Academic literature on the topic 'Phase diffusion coefficient'
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Journal articles on the topic "Phase diffusion coefficient"
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Gordillo, Jorge A. "Effective Diffusion Coefficient." Defect and Diffusion Forum 384 (May 2018): 130–35. http://dx.doi.org/10.4028/www.scientific.net/ddf.384.130.
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The diffusion of a B element into an A matrix was studied by the random walk theory. Considering that concentration of B element in the A matrix is very low, the jumps of diffusing atoms are independent of each other. The A matrix is a two-region material with different properties, such as a two-phase material, a single crystal with dislocations, or regions influenced by other solute and a polycrystalline material.It is assumed that material B has a penetration that allows it to cross each region of material A several times. This implies that jumps across the surface between those regions have an average frequency and, as a consequence, there is an interdiffusion coefficient between them. The interdiffusion coefficient between those regions is different than the coefficient of the diffusion in each region.Expressions were obtained that allow to delimit the ranges of validation with greater precision than the corrected Hart-Mortlock equation for solute diffusion. In addition, an original relationship was obtained between the segregation coefficient and parameters specific to the diffusion. New powerful tools were also found that can help to understand diffusion in nanocrystalline materials, diffusion in metals influenced by impurities and diffusion produced by different mechanisms.
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Stloukal, Ivo, and Jiří Čermák. "Diffusion of Zinc in Two-Phase Mg-Al Alloy." Defect and Diffusion Forum 263 (March 2007): 189–94. http://dx.doi.org/10.4028/www.scientific.net/ddf.263.189.
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Coefficient of 65Zn heterodiffusion in Mg17Al12 intermetallic and in eutectic alloy Mg - 33.4 wt. % Al was measured in the temperature region 598 – 698 K using serial sectioning and residual activity methods. Diffusion coefficient of 65Zn in the intermetallic can be written as DI = 1.7 × 10-2 m2 s-1 exp (-155.0 kJ mol-1 / RT). At temperatures T ≥ 648 K, where the mean diffusion path was greater than the mean interlamellar distance in the eutectic, the effective diffusion coefficient Def = 2.7 × 10-2 m2 s-1 exp (-155.1 kJ mol-1 / RT) was evaluated. At two lower temperatures, the diffusion coefficients 65Zn in interphase boundaries were estimated: Db (623 K) = 1.6 × 10-12 m2 s-1 and Db (598 K) = 4.4 × 10-13 m2 s-1.
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Kale, G. B. "Thermodynamic Diffusion Coefficients." Defect and Diffusion Forum 279 (August 2008): 39–52. http://dx.doi.org/10.4028/www.scientific.net/ddf.279.39.
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A new form of diffusion coefficient termed as thermodynamic diffusion coefficient is introduced in this paper. Conventionally, diffusion coefficients are evaluated using concentration gradient as driving force. But truly, chemical potential gradient is the actual driving force that determines the material flow in any part of the system. Thermodynamic diffusion coefficients are based on chemical potential gradient as driving force. The relation between thermodynamic diffusion coefficients and phenomenological coefficients has been established. The advantages of thermodynamic diffusion coefficients have been underlined, especially, in the cases of line compounds where concentration difference across the phase is zero or in case of intermetallic compounds with narrow homogeneity range. The intrinsic thermodynamic diffusion coefficients are equal to tracer diffusion coefficients. This helps in estimating tracer diffusivities in cases where tracers are not easily available. The advantages of thermodynamic diffusion coefficients are shown in binary and ternary systems by illustrating them in Ni-Al and Fe-Ni-Cr systems.
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Elberling, Bo. "Gas phase diffusion coefficient in cemented porous media." Journal of Hydrology 178, no. 1-4 (April 1996): 93–108. http://dx.doi.org/10.1016/0022-1694(95)02808-0.
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Sridharan, S., and R. I. Cukier. "Effective diffusion coefficient of a two-phase material." Journal of Physical Chemistry 91, no. 11 (May 1987): 2962–69. http://dx.doi.org/10.1021/j100295a063.
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Liu, Zizhong, and Hamid Emami-Meybodi. "Diffusion-Based Modeling of Gas Transport in Organic-Rich Ultratight Reservoirs." SPE Journal 26, no. 02 (February 10, 2021): 857–82. http://dx.doi.org/10.2118/201393-pa.
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Summary The complex pore structure and storage mechanism of organic-rich ultratight reservoirs make the hydrocarbon transport within these reservoirs complicated and significantly different from conventional oil and gas reservoirs. A substantial fraction of pore volume in the ultratight matrix consists of nanopores in which the notion of viscous flow may become irrelevant. Instead, multiple transport and storage mechanisms should be considered to model fluid transport within the shale matrix, including molecular diffusion, Knudsen diffusion, surface diffusion, and sorption. This paper presents a diffusion-based semianalytical model for a single-component gas transport within an infinite-acting organic-rich ultratight matrix. The model treats free and sorbed gas as two phases coexisting in nanopores. The overall mass conservation equation for both phases is transformed into one governing equation solely on the basis of the concentration (density) of the free phase. As a result, the partial differential equation (PDE) governing the overall mass transport carries two newly defined nonlinear terms; namely, effective diffusion coefficient, De, and capacity factor, Φ. The De term accounts for the molecular, Knudsen, and surface diffusion coefficients, and the Φ term considers the mass exchange between free and sorbed phases under sorption equilibrium condition. Furthermore, the ratio of De/Φ is recognized as an apparent diffusion coefficient Da, which is a function of free phase concentration. The nonlinear PDE is solved by applying a piecewise-constant-coefficient technique that divides the domain under consideration into an arbitrary number of subdomains. Each subdomain is assigned with a constant Da. The diffusion-based model is validated against numerical simulation. The model is then used to investigate the impact of surface and Knudsen diffusion coefficients, porosity, and adsorption capacity on gas transport within the ultratight formation. Further, the model is used to study gas transport and production from the Barnett, Marcellus, and New Albany shales. The results show that surface diffusion significantly contributes to gas production in shales with large values of surface diffusion coefficient and adsorption capacity and small values of Knudsen diffusion coefficient and total porosity. Thus, neglecting surface diffusion in organic-rich shales may result in the underestimation of gas production.
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Yarimitsu, Masakazu, and Masaru Aniya. "A Molecular Dynamics Study on Pressure Dependence of Ag Diffusion in Ag3SI." Advances in Science and Technology 72 (October 2010): 337–42. http://dx.doi.org/10.4028/www.scientific.net/ast.72.337.
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The pressure dependence of the diffusion coefficient in the superionic α- and β-phases of Ag3SI has been studied by using the method of molecular dynamics. It is shown that in the high temperature α-phase, the Ag diffusion coefficient decreases with pressure. On the hand, in the intermediate temperature β-phase, the Ag diffusion coefficient exhibits a maximum at around 2.8 GPa. The structural origin of this behavior is discussed through the pressure dependence of the pair distribution functions.
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Vasilev, A. N. "A Model of Gas Diffusion in a Metal Plate with Phase Transformation." Ukrainian Journal of Physics 64, no. 4 (May 16, 2019): 348. http://dx.doi.org/10.15407/ujpe64.4.348.
