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721.
Among the several materials under development for use as a cathodes in lithium-ion batteries olivine-type LiFePO4 is one of the most promising cathode material. However, its poor conductivity and low lithium-ion diffusion limits its practical
application. In this study, we report seven different carboxylic acids used to synthesize LiFePO4/C composite, and influences of carbon sources on electrochemical performance were intensively studied. The structure and
electrochemical properties of the LiFePO4/C were characterized by X-ray diffraction, scanning electron microscopy, electrical conductivity, and galvanostatic charge–discharge
measurements. Among the materials studied, the sample E with tartaric acid as carbon source exhibited the best cell performance
with a maximum discharge capacity of 160 mAh g−1 at a 0.1 C-rate. The improved electrochemical properties were attributed to the reduced particle size and enhanced electrical
contacts by carbon. 相似文献
722.
723.
Three‐center electric multipole moment integrals over Slater‐type orbitals (STOs) can be evaluated by translating the orbitals on one center to the other and reducing the system to an expansion of two‐center integrals. These are then evaluated using Fourier transforms. The resulting expression depends on the overlap integrals that can be evaluated with the greatest ease. They involve expressions for STO with different screening parameters that are known analytically. This work gives the overall expressions analytically in a compact form, based on Gegenbauer polynomials. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 相似文献
724.
Şuayip Yüzbaşi Niyazi Şahin Mehmet Sezer 《Numerical Methods for Partial Differential Equations》2012,28(4):1105-1123
This article is concerned with a generalization of a functional differential equation known as the pantograph equation which contains a linear functional argument. In this article, we introduce a collocation method based on the Bessel polynomials for the approximate solution of the pantograph equations. The method is illustrated by studying the initial value problems. The results obtained are compared by the known results. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011 相似文献
725.
Şuayip Yüzbaşı 《Mathematical Methods in the Applied Sciences》2012,35(8):885-893
In this paper, we will develop the Bessel collocation method to find approximate solutions of the Chen system, which is a three‐dimensional system of ODEs with quadratic nonlinearities. This scheme consists of reducing the problem to a nonlinear algebraic equation system by expanding the approximate solutions by means of the Bessel polynomials with unknown coefficients. By help of the collocation points and the matrix operations of derivatives, the unknown coefficients of the Bessel polynomials are calculated. The accuracy and efficiency of the proposed approach are demonstrated by two numerical examples and performed with the aid of a computer code written in MAPLE. In addition, comparisons between our method and the homotopy perturbation method numerical solutions are made with the accuracy of solutions. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
726.
727.
Şerban A. Basarab 《manuscripta mathematica》1979,30(3):279-327
The work is devoted to develop a general framework for the theory of formallyp-adic fields and to prove in this context some analogues of certain results of the theory of formallyp-adic fields in the sense of Kochen-Roquette. The general theory is illustrated by examples. 相似文献
728.
Şerife Tokalioğlu Şenol Kartal 《International journal of environmental analytical chemistry》2013,93(11):935-952
The contents of heavy metals in soil and vegetable samples collected from an urban garden in Kayseri, Turkey, were investigated. Both wet- and dry-ashing methods were used for dissolving vegetable samples. A sequential extraction procedure proposed by the Commission of the European Communities, Community Bureau of Reference (now superseded by the Standards, Measurement and Testing Programme, SM&T) was applied to the soil samples to extract the metals which are present in exchangeable and acid soluble (i.e. bound to carbonates), reducible (bound to Fe/Mn oxides), and oxidisable forms (bound to organic matter and sulphides) in the soil samples. Trace metals in the soil and vegetable samples were determined using flame atomic absorption spectrometry (FAAS). The total metal contents acquired by summing of metal levels in all the sequential extraction steps were compared with pseudo-total metal levels obtained with aqua regia for all the soil samples. The recovery values obtained by proportioning the results obtained by the BCR procedure to those of the pseudo-total digestion were found to be satisfactory. The limits of detection for the elements investigated were in the range of 0.04 to 0.59?µg?mL?1 for all the extraction stages of the BCR procedure. Similarities among the variables were identified by correlation analysis, principal component analysis and hierarchical cluster analysis. The relationship between the vegetable metal and soil-extractable metal concentrations was examined in order to evaluate the bioavailability of metals. 相似文献
729.
Abstract In this study the graft copolymerization of acrylamide (AAm) on swollen poly(ethylene terephthalate) (PET) fibers using cerium ammonium nitrate (CeAN) initiator was investigated. Five organic solvents, dimethylsulfoxide (DMSO), morpholine, acetic acid (HAc), n-butanol, and 1,2-dichloroethane (DCE), were used as swelling agents. DMSO was found to be the most suitable swelling agent. Solvent diffusion into the fibers was observed to increase with treatment time and temperature. The optimum graft yield was obtained when fibers were grafted after having been swollen in DMSO for a period of 1 hour at 140°C. Variation of graft yield with polymerization time and temperature, and monomer, initiator, and acid concentrations were investigated. Graft yields were observed to increase initially with polymerization time, then to level off, and were found to increase up to a certain monomer and Ce4+ concentration, then to decrease slightly. The effect of grafting on such fiber properties as diameter, viscosity, and moisture gain were also investigated. 相似文献
730.
Constantin Bolcu Gabriela Vlase Titus Vlase Paul Albu Nicolae Doca Eugen Şisu 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1409-1414
Polymeric materials by polyaddition reaction between aminated maltose and methylene diisocyanate, in different molar ratio, were synthesized. Aminated maltose was obtained by functionalization at the reductive end with methylene dianiline, under soft reductive conditions. The addition reaction was certified by comparative FTIR and Raman spectra of reactants and obtained materials. The thermooxidative stability of these materials was established under non-isothermal conditions. The thermal stability decreases by increasing the isocyanate/aminated maltose molar ratio. 相似文献