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61.
Zorica Mojović Aleksandra Milutinović-Nikolić Predrag Banković Slavko Mentus Dušan Jovanović 《Journal of Solid State Electrochemistry》2010,14(9):1621-1627
In order to enhance silver effectiveness for oxygen reduction reaction, pillared clay was used as a support for silver nanodispersion. Silver particles incorporation into pillared clay pores was attempted by impregnation/thermal degradation technique. X-ray diffraction as well as adsorption-desorption isotherms confirmed that pillaring procedure was successful. Scanning electron microscopy evidenced that a part of silver appeared outside the pillared clay cavities. Ag-pillared clay composite homogenized with 10 wt.% of nanodispersed carbon black (Vulcan), was applied on a flat glassy carbon surface and used as an electrode material. Oxygen reduction reaction was investigated in an O2-saturated aqueous 0.1 M NaOH solution. 相似文献
62.
Renato Fedele Dušan Jovanovi? Bengt Eliasson Padma K. Shukla 《Physics letters. A》2010,374(5):788-795
The possibility of the decomposition of the three-dimensional (3D) Gross-Pitaevskii equation (GPE) into a pair of coupled Schrödinger-type equations, is investigated. It is shown that, under suitable mathematical conditions, it is possible to construct the exact controlled solutions of the 3D GPE from the solutions of a linear 2D Schrödinger equation coupled with a 1D nonlinear Schrödinger equation (the transverse and longitudinal components of the GPE, respectively). The coupling between these two equations is the functional of the transverse and the longitudinal profiles. The applied method of nonlinear decomposition, called the controlling potential method (CPM), yields the full 3D solution in the form of the product of the solutions of the transverse and longitudinal components of the GPE. It is shown that the CPM constitutes a variational principle and sets up a condition on the controlling potential well. Its physical interpretation is given in terms of the minimization of the (energy) effects introduced by the control. The method is applied to the case of a parabolic external potential to construct analytically an exact BEC state in the form of a bright soliton, for which the quantitative comparison between the external and controlling potentials is presented. 相似文献
63.
Miroslav Stanković Margarita Gabrovska Jugoslav Krstić Peter Tzvetkov Maya Shopska Tsenka Tsacheva Predrag Banković Rumeana Edreva-Kardjieva Dušan Jovanović 《Journal of molecular catalysis. A, Chemical》2009,297(1):54-62
Silver modified Mg-Ni/diatomite materials with ratios of SiO2/Ni = 1.07 and Mg/Ni = 0.1, differing in Ag content (Ag/Ni = 0.025 and 0.1) were prepared by the precipitation–deposition method. The effects of silver presence and content on the structure, morphology, texture and H2-adsorption capacity of the obtained precursors were studied by X-ray diffraction, scanning electron microscopy, Hg-porosimetry and H2-chemisorption techniques. The catalytic performance of the corresponding catalysts in the soybean oil hydrogenation was investigated. The increase of the silver loading resulted in the development of macroporosity and increase in the total sample porosity. The decrease of both H2-adsorption capacity and hydrogenation activity are related to the metallic silver covering and blocking effects on the Ni2+ species, thus hampering the access of hydrogen. The decrease of hydrogenation activity and favorable limiting of cis–trans isomerization on the silver modified catalyst are explained by Horiuti–Polanyi mechanism based on the assumption that hydrogenation and isomerization proceed at the same active metallic nickel sites via half-hydrogenated intermediates.It was shown that the adjustment of the catalyst composition by changing the content of silver modifier offers the possibility to control the total amount of solid fat content, stearic acid and detrimental trans fatty acids in the hydrogenated derivatives. The catalyst with higher silver content is proposed as a promising candidate for selective edible oil hydrogenation catalyst. 相似文献
64.
A.V. Tripković K.Dj. Popović J.D. Lović V.M. Jovanović S.I. Stevanović D.V. Tripković A. Kowal 《Electrochemistry communications》2009,11(5):1030-1033
Oxidation of ethanol was studied at Snad modified and unmodified Pt3Sn/C and Pt/C catalysts. Pt3Sn/C and Pt/C catalysts were characterized by XRD. Potentiodynamic and chronoamperometric measurements were used to establish catalytic activity and stability. High activity achieved at Snad modified Pt3Sn/C catalyst has not been observed at any bimetallic catalyst so far. Promotional effect of Snad on the ethanol oxidation was related to the enhancement of CO oxidation rate in bifunctional mechanism. It was shown that electrodeposited Sn exhibited different effect on the catalytic activity compared to Sn in alloy. 相似文献
65.
