scattering so as to improve the performance or reduce the EM pollution. [1][2][3][4][5] With the extensive investigation in the past decades, various types of MAs have been developed and widely applied. Among them, magnetic MAs typically represented by composites containing ferrites or magnetic metal particles manifest much broader absorption bandwidth than nonmagnetic absorbers at the same thickness because of their high magnetic permeability. [6][7][8] However, they are reaching the ceiling of microwave absorption performance due to physical laws such as Snoek's limit, [9] as well as limited maneuverability of the material parameters. Moreover, they are all opaque due to the requirement of magnetic fillers with dark color. This makes them impossible to have the applications in window glass of stealth aircrafts and warships, [10] wireless local area network system, [11] radio frequency identification systems, [12] and electronic toll collection (ETC) system. [13] Recently, there have been increasing interests in metamaterials (MMs), which consist of sub-wavelength artificial unit cells. [14] With the proper design of the unit cells, the permittivity and permeability of MMs can be manipulated separately in a vast range beyond the conventional materials, bringing about some extraordinary properties, e.g., near-zero refractive index, [15] negative refraction, [16,17] and stimulating their applications in invisibility cloaks, [18,19] photon computer, [20] and super lens. [21] The design flexibility and abundant potential of the MMs also provide a chance to further improve the performance of MAs. [22][23][24][25] As a matter of fact, metamaterial absorbers (MMAs) have been demonstrated to show advantages such as near perfect absorption, [26] thin thickness, and light weight, [27] while the absorption bandwidth of MMAs has also been expanded significantly by developing a quantity of methods including the integration of multiple resonance units, [28,29] multilayered gradually varied structures, and more since their first demonstration. [30][31][32] Furthermore, for the absorption properties of MMAs depend highly on the structure and dimension of the unit cells rather than the optically obstructive microwave absorbing fillers as in conventional absorbers, the MMAs may also possess optical transparency. For example, the simple metamaterial consisting of indium tin oxide (ITO) square patches and a reflective backing spaced by a Optically transparent metamaterial microwave absorbers (MMAs) developed so far unexceptionally encounter an intrinsic contradiction between extending the absorption bandwidth and improving optical transparency, hindering their practical applications. This work, in its experiment and calculation, demonstrates an MMA with both broadband microwave absorption and excellent optical transparency by standing-up closed-ring resonators (CRRs) in an indium tin oxide backed Plexiglas board. The as-designed MMA shows a strong microwave absorption of 85% covering a wide frequency of 5.5-19.7 and 22.5-27.5 GHz u...
Monitoring the groundwater storage (GWS) changes is crucial to the rational utilization of groundwater and to ecological restoration in the Loess Plateau of China, which is one of the regions with the most extreme ecological environmental damage in the world. In this region, the mass loss caused by coal mining can reach the level of billions of tons per year. For this reason, in this work, in addition to Gravity Recovery and Climate Experiment (GRACE) satellite gravity data and hydrological models, coal mining data were also used to monitor GWS variation in the Loess Plateau during the period of 2005-2014. The GWS changes results from different GRACE solutions, that is, the spherical harmonics (SH) solutions, mascon solutions, and Slepian solutions (which are the Slepian localization of SH solutions), were compared with in situ GWS changes, obtained from 136 groundwater observation wells, and the aim was to acquire the most robust GWS changes. The results showed that the GWS changes from mascon solutions (mascon-GWS) match best with in situ GWS changes, showing the highest correlation coefficient, lowest root mean square error (RMSE) values and nearest annual trend. Therefore, the Mascon-GWS changes are used for the spatial-temporal analysis of GWS changes. Based on which, the groundwater depletion rate of the Loess Plateau was −0.65 ± 0.07 cm/year from 2005-2014, with a more severe consumption rate occurring in its eastern region, reaching about −1.5 cm/year, which is several times greater than those of the other regions. Furthermore, the precipitation and coal mining data were used for analyzing the causes of the groundwater depletion: the results showed that seasonal changes in groundwater storage are closely related to rainfall, but the groundwater consumption is mainly due to human activities; coal mining in particular plays a major role in the serious groundwater consumption in eastern region of the study area. Our results will help in groundwater resource management, ecological restoration, and policy planning for coal mining and economic development.
UiO-66 film is directly grown on the sensing area of a resonant microcantilever for toxic organophosphorus molecules detection.
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