10,213 research outputs found

    Consensus-based control for a network of diffusion PDEs with boundary local interaction

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    In this paper the problem of driving the state of a network of identical agents, modeled by boundary-controlled heat equations, towards a common steady-state profile is addressed. Decentralized consensus protocols are proposed to address two distinct problems. The first problem is that of steering the states of all agents towards the same constant steady-state profile which corresponds to the spatial average of the agents initial condition. A linear local interaction rule addressing this requirement is given. The second problem deals with the case where the controlled boundaries of the agents dynamics are corrupted by additive persistent disturbances. To achieve synchronization between agents, while completely rejecting the effect of the boundary disturbances, a nonlinear sliding-mode based consensus protocol is proposed. Performance of the proposed local interaction rules are analyzed by applying a Lyapunov-based approach. Simulation results are presented to support the effectiveness of the proposed algorithms

    Measurement of the production cross-section ratio of the charmonium states χc2 and χc1 in proton-proton collisions at 7TeV with CMS

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    This paper presents the observation of the χc resonances and the techniques for the measurement of the σ(pp → χc2 + X)/σ(pp → χc1 + X) ratio with the CMS detector at LHC. The measurement was performed with 4.0 fb−1 of pp collisions at √s = 7TeV collected in 2011. The χc mesons are observed through their radiative decay χc → J/ψ γ. The J/ψ were reconstructed through their μ+μ− decay while the photons were reconstructed through conversions in e+e− pairs in the CMS inner tracker. The kinematic range covered is |yJ/ψ| 0.5 GeV. Thanks to the excellent performance of the CMS tracking system, a very good separation between the two resonances is achieved

    Recent finding and new technologies in nephrolithiasis: a review of the recent literature

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    This review summarizes recent literature on advances regarding renal and ureteral calculi, with particular focus in areas of recent advances in the overall field of urolithiasis. Clinical management in everyday practice requires a complete understanding of the issues regarding metabolic evaluation and subgrouping of stone-forming patients, diagnostic procedures, effective treatment regime in acute stone colic, medical expulsive therapy, and active stone removal. In this review we focus on new perspectives in managing nephrolitihiasis and discuss recentadvances, including medical expulsive therapy, new technologies, and refinements of classical therapy such as shock wave lithotripsy, give a fundamental modification of nephrolithiasis management. Overall, this field appears to be the most promising, capable of new developments in ureterorenoscopy and percutaneous approaches. Further improvements are expected from robotic-assisted procedures, such as flexible robotics in ureterorenoscopy

    Un insediamento di età eneolitica nella Sardegna centro-occidentale: il villaggio di cultura Monte Claro nel sito di Cuccurada, Mogoro (OR)

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    Nel sito archeologico di Cuccurada, in comune di Mogoro, è stato posto in luce, a partire dagli anni ’90 del secolo scorso, un vasto insediamento pluristratificato che ha restituito varie fasi di occupazione preistorica e protostorica dal Neolitico Recente (cultura di Ozieri), passando dall’Eneolitico (cultura di Monte Claro) sino alle Età del Bronzo e del Ferro, con momenti di rioccupazione più tarda di epoca romana e medievale. In questo lavoro si espone in dettaglio la fase insediativa di età eneolitica, a cui sono riferibili resti monumentali e manufatti pertinenti alla cultura di Monte Claro. Si presentano inediti dati stratigrafici, materiali ceramici e spunti di analisi sulla cultura Monte Claro in questa zona della Sardegna centro-occidentale.In the archaeological site of Cuccurada, in municipality of Mogoro, the research has revealed, since the 90s of the last century, a large pluristratified settlement. Various phases of prehistoric and protohistoric occupation have been recognized, from recent Neolithic (Ozieri culture), with evidences ofCopper Age (Monte Claro culture), up to the Bronze Age and Iron Age; the site was later reoccupied in Roman and medieval age. In this work we expose in detail the settlement phase of the Copper Age, to which monumental remains and artifacts pertinent to the Monte Claro culture are referable. We present unpublished stratigraphical data, ceramic materials and new elements ofanalysis about the cultural phase ofMonte Claro in this zone ofcentral-western Sardinia

    Fasi finali e riutilizzo di età storica nel Nuraghe Cuccurada di Mogoro (OR)

