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Carbon-based polymer nanocomposites for 3D-printing
Get PDFIn this PhD project, novel polymer nanocomposites are developed with the aim to increase the performances of 3D-printed parts obtained by fused deposition modeling (FDM). The attention is focused on carbon-based nanomaterials incorporated into an acrylonitrile–butadiene–styrene (ABS) polymer by a solvent-free process. ABS-based nanocomposites were prepared by incorporating different kinds and amounts of graphene nanoplatelets (GNP), carbon nanotubes (CNT) and hybrid (GNP/CNT) systems. In order to understand the effect of the manufacturing process on the material’s properties, the samples were produced into two different processing routes: (i) melt compounding and compression molding, and (ii) melt compounding, following by filament extrusion, and fused deposition modelling (FDM). Several characterization techniques were employed in order to evaluate the flowablity, morphology, mechanical and functional properties of the materials.
In the first part of work, ABS-graphene nanocomposites are described. Two ABS matrices having different viscosity were compared with the addition of various types of commercial graphene nanoplatelets (xGnP® M5, C300, C500, and C750 by XG Sciences) in the range 2-8 wt%. The better processability and higher stiffening effect on compression molded plates were achieved by utilizing the low viscosity ABS. The effects of GNPs on the thermal, electromagnetic shielding (EMI SE), electrical and mechanical behaviour of an ABS matrix were investigated. Melt flow index (MFI) values almost linearly decreased with all the type of GNP, especially with the highest surface area nanofiller (GNP-C750). Due to large size of graphene, nanocomposites filled with GNP-M5 showed the better properties of in electromagnetic interference shielding efficiency (EMI SE) and stiffness. Consequently, GNP-M5 were selected and incorporated at 4 wt% in ABS filaments used to feed a FDM machine to obtain specimens with various build orientations. The elastic modulus and dynamic storage moduli of 3D printed parts along three different build orientations were increased by the presence of GNP-M5 in the ABS matrix. At the same time, a decrease in both strength and strain at break was observed when GNP-M5 is added to ABS. Moreover, higher thermal stability was induced on 3D printed parts by GNP, as indicated by a reduction in both coefficient of linear thermal expansion and creep compliance. A comparison between 3D printed and compression molded parts highlighted the importance of the orientation effects induced by the FDM process.
In the second part of work, the results of the investigation on ABS-carbon nanotubes nanocomposites are reported. ABS-CNT nanocomposites plate production by compression molding and their characterization was a preliminary step. Nanocomposite ABS/CNT filaments at 1-8 wt % were obtained by using direct melt compounding and extrusion. The optimal CNT content in the filaments for FDM was found to be 6 wt %; for this composite, a detailed investigation of the thermal, mechanical and electrical properties was performed. The presence of CNT in ABS filaments and 3D-printed parts resulted in a significant enhancement of the tensile modulus and strength, accompanied by a reduction of the elongation at break. As documented by dynamic mechanical thermal analysis, the stiffening effect of CNT in ABS is particularly pronounced at high temperatures. Besides, the presence of CNT in 3D-printed parts accounts for better creep and thermal dimensional stabilities of 3D-printed parts, accompanied by a reduction of the coefficient of thermal expansion. 3D-printed nanocomposite samples with 6 wt% of CNT exhibited a good electrical conductivity, even if lower than pristine composite filaments. In addition, the strain sensing capabilities of the conducting 3D-printed samples with 6 wt% of CNT with two different infill patterns (HC, and H45) were studied. Upon the strain applied, the resistance change and damage in the conductive FDM parts were detectable. Fatigue and creep loading on FDM products were also carried out.
