Simulations of incompressible fluid flows by a least squares finite element method

In this work simulations of incompressible fluid flows have been done by a Least Squares Finite Element Method (LSFEM) using velocity-pressure-vorticity and velocity-pressure-stress formulations, named u-p-ω) and u-p-τ formulations respectively. These formulations are preferred because the resulting equations are partial differential equations of first order, which is convenient for implementation by LSFEM. The main purposes of this work are the numerical computation of laminar, transitional and turbulent fluid flows through the application of large eddy simulation (LES) methodology using the LSFEM. The Navier-Stokes equations in u-p-ω and u-p-τ formulations are filtered and the eddy viscosity model of Smagorinsky is used for modeling the sub-grid-scale stresses. Some benchmark problems are solved for validate the numerical code and the preliminary results are presented and compared with available results from the literature. Copyright © 2005 by ABCM.

Infrared face recogniton by optimum-path forest

This paper presents a novel, fast and accurate appearance-based method for infrared face recognition. By introducing the Optimum-Path Forest classifier, our objective is to get good recognition rates and effectively reduce the computational effort. The feature extraction procedure is carried out by PCA, and the results are compared to two other well known supervised learning classifiers; Artificial Neural Networks and Support Vector Machines. The achieved performance asserts the promise of the proposed framework. ©2009 IEEE.

Low-temperature synthesis of nanosized bismuth ferrite by the soft chemical method

This paper describes research on a simple low-temperature synthesis route to prepare bismuth ferrite nanopowders by the polymeric precursor method using bismuth and iron nitrates. BiFeO 3 (BFO) nanopowders were characterized by means of X-ray diffraction analyses, (XRD), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy (Raman), thermogravimnetric analyses (TG-DTA), ultra-violet/vis (UV/Vis) and field emission scanning electron microscopy (FE-SEM). XRD patterns confirmed that a pure perovskite BiFeO 3 structure with a rhombohedral distorted perovskite structure was obtained by heating at 850 °C for 4 hours. Typical FT-IR spectra for BFO powders revealed the formation of a perovskite structure at high temperatures due to a metal-oxygen bond while Raman modes indicated oxygen octahedral tilts induced by structural distortion. A homogeneous size distribution of BFO powders obtained at 850 °C for 4 hours was verified by FE-SEM analyses. © 2012 Elsevier Ltd and Techna Group S.r.l.

Structural refinement, growth mechanism, infrared/Raman spectroscopies and photoluminescence properties of PbMoO4 crystals

Lead molybdate (PbMoO4) crystals were synthesized by the co-precipitation method at room temperature and then processed in a conventional hydrothermal (CH) system at low temperature (70 °C for different times). These crystals were structurally characterized by X-ray diffraction (XRD), Rietveld refinement, micro-Raman (MR) and Fourier transformed infrared (FT-IR) spectroscopies. Field emission scanning electron microscopy images were employed to observe the shape and monitor the crystal growth process. The optical properties were investigated by ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) measurements. XRD patterns and MR spectra indicate that these crystals have a scheelite-type tetragonal structure. Rietveld refinement data possibilities the evaluation of distortions in the tetrahedral [MoO 4] clusters. MR and FT-IR spectra exhibited a high mode ν1(Ag) ascribed to symmetric stretching vibrations as well as a large absorption band with two modes ν3(Eu and Au) related to anti-symmetric stretching vibrations in [MoO 4] clusters. Growth mechanisms were proposed to explain the stages involved for the formation of octahedron-like PbMoO4 crystals. UV-Vis absorption spectra indicate a reduction in optical band gap with an increase in the CH processing time. PL properties of PbMoO4 crystals have been elucidated using a model based on distortions of tetrahedral [MoO4] clusters due to medium-range intrinsic defects and intermediary energy levels (deep and shallow holes) within the band gap. © 2012 Elsevier Ltd. All rights reserved.

Influence of mineralizer agents on the growth of crystalline CeO 2 nanospheres by the microwave-hydrothermal method

Cystalline ceria (CeO2) nanoparticles have been synthesized by a simple and fast microwave-assisted hydrothermal (MAH) under NaOH, KOH, and NH4OH mineralizers added to a cerium ammonium nitrate aqueous solution. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transformed-IR and Raman spectroscopies. Rietveld refinement reveals a cubic structure with a space group Fm3m while infrared data showed few traces of nitrates. Field emission scanning microcopy (FEG-SEM) revealed a homogeneous size distribution of nanometric CeO2 nanoparticles. The MAH process in KOH and NaOH showed most effective to dehydrate the adsorbed water and decrease the hydrogen bonding effect leaving a weakly agglomerated powder of hydrated ceria. TEM micrographs of CeO2 synthesized under MAH conditions reveal particles well-dispersed and homogeneously distributed. The MAH enabled cerium oxide to be synthesized at 100 °C for 8 min. © 2012 Elsevier B.V. All rights reserved.

