Search

A review of: - Methodologies, methods and tools used for the construction and evaluation of food ontologies - Integration of food ontologies in real world application to solve real world problems

Ontologies contain an abundance of concepts, are frequently structured as hierarchies, and can cover different domains of knowledge. Polysemous concepts need to be disambiguated for annotation purposes, for example, a concept such as depression has a different meaning in the fields of psychology and economics. In this paper, we introduce the use of the maximum mean discrepancy to indicate whether sets of concepts sharing the same meaning should be merged. This method is a novel approach to ontology maintenance because it provides an objective metric that supports the decision-making of subject matter experts during the concept evaluation process. Our objective is thus to assist ontology maintenance, in particular the organization of concepts, through an analysis framework that gives insights into the polysemy of concepts.

Isolated intra-articular radial head (IARH) fractures in skeletally immature patients represent a rare injury. Despite their initial benign radiologic appearance, these fractures are at risk for progressive radial head subluxation and may end with degenerative irreversible changes of the radiocapitellar joint. The aim of this study is to highlight the seriousness of these injuries and the importance of early diagnosis and a proper follow-up to achieve optimal outcomes.

International audience; The extraction of the relevant and debated opinions from online social media and commercial websites is an emerging task in the opinion mining research field. Its growing relevance is mainly due to the impact of exploiting such techniques in different application domains from social science analysis to personal advertising. In this demo, we present our opinion summary application built on top of an ar-gumentation framework, a standard AI framework whose value is to exchange, communicate and resolve possibly conflicting viewpoints in distributed scenarios. We show how our application is able to extract relevant and debated opinions from a set of documents containing user-generated content from online commercial websites.

International audience; Opinion Mining is a topic which attracted a lot of interest in the last years. By observing the literature, it is often hard to replicate system evaluation due to the unavailability of the data used for the evaluation or to the lack of details about the protocol used in the campaign. In this paper, we propose an evaluation protocol, called DRANZIERA, composed of a multi-domain dataset and guidelines allowing both to evaluate opinion mining systems in different contexts (Closed, Semi-Open, and Open) and to compare them to each other and to a number of baselines.

Text-based and semantics-based methods are both studied intensively as methods for document retrieval. In order to gain insight in the respective merits of these two approaches, we have performed a controlled experiment where we executed a real-life task using both textbased and semantics-based techniques. To maximise the lessons that we could draw about the two approaches, we have performed an experiment where we used the same task (searching papers from the scientific literature needed for updating a medical guideline), the same test-case (updating the 2004 Dutch national breast-cancer guideline), the same gold standard (the updated 2012 Dutch national breast-cancer guideline) and the same corpus (PubMed). We then performed this task using two different methods: retrieving papers based on keywords (text-based approach) and retrieving papers based on semantic annotations (semantics-based approach). Based on this experiment, we discuss the insights that we gained from this dual set of experiments.

Ontologies are considered a necessary ingredient for communication among heterogeneous agents in the Web. With the multiplication of ontologies for the same domains, semantic interoperability has become a challenge. In this work, we study the use of ontology negotiation in a agent communication mechanism for agents with ontological reasoning. The resulting communication mechanism allows agents to exchange not only factual but also terminological knowledge about an individual domain and is closely related to available mechanisms in the literature such as KQML and FIPA-ACL.

Fault surfaces are characterized by an inhomogeneous friction distribution, that can be represented with asperity models. Fault mechanics is dominated by asperities, so that a fruitful approach is to use discrete models, where asperities are the basic elements and the state of the fault is described by the average values of stress, friction and slip on each asperity. Under reasonable assumptions, the equations of motion can be solved analytically, with a deeper understanding of the behavior of the system. Fault dynamics has a sticking mode, where asperities are stationary, and a number of slipping modes, corresponding to the separate or simultaneous motion of asperities. Any seismic event is a sequence of slipping modes and a large variety of source functions is possible. Many large earthquakes are observed to be the consequence of the failure of two asperities: a discrete two-asperity model shows a rich dynamics and allows a detailed study of interaction between asperities. In this framework, fault evolution during coseismic and interseismic intervals can be calculated in terms of fault slip, stress state, energy release and seismic spectrum, including viscoelastic relaxation, fault creep and stress perturbations from other faults. Discrete models may include interaction between neighboring faults, allowing to assess conditions for the occurrence of seismic sequences in a fault system. A review of recent work on this subject is presented with applications to real earthquakes.

