50,933 research outputs found
A statistical model for evaluating GOPEX uplink performance
This article describes a statistical model to analyze the signal intensity received at the solid-state imaging (SSI) camera of the Galileo optical communications system from an Earth-based transmitter (GOPEX) demonstration. The analytical model assumes that the optical beam possesses a Gaussian profile and the communication channel has a log-normal scattering characteristic. The atmospheric-induced jitter is modelled as two independent zero mean Gaussian random variables. By modelling the system parameters as a set of independent and identically distributed (iid) random variables, the combined impact of uncertainties due to system parameters and the turbulent atmosphere can be approximated by a log-normal distributed signal intensity at the spacecraft. A Monte-Carlo software simulation package was also developed to compute the confidence interval probabilities for general optical beam profiles. Numerical results show that the approximation is valid for a wide range of operation scenarios
Analysis of excited quark propagator effects on neutron charge form factor
The charge form factor and charge radius of neutron are investigated in the
perturbative chiral quark model (PCQM) with considering both the ground and
excited states in the quark propagator. A Cornell-like potential is extracted
in accordance with the predetermined ground state quark wavefunction, and the
excited quark states are derived by solving the Dirac equation with the
extracted PCQM potential numerically. The study reveals that the contributions
of the excited quark states are considerably influential in the charge form
factor and charge radius of neutron as expected, and the total results are
significantly improved and increased by nearly four times by including the
excited states in the quark propagator. The theoretical PCQM results are found,
including the ground and excited quark propagators, in good agreement with the
recent lattice QCD values at pion mass of about 130 MeV.Comment: 8 pages, 8 figure
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