Composite Material Characterization using Eddy Current by 3D FEM Associated with Iterative Technique

In this paper, an iterative technique, employing the T formulation associated with the finite element method, based on Maxwell's equations and the Biot-savart law, is used for analyzing the density of eddy currents in composite carbon fiber reinforced polymer (CFRP) materials. For this purpose, a code has been developed for solving an electromagnetic 3D non-destructive evaluation problem. This latter permits the characterization of this CFRP and determinate of fibers orientation using the impedance variation which is implanted in polar diagram. Firstly, the obtained results are compared with those of the analytical model. This comparison reveals a high concordance which proves the validity of the proposed method. Secondly, three different applications are shown for illustrating the characterization of unidirectional, bidirectional and multidirectional piece using a rectangular coil plotted in normalized impedance diagram

Widespread exploitation of the honeybee by early Neolithic farmers.

This is the author's version of an article subsequently published in Nature. The definitive version is available from the publisher via: doi: 10.1038/nature15757.Copyright © 2015, Rights Managed by Nature Publishing GroupThe pressures on honeybee (Apis mellifera) populations, resulting from threats by modern pesticides, parasites, predators and diseases, have raised awareness of the economic importance and critical role this insect plays in agricultural societies across the globe. However, the association of humans with A. mellifera predates post-industrial-revolution agriculture, as evidenced by the widespread presence of ancient Egyptian bee iconography dating to the Old Kingdom (approximately 2400 BC). There are also indications of Stone Age people harvesting bee products; for example, honey hunting is interpreted from rock art in a prehistoric Holocene context and a beeswax find in a pre-agriculturalist site. However, when and where the regular association of A. mellifera with agriculturalists emerged is unknown. One of the major products of A. mellifera is beeswax, which is composed of a complex suite of lipids including n-alkanes, n-alkanoic acids and fatty acyl wax esters. The composition is highly constant as it is determined genetically through the insect's biochemistry. Thus, the chemical 'fingerprint' of beeswax provides a reliable basis for detecting this commodity in organic residues preserved at archaeological sites, which we now use to trace the exploitation by humans of A. mellifera temporally and spatially. Here we present secure identifications of beeswax in lipid residues preserved in pottery vessels of Neolithic Old World farmers. The geographical range of bee product exploitation is traced in Neolithic Europe, the Near East and North Africa, providing the palaeoecological range of honeybees during prehistory. Temporally, we demonstrate that bee products were exploited continuously, and probably extensively in some regions, at least from the seventh millennium cal BC, likely fulfilling a variety of technological and cultural functions. The close association of A. mellifera with Neolithic farming communities dates to the early onset of agriculture and may provide evidence for the beginnings of a domestication process.Natural Environment Research Council (NERC)English HeritageEuropean Research Council (ERC)Leverhulme TrustMinistère de la Culture et de la CommunicationMinistère de l’Enseignement Supérieur et de la RechercheRoyal SocietyWellcome Trus

Application of the model predictive control and the SVPWM techniques on five-phase inverter

The multi-phase inverters have attracted recently much attention among the researchers, practitioners and industries due to their many advantages compared to their conventional count parts of single and three-phase inverters, which have been used widely in almost the domestic, commercial and industrial application. The present paper presents an invitation on the application of the space vector pulse width modulation (SVPWM) control technique and the model predictive control (MPC) technique on a five-phase inverter powering a star connected five-phase load. Firstly, the principle of each control technique has been presented in details, then two simulation experiments have been performed on five-phase two-level inverter feeding a balanced star five-phase RL load using the SVPWM control technique and the MPC control technique separately, where a load change is considered in this two tests. The main aim from this study is to discover the main pros and cons of each control technique and their applicability in ensuring the control of five-phase inverter under different operation constraints or conditions. The obtained results for the both cases are presented and discussed based on the main key factors such as the harmonics content, the THD, the dynamic response to the load variation, the dynamic behaviours at transient situation and the computing requirement. It can be said that the present comparative study has allowed shedding the light on the main features and requirements of the applicability of the both control techniques with multi-phase inverters, which are depending on the requirement of the related application and the merits of each control technique.This work was financially supported by the Applied Automation and Industrial Diagnostics Laboratory (LAADI), Ziane Achour University of Djelfa in Algeria under the Doctoral Habilitation approved by the decision of the Ministry of High Education and Scientific Research (MESRS)decision number 333 of 12th July 2015.Scopu

28-29 | Kirtēsii – Lutte

Ce volume, à l'origine publié par Edisud, est désormais diffusé par les Editions Peeters sous l'Isbn 978-90-429-2485-7