187 research outputs found

    Intégration des méthodes formelles dans le développement des RCSFs

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    In this thesis, we have relied on formal techniques in order to first evaluate WSN protocols and then to propose solutions that meet the requirements of these networks. The thesis contributes to the modelling, analysis, design and evaluation of WSN protocols. In this context, the thesis begins with a survey on WSN and formal verification techniques. Focusing on the MAC layer, the thesis reviews proposed MAC protocols for WSN as well as their design challenges. The dissertation then proceeds to outline the contributions of this work. As a first proposal, we develop a stochastic generic model of the 802.11 MAC protocol for an arbitrary network topology and then perform probabilistic evaluation of the protocol using statistical model checking. Considering an alternative power source to operate WSN, energy harvesting, we move to the second proposal where a protocol designed for EH-WSN is modelled and various performance parameters are evaluated. Finally, the thesis explores mobility in WSN and proposes a new MAC protocol, named "Mobility and Energy Harvesting aware Medium Access Control (MEH-MAC)" protocol for dynamic sensor networks powered by ambient energy. The protocol is modelled and verified under several features

    Bio-Based Materials: Contribution to Advancing Circular Economy

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    This reprint focuses on studies dealing with bio-based materials and its contribution to a circular economy. Research dealing with recycling, waste conversion to bio-based products, the development of bio-based composites, and surface treatments on cellulose fibres have been included in this reprint

    Digital Light Processing 3D printing of Thermosets via Reversible Addition-Fragmentation Chain Transfer Polymerization

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    Digital light processing (DLP) 3D printing is an efficient additive manufacturing technique for the fabrication of 3D objects with intricate structures. However, current photocurable resins for DLP printing are mainly based on uncontrolled radical polymerizations associated with limited control over formed networks and a high degree of heterogeneity in macromolecular structures. This uncontrolled process could only afford narrow manipulation over bulk material properties, restricting the wide applications of DLP 3D-printed materials. To access versatile control over bulk material properties, reversible-deactivation radical polymerization (RDRP) has been widely applied to tune the macromolecular structures of polymer networks. In particular, photo-mediated reversible addition-fragmentation chain transfer (photoRAFT) polymerization has been employed to design photocurable resins for DLP printing of materials with homogeneous networks and enhanced properties. To deepen the understanding of using photoRAFT polymerization in designing photocurable resins for DLP 3D printing processes, this body of work first investigated the role of RAFT agent architectures (i.e., different number of arms) in a visible-light-mediated photoinduced electron/energy transfer (PET)-RAFT system. The monofunctional RAFT agent resulted in optimal mechanical properties among the studied candidates. Subsequently, the optimized monofunctional RAFT agent was employed in silica nanoparticle-loaded composite photocurable resins based on type I-initiated RAFT polymerization, which produced composite materials with more homogeneous networks and improved tensile properties. As an extension of small molecule RAFT agents, macro-chain transfer agents (macroCTAs) were subsequently utilized to design photocurable resins for printing nanostructured materials via polymerization-induced microphase separation (PIMS). Similarly, macroCTA with 1, 2, and 4-arm were used to study the architecture effect in the PIMS process. The results demonstrated that the nanostructural domain sizes were precisely defined by the arm length of macroCTAs, while the 2 and 4-arm macroCTAs led to phase-inverted morphologies which were not observed in the case of using 1-arm macroCTAs. Afterward, diblock macroCTAs with varied compositions and sequences were employed in the PIMS printing system. Tuning ratio of network-incompatible A and B blocks in macroCTA enables a transition from bicontinuous to less connected morphologies. More importantly, the macroCTA block sequence was also found to significantly affect the PIMS process, nanostructure, and bulk properties of 3D printed materials

    3D/4D printing of cellulose nanocrystals-based biomaterials: Additives for sustainable applications

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    Cellulose nanocrystals (CNCs) have gained significant attraction from both industrial and academic sectors, thanks to their biodegradability, non-toxicity, and renewability with remarkable mechanical characteristics. Desirable mechanical characteristics of CNCs include high stiffness, high strength, excellent flexibility, and large surface-to-volume ratio. Additionally, the mechanical properties of CNCs can be tailored through chemical modifications for high-end applications including tissue engineering, actuating, and biomedical. Modern manufacturing methods including 3D/4D printing are highly advantageous for developing sophisticated and intricate geometries. This review highlights the major developments of additive manufactured CNCs, which promote sustainable solutions across a wide range of applications. Additionally, this contribution also presents current challenges and future research directions of CNC-based composites developed through 3D/4D printing techniques for myriad engineering sectors including tissue engineering, wound healing, wearable electronics, robotics, and anti-counterfeiting applications. Overall, this review will greatly help research scientists from chemistry, materials, biomedicine, and other disciplines to comprehend the underlying principles, mechanical properties, and applications of additively manufactured CNC-based structures

