Theory of high frequency, large-amplitude sinusoidal voltammetry for ideal surface-confined redox systems

2011 ◽  
Vol 56 (22) ◽  
pp. 7569-7579 ◽  
Author(s):  
Christopher G. Bell ◽  
Costas A. Anastassiou ◽  
Danny O’Hare ◽  
Kim H. Parker ◽  
Jennifer H. Siggers
Keyword(s):  
High Frequency ◽  
Large Amplitude ◽  
Redox Systems

scholarly journals Theoretical treatment of high-frequency, large-amplitude ac voltammetry applied to ideal surface-confined redox systems

2012 ◽  
Vol 64 ◽  
pp. 71-80 ◽  
Author(s):  
Christopher G. Bell ◽  
Costas A. Anastassiou ◽  
Danny O’Hare ◽  
Kim H. Parker ◽  
Jennifer H. Siggers
Keyword(s):  
High Frequency ◽  
Large Amplitude ◽  
Theoretical Treatment ◽  
Redox Systems ◽  
Ac Voltammetry

High-frequency vibration energy harvesting from repeated impulsive forcing utilizing intentional dynamic instability caused by strong nonlinearity

2016 ◽  
Vol 28 (4) ◽  
pp. 468-487 ◽  
Author(s):  
Kevin Remick ◽  
D Dane Quinn ◽  
D Michael McFarland ◽  
Lawrence Bergman ◽  
Alexander Vakakis
Keyword(s):  
Energy Harvesting ◽  
Mechanical System ◽  
High Frequency ◽  
Large Amplitude ◽  
Electromechanical Coupling ◽  
Dynamic Instability ◽  
Vibration Energy ◽  
Primary System ◽  
Vibration Energy Harvesting ◽  
Strongly Nonlinear

The work in this study explores the excitation of high-frequency dynamic instabilities to enhance the performance of a strongly nonlinear vibration-based energy harvesting system subject to repeated impulsive excitations. These high-fraequency instabilities arise from transient resonance captures (TRCs) in the damped dynamics of the system, leading to large-amplitude oscillations in the mechanical system. Under proper forcing conditions, these high-frequency instabilities can be sustained. The primary system is composed of a grounded, weakly damped linear oscillator, which is directly subjected to impulsive forcing. A light-weight, damped nonlinear oscillator (nonlinear energy sink, NES) is coupled to the primary system using electromechanical coupling elements and strongly nonlinear stiffness elements. The essential (nonlinearizable) stiffness nonlinearity arises from geometric and kinematic effects resulting from the traverse deflection of a piano wire coupling the two oscillators. The electromechanical coupling is composed of a neodymium magnet and inductance coil, which harvests the energy in the mechanical system and transfers it to the electrical system which, in this present case, is composed of a simple resistive element. The energy dissipated in the circuit is inferred as a measure of energy harvesting capability. The large-amplitude TRCs result in strong, nearly irreversible energy transfer from the primary system to the NES, where the harvesting elements work to convert the mechanical energy to electrical energy. The primary goal of this work is to numerically and experimentally demonstrate the efficacy of inducing sustained high-frequency dynamic instability in a system of mechanical oscillators to achieve enhanced vibration energy harvesting performance. This work is a continuation of a companion paper (Remick K, Quinn D, McFarland D, et al. (2015) Journal of Sound and Vibration Final Publication) where vibration energy harvesting of the same system subject to single impulsive excitation is studied.

scholarly journals Large-amplitude Dithering Mitigates Glitches in Digital-to-analogue Converters

2019 ◽  
Author(s):  
Arnfinn Eielsen ◽  
John Leth ◽  
Andrew J. Fleming ◽  
Adrian Wills ◽  
Brett Ninness
Keyword(s):  
Motion Control ◽  
High Precision ◽  
High Frequency ◽  
Large Amplitude ◽  
Control Law ◽  
Control Applications ◽  
Precision Motion Control ◽  
Low Pass ◽  
Converter Topologies ◽  
Precision Motion

This paper develops and experimentally evaluates a dither-based method for improved generation of arbitrary signals in digital-to-analogue converters that exhibits glitches --- essentially converting the glitches from high-frequency to low-frequency disturbances. One major benefit of this behaviour appears in closed-loop control applications, as the glitch disturbance can be moved from outside control law bandwidth to inside control law bandwidth, enabling suppression by feedback. A behavioural model of glitches is presented and the effect of applying a dither signal is analysed in detail. Analytical and experimental results demonstrate that a dither signal with sufficiently large amplitude can mitigate the effect of glitches, when used in conjunction with a low-pass filter. Severe glitches appear in various digital-to-analogue converter topologies, including converter topologies that are used in high-precision motion control applications, such as adaptive optics and scanning force microscopy. Glitches introduce impulse-like disturbances which have a broadband frequency distribution. Low-pass filtering alone does not provide sufficient attenuation, and in applications with feedback control only frequency content within the control law bandwidth is attenuated. Hence, a high-frequency disturbance such as a glitch will not be suppressed. The use of dithering to suppress glitches is therefore beneficial in applications where errors in signal conversion are a primary concern, such as high-precision motion control or accurate reference signal generation.

