A new steplength selection for scaled gradient methods with application to image deblurring

Gradient methods are frequently used in large scale image deblurring problems since they avoid the onerous computation of the Hessian matrix of the objective function. Second order information is typically sought by a clever choice of the steplength parameter defining the descent direction, as in the case of the well-known Barzilai and Borwein rules. In a recent paper, a strategy for the steplength selection approximating the inverse of some eigenvalues of the Hessian matrix has been proposed for gradient methods applied to unconstrained minimization problems. In the quadratic case, this approach is based on a Lanczos process applied every m iterations to the matrix of the most recent m back gradients but the idea can be extended to a general objective function. In this paper we extend this rule to the case of scaled gradient projection methods applied to non-negatively constrained minimization problems, and we test the effectiveness of the proposed strategy in image deblurring problems in both the presence and the absence of an explicit edge-preserving regularization term

On the filtering effect of iterative regularization algorithms for linear least-squares problems

Many real-world applications are addressed through a linear least-squares problem formulation, whose solution is calculated by means of an iterative approach. A huge amount of studies has been carried out in the optimization field to provide the fastest methods for the reconstruction of the solution, involving choices of adaptive parameters and scaling matrices. However, in presence of an ill-conditioned model and real data, the need of a regularized solution instead of the least-squares one changed the point of view in favour of iterative algorithms able to combine a fast execution with a stable behaviour with respect to the restoration error. In this paper we want to analyze some classical and recent gradient approaches for the linear least-squares problem by looking at their way of filtering the singular values, showing in particular the effects of scaling matrices and non-negative constraints in recovering the correct filters of the solution

Estimation of spatial and temporal overlap in three ungulate species in a Mediterranean environment

AbstractInterspecific interactions are key drivers in structuring animal communities. Sympatric animals may show such behavioural patterns as the differential use of space and/or time to avoid competitive encounters. We took advantage of the ecological conditions of our study area, inhabited by different ungulate species, to investigate the spatial and temporal distribution ofCapreolus capreolus,Dama damaandSus scrofa. We estimated intraspecific interaction arising from the concomitant use of resources by using camera trapping. We collected 2741 videos with the three ungulates, which showed peculiar activity patterns. The three species were observed in all the habitat types of the study area over the four seasons, thus highlighting an evident spatial overlap. Moreover, our analysis demonstrated that the three species did not avoid each other through temporal segregation of their activities, rather showing a high overlap of daily activity rhythms, though with differences among the species and the seasons. Despite the high spatial and temporal overlap, the three species seemed to adopt segregation through fine-scale spatial avoidance: at an hourly level, the proportion of sites where the species were observed together was relatively low. This spatio-temporal segregation revealed complex and alternative behavioural strategies, which likely facilitated intra-guild sympatry among the studied species. Both temporal and spatio-temporal overlap reached the highest values in summer, when environmental conditions were more demanding. Given these results, we may presume that different drivers (e.g. temperature, human disturbance), which are likely stronger than interspecific interactions, affected activity rhythms and fine-scale spatial use of the studied species

A comparison of edge-preserving approaches for differential interference contrast microscopy

In this paper we address the problem of estimating the phase from color images acquired with differential-interference-contrast microscopy. In particular, we consider the nonlinear and nonconvex optimization problem obtained by regularizing a least-squares-like discrepancy term with an edge-preserving functional, given by either the hypersurface potential or the total variation one. We investigate the analytical properties of the resulting objective functions, proving the existence of minimum points, and we propose effective optimization tools able to obtain in both the smooth and the nonsmooth case accurate reconstructions with a reduced computational demand

Assessment and analysis of the electromagnetic profile of prototype high-power-charging units for electric vehicles