    Cyber-Human Systems, Space Technologies, and Threats

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    CYBER-HUMAN SYSTEMS, SPACE TECHNOLOGIES, AND THREATS is our eighth textbook in a series covering the world of UASs / CUAS/ UUVs / SPACE. Other textbooks in our series are Space Systems Emerging Technologies and Operations; Drone Delivery of CBNRECy – DEW Weapons: Emerging Threats of Mini-Weapons of Mass Destruction and Disruption (WMDD); Disruptive Technologies with applications in Airline, Marine, Defense Industries; Unmanned Vehicle Systems & Operations On Air, Sea, Land; Counter Unmanned Aircraft Systems Technologies and Operations; Unmanned Aircraft Systems in the Cyber Domain: Protecting USA’s Advanced Air Assets, 2nd edition; and Unmanned Aircraft Systems (UAS) in the Cyber Domain Protecting USA’s Advanced Air Assets, 1st edition. Our previous seven titles have received considerable global recognition in the field. (Nichols & Carter, 2022) (Nichols, et al., 2021) (Nichols R. K., et al., 2020) (Nichols R. , et al., 2020) (Nichols R. , et al., 2019) (Nichols R. K., 2018) (Nichols R. K., et al., 2022)https://newprairiepress.org/ebooks/1052/thumbnail.jp

    Chapter 34 - Biocompatibility of nanocellulose: Emerging biomedical applications

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    Nanocellulose already proved to be a highly relevant material for biomedical applications, ensued by its outstanding mechanical properties and, more importantly, its biocompatibility. Nevertheless, despite their previous intensive research, a notable number of emerging applications are still being developed. Interestingly, this drive is not solely based on the nanocellulose features, but also heavily dependent on sustainability. The three core nanocelluloses encompass cellulose nanocrystals (CNCs), cellulose nanofibrils (CNFs), and bacterial nanocellulose (BNC). All these different types of nanocellulose display highly interesting biomedical properties per se, after modification and when used in composite formulations. Novel applications that use nanocellulose includewell-known areas, namely, wound dressings, implants, indwelling medical devices, scaffolds, and novel printed scaffolds. Their cytotoxicity and biocompatibility using recent methodologies are thoroughly analyzed to reinforce their near future applicability. By analyzing the pristine core nanocellulose, none display cytotoxicity. However, CNF has the highest potential to fail long-term biocompatibility since it tends to trigger inflammation. On the other hand, neverdried BNC displays a remarkable biocompatibility. Despite this, all nanocelluloses clearly represent a flag bearer of future superior biomaterials, being elite materials in the urgent replacement of our petrochemical dependence

    Analysis of Embedded Controllers Subject to Computational Overruns

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    Microcontrollers have become an integral part of modern everyday embedded systems, such as smart bikes, cars, and drones. Typically, microcontrollers operate under real-time constraints, which require the timely execution of programs on the resource-constrained hardware. As embedded systems are becoming increasingly more complex, microcontrollers run the risk of violating their timing constraints, i.e., overrunning the program deadlines. Breaking these constraints can cause severe damage to both the embedded system and the humans interacting with the device. Therefore, it is crucial to analyse embedded systems properly to ensure that they do not pose any significant danger if the microcontroller overruns a few deadlines.However, there are very few tools available for assessing the safety and performance of embedded control systems when considering the implementation of the microcontroller. This thesis aims to fill this gap in the literature by presenting five papers on the analysis of embedded controllers subject to computational overruns. Details about the real-time operating system's implementation are included into the analysis, such as what happens to the controller's internal state representation when the timing constraints are violated. The contribution includes theoretical and computational tools for analysing the embedded system's stability, performance, and real-time properties.The embedded controller is analysed under three different types of timing violations: blackout events (when no control computation is completed during long periods), weakly-hard constraints (when the number of deadline overruns is constrained over a window), and stochastic overruns (when violations of timing constraints are governed by a probabilistic process). These scenarios are combined with different implementation policies to reduce the gap between the analysis and its practical applicability. The analyses are further validated with a comprehensive experimental campaign performed on both a set of physical processes and multiple simulations.In conclusion, the findings of this thesis reveal that the effect deadline overruns have on the embedded system heavily depends the implementation details and the system's dynamics. Additionally, the stability analysis of embedded controllers subject to deadline overruns is typically conservative, implying that additional insights can be gained by also analysing the system's performance

    Synthesis and Characterization of Nanomaterials

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    Nanomaterial is defined a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm to 100 nm. Nanomaterials not only differ from the corresponding bulk materials in morphological properties but they can also demonstrate different physico-chemical characteristics. Manufactured nanomaterials are regarded as key components of innovations in various fields with high potential impact, such as energy generation and storage, electronics, photonics, diagnostics, integrated sensors, semiconductors, foods, textiles, structural materials, sunscreens, cosmetics, and coatings or drug delivery systems, and medical imaging equipment. Widespread use of nanomaterials raises concerns about their safety for humans and the environment, possibly limiting the impact of the nanotechnology-based innovation. The development of safe nanomaterials has to result in a safe, as well as functional material or product. Its safe use, and disposal at the end of its life cycle must be taken into account too. Responsibility for the safe handling of synthetic nanomaterials therefore rests with the manufacturer and importer. This book gathers and reviews the collection of five contributions (four articles and one review), with authors from Europe and America accepted for publication in the aforementioned Special Issue of Fibers

    Cellulose based aerogel microfibers for biomedical applications

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    Surface Engineering of C/N/O Functionalized Materials

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    This book discusses the latest developments in the surface engineering of C/N/O functionalized materials, including both experimental and theoretical studies on heat treatment and surface engineering of metals, ceramics, and polymers
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