In last part of work, ABS-GNP-CNT hybrid nanocomposites are described. ABS nanocomposites plates with addition GNP-M5 and CNT at 2-8 wt% were compared. A significant higher reduction in MFI value by the addition of CNT compared to GNP was observed. The ABS/GNP nanocomposites showed the slightly higher stiffness and the creep stability compared to the ABS/CNT nanocomposites, but showed the lower tensile strength. Also, the ABS/CNT samples showed significant higher electrical properties in comparison to ABS/GNP. The total nanofiller content of CNT/GNP hybrid plates was fixed at 6 wt%. The hybrid nanocomposites showed a linear increase in modulus and strength as a function to CNT/M5 ratio. Moreover, conductive hybrid nanocomposite plates were obtained by the addition of CNT. The composition of 50:50 of CNT/GNP at 6 wt% was selected for FDM process due to the good compromise between processability and properties (e.g. mechanical and electrical). In agreement with electrical resistivity, EMI SE of 6 wt% ABS/CNT and 50:50 hybrid ABS nanocomposites resulted to be -46 dB and -31.7 dB for plate samples. EMI SE of FDM parts is about for -14 dB HC and H45 build orientation and –25 dB for PC build orientation printing from ABS/CNT nanocomposites, while parts had EMI SE about -12 dB for HC and H45 and -16 dB for PC from hybrid nanocomposites
Allegiance in International Armed Conflicts: The Role of the Duty of Fidelity in International Humanitarian Law
Get PDFThe duty not to betray the social group is an ancient socio-political concept adopted by authorities to regulate the loyal behaviour of their members. Such duty has been legally regulated for centuries and now forms part of the domestic legal systems of contemporary states. Known in English as allegiance, the duty of fidelity is a fundamental concept of law that gains notoriety in times of armed conflicts. However, allegiance has been overlooked by scholars of international law as a factor in the design, interpretation and application of the rules of international humanitarian law (IHL) that protect individuals during armed conflicts and limit the capacity of states to choose methods of warfare.
This study analyses the role that the concept of allegiance plays in the rules of IHL applicable in international armed conflicts. This is done by determining the contemporary meaning of allegiance in state practice, the ways it has been introduced into international law, and its use by relevant actors in six areas of IHL. The investigation reveals a rich historical practice around the concept of allegiance, its incorporation in rules and discussions of IHL, and the employment of this concept for multiple and diverse purposes: from the alleged basis for conferring protected status to civilians, to the alleged basis for denying protected status to combatants; from a protected element of occupied population, to a corruptible element of enemy population outside occupation; and as a presumption of dangerousness for enemy aliens, the required mens rea for desertion, and a vague term to determine connection between belligerent parties and armed groups.
This study clarifies the contemporary understanding of allegiance, and confronts the concept with treaty provisions, case law, and academic debates relevant to the use of allegiance in IHL. Additionally, the study explores the relation between domestic law and international law applicable during international armed conflicts and the overlooked position of individuals of dubious loyalties such as traitors, collaborators, deserters, internal enemies, and corrupters
Towards a New Technological Paradigm Based on Industry 4.0: Opportunities and Challenges for Innovation Policies
Get PDFThe analysis of the complex and fast changing technological processes which today are summarized in the term ‘Industry 4.0’ reveals that the industrial system is shifting towards a new technological paradigm (Perez, 2009; 2010), implying systemic transformations at micro, meso and macro levels of analysis (Geels, 2005). These radical transformations are deeply changing the way products, production processes and business models are conceived, questioning the traditional separation between manufacturing and services, and making it more and more important for firms to adopt a collaborative approach to innovation (Hagedoorn et al., 2000). This rapid technological advance implies the need for the socio-economic players to adopt new strategic and operational measures in order to prevent the loss of competitive advantage of national and regional innovation systems. The recent debate on industrial policies shows that a mission-oriented industrial policy approach (Mazzucato, 2014; European Commission, 2018) may provide interesting inspirational principles able to guide these transformations, since it places at the centre of its reasoning the key role of the public actor able to stimulate the strategic coordination between multiple socio-economic players at different levels (Mazzucato and Perez, 2014; Rodrik, 2004). According to this approach, Public-Private research Partnerships, are assumed to be effective vehicles of governance able to improve technological development, stimulating strong links between the relevant socio-economic players and thus increasing the national and regional systems’ overall innovative potential (Mazzucato, 2014; Rodrik, 2004; 2014; Robin and Schubert, 2013; Kristensen and Scherrer, 2016). The aim of the present work is to understand how the strategic coordination between public and private players may be an opportunity for the definition of effective