136,627 research outputs found
Spagnolo C., La stabilizzazione incompiuta. Il piano Marshall in Italia (1947-1952), Carocci, Roma 2001
No full textRecensione al volume: Spagnolo C., La stabilizzazione incompiuta. Il piano Marshall in Italia (1947-1952), Carocci, Roma 200
Transient dynamics in driven long Josephson junctions.
No full textThe switching time from the superconductive metastable state of a long Josephson junction (LJJ)[1] is computationally analyzed in the framework of the perturbed sine-Gordon equation. The model includes an external bias current term and a stochastic noise source, i.e. a Lévy noise term. The effects of this noise on the mean escape time (MET) from the superconductive state are analyzed. The investigation is performed by considering a wide range of values of system parameters and different noise statistics: Gaussian, Cauchy-Lorentz and Lévy-Smirnov[2].
We found evidence of well known noise induced phenomena on the MET behavior, that is the noise enhanced stability (NES) and resonant activation (RA). Furthermore, the action of the noise source and oscillating bias current on the soliton motion[3] is deeply analyzed.
Finally, we take into account a different, more realistic, bias current configuration, by considering an inhomogeneous current density through the junction. Differences in the soliton dynamics are also found in this case.
1. G. Augello, D. Valenti, and B. Spagnolo, Eur. Phys. J. B 70, 145 (2009).
2. G. Augello, D. Valenti, and B. Spagnolo, Eur. Phys. J. B 78, 225 (2010).
3. A. V. Ustinov, Physica D 123, 315 (1998); D. W. McLaughlin, and A. C. Scott, Phys. Rew. A 18, 1652 (1978)
Diffractive optical element-based profilometer for surface inspection
No full textWe introduce a new 3-D sensor based on a diffractive optical element (DOE). Structured light is obtained by the interference of two beams. The design of the projection unit has the following features: the system is very simple, small and cheap and the fringe spacing is easily adjustable. Fringes generated by the DOE interferometer are analyzed by Fast Fourier Transform (FFT) method, which produced a 3-D perspective plot. The technique and the experimental results of real surface profiles are given
Low-Cost Optoelectronic System for Three-Dimensional Artwork Texture Measurement
No full textA new optoelectronic system based on a projection unit in which light, coming from a laser diode coupled to an optic fiber impinges on a diffractive optical element (DOE) to produce sinusoidal fringes is proposed for three-dimensional (3-D) texture measurement. If the projected fringe pattern is viewed at an angle different from the projection angle, the fringe profile is phase-modulated by the 3-D object shape. The 3-D map information is obtained with the aid of a fringe analyzer based on phase-shifting synthetic moiré pattern, Fast Fourier Transform (FFT), signal demodulation techniques and a robust and fast phase unwrapping performed by a specially developed software. The proposed system is based on a simple and low-cost equipment; furthermore, it is suitable for in situ measurements also by non-skilled operators. Some experimental examples illustrate its performance
Measurement of vibration amplitude by an optical fiber-based moiré interferometer
No full textA projected-fringe fiber-based moiré interferometer is proposed to measure the local amplitude vibration of a diffuse surface. The technique is based on an optical fiber interferometer which projects interference fringes on the object surface. The visibility of these carrier fringes is modulated by a function of local amplitude vibration. Full-field quantitative analysis is performed by analyzing the fringe pattern with a 2-D Fourier transform method. Theoretical details, and experimental results are presented
Continuities and discontinuities at the Oscurusciuto rock shelter (Ginosa, Taranto). The last Neanderthals in Southern Italy
No full textThe Oscurusciuto rock shelter, located in the Ginosa ravine (Taranto, Apulia), is a very important site for the understanding of Neandertal subsistence and settlement strategies in Southern Italy. The deposit, about 6 m thick and with a base of 60 m2 , is made up of several levels Middle Palaeolithic in age (fig. 1). The series so far investigated (between SU 1 and SU 15) ranges between 42,724±716 cal BP (Beta 181165 AMS) (SU 1) and 55 ± 2 kyrs (40Ar/39Ar) (SU 14 – tephra identified as the Mount Epomeo Ischia green tuff; Allen et alii 2000). Such a chronological interval is crucial in European prehistory as it falls upon the period of disappearance of Homo neanderthalensis and of the dispersal of the first groups of Anatomically Modern Humans. Excavations and studies on the Oscurusciuto Shelter are being led by the Unità di Ricerca di Preistoria e Antropologia of the Dipartimento di Scienze Fisiche, della Terra e dell’Ambiente of the University of Siena (Boscato, Ronchitelli 2008; Villa et alii 2009; Boscato et alii 2011; Ronchitelli et alii 2011; Spagnolo et alii 2015). The study comprises: taxonomic and taphonomic investigations on faunal remains, analysis of lithic production through a technological and techno-functional approach, micromorphological analyses of hearths and assessment of the spatial meaning of these features. The aim of this work is to individuate, from a diachronic point of view, the continuities and discontinuities inside the lithic techno-complexes, the site space management and the mobility patterns within the territory. Such objectives are reached by a multidisciplinary approach. The different datasets which have been gathered are statistically elaborated within a GIS platform in order to determine the modalities of space management. The different datasets which have been gathered are statistically elaborated within a GIS platform in order to determine the modalities of space management. The application of the RMU method (lithic raw material units), on technological and spatial bases, allows the recognition of single activities (Marciani 2013; Spagnolo 2013; Spagnolo et alii 2015). This research comprises the integrated study of the lower section of the series so far investigated in the Shelter: SU 15, SU 14, SU 13 and SU 11. These stratigraphic units are particularly interesting for the reconstruction of Neandertal behaviour, given that each of them shows peculiarities in terms of structural elements, spatial management, type of occupation and lithic production systems. SU 15 is a living floor in which a phase of abandonment is recorded and is sealed by the deposition of the SU 14 tephra. This surface is characterized by stone alignments which define two possible structures. SU 14 (fig. 2) is an almost sterile layer about 60 cm thick, made of volcanic ashes. Traces of a short frequentation can be seen only few centimetres under the top of the layer. SU 13 is a short palimpsest which represents the first stable re-colonization of the site after the environmental impact created by volcanic ash deposition. In this layer, 10 aligned hearths were found which divide up the site into areas devoted to different activities. The overlying SU 11 is a palimpsest about 30 cm thick, characterized by the superimposition of tens of hearths. The results of these studies will bring important and useful advances in research on the behavioural and settlement features of Neandertals, particularly at this time when there are many Italian and international projects which face these questions by means of different and innovative approaches
Air ions as possible environmental monitors
No full textMeasurements in air of both positive and negative ions ((0.001÷0.003) μm diameter) concentrations were made on a monthly basis in the following different sites: a mountain top and a natural Gallery of the Gran Sasso laboratory. From the analysis of preliminary data, these concentration values seem to be strictly dependent upon the environmental characteristics and might be used as environmental monitors. © 1991 Societá Italiana di Fisica
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