Abstract

Academic discourse is characterized by an abundance of abstract nouns such as analysis, research, process, concept, approach or role. These nouns are considered cohesive devices since their full content is determined by referring to their context and they have received numerous denominations (anaphoric, signaling, carrier, shell or metadiscursive nouns). This paper explores the metadiscursive role of shell nouns in a corpus of academic abstracts written by university students for their Senior Theses, based on Schmid’s (2000) and Jiang and Hyland’s (2016, 2017) proposals. The rhetorical, persuasive potential of these abstract nouns in this type of academic discourse is also addressed. The results show that advanced EFL writers deploy a wide range of abstract nouns in patterns that resemble those of scholars (Jiang & Hyland 2017). Different moves in the text seem to influence the type of noun employed. All in all, advanced English Studies majors are aware of academic disciplinary conventions but would benefit from training in abstract writing, particularly in the distribution of the text’s moves.

Abstract

Geometry is one of the main factors controlling the overall stability of levees, in addition to their hydraulic and mechanical characteristics, while in turn, their material strength strongly depends on their degree of saturation. Given that levees are usually partially saturated (Lo Presti et al., 2020) and that this partial saturation greatly contributes to their stability, any technique aimed at maintaining the levee in this condition is extremely useful. Protection of the levee sides by means of geogrids and biomats reduces the amount of infiltration by water, helps water adsorption by grass vegetation and contributes to mechanical strength thanks to the root apparatus of the grass cover. Vegetation is a good system for controlling slope erosion and instability. It can reduce the meteoric water that infiltrates into the soil and consequently the pore pressure. On the other hand, the root systems not only keep the soil partially saturated but also increase the soil shear strength with their mechanical contribution. The mechanical parameters of the root-soil system are important to evaluate the increase in soil shear strength due to the roots. Mechanically, roots contribute to the stabilization/reinforcement of soil by means of an additional apparent cohesion. It is believed that this apparent cohesion originates mainly from the root tensile strength, as well as capillary forces in partially saturated soils. In terms of root cohesion, an evaluation of this reinforcement can be obtained by means of direct shear tests. The authors set up a systematic experimental activity using a large direct shear box (Vannucci et al. 2019) with the purpose of considering the dual effect of suction and the soil tensile strength. A series of direct shear tests (large and standard shear box) were carried out. This paper presents the results of an experimental laboratory investigation on samples of rooted soil. In particular, the results of direct shear tests with a large shear box (300 × 300 × 100 mm) and with a standard shear box are shown. The results confirm an increase in the soil shear strength, in terms of cohesion, when roots are present. 1

Abstract

Granular flow is a complex process depending on a large set of parameters such as grain morphology, surface friction, flow geometry, stress field and cohesion (e.g. attractive interaction between grains). The latter arises from the presence of humidity, electrostatic charges and Van der Waals forces within the grains that lead, among other effects, to the appearance of surface flow fluctuations also called avalanches. Those surface fluctuations produce an intermittent granular flow and determine the processability of a powder in many application. In order to link the flow fluctuations and the cohesion between grains, we reproduced numerically with a DEM model the flow of cohesive granular materials in a 2D rotating drum. A simplified cohesive interaction between circular grains has been implemented and the granular flow has been analyzed through the flowing angle and the interface fluctuations. The numerical results are compared with experimental results obtained with GranuDrum instrument and a set of silicon carbide grains with different grain sizes and therefore different cohesiveness. The motivation behind this study is to determine to what extent a simplified model can reproduce a complex flow. The similarities between numerical and experimental results and also the discrepancies are discussed. This comparison gives a fundamental background to the cohesive index parameter measured with GranuDrum instrument from the interface fluctuations. Finally, we show that comparing the flow inside a rotating drum obtained numerically and experimentally is a practical way to calibrate a set of parameters before the simulation of a complex process.

Abstract

We present the equations obeyed by contacts forces in a granular system solved by the Contact Dynamics algorithm. We consider their resolution in a very simple case of cohesive interaction, i.e.for a straightforward two-body 2D normal collision. The equations predict that increasing time steps should coincide with an increase of the effective cohesion of the systems. Numerical simulations are performed to verify the predictions, in the case of cohesive granular piles falling in the gravity field. A discussion on how a seemingly purely numerical quantity may end up being a non-trivial ingredient in the physics of the simulated system ensues.

Abstract

Although intensive research on the flow of dry granular materials has allowed for the proposition of continuum rheology and modelling, the behaviour of flowing cohesive material has attracted less attention so far. To start modelling such cohesive flows, we first focus on the configuration of a granular collapse, which is a simple benchmark test. Specifically, we compare granular-collapse experiments of cohesive grains with numerical simulations, where we test a simple rheology for the material : the so-called µ(I)-rheology, supplmented by a yield stress for cohesion. This document reports the sensitivity of our numerical simulations on the parameters of the rheology, often challenging to measure in experiments.