7,897 research outputs found
The structure of robust observers
Conventional observers for linear time-invariant systems are shown to be structurally inadequate from a sensitivity standpoint. It is proved that if a linear dynamic system is to provide observer action despite arbitrary small perturbations in a specified subset of its parameters, it must: (1) be a closed loop system, be driven by the observer error, (2) possess redundancy, the observer must be generating, implicitly or explicitly, at least one linear combination of states that is already contained in the measurements, and (3) contain a perturbation-free model of the portion of the system observable from the external input to the observer. The procedure for design of robust observers possessing the above structural features is established and discussed
Production of J/-Particles at RHIC and LHC energies: An Alternative `Psi'-chology
We attempt here to understand successfully some crucial aspects of
-production in some high energy nuclear collisions in the light of a
non-standard framework outlined in the text. It is found that the results
arrived at with this main working approach here is fairly in good agreement
with both the measured data and the results obtained on the basis of some other
models of the `standard' variety. Impact and implications of this comparative
study have also been precisely highlighted in the end.Comment: 14 pages, 7 figures, to appear in Open Journal of Microphysics. arXiv
admin note: substantial text overlap with arXiv:0906.2612, arXiv:1110.5582,
and overlap with arXiv:1103.6269, arXiv:1007.451
Stability margins for multilinear interval systems by way of phase conditions: A unified approach
A simple way of checking the stability with respect to an arbitrary stability region of a family of polynomials containing a vector of parameters varying within prescribed intervals is discussed. It is assumed that the parameters appear affine multilinearly in the characteristic polynomial coefficients. The condition proposed is simply to check the phase difference of the vertex polynomials. This test based on the mapping theorem significantly reduces computational complexity. Mathematical proofs are omitted. The results can be used to determine various stability margins of control systems containing interconnected interval subsystems. These include the gain, phase, time-delay, H(sup infinity), and nonlinear sector bounded stability margins of multilinear interval systems
Parametric stability margin for multilinear interval control systems
Recently, a necessary and sufficient condition to determine the robust stability of a multilinear interval control system has been reported as an extension of the well-known Box theorem which deals with the linear affine case. A simple but computationally efficient algorithm, based on the above result, to check the robust stability of such systems is introduced. The method is also extended to find the parametric stability margin of such a system
Constraints on Fluid Dynamics from Equilibrium Partition Functions
We study the thermal partition function of quantum field theories on
arbitrary stationary background spacetime, and with arbitrary stationary
background gauge fields, in the long wavelength expansion. We demonstrate that
the equations of relativistic hydrodynamics are significantly constrained by
the requirement of consistency with any partition function. In examples at low
orders in the derivative expansion we demonstrate that these constraints
coincide precisely with the equalities between hydrodynamical transport
coefficients that follow from the local form of the second law of
thermodynamics. In particular we recover the results of Son and Surowka on the
chiral magnetic and chiral vorticity flows, starting from a local partition
function that manifestly reproduces the field theory anomaly, without making
any reference to an entropy current. We conjecture that the relations between
transport coefficients that follow from the second law of thermodynamics agree
to all orders in the derivative expansion with the constraints described in
this paper.Comment: Typos corrected, References adde
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