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Behaviour matters: towards reliable and adaptable systems
Get PDFIn today's technologically driven society, the critical importance of ensuring a predictable behaviour in component-based systems cannot be overlooked. Modern software engineering practices, e.g., application autoscaling and Continuous Integration/Continuous Deployment (CICD), promote effective adaptation to time-varying workloads, code quality and rapid deployment. Despite their effectiveness, these practices cannot guarantee the absence of unexpected events within complex systems. The consequences of misbehaviour, e.g., service unavailability, violation of the Quality of Service, highlight the pressing need for enhanced practices. In this Dissertation, we address these challenges through three primary objectives. First, we propose a new timed modelling/execution language to model the behaviour and simulate the execution of component-based systems. Such language enables the evaluation of system functioning early on in the software development lifecycle, giving DevOps teams the possibility of assessing the impact of their choices, e.g., deployment decisions and scaling policies, at the modelling stage. Then, we present orchestration-based architectural reconfiguration techniques targeted at ensuring the system reaches a given goal, e.g., service replication/migration. In particular, leveraging the knowledge of component properties, e.g., functional dependencies, required resources, is crucial: starting from declarative specifications of these properties, we can automatically synthesise correct-by construction orchestrations that guarantee to instil the desired behaviour in the system. Moreover, service replication techniques exploiting these orchestrations overcome the drawbacks, i.e., the "domino effect" caused by uncoordinated scaling, of existing service-level adaptation approaches, e.g., Kubernetes Horizontal Pod Autoscaler. Finally, we devise a theoretical machinery for behavioural-based analyses in object-oriented languages endowed with typestates, i.e., protocols attached to classes dictating order of method calls, and we implement it in a typestate-based checker for Java. Our type checker can be easily integrated in CICD pipelines, enhancing them with static analyses to proactively prevent component misbehaviours
CFD analysis of fluid dynamics and heat transfer for buildings and improvement of indoor thermal comfort
Get PDFNowadays, decarbonization goals coupled with the deep understanding of the importance of Indoor Environmental Quality (IEQ), pose high goals in buildings performances standards. Heating and Ventilation Air Conditioning systems (HVAC) are responsible for about 60 % of building energy usage thus, optimizing these systems to reduce energy consumption is essential. However, HVAC also represent the key feature of IEQ in the built environment. Studying IEQ is challenging, as it requires an understanding of the spatial distribution of key parameters. In this context, Computational Fluid Dynamics (CFD) emerges as a fast and reliable tool for designing and optimizing HVAC systems. This thesis presents a framework for using CFD simulations to assess and improve IEQ, focusing on Thermal Comfort (TC) and Air Quality (AQ). Various environments, including historical and modern office spaces, apartments, and a cafeteria, are analyzed. Each environment presents unique challenges impacting IEQ and energy efficiency. For instance, simple office rooms contrast with complex apartment layouts, while cafeterias involve large, high-occupancy spaces. Optimizing airflow, system configurations, and integrating innovative technologies can balance TC with local discomfort and AQ, even in difficult settings. However, achieving both TC and AQ simultaneously remains complex, requiring well-designed HVAC systems. In new office buildings, high TC and AQ levels are only attainable in renewal air mode. In cafeterias, ceiling-mounted fan coil units utilizing the Coanda effect improve TC but may negatively affect AQ during colder seasons by limiting ventilation in occupied zones. Optimizing furniture placement, especially in historical contexts, can enhance comfort without compromising aesthetics. Air-source heat pumps paired with fan coils are becoming more common, especially in residential settings. Retrofitting projects that replace radiators with fan coils can benefit from strategic furniture rearrangement to enhance thermal comfort. This thesis provides a systematic, CFD-driven approach to HVAC system design, prioritizing occupant wellness and energy efficiency
Variational and differential models for shape modeling
