Composite material identification as micropolar continua via an optimization approach

A strategy based on material homogenization and heuristic optimization for the structural identification of composite materials is proposed. The objective is the identification of the constitutive properties of a micropolar continuum model employed to describe the mechanical behaviour of a composite material made of rigid blocks and thin elastic interfaces. The micropolar theory (Cosserat) has been proved to be capable of properly accounting for the particles arrangements as well as their size and orientation. The constitutive parameters of the composite materials, characterized by different textures and dimensions of the rigid blocks, are identified through a homogenization procedure. Thus, the identification is repeated exploiting the static or modal response of the composite materials and using the Differential Evolution algorithm. The benchmark structures assumed as target are represented by discrete models implemented in ABAQUS where the blocks and the elastic interfaces are modelled by rigid bodies and elastic interfaces, respectively. The obtained results show that proposed strategies provide accurate results paving the way to the experimental validation and in field applications

Preface: Multiscale and multiphysics modeling of “complex” materials and engineering applications

none3noN.A.mixedTrovalusci P.; Fantuzzi N.; De Bellis M.L.Trovalusci P.; Fantuzzi N.; De Bellis M.L

Fast ADMM for Semidefinite Programs with Chordal Sparsity

Many problems in control theory can be formulated as semidefinite programs (SDPs). For large-scale SDPs, it is important to exploit the inherent sparsity to improve the scalability. This paper develops efficient first-order methods to solve SDPs with chordal sparsity based on the alternating direction method of multipliers (ADMM). We show that chordal decomposition can be applied to either the primal or the dual standard form of a sparse SDP, resulting in scaled versions of ADMM algorithms with the same computational cost. Each iteration of our algorithms consists of a projection on the product of small positive semidefinite cones, followed by a projection on an affine set, both of which can be carried out efficiently. Our techniques are implemented in CDCS, an open source add-on to MATLAB. Numerical experiments on large-scale sparse problems in SDPLIB and random SDPs with block-arrow sparse patterns show speedups compared to some common state-of-the-art software packages

Stress Field Evaluation in Orthotropic Microstructured Composites with Holes as Cosserat Continuum

It is known that the presence of microstructures in solids such as joints and interfaces has an essential influence on the studies of the development of advanced materials, rock mechanics, civil engineering, and so on. However, microstructures are often neglected in the classical local (Cauchy) continuum model, resulting in inaccurate descriptions of the behavior of microstructured materials. In this work, in order to show the impact of microstructures, an implicit ‘non-local’ model, i.e., micropolar continuum (Cosserat), is used to numerically investigate the effects of direction and scale of microstructures on the tension problem of a composite plate with a circular hole. The results show that distributions of field variables (such as displacements and stresses) have an obvious directionality with respect to the microstructures’ direction. As the scale of microstructures increases, such a direction effect becomes more evident. Unlike the isotropic material where stress concentration occurs at the vertex of the hole and the stress concentration factor is close to 3, for the microstructured composite, the stress concentration can be observed at any location depending on the microstructures’ directions, and the concentration factor can exceed 3 to a maximum close to 9 as the increasing scale of microstructures. In addition, differences in the mechanical behavior between Cosserat and Cauchy models can be also observed; such differences are more evident for the material showing a pronounced orthotropic nature

Flexural characterization of a novel recycled-based polymer blend for structural applications

