Topic
Frequency response
About: Frequency response is a research topic. Over the lifetime, 25705 publications have been published within this topic receiving 332249 citations.
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TL;DR: In this article, a compact fiber Bragg grating (FBG) vibration sensor consisting of a flat diaphragm and two L-shaped rigid cantilever beams for seismic measurement has been proposed and experimentally demonstrated.
Abstract: A compact fiber Bragg grating (FBG) vibration sensor consisting a flat diaphragm and two L-shaped rigid cantilever beams for seismic measurement has been proposed and experimentally demonstrated. The specially designed sensing configuration contributes many desirable features such as a wide frequency response range (10-120 Hz), an extremely high sensitivity coefficient (~100pm/g) together with a robust metal package for improving the mechanical strength and a decreased transverse sensitivity (<; 5%), making it a good candidate for in-field seismic wave measurement in oil and gas exploration.
76 citations
TL;DR: In this paper, four antennas are thoroughly studied by means of their theoretical and experimental behavior when measuring electromagnetic pulses radiated by PD activity and the results are analyzed in detail.
Abstract: Partial discharge (PD) detection is a widely extended technique for electrical insulation diagnosis. Ultrahigh-frequency detection techniques appear as a feasible alternative to traditional methods owing to their inherent advantages such as the capability to detect PDs online and to locate the piece of equipment with insulation problems in substations and cables. In this paper, four antennas are thoroughly studied by means of their theoretical and experimental behavior when measuring electromagnetic pulses radiated by PD activity. The theoretic study of the band of frequencies in which the pulse emits and the measurement of the parameters $S_{11}$ are complemented with the frequency response and wavelet transform of a set of 500 time signals acquired by the antennas, and the results are analyzed in detail.
76 citations
TL;DR: In this article, a sinusoidal perturbation of high amplitude is applied to the fuel cell current and the resulting voltage is analysed using the concept of higher order frequency response functions.
76 citations
TL;DR: The analysis of the electric field distribution, electron and hole concentration and drift velocities in the device shows that the enhanced gain-bandwidth-product at high bias voltages is due to a decrease of the transit time and avalanche build-up time limitation at high fields.
Abstract: In this work we report a separate-absorption-charge-multiplication Ge/Si avalanche photodiode with an enhanced gain-bandwidth-product of 845 GHz at a wavelength of 1310 nm. The corresponding gain value is 65 and the electrical bandwidth is 13 GHz at an optical input power of -30 dBm. The unconventional high gain-bandwidth-product is investigated using device physical simulation and optical pulse response measurement. The analysis of the electric field distribution, electron and hole concentration and drift velocities in the device shows that the enhanced gain-bandwidth-product at high bias voltages is due to a decrease of the transit time and avalanche build-up time limitation at high fields.
76 citations
TL;DR: The transfer functions clearly show that the rigidity of the head-neck system increases as a function of the continuous value of the applied force, which suggests that the system behaves as a quasi-linear second order system with two degrees of freedom.
Abstract: The response of the head-neck system to forces of small amplitude (up to 15 N) is described. Sinusoidal (0.6–20 Hz) and impulsive (duration: 100 msec) forces are applied in the sagittal plane to the head of the subject who is instructed to resist the disturbancy. In the case of sinusoidal forces of frequency less than about 2 Hz the active effort to resist the disturbancy results in a largely distorted sinusoidal displacement. Above this frequency the response becomes almost linear. The variations with frequency of the amplitude and the phase of the linear response relative to the applied force (transfer function) are used to characterize the dynamics of the system. The transfer functions evaluated from the impulse response are very similar in shape to those obtained with sinusoidal forces. In both cases the results suggest that the system behaves as a quasi-linear second order system with two degrees of freedom. The most prominent nonlinearities, beyond those present in the low frequency range, are related to the properties of the neck muscles. In particular, the transfer functions clearly show that the rigidity of the system increases as a function of the continuous value of the applied force. On the basis of previous work, both the passive properties of the muscles and those pertaining to the neuronal control system are pooled together in the form of viscoelastic parameters. A simple model of the system is introduced and applied to the experimental results. Its main features are 1) the presence of two centers of rotation. 2) the dependency of the viscoelastic parameters (stiffness and viscosity) on the frequency. It is suggested that both these features are necessary and sufficient to account for the observed behaviour above 2 Hz.
76 citations