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We demonstrate theoretically and experimentally the phenomenon of vibrational resonance in a periodic potential, using cold atoms in an optical lattice as a model system. A high-frequency (HF) drive, with a frequency much larger than any characteristic frequency of the system, is applied by phase modulating one of the lattice beams. We show that the HF drive leads to the renormalization of the potential. We used transport measurements as a probe of the potential renormalization. The very same experiments also demonstrate that transport can be controlled by the HF drive via potential renormalization.
Assuntos
Luz , Modelos Teóricos , Fenômenos Ópticos , Transporte Biológico , VibraçãoRESUMO
Motivated by recent work [D. Cubero et al., Phys. Rev. E 82, 041116 (2010)], we examine the mechanisms which determine current reversals in rocking ratchets as observed when varying the frequency of the drive. We found that a class of these current reversals in the frequency domain is precisely determined by dissipation-induced symmetry breaking. Our experimental and theoretical work thus extends and generalizes the previously identified relationship between dynamical and symmetry-breaking mechanisms in the generation of current reversals.
RESUMO
INTRODUCTION: The present study aimed to obtain preliminary tympanometric data of young Malay adults and to compare the results between genders. METHODS: 96 undergraduate students (49 males and 47 females), aged 19-25 (mean and standard deviation 21.14 +/- 1.31) years, participated in this study. Otoscopic examination, pure tone audiometry, qualitative tympanogram and ipsilateral acoustic reflex were measured to ensure a clear ear canal, normal hearing and normal middle ear function, prior to tympanometric measurement. As a result, a total of 154 ears (80 ears from males and 74 ears from females) were selected for further statistical analyses. The tympanometric parameters measured were peak compensated static acoustic admittance (Peak Y(tm)), tympanometric width (TW) and equivalent ear canal volume (V(ea)). RESULTS: The results showed that the mean Peak Y(tm), V(ea) and TW for males were 0.81 mmhos, 1.48 cubic cm and 113.67 daPa, respectively. The mean Peak Y(tm), V(ea) and TW for females were 0.63 mmhos, 1.12 cubic cm and 98.04 daPa, respectively. Males were found to have significantly higher mean V(ea) and mean Peak Y(tm) than females. However no significant gender difference was observed in the mean TW. CONCLUSION: The current study suggests that young Malay adults may require gender-specific Peak Y(tm) and V(ea) values when implementing a quantitative approach in tympanogram interpretation.
