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Search Results: 1 - 10 of 461908 matches for " A. Minotti "
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A new anti-neutrino detection technique based on positronium tagging with plastic scintillators
G. Consolati,D. Franco,C. Jollet,A. Meregaglia,A. Minotti,S. Perasso,A. Tonazzo
Physics , 2015, DOI: 10.1016/j.nima.2015.06.021
Abstract: The main signature for anti-neutrino detection in reactor and geo-neutrino experiments based on scintillators is provided by the space-time coincidence of positron and neutron produced in the Inverse Beta Decay reaction. Such a signature strongly suppresses backgrounds and allows for measurements performed underground with a relatively high signal-to-background ratio. In an aboveground environment, however, the twofold coincidence technique is not sufficient to efficiently reject the high background rate induced by cosmogenic events. Enhancing the positron-neutron twofold coincidence efficiency has the potential to pave the way future aboveground detectors for reactor monitoring. We propose a new detection scheme based on a threefold coincidence, between the positron ionization, the ortho-positronium (o-Ps) decay, and the neutron capture, in a sandwich detector with alternated layers of plastic scintillator and aerogel powder. We present the results of a set of dedicated measurements on the achievable light yield and on the o-Ps formation and lifetime. The efficiencies for signal detection and background rejection of a preliminary detector design are also discussed.
Experimental characterization of a low-current cutting torch
Kelly, H.;Mancinelli, B.;Prevosto, L.;Minotti, F.O.;Márquez, A.;
Brazilian Journal of Physics , 2004, DOI: 10.1590/S0103-97332004000800003
Abstract: an experimental characterization of a low-current (30-40 a) cutting torch is presented. to avoid contamination of the plasma arc by removed anode material, a rotating steel cylinder was used as the anode and the arc was anchored onto the cylinder lateral surface. the cathode-anode and cathode-nozzle voltage drops, together with the gas pressure in the plenum chamber were registered for different values of the mass flow rate injected into the plenum chamber. by employing an optical system with a large magnifi cation (? 15 x), the arc radius the nozzle exit was also determined with a digital optical camera. the obtained experimental quantities were used to evaluate several flow properties at the nozzle exit (hot arc plasma and cold gas temperatures, arc and gaz velocities, etc.) by employing a simplifi ed theoretical model for the plasma flow in the nozzle. the obtained results are in reasonable agreement with the data reported in the literature by other authors. explanations of the origin of the clogging effect and the nozzle voltage are also presented.
LES of a Meso Combustion Chamber with a Detailed Chemistry Model: Comparison between the Flamelet and EDC Models
Angelo Minotti,Enrico Sciubba
Energies , 2010, DOI: 10.3390/en3121943
Abstract: The goal of this paper is to contribute to the design of high-performance mesocombustors, a field currently under rapid development, in particular for propulsion, e.g., for UAVs, and micro/meso-electrical power generators. This study is focused on a cylindrical combustor of 29?cm 3, fuelled by methane and air, which provides 2?kW of thermal power. The device was entirely designed and built at the Sapienza University of Rome and coupled with an ultra-micro turbine. Two 3D LES simulations with detailed chemistry are presented. They differ only for the combustion models, so that a model comparison can be carried out. The calculated maximum temperature inside the chamber, the gas exhaust temperature and the combustion efficiency are compared and discussed. The results, reported at two different physical times, show the effects of the different combustion models, which predict different temperature and species concentration maps, but similar values for the combustion efficiency. Thermal, chemical and kinematic maps show that the Eddy Dissipation Concept allows for a more accurate estimatation of the performance parameters for application to first-order design procedures.
Modello coesivo per l’avanzamento di fratture mediante rilascio nodale di strutture discretizzate con elementi finiti
M. Minotti,P. Salvini
Frattura ed Integrità Strutturale , 2010,
Abstract: La simulazione numerica della propagazione di una frattura in MODO I, viaggiante ad elevata velocità in un acciaio a comportamento duttile è realizzata attraverso un modello coesivo che governa la distribuzione delle forze di rilascio nodale. Come noto, la ricerca di un valore di tensione all’apice non ha alcun senso nel caso elastico; infatti, la tensione può essere valutata solo mediante fattori di campo. Nel caso elastoplastico, incrudimento e softening di origine geometrica o legato al progressivo danneggiamento influiscono decisamente sull’andamento esponenziale del campo tensionale. è possibile comunque individuare un valore di riferimento, di entità finita, mediante estrapolazione delle tensioni elasto-plastiche nella zona di inizio softening della frattura. Tale grandezza può essere presa come fattore di riferimento per il calcolo delle forze di rilascio coesive e quindi dell’energia dissipata. Nel lavoro viene discusso come determinare, dal campo di tensione elasto-plastico locale, il valore che governa la zona coesiva al variare del T-stress
Scalar-tensor theory with enhanced gravitational effects
F. O. Minotti
Physics , 2011,
Abstract: It is shown that a Brans-Dicke scalar-tensor gravitational theory, which also includes Bekenstein's kind of interaction between the Maxwell and scalar fields, has a particular kind of solutions with highly enhanced gravitational effects as compared with General Relativity, prone to laboratory tests.
Scalar-tensor theories and asymmetric resonant cavities
Fernando O. Minotti
Physics , 2013, DOI: 10.1134/S0202289313030080
Abstract: Recently published experimental results indicate the appeareance of unusual forces on asymmetric, electromagnetic resonant cavities. It is argued here that a particular class of scalar-tensor theories of gravity could account for this effect.
Longitudinal forces in pinched electric currents
F. O. Minotti
Physics , 2014,
Abstract: It is shown that the theory of Mbelek and Lachi\`eze-Rey predicts longitudinal forces of gravitational origin in pinched current distributions, with magnitudes large enough to have noticeable effects.
On the completeness of classical electromagnetism
Fernando O. Minotti
Physics , 2006,
Abstract: The possibility of an incompletness of the equations of electromagnetism is analyzed using a thought experiment that shows a non-physical behavior according to classical electromagnetism. Basically, from Maxwell equations it is shown that a particular passive, isolated circuit could present a transient growth of its currents. Resolution of this problem is sought within the context of the usual electromagnetism and also using the possibly simplest generalization of Maxwell equations, a reduced version of Ohmura equations.
Asymptotic probability density functions in turbulence
F. O. Minotti,E. Speranza
Physics , 2007,
Abstract: A formalism is presented to obtain closed evolution equations for asymptotic probability distribution functions of turbulence magnitudes. The formalism is derived for a generic evolution equation, so that the final result can be easily applied to rather general problems. Although the approximation involved cannot be ascertained a priori, we show that application of the formalism to well known problems gives the correct results.
Maximum Likelihood Estimation of Gaussian Cluster Weighted Models and Relationships with Mixtures of Regression
Salvatore Ingrassia,Simona C. Minotti
Statistics , 2012,
Abstract: Cluster-weighted modeling (CWM) is a mixture approach for modeling the joint probability of a response variable and a set of explanatory variables. The parameters are estimated by means of the expectation-maximization algorithm according to the maximum likelihood approach. Under Gaussian assumptions, we analyse the complete-data likelihood function of cluster weighted models. Further, under suitable hypotheses we show that the maximization of the likelihood function of Gaussian cluster weighted models leads to the same parameter estimates of finite mixtures of regression and finite mixtures of regression with concomitant variables. In this sense, the latter ones can be considered as nested models of Gaussian cluster weighted models.
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