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- ItemUltra-high sensitive strain sensor based on post-processed optical fiber Bragg grating(Basel : MDPI AG, 2014) Ferreira, M.S.; Bierlich, J.; Becker, M.; Schuster, K.; Santos, J.L.; Frazão, O.An ultra-high sensitive strain sensor is proposed. The sensing head, based on the post-processing of a fiber Bragg grating, is used to perform passive and active strain measurements. Both wavelength and full width half maximum dependences with the applied strain are studied for the passive sensor, where maximum sensitivities of 104.1 pm/με and 61.6 pm/με are respectively obtained. When combining the high performance of this sensor with a ring laser cavity configuration, the Bragg grating will act as a filter and high resolution measurements can be performed. With the proposed sensor, a resolution of 700 nε is achieved.
- ItemMagnetic field effects of double-walled carbon nanotubes(São Carlos : Universidade Federal de São Carlos, 2006) Latgé, A.; Grimm, D.; Ferreira, M.S.A theoretical discussion of electronic and transport properties of a particular family of double-wall carbon nanotubes, named commensurate structures of the armchair type (n,n)@(2n,2n) is addressed. A single p-band tight binding hamiltonian is considered and the magnetic field is theoretically described by following the Peierls approximation into the hopping energies. Our emphasis is put on investigating the main effects of the geometrical aspects and relative positions of the tubes on the local density of states and on the conductance of the system. By considering intershell interactions between a set of neighboring atoms on the walls of the inner and outer tubes, we study the possibility of founding Aharonov-Bohm effects in the DWCNs when a magnetic field is applied along the axial direction.