52,011 research outputs found
Fluctuations and universality in a catalysis model with long-range reactivity
The critical properties of the Ziff-Gulari-Barshad (ZGB) model with the
addition of long-range reactivity [C.H. Chan and P.A. Rikvold, Phys. Rev. E 91,
012103 (2015)] are further investigated. The scaling behaviors of the order
parameter, susceptibility, and correlation length provide addi- tional evidence
that the universality class of the ZGB system changes from the two-dimensional
Ising class to the mean-field class with the addition of even a weak long-range
reactivity mechanism
Supernarrow spectral peaks near a kinetic phase transition in a driven, nonlinear micromechanical oscillator
We measure the spectral densities of fluctuations of an underdamped nonlinear
micromechanical oscillator. By applying a sufficiently large periodic
excitation, two stable dynamical states are obtained within a particular range
of driving frequency. White noise is injected into the excitation, allowing the
system to overcome the activation barrier and switch between the two states.
While the oscillator predominately resides in one of the two states for most
excitation frequencies, a narrow range of frequencies exist where the
occupations of the two states are approximately equal. At these frequencies,
the oscillator undergoes a kinetic phase transition that resembles the phase
transition of thermal equilibrium systems. We observe a supernarrow peak in the
power spectral densities of fluctuations of the oscillator. This peak is
centered at the excitation frequency and arises as a result of noise-induced
transitions between the two dynamical states.Comment: 4 pages, 4 figure
Statistical variability in implant-free quantum-well MOSFETs with InGaAs and Ge: a comparative 3D simulation study
Introduction of high mobility channel materials including III-Vs and Ge into future CMOS generations offer the
potential for enhanced transport properties compared to Si. The Implant Free Quantum Well (IFQW) architecture
offers an attractive design to introduce these materials, providing excellent electrostatic integrity. Statistical variability introduced by the discreteness of charge and granularity of matter has become a key factor for current and future generations of MOSFETs and in this work numerical simulations are used to critically assess the statistical
variability in IFQW transistors and compare results with equivalent conventional Si ‘bulk’ MOSFETs
An Improved Private Mechanism for Small Databases
We study the problem of answering a workload of linear queries ,
on a database of size at most drawn from a universe
under the constraint of (approximate) differential privacy.
Nikolov, Talwar, and Zhang~\cite{NTZ} proposed an efficient mechanism that, for
any given and , answers the queries with average error that is
at most a factor polynomial in and
worse than the best possible. Here we improve on this guarantee and give a
mechanism whose competitiveness ratio is at most polynomial in and
, and has no dependence on . Our mechanism
is based on the projection mechanism of Nikolov, Talwar, and Zhang, but in
place of an ad-hoc noise distribution, we use a distribution which is in a
sense optimal for the projection mechanism, and analyze it using convex duality
and the restricted invertibility principle.Comment: To appear in ICALP 2015, Track
Exterior optical cloaking and illusions by using active sources: a boundary element perspective
Recently, it was demonstrated that active sources can be used to cloak any
objects that lie outside the cloaking devices [Phys. Rev. Lett. \textbf{103},
073901 (2009)]. Here, we propose that active sources can create illusion
effects, so that an object outside the cloaking device can be made to look like
another object. invisibility is a special case in which the concealed object is
transformed to a volume of air. From a boundary element perspective, we show
that active sources can create a nearly "silent" domain which can conceal any
objects inside and at the same time make the whole system look like an illusion
of our choice outside a virtual boundary. The boundary element method gives the
fields and field gradients (which can be related to monopoles and dipoles) on
continuous curves which define the boundary of the active devices. Both the
cloaking and illusion effects are confirmed by numerical simulations
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