Number-space associations depend on inhibitory control in atypical young adults with attention-deficit/hyperactivity disorder

Presentation (2015, April)

Numbers Comparison during Arithmetic Task: Evidence from the Compatibility Effect.

Poster (2010)

Numbers reorient visuo-spatial attention during cancellation tasks

in Experimental Brain Research (2013), 225(4), 549-57

Numbers induce shifts of spatial attention on the left or the right sides of external space as a function of their magnitude. However, whether this number-space association is restricted to the linear ... [more ▼]

Numbers induce shifts of spatial attention on the left or the right sides of external space as a function of their magnitude. However, whether this number-space association is restricted to the linear horizontal extensions, or extends to the whole visual scene, is still an open question. This study investigates, by means of a cancellation paradigm, the influence of numerical magnitude during scanning tasks in which participants freely explore complex visual scenes unconstrained towards either the horizontal or the vertical unidimensional axes. Five cancellation tasks were adapted in which Arabic digits were used as targets or distracters, in structured (lines and columns) or unstructured visual displays, with a smaller (2 or 3 types of distracters) or larger (10 or more types of distracters) sets of stimuli. Results show that the participants' hits distribution was a function of number magnitude: shifted on the left for small and on the right for large numbers. This effect was maximised when numerical cues were sparse, randomly arranged and, critically, irrelevant to the task. Overall, this study provides novel evidence from visuo-spatial exploratory cancellation tasks for an attentional shift induced by number magnitude. [less ▲]

Numerical Analysis for the determination of Stress Percolation in Dry-Stacked Wall Systems

in Revue Technique (2016)

This paper comprises a portion of a PhD study concluding on the potential use of a new mortarless and modular masonry system by taking into consideration the outcome of a multidisciplinary study including ... [more ▼]

This paper comprises a portion of a PhD study concluding on the potential use of a new mortarless and modular masonry system by taking into consideration the outcome of a multidisciplinary study including aspects of experimental, numerical and analytical investigations in relation to a practical and economical development of modular load-bearing dry-stacked masonry systems. Different forms of interlocking masonry elements have been modelled and optimised thermo-mechanically. Full-scale masonry walls were assembled and tested experimentally under compressive, flexural, shear, cyclic and long term loads. The overall structural behaviour was compared to conventional masonry systems such as hollow and shuttering blocks. The investigations showed overall relative high structural performances for the developed dry-stacked elements. The effect of dry joint interfaces was extensively investigated experimentally and numerically under FE analysis. Based on the experimental observations, a numeric-analytical failure mechanism of the dry-stacked masonry structure is anticipated under axial and flexural loading. The structural investigations and engineering processes are completed by the development of a package of dry-stacked units consisting of interlocking modular masonries and an accompanying array of various other precast parts. This confirmed the practical issues and solutions towards the exploitation of the developed dry-stacked elements for the construction of ready-to-build, modular and load-bearing walls. The portion of work presented herein proposes a new numerical technique for the determination of stress-percolation in dry stacked load-bearing structures. The model is developed in three steps under a numerical computing environment. First, based on geometrical properties of the dry-stacked elements and with a linear-elastic material behaviour, the load percolation and intensity in dry-stacked masonry walls is determined. In a second step, a phenomenon known as a plastic accommodation which accompanies the redistribution of the stress percolations, is incorporated in the model. This enables the understanding of the evolution of the stress percolations in the post-elastic phase, which is crucial for the determination of the load capacity and stability of the structure in function of an increased external load. This paper also supports the better understanding of early fissuring in dry-stacked masonry structures which has an important influence on the overall stability of the structure. Finally, in a third step, the improvement of dry-stacked structures is pursued by further analysis of the results obtained through the algorithm. This paper represents a new tool for investigating the localized and randomly defined internal stress distribution induced by external compression forces on dry-stacked structures. Furthermore, the algorithm illustrates that experimental investigations on dry-stacked systems may only give real indications on the load capacity of the structure, when the number of joint interfaces and height to length ratio of the block is respected and that results of experimental investigations on reduced prism specimens may not be extrapolated to full sized walls as they may over-evaluate the effective loaded masonry sections and therefore the overall load capacity. [less ▲]

Numerical analysis of free-surface flow through rotating machines

Presentation (2013)

In the context of the transformation process currently taking place in the energy production sector, energy gained from renewable power sources shall replace the present mixture, which mostly relies on ... [more ▼]

