In an interweave cognitive radio system, cooperative spectrum sensing has been recognised as a key technology to enable secondary users to opportunistically access licensed spectrum band without harmful interference to primary users. At the same time, the unmanned aerial vehicle equipped with spectrum sensing and data transmission facilities is gaining more popularity in different applications. An unmanned aerial vehicle-based interweave cognitive radio is investigated in which the unmanned aerial vehicle is used as a secondary user, but unlike the participation of multiple secondary users in traditional cooperative spectrum sensing, a virtual cooperative spectrum sensing model is introduced into the periodic spectrum sensing frame structure. Afterwards, the authors further propose an energy-efficient virtual cooperative spectrum sensing with the sequential 0/1 fusion rule to reduce the average number of decisions without any loss in the detection performance. Sequentially, the authors formulate the optimisation of virtual cooperative spectrum sensing for unmanned aerial vehicle-based interweave cognitive ratio system as the optimal sequential 0/1 fusion problem on the basis of the K-out-of-N fusion rule and prove the formulated problem indeed has one optimal K, which yields the highest throughput. Finally, numerical simulations are presented to demonstrate the correctness of theoretical analyses and the effectiveness of the virtual cooperative spectrum sensing with the sequential 0/1 fusion rule.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Sulfonamides (SAs) are widespread
in soils, and their dissipation
behavior is important for their fate, risk assessment, and pollution
control. In this work, we investigated the dissipation behavior of
different SAs in a soil under aerobic condition, focusing on revealing
the relationship between overall dissipation (without sterilization
and in dark) and individual abiotic (sorption, hydrolysis)/biotic
(with sterilization and in dark) factors and taxonomy/function of
microbiomes. The results showed that dissipation of all SAs in the
soil followed the pseudo-first-order kinetic model with dissipation
time at 50% removal (DT50) of 2.16–15.27 days. Based
on, experimentally, abiotic/biotic processes and, theoretically,
partial least-squares modeling, a relationship between overall dissipation
and individual abiotic/biotic factors was developed with microbial
degradation as the dominant contributor. Metagenomic analysis showed
that taxonomic genera like Bradyrhizobium/Sphingomonas/Methyloferula and functions
like CAZy family GT51/GH23/GT2, eggNOG category S, KEGG pathway ko02024/ko02010,
and KEGG ortholog K01999/K03088 are putatively involved in SA microbial
degradation in soil. Spearman correlation suggests abundant genera
being multifunctional. This study provides some new insights into
SA dissipation and can be applied to other antibiotics/soils in the
future.
Terahertz perfect metamaterial absorbers (PMA) based on higher order resonances have exhibited important applications in detecting, sensing, and imaging. However, most of them suffer from polarization and incident-angle dependence due to their asymmetrical structure. Here, we numerically investigate a kind of ultrathin triple-band PMA with polarization stability and wide angle of incidence. Numerical results reveal that three resonance peaks with nearly 100% absorptivity are obtained at 1.605, 4.425, and 4.946 THz under different polarization angles. It is interestingly found that the absorptance of two higher order resonances is inversely increased when the size of the middle dielectric spacer is smaller. The three resonance peaks in transverse electric and transverse magnetic modes nearly maintain fixed for oblique incidence up to 60°. Importantly, another four-band and dual-band perfect absorptions are easily achieved by a complementary method without doing iterative numerical simulation. The complementary metamaterial based absorber reaches more than 98% absorptance at four resonance frequencies. The metamaterial absorber based on complementary resonator also obtains two absorption peaks at 2.65 and 5.84 THz.
The authors present a new asymmetric structure using an optimisable coil configuration and circuit model to eliminate frequency splitting and increase high‐efficiency transfer distance in wireless power transfer (WPT) via magnetic resonance coupling. A pair of non‐identical coils is proved theoretically and optimised to limit the coupling coefficient. The series–shunt mixed‐resonant circuit structure is adopted to promote the performance of WPT system. The advantages and characteristics of the asymmetric system using mixed‐resonant circuit structure based on appropriate non‐identical coils are depicted by numerical calculation and simulation. Moreover, the WPT system is finally set up to verify the theory prediction. All the calculated and experimental results show that frequency splitting is suppressed in close distance effectively. Moreover, the high‐efficiency transfer distance is proved to exceed the triple diameter of receiving coil. Therefore, a relatively high‐efficiency and long‐distance WPT system, which can be a good candidate for charging portable electronics, is obtained by selecting suitable circuit parameters and appropriate non‐identical coils.
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