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Registros recuperados: 55
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A new analytical formulation of retention effects on particle diffusion processes Anais da ABC (AABC)
Bevilacqua,Luiz; Galeão,Augusto C.N.R.; Costa,Flavio P..
The ultimate purpose of this paper is to present a new analytical formulation to simulate diffusion with retention in a reactive medium under stable thermodynamic conditions. The analysis of diffusion with retention in a continuum medium is developed after the solution of an equivalent problem using a discrete approach. The new law may be interpreted as the reduction of all diffusion processes with retention to a unifying phenomenon that can adequately simulate the retention effect namely a circulatory motion. It is remarkable that the governing equation requires a fourth order differential term as suggested by the discrete approach. The relative fraction of diffusion particles β is introduced as a control parameter in the diffusion-retention law as...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Diffusion; Retention; Constitutive law; Discrete approach; Population dynamics; Fourth order differential equations.
Ano: 2011 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652011000400031
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A numerical scheme for coastal morphodynamic modelling on unstructured grids ArchiMer
Guerin, Thomas; Bertin, Xavier; Dodet, Guillaume.
Over the last decade, modelling systems based on unstructured grids have been appearing increasingly attractive to investigate the dynamics of coastal zones. However, the resolution of the sediment continuity equation to simulate bed evolution is a complex problem which often leads to the development of numerical oscillations. To overcome this problem, addition of artificial diffusion or bathymetric filters are commonly employed methods, although these techniques can potentially over-smooth the bathymetry. This study aims to present a numerical scheme based on the Weighted Essentially Non-Oscillatory (WENO) formalism to solve the bed continuity equation on unstructured grids in a finite volume formulation. The new solution is compared against a classical...
Tipo: Text Palavras-chave: Morphodynamic modelling; Unstructured grid; WENO; Diffusion; Coastal environments; Exner equation.
Ano: 2016 URL: https://archimer.ifremer.fr/doc/00606/71851/70480.gif
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A self-regularising DVM–PSE method for the modelling of diffusion in particle methods ArchiMer
Mycek, Paul; Pinon, Gregory; Germain, Gregory; Rivoalen, Elie.
The modelling of diffusive terms in particle methods is a delicate matter and several models have been proposed in the literature. The Diffusion Velocity Method (DVM) consists in rewriting these terms in an advective way, thus defining a so-called diffusion velocity. In addition to the actual velocity, it is used to compute the particles displacement. On the other hand, the well-known and commonly used Particle Strength Exchange method (PSE) uses an approximation of the Laplacian operator in order to model diffusion. This approximation is based on an exchange of particles strength. Although DVM is particularly well suited to particle methods since it preserves their Lagrangian aspect, its major drawback stems in the fact that it suffers from severe...
Tipo: Text Palavras-chave: Particle method; Diffusion; DVM; PSE.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00159/27006/25254.pdf
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ADOPT: a tool for predicting adoption of agricultural innovations AgEcon
Kuehne, Geoff; Llewellyn, Rick S.; Pannell, David J.; Wilkinson, Roger; Dolling, P.; Ewing, Michael A..
A wealth of evidence exists about the adoption of new practices and technologies in agriculture but there does not appear to have been any attempt to simplify this vast body of research knowledge into a model to make quantitative predictions across a broad range of contexts. This is despite increasing demand from research, development and extension agencies for estimates of likely extent of adoption and the likely timeframes for project impacts. This paper reports on the reasoning underpinning the development of ADOPT (Adoption and Diffusion Outcome Prediction Tool). The tool has been designed to: 1) predict an innovation‘s likely peak extent of adoption and likely time for reaching that peak; 2) encourage users to consider the influence of a structured...
Tipo: Conference Paper or Presentation Palavras-chave: Adoption; Diffusion; Prediction; Research and Development/Tech Change/Emerging Technologies.
Ano: 2011 URL: http://purl.umn.edu/100570
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ALVES, E. R. de A. Fundamentos sobre sistema de produção. Infoteca-e
Existe num dado momento do tempo um estoque de conhecimentos que podem ser classificados em dois grupos. No primeiro grupo estão os conhecimentos "Sistematizados" ou seja podem ser deduzidos de um pequeno conjunto de princípios fundamentais. No segundo grupo estão os conhecjmentos que não foram ainda sistematizados. Estão a espera que se construa uma teoria que possa unificá-los.
Tipo: Documentos (INFOTECA-E) Palavras-chave: Tecnologia; Transferência de tecnologia; Assistência técnica; Extensao rural; Technology; Diffusion; Technical assistance; Rural extension; Sistema de produção; Agricultura.
Ano: 1985 URL: http://www.infoteca.cnptia.embrapa.br/handle/doc/90974
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Anais... Infoteca-e
ENCONTROS REGIONAIS SOBRE DIFUSÃO DE TECNOLOGIA, 1986, Brasília, DF..
Programacao dos encontros; Marco conceitual da difusao de tecnologia e organizacao do DDT; Propostas apresentadas pelo DDT; Problemas e sugestoes prioritarias por regioes.