In the context of the transformation process currently taking place in the energy production sector, energy gained from renewable power sources shall replace the present mixture, which mostly relies on fossil burnings. Therefore, in the future most of the energy shall be gained by harvesting power from sun, wind or water, geothermal heat or biomass. In case of converting energy from wind into electrical power wind turbines are used in general, while hydropower turbines are the state-of-the-art machinery to derive energy from running water. In order to convert the potential energy from running water as well water wheels pose the method of choice. Turbines in air or water represent mechanically a two-field system, in which the structure of the turbine is surrounded by a streaming fluid. Due to the elasticity of the rotor blades the stresses of the fluid onto the structure deform the blades, which in return yield a time-dependent flow domain. Therefore turbines in a streaming fluid represent a typical example of fluid-structure interaction. Furthermore, in case of water wheels the surrounding air as third field and additional fluid phase comes into play introducing a free surface. In this contribution the governing equations of incompressible fluid flow are presented using primal variables and discretised via the space-time finite element method [3]. The discretised model equations of the fluid are stabilised using an SUPG/PSPG approach. Shape and test functions are continuous within the space-time slabs, while across the space- time slabs the shape and test functions are continuous only in space, but discontinuous in time yielding a time-discontinuous Galerkin approach. Due to the moving rotor blades a mesh moving technique needs to be incorporated into the computational set-up. Considering the occurring large but regular displacements of the flow boundary arising from the rotating rotor blades the shear-slip mesh update method (SSMUM) [1] as discontinuous mesh moving technique is applied. In case of water wheels the free surface is described implicitly via a Level-Set function [2] yielding a single fluid phase with almost discontinuous density and viscosity. The verification and validation of the developed numerical scheme is carried out with the help of computing classical benchmark problems as well as via a comparison to existing experimental data. [less ▲]

Numerical Analysis of Interaction between a Reacting Fluid and a Moving Bed with Spatially and Temporally Fluctuating Porosity

Scientific Conference (2020, August 31)

The purpose of this study is to propose a numerical approach that combines low computational costs through the use of high computing efficiency, allowing the realistic use of the design with a sufficient ... [more ▼]

The purpose of this study is to propose a numerical approach that combines low computational costs through the use of high computing efficiency, allowing the realistic use of the design with a sufficient result's accuracy for industrial applications to investigate biomass combustion in a large-scale reciprocating grate. In the present contribution, a Biomass combustion chamber of a 16 MW geothermal steam super-heater, which is part of the Enel Green Power "Cornia 2" power plant,is being investigated with high-performance computing methods. For this purpose, the extended discrete element method (XDEM) developed at the University of Luxembourg is used in an HPC environment, which includes both the moving wooden bed and the combustion chamber above it. The XDEM simulation platform is based on a hybrid four-way coupling between the Discrete Element Method (DEM) and Computational Fluid Dynamics (CFD). In this approach, particles are treated as discrete elements that are coupled by heat, mass, and momentum transfer to the surrounding gas as a continuous phase. For individual wood particles, besides the equations of motion, the differential conservation equations for mass, heat, and momentum are solved, which describe the thermodynamic state during thermal conversion. The grate system has three different moving sections to ensure good mixing of the biomass parts and appropriate residence time. The primary air enters from below the grate and is split into four different zones. Furthermore, a secondary air is injected at high velocity straight over the fuel bed through nozzles. A Flue Gas Recirculation is present and partly injected through two jets along the vertical channel and partly from below the grate. The numerical 3D model presented is based on a multi-phase approach. The biomass particles are taken into consideration via the XDEM Method, while the gaseous phase is described by CFD with OpenFOAM. Thus, the combustion of the particles on the moving beds in the furnace is processed by XDEM through conduction, radiation and conversion along with the interaction with the surrounding gas phase accounted for by CFD. The coupling of CFD-XDEM as an Euler-Lagrange model is used. The fluid phase is a continuous phase handled with an Eulerian approach and each particle is tracked with a Lagrangian approach. Energy, mass and momentum conservation is applied for every single particle and the interaction of particles with each other in the bed and with the surrounding gas phase are taken into account. An individual particle can have a solid, liquid, gas or inert material phases (immobile species) at the same time. The different phases can undergo a series of conversion through various reactions that can be homogeneous, heterogeneous or intrinsic (drying, pyrolysis, gasification and oxidation). Our first results are consistent with actual data obtained from the sampling of the residual solid in the industrial plant. Our model is also able to predict gas flux behaviour inside the furnace, particularly the flue gas recirculation on the combustion process injection. [less ▲]

