1,720,960 research outputs found
Mechanochemistry: Versatile and Functional Strategy for the Realization and the Recycling of Multi-Phase Materials
Full text linkLa presente tesi di dottorato è incentrata sullo sviluppo di metodologie sostenibili per la modifica, la produzione ed il riciclo di materiali organici, concentrandosi su due classi di materiali:1) poliolefine e 2)biomasse cellulosiche e lignocellulosiche.
L'obiettivo è aumentare la sostenibilità dei processi aderendo ai principi della Green Chemistry, attraverso la progettazione di strategie che riducano l'uso di sostanze chimiche e solventi, evitino la generazione di rifiuti, consentano l'utilizzo di materie prime rinnovabili, promuovano la biodegradabilità.
Nello specifico, in questa tesi, sono stati sviluppati processi meccanochimici mediante l'utilizzo di un mulino a sfere planetario (ball milling, BM). Questo tipo di trattamenti si basa sull'applicazione di forze di taglio e compressione su materiali solidi attraverso l'azione di sfere orbitanti, al fine di indurre cambiamenti morfologici e strutturali e, in alcuni casi, modifiche chimiche nei materiali organici. Sono stati seguiti diversi approcci, per dimostrare la versatilità dei trattamenti meccanochimici per la realizzazione di diversi materiali. In un primo approccio (II capitolo), viene riportato uno studio approfondito sull'effetto dei trattamenti meccanochimici sul polipropilene (PP), uno dei polimeri più diffusi, per valutare sistematicamente gli effetti dei processi meccanochimici sul polimero. Lo scopo di questo studio è stato quello di esplorare la possibilità di indurre reazioni radicaliche nel PP e in miscele a base di PP attraverso processi meccanochimici allo stato solido, sia per promuovere la formazione di ramificazioni di catena e/o per ottenere l'innesto di diverse molecole. I campioni di PP trattati sono stati analizzati attraverso varie tecniche di caratterizzazione. In particolare, l'analisi in chemiluminescenza ha rivelato la formazione di specie reattive, generate da reazioni radicaliche, particolarmente numerose per trattamenti di BM lunghi. Per fornire un proof of concept del potenziale utilizzo dei radicali prodotti per modificare chimicamente il PP, i trattamenti di BM sono stati eseguiti in presenza di sostanze chimiche sensibili alle reazioni radicaliche, polibutadiene a basso PM (BR) e glicidil metacrilato (GMA). Dopo la reazione e la purificazione, l'analisi spettroscopica ha dato evidenza dell'innesto di una piccola quantità sia di GMA che di BR su PP.Nel III capitolo, il BM è stato sfruttato come strumento per valorizzare e riciclare rifiuti plastici eterogenei ricchi di poliolefine. In particolare, i trattamenti meccanochimici sono stati eseguiti su una frazione di film di piccole dimensioni recuperata dalla raccolta dei rifiuti domestici, per indagare gli effetti indotti dalle intense sollecitazioni meccaniche sulla morfologia e sulle proprietà dei materiali trattati. Per quanto riguarda la valorizzazione della cellulosa e delle biomasse, sono state svolte due principali attività di ricerca:In un primo studio, nel IV capitolo, sono stati realizzati compositi a base di acido poli(lattico) (PLA) contenenti materiali cellulosici come filler organico e un estere oligomerico dell'acido lattico come agente plasticizzante, al fine di migliorare e modulare le caratteristiche meccaniche e termiche di questo polimero biodegradabile. Il processo di BM è stato utilizzato in diverse condizioni come processo sostenibile e flessibile per indurre cambiamenti strutturali e morfologici nella cellulosa, prima della realizzazione del composito. Infine, nel V capitolo, viene riportato lo sviluppo di un coating completamente bio-based a base di coffee silverskin (CS), un sottoprodotto del processo di tostatura del caffè, mediante trattamento meccanochimico. Il trattamento di BM è stato proposto per la destrutturazione della struttura complessa del CS, in condizioni blande ed utilizzando solo acqua come solvente.The present doctoral thesis deals with the development of “greener” methodologies for the modification, the production and the recycling of organic materials, focusing on two classes of materials:1)polyolefins and 2) cellulose and ligno-cellulosic biomasses.The aim is to increase the sustainability of processes adhering to the principles of Green Chemistry, through the design of strategies that reduce the use of chemicals and solvents, avoid waste generation by extending recycling, enable the utilization of renewable raw materials, promote biodegradability.Specifically, in this thesis, mechanochemical processes were developed through the use of a ball-milling apparatus. This kind of treatments relies on the application of intense shear and compressive forces to solid materials through the action of the milling bodies, in order to induce morphological and structural changes and, in some cases, chemical modifications in organic materials. Different approaches were followed, to demonstrate the versatility of mechanochemical treatments for the realization of different materials. In a first approach (II chapter), an in-depth study on the effect mechanochemical treatments on polypropylene (PP), one of the most diffused commodity polymer, is reported to systematically evaluate the effects of mechanochemical processes on polymers. The aim of this study was to explore the possibility to induce radical reactions in PP and PP based mixtures through solid state mechanochemical processes, to either promote the formation of chain branching and/or to obtain the grafting of different molecules.Treated PP samples were analyzed through various characterization techniques. In particular, chemiluminescence analysis revealed the formation of reactive species, generated by radical reactions, especially abundant for long BM treatments.To provide a proof of concept of the exploitability of the produced radicals to chemically modify PP, BM treatments were performed in presence of chemicals susceptible to radical reactions, low MW polybutadiene (BR) and glycidyl methacrylate (GMA). After reaction, and purification, spectroscopic analysis gave evidence of the grafting of a small amount of both GMA and BR onto PP. In the III chapter, BM was exploited as a tool to valorize and recycle polyolefin rich heterogeneous plastic waste. In particular, the mechanochemical treatments were performed on a small-sized film fraction recovered from household waste collection, to investigate the effects induced by the intense mechanical stresses on morphology and properties. Regarding the valorization of cellulose and biomasses, two main research activities were carried out: in a first study, in the IV chapter, poly(lactic) acid (PLA)-based composites containing cellulosic materials as an organic filler and an oligomeric ester of lactic acid as a plasticizing agent were realized, in order to improve and modulate thermal and mechanical response of this biodegradable polymer. Ball milling was used in different conditions as a green, flexible process to induce structural and morphological changes in cellulose, before composite realization. Finally, in the V chapter, the development of a fully bio-based coating based on coffee silverskin (CS), a coffee roasting process by-products, by mechano-chemical treatment is reported. The BM treatment has been proposed for the deconstruction of the complex structure of CS, in mild conditions and using only water as solvent
