A triple-band metamaterial perfect absorber (MPA) is presented in monolayer graphene the THz region, which adjustable and polarization-independent. The first layer of structure from top patterned contains a ring at center frame with four wheel-shaped around it triangles corner. This proposed has caused to achieve 98.64%, 99.97%, 99.98% absorption peaks 8.17 THz, 9.74 11.95 respectively. We can ...

In order to solve the problem of low frequency noise engine, based on principle dual port asymmetric sound absorber, a kind gradually changing size absorbing metasurface is designed reduce engine acoustic liner. Firstly, theoretical analysis model and simulation resonance absorber are established, reduction mechanism revealed, influencing factors effect analyzed. Then an liner absorber. The ana...

We analyze a 137 ks exposure X-ray spectrum of the Seyfert 1 galaxy NGC 5548 obtained with the XMM-Newton Reflection Grating Spectrometer. Due to the long exposure time, the spectrum is of higher statistical quality than the previous observations of this AGN. Therefore, we detect for the first time in NGC 5548 inner-shell transitions from O III to O VI ions, and the Unresolved Transition Array ...

RESUMEN El resumen será traducido al español por los editores. We are exploring the connection between damped Ly-alpha absorbers (DLAs) s and Lyman break galaxies (LBGs) using deep – m lim,I (5σ)=26 m AB – broad band imaging (UBVI) of four wide fields (0.25deg 2 each) obtained at the Kitt Peak 4-m telescope with MOSAIC. Each field contains a DLA at z ∼ 3. We want to address the nature of DLAs a...