2,385 research outputs found
Decay rates for solutions of semilinear wave equations with a memory condition at the boundary
In this paper, we study the stability of solutions for semilinear wave equations whoseboundary condition includes a integral that represents the memory effect. We show that the dissipation is strong enough to produce exponential decay of the solution, provided the relaxation function also decays exponentially. When the relaxation function decays polinomially, we show that the solution decays polynomially and with the same rate
Global solutions and exponential decay for a nonlinear coupled system of beam equations of Kirchhoff type with memory in a domain with moving boundary
In this paper we prove the exponential decay in the case , as time goes to infinity, of regular solutions for a nonlinear coupled system of beam equations of Kirchhoff type with memory and weak damping
\begin{eqnarray*}
&&u_{tt}+\Delta^2 u-M(||\nabla u||^2_{L^2(\Omega_t)}+||\nabla
v||^2_{L^2(\Omega_t)})\Delta u\\
&&+\int^{t}_{0}g_1(t-s)\Delta u(s)ds
+\alpha u_{t}+h(u-v)=0 \quad \mbox{in} \quad \hat{Q},\\
&&v_{tt}+\Delta^2 v-M(||\nabla u||^2_{L^2(\Omega_t)}+||\nabla
v||^2_{L^2(\Omega_t)})\Delta v \\
&&+\int^{t}_{0}g_2(t-s)\Delta v(s)ds + \alpha v_{t}-h(u-v)=0 \quad
\mbox{in} \quad \hat{Q}
\end{eqnarray*}
in a non cylindrical domain of under suitable hypothesis on the scalar functions , , and , and where is a positive constant. We show that such dissipation is strong enough to produce uniform rate of decay. Besides, the coupling is nonlinear which brings up some additional difficulties, which plays the problem interesting. We establish existence and uniqueness of regular solutions for any
Solvability for a nonlinear coupled system of Kirchhoff type for the beam equations with nonlocal boundary conditions
In this paper, we investigate a mathematical model for a nonlinear coupled system of Kirchhoff type of beam equations with nonlocal boundary conditions. We establish existence, regularity and uniqueness of strong solutions. Furthermore, we prove the uniform rate of exponential decay. The uniform rate of polynomial decay is considered
Generalized Camassa-Holm Equations: Symmetry, Conservation Laws and Regular Pulse and Front Solutions
In this paper, we consider a member of an integrable family of generalized Camassa-Holm (GCH) equations. We make an analysis of the point Lie symmetries of these equations by using the Lie method of infinitesimals. We derive nonclassical symmetries and we find new symmetries via the nonclassical method, which cannot be obtained by Lie symmetry method. We employ the multiplier method to construct conservation laws for this family of GCH equations. Using the conservation laws of the underlying equation, double reduction is also constructed. Finally, we investigate traveling waves of the GCH equations. We derive convergent series solutions both for the homoclinic and heteroclinic orbits of the traveling-wave equations, which correspond to pulse and front solutions of the original GCH equations, respectively
Tempranillo physiological and agronomical responses to heat and drought stress – perspectives on its vulnerability under climate change scenarios
With the aim to characterize the ability of Tempranillo grapevines, one of the most widely
used varieties in Spain and Portugal, to withstand drought and heat stress, ecophysiological
and agronomical data from irrigation experiments conducted in the hot and dry region of
Alentejo, south of Portugal, are presented.
The impact of different irrigation treatments on physiological parameters (leaf water
potential, photosynthesis, and stomatal conductance) and water use efficiency are showed.
Leaf senescence observed in non-irrigated and deficit irrigated plants and its consequences on
cluster exposure and berry temperature are compared with those of fully irrigated plants. The
consequences on berry ripening and juice composition are discussed in order to evaluate the
vulnerability of Tempranillo to the expected global climatic changeinfo:eu-repo/semantics/publishedVersio
Effects of soil management and deficit irrigation strategies on physiological and agronomical responses of Aragonez field-grown grapevines
The use of irrigation in Mediterranean viticulture is now a common practice in intensive grapevine production to improve quality
of production. The negative effects of water deficits on grape berry development are well known but the underlying mechanisms
remain not fully understood. To avoid the unfavourable impacts of mechanization on the soil structure and biology some farmers
are using cover crops on their vineyards. Within this frame we have compared the traditional soil tillage with a high level of
mechanization with other system where we maintained a permanent soil cover between the rows. In both soil systems we
tested three different irrigation treatments, deficit irrigation (DI - 40% of evapotranspiration (ETc)); regulated deficit irrigation
(RDI); partial root drying (PRD) while in the soil cover treatment we also studied the full irrigation (FI) and the non irrigation (NI)
treatments. Compared to soil tillage the resident vegetation reduced soil water content during late Spring, before irrigation
started, inducing a significant reduction on vine vegetative growth berry weight and yield. Among irrigation strategies only RDI
treatment showed a significant reduction in the lateral leaf area development, berry weight and yield when compared to PRD
and DI treatments which presented similar values. No significant differences were observed in berry composition either for the
two floor management practices or for the three irrigation strategiesinfo:eu-repo/semantics/publishedVersio
Effect of sodium and nitrogen on yield function of irrigated maize in Southern Portugal
Salinization and nitrate leaching are two of the leading threats to the environment of the European Mediterranean regions. Inefficient use of water and fertilizers has led to a nitrate increase in the aquifers and reduction in crop yields caused by salts. In this study, a triple emitter source irrigation system delivers water, salt (Na+), and fertilizer (N) applications to maize (Zea mays L.). The objective of the study was to evaluate the combined effect of saline water and nitrogen application on crop yields in two different textured soils of Alentejo (Portugal) and to assess if increasing salinity levels of the irrigation water can be compensated by application of nitrogen while still obtaining acceptable crop yield. Maximum yield was obtained from both soils with an application of 13 g m−2 of nitrogen. Yield response to Na+ application was different in the two studied soils and depended on the total amount of Na+ or irrigation water applied. No significant interaction was found between nitrogen and sodium, but a positive effect on maize yield was observed in the medium textured soil for amounts of Na+ less than 905 g m−2 when applied in the irrigation water
An attempt to quantify grapevine water stress in a mediterranean environment
Aiming to quantify the effects of the intensity and duration of grapevine water stress, physiological and
agronomical data from an irrigation experiment conducted during 1999 at Alentejo, south of Portugal, with the
red variety Aragonez (syn. Tempranillo) were correlated with an water stress index (Sψ). This index was
calculated by the integral of predawn leaf water potential below –0.2 MPa between bloom and harvest.
