3,328 research outputs found
Direct identification of continuous-time LPV models
Controllers in the linear parameter-varying (LPV) framework are commonly designed in continuous time (CT) requiring accurate and low-order CT models of the system. Nonetheless, most of the methods dedicated to the identification of LPV systems are addressed in the discrete-time setting. In practice when discretizing models which are naturally expressed in CT, the dependency on the scheduling variables becomes non-trivial and over-parameterized. Consequently, direct identification of CT-LPV systems in an input-output setting is investigated. To provide consistent model parameter estimates in this setting, a refined instrumental variable approach is proposed. The statistical properties of this approach are demonstrated through a Monte Carlo simulation example
Identification of input-output LPV models
This chapter presents an overview of the available methods for identifying input-output LPV models both in discrete time and continuous time with the main focus on noise modeling issues. First, a least-squares approach and an instrumental variable method are presented for dealing with LPV-ARX models. Then, a refined instrumental variable approach is discussed to address more sophisticated noise models like Box-Jenkins in the LPV context. This latter approach is also introduced in continuous time and efficient solutions are proposed for both the problem of time-derivative approximation and the issue of continuous-time modeling of the noise
Parental CoâConstruction of 5â to 13âYearâOlds\u27 Global SelfâEsteem Through Reminiscing About Past Events
The current study explored parental processes associated with children\u27s global selfâesteem development. Eighty 5â to 13âyearâolds and one of their parents provided qualitative and quantitative data through questionnaires, openâended questions, and a laboratoryâbased reminiscing task. Parents who included more explanations of emotions when writing about the lowest points in their lives were more likely to discuss explanations of emotions experienced in negative past events with their child, which was associated with child attachment security. Attachment was associated with concurrent selfâesteem, which predicted relative increases in selfâesteem 16 months later, on average. Finally, parent support also predicted residual increases in selfâesteem. Findings extend prior research by including younger ages and uncovering a process by which two theoretically relevant parenting behaviors impact selfâesteem development
Modeling active electrolocation in weakly electric fish
In this paper, we provide a mathematical model for the electrolocation in
weakly electric fishes. We first investigate the forward complex conductivity
problem and derive the approximate boundary conditions on the skin of the fish.
Then we provide a dipole approximation for small targets away from the fish.
Based on this approximation, we obtain a non-iterative location search
algorithm using multi-frequency measurements. We present numerical experiments
to illustrate the performance and the stability of the proposed multi-frequency
location search algorithm. Finally, in the case of disk- and ellipse-shaped
targets, we provide a method to reconstruct separately the conductivity, the
permittivity, and the size of the targets from multi-frequency measurements.Comment: 37 pages, 11 figure
Spontaneous exciton condensation in 1T-TiSe2: a BCS-like approach
Recently strong evidence has been found in favor of a BCS-like condensation
of excitons in 1\textit{T}-TiSe. Theoretical photoemission intensity maps
have been generated by the spectral function calculated within the excitonic
condensate phase model and set against experimental angle-resolved
photoemission spectroscopy data. Here, the calculations in the framework of
this model are presented in detail. They represent an extension of the original
excitonic insulator phase model of J\'erome \textit{et al.} [Phys. Rev. {\bf
158}, 462 (1967)] to three dimensional and anisotropic band dispersions. A
detailed analysis of its properties and further comparison with experiment are
also discussedComment: Submitted to PRB, 11 pages, 7 figure
An optimal IV technique for identifying continuous-time transfer function model of multiple input systems
An instrumental variable method for continuous-time model identification is proposed for multiple input single output systems where the characteristic polynomials of the transfer functions associated with each input are not constrained to be identical. An associated model order determination procedure is shown to be reasonably successful. Monte Carlo simulation analyses are used to demonstrate the properties and general robustness of the model order selection and parameter estimation schemes. The results obtained to model a winding process and an industrial binary distillation column illustrate the practical applicability of the proposed identification scheme
Extragalactic database. VII Reduction of astrophysical parameters
The Lyon-Meudon Extragalactic database (LEDA) gives a free access to the main
astrophysical parameters for more than 100,000 galaxies. The most common names
are compiled allowing users to recover quickly any galaxy. All these measured
astrophysical parameters are first reduced to a common system according to well
defined reduction formulae leading to mean homogeneized parameters. Further,
these parameters are also transformed into corrected parameters from widely
accepted models. For instance, raw 21-cm line widths are transformed into mean
standard widths after correction for instrumental effect and then into maximum
velocity rotation properly corrected for inclination and non-circular velocity.
This paper presents the reduction formulae for each parameter: coordinates,
morphological type and luminosity class, diameter and axis ratio, apparent
magnitude (UBV, IR, HI) and colors, maximum velocity rotation and central
velocity dispersion, radial velocity, mean surface brightness, distance modulus
and absolute magnitude, and group membership. For each of these parameters
intermediate quantities are given: galactic extinction, inclination,
K-correction etc..
All these parameters are available from direct connexion to LEDA (telnet
lmc.univ-lyon1.fr, login: leda, no passwd
OR http://www-obs.univ-lyon1.fr/leda ) and distributed on a standard CD-ROM
(PGC-ROM 1996) by the Observatoire de Lyon via the CNRS (mail to
[email protected]).Comment: 13 pages, 12 figures. The CDROM of the extragalactic database LEDA is
available by mailing to: [email protected]
Temperature dependent photoemission on 1T-TiSe2: Interpretation within the exciton condensate phase model
The charge density wave phase transition of 1T-TiSe2 is studied by
angle-resolved photoemission over a wide temperature range. An important
chemical potential shift which strongly evolves with temperature is evidenced.
In the framework of the exciton condensate phase, the detailed temperature
dependence of the associated order parameter is extracted. Having a
mean-field-like behaviour at low temperature, it exhibits a non-zero value
above the transition, interpreted as the signature of strong excitonic
fluctuations, reminiscent of the pseudo-gap phase of high temperature
superconductors. Integrated intensity around the Fermi level is found to
display a trend similar to the measured resistivity and is discussed within the
model.Comment: 8 pages, 6 figure
Ce-L3-XAS study of the temperature dependence of the 4f occupancy in the Kondo system Ce2Rh3Al9
We have used temperature dependent x-ray absorption at the Ce-L3 edge to
investigate the recently discovered Kondo compound Ce2Rh3Al9. The systematic
changes of the spectral lineshape with decreasing temperature are analyzed and
found to be related to a change in the occupation number, n_f, as the
system undergoes a transition into a Kondo state. The temperature dependence of
indicates a characteristic temperature of 150K, which is clearly related
with the high temperature anomaly observed in the magnetic susceptibility of
the same system. The further anomaly observed in the resistivity of this system
at low temperature (ca. 20K) has no effect on n_f and is thus not of Kondo
origin.Comment: 7 pages, three figures, submitted to PR
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