3,249 research outputs found
A novel robust optimization model for nonlinear Support Vector Machine
No full textIn this paper, we present new optimization models for Support Vector Machine (SVM), with the aim of separating data points in two or more classes. The classification task is handled by means of nonlinear classifiers induced by kernel functions and consists in two consecutive phases: first, a classical SVM model is solved, followed by a linear search procedure, aimed at minimizing the total number of misclassified data points. To address the problem of data perturbations and protect the model against uncertainty, we construct bounded-by-norm uncertainty sets around each training data and apply robust optimization techniques. We rigorously derive the robust counterpart extension of the deterministic SVM approach, providing computationally tractable reformulations. Closed-form expressions for the bounds of the uncertainty sets in the feature space have been formulated for typically used kernel functions. Finally, extensive numerical results on real-world datasets show the benefits of the proposed robust approach in comparison with various SVM alternatives in the machine learning literature
Francia
No full textIl sistema francese di governo del territorio presenta varie analogie con quello italiano, anzitutto la caratterizzazione «conformativa» e l’articolata struttura delle competenze. Più progredito appare invece il tentativo di costruzione coerente delle strategie e di inquadramento delle procedure. Il sistema francese è qui analizzato nelle sue caratteristiche strutturali, negli strumenti tradizionali e innovativi di pianificazione spaziale e di governance urbana, nonché negli orientamenti del discorso politico e tecnico, illustrando infine il caso di una pratica innovativa di governance urbana: quello dei Conseils Citoyens a Parigi
Regno Unito
No full textIl sistema di governo del territorio nel Regno Unito è tipicamente caratterizzato da un’impostazione basata sull’uso di piani non legalmente vincolanti e su scelte di trasformazione spaziale decise attraverso specifiche valutazioni di merito. Il sistema è analizzato nelle sue caratteristiche strutturali, nell’evoluzione degli strumenti di pianificazione spaziale, negli orientamenti del discorso sul governo del territorio e, infine, nelle pratiche innovative di pianificazione spaziale attraverso l’approfondimento dei neighbourhood plans a Londra
A robust twin parametric margin support vector machine for multiclass classification
No full textIn this paper, we introduce novel Twin Parametric Margin Support Vector Machine (TPMSVM) models designed to address multiclass classification tasks under feature uncertainty. To handle data perturbations, we construct bounded-by-norm uncertainty sets around each training observation and derive the robust counterparts of the deterministic models using robust optimization techniques. To capture complex data structures, we explore both linear and kernel-induced classifiers, providing computationally tractable reformulations of the resulting robust models. Additionally, we propose two alternatives for the final decision function, enhancing models’ flexibility. Finally, we validate the effectiveness of the proposed robust multiclass TPMSVM methodology on real-world datasets, showing the good performance of the approach in the presence of uncertainty
Immunogenicity of anti-tumour necrosis factor drugs in rheumatic diseases.
No full textDespite the significant advantages in
clinical practice associated with TNFinhibitors, a loss of response over time
is sometimes observed, in some cases
possibly due to immunogenicity, i.e.
the development of antibodies direct
against the drug. This review evaluates
the immunogenicity of different antiTNF agents, and discusses its effects on
efficacy and safety. Available evidence
indicates that all anti-TNF drugs may
induce an immune response. However,
the variation in the occurrence of antidrug antibodies, as well as the variation
in the impact of antibodies on the efficacy and safety, can be explained by drug
conformation itself, use of concomitant
immunosuppressants and differences
in dosing regimen and route of administration. The association between the
development of anti-drug antibodies
and low drug serum concentrations is
clinically relevant since it is likely related to low response. Strict monitoring
of neutralising antibodies might be useful for tailoring therapeutic strategy.
There is no evidence of cross-reactivity
among different drugs: immunogenicity
(the development of specific anti-drug
antibodies to one TNF inhibitor) does
not seem to affect the effectiveness of
another anti-TNF agents; therefore,
switching to another drug of the same
class might be effective in patients who
have developed anti-drug antibodies to
a TNF inhibitor
Analisi e progettazione di azionamenti ad alta frequenza, modulari e ad elevato livello di integrazione
No full textGli azionamenti integrati -intesi come l’insieme di macchina elettrica e convertitore di potenza racchiusi all’interno di uno stessa struttura meccanica- sono stati introdotti all’inizio degli anni ’90. Nelle prime realizzazioni i problemi termici, meccanici e di limitata potenza specifica lato convertitore, non ne hanno consentito la diffusione sul mercato, nonostante avessero peculiarità tali da renderli vantaggiosi. Tuttavia, a seguito di recenti sviluppi nel campo dell’elettronica di potenza, introdotti dai semiconduttori ”wide bangap”, tali strutture sono state oggetto di un progressivo interesse.
