Discrete modelling of capillary mechanisms in multi-phase granular media

A numerical study of multi-phase granular materials based upon micro-mechanical modelling is proposed. Discrete element simulations are used to investigate capillary induced effects on the friction properties of a granular assembly in the pendular regime. Capillary forces are described at the local scale through the Young-Laplace equation and are superimposed to the standard dry particle interaction usually well simulated through an elastic-plastic relationship. Both effects of the pressure difference between liquid and gas phases and of the surface tension at the interface are integrated into the interaction model. Hydraulic hysteresis is accounted for based on the possible mechanism of formation and breakage of capillary menisci at contacts. In order to upscale the interparticular model, triaxial loading paths are simulated on a granular assembly and the results interpreted through the Mohr-Coulomb criterion. The micro-mechanical approach is validated with a capillary cohesion induced at the macroscopic scale. It is shown that interparticular menisci contribute to the soil resistance by increasing normal forces at contacts. In addition, more than the capillary pressure level or the degree of saturation, our findings highlight the importance of the density number of liquid bonds on the overall behaviour of the material

Using the incremental Hole-drilling technique for measuring residual stresses in fibre-reinforce polymer composites

The Incremental hole-drilling technique (IHD) seems to be a promising technique, among the destructive (relaxation) techniques, to determine in-depth non-uniform residual stresses in fibre-reinforced polymer composites. Hence, valid theoretical approaches for IHD residual stress determination in composite laminates, based on a set of strain-depth relaxation curves, are needed. Nevertheless, the influence of the drilling process itself on the initial residual stress state, i.e. existing prior to hole drilling, must be verified first. In this work, the IHD residual stress evaluation procedures in composite laminates will be reviewed and an original hybrid experimental-numerical methodology will be used to quantify the residual strain induced by the drilling process. Thus, residual strains induced by ultra-high speed drilling processes on carbon-epoxy laminates (CFRPs) have been quantified. The results seem to show that IHD technique can be improved to be successfully applied for measuring residual stresses in CFRPs

Las órdenes militares en la cruzada granadina de Alfonso el Benigno (1329-1334)

A la memoria de la Dra. Regina Sainz de la MazaEn este estudio se recupera la investigación las Órdenes militares catalanoaragonesas durante el siglo XIV. El interés del trabajo radica en el hecho de que en él se considera, de manera conjunta, la actuación en la cruzada de las cuatro Órdenes militares enclavadas en territorio catalanoaragonés, lo cual permite observar tanto su distinto grado de participación como la diferente actitud del monarca hacia cada una de ellas.Peer reviewe

Pain, Physical and Social Functioning, and Quality of Life in Individuals with Multiple Hereditary Exostoses in the Netherlands

Background: This study aimed to assess pain and quality of life in a large cohort of patients with multiple hereditary exostoses. Methods: All 322 known patients with multiple hereditary exostoses in the Netherlands were asked to participate. An age-specific questionnaire was sent to children (less than eighteen years old) and adults. The questionnaire focused on pain, daily activities, and school and/or professional situation. Adults also filled out the RAND-36 questionnaire.Results were statistically analyzed with use of the SPSS 15.0 software and with the chi-square test and multiple logistic regression. A p value of <0.05 was regarded as significant. Results: Two hundred and eighty-three patients (88%), including 184 adults (65%) and ninety-nine children (35%), completed the questionnaire. Multiple hereditary exostoses resulted in various physical and social consequences. The majority of adults (119) were employed; however, thirty-three (28%) had changed jobs because of the symptoms of multiple hereditary exostoses and twenty-five (21%) required adjustments in their working environment. Of the sixty-five adults who were not employed, thirteen were medically unfit to work. Of eighty-five children attending school, forty-five (53%) experienced problems at school. The symptoms of multiple hereditary exostoses caused twenty-seven children (27%) and eighty-five adults (46%) to stop participating in sporting activities. Pain was the greatest problem, with sixty-two children (63%) and 152 adults (83%) who reported recent pain. On multivariate analysis, pain in adults was correlated most significantly with age and problems at work, and pain in children was correlated with the perception of the disease and problems at school. Adult patients with multiple hereditary exostoses had a lower quality of life than the Dutch reference groups, with lower scores on six of eight RAND-36 subscales. Conclusions: Our study confirms that multiple hereditary exostoses is a chronic disease causing a profound impact on quality of life. The results suggest that pain is not the only problem associated with multiple hereditary exostoses, as it has an extensive influence on daily activities, as well as on social and psychological well-being, causing significant disability

