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Sinn, Thomas. "Smart deployable space structures". Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28327.
Pełny tekst źródłaMcHenry, John T. "Multicomputer networks for smart structures". Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40053.
Pełny tekst źródłaGharibnezhad, Fahit. "Robust damage detection in smart structures". Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/277544.
Pełny tekst źródłaLa presente tesis doctoral se dedica a la exploración y presentación de técnicas novedosas para la Monitorización y detección de defectos en estructuras (Structural Health Monitoring -SHM-) SHM es un campo actualmente en desarrollo que pretende asegurarse que las estructuras permanecen en su condición deseada para evitar cualquier catástrofe. En SHM se presentan diferentes niveles de diagnóstico, Este trabajo se concentra en el primer nivel, que se considera el más importante, la detección de los defectos. Las nuevas técnicas presentadas en esta tesis se basan en diferentes métodos estadísticos y de procesamiento de señales tales como el Análisis de Componentes Princpales (PCA) y sus variaciones robustas, Transformada wavelets, lógica difusa, gráficas de Andrew, etc. Estas técnicas de aplican sobre las ondas de vibración que se generan y se miden en la estructura utilizando trasductores apropiados. Dispositivos piezocerámicos (PZT's) se han escogido para este trabajo ya que presentan características especiales tales como: alto rendimiento, bajo consumo de energia y bajo costo. Para garantizar la eficacia de la metodología propuesta,se ha validado en diferentes laboratorios y estructuras a escala real: placas de aluminio y de material compuesto, fuselage de un avión, revestimiento del ala de un avóin, tubería, etc. Debido a la gran variedad de estructuras utilizadas, su aplicación en la industria aeroespacial y/o petrolera es prometedora. Por otra parte, los cambios ambientales pueden afectar al rendimiento de la detección de daños y propagación de la onda significativamente . En este trabajo , se estudia el efecto de las variaciones de temperatura ya que es uno de los principales factores de fluctuación del medio ambiente . Para examinar su efecto en la detección de daños, en primer lugar, todos los métodos propuestos se prueban para comprobar si son sensibles a los cambios de temperatura o no. Finalmente , se aplica un método de compensación de temperatura para garantizar que los métodos propuestos son estables y robustos incluso cuando las estructuras se someten a condiciones ambientales variantes
Ulker, Fatma Demet. "Active Vibration Control Of Smart Structures". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1098409/index.pdf.
Pełny tekst źródłacontrol strategies in order to suppress the free and forced vibrations of smart structures. The smart structures analyzed in this study were the smart beam and the smart ¯
n. They were aluminum passive structures with surface bonded PZT (Lead-Zirconate-Titanate) patches. The structures were considered in clamped-free con¯
guration. The ¯
rst part of this study focused on the identi¯
cation of nominal system models of the smart structures from the experimental data. For the experimentally identi¯
ed models the robust controllers were designed by using H1 and ¹
-synthesis strategies. In the second part, the controller implementation was carried out for the suppression of free and forced vibrations of the smart structures. Within the framework of this study, a Smart Structures Laboratory was established in the Aerospace Engineering Department of METU. The controller implementations were carried out by considering two di®
erent experimental set-ups. In the ¯
rst set-up the controller designs were based on the strain measurements. In the second approach, the displacement measurements, which were acquired through laser displacement sensor, were considered in the controller design. The ¯
rst two °
exural modes of the smart beam were successfully controlled by using H1 method. The vibrations of the ¯
rst two °
exural and ¯
rst torsional modes of the smart ¯
n were suppressed through the ¹
-synthesis. Satisfactory attenuation levels were achieved for both strain measurement and displacement measurement applications.
Hadjiprocopiou, Marios. "Fibre optic sensors for smart structures". Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/842922/.
Pełny tekst źródłaZhang, Jiaying. "Reconfiguring smart structures using approximate heteroclinic connections". Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=29529.
Pełny tekst źródłaVigilante, Domenico. "Numerical study of two-dimensional smart structures". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/42706.
