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- O aconselhamento científico independente na tomada de decisão em políticas públicasPublication . Correia, Isabel Sá; Jornal I
- Ambidextrous capacity in small and medium-sized enterprises.Publication . Felício, J. Augusto; Caldeirinha, Vítor; Dutra, AdemarThis study examines the ambidextrous capacity—the ability to respond simultaneously to both disruptive and incremental innovation processes—of small and medium-sized enterprises (SMEs) in Portugal. The purpose is to understand the organizational ambidexterity of SMEs and its relationship to organizational performance and innovation capacity. The objectives are to evaluate the characteristics that identify ambidextrous organizations and analyze the effect of organizational ambidexterity on performance, supported by the contingency-based approach, organizational theory, behavioral theory of the firm, and organizational learning theory. After factor analysis is performed, a structural equations model is used to analyze a sample of 202 valid responses. The analysis shows that, for SMEs, disruptive innovation factors relate mainly to innovation capacity and incremental innovation factors relate to organizational performance. The confirmation of organizational ambidexterity in SMEs and the increased recognition of the importance of disruptive innovation are relevant contributions to the literature.
- Failure analysis of cylinder head studs of a four stroke marine diesel enginePublication . Fonte, M.; Reis, L.; Infante, V.; Freitas, M.After about seven years in service, four cylinder head studs, which tight the block and cylinder heads of a marine main engine, have fractured. Meantime, they were changed for new ones without to determine the root cause of failure. The aim of this research work is to carry out a failure analysis in order to avoid recurrent damages in that engine. The fracture morphology and thread roots of fractured studs were carefully observed by optical devices. Thread material defects and corrosion were not found. However, the thread roots, where the stress concentration are higher, can be pointed as the local of fatigue crack initiation. As is well-known, all cylinder head stud bolts are pre-tensioned in order to increase the mean stress σm and reduce the stress amplitude σa. The steel alloy quality and design are of primordial importance for improving the lifetime of studs, and this is supervised by the Classification Societies (CS), as is indicated by an engraved stamp on each stud end, that certifies each one of them. The pre-tightening of the studs was calculated, and results point as root cause of failure a significant high stress concentration mainly at the second thread root of the studs, close to the bottom side of the nut, which are critical stress zones.
- Flexural testing and analysis of fullstrain-fields in sandwich composites.Publication . Marat-Mendes, R.; Martins, R.; Garcia, A.; Reis, L.The objective of this work was to characterize the full-field flexural behavior of composite sandwich beams. Finite element analysis was used to estimate the behavior of sandwich beams under three- and four-point-bending tests and were compared with experimental results obtained via digital image correlation and strain-gauges. Two different polyurethane core thicknesses and two different sandwich lengths were used to simulate short- and long-beam. Two distinct sandwich beams were used by means of two different faces: aluminum and basalt fiber reinforced polymer composite. Full-strain-fields and flexural displacements results were obtained showing that BFRP sandwiches exhibited higher flexibility and higher capacity of absorption energy than the aluminum specimens however with a higher prospect of core shear failure. For both face materials short-beams present higher strains than the long-beams and 4PB test specimens showed negative strain distribution in the upper side of the specimen and positive in the underside contrary to 3PB that presents positive strain distribution along the fulfilled. Moreover, results show that the strain distribution in not symmetric. Obtained experimental results are in good agreement with estimations; the digital image technique attested to be a complementary method to strain gages measurements in experimental full-strain-fields analysis.
- Ordinary differential equations with point interactions: An inverse problemaPublication . Dias, N.C.; C., Jorge; Prata, J.N.We study a class of linear ordinary differential equations (ODEs) with distributional coefficients. These equations are defined using an intrinsic multiplicative product of Schwartz distributions which is an extension of the Hörmander product of distributions with nonintersecting singular supports (Hörmander in The analysis of linear partial differential operators I, Springer, Berlin, 1983). We provide a regularization procedure for these ODEs and prove an existence and uniqueness theorem for their solutions. We also determine the conditions for which the solutions are regular and distributional. These results are used to study the Euler–Bernoulli beam equation with discontinuous and singular coefficients. This problem was addressed in the past using intrinsic products (under some restrictive conditions) and the Colombeau formalism (in the general case). Here we present a new intrinsic formulation that is simpler and more general. As an application, the case of a non-uniform static beam displaying structural cracks is discussed in some detail.