3,275 research outputs found
Bio-geomorphic patterns in tidal environments
Get PDFIn times of natural and anthropogenic climate change, tidal bio-geomorphic systems are most exposed to possibly irreversible transformations with far-reaching ecological and
socio-economic implications.
It is thus of critical importance to develop models for predicting the evolution of such systems under varying forcings and, if
present, their dynamically-accessible stable states.
The notion that freshwater and terrestrial ecosystems may switch
abruptly to alternative stable states as a result of feedbacks
between consumers and limiting resources is widely acknowledged. On the contrary, theoretical or observational proofs of the existence of alternative equilibrium states in intertidal ecosystems has until recently proven to be elusive.
This is due to a prevalent reductionist approach, which has until recently mostly produced either purely ecological or purely geomorphological models, while the coupled dynamics of landforms and biota in the intertidal zone has remained largely unexplored.
The presence and continued existence of tidal morphologies, and in particular of salt marshes, is intimately connected with biological activity, especially with the presence of halophytic vegetation. In fact, observations and models coupling geomorphological and biological processes indicate that vegetation crucially affects marsh equilibrium configurations through the production of organic soil, the capture of sediment, and the stabilization against erosion produced by wind waves. Often, different vegetation species live within very narrow
elevation intervals, associated with similarly narrow ranges of environmental pressures, thus leading to the emerge of the zonation phenomenon.
Here we present modeling analysis on the spatial distribution of geomorphological and vegetational spatial patterns in tidal landscapes arising as a result of two-way feedbacks between physical and biological processes.
We challenge the traditional interpretation of zonation as a one--way relation between dominant processes in the intertidal frame (i.e. competition vs. edaphic controls), which fails to capture the active role played by vegetation in engineering its own environment.
We use a point model of the coupled elevation-vegetation dynamics, which retains the description of the chief processes shaping these systems, to show how competing stable states are responsible for the formation of characteristic large-scale bio-geomorphic features in tidal landscapes worldwide.
Our analyses extended to a one-dimensional context allows us to explore the mechanism that leads to the formation of well-known, smaller-scale patterns associated with marsh vegetation species distributions.
We develop and present a model that for the first time incorporates species competition, species mutations, sediment transport and soil accretion in a spatially-extended setting, emphasizing that the formation of smaller-scale intertwined topographic and vegetation patterns are driven by bio-geomorphic feedbacks.
We finally analyze the robustness of large-scale and marsh-scale bio-geomorphic features to changes in the forcings, with implications for marsh ecosystem resilience to climate change and anthropogenic pressure
N=p-harmonic maps: Regularity for the sphere case
Get PDFWe introduce n/pα-harmonic maps as critical points of the energy En;pα (v)= Rn δ α /2 v pα where pointwise v W D n → SN-1, for the N-sphere SN-1 RN and pα D n/α . This energy combines the non-local behaviour of the fractional harmonic maps introduced by Rivière and the first author with the degenerate arguments of the n-Laplacian. In this setting, we will prove Hölder continuity. © 2014 de Gruyter
Large time behavior of solutions to parabolic equations with Neumann boundary conditions
No full textAbstractIn this paper we are interested in the large time behavior as t→+∞ of the viscosity solutions of parabolic equations with nonlinear Neumann type boundary conditions in connection with ergodic boundary problems which have been recently studied by Barles and the author in [G. Barles, F. Da Lio, On the boundary ergodic problem for fully nonlinear equations in bounded domains with general nonlinear Neumann boundary conditions, Ann. Inst. H. Poincaré Anal. Non Linèaire 22 (5) (2005) 521–541]
Caracterização psicopedagógica da formação do Licenciado em Pedagogia e Psicologia em Angola (1980-2010): Caracterização Psicopedagógica lio utungilo lio Licenciado ko Pedagogia kuenda Psicologia lio ISCED (1980-2010)
No full textThe training of education professionals in Angola dates back to 1962, with an elitist character, due to the opening of the General University Studies of Angola (Decree-Law No. 44530, 1962) which, in the light of Decree-Law No. 48790 (1968) became known as the University of Luanda. With the proclamation of national independence in 1975, the training of education professionals was transferred to the sphere of the Higher Institute of Educational Sciences (ISCED) founded in the city of Lubango, in the light of Decree No. 95/80 (1980), followed by the opening of ISCED in Huambo, Luanda and, later on, Benguela (1993/94). Our research aimed to characterize psychopedagogically the training of the graduate in Pedagogy and Psychology, by the mentioned ISCED, from its inception in 1980 until 2010, when the first two authors of this article graduated from ISCED Benguela. Thus, following a qualitative approach as the theoretical reference framework for analysis, we used the historical-logical method to describe the evolution of the training process of this professional, considering the elements that preceded it and served as a basis for it, articulated with the model of the essential logic of the profession, with a holistic configurational focus of the respective curriculum. This analysis allowed us to identify three major stages in the process of training these professionals, namely: the creation of university studies in Angola, the restructuring of the University of Angola and the restructuring and expansion of higher education. The analysis allowed us to identify gaps in the training of these professionals, for whose improvement we proposed to follow the investigation with empirical work. We concluded, however, that the training of these professionals went through various historical moments that gave it its own dynamics and led to the privileging of teaching skills and the neglect of others, as is the case of curricular design and development.
