Fresh state properties of concrete incorporating scrap tire rubber

The purpose of this work is to study fresh lightweight concrete containing recycled tire rubber aggregates. An experiment on concrete obtained by incorporating rubber aggregate with a ratio replacement of 5, 7.5 and 10% is done to evaluate the effect of these aggregates on the workability of two sets of concrete specimens. In the first set, coarse aggregates were replaced by different percentages by weight of granulate rubber and in the second set both coarse aggregates and sand were replaced rubber granulate and crumb rubber. Density, air content, compaction and slump tests are performed on the seven mixtures. Taking into account the density and water absorption differences between the natural aggregates and the rubber aggregates, the validity of the tests results are discussed. The results show that incorporating these rubber aggregates affects most rheological properties of lightweight concrete, for some application of concrete incorporating waste tire, rubber particles should be treated.info:eu-repo/semantics/publishedVersio

Semiclassical coherent state propagator for systems with spin

We derive the semiclassical limit of the coherent state propagator for systems with two degrees of freedom of which one degree of freedom is canonical and the other a spin. Systems in this category include those involving spin-orbit interactions and the Jaynes-Cummings model in which a single electromagnetic mode interacts with many independent two-level atoms. We construct a path integral representation for the propagator of such systems and derive its semiclassical limit. As special cases we consider separable systems, the limit of very large spins and the case of spin 1/2.Comment: 19 pages, no figure

Imaginary Phases in Two-Level Model with Spontaneous Decay

We study a two-level model coupled to the electromagnetic vacuum and to an external classic electric field with fixed frequency. The amplitude of the external electric field is supposed to vary very slow in time. Garrison and Wright [{\it Phys. Lett.} {\bf A128} (1988) 177] used the non-hermitian Hamiltonian approach to study the adiabatic limit of this model and obtained that the probability of this two-level system to be in its upper level has an imaginary geometric phase. Using the master equation for describing the time evolution of the two-level system we obtain that the imaginary phase due to dissipative effects is time dependent, in opposition to Garrison and Wright result. The present results show that the non-hermitian hamiltonian method should not be used to discuss the nature of the imaginary phases in open systems.Comment: 11 pages, new version, to appear in J. Phys.

Two interacting atoms in a cavity: exact solutions, entanglement and decoherence

We address the problem of two interacting atoms of different species inside a cavity and find the explicit solutions of the corresponding eigenvalues and eigenfunctions using a new invariant. This model encompasses various commonly used models. By way of example we obtain closed expressions for concurrence and purity as a function of time for the case where the cavity is prepared in a number state. We discuss the behaviour of these quantities and and their relative behaviour in the concurrence-purity plane.Comment: 10 pages, 3 figure

Qualidade do eucalipto clone h13 em sistemas integrados de produção de leite

Um dos grandes desafios nacionais, atualmente, é transformar áreas degradadas em áreas produtivas com a introdução de árvores em sistemas agropecuários como a integração lavoura pecuária floresta (iLPF) ou sistemas agrossilvipastoris. A presença de árvores em sistemas agropecuários pode proporcionar vários benefícios como a melhoria nos índices de conforto térmico animal, aumento na oferta de forragem ao longo do ano, redução da erosão, otimização do uso da energia solar e da ciclagem de nutrientes. Entretanto, ainda existem poucas informações em relação à qualidade do fuste em sistemas iLPF, que são fundamentais para acessar o mercado de madeira serrada, que propicia maior valor agregado e maiores taxas de retorno aos produtores. Com isso, objetivou-se avaliar a qualidade do fuste, fitossanidade e as características das árvores do clone de híbrido Eucaliptus grandis x Eucalyptus urophylla (clone H13) em sistema iLPF. O experimento foi instalado em blocos casualizados, com quatro repetições e dois tratamentos (1) R3: arranjo em renques triplos com espaçamento 3 x 2 entre árvores e 15 m entre renques de árvores (2) R2: renques duplos com espaçamento 3 x 2 m entre árvores e 50 m entre renques de árvores. O experimento está localizado no campo experimental da Embrapa Agrossilvipastoril, localizada no município de Sinop- MT, situado na região de transição dos biomas Cerrado e Floresta Amazônia. As avaliações da qualidade das árvores de eucalipto em sistema integrado foram realizadas aos 36 meses do plantio, durante a estação seca do ano, mediante observação visual qualidade do fuste (tortuosidade, bifurcações e posição da mesma), fitossanidade (pragas e doenças) e as características (copa, galhos e tronco quebrados, mortalidade, inclinação, e multibrotação das copas) das árvores. A qualidade do fuste encontra-se, em algum grau, comprometida em 68% e 74%, respectivamente, nos arranjos R2 e R3, sendo 55% e 65% da tortuosidade localizado na região apical da planta. No R2, 88% das árvores apresentou a fitossanidade comprometida por bovinos, sendo que 57% atingindo o lenho em mais de 5 cm. O arranjo R3 possui os mesmos danos, causados por bovinos, em 94% das árvores onde 53% são os mais severos com mais de 5cm do lenho exposto. Das características avaliadas, houve maior ocorrência em mortalidade das árvores no R3 com 65% e no R2 com 42%. O arranjo R2 mostrou-se mais vulnerável à quebra de copa com 13% e galhos também com 13%, quando comparado com o arranjo R3 que teve somente 5% das copas quebradas e 3% dos galhos