Significant relationships were found between the Sψ, yield components and berry composition. The multiple
regression analysis shows that the Sψ in the period bloom-veraison has a higher contribution to explain the
variation in berry weight, anthocyanins and phenolics concentration than the Sψ in the period veraison-harvest.
The knowledge of those relationships, together with the relationship between available soil water content and
predawn leaf water potential, may allow the adequate management of soil water availability to optimise the
yield/quality ratio for each ecological situationinfo:eu-repo/semantics/publishedVersio
Virtualization of pliocene sites in the Huelva province: valuating the paleontological heritage in differentiate educative settings I
El patrimonio paleontológico del Plioceno de la provincia de Huelva es uno
de los más importantes de España y referente europeo de moluscos de este
período. Sin embargo, no existe un inventario de catalogación básica de los
principales yacimientos ni de los principales grupos fósiles presentes, así como
de su importancia como patrimonio natural. El presente trabajo pretende rellenar
este notable vacío con una proyección tanto hacia materias preuniversitarias
como universitarias, así como hacia posibles instituciones y corporaciones
públicas susceptibles de utilizarlo en sus planes de ordenación. Por otro lado, se
pretende que actúe como mecanismo de interconexión entre titulaciones con bajo
número de alumnos de nuevo ingreso y los centros de Bachillerato, de forma que
incentive una posible elección de estos Grados por los alumnos de las opciones
científico-tecnológicas. También puede ser interesante para captar egresados
hacia Másteres Oficiales en Patrimonio Histórico y Natural. En este sentido, se
ha realizado un DVD documental sobre el patrimonio paleontológico del
Plioceno de la provincia de Huelva, concretamente de las formaciones “Arenas
de Huelva” y “Arenas de Bonares” desarrolladas en ambientes marinos someros
y costeros durante la última etapa de evolución neógena de la cuenca. Este
documental incluye una visión de conjunto de los principales yacimientos fósiles
de esta edad, así como una explicación de la evolución paleogeográfica de
nuestra provincia y los organismos que la han caracterizado en los últimos
millones de años. Esta aportación es aplicable en el trabajo de campo de varios
Grados y Posgrados universitarios y de fácil uso como material didáctico en
diversas asignaturas de E.S.O. y Bachillerato. Este trabajo se ha realizado en el
marco del proyecto de innovación docente (PID nº 10050) de la Universidad de
Huelva.The paleontological heritage from the Neogene in the province of Huelva is
one of the most important in Spain and it is considered a European reference site
for the mollusk fossil record from this period. However, there are not basic
inventories neither for the main sites nor the major fossil groups. Furthermore,
no inventories exist about their natural heritage importance. This work aims to
fill this significant gap for both pre-university and university levels, as well as to
public institutions and corporations that may use it in their management plans. In
addition, it is intended to act as an linking mechanism between university
degrees with low number of first-year students and high school centres, in order
to encourage a possible choice of these Bachelor’s degrees by scientific and
technological students. It may also be interesting to catch the attention of
graduates for Official Masters in Historical and Natural Heritage. In this sense, a
DVD-documentary has been made about the paleontological heritage from the
Pliocene in the province of Huelva, specifically from the “Arenas de Huelva”
and “Arenas de Bonares” formations. These units were developed in shallow
marine and coastal environments during the last stage of the Neogene evolution
in the Guadalquivir Basin. This documental includes an overview of main marine
fossil sites from this age and a brief explanation of the palaeogeographic
evolution of the Huelva province during the last million of years. This
contribution is useful for the fieldwork at Bachelor and Master Degree level and
it is easy to use as teaching materials in different ESO (Obligatory Secondary
Teaching) and High School subjects. This work has been support for an
Innovation in Teaching Project (PID No. 10050) of the Huelva University
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