innovation policies in the context of the current socio-technical transition. In order to reach this purpose, a multilevel approach (Geels, 2005) is adopted, taking into account both the national and the regional levels of analysis. A quantitative analysis is provided at national level in order to understand the relationship between a specific approach to innovation and technology policy, the overall innovation performance and the level of diffusion of cooperative innovation activities in a National Innovation System (Lundvall, 1988); moreover, it contributes to the existing literature on Public-Private research Partnerships (Hagedoorn et al., 2000) by testing the effectiveness of some main variables at industry and company level explaining the propensity of companies to get involved in formal cooperative innovation activities. This analysis is made taking into account data stemming from the 8th wave of the Community Innovation Survey, 2010-2012. Moreover, the results of a field research conducted at regional level are presented, aiming at understanding the elements of an institutional/organizational framework which are able to positively influence technological local development. In this case, the analysis takes into account a Regional Innovation System (Cooke et al., 1997): the Autonomous Province of Trento. Data have been gathered through both primary sources, based on 57 semi-structured interviews to local institutions and firms, and secondary sources, based on relevant documents and reports. The major conclusion of the present work is that, given the systemic nature of this socio-technical transition, only a mission-oriented policy approach to innovation policy based on strategic Public-Private research Partnerships may be able to trigger the necessary cross-level synergies between the different socio-economic players involved, managing the important challenges lying behind these transformations
Unpicking the fashion city: Theoretical issues and ideal types. An empirical analysis of London.
Get PDFLocal governments, ‘urban-booster’ commentaries and some academic approaches have increasingly focused on the idea of the ‘fashion city’ as a strategic factor for the economic development, growth and regeneration of major and minor cities across the world. Nowadays, in addition to established fashion’s world cities, there has been a proliferation of new fashion centres that have been termed as ‘second-tier’ cities of fashion. The growing and crucial importance of fashion in urban development strategies, together with the current diversity and variety of fashion centres, has created the need to broaden the knowledge of what constitutes a fashion city. To this day, either in academic or local policy field, little attention has been paid to defining the key elements that form a contemporary fashion centre. In light of these considerations, the aim of the present dissertation is to contribute to furthering the understanding of the actual meaning and significance of this concept and to possibly identifying distinctive models of fashion centres. Furthermore, the research seeks to explore the best suited methodologies to analyse the complexity and heterogeneity of contemporary fashion cities. The research is structured in four chapters, which address three main objectives. The first objective is to systematize the existing body of cross-disciplinary academic literature on the topic into a precise theoretical framework. In this regard, Chapter 1 presents a state of the art of fashion’s relation with cities by adopting a specific ‘creative approach’, which primarily focuses of fashion design as a cultural and creative industry (CCI) and on fashion designers as an example of the wider ‘creative class’. This analysis directs attention to a particular example of fashion centre that has been termed as the ‘creative fashion city’. The second objective is to develop an analytical framework to address the current heterogeneity of contemporary fashion centres. Chapter 2, drawing upon an extensive analysis of fashion’s world cities and ‘second-tier’ cities of fashion, suggests a framework of analysis for thinking about the diverse nature of fashion’s relation with the urban. It identifies multiple models of fashion’s world cities, as well as contrasting patterns in the development of newer fashion centres. Most importantly, through the adoption of Weber’s ideal type approach, it proposes three ideal types of fashion cities (‘manufacturing’, ‘design fashion’ and ‘symbolic’), which function as heuristic device to address the distinctive characteristics of fashion centres and to discuss future development pathways. The final and third objective is to understand how ‘real’ fashion cities can be studied, analysed and plotted on the ideal type model. To meet this objective, Chapter 3 and Chapter 4 present two analyses of London from a ‘supply’- and ‘demand-side’ perspective. The first one is based on the execution of 23 semi-structured interviews with key actors from London’s fashion ecosystem, as well as statistics and policy documents, to analyse the ‘material’ elements that underlie the development, transformation and current nature of this fashion centre. The second one explores the meaning embedded in two samples of around 30,000 tweets, which were collected at different times, to highlight the ‘symbolic’ representation of London as a fashion city on the social media platform Twitter. Both the ‘supply’- and ‘demand-side’ analyses draw a picture of London as a fashion centre that tends towards the ideal type of the ‘symbolic fashion city’.