Migration to microservices: a quality-driven approach
Full text linkMicroservices architecture has become increasingly popular among software practitioners in recent years as an effective approach to building complex applications that are more scalable, maintainable, and resilient. Top companies like Netflix, Amazon, and Uber have all successfully modernized their systems migrating them to microservices architecture. However, this migration process can pose certain challenges that require careful planning and execution to achieve desired outcomes and ensure that both functional and non-functional requirements are met.
One of the most significant challenges in microservices migration is the planning phase, as poor planning can lead to increased complexity, reduced scalability, and degraded performance of the final system. To address these challenges, we propose a quality-driven migration approach that considers software qualities in all the migration stages. Our approach aims to improve software qualities with the migration process by applying architectural refactoring techniques, such as antipatterns detecion analysis. By combining techniques from both migration and refactoring, our approach can help organizations to achieve the desired outcomes of microservices migration while improving or maintaining quality attributes throughout the process. In addition, we created a novel quality-driven (antipatterns-based) refactoring approach to be applied to microservices derived from the migration.
Given the industrial nature of the PhD of which this document represents the final Thesis, the research has been validated by applying it to a real case study from the BIM Italia company. In particular, the refactoring approach has been applied for refactoring two microservices of BIM Italia that suffered from significant performance degradation after migration. Industrial experimentation in BIM Italia has showcased the importance of quality-driven migration approaches in a microservices architecture.
This Thesis makes several contributions, including: i) conducting a thorough analysis of quality-driven migration approaches, ii) proposing a quality-driven migration process for microservices that relies on antipatterns analysis to ensure a successful migration, iii) introducing a graph-based software representation with annotations for antipatterns detection, and iv) developing and validation of a quality-driven refactoring approach for microservices resulting from the migration of a monolithic system.
The output of this Thesis is a set of guidelines for quality-driven migration to microservices that can help practitioners to avoid common pitfalls ensuring that their systems meet the expected quality requirements. Our work demonstrates the importance of considering quality attributes throughout the migration process and how architectural refactoring can help achieve these goals
The Quality-Driven Refactoring Approach in BIM Italia
No full textIn the last decade, many companies started modernizing their software systems by migrating to microservices. An accurate migration planning supports the creation of a microservices-based system faithful to the original while satisfying the required (quality) constraints. Contrariwise, poor migration planning can slow down the modernization process as it requires more iterations to meet requirements. This is the case of BIM Italia which undertook a migration process to modernize their 10 years old system. Unfortunately, the resulting system revealed to be less performant than expected.This paper presents a quality-driven, antipattern-based, refac-toring approach, and its application to the BIM Italia system, enabling the satisfaction of target performance quality constraints. The empirical evaluation performed shows that our proposed refactoring approach improved the response time of the refactored microservices up to five times with respect to the first version of the microservices
From Refactoring to Migration: a Quality-Driven Strategy for Microservices Adoption
No full textIn the contemporary landscape of software development, the transition towards microservices architecture is often a critical step for organizations aiming to enhance scalability and maintainability. However, maintaining quality standards during this transition is of paramount importance to ensure the continued success of the software system. In this paper, we introduce a migration to microservices approach that strictly considers quality constraints as the main driver of the migration. The approach is built on top of the knowledge acquired in our previous work where we used antipatterns analysis for the refactoring of microservices derived from the monolith. We applied our quality-driven migration approach to the industrial case study of BIM Italia. To measure the effectiveness of our approach we performed a comparative analysis of the time, cost, and effort-related dimensions between the quality-driven migration and the refactoring processes presented and applied in the same company in our previous work. Our findings highlight the effectiveness of our quality-driven migration process in reducing time, costs, and effort, showcasing its merits in practice. This research emphasizes the importance of quality-driven migration strategies when transitioning from monolithic systems to microservices. By employing these principles, organizations can migrate to microservices not only realizing the expected benefits of microservices adoption but also upholding essential quality standards
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Studio integrato con ecografia, mammografia e TC in paziente con metastasi intrammamarie da melanoma.
No full textAppropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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