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Wyświetlanie 1-15 z 111
Tytuł:
Some remarks on positron/positronium diffusion models
Autorzy:
Świątkowski, W.
Powiązania:
https://bibliotekanauki.pl/articles/148428.pdf
Data publikacji:
2003
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
diffusion
diffusion length
positron
positronium
Opis:
Positrons thermalized near the sample boundary (as well as Ps atoms formed in the sample) can reach the boundary as a result of diffusive movement. Observations of such effects as positron reemission or positron surface trapping as well as positronium emission allow one to calculate respective diffusion lengths. From the presented analysis it follows that some models used in such calculations give quite wrong results.
Źródło:
Nukleonika; 2003, 48, 3; 141-144
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Diffusion in Networks
Autorzy:
Kasprzak, R.
Powiązania:
https://bibliotekanauki.pl/articles/309179.pdf
Data publikacji:
2012
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
complex network
diffusion
probabilistic finitestate machine
Opis:
In this paper a concept of method and its application examining a dynamic of diffusion processes in networks is considered. Presented method was used as a core framework for system CARE (Creative Application to Remedy Epidemics).
Źródło:
Journal of Telecommunications and Information Technology; 2012, 2; 99-106
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Asymptotic dissipativity of the diffusion process in the asymptotic small diffusion scheme
Autorzy:
Kinash, A.
Chabanyuk, Y.
Khimka, U.
Powiązania:
https://bibliotekanauki.pl/articles/122512.pdf
Data publikacji:
2015
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
small series parameter
diffusion
asymptotic dissipativity
Opis:
This paper considers the random evolution with Markov switching. The resulting limited process is diffusion and depends on the small series parameter. The sufficient conditions of dissipativity of the limited process were obtained. Since the conditions of the Model Limit theorem and dissipativity conditions were set asymptotic dissipativity of the output process.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2015, 14, 4; 93-103
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Singlet oxygen lifetime and diffusion measurements
Autorzy:
Ożog, Łukasz
Aebisher, David
Powiązania:
https://bibliotekanauki.pl/articles/454834.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Rzeszowski. Wydawnictwo Uniwersytetu Rzeszowskiego
Tematy:
photodynamic therapy
singlet oxygen
diffusion
Opis:
Introduction. Photodynamic therapy (PDT) is considered to be a promising antitumor methodology due the cytotoxicity of singlet oxygen (1 O2 ). Aim. To present singlet oxygen which is highly reactive and decomposes to the ground state rapidly. Material and methods. Analysis of literature. Results. This review presents techniques to measure lifetime and diffusion of 1 O2.
Źródło:
European Journal of Clinical and Experimental Medicine; 2018, 2; 123-126
2544-2406
2544-1361
Pojawia się w:
European Journal of Clinical and Experimental Medicine
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Interface Diffusion Behavior of Co40Al-X (X = Ni, Cr, Ti) System by Diffusion Multiple
Autorzy:
Shang, Hang
Gao, Qiuzhi
Jiang, Yujiao
Ma, Qingshuang
Li, Huijun
Zhang, Hailian
Powiązania:
https://bibliotekanauki.pl/articles/2203747.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Co-Al-X system
diffusion multiple
interface
diffusion
mechanical properties
Opis:
Diffusion multiple method was applied to investigate the alloying elements distribution and interface diffusion reactions in Co-Al-X system, in order to accelerate the alloy development. The diffusion regions of Co-Al-X system at 1173 K were investigated by scanning electron microscope (SEM) and nanoindentation. SEM images show that phases of Co-Al-Ni diffusion interface consisted of β-CoAl + γ Co, γ Co, γ + γ'-(Co, Ni)3Al and γ Ni, while Co-Al-Cr diffusion interface is shaped with δ + γ + β, γ and σ region. TiNiX diffusion layer with high Ni-content was formed in Co-Al-Ti diffusion interface. The diffusion layers during diffusion multiple play an important role in mechanical properties in these alloying systems. The γ + γ' diffusion layer in Co-Al-Ni diffusion interface presented the best comprehensive performance, while the highest hardness (17.48 GPa) was confirmed in Co-Al-Cr diffusion interface due to a large number of brittle phases. Darken method was applied to determine the interdiffusion coefficients of alloying elements in pseudo-binary phase, accordingly the diffusion capacities of alloying elements can be ordered as Al > Ni > Cr in Co-based alloys.
