1,722,314 research outputs found
Resenha: Historical archaeology and environment. SOUZA, Marcos André Torres e COSTA, Diogo Menezes (Eds.). 2018.
No full textSOUZA, Marcos André Torres e COSTA, Diogo Menezes (Eds.). Historical archaeology and environment. Springer, 2018. 270pgs
Les Barbares et le vin
No full textPereira de Souza Marcos Alvito. Les Barbares et le vin. In: Recherches brésiliennes. Archéologie, histoire ancienne et anthropologie. Besançon : Université de Franche-Comté, 1994. pp. 145-162. (Annales littéraires de l'Université de Besançon, 527
Les Barbares et le vin
No full textPereira de Souza Marcos Alvito. Les Barbares et le vin. In: Recherches brésiliennes. Archéologie, histoire ancienne et anthropologie. Besançon : Université de Franche-Comté, 1994. pp. 145-162. (Annales littéraires de l'Université de Besançon, 527
Variability in the dynamic response of connected structures possessing spatially slowly varying properties
No full textThis thesis covers the modelling and analysis of the dynamic behaviour of coupled structures possessing slowly varying properties. A mobility method is used to dynamically couple beams to a plate through a series of point connections comprising rigid links or flexible ones, the latter in the form of elastic springs. This is a relevant problem for cable bundles providing electrical power or for communications in cars, satellites and airplanes. In the case of rigid links, the response of the coupled system will generally be governed by the response of the least mobile structure, but with additional modes. For flexible links, there is a frequency at which the response of the combined system uncouples. The flexible links can also be used to reduce the uncertainties due to one of the substructures. Uncertainties in the positioning of the connection points were also considered and they can be as important as uncertainties in the mechanical properties of the structures in terms of the coupled system response variability. The slowly varying properties are then introduced using a description given by a random field using the Karhunen–Loève expansion. For the slowly varying beams, the Wentzel–Kramers– Brillouin approximation is used to find analytical solutions of the flexural wave equation and subsequently expressions for the input and transfer mobilities. The slowly varying plate is solved combining Finite Element Analysis and a Perturbation Method in order to find the required mode shapes, natural frequencies and mobilities. Infinite and finite coupled structures were considered. The work presented here thus proposes an alternative to the standard technique used in the industry of considering the cable bundles as lumped mass at the connection points. This approximation is valid at lower frequencies, where they indeed behave as an additional mass. However, at higher frequencies they can contribute to adding some stiffness and apparent damping, as the response of the coupled system is now shared into more modal resonances, from the modes of the host structure and the attached cables. Experimental validation is presented showing the effects of randomly spaced connections and are in good agreement with numerical simulations. In order to capture the varying properties, a novel technique is proposed that combines a wavenumber correlation technique within a Bayesian framework in order to estimate the values of the bending stiffness of the particular cable bundles. The Bayes’ technique was also used to reconstruct random fields from synthetic data. It could subsequently be applied experimentally and provide the required input for models possessing slowly varying properties
Experimental investigation of the variability in the dynamics of connected structures
No full textHydraulic pipes and cable bundles attached to host structures are widely found in engineering. This paper explores how variability in the connection points between structures affects the coupled dynamics. One at a time, two different one-dimensional waveguides are attached to a thin plate through a different set of point connections. Measurements considering randomly spaced connections were made and the experimental results are presented and compared to previously developed models. When multiples attachments are considered, the structure accommodates standing-like waves between the attachments, amplifying its response. It was possible to see the variability due the random spacing and, in a frequency-averaged sense, good agreement between the experimental data and the models were obtained. A comparison of the spatial response of the experiment and the infinite system is also presented
The tadpole of Elachistocleis helianneae Caramaschi, 2010 (Anura: Microhylidae)
No full textDias-Souza, Marcos Roberto, Costa-Campos, Carlos Eduardo, Menin, Marcelo (2019): The tadpole of Elachistocleis helianneae Caramaschi, 2010 (Anura: Microhylidae). Zootaxa 4701 (6): 594-600, DOI: 10.11646/zootaxa.4701.6.1
The dynamics of coupled structures possessing inhomogeneous attachments
No full textStructures with hydraulic pipes and cable bundles attached to them are commonly found in engineering, therefore it is of interest to determine the effects of such attachments on the dynamics of the host structures and quantify them. Moreover, manufacturing processes often lead to deviations from the original design. One way to take these deviations into account is to consider small variations in the mechanical properties and/or geometry of the structures. This paper models the attachments as slowly varying inhomogeneous beams and uses the WKB (Wentzel, Kramers and Brillouin) approximation and wave propagation to derive the input and transfer mobilities of said beams. The properties of the beam are described as a random field and are expressed using the Karhunen-Loève expansion. Once the mobilities are known, a mobility approach can be used to couple the attachments to a host structure. Rigid connections are considered along with variations of the spacing between the attachments
The effect of isolation in controlling the variability of point connected structures with uncertain structural attachments
No full textAs the demand for the transmission of electric power and communication signals in automotive and aerospace vehicles increases, so does the number of structures comprising simplified one-dimensional attachments, such as electrical cabling, affixed to a host plate like primary structure. These attachments are typically uncertain in their geometric or material properties, potentially affecting the response of the built-up structure. Difficulties then arise in the prediction of the response of the assembly. This study shows how the variability, due to the uncertain attachments, might be reduced by considering flexible connections. A mobility analysis compares systems connected with either rigid links or elastic springs. A frequency is identified at which the assembly dynamically uncouples; the effect on the host response variability due to the uncertain attachment decreases above this frequency with a reduction of the order of 60 dB in the coefficient of variation. This uncoupling or effective isolation frequency can be simply estimated from the mobility of the elastic connection and the properties of the nominal structural attachment. For design purposes, this frequency can be adjusted to achieve a more predictable response above a given frequency
Conservation Units as a protection tool for social wasps in Minas Gerais state, Brazil
No full textOliveira, Glauco Cássio de Sousa, Henriques, Nathália Ribeiro, Clemente, Mateus Aparecido, Souza, Marcos Magalhães de (2021): Conservation Units as a protection tool for social wasps in Minas Gerais state, Brazil. Papéis Avulsos de Zoologia 61: 1-10, DOI: 10.11606/1807-0205/2021.61.25, URL: http://dx.doi.org/10.11606/1807-0205/2021.61.2
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