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Item Asymptotics of degrees and ED degrees of Segre products(Academic Press Inc., 2021-09) Ottaviani, Giorgio; Sodomaco, Luca; Ventura, Emanuele; University of Florence; Department of Mathematics and Systems Analysis; University of BernTwo fundamental invariants attached to a projective variety are its classical algebraic degree and its Euclidean Distance degree (ED degree). In this paper, we study the asymptotic behavior of these two degrees of some Segre products and their dual varieties. We analyze the asymptotics of degrees of (hypercubical) hyperdeterminants, the dual hypersurfaces to Segre varieties. We offer an alternative viewpoint on the stabilization of the ED degree of some Segre varieties. Although this phenomenon was incidentally known from Friedland-Ottaviani's formula expressing the number of singular vector tuples of a general tensor, our approach provides a geometric explanation. Finally, we establish the stabilization of the degree of the dual variety of a Segre product X×Qn, where X is a projective variety and Qn⊂Pn+1 is a smooth quadric hypersurface.Item Bayesian estimation for reliability engineering(Multidisciplinary Digital Publishing Institute (MDPI), 2021-03-24) Leoni, Leonardo; Bahootoroody, Farshad; Khalaj, Saeed; De Carlo, Filippo; Bahootoroody, Ahmad; Abaei, Mohammad Mahdi; University of Florence; University of Parsian; Department of Mechanical Engineering; Delft University of TechnologyOver the last few decades, reliability analysis has attracted significant interest due to its importance in risk and asset integrity management. Meanwhile, Bayesian inference has proven its advantages over other statistical tools, such as maximum likelihood estimation (MLE) and least square estimation (LSE), in estimating the parameters characterizing failure modelling. Indeed, Bayesian inference can incorporate prior beliefs and information into the analysis, which could partially overcome the lack of data. Accordingly, this paper aims to provide a closed-mathematical representation of Bayesian analysis for reliability assessment of industrial components while investigating the effect of the prior choice on future failures predictions. To this end, hierarchical Bayesian modelling (HBM) was tested on three samples with distinct sizes, while five different prior distributions were considered. Moreover, a beta-binomial distribution was adopted to represent the failure behavior of the considered device. The results show that choosing strong informative priors leads to distinct predictions, even if a larger sample size is considered. The outcome of this research could help maintenance engineers and asset managers in integrating their prior beliefs into the reliability estimation process.Item The chaos in calibrating crop models(ELSEVIER SCI LTD, 2021-11) Wallach, Daniel; Palosuo, Taru; Thorburn, Peter; Hochman, Zvi; Gourdain, Emmanuelle; Andrianasolo, Fety; Asseng, Senthold; Basso, Bruno; Buis, Samuel; Crout, Neil; Dibari, Camilla; Dumont, Benjamin; Ferrise, Roberto; Gaiser, Thomas; Garcia, Cecile; Gayler, Sebastian; Ghahramani, Afshin; Hiremath, Santosh; Hoek, Steven; Horan, Heidi; Hoogenboom, Gerrit; Huang, Mingxia; Jabloun, Mohamed; Jansson, Per Erik; Jing, Qi; Justes, Eric; Kersebaum, Kurt Christian; Klosterhalfen, Anne; Launay, Marie; Lewan, Elisabet; Luo, Qunying; Maestrini, Bernardo; Mielenz, Henrike; Moriondo, Marco; Nariman Zadeh, Hasti; Padovan, Gloria; Olesen, Jørgen Eivind; Poyda, Arne; Priesack, Eckart; Pullens, Johannes Wilhelmus Maria; Qian, Budong; Schütze, Niels; Shelia, Vakhtang; Souissi, Amir; Specka, Xenia; Srivastava, Amit Kumar; Stella, Tommaso; Streck, Thilo; Trombi, Giacomo; Wallor, Evelyn; Wang, Jing; Weber, Tobias K.D.; Weihermüller, Lutz; de Wit, Allard; Wöhling, Thomas; Xiao, Liujun; Zhao, Chuang; Zhu, Yan; Seidel, Sabine J.; INRAE; Luke Natural Resources Institute Finland; CSIRO; Arvalis Institut du Végétal; Technical University of Munich; Michigan State University; University of Nottingham; University of Florence; University of Liege; University of Bonn; University of Hohenheim; University of Southern Queensland; Department of Computer Science; Wageningen University and Research Centre; University of Florida; China Agricultural University; KTH Royal Institute of Technology; Ottawa Research and Development Centre; Centre de coopération internationale en recherche agronomique pour le développement (CIRAD); Leibniz Centre for Agricultural Landscape Research; Jülich Research Centre; Swedish University of Agricultural Sciences; Hillridge Technology Pty Ltd; Institute for Crop and Soil Science; CNR-ENEA-EURATOM Association; Aarhus University; Kiel University; Helmholtz Zentrum München - German Research Center for Environmental Health; Technische Universität Dresden; University of Carthage; Nanjing Agricultural UniversityCalibration, the estimation of model parameters based on fitting the model to experimental data, is among the first steps in many applications of process-based models and has an important impact on simulated values. We propose a novel method of developing guidelines for calibration of process-based models, based on development of recommendations for calibration of the phenology component of crop models. The approach was based on a multi-model study, where all teams were provided with the same data and asked to return simulations for the same conditions. All teams were asked to document in detail their calibration approach, including choices with respect to criteria for best parameters, choice of parameters to estimate and software. Based on an analysis of the