Absorption and percolation in the production of J/psi in heavy ion collisions

We present a simple model with string absorption and percolation to describe the J/psi suppression in heavy ion collisions. The NA50 data are fairly well explained by the model.Comment: 6 pages, 3 postscript figures include

Vibroacoustic analysis of plates with damping patches using a layerwise theory and the Rayleigh-Ritz

This work addresses issues on vibration and noise control studying an efficient model tosimulate the dynamic and vibroacoustic behavior of plates with constraining-layer dampingpatches. The proposed model, gathers the advantages of the layerwise models with thenumber of degrees of freedom of a single-layer theory. In addition, the Rayleigh-Ritz methodarises as a reliable alternative to the finite element method and offers a very efficient solutionregarding patches handling. Taking advantage of the resourceful solutions that this modeloffers the efficiency of the damping treatments is analyzed and discussed

Percolation approach to phase transitions in high energy nuclear collisions

We study continuum percolation in nuclear collisions for the realistic case in which the nuclear matter distribution is not uniform over the collision volume, and show that the percolation threshold is increased compared to the standard, uniform situation. In terms of quark-gluon plasma formation this means that the phase transition threshold is pushed to higher energies.Comment: 7 pages, 4 figures (PS), LaTeX2e using fontenc, amsmath, epsfi

Vibro-acoustic mitigation in composite structures using viscoelastic damping and soundproofing poroelastic technologies

This paper presents a numerical approach to study the vibro-acoustic behavior of composite structuresimmersed in a surrounding fluid medium. Such approach consists on the development of a coupled mitigationstrategy aiming either vibration suppression or acoustic attenuation. To this end, viscoelastic damping technologiesare applied to the composite host structure in a standard integrated layer damping configuration whereas surfacemounted poroelastic materials are included to perform the design of the damped and quieter composite structure.A finite element model is developed to model multi-layered structures which is based on the layerwise kinematicassumptions. On the other hand, poroelastic treatments are developed based on the Biot theory of poroelasticity.As a result, using the capabilities of the multi-layered model developed, different vibro-acoustic indicators are analyzed,namely, the mean square velocity and the radiation efficiency of the composite host plate, the transmissionloss of the fluid-plate system and the radiated sound power. In addition, a study addressing the physical couplingbetween both solid and fluid phases of the poroelastic material is performed in order to realise the consequences interms of the sound mitigation performance of the poroelastic treatment owing to the variability in the distributedstiffness of the host composite plate imposed by different fibers orientation

Percolation approach to quark gluon plasma in high energy pp collisions

We apply continuum percolation to proton-proton collisions and look for the possible threshold to phase transition from confined nuclear matter to quark gluon plasma. Making the assumption that J/Psi suppression is a good signal to the transition, we discuss this phenomenon for pp collisions, in the framework of a dual model with strings.Comment: 8 pages, 3 figure

Discrete layer finite element modeling of anisotropic laminated shells based on a refined semi - inverse mixed displacement field formulation

This paper concerns the finite element (FE) modeling of anisotropic laminated shells. A discretelayer approach is employed in this work and a single layer is first considered and isolatedfrom the multilayer shell structure. The weak form of the governing equations of theanisotropic single layer of the multilayer shell is derived with Hamiltons principle using amixed (stresses/displacements) definition of the displacement field, which is obtained througha semi-inverse (stresses/strains-displacements) approach. Results from 3-D elasticity solutionsare used to postulate adequate definitions of the out-of-plane shear stress components, which,in conjunction with the Reissner-Mindlin theory (or first order shear deformation theory) de-finitions of the shell in-plane stresses, are utilized to derive the mixed displacement field.Afterward, the single layer shell FE is regenerated to a 3-D form, which allows interlayerdisplacements and out-of-plane stresses continuity between adjacent interfaces of different layersto be imposed, and a multilayer shell FE is obtained by assembling, at an elemental FElevel, all the regenerated single layer FE contributions. A fully refined shell theory, wheredisplacement and full out-of-plane stresses continuity and homogeneous stress conditions onthe top and bottom surfaces are assured, is conceptually proposed, and a partially refined shelltheory, where the out-of-plane normal stress continuity is relaxed and a plane stress state is considered,is developed and used to derive a FE solution for segmented multilayer doubly-curvedanisotropic shells

Evolution of particle density in high-energy pp collisions

We study the evolution of the particle density, dn/d\eta at fixed \eta with the beam rapidity Y in the framework of string percolation model. Our main results are: (i) The width of the "plateau" increases proportionally to Y, (ii) limiting fragmentation is violated, and (iii) the particle density, reduces to a step function.Comment: 8 pages, 2 figures, to appear in Nuclear Physics A. Minor changes are don

Composição química e valor nutritivo de alimentos disponíveis na Amazônia para nutrição animal.

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