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

Local evolution equations for non-Markovian processes

A Fokker-Planck equation approach for the treatment of non-Markovian stochastic processes is proposed. The approach is based on the introduction of fictitious trajectories sharing with the real ones their local structure and initial conditions. Different statistical quantities are generated by different construction rules for the trajectories, which coincide only in the Markovian case. The merits and limitations of the approach are discussed and applications to transport in ratchets and to anomalous diffusion are illustated.Comment: Latex, 11 pages, 1 eps figur

NEMO-SN1 Abyssal Cabled Observatory in the Western Ionian Sea

The NEutrinoMediterranean Observatory—Submarine Network 1 (NEMO-SN1) seafloor observatory is located in the central Mediterranean Sea, Western Ionian Sea, off Eastern Sicily (Southern Italy) at 2100-m water depth, 25 km from the harbor of the city of Catania. It is a prototype of a cabled deep-sea multiparameter observatory and the first one operating with real-time data transmission in Europe since 2005. NEMO-SN1 is also the first-established node of the European Multidisciplinary Seafloor Observatory (EMSO), one of the incoming European large-scale research infrastructures included in the Roadmap of the European Strategy Forum on Research Infrastructures (ESFRI) since 2006. EMSO will specifically address long-term monitoring of environmental processes related to marine ecosystems, marine mammals, climate change, and geohazards

Torque Penetrometric Test for the in-situ characterisation of historical mortars: fracture mechanics interpretation and experimental validation

The assessment of historical structures requires appropriate knowledge of the behaviour of the investigated materials. Concerning masonry, its mechanical characterisation is a challenging task, since its composite nature requires the careful evaluation of the behaviour of its material components. In particular, the experimental assessment of the strength of existing mortar in historical structures still encounters several difficulties. This study investigates a novel Minor Destructive Testing (MDT) technique virtually equivalent to the vane test used for soils. The instrumentation, called herein Torque Penetrometric Test (TPT), is composed of a steel nail with four protruding teeth and a torque wrench. The test consists in inserting the toothed nail into a mortar joint and then applying a torque by means of a dynamometric key, until reaching the failure of the material. This work presents a novel interpretation theory based on basic concepts of fracture mechanics and applied to the micro-mechanical analysis of the stress state induced by the instrument on the investigated mortar. The proposed interpretative theory is validated through the execution of experimental tests in the laboratory and in a historical masonry building. The test proves to be effective for a quick in-situ MDT evaluation of the strength of existing mortars.Peer ReviewedPostprint (author's final draft

TSUNAMI DETECTION ALGORITHM

Real-time tsunami detection algorithms play a key role in any Tsunami Early Warning System. We have developed a new algorithm for tsunami detection based on the real-time tide removal and real-time band-pass filtering of seabed pressure recordings. The algorithm greatly increases the tsunami detection probability, shortens the detection delay and enhances detection reliability with respect to the most widely used tsunami detection algorithm, while containing the computational cost. The algorithm is designed to be used also in autonomous early warning systems with a set of input parameters and procedures which can be reconfigured in real time. We have also developed a methodology based on Monte Carlo simulations to test the tsunami detection algorithms. The algorithm performance is estimated by defining and evaluating statistical parameters, namely the detection probability, the detection delay, which are functions of the tsunami amplitude and wavelength, and the occurring rate of false alarms. Pressure data sets acquired by Bottom Pressure Recorders in different locations and environmental conditions have been used in order to consider real working scenarios in the test. We also present an application of the algorithm to the tsunami event which occurred at Haida Gwaii on 28 October 2012 using data recorded by the Bullseye underwater node of Ocean Networks Canada. The algorithm successfully ran for test purpose in year-long missions onboard abyssal observatories, deployed in the Gulf of Cadiz and in the Western Ionian Sea.EC NEAREST project (GOCE0307110) , LIDO - EC-ESONET DM Mission (036851) and RITMAREPublished636–6523A. Geofisica marinaJCR Journa

The Virtual 3D Reconstruction of the East Pediment of the Temple of Zeus at Olympia – Presentation of an Interactive CD-ROM

The paper gives an overview of a two-years project concerning a major monument of ancient Greek art and presents the interactive, bilingual (English/Hungarian) CD-ROM, which is intended to summarize and visualize its final results. The presented project approaches a century-old controversy in a new way by producing a virtual 3D reconstruction of a monumental marble group. Digital models of the statues were produced by scanning the original fragments and by reconstructing them virtually. The virtual model of the pediment surrounding the sculptures was prepared on the basis of the latest architectural studies and afterwards the reconstructed models were inserted in this frame, in order to test the technical feasibility and aesthetic effects the four possible arrangements. The resulting models enable easy and very instructive experimentation, which would be otherwise impossible with the originals and/or very expensive and not very practicable with traditional tools (e.g. real-size plaster models). The complete model can effectively be used to verify the results of earlier or more recent reconstructions presented only in simple drawings. In addition, the 3D models of the individual fragments can be used for further research and for visualization.  The documentary CD-ROM presenting the full background, the methods and the conclusions of the project contains beside a comprehensive text various kinds of supporting documents (images, 3D models, papers, broadcasts, audiovisual material). It is addressed to a mixed audience: a picture gallery, a short documentary movie some other attachments including a selected bibliography is intended for the general public, but scholarly publications, presentations on related problems are also included for specialists interested in certain details