Theoretical Analysis of Transitional and Partial Cavity Instabilities

2001 ◽  
Vol 123 (3) ◽  
pp. 692-697 ◽  
Author(s):  
Satoshi Watanabe ◽  
Yoshinobu Tsujimoto ◽  
Akinori Furukawa
Keyword(s):  
Stability Analysis ◽  
Theoretical Analysis ◽  
High Frequency ◽  
Large Amplitude ◽  
Cavity Length ◽  
Present Calculation ◽  
Blade Surface ◽  
Closed Cavity ◽  
Singularity Method ◽  
Time Marching

This paper describes a new time marching calculation of blade surface cavitation based on a linearized free streamline theory using a singularity method. In this calculation, closed cavity models for partial and super cavities are combined to simulate the transitional cavity oscillation between partial and super cavities. The results for an isolated hydrofoil located in a 2-D channel are presented. Although the re-entrant jet is not taken into account, the transitional cavity oscillation with large amplitude, which is known to occur when the cavity length exceeds 75 percent of the chord length, was simulated fairly well. The partial cavity oscillation with relatively high frequency was simulated as damping oscillations. The frequency of the damping oscillation agrees with that of a stability analysis and of experiments. The present calculation can be easily extended to simulate other cavity instabilities in pumps or cascades.

Theory of stimulated scattering of large-amplitude waves

2000 ◽  
Vol 64 (4) ◽  
pp. 353-357 ◽  
Author(s):  
L. STENFLO ◽  
P. K. SHUKLA
Keyword(s):  
Growth Rates ◽  
High Frequency ◽  
Large Amplitude ◽  
Electromagnetic Waves ◽  
Long Term Evolution ◽  
Stimulated Scattering ◽  
Term Evolution ◽  
Laboratory Plasmas ◽  
General Dispersion

Comprehensive comments on the theory of stimulated scattering instabilities of high-frequency electromagnetic waves in magnetized plasmas are presented. It is shown that our general dispersion relations are appropriate for deducing valuable information regarding the growth rates of scattering instabilities and the long-term evolution of modulationally unstable waves in space and laboratory plasmas as well as in astrophysical settings.

scholarly journals Performance of a Self-Paced Brain Computer Interface on Data Contaminated with Eye-Movement Artifacts and on Data Recorded in a Subsequent Session

2008 ◽  
Vol 2008 ◽  
pp. 1-13 ◽  
Author(s):  
Mehrdad Fatourechi ◽  
Rabab K. Ward ◽  
Gary E. Birch
Keyword(s):  
Eye Movements ◽  
Eye Movement ◽  
High Frequency ◽  
Large Amplitude ◽  
Low Frequency ◽  
Computer Interface ◽  
Robust Performance ◽  
Contaminated Data ◽  
Online Test ◽  
Movement Artifacts

The performance of a specific self-paced BCI (SBCI) is investigated using two different datasets to determine its suitability for using online: (1) data contaminated with large-amplitude eye movements, and (2) data recorded in a session subsequent to the original sessions used to design the system. No part of the data was rejected in the subsequent session. Therefore, this dataset can be regarded as a “pseudo-online” test set. The SBCI under investigation uses features extracted from three specific neurological phenomena. Each of these neurological phenomena belongs to a different frequency band. Since many prominent artifacts are either of mostly low-frequency (e.g., eye movements) or mostly high-frequency nature (e.g., muscle movements), it is expected that the system shows a fairly robust performance over artifact-contaminated data. Analysis of the data of four participants using epochs contaminated with large-amplitude eye-movement artifacts shows that the system's performance deteriorates only slightly. Furthermore, the system's performance during the session subsequent to the original sessions remained largely the same as in the original sessions for three out of the four participants. This moderate drop in performance can be considered tolerable, since allowing artifact-contaminated data to be used as inputs makes the system available for users at ALL times.

scholarly journals Nonlinear low-frequency gravity waves in a water-filled cylindrical vessel subjected to high-frequency excitations

2013 ◽  
Vol 469 (2153) ◽  
pp. 20120536 ◽  
Author(s):  
Chunyan Zhou ◽  
Dajun Wang ◽  
Song Shen ◽  
Jing Tang Xing
Keyword(s):  
Gravity Waves ◽  
High Frequency ◽  
Water Waves ◽  
Large Amplitude ◽  
Low Frequency ◽  
Approximation Model ◽  
Fluid Structure Interactions ◽  
Governing Equations ◽  
Low Frequencies ◽  
Nonlinear Fluid

In the experiments of a water storage cylindrical shell, excited by a horizontal external force of sufficient large amplitude and high frequency, it has been observed that gravity water waves of low frequencies may be generated. This paper intends to investigate this phenomenon in order to reveal its mechanism. Considering nonlinear fluid–structure interactions, we derive the governing equations and the numerical equations describing the dynamics of the system, using a variational principle. Following the developed generalized equations, a four-mode approximation model is proposed with which an experimental case example is studied. Numerical calculation and spectrum analysis demonstrate that an external excitation with sufficient large amplitude and high frequency can produce gravity water waves with lower frequencies. The excitation magnitude and frequencies required for onset of the gravity waves are found based on the model. Transitions between different gravity waves are also revealed through the numerical analysis. The findings developed by this method are validated by available experimental observations.

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