Resonant MEMS accelerometers offer the potential for very high resolution and wide bandwidth measurements over a large input dynamic range. The read-out is implemented by constructing an oscillator with the resonator as the primary frequency determining element. The noise of this oscillator front-end typically determines the resolution of the device, and the noise floor is set by the modulation of operative noise processes by the system dynamics. The resonator element is typically operated in the linear regime to prevent the detrimental impact of resonator non-linearities on noise conversion limiting frequency stability. However, by operating at higher drive power levels it is possible to also increase the signal-to-noise ratio for sufficiently large input frequencies. This paper shows that improved device performance over a wide bandwidth is possible by employing appropriate amplitude and phase feedback schemes to optimally bias the resonator thus enabling both short-term and long-term measurements with an electrically tunable resolution.
Oscillator; Radio Frequency; Circuit; Plasma; inverter; Fluorescence.
Contributors:Kavaler, Nathaniel, Lyon, Stephen A
We present a design for a heterojunction bipolar transistor based Colpitts oscillator for cryogenic capacitance measurement. We also present the design of an interdigitated capacitor to detect changes in dielectric constant of a fluid on the surface of a printed circuit board, along with frequency measurements of this system in air and liquid nitrogen. Designs and frequency measurements are also presented for a tunnel diode based oscillator.
Contributors:Be'Er, O, Ohadi, Hamid, Del Valle-Inclan Redondo, Yago, Ramsay, AJ, Tsintzos, SI, Hatzopoulos, Z, Savvidis, PG, Baumberg, Jeremy
We report spin and intensity coupling of an exciton-polariton condensate to the mechanical vibrations of a circular membrane microcavity. We optically drive the microcavity resonator at the lowest mechanical resonance frequency while creating an optically-trapped spin-polarized polariton condensate in different locations on the microcavity, and observe spin and intensity oscillations of the condensate at the vibration frequency of the resonator. Spin oscillations are induced by vibrational strain driving, whilst the modulation of the optical trap due to the displacement of the membrane causes intensity oscillations in the condensate emission. Our results demonstrate spin-phonon coupling in a macroscopically coherent condensate.
This paper deals with the definition of the lube-oil film thickness in the piston ring cylinder liner junction of an internal combustion engine. At first, a mathematical model for the estimation of the film thickness is established. It is used to point out the oscillating motion of the piston ring normal to the cylinder wall. For the first time, has been highlighted and analytically evaluated the oscillating behavior of the piston ring in its housing in the radial direction. Furthermore, it is demonstrated that the radial oscillationsfrequency is a function of piston ring stiffness, material and geometry.
A theory has been developed for small oscillations of a thin filament in the magnetosphere.
For the lowest-frequency even modes, the eigenfunctions are essentially buoyancy waves in the plasma sheet, but they are more like slow modes in the inner magnetosphere.
For the lowest-frequency even modes, the eigenfrequencies (radians/s) have peak values of approximately 0.07 s-1 between the inner plasma sheet and plasmapause, for an average magnetospheric field.
This includes software and model data used in this paper.
Submitted to JGR for review
Contributors:Peters, Steven Ray
Bibliography: p. 135-145,Some pages are in colour.,
Contributors:Samir Avdakovic, Amir Nuhanovic
Power system oscillations
Contributors:Farzad Rafieian, François Girardin, Zhaoheng Liu, Marc Thomas, Bruce Hazel
Detection of high-frequency repeating impacts in robotic grinding (detailed views). (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
... Impact-cutting map from the speed signal based on the experiment with the bump showing (─) a major regime of 2 impacts/revolution and (…) minor oscillations. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
... Vibration and rotational frequency in single-pass grinding (overview). (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
... Typical values of ω, ωmax and Δω during a cutting impact from measured rotational frequency in Test (3) at 4500rpm. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)
... Instantaneous angular frequency