The Central Andean Forearc (26°S) structure has been debated for decades. Extension, contraction, and strike-slip deformation are commonly proposed mechanisms to explain the main tectonic elements ...exposed in the Domeyko Cordillera, Salar de Pedernales Basin, and others partially exposed in the Coastal Cordillera and Central Depression. Although pre-Andean tectonic inheritance seems to have influenced the style and mechanisms of mountain uplift in this region, its current architecture and the way it controlled the shortening distribution during orogen evolution are highly speculative, mainly because some of the tectonic provinces in this segment consist of covered areas (e.g., the Central Depression). To address this question, we present the first balanced cross-section and pre-shortening restoration of the Andean forearc at 26°S. We integrated new field data from the Coastal and Domeyko cordilleras with well data and re-interpreted 2D seismic profiles from the Salar de Pedernales Basin to construct a regional-scale cross-section of 210 km length from the Coastal Cordillera to the current Volcanic Arc, thus showing a two-dimensional (2D tectonic model to help understand the tectonic evolution of the western Central Andes. The results indicate a pre-shortening architecture dominated by Late Permian–Jurassic half-graben structures related to continental rifting. West- and east-dipping basement-rooted normal faults controlled rift-related basins, along which kilometric-scale marine and continental syn-rift sequences accumulated. During early Andean orogenesis, the normal faults were partially inverted, and large anticlines developed at the hanging wall faults, which Upper Cretaceous progressively covered to Paleocene synorogenic units. This suggests that the initial topographic relief in the region resulted from a basin inversion. During the more advanced stages of orogenesis (mid-Cenozoic), new reverse and thrust faults (or shortcut faults) were created, which connected upward with incompetent stratigraphic units and facilitated the propagation of localized fold-and-thrust belts in the eastern Domeyko Cordillera and Salar de Pedernales basins. A minimum of 16.3 km of W-E shortening was reported; however, nearly 11 km was accommodated by the newly created thrusts, indicating that these were most relevant to mountain building.
•The 2D tectonic model of the Central Andes forearc at 26°S shows present-day and pre-orogenic architectures of the western Central Andes.•The structures consisted of thick-skinned and doubly verging structures.•16.3 km of W-E shortening was accommodated by the propagation of shortcut faults connecting the basement-involved to the thin-skinned structures.
Channel modeling is a critical issue when designing or evaluating the performance of reconfigurable intelligent surface (RIS)-assisted communications. Inspired by the promising potential of ...learning-based methods for characterizing the radio environment, we present a general approach to model the RIS end-to-end equivalent channel using the unsupervised expectation-maximization (EM) learning algorithm. We show that an EM-based approximation through a simple mixture of two Nakagami-<inline-formula> <tex-math notation="LaTeX">{m} </tex-math></inline-formula> distributions suffices to accurately approximate the equivalent channel, while allowing for the incorporation of crucial aspects into RIS's channel modeling such as beamforming, spatial channel correlation, phase-shift errors, arbitrary fading conditions, and coexistence of direct and RIS channels. Based on the proposed analytical framework, we evaluate the outage probability under different settings of RIS's channel features and confirm the superiority of this approach compared to recent results in the literature.
We provide some comments and subsequent corrections to a paper recently published in this Journal (see ibid., vol. 33, no. 1, pp. 111-119, Jan. 2015). More precisely, we show that the pdf for the κ-μ ...shadowed fading model given by S.L. Cotton cannot be obtained from the underlying statistical model proposed therein. To support this observation, we present a detailed mathematical analysis as well as some Monte Carlo simulations. We also demonstrate that by simply adopting the underlying statistical model for the κ-μ shadowed fading distribution proposed in an earlier and independent work by J.F. Paris enables the κ-μ shadowed pdf later presented by S.L. Cotton to be obtained.
