Search results for "solution"
showing 10 items of 5638 documents
Estimation of the volume of Posidonia oceanica detritus accumulations along Sicilian coasts by using very high resolution images
2019
Posidonia oceanica meadows are among the most important marine coastal ecosystems in the Mediterranean Sea due to several roles they are able to play. They, in fact, support high levels of primary production, enhance sedimentation of suspended particles through their canopies, prevent resuspension of marine sediments by means of roots and rhizomes and counteract coast erosion. Part of the primary production of this seagrass is not transferred to herbivores either immediately to detritus pathway but it can accumulate on the shore in form of banquette, typical structures exerting a significant role in protection of beaches from erosion. To accurately measure the extension, morphology, volume …
The use of very high-resolution images for mapping of Posidonia oceanica reef
2020
Posidonia oceanica is an endemic Mediterranean seagrass that forms wide and dense meadows from the surface up to about 40 m depth. P. oceanica can develop on matte, a typical terraced structure built up by itself, consisting of intertwined rhizomes, roots and sediment, which may allow shoots to reach the sea surface, where may form typical reefs (récif barrière) considered “natural monuments”. These structures have received increasing attention for the potential ecosystem services they provide in protecting the coasts from erosion, forming new habitats (coastal lagoons) and contributing to carbon sink. P. oceanica reefs are particularly exposed to the expected increase in temperature and to…
A large-area scintillating fibre detector for relativistic heavy ions
1998
Abstract A scintillating fibre detector for relativistic heavy ions with an active area of 50 × 50 cm 2 has been developed and was tested with various ion beams (1 ≤ Z ≤ 92). At count rates of up to 10 5 particles/s, the position resolution was found to be determined by the fibre width of 1 mm; depending on the nuclear charge of the beam, efficiencies between 89% and 100% and time resolutions between 800 and 200 ps (FWHM) were obtained.
The behavior of solutions of a parametric weighted (p, q)-laplacian equation
2021
<abstract><p>We study the behavior of solutions for the parametric equation</p> <p><disp-formula> <label/> <tex-math id="FE1"> \begin{document}$ -\Delta_{p}^{a_1} u(z)-\Delta_{q}^{a_2} u(z) = \lambda |u(z)|^{q-2} u(z)+f(z,u(z)) \quad \mbox{in } \Omega,\, \lambda &gt;0, $\end{document} </tex-math></disp-formula></p> <p>under Dirichlet condition, where $ \Omega \subseteq \mathbb{R}^N $ is a bounded domain with a $ C^2 $-boundary $ \partial \Omega $, $ a_1, a_2 \in L^\infty(\Omega) $ with $ a_1(z), a_2(z) &gt; 0 $ for a.a. $ z \in \Omega $, $ p, q \in (1, \infty) $ and $ \Delta_{p}^{a_1}, \Delta_{q}^{a_2} $ are weighted …
Positive solutions of discrete boundary value problems with the (p,q)-Laplacian operator
2017
We consider a discrete Dirichlet boundary value problem of equations with the (p,q)-Laplacian operator in the principal part and prove the existence of at least two positive solutions. The assumptions on the reaction term ensure that the Euler-Lagrange functional, corresponding to the problem, satisfies an abstract two critical points result.
A singular (p,q)-equation with convection and a locally defined perturbation
2021
We consider a parametric Dirichlet problem driven by the (p,q)-Laplacian and a reaction which is gradient dependent (convection) and the competing effects of two more terms, one a parametric singular term and a locally defined perturbation. We show that for all small values of the parameter the problem has a positive smooth solution.
An existence result for a Neumann problem
2015
The main result of this paper deals with the existence of at least one positive solution for a second order Neumann boundary value problem. Such a result is obtained by using an abstract coincidence point theorem that allows to get our conclusion under non standard conditions on the nonlinearity.
Bifurcation phenomena for the positive solutions of semilinear elliptic problems with mixed boundary conditions
2016
We consider a parametric semilinear elliptic equation with a Cara-theodory reaction which exhibits competing nonlinearities. It is "concave" (sub-linear) near the origin and "convex" (superlinear) or linear near $+\infty$. Using variational methods based on the critical point theory, coupled with suitable truncation and comparison techniques, we prove a bifurcation-type theorem, describing the set of positive solutions as the parameter varies.
Image quality analysis of
2019
Background 44Sc has been increasingly investigated as a potential alternative to 68Ga in the development of tracers for positron emission tomography (PET). The lower mean positron energy of 44Sc (0.63 MeV) compared to 68Ga (0.83 MeV) can result in better spatial image resolutions. However, high-energy γ-rays (1157 keV) are emitted at high rates (99.9%) during 44Sc decay, which can reduce image quality. Therefore, we investigated the impact of these physical properties and performed an unbiased performance evaluation of 44Sc and 68Ga with different imaging phantoms (image quality phantom, Derenzo phantom, and three-rod phantom) on two preclinical PET scanners (Mediso nanoScan PET/MRI, Siemen…
Quantum chemical modelling of point defects in KNbO3 perovskite crystals
2000
Abstract We present results of semi-empirical quantum chemical calculations for several perovskite KNb x Ta 1−x O 3 (KTN) solid solutions, as well as point intrinsic defects – F centers and hole polarons bound to K vacancy – in KNbO 3 . Method of the intermediate neglect of the differential overlap (INDO) was combined with typically 320-atom supercells and atomic geometry optimization. Analysis of the optimized atomic and electronic structure has clearly demonstrated that several nearest Nb atoms substituting for Ta in KTaO 3 – unlike Ta impurities in KNbO 3 – reveal the self-ordering effect, which probably triggers the ferroelectricity observed in KTN. We predict co-existence of one-site (…