Pełny tekst źródłaMaster of Science
Blanc, Arthur. "Control of Sound Radiation From Structures with Periodic Smart Skins". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35080.
Pełny tekst źródłaMaster of Science
Riddle, Brian K. "General purpose, data driven, extensible, computer interface for smart sensors". Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/18920.
Pełny tekst źródłaEastep, Jonathan M. (Jonathan Michael). "Smart data structures : an online machine learning approach to multicore data structures". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65967.
Pełny tekst źródłaThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 175-180).
As multicores become prevalent, the complexity of programming is skyrocketing. One major difficulty is eciently orchestrating collaboration among threads through shared data structures. Unfortunately, choosing and hand-tuning data structure algorithms to get good performance across a variety of machines and inputs is a herculean task to add to the fundamental difficulty of getting a parallel program correct. To help mitigate these complexities, this work develops a new class of parallel data structures called Smart Data Structures that leverage online machine learning to adapt themselves automatically. We prototype and evaluate an open source library of Smart Data Structures for common parallel programming needs and demonstrate signicant improvements over the best existing algorithms under a variety of conditions. Our results indicate that learning is a promising technique for balancing and adapting to complex, time-varying tradeoffs and achieving the best performance available.
by Jonathan M. Eastep.
Ph.D.
Maillard, Julien. "Advanced Time Domain Sensing For Active Structural Acoustic Control". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30335.
Pełny tekst źródłaPh. D.
Yousefi-Koma, Aghil. "Active vibration control of smart structures using piezoelements". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq26875.pdf.
Pełny tekst źródłaBravo, Rafael. "Vibration control of flexible structures using smart materials". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0034/NQ66256.pdf.
Pełny tekst źródłaGummadi, Lakshmana Nagesh Babu. "Active control of delaminations in smart composite structures". Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/13022.
Pełny tekst źródłaTridech, Charnwit. "Smart fibre coatings stiffness control in composite structures". Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529352.
Pełny tekst źródłaMiller, Scott E. (Scott Edward). "Distributed parameter active vibration control of smart structures". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/33473.
Pełny tekst źródłaAhrens, Christian P. "A real time embedded controller for smart structures". Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44102.
Pełny tekst źródłaThis thesis presents a simple Real Time Embedded Control System (RTECS) in an application of Intelligent Structure Monitoring. Research in smart structures, especially the area of vibration suppression, has warranted the investigation of advanced computing environments. Real time PC computing power has limited development of high order control algorithms. The system discussed allows for implementation of l/O intensive algorithms and provides capability for advanced system development.
In an application of Modal Domain Sensing for Vibration Control, RTECS is compared to a PC AT based system for overall functionality and speed. Using a model development procedure, the system is optimized for efficient operation and speed. This includes minimizing the computational overhead associated with I/O. A comparison shows an order of magnitude I increase in system speed with larger speed increases discussed. The results provide an avenue for high order control system design. This leads to more accurate device modeling and a higher level of system control.
RTECS employs a novel RISC microcontroller capable of 15 MIPs continuous performance and burst rates of 40 MIPs. Advanced CMOS circuits are integrated on a single printed circuit board measuring 100 mm by 160 mm and require only 1 Watt of power. An operating system written in Forth provides the flexibility for high speed operation in short development cycles.
Master of Science
Yousefi-Koma, Aghil Carleton University Dissertation Engineering Mechanical and Aerospace. "Active vibration control of smart structures using piezoelements". Ottawa, 1997.
Znajdź pełny tekst źródłaDennerlein, Jürgen. "Broadband vibration control of spatially distributed smart structures". Düsseldorf VDI-Verl, 2008. http://d-nb.info/993722431/04.
Pełny tekst źródłaGiammarruto, Alessio. "Smart structures: sperimentazione mediante attuatori e sensori innovativi". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amslaurea.unibo.it/93/.