Źródło:
Archives of Metallurgy and Materials; 2023, 68, 1; 275--286
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Alternative methodology to determine effective coefficient of methane diffusion in coal
Autorzy:
Koptoń, Henryk
Powiązania:
https://bibliotekanauki.pl/articles/1839042.pdf
Data publikacji:
2020
Wydawca:
Główny Instytut Górnictwa
Tematy:
mining
coal
sorption
diffusion
methane
diffusion coefficient
górnictwo
węgiel
sorpcja
dyfuzja
metan
współczynnik dyfuzji
Opis:
The article presents the results of research in to the development of an alternative method of determining the effective coefficient of methane diffusion in coal, based on a mathematical model following Fick's second law. The research was conducted based on the recorded courses of methane sorption kinetics in coal samples obtained in laboratory conditions with the precise gravimetric sorption system IGA-001. The value of the coefficient was treated as an element tuning the model in such a way that the average relative error of the ex post was as small as possible. Model verification indicated the correctness of its assumptions. The development of a more accurate methodology to determine the effective coefficient of methane diffusion in coal will enable the verification of the models applied in order to describe the physical and chemical mechanisms of the methane desorption natural phenomenon. It will also pave the way for further research aimed at the determination of: the gas bearing capacity of coal seams, the degree of degassing of seamswhich results from the mining operations being conducted; or to what extent it is possible to degas the deposits.
Źródło:
Journal of Sustainable Mining; 2020, 19, 2; 88-95
2300-1364
2300-3960
Pojawia się w:
Journal of Sustainable Mining
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mechanizmy dyfuzji wiedzy w regionie
The mechanisms of knowledge diffusion in the region
Autorzy:
Fic, Maria
Powiązania:
https://bibliotekanauki.pl/articles/534358.pdf
Data publikacji:
2011-12-15
Wydawca:
Uniwersytet Rzeszowski. Wydział Ekonomii
Tematy:
knowledge
diffusion
region
Opis:
The aim of the article is to present mechanisms of knowledge diffusion in the region. The authors discuss methods of aquisition of knowledge by agents functioning in the region, and channels of knowledge distribution - private persons' and public channels, institutional channels and channels based on information and communication systems. They show also the role of knowledge diffusion in the process of knowledge management in the region.
Źródło:
Przedsiębiorstwo i Region; 2011, 3; 16-23
2080-458X
Pojawia się w:
Przedsiębiorstwo i Region
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
From Diffusion to Translation and Back. Disembedding–Re-embedding and Re-invention in Sociological Studies of Diffusion
Autorzy:
Mica, Adriana
Powiązania:
https://bibliotekanauki.pl/articles/1930004.pdf
Data publikacji:
2013-03-21
Wydawca:
Polskie Towarzystwo Socjologiczne
Tematy:
diffusion
translation
disembedding–re-embedding of ideas
re-invention of innovations
Scandinavian institutionalism
Opis:
This paper reviews and parallels the thesis of disembedding–re-embedding of ideas, objects and practices in the translation paradigm (à la Scandinavian institutionalism) with the discussion of reinvention in the diffusion of innovations theory (as put forward by Everett M. Rogers). The main inquiry to be answered is the extent to which these two propositions might be taken as theoretical allomorphs of a generic treatment of the dialectics of circulation of ideas. The analysis of the two assumptions makes use of Djelic’s (2008) classification of three main framing types within sociological studies of diffusion: diffusion as epidemiology, diffusion as encounter with embeddedness, and diffusion as mediation and construction. The main input of the article is that it shows that the re-invention hypothesis links the diffusion of innovations theory with the diffusion as encounter with embeddedness model, while the disembedding–re-embedding of ideas perspective associates the translation paradigm with the diffusion as mediation and construction model. The paper further discusses the dynamics as well as the theoretical implications of these theoretical affinities for the Scandinavian translation stream.