66.
Based on analytical considerations about how near-wall turbulence needs to be modified in order to reduce the momentum loss towards solid walls and to yield lower energy losses, a mechanism of turbulent drag reduction is proposed. This mechanism suggests that drag reducing flow control at high Reynolds numbers should be designed to minimize the turbulent dissipation rate. A previously published approach on how a reduction of the turbulent dissipation in the near-wall region can be achieved is analyzed further. The obtained results provide some new insight on the parameters that need to be considered when designing flow control schemes for skin friction drag reduction. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
67.
Boško S. Jovanovi? 《Journal of Computational and Applied Mathematics》2010,235(3):519-534
An initial boundary value problem for a two-dimensional hyperbolic equation in two disjoint rectangles is investigated. The existence and uniqueness and a priori estimates for weak solutions in appropriate Sobolev-like spaces are proved. Few finite difference schemes approximating this problem are proposed and analyzed. 相似文献
68.
D. M. Minić I. Cekić F. T. Pastor V. Jovanović R. Marković 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(9):1458-1462
This study demonstrates the electrochemical activity of selected 2-alkylidene-4-oxothiazolidine compounds containing different
substituents at the C5-position on the Pt-electrode in 0.1 M TBAHFP + MeCN in the potential range from −2 V to 2 V. The mechanism
of electrode processes is discussed. It is shown that a chemical step is involved in irreversible electrochemical processes.
The effect of the substituent at the C5-position on reduction and oxidation potentials is also noted. The regions of a linear
dependence of the current peak on the concentration of the compounds examined are determined.
The text was submitted by the authors in English. 相似文献
69.
Svjetlana Sredi? Anne Spasjevic-de-Biré Marija Todorovi? Dušan Jovanovi? Polycarpos Pissis 《Journal of Physics and Chemistry of Solids》2008,69(8):1883-1890
Our previous experiences with incorporation of polyoxometalates (POMs) in different substrates have been very successful, because new nanocomposites with better conductive, catalytical and biochemical characteristics have been obtained. The results of intercalation of different mass% of ammonium decavanadate (ADV) in Al-pillared interlayered clays (Al-PILCs) are presented.The Al-PILCs were prepared using natural raw material, bentonite, containing a high percentage of montmorillonite (MM). Synthesis of ADV has been described in a previous paper. The structure of ADV hexahydrate was determined at low temperature, 100 K. A kappa refinement was performed to estimate the atomic charges.A sol-gel procedure was applied to obtain Al-PILCs composite intercalated with ADV hexahydrate (from 2 to 5 mass% of ADV). Structure and morphological properties of the new material, a nanocomposite of Al-PILCs-ADV, were investigated by X-ray powder diffraction (XRPD) and atomic force microscopy (AFM). To understand better how ADV is incorporated in the MM substrate, specific surface areas, pore structures and pore distributions were determined.Electrical and dielectric properties of the new materials were investigated by thermally stimulated depolarization currents (TSDCs) and broadband dielectric relaxation spectroscopy (DRS). The electrical conductivity of the nanocomposite was found to increase, in relation to MM, by intercalating with a small amount of ADV. 相似文献
70.
Z. P. Cherkezova-Zheleva M. G. Shopska J. B. Krstić D. M. Jovanović I. G. Mitov G. B. Kadinov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(9):1471-1476
Samples of one-(Fe) and two-component (Fe-Pd and Fe-Pt) catalysts were prepared by incipient wetness impregnation of four
different supports: TiO2 (anatase), γ-Al2O3, activated carbon, and diatomite. The chosen synthesis conditions resulted in the formation of nanosized supported phases—iron
oxide (in the one-component samples), or iron oxide-noble metal (in the two-component ones). Different agglomeration degrees
of these phases were obtained as a result of thermal treatment. Ultradisperse size of the supported phase was maintained in
some samples, while a process of partial agglomeration occurred in others, giving rise to nearly bidisperse (ultra-and highdisperse)
supported particles. The different texture of the used supports and their chemical composition are the reasons for the different
stability of the nanosized supported phases. The samples were tested as heterogeneous catalysts in total benzene oxidation
reaction.
The text was submitted by the authors in English. 相似文献