1,198 research outputs found
A novel quasi-open loop architecture for GNSS carrier recovery systems
No full textThe problem of designing robust systems to track global navigation satellite system (GNSS) signals in harsh environments has gained high attention. The classical closed loop architectures, such as phase locked loops, have been used for many years for tracking, but in challenging applications their design procedure becomes intricate. This paper proposes and demonstrates the use of a quasi-open loop architecture to estimate the time varying carrier frequency of GNSS signals. Simulation results show that this scheme provides an additional degree of freedom to the design of the whole architecture. In particular, this additional degree of freedom eases the design of the loop filter in harsh environment
The Pedagogical Approach of Guidance in Higher Education. An Educational Research Experience in Italian Universities
No full textIl contributo della street level evaluation per l'analisi delle politiche di contrasto alla povertà
No full textIl saggio ha l'obiettivo di ripercorrere e analizzare criticamente il processo di implementazione di due politiche di contrasto alla povertà, Sia e Rei, a partire dalla costruzione di un disegno di ricerca valutativa ispirato all'approccio innovativo della street level evaluation
A stalactite record of four relative sea-level highstands during the Middle Pleistocene Transition
No full textIce-sheet and sea-level fluctuations during the Early and Middle Pleistocene are as yet poorly understood. A stalactite from a karst cave in North West Sicily (Italy) provides the first evidence of four marine inundations that correspond to relative sea-level highstands at the time of the Middle Pleistocene Transition. The speleothem is located ∼97 m above mean sea level as result of Quaternary uplift. Its section reveals three marine hiatuses and a coral overgrowth that fixes the age of final marine ingression at 1.124 ± 0.2, thus making this speleothem the oldest stalactite with marine hiatuses ever studied to date. Scleractinian coral species witness light-limited conditions and water depth of 20–50 m. Integrating the coral-constrained depth with the geologically constrained uplift rate and an ensemble of RSL scenarios, we find that the age of the last marine ingression most likely coincides with Marine Isotope Stage 35 on the basis of a probabilistic assessment. Our findings are consistent with a significant Antarctic ice-sheet retreat. © 2017 Elsevier Lt
Pratiche partecipative e relazioni solidali nel sostegno a distanza. Il «posto della comunicazione»
No full textIl saggio si inserisce nell’ambito di una ricerca sulla valutazione delle pratiche partecipative e delle attività di engagement dei sostenitori del servizio di sostegno a distanza (Sad) nell’Associazione Famiglie nuove (Afn) onlus. Dalle evidenze empiriche raccolte emerge una dimensione privata di adesione al Sad, che si articola nella diffusione di pratiche simboliche, inedite
e per giunta non convenzionali di partecipazione associativa. Sono proprio queste pratiche, anche connesse al profilo etico e morale dei sostenitori – che si dichiarano diffusori di fiducia e promotori diretti della cultura del Sad – che orientano la riflessione sui principali cambiamenti che hanno investito il significato della «prossimità relazionale» fra sostenitore
e beneficiario del sostegno. Ponendo l’accento sui valori del dono e della reciprocità, il ruolo assunto dalla comunicazione 2.0 appare centrale per «salvaguardare» la qualità delle relazioni tra i diversi pubblici di Afn, e per estendere la loro portata (dimensionale e valoriale) verso le «comunità educanti» dei paesi terzi coinvolte nei progetti Sad
Flooding scenario for four italian coastal plains using three relative sea level rise models
No full textThe coastal areas of the central Mediterranean Sea are sensitive to climate change and the consequent relative sea level rise. Both phenomena may affect densely urbanized and populated areas, causing severe damages. Our maps show the land-marine flooding projections as effects of the expected relative sea level rise for four Italian coastal plains using (i) IPCC AR5 estimations, based on the IPCC RCP 8.5 emission scenarios and (ii) the Rahmstorf 2007 model. Isostatic and tectonic data were added to the global projections to estimate the relative sea changes expected along the coastline by 2100, as well as sea-flooding. The northern Adriatic map shows the study area, extending for about 5500 km2, and is presented at a scale of 1:300,000 with two inset maps at a scale of 1:150,000. The Oristano coastal plain is about 125 km2; the map scale is at 1:60,000 with an inset map scale at 1:33,000. The Cagliari coastal study area extends for 61 km2; the map scale is at 1:60,000 with two inset maps at 1:30,000. The Taranto area extends for 4.2 km2 and is represented at a scale map of 1:30,000, while the three inset maps are at a scale of 1:10,000. © 2017 The Author(s)
A Concerted Electrochemical and Theoretical Investigation of the Ag/TiO2 nano-heterojunction
No full textSuitably designed nano-heterojunctions are able to enhance synergistic functionalities of different materials yielding to “brave new systems” with innovative and sometimes unexpected physicochemical properties [1]. However, the complete understanding of these devices has to be deeply studied. In this work, a concerted theoretical and electrochemical investigation is proposed to gain insights into a metal-semiconductor interface, namely that created by the silver/anatase hybrid nanocomposite, a promising material for advanced sensing applications [2]. In particular, it provided the first photorenewable and anti-fouling sensor device, enhancing the analytical limits in terms of accuracy, sensitivity, detection limits, and photoactivity [3]. Furthermore, the hybrid material is proven to be extremely robust against aging, showing complete regeneration, also after one-year storage.
