108 research outputs found
Event Analysis of Pulse-reclosers in Distribution Systems Through Sparse Representation
The pulse-recloser uses pulse testing technology to verify that the line is
clear of faults before initiating a reclose operation, which significantly
reduces stress on the system components (e.g. substation transformers) and
voltage sags on adjacent feeders. Online event analysis of pulse-reclosers are
essential to increases the overall utility of the devices, especially when
there are numerous devices installed throughout the distribution system. In
this paper, field data recorded from several devices were analyzed to identify
specific activity and fault locations. An algorithm is developed to screen the
data to identify the status of each pole and to tag time windows with a
possible pulse event. In the next step, selected time windows are further
analyzed and classified using a sparse representation technique by solving an
l1-regularized least-square problem. This classification is obtained by
comparing the pulse signature with the reference dictionary to find a set that
most closely matches the pulse features. This work also sheds additional light
on the possibility of fault classification based on the pulse signature. Field
data collected from a distribution system are used to verify the effectiveness
and reliability of the proposed method.Comment: Accepted in: 19th International Conference on Intelligent System
Application to Power Systems (ISAP), San Antonio, TX, 201
Designing the Next Generation of Real-Time Control, Communication, and Computations for Large Power Systems
Analyzing intramolecular vibrational energy redistribution via the overlap intensity-level velocity correlator
Numerous experimental and theoretical studies have established that
intramolecular vibrational energy redistribution (IVR) in isolated molecules
has a heirarchical tier structure. The tier structure implies strong
correlations between the energy level motions of a quantum system and its
intensity-weighted spectrum. A measure, which explicitly accounts for this
correaltion, was first introduced by one of us as a sensitive probe of phase
space localization. It correlates eigenlevel velocities with the overlap
intensities between the eigenstates and some localized state of interest. A
semiclassical theory for the correlation is developed for systems that are
classically integrable and complements earlier work focusing exclusively on the
chaotic case. Application to a model two dimensional effective spectroscopic
Hamiltonian shows that the correlation measure can provide information about
the terms in the molecular Hamiltonian which play an important role in an
energy range of interest and the character of the dynamics. Moreover, the
correlation function is capable of highlighting relevant phase space structures
including the local resonance features associated with a specific bright state.
In addition to being ideally suited for multidimensional systems with a large
density of states, the measure can also be used to gain insights into the phase
space transport and localization. It is argued that the overlap intensity-level
velocity correlation function provides a novel way of studying vibrational
energy redistribution in isolated molecules. The correlation function is
ideally suited to analyzing the parametric spectra of molecules in external
fields.Comment: 16 pages, 13 figures (low resolution
Localization properties of groups of eigenstates in chaotic systems
In this paper we study in detail the localized wave functions defined in
Phys. Rev. Lett. {\bf 76}, 1613 (1994), in connection with the scarring effect
of unstable periodic orbits in highly chaotic Hamiltonian system. These
functions appear highly localized not only along periodic orbits but also on
the associated manifolds. Moreover, they show in phase space the hyperbolic
structure in the vicinity of the orbit, something which translates in
configuration space into the structure induced by the corresponding self--focal
points. On the other hand, the quantum dynamics of these functions are also
studied. Our results indicate that the probability density first evolves along
the unstable manifold emanating from the periodic orbit, and localizes
temporarily afterwards on only a few, short related periodic orbits. We believe
that this type of studies can provide some keys to disentangle the complexity
associated to the quantum mechanics of these kind of systems, which permits the
construction of a simple explanation in terms of the dynamics of a few
classical structures.Comment: 9 pages, 8 Postscript figures (low resolution). For high resolution
versions of figs http://www.tandar.cnea.gov.ar/~wisniack/ To appear in Phys.
Rev.
Tunneling Mechanism due to Chaos in a Complex Phase Space
We have revealed that the barrier-tunneling process in non-integrable systems
is strongly linked to chaos in complex phase space by investigating a simple
scattering map model. The semiclassical wavefunction reproduces complicated
features of tunneling perfectly and it enables us to solve all the reasons why
those features appear in spite of absence of chaos on the real plane.
Multi-generation structure of manifolds, which is the manifestation of
complex-domain homoclinic entanglement created by complexified classical
dynamics, allows a symbolic coding and it is used as a guiding principle to
extract dominant complex trajectories from all the semiclassical candidates.Comment: 4 pages, RevTeX, 6 figures, to appear in Phys. Rev.
Signatures of Dynamical Tunneling in the Wave function of a Soft-Walled Open Microwave Billiard
Evidence for dynamical tunneling is observed in studies of the transmission,
and wave functions, of a soft-walled microwave cavity resonator. In contrast to
previous work, we identify the conditions for dynamical tunneling by monitoring
the evolution of the wave function phase as a function of energy, which allows
us to detect the tunneling process even under conditions where its expected
level splitting remains irresolvable.Comment: 5 pages, 5 figure
Symmetry Decomposition of Potentials with Channels
We discuss the symmetry decomposition of the average density of states for
the two dimensional potential and its three dimensional
generalisation . In both problems, the energetically
accessible phase space is non-compact due to the existence of infinite channels
along the axes. It is known that in two dimensions the phase space volume is
infinite in these channels thus yielding non-standard forms for the average
density of states. Here we show that the channels also result in the symmetry
decomposition having a much stronger effect than in potentials without
channels, leading to terms which are essentially leading order. We verify these
results numerically and also observe a peculiar numerical effect which we
associate with the channels. In three dimensions, the volume of phase space is
finite and the symmetry decomposition follows more closely that for generic
potentials --- however there are still non-generic effects related to some of
the group elements
Stability of quantum motion and correlation decay
We derive a simple and general relation between the fidelity of quantum
motion, characterizing the stability of quantum dynamics with respect to
arbitrary static perturbation of the unitary evolution propagator, and the
integrated time auto-correlation function of the generator of perturbation.
Surprisingly, this relation predicts the slower decay of fidelity the faster
decay of correlations is. In particular, for non-ergodic and non-mixing
dynamics, where asymptotic decay of correlations is absent, a qualitatively
different and faster decay of fidelity is predicted on a time scale 1/delta as
opposed to mixing dynamics where the fidelity is found to decay exponentially
on a time-scale 1/delta^2, where delta is a strength of perturbation. A
detailed discussion of a semi-classical regime of small effective values of
Planck constant is given where classical correlation functions can be used to
predict quantum fidelity decay. Note that the correct and intuitively expected
classical stability behavior is recovered in the classical limit hbar->0, as
the two limits delta->0 and hbar->0 do not commute. In addition we also discuss
non-trivial dependence on the number of degrees of freedom. All the theoretical
results are clearly demonstrated numerically on a celebrated example of a
quantized kicked top.Comment: 32 pages, 10 EPS figures and 2 color PS figures. Higher resolution
color figures can be obtained from authors; minor changes, to appear in
J.Phys.A (March 2002
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