Conformant Planning via Symbolic Model Checking

We tackle the problem of planning in nondeterministic domains, by presenting a new approach to conformant planning. Conformant planning is the problem of finding a sequence of actions that is guaranteed to achieve the goal despite the nondeterminism of the domain. Our approach is based on the representation of the planning domain as a finite state automaton. We use Symbolic Model Checking techniques, in particular Binary Decision Diagrams, to compactly represent and efficiently search the automaton. In this paper we make the following contributions. First, we present a general planning algorithm for conformant planning, which applies to fully nondeterministic domains, with uncertainty in the initial condition and in action effects. The algorithm is based on a breadth-first, backward search, and returns conformant plans of minimal length, if a solution to the planning problem exists, otherwise it terminates concluding that the problem admits no conformant solution. Second, we provide a symbolic representation of the search space based on Binary Decision Diagrams (BDDs), which is the basis for search techniques derived from symbolic model checking. The symbolic representation makes it possible to analyze potentially large sets of states and transitions in a single computation step, thus providing for an efficient implementation. Third, we present CMBP (Conformant Model Based Planner), an efficient implementation of the data structures and algorithm described above, directly based on BDD manipulations, which allows for a compact representation of the search layers and an efficient implementation of the search steps. Finally, we present an experimental comparison of our approach with the state-of-the-art conformant planners CGP, QBFPLAN and GPT. Our analysis includes all the planning problems from the distribution packages of these systems, plus other problems defined to stress a number of specific factors. Our approach appears to be the most effective: CMBP is strictly more expressive than QBFPLAN and CGP and, in all the problems where a comparison is possible, CMBP outperforms its competitors, sometimes by orders of magnitude

Extraction of the beam elastic shape from uncertain FBG strain measurement points

Aim of the present paper is the analysis of the strain along the beam that is equipped with Glass Fibers Reinforced Polymers (GFRP) with an embedded set of optical Fiber Bragg Grating sensors (FBG), in the context of a project to equip with these new structural elements an Italian train bridge. Different problems are attacked, and namely: (i)during the production process [1] it is difficult to locate precisely the FBG along the reinforcement bar, therefore the following question appears: How can we associate the strain measurements to the points along the bar? Is it possible to create a signal analysis procedure such that this correspondence is found?(ii)the beam can be inflected and besides the strain at some points, we would like to recover the elastic shape of the deformed beam that is equipped with the reinforcement bars. Which signal processing do we use to determine the shape of the deformed beam in its inflection plane?(iii)if the beam is spatially inflected, in two orthogonal planes, is it possible to recover the beam spatial elastic shape? Object of the paper is to answer to these questions

Palaeobiology of Pliocene-Pleistocene shallow-water biocalcarenites (Northern Apennines, Italy) and their relationship with coeval sapropels

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cau, S., Roveri, M., & Taviani, M. Palaeobiology of Pliocene-Pleistocene shallow-water biocalcarenites (Northern Apennines, Italy) and their relationship with coeval sapropels. Bollettino Della Societa Paleontologica Italiana, 59(1), (2020): 25-40, doi:10.4435/BSPI.2020.04.The interplay between carbonate and siliciclastic sediment production in shallow marine environments may result in the development of mixed depositional systems showing a cyclical arrangement of sedimentary facies. The palaeoenvironmental record associated with these cyclical facies changes is not always univocally correlated with eustatic oscillations, suggesting that other forcing processes have played an additional role. The Castell’Arquato Basin (CAB: Pliocene-Pleistocene, Northern Apennines, Italy) offers the opportunity to integrate the study of small and large-scale stratigraphic architectures with that of shell beds in shelf to deep-water successions. The analysis of diversity trends allows a first insight into the structure of CAB benthic communities associated with minor and major biocalcarenites. Biofacies types are identified through a multivariate analysis of a large quantitative database including shells of all molluscs, serpulids and brachiopods. The study shows that these bio-detrital deposits and their bracketing marine mudstones developed at inner-shelf settings and that taphonomic feedback played an important role in the stratigraphic distribution of biofacies. Benthic communities from shelly bottoms depend on the winnowing of fines by bottom currents, a factor that is not related to water depth in a simple manner. Heterogeneity of the seafloor is associated to high-diversity of communities of topset strata of major biocalcarenites. Communities living in siliciclastic bottoms depend on factors that are largely depth-dependant. The study confirms the correlation of major biocalcarenite cycles with coeval deep-water sapropels, supporting the hypothesis of a more effective role of high-amplitude climatic changes driven by orbital forcing. This affects the source-to-sink dynamics of the whole basin and the biological structuring processes of shelfal depositional settings and related ecosystems.Thanks to Stefano Dominici (Museo di Storia Naturale, Università di Firenze) for his review and editorial handling. Ronald Nalin (Loma Linda University, California, USA) and an anonymous reviewer are acknowledged for their constructive comments and suggestions that improved an early version of the paper. We thank Alessandro Freschi, Gianluca Raineri (Riserva Geologica del Piacenziano e dello Stirone) and Carlo Francou (Museo Geopaleontologico “G. Cortesi”, Castell’Arquato) for their assistance with sample collection. This is ISMAR CNR, Bologna, scientific contribution n. 1950