Pełny tekst źródłaMoss, Scott. "Modelling and experimental validation of the acoustic electric feedthrough technique". Fishermans Bend, Victoria : Defence Science and Technology Organisation, 2008. http://hdl.handle.net/1947/9738.
Pełny tekst źródłaSingla, Geetika. "Activity recognition in complex smart environment settings". Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/g_singla_041409.pdf.
Pełny tekst źródłaTitle from PDF title page (viewed on April 5, 2010). "Department of Electrical Engineering and Computer Science." Includes bibliographical references (p. 105-110).
Lee, Seung Joon. "Nonlinear analysis of smart composite plate and shell structures". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2218.
Pełny tekst źródłaWang, Qishan. "Active vibration and buckling control of piezoelectric smart structures". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114328.
Pełny tekst źródłaL'objectif de cette thése est le contrôle de la vibration et de flambage à l'aide de l'analyse par éléments finis et LQR/LQG technologies de contrôle de rétroaction pour les structures composites stratifiées piézo-électriques qui sont liés ou incorporés de surface de capteurs et d'actionneurs piézoélectriques. Il ya principalement deux parties ciblées. La partie des éléments finis : Deux formulations éléments finis pour les poutres laminées piézo-basé sur le classique d'Euler-Bernoulli et la théorie des poutres de Timoshenko, respectivement, linéaires couplées piézoélectriques équations constitutives, et le principe de variation de Hamilton sont développés. Un C0 continue, cisaillement flexible, à huit nuds élément de coque à double courbure sérendipité pour les plaques piézocomposites stratifiés et de coquillages est également dérivée basée sur la théorie de la couche-sage déformation de cisaillement, linéaires piézo-électriques couplés relations constitutives mécaniques, et le principe de variation de Hamilton. Toute la poutre, plaque, et des éléments de coque développés ont considéré la rigidité, de masse et les effets de couplage électromécanique du capteur piézo-électrique et les couches de l'actionneur. Les éléments de structure développéssont capables de traiter les effets non linéaires de déformation en cisaillementtransversal et la non-linéarité des matériaux composites, piézoélectrique-mécanique d'accouplement, et peut prévoir plus précisément les modes supérieurs de vibration, et peut être appliquée à partir de minces d'épaisseur moyenne structures composites multicouches. Ils sont évalués à la fois les vibrations et analyse de flambage de la poutre, plaque, et structures en coque. La partie de commande actif : La vibration de supprimer d'un porte à faux piézo-collé poutre, les deux premiers modes de flambement contrôle d'un appui simple piézo-collé poutre, et la vibration et le flambage contrôle de la charge d'un cantilever piézoélectrique stratifié plaque composite sont étudiés. Les résultats de l'analyse par éléments finis sont utilisés pour concevoir un régulateur linéaire quadratique (LQR) contrôleur et un linéaire quadratique gaussienne (LQG) compensateur avec un observateur d'état dynamique pour atteindre toutes les commandes. Les conceptions de commandes commencent par une méthode modale modle pour déterminer un modle modal réduit approximative qui peut représenter la dynamique du systme avec les modes les moins systme inclus. Un modle modal espace d'état de la structure intelligente qui a intégré la structure d'accueil d'colléscapteurs et d'actionneurs piézoélectriques, est ensuite utilisé pour concevoir le systme de contrôle. Les contrôles visant commentaires LQR/LQG sont avérés succs dans la suppression de la vibration et de stabiliser les modes de flambement des structures. Tant l'analyse par éléments finis et les résultats de simulation de contrôle actives sont compatibles avec les résultats existants d'analyse théoriques et les données expérimentales de la littérature. Quelques conclusions importantes et des observations intéressantes sont obtenues.
Apichayakul, Phisut. "Spatio-temporal State Space Model Estimation for Smart structures". Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522539.
Pełny tekst źródłaLee, Young-Sup. "Active control of smart structures using distributed piezoelectric transducers". Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324821.
Pełny tekst źródłaSousa, Margarida Bucho Nunes de. "Smart macroporous structures for the purification of viral particles". Master's thesis, Faculdade de Ciências e Tecnologia, 2014. http://hdl.handle.net/10362/12179.
