Scaling attractors in interacting teleparallel dark energy

It has been proposed recently the existence of a non-minimal coupling between a canonical scalar field (quintessence) and gravity in the framework of teleparallel gravity, motivated by similar constructions in the context of General Relativity. The dynamics of the model, known as teleparallel dark energy, has been further developed, but no scaling attractor has been found. Here we consider a model in which the non-minimal coupling is ruled by a dynamically changing coefficient α≡f,φ/(f)1/2, with f(φ) an arbitrary function of the scalar field φ. It is shown that in this case the existence of scaling attractors is possible, which means that the universe will eventually enter these scaling attractors, regardless of the initial conditions. As a consequence, the cosmological coincidence problem could be alleviated without fine-tunings. © 2013 IOP Publishing Ltd and Sissa Medialab srl.

Multiplicity and transverse momentum dependence of two- and four-particle correlations in pPb and PbPb collisions

Measurements of two- and four-particle angular correlations for charged particles emitted in pPb collisions are presented over a wide range in pseudorapidity and full azimuth. The data, corresponding to an integrated luminosity of approximately 31nb-1, were collected during the 2013 LHC pPb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. The results are compared to 2.76 TeV semi-peripheral PbPb collision data, collected during the 2011 PbPb run, covering a similar range of particle multiplicities. The observed correlations are characterized by the near-side (|δφ|≈0) associated pair yields and the azimuthal anisotropy Fourier harmonics (vn). The second-order (v2) and third-order (v3) anisotropy harmonics are extracted using the two-particle azimuthal correlation technique. A four-particle correlation method is also applied to obtain the value of v2 and further explore the multi-particle nature of the correlations. Both associated pair yields and anisotropy harmonics are studied as a function of particle multiplicity and transverse momentum. The associated pair yields, the four-particle v2, and the v3 become apparent at about the same multiplicity. A remarkable similarity in the v3 signal as a function of multiplicity is observed between the pPb and PbPb systems. Predictions based on the color glass condensate and hydrodynamic models are compared to the experimental results. © 2013 CERN.

Cosmological dynamics of tachyonic teleparallel dark energy

A detailed dynamical analysis of the tachyonic teleparallel dark energy model, in which a noncanonical scalar field (tachyon field) is nonminimally coupled to gravitation, is performed. It is found that, when the nonminimal coupling is ruled by a dynamically changing coefficient α≡f ,φ/√f, with f(φ) an arbitrary function of the scalar field φ, the Universe may experience a field-matter-dominated era φMDE, in which it has some portions of the energy density of φ in the matter dominated era. This is the most significant difference in relation to the so-called teleparallel dark energy scenario, in which a canonical scalar field (quintessence) is nonminimally coupled to gravitation. © 2013 American Physical Society.

Optimal impulsive control in a powered Swing-By

This paper studies the problem of applying an impulsive control in a spacecraft that is performing a Swing-By maneuver. The objective is to study the changes in velocity, energy and angular momentum for this maneuver as a function of the three usual parameters of the standard Swing-By plus the three parameters (the magnitude of the impulse, the point of its application and the angle between the impulse and the velocity of the spacecraft) that specify the impulse applied. The dynamics used is the restricted three body problem under the regularization of Lemaitre, made to increase the accuracy of the numerical integration near the primaries. The present research develops an algorithm to calculate the variation of energy and angular momentum in a maneuver where the application of the impulsive control occurs before or after the passage of the spacecraft by the periapsis, but within the sphere of influence of the secondary body and in a non-tangential direction. Using this approach, it is possible to find the best position and direction to apply the impulse to maximize the energy change of the total maneuver. The results showed that the application of the impulse at the periapsis and in the direction of motion of the spacecraft is usually not the optimal solution.