Źródło:
Polish Sociological Review; 2013, 181, 1; 3-20
1231-1413
2657-4276
Pojawia się w:
Polish Sociological Review
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:
Change of composition and structure of diffusion chrome coating during friction
Autorzy:
Sharifov, Z. Z.
Bashirov, F. R.
Powiązania:
https://bibliotekanauki.pl/articles/359817.pdf
Data publikacji:
2013
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
diffusion
friction
phase matrix
Opis:
The paper studied the behavior of the composition and structure of the diffusion of chromium coatings in sliding. It was found that the strain in friction generates the secondary structure of chromium coatings and as a result of the deformation effect wear is accelerated due to separation of the coating.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2013, 33 (105); 96-99
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Drug diffusion transport through human skin
Autorzy:
Walicka, A.
Iwanowska-Chomiak, B.
Powiązania:
https://bibliotekanauki.pl/articles/265397.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
ludzka skóra
dyfuzja
dostarczanie leków
drug delivery
human skin
diffusion
Opis:
The stratum corneum (SC) forms the outermost layer of the human skin and is essentially a multilamellar lipid milieu punctuated by protein-filled corneocytes that augment membrane integrity and significantly increase membrane tortuosity. The lipophilic character of the SC, coupled with its intrinsic tortuosity, ensure that it almost always provides the principal barrier to the entry of drug molecules into the organism. Drugs can be administered either as suspensions or as solutions and the formulation can range in complexity from a gel or and ointment to a multilayer transdermal path. In this paper, we discuss theoretical principles used to describe transdermal release and we show that relatively simple membrane transport models based on the appropriate solution to the Fick’s second law of diffusion can be used to explain drug release kinetics into such a complex biological membrane as the human skin. To apply the Fick’s law we introduced into our considerations a brick-and-mortar model with two factors of tortuosity. Assuming that the mortar thickness is variable we also introduced the hindrance factor allowing us to model this variability. Having the modified Fick’s equation we presented its general solution and two special cases of this solution frequently applicable in permeation experiments. It seems that the solutions presented herein better approximate the real conditions of drug delivery then these well known.
Źródło:
International Journal of Applied Mechanics and Engineering; 2018, 23, 4; 977-988
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and 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:
The quantum diffusion of carbon in alfa-iron in low temperature
Autorzy:
Dąbrowski, L.
Andreev, A.
Georgiev, M.
Powiązania:
https://bibliotekanauki.pl/articles/147484.pdf
Data publikacji:
2006
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
carbon
diffusion
tunneling
adiabatic
polaron
Opis:
Recent experimental data on the diffusion coefficient of carbon in á-iron below liquid nitrogen temperature (LNT) question the classical approach to the observed temperature dependence. As the temperature is lowered below LNT, the diffusion constant tends to a nearly temperature-independent value rather than continuing its activated trend. The low temperature branch is apparently characteristic of a quantum mechanical process dominated by tunneling in ground state. Concomitantly we apply an occurrence-probability approach to describing the overall temperature dependence as a single continuous rate. Within the adiabatic approximation the electronic eigenvalue depending parametrically on the nuclear coordinates is taken to be the potential energy to control the motion of the nuclei. The resulting rate involves all horizontal-tunneling energy-conserving elastic transitions at the quantized energy levels of the migrating atom. A small though not negligible slope in the temperature dependence as the temperature is raised below 100 K is dealt with by complementing for the rate of a parallel one-phonon inelastic-tunneling process in excess to the basic elastic-tunneling rate. Our combined approach agrees well with the experimental data. In particular, the frequency of the coupled vibration is obtained virtually identical to the carbon vibrational frequency from inelastic neutron scattering data. The migrational barrier is also found to be within the limits expected for alfa-iron.