Pełny tekst źródłaThe increasing application of viral particles in vaccination and gene-based therapies, has led to the development of alternative and improved purification processes. Traditional purification methods include chromatographic techniques, however the chromatographic matrices used present limitations specially when aimed at the purification of large molecules. This work presents the preparation of chitosan-based monoliths using clean processes and easy functionalization techniques intending to improve Adenovirus serotype 5 (Ad5) purification. Monoliths were prepared by blending chitosan (CHT) with glycidylmethacrylate (GMA) or poly(vinyl alcohol) (PVA), using two preparation techniques, freeze-drying and a scCO2 – assisted drying process, and were subsequently functionalized with Q ligands by three different methods. In addition, monoliths blended with magnetic nanoparticles were also prepared using the same strategies to confer them a controlled magnetic response. The monoliths produced were characterized in terms of ligand immobilization yield, and evaluated for Ad5 purification. Two types of monoliths showed potential: the CHT/PVA(50:50) prepared by freeze drying and functionalized by the alternative plasma technique (M2) and the CHT/PVA(50:50) 7% monolith prepared by scCO2 – assisted drying process and functionalized by the epoxyactivation technique (M1). The amount of ligand Q immobilized on the supports was monitored by titration assays, among which the CHT/PVA(50:50) 7% M2 prepared by scCO2 – assisted drying process exhibited the highest immobilization yield (91%). Among the results for Ad5 purification, the CHT/PVA(50:50)M2 and the CHT/PVA(50:50)7% M1 resulted in a 40% and 14% of the viral particles, respectively. Protein-binding assays were conducted using bovine serum albumin (BSA) and lysozyme, to evaluate the anionic-exchange capacity of the supports. The results make us believe in the potential of the produced monoliths to be applied in chromatographic techniques. However further improvements are necessary to enhance virus binding and recovery, to obtain an improved purification process.
project PTDC/EBB-BIO/118317/2010
Hardy, Verity-Gay. "Design and construction of smart structures for technical textiles". Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/661/.
Pełny tekst źródłaMatsouka, Dimitroula. "Efficiency and durability of wearable smart materials and structures". Thesis, University of Bolton, 2018. http://ubir.bolton.ac.uk/1767/.
Pełny tekst źródłaNguyen, Van Ky Quan. "PIEZOELECTRIC ACTUATOR DESIGN OPTIMISATION FOR SHAPE CONTROL OF SMART COMPOSITE PLATE STRUCTURES". University of Sydney. Aerospace, Mechanical and Mechatronic, 2005. http://hdl.handle.net/2123/652.
Pełny tekst źródłaRuggiero, Eric John. "Active Dynamic Analysis and Vibration Control of Gossamer Structures Using Smart Materials". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32299.
Pełny tekst źródłaMaster of Science
Wang, Xiaodong. "The dynamic behaviour of interacting piezoelectric actuators in smart structures". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35363.pdf.
Pełny tekst źródłaBaillargeon, Brian P. "Active Vibration Suppression of Smart Structures Using Piezoelectric Shear Actuators". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/BailargeonBP2003.pdf.
Pełny tekst źródłaSekouri, El Mostafa. "Modeling and shape estimation of smart structures for active control". Mémoire, Montréal : École de technologie supérieure, 2004. http://wwwlib.umi.com/cr/etsmtl/fullcit?pNQ90331.
Pełny tekst źródła"Thesis presented to the École de technologie supérieure in partial fulfillment of the thesis requirement for the degree of philosophy doctor in engineering". Bibliogr.: f. [158]-164. Également disponible en version électronique.
Kim, JungMi. "System Identification of Smart Structures Using a Nonlinear WARMA Model". Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-theses/7.
Pełny tekst źródłaBerglin, Lena. "Interactive Textile Structures : Creating Multifunctional Textiles based on Smart Materials". Doctoral thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3490.