Torque Penetrometric Test for the in-situ characterisation of historical mortars: fracture mechanics interpretation and experimental validation

The assessment of historical structures requires appropriate knowledge of the behaviour of the investigated materials. Concerning masonry, its mechanical characterisation is a challenging task, since its composite nature requires the careful evaluation of the behaviour of its material components. In particular, the experimental assessment of the strength of existing mortar in historical structures still encounters several difficulties. This study investigates a novel Minor Destructive Testing (MDT) technique virtually equivalent to the vane test used for soils. The instrumentation, called herein Torque Penetrometric Test (TPT), is composed of a steel nail with four protruding teeth and a torque wrench. The test consists in inserting the toothed nail into a mortar joint and then applying a torque by means of a dynamometric key, until reaching the failure of the material. This work presents a novel interpretation theory based on basic concepts of fracture mechanics and applied to the micro-mechanical analysis of the stress state induced by the instrument on the investigated mortar. The proposed interpretative theory is validated through the execution of experimental tests in the laboratory and in a historical masonry building. The test proves to be effective for a quick in-situ MDT evaluation of the strength of existing mortars.Peer Reviewe

NEMO-SN1 Abyssal Cabled Observatory in the Western Ionian Sea

The NEutrinoMediterranean Observatory-Submarine Network 1 (NEMO-SN1) seafloor observatory is located in the central Mediterranean Sea, Western Ionian Sea, off Eastern Sicily (Southern Italy) at 2100-m water depth, 25 km from the harbor of the city of Catania. It is a prototype of a cabled deep-sea multiparameter observatory and the first one operating with real-time data transmission in Europe since 2005. NEMO-SN1 is also the first-established node of the European Multidisciplinary Seafloor Observatory (EMSO), one of the incoming European large-scale research infrastructures included in the Roadmap of the European Strategy Forum on Research Infrastructures (ESFRI) since 2006. EMSO will specifically address long-term monitoring of environmental processes related to marine ecosystems, climate change, and geohazards. NEMO-SN1 has been deployed and developed over the last decade thanks to Italian funding and to the European Commission (EC) project European Seas Observatory NETwork-Network of Excellence (ESONET-NoE, 2007-2011) that funded the Listening to the Deep Ocean-Demonstration Mission (LIDO-DM) and a technological interoperability test (http://www.esonet-emso.org). NEMO-SN1 is performing geophysical and environmental long-term monitoring by acquiring seismological, geomagnetic, gravimetric, accelerometric, physico-oceanographic, hydroacoustic, and bioacoustic measurements. Scientific objectives include studying seismic signals, tsunami generation and warnings, its hydroacoustic precursors, and ambient noise characterization in terms of marine mammal sounds, environmental and anthropogenic sources. NEMO-SN1 is also an important test site for the construction of the Kilometre-Cube Underwater Neutrino Telescope (KM3NeT), another large-scale research infrastructure included in the ESFRI Roadmap based on a large volume neutrino telescope. The description of the observatory and its most recent implementations is presented. On June 9, 2012, NEMO-SN1 was successfully deployed and is working in real time

Tsunami Early Warning System: Deep Sea Measurements in the Source Area.

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A New Method to Assess Long‐Term Sea‐Bottom Vertical Displacement in Shallow Water using a Bottom Pressure Sensor: Application to Campi Flegrei, Southern Italy

We present a new methodology using bottom pressure recorder (BPR) measurements in conjunction with sea level, water column, and barometric data to assess the long‐term vertical seafloor deformation to a few centimeters accuracy in shallow water environments. The method helps to remove the apparent vertical displacement on the order of tens of centimeters caused by the BPR instrumental drift and by seawater density variations. We have applied the method to the data acquired in 2011 by a BPR deployed at 96 m depth in the marine sector of the Campi Flegrei Caldera, during a seafloor uplift episode of a few centimeters amplitude, lasted for several months. The method detected a vertical uplift of the caldera of 2.5 ± 1.3 cm achieving an unprecedented level of precision in the measurement of the submarine vertical deformation in shallow water. The estimated vertical deformation at the BPR also compares favorably with data acquired by a land‐based GPS station located at the same distance from the maximum of the modeled deformation field. While BPR measurements are commonly performed in deep waters, where the oceanic noise is relatively low, and in areas with rapid, large‐amplitude vertical ground displacement, the proposed method extends the capability of estimating vertical uplifts from BPR time series to shallow waters and to slow deformation processes