65,974 research outputs found
Efficient computation of quasiperiodic oscillations in nonlinear systems with fast rotating parts
We present a numerical method for the investigation of quasiperiodic oscillations in applications modeled by systems of ordinary differential equations. We focus on systems with parts that have a significant rotational speed. An important element of our approach is to change coordinates into a co-rotating frame. We show that this leads to a dramatic reduction of computational effort in the case that gravitational forces can be neglected. As a practical example we study a turbocharger model for which we give a thorough comparison of results for a model with and without gravitational forces
An efficient nonlinear circuit simulation technique
This paper proposes a novel method for the analysis and simulation of integrated circuits (ICs) with the potential to greatly shorten the IC design cycle. The circuits are assumed to be subjected to input signals that have widely separated rates of variation, e.g., in communication systems, an RF carrier modulated by a low-frequency information signal. The proposed technique involves two stages. Initially, a particular order result for the circuit response is obtained using a multiresolution collocation scheme involving cubic spline wavelet decomposition. A more accurate solution is then obtained by adding another layer to the wavelet series approximation. However, the novel technique presented here enables the reuse of results acquired in the first stage to obtain the second-stage result. Therefore, vast gains in efficiency are obtained. Furthermore, a nonlinear model-order reduction technique can readily be used in both stages making the calculations even more efficient. Results will highlight the efficacy of the proposed approac
Time Domain Computation of a Nonlinear Nonlocal Cochlear Model with Applications to Multitone Interaction in Hearing
A nonlinear nonlocal cochlear model of the transmission line type is studied
in order to capture the multitone interactions and resulting tonal suppression
effects. The model can serve as a module for voice signal processing, it is a
one dimensional (in space) damped dispersive nonlinear PDE based on mechanics
and phenomenology of hearing. It describes the motion of basilar membrane (BM)
in the cochlea driven by input pressure waves. Both elastic damping and
selective longitudinal fluid damping are present. The former is nonlinear and
nonlocal in BM displacement, and plays a key role in capturing tonal
interactions. The latter is active only near the exit boundary (helicotrema),
and is built in to damp out the remaining long waves. The initial boundary
value problem is numerically solved with a semi-implicit second order finite
difference method. Solutions reach a multi-frequency quasi-steady state.
Numerical results are shown on two tone suppression from both high-frequency
and low-frequency sides, consistent with known behavior of two tone
suppression. Suppression effects among three tones are demonstrated by showing
how the response magnitudes of the fixed two tones are reduced as we vary the
third tone in frequency and amplitude. We observe qualitative agreement of our
model solutions with existing cat auditory neural data. The model is thus
simple and efficient as a processing tool for voice signals.Comment: 23 pages,7 figures; added reference
PID control system analysis and design
With its three-term functionality offering treatment of both transient and steady-state responses,
proportional-integral-derivative (PID) control provides a generic and efficient solution to realworld
control problems. The wide application of PID control has stimulated and sustained
research and development to "get the best out of PID", and "the search is on to find
the next key technology or methodology for PID tuning".
This article presents remedies for problems involving the integral and derivative terms. PID design objectives,
methods, and future directions are discussed. Subsequently, a computerized, simulation-based approach
is presented, together with illustrative design results for first-order, higher order, and nonlinear plants. Finally,
we discuss differences between academic research and industrial practice, so as to motivate new research
directions in PID control
Transmitting a signal by amplitude modulation in a chaotic network
We discuss the ability of a network with non linear relays and chaotic
dynamics to transmit signals, on the basis of a linear response theory
developed by Ruelle \cite{Ruelle} for dissipative systems. We show in
particular how the dynamics interfere with the graph topology to produce an
effective transmission network, whose topology depends on the signal, and
cannot be directly read on the ``wired'' network. This leads one to reconsider
notions such as ``hubs''. Then, we show examples where, with a suitable choice
of the carrier frequency (resonance), one can transmit a signal from a node to
another one by amplitude modulation, \textit{in spite of chaos}. Also, we give
an example where a signal, transmitted to any node via different paths, can
only be recovered by a couple of \textit{specific} nodes. This opens the
possibility for encoding data in a way such that the recovery of the signal
requires the knowledge of the carrier frequency \textit{and} can be performed
only at some specific node.Comment: 19 pages, 13 figures, submitted (03-03-2005
Memristors for the Curious Outsiders
We present both an overview and a perspective of recent experimental advances
and proposed new approaches to performing computation using memristors. A
memristor is a 2-terminal passive component with a dynamic resistance depending
on an internal parameter. We provide an brief historical introduction, as well
as an overview over the physical mechanism that lead to memristive behavior.
This review is meant to guide nonpractitioners in the field of memristive
circuits and their connection to machine learning and neural computation.Comment: Perpective paper for MDPI Technologies; 43 page
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