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    Wyświetlanie 1-7 z 7
    Tytuł:
    Impact of Values of Diffusion Coefficient on Results of Diffusion Modelling Driven by Chemical Potential Gradien
    Autorzy:
    Wróbel, Marek
    Burbelko, Andriy
    Powiązania:
    https://bibliotekanauki.pl/articles/2174626.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    foundry industry
    application of information technology
    diffusion modelling
    Calphad method
    chemical potential
    diffusion coefficient
    przemysł odlewniczy
    zastosowanie technologii informatycznej
    modelowanie dyfuzyjne
    metoda Calphad
    potencjał chemiczny
    współczynnik dyfuzji
    Opis:
    In the paper critical role of including the right material parameters, as input values for computer modelling, is stressed. The presented model of diffusion, based on chemical potential gradient, in order to perform calculations, requires a parameter called mobility, which can be calculated using the diffusion coefficient. When analysing the diffusion problem, it is a common practice to assume the diffusion coefficient to be a constant within the range of temperature and chemical composition considered. By doing so the calculations are considerably simplified at the cost of the accuracy of the results. In order to make a reasoned decision, whether this simplification is desirable for particular systems and conditions, its impact on the accuracy of calculations needs to be assessed. The paper presents such evaluation by comparing results of modelling with a constant value of diffusion coefficient to results where the dependency of Di on temperature, chemical composition or both are added. The results show how a given deviation of diffusivity is correlated with the change in the final results. Simulations were performed in a single dimension for the FCC phase in Fe-C, Fe-Si and Fe-Mn systems. Different initial compositions and temperature profiles were used.
    Źródło:
    Archives of Foundry Engineering; 2022, 22, 3; 81--90
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Diffusion Model of Binary Systems Controlled by Chemical Potential Gradient
    Autorzy:
    Wróbel, Marek
    Burbelko, Andriy
    Powiązania:
    https://bibliotekanauki.pl/articles/2105206.pdf
    Data publikacji:
    2022
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    diffusion
    modelling
    CALPHAD
    chemical potential
    Opis:
    The paper presents a model of diffusion in a single phase with chemical potential gradient as the driving force of the process. Fick’s laws are strictly empirical and the assumption that the concentration gradients are the driving forces of diffusion is far from precise. Instead, the gradient of chemical potential μi of component i is the real driving force. The matter of governing equations of models that incorporate this approach will be raised and discussed in this article. One of more important features is the ability to acquire results where diffusion against the concentration gradient may occur. The presented model uses the Finite Difference Method (FDM) and employs the CALPHAD method to obtain chemical potentials. The calculations of chemical potential are carried out for instant conditions – temperature and composition – in the entire task domain by Thermo-Calc via a TQ-Interface. Then the heterogeneity of chemical potentials is translated into mass transfer for each individual element. Calculations of two modelling tasks for one-dimension diffusion field were carried out. First: isothermal conditions with linear initial composition distribution and second: constant temperature gradient with uniform chemical composition in the specimen. Results for two binary solid solutions: Fe-C and Fe-Si, in the FCC phase for the given tasks will be presented. Modelling allows us to estimate the time needed to reach a desired state in a particular equilibrium or quasi-equilibrium state. It also shows the path of the composition change during the process. This can be used to determine whether the system at some point is getting close to the formation of another phase due to significant deviation from its initial conditions.
    Źródło:
    Journal of Casting & Materials Engineering; 2022, 6, 2; 39--44
    2543-9901
    Pojawia się w:
    Journal of Casting & Materials Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Uwalnianie środków aktywnych z hydrożeli - model dyfuzyjny i dyfuzyjno-desorpcyjny
    Active agent release from hydrogels - diffusion and diffusion-desorption models
    Autorzy:
    Nawrotek, K.
    Modrzejewska, Z.
