10,389 research outputs found
Electronic properties of quantum dots formed by magnetic double barriers in quantum wires
The transport through a quantum wire exposed to two magnetic spikes in series
is modeled. We demonstrate that quantum dots can be formed this way which
couple to the leads via magnetic barriers. Conceptually, all quantum dot states
are accessible by transport experiments. The simulations show Breit-Wigner
resonances in the closed regime, while Fano resonances appear as soon as one
open transmission channel is present. The system allows to tune the dot's
confinement potential from sub-parabolic to superparabolic by experimentally
accessible parameters.Comment: 5 pages, 5 figure
Real-Time Forcast Model Analysis of Daily Average Building Load for a Thermal Storage System Control
Thermal storage systems were originally designed to shift the on-peak cooling production to off-peak cooling production to reduce the on-peak demand. Based on the current electricity charging structure, the reduction of both on-peak and off-peak demands is becoming an exceedingly important issue. Reduction of both on-peak and off-peak demands can also extend the life span and defer or eliminate the replacement of power transformers due to potential shortage of building power capacity with anticipated equipment load increases. The next day daily average electricity demand is a critical set point to operate chillers and associated pumps at the appropriate time. For this paper, a mathematic analysis was conducted for annual daily average cooling of a building and three real-time building load forecasting models were developed. They are first-order autogressive model, random walk model and linear regression model. Finally, the comparison of results show the random walk model provides the best forecast
Simulations of black hole air showers in cosmic ray detectors
We present a comprehensive study of TeV black hole events in Earth's
atmosphere originated by cosmic rays of very high energy. An advanced fortran
Monte Carlo code is developed and used to simulate black hole extensive air
showers from ultrahigh-energy neutrino-nucleon interactions. We investigate the
characteristics of these events, compare the black hole air showers to standard
model air showers, and test different theoretical and phenomenological models
of black hole formation and evolution. The main features of black hole air
showers are found to be independent of the model considered. No significant
differences between models are likely to be observed at fluorescence telescopes
and/or ground arrays. We also discuss the tau ``double bang'' signature in
black hole air showers. We find that the energy deposited in the second bang is
too small to produce a detectable peak. Our results show that the theory of
TeV-scale black holes in ultrahigh-energy cosmic rays leads to robust
predictions, but the fine prints of new physics are hardly to be investigated
through atmospheric black hole events in the near future.Comment: 18 pages, 9 figure
Auto-oscillation threshold, narrow spectral lines, and line jitter in spin-torque oscillators based on MgO magnetic tunnel junctions
We demonstrate spin torque induced auto-oscillation in MgO-based magnetic
tunnel junctions. At the generation threshold, we observe a strong line
narrowing down to 6 MHz at 300K and a dramatic increase in oscillator power,
yielding spectrally pure oscillations free of flicker noise. Setting the
synthetic antiferromagnet into autooscillation requires the same current
polarity as the one needed to switch the free layer magnetization. The induced
auto-oscillations are observed even at zero applied field, which is believed to
be the acoustic mode of the synthetic antiferromagnet. While the phase
coherence of the auto-oscillation is of the order of microseconds, the power
autocorrelation time is of the order of milliseconds and can be strongly
influenced by the free layer dynamics
Single-qubit rotations in two-dimensional optical lattices with multiqubit addressing
Published versio
Reply to "Comment on 'Scalar-tensor gravity coupled to a global monopole and flat rotation curves' "
In Brans-Dicke theory of gravity we explain how the extra constant value in
the formula for rotation velocities of stars in a galactic halo can be obtained
due to the global monopole field. We argue on a few points of the preceding
Comment and discuss improvement of our model.Comment: 4 pages, RevTeX4 fil
Auto-oscillation threshold and line narrowing in MgO-based spin-torque oscillators
We present an experimental study of the power spectrum of current-driven
magnetization oscillations in MgO tunnel junctions under low bias. We find the
existence of narrow spectral lines, down to 8 MHz in width at a frequency of
10.7 GHz, for small applied fields with clear evidence of an auto-oscillation
threshold. Micromagnetics simulations indicate that the excited mode
corresponds to an edge mode of the synthetic antiferromagnet
Behavior of susceptible-infected-susceptible epidemics on heterogeneous networks with saturation
We investigate saturation effects in susceptible-infected-susceptible (SIS)
models of the spread of epidemics in heterogeneous populations. The structure
of interactions in the population is represented by networks with connectivity
distribution ,including scale-free(SF) networks with power law
distributions . Considering cases where the transmission
of infection between nodes depends on their connectivity, we introduce a
saturation function which reduces the infection transmission rate
across an edge going from a node with high connectivity . A mean
field approximation with the neglect of degree-degree correlation then leads to
a finite threshold for SF networks with . We
also find, in this approximation, the fraction of infected individuals among
those with degree for close to . We investigate via
computer simulation the contact process on a heterogeneous regular lattice and
compare the results with those obtained from mean field theory with and without
neglect of degree-degree correlations.Comment: 6 figure
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