84,919 research outputs found
Resonate and Fire Neuron with Fixed Magnetic Skyrmions
In the brain, the membrane potential of many neurons oscillates in a
subthreshold damped fashion and fire when excited by an input frequency that
nearly equals their eigen frequency. In this work, we investigate theoretically
the artificial implementation of such "resonate-and-fire" neurons by utilizing
the magnetization dynamics of a fixed magnetic skyrmion in the free layer of a
magnetic tunnel junction (MTJ). To realize firing of this nanomagnetic
implementation of an artificial neuron, we propose to employ voltage control of
magnetic anisotropy or voltage generated strain as an input (spike or
sinusoidal) signal, which modulates the perpendicular magnetic anisotropy
(PMA). This results in continual expansion and shrinking (i.e. breathing) of a
skyrmion core that mimics the subthreshold oscillation. Any subsequent input
pulse having an interval close to the breathing period or a sinusoidal input
close to the eigen frequency drives the magnetization dynamics of the fixed
skyrmion in a resonant manner. The time varying electrical resistance of the
MTJ layer due to this resonant oscillation of the skyrmion core is used to
drive a Complementary Metal Oxide Semiconductor (CMOS) buffer circuit, which
produces spike outputs. By rigorous micromagnetic simulation, we investigate
the interspike timing dependence and response to different excitatory and
inhibitory incoming input pulses. Finally, we show that such resonate and fire
neurons have potential application in coupled nanomagnetic oscillator based
associative memory arrays
Ultra-low-loss CMOS-Compatible Waveguide Crossing Arrays Based on Multimode Bloch Waves and Imaginary Coupling
We experimentally demonstrate broadband waveguide crossing arrays showing
ultra low loss down to dB/crossing (), matching theory, and
crosstalk suppression over dB, in a CMOS-compatible geometry. The
principle of operation is the tailored excitation of a low-loss spatial Bloch
wave formed by matching the periodicity of the crossing array to the difference
in propagation constants of the 1- and 3-order TE-like
modes of a multimode silicon waveguide. Radiative scattering at the crossing
points acts like a periodic imaginary-permittivity perturbation that couples
two supermodes, which results in imaginary (radiative) propagation-constant
splitting and gives rise to a low-loss, unidirectional breathing Bloch wave.
This type of crossing array provides a robust implementation of a key component
enabling dense photonic integration
Single polaron properties of the breathing-mode Hamiltonian
We investigate numerically various properties of the one-dimensional (1D)
breathing-mode polaron. We use an extension of a variational scheme to compute
the energies and wave-functions of the two lowest-energy eigenstates for any
momentum, as well as a scheme to compute directly the polaron Greens function.
We contrast these results with results for the 1D Holstein polaron. In
particular, we find that the crossover from a large to a small polaron is
significantly sharper. Unlike for the Holstein model, at moderate and large
couplings the breathing-mode polaron dispersion has non-monotonic dependence on
the polaron momentum k. Neither of these aspects is revealed by a previous
study based on the self-consistent Born approximation
Breathing synchronization in interconnected networks
Global synchronization in a complex network of oscillators emerges from the
interplay between its topology and the dynamics of the pairwise interactions
among its numerous components. When oscillators are spatially separated,
however, a time delay appears in the interaction which might obstruct
synchronization. Here we study the synchronization properties of interconnected
networks of oscillators with a time delay between networks and analyze the
dynamics as a function of the couplings and communication lag. We discover a
new breathing synchronization regime, where two groups appear in each network
synchronized at different frequencies. Each group has a counterpart in the
opposite network, one group is in phase and the other in anti-phase with their
counterpart. For strong couplings, instead, networks are internally
synchronized but a phase shift between them might occur. The implications of
our findings on several socio-technical and biological systems are discussed.Comment: 7 pages, 3 figures + 3 pages of Supplemental Materia
A chlorate candle/lithium hydroxide personal breathing apparatus
A portable coal mine rescue and survival equipment is reported that consists of a chlorate candle with a lithium hydroxide carbon-dioxide absorbent for oxygen generation, a breathing bag and tubing to conduct breathing to and from the man. A plastic hood incorporating a mouth piece for communication provides also eye protection and prevents inhalation through the nose. Manned testing of a prototype system demonstrated the feasibility of this closed circuit no-maintenance breathing apparatus that provides for good voice communication
SymbioCity: Smart Cities for Smarter Networks
The "Smart City" (SC) concept revolves around the idea of embodying
cutting-edge ICT solutions in the very fabric of future cities, in order to
offer new and better services to citizens while lowering the city management
costs, both in monetary, social, and environmental terms. In this framework,
communication technologies are perceived as subservient to the SC services,
providing the means to collect and process the data needed to make the services
function. In this paper, we propose a new vision in which technology and SC
services are designed to take advantage of each other in a symbiotic manner.
According to this new paradigm, which we call "SymbioCity", SC services can
indeed be exploited to improve the performance of the same communication
systems that provide them with data. Suggestive examples of this symbiotic
ecosystem are discussed in the paper. The dissertation is then substantiated in
a proof-of-concept case study, where we show how the traffic monitoring service
provided by the London Smart City initiative can be used to predict the density
of users in a certain zone and optimize the cellular service in that area.Comment: 14 pages, submitted for publication to ETT Transactions on Emerging
Telecommunications Technologie
The Appreciative Heart: The Psychophysiology of Positive Emotions and Optimal Functioning
This monograph is an overview of Institute of HeartMath's research on the physiological correlates of positive emotions and the science underlying two core HeartMath techniques which supports Heart-Based Living. The heart's connection with love and other positive emotions has survived throughout millennia and across many diverse cultures. New empirical research is providing scientific validation for this age-old association. This 21-page monograph offers a comprehensive understanding of the Institute of HeartMath's cutting-edge research exploring the heart's central role in emotional experience. Described in detail is physiological coherence, a distinct mode of physiological functioning, which is generated during sustained positive emotions and linked with beneficial health and performance-related outcomes. The monograph also provides steps and applications of two HeartMath techniques, Freeze-Frame(R) and Heart Lock-In(R), which engage the heart to help transform stress and produce sustained states of coherence. Data from outcome studies are presented, which suggest that these techniques facilitate a beneficial repatterning process at the mental, emotional and physiological levels
- …