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A model of gas diffusion in a metal plate has been proposed, in which a phase transformation “metal–gassed metal” takes place, when the gas concentration exceeds a certain critical value, and the properties of the system change qualitatively. The phase transformation is modeled by changing the coefficient of gas diffusion. In particular, a system of two phases with different diffusion coefficients and a moving interface between them is considered. The gas concentrations in both phases at the interface are assumed to be the known constants. An analytical solution is obtained in the approximation that the diffusion in the metal phase (the initial state of a metal layer) is much quicker than that in the gassed-metal one, with the both being much quicker than the motion of the phase interface. In the framework of this model, the spatial distribution of the gas concentration in the gassed-metal phase is calculated, and the analytic formula describing the motion of a phase interface is derived.
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Toivola, J., P. O. Michel, L. Gilbert, T. Lahtinen, V. Marjomäki, K. Hedman, M. Vuento, and C. Oker-Blom. "Monitoring human parvovirus B19 virus-like particles and antibody complexes in solution by fluorescence correlation spectroscopy." Biological Chemistry 385, no. 1 (January 5, 2004): 87–93. http://dx.doi.org/10.1515/bc.2004.011.
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AbstractFluorescence correlation spectroscopy (FCS) was used in monitoring human parvovirus B19 virus-like particle (VLP) antibody complexes from acute phase and pastimmunity serum samples. The Oregon Green 488-labeled VLPs gave an average diffusion coefficient of 1.7x10exp-7 cm(2)s(-1) with an apparent hydrodynamic radius of 14 nm. After incubation of the fluorescent VLPs with an acute phase serum sample, the mobility information obtained from the fluorescence intensity fluctuation by autocorrelation analysis showed an average diffusion coefficient of 1.5x10exp-8 cm(2)s(-1), corresponding to an average radius of 157 nm. In contrast, incubation of the fluorescent VLPs with a pastimmunity serum sample gave an average diffusion coefficient of 3.5x10exp-8 cm(2)s(-1) and a radius of 69 nm. A control serum devoid of B19 antibodies caused a change in the diffusion coefficient from 1.7x10exp-7 to 1.6x10exp-7 cm(2)s(-1), which is much smaller than that observed with acute phase or pastimmunity sera. Thus, VLP-antibody complexes with different diffusion coefficients could be identified for the acute phase and pastimmunity sera. FCS measurement of VLPimmune complexes could be useful in distinguishing between antibodies present in acute phase or past-immunity sera as well as in titration of the VLPs.
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Komiya, Atsuki, Juan F. Torres, and Shigenao Maruyama. "Measurement of Mass Diffusion Coefficient of Multi-Component System in Aqueous Media by Phase Shifting Interferometer." Defect and Diffusion Forum 297-301 (April 2010): 624–30. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.624.
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This paper describes a novel technique to determine mass diffusion coefficients of multi-component system within a transparent mixture by using an optical system. The mixture is composed of sodium chloride and lysozyme as solutes. Binary and multi-component solution experiments were conducted separately under constant temperature conditions. By measuring transient diffusion fields inside the cell, as well as for mixed multi-component solutions, it was confirmed that within the concentration ranges considered in this study, the diffusion of each solute inside the cell progresses independently. This indicates the superposition principle of concentration for certain levels of sodium chloride and lysozyme within the cell. Furthermore, by using this concentration superposition principle and an inverse analysis based on the conjugate gradient method, the diffusion coefficients of each solute in the mixture were successfully obtained from several multi-component experiments. Each obtained diffusion coefficient was good agreement with the determined diffusion coefficient from binary experiment.
Dissertations / Theses on the topic "Phase diffusion coefficient"
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Van, der Westhuizen Francois Erasmus. "Vapour phase mass transfer coefficients in structured packing." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/1966.
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Renault, Pierre. "Etude et modélisation du coefficient de diffusion en phase gazeuse en fonction de la morphologie de l'espace poral textural des sols cultivés." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37617984m.
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Renault, Pierre. "Étude et modélisation du coefficient de diffusion en phase gazeuse : en fonction de la morphologie de l'espace poral textural des sols cultivés." Toulouse, INPT, 1988. http://www.theses.fr/1988INPT074H.
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On montre que dans les couches de surface des sols cultives, l'espace poral lacunaire present entre les masses d'argile est le lieu privilegie des transferts de gaz par diffusion au niveau textural. Il est modelise par un reseau irregulier de pores a geometrie complexe. L'approche experimentale est basee sur l'utilisation de sols remanies ayant subi un cycle de dessiccation, et ou l'on etudie les blocages de pores du reseau lacunaire. Une ebauche de modelisation de type percolation du coefficient de diffusion est proposee
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Hevia, Montiel Nidiyare. "Analyse de l'imagerie par résonance magnétique du coefficient apparent de diffusion pour l'évaluation en phase aiguë du potentiel de croissance des infarctus cérébraux." Paris 11, 2006. http://www.theses.fr/2006PA112112.
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Nous présentons une nouvelle approche à la prédiction de la croissance finale de l'infarctus ischémique humaine en phase aiguë basée sur l'analyse de l'imagerie de résonance magnétique du coefficient apparent diffusion (ADC) en phase aiguë. Les cartographies d'ADC sont susceptibles d'indiquer des régions du cerveau appartenant à la pénombre ischémique, c'est-à-dire, des zones à risque qui pourraient être affectées par l'infarctus à très court terme. Dans ce contexte d'urgence absolue, l'imagerie IRM a pris une place considérable dans la décision thérapeutique de thrombolyse éventuelle. Cette dernière présente des risques hémorragiques secondaires importants et ne peut donc être administrée que chez les patientss dont l'infractus est susceptible de croître et d'atteindre des régions fonctionnelles cruciales. Nous avons donc développé dans ce travail de thèse des techniques d'analyse d'images automatiques en IRM de diffusion. La méthodologie sous-jacente repose sur un modèle de croissance de région qui va segmenter les régions cérébrables exposée à l'infarctus. Une étude rétrospective sur 77 patients a montré que la technique proposée possédait des performances supérieures à celles des techniques alternatives actuellement étudiéesWe introduce a new approach to the prediction of the final infarct growth in human acute ischemic stroke based on image analysis of the Apparent Diffusion Coefficient (ADC) MR maps acquired in the acute stage. The ADC maps are likely to reveal brain regions belonging to the ischemic penumbra, that is, areas that will certainly may be affected by the infarction in the following next few hours. In a context where “time is brain”, and contrarily to the much explored – though still-debated – perfusion-diffusion mismatch approach, the ADC MR sequences are fast to acquire and do not necessitate injection of a contrast agent. Image analysis consists of the segmentation of the ischemic penumbra using a fast 3D region-growing infarct approach. Retrospective evaluation on 77 patients has shown that our methodlology is superior to the alternative techniques with much less practical constraints to the clinical environment
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Ait, Ali Yahia Lyes. "Etude expérimentale de l’influence de la morphologie des agrégats de suies sur leur comportement thermophorétique." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1081.
