Push & Pull: autonomous deployment of mobile sensors for a complete coverage

Mobile sensor networks are important for several strategic applications devoted to monitoring critical areas. In such hostile scenarios, sensors cannot be deployed manually and are either sent from a safe location or dropped from an aircraft. Mobile devices permit a dynamic deployment reconfiguration that improves the coverage in terms of completeness and uniformity. In this paper we propose a distributed algorithm for the autonomous deployment of mobile sensors called Push&Pull. According to our proposal, movement decisions are made by each sensor on the basis of locally available information and do not require any prior knowledge of the operating conditions or any manual tuning of key parameters. We formally prove that, when a sufficient number of sensors are available, our approach guarantees a complete and uniform coverage. Furthermore, we demonstrate that the algorithm execution always terminates preventing movement oscillations. Numerous simulations show that our algorithm reaches a complete coverage within reasonable time with moderate energy consumption, even when the target area has irregular shapes. Performance comparisons between Push&Pull and one of the most acknowledged algorithms show how the former one can efficiently reach a more uniform and complete coverage under a wide range of working scenarios.Comment: Technical Report. This paper has been published on Wireless Networks, Springer. Animations and the complete code of the proposed algorithm are available for download at the address: http://www.dsi.uniroma1.it/~novella/mobile_sensors

Simplified relationships for estimating seismic slope stability

Eurocode 8 addresses seismic slope stability analysis with reference to limit state design, specifying a 50% re-duction of the peak horizontal inertia force of a potentially sliding mass. Such a coefficient has been shown to depend on several factors, including soil deformability and the frequency content of the seismic action. In this paper the reduction coefficient is expressed with reference to the above factors and compared to EC8 provisions for all soil classes. A simplified design procedure is then suggested by referring to updated correla-tions based on the Newmark sliding block model, including the influence of amplitude, duration and mean pe-riod of the ground motion on the predicted displacement. The reduction coefficient is further generalised to account for the slope ductility, i.e. the capability of sustain prescribed threshold displacements. The whole procedure has been calibrated through analyses carried out using acceleration time histories, selected from a database of records of Italian seismic events, on typical subsoil layering pertaining to the EC8 classes, also adopted by the Italian seismic Code

An Indicator to Evaluate the Environmental Impact of Olive Oil Waste Water's Shedding on Cultivated Fields

Several climatic, soil and topographic factors need to be considered when evaluating the impact of human actions on the environment. Such variables may be related in a complex way to environmental impact, thus making its evaluation difficult. Problems of this type emerge when evaluating the risks olive oil waste water pose to the environment when shed on cultivated soils. This paper proposes a fuzzy expert system to calculate a modular indicator, ICARO, which allows an evaluation of the potential environmental impact of the application of olive oil waste water in a field. Five modules were formulated, one ("Waste water") reflecting the nature of the waste water, two ("Groundwater", "Surface water") reflecting the risk for the most sensitive agro-environmental compartments (groundwater, surface water), one ("Crop") reflecting possible consequences on the cropping system adopted, and one ("Soil") reflecting the soil aptitude to receive waste waters.The input variables are therefore waste water amount and properties, site-specific conditions, and characteristics of the application considered. For each input variable, two functions describing membership to the fuzzy subsets Favorable (F) and Unfavorable (U) have been defined. The expert system calculates the value of each module according to both the degree of membership of the input variables to the subsets F and U, and a set of decision rules. The five modules can be considered individually or can be aggregated (again according to level of membership to fuzzy subsets F and U and a set of decision rules) into the synthetic indicator ICARO. Outcomes of a sensitivity analysis are presented. The system is flexible and can be used as a decision aid tool to authorize waste water's shedding or subordinate the distribution on fields to acceptance of some limitations (amount, timing, site, etc)

Valutazione degli spostamenti permanenti sismoindotti mediante un approccio accoppiato non lineare

Le procedure per valutare lo spostamento che può subire un pendio sotto l’azione sismica tipicamente si riferiscono a tre diverse classi di metodi: 1) relazioni semplificate; 2) metodi degli spostamenti (o analisi dinamica semplificata) e 3) analisi dinamica avanzata. Tali approcci differiscono sostanzialmente dal grado di conoscenza del modello geotecnico del pendio e dell’azione sismica richiesta. In particolare, la seconda classe di metodi presenta un buon compromesso tra la facilità di applicazione, legata a schemi di pendio semplificati, e l’affidabilità dei risultati che rende tali metodi competitivi rispetto alle analisi dinamiche avanzate. I metodi degli spostamenti prendono origine dal modello di blocco rigido di Newmark (1965) e dalla rimozione delle ipotesi che ne stanno alla base. In particolare l’ipotesi stessa di “blocco rigido” può essere rimossa attraverso due approcci: a) approccio “disaccoppiato”, in cui la deformabilità dei terreni che causa la risposta dinamica del sito e gli spostamenti del blocco sono calcolati separatamente o b) approccio “accoppiato” in cui la risposta del sito è valutata contemporaneamente nelle fasi di adesione e scorrimento del pendio. In questa nota, si sintetizzano gli sviluppi del codice ACST, implementato da Ausilio et al. (2008), effettuati nell’ambito del progetto ReLUIS MT 1.2 “Linee guida e codici per analisi di risposta sismica locale”. In particolare, si è introdotta la non linearità nell’analisi della risposta dei terreni attraverso la formulazione modificata dei criteri di Masing secondo la recente formulazione di Phillips & Hashash (2009). Si è, inoltre, implementata una procedura che permette di individuare automaticamente, durante il calcolo, la superficie di scorrimento di prima rottura. I risultati in termini di risposta sismica e spostamenti cumulati sono stati confrontati con quelli ottenuti con la prima versione del codice