Pełny tekst źródłaJanda, Oliver. "Modeling and Control of Sound and Vibration for Smart Structures". Phd thesis, Sierke-Verlag, 2014. https://tuprints.ulb.tu-darmstadt.de/4154/1/Diss_Janda_Final.pdf.
Pełny tekst źródłaLentzen, Sven. "Nonlinearly coupled thermopiezoelectric modelling and FE simulation of smart structures". Düsseldorf VDI-Verl, 2009. http://d-nb.info/993098843/04.
Pełny tekst źródłaZanotti, Nicola. "Strutture intelligenti (Smart Structures): sensori, attuatori e materiali self-healing". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4193/.
Pełny tekst źródłaWang, Peng. "Active vibration control in a specific zone of smart structures". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC007/document.
Pełny tekst źródłaThis research aims at solving a particular vibration control problem of smart structures. We aim at reducing the vibration in a specific zone of the smart structure under the disturbance that covers a wide frequency band. Moreover, at this specific zone, neither actuation nor sensing is possible.Here we face several main challenges. First, we need to control the vibration of a specific zone of the structure while we only have access to measurements at other zones. Second, the wide bandwidth of the disturbance implies that numerous modes should be controlled at the same time which requires the use of multiple actuators and sensors. This leads to a MIMO controller which is difficult to obtain using classical controller design methods. Third, the so-called spillover problem must be avoided which is to guarantee the closed-loop stability when the model-based controller is applied on the actual setup. To tackle these challenges, we investigate two control strategies: the centralized control and the distributed control.For centralized control, we propose a methodology that allows us to obtain a simple MIMO controller that accomplishes these challenges. First, several modeling and identification techniques are applied to obtain an accurate low-order model of the smart structure. Then, an H_∞ control based synthesis method with a particularly proposed H_∞ criterion is applied. This H_∞ criterion integrates multiple control objectives, including the main challenges. In particular, the spillover problem is transformed into a robust stability problem and will be guaranteed using this criterion. The obtained H_∞ controller is a standard solution of the H_∞ problem. The final controller is obtained by further simplifying this H_∞ controller without losing the closed-loop stability and degrading the performance. This methodology is validated on a beam structure with piezoelectric transducers and the central zone is where the vibration should be reduced. The effectiveness of the obtained controller is validated by simulations and experiments.For distributed control, we consider the same beam structure and the same control objectives. There exist methods aiming at designing distributed controllers of spatially interconnected system. This research proposes a FEM based method, combined with several model reduction techniques, that allows to spatially discretize the beam structure and deduce the state-space models of interconnected subsystems. The design of distributed controllers will not be tackled in this research
Kakani, Naveen Kumar. "Algorithms for Efficient Utilization of Wireless Bandwidth and to Provide Quality-of-Service in Wireless Networks". Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2635/.
Pełny tekst źródłaNguyen, Van Ky Quan. "PIEZOELECTRIC ACTUATOR DESIGN OPTIMISATION FOR SHAPE CONTROL OF SMART COMPOSITE PLATE STRUCTURES". Thesis, The University of Sydney, 2005. http://hdl.handle.net/2123/652.
Pełny tekst źródłaNwankwo, Cosmas Chidozie. "Smart offshore structure for reliability prediction process". Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/9335.
Pełny tekst źródłaBlockey, James Craig. "Feasibility in developing smart structures for use in wind turbine blades". Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/blockey/BlockeyJ0808.pdf.
Pełny tekst źródłaZheng, Xiang. "Active vibration control of flexible bodied railway vehicles via smart structures". Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9110.
Pełny tekst źródłaHassan, Mohd Roshdi. "Design, manufacturing and testing of SMA-based smart and cellular structures". Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434620.
Pełny tekst źródłaArsava, Kemal Sarp. "Modeling, Control and Monitoring of Smart Structures under High Impact Loads". Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/105.
Pełny tekst źródłaTemtem, Márcio Milton Nunes. "Development of biocompatible and “smart” porous structures using CO2-assisted processes". Doctoral thesis, FCT - UNL, 2009. http://hdl.handle.net/10362/1978.
