Evolution of Concentration Profiles and Diffusion Paths in Single-Phase Multicomponent Multilayered Assemblies

2009 ◽  
Vol 289-292 ◽  
pp. 593-599 ◽  
Author(s):  
Kaustubh N. Kulkarni ◽  
Mysore A. Dayananda
Keyword(s):  
Single Phase ◽  
Middle Layer ◽  
Diffusion Path ◽  
Alloy Layer ◽  
Concentration Profiles ◽  
Uphill Diffusion ◽  
Diffusion Paths ◽  
Set Up ◽  
The Individual ◽  
And Diffusion

An analysis of multilayered assemblies set up with multicomponent alloys selected in a single phase field has been recently developed on the basis of a matrix of constant interdiffusion coefficients. This analysis employs a transfer matrix method and is applicable to a study of evolution of concentration profiles and diffusion paths as a function of time for multilayered diffusion assemblies (MDAs) where any number of finite layers is sandwiched between two bulk terminal alloys. The analysis is utilized in this study to simulate concentration profiles and diffusion paths for MDAs assembled with (fcc) Cu-Ni-Zn alloys with two terminal alloys, A and B, sandwiching an alloy layer C in the middle. For short diffusion times the diffusion path of the ternary MDA, A/C/B, corresponds to two segments corresponding to the diffusion paths of the infinite diffusion couples, A/C and C/B. At longer times the diffusion zones of the two individual couples overlap and the diffusion path of the MDA varies continuously with time. The evolution of the concentration profiles and diffusion paths is presented and each intermediate path configuration is associated with a unique ratio of the middle layer thickness to the square root of diffusion time. The simulated concentration profiles clearly show the development of uphill diffusion and zero-flux planes (ZFP) for the individual components due to diffusional interactions among the components. At very long times, the diffusion path of the MDA approaches that of the infinite couple A/B between the two terminal alloys.

An Examination of Diffusion Paths in Terms of Interdiffusion Fluxes and Interdiffusion Coefficients

2007 ◽  
Vol 266 ◽  
pp. 83-99 ◽  
Author(s):  
Kevin M. Day ◽  
Mysore A. Dayananda
Keyword(s):  
National Science Foundation ◽  
Single Phase ◽  
Diffusion Path ◽  
Diffusion Couples ◽  
Eigenvalues And Eigenvectors ◽  
Internal Constraints ◽  
Two Phase ◽  
Uphill Diffusion ◽  
Diffusion Paths ◽  
Interdiffusion Coefficients

Selected diffusion couples investigated in the Cu-based and Fe-based multicomponent systems are examined for diffusion path development, zero-flux planes, uphill diffusion, and internal constraints for diffusion paths. The couples are analyzed for interdiffusion fluxes and interdiffusion coefficients with the aid of the “MultiDiFlux” program. Eigenvalues and eigenvectors are also determined from the interdiffusion coefficients determined over various ranges of composition in the diffusion zone. Slopes of diffusion paths at selected sections, including the path ends, are related to interdiffusion coefficients, interdiffusion fluxes and/or eigenvectors. These relations are explored with selected single phase diffusion couples in the Cu-Ni-Zn and Fe-Ni-Al systems and the calculated path slopes are compared with those directly determined from the concentration profiles. Relations between the gradient of interdiffusion flux and the concentration gradient are examined for each component in a two-phase Cu-Ni-Zn diffusion couple. The research is supported by the National Science Foundation.

Thermodynamic Aspects of Diffusion Paths in Ternary Systems

2007 ◽  
Vol 263 ◽  
pp. 135-140 ◽  
Author(s):  
Tony Laas ◽  
Ü. Ugaste ◽  
J. Priimets
Keyword(s):  
Thermodynamic Properties ◽  
Ternary Systems ◽  
Diffusion Path ◽  
Experimental Investigations ◽  
Ideal System ◽  
Diffusion Paths ◽  
Interdiffusion Coefficients ◽  
The Relationship ◽  
And Diffusion ◽  
Specific Influence

Description of diffusion paths is one of the most interesting and topical problems in experimental investigations of interdiffusion in multicomponent systems and, particularly, in ternary systems. The relationship between effective interdiffusion coefficients and diffusion paths in ternary systems has been discussed earlier but the specific influence of the mobility and thermodynamic properties of components on the characteristics of the diffusion path is still unclear. In this paper an attempt is made to clarify the separate influences of mobility and thermodynamics on the behavior of diffusion paths in ternary systems and the corresponding correlation is found. It is shown that in most cases the deviation of the diffusion path from linearity (an ideal system) is related to the deviation of the thermodynamic properties from the ideal. The results obtained are analyzed on the basis of thermodynamic data for the ternary system Cu-Fe-Ni.

