The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Giovanni P Galdi - One of the best experts on this subject based on the ideXlab platform.
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Spatial decay of the vorticity field of time periodic viscous flow past a body
Archive for Rational Mechanics and Analysis, 2021Co-Authors: Thomas Eiter, Giovanni P GaldiAbstract:We study the asymptotic Spatial Behavior of the vorticity field, $$\omega (x,t)$$ , associated to a time-periodic Navier–Stokes flow past a body, $${\mathscr {B}}$$ , in the class of weak solutions satisfying a Serrin-like condition. We show that, outside the wake region, $${\mathcal {R}}$$ , $$\omega $$ decays pointwise at an exponential rate, uniformly in time. Moreover, denoting by $${\bar{\omega }}$$ its time-average over a period and by $$\omega _P:=\omega -{\bar{\omega }}$$ its purely periodic component, we prove that inside $${\mathcal {R}}$$ , $${\bar{\omega }}$$ has the same algebraic decay as that known for the associated steady-state problem, whereas $$\omega _P$$ decays even faster, uniformly in time. This implies, in particular, that “sufficiently far” from $${\mathscr {B}}$$ , $$\omega (x,t)$$ behaves like the vorticity field of the corresponding steady-state problem.
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viscous flow past a body translating by time periodic motion with zero average
arXiv: Analysis of PDEs, 2019Co-Authors: Giovanni P GaldiAbstract:We study existence, uniqueness, regularity and asymptotic Spatial Behavior of a Navier-Stokes flow past a body moving by a time-periodic translational motion of period $T$, and with zero average. For example, $\mathscr B$ moves in an oscillating fashion. The flow is also time-periodic with same period $T$. However, sufficiently ``far" from the body, the oscillatory component decays faster than the averaged component, so that the flow shows there a distinctive steady-state character. This provides a rigorous proof of the ``steady streaming" phenomenon.
Ramon Quintanilla - One of the best experts on this subject based on the ideXlab platform.
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on the Spatial Behavior in two temperature generalized thermoelastic theories
Zeitschrift für Angewandte Mathematik und Physik, 2017Co-Authors: Alain Miranville, Ramon QuintanillaAbstract:This paper investigates the Spatial Behavior of the solutions of two generalized thermoelastic theories with two temperatures. To be more precise, we focus on the Green–Lindsay theory with two temperatures and the Lord–Shulman theory with two temperatures. We prove that a Phragmen–Lindelof alternative of exponential type can be obtained in both cases. We also describe how to obtain a bound on the amplitude term by means of the boundary conditions for the Green–Lindsay theory with two temperatures.
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phragmen lindelof alternative for an exact heat conduction equation with delay
Communications on Pure and Applied Analysis, 2012Co-Authors: Carme M Leseduarte, Ramon QuintanillaAbstract:In this paper we investigate the Spatial Behavior of the solutions for a theory for the heat conduction with one delay term. We obtain a Phragmen-Lindelof type alternative. That is, the solutions either decay in an exponential way or blow-up at infinity in an exponential way. We also show how to obtain an upper bound for the amplitude term. Later we point out how to extend the results to a thermoelastic problem. We finish the paper by considering the equation obtained by the Taylor approximation to the delay term. A Phragmen-Lindelof type alternative is obtained for the forward and backward in time equations.
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a phase field model based on a three phase lag heat conduction
Applied Mathematics and Optimization, 2011Co-Authors: Alain Miranville, Ramon QuintanillaAbstract:Our aim in this article is to study a phase-field system based on a three-phase-lag for the thermal flux vector. In particular, we prove the existence and uniqueness of solutions and then study the Spatial Behavior of the solutions in a semi-infinite cylinder, when such solutions exist.
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on the Spatial Behavior of solutions for porous elastic solids with quasi static microvoids
Mathematical and Computer Modelling, 2006Co-Authors: Antonio Magana, Ramon QuintanillaAbstract:The Spatial Behavior of solutions for the dynamic problem of elasticity with voids is well known. It has been analyzed making use of the usual techniques for hyperbolic differential equations. Here we consider a related but different problem, the problem determined by the dynamic deformations of porous elasticity with porous dissipation when the motion of the microvoids is supposed to be quasi-static. We think that this kind of dynamical problem deserves some consideration. However, little attention has been paid to it in the literature. On the one hand, the problem has interest from a mechanical point of view, because this is the system that one must study when the microvoids deformations are small enough as to assume that their acceleration is nearly zero. On the other hand, the problem has also interest from its mathematical structure, because the coupling of a parabolic equation with a hyperbolic one arises in the system.
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qualitative aspects in dual phase lag thermoelasticity
Siam Journal on Applied Mathematics, 2006Co-Authors: Ramon Quintanilla, Reinhard RackeAbstract:We consider the system of dual-phase-lag thermoelasticity proposed by Chandrasekharaiah and Tzou. First, we prove that the solutions of the problem are generated by a semigroup of quasi-contractions. Thus, the problem of the third order in time is well-posed. Then the exponential stability is investigated. Finally the Spatial Behavior of solutions is analyzed in a semi-infinite cylinder and a result on the domain of influence is obtained.
Christopher Monz - One of the best experts on this subject based on the ideXlab platform.