Źródło:
Nukleonika; 2006, 51, 2; 93-99
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy generation on mhd flow of Powell-Eyring fluid between radially stretching rotating disk with diffusion-thermo and thermo-diffusion effects
Autorzy:
Khan, N. A.
Aziz, S.
Ullah, S.
Powiązania:
https://bibliotekanauki.pl/articles/386796.pdf
Data publikacji:
2017
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
axisymmetric flow
entropy generation
stretching disk
Powell-Eyring fluid
diffusion
Opis:
An investigation is performed for an alyzing the effect of entropy generation on the steady, laminar, axisymmetric flow of an incompressible Powell-Eyring fluid. The flow is considered in the presence of vertically applied magnetic field between radially stretching rotating disks. The Energy and concentration equation is taking into account to investigate the heat dissipation, Soret, Dufour and Joule heating effects. To describe the considered flow non-dimensionalized equations, an exact similarity function is used to reduce a set of the partial differential equation into a system of non-linear coupled ordinary differential equation with the associated boundary conditions. Using homotopy analysis method (HAM), an analytic solution for velocity, temperature and concentration profiles are obtained over the entire range of the imperative parameters. The velocity components, concentration and temperature field are used to determine the entropy generation. Plots illustrate important results on the effect of physical flow parameters. Results obtained by means of HAM are then compared with the results obtained by using optimized homotopy analysis method (OHAM). They are in very good agreement.
Źródło:
Acta Mechanica et Automatica; 2017, 11, 1; 20-32
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Diffusion of boron in cobalt sinters
Dyfuzja boru w spiekach kobaltu
Autorzy:
Borowiecka-Jamrozek, J.
Lachowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/354296.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
diffusion
sinter
cobalt
boronizing
dyfuzja
spiek
kobalt
bor
Opis:
The paper describes the process of diffusion taking place at the surface of sinters produced from Co Extrafine powder after saturation with boron. Boronizing was performed at a temperature of 950°C for 6 and 12 hours by applying B4C powder as a depositing source, NH4Cl + NaF as an activator and Al2O3 as an inert filler. The study involved determining the diffusion coefficient, which required analyzing the microstructure and thickness of the layers and the process time. The images obtained with a Leica DM-4000 optical microscope revealed a two-phase structure of the boride layers. The presence of the two phases, i.e. CoB and Co2B, was confirmed by X-ray diffraction (XRD). A model of diffusion of boron atoms into the cobalt substrate was developed assuming the reaction diffusion mechanism. This model was used to calculate the diffusion coefficient. It required taking account of the interatomic potentials of boron and cobalt. The calculation results were compared with the experimental data concerning the diffusion of boron in other materials.
W pracy przedstawiono wyniki badań procesu dyfuzji w warstwach powierzchniowych uzyskanych w wyniku nasycenia borem spieków otrzymanych z proszku kobaltu gatunku Co Extrafine. Warstwy otrzymano przy zastosowaniu proszkowej metody borowania opartej na wykorzystaniu mieszaniny o składzie: B4C jako składnik podstawowy stanowiący źródło boru, (NH4Cl + NaF) aktywator i Al2O3 jako wypełniacz. Zachowane były następujące parametry procesu: temperatura 950°C, czas 6h i 12h. Badania obejmowały wyznaczenie współczynnika dyfuzji w oparciu o strukturę, grubość uzyskanych i czas nasycenia warstw. Obserwacji naniesionych warstw dokonano za pomocą mikroskopu optycznego Leica DM-4000. Zdjęcia ujawniły dwufazową strukturę warstw borkowych. Badania rentgenowskie potwierdziły występowanie faz o składzie: CoB i Co2B. Zbudowano model dyfuzji atomów boru w strukturze kobaltu zakładając dyfuzję reaktywną. Obliczono współczynnik dyfuzji w oparciu o model atomowy dyfuzji wykorzystując potencjały oddziaływan pomiędzy atomami boru i kobaltu. Otrzymane wyniki porównano z danymi doświadczalnymi dyfuzji boru w innych materiałach.
Źródło:
Archives of Metallurgy and Materials; 2013, 58, 4; 1131-1136
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 111

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