The neutron is a cornerstone in our depiction of the visible universe. Despite the neutron zero-net electric charge, the asymmetric distribution of the positively- (up) and negatively-charged (down) ...quarks, a result of the complex quark-gluon dynamics, lead to a negative value for its squared charge radius, Formula: see text. The precise measurement of the neutron's charge radius thus emerges as an essential part of unraveling its structure. Here we report on a Formula: see text measurement, based on the extraction of the neutron electric form factor, Formula: see text, at low four-momentum transfer squared (Q
) by exploiting the long known connection between the N → Δ quadrupole transitions and the neutron electric form factor. Our result, Formula: see text, addresses long standing unresolved discrepancies in the Formula: see text determination. The dynamics of the strong nuclear force can be viewed through the precise picture of the neutron's constituent distributions that result into the non-zero Formula: see text value.
The paper presents a fault location procedure for distribution networks based on the wavelet analysis of the fault-generated traveling waves. In particular, the proposed procedure implements the ...continuous wavelet analysis applied to the voltage waveforms recorded during the fault in correspondence of a network bus. In order to improve the wavelet analysis, an algorithm is proposed to build specific mother wavelets inferred from the fault-originated transient waveforms. The performance of the proposed algorithm are analyzed for the case of the IEEE 34-bus test distribution network and compared with those achieved by using the more traditional Morlet mother wavelet.
We have determined the proton and the neutron charge radii from a global analysis of the proton and the neutron elastic form factors, after first performing a flavor decomposition of these form ...factors under charge symmetry in the light cone frame formulation. We then extracted the transverse mean-square radii of the flavor dependent quark distributions. In turn, these are related in a model-independent way to the proton and neutron charge radii but allow us to take into account motion effects of the recoiling nucleon for data at finite but high momentum transfer. In the proton case we find
⟨
r
p
⟩
=
0.852
±
0
.
002
(
stat
.
)
±
0
.
009
(
syst
.
)
(
fm
)
, consistent with the proton charge radius obtained from muonic hydrogen spectroscopy
1
,
2
. The current method improves on the precision of the
⟨
r
p
⟩
extraction based on the form factor measurements. Furthermore, we find no discrepancy in the
⟨
r
p
⟩
determination among the different electron scattering measurements, all of which, utilizing the current method of extraction, result in a value that is consistent with the smallest
⟨
r
p
⟩
extraction from the electron scattering measurements
3
. Concerning the neutron case, past results relied solely on the neutron-electron scattering length measurements, which suffer from an underestimation of underlying systematic uncertainties inherent to the extraction technique. Utilizing the present method we have performed the first extraction of the neutron charge radius based on nucleon form factor data, and we find
⟨
r
n
2
⟩
=
-
0.122
±
0
.
004
(
stat
.
)
±
0
.
010
(
syst
.
)
(
fm
2
)
.
The paper presents a procedure for fault location in distribution networks, based on the use of the integrated time-frequency wavelet decompositions of the voltage transients associated with the ...fault-originated travelling waves. The proposed analysis of time-frequency wavelet decompositions has been found to improve the identification accuracy of the frequencies associated to the characteristic patterns of a fault location with respect to a sole frequency-domain wavelet analysis. Several laboratory fault tests, carried out by means of a reduced-scale model of a distribution feeder, are used to illustrate the characteristics and assess the performances of the proposed improved procedure. The paper also illustrates the application of the proposed procedure to a transient, originated by a permanent phase-to-phase fault, measured in a real distribution network in which a post-test analysis has identified the faulted branch.
The visible world is founded on the proton, the only composite building block of matter that is stable in nature. Consequently, understanding the formation of matter relies on explaining the dynamics ...and the properties of the proton's bound state. A fundamental property of the proton involves the response of the system to an external electromagnetic field. It is characterized by the electromagnetic polarizabilities
that describe how easily the charge and magnetization distributions inside the system are distorted by the electromagnetic field. Moreover, the generalized polarizabilities
map out the resulting deformation of the densities in a proton subject to an electromagnetic field. They disclose essential information about the underlying system dynamics and provide a key for decoding the proton structure in terms of the theory of the strong interaction that binds its elementary quark and gluon constituents. Of particular interest is a puzzle in the electric generalized polarizability of the proton that remains unresolved for two decades
. Here we report measurements of the proton's electromagnetic generalized polarizabilities at low four-momentum transfer squared. We show evidence of an anomaly to the behaviour of the proton's electric generalized polarizability that contradicts the predictions of nuclear theory and derive its signature in the spatial distribution of the induced polarization in the proton. The reported measurements suggest the presence of a new, not-yet-understood dynamical mechanism in the proton and present notable challenges to the nuclear theory.
•A method to locate lightning strikes and lightning-induced flashovers is presented.•The method is based on the Electromagnetic Time Reversal Theory and uses single measurement point.•The performance ...of the method is evaluated for different simulation case studies.•A sensitivity analysis is carried out with respect to various parameters and computational models.
The paper presents a method to identify the location of direct lightning strikes to overhead transmission lines and potential subsequent flashover(s). The method is based on the electromagnetic time reversal theory and relies on the use of a single measurement point to record voltage transient signals originated by a direct lightning strike either on the phase conductors or shielding wires, and possible flashovers. The measurement system is supposed to be installed on the secondary winding of the transformer located at the line feeding substation. The performance of the proposed method, applicable for different power network topologies, is validated by using different numerical simulations applied to various case studies. The paper also discusses the impact of the grounding system model, high-frequency transformer model, presence of surge arresters as well as soil electrical parameters.
•The proposed dynamic interval predictor does not depend directly on the method used for the point forecast.•It is able to take into account high dynamics.•It can produce results for any required ...confidence level.
We propose an ultra-short-term dynamic interval predictor (DIP) of solar irradiance. Our DIP relies on experimentally observed correlations between the derivative of the solar irradiance and the forecast error in the next time-step. The main originalities of this DIP are (i) its independence from the method used for the point forecast of solar irradiance, (ii) its independence from the error distribution of the point-forecast method. We compare the DIP with the most common prediction interval methods. By using significant data set covering several months of experimental observations, we have observed higher accuracy and lower width of the prediction intervals of the proposed DIP.
In this paper an investigation on the performance of a commercial Proton Exchange Membrane (PEM) fuel cell, installed at the laboratory of the University of Bologna, is carried out, taking into ...account the anodic exhaust management and its effects on the flooding phenomenon.
To address the problem of flooding, it is necessary to run periodically the purge process of the Fuel Fell (FC). Indeed, in this study the periodic anodic purge process in dead-end mode has been investigated. This operation is performed by opening a particular control valve, the Outlet Purge Valve (OPV), located along the anodic exhaust line.
The purge process has been analyzed at different FC power output levels. For each FC power level the optimized behavior of the FC operation was found, by regulating the time of flooding.
The aim of this analysis is to optimize the purge process to reduce the amount of hydrogen discharged with water, in order to increase the FC efficiency. An investigation on the benefits in terms of fuel utilization factor and costs, resulting from optimization of the FC purge process, is shown in the paper.
► Experimental investigation on a PEM fuel cell is carried out. ► Anodic exhaust management is performed via a purge valve. ► Various power output set points are considered. ► A significant efficiency gain at part-load is obtained by optimizing the purge times.
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