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L’objectif principal de ce travail de recherche est d’améliorer les connaissances concernant l’influence de la morphologie de particules issues de combustion sur leur comportement thermophorétique. A cet effet, un dispositif tri-therme (3T) original permettant le dépôt par thermophorèse de ce type de particules a été développé. Cet instrument est composé de trois tubes concentriques, permettant la création d’un espace annulaire où un gaz chargé en particules est injecté. Le tube interne est refroidi et le tube externe est chauffé, créant ainsi un gradient de température dans l’espace annulaire. Les particules se déposent donc par effet thermophorétique sur la paroi froide du tube interne du dispositif. Ce dernier est basé sur la méthode dite de pénétration, où des mesures de concentrations à l’amont et à l’aval du dispositif permettent l’évaluation de l’efficacité de dépôt par effet thermophorétique. Un modèle du rendement de dépôt développé dans cette étude a permis par la suite de calculer le coefficient de diffusion thermophorétique Kth. Afin de valider la mise en œuvre de ce dispositif expérimental, nous avons évalué les coefficients Kth de billes de latex monodispersées et de deux types de brouillards d’huiles mono et polydispersés. Le bon accord trouvé entre ces valeurs du coefficient Kth et celles déterminées par le modèle de Beresnev et Chernyak ou par des études expérimentales antérieure, a permis la validation du dispositif 3T. Nous avons par la suite appliqué le dispositif avec des agrégats de suies de morphologie et de nature physico chimique variables. Les résultats obtenus mettent en évidence l’augmentation du coefficient de diffusion thermophorétique avec le nombre de particules primaires, et donc avec la taille de l’agrégat, confirmant ainsi les résultats obtenus par Mackowski et Brugière. Une confrontation entre les coefficients de diffusion thermophorétique Kth obtenus pour les différents types d’agrégats a été proposée. Cette confrontation a permis de dégager des tendances vis-à-vis de l’influence de la taille des particules primaires, de la dimension fractale Df et du ratio EC/TC sur le comportement thermophorétique des agrégats de suiesThe main objective of this study is to improve the knowledge about the morphological influence of fractal aggregates on their thermophoretic behavior. For this purpose, an original tri thermal device aimed to capture this kind of particles by thermophoresis deposition was developed. This device is composed of three concentric tubes where particles flows through an annular space between the inner and outer tubes with imposed temperatures, the inner one is cooled and the outer is heated. Particles will deposit by thermophoresis on the cold wall of the inner tube. This device is based on the so called penetration method, where the deposition rate on a cold wall is obtained by particles concentrations measurements upstream and downstream of the test section. A deposition model developed in this study allowed us to determine the thermophoretic diffusion coefficient Kth. We validated the tri thermal device using monodispersed spherical latex particles and also mono and polydispersed spherical oil particles distributions. Indeed, a good agreement was found between our experimental determination of the thermophoretic diffusion coefficient and the theoretical values of Beresnev and Chernyak and also experimental results of the litterature. We finally conducted a study where we applied the device with soot aggregates that have variable morphology and physicochemical nature. This study confirmed the results presented by Mackowski and Brugière about the increase of the aggregates thermophoretic diffusion coefficients Kth with the primary particle number and therefore with the electrical mobility diameter. A confrontation between the coefficients Kth of the different types of aggregates allowed us to find an influence of the primary particles diameter, the fractal dimension Df and also the ratio EC/TC on the thermophoretic behavior of soot aggregates
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Hui, Zi. "Spatial structure of complex network and diffusion dynamics." Thesis, Le Mans, 2013. http://www.theses.fr/2013LEMA1005/document.
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Dans le développement récent des sciences de réseau, réseaux contraints spatiales sont devenues un objet d'une enquête approfondie. Spatiales des réseaux de contraintes sont intégrées dans l'espace de configuration. Leurs structures et les dynamiques sont influencées par la distance spatiale. Ceci est prouvé par les données empiriques de plus en plus sur des systèmes réels montrant des lois exponentielles ou de distribution d'énergie distance spatiale de liens. Dans cette thèse, nous nous concentrons sur la structure de réseau spatial avec une distribution en loi de puissance spatiale. Plusieurs mécanismes de formation de la structure et de la dynamique de diffusion sur ces réseaux sont pris en considération. D'abord, nous proposons un réseau évolutif construit en l'espace de configuration d'un mécanisme de concurrence entre le degré et les préférences de distance spatiale. Ce mécanisme est décrit par un a^'fc- + (1 — a)^'lL_,1, où ki est le degré du noeud i et rni est la distance spatiale entre les noeuds n et i. En réglant le paramètre a, le réseau peut être fait pour changer en continu à partir du réseau spatiale entraînée (a = 0) pour le réseau sans échelle (a = 1). La structure topologique de notre modèle est comparé aux données empiriques de réseau de courrier électronique avec un bon accord. Sur cette base, nous nous concentrons sur la dynamique de diffusion sur le réseau axé sur spatiale (a — 0). Le premier modèle, nous avons utilisé est fréquemment employée dans l'étude de la propagation de l'épidémie: ['spatiale susceptible-infecté-susceptible (SIS) modèle. Ici, le taux de propagation entre deux noeuds connectés est inversement proportionnelle à leur distance spatiale. Le résultat montre que la diffusion efficace de temps augmente avec l'augmentation de a. L'existence d'seuil épidémique générique est observée, dont la valeur dépend du paramètre a Le seuil épidémique maximum et le ratio minimum fixe de noeuds infectés localiser simultanément dans le intervalle 1.5 < a < 2.Puisque le réseau spatiale axée a bien défini la distance spatiale, ce modèle offre une occasion d'étudier la dynamique de diffusion en utilisant les techniques habituelles de la mécanique statistique. Tout d'abord, compte tenu du fait que la diffusion est anormale en général en raison de l'importante long plage de propagation, nous introduisons un coefficient de diffusion composite qui est la somme de la diffusion d'habitude constante D des lois de la Fick appliqué sur différentes distances de transfert possibles sur le réseau. Comme prévu, ce coefficient composite diminue avec l'augmentation de a. et est une bonne mesure de l'efficacité de la diffusion. Notre seconde approche pour cette diffusion anormale est de calculer le déplacement quadratique moyen (l²) à identifier une constante de diffusion D' et le degré de la anomalousness y avec l'aide de la loi de puissance (l²) = 4D'ty. D' comportements de la même manière que D, i.e.. elle diminue avec l'augmentation de a. y est inférieur à l'unité (subdiffusion) et tend à un (diffusion normale) que a augmenteIn the recent development of network sciences, spatial constrained networks have become an object of extensive investigation. Spatial constrained networks are embedded in configuration space. Their structures and dynamics are influenced by spatial distance. This is proved by more and more empirical data on real Systems showing exponential or power laws spatial distance distribution of links. In this dissertation, we focus on the structure of spatial network with power law spatial distribution. Several mechanisms of structure formation and diffusion dynamics on these networks are considered. First we propose an evolutionary network constructed in the configuration space with a competing mechanism between the degree and the spatial distance preferences. This mechanism is described by a ki + (1 — a), where ki is the degree of node i and rni is the spatial distance between nodes n and i. By adjusting parameter a, the network can be made to change continuously from the spatial driven network (a = 0) to the scale-free network (a = 1). The topological structure of our model is compared to the empirical data from email network with good agreement. On this basis, we focus on the diffusion dynamics on spatial driven network (a = 0). The first model we used is frequently employed in the study of epidemie spreading : the spatial susceptible-infected-susceptible (SIS) model. Here the spreading rate between two connected nodes is inversely proportional to their spatial distance. The result shows that the effective spreading time increases with increasing a. The existence of generic epidemic threshold is observed, whose value dépends on parameter a. The maximum épidemic threshold and the minimum stationary ratio of infected nodes simultaneously locate in the interval 1.5 < a < 2. Since the spatial driven network has well defined spatial distance, this model offers an occasion to study the diffusion dynamics by using the usual techniques of statistical mechanics. First, considering the fact that the diffusion is anomalous in general due to the important long-range spreading, we introduce a composite diffusion coefficient which is the sum of the usual diffusion constant D of the Fick's laws applied over different possible transfer distances on the network. As expected, this composite coefficient decreases with increasing a and is a good measure of the efficiency of the diffusion. Our second approach to this anomalous diffusion is to calculate the mean square displacement (l²) to identify a diffusion constant D' and the degree of thé anomalousness y with the help of the power law {l²} = 4D'ty. D' behaviors in the same way as D, i.e., it decreases with increasing a. y is smaller than unity (subdiffusion) and tends to one (normal diffusion) as a increases
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Hui, Zi. "Structure spatiale du réseau complexe et dynamique de diffusion." Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-00812604.
