DIMES https://hdl.handle.net/10955/31 2026-04-21T03:13:41Z 2026-04-21T03:13:41Z Zicari, Paolo Fortino, Giancarlo Folino, Gianluigi https://hdl.handle.net/10955/5627 2025-06-20T11:35:33Z 2021-06-21T00:00:00Z

Ensemble of deep learning prediction models for data analytics Zicari, Paolo; Fortino, Giancarlo; Folino, Gianluigi The abundance of available unstructured or raw text requires the automatic extraction of information for di↵erent tasks. One of the most relevant, Text Classification, extracts this information by assigning informative labels to raw texts from a pre-defined set. Deep Learning (DL) o↵ers challenging solutions to the automatic text classification problem. Despite the great potentialities of DL-based text classifiers, current solutions are exposed to a number of challenging issues that frequently occur in scenarios where text categorization is used in reallife applications. First of all, a large number of labelled data are usually necessary to train a deep model adequately, while labelling texts is timeconsuming, expensive, and very often requires specific knowledge. Moreover, configuring the structure and hyper-parameters of a Deep Neural Network (DNN) architecture is a difficult task, which entails long and careful design and tuning activities to make the DNN perform well. Typical scenarios are characterized by the fact that classes are often imbalanced. These issues entail a high risk of eventually obtaining a DNN-based classifier that overfits the training data and relies on non-general, biased and unreliable classification patterns. On the other hand, the black-box nature of a DNN model does not allow for easy reasoning on which features of a data instance drove the model to its classification decision. The work in this thesis, starting from the general problem of text classification, focuses on some challenging aspects associated with using an ensemble of deep learning methods to classify raw texts. More in detail, this work focuses on the analysis, exploration, study and test of algorithms and learning models to be employed in the proposal of novel techniques of Ensemble Deep Learning (EDL) aimed at performing classification and explanation tasks and on the research of semi-supervised strategies based on pseudo-labelling for improving classifier prediction performances in case of scarcity of labelled data. To this aim, this thesis proposes a complete framework based on the paradigm of ensembles of deep learning algorithms. The proposed framework is designed to furnish a valid instrument for exploring, validating and testing the proposed novel deep ensemble techniques contextualised in reallife applications, covering the entire classification process, including preprocessing, learning model building, explanation of the results, self-training for scarce labelled data, human-in-the-loop validating and model refining. Even though the methods proposed in this work could be used in any field of interest, the problem of extracting information from the raw text was specialised for two specific application contexts: automatic customer support ticket classification and the problem of fake detection. The first application scenario deals with the necessity of the Customer Care Department of most companies to answer their customer requests applied as tickets through several common channels like email, short message texts, social posts, etc. Ticket classification is necessary for automatic answer generation and routing to the specific human operator. Limiting the spread of misinformation, related to the high growth of social media dissemination and sharing of information, has raised the issue of distinguishing true news from fakes, with the challenging problem of processing long texts like news for fake detection. For this reason, the second scenario deals with the critical problem of discerning fake news from the vast amount of information circulating on the Web. In these research areas, the ensemble paradigm has been adopted only recently; thus, discovering the possible advantages when applying this technique is challenging. Experimental tests conducted on real data collected by two Customer Relationship Management (CRM) systems have proven the framework’s effectiveness in di↵erent ticket categorisation tasks and the practical value of their associated explanations. In addition, experiments conducted on two fake news datasets have proven the e↵ectiveness of the proposed semisupervised self-training ensemble-based strategy for improving performances when a few labelled data are available. Università della Calabria. Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica Dottorato di Ricerca in Information and Communication Technologies CICLO XXXV

2021-06-21T00:00:00Z Pirouz, Behzad Fortino, Giancarlo Gaudioso, Manlio https://hdl.handle.net/10955/5626 2025-06-20T10:38:03Z 2023-05-10T00:00:00Z

