Search results for "Method"
showing 10 items of 13253 documents
Zinc isotope variations in archeological human teeth (Lapa do Santo, Brazil) reveal dietary transitions in childhood and no contamination from gloves
2020
International audience; Zinc (Zn) isotope ratios of dental enamel are a promising tracer for dietary reconstruction in archeology, but its use is still in its infancy. A recent study demonstrated a high risk of Zn contamination from nitrile, and latex gloves used during chemical sample preparation. Here we assess the potential impact of the use of such gloves during enamel sampling on the Zn isotope composition of teeth from a population of early Holocene hunter gatherers from Lapa do Santo, Lagoa Santa, Minas Gerais, Brazil. We first examined the amount of Zn and its isotopic composition released from the gloves used in this study by soaking them in weak nitric acid and water. We compared …
Virtual element method for computational homogenization of composite and heterogeneous materials
2020
Abstract In this study, a two-dimensional multi-region framework, based on the use of the Virtual Element Method (VEM), is developed for computational materials homogenization and applied to different classes of widely employed heterogeneous materials. The VEM has recently emerged as a powerful generalisation of the Finite Element Method capable of dealing with very general polygonal mesh elements, including non-convex or highly distorted elements. Such features are appealing for the treatment of problems whose analysis domains present complex or statistical morphological features, which would generally require careful and time-consuming mesh/data preparation and regularization. In this wor…
Ritz Model for Damage Analysis in Variable Angle Tow Composite Plates
2022
In this work, a Ritz method is developed for progressive damage analysis of multilayered variable angle tow (VAT) composite plates under geometrically non-linear strains. The proposed model adopts a first order shear deformation theory and considers geometric non-linearities through the von Karman assumptions. A meso-modelling approach based on Continuum Damage Mechanics is adopted for analysing the initiation and evolution of damage. The onset of damage is predicted using the Hashin’s criteria. Four damage indices are defined and computed for expressing the degradation of the mechanical properties of the material, both for fibers and matrix under either tension and compression loading. A s…
A Fiber Optic Strain Gage Sensor for Measuring Preload in Thick Composite Bolted Joints
2019
Mechanical fastening is a popular choice in joining composites because of the ability to transfer high loads and the ease of assembly and disassembly. In this study, the failure behavior of composite–aluminum single lap bolted joint is investigated. In particular, the effects of varying the preload on the bolt are examined. In order to accurately measure the preload, a specialized sensor that uses a fiber Bragg grating sensor embedded in the bolt is proposed and created. This sensor is realized for the current tests but can be expanded to other applications. An experimental study of bolted single-lap joints varying the tightening torque value has been carried out and, in order to validate t…
Electrochemistry of TiO2–iron hexacyanocobaltate composite electrodes
2014
Abstract In this paper we investigate the electrochemical behavior of iron hexacyanocobaltate (FeHCC) in comparison to the cobalt hexacyanoferrate (CoHCF). The best results were achieved on electrochemical synthesized film of FeHCC on the TiO2 modified electrodes. The chemical and physical characterizations confirm the formation of the FeHCC with the classical cubic crystal structure of the Prussian blue analogs, with cell parameter a very close to 10 A, as well as the formation of micro aggregates of TiO2 covered by FeHCC. The synthesis was performed on various substrates such as glassy carbon (GC), graphite foil (GF) and indium tin oxide (ITO) in order to develop new technological applica…
Defining a reduced volume zone for the simulation of burst test on a composite pressure vessels
2018
International audience; A Fibre-Break Model (FBM) developed at Mines ParisTech can predict the burst pressure of high pressure composite vessels. This model uses random values of fibre strength at each Gauss point of the considered vessels meshed with finite element (FE). However, previous studies has determined the optimum FEs to be used on real-scale structures (0.1 mm x 0.1 mm x 8 mm). A simple calculation shows that, on a real-scale pressure vessel, this induces a gigantic number of FEs, hence the extensive computation time. To overcome this problem, the integral range method is proposed to find a reduced volume zone of the vessels, on which an equivalent calculation can be made and giv…
Using Technologies to Teach Different Age Groups Meaningfully
2018
Increasing use of technologies in schools is inevitable as technologies provide new opportunities for innovative ways of learning and naturally attract students’ attention as modern and even playful tools. However, use of technologies can be most effective if the tasks are suitable for the specific age of students. It is necessary for teachers to be aware of cognitive development of children in different age groups in order to offer teaching methods and tasks that can be well-perceived by students and that foster the development of their cognitive abilities. This chapter provides a brief overview of cognitive development of children at different school ages, including development of executi…
Teaching strategies to create visual representations of key ideas in content area text materials: A longterm intervention inserted in school curricul…
1995
This paper describes a long-term research in which middle-grade school children were taught how to represent visually text key ideas through idea-mapping techniques. It consists of three studies, one for each year of our research. Children were at sixth grade when the instruction began, and they were at eighth grade when it finished. Another group of children from a different public school served as control group. Instruction was very close to the real school conditions: instructors were ordinary teachers, instruction was inserted in the content area curriculum, and ordinary textbooks were regularly employed, though combined with specially elaborated materials. Results were positive in the …
Comprensió de la lectura en alumnes d'ensenyament secundari
2006
Aquest treball es planteja per conèixer més de primera mà la comprensió i assimilació de textos escrits, en alumnes de l'actual ensenyament secundari. La mostra emprada va ser de 28 alumnes entre 14 i 20 anys, de 3r d'ESO i COU majoritàriament, de l'Institut d'Ensenyament Secundari «Alameda de Osuna» de Madrid. Els resultats obtinguts en aquest estudi indiquen que, en els lectors de menor edat els processos de lectura són més simples i en alguns casos incomplets, mentre que els lectors de major edat fan una lectura que implica processos cognitius més complexos, adequats i profunds.
Approximation of piecewise smooth functions and images by edge-adapted (ENO-EA) nonlinear multiresolution techniques
2008
Abstract This paper introduces and analyzes new approximation procedures for bivariate functions. These procedures are based on an edge-adapted nonlinear reconstruction technique which is an intrinsically two-dimensional extension of the essentially non-oscillatory and subcell resolution techniques introduced in the one-dimensional setting by Harten and Osher. Edge-adapted reconstructions are tailored to piecewise smooth functions with geometrically smooth edge discontinuities, and are therefore attractive for applications such as image compression and shock computations. The local approximation order is investigated both in L p and in the Hausdorff distance between graphs. In particular, i…