1,721,043 research outputs found
Impact behavior of structural elements in concrete reinforced with PET grids
No full textRecycling of waste materials is one of the most important problems in the future to be solved in all possible ways. Polyethylene terephthalate (PET), for example, is a waste material that could be reused as concrete reinforcement.
In the present article the results of impact tests performed on reinforced concrete specimens with fibers made from waste PET bottles are reported. The fibers have been obtained by simply cutting the bottles and have been utilized as discrete long reinforcement of specimens in concrete in substitution of steel bars. A test set-up and slab specimens have been designed and manufactured for the impact tests.
The tests provided interesting results regarding the impact strength of PET reinforced concrete, suggesting a possible use of this material, in particular for those cases frequently subjected to shocks and impact forces, such as road and, especially, airport pavements, wharfs, etc. The reinforcement with PET has the advantage to be less corrosive and less expensive than reinforcement consisting of steel wire nets and carbon or glass nets
Stirring, Mixing, Growing: Microscale Processes Change Larger Scale Phytoplankton Dynamics
No full textThe quantitative description of marine systems is constrained by a major issue of scale separation: phytoplankton production processes occur at sub-centimeter scales, while the contribution to the Earth's biogeochemical cycles is expressed at much larger scales, up to the planetary one. In spite of vastly improved computing power and observational capabilities, the modeling approach has remained anchored to an old view that sees the microscales as unable to substantially affect larger ones. The lack of a widespread theoretical appreciation of the interactions between vastly different scales has led to the proliferation of numerical models with uncertain predictive capabilities. In this paper, we use the phenology of phytoplankton blooms as one example of a macroscopic ecosystem feature affected by microscale interactions. We describe two distinct mechanisms that produce patchiness within a productive water column: turbulent entrainment of less-productive water at the base of the mixed layer, and stirring by slow turbulence of a vertical phytoplankton gradient sustained by depth-dependent light availability. In current eddy-diffusive models, patchiness produced in this way is wiped out very rapidly, because the time scales of irreversible mixing largely overlap those of mechanical stirring. We propose a novel Lagrangian modeling framework that allows for the existence of microscale patchiness, even when that is not fully resolved. We show, with a mixture of theoretical arguments and numerical simulations of increasing realism, how the presence of patchiness, in turn, affects larger-scale properties, demonstrating that the timing of phytoplankton blooms and vertical variability of chlorophyll in the oceanic upper layers is determined by the mutual interplay between the stirring, mixing and growing processes
On a salt fingers model
Full text linkWe consider the model introduced in Paparella and von Hardenberg (2014), that consists in the homogeneous boundary value problem for a system of nonlinear degenerate parabolic equations. We prove the existence of global weak solutions and discuss their stability and asymptotic properties
Calcestruzzi fibrorinforzati con fibre di PET. Studio della resistenza all’impatto
No full textIl riciclaggio dei materiali di scarto è senza dubbio uno dei più importanti problemi da risolvere in futuro in tutti i modi possibili. Sta diventando sempre più necessario trovare soluzioni anche originali, fantasiose e brillanti che devono certamente essere testate prima di essere messe in pratica. Il Polietilene Tereftalato (PET), per esempio, è un materiale di rifiuto che si presta molto bene per essere riutilizzato come rinforzo del calcestruzzo.
Nel presente articolo sono riportati i risultati di alcune prove di impatto effettuate su piastre in calcestruzzo rinforzate con strisce ottenute da bottiglie di scarto in polietilene tereftalato (PET). Le fibre sono state ottenute semplicemente tagliando le bottiglie e sono state utilizzate come rinforzi continui per piastre in calcestruzzo. Per le prove di impatto è stato progettato e realizzato un set-up di prova “ad hoc”. Le prove fanno parte di una estesa ricerca sull’uso del PET come materiale di rinforzo per le strutture in calcestruzzo e in muratura. Le prove hanno fornito dei risultati interessanti circa la resistenza all’impatto del calcestruzzo rinforzato con PET, suggerendo un possibile uso di questo materiale, in particolare per quei casi che sono frequentemente soggetti a shock e a forze di impatto, come i guard-rail new-jersey, le pavimentazioni stradali e aeroportuali, le banchine dei porti. Il rinforzo con il PET ha il vantaggio di non subire fenomeni di corrosione e di essere economicamente vantaggioso rispetto al rinforzo con barre e reti di acciaio, e reti di carbonio o vetro, rendendo questo materiale più adatto per applicazioni in presenza di un ambiente aggressivo.*** Recycling of waste materials is, undoubtedly, one of the most important problems in the future to be solved in all possible ways. It is becoming increasingly necessary to find solutions, even original, imaginative and brilliant to be, of course, first tested before their practical application. Polietilene tereftalato (PET), for example, is a waste material that lends itself well to be reused as concrete reinforcement. In the present article the results of impact tests performed on concrete slab specimens reinforced with fibers made from waste (PET) bottles are reported. The fibers have been obtained by simply cutting the bottles and have been utilized as discrete long reinforcement of the slabs in concrete in substitution of steel bars. A test set-up and slab specimens have been designed and manufactured for the impact tests. The tests are part of an extensive investigation on the use of PET as a reinforcing material in concrete and masonry structures. The tests provided interesting results regarding the impact strength of PET reinforced concrete, suggesting a possible use of this material, in particular for those cases frequently subjected to shocks and impact forces, such as new-jersey guard-rails, road and, especially, airport pavements, wharfs. The reinforcement with PET has the advantage to be less corrosive and less expensive than reinforcement consisting of steel wire nets and carbon or glass nets, making this material more adequate for applications in presence of an aggressive environment
Reply to a comment by Franco Gabrielli and Daniela Di Bucci: "Communicating earthquake risk to the public: the trial of the 'L'Aquila Seven'''
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Metaverso e suoi problemi tributari
No full textL'introduzione esamina la particolare natura dell'algoritmo custodito nel metaverso, le difficoltà nel controllarne la circolazione in modi diversi dal possesso dei relativi codici informatici e i riflessi tributar
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
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