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Dans le développement récent des sciences de réseau, réseaux contraints spatiales sont devenues un objet d'une enquête approfondie. Spatiales des réseaux de contraintes sont intégrées dans l'espace de configuration. Leurs structures et les dynamiques sont influencées par la distance spatiale. Ceci est prouvé par les données empiriques de plus en plus sur des systèmes réels montrant des lois exponentielles ou de distribution d'énergie distance spatiale de liens. Dans cette thèse, nous nous concentrons sur la structure de réseau spatial avec une distribution en loi de puissance spatiale. Plusieurs mécanismes de formation de la structure et de la dynamique de diffusion sur ces réseaux sont pris en considération. D'abord, nous proposons un réseau évolutif construit en l'espace de configuration d'un mécanisme de concurrence entre le degré et les préférences de distance spatiale. Ce mécanisme est décrit par un a^'fc- + (1 -- a)^'lL_,1, où ki est le degré du noeud i et rni est la distance spatiale entre les noeuds n et i. En réglant le paramètre a, le réseau peut être fait pour changer en continu à partir du réseau spatiale entraînée (a = 0) pour le réseau sans échelle (a = 1). La structure topologique de notre modèle est comparé aux données empiriques de réseau de courrier électronique avec un bon accord. Sur cette base, nous nous concentrons sur la dynamique de diffusion sur le réseau axé sur spatiale (a -- 0). Le premier modèle, nous avons utilisé est fréquemment employée dans l'étude de la propagation de l'épidémie: ['spatiale susceptible-infecté-susceptible (SIS) modèle. Ici, le taux de propagation entre deux noeuds connectés est inversement proportionnelle à leur distance spatiale. Le résultat montre que la diffusion efficace de temps augmente avec l'augmentation de a. L'existence d'seuil épidémique générique est observée, dont la valeur dépend du paramètre a Le seuil épidémique maximum et le ratio minimum fixe de noeuds infectés localiser simultanément dans le intervalle 1.5 < a < 2.Puisque le réseau spatiale axée a bien défini la distance spatiale, ce modèle offre une occasion d'étudier la dynamique de diffusion en utilisant les techniques habituelles de la mécanique statistique. Tout d'abord, compte tenu du fait que la diffusion est anormale en général en raison de l'importante long plage de propagation, nous introduisons un coefficient de diffusion composite qui est la somme de la diffusion d'habitude constante D des lois de la Fick appliqué sur différentes distances de transfert possibles sur le réseau. Comme prévu, ce coefficient composite diminue avec l'augmentation de a. et est une bonne mesure de l'efficacité de la diffusion. Notre seconde approche pour cette diffusion anormale est de calculer le déplacement quadratique moyen (l²) à identifier une constante de diffusion D' et le degré de la anomalousness y avec l'aide de la loi de puissance (l²) = 4D'ty. D' comportements de la même manière que D, i.e.. elle diminue avec l'augmentation de a. y est inférieur à l'unité (subdiffusion) et tend à un (diffusion normale) que a augmente.
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Sagot, Benoît. "Contribution à l'étude du transfert thermophorétique, appliqué à l'intensification des processus de séparation gaz/particules en écoulement à phase dispersée." Compiègne, 2010. http://www.theses.fr/2010COMP1903.
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Ce travail de thèse est centré sur l’analyse des possibilités d’amélioration du rendement de capture d’un aérosol par utilisation de l’effet thermophorétique. Les particules liquides mises en oeuvre lors des essais possèdent des diamètres pouvant aller de quelques dizaines de nanomètres à quelques microns. Pour ces tailles de particule, on observe une forte dispersion des coefficients de diffusion thermophorétique Kth évalués avec les modèles disponibles dans la littérature. Une première partie de cette étude se concentre sur une détermination expérimentale du coefficient de diffusion thermophorétique, dans le régime de transition (valeurs du nombre de Knudsen comprises dans la plage 0,1 < Kn < 10), et pour une valeur moyenne du rapport des conductivités thermiques gaz/particule proche de 0,1. Un dispositif expérimental original, basé sur une évolution de la méthode de pénétration classique, a été mis en oeuvre. Il permet une détermination robuste du coefficient de diffusion thermophorétique Kth, et on a pu montrer que le modèle le plus pertinent est celui proposé par Beresnev et Chernyak, tandis que le modèle de Talbot conduit à une surévaluation importante du coefficient Kth dans le régime de transition. La deuxième partie de l’étude concerne l’analyse d’une configuration classique de jet impactant, qui permet d’étudier expérimentalement le couplage entre la dérive inertielle et la migration thermophorétique. On constate que pour toutes les classes granulométriques, une augmentation de l’écart de température jet chaud / paroi froide produit un gain de dépôt. Pour identifier les mécanismes qui produisent cette intensification, un modèle semi analytique a été proposé. Ce modèle a confirmé que l’intensification constatée pour les fines particules est bien due à une migration thermophorétique. Pour des tailles de particules plus importantes, on a établi qu’il existe un couplage entre les deux mécanismes de dérive, qui produit un décalage du diamètre de coupure de l’impacteur, et ainsi une augmentation significative du rendement de dépôt cumulé en masseThe present study investigates the improvement possibilities of aerosol capture efficiency, by the use of a thermophoretic effect. The liquid particles employed for measurements have diameters ranging from a few tens of nanometers to a few microns. For these particle sizes, one can note a great disparity of the thermophoretic diffusion coefficients Kth evaluated with the various models available in the literature. The first part of this study focuses on an experimental determination of the thermophoretic diffusion coefficient, in the transition regime (values of the Knudsen number in the range 0,1 < Kn < 10), and for an average value of the gas/particle conductivity ratio close to 0,1. An original experimental device was used, which is based on an evolution of the classical penetration method. With this device, a robust determination of the thermophoretic diffusion coefficient Kth is obtained, and we have shown that the most relevant model appears to be the one proposed by Beresnev and Chernyak, while Talbot’s model led to an important overvaluation of the Kth coefficient, in the transition regime. The second part of the study relates to the analysis of the classical impinging jet configuration, which is used to study experimentally the coupling possibilities between the inertial drift and the thermophoretic migration. It is noted that for any particle-size range, a deposition improvement is obtained when increasing the hot jet/cold wall temperature difference. To identify the mechanisms which produce this intensification, a semi-analytical model was proposed. This model confirmed that the intensification observed for the fine particles is due to a thermophoretic migration. For larger particle sizes, we established that a coupling between the two drift mechanisms is operating, which produces a shift of the impactor
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Yemloul, Mehdi. "Etude de la partie liquide d'une phase organogel (et de quelques autres systèmes) au moyen des paramètres dynamiques de la RMN (relaxation de spin, diffusion translationnelle)." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10122/document.