Physical layer multicasting exploits multiple antennas at the transmitter side to deliver a common message to a group of <inline-formula> <tex-math notation="LaTeX">K </tex-math></inline-formula> ...users. To this end, two formulations have been well addressed in the literature: i) the max-min-fair criterion, which maximizes the signal-to-noise ratio (SNR) of the worst user for a fixed transmit power; and ii) the quality of service (QoS) formulation, which minimizes the transmit power subject to a target SNR. Nevertheless, it is known that the performance and complexity of these approaches is severely degraded as the group size grows. In this paper, we propose a different formulation that aims at minimizing the required bandwidth needed to provide the multicast service. This is achieved by dividing the users into smaller groups and assigning the bandwidth required to provide a target rate to each group. Contrary to the common belief, it is shown that dividing the users into different groups that use orthogonal bandwidth allocations can lead to a smaller aggregated bandwidth than the single-group with single bandwidth allocation counterpart, if an intelligent grouping scheme is used. An iterative algorithm to derive the optimal number of groups is presented with an stopping criterion to reduce the numerical complexity. It is shown through simulation that our proposed approach greatly reduces the required bandwidth compared to existing schemes that rely on single bandwidth allocation. Interestingly, results reveal that our proposed scheme also leads to a greater SNR for a randomly chosen user, and it reduces the variance of the required bandwidth, which eases the implementation in real networks.
A Tractable Product Channel Model for Line-of-Sight Scenarios Fernandez-Plazaola, Unai; Moreno-Pozas, Laureano; Lopez-Martinez, F. Javier ...
IEEE transactions on wireless communications,
2020-March, 2020-3-00, 20200301, Letnik:
19, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We present a general and tractable fading model for line-of-sight (LOS) scenarios, which is based on the product of two independent and non-identically distributed κ-μ shadowed power envelopes. ...Simple closed-form expressions for the probability density function, cumulative distribution function and moment-generating function are derived, which are as tractable as the corresponding expressions derived from a product of Nakagami-m random variables. This model simplifies the challenging characterization of LOS product channels, as well as combinations of LOS channels with non-LOS ones. We leverage these results to analyze performance measures of interest in the contexts of wireless powered and backscatter communications, where both forward and reverse links are inherently of LOS nature, as well as in device-to-device communications subject to composite fading. In these contexts, the proposed model shows a higher flexibility when fitting field measurements with respect to conventional approaches based on product distributions with deterministic LOS, together with a more complete physical interpretation of the underlying propagation characteristics.
Ultra-short period (USP) planets are a class of exoplanets with periods shorter than one day. The origin of this sub-population of planets is still unclear, with different formation scenarios highly ...dependent on the composition of the USP planets. A better understanding of this class of exoplanets will, therefore, require an increase in the sample of such planets that have accurate and precise masses and radii, which also includes estimates of the level of irradiation and information about possible companions. Here we report a detailed characterization of a USP planet around the solar-type star HD 80653 ≡EP 251279430 using the K2 light curve and 108 precise radial velocities obtained with the HARPS-N spectrograph, installed on the Telescopio Nazionale
Galileo
. From the K2 C16 data, we found one super-Earth planet (
R
b
= 1.613 ± 0.071
R
⊕
) transiting the star on a short-period orbit (
P
b
= 0.719573 ± 0.000021 d). From our radial velocity measurements, we constrained the mass of HD 80653 b to
M
b
= 5.60 ± 0.43
M
⊕
. We also detected a clear long-term trend in the radial velocity data. We derived the fundamental stellar parameters and determined a radius of
R
⋆
= 1.22 ± 0.01
R
⊙
and mass of
M
⋆
= 1.18 ± 0.04
M
⊙
, suggesting that HD 80653 has an age of 2.7 ± 1.2 Gyr. The bulk density (
ρ
b
= 7.4 ± 1.1 g cm
−3
) of the planet is consistent with an Earth-like composition of rock and iron with no thick atmosphere. Our analysis of the K2 photometry also suggests hints of a shallow secondary eclipse with a depth of 8.1 ± 3.7 ppm. Flux variations along the orbital phase are consistent with zero. The most important contribution might come from the day-side thermal emission from the surface of the planet at
T
~ 3480 K.