About ergodicity in the family of limacon billiards

By continuation from the hyperbolic limit of the cardioid billiard we show that there is an abundance of bifurcations in the family of limacon billiards. The statistics of these bifurcation shows that the size of the stable intervals decreases with approximately the same rate as their number increases with the period. In particular, we give numerical evidence that arbitrarily close to the cardioid there are elliptic islands due to orbits created in saddle node bifurcations. This shows explicitly that if in this one parameter family of maps ergodicity occurs for more than one parameter the set of these parameter values has a complicated structure.Comment: 17 pages, 9 figure

Semiclassical Propagation of Wavepackets with Real and Complex Trajectories

We consider a semiclassical approximation for the time evolution of an originally gaussian wave packet in terms of complex trajectories. We also derive additional approximations replacing the complex trajectories by real ones. These yield three different semiclassical formulae involving different real trajectories. One of these formulae is Heller's thawed gaussian approximation. The other approximations are non-gaussian and may involve several trajectories determined by mixed initial-final conditions. These different formulae are tested for the cases of scattering by a hard wall, scattering by an attractive gaussian potential, and bound motion in a quartic oscillator. The formula with complex trajectories gives good results in all cases. The non-gaussian approximations with real trajectories work well in some cases, whereas the thawed gaussian works only in very simple situations.Comment: revised text, 24 pages, 6 figure

Occurrence of periodic Lam\'e functions at bifurcations in chaotic Hamiltonian systems

We investigate cascades of isochronous pitchfork bifurcations of straight-line librating orbits in some two-dimensional Hamiltonian systems with mixed phase space. We show that the new bifurcated orbits, which are responsible for the onset of chaos, are given analytically by the periodic solutions of the Lam\'e equation as classified in 1940 by Ince. In Hamiltonians with C_${2v}$ symmetry, they occur alternatingly as Lam\'e functions of period 2K and 4K, respectively, where 4K is the period of the Jacobi elliptic function appearing in the Lam\'e equation. We also show that the two pairs of orbits created at period-doubling bifurcations of touch-and-go type are given by two different linear combinations of algebraic Lam\'e functions with period 8K.Comment: LaTeX2e, 22 pages, 14 figures. Version 3: final form of paper, accepted by J. Phys. A. Changes in Table 2; new reference [25]; name of bifurcations "touch-and-go" replaced by "island-chain

Orbital Magnetism in Ensembles of Parabolic Potentials

We study the magnetic susceptibility of an ensemble of non-interacting electrons confined by parabolic potentials and subjected to a perpendicular magnetic field at finite temperatures. We show that the behavior of the average susceptibility is qualitatively different from that of billiards. When averaged over the Fermi energy the susceptibility exhibits a large paramagnetic response only at certain special field values, corresponding to comensurate classical frequencies, being negligible elsewhere. We derive approximate analytical formulae for the susceptibility and compare the results with numerical calculations.Comment: 4 pages, 4 figures, REVTE