This science for policy report discusses and analyses the electromagnetic compatibility (EMC) performance of three High-Power-Charging (HPC) columns at their standby based on IEC 61851-21-2 standard. All laboratory setups and results of the tests that are presented on this work were carried out inside VeLA 9 validated EMC semi-anechoic chamber (SAC) at the Joint Research Centre of the European Commission. The results of more than 150 different measured setups on radiated emissions, conducted emissions and radiated immunity are presented and discussed thoroughly. The applicable test methodologies and instrumentation used for the measurements are fully described. EMC troubleshooting techniques were also successfully carried out for some setups, while novel exploratory work, beyond IEC 61851-21-2 was also conducted. The findings and test data on this study can be a reference material to EMC engineers and contribute to the future policy making of the relevant EMC standards.JRC.C.4-Sustainable Transpor

The Virtual Museum of the Tiber Valley Project

[EN] The aim of the Virtual Museum of the Tiber Valley project is the creation of an integrated digital system for the knowledge, valorisation and communication of the cultural landscape, archaeological and naturalistic sites along the Tiber Valley, in the Sabina area between Monte Soratte and the ancient city of Lucus Feroniae (Capena). Virtual reality applications, multimedia contents, together with a web site, are under construction and they will be accessed inside the museums of the territory and in a central museum in Rome. The different stages of work will cover the building of a geo-spatial archaeological database, the reconstruction of the ancient potential landscape and the creation of virtual models of the major archaeological sites. This paper will focus on the methodologies used and on present and future results.[ES] El objetivo del proyecto del Museo Virtual del Valle del Tiber es la creación de un sistema digital integrado para el conocimiento, la valorización y la comunicación del paisaje cultural, arqueológico y natural a lo largo del valle del Tíber, en la zona Sabina entre Monte Soratte y la antigua ciudad de Lucus Feroniae (Capena). Actualmente están en proceso de construcción varias aplicaciones de realidad virtual, contenidos multimedia, junto con un sitio web, a los que se tendrá acceso en diversos museos de la zona así como en un museo central ubicado en Roma. Las diferentes fases de trabajo se centrarán en la construcción de una base de datos arqueológicos geo-espacial, en la reconstrucción del paisaje antiguo y en la creación de los modelos virtuales de los sitios arqueológicos más importantes. Este documento se centra en la metodología utilizada, desgranado los resultados presentes y futuros esperados.Arnoldus Huyzendveld, A.; Di Ioia, M.; Ferdani, D.; Palombini, A.; Sanna, V.; Zanni, S.; Pietroni, E. (2012). The Virtual Museum of the Tiber Valley Project. Virtual Archaeology Review. 3(7):97-101. https://doi.org/10.4995/var.2012.4396OJS9710137ADAM, J.P. (1988): L'arte di costruire presso i romani, Longanesi, Milano.CAMBI, F. (2004): "Le campagne di Falerii e di Capena dopo la romanizzazione", in Bridging the Tiber, London, pp. 75-102.COARELLI, F. (2009): "La romanizzazione della Sabina", in F. Coarelli et alii, "Falacrinae. Le origini di Vespasiano", Roma, pp. 11-17.DI GIUSEPPE, H. (2005): "Villae, villulae e fattorie nella Media Valle del Tevere, in Roman Villas around the Urbs: interaction with landscape and environment", in the Proceedings of a conference held at the Swedish Institute in Rome (September, 17-18, 2004), Roma.GROS, P. & TORELLI, M. (2007): Storia dell'urbanistica. Il mondo romano, Laterza, Roma.MORACHIELLO, P. & FONTANA, V. (2009): L'architettura del mondo romano, Laterza, Roma.PAROTTO, M. (2008): "Evoluzione paleogeografica dell'area romana: una breve sintesi", in Funiciello R., Praturlon A. & Giordano G. (ed) La Geologia di Roma dal centro storico alla periferia. Memorie Descrittive della Carta Geologica d'Italia, LXXX, pp. 25-39.SANTORO, P. (2006): "L'Etruria e i Sabini del Tevere: influenze culturali e commerciali", in Archeologia in Etruria meridionale, atti delle giornate di studio in ricordo di Mario Moretti (Civita Castellana, 14-15 novembre 2003), Roma, pp. 49-64.STERNINI, M. (2004): La Romanizzazione della Sabina Tiberina, Bari.TARQUINI, S., ISOLA, I., FAVALLI, M., MAZZARINI, F., BISSON, M., PARESCHI, M.T., BOSCHI, E. (2007): "TINITALY/01: a new Triangular Irregular Network of Italy", in Annals of Geophysics, nº 50, pp. 407-425.TARQUINI, S., VINCI, S., FAVALLI, M., DOUMAZ, F., FORNACIAI, A., NANNIPIERI, L. (2012): "Release of a 10-m-resolution DEM for the Italian territory: Comparison with global-coverage DEMs and anaglyph-mode exploration via the web", in Computers & Geosciences 38, 168-170. doi: doi:10.1016/j.cageo.2011.04.018. http://dx.doi.org/10.1016/j.cageo.2011.04.018VITRUVIO, De Architectura

