Fundamental frequency

About: Fundamental frequency is a research topic. Over the lifetime, 8941 publications have been published within this topic receiving 131583 citations.

Nonlocal Timoshenko beam theory for vibration of carbon nanotube-based biosensor

Abstract: This article studies vibration of carbon nanotube (CNT)-based biosensor A CNT-based biosensor is modeled as a nonlocal Timoshenko beam made of multiwall CNT carrying a spherical nanoscale bio-object at the free end, and the influence of the rotary inertia of the bio-object itself is considered The fundamental frequencies are computed via the transfer function method The effects of the attached spherical bio-object's rotary inertia and mass, the length-to-diameter of the CNT on the natural frequencies are discussed If the nonlocal parameter is neglected, the frequencies for four possible cases are compared Obtained results show that the rotary inertia decreases the fundamental frequency, while an increase in the diameter of the attached bio-object reduces the natural frequency, but causes frequency shift to rise The mass sensitivity of biosensor can be improved for short CNTs used The rotary inertia of the attached bio-object has a strong effect on the natural frequencies and cannot be simply neglected The nonlocal Timoshenko beam model is more adequate than the nonlocal Euler-Bernoulli beam model for short CNT biosensors Obtained results are helpful to the design of micro-cantilevered resonator as atomic-resolution mass sensor or biosensor

Complex pitch perception mechanisms are shared by humans and a New World monkey

Abstract: The perception of the pitch of harmonic complex sounds is a crucial function of human audition, especially in music and speech processing. Whether the underlying mechanisms of pitch perception are unique to humans, however, is unknown. Based on estimates of frequency resolution at the level of the auditory periphery, psychoacoustic studies in humans have revealed several primary features of central pitch mechanisms. It has been shown that (i) pitch strength of a harmonic tone is dominated by resolved harmonics; (ii) pitch of resolved harmonics is sensitive to the quality of spectral harmonicity; and (iii) pitch of unresolved harmonics is sensitive to the salience of temporal envelope cues. Here we show, for a standard musical tuning fundamental frequency of 440 Hz, that the common marmoset (Callithrix jacchus), a New World monkey with a hearing range similar to that of humans, exhibits all of the primary features of central pitch mechanisms demonstrated in humans. Thus, marmosets and humans may share similar pitch perception mechanisms, suggesting that these mechanisms may have emerged early in primate evolution.

On Design and Evaluation of Harmonic Transponders

Abstract: Performance and characterization of harmonic transponders is investigated both theoretically and experimentally. The harmonic response of a transponder based on a Schottky diode is analytically derived in the case when the excitation power is low. Theoretical calculations prove that at high frequencies, capacitive nonlinearity contributes more to frequency multiplication than resistive nonlinearity. This means that the feasibility of a particular diode for harmonic transponder applications largely depends on its varactor properties. Figures-of-merit (FOM) are derived both for the mixing diode and the transponder antenna. The validity of the proposed theoretical model is investigated experimentally using a harmonic transponder operating at 1 GHz fundamental frequency.

Inherent structure theory of networks and power system harmonics

Abstract: The inherent structure theory of networks, already applied in the literature at the fundamental frequency to a variety of planning problems, is extended to the field of power system harmonics. In the context of this theory, the harmonic admittance matrices are reformulated in terms of their eigenvalues and eigenvectors, showing that these expansions can be useful to create a framework in which the power system response to harmonic disturbances can be better understood. After the presentation of the theoretical background, some power system harmonic problems are tackled to show possible applications of this theory. Numerical experiments on a 17-busbar distribution system give evidence of the significance of application to the field of power system harmonics.