Pełny tekst źródłaOver the past three decades the use of supercritical carbon dioxide (scCO2) has received much attention as a green alternative in the synthesis and processing of polymers. The scope of this thesis is the development of biocompatible and “smart” porous structures using CO2-assisted processes. This thesis is organized in four main chapters. The first one reviews and highlights some potentialities of supercritical fluid technology and the following ones compile the experimental work developed. The work is divided in three main parts: in the first part (2nd chapter) a CO2-assisted phase inversion method was developed in order to prepare porous structures, namely membranes. In the second part (3rd chapter) the focus was the synthesis of “smart” polymers,especially thermo and pH sensitive polymers. Finally, these two areas were combined (4th chapter) for the preparation of “smart” porous structures. The common guide line was the preparation or processing of biodegradable and/or biocompatible materials with special emphasis on the preparation of porous matrices, namely membranes and scaffolds, with controlled morphology. For membrane preparation a new high pressure apparatus and a new high pressure cell were developed. Polysulfone membranes (a biocompatible polymer with numerous applications in the medical field) were prepared and the effect of the solvent affinity and depressurization rate in the morphology and in the performance in terms of pure water flux of the membranes was investigated. The incorporation of a foaming agent was also analyzed and the high pressure CO2 capability to swell and melt polycaprolactone (PCL) was used to produce and control the porosity and the properties of the membranes. Finally, a natural and water soluble polymer (chitosan) was processed. The presence of water in the casting solution introduced extraordinary difficulties due to the low affinity between water and CO2. To induce the phase inversion a co-solvent (ethanol)was introduced in the CO2 stream. The obtained devices (membranes and beads) were fabricated using moderate temperatures and “green” solvents (ethanol, water and CO2). The morphology and the three dimensional (3D) structures were controlled by altering the co-solvent (ethanol) composition in the CO2 non-solvent stream during the demixing induced process. Microarchitectural analysis by scanning electron microscopy identified the formation of particulate agglomerates when 10% of ethanol in the scCO2 stream was used and detected the development of porous membranes with different morphologies and mechanical properties depending on the programmed gradient mode and the entrainer percentage (2.5-5%) added to the scCO2 stream. These chitosan matrices exhibited low solubility at neutral pH conditions, with no further modifications, demonstrating their applicability in bioreactors as static (membranes) or stirred (beads) culture devices. It was also demonstrated that the current method is able to prepare, in a single-step, an implantable antibiotic release system by co-dissolving gentamicin with chitosan and the solvent. In addition, the cytotoxicity as well as the ability of these structures to support the adhesion and proliferation of human mesenchymal stem cells (hMSC) in vitro were also addressed. After 2 weeks in culture, a 9-fold increase was obtained (versus 6 of the control). More importantly, cells maintained their clonogenic potential and immunophenotype (>95% CD 105+ Cells after 7 days of culture). In this chapter, a hypothetical schematic ternary diagram for the systems polymer–solvent–CO2 is used to discuss and explain the results. Another goal of this thesis was the synthesis of “smart” polymers. Chapter 3, addresses the precipitation polymerization of a thermoresponsive hydrogel, poly(N-isopropylacrylamide)(PNIPAAm), in scCO2. This hydrogel has a transition temperature, hereinafter called low critical solution temperature (LCST), around 32 ºC in an aqueous solution, close to body temperature. A strategy of solvent-free impregnation/coating of polymeric surfaces with PNIPAAm was suggested, in order to further extend the applications of membranes or porous bulky systems. The in situ synthesis of PNIPAAm within a chitosan scaffold was tested as a proof of concept, in