    Zarzycki, R
    Powiązania:
    https://bibliotekanauki.pl/articles/2073408.pdf
    Data publikacji:
    2013
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    modelowanie matematyczne
    dyfuzja
    adsorpcja
    hydrożel
    mathematical modelling
    diffusion
    adsorption
    hydrogel
    Opis:
    Przedstawiono dwa modele uwalniania środków aktywnych z hydrożeli znany model dyfuzyjny oraz opracowany nowy model dyfuzyjno-desorpcyjny. Model ten uwzględnia procesy desorpcji z powierzchni fazy stałej matrycy oraz procesy dyfuzyjne zachodzące w porach matrycy. Kinetykę uwalniania opisano za pomocą współczynnika dyfuzji środka aktywnego v cieczy wypełniającej pory oraz współczynnika wnikania masy, który odpowiada szybkości desorpcji składnika aktywnego z powierzchni porów, przykładową symulację dla surowiczej albuminy wołowej (BSA) wykonano w programie MATLAB metodą różnic skończonych.
    The paper presents two models of release of active agents from hydrogels: the known diffusion model and a developed new diffusion-desorption model. The later model takes into account desorption processes from the surface of solid phase matrix and diffusion processes taking place in the matrix pores. The release kinetics is described by means of the diffusion coefficient of active agent in liquid filling the pores, and the mass transfer coefficient which corresponds to the desorption rate of active ingredient from the surface of pores. An exemplary simulation for bovine serum albumin (BSA) was performed in MATLAB using the finite differences method.
    Źródło:
    Inżynieria i Aparatura Chemiczna; 2013, 6; 548--549
    0368-0827
    Pojawia się w:
    Inżynieria i Aparatura Chemiczna
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Properties of water hydrating the galactolipid and phospholipid bilayers: a molecular dynamics simulation study
    Autorzy:
    Markiewicz, Michał
    Baczyński, Krzysztof
    Pasenkiewicz-Gierula, Marta
    Powiązania:
    https://bibliotekanauki.pl/articles/1038986.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    molecular modelling
    hydrogen bonds
    water diffusion
    water dipole orientation
    inter-lamellar water
    Opis:
    Molecular dynamics simulations of 1,2-di-O-acyl-3-O-β-D-galactopyranosyl-sn-glycerol (MGDG) and 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) bilayers were carried out to compare the effect of the lipid head group's chemical structure on the dynamics and orientational order of the water molecules hydrating the bilayer. The effect of the bilayers on the diffusion of water is strong for the neighbouring water molecules i.e., those located not further than 4 Å from any bilayer atom. This is because the neighbouring water molecules are predominantly hydrogen bonded to the lipid oxygen atoms and their mobility is limited to a confined spatial volume. The choline group of DOPC and the galactose group of MGDG affect water diffusion less than the polar groups located deeper in the bilayer interface, and similarly. The latter is an unexpected result since interactions of water with these groups have a vastly different origin. The least affected by the bilayer lipids is the lateral diffusion of unbound water in the bilayer plane (x,y-plane) - it is because the diffusion is not confined by the periodic boundary conditions, whereas that perpendicular to the plane is. Interactions of water molecules with lipid groups also enforce certain orientations of water dipole moments. The profile of an average water orientation along the bilayer normal for the MGDG bilayer differs from that for the DOPC bilayer. In the DOPC bilayer, the ordering effect of the lipid head groups extends further into the water phase than in the MGDG bilayer, whereas inside the bilayer/water interface, ordering of the water dipoles in the MGDG bilayer is higher. It is possible that differences in the profiles of an average water orientation across the bilayer in the DOPC and MGDG bilayers are responsible for differences in the lateral pressure profiles of these bilayers.