Visible to infrared energy conversion in Pr3+-Yb3+ co-doped fluoroindate glasses

Processes involving visible to infrared energy conversion are presented for Pr3+-Yb3+ co-doped fluoroindate glasses. The emission in the visible and infrared regions, the luminescence decay time of the Pr 3+:3P0 → 3H4 (482 nm), Pr3+:1D2 → 3H6 (800 nm), Yb3+:2F5/2 → 2F 7/2 (1044 nm) transitions and the photoluminescence excitation spectra were measured in Pr3+ samples and in Pr3+-Yb 3+ samples as a function of the Yb3+ concentration. In addition, energy transfer efficiencies were estimated from Pr3+: 3P0 and Pr3+:1D2 levels to Yb3+:2F7/2 level. Down-Conversion (DC) emission is observed due to a combination of two different processes: 1-a one-step cross relaxation (Pr3+:3P0 → 1G4; Yb3+:2F7/2 → 2F5/2) resulting in one photon emitted by Pr3+ (1G4 → 3H5) and one photon emitted by Yb3+ (2F7/2 → 2F5/2); 2-a resonant two-step first order energy transfer, where the first part of energy is transferred to Yb3+ neighbor through cross relaxation (Pr3+:3P0 → 1G4; Yb3+:2F7/2 → 2F5/2) followed by a second energy transfer step (Pr 3+:1G4 → 3H4; Yb3+:2F7/2 → 2F5/2). A third process leading to one IR photon emission to each visible photon absorbed involves cross relaxation energy transfer (Pr3+: 1D2 → 3F4; Yb 3+:2F7/2 → 2F5/2). © 2013 Elsevier B.V. All rights reserved.

Estudo dos efeitos da compensação série no desempenho transitório dos sistemas de energia elétrica sob o enfoque da energia

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

O uso da análise de Fourier, de Wavelets e dos expoentes de Lyapunov no estudo de um sistema dinâmico não-ideal com atrito seco e excitação externa

Pós-graduação em Física - IGCE

Renewable energy sources in Latin America and the Caribbean: situation and policy proposals

Includes bibliography

Controle nebuloso aplicado em asas adaptativas utilizando ligas de memória de forma

Pós-graduação em Engenharia Mecânica - FEIS

Interpretação do gráfico de Hingle através de rede competitiva angular

A saturação de água é a principal propriedade petrofísica para a avaliação de reservatórios de hidrocarbonetos, pois através da análise dos seus valores é definida a destinação final do poço recém perfurado, como produtor ou poço seco. O cálculo da saturação de água para as formações limpas é, comumente, realizado a partir da equação de Archie, que envolve a determinação da resistividade da zona virgem, obtida a partir de um perfil de resistividade profunda e o cálculo de porosidade da rocha, obtida a partir dos perfis de porosidade. A equação de Archie envolve ainda, a determinação da resistividade da água de formação, que normalmente necessita de definição local e correção para a profundidade da formação e da adoção de valores convenientes para os coeficientes de Archie. Um dos métodos mais tradicionais da geofísica de poço para o cálculo da saturação de água é o método de Hingle, particularmente útil nas situações de desconhecimento da resistividade da água de formação. O método de Hingle estabelece uma forma linear para a equação de Archie, a partir dos perfis de resistividade e porosidade e a representa na forma gráfica, como a reta da água ou dos pontos, no gráfico de Hingle, com saturação de água unitária e o valor da resistividade da água de formação é obtido a partir da inclinação da reta da água. Independente do desenvolvimento tecnológico das ferramentas de perfilagem e dos computadores digitais, o geofísico, ainda hoje, se vê obrigado a realizar a interpretação de ábacos ou gráficos, sujeito a ocorrência de erros derivados da sua acuidade visual. Com o objetivo de mitigar a ocorrência deste tipo de erro e produzir uma primeira aproximação para a saturação de água em tempo real de perfilagem do poço, insere-se o trabalho apresentado nesta dissertação, com a utilização de uma conveniente arquitetura de rede neural artificial, a rede competitiva angular, capaz de identificar a localização da reta da água, a partir da identificação de padrões angulares presentes nos dados dos perfis de porosidade e resistividade representados no gráfico de Hingle. A avaliação desta metodologia é realizada sobre dados sintéticos, que satisfazem integralmente a equação de Archie, e sobre dados reais.