order to produce smart partially-biodegradable scaffolds for tissue engineering applications. The LCST was tuned by copolymerization or graft polymerization of NIPAAm with other monomers. Copolymerization with hydroxyethyl methacrylate (HEMA) was used to decrease the LCST temperature from 32.2 ºC to approximately 27.7 ºC. Cloud point measurements of CO2 + HEMA system were used to optimize the polymerization temperature. Experimental data were obtained at 40 ºC, 50 ºC and 65 ºC and pressures up to 21.1 MPa. Soave-Redlich-Kwong equation of state with Mathias-Klotz-Prausnitz mixing rule was used to model experimental results and a good correlation was achieved. To increase the LCST, polyethylene oxide (an hydrophilic polymer) was grafted to PNIPPAAm. Dual stimulus (thermo and pH responsive) hydrogels were also prepared by copolymerizing methacrylic acid with PNIPAAm. As a proof of concept fluorouracil was incorporated in the hydrogels network and their release was controlled by temperature and pH stimulus. In chapter 4 the concepts of the previous chapters were put together envisaging the preparation of“smart” functional polymeric devices with targeted physical and chemical properties namely: (i) chitosan-based dual stimulus scaffolds (temperature and pH responsive); (ii) polysulfone-based thermoresponsive membranes and (iii) polymethylmethacrylate-based membranes. The chitosan scaffolds (pH sensitive) were coated/impregnated with a thermoresponsive polymer,poly(N-isopropylacrylamide) (PNIPAAm), using scCO2 as a carrier to homogeneously distribute the hydrogels monomer within the chitosan scaffolds and as a solvent to perform the polymerization reaction.
Fundação para a Ciência e Tecnologia através da bolsa de Doutoramento (SFRH/BD/16908/2004) e do projecto PTDC/CTM/70513/2006
Lara, Prieto Vianney. "Smart structures : a study of an MR fluid-based machine element". Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/34455.
Pełny tekst źródłaRamadan, Mohamed Refat Mostafa <1991>. "Numerical and experimental analysis of 3D printed smart structures and systems". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10425/1/MRefat_Ramadan_main.pdf.
Pełny tekst źródłaI meccanismi con elementi flessibili, noti col termine inglese “Compliant Mechanisms” (CM), consentono la realizzazione di strutture intelligenti ad alte prestazioni. Tuttavia, produrre tali strutture con i materiali e le tecniche di lavorazione tradizionali è molto difficile. Grazie al recente sviluppo delle tecniche di produzione additiva, una possibilità per la realizzazione di queste strutture è la stampa tridimensionale (3D) di compositi a matrice polimerica rinforzati con fibre continue, ad esempio mediante la stampante MarkTwo (MT) di Markforged. In questo contesto, lo scopo di questa tesi è di gettare le basi per la risoluzione di questi problemi. Una prima attività svolta riguarda lo studio sperimentale del comportamento a trazione e a flessione di lamine rettilinee flessibili (Straight Beam Flexures, SBF) realizzate mediante 3D-MT e caratterizzate da diverse frazioni volumetriche e disposizioni delle fibre all’interno del medesimo strato e in strati differenti. La seconda attività riguarda lo sviluppo di uno strumento per l’analisi numerica di queste SBF, basato sulla formulazione unificata di Carrera (Carrera Unified Formulation, CUF) utilizzando l'approccio “component-wise” (CW), che include un nuovo elemento di pre-elaborazione che consente di considerare tutte le regioni stampate in modo semplice e con un ridotto tempo computazionale. Tra i suoi vantaggi, l'approccio CUF-CW consente di raccogliere le frequenze naturali dei primi modi di vibrare e di prevedere il modulo di Young del composito sulla base di una formulazione del problema inverso. Per convalidare lo strumento, i risultati numerici sono confrontati con le frequenze naturali valutate sperimentalmente mediante un approccio basato sulla correlazione di immagini digitali. Come terza ed ultima attività, le potenzialità della stampa mediante MT, in associazione con l’ottimizzazione topologica e la progettazione di meccanismi con membri/giunti flessibili (Compliant Joint Design, CJD), sono state investigate nel contesto della realizzazione di meccanismi per macchine automatiche soggetti a carichi inerziali.