From Relational Data to Graphs: Inferring Significant Links using Generalized Hypergeometric Ensembles

The inference of network topologies from relational data is an important problem in data analysis. Exemplary applications include the reconstruction of social ties from data on human interactions, the inference of gene co-expression networks from DNA microarray data, or the learning of semantic relationships based on co-occurrences of words in documents. Solving these problems requires techniques to infer significant links in noisy relational data. In this short paper, we propose a new statistical modeling framework to address this challenge. It builds on generalized hypergeometric ensembles, a class of generative stochastic models that give rise to analytically tractable probability spaces of directed, multi-edge graphs. We show how this framework can be used to assess the significance of links in noisy relational data. We illustrate our method in two data sets capturing spatio-temporal proximity relations between actors in a social system. The results show that our analytical framework provides a new approach to infer significant links from relational data, with interesting perspectives for the mining of data on social systems.Comment: 10 pages, 8 figures, accepted at SocInfo201

Pore-scale Modeling of Viscous Flow and Induced Forces in Dense Sphere Packings

We propose a method for effectively upscaling incompressible viscous flow in large random polydispersed sphere packings: the emphasis of this method is on the determination of the forces applied on the solid particles by the fluid. Pore bodies and their connections are defined locally through a regular Delaunay triangulation of the packings. Viscous flow equations are upscaled at the pore level, and approximated with a finite volume numerical scheme. We compare numerical simulations of the proposed method to detailed finite element (FEM) simulations of the Stokes equations for assemblies of 8 to 200 spheres. A good agreement is found both in terms of forces exerted on the solid particles and effective permeability coefficients

Probing empirical contact networks by simulation of spreading dynamics

Disease, opinions, ideas, gossip, etc. all spread on social networks. How these networks are connected (the network structure) influences the dynamics of the spreading processes. By investigating these relationships one gains understanding both of the spreading itself and the structure and function of the contact network. In this chapter, we will summarize the recent literature using simulation of spreading processes on top of empirical contact data. We will mostly focus on disease simulations on temporal proximity networks -- networks recording who is close to whom, at what time -- but also cover other types of networks and spreading processes. We analyze 29 empirical networks to illustrate the methods

The Current State of Performance Appraisal Research and Practice: Concerns, Directions, and Implications

On the surface, it is not readily apparent how some performance appraisal research issues inform performance appraisal practice. Because performance appraisal is an applied topic, it is useful to periodically consider the current state of performance research and its relation to performance appraisal practice. This review examines the performance appraisal literature published in both academic and practitioner outlets between 1985 and 1990, briefly discusses the current state of performance appraisal practice, highlights the juxtaposition of research and practice, and suggests directions for further research

OPM magnetorelaxometry in the presence of a DC bias field

Spatial quantitative information about magnetic nanoparticle (MNP) distributions is a prerequisite for biomedical applications like magnetic hyperthermia and magnetic drug targeting. This information can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation of previously aligned MNP’s magnetic moments is measured by sensitive magnetometers and an inverse problem is solved. To remove or minimize the magnetic shielding in which MRX imaging is carried out today, the knowledge of the influence of background magnetic fields on the MNP’s relaxation is a prerequisite. We show MRX measurements using an intensity-modulated optically pumped magnetometer (OPM) in background magnetic fields of up to 100μT. We show that the relaxation parameters alter or may be intentionally altered significantly by applying static fields parallel or antiparallel to the MNP’s alignment direction. Further, not only the relaxation process of the MNP’s magnetic moments could be measured with OPM, but also their alignment due to the MRX excitation field. © 2020, The Author(s)

OPM magnetorelaxometry in the presence of a DC bias field

Spatial quantitative information about magnetic nanoparticle (MNP) distributions is a prerequisite for biomedical applications like magnetic hyperthermia and magnetic drug targeting. This information can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation of previously aligned MNP's magnetic moments is measured by sensitive magnetometers and an inverse problem is solved. To remove or minimize the magnetic shielding in which MRX imaging is carried out today, the knowledge of the influence of background magnetic fields on the MNP's relaxation is a prerequisite. We show MRX measurements using an intensity-modulated optically pumped magnetometer (OPM) in background magnetic fields of up to 100 [my]T. We show that the relaxation parameters alter or may be intentionally altered significantly by applying static fields parallel or antiparallel to the MNP’s alignment direction. Further, not only the relaxation process of the MNP's magnetic moments could be measured with OPM, but also their alignment due to the MRX excitation field