Determination of minimum fluidization velocity for gas-solid beds by experimental data and numerical simulations

The purpose of this work is to predict the minimum fluidization velocity Umf in a gas-solid fluidized bed. The study was carried out with an experimental apparatus for sand particles with diameters between 310μm and 590μm, and density of 2,590kg/m3. The experimental results were compared with numerical simulations developed in MFIX (Multiphase Flow with Interphase eXchange) open source code [1], for three different sizes of particles: 310mum, 450μm and 590μm. A homogeneous mixture with the three kinds of particles was also studied. The influence of the particle diameter was presented and discussed. The Ergun equation was also used to describe the minimum fluidization velocity. The experimental data presented a good agreement with Ergun equation and numerical simulations. Copyright © 2011 by ASME.

Update on the status of hadronic squeezed correlations at RHIC energies

In high energy heavy ion collisions a hot and dense medium is formed, where the hadronic masses may be shifted from their asymptotic values. If this mass modification occurs, squeezed back-to-back correlations (BBC) of particle-antiparticle pairs are predicted to appear, both in the femionic (fBBC) and in the bosonic (bBBC) sectors. Although they have unlimited intensity even for finite-size expanding systems, these hadronic squeezed correlations are very sensitive to their time emission distribution. Here we discuss results in case this time emission is parameterized by a Lévy-type distribution, showing that it reduces the signal even more dramatically than a Lorentzian distribution, which already reduces the intensity of the effect by orders of magnitude, as compared to the sudden emission. However, we show that the signal could still survive if the duration of the process is short, and if the effect is searched for lighter mesons, such as kaons. We compare some of our results to recent PHENIX preliminary data on squeezed correlations of K +K - pairs. © 2011 Pleiades Publishing, Ltd.

Oxidative stress, superoxide production, and apoptosis of neutrophils in dogs with chronic kidney disease

Oxidative stress is a key component in the immunosuppression of chronic kidney disease (CKD), and neutrophil function may be impaired by oxidative stress. To test the hypothesis that in uremic dogs with CKD, oxidative stress is increased and neutrophils become less viable and functional, 18 adult dogs with CKD were compared with 15 healthy adult dogs. Blood count and urinalysis were done, and the serum biochemical profile and plasma lipid peroxidation (measurement of thiobarbituric acid reactive substances) were determined with the use of commercial reagents. Plasma total antioxidant capacity (TAC) was measured with a spectrophotometer and commercial reagents, superoxide production with a hydroethidine probe, and the viability and apoptosis of neutrophils with capillary flow cytometry and the annexin V-PE system. The plasma concentrations of cholesterol (P = 0.0415), creatinine (P < 0.0001), and urea (P < 0.0001) were significantly greater in the uremic dogs than in the control dogs. The hematocrit (P = 0.0004), urine specific gravity (P = 0.015), and plasma lipid peroxidation (P < 0.0001) were significantly lower in the dogs that were in late stages of CKD than in the control group. Compared with those isolated from the control group, neutrophils isolated from the CKD group showed a higher rate of spontaneous (0.10 ± 0.05 versus 0.49 ± 0.09; P = 0.0033; median ± standard error of mean) and camptothecin-induced (18.53 ± 4.06 versus 44.67 ± 4.85; P = 0.0066) apoptosis and lower levels of superoxide production in the presence (1278.8 ± 372.8 versus 75.65 ± 86.6; P = 0.0022) and absence (135.29 ± 51.74 versus 41.29 ± 8.38; P = 0.0138) of phorbol-12-myristate-13-acetate stimulation. Thus, oxidative stress and acceleration of apoptosis occurs in dogs with CKD, the apoptosis diminishing the number of viable neutrophils and neutrophil superoxide production.

Scaling invariance of the diffusion coefficient in a family of two-dimensional Hamiltonian mappings

We consider a family of two-dimensional nonlinear area-preserving mappings that generalize the Chirikov standard map and model a variety of periodically forced systems. The action variable diffuses in increments whose phase is controlled by a negative power of the action and hence effectively uncorrelated for small actions, leading to a chaotic sea in phase space. For larger values of the action the phase space is mixed and contains a family of elliptic islands centered on periodic orbits and invariant Kolmogorov-Arnold-Moser (KAM) curves. The transport of particles along the phase space is considered by starting an ensemble of particles with a very low action and letting them evolve in the phase until they reach a certain height h. For chaotic orbits below the periodic islands, the survival probability for the particles to reach h is characterized by an exponential function, well modeled by the solution of the diffusion equation. On the other hand, when h reaches the position of periodic islands, the diffusion slows markedly. We show that the diffusion coefficient is scaling invariant with respect to the control parameter of the mapping when h reaches the position of the lowest KAM island. © 2013 American Physical Society.

