4,735 research outputs found
Recycled Noise Rectification: A Dumb Maxwell's Daemon
The one dimensional motion of a massless Brownian particle on a symmetric
periodic substrate can be rectified by re-injecting its driving noise through a
realistic recycling procedure. If the recycled noise is multiplicatively
coupled to the substrate, the ensuing feed-back system works like a passive
Maxwell's daemon, capable of inducing a net current that depends on both the
delay and the autocorrelation times of the noise signals. Extensive numerical
simulations show that the underlying rectification mechanism is a resonant
nonlinear effect: The observed currents can be optimized for an appropriate
choice of the recycling parameters with immediate application to the design of
nanodevices for particle transport.Comment: 7 pages, 6 figure
Vibrational ratchets
Transport in a one-dimensional symmetric device can be activated by the
combination of thermal noise and a bi-harmonic drive. For the study case of an
overdamped Brownian particle diffusing on a periodic one-dimensional substrate,
we distinguish two apparently different bi-harmonic regimes: (i) Harmonic
mixing, where the two drive frequencies are commensurate and of the order of
some intrinsic dynamical relaxation rate. A comparison of new simulation
results with earlier theoretical predictions shows that the analytical
understanding of this frequency mixing mechanism is not satisfactory, yet; (ii)
Vibrational mixing, where one harmonic drive component is characterized by a
high frequency but finite amplitude-to-frequency ratio. Its effect on the
device response to either a static or a low-frequency additional input signal
is accurately reproduced by rescaling each spatial Fourier component of the
substrate potential, separately. Contrary to common wisdom based on the linear
response theory, we show that extremely high-frequency modulations can indeed
influence the response of slowly (or dc) operated devices, with potential
applications in sensor technology and cellular physiology. Finally, the mixing
of two high-frequency beating signal is also investigated both numerically and
analytically.Comment: 8 pages, 9 figure
Trick or Heat? Manipulating Critical Temperature-Based Control Systems Using Rectification Attacks
Temperature sensing and control systems are widely used in the closed-loop
control of critical processes such as maintaining the thermal stability of
patients, or in alarm systems for detecting temperature-related hazards.
However, the security of these systems has yet to be completely explored,
leaving potential attack surfaces that can be exploited to take control over
critical systems.
In this paper we investigate the reliability of temperature-based control
systems from a security and safety perspective. We show how unexpected
consequences and safety risks can be induced by physical-level attacks on
analog temperature sensing components. For instance, we demonstrate that an
adversary could remotely manipulate the temperature sensor measurements of an
infant incubator to cause potential safety issues, without tampering with the
victim system or triggering automatic temperature alarms. This attack exploits
the unintended rectification effect that can be induced in operational and
instrumentation amplifiers to control the sensor output, tricking the internal
control loop of the victim system to heat up or cool down. Furthermore, we show
how the exploit of this hardware-level vulnerability could affect different
classes of analog sensors that share similar signal conditioning processes.
Our experimental results indicate that conventional defenses commonly
deployed in these systems are not sufficient to mitigate the threat, so we
propose a prototype design of a low-cost anomaly detector for critical
applications to ensure the integrity of temperature sensor signals.Comment: Accepted at the ACM Conference on Computer and Communications
Security (CCS), 201
Effects of noise suppression and envelope dynamic range compression on the intelligibility of vocoded sentences for a tonal language
Vocoder simulation studies have suggested that the carrier signal type employed affects the intelligibility of vocoded speech. The present work further assessed how carrier signal type interacts with additional signal processing, namely, single-channel noise suppression and envelope dynamic range compression, in determining the intelligibility of vocoder simulations. In Experiment 1, Mandarin sentences that had been corrupted by speech spectrum-shaped noise (SSN) or two-talker babble (2TB) were processed by one of four single-channel noise-suppression algorithms before undergoing tone-vocoded (TV) or noise-vocoded (NV) processing. In Experiment 2, dynamic ranges of multiband envelope waveforms were compressed by scaling of the mean-removed envelope waveforms with a compression factor before undergoing TV or NV processing. TV Mandarin sentences yielded higher intelligibility scores with normal-hearing (NH) listeners than did noise-vocoded sentences. The intelligibility advantage of noise-suppressed vocoded speech depended on the masker type (SSN vs 2TB). NV speech was more negatively influenced by envelope dynamic range compression than was TV speech. These findings suggest that an interactional effect exists between the carrier signal type employed in the vocoding process and envelope distortion caused by signal processing
Frequency modulated self-oscillation and phase inertia in a synchronized nanowire mechanical resonator
Synchronization has been reported for a wide range of self-oscillating
systems. However, even though it has been predicted theoretically for several
decades, the experimental realization of phase self-oscillation, sometimes
called phase trapping, in the high driving regime has been studied only
recently. We explored in detail the phase dynamics in a synchronized field
emission SiC nanoelectromechanical system with intrinsic feedback. A richer
variety of phase behavior has been unambiguously identified, implying phase
modulation and inertia. This synchronization regime is expected to have
implications for the comprehension of the dynamics of interacting
self-oscillating networks and for the generation of frequency modulated signals
at the nanoscal
- …