Feature Selection in Classification by means of Optimization and Multi-Objective Optimization Pirouz, Behzad; Fortino, Giancarlo; Gaudioso, Manlio The thesis is in the area of mathematical optimization with application to Machine Learning. The focus is on Feature Selection (FS) in the framework of binary classification via Support Vector Machine paradigm. We concentrate on the use of sparse optimization techniques, which are widely considered as the election tool for tackling FS. We study the problem both in terms of single and multi-objective optimization. We propose first a novel Mixed-Integer Nonlinear Programming (MINLP) model for sparse optimization based on the polyhedral k-norm. We introduce a new way to take into account the k-norm for sparse optimization by setting a model based on fractional programming (FP). Then we address the continuous relaxation of the problem, which is reformulated via a DC (Difference of Convex) decomposition. On the other hand, designing supervised learning systems, in general, is a multi-objective problem. It requires finding appropriate trade-offs between several objectives, for example, between the number of misclassified training data (minimizing the squared error) and the number of nonzero elements separating the hyperplane (minimizing the number of nonzero elements). When we deal with multi-objective optimization problems, the optimization problem has yet to have a single solution that represents the best solution for all objectives simultaneously. Consequently, there is not a single solution but a set of solutions, known as the Pareto-optimal solutions. We overview the SVM models and the related Feature Selection in terms of multi-objective optimization. Our multi-objective approach considers two simultaneous objectives: minimizing the squared error and minimizing the number of nonzero elements of the normal vector of the separator hyperplane. In this thesis, we propose a multi-objective model for sparse optimization. Our primary purpose is to demonstrate the advantages of considering SVM models as multi-objective optimization problems. In multi-objective cases, we can obtain a set of Pareto optimal solutions instead of one in single-objective cases. Therefore, our main contribution in this thesis is of two levels: first, we propose a new model for sparse optimization based on the polyhedral k-norm for SVM classification, and second, use multi-objective optimization to consider this new model. The results of several numerical experiments on some classification datasets are reported. We used all the datasets for single-objective and multi-objective models. UNIVERSITA’ DELLA CALABRIA Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica - DIMES Dottorato di Ricerca in Information and Communication Technologies (ICT). Ciclo XXXV

2023-05-10T00:00:00Z Vatalaro, Massimo Fortino, Giancarlo Crupi, Felice https://hdl.handle.net/10955/5625 2025-06-17T08:25:21Z 2023-02-23T00:00:00Z

Design of physically unclonable functions in cmos and emerging technologies for hardware security applications Vatalaro, Massimo; Fortino, Giancarlo; Crupi, Felice The advent of the IoT scenario heavily pushed the demand of preserving the information down to the chip level due to the increasing demand of interconnected devices. Novel algorithms and hardware architectures are developed every year with the aim of making these systems more and more secure. However, IoT devices operate with constrained area, energy and budget thus making the hardware implementation of these architectures not always feasible. Moreover, these algorithms require truly random key for guarantying a certain security degree. Typically, these secret keys are generated off chip and stored in a non-volatile manner. Unfortunately, this approach requires additional costs and suffers from reverse engineering attacks. Physically unclonable functions (PUFs) are emerging cryptographic primitives which exploit random phenomena, such as random process variations in CMOS manufacturing processes, for generating a unique, repeatable, random, and secure keys in a volatile manner, like a digital fingerprint. PUFs represent a secure and low-cost solution for implementing lightweight cryptographic algorithms. Ideally PUF data should be unique and repeatable even under noisy or different environmental conditions. Unfortunately, guarantying a proper stability is still challenging, especially under PVT variations, thus requiring stability enhancement techniques which overtake the PUF itself in terms of required area and energy. Nowadays, different PUF solutions have been proposed with the aim of achieving ever more stable responses while keeping the area overhead low. This thesis presents a novel class of static monostable PUFs based on a voltage divider between two nominally identical sub-circuits. The fully static behavior along with the use of nominally identical sub-circuits ensure that the correct output is always delivered even when on-chip noise occasionally flips the bit, and that randomness is always guaranteed regardless of the PVT conditions. Measurement results in 180-nm CMOS technology demonstrates the effectiveness of the proposed solution with a native instability (BER) of only 0.61% (0.13%) along with a low sensitivity to both temperature and voltage variations. However, these results were achieved at the cost of more area-hungry design (i.e., 7,222𝐹 ) compared to other relevant works. The proposed solution was also implemented with emerging paper based MoS2 nFETs by exploiting a LUT-based Verilog-A model, calibrated with experimental 𝐼 vs 𝑉 at different 𝑉 curves, whose variability was extracted from different 𝐼 vs 𝑉 curves of 27 devices from the same manufacturing lot. Simulations results demonstrate that these devices can potentially used as building block for next generation electronics targeting hardware security applications. Finally, this thesis also provides an application scenario, in which the proposed PUF solution is employed as TRNG module for implementing a smart tag targeting anti-counterfeiting applications. UNIVERSITA’ DELLA CALABRIA Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica Dottorato di Ricerca in Information and Communication Technologies CICLO XXXV

2023-02-23T00:00:00Z Cantini, Riccardo Fortino, Giancarlo Trunfio, Paolo Marozzo, Fabrizio https://hdl.handle.net/10955/5621 2025-05-30T11:09:07Z 2023-05-16T00:00:00Z

Distributed Big Social Data Analysis: Advanced Techniques and Execution Strategies Cantini, Riccardo; Fortino, Giancarlo; Trunfio, Paolo; Marozzo, Fabrizio UNIVERSITÀ DELLA CALABRIA Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica Dottorato di Ricerca in INFORMATION AND COMMUNICATION TECHNOLOGIES.Ciclo XXXV

2023-05-16T00:00:00Z