Get PDFThe spread of new technologies led to a crucial role for the modeling of 3D objects, in particular for shape modeling, in a variety of applications, such as architecture, cultural heritage, industrial design, computer graphics, 3D radar scanning and others. Every task demands tailored surface processing of 3D geometric models, which defines the objects’ shape and features. We tackled certain surface processing tasks using differential and variational models. The quality of the numerical solution depends on the integrity of the given data, possibly suffering from damage or noise, and on the desired geometric properties to be preserved. Differential models rely on physics-inspired Partial Differential Equations (PDEs) to process surface data such as position, curvature and normal vectors. They are able to provide smooth, continuous representations of geometric structures and to exploit well-known physics equations. On the other hand, variational models compute the desired surface as the minimum of a suitable energy functional. They are built to encode initial surface features, through a data-fidelity term, and an a priori knowledge about the geometry of the desired result, through regularization or deformation terms. For the numerical solution of the proposed linear and nonlinear PDE models, we applied explicit, implicit or semi-implicit evolutive finite differences schemes. The numerical optimization methods used to solve the proposed variational models range from the gradient descent method on manifolds to the Alternate Direction Method of Multipliers. A fundamental role in both mathematical approaches is played by the shape descriptors, i.e. the type of representation used for geometric models, based on Euclidean coordinates or on intrinsic representations, like the Differential Coordinates. The proposed differential and variational models are applied to tackle challenging problems in shape analysis, such as removing noise from surfaces, filling in missing parts of surfaces, transferring textures between surfaces, and segmenting surfaces into meaningful regions
Resource verification of quantum circuit description languages
Get PDFQuantum computing promises to enable a range of tasks currently deemed intractable by classical means, and as such it constitutes a blooming field of research. One important research direction in this area is that of quantum circuit description languages. These are classical programming languages in which quantum operations are buffered to a quantum circuit, which can eventually be executed, or reused to describe larger circuits. This approach allows for the implementation of sophisticated algorithms, which can involve trillions of gates and millions of qubits. Unfortunately, existing quantum architectures are small and noisy, which means that quantum circuit description programs often generate circuits that are simply too large for the underlying hardware. To address this issue, it is essential to develop static analysis techniques for the resource consumption of these programs. The contribution of this thesis is twofold. On one hand, we show how type systems with effects and refinements can be used to analyze the resource consumption of functional circuit description languages, such as Quipper. We present a type-and-effect system which is capable of deriving upper bounds on the size of the circuits generated by a program, according to varying notions of size. We also show that the type system is correct, under reasonable assumptions about the underlying size metric, and we provide an implementation of the theory in the form of a resource analysis tool called QuRA, which we show to be able to automatically verify the resource consumption of real-world quantum algorithms. On the other hand, we show how Hoare logics can be easily adapted to analyze the resource consumption of imperative circuit description languages, such as Qiskit. We formalize the circuit building semantics of the language and define a deduction system for Hoare triples, which we prove to be correct in the partial sense
Power electronics solutions and architectures for industrial and high-power applications
Get PDFThis PhD thesis, developed through a high-level apprenticeship between OCEM Power Electronics and the University of Bologna, focuses on power electronics solutions for industrial and high-power applications. It combines practical implementations with theoretical advancements to enhance efficiency, scalability, and flexibility in energy systems. The first three chapters cover work conducted at OCEM Power Electronics. Chapter one introduces the Poseidon Project, an EU-funded initiative on energy storage for marine applications. It explores hybrid storage solutions to improve power management, reduce fuel consumption, and lower emissions. Chapter two presents a study with ENEA Frascati on optimizing poloidal field (PF) coil power supplies in tokamak fusion reactors. Supercapacitors were used to enhance energy delivery while minimizing the system’s footprint. Chapter three details the design and testing of a high-voltage pulse generator prototype, achieving 25 kV pulses with fast rise times, though further refinements are suggested.The last two chapters focus on theoretical research at the University of Bologna. Chapter four investigates Modular Multilevel Converters, proposing a novel framework based on two-time scale analysis to improve performance. Chapter five explores matrix rectifiers as an efficient alternative to conventional rectifiers, leveraging a tailored control strategy for loss reduction
Protohistoric Walls of Sardinia. Spatial surveys, analysis and interpretation
