Conceptual-based design of an ultrabroadband microwave metamaterial absorber.

By introducing metallic ring structural dipole resonances in the microwave regime, we have designed and realized a metamaterial absorber with hierarchical structures that can display an averaged -19.4 dB reflection loss (∼99% absorption) from 3 to 40 GHz. The measured performance is independent of the polarizations of the incident wave at normal incidence, while absorption at oblique incidence remains considerably effective up to 45°. We provide a conceptual basis for our absorber design based on the capacitive-coupled electrical dipole resonances in the lateral plane, coupled to the standing wave along the incident wave direction. To realize broadband impedance matching, resistive dissipation of the metallic ring is optimally tuned by using the approach of dispersion engineering. To further extend the absorption spectrum to an ultrabroadband range, we employ a double-layer self-similar structure in conjunction with the absorption of the diffracted waves at the higher end of the frequency spectrum. The overall thickness of the final sample is 14.2 mm, only 5% over the theoretical minimum thickness dictated by the causality limit.

[Evaluation of Muscle Fatigue in Spinal Surgery Instruments Based on sEMG-JASA].

Based on the joint analysis of EMG spectrum and amplitude method (JASA), a study on muscle fatigue assessment of spinal surgical instruments based on surface EMG signals was carried out, and a comparative evaluation of the operating comfort before and after the optimization of spinal surgical instruments was completed. A total of 17 subjects were recruited to collect the surface EMG signals of their brachioradialis and biceps. Five surgical instruments before and after optimization were selected for data comparison, and the operating fatigue time proportion of each group of instruments under the same task was calculated based on the RMS and MF eigenvalues. The results showed that when completing the same operation task, the operation fatigue time of the surgical instruments before optimization was significantly higher than that after optimization (P<0.05); there was no significant difference in the fatigue status of brachioradialis and biceps when operating the same instrument (P>0.05). These results provide objective data and reference for the ergonomic design of surgical instruments and fatigue damage protection.

Simulation on antireflection of the oxide nanosphere monolayer film.

We theoretically simulate the antireflective effects of oxide nanosphere monolayer films in the visible spectrum. The essential geometric and material parameters of nanosphere films are simulated and different functions are proposed to describe the dependence of reflectance on the influencing factors. The rational function is fitted to describe the monotonic decreasing of reflectance on the ratio of nanospheres' radius to incident wavelength. At a wavelength of 550 nm and incidence at 75°, the reflectance of the glass substrate coated with SiO2 decreases to 14.1% compared with 41.7% of the uncoated glass. The results have an excellent potential for applications in optical devices such as filters, polarizing elements, and camera lenses.