13,812 research outputs found
Dynamical systems theory for music dynamics
We show that, when music pieces are cast in the form of time series of pitch
variations, the concepts and tools of dynamical systems theory can be applied
to the analysis of {\it temporal dynamics} in music. (i) Phase space portraits
are constructed from the time series wherefrom the dimensionality is evaluated
as a measure of the {\pit global} dynamics of each piece. (ii) Spectral
analysis of the time series yields power spectra () close to
{\pit red noise} () in the low frequency range. (iii) We define an
information entropy which provides a measure of the {\pit local} dynamics in
the musical piece; the entropy can be interpreted as an evaluation of the
degree of {\it complexity} in the music, but there is no evidence of an
analytical relation between local and global dynamics. These findings are based
on computations performed on eighty sequences sampled in the music literature
from the 18th to the 20th century.Comment: To appear in CHAOS. Figures and Tables (not included) can be obtained
from [email protected]
Modelling performance in a Balanced Scorecard : findings from a case study
Cet article s'intéresse à la mise en place de l'approche dite du "Balanced Scorecards" dans des unités opérationnelles plutôt qu'au niveau d'une direction générale. Il s'appuie sur une étude de cas. On propose de traiter les questions relatives à la coordination, à la fixation des objectifs et au contrôle en s'appuyant sur une méthodologie originale pour construire le modèle d'interaction entre les différentes entités de l'organisation. Cette méthodologie fait une part importante à l'apprentissage organisationnel permettant ainsi une compréhension mutuelle des degrés de liberté individuels et une meilleure observation réciproque. Cette approche "horizontale" est mieux adaptée à ce type de contexte que l'approche "verticale" plus traditionnelle du BCS.Pilotage;Tableaux de bord;Incitations;Apprentissage organisationnel
Complex resonance frequencies of a finite, circular radiating duct with an infinite flange
Radiation by solid or fluid bodies can be characterized by resonance modes.
They are complex, as well as resonance frequencies, because of the energy loss
due to radiation. For ducts, they can be computed from the knowledge of the
radiation impedance matrix. For the case of a flanged duct of finite length
radiating on one side in an infinite medium, the expression of this matrix was
given by Zorumski, using a decomposition in duct modes. In order to calculate
the resonance frequencies, the formulation used in Zorumski's theory must be
modified as it is not valid for complex frequencies. The analytical development
of the Green's function in free space used by Zorumski depends on the integrals
of Bessel functions which become divergent for complex frequencies. This paper
proposes first a development of the Green's function which is valid for all
frequencies. Results are applied to the calculation of the complex resonance
frequencies of a flanged duct, by using a formulation of the internal pressure
based upon cascade impedance matrices. Several series of resonance modes are
found, each series being shown to be related to a dominant duct mode. Influence
of higher order duct modes and the results for several fluid densities is
presented and discussed
Wavelet analysis of the multivariate fractional Brownian motion
The work developed in the paper concerns the multivariate fractional Brownian
motion (mfBm) viewed through the lens of the wavelet transform. After recalling
some basic properties on the mfBm, we calculate the correlation structure of
its wavelet transform. We particularly study the asymptotic behavior of the
correlation, showing that if the analyzing wavelet has a sufficient number of
null first order moments, the decomposition eliminates any possible long-range
(inter)dependence. The cross-spectral density is also considered in a second
part. Its existence is proved and its evaluation is performed using a von
Bahr-Essen like representation of the function \sign(t) |t|^\alpha. The
behavior of the cross-spectral density of the wavelet field at the zero
frequency is also developed and confirms the results provided by the asymptotic
analysis of the correlation
Statistical identification of geometric parameters for high speed train catenary
Pantograph/catenary interaction is known to be strongly dependent on the static geometry of the catenary, this research thus seeks to build a statistical model of this geometry. Sensitivity analyses provide a selection of relevant parameters affecting the geometry. After correction for the dynamic nature of the measurement, provide a database of measurements. One then seeks to solve the statistical inverse problem using the maximum entropy principle and the maximum likelihood method. Two methods of multivariate density estimations are presented, the Gaussian kernel density estimation method and the Gaussian parametric method. The results provide statistical information on the significant parameters and show that the messenger wire tension of the catenary hides sources of variability that are not yet taken into account in the model
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