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Cette thèse a trait aux paramètres dynamiques de la RMN, ceux-ci permettant d'accéder aux différents types de mouvement : la réorientation moléculaire, accessible via les paramètres de relaxation, et la translation, directement caractérisée par le coefficient d'auto-diffusion. Après une introduction aux concepts théoriques de la relaxation de spin, c'est à travers trois applications que nous mettons en oeuvre différents paramètres dynamiques (temps de relaxation, paramètres d'Effet Overhauser Nucléaire, coefficients d'auto-diffusion). L'interprétation des résultats expérimentaux conduit à des informations très variées qui ne concernent pas uniquement la dynamique des molécules mais également leur structure, comme par exemple les distances interatomiques, ou les arrangements dans des systèmes supramoléculaires. La caractérisation structurale et dynamique d'un organogel constitue le fil conducteur de cette thèse. Chacun des trois chapitres suivants est en effet dédié à une technique RMN appliquée, entre autres, à ce système afin de mettre en évidence la relation qui existe entre la structure du gélateur et son pouvoir gélifiant, et de déterminer le rôle joué par le solvant dans le processus d'organogélation. Deux autres applications sont envisagées : au troisième chapitre, consacré à la relaxation croisée, nous mettons en évidence la configuration Z ou E d'un intermédiaire de synthèse; dans le quatrième chapitre, consacré à la diffusion translationnelle, nous proposons une méthode très simple pour analyser les composants d'un mélange de trois terpènes à partir des coefficients d'auto-diffusion déterminés par RMN du carbone-13This thesis deals with NMR dynamical parameters, the latter leading to the two types of molecular motion: reorientation, obtained via relaxation parameters, and translation motion, directly probed by self-diffusion coefficient. First, spin relaxation concepts are introduced theoretically. Then, various dynamical parameters (relaxation times, Nuclear Overhauser Effet parameters, self-diffusion coefficients) are envisioned for studying three different systems. The interpretation of experimental results provides a variety of information that does not only concern the dynamics of molecules but also their structure, such as interatomic distances, or their organization in supramolecular systems. Structural and dynamic characterization of an organogel is the lead of this thesis. Indeed, each of the three following chapters is dedicated to a given NMR technique which is applied, among other things, to this system in order to study: i) the correlation between the gelator structure and its gel formation ability, ii) the role played by the solvent in the gelification process. Two other applications are considered: in the third chapter, devoted to cross-relaxation, we discriminate the Z or E configurations of a synthetic intermediate. In the fourth chapter, devoted to translational diffusion, we propose a very simple method for analyzing a mixture of three terpenes from NMR carbon-13 experiments
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Borsali, Redouane. "Etude theorique du comportement dynamique des melanges ternaires de polymere en solution : etude experimentale par spectroscopie rayleigh quasi-elastique." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13138.
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L'etude d'un melange ternaire de polymeres en solution semidiluee presente deux modes de relaxation. Mise en evidence par diffusion de lumiere quasi-elastique de deux processus de diffusion: le premier, lent, correspond au mouvement relatif des deux polymeres; le second, rapide, correspond au mouvement cooperatif du reseau physique forme par les deux polymeres
Books on the topic "Phase diffusion coefficient"
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Center, NASA Glenn Research, ed. Novel diffusivity measurement technique. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2001.
Find full textBook chapters on the topic "Phase diffusion coefficient"
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Tinker, Peter B., and Peter Nye. "Local Movement of Solutes in Soil." In Solute Movement in the Rhizosphere. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195124927.003.0008.
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In the previous chapter, we dealt with the distribution of solutes between gas, liquid and solid phases in the soil at equilibrium; and with the rates of redistribution between these phases within soil pores. In this chapter, we consider movement of the order of 1 –1000 mm from one volume of soil to another. Such movements occur largely by diffusion and mass flow of the soil solution or soil air, and by mass movement of the body of the soil. Major movements that involve the balance and amount of solutes in the whole soil profile, including plant uptake and drainage losses, are treated in chapter 11. The process of diffusion results from the random thermal motion of ions, atoms or molecules. Consider a long column of unit cross-section orientated along the x axis, and containing a mixture of components in a single phase at constant temperature and external pressure. If the concentration of an uncharged component is greater at section A than at section B, then on average more of its molecules will move from A to B than from B to A. The net amount crossing a unit section in unit time, which is the flux, is given by the empirical relation known as Pick’s first law: . . . F = − D dC/dx (4.1) . . . where F is the flux, and dC/dx is the concentration gradient across the section. The minus sign arises because movement is from high to low concentration in the direction of increasing x. The diffusion coefficient, D, is thus defined by the equation as a coefficient between two quantities, F and dC/dx, which can be measured experimentally. It is not necessarily a constant. The diffusion coefficient of the molecules in a phase is directly proportional to their absolute mobility, u, which is the limiting velocity they attain under unit force. Terms D and u are related by the Nernst-Einstein equation: . . . D = ukT (4.2) . . . where k is the Boltzmann constant and T is the temperature on the Kelvin scale. The Nernst-Einstein equation is derived as follows (Atkins 1986, p. 675).
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Jonas, Ana, and Xiangdong Peng. "NMR Studies of the Order and Dynamics of Dipalmitoylphosphatidylchoiine Bilayers as a Function of Pressure." In High Pressure Effects in Molecular Biophysics and Enzymology. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195097221.003.0023.
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We have used 2H NMR methods to examine the order and dynamics of dipalmitoylphosphatidylcholine (DPPC) in multilamellar and small unilamellar vesicles in water as a function of pressure. Multipulse 2H NMR techniques were used with selectively deuterated DPPC on both chains at positions C-2, C-9, or C-13, to obtain lineshapes, spin-lattice relaxation times (T1), and spin-spin relaxation times (T2) at 50 °C from 1 bar to 5.2 kbar pressure. This pressure range allowed us to explore the phase behavior of DPPC from the liquid crystalline (LC) phase through various gel phases (Gl, Gll, Glll, GX), including the interdigited Gi phase. Pressure has an ordering effect: on all chain segments in all the phases. In the LC phase, the order parameter (SCD) decreases from C-2 > C-9 > C-13, while in the gel phases SCD decreases from C-9 > C-13 > C-2, indicating that in the gel phases the middle segments of the chains are more restricted in their motions than the ends. In the LC phase, T1 and T2 values for all segments decrease with pressure and have an order from C-13 > C-9 > C-2. These results suggest that similar conformational motions and molecular rotational motions occur in the LC state in all segments, but have increased amplitudes and frequencies toward the methyl ends. At the phase transitions, discontinuities and abrupt reversal of the slopes for the T1 or T2 dependences on pressure indicate major changes in motional modes and rates for DPPC molecules in the different structures. In the second part of this study, we have measured the lateral diffusion of DPPC in sonicated vesicles in D2O as a function of pressure. The spin-lattice relaxation rate in the rotating frame T−11p was plotted as a function of the square root of the spin-locking field angular frequency (ω1)1/2, and the lateral diffusion coefficient (D) was calculated from the slope. Pressure effects are observed on lateral diffusion in the LC phase (D = 5.4 − 2 × 10−9 cm2 seconds, from 1 to 300 bar) but are negligible in the GI phase (D ≈ 1.0 × 10−9 cm2 seconds, from 400 to 800 bar).
