59 documents found, page 1 of 6
On the hyperbolicity of the Krein space numerical range
Bebiano, N.; Lemos, R.; Soares, G.In this paper a necessary and sufficient condition for hyperbolicity of the indefinite numerical range is established. As a consequence, an indefinite version of Brown–Spitkovsky theorem stating the ellipticity of the numerical range of certain tridiagonal matrices is revisited. This result leads to necessary and sufficient conditions for hyperbolicity of indefinite numerical ranges of new classes of tridiagona...
Log-majorization type inequalities
Lemos, R.; Bebiano, N.; Soares, G.Several inequalities have been established in the context of Hilbert spaces operators or operator algebras. Our discussion will be limited to matrices. Important inequalities in mathematics and other sciences, such as Golden-Thompson inequality or von Neumann trace inequality, and extensions, are revisited. Our main goal is to emphasize the link between majorization theory and other relevant inequalities.
Carbon nanotubes-reinforced cell-derived matrix-silk fibroin hierarchical scaff...
Lemos, R.; Maia, F. Raquel; Ribeiro, Viviana Pinto; Costa, João Pedro Bebiano; Coutinho, Paulo J. G.; Reis, R. L.; Oliveira, J. M.In bone tissue engineering, the development of advanced biomimetic scaffolds has led to the quest for biomotifs in scaffold design that better recreate bone matrix structure and composition and hierarchy at different length scales. In this study, an advanced hierarchical scaffold consisting of silk fibroin combined with decellularized cell-derived extracellular matrix and reinforced with carbon nanotubes was de...
Some log-majorizations and an extension of a determinantal inequality
Lemos, R.; Soares, G.An eigenvalue inequality involving a matrix connection and its dual is established, and some log-majorization type results are obtained. In particular, some eigenvalues inequalities considered by F. Hiai and M. Lin [9], an associated conjecture, and a singular values inequality by L. Zou [20] are revisited. A reformulation of the inequality det(A+U^⁎B)≤det(A+B), for positive semidefinite matrices A,B, with U a ...
Toe berm damage progression analysis using a stereophotogrammetric survey techn...
Pedro, F.; Bastos, M.; Lemos, R.; Fortes, C. J. E. M.; Santos, J. A.This paper focuses the toe berm damage progression analysis using image processing tools, in order to test their applicability to scale model tests. Damage can be characterized either by counting the number of displaced units or by measuring the eroded profile of the armor slope. Nevertheless, qualitative and quantitative damage assessment is not always easy. In order to ease and speed up those tasks, some imag...
O papel da modelação física no apoio aos estudos de engenharia costeira e portu...
Fortes, C. J. E. M.; Capitão, R.; Lemos, R.; Neves, M. G.; Pinheiro, L.; Reis, M. T. L. G. V.Neste artigo, apresenta-se uma descrição do papel da modelação física no apoio aos estudos de Engenharia Costeira e Portuária, ilustrando-se as suas potencialidades com exemplos de casos de estudo. Referem-se os contributos inovadores em conceitos, equipamentos, técnicas e procedimentos experimentais que têm sido desenvolvidos nos recentes anos. Assim, apresentam-se metodologias a explorar no futuro, tais como ...
Application of stereo photogrammetry to physical scale model tests with mobile ...
Pedro, F.; Lemos, R.; Fortes, C. J. E. M.; Santos, J. A.The phenomenon of scour in the vicinity of coastal and harbour protection structures, wind farms, offshore platforms and marine outfalls is one of the causes associated with its collapse. During the design of such structures, the prediction of the maximum erosion depth located in the vicinity of the structure is of utmost importance, requiring, frequently, a validation by scale-model tests. The objective of thi...
Run-up on a rubble mound breakwater: comparison of empirical formulae and physi...
Poseiro, P.; Reis, M. T. L. G. V.; Lemos, R.; Fortes, C. J. E. M.; Garcia, T.The present study focuses on the comparison of measured wave run-up values obtained in physical model tests with those predicted by different empirical formulae. Tests were carried out in a flume for a cross-section of a rubble mound breakwater with an armour layer of tetrapods and rock, and a recurved wave return wall. The model represents the cross-section of the south breakwater of Praia da Vitória harbour (...
Physical modelling as a fundamental tool for the design of harbours and maritim...
Reis, M. T.; Silva, L. G.; Neves, M. G.; Lemos, R.; Capitão, R.; Fortes, C. J. E. M.In this paper, a brief description of the role of physical modelling to support the design of harbours and maritime structures is presented, followed by an example of the tests carried out for the studies of the expansion of Rabo de Peixe fi shing harbour, at São Miguel – Azores. The variety of physical model tests conducted for this case study illustrates the fundamental potential of this modelling technique. ...
Rubble-mound breakwater armour units displacement analysis by means of digital ...
Courela, J.M.; Carvalho, R.; Lemos, R.; Fortes, C. J. E. M.; Leandro, J.Rubble-mound structures are commonly used for coastal and port protection and needs a properly design as well as inspection and maintenance during its lifetime. The design of such breakwaters usually requires a physical scale model to be tested under different irregular incident wave and tide conditions in order to evaluate its hydraulic and structural behaviour, namely the stability of the proposed design. Arm...