Electronic and Optical Analysis of Strained Germanium Carbide Nanotubes Using a Density Functional Theory Approach
Ghobad Mohammad kari
Abstract Abstract
In this study, the electronic and optical properties of germanium carbide nanotubes (GeCNTs) with different chiral indices under applied strain were investigated using first-principles calculations based on density functional theory (DFT) within the PBE-GGA approximation. The results show that the (5,0) GeCNT exhibits a near-zero direct band gap with quasi-metallic behavior, whereas the (10,0) nanotube is a direct-band-gap semiconductor with a band gap of 1.29 eV. Optical analyses reveal that the main absorption and reflectivity features in out-of-plane polarization occur within the energy range of 1.5–4.0 eV, and their responses are significantly influenced by chirality and applied strain. These findings demonstrate that the tunable electronic and optical properties of GeCNTs make them promising candidates for optical sensors, nanoscale photonic devices, and infrared detection technologies.
Robust Adaptive Integrator Backstepping Control for Quadrotor UAV Stabilization Under Unknown Mass Uncertainty
Ali Hosseini Lagha
Abstract Quadrotor unmanned aerial vehicles are highly nonlinear, underactuated, and strongly coupled systems whose performance is sensitive to physical parameter uncertainties. Among these uncertainties, mass variation is especially important because it directly affects the altitude dynamics through the thrust-to-mass ratio. In practical missions, the quadrotor mass may change due to payload variation, battery replacement, mounted equipment, or modeling errors. Therefore, designing a stabilizing controller that does not require exact prior knowledge of the vehicle mass is essential for improving flight reliability and robustness.