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Chimowitz, Eldred H. "Supercritical Adsorption." In Introduction to Critical Phenomena in Fluids. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195119305.003.0008.
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In this chapter, we discuss adsorption phenomena in supercritical systems, a situation that occurs in many application areas in chemical-process and materials engineering. An example of a commercial application in this area, which has achieved wide acceptance as a tool in analytical chemistry, is supercritical fluid chromatography (SFC). Not only is SFC a powerful technique for chemical analysis, but it also is a useful method for measuring transportive and thermodynamic properties in the near-critical systems. In the next section, we analyze adsorption-column dynamics using simple dynamic models, and describe how data from a chromatographic column can be used to estimate various thermodynamic and transport properties.We then proceed to discuss the effects of proximity to the critical point on adsorption behavior in these systems. The closer the system is to its critical point, the more interesting is its behavior. For very dilute solute systems, like those considered here, the energy balance is often ignored to a first approximation; this leads to a simple set of mass-balance equations defining transport for each species. These equations can be developed to various levels of complexity, depending upon the treatment of the adsorbent (stationary phase). The conceptual view of these phases can span a wide range of possibilities ranging from completely nonporous solids (fused structures) to porous materials with complicated ill-defined pore structures. Given these considerations, it is customary to make the following assumptions in the development of a simple model of adsorber-bed dynamics: . . .1. The stationary and mobile phases are continuous in the direction of the flow, with the fluid phase possessing a flat velocity profile (“plug” flow).. . . . . . 2. The porosity of the stationary phase is considered constant irrespective of pressure and temperature conditions (i.e., it is incompressible). . . . . . .3. The column is considered to be radially homogeneous, leading to a set of equations with one spatially independent variable, representing distance along the column axis. . . . . . . 4. The dispersion term in the model equation represents the combined effects of molecular diffusion and dispersion due to convective stirring in the bed. These effects are combined into an effective phenomenological dispersion coefficient, considered to be constant throughout the column. . . .
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Jan, C. H., D. Swenson, and Y. A. Chang. "A methodology for obtaining diffusion coefficients in a three-phase ternary couple: GaAs/nickel." In Fundamentals and Applications of Ternary Diffusion, 127–41. Elsevier, 1990. http://dx.doi.org/10.1016/b978-0-08-040412-7.50019-0.
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Silvestroni, Laura, and Diletta Sciti. "Effect of Transition Metal Silicides on Microstructure and Mechanical Properties of Ultra-High Temperature Ceramics." In MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments, 125–79. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-4066-5.ch005.
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The IV and V group transition metals borides, carbides, and nitrides are widely known as ultra-high temperature ceramics (UHTCs), owing to their high melting point above 2500°C. These ceramics possess outstanding physical and engineering properties, such as high hardness and strength, low electrical resistivity and good chemical inertness which make them suitable structural materials for applications under high heat fluxes. Potential applications include aerospace manufacturing; for example sharp leading edge parts on hypersonic atmospheric re-entry vehicles, rocket nozzles, and scramjet components, where operating temperatures can exceed 3000°C. The extremely high melting point and the low self-diffusion coefficient make these ceramics very difficult to sinter to full density: temperatures above 2000°C and the application of pressure are necessary conditions. However these processing parameters lead to coarse microstructures, with mean grain size of the order of 20 µm and trapped porosity, all features which prevent the achievement of the full potential of the thermo-mechanical properties of UHTCs. Several activities have been performed in order to decrease the severity of the processing conditions of UHTCs introducing sintering additives, such as metals, nitrides, carbides or silicides. In general the addition of such secondary phases does decrease the sintering temperature, but some additives have some drawbacks, especially during use at high temperature, owing to their softening and the following loss of integrity of the material. In this chapter, composites based on borides and carbides of Zr, Hf and Ta were produced with addition of MoSi2 or TaSi2. These silicides were selected as sintering aids owing to their high melting point (>2100°C), their ductility above 1000°C and their capability to increase the oxidation resistance. The microstructure of fully dense hot pressed UHTCs containing 15 vol% of MoSi2 or TaSi2, was characterized by x-ray diffraction, scanning, and transmission electron microscopy. Based on microstructural features detected by TEM, thermodynamical calculations, and the available phase diagrams, a densification mechanism for these composites is proposed. The mechanical properties, namely hardness, fracture toughness, Young’s modulus and flexural strength at room and high temperature, were measured and compared to the properties of other ultra-high temperature ceramics produced with other sintering additives. Further, the microstructural findings were used to furnish possible explanations for the excellent high temperature performances of these composites.
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Secuianu, Catinca, and Sergiu Sima. "Phase Equilibria for Carbon Capture and Storage." In Carbon Capture [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.95136.
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Carbon dioxide (CO2) is an important material in many industries but is also representing more than 80% of greenhouse gases (GHGs). Anthropogenic carbon dioxide accumulates in the atmosphere through burning fossil fuels (coal, oil, and natural gas) in power plants and energy production facilities, and solid waste, trees, and other biological materials. It is also the result of certain chemical reactions in different industry (e.g., cement and steel industries). Carbon capture and storage (CCS), among other options, is an essential technology for the cost-effective mitigation of anthropogenic CO2 emissions and could contribute approximately 20% to CO2 emission reductions by 2050, as recommended by International Energy Agency (IEA). Although CCS has enormous potential in numerous industries and petroleum refineries due their large CO2 emissions, a significant impediment to its utilization on a large scale remains both operating and capital costs. It is possible to reduce the costs of CCS for the cases where industrial processes generate pure or rich CO2 gas streams, but they are still an obstacle to its implementation. Therefore, significant interest was dedicated to the development of improved sorbents with increased CO2 capacity and/or reduced heat of regeneration. However, recent results show that phase equilibria, transport properties (e.g., viscosity, diffusion coefficients, etc.) and other thermophysical properties (e.g., heat capacity, density, etc.) could have a significant effect on the price of the carbon. In this context, we focused our research on the phase behavior of physical solvents for carbon dioxide capture. We studied the phase behavior of carbon dioxide and different classes of organic substances, to illustrate the functional group effect on the solvent ability to dissolve CO2. In this chapter, we explain the role of phase equilibria in carbon capture and storage. We describe an experimental setup to measure phase equilibria at high-pressures and working procedures for both phase equilibria and critical points. As experiments are usually expensive and very time consuming, we present briefly basic modeling of phase behavior using cubic equations of state. Phase diagrams for binary systems at high-pressures and their construction are explained. Several examples of phase behavior of carbon dioxide + different classes of organic substances binary systems at high-pressures with potential role in CCS are shown. Predictions of the global phase diagrams with different models are compared with experimental literature data.
