Meso-level Structure Research Articles

The Impact of Multilevel Governmental Policy on Rural Catalonia: Voices From the Grassroots

One decade on from the launch of the European Youth Guarantee Initiative, there is still limited research into its efficacy in rural areas. In Spain, a country with significant urban-rural disparity, the complexity of the governmental structure across the country has made investigations into the effectiveness of youth employment strategies less common as compared with other European states. Our study analyses the meso-level structure of the Spanish government and how the Public Employment Services (PES) factor into the overall process of disseminating active labour market policies across the country. The study is based in the autonomous community of Catalonia and includes a case study in the region of Lleida. Through open-ended interviews with members at different levels of the local PES, including the director and various other staff, as well as with local policymakers, youth workers in local organisations, and the youth themselves, we aim to shed light on how the Youth Guarantee is being implemented on the ground. This will take into account the structural constraints, needs, and challenges under the new law as expressed by the various stakeholders. The results indicate that both youth and local PES are negatively impacted by some centralised aspects of employment policy, such as the stringent requirements for training courses that prove prohibitive for rural areas, as well as the urban-centric design of training courses. Further, the youth collectively express a strong desire for their voice to find expression in the design of active labour market policies.

Uneasy belonging in the mobility capsule: Erasmus Mundus students in the European Higher Education Area

ABSTRACT Taking Erasmus Mundus Joint Masters students as exemplifications of the intensification of mobility in educational trajectories, this article considers their modes of belonging in super-mobility. Their educational experiences take place within a consortium of universities, necessitating intensive and routinized collective movement to multiple locations. This novel way of practising mobility within higher education calls for new frames to describe the distinctiveness of the super-mobility experience and how belonging is enacted and reflected in this transnational space. It aligns itself with the critical approach to hypermobility, especially with regard to its impact on mental well-being. Through an empirical, multi-year qualitative study of student experiences, we propose a new concept of the mobility capsule as both a meso-level structure and a particular way of practicing mobility which implies a transnational group experience, usually organised within an institutional framework of studies. Our results show that the experience of the mobility capsule is characterised by intense speed, routine uprootedness and cosmopolitan social closure. These features weigh heavily on the construction of personal and group belonging and have particular consequences for well-being. We conclude with a critique of such institutional set ups given the persistent glorification of hypermobility.

Efficiently counting complex multilayer temporal motifs in large-scale networks

This paper proposes novel algorithms for efficiently counting complex network motifs in dynamic networks that are changing over time. Network motifs are small characteristic configurations of a few nodes and edges, and have repeatedly been shown to provide insightful information for understanding the meso-level structure of a network. Here, we deal with counting more complex temporal motifs in large-scale networks that may consist of millions of nodes and edges. The first contribution is an efficient approach to count temporal motifs in multilayer networks and networks with partial timing, two prevalent aspects of many real-world complex networks. We analyze the complexity of these algorithms and empirically validate their performance on a number of real-world user communication networks extracted from online knowledge exchange platforms. Among other things, we find that the multilayer aspects provide significant insights in how complex user interaction patterns differ substantially between online platforms. The second contribution is an analysis of the viability of motif counting algorithms for motifs that are larger than the triad motifs studied in previous work. We provide a novel categorization of motifs of size four, and determine how and at what computational cost these motifs can still be counted efficiently. In doing so, we delineate the “computational frontier” of temporal motif counting algorithms.

