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On the adaptive wavelet deconvolution of a density for strong mixing sequences
Chesneau, Christophe 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.4
This paper studies the estimation of a density in the convolution density model from strong mixing observations. The ordinary smooth case is considered. Adopting the minimax approach under the mean integrated square error over Besov balls, we explore the performances of two wavelet estimators: a linear one based on projections and a non-linear one based on a hard thresholding rule. The feature of the non-linear one is to be adaptive, i.e., it does not require any prior knowledge of the smoothness class of the unknown density in its construction. We prove that it attains a fast rate of convergence which corresponds to the optimal one obtained in the standard i.i.d. case up to a logarithmic term.
On the adaptive wavelet deconvolution of a density for strong mixing sequences
Christophe Chesneau 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.4
This paper studies the estimation of a density in the convolution density model from strong mixing observations. The ordinary smooth case is considered. Adopting the minimax approach under the mean integrated square error over Besov balls, we explore the performances of two wavelet estimators: a linear one based on projections and a non-linear one based on a hard thresholding rule. The feature of the non-linear one is to be adaptive,i.e., it does not require any prior knowledge of the smoothness class of the unknown density in its construction. We prove that it attains a fast rate of convergence which corresponds to the optimal one obtained in the standard i.i.d. case up to a logarithmic term.
Wavelet block thresholding for density estimation in the presence of bias
Christophe Chesneau 한국통계학회 2010 Journal of the Korean Statistical Society Vol.39 No.1
We consider the density estimation problem from i.i.d. biased observations. The bias function is assumed to be bounded from above and below. A new adaptive estimator based on wavelet block thresholding is constructed. We evaluate these theoretical performances via the minimax approach under the Lp risk with p ≥ 1 (not only for p D 2) over a wide range of function classes: the Besov classes, Bs pi,r (with no particular restriction on the parameters pi and r). Under this general framework, we prove that it attains near optimal rates of convergence. The theory is illustrated by a numerical example.
Understanding the behavior of Li–oxygen cells containing LiI
Kwak, Won-Jin,Hirshberg, Daniel,Sharon, Daniel,Shin, Hyeon-Ji,Afri, Michal,Park, Jin-Bum,Garsuch, Arnd,Chesneau, Frederick Francois,Frimer, Aryeh A.,Aurbach, Doron,Sun, Yang-Kook The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.16
<▼1><P>This work deals with core issues of Li–oxygen battery systems; intrinsic stability of polyether electrolyte solutions and the role of important redox mediators such as LiI/I2.</P></▼1><▼2><P>Mankind has been in an unending search for efficient sources of energy. The coupling of lithium and oxygen in aprotic solvents would seem to be a most promising direction for electrochemistry. Indeed, if successful, this system could compete with technologies such as the internal combustion engine and provide an energy density that would accommodate the demands of electric vehicles. All this promise has not yet reached fruition because of a plethora of practical barriers and challenges. These include solvent and electrode stability, pronounced overvoltage for oxygen evolution reactions, limited cycle life and rate capability. One of the approaches suggested to facilitate the oxygen evolution reactions and improve rate capability is the use of redox mediators such as iodine for the fast oxidation of lithium peroxide. In this paper we have examined LiI as an electrolyte and additive in Li oxygen cells with ethereal electrolyte solutions. At high concentrations of LiI, the presence of the salt promotes a side reaction that forms LiOH as a major product. In turn, the presence of oxygen facilitates the reduction of I3<SUP>−</SUP> to 3I<SUP>−</SUP> in these systems. At very low concentrations of LiI, oxygen is reduced to Li2O2. The iodine formed in the anodic reaction serves as a redox mediator for Li2O2 oxidation.</P></▼2>
de la Llave, Ezequiel,Borgel, Valentina,Park, Kang-Joon,Hwang, Jang-Yeon,Sun, Yang-Kook,Hartmann, Pascal,Chesneau, Frederick- Francois,Aurbach, Doron American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.3
<P>The electrochemical behavior of Na-ion and Li-ion full cells was investigated, using hard carbon as the anode material, and NaNi0.5Mn0.5O2 and LiNi0.5Mn0.5O2 as the cathodes. A detailed description of the structure, phase transition, electrochemical behavior and kinetics of the NaNi0.5Mn0.5O2 cathodes is presented, including interesting comparison with their lithium analogue. The critical effect of the hard carbon anodes pretreatment in the total capacity and stability of full cells is clearly demonstrated. Using impedance spectroscopy in three electrodes cells, we show that the full cell impedance is dominated by the contribution of the cathode side. We discuss possible reasons for capacity fading of these systems, its connection to the cathode structure and relevant surface phenomena.</P>