A new algorithm for computing the indentation of a rigid body of arbitrary shape on a viscoelastic half-space

In this paper the contact problem between a rigid indenter of arbitrary shape and a viscoelastic half-space is considered. Under the action of a normal force the penetration of the indenter and the distribution of contact pressure change. We wish to find the relations which link the pressure distribution, the resultant force on the indenter and the penetration on the assumption that the surfaces are frictionless. For indenters of arbitrary shape the problem may be solved numerically by using the Matrix Inversion Method (MIM), extended to viscoelastic case. In this method the boundary conditions are satisfied exactly at specified "matching points" (the mid-points of the boundary elements). It can be validated by comparing the numerical results to the analytic solutions in cases of a spherical asperity (loading and unloading) and a conical asperity (loading only)

Supporting a Multi-formalism Model Driven Development Process with Model Transformation, a TOPCASED implementation

International audienceThe ASSERT (Automated proof based System and Software Engineering for Real-Time Applications) European Integrated Project (IST-FP6-004033, http://www.assert-project.net/) defined and experimented a multi formalism Model Driven Engineering (MDE) process, enforcing an approach with separated specification and refinement of functional and non-functional properties.• Functional specification, design and development is based on UML profiles to support AADL concepts [2] and behavioural specification.• Real time Architecture properties are based on extensions targeting Ravenscar Computing execution Model (RCM see [6]) constraints upon component interface and ports.• Model transformation is supporting correctness preserving rules towards a Virtual Machine execution environment or a verification dedicated environment.A tool chain called IDEA (Integrated Development Environment for ASSERT) supporting the process was developed by the CS ASSERT team on top of the Eclipse/TOPCASED environment allowing:• Integrated use of several formalisms in a development life-cycle (UML, AADL, IF[4]) .• Model transformation from UML to IF, AADL to RCM and RCM to Ada• Automated code generationThe approach experimented allows combined use of best suited formalisms and features for MDE developments. The TOPCASED tool proved to be a unique integrated toolset for prototyping UML and meta models supporting tools.The main feedback gained from applying the notations and approach on small to medium case studies is that UML profiling is not scalable, and that use of several Domain Specific Languages (DSL) seems far more suitable. Semantic clashes can be limited by raising the abstraction level, and by partitioning properties for verification

Gaspard2 UML profile documentation

This document describes the current UML profile of Gaspard2. This profile extends the UML semantics to allow the user to describe a SoC (System-on-Chip) in three steps: the application (behavior of the Soc), the hardware architecture, and the association of the application to the hardware architecture. The application is represented following a data flow model, but additional mechanisms permit the usage of control flow on those applications. In addition to those notions, the profile contains a package introducing factorization mechanisms to enable the compact description of massively parallel and repetitive systems

Declines in Pediatric Bacterial Meningitis in the Republic of Benin Following Introduction of Pneumococcal Conjugate Vaccine: Epidemiological and Etiological Findings, 2011-2016.

BACKGROUND: Pediatric bacterial meningitis (PBM) remains an important cause of disease in children in Africa. We describe findings from sentinel site bacterial meningitis surveillance in children <5 years of age in the Republic of Benin, 2011-2016. METHODS: Cerebrospinal fluid (CSF) was collected from children admitted to Parakou, Natitingou, and Tanguieta sentinel hospitals with suspected meningitis. Identification of Streptococcus pneumoniae (pneumococcus), Haemophilus influenzae, and Neisseria meningitidis (meningococcus) was performed by rapid diagnostic tests, microbiological culture, and/or polymerase chain reaction; where possible, serotyping/grouping was performed. RESULTS: A total of 10 919 suspected cases of meningitis were admitted to the sentinel hospitals. Most patients were 0-11 months old (4863 [44.5%]) and there were 542 (5.0%) in-hospital deaths. Overall, 4168 CSF samples were screened for pathogens and a total of 194 (4.7%) PBM cases were confirmed, predominantly caused by pneumococcus (98 [50.5%]). Following pneumococcal conjugate vaccine (PCV) introduction in 2011, annual suspected meningitis cases and deaths (case fatality rate) progressively declined from 2534 to 1359 and from 164 (6.5%) to 14 (1.0%) in 2012 and 2016, respectively (P < .001). Additionally, there was a gradual decline in the proportion of meningitis cases caused by pneumococcus, from 77.3% (17/22) in 2011 to 32.4% (11/34) in 2016 (odds ratio, 7.11 [95% confidence interval, 2.08-24.30]). Haemophilus influenzae meningitis fluctuated over the surveillance period and was the predominant pathogen (16/34 [47.1%]) by 2016. CONCLUSIONS: The observed decrease in pneumococcal meningitis after PCV introduction may be indicative of changing patterns of PBM etiology in Benin. Maintaining vigilant and effective surveillance is critical for understanding these changes and their wider public health implications

