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141.
S. H. Leal J. C. Sczancoski L. S. Cavalcante M. T. Escote J. M. E. Matos M. R. M. C. Santos F. M. Pontes E. Longo J. A. Varela 《Journal of Sol-Gel Science and Technology》2010,53(1):21-29
Pb1−x
Sr
x
)TiO3 powders with different compositions (x = 0, 0.10, 0.50, 0.90 and 1) were synthesized by the polymeric precursor method and heat treated at 800 °C for 2 h under
air atmosphere. The thermogravimetric and differential scanning calorimetry analyses were performed in the range from 25 to
800 °C in order to estimate the stages corresponding to the water evaporation, organic decomposition and crystallization of
these materials. X-ray diffraction patterns and Rietveld analyses showed that the (Pb1−x
Sr
x
)TiO3 phases with strontium content up to x = 0.1 crystallize in a tetragonal structure. The micrographs obtained by scanning electron microscopy and transmission electron
microscopy showed that the powders have agglomerated nature, presenting irregular morphologies and polydisperse particle size
distribution. The energy dispersive X-ray spectrometry indicated the presence of pure (Pb0.50Sr0.50)TiO3 phase. 相似文献
142.
J.C. Sczancoski L.S. Cavalcante T. Badapanda S.K. Rout S. Panigrahi V.R. Mastelaro J.A. Varela M. Siu Li E. Longo 《Solid State Sciences》2010,12(7):1160-1167
[Ba1–xY2x/3](Zr0.25Ti0.75)O3 powders with different yttrium concentrations (x = 0, 0.025 and 0.05) were prepared by solid state reaction. These powders were analyzed by X-ray diffraction (XRD), Fourier transform Raman scattering (FT-RS), Fourier transform infrared (FT-IR) and X-ray absorption near-edge (XANES) spectroscopies. The optical properties were investigated by means of ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements. Even with the addition of yttrium, the XRD patterns revealed that all powders crystallize in a perovskite-type cubic structure. FT-RS and FT-IR spectra indicated that the presence of [YO6] clusters is able to change the interaction forces between the O–Ti–O and O–Zr–O bonds. XANES spectra were used to obtain information on the off-center Ti displacements or distortion effects on the [TiO6] clusters. The different optical band gap values estimated from UV–vis spectra suggested the existence of intermediary energy levels (shallow or deep holes) within the band gap. The PL measurements carried out with a 350 nm wavelength at room temperature showed that all powders present typical broad band emissions in the blue region. 相似文献
143.
Synthesis of niobia nanocrystals with controlled morphology 总被引:1,自引:0,他引:1
In this work, TT niobia-phase nanocrystals with controlled morphology were obtained by the hydrothermal treatment of a niobium peroxo complex precursor at very low temperatures. The materials obtained by this route presented a very high surface area (ranging from 79 to 327 m(2)/g), disordered NbO(6), NbO(7), and NbO(8) polyhedra, Nb-O superficial sites, and a superficial OH group, which must have ensured the acidic characteristics of this oxide. 相似文献
144.
We study the general structure of Fermi conformal nets of von Neumann algebras on S
1 and consider a class of topological representations, the general representations, that we characterize as Neveu–Schwarz or
Ramond representations, in particular a Jones index can be associated with each of them. We then consider a supersymmetric
general representation associated with a Fermi modular net and give a formula involving the Fredholm index of the supercharge
operator and the Jones index. We then consider the net associated with the super-Virasoro algebra and discuss its structure.
If the central charge c belongs to the discrete series, this net is modular by the work of F. Xu and we get an example where our setting is verified
by taking the Ramond irreducible representation with lowest weight c/24. We classify all the irreducible Fermi extensions of any super-Virasoro net in the discrete series, thus providing a classification
of all superconformal nets with central charge less than 3/2.
Sebastino Carpi: Supported by MIUR, GNAMPA-INDAM and EU network “Noncommutative Geometry” MRTN-CT-2006-0031962
Yasuyuki Kawahigashi: Supported in part by the Grants-in-Aid for Scientific Research, JSPS.
Submitted: March 3, 2008. Accepted: May 5, 2008. 相似文献
145.
146.
