Wave reflection and cut-off frequencies in coupled FE-peridynamic grids

International Journal for Numerical Methods in Engineering Published by John Wiley & Sons, Ltd. Reflections are typically observed when pulses propagate across interfaces. Accordingly, spurious reflections might occur at the interfaces between different models used to simulate the same medium. Examples of such coupled models include classical continuum descriptions with molecular dynamics or peridynamic (PD) grids. In this work, three different coupling approaches are implemented to couple bond-based PDs with finite element (FE) solvers for solid mechanics. It is observed that incorporation of an overlapping zone, over which the coupling between FE and PD occurs, can lead to minimization of the reflected energy compared to a standard force coupling at the FE domain/PD grid interface. However, coupling with other existing methodologies, like the addition of ghost particles, achieves comparable accuracy at lower computational cost. Furthermore, the prudent selection of the discretization parameters is of pivotal importance as they control the high frequency cut-off limit. Mismatch between the cut-off frequencies of the different descriptions can lead to unrealistic results

Thermoelastic Waves in Microstructured Solids

Thermoelastic wave propagation suggests a coupling between elastic deformation and heat conduction in a body. Microstructure of the body influences the both processes. Since energy is conserved in elastic deformation and heat conduction is always dissipative, the generalization of classical elasticity theory and classical heat conduction is performed differently. It is shown in the paper that a hyperbolic evolution equation for microtemperature can be obtained in the framework of the dual internal variables approach keeping the parabolic equation for the macrotemperature. The microtemperature is considered as a macrotemperature fluctuation. Numerical simulations demonstrate the formation and propagation of thermoelastic waves in microstructured solids under thermal loading

Grapevine rootstocks shape underground bacterial microbiome and networking but not potential functionality

BackgroundThe plant compartments of Vitis vinifera, including the rhizosphere, rhizoplane, root endosphere, phyllosphere and carposphere, provide unique niches that drive specific bacterial microbiome associations. The majority of phyllosphere endophytes originate from the soil and migrate up to the aerial compartments through the root endosphere. Thus, the soil and root endosphere partially define the aerial endosphere in the leaves and berries, contributing to the terroir of the fruit. However, V. vinifera cultivars are invariably grafted onto the rootstocks of other Vitis species and hybrids. It has been hypothesized that the plant species determines the microbiome of the root endosphere and, as a consequence, the aerial endosphere. In this work, we test the first part of this hypothesis. We investigate whether different rootstocks influence the bacteria selected from the surrounding soil, affecting the bacterial diversity and potential functionality of the rhizosphere and root endosphere.MethodsBacterial microbiomes from both the root tissues and the rhizosphere of Barbera cultivars, both ungrafted and grafted on four different rootstocks, cultivated in the same soil from the same vineyard, were characterized by 16S rRNA high-throughput sequencing. To assess the influence of the root genotype on the bacterial communities’ recruitment in the root system, (i) the phylogenetic diversity coupled with the predicted functional profiles and (ii) the co-occurrence bacterial networks were determined. Cultivation-dependent approaches were used to reveal the plant-growth promoting (PGP) potential associated with the grafted and ungrafted root systems.ResultsRichness, diversity and bacterial community networking in the root compartments were significantly influenced by the rootstocks. Complementary to a shared bacterial microbiome, different subsets of soil bacteria, including those endowed with PGP traits, were selected by the root system compartments of different rootstocks. The interaction between the root compartments and the rootstock exerted a unique selective pressure that enhanced niche differentiation, but rootstock-specific bacterial communities were still recruited with conserved PGP traits.ConclusionWhile the rootstock significantly influences the taxonomy, structure and network properties of the bacterial community in grapevine roots, a homeostatic effect on the distribution of the predicted and potential functional PGP traits was found

DSC analysis of Al6061 aluminum alloy powder by rapid solidification

Differential scanning calorimetry (DSC) is a powerful technique that measures the heat evolution from a sample under a controlled condition and studies the phase transformation, precipitation, and dissolution activities. In this work, we investigated the influence of admixed silicon and silicon carbide and the effect of different atmospheres on the heat flow properties and microstructure of atomized Al6061 powder using DSC and scanning electron microscopy. The DSC analysis revealed the addition of silicon considerably decreased the temperature of first endothermic peaks. With an increase in silicon content the enthalpy for the first endothermic peak increased, whereas the second endothermic peak decreased. An endothermic peak, indicating the formation of AlN, was observed for powders without the silicon addition, but was noticeably absent in the case of alloys with Si addition. The SiC addition has no influence on changing the enthalpy of the systems we investigated. The reason for this behavior is analyzed and presented in this article.X1144sciescopu

Multiscale Modeling of Social Systems: Scale Bridging via Decision Making

Part 13: Collaborative TechnologyInternational audienceIn recent years technological advancement makes it possible to connect heterogeneous systems at hierarchical levels, such as macro level where strategic decisions are made, and micro level where organizations interact with the users. Modeling of these connections alongside with systems is one of the problems, which can be solved by modeling techniques that take hierarchical nature of the systems into consideration. In this paper, we propose a multiscale modeling approach for social systems. We suggest to design a model by adopting certain entities: decision makers, resources, actions and propagation variables. The proposed approach is evaluated on an example of collaboration between two systems: electricity suppliers and manufacturers. Results of the computational experiments demonstrate the effectiveness of the proposed technique