176,509 research outputs found
A self-learning particle swarm optimizer for global optimization problems
Copyright @ 2011 IEEE. All Rights Reserved. This article was made available through the Brunel Open Access Publishing Fund.Particle swarm optimization (PSO) has been shown as an effective tool for solving global optimization problems. So far, most PSO algorithms use a single learning pattern for all particles, which means that all particles in a swarm use the same strategy. This monotonic learning pattern may cause the lack of intelligence for a particular particle, which makes it unable to deal with different complex situations. This paper presents a novel algorithm, called self-learning particle swarm optimizer (SLPSO), for global optimization problems. In SLPSO, each particle has a set of four strategies to cope with different situations in the search space. The cooperation of the four strategies is implemented by an adaptive learning framework at the individual level, which can enable a particle to choose the optimal strategy according to its own local fitness landscape. The experimental study on a set of 45 test functions and two real-world problems show that SLPSO has a superior performance in comparison with several other peer algorithms.This work was supported by the Engineering and Physical Sciences Research Council of U.K. under Grants EP/E060722/1 and EP/E060722/2
Xenon fluorides show potential as fluorinating agents
Xenon fluorides permit the controlled addition of fluorine across an olefinic double bond. They provide a series of fluorinating agents that permit ready separation from the product at a high purity. The reactions may be carried out in the vapor phase
Power-law Behavior of High Energy String Scatterings in Compact Spaces
We calculate high energy massive scattering amplitudes of closed bosonic
string compactified on the torus. We obtain infinite linear relations among
high energy scattering amplitudes. For some kinematic regimes, we discover that
some linear relations break down and, simultaneously, the amplitudes enhance to
power-law behavior due to the space-time T-duality symmetry in the compact
direction. This result is consistent with the coexistence of the linear
relations and the softer exponential fall-off behavior of high energy string
scattering amplitudes as we pointed out prevously. It is also reminiscent of
hard (power-law) string scatterings in warped spacetime proposed by Polchinski
and Strassler.Comment: 6 pages, no figure. Talk presented by Jen-Chi Lee at Europhysics
Conference (EPS2007), Manchester, England, July 19-25, 2007. To be published
by Journal of Physics: Conference Series
350 Micron Observations of Ultraluminous Infrared Galaxies at Intermediate Redshifts
We present 350micron observations of 36 ultraluminous infrared galaxies
(ULIRGs) at intermediate redshifts (0.089 <= z <= 0.926) using the
Submillimeter High Angular Resolution Camera II (SHARC-II) on the Caltech
Submillimeter Observatory (CSO). In total, 28 sources are detected at S/N >= 3,
providing the first flux measurements longward of 100micron for a statistically
significant sample of ULIRGs in the redshift range of 0.1 < z < 1.0. Combining
our 350micron flux measurements with the existing IRAS 60 and 100micron data,
we fit a single-temperature model to the spectral energy distribution (SED),
and thereby estimate dust temperatures and far-IR luminosities. Assuming an
emissivity index of beta = 1.5, we find a median dust temperature and far-IR
luminosity of Td = 42.8+-7.1K and log(Lfir/Lsolar) = 12.2+-0.5, respectively.
The far-IR/radio correlation observed in local star-forming galaxies is found
to hold for ULIRGs in the redshift range 0.1 < z < 0.5, suggesting that the
dust in these sources is predominantly heated by starbursts. We compare the
far-IR luminosities and dust temperatures derived for dusty galaxy samples at
low and high redshifts with our sample of ULIRGs at intermediate redshift. A
general Lfir-Td relation is observed, albeit with significant scatter, due to
differing selection effects and variations in dust mass and grain properties.
The relatively high dust temperatures observed for our sample compared to that
of high-z submillimeter-selected starbursts with similar far-IR luminosities
suggest that the dominant star formation in ULIRGs at moderate redshifts takes
place on smaller spatial scales than at higher redshifts.Comment: (24 pages in preprint format, 1 table, 7 figures, accepted for
publication in ApJ
New high fill-factor triangular micro-lens array fabrication method using UV proximity printing
A simple and effective method to fabricate a high fill-factor triangular
microlens array using the proximity printing in lithography process is
reported. The technology utilizes the UV proximity printing by controlling a
printing gap between the mask and substrate. The designed approximate triangle
microlens array pattern can be fabricated the high fill-factor triangular
microlens array in photoresist. It is due to the UV light diffraction to
deflect away from the aperture edges and produce a certain exposure in
photoresist material outside the aperture edges. This method can precisely
control the geometric profile of high fill factor triangular microlens array.
The experimental results showed that the triangular micro-lens array in
photoresist could be formed automatically when the printing gap ranged from 240
micrometers to 840 micrometers. The gapless triangular microlens array will be
used to increases of luminance for backlight module of liquid crystal displays.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/handle/2042/16838
Contact law and impact responses of laminated composites
Static identation tests were performed to determine the law of contact between a steel ball and glass/epoxy and graphite/epoxy laminated composites. For both composites the power law with an index of 1.5 was found to be adequate for the loading curve. Substantial permanent deformations were noted after the unloading. A high order beam finite element was used to compute the dynamic contact force and response of the laminated composite subjected to the impact of an elastic sphere. This program can be used with either the classical Hertzian contact law or the measured contact law. A simple method is introduced for estimating the contact force and contact duration in elastic impacts
Theoretical and experimental studies of a novel cone-jet sensor
Modeling of a novel cone-jet sensor using two-dimensional (2-D) finite element analysis was investigated for dimensional measurement. Theoretical and experimental studies demonstrated that a cone-jet sensor supplied with air can be used to accurately measure displacement, and its work range of 1.5 to 4.2 mm is some ten times greater than a simple back-pressure sensor. It is anticipated that this type of sensor will find wide applications in manufacturing industry due to its wider working range, high precision, and other features
Cooperative emission of a pulse train in an optically thick scattering medium
An optically thick cold atomic cloud emits a coherent flash of light in the
forward direction when the phase of an incident probe field is abruptly
changed. Because of cooperativity, the duration of this phenomena can be much
shorter than the excited lifetime of a single atom. Repeating periodically the
abrupt phase jump, we generate a train of pulses with short repetition time,
high intensity contrast and high efficiency. In this regime, the emission is
fully governed by cooperativity even if the cloud is dilute.Comment: 5 pages, 3 figure
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