Search results for " Error."
showing 10 items of 1034 documents
Flexibilité du contrôle moteur dans les mouvements complexes dirigés
2011
The main objective of this thesis is to study the motor flexibility in complex movements when an unexpected event makes the initial motor plan inefficient. In this way, three kinematic and electromyographic studies and a fourth with functional magnetic resonance imaging were realized. (1)The main result of the first study clearly demonstrate that during complex movements express motor corrections in the upper and lower limbs, with latency responses of less than 100 ms, were revealed by contrasting electromyographic activities in perturbed and unperturbed trials. Such findings could indicate that visual on-going movement corrections may be accomplished via fast loops at the level of the uppe…
A priori parameterisation of the CERES soil-crop models and tests against several European data sets
2002
Mechanistic soil-crop models have become indispensable tools to investigate the effect of management practices on the productivity or environmental impacts of arable crops. Ideally these models may claim to be universally applicable because they simulate the major processes governing the fate of inputs such as fertiliser nitrogen or pesticides. However, because they deal with complex systems and uncertain phenomena, site-specific calibration is usually a prerequisite to ensure their predictions are realistic. This statement implies that some experimental knowledge on the system to be simulated should be available prior to any modelling attempt, and raises a tremendous limitation to practica…
Rational expectations behaviour of households : indicators, measures and tests
1996
The analysis of household survey data regularly conducted by INSEE from 1973 to 1994 allows to detect behaviors about anticipation and perception purpose concerning price and employment. The nature of available information offers the opportunity first to develop a rational expectation test for qualitative data, then to point out expectation errors associated to optimistic and/or pessimistic attitudes for the evolution of these two economic variables. The paper provides a series of synthetic and desegregated indicators (developed usually by psychologists, sociologists, economists, ...) then rational expectation tests and correct anticipation tests. Empirical results permit to establish rathe…
Performances of neural networks for deriving LAI estimates from existing CYCLOPES and MODIS products
2008
International audience; This paper evaluates the performances of a neural network approach to estimate LAI from CYCLOPES and MODIS nadir normalized reflectance and LAI products. A data base was generated from these products over the BELMANIP sites during the 2001-2003 period. Data were aggregated at 3 km x 3 km, resampled at 1/16 days temporal frequency and filtered to reject outliers. VEGETATION and MODIS reflectances show very consistent values in the red, near infrared and short wave infrared bands. Neural networks were trained over part of this data base for each of the 6 MODIS biome classes to retrieve both MODIS and CYCLOPES LAI products. Results show very good performances of neural …
On a posteriori error bounds for approximations of the generalized Stokes problem generated by the Uzawa algorithm
2012
In this paper, we derive computable a posteriori error bounds for approximations computed by the Uzawa algorithm for the generalized Stokes problem. We show that for each Uzawa iteration both the velocity error and the pressure error are bounded from above by a constant multiplied by the L2-norm of the divergence of the velocity. The derivation of the estimates essentially uses a posteriori estimates of the functional type for the Stokes problem. peerReviewed
Analysis of errors caused by incomplete knowledge of material data in mathematical models of elastic media
2011
Reliable numerical solution of a class of nonlinear elliptic problems generated by the Poisson-Boltzmann equation
2020
We consider a class of nonlinear elliptic problems associated with models in biophysics, which are described by the Poisson-Boltzmann equation (PBE). We prove mathematical correctness of the problem, study a suitable class of approximations, and deduce guaranteed and fully computable bounds of approximation errors. The latter goal is achieved by means of the approach suggested in [S. Repin, A posteriori error estimation for variational problems with uniformly convex functionals. Math. Comp., 69:481-500, 2000] for convex variational problems. Moreover, we establish the error identity, which defines the error measure natural for the considered class of problems and show that it yields computa…
Light vergence detection in monocular and monochromatic accommodation
2017
El ojo proyecta información desde el mundo tridimensional a la retina, la cual es una superficie bidimensional. Por este motivo, teóricamente sólo objetos que se encuentren en el plano conjugado a la retina pueden ser enfocados de forma correcta y, por tanto, objetos que se encuentren por delante o por detrás del plano conjugado, serán percibidos como imágenes borrosas. Por suerte, la acomodación ocular permite al ojo joven ver objetos situados a diferentes distancias de forma nítida. Este sistema de autoenfoque se consigue gracias al cambio de potencia dióptrica experimentado por el ojo como consecuencia del cambio en la morfología del cristalino. Debido a la alta frecuencia temporal de la…
Non-commutative Ring Learning with Errors from Cyclic Algebras
2022
AbstractThe Learning with Errors (LWE) problem is the fundamental backbone of modern lattice-based cryptography, allowing one to establish cryptography on the hardness of well-studied computational problems. However, schemes based on LWE are often impractical, so Ring LWE was introduced as a form of ‘structured’ LWE, trading off a hard to quantify loss of security for an increase in efficiency by working over a well-chosen ring. Another popular variant, Module LWE, generalizes this exchange by implementing a module structure over a ring. In this work, we introduce a novel variant of LWE over cyclic algebras (CLWE) to replicate the addition of the ring structure taking LWE to Ring LWE by add…