3499 research outputs found
Sort by
A finite element framework for the interplay between delamination and buckling of rubber-like bi-material systems and stretchable electronics
No full textIn this study, a finite element (FE) framework for the analysis of the interplay between buckling and delamination of thin layers bonded to soft substrates is proposed. The current framework incorporates the following modeling features: (i) geometrically nonlinear solid shell elements, (ii) geometrically nonlinear cohesive interface elements, and (iii) hyperelastic material constitutive response for the bodies that compose the system. A fully implicit Newton–Raphson solution strategy is adopted to deal with the complex simultaneous presence of geometrical and material nonlinearities through the derivation of the consistent FE formulation. Applications to a rubber-like bi-material system under finite bending and to patterned stiff islands resting on soft substrate for stretchable solar cells subjected to tensile loading are proposed. The results obtained are in good agreement with benchmark results available in the literature, confirming the accuracy and the capabilities of the proposed numerical method for the analysis of complex three-dimensional fracture mechanics problems under finite deformations
Adhesive behaviour of bonded paper layers: Mechanical testing and statistical modelling
No full textIn this study, an experimental methodology based on micromechanical testing inside a scanning electron microscope is proposed to characterise bonding of paper layers connected by wet pressing. The peeling force–displacement evolution law that characterises the delamination of micromechanical double cantilever beam specimens of paper tissue have been extracted from such peeling tests. It is observed that the force–displacement evolution curve achieves a steady-state value related to the effective adhesive energy of the interface. This behaviour is explained by examining the complex load transfer mechanism between the layers exerted by cellulose fibrils. A statistical approach is used for the computation of the effective adhesive energy. It is argued that the observed force–displacement evolution law may be satisfactory described by a stochastic model that depends on the distribution function of the fibrils strength, and on two geometrical distribution functions related to the in-plane and out-of-plane fibrils angles with respect to the undeformed interface configuration. Some applications of the proposed model are demonstrated on examples
Dispersive wave propagation in two-dimensional rigid periodic blocky materials with elastic interfaces
No full textDispersive waves in two-dimensional blocky materials with periodic microstructure made up of equal rigid units having polygonal centro-symmetric shape with mass and gyroscopic inertia, connected each other through homogeneous linear interfaces, have been analysed. The acoustic behavior of the resulting discrete Lagrangian model has been obtained through a Floquet-Bloch approach. From the resulting eigenproblem derived by the Euler-Lagrange equations for harmonic wave propagation, two acoustic branches and an optical branch are obtained in the frequency spectrum. A micropolar continuum model to approximate the Lagrangian model has been derived based on a second-order Taylor expansion of the generalized macro-displacement field. The constitutive equations of the equivalent micropolar continuum have been obtained, with the peculiarity that the positive definiteness of the second-order symmetric tensor associated to the curvature vector is not guaranteed and depends both on the ratio between the local tangent and normal stiffness and on the block shape. The same results has been obtained through an extended Hamiltonian derivation of the equations of motion for the equivalent continuum that is related to the Hill-Mandel macro homogeneity condition. Moreover, it is shown that the hermitian matrix governing the eigenproblem of harmonic wave propagation in the micropolar model is exact up to the second order in the norm of the wave vector with respect to the same matrix from the discrete model. To appreciate the acoustic behavior of some relevant blocky materials and to understand the reliability and the validity limits of the micropolar continuum model, some blocky patterns have been analysed: rhombic and hexagonal assemblages and running bond masonry
Foundations of Session Types and Behavioural Contracts
No full textBehavioural type systems, usually associated to concurrent or distributed computations, encompass concepts such as interfaces, communication protocols, and contracts, in addition to the traditional input/output operations. The behavioural type of a software component specifies its expected patterns of interaction using expressive type languages, so types can be used to determine automatically whether the component interacts correctly with other components. Two related important notions of behavioural types are those of session types and behavioural contracts. This article surveys the main accomplishments of the last 20 years within these two approaches
Global Value Chains Participation and Productivity Gains for North African Firms
No full textThis paper analyzes the participation of North African countries and Örms into Global Value Chains
(GVCs) and its implications for competitiveness. First it shows that North African countries are
not (yet) fully integrated into international production networks, although large part of their (low)
trade is due to value added related upstream activities, and the importance of global linkages
has been increasing over time. Then, it empirically investigates if and how the performance of
North African Örms is a§ected by GVC participation. We Önd that Örms that have had access
to international supply chains perform better, showing further productivity gains over time. The
ability to get such improvements however relies on speciÖc characteristics, such as an adequate
level of quality and compliance with international standards, along with specialized skills. Policies
designed to support the latter represent then an important tool for linking developing countries to
global production and trade, with possible positive consequences on their economic development
Networks of plants: how to measure similarity in vegetable species
No full textDespite the common misconception of nearly static organisms, plants do interact continuously with the environment and with each other. It is fair to assume that during their evolution they developed particular features to overcome similar problems and to exploit possibilities from environment. In this paper we introduce various quantitative measures based on recent advancements in complex network theory that allow to measure the effective similarities of various species. By using this approach on the similarity in fruit-typology ecological traits we obtain a clear plant classification in a way similar to traditional taxonomic classification. This result is not trivial, since a similar analysis done on the basis of diaspore morphological properties do not provide any clear parameter to classify plants species. Complex network theory can then be used in order to determine which feature amongst many can be used to distinguish scope and possibly evolution of plants. Future uses of this approach range from functional classification to quantitative determination of plant communities in nature
Developing sustainable cultural policies in Turkey: an investigation of public opinion on the theatre scene
No full textThe arts scene in Turkey has been witnessing many discussions with the revealing of the governmental reform agenda on the state support model for the arts that includes establishment of an arts council type institution, the closure of the State Theatres and, the State Opera and Ballet. Nevertheless, despite strong public criticism on this reform agenda, there has never been any comprehensive research to reflect the public opinion. Therefore, this study aims to contribute to recent discussions by providing data on public opinion regarding such a fundamental change, with a particular focus on theatre. Towards this end, a survey was conducted in Istanbul. The findings demonstrate that the majority, including both users and non-users of theatre, value the State Theatres and are in favour of sustaining it. There is also a common belief that in case of the State Theatres’ closure, the private theatres cannot undertake its public mission
Sparse optimization for automated energy end use disaggregation
No full textRetrieving the household electricity consumption at individual appliance level is an essential requirement to assess the contribution of different end uses to the total household consumption, and thus to design energy saving policies and user-tailored feedback for reducing household electricity usage. This has led to the development of nonintrusive appliance load monitoring (NIALM), or energy disaggregation, algorithms, which aim to decompose the aggregate energy consumption data collected from a single measurement point into device-level consumption estimations. Existing NIALM algorithms are able to provide accurate estimate of the fraction of energy consumed by each appliance. Yet, in the authors' experience, they provide poor performance in reconstructing the power consumption trajectories overtime. In this brief, a new NIALM algorithm is presented, which, besides providing very accurate estimates of the aggregated consumption by appliance, also accurately characterizes the appliance power consumption profiles overtime. The proposed algorithm is based on the assumption that the unknown appliance power consumption profiles are piecewise constant overtime (as it is typical for power use patterns of household appliances) and it exploits the information on the time-of-day probability in which a specific appliance might be used. The disaggregation problem is formulated as a least-square error minimization problem, with an additional (convex) penalty term aiming at enforcing the disaggregate signals to be piecewise constant overtime. Testing on household electricity data available in the literature is reported