1,721,809 research outputs found
A data-driven fuzzy approach for predicting the remaining useful life in dynamic failure scenarios of a nuclear system
No full textThis paper presents a similarity-based approach for prognostics of the Remaining Useful Life (RUL) of a system, i.e. the lifetime remaining between the present and the instance when the system can no longer perform its function. Data from failure dynamic scenarios of the system are used to create a library of reference trajectory patterns to failure. Given a failure scenario developing in the system, the remaining time before failure is predicted by comparing by fuzzy similarity analysis its evolution data to the reference trajectory patterns and aggregating their times to failure in a weighted sum which accounts for their similarity to the developing pattern. The prediction on the failure time is dynamically updated as time goes by and measurements of signals representative of the system state are collected. The approach allows for the on-line estimation of the RUL. For illustration, a case study is considered regarding the estimation of RUL in failure scenarios of the Lead Bismuth Eutectic eXperimental Accelerator Driven System (LBE-XADS). © 2009 Elsevier Ltd. All rights reserved
Fuzzy clustering classification of dynamic scenarios of digital I&C in NPPs
No full textSafety analysis of Nuclear Power Plants (NPPs) employing digital Instrumentation and Control (I&C) implies that the influence of events timing and magnitudes on the accidental scenarios be taken into account. This entails the simulation of a number of scenarios much larger than that considered for the classical Event Tree/Fault Tree (ET/FT)-based analysis. Consequently, the post-simulation retrieval of information becomes quite difficult and computationally burdensome. This paper reports the results of an investigation with respect to the classification of the numerous accidental scenarios generated in a dynamic safety analysis of a NPP with digital I&C. The method investigated is based on a Fuzzy C-Means clustering algorithm in which the classification takes into account not only the final system states reached at the end of the accidental scenarios but also the timing of the occurring events, the fault magnitudes and the characteristics of the process evolution. A case study is considered regarding the scenarios generated by a SIMULINK model of the Lead Bismuth Eutectic experimental Accelerator Driven System (LBE-XADS) embedded within a Monte Carlo (MC) sampling procedure for injecting single and multiple faults at random times and of random magnitudes. The accidental scenarios generated are classified on the basis of three different system failure modes, which relate to the value reached by the diathermic oil secondary coolant temperature with respect to maximum and minimum safety threshold values set to avoid primary coolant thermal shocks and degradation of the oil physical and chemical properties
A Framework based on Finite Mixture Models and Adaptive Kriging for Characterizing Non-Smooth and Multimodal Failure Regions in a Nuclear Passive Safety System
Full text linkIn the safety analyses of passive systems for nuclear energy applications, computationally demanding models can be substituted by fast-running surrogate models coupled with adaptive sampling techniques; for speeding up the exploration of the components and system state-space and the characterization of the conditions leading to failure (i.e., the system Critical failure Regions, CRs). However, in some cases of non-smoothness and multimodality of the state-space, the existing approaches do not suffice. In this paper, we propose a novel methodological framework, based on Finite Mixture Models (FMMs) and Adaptive Kriging (AK-MCS) for CRs characterization in case of non-smoothness and/or multimodality of the output. The framework contains three main steps: 1) dimensionality reduction through FMMs to tackle the output non-smoothness and multimodality, while focusing on its clusters defining the system failure; 2) adaptive training (AK-MCS) of the metamodel on the reduced space to mimic the time-demanding model and, finally, 3) use of the trained metamodel provide the output for new input combinations and retrieve information about the CRs. The framework is applied to the case study of a generic Passive Safety System (PSS) for Decay Heat Removal (DHR) designed for advanced Nuclear Power Plants (NPPs). The PSS operation is modelled through a time-demanding Thermal-Hydraulic (T-H) model and the pressure selected for characterizing the PSS response to accidental conditions shows a strong non-smooth and multimodal behavior. A comparison with an alternative approach of literature relying on the use of Support Vector Classifier (SVC) to cluster the output domain is presented to support the framework as a valid approach in challenging CRs characterization
L'opera di Ottiero Ottieri
Full text linkIl candidato analizza, in questa tesi monografica, il percorso letterario di Ottieri Ottieri dal primo romanzo Memorie dell' incoscienza (1954) all' Irata sensazione di peggioramento (2002), ponendo l' attenzione sulle tre tematiche che emergono dalla poetica dell' autore: l' industria, la clinica e la politica.
Il lavoro è strutturato in sette capitoli, ciascuno dedicato ad un tema ed un periodo specifico della produzione dello scrittore. Nell' introduzione si rilevano i caratteri della letteratura di Ottieri, inclassificabile e originale, il quale ha voluto concretizzare un progetto letterario di ampio respiro, attraverso trenta opere legate tra loro in un perpetuo intreccio di temi, motivi, riprese, rifacimenti che s' intersecano in diverse materie, dalla letteratura italiana ed europea alla storia, dalla psicologia alla filosofia, dalla psichiatria alla sociologia, dalla politica all'arte.