ERS: A simple scoring system to predict early recurrence after surgical resection for hepatocellular carcinoma.

peer reviewed[en] BACKGROUND: Surgical resection (SR) is a potentially curative treatment of hepatocellular carcinoma (HCC) hampered by high rates of recurrence. New drugs are tested in the adjuvant setting, but standardised risk stratification tools of HCC recurrence are lacking. OBJECTIVES: To develop and validate a simple scoring system to predict 2-year recurrence after SR for HCC. METHODS: 2359 treatment-naïve patients who underwent SR for HCC in 17 centres in Europe and Asia between 2004 and 2017 were divided into a development (DS; n = 1558) and validation set (VS; n = 801) by random sampling of participating centres. The Early Recurrence Score (ERS) was generated using variables associated with 2-year recurrence in the DS and validated in the VS. RESULTS: Variables associated with 2-year recurrence in the DS were (with associated points) alpha-fetoprotein (100: 3), size of largest nodule (≥40 mm: 1), multifocality (yes: 2), satellite nodules (yes: 2), vascular invasion (yes: 1) and surgical margin (positive R1: 2). The sum of points provided a score ranging from 0 to 11, allowing stratification into four levels of 2-year recurrence risk (Wolbers' C-indices 66.8% DS and 68.4% VS), with excellent calibration according to risk categories. Wolber's and Harrell's C-indices apparent values were systematically higher for ERS when compared to Early Recurrence After Surgery for Liver tumour post-operative model to predict time to early recurrence or recurrence-free survival. CONCLUSIONS: ERS is a user-friendly staging system identifying four levels of early recurrence risk after SR and a robust tool to design personalised surveillance strategies and adjuvant therapy trials

The noise-lovers: cultures of speech and sound in second-century Rome

This chapter provides an examination of an ideal of the ‘deliberate speaker’, who aims to reflect time, thought, and study in his speech. In the Roman Empire, words became a vital tool for creating and defending in-groups, and orators and authors in both Latin and Greek alleged, by contrast, that their enemies produced babbling noise rather than articulate speech. In this chapter, the ideal of the deliberate speaker is explored through the works of two very different contemporaries: the African-born Roman orator Fronto and the Syrian Christian apologist Tatian. Despite moving in very different circles, Fronto and Tatian both express their identity and authority through an expertise in words, in strikingly similar ways. The chapter ends with a call for scholars of the Roman Empire to create categories of analysis that move across different cultural and linguistic groups. If we do not, we risk merely replicating the parochialism and insularity of our sources.Accepted manuscrip

