made of wet paper with asymmetric mass distribution. The rotor has shown the capability of reaching angular velocities of more than 30 rad/s and prolonged the rotation duration through refueling with water. We experimentally investigated the influence of mass repartition and substrate heating temperature on the rotation behavior of the rotor. It was found that both the initial acceleration and the maximum angular velocity increase with the increasing mass ratio of the connector over the evaporator within the rotor and the substrate heating temperature. A theoretical model was proposed to simulate the trend, and the simulated results are in good agreement with the experimental results. The paper-based Leidenfrost rotor provides an alternative way to utilize the Leidenfrost effect for exploring self-propelled movement and relevant applications such as surface cleaning and rotary heat engines. [ABSTRACT FROM AUTHOR]

This work presents the recovery of thermal energy through the oscillation of liquid plugs induced by phase transition within the oscillating heat pipe (OHP) during the quick heat-transfer process of the OHP. Using the electrical double layer at the liquid-solid interface in the OHP, this study demonstrated that the waste heat can be recycled and converted into useful electric energy. This recycling system generated more than 1 V of output voltage and more than 1.6 μW of peak power. The electric output generated from such a process can be used to power up small electronic devices, such as capacitors and light-emitting diodes (LEDs). The findings in this work provide an alternative approach to harvest waste heat in many devices or systems that involve the generation and removal of waste heat. [ABSTRACT FROM AUTHOR]