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Highlights: Drawing wisdom and inspiration from nature, an eco-mimetic nanoarchitecture is constructed, featuring tunable electromagnetic properties and high-efficiency energy attenuation. Through in-depth insight into the microstructure, the material basis of electromagnetic response is clearly revealed to establish an intrinsic connection between microscopic electronic structure and macroscopic electromagnetic properties. A creative self-powered energy conversion device is constructed, with the integrated functions including electromagnetic protection and waste energy recycling, which offers a new horizon for the fields of energy and environment. Advanced electromagnetic devices, as the pillars of the intelligent age, are setting off a grand transformation, redefining the structure of society to present pluralism and diversity. However, the bombardment of electromagnetic radiation on society is also increasingly serious along with the growing popularity of "Big Data". Herein, drawing wisdom and inspiration from nature, an eco-mimetic nanoarchitecture is constructed for the first time, highly integrating the advantages of multiple components and structures to exhibit excellent electromagnetic response. Its electromagnetic properties and internal energy conversion can be flexibly regulated by tailoring microstructure with oxidative molecular layer deposition (oMLD), providing a new cognition to frequency-selective microwave absorption. The optimal reflection loss reaches ≈ − 58 dB, and the absorption frequency can be shifted from high frequency to low frequency by increasing the number of oMLD cycles. Meanwhile, a novel electromagnetic absorption surface is designed to enable ultra-wideband absorption, covering almost the entire K and Ka bands. More importantly, an ingenious self-powered device is constructed using the eco-mimetic nanoarchitecture, which can convert electromagnetic radiation into electric energy for recycling. This work offers a new insight into electromagnetic protection and waste energy recycling, presenting a broad application prospect in radar stealth, information communication, aerospace engineering, etc. [ABSTRACT FROM AUTHOR]

As two mathematical tools for dealing with uncertainty, the covering rough set theory and the evidence theory have close relationships with each other. Different covering rough set models are characterized by evidence theory. The purpose of this paper is to interpret belief functions with two pairs of covering approximation operators. The two pairs of covering approximation operators are equivalent to a pair of relation approximation operators. Then, based on a necessary and sufficient condition for a belief structure to be the belief structure induced by the pair of relation approximation operators, necessary and sufficient conditions for a belief structure to be the belief structure induced by the covering approximation operators are presented. Moreover, two kinds of covering reductions in covering information systems defined from the two pairs of covering approximation operators are characterized by the belief and plausibility functions. [ABSTRACT FROM AUTHOR]

Granular computing is an emerging computing paradigm of information processing. Rough set theory is a kind of models of granular computing and is used to deal with the vagueness and granularity in information systems. Covering-based rough set theory is one of the most important extensions of the classical Pawlak rough set theory. In the covering-based rough set theory, the covering lower and upper approximation operators are two basic concepts. The axiomatic characterizations of covering-based approximation operators guarantee the existence of coverings reproducing the operators, so the rough set axiomatic system is the foundation of the covering-based rough set theory. In this paper, we present a new covering upper approximation operator and explore the basic properties of the covering upper approximation operator to find an axiomatic set for characterizing the covering upper approximation operator. We also discuss the relationships between the covering upper approximation operator and three other covering upper approximation operators, compare the covering upper approximation operator with the other covering upper approximation operators by defining precision degrees and rough degrees, and present the necessary and sufficient conditions for the covering upper approximation operators to be identical. The results not only are beneficial to enrich the kinds of the covering rough sets, but also have theoretical and actual significance to covering rough sets. [ABSTRACT FROM AUTHOR]

Chaotic vibrations, stability and synchronization are important topics in nonlinear dynamics, and thus are studied in this paper for a new chaotic system with quadratic and cubic nonlinearly. The modified Duffing-Rayleigh system with piecewise quadratic function is presented firstly. Then, by taking the Melnikov function method, necessary conditions for chaotic motion of the modified Duffing-Rayleigh system are given. Fractional modified Duffing-Rayleigh oscillator is also discussed, and results of computer simulation demonstrate the chaotic dynamic behaviors of the fractional-order modified Duffing-Rayleigh system with order less than 2. Furthermore, generalized projective synchronization of two fractional modified Duffing-Rayleigh oscillators is explored by the active control technology. Adaptive synchronization and parameter identification of a fractional modified Duffing-Rayleigh oscillator with unknown parameters are also investigated. Numerical results validate the effectiveness and applicability of the proposed synchronization schemes. [ABSTRACT FROM AUTHOR]

In this work, the NiFeO-reduced graphene oxide (NiFeO-rGO) was achieved via a one-step hydrothermal method. The microstructure, permittivity and permeability and electromagnetic attenuation properties of NiFeO-rGO are investigated. The minimum reflection loss reaches −46.8 dB at d = 4.8 mm. The introduction of NiFeO nanocrystals enhances electromagnetic attenuation due to the synergetic effect of dielectric and magnetic loss as well as the enhanced exchange resonance. It is believed that the deposition of magnetic nanocrystals is a way to generate light-weight and high-efficient microwave absorbers. The NiFeO-rGO is a promising candidate for electromagnetic attenuation in various fields. [ABSTRACT FROM AUTHOR]