Comment on "Tricritical Behavior in Rupture Induced by Disorder"

In their letter, Andersen, Sornette, and Leung [Phys. Rev. Lett. 78, 2140 (1997)] describe possible behaviors for rupture in disordered media, based on the mean field-like democratic fiber bundle model. In this model, fibers are pulled with a force which is distributed uniformly. A fiber breaks if the stress on it exceeds a threshold chosen from a probability distribution, and the force is then redistributed over the intact fibers. Andersen et al. claim the existence of a tricritical point, separating a "first-order" regime, characterized by a sudden global failure, from a "second-order" regime, characterized by a divergence in the breaking rate. We show that a first-order transition is an artifact of a (large enough) discontinuity put by hand in the disorder distribution. Thus, in generic physical cases, a first-order regime is not present. This result is obtained from a graphical method, which, unlike Andersen at al.'s analytical solution, enables us to distinguish the various classes of qualitatively different behaviors of the model.Comment: 1 page, 1 figure included, revte

An Introduction to Breakdown Phenomena in Disordered Systems

The rupture of a medium under stress typifies breakdown phenomena. More generally, the latter encompass the dynamics of systems of many interacting elements governed by the interplay of a driving force with a pinning disorder, resulting in a macroscopic transition. A simple mean-field formalism incorporating these features is presented and applied to systems representative of fracture phenomena, social dilemmas, and magnets out of equilibrium. The similarities and differences in the corresponding mathematical structures are emphasized. The solutions are best obtained from a graphical method, from which very general conclusions may be drawn. In particular, the various classes of disorder distribution are treated without reference to a particular analytical or numerical form, and are found to lead to qualitatively different transitions. Finally, the notion of effective (or phenomenological) theory is introduced and illustrated for non-equilibrium disordered magnets.Comment: Pedagogical article published as part of a special issue on thermodynamics and statistical physics; 20 page

Cuidados no vinhedo que antecedem à colheita, para obtenção de uva de qualidade.

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Dynamics of a Generalized Cosmological Scalar-Tensor Theory

A generalized scalar-tensor theory is investigated whose cosmological term depends on both a scalar field and its time derivative. A correspondence with solutions of five-dimensional Space-Time-Matter theory is noted. Analytic solutions are found for the scale factor, scalar field and cosmological term. Models with free parameters of order unity are consistent with recent observational data and could be relevant to both the dark-matter and cosmological-"constant" problems.Comment: 13 page

AIR VELOCITY PROFILES IN AIR BLAST FREEZERS FILLED WITH BOXES OF FRUIT PULP MODELS

The changes in the air velocities caused by the resistance for the air flow due to fruit pulp model packaged (100 grams) and conditioned in multi layers boxes during freezing process were evaluated and air flow rate were estimated using a method of treatment of the experimental data. The air velocities were measured before the air pass through the pillage of multi layer boxes in the air stream. For the measurements processing was used a non linear regression routine. Air flow rate measured by the present method resulted of the numerical integration of air velocities adjusted profile. Results presented a relative difference 10 % higher than the standard average procedure, which consists in averaging the air velocity measurements performed at each point of the section. In the same fan operation conditions, the results shown for the 7 layers arrays of product in the boxes which the air velocity was 62% lower than the 3 layers arrays and 50.9 % lower than the 5 layers arrays of product. These results were proportional to the bulk area for the air flow

Macroeducação e permacultura urbana: Análise do impacto da macroeducação em unidades familiares e a eficácia da adoção de tecnologia alternativa.

Resumo: A crescente urbanização tem acarretado grandes problemas com relação aos recursos hídricos disponíveis. A permacultura se apresenta como ferramenta socioambiental, e juntamente com os conceitos da bioconstrução servem de motivação à adoção de práticas sustentáveis numa relação de equilíbrio entre homem e natureza. A educação ambiental se propõe de forma pedagógica a estimular a formação de comunidades sustentáveis, por onde, segundo os conceitos da Macro-educação, é possível aplicar de uma forma eficaz e objetiva, o planejamento estratégico, estimulando a adoção de tecnologias sustentáveis e um uso mais consciente dos recursos naturais. Este trabalho visa sensibilizar a comunidade do bairro Jardim Santana no município de Campinas a adotar novos hábitos e atitudes ecologicamente corretos, e estimular a adoção de tecnologias alternativas como kit de captação de águas pluviais com garrafas pet, que terá como aplicação alternativa a irrigação da horta urbana, de uma unidade familiar, com o intuito de reduzir o consumo da água tratada disponibilizada pelas entidades locais. Abstract: Increasing urbanization has caused major problems in relation to the available water resources. The permaculture presents itself as a socio-environmental tool, and with the concepts of bio construction, is used as motivation for adoption of sustainable practices balancing man and nature. Environmental education is proposed as pedagogical to stimulate the sustainable communities generation, where, according to the concepts of Macro-education, it is possible to apply in an effective way and objective, the strategic planning, encouraging the adoption of sustainable Technologies and a conscious usage of the natural resources. This work aims to involve the community in Santana neighborhood in Campinas, to adopt new friendly environmental habits and attitudes and encourage adoption of alternative technologies to implement a kit of rainwater reception with pet bottles. This will be applied in irrigation of urban plantation at residential units, with the aim of reducing the cost of the treated water made available by the local authorities

Implantação e manejo de vinhedos de base ecológica.

bitstream/item/55337/1/Documentos-75.pd