Research on softening curve of recycled concrete using base force element method in meso-level

PurposeBased on the base force element method, a two-dimensional random circle aggregate model with Monte Carlo principle is proposed to carry out research on softening curve in meso-level.Design/methodology/approachThe meso-level structure of recycled concrete is considered as the five-phase materials composed of aggregate, old interfacial transition zone, old mortar, new interfacial transition zone and new mortar. A multi-polyline damage model is adopted to describe the nonlinear mechanical behavior of recycled concrete material. The destruction state of the element is determined by the first strength theory. The research studies on damage process of recycled concrete under the loading conditions of uniaxial tension were established using the base force element method.FindingsThe softening curves of recycled concrete are obtained, which are in good agreement with experiment results. Simulation results show that the macroscopic mechanical properties and failure mechanism can analyze more reasonably from mesoscopic structure. Besides that, it can be investigated from the numerical results of the size effect in recycled concrete through the mesoscopic heterogeneity. Furthermore, the form of aggregate distribution has influence on the crack path but little effect on the tensile strength of recycled concrete.Originality/valueThe results show that the base force element method has been successfully applied to the study of softening curve of recycled concrete under uniaxial tension.

Understanding variability in recycled aggregate concrete mechanical properties through numerical simulation and statistical evaluation

This paper investigates the effects of adhered mortar content on the mechanical properties of recycled aggregate concrete (RAC) systems using two-dimensional finite element analysis of RAC specimens subjected to uniaxial compression. Sensitivity and statistical analyses of RAC systems were conducted to explore how individual material stiffnesses (aggregate, mortar matrix, adhered mortar, new Interfacial Transition Zone (ITZ), and old ITZ) and adhered mortar contents (2, 10, 20 and 50%) influence RAC mechanical performance. In total, 128 simulation results were performed to understand variability in stress development, damage progression, compressive strength, and elastic modulus of RAC systems. Statistical inferences on the effects of variability in material stiffness and adhered mortar content were made based on frequency distributions, probability density functions, Pareto charts, main effects plots, and bivariate contour plots. Numerical results showed that compressive strength and elastic modulus decreased with increasing adhered mortar contents, while the strain corresponding to compressive softening increased with adhered mortar contents. Statistical results showed that compressive strength was most significantly influenced by aggregate stiffness and mortar matrix stiffness. Strain localizations were observed near the aggregate boundaries due to large material stiffness discontinuities in the RAC meso-level structure. RAC elastic modulus and ultimate compressive strain were mainly governed by the stiffness of the mortar matrix. Based on the numerical results, bivariate contour plots were developed to understand how variations in material stiffness and adhered mortar content influence the strength and stiffness of RAC systems.

From nano to macro: Enabling Nanotechnologies for Human Organ Biofabrication (Electrospun Nanofibers and Hybrid Technique)

This review proposes to present how materials at nanolevel scale can contribute to the development of three-dimensional (3D) structures, human tissues, and organs which have macrolevel organization. Specific nanomaterials such as nanofibers and nanoparticles are presented and discussed in their application for biofabricating 3D human tissues and organs. The concept of self-assembling magnetic tissue spheroids as an intermediate mesolevel structure between nano and macrolevel organization and building blocks for biofabrication in dual scale level of complex 3D human tissues and organs is detached. The challenges and perspectives of employing nanomaterials and nanotechnological strategies in the biofabrication were also traced.

An advanced geometrical model for laminated woven fabrics using Lamé exponents with enhanced accuracy

Three-dimensional stiffness tensors of laminated woven fabrics used in high-performance composites need precise prediction. To enhance the accuracy in three-dimensional stiffness tensor prediction, the fabric’s architecture must be precisely modeled. We tested the hypotheses that: (i) an advanced geometrical model describes the meso-level structure of different fabrics with a precision higher than established models, (ii) the deviation between predicted and experimentally determined mean fiber-volume fraction ( cf) of laminates is below 5%. Laminates of different cf and fabrics were manufactured by resin transfer molding. The laminates’ meso-level structure was determined by analyzing scanning electron microscopy images. The prediction of the laminates’ cf was improved by up to 5.1 vol% ([Formula: see text]%) compared to established models. The effect of the advanced geometrical model on the prediction of the laminate’s in-plane stiffness was shown by applying a simple mechanical model. Applying an advanced geometrical model may lead to more accurate simulations of parts for example in automotive and aircraft.

