Design of semantic information broker for localized computing environments in the internet of things

Emerging communication technologies of the Internet of Things (IoT) make all the devices of a spatial-limited physical computing environment locally interconnected as well as connected to the Internet. Software agents running on devices make the latter “smart objects” that are visible in our daily lives as real participating entities. Based on the M3 architecture for smart spaces, we consider the problem of creating a smart space deploying a Semantic Information Broker (SIB) in a localized IoT-environment. SIB supports agent interaction in the smart space via sharing and self-generating information and its semantics. This paper proposes a renewed SIB design with increased extensibility, dependability, and portability. The research done is a step towards an efficient open interoperability platform for the smart space application development

Политическая аккомодация культурных различий в индустриально развитых обществах

The notion of "political accommodation" applied to the theory and practice of managing cultural diversity could enrich the Russian academic dictionary. Liberal democratic states invented specific mechanisms for political accommodation of cultural differences. Thanks to these mechanisms, the part of the population of a democratic state that is not ready to dissolve into the ethnocultural majority is more or less protected. The law not only prohibits forced assimilation, but also contains a number of norms that allow ethnocultural minorities to maintain their distinctiveness by passing it on from generation to generation. However, this is the case in liberal democracies with a long history. In states that emerged as a result of the collapse of two multinational policies - Yugoslavia and the USSR - the situation sometimes looks quite specific. They take more active measures for cultural homogenization than in previous years. As for Russia, in recent years there have been symptomatic changes in the sphere of ethno-cultural policy, which, although with a number of reservations, can be described in terms of "nationalization"

Compaction behaviour of dense sheared woven preforms:Experimental observations and analytical predictions

AbstractYarn-scale modelling of textile preforms relies on the realistic reconstruction of internal geometry. The paper presents a model of fabric compaction, which shows that fine features of dense woven preforms, conventionally neglected in consolidation analysis, have a significant impact on thickness and consequently on fibre volume fraction and yarn crimp inside the composite. The model relies on single yarn compaction test and geometrical characteristics of preform in compacted and original configurations. The model is validated against compaction experiments on dense sheared single ply and nested carbon twill 2/2 fabrics. This exercise aims at decreasing or eliminating phenomenological parameters being introduced when calibrating geometrically and physically complex numerical models at the yarn scale

Identification of damage initiation and development in textile composite materials using acoustic emission

Damage in textile composites is closely connected with the internal micro- and mesogeometry of the reinforcement, and reveals features different from classical laminates. This paper presents a test sequence to characterise damage in textile composites and its dynamics of initiation and development on different scale levels in order to achieve a deep understanding of the relevant phenomena. The proposed test sequence consists of the following steps: 1) Tensile tests on samples cut in characteristic directions of the textile reinforcement with acoustic emission (AE) and full-field strain measurement on the surface. The test produces stress-strain diagrams and identifies based on the AE characteristic strain levels: Full-field strain measurement highlights relation between strain concentrations (linked with the damage initiation) and the reinforcement structure. 2) Samples loaded are examined with microfocus-X-ray computed tomography and radiography, revealing the damage pattern and allowing a quantitative analysis of the damage development. 3) Microscopic examination of cross-sections through the damage sites, determined with X-ray, identifies the local damage modes. Macro-, meso- and microcharacterisation of damage result in a thorough understanding of the material behaviour. The paper presents and discusses the results of the proposed experimental protocol for carbon/epoxy 3-axial braided and quasi-UD composites.status: publishe

Identification of damage initiation and development in textile composite materials using acoustic emission

Damage in textile composites is closely connected with the internal micro- and meso-geometry of the reinforcement, and reveals features different from classical laminates. This paper presents a test sequence to characterise damage in textile composites and its dynamics of initiation and development on different scale levels in order to achieve a deep understanding of the relevant phenomena. The proposed test sequence consists of the following steps: 1) Tensile tests on samples cut in characteristic directions of the textile reinforcement with acoustic emission (AE) and full-field strain measurement on the surface. The test produces stress-strain diagrams and identifies based on the AE characteristic strain levels: Full-field strain measurement highlights relation between strain concentrations (linked with the damage initiation) and the reinforcement structure. 2) Samples loaded are examined with microfocus-X-ray computed tomography and radiography, revealing the damage pattern and allowing a quantitative analysis of the damage development. 3) Microscopic examination of cross-sections through the damage sites, determined with X-ray, identifies the local damage modes. Macro-, meso- and micro-characterisation of damage result in a thorough understanding of the material behaviour. The paper presents and discusses the results of the proposed experimental protocol for carbon/epoxy 3-axial braided and quasi-UD composites.status: publishe