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the influence of visitor use levels on visitor Spatial Behavior in off trail areas of dispersed recreation use
Journal of Environmental Management, 2016Co-Authors: Ashley Dantonio, Christopher MonzAbstract:A variety of social and ecological factors influence the level and extent of ecological change that occurs in a park or protected area. Understanding these factors and how they are interrelated can help managers prevent undesirable ecological impacts, especially in areas without formal trails and visitor sites. This study examines the relationship between levels of visitor use and Spatial patterns of visitor Behavior at a variety of backcountry recreation destinations. Current assumptions in both the literature and simulation modeling efforts assume that visitor Behavior either does not change with use level or that visitors are more likely to disperse at high levels of visitor use. Using visitor counts and GPS tracks of visitor Behavior in locations where visitors could disperse off-trail, we found that visitors' Spatial Behavior does vary with visitor use level in some recreation settings, however the patterns of visitor Behavior observed in this study are sometimes contrary to current generalizations. When visitor Behavior does vary with use level, visitors are dispersing more at low levels of visitor use not when use level is high. Overall, these findings suggest that in certain situations the amount of visitor use at a recreation destination may be a less important driver of ecological change than visitor Behavior.
Qin Xia - One of the best experts on this subject based on the ideXlab platform.
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methods in urban temporal and Spatial Behavior research in the big data era
Progress in geography, 2013Co-Authors: Qin XiaAbstract:The rapid development of information technology has taken us into the "Big Data Era",changed the organization and structure of urban space and residents' Behavior,and also caused transformation of the methods in urban temporal and Spatial Behavior research.On the basis of summarizing the problems of traditional methods such as poor data accuracy,small sample size,weak continuity,and higher costs,this paper first combs through the data acquisition and processing technology for web data mining,residents' Behavior data collection and analysis,and network map integration and visual development,which can affect the transformation of the research methods.Then it reviews the latest progress in applying big data to urban temporal and Spatial Behavior research at home and abroad from the perspectives of residents' Behavior,urban space,and urban hierarchy,and builds up a method framework for urban temporal and Spatial Behavior research based on big data application.The methods in urban temporal and Spatial Behavior research are going through a great transformation because of the emergence of massive and various information data.Data collection methods have changed from yearbook statistics,social questionnaire survey,in-depth interview to mining of network data(social network data) and application of new Spatial position technology(GPS,smart mobile phone,LBS,etc.),and the data shows obviously new characteristics such as large sample size,real-time dynamic,micro and detail,with more attention paid to the extraction of residents' geographic position information.However,as to specific research methods,the traditional ones are still widely used,such as descriptive statistical analysis,cluster analysis,factor analysis,gravity model,network analysis,space-time prism,etc.Generally speaking,the researches of urban temporal and Spatial Behavior have obvious characteristics of using "new" data and "old" methods to study "newer" and "older" problems at the present stage,and their research scope has also expanded from residential scale to urban space and regional range.However,problems still exist with the current research,such as how to eliminate fictitious data,how to learn and innovate analytical methods,how to expand research field and embody characteristics of the era.Therefore,it is necessary to promote the cross and integration of related disciplines such as sociology,economic geography,cultural geography,tourism geography,computer science,mathematics and geographic information science,in order to find new analysis methods,and also reinforce the research of residents' Behavior and urban space by using social network(Twitter,Flikr,Facebook,Sina Microblog,etc.) data or other web(SouFun.com,Dianping.com,Zhaopin.com,Taobao.com,etc.) data,and guide innovation of urban planning methods.
D. B. Myers - One of the best experts on this subject based on the ideXlab platform.
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Associations between soil carbon and ecological landscape variables at escalating Spatial scales in Florida, USA
Landscape Ecology, 2012Co-Authors: Gustavo M. Vasques, Sabine Grunwald, D. B. MyersAbstract:The Spatial distribution of soil carbon (C) is controlled by ecological processes that evolve and interact over a range of Spatial scales across the landscape. The relationships between hydrologic and biotic processes and soil C patterns and Spatial Behavior are still poorly understood. Our objectives were to (i) identify the appropriate Spatial scale to observe soil total C (TC) in a subtropical landscape with pronounced hydrologic and biotic variation, and (ii) investigate the Spatial Behavior and relationships between TC and ecological landscape variables which aggregate various hydrologic and biotic processes. The study was conducted in Florida, USA, characterized by extreme hydrologic (poorly to excessively drained soils), and vegetation/land use gradients ranging from natural uplands and wetlands to intensively managed forest, agricultural, and urban systems. We used semivariogram and landscape indices to compare the Spatial dependence structures of TC and 19 ecological landscape variables, identifying similarities and establishing pattern–process relationships. Soil, hydrologic, and biotic ecological variables mirrored the Spatial Behavior of TC at fine (few kilometers), and coarse (hundreds of kilometers) Spatial scales. Specifically, soil available water capacity resembled the Spatial dependence structure of TC at escalating scales, supporting a multi-scale soil hydrology-soil C process–pattern relationship in Florida. Our findings suggest two appropriate scales to observe TC, one at a short range (autocorrelation range of 5.6 km), representing local soil-landscape variation, and another at a longer range (119 km), accounting for regional variation. Moreover, our results provide further guidance to measure ecological variables influencing C dynamics.