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    Nel sito archeologico in località Cuccurada, in territorio comunale di Mogoro, le ricerche hanno evidenziato un insediamento pluristratificato, con fasi di occupazione del Neolitico recente (cultura di Ozieri), dell’Eneolitico (cultura di Monte Claro) e delle Età del Bronzo e del Ferro, con un riutilizzo dell’area in epoca romana e medievale. Il complesso è già abbastanza noto in letteratura, ma ancora parzialmente inedito per quanto riguarda i materiali e i dati di scavo. Nel presente contributo si vuole presentare nel dettaglio le diverse fasi di occupazione del sito, soprattutto in relazione ai momenti finali della frequentazione protostorica (Bronzo Finale/I Ferro) ed alla rioccupazione del complesso in età romana e medievale.In the archaeological site of Cuccurada, in the territory of Mogoro, the researches have evidenced a pluristratified settlement, with phases of occupation of the recent Neolithic (culture of Ozieri), of the Eneolithic age (culture of Monte Claro) and of the Bronze and Iron Ages, with a re-use of the area in roman and medieval period. The complex is already enough famous in literature, but still partially unknown regarding the materials and the excavation data. In the present work we want to present in detail the different occupation phases of the site, especially in relationship to the final moments of the proto-historic frequentation (Final Bronze/I Iron Age) and to the last re-use of the complex in Roman and medieval age

    Combined Backstepping/Second-Order Sliding-Mode Boundary Stabilization of an Unstable Reaction-Diffusion Process

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    In this letter we deal with a class of open-loop unstable reaction-diffusion PDEs with boundary control and Robin-type boundary conditions. A second-order sliding mode algorithm is employed along with the backstepping method to asymptotically stabilize the controlled plant while providing at the same time the rejection of an external persistent boundary disturbance. A constructive Lyapunov analysis supports the presented synthesis, and simulation results are presented to validate the developed approach

    Robust distributed secondary voltage restoration control of ac microgrids under multiple communication delays

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    This paper focuses on the robust distributed secondary voltage restoration control of AC microgrids (MGs) under multiple communication delays and nonlinear model uncertainties. The problem is addressed in a multi-agent fashion where the generators’ local controllers play the role of cooperative agents communicating over a network and where electrical couplings among generators are interpreted as disturbances to be rejected. Communications are considered to be affected by heterogeneous network-induced time-varying delays with given upper-bounds and the MG is subjected to nonlinear model uncertainties and abrupt changes in the operating working condition. Robustness against uncertainties is achieved by means of an integral sliding mode control term embedded in the control protocol. Then, the global voltage restoration stability, despite the communication delays, is demonstrated through a Lyapunov-Krasovskii analysis. Given the delays’ bounds, and because the resulting stability conditions result in being non-convex with respect to the controller gain, then a relaxed linear matrix inequalities-based tuning criteria is developed to maximize the controller tuning, thus minimizing the restoration settling-time. By means of that, a criteria to estimate the maximal delay margin tolerated by the system is also provided. Finally, simulations on a faithful nonlinear MG model, showing the effectiveness of the proposed control strategy, are further discussed

    A Sliding Mode Observer design for the Average State Estimation in Large-Scale Systems

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    In this letter the average state estimation problem on a large-scale system with only few gateway nodes available for measurements is solved as the design problem of a reduced-order sliding mode observer subjected to unmatched perturbations. Necessary and sufficient conditions to guarantee the exact estimation are derived. Still, even in the case such conditions are not fulfilled, the boundedness of the estimation error is proved. Finally, a criteria to minimize such bound, and a gain adaptation law to trade-off that bound and its convergence rate are provided. Neither the observer complexity nor the estimation error depend explicitly on the size of the system, thus making the approach scalable and computationally tractable. Simulations supporting the effectiveness of the proposed strategy and a comparison with other existing strategies are also provided

    A device to characterize optical fibres

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    ATLAS is a general purpose experiment approved for the LHC collider at CERN. An important component of the detector is the central hadronic calorimeter; for its construction more than 600,000 Wave Length Shifting (WLS) fibres (corresponding to a total length of 1,120 Km) have been used. We have built and put into operation a dedicated instrument for the measurement of light yield and attenuation length over groups of 20 fibres at a time. The overall accuracy achieved in the measurement of light yield (attenuation length) is 1.5% (3%). We also report the results obtained using this method in the quality control of a large sample of fibres.Comment: 17 pages 20 figeres submitted to NIM journa
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