Parts internal structure definition using non-uniform patterned lattice optimization for mass reduction in additive manufacturing

Today, being able to generate and produce shapes that fit mechanical and functional requirements and having as low as possible mass is crucial for aerospace and automotive applications. Besides, the rise of new additive manufacturing technologies has widened the possibilities for designing and producing complex shapes and internal structures. However, current models, methods and tools still represent a limitation to that new horizon of printable shapes. This paper addresses the way internal lattice structures can be generated and optimized to reduce the mass of a product. A new framework is introduced that allows the modeling and optimization of non-uniform patterned lattice structures. Using non-uniform structures, additional degrees of freedom are introduced and allow the definition of a wide variety of shapes which can better fit the requirements. First, a non-uniform patterned lattice structure is generated using the results of an initial finite element analysis. This initial structure is then optimized while iteratively removing the beams considered as useless with respect to a user-specified mechanical criteria. At each iteration, the lattice structure is sent to a finite element solver that returns the von Mises stress map used to drive the simplification process. Here, the simulations are performed on the wireframe lattice structures to speed up the optimization loops. Once this process is completed, the final structure is no longer fully patterned, but it is re-organized to reduce the mass while satisfying the mechanical criteria. This approach is illustrated with examples coming from our prototype software

Lattice structure lightweight triangulation for additive manufacturing

Additive manufacturing offers new available categories of geometries to be built. Among those categories, one can find the well developing field of lattice structures. Attention has been paid on lattice structures for their lightweight and mechanical efficiency ratio, thus leading to more optimized mechanical parts for systems. However this lightness only holds true from a mass related point of view. The files sent to additive manufacturing machines are quite large and can go up to such sizes that machines can freeze and get into malfunction. This is directly related to the lattice structures tendency to be of a high geometric complexity. a large amount of vertices and triangles is necessary to describe them geometrically, thus leading to larger file sizes. With the increasing use of lattice structures, the need for their files to be lighter is also rising. This paper aims at proposing a method for tessellating a certain category of such structures, using topologic and geometric criteria to generate as few as possible triangles, thus leading to lightweight files. The triangulation technique is driven by a chordal error that control the deviation between the exact and tessellated structures. It uses interpolation, boolean as well as triangulation operators. The method is illustrated and discussed through examples from our prototype software

Parts internal structure definition using lattice patterns optimization for mass reduction in additive manufacturing

With the rise of additive manufacturing, complex internal structure optimization is now a relevant topic. Additive manufacturing allows designers and engineers to go further in their modeling, designing and optimization process, allowing new complex shapes to be produced, including the optimization of their internal structure. However modeling, design and optimization tools still represent a limitation to that new horizon of printable shapes. In this article, we define the framework in term of new designs, 3D modeling and optimization approach dedicated to the shape definition of patterned (or organized) lattice structures1 produced using additive manufacturing processes. The goal being to generate shapes that fit the mechanical requirements with an “as reduced as possible” mass, this issue is still today a niche market for Aerospace and Automotive, but could soon lead to a wider range of applications. Optimizing topology can be slow, so we will show a way of reducing computation time by using relative criteria for removing material. This new approach is based on the use of organized lattice structures to allow a wide range of shapes, thus opening the field for finding better optimized shapes. Once the patterned lattice structure is defined, it is send to a Finite Element solver software that returns the constraints and/or displacements map. This is then used as a basis for a statistical calculus that determines the elements that can or cannot be removed from the lattice. After a few iterations, the general structure is no longer patterned, but organized in a way that suits its mechanical environment, allowing lighter general structure and ensuring its rigidity. This approach is illustrated with examples coming from a prototype software

Residual Doping in Homoepitaxial Zinc Oxide Layers Grown by Metal Organic Vapor Phase Epitaxy

International audienceFull maximum entropy mobility spectrum analysis was carried out on the basis of temperature and magneticfield- dependent Hall measurements to assess the transport properties of homoepitaxial metal organic vapor phase epitaxy zinc oxide layers. Two different conductivity channels were clearly identified and the channel with higher mobility and higher carrier concentration is associated with the epitaxial layer. Hydrogen impurity acting as residual donor and as a passivating species for acceptors is proposed to explain the higher carrier concentration and mobility in the epilayer. In contrast to heteroepitaxial layers, no conduction channel is observed from the substrate to epilayer interface

The inositol Inpp5k 5-phosphatase affects osmoregulation through the vasopressin-aquaporin 2 pathway in the collecting system

