Multi-scale topology optimization of structures with multi-material microstructures using stiffness and mass design criteria

Publisher Copyright: © 2023 The Author(s)Nowadays, there is a great interest on the part of the automotive and aerospace industry to design environmentally-friendly structures. To that purpose, stiffness-oriented designs are proposed here by extending previous work on multi-scale topology optimization to the multi-material setting reformulating the problem to include appropriately mass constraints and discussing different design domain parametrizations and algorithmic strategies. On the macroscale, the problem of minimizing the compliance subject to a global mass constraint is addressed. On the microstructure scale, the multi-material design is carried out by solving the problem of minimizing the local complementary strain energy density with mass density constraint. As a result, very efficient structures composed of spatially varying porous and multi-material microstructures are obtained. The optimal design of the multi-material microstructure can be done either in a pointwise manner or in larger subdomains, to promote design uniformity. These parametrizations are here compared and discussed. Moreover, two different algorithmic strategies to solve the multi-scale problem are proposed, and their pros and cons discussed. They differ in the way the macro and micro design variables are related and updated. The macro design variables consider the mass density distribution along the structure, while the micro variables define the microstructure's topology using a multi-material SIMP interpolation scheme. The results show very efficient structures with locally optimized multi-material microstructures, which can outperform their single-material counterparts with regards to stiffness while maintaining the same mass. Additionally, the maximum stress verified on multi-material structures tends to be lower than the one obtained in the single-material counterparts.publishersversionpublishe

Two different approaches for analysing heat transfer in a power-law fluid flow between parallel plates

In this paper, Nusselt numbers for a power-law fluid in a fully developed laminar flow between parallel plates with constant, and different, wall heatfluxes in the presence of dissipation effects are presented. The Nusselt numbers values were obtained following two different approaches. One is the"classical" approach, based on a single bulk temperature, and this approach is used in this work to obtain for the first time generic analyticalexpressions for Nusselt numbers. In the new approach, different bulk temperatures are used for each Nu′ determination, one bulk temperature foreach side of the location of the temperature profile where the derivative∂T/∂y=0

Stiffness and strength-based lightweight design of truss structures using multi-material topology optimization

Authors wish also to thank Professor Krister Svanberg (Royal Institute of Technology, Stockholm, Sweden) for the MMA optimization code. Publisher Copyright: © 2021 9th International Conference on Computational Methods for Coupled Problems in Science and Engineering, COUPLED PROBLEMS 2021. All rights reserved.Stiffness and strength are important structural design criteria. However, most contributions to Topology Optimization (TO) deal with the compliance minimization problem. Controlling stresses in a structure is very important to avoid material failure, but that raises complications in TO, such as: nonlinearity, singularity and high computational cost. The total weight of a structure is also another important criterion in optimal design. The multi-material setting is considered in the present work as it opens the possibility to improve structural performance even further allowing extra weight reduction. Recursive SIMP is used as the material interpolation scheme and design solutions are sought using the ground structure approach. This means that truss-like (lattice) designs are obtained here. The problem is relaxed to the continuum by introducing an artificial density variable and it is solved by a gradientbased algorithm (MMA). A stress-constraint relaxation technique (qp-approach) is applied to overcome the stress singularity phenomenon. A continuation approach is used to guarantee discrete solutions, i.e., only the presence or absence of bars is identified. Therefore, design uniformity in terms of bars cross section areas is ensured. Hence, this work proposes a methodology to perform Multi-Material Topology Optimization (MMTO) of truss structures, with density-based design variables, and subject to stress constraints. To discuss the differences between stiffness and strength-oriented optimal designs, a compliance minimization problem subject to mass constraint is also considered. The example chosen demonstrates the viability of the proposed design methodology and it also reveals differences between the strongest and the stiffest designs.authorsversionpublishe

Towards a Low-SWaP 1024-beam Digital Array: A 32-beam Sub-system at 5.8 GHz

Millimeter wave communications require multibeam beamforming in order to utilize wireless channels that suffer from obstructions, path loss, and multi-path effects. Digital multibeam beamforming has maximum degrees of freedom compared to analog phased arrays. However, circuit complexity and power consumption are important constraints for digital multibeam systems. A low-complexity digital computing architecture is proposed for a multiplication-free 32-point linear transform that approximates multiple simultaneous RF beams similar to a discrete Fourier transform (DFT). Arithmetic complexity due to multiplication is reduced from the FFT complexity of $\mathcal{O}(N\: \log N)$ for DFT realizations, down to zero, thus yielding a 46% and 55% reduction in chip area and dynamic power consumption, respectively, for the $N=32$ case considered. The paper describes the proposed 32-point DFT approximation targeting a 1024-beams using a 2D array, and shows the multiplierless approximation and its mapping to a 32-beam sub-system consisting of 5.8 GHz antennas that can be used for generating 1024 digital beams without multiplications. Real-time beam computation is achieved using a Xilinx FPGA at 120 MHz bandwidth per beam. Theoretical beam performance is compared with measured RF patterns from both a fixed-point FFT as well as the proposed multiplier-free algorithm and are in good agreement.Comment: 19 pages, 8 figures, 4 tables. This version corrects a typo in the matrix equations from Section

