It is increasingly the case that models of natural phenomena and materials processing systems involve viscous flows with free surfaces. These free boundaries are interfaces of the fluid with either second immiscible f...
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ISBN:
(数字)9781461384137
ISBN:
(纸本)9781461384151
It is increasingly the case that models of natural phenomena and materials processing systems involve viscous flows with free surfaces. These free boundaries are interfaces of the fluid with either second immiscible fluids or else deformable solid boundaries. The deformation can be due to mechanical displacement or as is the case here, due to phase transformation; the solid can melt or freeze. This volume highlights a broad range of subjects on interfacial phenomena. There is an overview of the mathematical description of viscous free-surface flows, a description of the current understanding of mathematical issues that arise in these models and a discussion of high-order-accuracy boundary-integral methods for the solution of viscous free surface flows. There is the mathematical analysis of particular flows: long-wave instabilities in viscous-film flows, analysis of long-wave instabilities leading to Marangoni convection, and de§ scriptions of the interaction of convection with morphological stability during directional solidification. This book is geared toward anyone with an interest in free-boundary problems, from mathematical analysts to material scientists; it will be useful to applied mathematicians, physicists, and engineers alike.
Compositional changes in the underlying alloy during protective oxidation according to parabolic, cubic and logarithmic rate laws are calculated. A finite difference method is used for the solution of the general diff...
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Compositional changes in the underlying alloy during protective oxidation according to parabolic, cubic and logarithmic rate laws are calculated. A finite difference method is used for the solution of the general diffusion equation. Assuming that only one of the alloy constituents is oxidized ( A in the hypothetical alloy AB ), the concentration of A at the alloy/oxide interface is mainly dependent on the three constants ξ, the ratio of oxidation rate constant to alloy interdiffusion coefficient, ε, the ratio of the concentration of A in the oxide to that in the bulk alloy, and δ the Pilling-Bedworth ratio for the oxide. The concentration profiles of A in the underlying alloy are also influenced by the particular oxidation rate law being followed. Typical values of the three constants, ξ, ε and δ, are given for alloys in three systems, Ni-Cr, Fe-Cr and Fe-Al, and the expected compositional changes at the alloy/oxide interface are discussed. On calcule les variations de composition dans l'alliage sous-jacent accompagnant l'oxydation protectrice pour les lois de vitesse parabolique, cubique et logarithmique. On résout l'équation générale de la diffusion par une méthode de différences finies. En supposant qu'un seul constituant de l'alliage est oxydé ( A dans l'alliage hypothétique AB ), la concentration en A à l'interface alliage-oxyde dépend principalement de trois constantes: ξ, rapport de la constante de vitesse d'oxydation au coefficient d'interdiffusion de l'alliage, ε, rapport de la concentration en A de l'oxyde à celle de la masse de l'alliage, et δ, rapport de Pilling-Bedworth pour l'oxyde. Les profils de concentration de A dans l'alliage sous-jacent sont aussi influencés par celle des lois de vitesse d'oxydation qui est suivie. On donne les valeurs typiques des trois constantes ξ, ε, et δ pour les alliages des trois systémes Ni-Cr, Fe-Cr et Fe-Al et on discute les variations attendues de composition à l'interface alliage/oxyde. Änderungen der Zusammensetzung
The phase transformation from liquid to solid is a phenomenon central to a wide range of manufacturing and natural processes. The presence of phase transformation can drive convection in the melt through the liberatio...
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ISBN:
(数字)9789401128094
ISBN:
(纸本)9780792319108;9789401052481
The phase transformation from liquid to solid is a phenomenon central to a wide range of manufacturing and natural processes. The presence of phase transformation can drive convection in the melt through the liberation of latent heat, the rejection of solute, and the change of density upon freezing. The fluid mechanics itself can playa central role; the phase transformation can be strongly altered by convective transport in the liquid through the modification of the thermal and solutal environment of the solid-liquid interface; these local fields control the freezing characteristics at the interface. The convection can be generated naturally by buoyancy forces arising from gradients of temperature and concentration in the liquid, by density changes upon freezing, and by thermocapillary and solutocapillary forces on liquid-solid interfaces. The interactive coupling between solidification and convection forms the subject of this volume. Such coupled processes are significant on a large range of scales. Among the applications of interest are the manufacture of single crystals, the processing of surfaces using laser or molecular beams, and the processes of soldering and welding. One wants to understand and predict macrosegregation in castings, transport and fractionation in geological and geophysical systems, and heat accumulation in energy redistribution and storage systems. This volume contains papers presented at the NATO Advanced Research Workshop on "Interactive Dynamics of Convection and Solidification" held in Chamonix, France, March 8-13, 1992.
Mathematical models of the human left ventricle are presented to determine the physiological response-oriented mechanical parameters of the LV, which have diagnostic significance. These parameters are (i) the rheologi...
