200 research outputs found
Finite-time singularity versus global regularity for hyper-viscous Hamilton-Jacobi-like equations
The global regularity for the two- and three-dimensional Kuramoto-Sivashinsky equations is one of the major open questions in nonlinear analysis. Inspired by this question, we introduce in this paper and family of hyper-viscous Hamilton-Jacobi-like equations parametrized by the exponent in the nonlinear term, p, where in the case of the usual Hamilton-Jacobi nonlinearity, p = 2. Under certain conditions on the exponent p we prove the short-time existence of weak and strong solutions to this family of equations. We also show the uniqueness of strong solutions. Moreover, we prove the blow-up in finite time of certain solutions to this family of equations when the exponent p > 2. Furthermore, we discuss the difference in the formation and structure of the singularity between the viscous and hyper-viscous versions of this type of equation
Local existence of analytical solutions to an incompressible Lagrangian stochastic model in a periodic domain
We consider an incompressible kinetic Fokker Planck equation in the flat
torus, which is a simplified version of the Lagrangian stochastic models for
turbulent flows introduced by S.B. Pope in the context of computational fluid
dynamics. The main difficulties in its treatment arise from a pressure type
force that couples the Fokker Planck equation with a Poisson equation which
strongly depends on the second order moments of the fluid velocity. In this
paper we prove short time existence of analytic solutions in the
one-dimensional case, for which we are able to use techniques and functional
norms that have been recently introduced in the study of a related singular
model.Comment: 32 page
Role of a Compatibilizer in the Structure and Micromechanical Properties of Recycled Poly(ethylene terephthalate)/Polyolefin Blends with Clay
The comparison of the degree of crystallinity
and the micromechanical properties in the blends of recycled amorphous poly(ethylene terephthalate) (PET)with isotactic polypropylene (iPP) and high-density polyethylene (HDPE) with a compatibilizer in different proportions is reported. The physical study of the composites of the compatibilized blends and clay is also discussed. The analysis, performed by means of wide-angle X-ray scattering and differential scanning calorimetry techniques, permits us to describe, at microscale level, the role of the
compatibilizer on the structure and microhardness of the polymer blends that we studied. The results reveal that PET was incompatible with both iPP and HDPE. However,
the presence of the compatibilizer, a styreneâethylene/butyleneâstyrene block copolymer grafted with maleic anhydride,
allowed the compatibilization of these polymers. In the PET/iPP blends, the clay seemed to have a nucleating effect on the iPP and also induced a hardness increase in the compatibilized blends. On the other hand, in case of PET/HDPE, the crystallinity of these samples (pure blends,blends with compatibilizer, and blends with compatibilizer plus clay) only depended on their composition. Similarly to the PET/iPP blends, the addition of clay induced an increase in the hardness of the ompatibilized blends.Peer reviewe
Uniqueness of the compactly supported weak solutions of the relativistic Vlasov-Darwin system
We use optimal transportation techniques to show uniqueness of the compactly
supported weak solutions of the relativistic Vlasov-Darwin system. Our proof
extends the method used by Loeper in J. Math. Pures Appl. 86, 68-79 (2006) to
obtain uniqueness results for the Vlasov-Poisson system.Comment: AMS-LaTeX, 21 page
On the analyticity and Gevrey class regularity up to the boundary for the Euler Equations
We consider the Euler equations in a three-dimensional Gevrey-class bounded
domain. Using Lagrangian coordinates we obtain the Gevrey-class persistence of
the solution, up to the boundary, with an explicit estimate on the rate of
decay of the Gevrey-class regularity radius
Eternal solutions to a singular diffusion equation with critical gradient absorption
The existence of nonnegative radially symmetric eternal solutions of exponential self-similar type is investigated for the singular diffusion equation with critical gradient absorption \begin{equation*} \partial_{t} u-\Delta_{p} u+|\nabla u|^{p/2}=0 \quad \;\;\hbox{in}\;\; (0,\infty)\times\real^N \end{equation*} where . Such solutions are shown to exist only if the parameter ranges in a bounded interval which is in sharp contrast with well-known singular diffusion equations such as when or the porous medium equation when . Moreover, the profile decays to zero as in a faster way for than for but the algebraic leading order is the same in both cases. In fact, for large , decays as while behaves as when
DIAGNĂSTICO DA QUALIDADE DA ĂGUA AO LONGO DE UM CANAL DE CONCRETO: UM ESTUDO DE CASO DO CANAL DO SERTĂO ALAGOANO - BRASIL
Para atender a demanda, a transferĂȘncia de ĂĄgua de rios por canal Ă© uma prĂĄtica comum no Nordeste brasileiro. O Canal do SertĂŁo Alagoano capta ĂĄgua do rio SĂŁo Francisco (no reservatĂłrio ApolĂŽnio Sales) para abastecer municĂpios do estado de Alagoas. O objetivo deste trabalho foi analisar a evolução de parĂąmetros fĂsico-quĂmicos da ĂĄgua (temperatura, pH, turbidez, condutividade, dureza, sulfatos, cloretos, nitrogĂȘnio total e fĂłsforo total) ao longo dos 29 km iniciais. Foram realizadas duas coletas no perĂodo seco em 10 pontos. Por meio do teste nĂŁo-paramĂ©trico MannWhitney, evidenciou-se que temporalmente as duas coletas sĂŁo significativamente diferentes para todos os parĂąmetros, mesmo sendo ambas realizadas no perĂodo seco. Longitudinalmente, nas duas coletas, temperatura, pH e condutividade, foram significativamente diferentes entre o inĂcio e o final dos 29 km, apresentando uma tendĂȘncia crescente nos valores. Quanto Ă qualidade, conforme a Resolução 357/2005 do CONAMA, a ĂĄgua do Canal apresentou valores dentro da Classe 1, com exceção do fĂłsforo total
Probabilistic representation for solutions of an irregular porous media type equation: the degenerate case
We consider a possibly degenerate porous media type equation over all of
with , with monotone discontinuous coefficients with linear
growth and prove a probabilistic representation of its solution in terms of an
associated microscopic diffusion. This equation is motivated by some singular
behaviour arising in complex self-organized critical systems. The main idea
consists in approximating the equation by equations with monotone
non-degenerate coefficients and deriving some new analytical properties of the
solution
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