Multiphase Ni-Cr-Al Diffusion: Experiment and Simulations

2016 ◽  
Vol 369 ◽  
pp. 77-82 ◽  
Author(s):  
Marek Zajusz ◽  
Bogdan Bożek ◽  
Katarzyna Tkacz-Śmiech ◽  
K. Berent ◽  
Marek Danielewski
Keyword(s):  
Diffusion Couple ◽  
Hot Isostatic Pressing ◽  
Concentration Profiles ◽  
Diffusion Experiment ◽  
Phase Zone ◽  
Two Phase ◽  
Post Annealing ◽  
Wide Line ◽  
Diffusion Paths ◽  
And Diffusion

Interdiffusion in two-phase Ni-Cr-Al diffusion couple was studied experimentally and simulated numerically. The diffusion multiples were prepared by hot isostatic pressing, HIP and post-annealing at 1200°C. The concentration profiles were measured with wide line EDS technique – a method suitable to study multiphases. Hence the diffusion paths were determined. The experimental profiles and diffusion paths were compared with numerical results simulated with application of the Darken bi-velocity method implemented to describe interdiffusion in a two-phase zone.

On models for predicting thermodynamic regimes in high-pressure turbulent mixing and combustion of multispecies mixtures

2018 ◽  
Vol 843 ◽  
pp. 536-574 ◽  
Author(s):  
Giacomo Castiglioni ◽  
Josette Bellan
Keyword(s):  
High Pressure ◽  
Single Phase ◽  
Free Stream ◽  
Complex Mixture ◽  
Mathematical Formalism ◽  
State Transitions ◽  
Uphill Diffusion ◽  
Turbulent Characteristics ◽  
Thermodynamic Regime ◽  
The Individual

The thermodynamic regime of a complex mixture depends on the composition, the pressure and the temperature; the spinodal locus separates the regime of thermodynamic instability from the remainder of the phase space. Since diffusion is one of the phenomena affecting the local chemical composition, the first focus is here on evaluating diffusion models in the context of high-pressure (high-$p$) multispecies mixing and combustion. It is shown that the diffusion model equations previously used to create two high-$p$ direct numerical simulation (DNS) databases can reproduce classical experimental observations of uphill diffusion in an accurate spatiotemporal manner, whereas the popular model which has a diagonal diffusion matrix and uses a velocity correction lacks spatiotemporal accuracy. Further, a mathematical formalism is used to compute the spinodal locus for mixtures for which either experimental data or previous computations from the literature are available, and it is shown that the agreement of the present calculations with that previously existing information is excellent. Using the spinodal-calculation mathematical formalism, the aforementioned DNS databases are then examined to determine the thermodynamic regime of the mixture at important stages of the simulations. In the first subset of the DNS databases that portrays mixing of five species under high-$p$ conditions, this stage is that of the transitional state representing the individual time station at which each simulation, having been initiated in a laminar state, transitions to a state having turbulent characteristics. In the second subset of the DNS databases that portrays high-$p$ turbulent combustion, this stage represents the individual time station at the peak $p$ achieved during the calculations. In both databases, the influence of the initial Reynolds number, the free-stream composition and the free-stream $p$ is studied. The results show that in all cases the mixture is in the single-phase regime. The present DNS databases have only five species, but it is shown that the methodology for computing the spinodal locus can be applied to very complex mixtures, with examples given for a twelve-species mixture and surrogate diesel fuels, thereby boding well for determining the thermodynamic regime of practical mixtures in high-$p$ turbulent flow simulations for engineering applications. According to these calculations, diesel-fuel surrogates are always in the single-phase regime at injection-conditions $p$ and temperatures existing in diesel-engine combustion chambers.

An Overview of Selected Phenomena in Multicomponent Diffusion

2015 ◽  
Vol 4 ◽  
pp. 3-21
Author(s):  
Mysore A. Dayananda
Keyword(s):  
Single Phase ◽  
Multicomponent Diffusion ◽  
Nuclear Fuels ◽  
Uphill Diffusion ◽  
Diffusion Studies ◽  
Isothermal Diffusion ◽  
Diffusion Paths ◽  
Multiphase Diffusion ◽  
Layer Development

There exist several interesting phenomena and observations reported in literature for isothermal diffusion in multicomponent systems. Such phenomena include uphill diffusion, development of zero-flux planes and flux reversals for individual components, flux reversals at interfaces, and instability at interfaces and multiphase layer development. In addition, uncommon diffusion structures exhibiting unusual diffusion paths can develop in both single phase and multiphase diffusion assemblies. An overview of such phenomena is presented to highlight the role of interactions among diffusing components with the aid of selected diffusion studies carried out in multicomponent alloy systems, aluminides, silicides, and nuclear fuels.

scholarly journals Research on the Influencing Factors of Brand Diffusion via Social Media

2020 ◽  
Vol 189 ◽  
pp. 03032
Author(s):  
Peng Yunan ◽  
Wang Zongshui ◽  
Zhang Jian
Keyword(s):  
Social Media ◽  
Diffusion Path ◽  
Impact Factors ◽  
Audience Participation ◽  
Factors Influencing ◽  
Diffusion Paths ◽  
Main Factors ◽  
The Impact ◽  
And Diffusion ◽  
Content Information

[Purpose] The paper aims to identify the impact factors of brand diffusion via social media. It provides a theoretical reference for enterprises to choose social media and improves brand influence. [Method] First, we summarize the general path of brand diffusion through social media by studying the relevant literatures. Next, four popular social media WeChat, Weibo, Tiktok, and Taobao have been selected as research samples to analyze the different brand diffusion paths. Finally, we summarize the impact of brand diffusion on social media according to the paths. [Results] The result shows that the main factors influencing brand diffusion on social media are diffusion content, information credibility, audience participation, and diffusion path.