advantages and disadvantages of the various choices, we propose calibration recommendations that cover a comprehensive list of decisions and that are based on actual practices.Item Degrees of Kalman varieties of tensors(Academic Press Inc., 2023-01-01) Shahidi, Zahra; Sodomaco, Luca; Ventura, Emanuele; University of Florence; Department of Mathematics and Systems Analysis; Polytechnic University of TurinKalman varieties of tensors are algebraic varieties consisting of tensors whose singular vector k-tuples lay on prescribed subvarieties. They were first studied by Ottaviani and Sturmfels in the context of matrices. We extend recent results of Ottaviani and the first author to the partially symmetric setting. We describe a generating function whose coefficients are the degrees of these varieties and we analyze its asymptotics, providing analytic results à la Zeilberger and Pantone. We emphasize the special role of isotropic vectors in the spectral theory of tensors and describe the totally isotropic Kalman variety as a dual variety.Item The distance function from a real algebraic variety(Elsevier, 2020-10) Ottaviani, Giorgio; Sodomaco, Luca; University of Florence; Department of Mathematics and Systems AnalysisFor any (real) algebraic variety X in a Euclidean space V endowed with a nondegenerate quadratic form q, we introduce a polynomial EDpolyX,u(t2) which, for any u∈V, has among its roots the distance from u to X. The degree of EDpolyX,u is the Euclidean Distance degree of X. We prove a duality property when X is a projective variety, namely EDpolyX,u(t2)=EDpolyX∨,u(q(u)−t2) where X∨ is the dual variety of X. When X is transversal to the isotropic quadric Q, we prove that the ED polynomial of X is monic and the zero locus of its lower term is X∪(X∨∩Q)∨.Item Entanglement protection via periodic environment resetting in continuous-time quantum-dynamical processes(2018-10-02) Bullock, Thomas; Cosco, Francesco; Haddara, Marwan; Raja, Sina Hamedani; Kerppo, Oskari; Leppäjärvi, Leevi; Siltanen, Olli; Talarico, N. Walter; De Pasquale, Antonella; Giovannetti, Vittorio; Maniscalco, Sabrina; University of Turku; University of Florence; CNR-ENEA-EURATOM Association; Centre of Excellence in Quantum Technology, QTF; Department of Applied PhysicsThe temporal evolution of entanglement between a noisy system and an ancillary system is analyzed in the context of continuous-time open quantum system dynamics. Focusing on a couple of analytically solvable models for qubit systems, we study how Markovian and non-Markovian characteristics influence the problem, discussing in particular their associated entanglement-breaking regimes. These performances are compared with those one could achieve when the environment of the system is forced to return to its input configuration via periodic instantaneous resetting procedures.Item Metamodeling Servitization: conceptualizations of transition(2013-05) Brax, Saara; Visintin, Filippo; Department of Industrial Engineering and Management; University of Florence; Baines, Tim; Lightfoot, HowardIn this paper we identify three generic conceptualizations of the transition associated with servitization in the literature; the basic continuum model, the continuum with steps, and the model of punctuated stages. Keywords: industrial services, servitization, transition process, integrated solutions, capital goods.Item On risk-based maintenance(Elsevier BV, 2021-09) Leoni, Leonardo; De Carlo, Filippo; Technology, Norwegian University of Science; Sgarbossa, Fabio; BahooToroody, Ahmad; University of Florence; Norwegian University of Science and Technology; Department of Mechanical EngineeringSince gas plants are progressively increasing near urban areas, a comprehensive tool to plan maintenance and reduce the risk arising from their operations is required. To this end, a comparison of three Risk-Based Maintenance methodologies able to point out maintenance priorities for the most critical components, is presented in this paper. Moreover, while the literature is mostly focused on probabilistic analysis, a particular attention is directed towards consequence analysis throughout this study. The first developed technique is characterized by a Hierarchical Bayesian Network to perform the occurrence analysis and a Failure Modes, Effects and Criticality Analysis to assess the magnitude of the adverse outcomes. The second approach is a Quantitative Risk Analysis carried out via a software named Safeti. Finally, another software called Synergi Plant is adopted for the third methodology, which provides a Risk-Based Inspection plan, through a semiquantitative risk analysis. The proposed study can assist asset manager in adopting the most appropriate methodology to their context, while highlighting priority components. To demonstrate the applicability of the approaches and compare their rankings, a Natural Gas Regulating and Measuring Station is considered as case study. The results showed that the most suited method strongly depends on the available data.Item Reliability Estimation under Scarcity of Data: A Comparison of Three Approaches(Hindawi Publishing Corporation, 2021-03-20) Leoni, Leonardo; Cantini, Alessandra; Bahootoroody, Farshad; Khalaj, Saeed; De Carlo, Filippo; Abaei, Mohammad Mahdi; BahooToroody, Ahmad; University of Florence; University of Parsian; Delft University of Technology; Marine Technology; Department of Mechanical EngineeringDuring the last decades, the optimization of the maintenance plan in process plants has lured the attention of many researchers due to its vital role in assuring the safety of operations. Within the process of scheduling