In the context of near surface seismic imaging (a few hundreds of metres), we propose an alternative approach for inversion of surface waves in 2-D media with laterally varying velocities. It is ...based on Full Waveform Inversion (FWI) but using an alternative objective function formulated in the frequency–wavenumber f − k domain. The classical FWI objective function suffers from severe local minima problems in the presence of surface waves. It thus requires a very accurate initial model. The proposed objective function is similar to the one used in classical surface wave analysis. In this approach, the data are first split using sliding windows in the time–space t − x domain. For each window, the amplitude of the f − k spectrum is computed. The objective function measures the least-squares misfit between the amplitude of observed and modelled 2-D Fourier transformed data sets. We call this formulation the windowed-amplitude waveform inversion (w-AWI).
The w-AWI objective function reduces some local minima problems as shown here through numerical examples. The global minimum basin is wider in the w-AWI approach than in FWI. Synthetic examples show that w-AWI may achieve convergence if the lowest data frequency content is twice higher than the one needed by FWI. For elastic inversion, w-AWI can be used to reconstruct a velocity model explaining surface waves. This surface wave inversion procedure can be used to retrieve near-surface model parameters in lateral-varying media.
Recently it was stated that temporal disorder constitutes a relevant perturbation in absorbing phase transitions for all dimensions. However, its effect on systems other than the standard contact ...process (CP), its competition with other ingredients (e.g., particle diffusion), and other kinds of disorder (besides the standard types) are unknown. In order to shed some light on the above-mentioned points, we investigate a variant of the usual CP, namely, the triplet annihilation model, in which the competition between triplet annihilation and single particle diffusion leads to an unusual phase diagram behavior, with reentrant shape and endless activity for sufficiently large diffusion rates. Two kinds of time-dependent disorder have been considered. In the former, it is introduced in the creation-annihilation parameters (as commonly considered in recent studies), whereas in the latter, the diffusion rate D is allowed to be time dependent. In all cases, the disorder follows a uniform distribution with fixed mean and width σ. Two values of σ have been considered in order to exemplify the regime of "weaker" and "stronger" temporal disorder strengths. Our results show that in the former approach, the disorder suppresses the reentrant phase diagram with a critical behavior deviating from the directed percolation (DP) universality class in the regime of low diffusion rates, while they strongly suggest that the DP class is recovered for larger hopping rates. An opposite scenario is found in the latter disorder approach, with a substantial increase of reentrant shape and the maximum diffusion, in which the reentrant shape also displays a critical behavior consistent with the DP universality class (in similarity with the pure model). In order to compare with very recent claims, the results from taking a bimodal distribution and critical behavior in the limit of strong disorder are presented. Also, the results derived from the mean-field theory are performed, presenting partial agreement with numerical results. Lastly, a comparison with the diffusive disordered CP is undertaken.
One of the major uncertainty sources affecting Global Positioning System (GPS) satellite orbits is the direct solar radiation pressure. In this paper a new model for the solar radiation pressure on ...GPS satellites is presented that is based on a box-wing satellite model, and assumes nominal attitude. The box-wing model is based on the physical interaction between solar radiation and satellite surfaces, and can be adjusted to fit the GPS tracking data.
To compensate the effects of solar radiation pressure, the International GNSS Service (IGS) analysis centers employ a variety of approaches, ranging from purely empirical models based on in-orbit behavior, to physical models based on pre-launch spacecraft structural analysis. It has been demonstrated, however, that the physical models fail to predict the real orbit behavior with sufficient accuracy, mainly due to deviations from nominal attitude, inaccurately known optical properties, or aging of the satellite surfaces.
The adjustable box-wing model presented in this paper is an intermediate approach between the physical/analytical models and the empirical models. The box-wing model fits the tracking data by adjusting mainly the optical properties of the satellite’s surfaces. In addition, the so called Y-bias and a parameter related to a rotation lag angle of the solar panels around their rotation axis (about 1.5° for Block II/IIA and 0.5° for Block IIR) are estimated. This last parameter, not previously identified for GPS satellites, is a key factor for precise orbit determination.
For this study GPS orbits are generated based on one year (2007) of tracking data, with the processing scheme derived from the Center for Orbit Determination in Europe (CODE). Two solutions are computed, one using the adjustable box-wing model and one using the CODE empirical model. Using this year of data the estimated parameters and orbits are analyzed. The performance of the models is comparable, when looking at orbit overlap and orbit prediction errors. Nevertheless, the models show important differences between orbits at the 1–2cm level and total accelerations (up to 5×10-9m/s2). The differences are mainly due to the fact that the box-wing model is based on the physical interaction between solar radiation and satellite, while the CODE empirical model is not.
