86,804 research outputs found
“Il dibattito teorico sugli aiuti agli studenti nell'istruzione superiore e le sue possibili implicazioni per il caso italiano”
No full textA cura di A. Petretto e G. Pignatar
Infrastruttura stradale e psicologia viaria
No full textIl rapporto tra psicologia del conducente e infrastruttura stradale è complesso ed integrato: la psicologia e la sperimentazione aiutano a comprenderlo. Si evidenzia inoltre come la sicurezza della circolazione dipenda dal rapporto integrato e complesso della psicologia del conducente del veicolo, del traffico, del veicolo stesso, dell'ambiente, dell'infrastruttura stradale
Dalle prove tradizionali allo Zero Shear Viscosity, la reologia dei leganti bituminosi
No full textAt the beginning of asphalt rheology, the tests used for the characterization of bitumen were empirical, based primarily on the experience of technicians. These traditional tests were not able to measure the physical asphalt binder properties directly related with their service life performance. In 1987, the Strategic Highway Research Program (SHRP) brought some new tests for the so called performance rheology aiming to measure properties directly related to the field performance, under rigorous engineering principles. However, a number of recent studies have shown that some SHRP parameters are not fully representative of the PmBs rheology
Comparison between 2PB and 4PB methodology based on the Dissipated Energy Approach
No full textTwo and four point bending tests are among the most common methodologies adopted in Europe and United States for the fatigue characterization of asphalt mixes. Both tests tend to simulate the flexural stresses generated by traffic applying uniaxial rather than triaxial loading. The main differences between these procedures are: the direction of load application, the constrains and the volume of material subjected to fatigue.
In this study, based on Fatigue data, the Elletipi horizontal two point bending (2PB) and a traditional four point bending (4PB) results are compared. The peculiarity of the 2PB flexural device is the horizontal position of the trapezoidal specimen during the test.
All tests were performed in strain controlled conditions at different temperatures. The research focuses on the influence of the loading waveform by comparing the effects of sinusoidal and haversine loads of equivalent strain amplitudes. The Ratio of Dissipated Energy Change (RDEC) approach, based on the energy balance classical theory, was the application of choice for the analysis of results. Finally, the influence of specimen volume on fatigue resistance was assessed performing horizontal 2PB tests on trapezoidal specimens of different thickness
Permanent Deformations of WMAs related to the Bituminous Binder Temperature Susceptibility
No full textThe purpose of this study is to evaluate the growth of permanent deformations in Warm Mix Asphalts related to their binder temperature susceptibility. Rutting builds up in the pavement under the repeated loading generated by the traffic along the wheels path. The distress develops in two different ways, the pre-consolidation rutting, deformation at variable volume, and the instability rutting, deformation at constant volume. These phenomena are directly related to the loading time, the shape of aggregates, the content of air voids, the type of binder and its temperature susceptibility. This study focuses on the binder contribution to rutting when subjected to high temperature variation. An accurate laboratory investigation was completed to assess how this material property influences the different propagation of permanent deformations. The EN 12697 - 22 Wheel Tracking test was performed at three different temperatures (40 - 50 - 60°C) on two gap graded asphalt mixtures. In order to evaluate how, at these temperatures, the properties of the bitumen act on the asphalt concrete tendency to exhibit permanent deformations, a series of DSR rheological tests were also conducted
The Use of Cryogenic Crumb Rubber in the Cold Recycling Technique
No full textIn the recent years, recycling has become one of the most attractive pavements rehabilitation alternatives and different recycling methods are now available to address specific pavement distresses and structural needs. Cold recycling is an economically efficient and environmental-friendly method for producing bituminous layers of adequate strength. This technique has been successfully used in Italy during the past 15 years to rehabilitate or upgrade many thousands of kilometers of highways and motorways’ pavements. Currently a wide range of materials can be used and consequently large is the number of variables to be considered in the mixdesign process. Being this a relatively new technique, new products are continually introduced or developed for recycling purposes.
The main objective of this study is to investigate and evaluate the effects of crumb rubber, cement and bitumen proportions on the engineering properties of fully
recycled cold mixes. In fact, the experimental plan includes the use of various quantities of Cryogenic Crumb Rubber (CCR) in mixtures containing 100% of Reclaimed Asphalt Pavement, bituminous emulsion and Portland cement. Thanks to the new European and national regulations, the use of recycled rubber in road construction applications has been growing so far and this application could
represent a valid alternative to the classical use of rubber in HMAs
Indagine sugli Aggregati da C&D
No full textLe Strade presenta, a firma di un team di ricercatori delle Università di Bologna e Pisa, la sintesi di una sperimentazione condotta su un rilevato realizzato ad hoc e finalizzata allo studio di diverse miscele provenienti da costruzioni e demolizioni. L'obiettivo: valutare la capacità portante in prospettiva di un reimpiego in sottofondi e fondazioni stradali. L'indagine ha dimostrato,anche attraverso l'integrazione di compattazione intelligente e prove deflettometriche, che i materiali derivanti da un processo mirato di riciclaggio possono fornire risultati paragonabili, se non superiori, a quelli ottenibili da aggregati vergini
Systems genetics as a tool to identify master genetic regulators in complex disease
No full textSystems genetics stems from systems biology and similarly employs integrative modeling approaches to describe the perturbations and phenotypic effects observed in a complex system. However, in the case of systems genetics the main source of perturbation is naturally occurring genetic variation, which can be analyzed at the systems-level to explain the observed variation in phenotypic traits. In contrast with conventional single-variant association approaches, the success of systems genetics has been in the identification of gene networks and molecular pathways that underlie complex disease. In addition, systems genetics has proven useful in the discovery of master trans-acting genetic regulators of functional networks and pathways, which in many cases revealed unexpected gene targets for disease. Here we detail the central components of a fully integrated systems genetics approach to complex disease, starting from assessment of genetic and gene expression variation, linking DNA sequence variation to mRNA (expression QTL mapping), gene regulatory network analysis and mapping the genetic control of regulatory networks. By summarizing a few illustrative (and successful) examples, we highlight how different data-modeling strategies can be effectively integrated in a systems genetics study
Characterization of Wind and Solar generation and their influence on distribution network performances
No full textThe paper is aimed at focusing the influence and more in general the benefits and the problems that medium size wind turbines, photovoltaic power plants, and small cogenerative generators embedded in a radial distribution network can produce regarding voltage profiles and power balance. Simulations, performed by a widely used power system analysis code, are reported and commented
Adsorption and desorption of imazapyr by soil
No full textThe adsorption and desorption of imazapyr, (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H- imidazol-2-yl]-3-pyridinecarboxylic acid, by six soils were studied. Adsorption isotherms conformed to the Freundlich equation. A multiple regression analysis indicated that K-f(ads) values were better correlated if cation exchange capacity and pH (r = 0.984) were simultaneously taken into account. The results show that the herbicide adsorption is strongly affected by the pH and the charge of the adsorbing component. The organic matter is effective in imazapyr retention, but only at pH <5. Enhanced adsorption was observed in amorphous iron oxide, most likely because of a ligand exchange process
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