On line estimation of rolling resistance for intelligent tires

The analysis of a rolling tire is a complex problem of nonlinear elasticity. Although in the technical literature some tire models have been presented, the phenomena involved in the tire rolling are far to be completely understood. In particular, small knowledge comes even from experimental direct observation of the rolling tire, in terms of dynamic contact patch, instantaneous dissipation due to rubber-road friction and hysteretic behavior of the tire structure, and instantaneous grip. This paper illustrates in details a new powerful technology that the research group has developed in the context of the project OPTYRE. A new wireless optical system based on Fiber Bragg Grating strain sensors permits a direct observation of the inner tire stress when rolling in real conditions on the road. From this information, following a new suitably developed tire model, it is possible to identify the instant area of the contact patch, the grip conditions as well the instant dissipation, which is the object of the present work

Energy exchange between nonlinear oscillators: An entropy foundation

In the field of vibrations of complex structures, energy methods like SEA and a series of mid-frequency methods, represent an important resource for computational analysis. All these methods are based in general on a linear formulation of the elastic problem. However, when nonlinearities are present, for example related to clearance or stiffening of joints, these methods, in principle, cannot be applied. This paper, on the basis of a theory presented recently by one of the authors, proposes a foundation of a new energy method able to deal with nonlinearities when studying the energy exchange between subsystems. The idea relies on the concept of a thermodynamic vibroacoustic temperature, that can be directly defined when introducing the entropy of a vibrating structure. The theory is introduced in general, and examples of calculation of the power flow between nonlinear resonators are presented introducing stiffening and clearences for systems with many degrees of freedom

Prototyping a new car semi-active suspension by variational feedback controller

New suspension systems electronically controlled are presented and mounted on board of a real car. The system consists of variable semi-active magneto-rheological dampers that are controlled through an electronic unit that is designed on the basis of a new optimal theoretical control, named VFC-Variational Feedback Controller. The system has been mounted on board of a BMW Series 1 car, and a set of experimental tests have been conducted in real driving conditions. The VFC reveals, because of its design strategy, to be able to enhance simultaneously both the comfort performance as well as the handling capability of the car. Preliminary comparisons with several industrially control methods adopted in the automotive field, among them skyhook and groundhook, show excellent results

Change Detection in Multivariate Datastreams: Likelihood and Detectability Loss

We address the problem of detecting changes in multivariate datastreams, and we investigate the intrinsic difficulty that change-detection methods have to face when the data dimension scales. In particular, we consider a general approach where changes are detected by comparing the distribution of the log-likelihood of the datastream over different time windows. Despite the fact that this approach constitutes the frame of several change-detection methods, its effectiveness when data dimension scales has never been investigated, which is indeed the goal of our paper. We show that the magnitude of the change can be naturally measured by the symmetric Kullback-Leibler divergence between the pre- and post-change distributions, and that the detectability of a change of a given magnitude worsens when the data dimension increases. This problem, which we refer to as \emph{detectability loss}, is due to the linear relationship between the variance of the log-likelihood and the data dimension. We analytically derive the detectability loss on Gaussian-distributed datastreams, and empirically demonstrate that this problem holds also on real-world datasets and that can be harmful even at low data-dimensions (say, 10)

