1,720,996 research outputs found
Multiscale topology optimization with embedded TPMS architected materials
No full textTopology optimization has emerged as a critical computational tool for designing lightweight, robust, resilient and efficient structures. Recent advances in additive manufacturing technologies enable the production of complex objects across multiple scales, fostering the development of novel architectures endowed with diverse topologies and material classes, tailored to specific performance requirements. In this work we explore the use of Triply Periodic Minimal Surface (TPMS) architected materials, which mimic natural and biological systems to achieve exceptional mechanical efficiency and scalability. To this aim, we present a multiscale, multi-material topology optimization framework that leverages a gradient-based scheme to minimize compliance under multiple volume constraints. TPMS microstructures are generated via the Fourier Series Function (FSF) method, seamlessly integrated into the optimization process through homogenization theory. The Solid Isotropic Material with Penalization (SIMP) model is coupled with Discrete Material Optimization (DMO) interpolation, introducing a continuation parameter that transitions smoothly from a convex problem to a non-convex problem. To handle volume constraints effectively, the ZPR-BFGS design variable update scheme is adapted to the continuum setting, allowing constraints to be updated independently, sequentially, or in parallel. This framework enables flexible volume constraints, which can govern either all or a subset of materials at both global and local scales. Additionally, we introduce a voxel-based post-processing strategy to ensure scalable designs, smooth material transitions, and tunable scale separation. Key insights are illustrated through meaningful numerical examples, demonstrating the effectiveness of the proposed framework. The methodology highlights the versatility of TPMS-based architectures in achieving optimal material distribution with arbitrary geometric complexity
Multi-scale topology optimization for innovative 3D-printed walls and shell structures
No full textTopology optimization is a computational design tool that allow to optimize specific properties in a design domain imposing a priori conditions. A common topology optimization formulation adopted for civil engineering problem is the minimization of compliance, which is equivalent to maximize the stiffness. In this work, we propose a homogenization-based multiscale approach with a compliance minimization formulation for large-scale 3D printing of innovative in-plane loaded walls and shells for building engineering. This approach entails a two-dimensional structural optimization scheme, that accounts for the presence of predefined microstructures and different material properties. Afterwards, the three-dimensional layout of the optimized structure is reconstructed at the micro-scale starting from the obtained optimal layout by means of a specifically tailored 2.5-D post-processing algorithm. The proposed multiscale topology optimization approach is demonstrated by several meaningful numerical examples
Method for the deconvolution of auditory steady-state responses
No full textThe potential evoked by a 'train' of N equally spaced auditory clicks, with an inter-click period shorter than the duration of the response to an isolated click, is said to be a steady-state response (SSR). Extracting the individual responses evoked by the clicks of the train during steady state can be key to understanding of the neurophysiological mechanisms underlying SSR generation. In the literature, this task has been dealt with only under the (unwarranted) assumption that the response of the system does not vary during the presentation of the clicks, i.e. no neurophysiological adaptation is present. In this work, a new, non-parametric algorithm is proposed that, relaxing the time-invariance hypothesis, allows the extraction from the SSR of the N waveforms individually evoked by the N clicks of the train. The performance of the approach is evaluated on simulated SSRs and on real data recorded from the temporal cortex of awake rats. Results show that the method is able to detect and assess possible adaptation of the neurophysiological system in the generation of SSRs
Enhanced hydrogen release of metal borohydrides M(BH4)n (M = Li, Na, Mg, Ca) mixed with reduced graphene oxide
No full textMixtures of light metal borohydrides M(BH4)n, M = Li, Na, Mg, Ca and reduced graphene oxide (rGO) or graphite with molar ratio 70:30 were prepared by high energy ball milling. Samples were investigated with thermal programmed desorption (TPD) volumetric analysis to test their gas release profiles. The presence of rGO led to a lower decomposition temperature for every mixture and to a different gas-release profile compared to pristine borohydrides and mixtures with graphite. The onset of decomposition temperature was reduced by 200 °C for LiBH4, 360 °C for NaBH4, 130 °C for Mg(BH4)2 and 50 °C for Ca(BH4)2. The comparison of XRD profiles of decomposed samples showed a different pattern for each metal cation, confirming an interaction of the decomposition products with rGO sheets and suggesting a different pathway for the decomposition reaction. Reduced graphene oxide was prepared by clean thermal treatment in H2 atmosphere from graphene oxide obtained by modified wet chemical synthesis, and its presence significantly affected the gas release performance
Una nuova metodica per la deconvoluzione dei potenziali evocati uditivi di stato stazionario
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Large-scale additive manufacturing of optimally-embedded spinodal material architectures
No full textWe present a synergistic methodology to design large-scale 3D-printed structures based on a multi-material topology optimization formulation, which leads to the realization of three-dimensional hierarchical structures with spatially oriented non-periodic spinodal microstructures. The inherent characteristics of these unstructured architectures allow the design of optimized layouts with smooth transitions of spinodal material classes, accounting for varying porosity and orientation. The design and manufacturing processes are bridged by a topology-by-material optimization approach, in which the iterative process preserves the macro-scale continuity, while the microstructural topological space is optimized by a suitable distribution of multiple spinodal architected materials. To illustrate both the design and the manufacturing processes, we leverage the features of a large-scale water jetting powder-bed 3D printing technology, which makes use of aggregates obtained from powdered stone-like materials and magnesium-based binders. The optimized model is transferred to the printer by means of a voxel-based generation strategy. The approach, exemplified by means of several numerical simulations and physical 3D-printed samples, connects design conceptualization, material properties at different length scales, and the complex process of additively manufacturing load-bearing structures in a large-scale framework
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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