An updated revision of shortfin mako size distributions in the Atlantic

As part of an ongoing cooperative program for fisheries and biological data collection within the ICCAT Sharks Working Group, information collected by fishery observers and scientific projects from several fishing nations in the Atlantic were analyzed. Datasets included information on geographic location, size and sex. A total of 42,979 shortfin mako records collected between 1989 and 2017 were compiled. Sizes considered ranged between 60 and 353 cm FL (fork length). Of those, sex information was available for 24,316 specimens. Considerable variability was observed in the size distribution by region and season, with larger sizes tending to occur in equatorial and tropical regions and smaller sizes in higher latitudes. Variability between coastal and more oceanic waters is also likely. Most fleets showed unimodal distributions, but in some cases there were bimodal patterns. The distributional patterns presented in this study provide an advance in the understanding of shortfin mako size distribution in the Atlantic, and can be used in the next update of the ICCAT shortfin mako stock assessment.info:eu-repo/semantics/publishedVersio

Questionário de diagnóstico compartilhado da atenção básica: equipes de Saúde da Família típicas x ampliadas

A adscrição de clientela, a relação entre a equipe de atenção básica com as especialidades, as atividades de promoção à saúde e condições de infraestrutura são fatores organizacionais necessários para a Estratégia de Saúde da Família contribuir para proporcionar o cuidado integral no Sistema Único de Saúde (SUS). O objetivo deste artigo é comparar os resultados da aplicação do Questionário de Diagnóstico Compartilhado da Atenção Básica (QDCAB), no tocante aos quesitos referentes à integralidade, entre equipes de Saúde da Família típicas e ampliadas em um município paulista. O método e o QDCAB foram aplicados a equipes de Saúde da Família típicas e àquelas com especialistas das grandes áreas (equipes ampliadas), e a análise foi realizada utilizando o teste de Wilcoxon-Mann-Whitney, permitindo a comparação da distribuição das respostas entre os dois modelos de equipe. As equipes ampliadas estabelecem vínculo de forma mais coletiva (0,0026), porém, não houve diferença nos resultados dos esforços realizados nesse sentido entre os dois modelos de equipe (0,7227). As notas baixas atribuídas às questões relativas à relação da equipe com os especialistas, de uma forma geral, revelam as dificuldades para garantir a integralidade da atenção. As atividades de promoção à saúde receberam notas altas de ambos os modelos. A adequação da estrutura física do centro de saúde recebeu menores notas das equipes típicas (< 0,0001). A relação das equipes com os especialistas é um obstáculo para a garantia da integralidade e, para as equipes típicas, o excesso de demanda e as condições de infraestrutura também representam dificuldades

Ferromagnetic Levan Composite: An Affinity Matrix to Purify Lectin

A simple and inexpensive procedure used magnetite and levan to synthesize a composite recovered by a magnetic field. Lectins from Canavalia ensiformis (Con A) and Cratylia mollis (Cramoll 1 and Cramoll 1, 4) did bind specifically to composite. The magnetic property of derivative favored washing out contaminating proteins and recovery of pure lectins with glucose elution. Cramoll 1 was purified by this affinity binding procedure in two steps instead of a previous three-step protocol with ammonium sulfate fractionation, affinity chromatography on Sephadex G-75, and ion exchange chromatography through a CM-cellulose column

Morphological analysis and description of the ovaries of female silky sharks, Carcharhinus falciformis (Müller & Henle, 1839)

This work aims to study the female reproductive tract of silky sharks, Carcharhinus falciformis, captured in the South and Equatorial Atlantic Ocean. Samples were collected between January 2008 and March 2010 through oceanic commercial vessels that targeted tuna and swordfish, with a total of 17 females collected. The methodologies followed for analyzing the ovaries of those females included both macroscopic and histological analysis. Macroscopically, it was possible to determine that the ovaries on these sharks is suspended by mesenteries in the anterior section of the body cavity, heavily irrigated by blood vessels, and contains a wide range of oocytes. Ovaries were found in three distinct maturational stages: Stage I (Immature), Stage II (Maturing) and Stage III (Mature). Immature ovaries were small, with widths ranging from 1.0 to 3.1 cm, and had a gelatinous or granulose internal structure; maturing ovaries were slightly larger, ranging in width between 5.2 and 6.0 cm; mature ovaries ranged in width between 6.5 and 7.8 cm, and had a more rounded shape and the presence of large and well developed oocytes. Under microscopic examination, it was observed that the ovaries were covered with simple epithelial tissue during the early development stages and a simple cubic epithelium in the final stages of maturation. During the initial maturation stages the epigonal organ was not differentiated from the ovary. In mature specimens, the ovary showed a simple cubic epithelium and just below this epithelium there was a layer of dense connective tissue and muscle with the presence of vitellogenic oocytes and fat cells. A thin yolk membrane enclosing the oocytes was also evident. Finally, it was possible to distinguish a zona pellucida, separating the oocytes from the follicle wall and a basal lamina between the granular layers and the teak layer.info:eu-repo/semantics/publishedVersio