1,721,044 research outputs found
A dynamic identification of continuous discontinuities in geodynamic numerical models
Full text linkDiscontinuities affect the Earth’s dynamics, yet the Earth is often represented in geodynamical models as a continuous material. The challenge of representing discontinuities in numerical models has been addressed in several ways in literature. The split node method, originally introduced by Jungels (1973) and Jungels and Frazier (1973) for elastic rheology and then modified by Melosh and Raefsky (1981) to simplify its implementation, allows the introduction of discontinuity into a finite element model by imposing an a-priori slip at a designated node, where the displacement depends on the element which the node is referred to. Originally, this method requires that the discontinuity’s geometry and slip are pre-established.
More recently, Marotta et al. (2020) modify this approach by introducing a coupling factor that indicates the percentage difference between the velocities of the element to which the slip node belongs, while the velocity consistently derives from the dynamic evolution of the system. However, this method still requires the pre-establishment of the discontinuity’s geometry. We here present a new technique that enables the dynamic identification of the discontinuity’s during the thermomechanical evolution of the system, based on physical parameters and without predefining the slip or the geometry.
We have implemented a new algorithm that identifies one or more discontinuities in a finite-element scheme operating through two phases: nucleation and propagation. Nucleation involves selecting a yield physical property and identifying the potential slip nodes, i.e., nodes on which the chosen physical property exceeds a yield value. The nucleus is then identified as the potential slip node where the chosen property most exceeds the yield. Propagation can be performed by choosing between three approaches of propagation: single simple fault, multiple simple fault and single double fault; and three schemes for the identification of neighboring nodes: grid-bounded, pseudo-free and free. The resulting discontinuity is the line connecting the nucleus and the propagation nodes. Once the discontinuity has been identified, a coupling factor is introduced and the algorithm continues to operate following the Marotta et al., (2020)’s scheme.
The results of several benchmark tests, performed through both simple and complex finite-elements models, confirm the success of the algorithm in recognizing yield conditions and introducing a discontinuity into a finite-element model and demonstrate the correctness of the propagation’s geometry
A new dynamic method for the implementation of faults in finite-element models
No full textFaults strongly affect the seismotectonic but in geodynamic modelling the Earth is often represented as a continuous material. The challenge in representing these structures in FE models is still open.
We propose a new method that enables the dynamic identification of the fault during the system evolution, without predefining either its geometry or the slip.
Our method is an advancement of Marotta et al. (2020) method, which, in turn, modified the classical split node method (Jungles and Frazier, 1973; Melosh and Raefsky, 1981) by replacing the prescribed slip with a coupling factor along the fault plane.
We developed an algorithm that, in the frame of a finite element approach, identifies the faults as the envelope of nodes on which a rupture criterion is satisfied. The breaking point is identified as the node on which the rupture condition is mostly exceeded; then the propagation proceeds along a line of neighboring nodes. The elements adjacent to the fault are classified as left or right, and the coupling factor is assigned. An AMR has been developed in such a way that where the fault cuts an element, the grid is recalculated.
We show the results of some benchmarks performed to test the correctness of the propagation algorithm, and the localization of a shear zone in a complex tectonic context.
References
Jungles and Frazier, 1973, DOI: 0.1029/JB078i023p05062
Marotta et al., 2020, DOI: 0.1093/gji/ggaa029
Melosh and Raefsky, 1981, DOI: 10.1785/BSSA071005139
A dynamic identification of continuous discontinuities in geodynamic numerical models
Full text linkDiscontinuities affect the Earth’s dynamics, yet the Earth is often represented in geodynamical models as a continuous material. The challenge of representing discontinuities in numerical models has been addressed in several ways in literature. The split node method, originally introduced by Jungels (1973) and Jungels and Frazier (1973) for elastic rheology and then modified
by Melosh and Raefsky (1981) to simplify its implementation, allows the introduction of discontinuity into a finite element model by imposing an a-priori slip at a designated node, where the displacement depends on the element which the node is referred to. Originally, this method requires that the discontinuity’s geometry and slip are pre-established.
More recently, Marotta et al. (2020) modify this approach by introducing a coupling factor that indicates the percentage difference between the velocities of the element to which the slip node belongs, while the velocity consistently derives from the dynamic evolution of the system. However, this method still requires the pre-establishment of the discontinuity’s geometry.
We here present a new technique that enables the dynamic identification of the discontinuity’s during the thermomechanical evolution of the system, based on physical parameters and without predefining the slip or the geometry. We have implemented a new algorithm that identifies one or more discontinuities in a finite-element scheme operating through two phases: nucleation and propagation. Nucleation involves selecting a yield physical property and identifying the potential slip nodes, i.e., nodes on which the chosen physical property exceeds a yield value. The nucleus is then identified as the potential slip node where the chosen property most exceeds the yield. Propagation can be performed by choosing between three approaches of propagation: single simple fault, multiple simple fault and
single double fault; and three schemes for the identification of neighboring nodes: grid-bounded, pseudo-free and free. The resulting discontinuity is the line connecting the nucleus and the propagation nodes. Once the discontinuity has been identified, a coupling factor is introduced and the algorithm continues to operate following the Marotta et al., (2020)’s scheme.
The results of several benchmark tests, performed through both simple and complex finite-elements models, confirm the success of the algorithm in recognizing yield conditions and introducing a discontinuity into a finite-element model and demonstrate the correctness of the propagation’s geometry
Interpretations. Market, Work, Training
No full textWhat of the labour market in the era of Brexit and in the international arena of the Trump presidency? Naturally, there are various perspectives, but forms of emotive or propagandist rhetoric threaten to hold sway here. Above all, Guidance Towards the Labour Market means recognising the complexities of geopolitical change within our information-sharing and collaborative networks, as well as the various and contrasting interpretations that arise.
The current decline of the European Union - of which the UK public referendum result is symptomatic - and the “America first” slogan, now a distinguishing feature of the current US government, are only two of the multiple forces interacting and defining pervasive transformations in economic, labour and educational policy.
Conflicting views abound. Take, for example, the challenge of agreeing on multilateral interventions to address the issue of immigration. Or the relationships between market, work and training in light of Europe’s infringement procedures for excessive debt, which affected Greece so drastically, and the lack of any formal rebuke by EU authorities for Germany’s excessive trade surplus
L'economia del futuro comincia dalla città
No full texti flussi creativi dentro le città e il grado di attrattività dei talenti da parte del territori
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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