A multisensing setup for the intelligent tire monitoring

The present paper offers the chance to experimentally measure, for the first time, the internal tire strain by optical fiber sensors during the tire rolling in real operating conditions. The phenomena that take place during the tire rolling are in fact far from being completely understood. Despite several models available in the technical literature, there is not a correspondently large set of experimental observations. The paper includes the detailed description of the new multi-sensing technology for an ongoing vehicle measurement, which the research group has developed in the context of the project OPTYRE. The experimental apparatus is mainly based on the use of optical fibers with embedded Fiber Bragg Gratings sensors for the acquisition of the circumferential tire strain. Other sensors are also installed on the tire, such as a phonic wheel, a uniaxial accelerometer, and a dynamic temperature sensor. The acquired information is used as input variables in dedicated algorithms that allow the identification of key parameters, such as the dynamic contact patch, instantaneous dissipation and instantaneous grip. The OPTYRE project brings a contribution into the field of experimental grip monitoring of wheeled vehicles, with implications both on passive and active safety characteristics of cars and motorbikes

An integrated environmental assessment of the water and sediments from the coastal areas of Guarujá, São Paulo, Brazil: a physico-chemical, biological and ecotoxicological approach

O município de Guarujá, litoral do Estado de São Paulo, Brasil, considerado um dos principais destinos turísticos brasileiros, possui uma sub-bacia hidrográfica sob forte pressão antrópica. Isto ocorre porque embora possua uma área de drenagem de aproximadamente 143 km², cerca de 107 km² são áreas ambientalmente protegidas e, portanto, 316.000 habitantes se concentram em uma pequena fração territorial (correspondente a 36 km2). Durante o verão, quando o turismo intensifica, a população chega a duplicar. Em decorrência deste forte adensamento populacional e da ausência de planeamento urbano, Guarujá sofre há décadas com problemas socioambientais e de infraestrutura urbana, principalmente porque mais de 64.000 moradores habitam áreas de favelas (principalmente nos bairros da Enseada e do Perequê) e, portanto, não possuem saneamento básico. Desta forma, embora a rede de coleta e tratamento de esgotos municipal esteja dimensionada para uma população de 450.000 habitantes, o destino dos esgotos clandestinos destas favelas acaba sendo os 43 canais artificiais de drenagem urbana, que descarregam uma mistura complexa (composta por esgoto doméstico e carga difusa urbana) diretamente para as praias do município e, portanto, podendo comprometer a saúde pública e ambiental de Guarujá. Embora avaliar a qualidade balnear, se mostre emergencial no Guarujá, estes estudos ainda são escassos no município. Diante deste cenário, o objetivo geral desta tese foi avaliar a qualidade da água e do sedimento nos canais de drenagem urbana localizados em quatro diferentes praias do Guarujá: Tombo (certificada com Bandeira Azul), Enseada (com alta visitação turística), Perequê (habitada por uma comunidade pesqueira) e Iporanga (localizada numa unidade de conservação). Além destes quatro canais, foi investigada a coluna de água e o sedimento da zona de mistura do emissário oceânico submarino, cujo esgoto municipal passa por um tratamento preliminar em terra. Para atender a estes objetivos, amostras mensais foram obtidas no período entre outubro de 2017 a agosto de 2018, e trinta e oito variáveis ambientais selecionadas (físicas, químicas, biológicas e ecotóxicológicas), juntamente com vinte e três compostos farmacêuticos de diferentes classes terapêuticas, foram analisados utilizando testes estatísticos padrão e/ou diferentes índices de qualidade da água. Nos canais de drenagem urbana, os resultados mais expressivos obtidos desta tese, foram: (i) há evidenciais de que os canais do Guarujá são importantes veículos de transporte de poluentes convencionais e emergentes para o Oceano Atlântico Sul; (ii) áreas com déficit de saneamento (principalmente na Enseada e Perequê), juntamente com o período de maior afluência turística (verão brasileiro/período chuvoso), foram fatores que potencializaram a piora da qualidade da água; (iii) de maneira geral, a melhor qualidade da água foi registrada em Iporanga (mais de 90% em conformidade com a legislação brasileira); (iv) os canais do Tombo, Enseada e Perequê foram classificados como muito ruins (apenas 34-43% em conformidade com a legislação vigente) e, como consequência, altas concentrações das bactérias Escherichia coli e Enterococcus ssp foram detectadas nestes canais. Além disso, a presença de mastadenovírus humanos (espécies C, D e F) na Enseada e Perequê, também foram importantes