9,190 research outputs found

    SHIP MOTION SHORT TERM TIME DOMAIN SIMULATOR AND ITS APPLICATION TO COSTA CONCORDIA EMERGENCY MANOEUVRES JUST BEFORE THE JANUARY 2012 ACCIDENT

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    In this paper we will present a simple but reliable methodology for short term prediction of a cruise ship behaviour during manoeuvres. The methodology is quite general and could be applied to any kind of ship, because it does not require the prior knowledge of any structural or mechanical parameter of the ship. It is based only on the results of manoeuvrability data contained in the Manoeuvring Booklet, which in turn is filled out after sea trials of the ship performed before his delivery to the owner. We developed this method to support the investigations around the Costa Concordia shipwreck, which happened near the shores of Italy in January 2012. It was then validated against the data recorded in the “black box” of the ship, from which we have been able to extract an entire week of voyage data before the shipwreck. The aim was investigating the possibility of avoiding the impact by performing an evasive manoeuvre (as ordered by the Captain some seconds before the impact, but allegedly misunderstood by the helmsman). The preliminary validation step showed a good matching between simulated and real values (course and heading of the ship) for a time interval of a few minutes. The fact that the method requires only the results registered in the VDR (Voyage Data Recorder) during sea trial tests, makes it very useful for several applications. Among them, we can cite forensic investigation, the development of components for autopilots, the prediction of the effects of a given manoeuvre in shallow water, the “a posteriori” verification of the correctness of a given manoeuvre and the use in training simulators for ship pilots and masters

    Constraining the abundances of complex organics in the inner regions of solar-type protostars

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    The high abundances of Complex Organic Molecules (COMs) with respect to methanol, the most abundant COM, detected towards low-mass protostars, tend to be underpredicted by astrochemical models. This discrepancy might come from the large beam of the single-dish telescopes, encompassing several components of the studied protostar, commonly used to detect COMs. To address this issue, we have carried out multi-line observations of methanol and several COMs towards the two low-mass protostars NGC1333-IRAS2A and -IRAS4A with the Plateau de Bure interferometer at an angular resolution of 2 arcsec, resulting in the first multi-line detection of the O-bearing species glycolaldehyde and ethanol and of the N-bearing species ethyl cyanide towards low-mass protostars other than IRAS 16293. The high number of detected transitions from COMs (more than 40 methanol transitions for instance) allowed us to accurately derive the source size of their emission and the COMs column densities. The COMs abundances with respect to methanol derived towards IRAS2A and IRAS4A are slightly, but not substantitally, lower than those derived from previous single-dish observations. The COMs abundance ratios do not vary significantly with the protostellar luminosity, over five orders of magnitude, implying that low-mass hot corinos are quite chemically rich as high-mass hot cores. Astrochemical models still underpredict the abundances of key COMs, such as methyl formate or di-methyl ether, suggesting that our understanding of their formation remains incomplete.Comment: 60 pages, 10 figures, 17 tables. Accepted for publication in Ap

    Comparison of markets for organic food in six EU states.

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    This report was presented at the UK Organic Research 2002 Conference. Recent research confirms that the decision to convert is now highly influenced by financial incentives arising from EU regulations but the exact mix of incentives depends on prevailing government policies and access to premium markets so that the organic sector in most countries is now referred to as either government-led or market-driven. The objective of the paper is to compare development of the sector along these two polarities but set within the context of "common elements of interest" within new agrifood methodologies: time, space, power, and meaning (Cooke, Uranga and Etxebarria 1998; Morgan and Murdoch 2000). The paper presents preliminary findings relating to six EU States: UK, Ireland, Austria, Denmark, Portugal and Italy, and through the application of "worlds of production" to market outlets and suggests discourses that define these outlets. The analysis aims to inform the further study of farmer marketing decisions and practices

    Seismotomography of the crust in the transition zone between the southern Tyrrhenian and Sicilian tectonic domains

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    A crustal tomography of seismic wave velocity was performed in the contact zone between the southern Tyrrhenian, Sicilian and Ionian tectonic units, a zone where the lithospheric structure can be expected to furnish evident signatures of dynamics related to the Tyrrhenian subduction process. A dataset of 10241 P and 5597 S readings from 932 local earthquakes recorded between 1978 and 2001 by stations operating in Sicily and Calabria was inverted by the SIMULPS12 algorithm for simultaneous computation of hypocenter parameters and Vp and Vp/Vs three dimensional distributions. The study brought significant improvement in the knowledge of the local velocity structure, furnishing new information useful to better identify the local tectonic units. The results appear to be compatible with the most recent hypotheses regarding the geodynamics of the study region

    Seismic strain and seismogenic stress regimes in the crust of the southern Tyrrhenian region

