5,461 research outputs found
Applications of system identification methods to the prediction of helicopter stability, control and handling characteristics
A set of results on rotorcraft system identification is described. Flight measurements collected on an experimental Puma helicopter are reviewed and some notable characteristics highlighted. Following a brief review of previous work in rotorcraft system identification, the results of state estimation and model structure estimation processes applied to the Puma data are presented. The results, which were obtained using NASA developed software, are compared with theoretical predictions of roll, yaw and pitching moment derivatives for a 6 degree of freedom model structure. Anomalies are reported. The theoretical methods used are described. A framework for reduced order modelling is outlined
Dynamic modelling and estimation of the error due to asynchronism in a redundant asynchronous multiprocessor system
The use of Redundant Asynchronous Multiprocessor System to achieve ultrareliable Fault Tolerant Control Systems shows great promise. The development has been hampered by the inability to determine whether differences in the outputs of redundant CPU's are due to failures or to accrued error built up by slight differences in CPU clock intervals. This study derives an analytical dynamic model of the difference between redundant CPU's due to differences in their clock intervals and uses this model with on-line parameter identification to idenitify the differences in the clock intervals. The ability of this methodology to accurately track errors due to asynchronisity generate an error signal with the effect of asynchronisity removed and this signal may be used to detect and isolate actual system failures
Deformed Schrodinger symmetry on noncommutative space
We construct the deformed generators of Schroedinger symmetry consistent with
noncommutative space. The examples of the free particle and the harmonic
oscillator, both of which admit Schroedinger symmetry, are discussed in detail.
We construct a generalised Galilean algebra where the second central extension
exists in all dimensions. This algebra also follows from the Inonu--Wigner
contraction of a generalised Poincare algebra in noncommuting space.Comment: 9 pages, LaTeX, abstract modified, new section include
On Maximal Unbordered Factors
Given a string of length , its maximal unbordered factor is the
longest factor which does not have a border. In this work we investigate the
relationship between and the length of the maximal unbordered factor of
. We prove that for the alphabet of size the expected length
of the maximal unbordered factor of a string of length~ is at least
(for sufficiently large values of ). As an application of this result, we
propose a new algorithm for computing the maximal unbordered factor of a
string.Comment: Accepted to the 26th Annual Symposium on Combinatorial Pattern
Matching (CPM 2015
Equivariant quantization of orbifolds
Equivariant quantization is a new theory that highlights the role of
symmetries in the relationship between classical and quantum dynamical systems.
These symmetries are also one of the reasons for the recent interest in
quantization of singular spaces, orbifolds, stratified spaces... In this work,
we prove existence of an equivariant quantization for orbifolds. Our
construction combines an appropriate desingularization of any Riemannian
orbifold by a foliated smooth manifold, with the foliated equivariant
quantization that we built in \cite{PoRaWo}. Further, we suggest definitions of
the common geometric objects on orbifolds, which capture the nature of these
spaces and guarantee, together with the properties of the mentioned foliated
resolution, the needed correspondences between singular objects of the orbifold
and the respective foliated objects of its desingularization.Comment: 13 page
Exotic galilean symmetry and the Hall effect
The ``Laughlin'' picture of the Fractional Quantum Hall effect can be derived
using the ``exotic'' model based on the two-fold centrally-extended planar
Galilei group. When coupled to a planar magnetic field of critical strength
determined by the extension parameters, the system becomes singular, and
``Faddeev-Jackiw'' reduction yields the ``Chern-Simons'' mechanics of Dunne,
Jackiw, and Trugenberger. The reduced system moves according to the Hall law.Comment: Talk given by P. A. Horvathy at the Joint APCTP- Nankai Symposium.
Tianjin (China), Oct.2001. To appear in the Proceedings, to be published by
Int. Journ. Mod. Phys. B. 7 pages, LaTex, IJMPB format. no figure
- …