Multiple frequencies in quantum oscillations from underdoped YBa_2Cu_3O_6.5
High-precision measurements of the de Haas-van Alphen effect in the underdoped high-temperature superconductor \Y reveal three distinct frequencies in the quantum oscillations spectra. Analysis based on the standard Lifshitz-Kosevich theory reveal two satellite frequencies at F$_2$ = 450 T and F$_3$ = 630 T, on either side of a dominant frequency at F$_1$ = 540 T. Apart from a second harmonic of F$_1$, no other frequency is detected. We discuss the possibility that the satellite frequencies arise from bilayer splitting and warping of a single quasi-2D Fermi surface with c-axis dispersion, which indicates that c-axis coherence is restored at low temperature.
Through the study of the high-speed signal PCB(Printed Circuit Board)layout in the structure of the signal trace,for needs of smooth and controllable in PCB layout of high-speed digital server motherboard system,this paper proposes a three degree quasi-uniform B-spline dynamical fitting method.By reading overlap shape points in batches,property of high-speed signal traces with whole three degree quasi-uniform B-spline is realized.Through circuit debugging simulation,this dynamic fitting algorithm reduces high-speed signal attenuation effectively.