3,860 research outputs found
Prescribed performance control of underactuated surface vessels' trajectory using a neural network and integral time-delay sliding mode
summary:To tackle the underactuated surface vessel (USV) trajectory tracking challenge with input delays and composite disturbances, an integral time-delay sliding mode controller based on backstepping is discussed. First, the law of virtual velocity control is established by coordinate transformation and the position error is caused to converge utilizing the performance function. At the same time, based on the estimation of velocity vector by the high-gain observer (HGO), radial basis function (RBF) neural network is applied to compensate for both the uncertainty of model parameters and external disturbances. The longitudinal and heading control laws are presented in combination with the integral time-delay sliding mode control. Then, on the basis of Lyapunov - Krasovskii functional and stability proof, virtual velocity error is guaranteed to converge to 0 in finite time. Finally, the outcomes of the numerical simulation demonstrate the reliability and efficiency of the proposed approach
Chromopolarizability of charmonium and final state interaction revisited
The chromopolarizability of a quarknonium describes the quarknonium's
interaction with soft gluonic fields and can be measured in the heavy
quarkonium decays. Within the framework of dispersion theory which consider the
final state interaction (FSI) model-independently, we analyze the
transition and obtain the
chromopolarizability and the parameter . It
is found that the FSI plays an important role in extracting the
chromopolarizability from the experimental data. The obtained
chromopolarizability with the FSI is reduced to about 1/2 of that without the
FSI. With the FSI, we determine the chromopolarizability
GeV and the parameter
Our results could be useful in studying the
interactions of charmonium with light hadrons.Comment: 8 pages, 1 figur
Analyses of pion-nucleon elastic scattering amplitudes up to in extended-on-mass-shell subtraction scheme
We extend the analysis of elastic pion-nucleon scattering up to
level using extended-on-mass-shell subtraction scheme within the framework of
covariant baryon chiral perturbation theory. Numerical fits to partial wave
phase shift data up to GeV are performed to pin down the free
low energy constants. A good description to the existing phase shift data is
achieved. We find a good convergence for the chiral series at ,
considerably improved with respect to the -level analyses found in
previous literature. Also, the leading order contribution from explicit
resonance and partially-included loop
contribution are included to describe phase shift data up to
GeV. As phenomenological applications, we investigate chiral correction to the
Goldberger-Treiman relation % and find that it converges rapidly,
and the correction is found to be very small: . We also
get a reasonable prediction of pion-nucleon sigma term up to
by performing fits including both the pion-nucleon partial wave phase
shift data and the lattice QCD data. We report that MeV
from the fit without , and MeV from the
fit with explicit .Comment: The final version published in Phys.Rev. D 87, 054019 (2013
Momentum-dependence of mixing in the pion vector form factor and its effect on
The inclusion of the mixing effect is crucial for a good
description of the pion electromagnetic form factor in the process, which quantifies the two-pion contribution to the
anomalous magnetic moment of the muon . In this paper, we try to analyze
the impact of the momentum-dependence of the mixing within the
framework of resonance chiral theory. The momentum-dependence of the
mixing is incorporated due to the calculation of loop
contributions at the next-to-leading order in the expansion. The work
of {[}Y. H. Chen, D. L. Yao, and H. Q. Zheng, Commun. Theor. Phys. 69 (2018)
1{]} is revisited taking into account the contribution due to the kaon mass
splitting in the kaon loops and the latest experimental data. We perform two
kinds of fits (with momentum-independent or momentum-dependent
mixing amplitude) describing the and
data in the energy region of 600900 MeV
and the decay width of , and compare their
results. It is found that taking account of the momentum-dependence of
mixing can describe the pion vector form factor data a little
better. For the contribution to the anomalous magnetic moment of the muon
, the values of the results in the fits
considering the momentum-dependent mixing amplitude are agree
well with those in the fits without including the momentum-dependence of the
mixing within errors. In addition, based on the fitted values of
the involved parameters, we find that in the decay width of the contribution from the direct coupling is
comparable with the contribution due to the mixing.Comment: 21 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1710.1144
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