20,075 research outputs found
Parameter estimation of ODE's via nonparametric estimators
Ordinary differential equations (ODE's) are widespread models in physics,
chemistry and biology. In particular, this mathematical formalism is used for
describing the evolution of complex systems and it might consist of
high-dimensional sets of coupled nonlinear differential equations. In this
setting, we propose a general method for estimating the parameters indexing
ODE's from times series. Our method is able to alleviate the computational
difficulties encountered by the classical parametric methods. These
difficulties are due to the implicit definition of the model. We propose the
use of a nonparametric estimator of regression functions as a first-step in the
construction of an M-estimator, and we show the consistency of the derived
estimator under general conditions. In the case of spline estimators, we prove
asymptotic normality, and that the rate of convergence is the usual
-rate for parametric estimators. Some perspectives of refinements of
this new family of parametric estimators are given.Comment: Published in at http://dx.doi.org/10.1214/07-EJS132 the Electronic
Journal of Statistics (http://www.i-journals.org/ejs/) by the Institute of
Mathematical Statistics (http://www.imstat.org
The President and Nuclear Weapons: Authorities, Limits, and Process
There is no more consequential decision for a president than ordering a nuclear strike. In the Cold War, the threat of sudden nuclear annihilation necessitated procedures emphasizing speed and efficiency and placing sole decision-making authority in the president’s hands. In today’s changed threat environment, the legal authorities and process a U.S. president would confront when making this grave decision merit reexamination. This paper serves as a resource in the national discussion about a president’s legal authority and the procedures for ordering a nuclear strike, and whether to update them
Is internet an acceleration factor in voluntary lifelong learning ?
IT Technologies are said to make access to learning easier and cheaper. Virtually all theorical knowledge is available in one form or another on the web, with possibilities for beginners as well as, in certain cases, for extremely sophisticated users.informal learning; lifelong learning; e-learning; Internet; Knowledge, quantitative methodology
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