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Mathematical models of the human left ventricle are presented to determine the physiological response-oriented mechanical parameters of the LV, which have diagnostic significance. These parameters are (i) the rheological parameters of the left ventricular muscle, namely the instantaneous values of stiffness of series elasticity, parallel elasticity, and the stress-strain rate relationship for the contractile unit that characterizes the deviatric stress-strain response of a left ventricular muscle element, (ii) the effective modulus of the LV, and (iii) the state of stress in the LV. The rheological parameters are obtained from a continuum model of the LV whose stress state equilibrates the chamber pressure and whose strain state equals the instantaneous strains in the actual LV, obtained from instantaneous changes in the geometry of the LV (as noted from cineangiocardiography); the constitutive equations for the model incorporate the known existing rheological models for the isolated cardiac muscle. The effective moduli of the LV are obtained by correlating the fundamental frequency of vibration of a spherical model of the LV with the corresponding frequencies of the second component of the first heart sound and the third heart sound; thus the values of representative moduli (and hence indices of the left ventricular stiffnesses) at systole and diastole are obtained. The stress state in the LV is obtained by utilizing single plane cineangiocardiographic information of the irregular geometry of the LV in anteroposterior projection. Plane stress finite element analysis of this planor irregular geometry of the LV is done and the resulting stresses are reduced by a factor, heuristically determined to make allowance for the actual 3-dimensional geometry of the LV; the stresses obtained thus bring out effects of irregular boundary of varying (and at times high) curvature.
A capillary surface is an interface between two fluids whose shape is determined primarily by surface tension. Sessile drops, liquid bridges, rivulets, and liquid drops on fibers are all examples of capillary shapes i...
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A capillary surface is an interface between two fluids whose shape is determined primarily by surface tension. Sessile drops, liquid bridges, rivulets, and liquid drops on fibers are all examples of capillary shapes influenced by contact with a solid. Capillary shapes can reconfigure spontaneously or exhibit natural oscillations, reflecting static or dynamic instabilities, respectively. Both instabilities are related, and a review of static stability precedes the dynamic case. The focus of the dynamic case here is the hydrodynamic stability of capillary surfaces subject to constraints of (a) volume conservation, (b) contact-line boundary conditions, and (c) the geometry of the supporting surface.
In rural, depopulated areas, agritourism, as a development model, could serve the goal of non- exclusively seasonal tourism while creating additional economic opportunities for the locals who are mainly engaged in agr...
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In rural, depopulated areas, agritourism, as a development model, could serve the goal of non- exclusively seasonal tourism while creating additional economic opportunities for the locals who are mainly engaged in agriculture. Kasos is an isolated island of the Dodecanese, Greece, preserving interesting elements of the authentic agricultural practices and architecture like terraces serving the island’s agricultural cultivation, mills and mitata, small stone- built *** served as a case study of AEI program (Sustainable Development of Less Developed Regions and Isolated Areas by Creating New Touristic Resources and Products through Analysis, Documentation and Modelling of Cultural Assets using Innovative ICT Applications, project code:T2EDK- 01278). For thιs island that lies within the wider region of Rhodes, it is possible with the appropriate development of new touristic resources and products through the advancement of the unique architectural, cultural and environmental assets to orient towards them special parts of the touristic flow from Rhodes, creating new touristic activity by increasing the residence beyond the daily or short time tourism, as it stands for *** the analysis of the study area, research in local archives and communication with the municipality and local stakeholders was conducted. Thus, both the special features of the island and the needs of the local community were identified, organized, classified and presented in GIS maps. The implementation of a GIS for Kasos Island aims to provide a comprehensive representation of the different aspects of the island, providing useful information for policy-making and the development of strategic cultural and agrotourism plans to the local authorities and *** to the integrated plan for Kasos by AEI program, the island could preserve its special rural identity while revealing its cultural and environmental assets and attracting external economies within an agritourism mod
Compositional changes in Fe-27.4, 37.4 and 59.5% Cr alloys during the formation of Cr 2 O 3 -rich scales have been measured by electron probe microanalysis and calculated by solution of the appropriate transport equat...
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Compositional changes in Fe-27.4, 37.4 and 59.5% Cr alloys during the formation of Cr 2 O 3 -rich scales have been measured by electron probe microanalysis and calculated by solution of the appropriate transport equations. Agreement between corresponding results is within the limits of experimental error. Chromium concentration profiles have also been calculated for Fe-14.0 and Fe-18.0% Cr by a similar method, allowance being made for the formation of γ-phase at the surface of the alloy. The chromium concentration at the alloy/oxide interface never falls below the limiting value for thermodynamic stability of a Cr 2 O 3 scale. chemical transformation of the Cr 2 O 3 scales from within is therefore not possible and the failure of such scales on Fe-14.0 and Fe-18.0% Cr is attributed to mechanical causes. On a mesuré par microanalyse à la sonde électronique et calculé par résolution des équations de transport appropriées les changements de composition survenant dans des alliages Fe-27,4%, 37,4%, et 59,5% Cr pendant la formation d'écaillés riches en Cr 2 O 3 . L'accord entre les résultats correspondants se situe dans les limites de l'erreur expérimentale. On a aussi calculé les profils de concentration en chrome pour Fe-14,0 et Fe-18,0% Cr par une méthode similaire, en tenant compte de la formation de la phase γ à la surface de l'alliage. La concentration en chrome à l'interface alliage-oxyde ne tombe jamais en-dessous de la valeur critique pour la stabilité d'une écaille de Cr 2 O 3 . Une transformation chimique venant de l'intérieur des écailles de Cr 2 O 3 n'est donc pas possible et leur disparition sur Fe-14,0 et Fe-18,0% Cr est attribuée à des causes mécaniques. Veränderungen der Zusammensetzung in Fe-27,4%, 37,4% und 59,9%Cr-Legierungen während der Bildung von Cr 2 O 3 -reichen Schichten wurden mit Hilfe von Elektronensonden-Mikrianalysen gemessen und durch Lösung der entsprechenden Transportgleichungen berechnet. Innerhalb der Fehlergrenzen besteht Äbereinstimmun
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