A Hardware-in-the-Loop test platform for the performance assessment of a PMU-based Real-Time State Estimator for Active Distribution Networks

The paper describes the development of a Hardware- in-the-Loop (HIL) test platform for the performance assessment of a PMU-based sub-second linear Real-Time State Estimator (RTSE) for Active Distribution Networks (ADNs). The estimator relies on the availability of data coming from Phasor Measurement Units (PMUs) and can be applied to both balanced and unbalanced ADNs. The paper first illustrates the architecture of the experimental HIL setup that has been fully designed by the Authors. It consists of a Real-Time Simulator (RTS) that models the electrical network model as well as the measurement infrastructure composed by virtual PMUs. These virtual devices stream their data to a real Phasor Data Concentrator (PDC) suitably coupled with a Discrete Kalman Filter State Estimator (DKF-SE). By using this experimental setup, the paper discusses the performance assessment of the whole process in terms of estimation accuracy and time latencies. In the RTS, a real ADN located in the Netherlands has been modeled together with the associated PMUs

Fault Detection and Faulted Line Identification in Active Distribution Networks Using Synchrophasors-based Real-Time State Estimation

We intend to prove that PMU-based state estimation processes for active distribution networks exhibit unique time determinism and refresh rate that make them suitable to satisfy the time-critical requirements of protections as well as the accuracy requirements dictated by faulted line identification. In this respect, we propose a real-time fault detection and faulted line identification functionality obtained by computing parallel synchrophasor-based state estimators. Each state estimator is characterized by a different and augmented topology in order to include a floating fault bus. The selection of the state estimator providing the correct solution is done by a metric that computes the sum of the weighted measurement residuals. The proposed process scheme is validated by means of a real-time simulation platform in which an existing active distribution network is simulated together with a PMU-based monitoring system. The proposed process is shown to be suitable for active and passive networks, with solid-earthed and unearthed neutral, for low and high impedance faults of any kind (symmetric and asymmetric) occurring at different locations

Probabilistic assessment of the process-noise covariance matrix of discrete Kalman filter state estimation of active distribution networks

The accuracy of state estimators using the Kalman Filter (KF) is largely influenced by the measurement and the process noise covariance matrices. The former can be directly inferred from the available measurement devices whilst the latter needs to be assessed, as a function of the process model, in order to maximize the KF performances. In this paper we present different approaches that allow assessing the optimal values of the elements composing the process noise covariance matrix within the context of the State Estimation (SE) of Active Distribution Networks (ADNs). In particular, the paper considers a linear SE process based on the availability of synchrophasors measurements. The assessment of the process noise covariance matrix, related to a process model represented by the ARIMA [0,1,0] one, is based either on the knowledge of the probabilistic behavior of nodal network injections/absorptions or on the a-posteriori knowledge of the estimated states and their accuracies. Numerical simulations demonstrating the improvements of the KF-SE accuracy achieved by using the calculated matrix Q are included in the paper. A comparison with the Weighted Least Squares (WLS) method is also given for validation purposes