Longitudinal elastic nonlinearity of composite material

It is known that the initial waviness of the fiber affects the stiffness characteristics and strength of the polymer composite material. The article presents a continuum model taking into account the nonlinearity of the longitudinal stiffness of the unidirectional composite. In this study, a finite element experiment was conducted to investigate the variations in the longitudinal stiffness of the composite material subjected to uniaxial compression. The experiment considered a range of different degree of fiber’s waviness to comprehensively examine the impact on the material's stiffness. Obtained results explain the difference in stiffness observed in fiber composites in the longitudinal direction under uniaxial tension and compression. Special constitutive relations proposed to model compressive stiffness reduction in longitudinal direction. &nbsp

Influence of manufacturing shrinkage and microstructural features on the strength properties of carbon fibers/PEEK composite material

This research discusses the micromechanical modelling for thermoplastic composite material. Elastoplastic and damage model for PEEK matrix composite with the dependency of properties to stress state is presented. Plasticity initiation conditions and failure criterion are analyzed. The influence of manufacturing residual stresses is considered. All typical engineering experiments for neat PEEK under different stress state are good predicted by the model. Numerical experiment for macro-properties estimation based on micromechanical model is conducted and the results are compared with the test data

Clustering Without Knowing How To: Application and Evaluation

Crowdsourcing allows running simple human intelligence tasks on a large crowd of workers, enabling solving problems for which it is difficult to formulate an algorithm or train a machine learning model in reasonable time. One of such problems is data clustering by an under-specified criterion that is simple for humans, but difficult for machines. In this demonstration paper, we build a crowdsourced system for image clustering and release its code under a free license at https://github.com/Toloka/crowdclustering. Our experiments on two different image datasets, dresses from Zalando's FEIDEGGER and shoes from the Toloka Shoes Dataset, confirm that one can yield meaningful clusters with no machine learning algorithms purely with crowdsourcing.Comment: accepted at ECIR 2023 Demonstration Trac

Link between Epigenomic Alterations and Genome-Wide Aberrant Transcriptional Response to Allergen in Dendritic Cells Conveying Maternal Asthma Risk

We investigated the link between epigenome-wide methylation aberrations at birth and genomic transcriptional changes upon allergen sensitization that occur in the neonatal dendritic cells (DC) due to maternal asthma. We previously demonstrated that neonates of asthmatic mothers are born with a functional skew in splenic DCs that can be seen even in allergen-naïve pups and can convey allergy responses to normal recipients. However, minimal-to-no transcriptional or phenotypic changes were found to explain this alteration. Here we provide in-depth analysis of genome-wide DNA methylation profiles and RNA transcriptional (microarray) profiles before and after allergen sensitization. We identified differentially methylated and differentially expressed loci and performed manually-curated matching of methylation status of the key regulatory sequences (promoters and CpG islands) to expression of their respective transcripts before and after sensitization. We found that while allergen-naive DCs from asthma-at-risk neonates have minimal transcriptional change compared to controls, the methylation changes are extensive. The substantial transcriptional change only becomes evident upon allergen sensitization, when it occurs in multiple genes with the pre-existing epigenetic alterations. We demonstrate that maternal asthma leads to both hyper- and hypomethylation in neonatal DCs, and that both types of events at various loci significantly overlap with transcriptional responses to allergen. Pathway analysis indicates that approximately 1/2 of differentially expressed and differentially methylated genes directly interact in known networks involved in allergy and asthma processes. We conclude that congenital epigenetic changes in DCs are strongly linked to altered transcriptional responses to allergen and to early-life asthma origin. The findings are consistent with the emerging paradigm that asthma is a disease with underlying epigenetic changes

LEGAL MEANS OF ENSURING PUBLIC SAFETY AS A BASIS FOR THE PROGRESSIVE DEVELOPMENT OF SOCIETY

Objective: The article investigates the key areas to improve the effectiveness of legal means for human rights protection in the conditions of spreading ideology that promotes the development of extremist and terrorist activities. Methods: Close attention is paid to the scale of spreading extremism and terrorism ideology at transnational, interstate and national levels. Results: The focus of activity in terrorist organizations is emphasized on destruction or disruption of transport infrastructure, life support facilities, intimidation of population and committing acts of nuclear terrorism. Conclusions: It is necessary to develop a legal policy that promotes the implementation of measures to protect human rights, regardless to the nature of the political and legal system in the state. The universality of measures for the protection of human rights implies their viability in various socially interactive legal systems. The necessity to develop new approaches to justify the formation of ideology of terrorism and extremism is determined. Attention is paid to the necessity to improve legal grounds for understanding terrorism and extremism

Process modeling of carbon-epoxy composites: residual stress development during cure and analysis of free edge effects

Last decades, increased attention is paid to the deep understanding of the process induced residual stresses (locked-in) and their effect on shape distortion and fracture. Residual stresses evaluation is particularly important in multilayered composites with anisotropic thermo-mechanical properties, where the ply orientations and stacking sequences highly influence the appearing of manufacturing stresses. In the present study, the effect of free edge on residual stresses inherited during manufacturing of thermoset multilayered composites was investigated. In order to understand the stress-strain state in samples after free edge cut a simplified 2D plane strain finite element analysis was performed. Many phenomena, such as sensitivity of the results to the size of the numerical grid, stress redistribution and size of the area affected by free edge was analyzed. In the current research, the behavior of AS4/8552-1 carbon-epoxy composite during manufacturing cycle was studied by means of finite element modeling in ABAQUS. To describe the behavior of the composite material during the manufacturing process − including processes of formation, polymerization, development of residual strains and stresses was done by developed user subroutine-UMAT, describing the visco-elastic material behavior of the material. The program was implemented in ABAQUS and validated on the basis of literature data. The results of the study can be applied for prediction of residual stresses in composite structure by means of virtual simulation and further understanding the nature of fracture of composites

EBSD mapping of herringbone domain structures in tetragonal piezoelectrics

Herringbone domain structures have been mapped using electron backscatter diffraction (EBSD) in two tetragonal piezoelectrics, lead zirconate titanate, [Pb(Zr,Ti)O<sub>3</sub>] and bismuth ferrite – lead titanate, [(PbTi)<sub>0.5</sub>(BiFe)<sub>0.5</sub>O<sub>3</sub>]. Analysis of the domain misorientations across the band junctions shows that the structures correspond very well to crystallographic models. High resolution mapping with a 20 nm step size allowed the crystal rotation across one of these band junctions in lead zirconate titanate to be studied in detail and allowed an improved estimation of the peak strain at the junction, of 0.56 GPa. The significance of this for crack nucleation and propagation in such materials is discussed