A Numerical approach for the evaluation of particle-induced erosion in an Abrasive Waterjet focusing tube

in Powder Technology (2018)

In this work, a numerical approach to study erosion phenomena inside a focusing tube for Abrasive Water Jet (AWJ) is presented. The goal of this approach is to capture the erosive action of the particle ... [more ▼]

In this work, a numerical approach to study erosion phenomena inside a focusing tube for Abrasive Water Jet (AWJ) is presented. The goal of this approach is to capture the erosive action of the particle-laden flow developing inside the focusing tube as a result of cumulated impact phenomena. This is fundamental in the research and development of this sector in order to optimize cost and reliability of the AWJ system. With this purpose, a multiscale algorithm for CFD-DEM is used in combination with erosion models presented in the literature so to retrieve erosion profiles comparable to the one obtained by the most common experiments in this field. The approach is shown to provide insight into the process of wear development as the identification of areas characterized by brittle and cut phenomena. Preliminary parametric studies on the influence of impact models and particle diameters are proposed to show the potentialities of the method in describing the physics of the nozzle. [less ▲]

A Numerical Approach to the Merging of Argumentation Networks

in Fisher, Michael; Torre, Leon; Dastani, Mehdi (Eds.) et al Computational Logic in Multi-Agent Systems (2012)

In this paper, we propose a numerical approach to the problem of merging of argumentation networks. The idea is to consider an augmented network containing the arguments and attacks of all networks to be ... [more ▼]

In this paper, we propose a numerical approach to the problem of merging of argumentation networks. The idea is to consider an augmented network containing the arguments and attacks of all networks to be merged and then associate a weight to each of its components based on how they are perceived by the agents associated with the local networks. The combined weighted network is then used to define a system of equations from which the overall strength of the arguments is calculated. [less ▲]

Numerical check of the Meyerhof bearing capacity equation for shallow foundations

in Innovative Infrastructure Solutions (2018), 3(9), 1-13

Most geotechnical design codes and books use the equations of Meyerhof or Terzaghi to calculate shallow foundations. These equations are based on the failure mechanism published by Prandtl for shallow ... [more ▼]

Most geotechnical design codes and books use the equations of Meyerhof or Terzaghi to calculate shallow foundations. These equations are based on the failure mechanism published by Prandtl for shallow strip foundations. The common idea is that failure of a footing occurs in all cases according to a Prandtl-wedge failure mechanism. To check the failure mechanism and the equations of the currently used bearing capacity factors and correction factors, a large number of finite-element calculations of strip and circular footings have been made. The finite-element calculations show that in cases of soils with high friction angles, soils without cohesion or a surcharge, footings with inclined loading or circular footings, not the Prandtl-wedge failure mechanism, but other failure mechanisms occur. In addition, the currently used equations for the bearing capacity factors and correction factors are too high. Therefore, new equations have been presented in this article. For some correction factors, for example, the inclination factors and the cohesion slope factor, an analytical solution is found. [less ▲]

Numerical competencies of young children

Scientific Conference (2007)

Numerous studies show that wide ranges of competencies in different fields are necessary to develop a good numerical competency. Our research tried to find an answer to the question, which out of various ... [more ▼]

Numerous studies show that wide ranges of competencies in different fields are necessary to develop a good numerical competency. Our research tried to find an answer to the question, which out of various factors mainly influence the numerical competencies of young children. We focused on visuospatial, perceptive and tactile skills as determinants of the quality of early numerical representations. We adopted a longitudinal research design with three periods of data collection (two data collections during the second year of kindergarten and one at the end of first grade). Our test setting for the kindergarten included tests in the three areas mentioned above. The evaluation of these results shows that the numerical competencies are influenced by visuospatial competencies and knowledge of pre-numerical facts. An importance of the perceptive and tactile skills could not be established. At the end of first grade, after formal mathematical instruction, we made a mathematical competency test. A structural equation model of the subtests shows that the numerical knowledge at this stage can be divided in two separate factors: 1. A representational numerical factor (analogical representation of quantities: Triple Code model of Dehaene) 2. A more formal knowledge of mathematics (visual Arabic representation: Triple Code model of Dehaene, 1992). Predicting these two factors from the competency profile measured in kindergarten showed that the representational numerical factor was very well predicted from a general spatio-numerical factor found in the previous year, while the formal knowledge was predicted to a lesser degree by tactile skills measured at the end of kindergarten. Implications for numerical teaching in Kindergarten will be discussed. [less ▲]