Get PDFLe muraglie della Sardegna non sono state oggetto di indagini diffuse e di esse non è neppure mai stata realizzata un’esaustiva carta di distribuzione. Sarà analizzato il concetto di recinto, di muraglia e più in generale di fortificazione, interrogandosi sulle motivazioni che possono aver portato alla loro costruzione, ricercando quegli elementi strutturali che possono testimoniare scopi funzionali, difensivi o meno. Per contestualizzare le muraglie sarde si analizzeranno esempi di muraglie e fortificazioni protostoriche in pietra del Mediterraneo. In seguito si descriverà la metodologia utilizzata per l’individuazione e la documentazione sul campo delle muraglie sarde, illustrando il sistema di schedatura ed elaborazione dei dati inediti ricavati. Saranno poi descritte le muraglia individuate, documentate e schedate durante il lavoro sul campo. Lo scavo del sito di Suvegliu a Oliena (NU), compiuto da parte di chi scrive sotto la direzione scientifica di Maurizio Cattani, sarà un punto molto rilevante di questo elaborato. In conclusione i dati frutto dei rilievi e delle ricognizioni sul campo saranno incrociati e confrontati con l’edito, definendo così un quadro generale delle muraglie protostoriche della Sardegna.The walls of Sardinia have not been the subject of widespread investigation, and a comprehensive distribution map of them has never even been produced. The concept of enclosure, wall and more generally of fortification will be analyzed, questioning the motivations that may have led to their construction, searching for those structural elements that may testify to functional purposes, defensive or otherwise. To contextualize Sardinian walls, examples of protohistoric Mediterranean stone walls and fortifications will be analyzed. Next, the methodology used for the identification and field documentation of Sardinian walls will be described, illustrating the system of filing and processing the unpublished data obtained. The walls identified, documented and catalogued during the fieldwork will then be described. The excavation of the site of Suvegliu in Oliena (NU), carried out by the writer under the scientific direction of Maurizio Cattani, will be a very relevant point of this paper. In conclusion, the data resulting from the field surveys and reconnaissance will be cross-referenced and compared with the edited paper, thus defining a general picture of the protohistoric walls of Sardinia
A new magneto-optical trap for cold rubidium atoms in hollow-core fibres
Get PDFAs the second quantum revolution is reaching full maturity, more and more applications of quantum objects are being developed in the field now known as quantum technologies. The objective of my work was in fact to realise an experimental setup to cool and trap rubidium (Rb) atoms: first via a Magneto-Optical Trap (MOT), then inside a Hollow-Core Photonic-Crystal Fibre (HCPCF). The final aim is to demonstrate the possibility of delivering these atoms through a HCPCF with one end inside the vacuum chamber and the other (sealed) far from it, to use them for magnetometry or accelerometry applications. While doing so, the interaction of light with the atoms confined in the fibre also has to be studied. My work was devoted to the assembling of the Ultra-High Vacuum (UHV) setup hosting the MOT, and the laser system necessary to interact with the atoms. The latter was fully realised in-house, using only fibre components to make it more compact, easily operable and maintainable. Both target tasks were successfully achieved. The vacuum chamber can reach stable pressures ≃8×10^−10mbar. The laser setup is capable of delivering up to ≃40mW of optical power at 780nm, with line-width ≃0.6MHz. These values were also proven to be functional by effectively achieving MOTs of ≃8×10^7 atoms in a consistent way. Future prospects for my work will be to finalise a “conveyor belt” dipole trap setup, to trap the atoms from the MOT without magnetic fields, and move them directly inside the HCPCF. Subsequently, the physical processes relative to the atom-light interactions in the quasi-1D confinement of the fibre core can be studied. Quantum sensing measurements with atoms, both in free-space and within the fibre, can also be performed
Study and development of new silicon technologies for the ALICE 3 Time-Of-Flight detector
Get PDFIn preparation for the future ALICE 3 experiment proposed to be installed at the LHC at CERN in 2036, an extensive R&D program is actively addressing the challenge of developing a 20-picosecond technology for the Time-Of-Flight (TOF) detector. Various silicon technologies are under investigation to achieve this goal. Among those, Low Gain Avalanche Detectors (LGADs) constitute a promising solution. In this thesis, comprehensive R&D efforts focused on state-of-the-art LGADs are presented. A wide range of LGADs, both single channel sensors and matrices, including different thickness, area, doping and inter-pad design have been fully characterized with laboratory measurements and studied first with a laser setup and subsequently using particle beams at CERN facilities. First tests of 25 μm and 35 μm LGADs compared to 50 μm-thick sensors highlighted the potential of a thinner design for improved time resolution. This prompted further investigations into progressively thinner sensors, arriving to test the first 15 \textmu m-thick LGADs ever produced by FBK. Additionally, the innovative double-LGAD concept was introduced to address the challenge of small input signals in the electronics. Notably, this new concept not only yields the significant benefit of an enhancement of the charge at the input of electronics which allows for reduced power consumption, but also translates into an improvement in overall time resolution.
