RESUMEN
Localized electrons subject to applied magnetic fields can restart to propagate freely through the lattice in delocalized magnetic Bloch states (MBSs) when the lattice periodicity is commensurate with the magnetic length. Twisted graphene superlattices with moiré wavelength tunability enable experimental access to the unique delocalization in a controllable fashion. Here, we report the observation and characterization of high-temperature Brown-Zak (BZ) oscillations which come in two types, 1/B and B periodicity, originating from the generation of integer and fractional MBSs, in the twisted bilayer and trilayer graphene superlattices, respectively. Coexisting periodic-in-1/B oscillations assigned to different moiré wavelengths are dramatically observed in small-angle twisted bilayer graphene, which may arise from angle-disorder-induced in-plane heteromoiré superlattices. Moreover, the vertical stacking of heteromoiré supercells in double-twisted trilayer graphene results in a mega-sized superlattice. The exotic superlattice contributes to the periodic-in-B oscillation and dominates the magnetic Bloch transport.
RESUMEN
The on-line measurement of clamping force is essential for injection molding equipment and process. A method for on-line measurement of clamping force using ultrasonic technology is proposed in this study. Based on the sono-elasticity theory, a new mathematical model is established to describe the relationship between ultrasonic propagation time and clamping force. A series of experiments are then performed to validate the proposed method. Findings show this method corresponds well with the magnetic enclosed type clamping force tester method, with difference squares less than 0.65â¯(MPa)2, and standard deviations less than 0.11â¯MPa. Ultrasonic parameters influence measurement results, with larger ultrasonic probe wafer diameter and higher ultrasonic probe frequency producing better measurement accuracy. Additionally, measurement accuracy is insensitive to the sampling frequency of ultrasonic signals. The proposed method has the advantages of high accuracy and high stability, being non-interfering, non-destructive, low-cost, on-line and with good adherence to health and safety, and it has significant application prospects in injection molding production.
RESUMEN
In this manuscript we reveal the formation of bilayered hybrid perovskites of a new lower dimensional perovskite family, (CHMA)2(MA)n-1PbnI3 with n = 1-5, with high ambient stability via its crystallization driven self-assembly process. The spun-coated perovskite solution tends to crystallize and undergo phase separation during annealing, resulting in the formation of 2D/3D bilayered hybrid perovskites. Remarkably, this 2D/3D hybrid perovskites possess striking moisture resistance and displays high ambient stability up to 65 days. The bilayered approach in combining 3D and 2D perovskites could lead to a new era of perovskite research for high-efficiency photovoltaics with outstanding stability, with the 3D perovskite providing excellent electronic properties while the 2D perovskite endows it moisture stability.