The present dissertation has implications either for the academic and local policy field. It contributes to investigating the importance of different kinds of position that fashion plays in urban economies, drawing attention to fashion’s qualities as rather more than a conventional urban CCI. There emerges a growing emphasis on the symbolic economy as a tool for cementing the reputation of contemporary fashion centres, either specialised in manufacturing, fashion design or image-making activities. Furthermore, the ideal type approach complements and extends the now very familiar division between ‘fashion’s world cities’ and ‘second-tier cities’ and shifts away from the simplistic ‘tool-kit’ approach that has sought to promote new fashion centres as developing versions of ‘models’ set by established fashion’s world cities. In this respect, the accentuated ideal type of the ‘symbolic fashion city’ points to the risks of what can described as a ‘hollowing-out’ of the fashion city, which is detached not only from making and designing clothing but also from urban fashion cultures. Thus, what is important is not about fixed strategies for the development of a fashion centre, but the need for ad-hoc fashion policies specifically adapted to different historical and cultural local contexts
Catchment scale modelling of micro and emerging pollutants
Get PDFThe fate and transport of solutes introduced into a watershed and sampled at the catchment outlet depends on many environmental, chemical and hydro-climatological forces.Moreover, if the solutes are micro and emerging pollutants (i.e. pharmaceuticals), which are non-regulated contaminants not routinely monitored but often-detected in fresh waters, the description of the transport sources and routes becomes an interesting and challenging topic to investigate and describe, especially in conjunction with the well-known travel time transport approach at the catchment-scale. In fact, with the travel time approach to pharmaceuticals represents a framework that allows dealing in a unitary and simple way the main two mitigation mechanisms controlling them, which are dilution and biological decay. Moreover, possible consequences on the health of humans and of aquatic organisms have become issue of increasing concern by the scientific community worldwide. The topics have been extensively studied in the last decades, with some recent benchmark contributions. Nevertheless, there is still room for further development for emerging contaminant models and there is still the necessity of complementing the applications with measured data. This doctoral thesis aimed at contributing with new insights into the multi-faceted aspects of solute transport at catchment-scale, proposing novel solutions, with applications to real-world case studies and including a detailed description of the major aspects that influence the water quality dynamics in rivers. The thesis is divided into three interconnected and chronological subsequent parts. In the first part, a detailed description of three large European river basins are presented (i.e. Adige, Ebro and Sava), believing that an accurate analysis of existing information is therefore useful and necessary to identify stressors that may act in synergy and to design new field campaigns. In addition, a detailed data analysis of the main water quality variables is presented: advanced statistical analyses (i.e. Spearman rank correlation, Principal Component Analysis, andMann-Kendall trend tests) were applied to long-term time series of water quality data both in the Adige River Basin and in the Ebro and Sava catchments, aiming at providing an integrated and comparative analysis of recent trends, in order to investigate the relationships between water quality parameters and the main factors controlling them (i.e. climate change, streamflow, land use, population) in the Mediterranean region. These catchments are included into the EU project “Globaqua ”, dealing with the analysis of the combined effect of several stressors on the freshwater ecosystems inMediterranean rivers. In fact, little attention has been paid to linkages between long-term trends in climate, streamflow and water quality in European basins; nevertheless, such analysis can represent, complementary to a deep knowledge of the investigated systems, a reliable tool for decision makers in river basin planning by providing a reliable estimate of the impacts on the aquatic ecosystem of the studied basins. In the second part, sampling campaigns performed in our study basin, the Adige catchment, are presented in detail. Special attention is also given to emerging pollutants, whose study on the occurrence patterns and spatiotemporal variability in the Adige River Basin has been conducted in conjunction with population patterns and touristic fluxes. In the third and last part, novel theoretical solutions of the well-known advection-dispersion-reaction (ADR) equation are presented. The theory was developed for both general water quality variables and pharmaceuticals, evidencing differences and analysing the main factors that influence water quality dynamics. An application is also proposed to the Adige catchment
Optimization-Based Methodology for the Exploration of Cyber-Physical System Architectures
Get PDFIn this thesis, we address the design space exploration of cyber-physical system architectures to select correct-by-construction configuration and interconnection of system components taken from pre-defined libraries. We formulate the exploration problem as a mapping problem and use optimization to solve it by searching for a minimum cost architecture that meets system requirements.
