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Preparation of High Purity Neodymium Oxide from Brazilian Monazite by Ion Exchange

Journal of Energy and Power Engineering 2015年第7期9卷 616-621页

作者： Carlos Alberto da Silva Queiroz jose Antonio Seneda Walter dos Reis Pedreira filho IPEN/CNEN-SP (Instituto de Pesquisas Energeticas e Nucleares/Comissao Nacional de Eneergia Nuclear-Sao Paulo) Cidade Universitaria Sao Paulo 05508-000. Brazil Fundacao Jorge Duprat Figueiredo de Seguranca e Medicina do Trabalho-FUNDACENTRO Sao Paulo 05409-002 Brazil

A simple and economical chemical process for obtaining high purity neodymium oxide is discussed. The raw material in the form of RE （rare earth） carbonates is produced industrially in Brazil from monazite. Using this concentrate as the feed material, ion exchange with a strong cationic resin, commonly used for water treatment, and without the use of retention ions was used for the fractionating of the REE （rare earth elements）. The eluent was ammonium salt of EDTA （ethylenediaminetetraacetic acid） at pH 4.0. The complex of EDTA-neodymium was transformed into neodymium oxides via oxalate precipitation. We produced 99.9% pure Nd203 in yields greater than or equal to 80%. Molecular absorption spectrophotometry was used to monitor the neodymium content during the process and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the neodymium oxides. The typical neodymium oxides obtained contained the followings contaminants in micrograms per gram： Sc （4.09）; Y （0.39）; La （0.78）; Ce （5.62）; Pr （4.56）; Sm （11.10）; Eu （1.10）; Gd （14.30）; Tb （29.3）; Dy （4.15）; Ho （8.39）; Er （13.80）; Tm （0.23）; Yb （2.29）; Lu （0.39）. High purity neodymium oxides obtained from this procedure replaced the imported product used in research and development work on rare earth at IPEN/CNEN-SP （Instituto de Pesquisas Energeticas e Nucleares/Comissfio Nacional de Eneergia Nuclear-Sao Paulo）.

关键词： Neodymium oxide elemental rare earths separation rare earths.

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Decay of a Mass-Less Field Far from Horizon of a Black Hole

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Communications in Theoretical Physics 2011年第3期55卷 445-448页

作者： jose L. Martinez-Moralest Institute of Mathematics National Autonomous University of Mexico A.P. 273 Admin. De Correos #3 CuernavacaMO 62251 Mexico

Far from the horizon of a black hole of even space dimension n, a mass-less field decays as t1-2t-n in the time, where 1 is a harmonic mode of the sphere.

关键词： black hole horizon even space dimension mass-less field

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Effects of Silver Nanoparticles on the Activities of Soil Enzymes Involved in Carbon and Nutrient Cycling

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Pedosphere 2018年第2期28卷 209-214页

作者： Frieda EIVAZI Zahra AFRASIABI Elizabeth jose Department of Agriculture and Environmental Sciences Lincoln University Department of Environmental Studies Soka University Department of Physiology and Cell Biology The Ohio State University

Soils are continuously exposed to large amounts of engineered nanoparticles, especially silver nanoparticles (AgNPs), which can affect the activity, stability, and specificity of microbial enzymes. Therefore, the measurement of specific enzyme activity can be used to identify major changes in soil environments. Accordingly, the aim of the present study was to investigate the effects of AgNPs on soil enzymes that play critical roles in mineralizing carbon and nutrients in soil. Soil samples (silt loam and sandy loam) were collected from the surface layer (0–15 cm) of a field at the George Washington Carver Farm, Lincoln University of Missouri, USA. The soils were then treated with AgNP solutions at 0, 1 600, or 3 200 μg Ag kg^(-1) dry soil, using either 10- or 50-nm AgNPs and a randomized complete block design, with three replicates per treatment. The AgNP-treated soil samples were homogenized and incubated for one month, and soil acid phosphatase, β-glucosaminidase, β-glucosidase, and arylsulfatase activities were measured after one hour, one week, and one month of incubation. The activities of all four enzymes were reduced by AgNP treatment after one hour and one ***, AgNP size had no effect. After one month of incubation, the AgNP treatments had mixed effects, which suggests that soil enzymes are only affected on a short-term basis. Further studies are required to determine the mechanisms by which AgNPs reduce soil enzyme activity.

