11,135 research outputs found
Accurate angle-of-arrival measurement using particle swarm optimization
As one of the major methods for location positioning, angle-of-arrival (AOA) estimation is a significant technology in radar, sonar, radio astronomy, and mobile communications. AOA measurements can be exploited to locate mobile units, enhance communication efficiency and network capacity, and support location-aided routing, dynamic network management, and many location-based services. In this paper, we propose an algorithm for AOA estimation in colored noise fields and harsh application scenarios. By modeling the unknown noise covariance as a linear combination of known weighting matrices, a maximum likelihood (ML) criterion is established, and a particle swarm optimization (PSO) paradigm is designed to optimize the cost function. Simulation results demonstrate that the paired estimator PSO-ML significantly outperforms other popular techniques and produces superior AOA estimates
Limit theorems for functions of marginal quantiles
Multivariate distributions are explored using the joint distributions of
marginal sample quantiles. Limit theory for the mean of a function of order
statistics is presented. The results include a multivariate central limit
theorem and a strong law of large numbers. A result similar to Bahadur's
representation of quantiles is established for the mean of a function of the
marginal quantiles. In particular, it is shown that
as , where is a constant and are
i.i.d. random variables for each . This leads to the central limit theorem.
Weak convergence to a Gaussian process using equicontinuity of functions is
indicated. The results are established under very general conditions. These
conditions are shown to be satisfied in many commonly occurring situations.Comment: Published in at http://dx.doi.org/10.3150/10-BEJ287 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Structure formation in electromagnetically driven granular media
We report structure formation in submonolayers of magnetic microparticles
subjected to periodic electrostatic and magnetic excitations. Depending on the
excitation parameters, we observe the formation of a rich variety of
structures: clusters, rings, chains, and networks. The growth dynamics and
shapes of the structures are strongly dependent on the amplitude and frequency
of the external magnetic field. We find that for pure ac magnetic driving at
low densities of particles, the low-frequency magnetic excitation favors
clusters while high frequency excitation favors chains and net-like structures.
An abrupt phase transition from chains to a network phase was observed for a
high density of particles.Comment: 4 pages, 5 figure
Simulation of a paging drum channel
Simulation of paging drum channel system by ALGOL and SIMULA programs on Univac 110
Integro-differential diffusion equation for continuous time random walk
In this paper we present an integro-differential diffusion equation for
continuous time random walk that is valid for a generic waiting time
probability density function. Using this equation we also study diffusion
behaviors for a couple of specific waiting time probability density functions
such as exponential, and a combination of power law and generalized
Mittag-Leffler function. We show that for the case of the exponential waiting
time probability density function a normal diffusion is generated and the
probability density function is Gaussian distribution. In the case of the
combination of a power-law and generalized Mittag-Leffler waiting probability
density function we obtain the subdiffusive behavior for all the time regions
from small to large times, and probability density function is non-Gaussian
distribution.Comment: 12 page
Spectroscopy in Liquid‐Rare‐Gas Solvents. Infrared Spectra of CH_4 in Argon and of HCl in Xenon
A low‐temperature cell employing barium fluoride windows and indium metal gaskets has been built and is being used for the study of rotational, vibrational, and electronic motions of molecules in liquid rare gases. The ν_3 fundamental of CH_4 in liquid argon shows a single, relatively sharp Q branch. The P and R branches are probably present but apparently are lost in the wings of the Q branch. The infrared spectrum near 3.5 μ of HCl in liquid xenon shows well‐resolved P, Q, and R branches, but the individual rotational lines are not resolved. The O branch is not resolved from the tail of the P branch, but there is some indication of the S branch on the high‐frequency side of the spectrum. The Q branch is shifted 36 cm^(-1) to the low‐frequency side of its gas‐phase position. The appearance of O, Q, and S branches is expected because of the presence of an induced dipole moment through the polarizability of the solvent. The agreement between the observed spectrum and that anticipated on the basis of nearly free rotation gives good evidence for the existence of quantized rotational motions of HCl in liquid xenon
Simulation of a single-server model for a paging drum channel system
Simulation of single-server model for paging drum channel syste
Realization of Artificial Ice Systems for Magnetic Vortices in a Superconducting MoGe Thin-film with Patterned Nanostructures
We report an anomalous matching effect in MoGe thin films containing pairs of
circular holes arranged in such a way that four of those pairs meet at each
vertex point of a square lattice. A remarkably pronounced fractional matching
was observed in the magnetic field dependences of both the resistance and the
critical current. At the half matching field the critical current can be even
higher than that at zero field. This has never been observed before for
vortices in superconductors with pinning arrays. Numerical simulations within
the nonlinear Ginzburg-Landau theory reveal a square vortex ice configuration
in the ground state at the half matching field and demonstrate similar
characteristic features in the field dependence of the critical current,
confirming the experimental realization of an artificial ice system for
vortices for the first time.Comment: To appear in Phys. Rev. Let
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