Waveform modelling is essential for seismic imaging and inversion. Because including more physical characteristics can potentially yield more accurate Earth models, we analyse strategies for elastic ...seismic wave propagation modelling including topography. We focus on using finite differences on modified staggered grids. Computational grids can be curved to fit the topography using distribution functions. With the chain rule, the elasto-dynamic formulation is adapted to be solved directly on curved staggered grids. The chain-rule approach is computationally less expensive than the tensorial approach for finite differences below the 6th order, but more expensive than the classical approach for flat topography (i.e. rectangular staggered grids). Free-surface conditions are evaluated and implemented according to the stress image method. Non-reflective boundary conditions are simulated via a Convolutional Perfect Matching Layer. This implementation does not generate spurious diffractions when the free-surface topography is not horizontal, as long as the topography is smoothly curved. Optimal results are obtained when the angle between grid lines at the free surface is orthogonal. The chain-rule implementation shows high accuracy when compared to the analytical solution in the case of the Lamb’s problem, Garvin’s problem and elastic interface.
Accelerator based neutrino oscillation experiments seek to measure the relative number of electron and muon (anti)neutrinos at different
L
/
E
values. However high statistics studies of neutrino ...interactions are almost exclusively measured using muon (anti)neutrinos since the dominant flavor of neutrinos produced by accelerator based beams are of the muon type. This work reports new measurements of electron (anti)neutrinos interactions in hydrocarbon, obtained by strongly suppressing backgrounds initiated by muon flavor (anti)neutrinos. Double differential cross sections as a function of visible energy transfer,
E
avail
, and transverse momentum transfer,
p
T
, or three momentum transfer,
q
3
are presented.
Published by the American Physical Society
2024
Charged-current antineutrino interactions on a hydrocarbon scintillator in the MINERvA detector are used to study activity from their final-state neutrons. To ensure that most of the neutrons are ...from the primary interaction, rather than hadronic reinteractions in the detector, the sample is limited to momentum transfers below 0.8 GeV/c. From 16 129 interactions, 15 246 neutral particle candidates are observed. The reference simulation predicts 64% of these candidates are due to neutrons from the antineutrino interaction directly but also overpredicts the number of candidates by 15% overall. This discrepancy is beyond the standard uncertainty estimates for models of neutrino interactions and neutron propagation in the detector. We explore these two aspects of the models using the measured distributions for energy deposition, time of flight, position, and speed. We also use multiplicity distributions to evaluate the presence of a two-nucleon knockout process. These results provide critical new information toward a complete description of the hadronic final state of neutrino interactions, which is vital to neutrino oscillation experiments.
We measure neutrino charged-current quasielasticlike scattering on hydrocarbon at high statistics using the wideband Neutrinos at the Main Injector beam with neutrino energy peaked at 6 GeV. The ...double-differential cross section is reported in terms of muon longitudinal (p_{∥}) and transverse (p_{⊥}) momentum. Cross section contours versus lepton momentum components are approximately described by a conventional generator-based simulation, however, discrepancies are observed for transverse momenta above 0.5 GeV/c for longitudinal momentum ranges 3-5 and 9-20 GeV/c. The single differential cross section versus momentum transfer squared (dσ/dQ_{QE}^{2}) is measured over a four-decade range of Q^{2} that extends to 10 GeV^{2}. The cross section turnover and falloff in the Q^{2} range 0.3-10 GeV^{2} is not fully reproduced by generator predictions that rely on dipole form factors. Our measurement probes the axial-vector content of the hadronic current and complements the electromagnetic form factor data obtained using electron-nucleon elastic scattering. These results help oscillation experiments because they probe the importance of various correlations and final-state interaction effects within the nucleus, which have different effects on the visible energy in detectors.
Due to its zero-marginal-cost, the high penetration of renewable energy sources in the electricity markets threatens incumbents’ business models who are gradually shifting towards fixed power charges ...instead of the traditional energy charges. The purpose of this study is to assess the impacts of these fixed power charges on the economics of PV systems under self-consumption schemes. Using real demand and generation data, simulations include detailed computation of annual billing savings, payback-time, self-consumption and self-sufficiency of a dwelling coupled with PV-battery system. A range of PV array and battery sizes are explored for different storage control strategies. Billing scenarios include a) only energy charges, b) Portuguese case (high energy charges and low fixed charges), c) Spanish case (low energy charges and high fixed charges), and d) only fixed charges. Results show that fixed charges require adding storage to residential PV systems. In spite of battery relative high costs, results also show that photovoltaics can be profitable with payback times below 10 years in all scenarios, as long as appropriately sized and with the suitable storage control strategy.
•The impact of changing fixed charges in the bill electricity structure was analysed.•Four tariff scenarios were compared, including Portuguese and Spanish cases.•Both optimizing PV self-consumption and peak-shaving control strategies are used.•The peak-shaving strategy is useful when bill structures are based on fixed charges.•The optimizing self-consumption strategy is useful in bills based on energy charges.
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