Frictional dynamics of viscoelastic solids driven on a rough surface

We study the effect of viscoelastic dynamics on the frictional properties of a (mean field) spring-block system pulled on a rough surface by an external drive. When the drive moves at constant velocity V, two dynamical regimes are observed: at fast driving, above a critical threshold Vc, the system slides at the drive velocity and displays a friction force with velocity weakening. Below Vc the steady sliding becomes unstable and a stick-slip regime sets in. In the slide-hold-slide driving protocol, a peak of the friction force appears after the hold time and its amplitude increases with the hold duration. These observations are consistent with the frictional force encoded phenomenologically in the rate-and-state equations. Our model gives a microscopical basis for such macroscopic description.Comment: 10 figures, 7 pages, +4 pages of appendi

Tuning spreading and avalanche-size exponents in directed percolation with modified activation probabilities

We consider the directed percolation process as a prototype of systems displaying a nonequilibrium phase transition into an absorbing state. The model is in a critical state when the activation probability is adjusted at some precise value p_c. Criticality is lost as soon as the probability to activate sites at the first attempt, p1, is changed. We show here that criticality can be restored by "compensating" the change in p1 by an appropriate change of the second time activation probability p2 in the opposite direction. At compensation, we observe that the bulk exponents of the process coincide with those of the normal directed percolation process. However, the spreading exponents are changed, and take values that depend continuously on the pair (p1, p2). We interpret this situation by acknowledging that the model with modified initial probabilities has an infinite number of absorbing states.Comment: 9 pages, 11 figure

The thin film microwave iris

Development of waveguide iris for microwave coupling applications using thin film techniques is discussed. Production process and installation of iris are described. Iris improves power transmission properties of waveguide window

The influence of the brittle-ductile transition zone on aftershock and foreshock occurrence

Aftershock occurrence is characterized by scaling behaviors with quite universal exponents. At the same time, deviations from universality have been proposed as a tool to discriminate aftershocks from foreshocks. Here we show that the change in rheological behavior of the crust, from velocity weakening to velocity strengthening, represents a viable mechanism to explain statistical features of both aftershocks and foreshocks. More precisely, we present a model of the seismic fault described as a velocity weakening elastic layer coupled to a velocity strengthening visco-elastic layer. We show that the statistical properties of aftershocks in instrumental catalogs are recovered at a quantitative level, quite independently of the value of model parameters. We also find that large earthquakes are often anticipated by a preparatory phase characterized by the occurrence of foreshocks. Their magnitude distribution is significantly flatter than the aftershock one, in agreement with recent results for forecasting tools based on foreshocks

The thin film iris

Thin film microwave irises with capacitive reactanc

Less Worthy Lives? We Must Prioritize People with Intellectual and Developmental Disabilities in COVID-19 Vaccine Allocation

Individuals with developmental and intellectual disability should prioritized during COVID-19 vaccination allocation

Indications for phosphorus fertilizer-derived uranium mobilization from arable soils to groundwater

Uranium (U) and many trace elements are enriched in phosphorus fertilizers. Concentrations up to 260 mg/kg P2O5 indicate the potential of U contamination of the environment. Two fertilized long-time soil monitoring fields (BDF) in Lower Saxony have higher top soil concentration than comparable unfertilized top soils sampled at the Green-Belt in the vicinity of the BDFs. Extraction experiments could show that fertilizer-derived U is easier mobilized and hence might be leached faster to the groundwater than the geogenic U in soils. Groundwater analyses in an area of intense agricultural production show U in correlation with nitrate, indicating an impact of anthropogenic fertilization on the U concentration in shallow groundwater. The results of soil, soil extract and groundwater analyses are giving indications for fertilizer-derived U leaching to groundwater aquifers and hence show the potential hazard for our drinking water resources

COVID-19 Trends Among Adults with Intellectual and Developmental Disabilities (IDD) Living in Residential Group Homes in New York State through July 10, 2020

While COVID-19 case rates increased between April 10, 2020 and July 10, 2020 for both groups, from April 10 to May 1, the case rate increased by 2.5 times for people with IDD, from 2,225 to 5,544 cases per 100,000, but only increased by 1.6 times for New York State, from 886 to 1,584 cases per 100,000

A BENCHMARK FOR LARGE-SCALE HERITAGE POINT CLOUD SEMANTIC SEGMENTATION

The lack of benchmarking data for the semantic segmentation of digital heritage scenarios is hampering the development of automatic classification solutions in this field. Heritage 3D data feature complex structures and uncommon classes that prevent the simple deployment of available methods developed in other fields and for other types of data. The semantic classification of heritage 3D data would support the community in better understanding and analysing digital twins, facilitate restoration and conservation work, etc. In this paper, we present the first benchmark with millions of manually labelled 3D points belonging to heritage scenarios, realised to facilitate the development, training, testing and evaluation of machine and deep learning methods and algorithms in the heritage field. The proposed benchmark, available at http://archdataset.polito.it/, comprises datasets and classification results for better comparisons and insights into the strengths and weaknesses of different machine and deep learning approaches for heritage point cloud semantic segmentation, in addition to promoting a form of crowdsourcing to enrich the already annotated databas

Is copyright blind to the visual?

This article argues that, with respect to the copyright protection of works of visual art, the general uneasiness that has always pervaded the relationship between copyright law and concepts of creativity produces three anomalous results. One of these is that copyright lacks much in the way of a central concept of 'visual art' and, to the extent that it embraces any concept of the 'visual', it is rooted in the rhetorical discourse of the Renaissance. This means that copyright is poorly equipped to deal with modern developments in the visual arts. Secondly, the pervasive effect of rhetorical discourse appears to have made it particularly difficult for copyright law to strike a meaningful balance between protecting creativity and permitting its use in further creative works. Thirdly, just when rhetorical discourse might have been useful in identifying the significance and materiality of the unique one-off work of visual art, copyright law chooses to ignore its implications