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The Janus functional thermal device (JFTD) can produce different thermal modulation effects on the heat flow incident from different directions. To solve the problems of material anisotropy and non-interaction with the external environment in the thermal target region of the previous JFTD, an open JFTD is proposed by using a moving thermal conductive medium in four rectangular modules on the background thermal conductive plate. The thermal target region within the proposed open JFTD is an isotropic thermal conductive medium (e.g., the same as the background medium), which can be connected to the external region. The simulated results show that the proposed open JFTD performs as a thermal concentrator for the heat flows with incident angles between 0° and the critical angle and a thermal cloak for the heat flows with incident angles between the critical angle and 90°, which can be applied to the separate processing of multiple heat flows from different directions in various integrated systems. [ABSTRACT FROM AUTHOR]

High-entropy oxide (HEO) nanoparticles have been regarded as a promising catalytic material system for oxygen evolution reaction in recent years. However, their traditional physical and chemical synthesis remains challenges due to the limitation of fabricating controllable small size HEO nanoparticles. Herein, a general and novel method of low-energy-recoil ion implantation and subsequent annealing is successfully developed to synthesize high-entropy oxide nanoparticles catalysts. By controlling the fluence of irradiation Ar+ ions, the size and the load of HEO nanoparticles can be accurately controlled. The obtained (FeCoNiCrAl)O HEO nanoparticles exhibit an overpotential of 295 mV at 10 mA cm−2, a small Tafel slope of 39 mV dec−1 and good stability in 1 M KOH, which is much better than the properties of binary and medium entropy oxide counterparts prepared by the same method, showing the good application prospect of low-energy-recoil ion implantation in the preparation of complicated multi-element-metal oxide nanoparticles. [ABSTRACT FROM AUTHOR]

Electromagnetic invisible devices usually designed by transformation optics are rather complicated in material parameters and not suitable for general applications. Recently, a topology optimized cloak based on level-set method was proposed to realize nearly perfect cloaking [Fujii et al., Appl. Phys. Lett. 102, 251106 (2013)]. In this work, we experimentally implemented this idea and fabricated a unidirectional cloak with a relative large invisible region made of single dielectric material. Good cloaking performance was verified through measurement which consists very well with numerical simulation. The advantages and disadvantages of this optimization method are also discussed. [ABSTRACT FROM AUTHOR]