    Źródło:
    Acta Biochimica Polonica; 2015, 62, 3; 475-481
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mathematical modelling by convection-diffusion with reaction of organic pollution in the wadi Mouillah stream, north-western Algeria
    Autorzy:
    Benadda, Lotfi
    Djelita, Belkheir
    Chiboub-Fellah, Abdelghani
    Powiązania:
    https://bibliotekanauki.pl/articles/2174337.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Technologiczno-Przyrodniczy
    Tematy:
    biochemical oxygen demand
    BOD5
    diffusion
    Hammam Boughrara dam
    mathematical modelling
    pollution
    total phosphorus
    wadi Mouillah
    Opis:
    This work describes the behaviour of organic pollutants along the wadi Mouillah watercourse and its main tributaries and their impacts on the Hammam Boughrara dam, located in the NW of Algeria, in the Wilaya of Tlemcen. The use of a database relating to physico-chemical, biotic and hydrological variables, covering the period from January 2006 to December 2009, contributed to the understanding of the spatiotemporal evolution of each variable. The application of a mathematical model of the diffusion by convection-dispersion with a reaction on two characteristic parameters of organic pollution, the biochemical oxygen demand (BOD5) which records values above the norm, with peaks that can reach 614%, and total phosphorus (Ptot), which the concentration is always higher with maxima reaching 53 mg∙dm-3 favouring eutrophication; this made it possible with precision to synthesise the propagation of pollutants in the liquid mass. The results obtained on the waters of Wadi Mouillah are therefore of poor quality; there is a need to set up a rigorous water quality monitoring system, with water treatment and decontamination devices to preserve the water resources. This will allow to contribute to better management of water quality in terms of combating the spread of pollution. Therefore, they can be used to support decisions in the context of sustainable development.
    Źródło:
    Journal of Water and Land Development; 2022, 54; 26--37
    1429-7426
    2083-4535
    Pojawia się w:
    Journal of Water and Land Development
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Methane oxidation in homogenous soil covers of landfills: a finite element analysis of the influence of gas diffusion coefficient
    Autorzy:
    Stepniewski, W.
    Zygmunt, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/24950.pdf
    Data publikacji:
    2000
    Wydawca:
    Polska Akademia Nauk. Instytut Agrofizyki PAN
    Tematy:
    methanotrophic capacity
    environment protection
    gas diffusivity
    municipal waste
    landfill
    methane oxidation
    modelling
    homogenous soil
    gas diffusion coefficient
    Źródło:
    International Agrophysics; 2000, 14, 4
    0236-8722
    Pojawia się w:
    International Agrophysics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of the molecular dynamics method for modelling of mass transfer on the border of Ni-Al bimetal
    Zastosowanie metody dynamiki molekularnej do modelowania transferu masy na granicy bimetalu Ni-Al
    Autorzy:
    Starostenkov, M.
    Demina, I.
    Popova, G.
    Denisova, N.
    Smolarz, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/408811.pdf
    Data publikacji:
    2012
    Wydawca:
    Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
    Tematy:
    modelowanie komputerowe
    proces dyfuzji
    wakans
    metoda dynamiki molekularnej
    atom międzywęzłowy
    sieć krystaliczna
    transport masy
    method of computer modelling
    diffusion process
    vacancy
    method of molecular dynamics
    internodal atom
    crystalline lattice
    mass transfer
    Opis:
    One of the basic issues of examination of process of interaction of two-component alloys is the study of the mass transfer process in the presence of dot flaws: internodal atoms and vacancies. The study of this process in real experiments is impossible; therefore it is reasonable to apply computer modelling. The authors present a model of Ni-Al bimetal diffusion process produced by the method of molecular dynamics.
    Jednym z podstawowych zagadnień analizy procesu interakcji stopów dwuskładnikowych jest badanie procesu wymiany masy w obecności defektów punktowych: atomów międzywęzłowych i wakansów. Badania tego procesu w rzeczywistych eksperymentach jest niemożliwe, dlatego uzasadnione jest zastosowanie modelowania komputerowego. Autorzy przedstawiają model procesu dyfuzji w bimetalu Ni-Al stworzony metodą dynamiki molekularnej.
    Źródło:
    Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska; 2012, 1; 36-38
    2083-0157
    2391-6761
    Pojawia się w:
    Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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