Simulation of Chua's Circuit by Means of Interval Analysis

The Chua's circuit is a paradigm for nonlinear scientific studies. It is usually simulated by means of numerical methods under IEEE 754-2008 standard. Although the error propagation problem is well known, little attention has been given to the relationship between this error and inequalities presented in Chua's circuit model. Taking the average of round mode towards $+\infty$ and $-\infty$, we showed a qualitative change on the dynamics of Chua's circuit.Comment: 6th International Conference on Nonlinear Science and Complexity - S\~ao Jos\'e dos Campos, 2016, p. 1-

On fermionic tilde conjugation rules and thermal bosonization. Hot and cold thermofields

A generalization of Ojima tilde conjugation rules is suggested, which reveals the coherent state properties of thermal vacuum state and is useful for the thermofield bosonization. The notion of hot and cold thermofields is introduced to distinguish different thermofield representations giving the correct normal form of thermofield solution for finite temperature Thirring model with correct renormalization and anticommutation properties.Comment: 13 page

Attractive Casimir effect in an infrared modified gluon bag model

In this work, we are motivated by previous attempts to derive the vacuum contribution to the bag energy in terms of familiar Casimir energy calculations for spherical geometries. A simple infrared modified model is introduced which allows studying the effects of the analytic structure as well as the geometry in a clear manner. In this context, we show that if a class of infrared vanishing effective gluon propagators is considered, then the renormalized vacuum energy for a spherical bag is attractive, as required by the bag model to adjust hadron spectroscopy.Comment: 7 pages. 1 figure. Accepted for publication in Physical Review D. Revised version with improved analysis and presentation, references adde

A Educomunicação na Pedagogia.

Considerando a importância da formação profissional de educadores reflexivos e com visão crítica diante do contexto da Sociedade da Informação, este artigo discute a relevância da Educomunicação, a partir de uma pesquisa desenvolvida na Faculdade de Educação da Universidade Estadual de Campinas - UNICAMP que procurou apurar qual a concepção de Educomunicação que norteia a racionalidade dos formandos em Pedagogia. O objetivo geral foi compreender como poderiam ser introduzidos os paradigmas conceituais da Educomunicação no currículo do curso de Pedagogia, de forma que fosse possível também se identificar estratégicas que, sendo adotadas, poderiam favorecer a introdução deste conceito na formação e na prática profissional dos futuros educadores, a partir da introdução de um currículo que incorpore esta lógica, desde o início do processo de formação.Intercom 2013

Coherent pressure structures in turbulent channel flow

Most of the studies on pressure fluctuations in wall-bounded turbulent flows aim at obtaining statistics as power spectra and scaling laws, especially at the walls. In the present study we study energetic coherent pressure structures of turbulent channel flows, aiming at a characterization of dominant coherent structures throughout the channel. Coherent structures are detected using spectral proper orthogonal decomposition (SPOD) and modeled using resolvent analysis, similar to related works dealing with velocity fluctuations, but using pressure fluctuations as the output of interest. The resolvent operator was considered with and without the Cess eddy viscosity model. Direct numerical simulations (DNSs) of incompressible turbulent channel flows at friction Reynolds numbers of approximately 180 and 550 were employed as databases. Three representative dominant structures emerged from a preliminary spectral analysis: near-wall, large-scale and spanwise-coherent structures. For frequency-wavenumber combinations corresponding to these three representative structures, SPOD results show a strong dominance of the leading mode, highlighting low-rank behavior of pressure fluctuations. The leading resolvent mode closely agrees with the first SPOD mode, providing support to studies that showed better performance of resolvent-based estimators when predicting pressure fluctuations compared to velocity fluctuations. The dominant mechanisms of the analyzed modes are seen to be the generation of quasi-streamwise vortices with pressure fluctuations appearing close to vortex centers. A study on the individual contributions of the nonlinear terms (treated as forcing in resolvent analysis) to the pressure output reveals that each forcing component plays a constructive role to the input-output formulation, which also helps understanding the weaker role of forcing color in driving pressure fluctuations.Comment: 24 pages, 23 figure

Development of structural layers PVC incorporating phase change materials for thermal energy storage

