20,048 research outputs found
An Improved NSGA-II and its Application for Reconfigurable Pixel Antenna Design
Based on the elitist non-dominated sorting genetic algorithm (NSGA-II) for multi-objective optimization problems, an improved scheme with self-adaptive crossover and mutation operators is proposed to obtain good optimization performance in this paper. The performance of the improved NSGA-II is demonstrated with a set of test functions and metrics taken from the standard literature on multi-objective optimization. Combined with the HFSS solver, one pixel antenna with reconfigurable radiation patterns, which can steer its beam into six different directions (ΞDOA = ± 15°, ± 30°, ± 50°) with a 5 % overlapping impedance bandwidth (S11 < â 10 dB) and a realized gain over 6 dB, is designed by the proposed self-adaptive NSGA-II
On the VLSI design of a pipeline Reed-Solomon decoder using systolic arrays
A new very large scale integration (VLSI) design of a pipeline Reed-Solomon decoder is presented. The transform decoding technique used in a previous article is replaced by a time domain algorithm through a detailed comparison of their VLSI implementations. A new architecture that implements the time domain algorithm permits efficient pipeline processing with reduced circuitry. Erasure correction capability is also incorporated with little additional complexity. By using a multiplexing technique, a new implementation of Euclid's algorithm maintains the throughput rate with less circuitry. Such improvements result in both enhanced capability and significant reduction in silicon area
Decay of scalar variance in isotropic turbulence in a bounded domain
The decay of scalar variance in isotropic turbulence in a bounded domain is
investigated. Extending the study of Touil, Bertoglio and Shao (2002; Journal
of Turbulence, 03, 49) to the case of a passive scalar, the effect of the
finite size of the domain on the lengthscales of turbulent eddies and scalar
structures is studied by truncating the infrared range of the wavenumber
spectra. Analytical arguments based on a simple model for the spectral
distributions show that the decay exponent for the variance of scalar
fluctuations is proportional to the ratio of the Kolmogorov constant to the
Corrsin-Obukhov constant. This result is verified by closure calculations in
which the Corrsin-Obukhov constant is artificially varied. Large-eddy
simulations provide support to the results and give an estimation of the value
of the decay exponent and of the scalar to velocity time scale ratio
Critical phenomena and thermodynamic geometry of charged Gauss-Bonnet AdS black holes
In this paper, we study the phase structure and equilibrium state space
geometry of charged topological Gauss-Bonnet black holes in -dimensional
anti-de Sitter spacetime. Several critical points are obtained in the canonical
ensemble, and the critical phenomena and critical exponents near them are
examined. We find that the phase structures and critical phenomena drastically
depend on the cosmological constant and dimensionality . The
result also shows that there exists an analogy between the black hole and the
van der Waals liquid gas system. Moreover, we explore the phase transition and
possible property of the microstructure using the state space geometry. It is
found that the Ruppeiner curvature diverges exactly at the points where the
heat capacity at constant charge of the black hole diverges. This black hole is
also found to be a multiple system, i.e., it is similar to the ideal gas of
fermions in some range of the parameters, while to the ideal gas of bosons in
another range.Comment: 17 pages, 8 figures, 3 table
Competitive contract design in a retail supply chain under demand uncertainty
This article studies the design of contracts involving a single retailer and multiple competing manufacturers who supply substitutable products. We consider a retail context in which contracts with manufacturers are negotiated relatively infrequently and signed before the demand environment is known, and the retail prices are determined when the demand is known. We develop a Stackelberg model to study the retailer's product selection and pricing decisions and the manufacturers' contract design decisions. We show that it is optimal for each manufacturer to offer a contract with nonlinear prices so that total payments are the total production cost plus a fixed additional cost. In the case of two manufacturers this result allows us to characterize an equilibrium in which the retailer's choice maximizes the supply chain profit, each manufacturer makes a profit equal to its marginal contribution to the supply chain, and the retailer takes the remaining profit. We also find that while increasing demand correlation always benefits the retailer, it benefits the manufacturers only when the production costs are convex. In an extension it is found that our equilibrium continues to hold when the retailer's reservation profit is below a threshold, but the competition dynamics may change when the reservation profit is above the threshold. Finally, we show that the equilibrium results remain true for the case with more than two manufacturers under a submodularity property, which holds in the case of quadratic costs and linear demand