A Comparative Study of Thin-Film and Bulk Reaction Kinetics and Diffusion Path: the Ir/GaAs System

1988 ◽  
Vol 144 ◽  
Author(s):  
Kevin J. Schulz ◽  
Y. Austin Chang
Keyword(s):  
Thin Film ◽  
Reaction Kinetics ◽  
Equilibrium Phase ◽  
Bulk Diffusion ◽  
Diffusion Path ◽  
Phase Sequence ◽  
Bulk Reaction ◽  
Diffusion Paths ◽  
Kinetics Of ◽  
And Diffusion

ABSTRACTControl of the structure and chemistry at the interfaces of compound semiconductors is essential for the commercial use of these materials in electronic and optical technologies. This can only be achieved when the governing thermodynamics and kinetics of interfacial reactions are understood. Based primarily on the experience of metal/Si interactions, however, a prevailing belief was born that thin-film reactions follow a separate set of thermodynamic and kinetic “rules” which are different from bulk reactions. The intent of our work has been to not only characterize metal/GaAs contact reactions but also to rationalize these reactions with equilibrium phase diagrams and bulk metal/GaAs diffusion couple experiments. Through this approach, a better understanding of thin-film and bulk differences has been obtained.The Ir/GaAs system is used as an example. Phase formation and reaction kinetics were studied for 30 nm Ir films on (100) GaAs using TEM, XTEM, and AEM. Bulk diffusion between 0.25 mm thick Ir foil and (100) GaAs wafers was studied with SEM and electron probe microanalysis (EPMA). The diffusion paths and kinetics were the same for thin-film and bulk. The phase sequence Ir/IrGa/IrAs2/GaAs formed for all diffusion couples. Reaction kinetics were parabolic with an activation energy of 3.0 eV for both thin-film and bulk, and the data was colinear in an Arrhenius plot. Reacted layer morphology in both cases was layered. The effects of grain size, crystallographic texturing, and the relative diffusivities of the components on the reaction mechanisms in bulk versus thin-film reactions are considered.

Patient Scheduling — (Bibliography)

1977 ◽  
Vol 16 (02) ◽  
pp. 112-115 ◽  
Author(s):  
C. O. Köhler ◽  
G. Wagner ◽  
U. Wolber
Keyword(s):  
Information Processing ◽  
Medical Care ◽  
Medical Informatics ◽  
Relevant Literature ◽  
Patient Scheduling ◽  
Individual Scientist ◽  
Set Up ◽  
The Individual ◽  
New Literature ◽  
Current Systems

The entire field of information processing in medicine is today already spread out and branched to such an extent that it is no longer possible to set up a survey on relevant literature as a whole. But even in narrow parts of medical informatics it is hardly possible for the individual scientist to keep up to date with new literature. Strictly defined special bibliographies on certain topics are most helpful.In our days, problems of optimal patient scheduling and exploitation of resources are gaining more and more importance. Scientists are working on the solution of these problems in many places.The bibliography on »Patient Scheduling« presented here contains but a few basic theoretical papers on the problem of waiting queues which are of importance in the area of medical care. Most of the papers cited are concerned with practical approaches to a solution and describe current systems in medicine.In listing the literature, we were assisted by Mrs. Wieland, Mr. Dusberger and Mr. Henn, in data acquisition and computer handling by Mrs. Gieß and Mr. Schlaefer. We wish to thank all those mentioned for their assistance.

scholarly journals Nudge Versus Boost: Agency Dynamics Under Libertarian Paternalism

2019 ◽  
Vol 130 (629) ◽  
pp. 1384-1415 ◽  
Author(s):  
Ralph Hertwig ◽  
Michael D Ryall
Keyword(s):  
Cognitive Biases ◽  
Policy Implications ◽  
Best Interests ◽  
Libertarian Paternalism ◽  
The Future ◽  
Set Up ◽  
The Individual

ABSTRACT Thaler and Sunstein (2008) advance the concept of ‘nudge’ policies—non-regulatory and non-fiscal mechanisms designed to enlist people's cognitive biases or motivational deficits so as to guide their behaviour in a desired direction. A core assumption of this approach is that policymakers make artful use of people's cognitive biases and motivational deficits in ways that serve the ultimate interests of the nudged individual. We analyse a model of dynamic policymaking in which the policymaker's preferences are not always aligned with those of the individual. One novelty of our set-up is that the policymaker has the option to implement a ‘boost’ policy, equipping the individual with the competence to overcome the nudge-enabling bias once and for all. Our main result identifies conditions under which the policymaker chooses not to boost in order to preserve the option of using the nudge (and its associated bias) in the future—even though boosting is in the immediate best interests of both the policymaker and the individual. We extend our analysis to situations in which the policymaker can be removed (e.g., through an election) and in which the policymaker is similarly prone to bias. We conclude with a discussion of some policy implications of these findings.

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