Universal fluctuations in tropospheric radar measurements

We present methods and results from interferometric data processing of a long-lasting survey campaign monitoring the Planpincieux glacier, located on the Italian side of the Mont Blanc, using a ground-based synthetic aperture radar (GB-SAR). Monitoring a European Alpine glacier during the winter, when the meteorological conditions are highly variable, presents some difficulties in radar data interpretation. The main issues to tackle in interferometric processing are unwrapping errors and high amplitude dispersion (DA), mainly due to the high velocity and dielectric heterogeneity of the backscattering surface. To improve the reliability of the results, a coherence-driven pixel-selection criterion for identifying the glacier area and a simple approach to reduce possible unwrapping errors in interferograms with low coherence are here proposed. The development of a new 2D polynomial regression model, as a function of elevation, for atmospheric phase screen (APS) estimation is also discussed. A comparison with the results obtained with a vision-based approach gave showed good agreement. ARTICLE HISTORY

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“…wave phase (Iannini and Monti Guarnieri 2011;Barucci et al 2010). For these reasons, the reliability of the results of this area is low.…”

Section: Resultsmentioning

confidence: 99%

Monitoring Alpine glacier surface deformations with GB-SAR

Dematteis

Luzi

Giordan

et al. 2017

Remote Sensing Letters

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“…The model assumes that as the data increase, so does the seasonal pattern. Several time series exhibit such a pattern (Barucci et al 2010). The multiplicative model is expressed as: Yt = Trend * Seasonal * Error, where Yt is the observation at time t. An approximate confidence interval (95%) of the prediction using a rule of thumb prediction ± 2·x Standard Error were also plotted.…”

Section: Time Series Decompositionmentioning

confidence: 99%

Regional and temporal characteristics of bovine tuberculosis of cattle in Great Britain

Moustakas

Evans

2015

Stoch Environ Res Risk Assess

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Bovine tuberculosis (TB) is a chronic disease in cattle that causes a serious food security challenge to the agricultural industry in terms of dairy and meat production. Spatio-temporal disease analysis in terms of time trends and geographic disparities of disease dynamics can provide useful insights into the overall efficiency of control efforts as well as the relative efficiency of different management measures towards eradication. In GB, Scotland has had a risk based surveillance testing policy under which high risk herds are tested frequently, and in September 2009 was officially declared as TB free. Wales have had an annual or more frequent testing policy for all cattle herds since January 2010, while in England several herds are still tested every 4 years except some high TB prevalence areas where annual testing is applied. Time series analysis using publicly available data for total tests on herds, total cattle slaughtered, new herd incidents, and herds not TB free, were analysed globally for GB and locally for the constituent regions of Wales, Scotland, West, North, and East England. After detecting trends over time, underlying regional differences were compared with the testing policies in the region. Total cattle slaughtered are decreasing in Wales, Scotland and West England, but increasing in the North and East English regions. New herd incidents, i.e., disease incidence, are decreasing in Wales, Scotland, West English region, but increasing in North and East English regions. Herds not TB free, i.e., disease prevalence, are increasing in West, North, and East English regions, while they are decreasing in Wales and Scotland. Total cattle slaughtered were positively correlated with total tests in the West, North, and East English regions, with high slopes of regression indicating that additional testing is likely to facilitate the eradication of the disease. There was no correlation between total cattle slaughtered and total tests on herds in Wales indicating that herds are tested frequent enough in order to detect all likely cases and so control TB. The main conclusion of the analysis conducted here is that more frequent testing is leading to lower TB infections in cattle both in terms of TB prevalence as well as TB incidence.

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“…5 C ). By contrast, the distribution of the instantaneous correlations in the perturbed state are highly non-Gaussian and can be captured by a distribution that is commonly used for scale-free processes, the generalized Gumbel distribution ( 60 , 61 ):

where

and

. Here,

is the gamma function of

;

and

are the mean and SD of

; and

and

in Eq.…”

Section: Resultsmentioning

confidence: 99%

Microscopic dynamics underlying the stress relaxation of arrested soft materials

Song

Zhang

Quesada

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Arrested soft materials such as gels and glasses exhibit a slow stress relaxation with a broad distribution of relaxation times in response to linear mechanical perturbations. Although this macroscopic stress relaxation is an essential feature in the application of arrested systems as structural materials, consumer products, foods, and biological materials, the microscopic origins of this relaxation remain poorly understood. Here, we elucidate the microscopic dynamics underlying the stress relaxation of such arrested soft materials under both quiescent and mechanically perturbed conditions through X-ray photon correlation spectroscopy. By studying the dynamics of a model associative gel system that undergoes dynamical arrest in the absence of aging effects, we show that the mean stress relaxation time measured from linear rheometry is directly correlated to the quiescent superdiffusive dynamics of the microscopic clusters, which are governed by a buildup of internal stresses during arrest. We also show that perturbing the system via small mechanical deformations can result in large intermittent fluctuations in the form of avalanches, which give rise to a broad non-Gaussian spectrum of relaxation modes at short times that is observed in stress relaxation measurements. These findings suggest that the linear viscoelastic stress relaxation in arrested soft materials may be governed by nonlinear phenomena involving an interplay of internal stress relaxations and perturbation-induced intermittent avalanches.

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Universal fluctuations in tropospheric radar measurements

Cited by 9 publications

References 21 publications

Monitoring Alpine glacier surface deformations with GB-SAR

Monitoring Alpine glacier surface deformations with GB-SAR

Regional and temporal characteristics of bovine tuberculosis of cattle in Great Britain

Microscopic dynamics underlying the stress relaxation of arrested soft materials

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