A model-scale naval surface combatant, DTMB 5512, is studied experimentally in steady forward speed and regular head waves
with the Iowa Institute of Hydraulic Research towing-tank facilities. Unsteady resistance, heave force, pitch moment and free-surface
elevations are investigated with different measurement systems for a fairly wide range of test conditions. Test data is procured
for validation of RANS computational fluid dynamics codes and for understanding the physics of unsteady ship hydrodynamics.
In the first part of the two-part paper, details of data reductions, measurement systems and uncertainty assessment procedures
are provided.
Received: 4 October 2000 / Accepted: 23 April 2001 相似文献
147.
Mary C. F. Alves Soraia C. Souza S. J. G. Lima E. Longo A. G. Souza Iêda M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2007,87(3):763-766
CaSnO3 was synthesized by the polymeric precursor
method, using different precursor salts as (CH3COO)2Ca·H2O,
Ca(NO3)2·4H2O,
CaCl2·2H2O and CaCO3,
leading to different results. Powder precursor was characterized using thermal
analysis. Depending on the precursor different thermal behaviors were obtained.
Results also indicate the formation of carbonates, confirmed by IR spectra.
After calcination and characterization by XRD, the formation of perovskite
as single phase was only identified when calcium acetate was used as precursor.
For other precursors, tin oxide was observed as secondary phase. 相似文献
148.
Ambrosio M Antolini R Auriemma G Baker R Baldini A Bam B Barbarino GC Barish BC Battistoni G Bellotti R Bemporad C Bernardini P Bilokon H Bisi V Bloise C Bower C Bussino S Cafagna F Calicchio M Campana D Carboni M Corona A Cecchini S Cei F Chiarella V Cormack R Coutu S DeCataldo G Dekhissi H DeMarzo C De Vincenzi M Di Credico A Diehl E Erriquez O Favuzzi C Forti C Fusco P Giacomelli G Giannini G Giglietto N Grassi M Green P Grillo A Guarino F Guarnaccia P Gustavino C Habig A Heinz R Hong JT 《Physical review D: Particles and fields》1994,50(5):3046-3058
149.
A duality for Hopf algebras and for subfactors. I 总被引:2,自引:0,他引:2
Roberto Longo 《Communications in Mathematical Physics》1994,159(1):133-150
We provide a duality between subfactors with finite index, or finite dimensional semisimple Hopf algebras, and a class ofC
*-categories of endomorphisms.Dedicated to Masamichi Takesaki on the occasion of his sixtieth birthdaySupported in part by MURST and CNR-GNAFA 相似文献
150.
Structural properties of nonionic cyclodextrin colloids in water 总被引:1,自引:0,他引:1
Lombardo D Longo A Darcy R Mazzaglia A 《Langmuir : the ACS journal of surfaces and colloids》2004,20(4):1057-1064
The amphiphilic character in water of a novel class of chemically modified cyclodextrins has been investigated by means of small-angle X-ray scattering and light scattering. The introduction ofhydrophilic oligo(ethylene glycol) onto the secondary side of heptakis[6-alkylthio-6-deoxy-2-oligo(ethylene glycol)]-beta-cyclodextrins produces an enhanced water solubility of these molecules. Shape and dimensions of the generated micellar aggregates, analyzed in terms of a suitable core-shell model, remain stable in the wide concentration range explored. The highly associative behavior of these macromolecules is evidenced by the very low value of the critical micelle concentration (cmc), which is about 2 orders of magnitude smaller than the cmc usually obtained for traditional surfactant. Despite the complex geometry of this novel macromolecule, shape and dimensions of generated micellar aggregates can be properly described according to the thermodynamic approaches generally used for amphiphilic molecules and block copolymers. Results show how the modulation of hydrophobic and hydrophilic components sensitively influence the structural features of the generated aggregates thus offering the possibility to control molecular organization in a manner similar to that for traditional colloids. For all the classes of the investigated systems, the small micelles have been found in equilibrium with polydisperse large aggregates of entangled micelles. These novel nonionic colloidal systems combine inclusion and transport properties of host macrocycles, such as cyclodextrin, together with the increased stability of colloidal aggregates, and may be of interest for their potential application as innovative drug delivery systems. 相似文献