descobertas, potencialmente preocupantes para a saúde pública local; (v) táxons da macrofauna bentônica, tolerantes à poluição orgânica, foram inventariados no sedimento adjacente aos canais (por exemplo, Oligochaeta, Ceratopogonidae, Chironomidae e Chironomus); (vi) dezasseis compostos farmacêuticos foram detectados, sendo que cinco deles (cafeína, acetaminofeno, diclofenaco, valsartan e losartan), indicaram riscos escológicos moderados a altos para algas, crustáceos e/ou peixes; e (vii) toda esta complexa mistura de poluentes dos canais, indicaram uma alta toxicidade aguda e crônica para os microcrustáceos Daphnia simillis e Ceriodaphnia dúbia, respectivamente. Já na descarga marinha de esgotos, os resultados mais importantes, na coluna de água, foram: (i) das trinta e três variáveis fisicoquímicas e bacteriológicas analisadas, nove não atenderam à legislação vigente e, portanto, a água foi classificada como de qualidade regular; (ii) dez compostos farmacêuticos foram detectados, sendo que três deles (cafeína, diclofenaco e acetaminofeno), indicaram riscos baixos a moderados para algas, crustáceos e/ou peixes. Já nos sedimentos, as baixas concentrações de seis metais pesados, a boa representatividade de anfípodes e poliquetas (dentre os vinte e cinco táxons bentônicos inventariados), além da ausência de toxicidade aguda para o tanaidaceo Kalliapseudes schubartii, indicaram sedimentos pouco poluídos. Com a evidência da forte interferência antrópica na qualidade da água do Guarujá, melhorias em benefício da saúde pública e da proteção dos sistemas ecológicos (fundamentadas em boas práticas internacionais e na legislação brasileira vigente) foram sugeridas, como sejam: (i) programas de educação e conscientização ambiental; (ii) programas de recolhimento de resíduos de medicamentos; (iii) manutenção de vias públicas; (iv) fiscalização das ligações clandestinas de esgotos no bairro do Tombo; (v) regularização fundiária das favelas da Enseada e do Perequê; (vi) instalação de um sistema de comporta, interceptor oceânico e barreiras de conteção nos canais de drenagem. E por fim, foi sugerida a modernização do sistema de tratamento de esgotos do município, através da instalação de um tratamento, no mínimo, com um nível secundário.The municipality of Guarujá, on the coast of the State of São Paulo, Brazil, considered one of the main tourist destinations in Brazil, has a sub-basin under strong anthropic pressure. This occurs because although it has a drainage area of approximately 143 km², about 107 km² are environmentally protected areas and, therefore, 316,000 inhabitants are concentrated in a small territorial fraction (corresponding to 36 km2). During the summer, when tourism intensifies, the population almost doubles. As a result of this high-population density and absence of urban planning, Guarujá has suffered for decades from socio-environmental and urban infrastructure problems, mainly because more than 64,000 residents live in slum areas (locally named “favelas”, mainly in the Enseada and Perequê neighbourhoods) and therefore do not have basic sanitation. Thus, although the municipal sewage collection and treatment network is sized for a population of 450,000 inhabitants, the destination of clandestine sewage from the “favelas” ends up on the 43 artificial urban drainage channels, which drain a complex mixture (composed of domestic sewage and urban diffuse load) directly to the beaches of the municipality and, therefore, may compromise the public and environmental health of Guarujá. Although the assessment of the bathing water quality is a priority in Guarujá, these studies are scarce in the municipality. In this scenario, the general objective of this thesis was to evaluate the water and sediment quality in urban drainage channels located in four different beaches of Guarujá: Tombo (Blue Flag certified), Enseada (high tourist visitation), Perequê (inhabited by a fishing community) and Iporanga (located in a conservation unit). In addition to these four channels, the water column and the sediment of the mixing zone of the submarine ocean outfall, whose municipal sewage undergoes preliminary treatment on land, were investigated. To meet these objectives, monthly samples were obtained during the period from October 2017 to August 2018, and thirty-eight selected environmental variables (physical, chemical, biological and ecotoxicological), together with the twenty-three pharmaceutical compounds of different therapeutic classes, were analysed using standard statistical tests and/or different water quality indices. In the urban drainage channels, the most expressive results obtained from this thesis, were: (i) there is evidence that the channels of Guarujá are important vehicles for the transport of conventional and emerging pollutants to the South Atlantic Ocean; (ii) areas with sanitation deficit (mainly in Enseada and Perequê), together with the period of