Energy substrate used by workers of leaf-cutting ants during nest excavation

Energy substrate used by workers of leaf-cutting ants during nest excavation. In this study we aimed to ascertain whether leaf-cutting ant workers lose body reserves (fat or sugars) as a function of nest excavation. For each treatment, we isolated 10 workers of Atta sexdens into two experimental groups, Control (C- without excavation) and Soil (S- with excavation), which were kept for different time intervals (0, 24, 48 or 72 hours), totaling 700 tested workers. We then determined the concentration of soluble carbohydrates and total lipid content in them. The total carbohydrates were determined colorimetrically, based on the reaction between carbohydrates and sulfuric acid-phenol. For determination of lipids, the insects were immersed in organic solvent until they reached a constant weight. Our results showed that carbohydrates are consumed during nest excavation activities. In the experimental groups S24, S48 and S72, there was an average reduction of 5.82 (20.42%), 14.31 (44.96%) and 13.27 (43.96%) µ.mg-1 in soluble sugar when compared with the experimental groups that did not excavate. Furthermore, the lipids were not used during this activity. With respect to dry mass of the workers, their values were C0 = 8%, C24 = 10.4%, C48 = 9.2%, C72 = 10%, S24 = 9.2%, S48 = 8.7% and S72 = 8.5%. Our results show experimentally that the source of energy for nest excavation is carbohydrates, whereas lipids are conserved for other activities.

Controle coordenado de múltiplos dipositivos facts com vistas à estabilidade transitória de SEE

Pós-graduação em Engenharia Elétrica - FEIS

Angular analysis and branching fraction measurement of the decay B-0 -> K*(0)mu(+)mu(-)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparative Analysis of Approaches for Assessing Energy Intake Underreporting by Female Bariatric Surgery Candidates

Objective: To test six variations in the Goldberg equation for evaluating the underreporting of energy intake (EI) among obese women on the waiting list for bariatric surgery, considering variations in resting metabolic rate (RMR), physical activity, and food intake levels in group and individual approaches.Methods: One hundred obese women aged 20 to 45years (33.3 6.08) recruited from a bariatric surgery waiting list participated in the study. Underreporting assessment was based on the difference between reported energy intake, indirect calorimetry measurements and RMR (rEI:RMR), which is compatible with the predicted physical activity level (PAL). Six approaches were used for defining the cutoff points. The approaches took into account variances in the components of the rEI:RMR = PAL equation as a function of the assumed PAL, sample size (n), and measured or estimated RMR.Results: The underreporting percentage varied from 55% to 97%, depending on the approach used for generating the cutoff points. The ratio rEI:RMR and estimated PAL of the sample were significantly different (p = 0.001). Sixty-one percent of the women reported an EI lower than their RMR. The PAL variable significantly affected the cutoff point, leading to different proportions of underreporting. The RMR measured or estimated in the equation did not result in differences in the proportion of underreporting. The individual approach was less sensitive than the group approach.Conclusion: RMR did not interfere in underreporting estimates. However, PAL variations were responsible for significant differences in cutoff point. Thus, PAL should be considered when estimating underreporting, and even though the individual approach is less sensitive than the group approach, it may be a useful tool for clinical practice.

Body Composition and Net Energy Requirements for Maintenance of Non-Castrated Water Buffaloes (Bubalus bubalis)

The research aimed to estimate body contents of protein and energy and net requirements of energy for maintenance of buffaloes, slaughtered at different stages of maturity. There were used 14 Mediterranean intact males with initial average body weight of 352.2 +/- 24.3 kg and average age of 24 months. The animais were randomly divided into four experimental groups. One group was designed to slaughter at the beginning of the experimental period (IS). The animals of another group were restricting fed, receiving, individually, levels of protein and energy 15% above maintenance (RF). The animals of the two remaining groups were individually fed ad libitum (SW450 and SW500) to reach weights corresponding to 100 and 110 percent of the mature weight of the buffalo cows (respectively 450 and 550 kg). The ration contained ground-corn cobs, soybean meal, urea, minerals, and signal-grass (Brachiaria decumbens) hay, with a concentrate: roughage ratio of 50: 50 and 13% of crude protein on a dry matter basis. To estimate changes in body composition inside the range of weights included in the trial, linear regression equations of log protein (kg), fat (kg) and energy (Mcal) as a function of log empty-body-weight (EBW), in kg, were fitted. Energy requirements for maintenance were obtained as estimated heat production at zero level of energy intake. Buffaloes submitted to fattening in feedlot presented early body fat deposition, and had with the same live weight lower protein content and higher fat content and energy per unit weight than european-zebu crossbred cattle.