Simulation of subcritical crack propagation in quase-brittle materials applying a version of the discrete element method formed by beams

Há numerosas aplicações de interesse tecnológico onde materiais de comportamento quase frágil, como é o caso de materiais cimentícios, rochas e materiais compostos formados pela mistura de cerâmicas com outras fases, são submetidos a cargas oscilantes e sofrem degradação das suas propriedades. Desenvolver ferramentas de análise que permitam entender e prever os mecanismos que governam esta degradação é um problema aberto na engenharia moderna. Neste contexto, no presente trabalho, se utiliza uma versão do método dos elementos discretos (DEM) formado por barras para explorar as possibilidades do mesmo na simulação dos mecanismos de degradação que ocorrem em materiais quase frágeis quando submetidos à fadiga. Simulações sobre corpos de prova de geometria simples são apresentadas e vários aspectos deste problema são discutidos, entre eles: é explorada a relação entre os parâmetros micro e macromecânicos do modelo empregado e como o efeito de escala é capturado e influi nesta relação. Os resultados preliminares apresentados deixam em evidência a potencialidade da metodologia proposta para compreender os micromecanismos de dano que ocorrem nos materiais quase frágeis e também para predizer sua evolução.There are numerous applications, of technological interest, where materials of quasi‐brittle behavior, as in the case of cement‐based composite materials, rocks and composites formed by the mixture of ceramics with other phases, are subjected to oscillating loads and suffer degradation of its properties. To develop analysis tools that allow to understand and to predict this degradation governing mechanisms is an opened problem in modern engineering. In this context, in the present work, it is used a version of the discrete element method formed by beams to explore its possibilities in simulating the degradation mechanisms that occur in quasi‐brittle materials when subjected to fatigue. Simulations over simple geometry test subjects are presented and several aspects of this problem are discussed and among the problems: it is explored the relationship between micro and macro mechanic parameters of the used model and how the scale effect is captured and influences this relationship. The presented preliminary results show the potentiality of the proposed methodology to understand the micro mechanisms of damage that occur in quasi‐brittle materials and also to predict its evolution.Peer Reviewe

Prototype implementation of a smart locker

Smart lockers are intelligent storage units that are increasingly being adopted to help solving the last mile problem. This paper focuses on the concept of an individual smart locker that can be installed at the entrance of a residential house. First, the operational principle and advantages of this concept are discussed. Then, the design, development and implementation of a functional prototype is demonstrated. The prototype was submitted to tests and can be used as a proof of concept.info:eu-repo/semantics/publishedVersio

Consequences of temperature fluctuations in observables measured in high energy collisions

We review the consequences of intrinsic, nonstatistical temperature fluctuations as seen in observables measured in high energy collisions. We do this from the point of view of nonextensive statistics and Tsallis distributions. Particular attention is paid to multiplicity fluctuations as a first consequence of temperature fluctuations, to the equivalence of temperature and volume fluctuations, to the generalized thermodynamic fluctuations relations allowing us to compare fluctuations observed in different parts of phase space, and to the problem of the relation between Tsallis entropy and Tsallis distributions. We also discuss the possible influence of conservation laws on these distributions and provide some examples of how one can get them without considering temperature fluctuations.Comment: Revised version of the invited contribution to The European Physical Journal A (Hadrons and Nuclei) topical issue about 'Relativistic Hydro- and Thermodynamics in Nuclear Physics' guest eds. Tamas S. Biro, Gergely G. Barnafoldi and Peter Va

Rare Decays of \Lambda_b->\Lambda + \gamma and \Lambda_b ->\Lambda + l^{+} l^{-} in the Light-cone Sum Rules

Within the Standard Model, we investigate the weak decays of $\Lambda_b \to \Lambda + \gamma$ and $\Lambda_b \to \Lambda + l^{+} l^{-}$ with the light-cone sum rules approach. The higher twist distribution amplitudes of $\Lambda$ baryon to the leading conformal spin are included in the sum rules for transition form factors. Our results indicate that the higher twist distribution amplitudes almost have no influences on the transition form factors retaining the heavy quark spin symmetry, while such corrections can result in significant impacts on the form factors breaking the heavy quark spin symmetry. Two phenomenological models (COZ and FZOZ) for the wave function of $\Lambda$ baryon are also employed in the sum rules for a comparison, which can give rise to the form factors approximately 5 times larger than that in terms of conformal expansion. Utilizing the form factors calculated in LCSR, we then perform a careful study on the decay rate, polarization asymmetry and forward-backward asymmetry, with respect to the decays of $\Lambda_b \to \Lambda \gamma$, $\Lambda l^{+}l^{-}$.Comment: 38 pages, 15 figures, some typos are corrected and more references are adde

Economic analysis of an agrosilvipastoral system for a mountainous area in Zona da Mata Mineira, Brazil

The objective of this work was to evaluate the economic viability of an agrosilvipastoral system developed for Zona da Mata mountainous areas in Minas Gerais state, Brazil, as well as to compare different options for wood (Eucalyptus grandis and Acacia mangium) commercialization of the second thinning. The data were obtained from a 10 year-old agrosilvipastoral system established in four hectares at Embrapa Gado de Leite station in Coronel Pacheco, MG, Brazil. As evaluation criteria for the economic viability analysis, the adopted methods were the net present value (NPV) and the internal rate of return (IRR), both calculated at 6% interest rate. Despite the small difference, adding value to forest products increased the attractiveness of the proposed system. Considered separately, the agricultural activity was impracticable, whereas the forestry and livestock activities were independently viable. The studied system seems to be equally tolerant to price variations for forest and livestock products, as well as strongly tolerant to variations in production costs