Finally, a dedicated study has been performed to determine the impact of particle incidence angles on the time resolution, a crucial aspect to be taken into account in the ALICE 3 experiment. Overall, this R&D campaign on LGAD detectors, finally resulted in sensors that meet the time resolution requirements of ALICE 3 Time-Of-Flight detector, establishing them also as strong candidates for future-generation experiments
Dynamic nitrogen fertigation with reflectance sensors: exploration of statistical modeling approaches to optimize N fertilization in processing tomato (Solanum lycopersicum L.)
Get PDFDynamic nitrogen (N) fertigation guided by reflectance sensors presents a valuable opportunity to improve the N use efficiency in vegetable cropping systems, and this thesis explores multiple modeling approaches to optimize N fertilization in processing tomato using multispectral and hyperspectral reflectance sensors. The development of threshold curves of the green vegetation index (GVI) to trigger the N fertigation represents the simplest approach to guide the dynamic fertigation, and multiple modelling strategies to build the GVI thresholds were explored in the thesis. Besides the GVI threshold adopted, field validation trial demonstrated that dynamic N fertigation guided by GVI thresholds can save up to 38-60% of N fertilizers as compared to conventional N fertilization. Dynamic fertigation guided by the GVI helps maintain yield levels, reduce fertilization costs and greenhouse gas emissions, and potentially enhance fruit quality. Among the GVI threshold curves, monitoring the GVI in crops under non-limiting N conditions in the past growing seasons represents an effective, simple, and fast modeling approach. Furthermore, different approaches to defining the optimal N rate were investigated. A low-computational demanding approach, consisting of the integration of the N balance sheet with the GVI threshold curve, was successfully validated in a field trial. On the other hand, reflectance data were used to retrieve crop traits, including aboveground biomass (AGB), N uptake, leaf area index (LAI), and the Nitrogen Nutrition Index (NNI). In turn, these crop parameters were used to initialize a crop model, the critical N uptake curve, to calculate the optimal N rate. Different regression approaches were explored to retrieve such parameters, including linear regression with vegetation indices, nonlinear regression with vegetation indices hybridized with agroclimatic data, and linear and nonlinear non-parametric regression (machine learning regression algorithms). The thesis encompasses the research findings as well as future priorities for investigation
Green computing for particle physics
Get PDFClimate change-related events are starting to deeply concern modern societies and scientific communities all over the world, who agree that human activities have contributed to this phenomenon and actions will be required to curb our current and future impact. Among these activities, due to its scale and pervasiveness, computing has been recognized having a relevant footprint on the environment. Several scientific computing communities are therefore taking action to acknowledge their computational footprint and reduce it, aiming at guaranteeing an “optimal” energy consumption-per-unit-of-knowledge obtained. HEP physicists, given the upcoming HL-LHC phase of the LHC experiment which will scale computing to exascale, have recently started taking action aimed at evaluating the footprint of current activities to ensure the sustainability of future scientific efforts at LHC. This thesis, in continuity with the aforementioned collective effort and with the goal of helping physicists to easily acknowledge their computational and energy footprint, presents the containerized prototype of an energy footprint monitoring software of arbitrary computing tasks running on common computing platforms. The software leverages basic properties of Linux systems to seamlessly perform the estimation of the energy consumption of tasks without including other processes running on the machine in the estimation. In order to test this software prototype, benchmark CMS workflows related to event generation and simulation, digitization, and reconstruction have been analyzed. The obtained results are reported and used for further analysis aimed at finding margins of sustainability improvements. We show that optimal working points can be extracted and used to prompt a less energy-eager job submission on older platforms, in exchange of a moderate increase in the running time of the job