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RISS 인기검색어
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- 저자 : Saracco, (검색결과 8 건)
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Cluster-based Sliced Inverse Regression
Jérôme Saracco,Vanessa Kuentz 한국통계학회 2010 Journal of the Korean Statistical Society Vol.39 No.2
In the theory of sufficient dimension reduction, Sliced Inverse Regression (SIR) is a famous technique that enables us to reduce the dimensionality of regression problems. This semiparametric regression method aims at determining linear combinations of a pdimensional explanatory variable x related to a response variable y. However it is based on a crucial condition on the marginal distribution of the predictor x, often called the linearity condition. From a theoretical and practical point of view, this condition appears to be a limitation. Using an idea of Li, Cook, and Nachtsheim (2004) in the Ordinary Least Squares framework, we propose in this article to cluster the predictor space so that the linearity condition approximately holds in the different partitions. Then we apply SIR in each cluster and finally estimate the dimension reduction subspace by combining these individual estimates. We give asymptotic properties of the corresponding estimator. We show with a simulation study that the proposed approach, referred as cluster-based SIR,improves the estimation of the e.d.r. basis. We also propose an iterative implementation of cluster-based SIR and show in simulations that it increases the quality of the estimator. Finally the methodology is applied on the horse mussel data and the comparison of the prediction reached on test samples shows the superiority of cluster-based SIR over SIR.
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Tackling the Problem of Sulfur Poisoning of Perovskite Catalysts for Natural Gas Combustion
Rosso, Ilaria,Saracco, Guido,Specchia, Vite 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.2
LaMn_0.5Mg_0.5O_3 y MgO and LaCr_0.5-xMn_xMg_0.5O_3 y MgO catalysts(x=0-0.25, y=0-17) were prepared, characterized (XRD, BET, SEM-EDS, TEM, FTIR, chemical and atomic absorption analyses), tested for high-temperature methane combustion and aged in presence of SO_2 to investigate sulfur effect on catalytic activity. Different roles of manganese and chromium in the perovskite structure have been assessed:(i) manganese improves the activity of catalysts in the fresh state, whereas chromium worsens it;(ii) owing to its basic nature, manganese makes perovskites more prone to adsorb SO_2 and so less resistant to sulfur poisoning, whereas chromium, owing to its acidic nature, has opposite effects; (iii) the partial solubility of chromium oxide in basic media renders Cr-catalyst regeneration by NH_3 leaching less effective. MgO promotes catalytic activity of fresh LaCr_0.5Mg_0.5O_3 y MgO catalysts and slows down sulfur poisoning of LaMn_0.5Mg_0.5O_3 y MgO and LaCr_0.5Mn_0.5O_3 17 y MgO catalysts only.
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Diesel Particulate Traps Regenerated by Catalytic Combustion
Fino, Debora,Fino, Paolo,Saracco, Guido,Specchia, Vito 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.3
The development of catalytic means for the regeneration of particulate-laden traps for diesel exhaust cleaning is the main topic of this paper. All the steps of the catalytic trap preparation are dealt with, including: the synthesis and choice of the proper catalyst and trap materials, the development of in situ catalyst deposition, and the bench testion of the derived catalytic traps. Two different traps were considered(i.e., silicon carbide and cordierite wallflow monoliths operating via a shallow-bed filtration mechanism), whereas the best catalyst selected was the perovskite LaCr_0.9O_3. The filtration efficiency and the pressure drops of the catalytic and non-catalytic monoliths were evaluated on a diesel engine bench under various operating conditions. On the basis of the obtained results the catalysed SiC converter was found to be the most satisfactorty converter to be placed on the exhaust line of the modern commonrail diesel-engine cars.
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Ionization Cross Sections for Low Energy Electron Transport
Hee Seo,Pia, M. G.,Saracco, P.,Chan Hyeong Kim IEEE 2011 IEEE transactions on nuclear science Vol.58 No.6
<P>Two models for the calculation of ionization cross sections by electron impact on atoms, the Binary-Encouter-Bethe and the Deutsch-Märk models, have been implemented; they are intended to extend and improve Geant4 simulation capabilities in the energy range below 1 keV. The physics features of the implementation of the models are described, and their differences with respect to the original formulations are discussed. Results of the verification with respect to the original theoretical sources and of extensive validation with respect to experimental data are reported. The validation process also concerns the ionization cross sections included in the Evaluated Electron Data Library used by Geant4 for low energy electron transport. Among the three cross section options, the Deutsch-Märk model is identified as the most accurate at reproducing experimental data over the energy range subject to test.</P>
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Mobile and Non-mobile Catalysts for Diesel-Particulate Combustion : A Kinetic Study
Fino, Debora,Russo, Nunzio,Badini, Claudio,Saracco, Guido,Specchia, Vito 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.3
One of the potential ways to solve the problem of diesel particulate emission from both stationary and mobile sources is the use of traps carrying a suitable catalyst for promoting particulate combustion as soon as it is filtered. A Cu-K-V based catalyst, considered among the most promising in the literature, the KVO_3+C_sCl and the K_0.7Cu0.3VO_3+KCl catalysts were prepared and investigated. Their performance was compared to a reference V_2O_5 catalyst. The superior performance of the Cu-K-V catalyst is based on the grounds of both microreactor(temperature programmed combustion) and catalytic trap tests. Based on experimental data and modelling calculations, this paper elucidates how the mobility of catalyst components is the main reason for such an outcome performance and is a prerequisite to achieve an activity sufficient for trap self-regeneration.
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A new approach on recursive and non-recursive SIR methods
Bernard Bercu,Thi Mong Ngoc Nguyen,Jérôme Saracco 한국통계학회 2012 Journal of the Korean Statistical Society Vol.41 No.1
We consider a semiparametric single index regression model involving a p-dimensional quantitative covariable x and a real dependent variable y. A dimension reduction is included in this model via an index x′β. Sliced inverse regression (SIR) is a well-known method to estimate the direction of the Euclidean parameter β which is based on a ‘‘slicing step’’ of y in the population and sample versions. The goal of this paper is twofold. On the one hand,we focus on a recursive version of SIR which is also suitable for multiple indices model. On the other hand, we propose a new method called SIRoneslice when the regression model is a single index model. The SIRoneslice estimator of the direction of β is based on the use of only one ‘‘optimal’’ slice chosen among the H slices. Then, we provide its recursive version. We give an asymptotic result for the SIRoneslice approach. Simulation study shows good numerical performances of the SIRoneslice method and clearly exhibits the main advantage of using recursive versions of the SIR and SIRoneslice methods from a computational time point of view. A real dataset is also used to illustrate the approach. Some extensions are discussed in concluding remarks. The proposed methods and criterion have been implemented in R and the corresponding codes are available from the authors.
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