Effect of the composition on the thermal behaviour of the SrSn1-xTixO3 precursor prepared by the polymeric precursor method

Strontium stannate titanate Sr(Sn, Ti)O3 is a solid solution between strontium stannate (SrSnO3) and strontium titanate (SrTiO3). In the present study, it was synthesized at low temperature by the polymeric precursor method, derived from the Pechini process. The powders were calcined in oxygen atmosphere in order to eliminate organic matter and to decrease the amount of SrCO3 formed during the synthesis. The powders were annealed at different temperatures to crystallize the samples into perovskites-type structures. All the compositions were studied by thermogravimetry (TG) and differential thermal analysis (DTA), infrared spectroscopy (IR) and X-ray diffraction (XRD). The lattice former, Ti4+ and Sn4+, had a meaningful influence in the mass loss, without changing the profile of the TG curves. On the other hand, DTA curves were strongly modified with the Ti4+:Sn4+ proportion in the system indicating that intermediate compounds may be formed during the synthesis being eliminated at different temperature ranges, while SrCO3 elimination occurs at higher temperature as shown by XRD and IR spectra. © 2013 Akadémiai Kiadó, Budapest, Hungary.

A heuristic approach for accessing and employing the infrared behavior of Yang-Mills correlation functions

This work analyses a hypothetically improved perturbative approach taking a dressed massive-like gluon propagator and an effective coupling into account. As an early step, corrections were calculated to the ghost and gluon propagators, and the ghost-gluon vertex in the Landau gauge, pure SU(3) Yang-Mills theory. Results were satisfactorily compared with lattice data. © 2013 American Institute of Physics.

Hot turning of a difficult-to-machine steel (sae xev-f) aided by infrared radiation

A possible way for increasing the cutting tool life can be achieved by heating the workpiece in order to diminish the shear stress of material and thus decrease the machining forces. In this study, quartz electrical resistances were set around the workpiece for heating it during the turning. In the tests, heat-resistant austenitic alloy steel was used, hardenable by precipitation, mainly used in combustion engine exhaustion valves, among other special applications for industry. The results showed that in the hot machining the cutting tool life can be increased by 340% for the highest cutting speed tested and had a reduction of 205% on workpiece surface roughness, accompanied by a force decrease in relation to conventional turning. In addition, the chips formed in hot turning exhibited a stronger tendency to continuous chip formation indicating less energy spent in material removal process. Microhardness tests performed in the workpieces subsurface layers at 5 m depth revealed slightly higher values in the hot machining than in conventional, showing a tendency toward the formation of compressive residual stress into plastically deformed layer. The hot turning also showed better performance than machining using cutting fluid. Since it is possible to avoid the use of cutting fluid, this machining method can be considered better for the environment and for the human health.

Predicting soluble solid content in intact jaboticaba [Myrciaria jaboticaba (Vell.) O. Berg] fruit using near-infrared spectroscopy and chemometrics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

LaNiO3 nanotubes produced using a template-assisted method

We have studied the experimental conditions needed to produce LaNiO3 (LNO) nanostructures using a template-assisted method. In this route, a mesoporous anodic aluminum oxide template was filled with a chemical solution that had been prepared with polymeric precursors route. The precursor solutions and synthesized samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis, infrared spectroscopy and high-resolution scanning electron microscopy (HRSEM). The XRD results for the samples that were heat-treated at 700 degrees C revealed that these samples crystallize in a perovskite-like LaNiO3 structure. HRSEM images revealed that the samples prepared with different deposition times (0.5, 1 and 2 h) promoted the formation of LaNiO3 nanotubes with different wall thicknesses.

Assessment of a new infrared laser transillumination technology (808nm) for the detection of occlusal caries-an in vitro study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Rietveld refinement and optical properties of SrWO4:Eu3+ powders prepared by the non-hydrolytic sol-gel method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Classification of intact açai (Euterpe oleracea Mart.) and jucara (Euterpe edulis Mart) fruits based on dry matter content by means of near infrared spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development and validation of the quantitative analysis of cefuroxime sodium in powder for injection by infrared spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development and validation of the quantitative analysis of ampicillin sodium in powder for injection by Fourier-transform infrared spectroscopy (FT-IR)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)