An analysis of diurnal cycles in the mass of ambient aerosols derived from biomass burning and agro-industry

Strong diurnal cycles in ambient aerosol mass were observed in a rural region of Southeast Brazil where the trace composition of the lower troposphere is governed mainly by emissions from agro-industry. An optical particle counter was used to record size-segregated aerosol number concentrations between 13 May 2010 and 15 March 2011. The data were collected every 10 min and used to calculate aerosol mass concentrations. Aerosol samples were also collected onto filters during daytime (10:00-16:00 local time) and nighttime (20:00-06:00) periods, for subsequent analysis of soluble ions and water-soluble organic carbon. Biomass burning aerosols predominated during the dry winter, while secondary aerosols were most important in the summer rainy season. In both seasons, diurnal cycles in calculated aerosol mass concentrations were due to the uptake of water by the aerosols and, to a lesser extent, to emissions and secondary aerosol formation. In neither season could the observed mass changes be explained by changes in the depth of the boundary layer. In the summer, nighttime increases in aerosol mass ranged from 2.7-fold to 81-fold, depending on particle size, while in the winter, the range was narrower, from 2.2-fold to 9.5-fold, supporting the possibility that the presence of particles derived from biomass burning reduced the overall ability of the aerosols to absorb water. Key Points Diurnal cycle of agro-industrial aerosol mass governed by humidity Biomass burning emissions act to suppress particle growth Need to consider diurnal mass cycles in aerosol dry deposition models ©2013. American Geophysical Union. All Rights Reserved.

Structure and kinetics of formation of APTS/GPTS-derived organic/inorganic hybrids

The structure and the kinetics of formation of APTS/GPTS-derived organic/inorganic hybrids were studied in situ by small-angle-X-ray scattering. The data were interpreted in terms of a process of primary particles formation and growth of mass-fractal clusters. At the very early stage, the population of the nonfractal primary particles (D = 3) increases with time. As the mass-fractal clusters appear (D < 3) as a result of the aggregation process, the radius of gyration, Rg, of the clusters increases on average. At advanced stages of aggregation, the clusters grow in a mechanism in which the number of particles per clusters increases while the number of clusters diminishes with time, in such a way that the correlation volume of the clusters, Vc, fulfills the relationship Vc â̂ R g D, in agreement with a mass-fractal character of the clusters. These results supporting a cluster-cluster aggregation process, together with the typically very low value found for the mass-fractal dimension D, are in favor of a diffusion-controlled cluster aggregation mechanism. © 2013 American Chemical Society.

Dissipação via arrasto viscoso como mecanismo de supressão da aceleração de Fermi no bilhar elíptico-ovoide com fronteira dependente do tempo

Pós-graduação em Física - IGCE

Estudo dos fotoiniciadores utilizados em resinas compostas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

On the prediction of pickup and saltation velocities in pneumatic conveying

This paper presents a comparative study of the critical pickup and saltation velocities of particles in horizontal pipelines for pneumatic conveying design. A comparative study is performed using different existing correlations in the literature for the determination of the minimum velocity of transport as a function of the particle and pipe diameter, particle density, solid mass flow rate and particle sphericity. Their limitations and difficulties in predicting those critical velocities are analyzed. For the pickup velocity, an experimental study was also carried out in order to support the analysis. Recommendations are presented on the use of such correlations.

Synthesis and photocatalytic properties of bismuth titanate with different structures via oxidant peroxo method (OPM)

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

A theoretical characterization of scaling properties in a bouncing ball system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Enhanced photoabsorption properties of composites of Ti/TiO2 nanotubes decorated by Sb2S3 and improvement of degradation of hair dye

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

On the shock performance of a nonlinear vibration isolator with high-static-low-dynamic-stiffness

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fluid-dynamic assessment of sugarcane bagasse to use as feedstock in bubbling fluidized bed gasifiers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Gestão ambiental aplicada a prevenção, controle e recuperação de erosão linear acelerada no município de Ipeúna-SP

The erosion is a natural process of detachment, transport and deposition of soil and rock particles from one place to another. Human activities with no previous planning may accelerate this process, causing several damages to the environment and to society. In order to control the acceleration of these erosion processes caused by humans, prevention and improvement initiatives emerge. Regarding works which interfere directly in some of the natural resources, these initiatives must respect the intrinsic physical properties of the area of interest, if they aim to obtain effective results. Based on this scenario, this work proposes a few methods of accelerated linear erosion prevention, control and recovery in a specific area of the municipal district of Ipeúna (SP). For that matter, this study is based on a method of physiographic compartmentalization of the area, considering and integrating soil, relief, geology and the use and land cover properties of the study area. Plus, a flowchart with general orientations regarding management of eroded areas was produced, focused on the control and recovery of linear erosion. The result demonstrates the importance of careful erosion control, respecting the physical properties of each physiographic unit. The vegetative and mechanical conservationists methods, and the discipline of water flow, have found wide applicability in the study area.