Smart Table Based on Metasurface for Wireless Power Transfer

Metasurfaces have been investigated and its numerous exotic functionalities and the potentials to arbitrarily control of the electromagnetic fields have been extensively explored. However, only limited types of metasurface have finally entered into real products. Here, we introduce a concept of a metasurface-based smart table for wirelessly charging portable devices and report its first prototype. The proposed metasurface can efficiently transform evanescent fields into propagating waves which significantly improves the near field coupling to charge a receiving device arbitrarily placed on its surface wirelessly through magnetic resonance coupling. In this way, power transfer efficiency of 80$\%$ is experimentally obtained when the receiver is placed at any distances from the transmitter. The proposed concept enables a variety of important applications in the fields of consumer electronics, electric automobiles, implanted medical devices, etc. The further developed metasurface-based smart table may serve as an ultimate 2-dimensional platform and support charging multiple receivers.Comment: 8 pages, 7 figure

Nonradiating sources for efficient wireless power transfer

Nonradiating sources of energy realized under a wave scattering on high-index dielectric nanoparticles have attracted a lot of attention in nano-optics and nanophotonics. They do not emit energy to the far-field, but simultaneously provides strong near-field energy confinement. Near-field wireless power transfer technologies suffer from low efficiency and short operation distance. The key factor to improve efficiency is to reduce the radiation loss of the resonators included in the transmitter and receiver. In this paper, we develop a wireless power transfer system based on nonradiating sources implemented using colossal permittivity dielectric disk resonator and a subwavelength metal loop. We demonstrate that this nonradiating nature is due to the hybrid anapole state originated by destructive interference of the fields generated by multipole moments of different parts of the nonradiating source, without a contribution of toroidal moments. We experimentally investigate a wireless power transfer system prototype and demonstrate that higher efficiency can be achieved when operating on the nonradiating hybrid anapole state compared to the systems operating on magnetic dipole and magnetic quadrupole modes due to the radiation loss suppression. © 2021 Esmaeel Zanganeh et al., published by De Gruyter, Berlin/Boston

Anomalous Reflection From Hyperbolic Media

Despite the apparent simplicity, the problem of refraction of electromagnetic waves at the planar interface between two media has an incredibly rich spectrum of unusual phenomena. An example is the paradox that occurs when an electromagnetic wave is incident on the interface between a hyperbolic medium and an isotropic dielectric. At certain orientations of the optical axis of the hyperbolic medium relative to the interface, the reflected and transmitted waves are completely absent. In this paper, we formulate the aforementioned paradox and present its resolution by introduction of infinitesimal losses in a hyperbolic medium. We show that the reflected wave exists, but became extremely decaying as the loss parameter tends to zero. As a consequence, all the energy scattered into the reflected channel is absorbed at the interface. We support our reasoning with analytical calculations, numerical simulations, and an experiment with self-complementary metasurfaces in the microwave region. In addition to the great fundamental interest, this paradox resolution discovers a plethora of applications for the reflectors, refractors, absorbers, lenses, antennas, camouflage and holography applications.Comment: 16 pages, 4 figure

Vegetation Landscape Changes and Driving Factors of Typical Karst Region in the Anthropocene

Vegetation degeneration has become a serious ecological problem for karst regions in the Anthropocene. According to the deficiency of long serial and high-resolution analysis of karst vegetation, this paper reconstructed the variation of vegetation landscape changes from 1987 to 2020 in a typical karst region of China. Using Landsat time series data, the dynamic changes and driving factors of natural karst vegetation were identified at the landscape scale. On the premise of considering the time-lag effect, the main climatic factors that influence vegetation growth were presented at the interannual timescale. Then, the approach of residual analysis was adopted to distinguish the dominant factors affecting vegetation growth. Results of trend analysis revealed that 21.5% of the forestland showed an overall significant decline in vegetation growth, while only 1.5% showed an increase in vegetation growth during the study period. Precipitation and radiation were the dominant meteorological factors influencing vegetation at the interannual timescale, as opposed to temperature. More than 70% of the natural vegetation growth was dominated by climatic factors. The area percentage of negative human impact has increased gradually since 2009 and reached 18.5% in 2020, indicating the currently serious situation of vegetation protection; fortunately, in recent years, human disturbances on vegetation have been mitigated in karst areas with the promotion of ecological conservation and restoration projects