Tipo: Documentos (INFOTECA-E) Palavras-chave: Difusao; Policy; Articulation; Communication; Agricultura; Articulação; Comunicação; Política; Tecnologia; Agriculture; Diffusion.
Ano: 1990 URL: http://www.infoteca.cnptia.embrapa.br/infoteca/handle/doc/85151
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Analysis of the economic impact of sorghum and millet research in Mali Open Agri
A.M..
Palavras-chave: Millets; Sorghum; Breeds (animals); Diffusion; Early maturation; Budgets; Cereals; Germplasm; Introduced varieties.
Ano: 2000 URL: http://agropedia.iitk.ac.in/openaccess/?q=node/4219
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Assessing Adoption Potential of New Groundnut Varieties in Malawi Open Agri
H.A..
Palavras-chave: Gene banks; Variety trials; Groundnuts; On-farm research; Economic indicators; Diffusion; Research methods; Sowing rates; Early maturation; Agronomy.
Ano: 2002 URL: http://agropedia.iitk.ac.in/openaccess/?q=node/3746
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Assessment of the economic impact of sorghum variety S 35 in Chad Open Agri
A.M..
Palavras-chave: Variable costs; Sorghum; Diffusion; Extension activities; Sowing date; Fixed costs; Repellents; Seed dressing; Farm inputs; Costs.
Ano: 1999 URL: http://agropedia.iitk.ac.in/openaccess/?q=node/4206
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Characterization of sea water ageing effects on mechanical properties of carbon/epoxy composites for tidal turbine blades ArchiMer
Tual, Nicolas; Carrere, N.; Davies, Peter; Bonnemains, T.; Lolive, E..
In recent years, many tidal turbine projects have been developed using composites blades. Tidal turbine blades are subject to ocean forces and sea water aggressions, and the reliability of these components is crucial to the profitability of ocean energy recovery systems. The majority of tidal turbine developers have preferred carbon/epoxy blades, so there is a need to understand how prolonged immersion in the ocean affects these composites. In this study the long term behaviour of different carbon/epoxy composites has been studied using accelerated ageing tests. A significant reduction of composite strengths has been observed after saturation of water in the material. For longer immersions only small further changes in these properties occur. No...
Tipo: Text Palavras-chave: Carbon; Seawater ageing; Diffusion; Mechanical testing.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00278/38964/37504.pdf
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Determination of drying characteristics and kinetics of bitter kola (garcinia kola) using page’s model CIGR Journal
Chinaka, Ehiem James.
Single-layer drying characteristics and kinetics of garcinia kola was studied with slice thicknesses of 1mm, 3mm, 5mm and 7mm at temperatures 45oC, 55oC, 65oC and 75oC using natural convention laboratory oven . The results obtained revealed that garcinia kola slices dried in the falling rate period. Moisture ratio, characteristics drying rate constant, drying time, effective diffusivity and activation energy were significantly (p
Tipo: Info:eu-repo/semantics/article Palavras-chave: Agricultural & Bioresources Engineering/Postharvest Processing and Storage Engineering Garcinia kola; Kinetics; Diffusion; Activation energy; Page’s model.
Ano: 2014 URL: http://www.cigrjournal.org/index.php/Ejounral/article/view/2987
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Diffusion mechanisms associated with ammonia volatilization in lowland rice International Rice Research Institute
Sivaprasad, Bandarupalli.
218 l. : ill. Thesis (Ph.D.) -- Indian Agricultural Research Institute
Tipo: Thesis Palavras-chave: Rice; Soil; Ammonia; Volatilization; Diffusion; Soil chemistry; Nitrogen; Losses from soil; Lowlands; Lowland rice.
Ano: 1988 URL: http://hdl.handle.net/123456789/1190
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Diffusion parameters of grain-growth inhibitors in WC based hardmetals with Co, Fe/Ni and Fe/Co/Ni binder alloys ArchiMer
Buchegger, Christoph; Lengauer, Walter; Bernardi, Johannes; Gruber, Jakob; Ntaflos, Theo; Kiraly, Franz; Langlade, Jessica.
The diffusion behaviour of the grain-growth inhibitors (GGI) Cr and V during early sintering stages from 950-1150 °C was investigated by means of diffusion couples of the type WC-GGI-binder/WC-binder. Besides Co, also alternative Fe/Ni and Fe/Co/Ni binder alloys were investigated. It was found that the diffusion in green bodies differs significantly from sintered hardmetals. Diffusivities in the binder phase were determined from diffusion couples prepared from model alloys and were found to be almost equal for Co and alternative binder alloys. The diffusion parameters determined from green bodies allowed to estimate the GGI distribution in a hardmetal during heat up. This was subsequently used to estimate an appropriate grain size of VC and Cr3C2 in...
Tipo: Text Palavras-chave: Hardmetal; Early sintering stage; Grain-growth inhibitor; Diffusion; Alternative binder.
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00194/30491/28896.pdf
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Diffusion Signal in Magnetic Resonance Imaging: Origin and Interpretation in Neurosciences Biol. Res.
