Browsing by Author "Ribeiro, P."
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- A case of multicentric undifferentiated bronchioloalveolar adenocarcinoma in an autochthonous cowPublication . Alves, A.; Pinto, M.; Ribeiro, P.; Vala, Helena
- Development and characterization of a ewe’s creamy cheese with aromatic plantsPublication . Guiné, R. P. F.; Teixeira-Lemos, Edite; Ribeiro, P.; Ferreira, M.; Oliveira, A. M.; Teixeira, A. R.; Castro, B.; Rodrigues, R.; Santos, S.; Rodrigues, A.; Santos, A.This work aimed at developing a new dairy product, made of ewe’s milk that cannot be used for making the Serra da Estrela cheese (with Protected Designation of Origin) for not filling the exact specifications. In this way are allied economic with environmental advan- tages. Because this unusable milk represents econom- ic loss for the producers while at the same time increas- ing the volume of effluents that need treatment, this alternative usage allies economic with environmental advantages. A total of 19 samples were produced, and these de- veloped creamy cheeses were evaluated according to formulation and conservation properties, and then submitted to a sensory evaluation and finally analysed in terms of physico-chemical microbiological and nu- tritional properties. The 19 formulations were tested to optimize formulations that would be acceptable in organoleptic terms as well as conservation capac- ity, under refrigeration, for an observational period of 3 weeks. This essay allowed selecting 5 versions of the product that showed best conservation capacity, which were then submitted to sensory evaluation. The sensory analyses involved two types of tests: de- scriptive sensory profile and preference test, and the obtained results allowed selecting the 2 best formu- lations as those most appreciated and with potential for commercialization: a control cheese and one with oregano, which were then analysed. Microbiological analyses were undertaken to verify if the products met the legally established microbiological limits, name- ly for assessing the presence of coagulase-positive staphylococci (Staphylococcus aureus) and Escherichia coli. Moisture, protein, lipids, salt and carbohydrates were analysed by Fourier transform near-infrared (FT- NIR) spectroscopy method and antioxidant activity was evaluated by reaction with the 2,2-diphenyl-1-pic- rylhydrazyl (DPPH) radical. Chemical composition revealed two similar products, but the sample with oregano had higher antioxidant activity as compared with control (70.96 ± 0.36 and 64.99 ± 2.74 mg/L TE, respectively). From the microbi- ological point of view both products were considered safe, with values of staphylococci and E. coli under the applicable regulation limits. In terms of nutritional val- ue, both sample shave high protein content (11.9 and 11.4 g/100 g, respectively for control and sample with oregano) but also high fat (13.9 and 12.3 g/100 g, re- spectively for control and sample with oregano) while being low in sugars (3.4 and 3.8 g/100 g), fiber (< 1%) or salt (< 1%). Energy of both samples was found to be 186 kcal/100 g for the control and 172 g/100g for sam- ple with oregano. In conclusion, in nutritional terms the samples could be considered safe High Protein content foods. More- over, as dairy products contain almost all the essential nutrients, the developed creamy cheeses should be consumed as part of a balanced diet. Finally, the production of these products allows the utilization of the milk that otherwise would have to be discarded, so bringing economic profit while at the same time mini- mizing the need to process it as effluent.
- From periodic to chaotic oscillations in composite laminated platesPublication . Ribeiro, P.; P. Duarte, RuiThe geometrically non-linear, linear elastic, oscillations of composite laminated plates are studied in the time domain by direct numeric integration of the equations of motion. A p-version finite element, where first-order shear deformation is followed and that was recently proposed for moderately thick plates, is employed to define the mathematical model. By applying transverse harmonic forces, the variation of the oscillations with the angle of the fibres is investigated. With this kind of excitation, only periodic motions with a period equal to the one of the excitation are found. However, introducing in-plane forces, m-periodic or quasi-periodic oscillations, as well as chaotic oscillations are computed. The existence of chaos is confirmed by calculating the largest Lyapunov exponent.
- Time Domain Analysis of Geometrically Nonlinear Vibrations of Composite Laminated Plates by the Hierarchical Finite Element MethodPublication . P. Duarte, Rui; Ribeiro, P.Composite laminated plates are employed in many areas of engineering such as aeronautics, space engineering and naval industry [1,2,3]. For example in aircrafts they are submitted to large acoustic, aerodynamic and inertia excitations and therefore experience vibrations with large amplitude, i.e., in the geometrically nonlinear regime. Vibrations with large amplitude cause large stresses and the diminution of life due to fatigue. Quasi periodic and chaotic behaviours are other possible consequences of non-linearity, completely ignored by the linear models which are normally used in engineering design. Non-symmetrical laminated plates have been rarely studied, particularly in non-linear dynamics. In this work, a hierarchical finite element, in which the model is improved by increasing the number of shape functions in each element, is formulated. The element is general, in the sense that it applies to symmetric or asymmetric plates. Compared with h-version elements, it has the major advantages of requiring a small number of degrees of freedom for accuracy and of being free from shear locking. Different shear deformation theories (SDT) have been developed to include the effect of transverse shear deformation [1,2,3]. The first order shear deformation laminated plate theory is followed here. Hence, Kirchhoff's hypothesis [4] is relaxed by removing the third part, that is the transverse normals do not remain perpendicular to the mid-surface after deformation. 1 2 3 4 5 6 7 8 9 In this paper, the shape functions used are the Legendre polynomials in the Rodrigue's form [5,6,7,8,9]. A different number of transverse, middle plane, rotation about y and rotation about x, displacement shape functions are employed, and the convergence of the linear natural frequencies studied. Two symmetric, rectangular, graphite/epoxy composite laminated plates with constant thickness , width and length , composed of orthotropic layers oriented at different angles are considered. The element derived is employed to study the non-linear dynamic behaviour of some these laminated plates, in the time domain. The direct integration of the system of equations of motion is carried out by Newmark's method. In order to uncover the characteristics of the motions computed, time plots, phase planes and Fourier spectra are defined. For different fibre orientations, it is confirmed that the linear natural frequencies of the thick plate model are smaller than the thin plate ones. Harmonic excitations are applied, and the responses of the plates are determined with a reasonable computational cost, due to the reduced number of degrees of freedom of the model. For amplitudes of vibration much lower than the thickness of the plate, the solutions found are always periodic and highly dominated by the harmonic with frequency equal to the excitation frequency (principal harmonic). Increasing the force applied, the response amplitude increased in a non-linear way, the motions found are still periodic, but the time and phase plots show that higher harmonics are important.