1,721,043 research outputs found
La particella alla fine dell'universo. La caccia al bosone di Higgs e le nuove frontiere della fisica
No full text
Role of hydrostatic paradoxes towards the formation of the scientific thought of students at academic level
Get PDFThe importance of fluid mechanics is often underrated. Besides studying the mechanisms governing static and dynamic fluids, this discipline could have a great role in the understanding of many principles, topics and concepts of general mechanics. When approached in a proper way, fluid mechanics provides numerous 'case studies' apt to clarify the physical content of several mechanical laws. Unfortunately, fluid mechanics, in physics classes, is generally viewed as a 'lower branch' of mechanics. Its rules and laws too often are regarded as too particular, or even as special cases, to deserve the same attention paid to other arguments. The help that fluid mechanics could return in the learning process can be proved by some easy considerations. In this frame, the so-called hydrostatic paradoxes could provide a tremendous contribution to the learning processes
Track Constrained RTK-like Positioning for Railway Applications
Get PDFHere, we investigate PVT solutions based on multi-constellation receivers and dedicated augmentation networks allowing to determine the track on which a train is operating with a very high safety Integrity level. Because the time needed to accomplish this task has a relevant impact on the rail traffic management performance and, therefore, it is considered a key performance indicator by rail infrastructure managers, a double frequency solution is investigated. Particularly, we focus our attention on the advantages of relative positioning solutions, based on Double-Difference Wide-Laning Carrier Phase measurement combination, exploiting the fact that the train location is completely determined by its mileage due to the track constraint, to speed up track discrimination. No ambiguity fix is required at this scope. Here, a detailed description of the overall processing and achievable performance is given. Performance assessment is provided by means of Monte Carlo simulations based on observations recorded on field campaigns. © 2018 The Authors. Navigation published by Wiley Periodicals, Inc. on behalf of Institute of Navigation
Tuning the surface morphology of self-assembled graphene-like thin films through pH variation
No full textGraphene-like (GL) layers were prepared through a two steps oxidation/reduction method starting from a high surface carbon black, and pH of the GL layers in water suspension was varied. The effect of pH of such suspension on the morphology of self-assembled GL films has been studied. Zeta potentials of the water suspensions were measured to estimate the stability of the suspension at several pH values and to select the samples for deeper investigation by atomic force microscopy (AFM). AFM measurements on four different samples are then described and discussed. The reported results show how the surface roughness and morphology are affected by the pH in the preparation process: in particular, the lowest pH sample exhibits a granular surface, while at higher pH more regular morphologies are produced, with interesting observations as concerns the thickness of some surface features. The observations are interpreted in terms of the forces acting in water suspension and of the role of hydrophobic or hydrophilic behaviors. The results demonstrate the possibility to tune the surface properties of GL films by simply acting on the pH of the suspension during the fabrication, and help to understand the microscopic physical mechanisms involved in the film assembly
High Integrity Two-tiers Augmentation Systems for Train Control Systems
No full textThis paper deals with high integrity systems based on a two-tiers Augmentation system architecture. The Augmentation System is based on a regional system and a local system. This work intends to define a Formal mathematical approach to improve the performance in terms of Integrity of a Local Area Augmentation and Integrity Monitoring Network. Such model is due to the stringent requirements in railways application that are described by SIL-4 (Integrity Risk < 10-9 during 1 hour). The Integrity Monitoring is performed on three different levels: Reference Station, Satellite, Constellation. For each of them the fault identification and exclusion algorithms are defined and analyzed. The novelty of this work is the integration of Local Area Augmentation Networks with single regional SBAS Systems in order to develop a 2-tiers High Accuracy and High Integrity Augmentation Systems able to reach the above Integrity requirements. At this aim the false alarm probability has been rigorously defined including 2-tiers Reference Stations fault probabilities. Simulation framework has been developed to assess both satellite and Reference Station faults and evaluate relevant 2-tier Augmentation Systems performances
Synthesis and characterization of conductive copper-based metal-organic framework/graphene-like composites
Get PDFMetal-organic framework (MOP) incorporating conductive graphene-like layers were synthesized and characterized. The selected MOF, HKUST-1, combines high surface area, water stability, simple preparation and low costs. Graphene-like layers incorporated into the MOF structure were obtained by a two-step oxidation/reduction wet treatment of a high surface carbon black. MOF composites were produced at different carbonaceous layers content. It was shown, through a wide characterization of the samples, that the composites preserve the main features of the parent MOF, additional exhibiting a tunable electrical conductivity
A teaser made simple: a didactic measurement of the spectral answer of a human-eye-calibrated lux meter
No full textA simple didactic experiment has been designed and realized, in order to illustrate to undergraduate students in scientific faculties some basic concepts lying behind the fundamentals of geometrical optics. The spectral response of a human-eye-calibrated lux meter was measured using a very trivial experimental arrangement. The white light of a halogen lamp was decomposed into its spectral components through a diffraction grating, so that collecting the radiation at different dispersion angles allowed one to measure the intensity as a function of wavelength. The experiment can be used to effectively illustrate the concepts of spectral distribution, the radiometry versus photometry conversion and photopic response, and the famous historical experience by Herschel on the 'temperature of colours'
- …