SUMMARY There is evidence that magma chambers are not fed by a continuous flow, but in the form of discrete magma batches. The possibility is considered that the chamber is fed by a magma bubble ascending through the region underneath, driven by buoyancy force. Due to the high ambient temperatures, it is assumed that the bubble moves through a viscoelastic medium with temperature-dependent viscosity. The motion of a spherical magma bubble and its inflow into the chamber are studied. The bubble volume is assumed to be at least equal to magma volumes in typical effusive eruptions on Mount Etna, corresponding to bubble radii of a few hundred metres. Under some simplifying assumptions, the problem is solved analytically. The bubble velocity is directly proportional to the square of its radius and inversely to the viscosity of surrounding rocks, but it is independent of magma viscosity. Velocity can reach values of the order of tens of metres per year in the proximity of the chamber. Since the characteristic time for heat diffusion is several hundred years, the bubble can cover several kilometres with only moderate cooling. During ascent, forced convection takes place in the bubble. Equations for convection streamlines are obtained and traveltimes of magma are calculated, giving a mixing time of the order of hundred years below the chamber. Inflow of the bubble in the magma chamber produces a pulse in flow rate. Under reasonable assumptions, pulse shape and duration are calculated analytically. Pulse duration can be several tens of years and can give rise to a sequence of eruptions, depending on the size of the bubble and the critical overpressure for eruption.

SUMMARY Atmospheric shock waves are a common phenomenon in explosive volcanic eruptions. We consider the motion of a spherical shock wave generated by a point source in the strong shock approximation. The shock front corresponds to discontinuities in the gas velocity, density, pressure and temperature, which are calculated as functions of the energy of the explosion. The problem is solved analytically for the distributions of velocity, density, pressure and temperature in the atmosphere as functions of the distance from the source. The motion of the shock wave being supersonic, the solution is valid for a few seconds after the explosion, corresponding to a distance of few kilometres. The acoustic effect of the shock wave, expressed by the peak sound pressure level, is calculated and may reach hundreds of decibels. The pressure waveform that could be recorded in the vicinity of the volcano is calculated and compared with typical waveforms in weak shock conditions. The change in the refractive index of air due to density inhomogeneity is calculated and the conditions under which a condensation cloud is formed behind the shock front are investigated.

The 2010 Maule earthquake was a megathrust event that occurred along the Peru–Chile Trench. The earthquake source can be modelled as a fault with two asperities with different areas and strengths. By employing a discrete fault model, where asperities are the basic elements, the event can be described as a sequence of three dynamic modes involving simultaneous asperity slip. Interaction between asperities by mutual stress transfer plays a crucial role during fault slip. With a careful choice of values for the model parameters, the mode durations, the slip distribution, the seismic moment rate and the final moment calculated from the model are found to be consistent with the observed values. An important amount of frictional heat is produced by an event of this size and is calculated by summing up the contributions of each asperity. The seismic event produces a heat pulse propagating through the Earth’s crust and contributing to the average heat flow in the region. The calculated heat production is equal to about 2×1017 J and the peak value of the heat pulse is equal to 6×10−3 mW m−2 or about 10−4 of the average surface heat flow density, with a characteristic diffusion time in the order of 106 a.

Much information is conveyed within tables, which can be semantically annotated by humans or (semi)automatic approaches. Nevertheless, many applications cannot take full advantage of semantic annotations because of the low quality. A few methodologies exist for the quality assessment of semantic annotation of tabular data, but they do not automatically assess the quality as a multidimensional concept through different quality dimensions. The quality dimensions are implemented in STILTool 2, a web application to automate the quality assessment of the annotations. The evaluation is carried out by comparing the quality of semantic annotations with gold standards. The work presented here has been applied to at least three use cases. The results show that our approach can give us hints about the quality issues and how to address them.

Effusion rate in basaltic eruptions typically depends on time: there is an initial, relatively fast increase followed by a much slower decrease until the eruption vanishes; in addition, changes are observed in the effusion rate having durations much shorter than the total duration of the eruption. For an effusive eruption, we calculate the deformation of the volcanic conduit due to short-term pressure oscillations. The model considers an elliptical conduit embedded in a viscoelastic medium, described by a Maxwell body. As a consequence of pressure oscillations, the semi axes of the conduit are quasi periodic functions of time with the same period as pressure. For volcanic fissures the viscoelastic rheology entails a remarkable increase in oscillation amplitude of flow rate with respect to the elastic case and a time delay in flow rate oscillation with respect to overpressure oscillation. For a given value of overpressure amplitude, this effect is controlled by the conduit eccentricity and the ratio between overpressure period and Maxwell time; for larger values of this ratio and/or for eccentricity values closer to unity, flow rate oscillates around a value larger than its initial value and can vary from 5% to 30% with respect to it. The model can approximate the in-situ observations of short-time fluctuations of flow rate during the 2018 eruption of Kı̄lauea Volcano.

We assume that a magma pulse enters a magma chamber from the plumbing system, producing an overpressure triggering an effusive volcanic eruption. The chamber is modeled as a spherical cavity in an elastic half-space, connected to the Earth's surface by a vertical conduit, and the magma as an incompressible Newtonian liquid. Overpressure in the chamber is calculated as a function of time during the eruption and has different behaviors depending on the characteristics of the magma pulse and of the volcanic system. The time history of effusion rate is controlled by the pulse duration and the geometrical and rheological parameters of the model. The calculated effusion rates are compared with different classes of effusion rates extrapolated from historical data of Mount Etna, which are asymmetric functions of time. For appropriate values of the model parameters, the calculated time histories are found to fit well those derived from observation.