3D model of intra-yarn fiber volume fraction gradients of woven fabrics

Accurate predictions of laminate strength is important for engineering. Overestimations of laminate strength can be due to variations in local fiber volume fraction. However, intra-yarn fiber volume fraction gradients (G) within laminated plain woven fabrics (PWF) have not been investigated sufficiently to consider their effect in laminated strength predictions. This study addresses this shortening by a proper determination of G in laminated PWFs and proposes a corresponding model (GM). We tested the hypothesis that G can be modeled according to analytical models of the laminates meso-level structure. All required parameters were determined from scanning electron microscopy images of laminated PWFs of different fiber volume fraction. The GM was implemented in Matlab and matches the experimental data well. In addition, finite element simulation of interlaced yarns were conducted to understand the origin of G. The proposed model is a 3D description of G in PWFs. Using this model may lead to a significantly improved prediction of the laminate strength.

Method of meshing ITZ structure in 3D meso-level finite element analysis for concrete

Meso-level finite element analysis (FEA) is a popular way to study the influences of meso-level structure of concrete (namely the aggregate, the mortar and the Interfacial Transitional Zone (ITZ) structures) on the macro-level properties. However, it’s been a huge challenge to mesh the ITZ structure in concrete because of the unique layer structure of ITZ, which is 10–50µm thick and rather small compared to the normal sizes of coarse aggregates. If ITZ were meshed by hexahedral elements or tetrahedral elements which were 10–50μm in all three dimensions, millions of ITZ elements would be generated and it’s impossible to perform FEA on such a huge concrete model. In the current meso-level FEA in the literature, ITZ is either represented by zero-thick interface elements or over-thick elements, either of which is far from the real dimension of ITZ, leading to big discrepancies between the numerical results and experimental results. In this paper a method to generate ITZ meshes called aggregate-expansion method (AEM) is proposed to generate wedge elements around 50µm thick to represent ITZ’s layer structure. The total number of generated ITZ meshes is limited and acceptable in meso-level FEA for concrete. A digital concrete specimen is generated from CT images with ITZ meshes generated by AEM and effects of ITZ on the compressive stress/strain/displacement distributions of concrete were studied. The characteristics of stress–strain response of the digital concrete specimen under tension were also studied and compared with experimental data.

Moving beyond Stylized Economic Network Models: The Hybrid World of the Indian Firm Ownership Network.

A central theme of economic sociology has been to highlight the complexity and diversity of real world markets, but many network models of economic social structure ignore this feature and rely instead on stylized one-dimensional characterizations. Here, the authors return to the basic insight of structural diversity in economic sociology. Using the Indian interorganizational ownership network as their case, they discover a composite-or "hybrid"-model of economic networks that combines elements of prior stylized models. The network contains a disconnected periphery conforming closely to a "transactional" model; a semiperiphery characterized by small, dense clusters with sporadic links, as predicted in "small-world" models; and finally a nested core composed of clusters connected via multiple independent paths. The authors then show how a firm's position within the mesolevel structure is associated with demographic features such as age and industry and differences in the extent to which firms engage in multiplex and high-value exchanges.

Microporous Aluminophosphate Nanosheets and Their Nanomorphic Zeolite Analogues Tailored by Hierarchical Structure-Directing Amines

Multiamines with amphiphilic structures have been synthesized to serve as simultaneous structure-directing agents in micro- and meso-structural levels for aluminophosphate materials (AlPOs) and their analogues, such as silicoaluminophosphate, cobalt aluminophosphate, and gallium phosphate. The amine molecules are assembled into a micelle with a specific morphology to function as a meso-level structure director. Individual amine groups in the micelle are able to direct the formation of microporous crystalline AlPO structure. The resultant meso-level morphologies of the AlPOs are typically nanosheets of uniform thickness, which can be tailored in the range of 2-5 nm by the number of amine groups. Sponge-like disordered mesoporous morphologies can be generated, depending on the amine structures. Using such multiamines provides a versatile route to various phosphate materials with a structural hierarchy for enhanced porous functionalities.