Using a graph-based representation of a system architecture, we define a set of generic mixed integer linear constraints over graph vertices, edges and paths, and use these constraints to instantiate a variety of design requirements (e.g., interconnection, flow, workload, timing, reliability, routing). We implement a comprehensive toolbox that supports all steps of the proposed methodology. It provides a pattern-based formal language to facilitate requirements specification and a set of scalable algorithms for encoding and solving exploration problems.
We prove our concepts on a set of case studies for different cyber-physical system domains, such as electrical power distribution networks, reconfigurable industrial production lines and wireless sensor networks
Structural hybrid simulation with model updating of material constitutive model
Get PDFWhen hybrid simulation (HS) with substructures is employed for assessing the seismic behavior of a large complex structure, it is unrealistic to test all the components that may exhibit strong nonlinearity. Hence, the accuracy of the numerical substructure (NS) faces an increased challenge. To this end, this paper will emphasize on improving the accuracy of the NS in hybrid simulation based on the model updating approach. Most hybrid simulations with model updating (UHS) focus on updating the parameters of the component constitutive model (story shear model) leading to large modeling errors and the unknown detail responses. Moreover, the most extensively used component constitutive models, such as the Bouc-Wen model, are the models in a narrow sense because they are different for various RC members when the size of the component, boundary conditions, axial compression ratio, and the volumetric stirrup ratio are different from one component to the other. Thus, numerous parameters are needed to describe the displacement-force relations of different components, which leads to the huge computational burden. With this respect, this paper proposes a novel hybrid simulation approach based on identifying and updating the parameters of the material constitutive model. The main work and results are concluded as follows,
1. The unified constitutive model of unconfined and confined concrete is derived from the existing uniaxial concrete constitutive models by introducing the volumetric stirrup ratio.
2. To solve the problem that the relation of the measurements (force of the specimen of a RC member) and the identified parameters (concrete constitutive parameters) are difficult to analytical expressed, an OpenSees embedded unscented Kalman filter is proposed for parameter identification. To this end, several parts of the OpenSees source codes are developed and modified.
3. The proposed identification method and hybrid simulation based on updating the concrete constitutive parameters are respectively validated through a monotonic loading test on a RC column and a UHS on a RC frame. The results show that the convergence values of each parameter under various experimental cases are close to each other with a small variance, which indicates that the proposed identification method is robust and reliable. Comparing to the standard HS, the accuracy of the NS, hence the UHS, is significantly improved.
4. Apply the proposed UHS to a RC continuous rigid bridge with tall thin-walled piers. It concludes that the performance of the identification method is still quite good. Contrasting to the simpler structure, the improved accuracy of a large complex structure is even greater. Moreover, the accuracy of the NS can be greatly increased even though the model error is increased. By tuning the initial values of constitutive parameters, the negative influence of model error is decreased to further improve the precision of the NS. By observing the specimen, it is found that the thin-walled hollow section specimen is a bending-shear type damage mode and finally damaged due to the tensile rupture of the stirrup
Strutture di combustione a Lugo di Grezzana (VR). L'uso dell'archeologia sperimentale per l'interpretazione di processi archeologici
Get PDFNell'ambito dell'analisi delle strutture d'abitato è facile imbattersi in tracce di utilizzo del fuoco. Esse sono riferibili ad attività di vario genere, sia domestiche che artigianali: possono essere legate all'illuminazione, al riscaldamento, alla cottura del cibo e a molte altre che spesso sono difficili da individuare. Quello che rimane sono le strutture di combustione impiegate che, a partire dal Neolitico, assumono un ruolo determinante anche in relazione a nuove attività produttive legate a modi di vita stanziali. In questo lavoro, al fine di elaborare un quadro delle evidenze note durante il Neolitico è stata effettuata una classificazione delle attestazioni di strutture di combustione nella nostra penisola e al di fuori dei suoi confini. Il caso studio è rappresentato dal sito di Lugo di Grezzana (VR) ubicato ai piedi dei Monti Lessini oggetto di ricerche sistematiche che hanno permesso di mettere in luce un abitato inquadrabile nel Neolitico antico e attribuibile alla cultura di Fiorano, 5500 - 4900 a. C. cal. Nel dettaglio vengono presentate e analizzate le strutture di combustione in fossa rinvenute nel sito. Esse si contraddistinguono per la presenza di tutte quelle tracce considerate identificative di processi di combustione: forti alterazioni termiche del suolo (rubefazione), presenza di carboni, ceneri, concotti e travi carbonizzate. Il lavoro è stato integrato da analisi archeometriche mirate alla caratterizzazione dei campioni di concotto disponibili (spettroscopia a infrarossi con Trasformata di Fourier, FT-IR, microscopia elettronica a scansione, SEM).