CHABERT,STEREN; SCIFO,PAOLA.
Diffusion Magnetic Resonance Imaging provides images of unquestionable diagnostic value. It is commonly used in the assessment of stroke and in white matter fiber tracking, among other applications. The diffusion coefficient has been shown to depend on cell concentration, membrane permeability, and cell orientation in the case of white matter or muscle fiber tracking; yet a clear relation between diffusion measurements and known physiological parameters is not established. The aim of this paper is to review hypotheses and actual knowledge on diffusion signal origin to provide assistance in the interpretation of diffusion MR images. Focus will be set on brain images, as most common applications of diffusion MRI are found in neuroradiology. Diffusion signal...
Tipo: Journal article Palavras-chave: Diffusion; Magnetic Resonance Imaging; Interpretation; Non Gaussian.
Ano: 2007 URL: http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602007000500003
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Documento orientador da pesquisa em difusão de tecnologia. Infoteca-e
EMBRAPA..
1983
Tipo: Documentos (INFOTECA-E) Palavras-chave: Tecnologia; Difusão; Technology; Diffusion.
Ano: 1983 URL: http://www.infoteca.cnptia.embrapa.br/handle/doc/89269
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DRYING KINETICS OF UNRIPE PLANTAIN CHIPS USING CHARCOAL FUELLED CABINET DRYER. CIGR Journal
Famurewa, John Alaba Victor.
This study presents the thin layer drying behavior of unripe plantain slices (Musa paradisiaca) in a developed biomass cabinet dryer. The developed dryer provided an environment with an optimum operating temperature between 50 - 700C meant for drying agricultural materials. The use of thin layer drying mechanisms and equations contribute to better understanding of drying food materials. The thin layer drying behaviour of agricultural products was identified based on the mathematical models which describe the heat and mass transfer phenomena of the products. In order to select a suitable drying model, fourteen different thin layer drying models were fitted to experimental data. Fick’s second law was used to calculate the moisture diffusivity with some...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Food Engineering Thin layer; Mathematical modelling; Diffusion; Drying biomass fuel.
Ano: 2015 URL: http://www.cigrjournal.org/index.php/Ejounral/article/view/3028
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Effective diffusivity and convective mass transfer coefficient during the drying of bananas REA
Silva,Cleide M. D. P. da S. e; Silva,Wilton P. da; Farias,Vera S. de O.; Gomes,Josivanda P..
In this article, a methodology is used for the simultaneous determination of the effective diffusivity and the convective mass transfer coefficient in porous solids, which can be considered as an infinite cylinder during drying. Two models are used for optimization and drying simulation: model 1 (constant volume and diffusivity, with equilibrium boundary condition), and model 2 (constant volume and diffusivity with convective boundary condition). Optimization algorithms based on the inverse method were coupled to the analytical solutions, and these solutions can be adjusted to experimental data of the drying kinetics. An application of optimization methodology was made to describe the drying kinetics of whole bananas, using experimental data available in...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Drying kinetics; Algorithm optimization; Diffusion; Porous media.
Ano: 2012 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-69162012000200014
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Effective diffusivity in yacon potato cylinders during drying AGRIAMBI
Lisboa,Cícera G. C. de; Gomes,Josivanda P.; Figueirêdo,Rossana M. F. de; Queiroz,Alexandre J. de M.; Diógenes,Adelino de M. G.; Melo,João C. S. de.
ABSTRACT The aim of this study was to obtain the effective diffusivity of yacon potato in fixed-bed dryer at different temperatures (50, 60 and 70 ºC) and drying air velocities (1.0, 1.5 and 2.0 m s-1). Non-linear regression analysis was performed by the Quasi-Newton method using the program Statistica 7.0, where the parameters of the models were estimated as a function of the drying air temperature. Approximation of Diffusion, Two Terms, Henderson & Pabis, and Page models fitted well the experimental data. Drying air temperature and speed influenced the drying time of the samples. The effective diffusivity increased with increasing temperature, ranging from 1.18 x 10-9 to 2.15 x 10-9 m2 s-1.
Tipo: Info:eu-repo/semantics/article Palavras-chave: Smallanthus sonchifolia; Mathematical modelling; Diffusion.
Ano: 2018 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662018000800564
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Efficiency and sustainability gains from adoption of short-duration pigeonpea in nonlegume - based cropping systems Open Agri
M.C.S.( editor ).
Palavras-chave: Pigeonpeas; Millets; Grain legumes; Tropical zones; Wheats; Soil fertility; Diffusion; Cropping systems; Legumes; Electrophoresis.
Ano: 1999 URL: http://agropedia.iitk.ac.in/openaccess/?q=node/3147
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Efficiency and sustainability gains from adoption of short-duration pigeonpea in nonlegume-based cropping systems Open Agri
M.C.S..
Palavras-chave: Pigeonpeas; Millets; Grain legumes; Tropical zones; Wheats; Soil fertility; Diffusion; Cropping systems; Legumes; Electrophoresis.
Ano: 1999 URL: http://agropedia.iitk.ac.in/openaccess/?q=node/4212
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