greatest tourist affluence (Brazilian summer/rainy season), were factors that potentiated the worsening of water quality; (iii) in general, the best water quality was recorded at Iporanga (more than 90% of compliance with the Brazilian legislation); (iv) the Tombo, Enseada and Perequê channels were classified as very bad (only 34-43% of compliance with the current legislation) and, as a consequence, high concentrations of the bacteria Escherichia coli and Enterococcus ssp were detected in these channels. Furthermore, the presence of human mastadenovirus (species C, D and F) in Enseada and Perequê were also important findings, and raises great concern for local public health; (v) benthic macrofauna taxa, tolerant to organic pollution, were inventoried in the sediment adjacent to the channels (e.g. Oligochaeta, Ceratopogonidae, Chironomidae and Chironomus); (vi) sixteen pharmaceutical compounds were detected, five of which (caffeine, acetaminophen, diclofenac, valsartan and losartan), indicated a moderate to high ecological risks to algae, crustaceans and/or fish; and (vii) this whole complex mixture of pollutants from the channels, indicated high acute and chronic toxicity to the microcrustaceans Daphnia simillis and Ceriodaphnia dubia, respectively. As for the marine sewage discharge, the most important results, in the water column, were: (i) of the thirty-three physicochemical and bacteriological variables analysed, nine did not comply with the current legislation and, therefore, the water was classified as regular; (ii) ten pharmaceutical compounds were detected, three of them (caffeine, diclofenac and acetaminophen), indicating low to moderate risks for algae, crustaceans and/or fish. In the sediments, the low concentrations of six heavy metals, the good representation of amphipods and polychaetes (among the twenty-five benthic taxa inventoried), besides the absence of acute toxicity for the tanaidaceous Kalliapseudes schubartii, indicated slightly polluted sediments. With the evidence of the strong anthropic interference in the quality of the water of Guarujá, improvements for the benefit of public health and the protection of the ecological systems (based on good international practices and on the Brazilian legislation in force) were suggested, such as: (i) community awareness and educational programs; (ii) drug disposal programs; (iii) public road maintenance; (iv) inspection of clandestine sewage connections in the Tombo neighbourhood; (v) land regularization of the Enseada and Perequê favelas; (vi) installation of a floodgate system, ocean interceptor and containment barriers in the drainage channels. Finally, it was suggested that the municipal sewage system should be modernised by installing, at least, a secondary level of treatment.La municipalité de Guarujá, sur la côte de l'État de São Paulo, au Brésil, considérée comme l'une des principales destinations touristiques du Brésil, possède un sous-bassin soumis à une forte pression anthropique. En effet, bien qu'elle ait une zone de drainage d'environ 143 km², 107 km² sont des zones protégées sur le plan environnemental et, par conséquent, 316 000 habitants sont concentrés dans une petite fraction territoriale (correspondant à 36 km2). Pendant l'été, lorsque le tourisme s'intensifie, la population presque double. En raison de cette forte densité de la population et de l'absence de planification urbaine, Guarujá souffre depuis des décennies de problèmes socio-environnementaux et d'infrastructure urbaine, principalement parce que plus de 64 000 habitants habitent les bidonvilles (localement appelés « favelas », principalement dans les quartiers d'Enseada et de Perequê) sans aucun système sanitaire de base. Ainsi, bien que le système municipal de collecte et de traitement des eaux usées soit dimensionné pour une population de 450 000 habitants, la destination des effluents clandestines des « favelas » est les 43 canaux artificiels de drainage urbain, qui drainent un mélange complexe (composé d'eaux usées domestiques et de charge urbaine diffuse) directement vers les plages de la municipalité et, par conséquent, peuvent compromettre la santé publique et environnementale de Guarujá. Bien que l'évaluation de la qualité des eaux balnéaires soit une urgence à Guarujá, ces études sont encore rares dans la municipalité. Compte tenu de ce scénario, l'objectif général de cette thèse était d'évaluer la qualité de l'eau et des sédiments dans les canaux de drainage urbains situés sur quatre plages différentes de Guarujá: Tombo (certifié Pavillon Bleu), Enseada (forte fréquentation touristique), Perequê (habité par une communauté de pêcheurs) et Iporanga (situé dans une unité de conservation). En plus de ces quatre canaux, la colonne d'eau et les sédiments de la zone de mélange de l'émissaire sous-marin, dont les eaux usées municipales subissent un traitement préliminaire à terre, ont été étudiés. Pour