On modelling of damage evolution in textile composites on meso-level via property degradation approach

The continuous damage mechanics (CDM) approach is a popular tool for modelling of damage evolution in textile composites on the meso-level. It is based on the assumption that a material with defects can be replaced by a fictitious material with no defects but with degraded elastic constants. In such way the presence of defects is only reflected in the material elastic properties and damage evolution is recorded through the loss of these properties. The CDM approach incorporated into finite element analysis often predicts unphysically wide damage zones and in some cases failure across yarns – findings that are not supported by experimental data. The current work is geared toward identifying the source of inconsistencies between experiment and modelling by revisiting basic assumptions of CDM. A test problem is proposed to illustrate a break down of the CDM approach where a single crack-like defect in a yarn is modelled as an inhomogeneity with elastic constants reduced according to Murakami–Ohno model. It is shown that CDM in combination with local stress analysis of failure may predict a different direction of damage evolution as well as an incorrect failure mode in comparison with the crack problem. We also investigate whether the Murakami–Ohno model adopted for calculation of properties of a fictitious inhomogeneity contributes to the unphysical results. For this we compare contributions of a crack and an inhomogeneity into material elastic response. A new property degradation procedure is suggested (referred here as an effective elastic response model) where the size of an inhomogeneity and properties of the surrounding material are taken into account.status: publishe

Strain mapping analysis of textile composites

The focus of the work is meso-scale analysis (scale level of the fabric unit cell) of textile composite deformation and failure. The surface strain measurement is used for: (1) experimental investigation, which includes study of strain distribution at various stages of deformation, plasticity detection, damage initiation; (2) numerical validation of the correspondent finite element (FE) models. Two examples are considered: carbon-epoxy triaxial-braided and glass polypropylene-woven composite. The surface strain measurement (by digital image correlation technique) accompanies the tensile tests, aiming at: (1) elastic anisotropic constants characterisation, (2) study of non-linear material behaviour (for the thermoplastic composite), (3) control of homogeneity of the macro-strain distribution, and (4) analysis of damage initiation in brittle composites. Validation of meso-FE models by strain measurements encounters difficulties arising from (1) resolution of the strain measurements, (2) irregularities of the initial structure such as random layer nesting, ply interaction, and deviation of yams from their theoretical position, which affects the measured strain fields. The paper discusses these difficulties and demonstrates a qualitative agreement with the FE analysis of idealised composite configurations.status: publishe

Stress distribution in outer and inner plies of textile laminates and novel boundary conditions for unit cell analysis

The local stress-strain distribution in a unit cell of a textile laminate depends on the distance of the ply to the surface, the number of plies in the laminate, and the stacking sequence A conventional meso FE analysis employs boundary conditions for a unit cell of the textile composite based on the assumption of periodicity in the thickness direction In that case, the stress concentration can be drastically underestimated, especially in outer plies This paper describes the interaction of plies, local stresses and displacements To avoid the analysis of the whole laminate and to reduce it to the boundary value problem on one unit cell only, novel boundary conditions are introduced. These conditions are based on the analysis of a single unit cell, they account for the number of the plies in the laminate, distinguish between the outer and inner plies, and reproduce the meso stress-strain state with good precision.status: publishe

Meso-scale damage modelling of textile composite using the embedded element technique and contact algorithm

The paper investigates feasibility of application of embedded element technique to damage modelling of textile composites on an example of a woven laminate. The geometrical model of yarns is imported to Abaqus form WiseTex software. The yarns and matrix meshes are superimposed using embedded element technique. Damage initiation and development under tensile loading and the resulting stress strain curve is simulated using continuous damage mechanics approach based on Puck damage criterion and Zinoviev-type damage variables. The results show acceptable agreement with the damage modelling based on continuous mesh and with experimental data.status: publishe