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"Using CFD to Estimate External Mass Transfer Coefficients and Intra-Particle Diffusional Effects on the Supercritical Hydrogenation of Sunflower Oil." In Single and Two-Phase Flows on Chemical and Biomedical Engineering, edited by A. Guardo, E. Ramírez, M. A. Larrayoz, and F. Recasens, 174–95. BENTHAM SCIENCE PUBLISHERS, 2012. http://dx.doi.org/10.2174/978160805295011201010174.
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SCHÖBEL, G., and R. MEMMER. "COMPUTER SIMULATION OF CHIRAL LIQUID CRYSTAL PHASES DETERMINATION OF THE SELF-DIFFUSION COEFFICIENT TENSOR OF CHOLESTERIC LIQUID CRYSTALS." In Molecular Dynamics On Parallel Computers, 332–33. WORLD SCIENTIFIC, 2000. http://dx.doi.org/10.1142/9789812793768_0028.
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Criss, Robert E. "Nonequilibrium Fractionation and Isotopic Transport." In Principles of Stable Isotope Distribution. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195117752.003.0006.
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At the Earth’s surface, isotopic disequilibrium is far more common than isotopic equilibrium. Although isotopic equilibrium is approached in certain instances, numerous constituents of the lithosphere, hydrosphere, atmosphere, and biosphere are simply not in mutual isotopic equilibrium. This condition is consistent with the complex and dynamic conditions typical of the Earth’s surface, particularly the large material fluxes, the rapid changes in temperature, and the biological mediation of chemical systems. Fortunately, several aspects of isotopic disequilibrium may be understood in terms of elementary physical laws. For homogeneous phases such as gases or well-stirred liquids, or for cases where spatial gradients in isotopic contents are not of primary interest, then the principles of elementary kinetics can be applied. For cases where isotopic gradients are important, the laws of diffusion are applicable. If two phases are out of isotopic equilibrium, they will progressively tend to approach the equilibrium state with the passage of time. This phenomenon occurs by the process of isotopic exchange, and its rate may be understood by examining isotopic exchange reactions from the viewpoint of elementary kinetic theory. In particular, consider the generalized exchange reaction where A and B are two phases that share a common major element, and A* and B* represent the same phases in which the trace isotope of that element is present. The present analysis is simplified if the exchange reaction is written so that only one atom is exchanged, in which case the stoichiometric coefficients are all unity. For reaction 4.1, kinetic principles assert that the forward and reverse reactions do not, in general, proceed at identical rates, but rather at the rates indicated by the quantities kα and k written by the arrows, multiplied by the appropriate concentrations terms. Assuming that the reaction is first order, then the reaction progress, represented by the quantity dA*/dt, may be expressed by the difference between these forward and reverse rates, as follows: . . . dA*/dt = kα(A)(B*) − k(A*)(B) (4.2) . . . In order to evaluate the exchange process more completely, is important to carefully chose a consistent set of concentrations for substitution equation 4.2.
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Zhang, Weigang, Changming Xie, Xi Wei, and Min Ge. "C/C-ZrB2-ZrC-SiC Composite Derived from Polymeric Precursor Infiltration and Pyrolysis." In MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments, 435–59. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-4066-5.ch014.
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Part II. Mechanical and ablation properties of the 2D C/C-ZrB2-ZrC-SiC composites with a fiber volume fraction of 17.6%, fabricated by infiltration and co-pyrolysis of blended polymeric precursors, were studied in this Part II. Flexural strength and fracture toughness of the composites were found to be influenced strongly by the thickness of the deposited pyrolytic carbon interphase, a composite with the pyrolytic carbon volume fraction of 22.3% exhibits improved bending strength and fracture toughness of 127.9 MPa and 6.23 MPa·m1/2, respectively. The pseudo-plastic strain to failure of the composite is ascribed to sliding of the interphase and pulling out of carbon fibers from the brittle ceramics matrix. Ablation properties of the composite were investigated with a plasma torch and arc-heated wind tunnel tests at temperatures above 1800~2200°C. The composite exhibits very low ablation rates of 0.18×10-3 mm/s at 1800°C and 0.37×10-3 mm/s at 2000°C in the plasma torch after 1000s testing, as compared to a similar rate of 0.30×10-3 mm/s in the wind tunnel at 1900°C after 600s testing. Ablation rates increase with increasing of temperatures from 1800 to 2200°C. The maximum ablation rate is only 1.67×10-3 mm/s in a plasma torch at 2200°C for 1000s, decreased by 71.0% as compared with the C/C-SiC composite with the same fiber and interphase contents. The 2D C/C-ZrB2-ZrC-SiC composite simultaneously showed excellent thermal shock resistance, on account of no cracks on the surface and breakage of the material being detected after these abrupt temperature increasing and long time ablations. The heating-up rate at the center of the composite specimen was found as high as above 30K/s in the plasma torch tests. Excellent ablation and thermal shock resistances of the composite can be attributed to its architecture of carbon fiber and interphase, as well as its matrix microstructures characterized by nano sized dispersions of ZrB2-Zr-SiC phases inherent formed by co-pyrolysis of three polymeric precursors. These meso- and microstructures make the composites possess very small and steady coefficients of thermal expansion (CTE) around 1.5~2.5×10-6/K and high thermal conductivities around 10~14 W/mK (which increases with increasing of temperature) from room temperature to 1300°C, respectively. Surface products and cross sectional morphologies of the composite after the ablation tests were also investigated using SEM and XRD, it was found that a homogeneous distributed and continuous glass layer composing of ZrO2-SiO2 with zirconia as a skeleton was in-situ formed. These special features of coating benefits from the merits of matrix microstructures, and inhibits the inward diffusion of oxygen and protects the composite from further oxidation and spalled off by strong gas fluid.
Conference papers on the topic "Phase diffusion coefficient"
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Fen, C. S. "Effective gas-phase diffusion coefficient in soils." In BROWNFIELDS 2006. Southampton, UK: WIT Press, 2006. http://dx.doi.org/10.2495/bf060111.
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Todd, Nick, E. K. Jeong, and Dennis L. Parker. "Alternatives to Phase Map Thermometry: Apparent Diffusion Coefficient and Spectroscopy." In 6TH INTERNATIONAL SYMPOSIUM ON THERAPEUTIC ULTRASOUND. AIP, 2007. http://dx.doi.org/10.1063/1.2744287.
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Sun, Chunliu, Jirui Hou, Jianfang Jiang, Linghui Sun, Weidong Liu, and Chong Liang. "A New Method for Measuring Diffusion and Dispersion Coefficient of Surfactant Diffusing to Crude Oil Phase." In The 3rd International Conference on Machinery, Materials Science and Energy Engineering (ICMMSEE 2015). WORLD SCIENTIFIC, 2015. http://dx.doi.org/10.1142/9789814719391_0083.