We show that for a legitimate communication under multipath quasi-static fading with a reduced number of scatterers, it is possible to achieve perfect secrecy even in the presence of a passive ...eavesdropper for which no channel state information (CSI) is available. Specifically, we show that the outage probability of secrecy capacity (OPSC) is zero for a given range of average signal-to-noise ratios (SNRs) at the legitimate and eavesdropper's receivers. As an application example, we analyze the OPSC for the case of two scatterers, explicitly deriving the relationship between the average SNRs, the secrecy rate <inline-formula> <tex-math notation="LaTeX">R_{S} </tex-math></inline-formula> and the fading model parameters required for achieving perfect secrecy. The impact of increasing the number of scatterers is also analyzed, showing that it is always possible to achieve perfect secrecy in this scenario, provided that (<inline-formula> <tex-math notation="LaTeX">{i} </tex-math></inline-formula>) the dominant specular component for the legitimate channel is sufficiently large compared to the remaining scattered waves, and ( ii ) a exclusion area on which no eavesdroppers can be placed is considered.
We investigate the impact of fading correlation on the performance of the doubly dirty fading multiple access channel (MAC) with non-causally known side information at transmitters. Using Copula ...theory, we derive closed-form expressions for the outage probability (OP) and the coverage region under positive/negative dependence conditions. We show that a positive dependence structure between the fading channel coefficients is beneficial for the system performance, as it improves the OP and extends the coverage region compared to the case of independent fading. Conversely, a negative dependence structure has a detrimental effect on both performance metrics.
The analysis of complex patterns in human gait dynamics typically relies on measuring stride intervals. Several studies have revealed that the dynamics of stride intervals exhibit fractal ...characteristics that depend on health, age, and task conditions. However, with current measurement devices, other gait parameters such as the swing and stance intervals can also be measured. This prompts the question of whether multivariate analysis provides a more detailed view of gait dynamics. This work aims to use multivariate rescaled range (MR/S) analysis to characterize the fractality of the combined behavior of the stride, stance, and swing intervals in terms of the Hurst exponent, which is an index of the fractality of a time series. The MR/S method was equipped with a surrogate data analysis, to refer to a corrected Hurst exponent, which is defined as a distance to randomness. Datasets of neurodegenerative conditions (amyotrophic lateral sclerosis, Huntington's disease and Parkinson's disease) from Physionet were used to evaluate the ability of MR/S analysis to characterize different phases of gait dynamics. An index of distance to randomness relative to a 95 % confidence interval obtained from surrogate data was introduced to alleviate biased estimation of the Hurst exponent for relatively small samples. The results showed that the distance to randomness of stance and stride intervals was higher (p < 0.05) than that of swing intervals. On the other hand, the stride interval discriminated (p < 0.05) the control conditions from the neurodegenerative conditions. In contrast, the swing interval discriminated (p < 0.05) the Parkinson's disease from ALS and Huntington's disease. Overall, the results indicate that multivariate analysis is a suitable approach for a detailed characterization of the impact of different gait phases on gait dynamics.
•Multivariate analysis is a suitable approach for a characterization of the effects of different gait phases.•The use of neurodegenerative data to assess the ability of multivariate rescaled range analysis.
The physical layer security of uplink non-orthogonal multiple access (NOMA) is analyzed. A stochastic geometry approach is applied to analyze the coverage probability and effective secrecy throughput ...(EST) of the <inline-formula> <tex-math notation="LaTeX">kth </tex-math></inline-formula> NOMA user, where a fixed or an adaptive transmission rate can be used. We consider a protected zone around the legitimate terminals to establish an eavesdropper-exclusion area. We assume that the channel state information associated with eavesdroppers is not available at the base station. We also consider that the base station is equipped with multiple antennas. The impact of imperfect successive interference cancellation is also taken into account in this paper. Our framework allows to compute, numerically, the wiretap code rates that maximize the EST. In addition, our framework also allows an optimum selection of other system parameters, such as the transmit power or the eavesdropper-exclusion radius.
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