Search results for "Ocean Engineering"
showing 10 items of 404 documents
On reliability of systems with moving material subjected to fracture and instability
2015
Abstract The reliability of systems with moving cracked elastic and isotropic material is considered. The material is modeled as a moving plate which continually has a crack on the edge. The plate is subjected to homogeneous tension acting in the traveling direction and the tension varies temporally around a constant value, the set tension. The tension and the length of the crack are modeled by an Ornstein–Uhlenbeck process and an exponential Ornstein–Uhlenbeck process, respectively. Failure is regarded as the state at which the plate becomes unstable or fractures (or both) and a lower bound for the reliability of the system is derived. Considering reliability of the system leads to first p…
Stochastic analysis of the critical velocity of an axially moving cracked elastic plate
2014
In this study, a probabilistic analysis of the critical velocity for an axially moving cracked elastic and isotropic plate is presented. Axially moving materials are commonly used in modelling of manufacturing processes, like paper making and plastic forming. In such systems, the most serious threats to runnability are instability and material fracture, and finding the critical value of velocity is essential for efficiency. In this paper, a formula for the critical velocity is derived under constraints for the probabilities of instability and fracture. The significance of randomness in different model parameters is investigated for parameter ranges typical of paper material and paper machin…
Un escarpement sous-marin permanent du Lias à l'Eocène, dans la dorsale calcaire Péloritaine (Sicile, Italie)
1999
The schistosity of the Palaeozoic basement of the Capo San Andrea unit (Peloritan Dorsale) is cut by Liassic to Eocene neptunian dykes which developed along a pelagic fault scarp exposed on the sea bottom for 140 My. The Mesozoic structures determined the location of the Alpine deformation.
Spatial and temporal distribution of ooids along a Jurassic carbonate ramp: Amellago outcrop transect, High-Atlas, Morocco
2010
Carbonate ramp systems are widespread throughout the geological record, but very few areas have seismic-scale, continuous and structurally undeformed outcrops that allow reliable interpretation of facies distributions and stacking patterns. The Amellago outcrop shows the detailed depositional and stratigraphic relationships of an ooid-dominated ramp system that is almost completely exposed along a dip profile (37 km long and 1000 m thick) in the Lower to Middle Jurassic of the southern High Atlas, Morocco. Ammonite and brachiopod fauna provide excellent biostratigraphic control on small scale stacking patterns. At Amellago, the evolution of depositional environments is evident at different …
Un exemple de spéciation lié à l'eustatisme: l'apparition précoce de Schackoina cabri (foraminifère planctonique mésogéen)
1997
Investigation of planktic foraminifers from the Lower Aptian of the Vocontian Basin (SE France) reveals that Schackoina cabri makes a very discrete first appearance in the Weissi ammonite zone and not in the Deshayesi zone, i.e. before the global anoxic event OAE 1a and not after as was accepted in the literature. This discovery seems to support the recent model whereby speciation of planktic foraminifers occurred in marine lowstands and their real expansion during the ensuing sea-level rise.
Apparition d'une morphologie scaphitomorphe par miniaturisation chez une ammonite oxfordienne : Scaphitodites scaphitoides ()
1997
The pyritized fossil-bearing marls of the Jura (Lower Oxfordian) contain an ammonite that is remarkable because of its tiny adult size (less than 16 mm) and of the scaphitoidal coiling of its body chamber, which is similar to that of certain Cretaceous Scaphitaceae. Anatomical and ontogenetic analysis demonstrates that these individuals, which are ascribed to Scaphitodites scaphitoides (Coquand, 1853), formed a single species. We argue that the genus Scaphitodites derived from Taramelliceras by a complex process of progenesis (sensu Landman et al., 1991).
Non-linear oscillators under parametric and external poisson pulses
1994
The extended Ito calculus for non-normal excitations is applied in order to study the response behaviour of some non-linear oscillators subjected to Poisson pulses. The results obtained show that the non-normality of the input can strongly affect the response, so that, in general, it can not be neglected.
Domain decomposition in the symmetric boundary element analysis
2002
Recent developments in the symmetric boundary element method (SBEM) have shown a clear superiority of this formulation over the collocation method. Its competitiveness has been tested in comparison to the finite element method (FEM) and is manifested in several engineering problems in which internal boundaries are present, i.e. those in which the body shows a jump in the physical characteristics of the material and in which an appropriate study of the response must be used. When we work in the ambit of the SBE formulation, the body is subdivided into macroelements characterized by some relations which link the interface boundary unknowns to the external actions. These relations, valid for e…
Elastic plastic analysis iterative solution
1998
The step-by-step analysis of finite element elastic plastic structures subjected to an assigned (quasi-static) loading history, is considered; it identifies with the well-known sequence of linear complementarity problems. An iterative technique devoted to solve the relevant linear complementarity problem is presented. It is based on the recursive solution of a suitable linear complementarity problem, deduced from the relevant one and easier than it. The procedure convergency is proved. Some noticing particular cases are examined. The physical meaning of the procedure is shown to be a plastic relaxation. The suitable numerical ranges for some check parameter values, to be utilized in the app…
Filter approach to the stochastic analysis of MDOF wind-excited structures
1999
Abstract In this paper, an approach useful for stochastic analysis of the Gaussian and non-Gaussian behavior of the response of multi-degree-of-freedom (MDOF) wind-excited structures is presented. This approach is based on a particular model of the multivariate stochastic wind field based upon a particular diagonalization of the power spectral density (PSD) matrix of the fluctuating part of wind velocity. This diagonalization is performed in the space of eigenvectors and eigenvalues that are called here wind-eigenvalues and wind-eigenvectors, respectively. From the examination of these quantities it can be recognized that the wind-eigenvectors change slowly with frequency while the first wi…