3,870 research outputs found

    Women in the mutual societies of Portugal from the end of the nineteenth century to the 1930s

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    This chapter aims to express recent research on the history of women’s work and activism by focusing on women in the mutual societies of Portugal from a gender perspective. The main objective is thus analysing women’s rights and the discrimination prevailing in mixed associations (including women and men as members). Another central purpose involves recognising women-only associations as a space for meeting and collaboration amongst working-class women and feminists that attained a voice in the mutualism movement in which their claims on welfare issues targeted both themselves and their children. Furthermore, we seek to demonstrate that only in women’s mutual associations did the ideals of democracy and equality, advocated by mutualism, become fulfilled for women. However, in fact, only a few women participated in the mutualism congresses during the First Republic, with some women gaining prominent places in the Assemblies but without any known public interventions according to the sources.info:eu-repo/semantics/acceptedVersio

    Self interacting Brans Dicke cosmology and Quintessence

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    Recent cosmological observations reveal that we are living in a flat accelerated expanding universe. In this work we have investigated the nature of the potential compatible with the power law expansion of the universe in a self interacting Brans Dicke cosmology with a perfect fluid background and have analyzed whether this potential supports the accelerated expansion. It is found that positive power law potential is relevant in this scenario and can drive accelerated expansion for negative Brans Dicke coupling parameter ω\omega. The evolution of the density perturbation is also analyzed in this scenerio and is seen that the model allows growing modes for negative ω\omega.Comment: 8pages, 5 figures, PRD style, some changes are made, figures added, reference added. To be published in Int. J. Mod. Phys.

    Generalized fractional maxwell model : parameter estimation of a viscoelastic material

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    In this paper, we show how fractional viscoelastic models can be efficient in the modeling of linear viscoelastic behavior, increasing the fitting accuracy of classic generalized viscoelastic models, such as the Generalized Maxwell model. Experimental data (Loss and Storage modulus in the frequency domain) were retrieved from a Dynamic Mechanical Analysis test considering Carbon Fibre Reinforced Polymer samples. The estimated parameters, for the derived fractional viscoelastic models, were obtained through numerical optimization techniques that minimize the difference between model-predicted values and experimental data. An excellent correlation between analytical and experimental results was observed, minimizing numerical instabilities found on a previous work, for the same experimental setup.This work was financed by FEDER funds through COMPETE-Programa Operacional Fatores de Competitividade and by portuguese funds through FCT-Fundação para a Ciência e a Tecnologia within projects PEst-C/MAT/UI0013/ 2011

    Dynamical estimates of chaotic systems from Poincar\'e recurrences

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    We show that the probability distribution function that best fits the distribution of return times between two consecutive visits of a chaotic trajectory to finite size regions in phase space deviates from the exponential statistics by a small power-law term, a term that represents the deterministic manifestation of the dynamics, which can be easily experimentally detected and theoretically estimated. We also provide simpler and faster ways to calculate the positive Lyapunov exponents and the short-term correlation function by either realizing observations of higher probable returns or by calculating the eigenvalues of only one very especial unstable periodic orbit of low-period. Finally, we discuss how our approaches can be used to treat data coming from complex systems.Comment: subm. for publication. Accepted fpr publication in Chao

    Parameter estimation of viscoelastic materials : a test case with different optimization strategies

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    In this work, and based on numerical optimization techniques, constitutive parameters for viscoelastic materials are determined using a inverse problem formulation. The optimization methodology is based on experimental results obtained in the frequency domain, for a CFRP-Carbon Fibre Reinforced Polymer, through DMA-Dynamic Mechanical Analysis. The relaxation modulus of viscoelastic materials is given by a summation of decaying exponentiating functions, known as Prony series. Prony series, in time domain, are normally used to determine constitutive parameters for viscoelastic materials. In this paper, using the Fourier transform of the time domain Prony series, a nonlinear constrained least square problem based on Prony series representations of storage and loss modulus, for the considered material, is analyzed. A case study considering the estimation of 2N viscoelastic parameters, N = 1,2, ···11, is taken as a benchmark. The nonlinear constrained least square problems are solved using global and local optimization solvers. The computational results as well as the main conclusion are shown

    A modified fractional zener model to describe the behaviour of a carbon fibre reinforced polymer

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    In this work a modified conventional Fractional Zener Model is deduced and applied to estimate the viscoelastic constitutive parameters of a Carbon Fibre Reinforced Polymer. The accuracy of this modified model was studied against conventional Fractional Zener model and Fractional Maxwell model, considering experimental data in the frequency domain. The set of parameters was found by solving a nonlinear constrained least square problem based on the variation of the storage and loss moduli with frequency.This work was financed by FEDER funds through COMPETE (Operational Programme Thematic Factors of Competitiveness) and by portuguese funds through FCT (Foundation for Science and Technology) within the project PEst-C/MAT/UI0013/ 2011

    Gravitational Waves in Generalised Brans-Dicke Theory

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    We have solved cosmological gravitational Wave(GW)equation in the frame work of Generalised Brans-Dicke(GBD) theory for all epochs of the Universe.The solutions are expressed in terms of the present value of the Brans-Dicke coupling parameter ω(ϕ)\omega(\phi).It is seen that the solutions represent travelling growing modes for negative values of ω0\omega_{0} for all epochs of the Universe.Comment: 7Pages,no figure

    Reconstruction of eye movements during blinks

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    In eye movement research in reading, the amount of data plays a crucial role for the validation of results. A methodological problem for the analysis of the eye movement in reading are blinks, when readers close their eyes. Blinking rate increases with increasing reading time, resulting in high data losses, especially for older adults or reading impaired subjects. We present a method, based on the symbolic sequence dynamics of the eye movements, that reconstructs the horizontal position of the eyes while the reader blinks. The method makes use of an observed fact that the movements of the eyes before closing or after opening contain information about the eyes movements during blinks. Test results indicate that our reconstruction method is superior to methods that use simpler interpolation approaches. In addition, analyses of the reconstructed data show no significant deviation from the usual behavior observed in readers

    Cutting forces and wear analysis of Si3N4 diamond coated tools in high speed machining

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    Si3N4 tools were coated with a thin diamond film using a Hot-Filament Chemical Vapour Deposition (HFCVD) reactor, in order to machining a grey cast iron. Wear behaviour of these tools in high speed machining was the main subject of this work. Turning tests were performed with a combination of cutting speeds of 500, 700 and 900 m min−1, and feed rates of 0.1, 0.25 and 0.4 mm rot−1, remaining constant the depth of cut of 1 mm. In order to evaluate the tool behaviour during the turning tests, cutting forces were analyzed being verified a significant increase with feed rate. Diamond film removal occurred for the most severe set of cutting parameters. It was also observed the adhesion of iron and manganese from the workpiece to the tool. Tests were performed on a CNC lathe provided with a 3-axis dynamometer. Results were collected and registered by homemade software. Tool wear analysis was achieved by a Scanning Electron Microscope (SEM) provided with an X-ray Energy Dispersive Spectroscopy (EDS) system. Surface analysis was performed by a profilometer
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