maintenance activities, one of the most significant challenges is estimating the reliability of the involved systems, especially in case of data scarcity. Overestimating the average time between two consecutive failures of an individual component could compromise safety, while an underestimate leads to an increase of operational costs. Thus, a reliable tool able to determine the parameters of failure modelling with high accuracy when few data are available would be welcome. For this purpose, this paper aims at comparing the implementation of three practical estimation frameworks in case of sparse data to point out the most efficient approach. Hierarchical Bayesian modelling (HBM), maximum likelihood estimation (MLE), and least square estimation (LSE) are applied on data generated by a simulated stochastic process of a natural gas regulating and metering station (NGRMS), which was adopted as a case of study. The results identify the Bayesian methodology as the most accurate for predicting the failure rate of the considered devices, especially for the equipment characterized by less data available. The outcomes of this research will assist maintenance engineers and asset managers in choosing the optimal approach to conduct reliability analysis either when sufficient data or limited data are observed.Item Scale coding bag of deep features for human attribute and action recognition(2017) Khan, Fahad Shahbaz; van de Weijer, Joost; Anwer, Rao Muhammad; Bagdanov, Andrew D.; Felsberg, Michael; Laaksonen, Jorma; Linköping University; Autonomous University of Barcelona; Department of Computer Science; University of FlorenceMost approaches to human attribute and action recognition in still images are based on image representation in which multi-scale local features are pooled across scale into a single, scale-invariant encoding. Both in bag-of-words and the recently popular representations based on convolutional neural networks, local features are computed at multiple scales. However, these multi-scale convolutional features are pooled into a single scale-invariant representation. We argue that entirely scale-invariant image representations are sub-optimal and investigate approaches to scale coding within a bag of deep features framework. Our approach encodes multi-scale information explicitly during the image encoding stage. We propose two strategies to encode multi-scale information explicitly in the final image representation. We validate our two scale coding techniques on five datasets: Willow, PASCAL VOC 2010, PASCAL VOC 2012, Stanford-40 and Human Attributes (HAT-27). On all datasets, the proposed scale coding approaches outperform both the scale-invariant method and the standard deep features of the same network. Further, combining our scale coding approaches with standard deep features leads to consistent improvement over the state of the art.Item The span of singular tuples of a tensor beyond the boundary format(Academic Press, 2024-01-01) Sodomaco, Luca; Teixeira Turatti, Ettore; Department of Mathematics and Systems Analysis; University of Florence; Department of Mathematics and Systems AnalysisA singular k-tuple of a tensor T of format (n1,…,nk) is essentially a complex critical point of the distance function from T constrained to the cone of tensors of format (n1,…,nk) of rank at most one. A generic tensor has finitely many complex singular k-tuples, and their number depends only on the tensor format. Furthermore, if we fix the first k−1 dimensions ni, then the number of singular k-tuples of a generic tensor becomes a monotone non-decreasing function in one integer variable nk, that stabilizes when (n1,…,nk) reaches a boundary format. In this paper, we study the linear span of singular k-tuples of a generic tensor. Its dimension also depends only on the tensor format. In particular, we concentrate on special order three tensors and order-k tensors of format (2,…,2,n). As a consequence, if again we fix the first k−1 dimensions ni and let nk increase, we show that in these special formats, the dimension of the linear span stabilizes as well, but at some concise non-sub-boundary format. We conjecturethat this phenomenon holds for an arbitrary format with k>3. Finally, we provide equations for the linear span of singular triples of a generic order three tensor T of some special non-sub-boundary format. From these equations, we conclude that T belongs to the linear span of its singular triples, and we conjecture that this is the case for every tensor format.Item Time and classical equations of motion from quantum entanglement via the Page and Wootters mechanism with generalized coherent states(Nature Publishing Group, 2021-12) Foti, Caterina; Coppo, Alessandro; Barni, Giulio; Cuccoli, Alessandro; Verrucchi, Paola; Department of Applied Physics; University of FlorenceWe draw a picture of physical systems that allows us to recognize what “time” is by requiring consistency with the way that time enters the fundamental laws of Physics. Elements of the picture are two non-interacting and yet entangled quantum systems, one of which acting as a clock. The setting is based on the Page and Wootters mechanism, with tools from large-N quantum approaches. Starting from an overall quantum description, we first take the classical limit of the clock only, and then of the clock and the evolving system altogether; we thus derive the Schrödinger equation in the first case, and the Hamilton equations of motion in the second. This work shows that there is not a “quantum time”, possibly opposed to a “classical” one; there is only one time, and it is a manifestation of entanglement.