The use of poly(vinyl chloride) (PVC) structural layers incorporating phase change materials (PCM) for latent heat thermal energy storage (LHTES) has become more attractive in the recent years compared to other supporting materials. In this study, PVC layers with different types of PCM were prepared using blending and compression moulding methods. Two types of synthesized PCM, one based on paraffin and calcium carbonate (PCM@CaCO3) and the other on paraffin, silica and graphene oxide (PCM@SiGO) have been developed to enhance the thermal conductivity of the PVC matrix and thus achieve a more effective charging and discharging process. PVC layers prepared using a commercial PCM (PCM@BASF) were also prepared for comparison. SEM images and DSC results reveal homogeneous distribution of the PCM in PVC layers and that most PCM particles are undamaged. The shell material (in the case of PCM@BASF) and the shape stability (in the case of synthesized PCM@CaCO3 and PCM@SiGO) prevent leakage of molten paraffin during the PVC layer production. The thermal conductivity profile of the PVC layer without PCM have a decreasing tendency with the temperature increase when determined using different measurement approaches, the transient plane heat source method (HotDisk Analyser, TPS 2500 S) and thermal flux meter method (steady-state method). However, for PVC layers with PCM the thermal conductivity profile shows a different behaviour when the mean surface temperature of the specimen is below the phase change transition temperature range (increasing tendency). During phase change transition (18–26 °C), the thermal conductivity presents two distinct tendencies. Firstly, the thermal conductivity reveals a decreasing tendency as the mean temperature of the specimen rises and afterwards an increasing tendency. Secondly, when the mean surface temperature is above the phase change transition temperature range, the thermal conductivity profile shows a decreasing tendency, independent of the PCM. The mechanical properties of PVC layers were also assessed and the results obtained revealed that the incorporation of PCM into the PVC matrix reduces the mechanical performance of the composites, however for LHETS applications not subjected to high tensile stress levels (over 1 kPa), this is not a significant drawback.publishe

Analytical solution of a model for complex food webs

We investigate numerically and analytically a recently proposed model for food webs [Nature {\bf 404}, 180 (2000)] in the limit of large web sizes and sparse interaction matrices. We obtain analytical expressions for several quantities with ecological interest, in particular the probability distributions for the number of prey and the number of predators. We find that these distributions have fast-decaying exponential and Gaussian tails, respectively. We also find that our analytical expressions are robust to changes in the details of the model.Comment: 4 pages (RevTeX). Final versio

Acompanhamento de um biodigestor de fluxo ascendente para tratamento de efluentes da suinocultura.

Projeto/Plano de Ação: 02.07.06.007

Determinação do teor de fibra de cana-de-açúcar em diferentes biomas visando o processamento de resíduos para a produção de biocombustíveis sólidos e biomassa energética.

A demanda mundial por energia vem aumentando rapidamente ? muito mais rapidamente do que o ritmo de crescimento da população. O Brasil é hoje o 9o maior consumidor de energia do mundo e espera-se um crescimento da demanda energética em mais de 50% até 2030. O desafio é atender essa crescente demanda por energia de forma confiável, escalável, sustentável e economicamente eficiente. A cultura da cana-de-açúcar é uma opção bioenergética que merece muito destaque, haja vista que, apesar de todo o desenvolvimento do setor sucro-alcooleiro brasileiro, apenas 26% da energia presente na cana é convertida em energia útil (na forma de etanol). Isto se deve ao subaproveitamento ou não uso do bagaço e da palha na produção de energias elétrica, térmica ou de etanol de 2a geração. Uma tonelada de cana-de-açúcar (colmo + bagaço) produz energia equivalente a 0,17 tonelada de petróleo, podendo gerar 17,4 toneladas de petróleo/ha, considerando a produtividade média da cultura no Brasil. Desta maneira, pode-se desenvolver e produzir variedades de cana-de-açúcar específicas para o uso integral de toda a sua parte aérea diretamente na alimentação de fornos e caldeiras, para produção de energias elétrica e térmica. De forma que o objetivo deste trabalho foi investigar a possível existência de diferença maior do que 20% nos teores de fibras de duas variedades de cana-de-açúcar cultivadas em diferentes biomas brasileiros em contraste com o Bioma Caatinga, que traria como vantagem consequente a elevação do Poder Calorífico Total da biomassa destas variedades