Seismic displacement analysis of homogeneous slopes: a review of existing simplified methods with reference to Italian seismicity.

The simplified displacement-based procedures for seismic slope stability represent a good-working balance between simplicity and reliability, since both slope ductility (i.e. the capacity of sustain permanent displacements) and deformability (basically affecting the asynchronous slope motion) are accounted for. In this paper the procedure proposed by Bray & Rathje (1998) is reviewed with particular reference to Italian seismicity on a set of subsoil models, representative of the different soil classes specified by Italian and European codes. The relationship expressing the decrease of the equivalent acceleration with increasing earthquake/soil frequency ratio is then obtained by means of dynamic 1D site response analyses. Statistical correlations between calculated Newmark displacements, significant ground motion parameters and the ratio of seismic load resistance to peak demand are then derived and compared to similar relationships proposed in literature

Parametri di intensità sismica per la stima degli spostamenti permanenti di pendii omogenei

Gli attuali criteri di progettazione in condizioni sismiche si avvalgono di procedure legate alla valutazione della prestazione del sistema espressa in termini di perdite quantificabili (costi di riparazione), di funzionalità o di beni inestimabili (vite umane, beni storico-culturali). In tale ottica il parametro rappresentativo della risposta è correlato attraverso procedure più o meno sofisticate a uno o più parametri che descrivano le caratteristiche del moto sismico. La scelta di tali parametri deve essere effettuata attraverso criteri di efficienza e sufficienza (cfr. p.es. Tothong & Luco, 2007; Luco & Cornell, 2007) inoltre devono poter essere prevedibili attraverso opportune leggi di ricorrenza. In tale ambito, la presente nota propone una applicazione dei criteri citati per la stima della curva di pericolosità degli spostamenti cosismici dei pendii e per la valutazione critica dell’efficienza dei parametri di intensità del moto considerati significativi. In particolare vengono confrontate alcune relazioni indicate nella letteratura nazionale ed internazionale, e viene presentata una relazione che tiene conto dell’intensità di Housner, IH, quale parametro efficace per la stima degli spostamenti. Per la previsione del parametro IH viene proposta, inoltre, una legge di attenuazione in funzione di magnitudo e distanza

A 22-Week-Old Fetus with Nager Syndrome and Congenital Diaphragmatic Hernia due to a Novel SF3B4 Mutation.

Nager syndrome, or acrofacial dysostosis type 1 (AFD1), is a rare multiple malformation syndrome characterized by hypoplasia of first and second branchial arches derivatives and appendicular anomalies with variable involvement of the radial/axial ray. In 2012, AFD1 has been associated with dominant mutations in SF3B4. We report a 22-week-old fetus with AFD1 associated with diaphragmatic hernia due to a previously unreported SF3B4 mutation (c.35-2A>G). Defective diaphragmatic development is a rare manifestation in AFD1 as it is described in only 2 previous cases, with molecular confirmation in 1 of them. Our molecular finding adds a novel pathogenic splicing variant to the SF3B4 mutational spectrum and contributes to defining its prenatal/fetal phenotype

Lapex: A Phoswich balloon experiment for hard X-ray astronomy

Satellite and balloon observations have shown that several classes of celestial objects are hard ( 15 keV) energy band with a sensitivity of approx 10 mCrab has been performed with the UCSD/MIT instrument (A4) on board the HEAO 1 satellite. About 70 X-ray sources were detected, including galactic and extragalactic objects. Hard X-ray emission has been detected in the Galaxy from X-ray pulsars. Extragalactic sources of hard X-ray emission include clusters of galaxies, QSOs, BL Lac objects, Seyfert galaxies. The essential characteristics of the Large Area Phoswich Experiment (LAPEX) for crowded sky field observations are described. It has: (1) a broad energy band of operation (20-300 keV); (2) a 3 sigma sensitivity of about 1 mCrab in 10,000 s of live observing time; and (3) imaging capabilities with an angular resolution of about 20'