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    An investigation has been performed to identify and characterize the seismic deformation zones active over the last decades in the region of Italy that has experienced the strongest seismicity during the last centuries. The study is based on the estimate of hypocenter locations, fault plane solutions, seismogenic stress and seismic strain tensor orientations carried out using the entire dataset of the national and local seismic networks, and the recently improved three-dimensional (3D) crustal velocity model of the study area. A series of simulation tests have been performed to evaluate the significance of the earthquake space distribution obtained and whether it was influenced by network geometry problems related to the sea and the lack of ocean bottom seismometers. In the sectors where hypocentral location was synthetically proved to be reliable, space distributions of earthquakes located with epicenter and focal depth errors less than 3 and 4 km, respectively, have been compared with local geology in order to identify seismogenic faults. The dataset of 32 fault plane solutions estimated with fault parameter errors less than 20° has been used to investigate space variations of seismogenic stress and seismic strain orientations over the study area. Stress was found to be uniform in the Messina Strait and southern Calabria where inversion of the available set of 11 fault plane solutions showed clear evidence of an extensional regime. The different orientations of the minimum compressive stress and strain found in this sector, together with the information available on local geology and tectonics, lead us to propose that the seismicity occurring over the last decades in the Messina Strait and southern Calabria was not in general produced at the main faults, but at minor faults activated by the main tectonic stress field acting in the area. To the west, in the sector including western Etna, the Nebrodi chain and the western Aeolian Islands, analysis of the available set of 16 fault plane solutions revealed a certain degree of stress heterogeneity with an apparent prevalence of north–south compression. This east to west change of stress–strain regimes is evaluated in the light of current hypotheses regarding the geodynamics of the study region

    The IC1396N proto-cluster at a scale of 250 AU

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    We investigate the mm-morphology of IC1396N with unprecedented spatial resolution to analyze its dust and molecular gas properties, and draw comparisons with objects of similar mass. We have carried out sensitive observations in the most extended configurations of the IRAM Plateau de Bure interferometer, to map the thermal dust emission at 3.3 and 1.3mm, and the emission from the JJ=13k→12k_k\to12_k hyperfine transitions of methyl cyanide (CH3_3CN). We unveil the existence of a sub-cluster of hot cores in IC1396N, distributed in a direction perpendicular to the emanating outflow. The cores are embedded in a common envelope of extended and diffuse dust emission. We find striking differences in the dust properties of the cores (ÎČ≃\beta\simeq 0) and the surrounding envelope (ÎČ≃\beta\simeq 1), very likely testifying to differences in the formation and processing of dust material. The CH3_3CN emission peaks towards the most massive hot core and is marginally extended in the outflow direction

    Anatomy of HH 111 from CO observations : a bow shock driven molecular outflow

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    We present millimeter line observations of the HH 111 outflow and its driving source. The molecular gas emission observed with IRAM 30m and the CSO reveals a small condensation of cold and dense gas. The low-velocity outflow has been mapped with the IRAM PdBI interferometer. The cold gas is distributed in a hollow cylinder surrounding the optical jet. The formation of this cavity and its kinematics are well accounted for in the frame of outflow gas entrainment by jet bow shocks. Evidence of gas acceleration is found along the cavity walls, correlated with the presence of optical bow shocks. The cavity has been expanding with a mean velocity of 4 km/s on a timescale of 8700 yr, similar to the dynamical age of the optical jet. The separation of the inner walls reaches 8"-10", which matches the transverse size of the wings in the bow shock. CSO observations of the J=7-6 line show evidence of a high-velocity and hot gas component (T=300-1000 K) with a low filling factor, associated with shocked molecular gas in the jet. [CI] observations are consistent with C-type non-dissociative shocks. Mapping of the high-velocity molecular bullets B1-B3 located beyond the optical jet, with the PdBI, reveals small structures of 3" by 7" flattened perpendicular to the flow direction. They are made of cold gas of moderate density(a few 10^3 cm-3). The bullets appear to expand into the low-density surrounding medium. We conclude that they are probably shocked gas knots resulting from past time-variable ejections in the jet.Comment: 21 pages + 4 figures (JPG). To appear in Astrophysical Journa

    A methodological approach exploiting modern techniques for forest road network planning

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    A well-developed road network allows all forest activities, including wood harvesting, firefighting and recreational activities. However, forest road construction and maintenance involve economic and environmental costs. For these reasons, forest road network planning is a fundamental phase of forest management, maximising the benefits and reducing costs and impacts. Thanks to modern technologies in data collection both for terrestrial and forest characteristics, new methods and tools have been developed to improve and facilitate road planning. The aim of this study was the development of a Decision Support System for helping managers during forest road network planning, exploiting Multi-Criteria Analysis, an Analytic Hierarchy Process and Geographic Information Systems. Three steps characterised the study: Þ an in-depth survey of the existing forest road network Þ an accessibility evaluation, based on a commonly applied Italian definition, taking into account the morphological characteristics of the land Þ an estimation of the accessibility requirements through the analysis of experts’ opinions, defined as Road Needs Index, based on different factors These phases were applied to a forest property located in northern Italy, and some improvements were proposed simulating a manager’s approach during planning. The results showed interesting features in accessibility evaluation, which identified three different classes of accessibility, represented in a map. The estimation of Road Needs Index assigned a class regarding road requirements to each forest management unit: »low«, »medium«, »high« and »very high«. This information was merged, becoming a useful tool to identify the forest areas with the highest problems in relation to the forest road network
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