The electrochemical/electroanalytical virtues of the Ag/TiO2 junction were evaluated in terms of current densities and reproducibility, providing their explanation at the atomic-scale level and demonstrating how and why the final device can act as silver-cation positive electrode [4]. Moreover, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy were used in combination with periodic plane-wave DFT calculations, giving comparable qualitative but also quantitative results. In particular, we theoretically estimated the overall amount of electron transfer toward the semiconductor side of the interface at equilibrium and suitably designed electrochemical experiments, which strictly agree with the theoretical charge transfer estimates. Moreover, photoelectrochemical measurements and theoretical predictions show the unique permanent charge separation occurring in the device [4].
[1] A.V. Emeline, V.N. Kuznetsov, V.K. Ryabchuk, N. Serpone, Environ. Sci. Pollut. Res., 2012, 19, 3666–3675.
[2] G. Soliveri, V. Pifferi, G. Panzarasa, S. Ardizzone, G. Cappelletti, D. Meroni, K. Sparnacci, L. Falciola, Analyst, 2015, 140, 1486–1494.
[3] V. Pifferi, G. Soliveri, G. Panzarasa, G. Cappelletti, D. Meroni, L. Falciola, Anal. Bioanal. Chem., 2016, 408, 7339–7349.
[4] G. Di Liberto, V. Pifferi, L. Lo Presti, M. Ceotto, L. Falciola, J. Phys. Chem. Lett., 2017, 8, 5372–5377
Spatial extent of recent vertical tectonic motions misured in NE Sicily coastal area. Insights from marine geology and coastal geomorphology studies.
No full textVertical position of sea-level, pointed out by related deposits and morphologies, provide useful markers to estimate tectonic uplift rates. For the Holocene very high uplift rates are misured in the northeast Sicily coast (Antonioli et al., 2009). This study compare vertical tectonic movements and marine geology data in the coastal sector between Capo d’Orlando and Brolo (NE Sicily); tectonic lineaments show different trends both onland (Nigro & Sulli, 1995) and offshore (Nicolich et al.,1982) and also the morphological response follow closely this difference. The geomorphologic survey provided data on Holocene uplift rates. We studied an archaeological ancient quarry of grinding wheels for oil that has been found in the Capo d’Orlando inshore (Scicchitano et al., 2011). They present semi submerged circular holes in Stilo-Capo d’Orlando deposits (Carbone et al., 1998). The tectonic uplift was evaluated as the difference between the observed local paleo-sea level position and the predicted sea-level curve for the same locality (Lambeck et al., 2011). The resulting uplift rates is 0.36 mm/yr (Scicchitano et al., 2011). In this area we studied also the Brolo stack. It is a metamorphic rocks emerging at 450 m from the coastline. The study led to discovery a fossils-bearing conglomerate in protected trays at 3.5 m a.s.l.. Radiocarbon analysis on a gastropod, gave us an age of 4965 years +-70 cal BP. If we compare this data with the predicted local sea level curves (Lambeck et al., 2011), we obtain an uplift rate about 1.5 mm/yr (Lo Presti et al., 2010), which is higher than that calculated in the study of archaeological rest. A detailed study of Brolo sector show us different morphological coastline position of Brolo plain. A picture of the year 1847 shows the coastline about 200 m landward. In Brolo coastal plain we have also found a Spondylus at -6 m b.s.l. We wait for the radiocarbon dating which allows us to have a new uplift rate data.
The analysis of marine geology data (Multibeam) evidenced structures connected to different faults systems, such as the submarine canyons that are the continuation of river beds. Multibeam data evidenced also tilted NE-ward submerged surfaces, indicating existing structural movements, interesting only restricted areas. So, very different uplift rates in the Holocene in very close areas distant only about 10 kilometers: both 0.36 mm/yr (Scicchitano et al. 2011) and 1.5 mm/yr (Lo Presti et al. 2010), and morphobathymetric data (tilted surfaces), evidence the important role of active tectonic lineaments. Seismic reflection profiles support this assumption, showing the metamorphic basement strongly dissected by high-angle faults, which at place determines the occurrence of emergent rock bodies (e.g. the Brolo stack). All this suggesting the occurrence of “restricted regions” in the coastal-marine sector with different geological behavior as response to prominent tectonic releasing bands, determining their horizontal and vertical movements
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