关键词： engineered nanoparticles nanotechnology nanoparticle concentration nanoparticle size soil environment

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Twists and Gromov Hyperbolicity of Riemann Surfaces

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Acta Mathematica Sinica,English Series 2011年第1期27卷 29-44页

作者： Katsuhiko MATSUZAKI jose M. RODRIGUEZ Department of Mathematics School of Education Waseda University Shinjuku Tokyo 169-8050 Japan Departamento de Matemdticas Universidad Carlos IH de Madrid Avenida de la Universidad 30 28911 Legangs Madrid Spain

The main aim of this paper is to study whether the Gromov hyperbolicity is preserved under some transformations on Riemann surfaces （with their Poincare metrics）. We prove that quasiconformal maps between Riemann surfaces preserve hyperbolicity; however, we also show that arbitrary twists along simple closed geodesics do not preserve it, in general.

关键词： Quasiconformal maps Riemann surfaces Gromov hyperbolicity

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THE INTEGRATION OF STIFF SYSTEMS OF ODEs USING NDFs AND MEBDFs

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Journal of Computational Mathematics 2013年第2期31卷 175-189页

作者： Elisabete Alberdi Celaya Juan jose Anza Department of Applied Mathematics EUIT de Minas y Obras P(tblicas Universidad del Pals Vasco UPV/EHU Colina de Beurko s/n 48902 Barakaldo Spain Department of Applied Mathematics ETS de Ingenieria de Bilbao Universidad del Pals Vasco UPV/EHU Alameda de Urquijo s/n 48013 Bilbao Spain

In this paper we modify the MEBDF method using the NDFs as predictors instead of the BDFs. We have done it in three different ways： changing both predictors of the MEBDF, changing only the first predictor and changing only the second one. We have called the new methods MENDF, MENBDF and MEBNDF respectively. The new methods are A-stable up to order 4 and the stability properties of the new methods are better than the MEBDF method.

关键词： BDF NDF MEBDF Stiff ODEs Stability.

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Contrasting size-dependent life history strategies of an insular lizard

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Current Zoology 2020年第6期66卷 625-633页

作者： Andreu Rotger jose Manuel Igual Giacomo Tavecchia Animal Demography and Ecology Unit GEDAIMEDEA(CSIC-UIB)c M.Marques 2101790EsporlesSpain

In many species with continuous growth,body size is an important driver of life-history tactics and its relative importance is thought to reflect the spatio-temporal variability of selective *** developed a deterministic size-dependent integral projection model for 3 insular neighboring lizard populations with contrasting adult body sizes to investigate how size-related selective pressures can influence lizard life-history *** each population,we broke down differences in population growth rates into contributions from size-dependent body growth,survival,and feeundity.A life table response experiment(LTRE)was used to compare the population dynamics of the 3 populations and quantify the contributions of intrinsic demographic coefficients of each population to the population growth rate(z).Perturbation analyses revealed that the largest adults contributed the most to the population growth rate,but this was not true in the population with the smallest adults and size-independent *** we were not able to identify a single factor responsible for this difference,the combination of the demographic model on a continuous trait coupled with an LTRE analysis revealed how individuals from sister populations of the same species follow different life strategies and showed different compensatory mechanisms among survival,individual body growth,and *** results indicate that body size can play a contrasting role even in closely-related and closely-spaced populations.

关键词： body size capture-recapture integral projection model Lilfords lizard size-dependent mortality

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A New Phasor Estimator for PMU Applications:P Class and M Class

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Journal of Modern Power Systems and Clean Energy 2020年第1期8卷 55-66页

作者： jose R.Razo-Hernandez Arturo Mejia-Barron David Granados-Lieberman Martin Valtierra-Rodriguez jose F.Gomez-Aguilar ENAP-Research Group Facultad de IngenieríaUniversidad Autónoma de Querétaro(UAQ)San CayetanoC.P.76807México ENAP-Research Group Departamento de Ingeniería ElectromecánicaInstituto Tecnológico Superior de Irapuato(ITESI)Colonia El CopalC.P.36821México CONACyT-Centro Nacional de Investigación y Desarrollo Tecnológico(CENIDET) Tecnológico Nacional de MéxicoInterior Internado Palmira S/NCol.PalmiraC.P.62490México

