Tracer Diffusion
Mostrando 1-12 de 46 artigos, teses e dissertações.
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1. Self-diffusion coefficients of na+ in water-methanol mixtures
Uma versão modificada do método do capilar aberto de Anderson e Saddington foi empregada na determinação do coeficiente de autodifusão do íon de Na+ em solvente misto p-metanol. O 22~af+oi utilizado como radiotrapador e a técnica foi testada com uma solução aquosa de NaC1. Foram determinados coeficientes de autodifusão do Na+ para diversas proporç
Publicado em: 2011
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2. Partially aerated attached biomass bed reactor applied to treatment sanitary sewage treatment / Reator com leito de biomassa aderida aerado parcialmente aplicado ao tratamento de esgoto sanitário
This work aimed to evaluate the performance of a full scale up-flow attached biomass bed reactor (159 M POT.3) and with continuous aeration at 7 m above bottom of the reactor to sanitary sewage treatment. The bed of the reactor was constituted for activated granular carbon, anthracite carbon and sand. The work was divided into two stages. In the first stage,
Publicado em: 2010
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3. Oxygen diffusion in Bi2O3-doped ZnO
In order to clarify the influence of Bi-doping on oxygen diffusion in ZnO, the bulk and grain boundary oxygen diffusion coefficients were measured in Bi2O3-doped ZnO polycrystals by means of the gas-solid exchange method using the isotope 18O as the oxygen tracer. The experiments were performed on ZnO sintered samples containing 0.1, 0.3 and 0.5 mol% Bi2O3.
Materials Research. Publicado em: 2008-06
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4. Uma nova abordagem numérica para a injeção de traçadores em reservatórios de petróleo / A new numerical approach for the injection of tracers in petroleum reservoirs
The injection of tracers are used in the investigation of ows in heterogeneous porous media, in studies related to the simulation of miscible dispacements in petroleum reservoirs and the dispersion of contaminants in aquifers. In this work we present new algorithms for the numerical approximation of tracer injection problems. We discuss recent developments o
Publicado em: 2008
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5. Transporte atômico e reação química em nanoestruturas TiN e TiN/Ti em aço nitretado a plasma
The use of cutting tools in progressively more severe conditions in the metal-mechanics industry and the requirement to increase tool life against friction, wear and high temperature corrosion made of surface treatments an important protection method. One of the most modern treatments is the so-called duplex, that consists of plasma nitriding and deposition
Publicado em: 2008
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6. Oxygen diffusion in pure and doped ZnO
Oxygen diffusion coefficients in pure and doped ZnO polycrystals were determined by means of the gas-solid isotope exchange method using the isotope 18O as oxygen tracer. The diffusion experiments were performed from 900 to 1000 °C, under an oxygen pressure of 10(5) Pa. After the diffusion annealings, the 18O diffusion profiles were determined by secondary
Materials Research. Publicado em: 2003-06
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7. Diffusion of the 65Zn radiotracer in ZnO polycrystalline ceramics
Zinc self-diffusion coefficients were measured in polycrystalline ZnO of high density (>99% of the theoretical density) and of high purity (> 99.999%). The diffusion experiments were performed from 1006 to 1377 °C, in oxygen atmosphere, for times between 16 and 574 h. The diffusion profiles were established by means of Residual Activity Method using the 65Z
Materials Research. Publicado em: 2003-06
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8. The Trouble with Diffusion
The phenomenological formalism, which yields Fick's Laws for diffusion in single phase multicomponent systems, is widely accepted as the basis for the mathematical description of diffusion. This paper focuses on problems associated with this formalism. This mode of description of the process is cumbersome, defining as it does matrices of interdiffusion coeff
Materials Research. Publicado em: 2002-09
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9. ANALYSIS OF TRICKLE BED AND PACKED BUBBLE COLUMN BIOREACTORS FOR COMBINED CARBON OXIDATION AND NITRIFICATION
Biological removal of nitrogen and carbon by combined nitrification-oxidation in gas-liquid trickle-bed reactors (TBRs) and packed bubble columns (PBCs) was analyzed theoretically using a transient two-dimensional model. The model describes TBR and PBC performances at steady state as well as their transient response to a pulse or step increase in inlet metha
Brazilian Journal of Chemical Engineering. Publicado em: 2002-03
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10. Esquemas de alta resolução para controle da dispersão numerica em simulação de reservatorios
Standard finite-diference reservoir simulation normally uses single-point upstream welghting to approximate the components of the convective flow term at the interfaces between blocks. This procedure stabilizes the numerical solution, but introduces high levels of numerical dispersion, difficulting the correct interpretation of the simulated results. Exponen
Publicado em: 1991
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11. Tracer diffusion of globular proteins in concentrated protein solutions.
The diffusion of tracer proteins at low concentration was measured in solutions containing "background" proteins at concentrations of up to 200 g/liter. The fractional reduction of the diffusion coefficient of tracer in the presence of a given weight/volume concentration of background species generally increases with increasing size of tracer species and wit
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12. Tracer diffusion through F-actin: effect of filament length and cross-linking.
We have determined diffusion coefficients for small (50- to 70-nm diameter) fluorescein-thiocarbamoyl-labeled Ficoll tracers through F-actin as a function of filament length and cross-linking. fx45 was used to regulate filament length and avidin/biotinylated actin or ABP-280 was used to prepare cross-linked actin gels. We found that tracer diffusion was gene