Near-zero-index (NZI) media, a medium with near zero permittivity and/or permeability, exhibits unique wave phenomena and exciting potential for multiple applications. However, previous proof-of-concept realizations of NZI media based on bulky and expensive platforms are not easily compatible with low-cost and miniaturization demands. Here, we propose the method of substrate-integrated (SI) photonic doping, enabling the implementation of NZI media within a printed circuit board (PCB) integrated design. Additionally, the profile of the NZI device is reduced by half by using symmetries. We validate the concept experimentally by demonstrating NZI supercoupling in straight and curve substrate integrated waveguides, also validating properties of position-independent photonic doping, zero-phase advance and finite group delay. Based on this platform, we propose design of three NZI devices: a high-sensitivity dielectric sensor, an efficient acousto-microwave modulator, and an arbitrarily-curved ‘electric fiber’. Our results represent an important step forward in the development of NZI technologies for microwave/terahertz applications.

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We designed simulations for the high-temperature event that occurred on 23 July 2003 in East China using a series of forecast lead times, from short-range to medium-range, and four land surface schemes (LSSs) (i.e., SLAB, NOAH, RUC, and PX) in the Weather Research and Forecasting Model (WRF), Version 3. The sensitivities of short and medium-range simulations to the LSSs systematically varied with the lead times. In general, the model reproduced short-range, high-temperature distributions. The simulated weather was sensitive to the LSSs, and the LSS-induced sensitivity was higher in the medium range than in the short-range. Furthermore, the LSS performances were complex, i.e., the PX errors apparently increased in the medium range (longer than 6 days), RUC produced the maximum errors, and SLAB and NOAH had approximately equivalent errors that slightly increased. Additional sensitivity simulations revealed that the WRF modeling system assigns relatively low initial soil moisture for RUC and that soil moisture initialization plays an important role that is comparable to the LSS choice in the simulations. LSS-induced negative feedback between surface air temperature (SAT) and atmospheric circulation in the lower atmosphere was found in the medium range. These sensitivities were mainly caused by the LSS-induced differences in surface sensible heat flux and by errors associated with the lead times. Using the SAT equation, further diagnostic analyses revealed LSS deficiencies in simulating surface fluxes and physical processes that modify the SAT and indicated the main reasons for these deficiencies. These results have implications for model improvement and application.

The metasurfaces have recently been demonstrated to provide full control of the phase responses of electromagnetic (EM) wave scattering over subwavelength scales, enabling a wide range of practical applications. Here, we propose a comprehensive scheme for the efficient and flexible design of metasurface Salisbury screen (MSS) capable of absorbing the impinging EM wave in an ultra-wide frequency band. We show that properly designed reflective metasurface can be used to substitute the metallic ground of conventional Salisbury screen for generating diverse resonances in a desirable way, thus providing large controllability over the absorption bandwidth. Based on this concept, we establish an equivalent circuit model to qualitatively analysis the resonances in MSS and design algorithms to optimize the overall performance of the MSS. Experiments have been carried out to demonstrate that the absorption bandwidth from 6 GHz to 30 GHz with an efficiency higher than 85% can be achieved by the proposal, which is apparently much larger than that of conventional Salisbury screen (7 GHz - 17 GHz). The proposed concept of MSS could offer opportunities for flexibly designing thin electromagnetic absorbers with simultaneously ultra-wide bandwidth, polarization insensitivity, and wide incident angle, exhibiting promising potentials for many applications such as in EM compatibility, stealth technique, etc.

A heavy rainfall event occurring in the Yangtze‐Huaihe valley and south China during late June, 2003 was simulated to examine the effects of different land‐surface schemes on simulated precipitations using the Weather Research and Forecasting Model (WRF) Version 3.1 and National Centers for Environmental Prediction (NCEP) analysis data. The simulation was performed in the short‐range mode for 24‐h integrations. The results show that generally the simulated heavy rainfall event is sensitive to different land‐surface schemes, the scheme‐induced difference of threat score becomes larger as the forecast categories of rainfall gets higher within the relatively large study subarea, where the scheme‐induced relative differences of precipitation can amount up to 30% with an average of 7%, while the maximum values of daily precipitation differences can be as large as 100%~150%, and different schemes lead to simulated systematic differences in averaged sensible and latent heat fluxes that are characterized by regional distributions. Finally, the land‐surface schemes can substantially affect the simulated precipitations via two mechanisms, i.e., by affecting land surface evaporation, and by affecting low‐level atmospheric circulation and water vapor convergence, the schemes exert great influences, respectively, on the simulated rainfall over a relatively large area of the model domain (e.g., with an average difference of 7% and a maximum difference of ~30%), and on simulated heavy rainfalls within small areas including rainfall centers (e.g., up to differences within 100%~150%). All these suggest that different land surfaces affect heavy rainfall weather at different spatial scales and to different extents, and that improving the land‐surface schemes can lead to better simulation of the heavy‐rainfall weather with the WRF model.