Feasibility studies for quarkonium production at a fixed-target experiment using the LHC proton and lead beams (AFTER@LHC)
Used in the fixed-target mode, the multi-TeV LHC proton and lead beams allow
for studies of heavy-flavour hadroproduction with unprecedented precision at
backward rapidities - far negative Feyman-x - using conventional detection
techniques. At the nominal LHC energies, quarkonia can be studies in detail in
p+p, p+d and p+A collisions at sqrt(s_NN) ~ 115 GeV as well as in Pb+p and Pb+A
collisions at sqrt(s_NN) ~ 72 GeV with luminosities roughly equivalent to that
of the collider mode, i.e. up to 20 fb-1 yr-1 in p+p and p+d collisions, up to
0.6 fb-1 yr-1 in p+A collisions and up to 10 nb-1 yr-1 in Pb+A collisions. In
this paper, we assess the feasibility of such studies by performing fast
simulations using the performance of a LHCb-like detector.Comment: 12 pages, 14 figure
Adiabatic Fidelity for Atom-Molecule Conversion in a Nonlinear Three-Level \Lambda-system
We investigate the dynamics of the population transfer for atom-molecule
three-level -system on stimulated Raman adiabatic passage(STIRAP). We
find that the adiabatic fidelity for the coherent population trapping(CPT)
state or dark state, as the function of the adiabatic parameter, approaches to
unit in a power law. The power exponent however is much less than the
prediction of linear adiabatic theorem. We further discuss how to achieve
higher adiabatic fidelity for the dark state through optimizing the external
parameters of STIRAP. Our discussions are helpful to gain higher atom-molecule
conversion yield in practical experiments.Comment: 4 pages, 5 figure
Comparing the Host Galaxies of Type Ia, Type II and Type Ibc Supernovae
We compare the host galaxies of 902 supernovae, including SNe Ia, SNe II and
SNe Ibc, which are selected by cross-matching the Asiago Supernova Catalog with
the SDSS Data Release 7. We further selected 213 galaxies by requiring the
light fraction of spectral observations 15%, which could represent well the
global properties of the galaxies. Among them, 135 galaxies appear on the
Baldwin-Phillips-Terlevich diagram, which allows us to compare the hosts in
terms of star-forming, AGNs (including composites, LINERs and Seyfert 2s) and
"Absorp" (their related emission-lines are weak or non-existence) galaxies. The
diagrams related to parameters D(4000), H, stellar masses, SFRs
and specific SFRs for the SNe hosts show that almost all SNe II and most of SNe
Ibc occur in SF galaxies, which have a wide range of stellar mass and low
D(4000). The SNe Ia hosts as SF galaxies follow similar trends. A
significant fraction of SNe Ia occurs in AGNs and Absorp galaxies, which are
massive and have high D(4000). The stellar population analysis from
spectral synthesis fitting shows that the hosts of SNe II have a younger
stellar population than hosts of SNe Ia. These results are compared with those
of the 689 comparison galaxies where the SDSS fiber captures less than 15% of
the total light. These comparison galaxies appear biased towards higher
12+log(O/H) (0.1dex) at a given stellar mass. Therefore, we believe the
aperture effect should be kept in mind when the properties of the hosts for
different types of SNe are discussed.Comment: 15 pages, 9 figure
Metastable behavior of vortex matter in the electronic transport processes of homogenous superconductors
We study numerically the effect of vortex pinning on the hysteresis voltage-temperature (V-T) loop of vortex matter. It is found that different types of the V-T loops result from different densities of vortex pinning center. An anticlockwise V-T loop is observed for the vortex system with dense pinning centers, whereas a clockwise V-T loop is brought about for vortices with dilute pinning centers. It is shown that the size of the V-T loop becomes smaller for lower experimental speed, higher magnetic field, or weak pinning strength. Our numerical observation is in good agreement with experiments
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