Phasor measurement units(PMUs)are fundamental tools in the applications of modern power systems,where synchronized phasor estimations are *** accuracy and dynamic performance requirements for phasor,frequency,and rate of change of frequency(ROCOF)estimations are established in the IEEE Std.C37.118.1-2011 along with the IEEE Std.C37.118.1 a-2014,where two PMU performances are suggested:P class filters for applications requiring fast response and M class filters for applications requiring high rejection to aliased *** this paper,a methodology to design new phasor estimators that satisfy the P class and M class requirements in PMUs is *** proposed methodology is based on finite impulse response filters,brick-wall filters,and complex filter design concepts,where frequency range,time performance,harmonic rejection and out-of-band interference requirements are considered in its design.A comparative analysis using the reference model given by the IEEE Std.C37.118.1 is *** results show the effectiveness of the phasor estimators under steady-state and dynamic conditions according to the PMU standard,making them suitable tools for applications in power systems.

关键词： Brick-wall filter complex filter IEEE Std.C37.118.1 M class P class phasor measurement unit(PMU) phasor estimator

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Optimal Multimodel Representation by Laguerre Filters Applied to a Communicating Two Tank System

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Journal of Systems Science & Complexity 2018年第3期31卷 621-646页

作者： SAMEH Adaily ABDELKADER Mbarek TAREK Garna jose Ragot Laboratory of Automatic Control Signal and Image Processing National Engineering School of Monastir University of Monastir 5019 Tunisia Higher Institute of Applied Science and Technology of Sousse University of Sousse 4003 Tunisia Center of Research on Automatic of Nancy CNRS 2 Avenue de la for de Haye 54516 Vandoeuvre Cedex France.

This paper presents the development of a new nonlinear representation by exploiting the multimodel approach and the new linear representation ARX-Laguerre for each operating region. The resulting multimodel, entitled ARX-Laguerre multimodel, is characterized by the parameter number reduction with a recursive representation. However, a significant reduction of this multimodel is subject to an optimal choice of Laguerre poles characterizing each local linear model ARX-Laguerre. Therefore, the authors propose an optimization algorithm to estimate, from input/output measurements, the optimal values of Laguerre poles. The ARX-Laguerre multimodel as well as the proposed optimization algorithm are tested on a continuous stirred tank reactor system （CSTR）. Moreover, the authors take into account a practical validation on an experimental communicating two tank system （CTTS）.

关键词： ARX-Laguerre model Laguerre poles multimodel approach optimization

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An overview on nucleation theories and models

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Journal of Rare Earths 2019年第10期37卷 1015-1022页

作者： Marcos Flavio de Campos jose Adilson de Castro Department of Mechanical Engineering Federal Fluminense University

Several different models for coercivity are discussed. There are two main situations: i) nanocrystalline magnets, with grain size bellow the single domain particle size, and ii) magnets with grain size above single domain particle size. The described theories and models are general, and can be applied in either NdFeB magnets, SmFeCoCuZr or strontium ferrite magnets. The spring effect observed in isotropic nanocrystalline magnets can be explained with the Stoner-Wohlfarth model. Modifications of the StonerWohlfarth model are necessary to take into account the effect of interaction between grains. When the grain size is above the single domain size, energy considerations show that nucleation should occur at the surface of grains. Nucleation is interpreted as a two-step process, where domain wall displacement occurs for grain size above single domain size, after a nucleus is first formed. The effect of grain size on the coercive field is discussed.

关键词： Coercivity Nucleation Grain size Spring effect Nd-Fe-B Permanent magnet

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Weighted variation inequalities for differential operators and singular integrals in higher dimensions

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Science China Mathematics 2017年第8期60卷 1419-1442页

作者： MA Tao TORREA jose L. XU QuanHua School of Mathematics and Statistics Wuhan University Departamento de Matemticas Universidad Autónoma de Madrid Institute for Advanced Study in Mathematics Harbin Institute of Technology Laboratoire de Mathematiques Universite de Franche-Comte Institut Universitaire de France

We prove weighted q-variation inequalities with 2 详细信息

We prove weighted q-variation inequalities with 2

关键词： variation inequalities A_(p) weights differential operators singular integrals vector-valued variationin equalities

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