Effective viscosity of grease ice in linearized gravity waves

Grease ice is an agglomeration of disc-shaped ice crystals, named frazil ice, which forms in turbulent waters of the Polar Oceans and in rivers as well. It has been recognized that the properties of grease ice to damp surface gravity waves could be explained in terms of the effective viscosity of the ice slurry. This paper is devoted to the study of the dynamics of a suspension of disc-shaped particles in a gravity wave field. For dilute suspensions, depending on the strength and frequency of the external wave flow, two orientation regimes of the particles are predicted: a preferential orientation regime with the particles rotating in coherent fashion with the wave field, and a random orientation regime in which the particles oscillate around their initial orientation while diffusing under the effect of Brownian motion. For both motion regimes, the effective viscosity has been derived as a function of the wave frequency, wave amplitude and aspect ratio of the particles. Model predictions have been compared with wave attenuation data in frazil ice layers grown in wave tanks.Comment: 13 pages, 3 eps figures included; one more section on inertia effect

Gap analysis on Research and Innovation for Cyber-Physical Systems in Manufacturing

In defining the Roadmap of the Research Priorities for the adoption of CPS in manufacturing industry, it is crucial to identify the key elements preventing a fast and smooth transition from the current status to the desired one. In such complex environments characterized by many industrial sectors and processes, external factors and social/economical influences, it is important to address only the main issues to achieve the result. This paper is aiming to illustrate the results of the Gap Analysis activities carried out in the sCorPiuS (http://scorpius-project.eu/) project

Diffusion of gravity waves by random space inhomogeneities in pancake-ice fields. Theory and validation with wave buoys and synthetic aperture radar

We study the diffusion of ocean waves by floating bodies such as pancakes and ice floes much smaller than a wavelength. We argue that the combined effect of hydrodynamic interaction of the ice bodies and inhomogeneities in the ice cover at scales comparable to that of the wavelength significantly increases diffusion, producing a contribution to wave attenuation comparable to what is observed in the field and usually explained by invoking viscous effects. The resulting attenuation spectrum is characterized by a peak at the scale of the inhomogeneities in the ice cover, thereby providing a new possible explanation of the rollover of the attenuation profile at small wavelengths experimentally observed over the years. The proposed attenuation mechanism has the same effect as a viscous wave model with effective viscosity linearly dependent on the ice thickness, which may explain recent findings that viscous wave models require a thickness-dependent viscosity to fit experimental attenuation data. Experimental validation is carried out using wave buoy attenuation data and synthetic aperture radar image analysis.Comment: 29 pages, 5 figure

Cyber-physical systems in manufacturing: Future trends and research priorities

In the last decades, the manufacturing ecosystem witnessed an unprecedented evolution of disruptive technologies forging new opportunities for manufacturing companies to cope the ever-growing market pressure. Moreover, the race to create value for the customers has been hindered by several issues that both small and large companies have been facing, such as shorter product life cycles, rapid time-to-market, product complexity, cost pressure, increased international competition, etc. In this scenario, ICT represent a crucial enabler for preserving competitiveness and fostering industry innovation. In particular, among these technologies, Cyber-Physical Systems (CPS) is growing an ever-high interest of industry stakeholders, researchers, practitioners and policy makers as they are considered the key technology that will transform manufacturing industry to the next generation. Indeed, CPS is a breakthrough research area for ICT in manufacturing and represents the cornerstone for achieving the EU2020 "smart everywhere" vision. At this early development phase, there is the urgent need to set the ground for future research streams, create a common understanding and consensus, define viable migration paths and support standards definition. This paper describes the identified research challenges and the future trends that will drive to the adoption of CPS in manufacturing. The main evidences on researches challenges expected for CPS in manufacturing are outlined by the authors that have been involved in the sCorPiuS project 'European Roadmap for Cyber- Physical Systems in Manufacturing', promoted by the European Commission to define a roadmap for future CPS in manufacturing adoption research agenda

Chapter Mapping of the risk of coastal erosion for two case studies: Pianosa island (Tuscany) and Piscinas (Sardinia)

This study focuses on the use of remote sensing to generate coastal erosion risk maps for Pianosa Island (Tuscany) and Piscinas dune system (Sardinia). The method made use of both ancillary and satellite data (Sentinel-2), in addition to SAR images (COSMO SkyMed and Sentinel-1B). TOA radiance products were atmospherically corrected and processed using Sen2Coral and BOMBER in order to map different marine substrates and bathymetry. The coastal erosion risk maps have been generated based on these output and the results confirm that the coasts of these sites don’t have coastal erosion problems

SAR Based Sea Surface Complex Wind Fields Estimation: An Analysis over the Northern Adriatic Sea

Nowadays, sea surface analysis and monitoring increasingly use remote sensing, with particular interest in Synthetic Aperture Radar (SAR). Several SAR techniques exist in literature to understand the marine phenomena affecting the sea surface. In this work, we focus on the Doppler Centroid Anomaly (DCA), which accounts for the Doppler shift induced by sea surface movements. Starting from SAR raw data, we develop a processing chain to elaborate them and output the surface velocity map using DCA. The DCA technique has often been presented in the marine literature for estimating sea surface velocity, but more recently it has also been used to detect near-surface wind fields. This paper deals with estimating the sea surface wind field using Doppler information and SAR backscatter, combined with wind information provided by ECMWF and geophysical wind and Doppler model functions. We investigate the application of the approach in the coastal area of the northern Adriatic Sea (Northeast Italy). The test site is interesting, both for its particular orography, as it is a semi-enclosed basin largely surrounded by mountains, and for its complex meteorological phenomena, such as the Bora wind. Results obtained combining SAR backscatter and DCA information show an improvement in wind field estimation

On the synergistic use of SAR and optical imagery to monitor cyanobacteria scum in inland waters

Optical remote sensing is a validated tool for detecting, monitoring and developing methodologies aimed at a better understanding of the state of lakes. However, it is highly hindered by clouds. For regions with frequent cloud cover, this means loss of data, which derails the purpose of sensing. This makes difficult to spatially and temporally characterize scum area for a comprehensive ecological analysis. Combining data obtained using different types of sensors can be an option worth investigating, and a good candidate for this purpose is the synthetic aperture radar (SAR), due to its capacity to collect data independent of cloudy cover. We use a synergistic approach involving optical and SAR images together with meteorological param- eters to monitor algal cyanobacteria blooms in lakes. The satellite images are provided by the Senti- nel 1 and 2 satellites. Meteorological parameters come from in situ stations or from the European Centre for Medium-Range Weather Forecasts (ECMWF) database. Poster presented at 'Dragon 4 Mid-term Results Symposium, Xi’an, P.R. China, 19-22 June 2018