1,721,582 research outputs found
Self-healing cement-based materials: an asset for sustainable construction industry
Full text linkWorldwide increasing consciousness for sustainable use of natural resources has
made “overcoming the apparent contradictory requirements of cost and performance
effectiveness a challenging task” as well as a major concern. Self-healing cement-based
materials, by controlling and repairing cracks, could prevent “permeation of driving factors for
deterioration”, thus extending the structure service life, and even provide partial recovery of
the engineering properties relevant to the application. This paper will outline the current state
of art on self-healing cement-based materials and experimental methods for the assessment of
the self-healing capacity. Moreover, it will also critically analyse the current hindrances which
challenge the engineering community in paving the way towards the reliable and consistent
incorporation of self-healing concepts and effects into a durability-based design framework for
buildings and structures made of or retrofitted with self- healing concrete and cementitious
composites
Residuals-based fault diagnosis of industrial automation systems using timed and untimed Interpreted Petri nets
No full textThe problem of detecting and isolating a fault using a discrete event model has received a lot of attention over the last two decades. Indeed, industrial automated systems can be usually modelled by a discrete event system. The problem is particularly significant if a fault-free model is used. Recently, residuals, well-known in continuous time systems context, have been proposed to obtain set of candidate faults from real time observations for discrete event system also. They have been obtained using finite state automata. In this paper, inspired by these works, residuals are formulated using Petri net models, both timed and un-timed ones. The computation of residuals for net models requires some efforts to update and predict the state, especially in timed models, but it returns to be highly efficient and scalable thanks to the local state representation and intrinsic distributed nature of the these models. A practical example, consisting of a plant simulated by using a 3D environment interfaced to a Programmable Logic Controller to simulate/emulate the closed-loop behaviour, is used to illustrate the results of the paper
Validation of Industrial Automation Systems Using a Timed Model of System Requirements
No full textValidation of industrial automation systems is the process of checking that commissioner requirements are successfully implemented. Formal approaches are needed when the considered system is critical. The method presented in this article relies on a model-based approach that exploits the compactness and graphical representation of time-interpreted Petri nets, which adds input-output interpretation to transitions/places and embeds time information. These nets are here used with multiple-server semantic to allow effective modeling of typical automation system requirements. The key idea of the system validation approach is to compare the observed behavior of the automation system with the expected behavior, as generated by updating online the model of system requirements using a state estimation algorithm. Also, an off-line procedure is provided to evaluate the evolutions admitted by the model but not observed. Both procedures yield useful data to the validation engineer, allowing to speed up the validation process. Technological issues due to the synchronous nature of controllers and the implications of their programming are considered
A Matlab toolbox implementing MSCG computation
No full textModified State Class Graph collects in a compact form the main information on all the possible evolutions of a given labeled TPN system initialized at a given marking. Recently, it has been used to solve different problems, in particular supervisor control synthesis, state estimation and system validation. It employs a symbolic characterization of the firing time intervals of the enabled transitions. This paper presents a set of MATLAB functions implementing the computation of MSCG in different ways, useful for applications
From supervisory control to PLC code: A way to speed-up Constructive/Virtual Commissioning of Manufacturing Systems
No full textThis paper demonstrates that it is nowadays possible to successfully adopt a virtual/constructive approach in the contest of automated manufacturing systems. The design and the implementation of the control software is usually not considered a crucial step in the development cycle of these systems but it plays a key role to reduce time and costs of the real commissioning. In this paper, recent computer technology progress, some results from discrete event systems research and a proposed software are exploited to show that a virtual/constructive approach can effectively speed-up the design and the implementation of the control software
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Deux Eretmapodites nouveaux du Cameroun, appartenant au groupe oedipodius Graham, 1909 (DIPT. CULICIDAE)
No full textRickenbach André, Ferrara L., Eouzan Jean-Pierre. Deux Eretmapodites nouveaux du Cameroun, appartenant au groupe oedipodius Graham 1909 [Dipt. Culicidae]. In: Bulletin de la Société entomologique de France, volume 72 (9-10), Novembre-décembre 1967. pp. 297-300
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