Influence de la texture de chaussée sur le bruit de contact pneumatique/chaussée

Ce travail de thèse concerne l'étude expérimentale et numérique du contact pneumatique/chaussée pour la prévision du bruit de roulement. Les efforts de contact dynamiques entre le pneu et la chaussée sont modélisés par une succession d'états statiques entre un massif semi-infini élastique et plusieurs aspérités parfaitement rigides. Le problème de contact statique est résolu à l'aide d'une Méthode Itérative à Deux Échelles (MIDE) plus rapide que les méthodes numériques classiques. Au niveau expérimental, les efforts de contact mesurés entre un pavé de gomme et plusieurs pointes sphériques sont en bon accord avec ceux donnés par la MIDE. Dans le cas du contact statique entre un pneu lisse et différentes surfaces rugueuses, les comparaisons essais/calculs restent bonnes pour des surfaces composées de pointes sphériques et des revêtements de chaussée à macrotexture modérée. Elles se dégradent pour des revêtements à forte ou faible macrotexture. Ces résultats sont encourageants étant donné la précision de mesure et les hypothèses simples du modèle par rapport à la complexité du contact pneumatique/chaussée. Enfin, des mesures de force de contact et de bruit sont réalisées sur site réel pour un pneu lisse roulant sur différentes surfaces routières. Il semblerait que les efforts de contact dynamiques soient influencés par la visco-élasticité de la gomme et par la vibration du pneumatique au cours du roulement. Ces phénomènes pourront être introduits dans le modèle à l'avenir. D'autre part, les niveaux de force et de bruit mesurés sont très fortement corrélés autour de 800 Hz, fréquence qui pourrait directement être liée à la texture de chaussée.This work deals with experimental and numerical investigations on tyre/road contact for the prediction of tyre/road noise. The dynamical contact stresses between the tyre and the road are modeled by successive static states between an elastic half-space and several perfectly rigid asperities. The problem in statics is solved using a Two-scale Iterative Method (TIM) which is faster than classical numerical methods. Concerning experiments, the contact stresses measured between a rubber block and several spherical punches are in good agreement with the results of the TIM. For the contact in statics between a slick tyre and many rough surfaces, the comparisons between experiments and calculation are still good for surfaces composed of spherical indenters and road surfaces with medium macrotexture. The results are less good for road surfaces with high or small macrotexture. These results are encouraging considering the precision of the measurement system and the simple hypotheses used in the model in comparison with the complexity of tyre/road contact. Finally, in situ measurements of contact forces and tyre/road noise were carried out for a slick tyre rolling on several road surfaces. It seems that dynamical contact stresses are influenced by the visco-elastic behavior of the rubber and by the vibration of the tyre during rolling. These phenomena could be included in the model in the future. Moreover, the measured levels of contact forces and noise were greatly correlated around 800 Hz, which frequency could be directly linked to road texture.NANTES-BU Sciences (441092104) / SudocNANTES-Ecole Centrale (441092306) / SudocMARNE LA VALLEE-ENPC-RECHERCHE (774682302) / SudocSudocFranceF

Experimental study of dynamical contact forces for tyre/road noise application

International audienceThis paper deals with the experimental study of tyre/road contact forces in rolling conditions for tyre/road noise investigation. In situ measurements of contact forces were carried out for a slick tyre rolling on six different road surfaces at rolling speeds between 30 km/h and 50 km/h. Contact stresses were measured at a sampling frequency of 10752 Hz using a single array of pressure sensitive cells placed both along and perpendicular to the rolling direction. The contact areas obtained during rolling were smaller than the one measured in statics. This could be due to an influence of the viscoelastic behavior of the rubber of the tyre tread during rolling. Additionally the root-mean-square of the resultant contact forces at various speeds was in the same order for a given road surface, while their spectra at various speeds were quite different. This could be explained by a spectral influence of the vibration of the tyre during rolling

Prediction of contact stresses for tyre-road noise modelling

International audienceTyre/road noise is greatly influenced by the dynamic forces generated in the contact patch. The current research for predicting the contact stresses is based on analytical formulations in two or three dimensions. The paper deals with the validation of an analytical multipoint contact pattern currently developed for introduction in a full model for tyre/road noise. The tyre tread is modelled by an elastic half-space and the road surface by several rigid asperities with random shapes. The contact law for each indenter depends on the interpenetrated volume, the area and the perimeter of its base. The model is three-dimensional and considers the interaction between the contact points. The contact between a rubber block and a periodic surface composed of spherical indenters was studied. The contact areas and stresses were measured using pressure sensitive Fuji Prescale films. The accuracy of the measurement method was estimated using the hertzian contact between a spherical indenter and the rubber block. The experimental results were compared with the multipoint model. Next work will focus on the validation of the model for real road surfaces, by evaluating the contact stresses first in statics and then in rolling conditions