Search results for "Diffusion"
showing 10 items of 1615 documents
Prediction of mass fluxes in the pervaporation process of the ethanol dehydration, based on the free volume theory
2014
Metodę obliczania współczynników dyfuzji Maxwella-Stefana opartą na współczynnikach dyfuzji własnej przewidywanych wg zależności wynikających z teorii wolnych objętości, zastosowano do obliczania strumieni masy w procesie perwaporacyjnego odwadniania etanolu na membranie z alkoholu poliwinylowego PVA. Parametry metody wolnych objętości dla badanego układu wyznaczono oraz obliczono stężenia równowagowe w PVA stosując zmodyfikowaną metodę UNIFAC-FV a następnie obliczono udziały masowe w permeacie oraz współczynniki wzbogacenia. Obliczenia przeprowadzono dla danych eksperymentalnych opublikowanych w pracy [3]. Wyniki obliczeń porównano z wynikami uzyskanymi na instalacji doświadczalnej.
Diffusion-weighted imaging in oncology: An update
2020
To date, diffusion weighted imaging (DWI) is included in routine magnetic resonance imaging (MRI) protocols for several cancers. The real additive role of DWI lies in the “functional” information obtained by probing the free diffusivity of water molecules into intra and inter-cellular spaces that in tumors mainly depend on cellularity. Although DWI has not gained much space in some oncologic scenarios, this non-invasive tool is routinely used in clinical practice and still remains a hot research topic: it has been tested in almost all cancers to differentiate malignant from benign lesions, to distinguish different malignant histotypes or tumor grades, to predict and/or assess treatment resp…
Non-LTE radiation hydrodynamics in PLUTO
2019
Modeling the dynamics of most astrophysical structures requires an adequate description of the radiation-matter interaction. Several numerical (magneto)hydrodynamics codes were upgraded with a radiation module to fulfill this request. However, those among them that use either the flux-limited diffusion (FLD) or the M1 radiation moment approaches are restricted to the local thermodynamic equilibrium (LTE). This assumption may be not valid in some astrophysical cases. We present an upgraded version of the LTE radiation-hydrodynamics module implemented in the PLUTO code, originally developed by Kolb et al. (2013), which we have extended to handle non-LTE regimes. Starting from the general freq…
Light absorption and conversion in solar cell based on Si:O alloy
2013
Thin film Si:O alloys have been grown by plasma enhanced chemical vapor deposition, as intrinsic or highly doped (1 to 5 at. % of B or P dopant) layers. UV-visible/near-infrared spectroscopy revealed a great dependence of the absorption coefficient and of the optical gap (Eg) on the dopant type and concentration, as Eg decreases from 2.1 to 1.9 eV, for the intrinsic or highly p-doped sample, respectively. Thermal annealing up to 400 °C induces a huge H out-diffusion which causes a dramatic absorption increase and a reduction of Eg, down to less than 1.8 eV. A prototypal solar cell has been fabricated using a 400 nm thick, p-i-n structure made of Si:O alloy embedded within flat transparent c…
The dynamics of technological substitution: the case of eco-innovation diffusion of surface cleaning products
2016
Some eco-innovations have already reached a mature state, but they diffuse slowly. There is little known about the importance of various factors on the diffusion process of eco-innovations. The aim of this research is to propose a conceptual model for eco-innovation diffusion, where particular case study of eco-innovation – micro-fibre cloth (MFC) for surface cleaning purposes – is given. The work will study the relative importance of various motivations on diffusion processes as well as the influence of information campaigns. This novel methodology has been developed under the system dynamics framework and is coupled with the logistic regression model. Structural validation tests were done…
Well-posedness of the boundary layer equations
2004
We consider the mild solutions of the Prandtl equations on the half space. Requiring analyticity only with respect to the tangential variable, we prove the short time existence and the uniqueness of the solution in the proper function space. Theproof is achieved applying the abstract Cauchy--Kowalewski theorem to the boundary layer equations once the convection-diffusion operator is explicitly inverted. This improves the result of [M. Sammartino and R. E. Caflisch, Comm. Math. Phys., 192 (1998), pp. 433--461], as we do not require analyticity of the data with respect to the normal variable.
Economic and Technical Feasibility of Betanin and Pectin Extraction from Opuntia ficus-indica Peel via Microwave-Assisted Hydrodiffusion
2019
Investigating the feasibility of betanin and pectin extraction from Opuntia ficus-indica peel via microwave-assisted hydrodiffusion and gravity, this study identifies selected important economic and technical aspects associated with this innovative production route starting from prickly pear fruit discards. Which benefits would be derived from this process? Would production be limited to Opuntia-growing countries or, likewise to what happens with dried lemon peel chiefly imported from Argentina, would production take place abroad also? Can distributed manufacturing based on clean extraction technology compete with centralized production using conventional chemical processes?
The kinetics of the olivine dissolution under the extreme conditions of nano-silica production
2015
Abstract This article addresses the kinetics of the dissolution of olivine for nano-silica production at extreme conditions. The extreme conditions are pH values between −0.7 and 1, temperature between 50 and 90 °C, solid content around 250 g/L and percentage dissolved between 80% and 99%. This work is structured in 3 parts: (1) chemical and mineralogical characterization of the dunites employed; (2) mechanism of the olivine dissolution focusing on the possible resistances to the transport; and (3) determination of the kinetic parameters kT and n. The results shown here demonstrate that: (1) the limiting step of this process is not the diffusion through a silica layer but the surface reacti…
Orthogonal Ambipolar Semiconductor Nanostructures for Complementary Logic Gates.
2016
We report orthogonal ambipolar semiconductors that exhibit hole and electron transport in perpendicular directions based on aligned films of nanocrystalline "shish-kebabs" containing poly(3-hexylthiophene) (P3HT) and N,N'-di-n-octyl-3,4,9,10-perylenetetracarboxylic diimide (PDI) as p- and n-type components, respectively. Polarized optical microscopy, scanning electron microscopy, and X-ray diffraction measurements reveal a high degree of in-plane alignment. Relying on the orientation of interdigitated electrodes to enable efficient charge transport from either the respective p- or n-channel materials, we demonstrate semiconductor films with high anisotropy in the sign of charge carriers. Fi…
Experimental investigation and modeling of diffusion dialysis for HCl recovery from waste pickling solution
2019
Abstract Hydrochloric acid recovery from pickling solutions was studied by employing a batch diffusion dialysis (DD) laboratory test-rig equipped with Fumasep membranes. The effect of main operating parameters such as HCl concentration (0.1–3 M) and the presence of Fe2+ (up to 150 g/l) was investigated to simulate the system operation with real industrial streams. The variation of HCl, Fe2+ and water flux was identified. When only HCl is present, a recovery efficiency of 100% was reached. In the presence of FeCl2, higher acid recovery efficiencies, up to 150%, were observed due to the so-called “salt effect”, which promotes the passage of acid even against its concentration gradient. A 7% l…