139,771 research outputs found
Modulo Three Problem With A Cellular Automaton Solution
An important global property of a bit string is the number of ones in it. It
has been found that the parity (odd or even) of this number can be found by a
sequence of deterministic, translational invariant cellular automata with
parallel update in succession for a total of O(N^2) time. In this paper, we
discover a way to check if this number is divisible by three using the same
kind of cellular automata in O(N^3) time. We also speculate that the method
described here could be generalized to check if it is divisible by four and
other positive integers.Comment: 10 pages in revtex 4.0, using amsfont
Channel Parameters Estimation Algorithm Based on The Characteristic Function under Impulse Noise Environment
Under communication environments, such as wireless sensor networks, the noise observed usually exhibits impulsive as well as Gaussian characteristics. In the initialization of channel iterative decoder, such as low density parity check codes, it is required in advance to estimate the channel parameters to obtain the prior information from the received signals. In this paper, a blind channel parameters estimator under impulsive noise environment is proposed, which is based on the empirical characteristic function in MPSK/MQAM higher-order modulation system. Simulation results show that for various MPSK/MQAM modulations, the estimator can obtain a more accurate unbiased estimation even though we do not know which kind of higher-order modulation is used
Finding The Sign Of A Function Value By Binary Cellular Automaton
Given a continuous function , suppose that the sign of only has
finitely many discontinuous points in the interval . We show how to use
a sequence of one dimensional deterministic binary cellular automata to
determine the sign of where is the (number) density of 1s in
an arbitrarily given bit string of finite length provided that satisfies
certain technical conditions.Comment: Revtex, uses amsfonts, 10 page
Barkhausen noise in the Random Field Ising Magnet NdFeB
With sintered needles aligned and a magnetic field applied transverse to its
easy axis, the rare-earth ferromagnet NdFeB becomes a
room-temperature realization of the Random Field Ising Model. The transverse
field tunes the pinning potential of the magnetic domains in a continuous
fashion. We study the magnetic domain reversal and avalanche dynamics between
liquid helium and room temperatures at a series of transverse fields using a
Barkhausen noise technique. The avalanche size and energy distributions follow
power-law behavior with a cutoff dependent on the pinning strength dialed in by
the transverse field, consistent with theoretical predictions for Barkhausen
avalanches in disordered materials. A scaling analysis reveals two regimes of
behavior: one at low temperature and high transverse field, where the dynamics
are governed by the randomness, and the second at high temperature and low
transverse field where thermal fluctuations dominate the dynamics.Comment: 16 pages, 7 figures. Under review at Phys. Rev.
Search for Compact Extragalactic Radio Sources Near Massive Star Forming Regions
We have used the Very Large Array to search for compact milliarcsecond-size
radio sources near methanol masers in high-mass star-forming regions. Such
sources are required for Very Long Baseline Interferometry phase-referencing
observations. We conducted pointed observations of 234 compact sources found in
the NVSS survey and find 92 sources with unresolved components and synchrotron
spectral indexes. These sources are likely the cores of AGNs and, thus, good
candidates for astrometric calibrators.Comment: 23 pages, lots of figures, accepted in ApJ
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