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Utungilo umesele elongiso, vongola kulima 1962 (Ohulukãi ovita ecea lakui epandu lavali) ocisimïlo lia kuyulula elilonguiso liamako (Decreto-Lei n° 44530, 1969) kuenda vocïnyi lio Decreto -Lei n° 4879 (1968) liapita okuvilikia Universidade lio Luanda. Ocitua coku likalela lio feka utungilo umesele elongiso lia sandoloka ko Instituto Superior de Ciência de Educação (ISCED) lia fetika ko lupale lio Luvango (Lubango), kocinyi lio Decreto 95/80 (1980) okukuamamo wayulula ko ISCED ko Wambo (Huambo), ko Luanda noke Kobaka (Benguela) 1993/94. Oku kulihiso wetu lia tiama okupopia Psicopedagógicamente ulungilo lia Licenciado ko elongiso Pedagogia kuenda Psicologia, ko ISCED kuenda cia fetikila toke 2010, kotembo olio okuti asovoli avali lio ocikuata vatanga ko fetikilo olio. Kuenda okukuamamo okupopia qualitativo, tua lupukila ko método histórico-lógico, oco tusoneha oku amako onjila yoku linga eluliko umesele, oku sima ocina ciñila vicina cikuava via tukuama via silivila ndo lubombo lia utungilo ko ISCED okukuama lio ocisetahãi lio ukulihiso wolonduge oco cilomboloke tukapa kuluando luetu
A SYMBOLIC APPROACH FOR AUTOMATIC GENERATION OF THE EQUATIONS OF MOTION OF MULTIBODY SYSTEMS
No full textThis paper describes a collection of methods and procedures for the automatic generation of the equations of motion of multibody systems using general-purpose Computer Algebra Software. A brief review of existing symbolic multibody systems is given, and advantages and disadvantages of symbolic approaches compared with numerical ones are discussed. Then, a set of methods for symbolic modeling of multibody systems is explained. The first step of the modeling procedure consists of the description of the multibody system, by defining objects (such as points, vectors, rigid bodies, forces and torques, special objects) and the relationships between them (kinematic chains, constraints). The second step is the derivation of the equations of motion, which can be performed in a quasiautomatic way. A further step is the linearization of the equations and the calculation of the system's frequency response functions. By way of example, a dynamic model of the motorcycle is developed, obtaining the nonlinear equations of motion in a dependent coordinates' formulation. Next, the equations of motion are linearized and reduced to an independent formulation, reobtaining the well known Sharp's model of the straight running of the motorcycle. Root loci and frequency response functions are also calculated. This example demonstrates the power of the given symbolic procedures and shows how a model suitable for stability, handling and control analysis can be developed quickly and easily. The procedure described in this paper has been implemented in a Maple package called 'MBSymba', which is available on the web page www.dim.unipd.it/lot/mbsymba.html
Existence and uniqueness of Lipschitz continuous graphs with prescribed Levi curvature
No full textIn this paper we prove comparison
principles between viscosity semicontinuous sub- and
supersolutions of the generalized Dirichlet problem (in the sense
of viscosity solutions) for the {\it Levi Monge-Amp\`{e}re}
equation. As a consequence of this result and of the Perron's
method we get the existence of a continuous solution of the
Dirichlet problem related to the prescribed Levi curvature
equation under suitable assumptions on the boundary data and on
the Levi curvature of the domain. We also show that such a
solution is Lipschitz continuous by building Lipschitz continuous
barriers and by applying a weak Bernstein method
Comparison and existence results for evolutive non-coercive first-order Hamilton-Jacobi equations
No full textIn this paper we prove a comparison result between viscosity subsolutions and supersolutions to Hamilton-Jacobi equations of the form u_t+H(x,Du)=0 in R^Nx(0,T) where the Hamiltonian H may be noncoercive in the gradient Du. As a consequence of the comparison result and the Perron's method we get the existence of a continuous solution of this equation
Multiple and Multimodal Literacies in Foreign and Second Language Learning in the Digital Age
No full text[...] Gli ultimi decenni hanno visto il termine Literacy cambiare radicalmente ed emergere, insieme alle sue molteplici sfaccettature, come elemento chiave nell'insegnamento e nell'apprendimento delle lingue. Questo progetto di ricerca traccia l'evoluzione dei diversi aspetti che fanno parte del concetto di Literacy attraverso la lente dell'educazione linguistica, analizzando sia i punti di forza che le criticità evidenziate dalla ricerca. L'enfasi viene posta sul rapporto tra casi di studio e aule di lingua, dove la promozione di literacies multiple, multimodali e digitali sembra ancora difficile da raggiungere.
Per raccogliere dati è stata utilizzata una metodologia di ricerca mista, principalmente attraverso un questionario costruito attorno al concetto di Literacy nell'educazione linguistica, esplorando il rapporto che gli intervistati hanno con la ricerca, con gli specifici obiettivi di apprendimento stabiliti per la lingua target e con le tecnologie dell'informazione e della comunicazione. Sono stati inoltre utilizzati strumenti di raccolta di dati qualitativi, quali interviste e focus group, ed si è svolta un'analisi documentale incentrata sui riferimenti normativi che regolano l'insegnamento e l'apprendimento delle due lingue (inglese nelle scuole superiori italiane e italiano nelle scuole superiori slovene). Hanno partecipato docenti della scuola secondaria superiore di inglese come lingua straniera in Italia e di italiano come seconda lingua in Slovenia. [...
Partial Regularity for Stationary Solutions to Liouville-Type Equation in dimension 3
No full textIn dimension , we prove that the singular set of any stationary solution to the Liouville equation , which belongs to , has Hausdorff dimension at most
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