Gli switch ai Nitruri di Gallio od ai Carburi di Silicio permettono invero di operare a frequenze di switching ed a temperature operative ben maggiori di quelle ottenibili con i tradizionali componenti al Silicio, pur preservando redimenti elevati. La maggiorazione delle temperature operative ammesse mitiga le problematiche termiche; allo stesso tempo, il funzionamento ad alte frequenze conduce ad una diminuzione intrinseca dei pesi e dei volumi dei componenti passivi, calmierando le problematiche di tipo meccanico.
Dal punto di vista della macchina elettrica, le alte frequenze di switching aprono la strada a macchine ad elevato numero di poli ed elevata velocità di rotazione, le quali sono naturalmente caratterizzate da coppie e potenze specifiche maggiori. Va evidenziato però, che se non opportunamente trattate esse sono causa di perdite aggiuntive.
Questa tesi di dottorato esplora l’utilizzo dei semiconduttori di ultima generazione negli azionamenti ad elevato grado di integrazione di tipo modulare, caratterizzati da un’elevata resilienza al guasto. Al fine di beneficiare appieno dei vantaggi di questa soluzione, e di limitarne gli svantaggi, viene proposto l’impiego della macchina elettrica a flusso assiale a magneti permanenti con avvolgimento di tipo coreless ed avente un rapporto poli-bobine frazionario. Nella tesi vengono inoltre sviluppati gli strumenti per l’analisi e la progettazione della macchina elettrica e del convertitore di potenza; di entrambi vengono costruiti dei prototipi, la cui sperimentazione al banco prova fornisce i dati per la
validazione finale degli argomenti trattati nel lavoro di tesi
Firenze, Biblioteca Medicea Laurenziana, Conv.Soppr.204
No full textScheda catalografica del manoscritto con segnatura Conv.Soppr.204 della Biblioteca Medicea Laurenziana di Firenze
A stochastic electric vehicle routing problem under uncertain energy consumption
No full textThe increasing adoption of Electric Vehicles (EVs) for service and goods distribution operations has led to the emergence of Electric Vehicle Routing Problems (EVRPs), a class of vehicle routing problems addressing the unique challenges posed by the limited driving range and recharging needs of EVs. While the majority of EVRP variants have considered deterministic energy consumption, this paper focuses on the Stochastic Electric Vehicle Routing Problem with a Threshold
recourse policy (SEVRP-T), where the uncertainty in energy consumption is considered, and a recourse policy is employed to ensure that EVs recharge at Charging Stations (CSs) whenever their State of Charge (SoC) falls below a specified threshold. We formulate the SEVRP-T as a two-stage stochastic mixed-integer second-order cone model, where the first stage determines the sequences of customers to be visited, and the second stage incorporates charging activities. The objective is
to minimize the expected total duration of the routes, composed by travel times and recharging operations. To cope with the computational complexity of the model, we propose a heuristic based on an Iterated Local Search (ILS) procedure coupled with a Set Partitioning problem. To further speed up the heuristic, we develop two lower bounds on the corresponding first-stage customer sequences. Furthermore, to handle a large number of energy consumption scenarios, we employ
a scenario reduction technique. Extensive computational experiments are conducted to validate
the effectiveness of the proposed solution strategy and to assess the importance of considering the stochastic nature of the energy consumption. The research presented in this paper contributes to the growing body of literature on EVRP and provides insights into managing the operational deployment of EVs in logistics activities under uncertainty
The Influence of Insecure Romantic Attachment on Generativity
No full textExisting research concerning the development of generativity, the capacity to provide care and guidance to future generations, has primarily focused on the role of sociodemographic variables. However, one important feature that might be of importance for the study of generativity is insecure romantic attachment, given its influence on how people establish relationships with others. Still, the role of the two dimensions of insecure romantic attachment (i.e., anxiety and avoidance) on the most studied aspects of generativity (i.e., generative concern and generative acts) remains largely underexplored. Therefore, the present study investigates what contributes to generativity by exploring the role of sociodemographic features (i.e., age, gender, having children, years of education) and above all the two dimensions of insecure romantic attachment on generative concern and acts. A sample of 427 adults (age range: 25–65 years old) completed an online survey including romantic attachment and generativity measures. Afterwards, correlational and regression analyses were conducted to explore the data. Results showed that years of education positively predicted generative concern, whereas both anxiety and avoidance negatively predicted it. Yet, no sociodemographic feature nor dimension of insecure romantic attachment predicted generative acts. Thus, insecure romantic attachment could be a useful key to understanding generative concern. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature
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