atteindre ces objectifs, des échantillons mensuels ont été obtenus entre octobre 2017 et août 2018, et trente-huit variables environnementales sélectionnées (physiques, chimiques, biologiques et écotoxicologiques), ainsi que vingt-trois composés pharmaceutiques de différentes classes thérapeutiques, ont été analysés en utilisant des tests statistiques standard et/ou différents indices de qualité de l'eau. Dans les canaux de drainage urbains, les résultats les plus expressifs obtenus dans le cadre de cette thèse, ont été: (i) il est prouvé que les canaux de Guarujá sont d'importants véhicules de transport de polluants conventionnels et émergents vers l'océan Atlantique Sud; (ii) les plages présentant un déficit sanitaire (principalement à Enseada et Perequê), ainsi que la période de plus grande affluence touristique (été brésilien/saison des pluies), sont des facteurs qui ont potentialisé la détérioration de la qualité de l'eau; (iii) en général, la meilleure qualité d'eau a été enregistrée à Iporanga (plus de 90% de conformité avec la législation brésilienne); (iv) les canaux Tombo, Enseada et Perequê ont été classés comme très mauvais (seulement 34-43% de conformité avec la législation en vigueur) et, en conséquence, de fortes concentrations des bactéries Escherichia coli et Enterococcus ssp ont été détectées dans ces canaux. En outre, la présence de mastadenovirus humains (espèces C, D et F) à Enseada et Perequê a également été constatée, ce qui a suscité une grande inquiétude pour la santé publique locale; (v) des taxons de la macrofaune benthique, tolérante à la pollution organique, ont été inventoriés dans les sédiments adjacents aux canaux (par exemple Oligochaeta, Ceratopogonidae, Chironomidae et Chironomus); (vi) seize composés pharmaceutiques ont été détectés, et cinq d'entre eux (caféine, acétaminophène, diclofénac, valsartan et losartan), ont indiqué des risques escologiques modérés et élevés pour les algues, les crustacés et/ou les poissons; et (vii) tout ce mélange complexe de polluants provenant des canaux, a indiqué une toxicité aiguë et chronique élevée pour les microcrustacés Daphnia simillis et Ceriodaphnia dubia, respectivement. En ce qui concerne le rejet des eaux usées en mer, les résultats les plus importants dans la colonne d'eau ont été obtenus: (i) sur les trente-trois variables physico-chimiques et bactériologiques analysées, neuf ne répondaient pas à la législation en vigueur et, par conséquent, l'eau a été classée comme régulière; (ii) dix composés pharmaceutiques ont été détectés, dont trois (caféine, diclofénac et acétaminophène), indiquant des risques faibles et modérés pour les algues, les crustacés et/ou les poissons. Dans les sédiments, les faibles concentrations de six métaux lourds, la bonne représentation des amphipodes et des polychètes (parmi les vingt-cinq taxons benthiques inventoriés), outre l'absence de toxicité aiguë pour le tanaidacé Kalliapseudes schubartii, indiquaient des sédiments peu pollués. Compte tenu des preuves de la forte interférence anthropique dans la qualité de l'eau de Guarujá, des améliorations au profit de la santé publique et de la protection des systèmes écologiques (basées sur les bonnes pratiques internationales et sur la législation brésilienne en vigueur) ont été suggérées, parmi lesquelles : (i) programmes de sensibilisation environnementale et d'information de la communauté ; (ii) programmes de collecte des déchets médicaux; (iii) amélioration de la voie publique; (iv) surveillance des branchements clandestins d'eaux usées dans le quartier de Tombo; (v) régularisation foncière des favelas d'Enseada et de Perequê; (vi) installation d'un système de vannes, d'un intercepteur océanique et de barrières de confinement dans les canaux de drainage. Finalement, il a été suggéré de moderniser le réseau d'égouts municipal en installant, au moins, un système de traitement secondaire

Learning Discrete-Time Markov Chains Under Concept Drift

Learning under concept drift is a novel and promising research area aiming at designing learning algorithms able to deal with nonstationary data-generating processes. In this research field, most of the literature focuses on learning nonstationary probabilistic frameworks, while some extensions about learning graphs and signals under concept drift exist. For the first time in the literature, this paper addresses the problem of learning discrete-time Markov chains (DTMCs) under concept drift. More specifically, following a hybrid active/passive approach, this paper introduces both a family of change-detection mechanisms (CDMs), differing in the required assumptions and performance, for detecting changes in DTMCs and an adaptive learning algorithm able to deal with DTMCs under concept drift. The effectiveness of both the proposed CDMs and the adaptive learning algorithm has been extensively tested on synthetically generated experiments and real data sets