Search results for "Proa"
showing 10 items of 1834 documents
Charoite, as an example of a structure with natural nanotubes
2012
Charoite from the Murun massif in Yakutiya, Russia (Vorob’ev 2008) was investigated using automated electron diffraction tomography (ADT) (Kolb et al. 2007, 2008; Mugnaioli et al. 2010) and precession electron diffraction (PED) (Mugnaioli et al. 2010, 2009), which allowed to determine the structure of charoite for the first time. The structure was solved ab initio in space group P21/m by direct methods using a fully kinematic approach. The least squares refinements with 2878 reflections F(hkl) >4s F converged to unweighted/weighted residuals R 1/wR 2 • 0.173/0.21 (Rozhdestvenskaya et al. 2010).
Approach to rotor-shaft hysteretic whirl using Krylov-Bogoliubov techniques
2013
The internal friction associated with the shaft hysteresis or with the possible release of some shrink-fit coupling exerts a destabilizing effect on the over-critical rotor running, but may be efficiently counteracted by other external dissipative sources or by a proper anisotropic configuration of the support stiffness. The present analysis considers a symmetric rotor-shaft system on viscous-flexible supports with different stiffness on two orthogonal planes containing the bearing axis. The internal friction of the shaft is described either by a linear hysteretic model or by a nonlinear Coulombian force contrasting the rotor motion relative to the shaft ends. The nonlinear equations of mo…
A quantitative analysis of university student reasoning lines in the field of thermally activated phenomena
2018
In this contribution we present a research aimed at studying the effectiveness of two workshops in improving reasoning skills in undergraduate students. Both the workshops are based on the Feynman Unifying Approach. A questionnaire containing six open-ended questions on the temperature dependence of evaporation of a liquid and of a chemical reaction was administered to the students of both groups before instruction. A second one, similar to the first but focused on a physical content different from both the pre-instruction test one and the content dealt with during the workshops, was administered after instruction. The responses to the pre- and post-instruction questionnaires are analyzed b…
Teacher professional development in the context of the “Open Discovery of STEM laboratories” project: Is the MOOC methodology suitable for teaching p…
2020
Abstract The “Open Discovery of STEM Laboratories” (ODL) project, funded by the European Erasmus+ KA2 program, was aimed at introducing the use of MOOCs in school curricula. In particular, it fostered teacher collaboration in creating and using micro-MOOCs for the inclusion of STEM (Science, Technology, Engineering and Mathematics) online remote or virtual laboratories in the everyday teaching practice. The project focused on teachers, educators and curriculum designers with the aim to strengthen their profile by supporting them to deliver high quality teaching practices and to adopt new methods and tools. Thanks to the project, in service and pre-service teachers had the opportunity to ext…
From led light signboards to the Planck’s constant
2018
Recent studies have highlighted an alarming decline in young people’s interest towards the study of scientific subjects, often considered interesting but not easily understood and appreciated by students. In particular, the introduction of Modern Physics (MP) key-topics at secondary school level is a difficult and complex task because MP involves abstract ideas and requires a strong mathematical background. In this communication we present and discuss the results of an inquiry-based teaching/learning path aimed at surmounting the difficulties of an exclusively theoretical approach to the introduction of MP topics. In particular, we planned and realized an inquiry-driven learning environment…
A Fractional Approach to Non-Newtonian Blood Rheology in Capillary Vessels
2019
In small arterial vessels, fluid mechanics involving linear viscous fluid does not reproduce experimental results that correspond to non-parabolic profiles of velocity across the vessel diameter. In this paper, an alternative approach is pursued introducing long-range interactions that describe the interactions of non-adjacent fluid volume elements due to the presence of red blood cells and other dispersed cells in plasma. These non-local forces are defined as linearly dependent on the product of the volumes of the considered elements and on their relative velocity. Moreover, as the distance between two volume elements increases, the non-local forces decay with a material distance-decaying …
Photoproduction of K∗ for the study of Λ(1405)
2004
Abstract The photo-induced K ∗ vector meson production is investigated for the study of the Λ(1405) resonance. This reaction is particularly suited to the isolation of the second pole in the Λ(1405) region which couples dominantly to the K N channel. We obtain the mass distribution of the Λ(1405) which peaks at 1420 MeV, and differs from the nominal one. Combined with several other reactions, like the π−p→K0πΣ which favours the first pole, this detailed study will reveal a novel structure of the Λ(1405) state.
The small K pi component in the K* wave functions
2013
We use a recently developed formalism which generalizes Weinberg's compositeness condition to partial waves higher than s-wave in order to determine the probability of having a K pi component in the K* wave function. A fit is made to the K pi phase shifts in p-wave, from where the coupling of K* to K pi and the K pi loop function are determined. These ingredients allow us to determine that the K* is a genuine state, different from a K pi component, in a proportion of about 80%.
On the measured lifetime of light hypernuclei 3ΛH and 4ΛH
2014
A statistical combination of the experimental lifetime estimations available in the literatures is performed for 3 Λ H and 4 Λ H, including several recent measurements. The combined average values of the lifetime for 3 Λ H and 4 Λ H are respectively 216−16+19 ps and 192−18+20 ps with a reduced χ2 of 0.89 and 0.48. A new insight into the lifetime estimation of the HypHI Phase 0 experiment by a Bayesian approach is also presented. In this approach, several different prior distributions including the combination of previous lifetime data and a Jeffrey prior are used. The principal mode and the smallest credible interval at 68% of the posterior distribution, given by the prior belief of the pre…
In-medium modifications of the pi pi interaction in photon-induced reactions
2002
Differential cross sections of the reactions $(\gamma,\pi^\circ\pi^\circ)$ and $(\gamma,\pi^\circ\pi^++\pi^\circ\pi^-)$ have been measured for several nuclei ($^1$H,$^{12}$C, and $^{\rm nat}$Pb) at an incident-photon energy of $E_{\gamma}$=400-460 MeV at the tagged-photon facility at MAMI-B using the TAPS spectrometer. A significant nuclear-mass dependence of the $\pi\pi$ invariant-mass distribution is found in the $\pi^\circ\pi^\circ$ channel. This dependence is not observed in the $\pi^\circ\pi^{+/-}$ channel and is consistent with an in-medium modification of the $\pi\pi$ interaction in the $I$=$J$=0 channel. The data are compared to $\pi$-induced measurements and to calculations within …