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Komiya, Atsuki, Shigenao Maruyama, and S. Moriya. "MEASUREMENT OF MASS DIFFUSION COEFFICIENT OF MICRO QUANTITY PROTEINS USING PHASE SHIFTING INTERFEROMETER." In Annals of the Assembly for International Heat Transfer Conference 13. Begell House Inc., 2006. http://dx.doi.org/10.1615/ihtc13.p10.100.
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Komiya, Atsuki, Juan F. Torres, Junnosuke Okajima, Shuichi Moriya, Shigenao Maruyama, and Masud Behnia. "An Investigation of Concentration Dependency of Mass Diffusion Coefficients in Multi-Component Diffusion." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22501.
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In this paper the concentration dependency of mass diffusion coefficients in binary system was investigated. We have developed a novel and accurate visualization system using a small area of transient diffusion fields by adopting a phase shifting technique. Through accurate visualization of the transient diffusion field, it is possible to determine the mass diffusion coefficient. Unlike a conventional interferometer, the proposed system provides high spatial resolution profiles of concentration even though the target area is less than 1.0 mm. This allows the measurement of local transient diffusion field with a high accuracy. The determination of mass diffusion coefficient of each component in multi-component system was also conducted. For the accurate and reliable measurement of mass diffusion coefficient, the experimental error should be taken into account. The experimental data usually contains unexpected accidental error and inherent errors of the measurement system. In this study, an optimization technique using conjugate gradient method is developed for the precise determination of the mass diffusion coefficients. The difference between the experimental and numerical concentration distribution is set as the objective function for the optimization method. The conjugate gradient method searches the optimal value by minimizing the objective function. For the concentration dependency evaluation, sodium chloride (NaCl) in pure water was selected as solute. For determination of each mass diffusion coefficient in multi-component system, NaCl and lysozyme in buffer solution was selected. The experiments were performed under isothermal conditions. The proposed measurement method was validated by comparing the measured data with those available in the literature. The results indicated that the concentration dependency was successfully investigated from the experimental data. The mass diffusion coefficient of each component also could be determined from the experimental data as evidenced by good agreement with the published data. The difference between the reference and determined value of mass diffusion coefficient was less than 10%. It can be said that the diffusion of each solute inside the cell progresses independently within the dilute concentration ranges and the superposition principle of concentration of NaCl and lysozyme was satisfied. The influence of concentration of solution on the diffusion process and allowable concentration range of the superposition principle are determined and discussed.
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Gao, Wenqian, Fei Liu, and Honghan Chen. "Gas Phase Effective Diffusion Coefficient of Gasoline and Characteristic Components in Dry Fine Sand." In 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5162875.
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Komiya, Atsuki, Shigenao Maruyama, and Shuichi Moriya. "Development of Precise Visualization System for Small Transient Diffusion Field of Protein Using Phase Shifting Interferometer." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32617.
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This paper deals with a development of precise visualization system for mass diffusion field of micro quantity proteins by using phase shifting interferometer. The visualization system developed in this study could solve several measurement difficulties and accomplish quick and precise measurement of mass diffusion coefficient. For the observation of small transient diffusion field, Mach-Zehnder type phase shifting interferometer and small shearing cell were utilized. The designed small shearing cell requires only 10 micro liter solutions to form the transient diffusion field. As a target protein, lysozyme extracted from hen egg white was used. For the avoidance of protein denaturation, the lysozyme was dissolved in universal buffer solution over a wide pH range from pH 4.29 to 8.44. This range corresponds to that of digestive system in human body. Also, to investigate concentration dependency of mass diffusion coefficient, solutions over a wide range of concentration were prepared. The experimental results indicated that the concentration profile in a diffusion field could be detected clearly even though the field of view is smaller than 1.0mm square. The mass diffusion coefficient was derived by an analytical method proposed by authors. This method can derive mass diffusion coefficient as a function of concentration from one measurement datum. From the experimental data, the dependency of pH value of surrounding buffer and that of concentration on diffusion phenomena were discussed.
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Sikora, Janusz, Joseph P. Cusumano, and William A. Jester. "Stability and Bifurcations in a Model of Phase Transitions With Order Parameter." In ASME 1997 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1997. http://dx.doi.org/10.1115/detc97/vib-4106.
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Abstract A one-dimensional model of phase transitions with convex strain energy is investigated within the limits of nonlinear bar theory. The model is a special case of a coupled field theory that has been developed by Fried and Gurtin to study the nucleation and propagation of phase boundaries. The system of governing equations studied here consists of a wave equation coupled to a nonlinear reaction-diffusion equation. Using phase plane methods, the equilibria of the system have been constructed in order to obtain the macroscopic response of the bar and the bifurcation diagram. It is demonstrated that a large number of coexisting spatially periodic, inhomogeneous solutions can occur, with the number of these solutions being inversely proportional to the diffusion coefficient in the reaction-diffusion subsystem. A stability analysis of the equilibria is presented.
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Magin, Richard L., and Dumitru Baleanu. "NMR Measurements of Anomalous Diffusion Reflect Fractional Order Dynamics." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34224.
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Diffusion weighted MRI is often used to detect and stage neurodegenerative, malignant and ischemic diseases. The correlation between developing pathology and localized diffusion measurements relies on the design of selective phase encoding pulses that alter the intensity of the acquired signal according to biophysical models of spin diffusion in tissue. The most common approach utilizes a bipolar or Stejskal-Tanner gradient pulse sequence to encode the apparent diffusion coefficient as an exponential, multi-exponential or stretched exponential function of experimentally-controlled parameters. Several studies have investigated the ability of the stretched exponential to provide an improved fit to diffusion-weighted imaging data. These results were recently analyzed by establishing a direct link between water diffusion, as measured using NMR, and fractal structural models of tissues. In this paper we suggest an alternative description for stretched exponential behavior that reflects fractional order dynamics of a generalized Bloch-Torrey equation in either space or time. Such generalizations are the basis for similar anomalous diffusion phenomena observed in optical spectroscopy, polymer dynamics and electrochemistry. Here we demonstrate a correspondence between the detected NMR signal and anomalous diffusional dynamics of water through the Riesz fractional order space derivative and the Caputo form of the fractional order Riemann-Liouville time derivative.
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Garvey, Julie, David Newport, and Tara Dalton. "Liquid Diffusion Measurement in Micro/Mini Channels From Full-Field Digital Phase Measurement Interferometry (PMI)." In ASME 2004 2nd International Conference on Microchannels and Minichannels. ASMEDC, 2004. http://dx.doi.org/10.1115/icmm2004-2365.
Full textAbstract:
This paper considers division of amplitude interferometry as a means to extract fluid information from micro-systems. Initially the phase measurement technique is analysed and the measurement limitations of mixing measurement are assessed. Accurate phase measurements are then made of the concentration in a 3 dimensional channel flow. A mini sized channel with tow fluid flows at Reynolds numbers of 0.848 and 0.0848 is numerically analysed. The same channel is experimentally tested and the results for the mixing concentration gradients in channel flow are compared with those obtained numerically. The requirement for experimental measurement for accurate measurement of binary liquid diffusion is observed by the variation between experimental and numerical results. The diffusion coefficient measurement verifies PMI as a means of mixture measurement, or more broadly as a phase measurement technique for small-scale, or micro scale, fluidic analysis. PMI’s potential is finally discussed as a measurement technique for concentration, and hence fluidic analysis of micro channel mixing.