The use of recycled plastic in construction fields, among others, is becoming a turning point for resolving significant related problems such as resource management, sustainability and plastic waste generation. Hence, in the context of sustainability, the "Three R’s": reduce, reuse and recycle, are getting more attention day after day. There has been a huge surge in the recycling and reuse of plastic composites due to their eco-friendliness, lightweight, life cycle superiority and low cost. However, because of a lack of knowledge of their performance and behavior, their application is still limited in the real world. The aim of this research is to understand the behavior of recycled plastic and derive its material properties which can be used in the design of structural and non-structural elements. In the present study, three stiffened plates are manufactured from 80% of recycled plastic (around 50% of recycled Polypropylene rPP, and around 50% of High Density Polyethylene PEHD with a little part of Low Density Polyethylene PELD) and 20% of virgin polypropylene PP Copolymer. Three-point bending test is performed on the three specimens. In the experimental campaign, the behavior of these stiffened plates under pure bending loads has been studied. After that, the material properties are extracted from the data collected during the experiment using Ramberg–Osgood equation. Then, once implemented in finite elementcmodels, it was observed that the simulated material shows similar behavior to the one registered during the experiment. As a conclusion, the derived material properties show reliability and they can be used to study a design of a structural or non-structural component including recycled plastic

The shell middens of the Bay of Daun: environmental changes and human impact along the coast of Las bela (Balochistan, Pakistan) between the 8th and the 5th millennium BP

The discovery of shell middens around the bay of Daun and Lake Siranda (Las Bela, Balochistan) shows that groups of prehistoric gatherers settled alon the coast of Las Bela at least sincethe last two centuries of the 8th millennium BP. The radiocarbon dating of the Daun sites indicates that the exploitation of the mangrove resources was not continuous, but took place mainly during distinct periods of the 7th and 5th millennia BP. The radiocarbon dates from marine and mangrove shells from the Tharro anf Makli Hills (Lower Sindh) suggest that the coastal seafaring along the northern coast of the Arabian Sea began already around the beginingof the 7th millennium B

Low-carbon fuels for aviation

The aviation industry is responsible for 2.1% of global CO2 emissions and represents 12% of CO2 emissions from all transport sources. Aviation is a particularly difficult sector to decarbonise because alternative fuels are relatively expensive, produce highly distributed greenhouse gas emissions in their production and combustion, and should preferably be compatible with existing aviation infrastructure. Emissions from aviation also include nitrogen oxides (NOx), water vapour, particulates, carbon monoxide, unburned hydrocarbons, and sulfur oxides (SOx). These have a 2-3 times greater climate change impact than CO2 alone. The non-CO2 emissions of alternative low-carbon aviation fuels can differ significantly from those of kerosene and have not been fully evaluated. Biofuels • Bio-jet fuels are currently the most technologically mature option for low-carbon aviation fuels because some of these feedstocks and processes are already deployed at scale for other uses. • Bio-jet fuels must be blended with kerosene to achieve certification and can then be used with existing aviation infrastructure. This blending proportionally decreases any potential CO2 emission saving. • Bio-jet fuels can be made from a range of feedstocks, which are restricted in the UK to waste materials. UK biofuel feedstock availability is sufficient for only a small proportion of UK aviation fuel demand (<20%). With blending, their contribution to CO2 emissions saving is much less (<<10%). • Life cycle assessment scenarios show very variable impacts on CO2 emissions for biofuel processes: only some deliver emissions savings compared to fossil fuel kerosene. Calculations for forest residues appear to show consistent savings in CO2 emissions compared to jet fuel, but these do not take account of the difference in timescale between emission and re-absorption, leading to a major underestimation of emissions. The diversion of agricultural and forestry waste to bio-jet fuel production will have detrimental effects, for example on soil quality. Power-to-Liquid fuels • PtL fuels must be blended with kerosene to achieve certification and can then be used with existing aviation infrastructure. This blending proportionally decreases any potential CO2 emission saving. • PtL fuels are currently not produced at scale. Significant technological development is required to reduce production costs and increase production scale. • Use of PtL fuels in aviation would require a very significant increase of UK low-carbon electricity generation and storage capacity to power production of green hydrogen and CO2 from direct air capture. • Life cycle assessment scenarios show that PtL fuels could have 3-10 times lower emissions impact than fossil fuel kerosene if renewable electricity and CO2 from direct air capture are used to produce the fuel. Hydrogen • Hydrogen cannot be used as a drop-in fuel for aircraft, and its use will require significant redesign of aviation infrastructure. • The greenhouse gas emissions impact of hydrogen depends on its mode of production. Currently, global hydrogen production is mostly from fossil fuel sources, with much less than 1% generated from low-carbon sources. • Increasing low-carbon hydrogen production via electrolysis (green hydrogen) will require the building of additional low-carbon electricity generation capacity. • Low-carbon hydrogen production via methane reforming with carbon capture and storage (blue hydrogen) should use natural gas obtained from producers with low emissions intensity. The goal of policy will be to promote whichever technologies achieve the desired sustainability targets. A molecular science and engineering approach combines an understanding of molecular behaviour with a problem-solving mindset derived from engineering. This approach is crucial to the development and the eventual deployment of the fuel technologies discussed in this paper