Inositol Inpp5k (or Pps, SKIP) is a member of the inositol polyphosphate 5-phosphatases family with a poorly characterized function in vivo. In this study, we explored the function of this inositol 5-phosphatase in mice and cells overexpressing the 42-kDa mouse Inpp5k protein. Inpp5k transgenic mice present defects in water metabolism characterized by a reduced plasma osmolality at baseline, a delayed urinary water excretion following a water load, and an increased acute response to vasopressin. These defects are associated with the expression of the Inpp5k transgene in renal collecting ducts and with alterations in the arginine vasopressin/aquaporin-2 signalling pathway in this tubular segment. Analysis in a mouse collecting duct mCCD cell line revealed that Inpp5k overexpression leads to increased expression of the arginine vasopressin receptor type 2 and increased cAMP response to arginine vasopressin, providing a basis for increased aquaporin-2 expression and plasma membrane localization with increased osmotically induced water transport. Altogether, our results indicate that Inpp5k 5-phosphatase is important for the control of the arginine vasopressin/aquaporin-2 signalling pathway and water transport in kidney collecting duct

« Bronzes grecs et romains, recherches récentes » — Hommage à Claude Rolley

Philologue, archéologue, historien, spécialiste des bronzes, Claude Rolley, disparu en 2007, occupa une place originale parmi les spécialistes du monde méditerranéen antique. Marqué par la découverte du cratère de Vix (en 1953) qu’il ne cessa d’étudier tout au long de sa carrière, il sut croiser recherches et approches sur les périodes à la fois classique et proto-historique, de la Laconie à la Bourgogne jusqu’à la Grande Grèce. Les bronzes, de toutes dimensions ou origines, dont il tint la chronique pendant près de 25 ans dans la Revue archéologique, étaient pour lui une source de réflexion multiple : stylistique, technique – il prenait en compte aussi bien les questions d’assemblage ou de fonte que la composition chimique des objets –, ou culturelle – ses travaux ont apporté des éclairages décisifs sur la formation des ateliers et la circulation des objets d’un centre de production à l’autre. À l’initiative de plusieurs de ses disciples, un colloque lui a rendu hommage (INHA, 16-17 juin 2009) : les textes qui suivent en sont le fruit

Agroécologie : la difficile voie vers le zéro pesticide, article en ligne et vidéo youtube https://www.youtube.com/watch?v=Y4kux6xy2c4&t=81s

National audienceL'Inrae teste à grande échelle une agriculture sans pesticides et presque sans travail du sol. L'ambition : concevoir une agriculture résiliente tout en affichant des rendements qui talonnent ceux de l'agriculture conventionnelle. Un défi complexe

Etude de la régulation de la concentration extracellulaire de D-sérine dans le système nerveux central à l'aide d'un microbiocapteur enzymatique

LE KREMLIN-B.- PARIS 11-BU Méd (940432101) / SudocSudocFranceF

Equivalence of donor and acceptor fits of temperature dependent Hall carrier density and Hall mobility data: Case of ZnO

International audienceIn this work, statistical formulations of the temperature dependence of ionized and neutral impurityconcentrations in a semiconductor, needed in the charge balance equation and for carrier scatteringcalculations, have been developed. These formulations have been used in order to elucidate aconfusing situation, appearing when compensating acceptor (donor) levels are located sufficientlyclose to the conduction (valence) band to be thermally ionized and thereby to emit (capture) anelectron to (from) the conduction (valence) band. In this work, the temperature dependent Hall carrierdensity and Hall mobility data adjustments are performed in an attempt to distinguish the presence ofa deep acceptor or a deep donor level, coexisting with a shallower donor level and located near theconduction band. Unfortunately, the present statistical developments, applied to an n-typehydrothermal ZnO sample, lead in both cases to consistent descriptions of experimental Hall carrierdensity and mobility data and thus do not allow to determine the nature, donor or acceptor, of the deeplevel. This demonstration shows that the emission of an electron in the conduction band, generallyassigned to a (0/+1) donor transition from a donor level cannot be applied systematically and couldalso be attributed to a (-1/0) donor transition from an acceptor level. More generally, this result canbe extended for any semiconductor and also for deep donor levels located close to the valence band(acceptor transition

Weather impacts on indoor radon short-term measurements in Switzerland

Radon is a natural and radioactively well-known carcinogenic indoor air pollutant. Since 2020, a radon short-term proactive methodology has been proposed by Swiss authorities, which aims to evaluate the probability of overpassing the national reference value. This study aims to assess the influence of different weather parameters on indoor radon levels monitored using this methodology. To this end, different statistical tools are used, such as correlations, auto-correlations, cross-correlations, and multiple linear regressions between meteorological parameters and indoor radon levels. We show a strong influence of weather conditions on indoor radon levels in occupied, but especially unoccupied spaces. Outdoor air temperature, followed by atmospheric pressure, was identified as the most significant parameter impacting indoor radon levels. Moreover, meteorological conditions monitored five days prior to the beginning of the radon measurements might affect radon levels. We come to the conclusion that it is of paramount importance to take these meteorological conditions into account when analyzing the results of short-term measurements, and more specifically, to consider the evolution of the weather conditions five days prior to the radon measurement. This paper helps to ensure the relevance of this short-term measurement method available in Switzerland