Nel primo capitolo si affronta l' adesione giovanile di Ottieri al fascismo, in seguito definito " incosciente" , ed i ricordi ad esso legati nelle Memorie dell' incoscienza, romanzo autobiografico in cui un alter ego (espediente narrativo che Ottieri utilizzerà in tutta la sua produzione letteraria) analizza sulla propria persona il disfacimento della patria. Nel secondo capitolo si affronta il tema dell' industria nella letteratura con l' analisi di quattro opere (i due romanzi Tempi stretti e Donnarumma all' assalto, il diario La linea gotica e la commedia I venditori di Milano) per le quali Ottieri viene considerato il pioniere della letteratura industriale in Italia. Dal terzo al quinto capitolo, la tematica predominante è la clinica dove le malattie mentali si presentano in molteplici aspetti tra cui la depressione, la schizofrenia, l' alienazione, che diventano, nel corso dei decenni, non solo materia letteraria ma soprattutto essenza vitale della letteratura di Ottieri. Il sesto capitolo affronta il tema politico mediante lo studio di due opere basilari: La storia del PSI ed Il poema osceno dove lo scrittore condensa cinquant' anni della storia dâ Italia dal fascismo adolescenziale all' illusione del socialismo fino alle soglie del Ventunesimo secolo. Il settimo capitolo riguarda gli ultimi romanzi di Ottieri che, cosciente della morte ormai imminente, riassume la sua vita di uomo borderline, di scrittore non di successo, di "caso letterario" rilevante nel panorama della letteratura italiana del secondo Novecento. Nell' appendice è presente un' antologia dell' epistolario giovanile di Ottieri, importante per comprendere le strette correlazioni tra le esperienze di vita dell' autore e le conseguenti elaborazioni letterarie.The subject of this thesis concerns the Ottieriâ s literary work from his first novel Memorie dellâ incoscienza (1954) to Una irata sensazione di peggioramento (2002), analysing three themes which come over his poetry: industry, sanatorium and politics.
The thesis is planned on seven chapters. In the introduction, the characteristics of Ottieriâ s novels are developed: original and unclassifiable, Ottieri has organized an extensive literary project through thirty works connected by a continuous plot of themes and leitmotivs which are linked on different subject as Italian and European literature, history, psychiatry, art, politics.
In the first chapter, the Ottieriâ s youthful devotion to fascism is analysed in the light of his own memories (Memorie dellâ incoscienza), an autobiographic novel in which an alter ego (Lorenzo Bandini) analyses the dramatic issues of Italy during the Second World War.
In the second chapter the emergent theme concerns the industrial world through four works (two novels: Tempi stretti and Donnarumma allâ assalto, the diary La linea gotica and the play I venditori di Milano) which allow him to be the â pioneerâ of Italian industrial literature.
From the third to the fifth chapter, the principal theme which comes over is mental illness; depression, schizophrenia, alienation are bound to be the centre of his literary works and not only of his life.
The sixth chapter studies two novels, La storia del PSI and Il poema osceno, which are the summary of his political ideas.
The seventh chapter is about the last works of Ottieri; aware of his imminent death, the poet describes his life as a borderline individual and as an unsuccessful writer
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effect of some organic materials on root-knot nematodes on tomatoes in field. Preliminary experiments.
No full text
A Modeling Framework for the Analysis of Integrated Energy Systems Exposed to NaTech Events Induced by Climate Change
No full textThis paper proposes a modeling framework for the analysis of Integrated Energy Systems (IESs) that comprise nuclear, conventional and renewable power plants, and the electricity infrastructure. With such framework, standard Centralized Systems (CS), IES with Distributed Generation (IESDG) and IES with bidirectional energy conversion (IES+P2G) enabled by power-to-gas (P2G) facilities can be analyzed by innovatively considering the effects of both climate-induced and stochastic failures on their performance. The developed analysis framework has been applied to a typical case study of an IES+P2G that comprises two Combined Cycle Gas Turbine Plants (CCGT), a Nuclear Power Plant (NPP), two Wind Farms (WF), a Solar Photovoltaics (PV) field and a Power-to-Gas station (P2G)
A Modeling and Analysis Framework for Integrated Energy Systems Exposed to Climate Change-Induced NaTech Accidental Scenarios
Full text linkThis paper proposes a novel framework for the analysis of integrated energy systems (IESs) exposed to both stochastic failures and “shock” climate-induced failures, such as those characterizing NaTech accidental scenarios. With such a framework, standard centralized systems (CS), IES with distributed generation (IES-DG) and IES with bidirectional energy conversion (IES+P2G) enabled by power-to-gas (P2G) facilities can be analyzed. The framework embeds the model of each single production plant in an integrated power-flow model and then couples it with a stochastic failures model and a climate-induced failure model, which simulates the occurrence of extreme weather events (e.g., flooding) driven by climate change. To illustrate how to operationalize the analysis in practice, a case study of a realistic IES has been considered that comprises two combined cycle gas turbine plants (CCGT), a nuclear power plant (NPP), two wind farms (WF), a solar photovoltaicS (PV) field and a power-to-gas station (P2G). Results suggest that the IESs are resilient to climate-induced failures
- …