Photoelectrochemistry of Photosystem II in Vitro vs in Vivo.

Factors governing the photoelectrochemical output of photosynthetic microorganisms are poorly understood, and energy loss may occur due to inefficient electron transfer (ET) processes. Here, we systematically compare the photoelectrochemistry of photosystem II (PSII) protein-films to cyanobacteria biofilms to derive: (i) the losses in light-to-charge conversion efficiencies, (ii) gains in photocatalytic longevity, and (iii) insights into the ET mechanism at the biofilm interface. This study was enabled by the use of hierarchically structured electrodes, which could be tailored for high/stable loadings of PSII core complexes and Synechocystis sp. PCC 6803 cells. The mediated photocurrent densities generated by the biofilm were 2 orders of magnitude lower than those of the protein-film. This was partly attributed to a lower photocatalyst loading as the rate of mediated electron extraction from PSII in vitro is only double that of PSII in vivo. On the other hand, the biofilm exhibited much greater longevity (>5 days) than the protein-film (<6 h), with turnover numbers surpassing those of the protein-film after 2 days. The mechanism of biofilm electrogenesis is suggested to involve an intracellular redox mediator, which is released during light irradiation

The Middle Holocene mangrove shellfish gatherers of Las Bela coast (Balochistan, Pakistan): new AMS dates from Lake Siranda shell middens

The discovery and AMS dating of many shell middens along the shores of the dry basin of Lake Siranda (Las Bela, Balochistan, Pakistan) have shown that it was a lagoon in the northern coast of the Arabian Sea in Neolithic times, densely settled by communities of mangrove shellfish gatherers

Diabetes primary prevention program: new insights from data analysis of recruitment period

Primary Prevention of Diabetes Program in Buenos Aires Province evaluates the effectiveness of adopting healthy lifestyle to prevent type 2 diabetes (T2D) in people at high risk of developing it. We aimed to present preliminary data analysis of FINDRISC and laboratory measurements taken during recruitment of people for the Primary Prevention of Diabetes Program in Buenos Aires Province in the cities of La Plata, Berisso, and Ensenada, Argentina.Fil: Gagliardino, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Elgart, Jorge Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Bourgeois, Marcelo Javier. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro Interdisc.universitario Para la Salud; ArgentinaFil: Etchegoyen, Graciela Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Fantuzzi, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Ré, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Ricart, Juan P.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: García, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Giampieri, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Gonzalez, Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Suárez Crivaro, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; ArgentinaFil: Kronsbein, Peter. Niederrhein University of Applied Sciences Mönchengladbach; AlemaniaFil: Angelini, Julieta M.. Universidad Nacional de La Plata; ArgentinaFil: Martinez, Camilo. Universidad Nacional de La Plata; ArgentinaFil: Martinez, Jorge. Universidad Nacional de La Plata; ArgentinaFil: Ricart, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Humanidades y Ciencias Sociales. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales; ArgentinaFil: Spinedi, Eduardo Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Endocrinología Experimental y Aplicada. Universidad Nacional de la Plata. Facultad de Cs.médicas. Centro de Endocrinología Experimental y Aplicada; Argentin