40,322 research outputs found
Robust H∞ control of networked control systems with access constraints and packet dropouts
We consider a class of networked control systems (NCSs) where the plant has time-varying norm-bounded parameter uncertainties, the network only provides a limited number of simultaneous accesses for the sensors and actuators, and the packet dropouts occur randomly in the network. For this class of NCSs with uncertainties and access constraints as well as packet dropouts, we derive sufficient conditions in the form of linear matrix inequalities that guarantee robust stochastic stabilisation and synthesis of H∞ controller. An example is provided to illustrate our proposed method
Small scale aspects of warm dark matter : power spectra and acoustic oscillations
We provide a semi-analytic study of the small scale aspects of the power
spectra of warm dark matter (WDM) candidates that decoupled while relativistic
with arbitrary distribution functions. These are characterized by two widely
different scales and k_{fs}=
\sqrt{3}\,k_{eq}/2\,^{1/2} with the
velocity dispersion at matter radiation equality. Density perturbations evolve
through three stages: radiation domination when the particle is relativistic
and non-relativistic and matter domination. An early ISW effect during the
first stage leads to an enhancement of density perturbations and a plateau in
the transfer function for . An effective fluid description
emerges at small scales which includes the effects of free streaming in initial
conditions and inhomogeneities. The transfer function features
\emph{WDM-acoustic oscillations} at scales . We study the
power spectra for two models of sterile neutrinos with
produced non-resonantly, at the QCD and EW scales respectively. The latter case
yields acoustic oscillations on mass scales . Our
results reveal a \emph{quasi-degeneracy} between the mass, distribution
function and decoupling temperature suggesting caveats on the constraints on
the mass of a sterile neutrino from current WDM N-body simulations and
Lyman- forest data. A simple analytic interpolation of the power
spectra between large and small scales and its numerical implementation is
given.Comment: 47 pages, 17 figures, section with comparison with Boltzmann code
- …