Browsing by Author "Lee, Y. H."

Now showing 1 - 4 of 4

Dichotomy of photoinduced quasiparticle on CuO2 planes of YBa2Cu3O7 directly revealed by femtosecond polarization spectroscopy
(2007-08-01)
Luo, C. W.
;
Chen, L. Y.
;
Lee, Y. H.
;
Wu, K. H.
;
Juang, J. Y.
The dichotomy of photoinduced quasiparticle dynamics in the anisotropic high T, superconductors (YBa2CU3O7) is revealed by using the orientation-resolved ferntosecond reflection spectroscopy in the specially designed thin films. The transient reflectivity Delta R/R along the ab diagonal and b axis are totally different in the slow relaxation process which relates to the opening of the superconducting gap. In addition, the distribution of the temperature evolution of Delta R/R on the CuO2 planes of YBa2Cu3O7 may indicate the d-wave symmetry of the superconducting gap in high T, superconductors. (c) 2007 American Institute of Physics.
Speech Recognition for Cochlear Implant Users in the Noisy Environment: The Role of Envelope and Fine Structure
(2015)
Lee, Y. C.
;
Lee, Y. H.
;
Choi, Charles T. M.
;
電機學院
;
College of Electrical and Computer Engineering
Sound signal can be decomposed to a slowly varying envelope cue and a rapidly varying fine structure cue. These cues can help people to sound perception, sound lateralization, speech recognition in noise, and so on. Cochlear implant can help people with hearing loss to hear the sound. However, there are still many restrictions with cochlear implant user and a gap between normal hearing and cochlear implant user. This study investigated the contribution of envelope and fine structure cues with different SNR and simulated cochlear implant in Taiwanese mandarin speech recognition in noise. Ten normal hearing subjects participated in this experiment. Our result shows sentence recognition in noise almost depends on the envelope cues, but the fine structure cues still have limited contributions.
Ultrafast Dynamics in Optimally Doped YBa(2)Cu(3)O(7-delta) Observed with White Light Pump-probe Spectroscopy
(2011-01-01)
Wang, Y. T.
;
Lee, Y. H.
;
Chen, Y. -J.
;
Tang, W. T.
;
Luo, C. W.
The quasiparticle relaxation dynamics in optimally doped (001) YBa(2)Cu(3)O(7-delta) thin films were measured at various temperatures by white light pump-probe technique. The 2D ultrafast spectroscopy with broadband (similar to 200 nm) and high time-resolution (similar to 9 fs) was performed by the non-collinear optical parametric amplifier (NOPA). The relaxation time and the amplitude of the transient transmissivity changes (Delta T/T) are wavelength-dependent. The maximum Delta T/T appears at around 625 nm (similar to 1.98 eV) which corresponds to the transition between the Fermi level and the UHB (upper Hubbard band). Furthermore, the oscillations with similar to 150, similar to 320, similar to 500 cm(-1) have been clearly observed in the Fourier transformed graph of the 2D ultrafast spectroscopy, which are consistent with the phonon modes in Raman-scattering spectra.
Ultrafast Dynamics in Optimally Doped YBa2Cu3O7-delta Observed with White Light Pump-probe Spectroscopy
(2011-01-01)
Wang, Y. T.
;
Lee, Y. H.
;
Chen, Y. -J.
;
Tang, W. T.
;
Luo, C. W.
The quasiparticle relaxation dynamics in optimally doped (001) YBa2Cu3O7-delta thin films were measured at various temperatures by white light pump-probe technique. The 2D ultrafast spectroscopy with broadband (similar to 200 nm) and high time-resolution (similar to 9 fs) was performed by the non-collinear optical parametric amplifier (NOPA). The relaxation time and the amplitude of the transient transmissivity changes (Delta T/T) are wavelength-dependent. The maximum Delta T/T appears at around 625 nm (similar to 1.98 eV) which corresponds to the transition between the Fermi level and the UHB (upper Hubbard band). Furthermore, the oscillations with similar to 150, similar to 320, similar to 500 cm(-1) have been clearly observed in the Fourier transformed graph of the 2D ultrafast spectroscopy, which are consistent with the phonon modes in Raman-scattering spectra.