L'uso dell'archeologia sperimentale come metodo di verifica di specifiche ipotesi che favoriscano una migliore interpretazione delle evidenze in esame è parte fondamentale della ricerca. Attraverso repliche di cottura in buca svolte sul campo, in prossimità del sito originario, è stato possibile risalire alle cause che possono essere state all'origine della formazione delle tracce presenti nel record archeologico. I rapporti di causa-effetto connessi alla combustione e le relative ripercussioni sulla struttura impiegata, sono stati dunque oggetto di indagine e hanno permesso di rispondere ad una serie di interrogativi e confermare o meno le ipotesi di volta in volta formulate. E' stato possibile comprendere meglio i processi legati all'alterazione termica dei sedimenti e alla preservazione di travi sul fondo la cui presenza, potrebbe esser riconducibile ad una funzione ben specifica. Le repliche hanno permesso inoltre di approfondire le conoscenze sulla capacità termica delle strutture in fossa e i risultati consentono di considerarle potenzialmente adatte per la cottura di una classe ceramica come la figulina, come attestato dalle temperature massime raggiunte (700° C - 900° C). I risultati ottenuti permettono di sottolineare l'importanza di una disciplina come l'archeologia sperimentale che, grazie all'osservazione di fenomeni "dinamici" costituisce un importantissimo strumento per la comprensione del record archeologico
Clearing mechanism in real and financial markets
Get PDFThe present thesis is a collection of contributions concerning the application of the clearing principle in real and financial markets. In particular, two issues are deepened. The first concerns the effect of bilateral clearing of interbank deposits in the reduction of systemic risk. The second focuses on the endogenous formation process of clearing houses that manage payments. The methodology applied in the three contributions is the network analysis combined with agent-based models and computer simulations. The work is structured in four sections. The first defines and describes the more popular clearing agreements from a legal and economic point of view and provides a presentation of the three collected papers. The second section investigates the effect of bilateral netting on financial stability during a liquidity crisis. The third section analyzes how bilateral netting affects the resilience of an interbank credit network in the event of a shock affecting the assets of an intermediary. The fourth section analyzes the endogenous formation of clearing houses in both corporate barter circuits and interbank payment networks
Specification-based Predictive Continuous Monitoring for Cyber Physical Systems with Unobservables
Get PDFCyber Physical Systems (CPS), like IoT and industrial control systems, are typically vulnerable to cyber threats due to a lack of cyber security measures and hard change management. Security monitoring is aimed at improving the situational awareness and the resilience to cyber attacks.
Solutions tailored to CPS are required for greater effectiveness. This PhD work proposes a monitoring framework that leverages the knowledge of the CPS in order to specify, check, and predict known critical conditions. This approach is particularly suitable to CPS which are designed for a precise purpose, well documented, and predictable to a good extent. The framework uses a formal logical language to specify quantitative critical conditions and an optimisation linear programming and SMT-based engine. The framework computes a quantitative measure of the criticality of the current CPS system: checking how criticality changes in time enables to predict whether the system is approaching to a critical condition or reaching back a licit state.
An important novelty of the approach is the capability of dealing with unobservable variables, for a greater feasibility for real cases, and the possibility to use observation times in critical specifications. This work presents the formal framework, a prototype, a testbed, and first experimental results that validate the feasibility of the approach