Metasurface for Near-Field Wireless Power Transfer with Reduced Electric Field Leakage

Wireless power transfer is a breakthrough technology which can be used in all aspects of humans daily life. Here, a bi-layer metasurface as a transmitter for near-field wireless power transfer is proposed and studied. The novelty and advantage of the proposed metasurface is the spatial separation of the electric and magnetic near fields. Magnetic fields responsible for power transfer are sufficiently high on top of the metasurface whereas the electric fields are almost completely confined between two layers of the metasurface. These unique properties have been obtained due to the special metasurface design based on two orthogonal layers of resonant wires immersed in high-permittivity background. The theoretical and experimental study reveal the quasi-uniform magnetic field distribution over the metasurface dimensions of $40\times 40$ cm2 that makes it suitable for wireless power transfer via resonant magnetic coupling to one or several receivers placed above it. Compared with a conventional planar spiral coilsolution, the specific absorption rate of the proposed metasurface is reduced by 47 times, which enables to greatly increase the allowable transferred power without violating the safety regulation and reducing the efficiency.Peer reviewe

Analysis of influencing factors of job demands of healthcare workers working in mobile cabin hospitals in China

Abstract Aim To explore the job demands of healthcare workers (HCWs) working in mobile cabin hospitals in Shanghai and identify the influencing factors. Design The study had a cross‐sectional design. Methods Using the convenience sampling method, we selected 1223 HCWs (medical team members) working in these mobile cabin hospitals during April–May 2022. The findings of the general information questionnaire and the hierarchy scale of job demands of HCWs working in mobile cabin hospitals were used for the investigation. Results The total score of job demands of the included HCWs was 132.26 ± 9.53; the average score of the items was 4.73 ± 0.34. Multivariate linear regression analyses showed that the following HCWs had significantly higher job demands: female HCWs and HCWs who received psychological training or intervention during the COVID‐19 pandemic, were satisfied with the doctor/nurse–patient relationship, received support from family members/friends/colleagues, believed that the risk of working in mobile cabin hospitals was high, had adapted to the working environment of mobile cabin hospitals and had college/undergraduate level of education. They would benefit from increased social support and better training in terms of psychological coping mechanisms(both theoretical knowledge and applicable skills) and COVID‐19 prevention,control and treatment abilities

CO2-Involved and Isocyanide-based Three-component Polymerization toward Functional Heterocyclic Polymers with Self-assembly and Sensing Properties

CO2 utilization has been a hot research topic in academic and industrial respects. Besides converting CO2 into chemicals and fuels, incorporating it into the polymers to construct functional materials is another promising strategy. However, the CO2-involved polymerization techniques should be further developed. In this work, a facile and efficient CO2-involved multicomponent polymerization is successfully developed. The reaction of monomers of CO2, isocyanides and 2-iodoanilines readily produces soluble and thermally stable poly(benzoyleneurea)s with well-defined structures under mild conditions. Thanks to the formed amide groups in the heterocyclic units in the main-chains, the resultant polymers could self-assemble into spheres with sizes between 200 and 1000 nm. The polymers containing tetraphenylethylene (TPE) unit show the unique aggregation-enhanced emission (AEE) features, which could be used to visualize the self-assembly process and morphologies under UV irradiation, and serve as fluorescence probe to selectively and sensitively detect Au3+ ions. Notably, the polymers containing cis- and trans-TPE units exhibit different behaviors in self-assembly and limit of detection for Au3+ ions due to the different intermolecular interactions. Thus, this work not only provides a new strategy for CO2 utilization but also furnishes a series of functional heterocyclic polymers for diverse applications