The acceleration of gravity in Earth’s interior is determined by the density distribution in Earth. A remarkable result is that the acceleration is approximately constant all over the mantle, which amounts to about 84% of Earth’s volume. This result can be explained by a simple two-layer model of Earth, showing that the constancy of the acceleration in the mantle is a consequence of the particular size and density of Earth’s core with respect to the size and density of the whole Earth. In other planets, with different mass distributions, the dependence of acceleration on depth could be very different.

The 2018 Gulf of Alaska earthquake (Mw 7.9) occurred in a region of the Pacific plate southwest of the Alaskan subduction zone. The earthquake was a strike-slip event, with the hypocenter located at a depth of about 25 km and a seismic moment equal to 0.96 × 1021 Nm. Two observed moment rates have been obtained by the Geoscope Observatory, France, and by the United States Geological Survey (USGS). Both of them can be interpreted as due to the failure of two asperities on the fault surface. We consider a discrete fault model, with two asperities of different areas and strengths, and show that the observed moment rates can be reproduced by appropriate values of the model parameters, as inferred from the available data. A good fit to the observed moment rates is obtained by a sequence of three dynamic modes of the system, including a phase of simultaneous slip of the asperities. The two moment rates are however characterized by different initial conditions, in terms of different initial shear stress distributions on the fault. Shear stresses on the asperities are calculated as functions of time during the event and show a similar evolution in the two cases, but with different final values. The model results show that the presence of simultaneous asperity motion can significantly increase the seismic moment of a large earthquake.

We consider a thermo-rheological model made of a viscoelastic half-space with Maxwell rheology and temperature-dependent viscosity. The half-space is made of layers with different values of density, thermal conductivity, activation energy and heat productivity. The model relates the surface heat flow to the depth of the brittle-ductile transition and the thickness of the seismogenic layer. The model is applied to the Gargano area (Italy) which is subject to a frequent low-magnitude seismic activity, although it lies out of the Apennine axis, which is the main Italian seismogenic area. The seismic activity in the Gargano area and surroundings occurs at depths that are systematically different in the north-eastern zone with respect to the south-western zone. In correspondence with the change in depth of earthquake foci, we observe a change in the value of surface heat flow. Starting from these observations and from the knowledge of the lithospheric structure, we propose two different geotherms for the two zones. Assuming a constant strain rate, the shear stress is computed as a function of depth and the thickness of the seismogenic layer in the two zones is inferred. The comparison of the results of the thermo-rheological model with the seismological observation is good.

A fault containing two asperities with different strengths is considered. The fault is embedded in a viscoelastic shear zone, subject to a constant strain rate by the motions of adjacent tectonic plates. The fault is modelled as a discrete dynamical system where the average values of stress, friction and slip on each asperity are considered. The state of the fault is described by three variables: the slip deficits of the asperities and the viscoelastic deformation. The system has four dynamic modes, for which the analytical solutions are calculated. The relationship between the state of the fault before a seismic event and the sequence of slipping modes in the event is enlightened. Since the moment rate depends on the number and sequence of slipping modes, the knowledge of the source function of an earthquake constrains the orbit of the system in the phase space. If the source functions of a larger number of consecutive earthquakes were known, the orbit could be constrained more and more and its evolution could be predicted with a smaller uncertainty. The model is applied to the 1964 Alaska earthquake, which was the effect of the failure of two asperities and for which a remarkable postseismic relaxation has been observed in the subsequent decades. The evolution of the system after the 1964 event depends on the state from which the event was originated, that is constrained by the observed moment rate. The possible durations of the interseismic interval and the possible moment rates of the next earthquake are calculated as functions of the initial state.

We study the dynamics of a fault containing two asperities having different strengths and subject to a constant strain rate. The fault is modeled by a discrete dynamical system with two degrees of freedom that are the slip deficits of the asperities. The radiation of elastic waves during the slipping modes is taken into account by introducing a term proportional to slip rate in the equations of motion. We give a complete analytical solution of the four dynamic modes of the system. Any seismic event can be expressed as a sequence of modes, for which the moment rate, the spectrum and the total seismic moment can be calculated. We consider the energy budget of the event and calculate the seismic efficiency. The presence of radiation may remarkably change the evolution of the system from a given state, since it moves the boundaries between the different subsets of the sticking region. In addition, the slip amplitude in a seismic event is smaller, while the slip duration is longer in the presence of radiation. The shape of the moment rate function depends on the seismic efficiency and the seismic moment decreases with increasing efficiency, at constant radiated energy. As an application of the model, we consider the 1964 Great Alaska earthquake and calculate the mode durations, the slip distribution, the moment rate function and the seismic moment of the earthquake, obtaining values that are consistent with observations.