A Comparison Study on Performance of an Adaptive Filter with Other Estimation Methods for State Estimation in High-Dimensional System

In this chapter, performance comparison between the adaptive filter (AF) and other estimation methods, especially with the variational method (VM), is given in the context of data assimilation problem in dynamical systems with (very) high dimension. The emphasis is put on the importance of innovation approach which is a basis for construction of the AF as well as the choice of a set of tuning parameters in the filter gain. It will be shown that the innovation representation for the initial dynamical system plays essential role in providing stability of the assimilation algorithms for stable and unstable system dynamics. Numerical experiments will be given to illustrate the performance of the AF

Neutral Network Adaptive Filter with Application to Ocean Current Energy Estimation

This chapter proposes a new approach for the design of an adaptive filter (AF), which is based on an artificial neural network (NN) structure for estimating the system state. The NNs are now widely used as a technology offering a way to solve complex and nonlinear problems such as time-series forecasting, process control, parameter state estimation, and fault diagnosis. The proposed NN-based adaptive filtering (NNAF) is designed by considering the filtering algorithm as an input–output system and two-stage optimization procedure. The first concerns a learning process where the weights of the NNAF are estimated to minimize the error between the filtered state and the state samples generated by a numerical model. The adaptation is carried out next to minimize the mean prediction error (MPE) of the system outputs (error between the observations and the system output forecast) subject to the coefficients associated with the estimated NN weights. Simulation results for different numerical models, especially for state estimation of the chaotic Lorenz system as well as for the ocean current at different deep layers which is important for renewable energy device placements, are presented to show the efficiency of the NNAF

On Optimal and Simultaneous Stochastic Perturbations with Application to Estimation of High-Dimensional Matrix and Data Assimilation in High-Dimensional Systems

This chapter is devoted to different types of optimal perturbations (OP), deterministic, stochastic, OP in an invariant subspace, and simultaneous stochastic perturbations (SSP). The definitions of OPs are given. It will be shown how the OPs are important for the study on the predictability of behavior of system dynamics, generating ensemble forecasts as well as in the design of a stable filter. A variety of algorithm-based SSP methodology for estimation and decomposition of very high-dimensional (Hd) matrices are presented. Numerical experiments will be presented to illustrate the efficiency and benefice of the perturbation technique

Adaptive Filter as Efficient Tool for Data Assimilation under Uncertainties

In this contribution, the problem of data assimilation as state estimation for dynamical systems under uncertainties is addressed. This emphasize is put on high-dimensional systems context. Major difficulties in the design of data assimilation algorithms is a concern for computational resources (computational power and memory) and uncertainties (system parameters, statistics of model, and observational errors). The idea of the adaptive filter will be given in detail to see how it is possible to overcome uncertainties as well as to explain the main principle and tools for implementation of the adaptive filter for complex dynamical systems. Simple numerical examples are given to illustrate the principal differences of the AF with the Kalman filter and other methods. The simulation results are presented to compare the performance of the adaptive filter with the Kalman filter

Developpement de schemas numeriques adaptes a l'hydrodynamique. Une methode numerique a pas fractionnaires. Application aux calculs d'ecoulements hypersoniques reactifs non visqueux. Formulation du schema M.U.S.C.L. de Van Leer pour une configuration axisymetrique

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 81174 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Electronic structure of pyrite-type manganese disulfide (pMnS2): an ab initio study

International audienceThe LCAO as implemented in the CRYSTAL95 code has been used to obtain the electronic structure of the pyrite-type manganese disulfide in the ferromagnetic state. Calcns. made at the UHF and local d. approxn. levels show that this compd. has a larger ionic character within the HF approach. The band structures obtained with both methods of calcn. are significantly different. In particular, the valence band is mainly occupied by the p orbitals of sulfur in the UHF approach and the compd. is described as an insulator, whereas, at the LDA level, the Mn d orbitals also lie in this band and the compd. then has a conductor characte

A seasonal dipolar eddy near Ras Al Hamra (Sea of Oman)

Trajectories and hydrological data from two Argo floats indicate that warm and salty water at 200–300-m depths was ejected from the coast of Oman, near Ras al Hamra, in spring 2008, 2011, and 2012. This warm and salty water, Persian Gulf Water (PGW), once ejected from the coast, recirculated cyclonically in the western Sea of Oman, but also flowed eastward along the Iranian and Pakistani coasts. There, it was expelled seaward by mesoscale eddies as shown by other float data. Seasonal maps of salinity were computed from all available Argo floats; they showed that, in spring, PGW is present in the middle and north of the Sea of Oman, contrary to fall, when the salinity maxima lie southeast of Ras al Hadd. The ejection of PGW from Ras al Hamra is related here to the influence of a mesoscale dipolar eddy which often appears near this cape in spring. The time-averaged and empirical orthogonal functions of altimetric maps over 11 years for this season confirm the frequent presence and the persistence of this feature. From surface currents and hydrology, deep currents were computed via thermal wind balance, and the associated shear and strain fields were obtained. This deformation field is intense near Ras al Hamra, with an offshore direction. This flow structure associated with the mesoscale dipole explains PGW ejection from the coast. This observation suggests that PGW distribution in the Northern Arabian Sea can be strongly influenced by seasonal mesoscale eddies

Le modele adjoint de MICOM Partie 1 : la version adiabatique

Available from INIST (FR), Document Supply Service, under shelf-number : RP 14893 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Conditions aux limites non reflechissantes pour un modele Shallow-Water bidimensionnel barotrope linearise

Available at INIST (FR), Document Supply Service, under shelf-number : RP 14374 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Modele Shallow-Water multicouches isopycnal de Miami

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : RP 13148 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc