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Vouillot, Léna. "Développement des motoneurones chez un modèle amphibien d'amyotrophie spinale généré à l'aide de nucléases." Thesis, Evry-Val d'Essonne, 2014. http://www.theses.fr/2014EVRY0038.
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Les amyotrophies spinales proximales sont des maladies génétiques neuromusculaires caractérisées par la dégénérescence des motoneurones spinaux et une atrophie des muscles squelettiques proximaux. La perte de fonction du gène smn1, un gène essentiel à la survie des motoneurones, entraîne une réduction drastique du niveau de protéine SMN et est, à l’origine des symptômes observés chez les patients. L'amphibien anoure Xenopus tropicalis constitue un très bon petit animal modèle pour étudier cette maladie ainsi que le développement des motoneurones. En effet une diminution de la production de la protéine SMN via l’utilisation de morpholinos a permis de montrer chez les têtards, des défauts de migration des motoneurones ainsi qu’une atrophie des muscles caudaux. Pour développer un modèle héritable de SMA, nous avons utilisé des nucléases tels que les ZFN ou le système CRISPR/Cas pour générer des mutations du gène smn chez Xenopus tropicalis. Nous avons conçu les outils moléculaires pour induire différentes mutations du gène smn avec des ZFN ou le système CRISP/Cas9. Nous avons ensuite validé l'efficacité de ces nucléases dans des embryons in vivo et développé une méthode de recherche de mutations basée sur l’utilisation des endonucléases T7EI et Surveyor. Nous avons obtenu un animal fondateur mutant qui permettra de générer des embryons homozygotes pour la mutation. En parallèle, nous avons développé une lignée transgénique chez Xenopus tropicalis permettant de visualiser les populations de motoneurones spinaux, pour mieux caractériser les animaux mutants smn in vivo. La combinaison de ces deux lignées permettra de mieux comprendre la physiopathologie motoneuronal liée à des mutations de smnSpinal muscular atrophy (SMA) is a neurodegenerative disease characterized by motor neuron loss and skeletal muscle atrophy. In human the loss of function of the smn1 gene, the main supplier of survival motor neuron protein (SMN), leads to reduced levels of SMN and eventually to SMA. The anuran amphibian Xenopus tropicalis is a good animal model for the study of SMA and motor neurons development. Indeed the inhibition of the production of SMN using antisense morpholinos leads to caudal muscular atrophy in tadpoles. To develop an inheritable SMA model, we edited the smn gene in X. tropicalis using zinc-finger nucleases (ZFNs) and CRISPR/Cas system. As a first step, we designed the molecular tools needed to induce mutations of the smn gene using ZFN and CRISPR/cas9. Next we probed the efficiency of these tools and developed a method to identify mutations using T7EI and Surveyor endonucleases. We obtained a mutant frog and thus we will be able to produce homozygous mutant embryos for smn. In parallel we developed a transgenic line of Xenopus tropicalis frogs in which we can image motor neurons populations in vivo. The combination of both lines should enable to increase our knowledge and understanding of motor neuron physiopathology due to smn mutations
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Henriques, Moreira Daniel. "SimPatrol: um simulador de sistemas multiagentes para o patrulhamento." Universidade Federal de Pernambuco, 2008. https://repositorio.ufpe.br/handle/123456789/2248.
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Previous issue date: 2008Conselho Nacional de Desenvolvimento Científico e Tecnológico
Apesar de sistemas multiagentes estarem se tornando cada vez mais comuns no desenvolvimento de software, há ainda que se chegar a um consenso sobre como modelar e comparar diferentes soluções de sistemas multiagentes para um mesmo problema. Em outras palavras, os pesquisadores de tal área ainda estão à procura de benchmarks que sirvam de referência para a comparação de abordagens distintas. Dada a importância do estabelecimento de benchmarks para sistemas multiagentes, uma questão que surge entre os pesquisadores da área de patrulhamento é a possibilidade e o potencial do problema do patrulhamento como um destes benchmarks. Apesar da quantidade de trabalho produzido até este ponto, tem-se encontrado dificuldades para comparar precisamente as soluções propostas para o patrulhamento. Estas dificuldades remetem principalmente à ausência de ferramentas (em especial um simulador unificado) que permitam aos estudiosos se concentrarem na solução do problema em si, e não na sua representação. Partindo deste cenário, este trabalho tem como objetivo discutir o estabelecimento do patrulhamento enquanto um benchmark para sistemas multiagentes. Adicionalmente, como um primeiro passo no sentido de preencher as lacunas que dificultam tal estabelecimento, introduz-se o SimPatrol, um novo simulador voltado para a tarefa de patrulhamento, fortemente inspirado pelos simuladores da RoboCup e TAC. Novos resultados são produzidos a partir de uma avaliação de parte das técnicas propostas pelas pesquisas anteriores frente às novas funcionalidades implementadas pelo simulador, em especial a inédita medida de ociosidade dos vértices, que leva em consideração o tempo de raciocínio gasto pelos patrulheiros
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Paredes, Matta Elizabeth Victoria Adela. "Comportamiento mecánico de las mezclas tipo SMA (STONE MASTIC ASPHALT)." Bachelor's thesis, Universidad Ricardo Palma. Programa Cybertesis PERÚ, 2010. http://cybertesis.urp.edu.pe/urp/2010/paredes_ev/html/index-frames.html.
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Pachalla, Seshadri Rajagopal. "Analysis of oscillating flow cooled SMA actuator." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2669.
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Shape Memory Alloys (SMA) are a group of metallic alloys that have the ability to return to some previously defined shape or size when subjected to an appropriate thermal cycling procedure. In recent years there has been a lot of research on the development of small, light and, yet, powerful actuators for use in areas like robotics, prosthetics, biomimetics, shape control and grippers. Many of the miniaturized conventional actuators do not have sufficient power output to be useful and SMAs can be used advantageously here.
The widespread use of SMAs in actuators is limited by their low bandwidth. Use of SMAs in two-way actuators requires that they undergo thermal cycling (heating and cooling). While SMAs can be heated quickly by resistive heating, conventional convection cooling mechanisms are much slower as the exothermic austenitic to martensitic phase transformation is accompanied by the release of significant amount of latent heat.
While a number of cooling mechanisms have been studied in SMA actuator literature, most of the cooling mechanisms involve unidirectional forced convection. This may not be the most effective method. Oscillating flow in a channel can sometimes enhance heat transfer over a unidirectional flow. One possible explanation for this heat transfer enhancement is that the oscillatory flow creates a very thin Stokes viscous boundary-layer and hence a large time-dependent transverse temperature gradient at the heated wall. Therefore heat transfer takes place at a large temperature difference, thereby enhancing the heat transfer.
In this work, the heat transfer from an SMA actuator under an oscillating channel is investigated and is compared to steady, unidirectional flow heat transfer.
Oscillating flow is simulated using a finite volume based method. The resulting velocity field is made use of in solving the heat transfer problem using a finite difference scheme. A parametric study is undertaken to identify the optimal flow conditions required to produce the maximum output for a given geometry of the SMA actuator. The latent heat of transformation of the SMA is accounted for by means of a temperature dependent specific heat.
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Dano, Marie-Laure. "SMA-Induced Deformations In general Unsymmetric Laminates." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30390.
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General unsymmetric laminates exhibit large natural curvatures at room temperature. Additionally, inherent to most unsymmetric laminates is the presence of two stable configurations. Multiple configurations and stability issues arise because of the geometric nonlinearities associated with the large curvatures. The laminate can be changed from one stable configuration to the other by a simple snap-through action. This situation offers the opportunity to use shape memory alloys (SMA) attached to the laminate to generate the snap-through forces and change the shape of the laminate on command. Presented is a model which can predict SMA-induced deformations in general unsymmetric laminates and, particularly, the occurrence of the snap through. First, a methodology is developed to predict the deformations of flat general unsymmetric epoxy-matrix composite laminates as they are cooled from their elevated cure temperature. Approximations to the strain fields are used in the expression for the total potential energy, and the Rayleigh-Ritz approach is used to study equilibrium. To further study the laminate deformations, finite-element analyses are performed. Experimental results are presented which confirm the predictions of the developed theory and the finite-element analyses regarding the existence of multiple solutions and the magnitude of the deformations. Results are compared with those of several other investigators. Next, the deformation behavior of general unsymmetric laminates subjected to applied forces is studied. The principle of virtual work is used to derive the equilibrium equations relating the laminate deformations to the applied forces. By solving the equilibrium equations as a function of the force level, relations between the laminate deformations and the applied force are derived, and the force level at which the laminate changes shape is determined. Finally, an existing SMA constitutive model is implemented into the developed theory to predict the deformations of simple structures to SMA-induced forces. Experiments on a narrow aluminium plate with an externally attached SMA actuator are conducted. The experimental results show good agreement with the predictions from the developed theory. Next, the deformation behavior of general unsymmetric laminates subjected to SMA actuators is predicted using the developed theory. Experiments using SMA actuators to generate the snap through of nsymmetric laminates are conducted. Good correlation with the developed theory is obtained.Ph. D.
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Anjum, Sadaf Saad. "Fabrication of smart intercalated polymer-SMA nanocomposite." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9384.
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Mimicking nature gives rise to many important facets of biomaterials. This study is inspired by nature and reports on the fabrication of an intercalated polymer-NiTi nanocomposite that mimics the structural order of urethral tissue performing micturition. PTFE is chosen due to its hydrophobicity, low surface energy, and thermal and chemical stability. NiTi has been selected as a prime candidate for this research due to its excellent mechanical stability, corrosion resistance, energy absorbance, shape memory and biocompatibility. Nanoscale engineering of intercalated nanocomposites is done by PVD sputtering PTFE and NiTi. FTIR spectroscopy confirms that PTFE reforms as polymer chains after sputtering. Suitable PVD sputtering parameters were selected by investigating their influence on deposition rates, microstructure and properties of PTFE and NiTi thin films. PTFE forms stable nanocomposite coatings with NiTi and displays favourable surface interactions, known as ‘intercalation’. Intercalated PTFE-NiTi films were fabricated as layered and co-sputtered thin films. Co-sputtered nanocomposites contained nearly one-third vacant sites within its internal microstructure because of intercalation while intercalation introduced minute pits in fibrous NiTi columns of layered nanocomposites. These pits allow PTFE to extend their chains and crosslinks, resulting in microstructural and functional changes in the thin films. Intercalated PTFE-NiTi nanocomposites offer a close match to the natural tissue in terms of responding to the fluid contact (wetting angle modifications), and allow the soft and hard matter to incorporate in one framework without any chemical reactions (intercalation). An intercalated microstructure in co-sputtered and layered nanocomposites was verified by EDS-SEM and EDS-TEM techniques. The functional responses were witnessed by changes in water contact angle (WCA) and coefficient of friction (CoF) values measured on the film surface. The WCA (99°) and CoF (0.1 – 0.2) of the intercalated nanocomposite (sample PNT12) were different to the NiTi (top layer). WCA and CoF indicate the internal microstructural interactions because of intercalation. Although the pseudoelastic behaviour of NiTi can provide additional fluid response but the difficulty is an absence of crystallinity in as-deposited NiTi, and the heat treatment that melts PTFE. However, DSC and XRD techniques were employed to find the optimum NiTi composition and transition temperatures for phase transformation related to pseudoelasticity. This study provides the basis to incorporate the shape memory (pseudoelasticity or thermal shape memory effect (shape memory effect)) features of NiTi into the intercalated nanocomposite in future. The intercalated PTFE-NiTi nanocomposite reveals a fascinating research precinct, having the response generating characteristics similar to that of natural tissue.
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Quenum, José Ghislain. "Conception et éxécution d' interactions dans les SMA [Systèmes multi-agents] : spécialisation et sélection de protocoles génériques." Paris 6, 2005. http://www.theses.fr/2005PA066457.
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Yariz, Kemal Oral. "The Chronicles of X-Linked Spinal Muscular Atrophy: The Linkage, The Gene and The SMN Complex." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/115.
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Spinal Muscular Atrophy (SMA) is an autosomal recessive motor neuron disease. SMA is associated with homozygous mutations in the Survival of Motor Neuron gene I (SMN1). SMN protein does not appear to exist in cells in isolation but associates with several proteins to form a large multi-protein complex. The functions of SMN complex include assembly, metabolism and transport of diverse classes of ribonucleoproteins. X- Linked Spinal Muscular Atrophy is a rare congenital disorder characterized by multiple joint contractures. It is associated with hypotonia, areflexia, chest deformities and congenital joint contractures. A candidate interval was defined for XL-SMA in Xp11.3-Xq11.2 in 1995. The purpose of this study was to refine the XL-SMA gene region and discover the XL-SMA gene. In addition to that, the gene product was investigated to delineate the genotype-phenotype correlation. My studies were focused on single nucleotide polymorphism (SNP) analysis. The candidate gene interval was refined by studying 14 SNPs in the three largest families. This analysis revealed a recombination event which allowed elimination of the NDP gene. Significantly positive LOD scores were obtained from these SNP studies. The exons and exon-intron boundaries of 12 genes were screened. No mutations were found in these genes in affected male samples. In late 2006, UBE1 (Ubiquitin activating enzyme 1) was discovered as the XL-SMA gene. UBE1 protein is responsible for the first step of ubiquitination of proteins in a cell. To investigate a possible common molecular mechanism between SMA and XL-SMA, proteins in the SMN Complex in XL-SMA patient cell lines were studied. SMN and Gemin3 protein levels were found to be consistently lower in XL-SMA patient cell lines (lymphoblasts) compared to healthy cell line. These results imply that there may be a common disease mechanism. To understand if the SMN and Gemin3 RNA levels decrease. RNA expression studies were performed. These studies confirmed that there is no difference of RNA expression of SMN and Gemin3 in XL-SMA cell lines when compared to healthy cell lines. As for UBE1, the same experimental procedure for SMN Complex proteins were repeated with antibodies to UBE1 to determine if there is any decline of UBE1 protein levels in XL-SMA patient cell lines compared to a healthy cell line. There was a decline in protein levels of UBE1 in XL-SMA patients. Two possible models are proposed for a molecular mechanism in XL-SMA: 1) UBE1 involves in degradation of a protein which downregulates SMN Complex (or a protein which stabilizes SMN Complex). When UBE1 is mutated, the protein in question is not degraded and this results in excess downregulation of SMN Complex (maybe via a pathway involving SMN-Gemin3 interaction). 2) UBE1 and UBA6 interact with the proteins of SMN Complex as they monoubiquinate them for different cellular processes. When UBE1 is mutated, UBA6 cannot compensate the deficiency of UBE1, which in turn disrupts normal cellular RNA metabolism required for motor neuron development and survival.
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Miguel-Aliaga, Irene. "Spinal muscular atrophy : of flies, worms and men." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343478.
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Pardon, Gaspard. "A feasibility Study of SMA Powder Composite Actuators." Thesis, KTH, Mikrosystemteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91283.
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Aghamaleky, Sarvestany Arwin. "Schwann cell pathology in spinal muscular atrophy (SMA)." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/15908.
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The childhood neuromuscular disease spinal muscular atrophy (SMA) is caused by low levels of survival motor neuron (SMN) protein. Historically, SMA has been characterised as a disease primarily affecting lower motor neurons. However, recent breakthroughs have revealed defects in other non-neuronal cells and tissues. In vivo analysis of peripheral nerve showed defects in Schwann cells, manifesting as abnormal myelination and delayed maturation of axo-glia interactions. The experiments in this thesis were designed to build on these observations and examine whether Schwann cell defects are intrinsic and occur as a primary result of low levels of SMN in that cell type, or rather represent a secondary consequence of pathology in neighbouring motor neurons. I initially developed a protocol to allow isolation of high-yields of purified, myelination-competent Schwann cells from ‘Taiwanese’ SMA mice. SMA-derived Schwann cells had significantly reduced SMN levels and failed to respond normally to differentiation cues. Increasing SMN levels restored myelin protein expression in Schwann cells from SMA mice. Perturbations in expression of key myelin proteins were likely due to failure of protein translation and/or stability rather than transcriptional defects. Co-cultures of healthy neurons with SMA Schwann cells revealed a significant reduction in myelination compared to cultures where wild-type Schwann cells were used. The presence of SMA Schwann cells also disrupted neurite stability. Perturbations in the expression of key extracellular matrix proteins, such as laminin α2, in SMA-derived Schwann cells suggests that Schwann cells were influencing neurite stability by modulating the composition of the extracellular matrix. Previous studies have demonstrated that low levels of SMN lead to disruption of ubiquitin homeostasis and decreased expression of ubiquitin-like modifier activating enzyme (UBA1) in the neuromuscular system, driving neuromuscular pathology via a beta-catenin dependent pathway. Label-free proteomics analysis of SMA and control Schwann cells identified 195 proteins with modified expression profiles. Bioinformatic analysis of these proteins using Ingenuity Pathway Analysis (IPA) software confirmed that major disruption of protein ubiquitination pathways was also present in Schwann cells from SMA mice. Immunolabeling and proteomics data both revealed that UBA1 levels were significantly reduced in SMA-derived Schwann cells. However, loss of UBA1 in Schwann cells did not lead to downstream modifications in beta-catenin pathways. Pharmacological inhibition of UBA1 in healthy Schwann cells was sufficient to induce defects in myelin protein expression, suggesting that UBA1 defects contribute directly to Schwann cell disruption in SMA. I conclude that low levels of SMN induce intrinsic defects in Schwann cells, mediated at least in part through disruption to ubiquitination pathways.
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Dano, Marie-Laure. "SMA-induced deformations in unsymmetric cross-ply laminates." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09122009-040504/.
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Aphanuphong, Sutha. "Embedded heaters and sensors for micro SMA actuators." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1458441.
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Acuna, Subia Luis Carlos. "Vlastnosti asfaltových směsí typu SMA s R-materiálem." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-371816.
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The aim of the diploma thesis is to verify and compare the properties of bituminous stone mastic asphalt, namely SMA 11S with modified PMB 45 / 80-55 asphalt binder or 50/70 road bitumen binder with rubber granulate. Comparison of properties is performed using functional tests. The thesis is divided into the theoretical and practical part. The theoretical part deals with the familiarization with the use of the SMA mixture, the selected concepts concerning recycling of non-leveled roads are described and described. Attention is paid especially to the recycling of roads in the Czech Republic with an emphasis on hot recycling on the incinerator, which allows increased dosing of Reclaimed Asphalt into asphalt mixtures. In the practical part, the results of the functional tests of the SMA 11S mixture, which have been taken from the test section, are processed and evaluated.
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Akbulut, Huseyin. "The properties and performance of cellulose fibre reinforced stone mastic asphalt." Thesis, University of Ulster, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342415.
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Chali, Farah. "Innovation physiothérapeutique dans l'amyotrophie spinale infantile : du modèle animal au patient." Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05T075.
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L’amyotrophie spinale infantile (SMA) est une maladie neurodégénérative rare, caractérisée par une perte progressive des motoneurones de la moelle épinière, et pour laquelle aucun traitement curatif n’est disponible. Cette maladie est causée par la mutation du gène SMN1 qui induit une diminution de l’expression de la protéine SMN. Depuis plusieurs des années, notre l’équipe examine les effets de l’exercice sur le développement ou le maintien de l’unité motrice dans des maladies neurodégénératives affectant spécifiquement le motoneurone. Ces études ont notamment permis de mettre en évidence que l’exercice physique pourrait avoir des effets bénéfiques pour l’amyotrophie spinale, dans un modèle de souris SMA de type 2 soumis à un exercice de course sur roue pendant 5 jours (Grondard et al., 2005). Dans notre étude, nous avons comparé les effets de deux programmes d’entraînement différents, d’une durée de 10 mois, basés sur un exercice de course ou sur un exercice de nage, sur des populations de souris SMA de type 3, la forme la moins sévère de la maladie. Dans nos conditions, la course est un exercice de faible intensité et de faible amplitude, mais qui induit plus de lésions musculaires, au contraire de la nage, comme le confirme les mesures de lactate et de créatine kinase circulants. Ces deux paramètres ont des valeurs anormalement hautes chez les souris SMA, suggérant des anomalies métaboliques et de fragilité musculaire, qui sont limitées par les deux programmes d’entraînement. Les analyses du comportement moteur indiquent également que les 10 mois d’entraînement améliorent significativement les capacités motrices des souris SMA, et notamment la résistance à la fatigue avec la nage. Comme attendu, la perte de 46% des motoneurones spinaux enregistrée à 12 mois chez les souris SMA sédentaires est significativement limitée par les deux types d’entrainement, mais avec des efficacités différentes sur les différentes sous‐populations de motoneurones spinaux. En effet, la course protège préférentiellement les motoneurones de faible surface et exprimant ERR‐β, assimilés à des motoneurones lents, et la nage les motoneurones de large surface et exprimant Chodl, assimilés à des motoneurones rapides. De manière surprenante, la neuroprotection induite par l’exercice est indépendante de l’expression de SMN dans la moelle épinière des souris SMA. Une étude de la forme et de la surface des jonctions neuromusculaires dans trois muscles du mollet, le soleus, le plantaris et le tibialis, et une étude du phénotype musculaire de ces mêmes trois muscles confirment le rôle bénéfique de l’entrainement mais aussi les effets différentiels des deux programmes, avec un effet plus important pour la nage. Les améliorations de l’unité motrice, induites par l’exercice, permettent un meilleur fonctionnement neuromusculaire, comme le suggère les mesures électrophysiologiques du muscle plantaire. Pris tous ensemble, ces résultats suggèrent qu’un exercice de nage, à haute intensité, dans des conditions anaérobies, et axé sur le recrutement des muscles extenseurs pourrait être bénéfique pour les patients SMA, notamment pour améliorer les capacités motrices et donc la qualité de vie des patientsObjective: Spinal Muscular Atrophy (SMA) is a group of autosomal recessive neurodegenerative diseases differing in their clinical outcome, characterized by the specific loss of spinal motor‐neurons, caused by insufficient levels of SMN protein expression. No cure is presently available for SMA. While physical exercise might represent a promising approach for alleviating SMA symptoms, the lack of data dealing with the effects of different exercise types on diseased motor‐units still precludes the use of exercise in SMA patients. Methods: We have evaluated the efficiency of two long‐term physical exercise paradigms, either based on high intensity swimming or on low intensity running, in alleviating SMA symptoms in a mild type 3 SMA‐like mouse model. Results: We found that a 10‐month physical training induced significant benefits in terms of resistance to muscle damages, energetic metabolism, muscle fatigue and motor behavior. Both exercise types significantly enhanced motor‐neuron survival, independently of SMN expression, leading to the maintenance of neuromuscular junctions and skeletal muscle phenotypes, particularly in the soleus, plantaris and tibialis of trained mice. Most importantly, both exercises significantly improved neuromuscular excitability properties. Besides, all these training‐induced benefits are quantitatively and qualitatively related to the specific characteristics of each exercise, suggesting that the related neuroprotection is strongly dependent on the specific activation of some motor‐neuron subpopulations. Interpretation: Taken together, the present data show significant long‐term exercise benefits in a mild type 3 SMA context and provide important clues for designing rehabilitation programs in patients
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Hariri, Mohammed, and not supplied. "Control of Structures Using SMA Wires and Piezoelectric Patches." RMIT University. Aerospace, Mechanical & Manufacturing Engineering, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091001.154507.
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Smart materials and structures systems are increasingly being developed to handle more complex problems. One of the main research schemes is the augmentation of the control authority of the smart actuators used in such systems. The augmentation can be obtained by constructing hybrid and multi- smart materials actuator systems and/or by the optimization of the location and orientation of those actuators. In the first part of this study, the alteration of the natural frequency of composite structures using Nitinol-based Shape Memory Alloy (SMA) wires will be presented using the analyses of strain energy perturbations on a plate. These governing strain equations were solved analytically and numerically to show the effect of point forces acting in a distributive manner and the subsequent effect it has on the plate's stiffness and hence it's natural frequency. In the second part of the thesis, a more complex loading condition is considered to investigate piezoceramic actuator control authority in relation to wing flutter control. The advancement in the application of active material induced-strain actuation such as piezoelectric materials in suppression of structural vibrations drew wide interest in its use for wing flutter control. Higher flutter speed and hence wider operating envelope was achieved by delaying the coalescence of the eigenvalues for plunge and twist modes. . This delay is obtained by adding more strain energy to the system as a result of the activation of the piezoelectric actuators. Most of the studies done were by controlling the plunge/bending motion, where the piezoelectric actuators are bonded longitudinally to produce bending moments. In this study, the control of the pitch/twisting motion was investigated and it showed better control of flutter by using simultaneous multi-actuations compared to single piezo actuations. It was shown that within the scope of the angular orientations of the piezoelectric patches investigated in this study, piezoelectric patches oriented about +150 from the beam's longitudinal ax is resulted in the most optimal piezo-configuration. This was corroborated by both the numerical flutter speed and actuator moment evaluations. In addition, the orientation of the piezoelectric patches was shown to significantly affect the pitch angle of the beam relative to each other. The damping ratio was also investigated and this showed greater instability for piezoelectric patches oriented at negative angles, thus further supporting the finding of the aforementioned optimal orientation of +150. These findings confirmed the dominance of the base (closest to the fixed portion of the beam) piezo when actuated with other piezos.
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Sitnikova, Elena. "Dynamic behaviour of an impact system with SMA restraint." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=202764.
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The interest in use of SMAs in vibrational systems is stimulated by their ability to dissipate energy and consequently their potential to control the dynamic behaviour of the system. In this thesis nonlinear dynamics of an impact oscillator with one sided motion constraint made of a shape memory alloy (SMA) is investigated. The pseudoelastic behaviour of SMAs is characterized by high non-linear recovery deformations and energy dissipation due to the occurrence of hysteresis. The thermo-mechanical description of the SMA element follows the formulation proposed by Bernardini et al. [1,2]. Extensive numerical investigations into the influence of the forcing parameters, which characterize the intensity of the load acting on the SMA has been carried out. They suggest that the system can exhibit complex dynamic responses, which if appropriately controlled can be used for vibration reduction. The comparison with the equivalent elastic oscillator response has shown that the use of the SMA can significantly change the dynamic response of the system. Whereas low amplitude regimes are not affected by the SMA element, at resonances when the response amplitudes are large, a significant vibration reduction is achieved due to the phase transformation hysteresis loop. Two types of periodic response co-existence is also revealed in these regions. At the same time, in other frequency ranges the existence of additional modes of motion in the pseudoelastic oscillator can cause new large amplitude responses (both periodic and chaotic) to be generated, as well as eliminate some of the co-existing responses. Various bifurcation scenarios are constructed and the influence of the SMA element is discussed. To verify the obtained theoretical predictions, an experimental rig was designed and limited experimental studies have been conducted. The substantial response amplitude reduction at resonances has been captured, as well as the jumps to higher amplitude responses due to the softening behaviour of SMA. The numerical results appeared to be in a good agreement with the experimental data.
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Moreira, Maria Isabel Giusti. "Um modelo de sistema AVA-SMA orientado à legislação." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/171382.
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Dentro da Educação a Distância (EaD), os softwares de apoio como os Ambientes Virtuais de Aprendizagem (AVA) são considerados recursos que favorecem a comunicação entre os atores envolvidos, permitindo a troca de informação. Atribuir Inteligência Artificial a esses AVAs, utilizando Sistemas Multiagentes (SMA) e uma forma de procurar que os mesmos tenham um bom desempenho e que seus recursos facilitem o processo de aprendizagem. Esse trabalho cont em um estudo sobre os principais AVAs existentes e sobre os métodos alternativos de integração de AVA com SMA. Ao analisar o estado da arte dos AVAs pode-se observar que todos trabalham como ferramentas de auxílio ao aluno, por em nenhum deles trabalha aspectos da gestão da EaD dando suporte aos aspectos relevantes da legislação dessa modalidade. Por esse motivo, essa Tese tem por objetivo a criação de um modelo de integração AVA-SMA que possa tornar o AVA MOODLE capaz de auxiliar os gestores da EaD em suas diferentes tarefas, com base na incorporação, ao mesmo, de um modelo de representação de legislação. Para realizar essa integração do modelo AVA-SMA orientado a Legislação foi desenvolvido um espec co modelo organizacional de Sistema Multiagente. Por m com base em um estudo de caso, ser a realizado simulações para veri car as funcionalidades do Modelo de Sistema AVA-SMA orientado a Legislação, proposto nesta Tese.In Distance Learning (EaD), supporting software such as Virtual Learning Environments (VLE) are considered resources that favor communication between the actors involved, allowing the exchange of information. Assigning Arti cial Intelligence to these VLEs, using Multi-Agent Systems (MAS) is a way of ensuring they have a good performance and that its resources facilitate the learning process. This work contains a study on the major existing VLEs and on alternative methods to integrate VLE with MAS. When analyzing the state of the art of the VLEs it is possible to see that all of them work as aid tools for students, but none of them work on management aspects of distance learning that support the relevant aspects of the legislation for this type of education. Therefore, this thesis aims to create a VLE-MAS integration model that can make the VLE MOODLE able to help distance learning managers in their di erent tasks, based on incorporating a legislation representation model to it. To accomplish this integration of the legislation-oriented VLE-MAS model, a speci c Multi-Agent System organizational model was developed. At last, based on a case study, simulations will be conducted to verify the functionalities of the VLE-MAS System Model oriented to legislation, proposed in this thesis.
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Paine, Jeffrey S. "Multi-functional SMA hybrid composite materials and their applications." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/38219.
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Shape memory alloy (SMA) materials such as nitinol have unique properties associated with the shape recovery effect and the material’s phase changes that have been used in a variety of actuator and sensing applications. By embedding SMA elements into host composite materials, control or modification of the SMA hybrid composite’s structural properties can be accomplished inservice, thereby increasing the hybrid composite’s structural functionality. Previous studies addressed increasing composite materials’ functionality by enabling in-service control of their dynamic response. Utilizing the SMA’s substantial recovery stress and capacity to dissipate strain energy to increase the hybrid composite’s static functionality is addressed herein. Specific applications for SMA hybrid composites include improving composite material’s impact damage resistance and composite cylinder stress and deflection control.
In stress and deflection control of cylindrical structures, SMA actuators are placed within the composite cylinder to form an active compound cylinder. The active SMA elements can significantly reduce the internal pressure-induced radial dilation and creep so that under severe loading, piston to cylinder tolerances may be maintained. Similar to a conventional metallic compound cylinder, the active compound cylinder also reduces peak cylinder hoop stresses. Hybridizing composites with nitinol improves their impact resistance because of nitinol’s tremendous capacity to absorb impact strain energy through the stress-induced martensitic phase transformation. The amount of impact damage is reduced and the material’s resistance to impact perforation at various velocities is improved. The experimental response of nitinol hybrid composites and the associated mechanics are presented. The unique toughness and resistance to permanent deformation that is a result of the stress-induced martensitic phase transformation enables the nitinol to absorb on the order of 4 times the strain energy of high alloy steel and 16 times that of many graphite/epoxy composites.
In most static applications where SMA elements are used for reinforcement, maintaining the integrity of the interface between the SMA elements and the host polymeric matrix composite material is critical to operation. The relationship between preparation of SMA elements for hybrid composite fabrication and interfacial bond strength is presented to address this issue. The mechanics of interfacial shear failure between SMA element and composite is also presented.Ph. D.
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Zhu, Shijie. "3D SMA Foams : Geometrical Reconstitution, Modelling and Numerical Simulation." Thesis, Troyes, 2018. http://www.theses.fr/2018TROY0021.
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Un nouveau type de matériau cellulaire en Alliages à Mémoire de Forme possédant des caractéristiques intéressantes dues à la structure légère, super-élasticité et effet de mémoire de forme fait l’objet d’un intérêt croissant. L’objectif de la thèse est de concevoir la structure 3D de mousses en NiTi en utilisant des unités de cellules les plus représentatives de la microstructure du volume représentatif. Trois méthodes de reconstruction sont proposées : une reconstruction utilisant la méthode de Conception Assistée par Ordinateur, une reconstruction utilisant la méthode de tomodensitométrie et une méthode mixte. Des algorithmes de reconstruction intégrant les caractéristiques géométriques et les distributions aléatoires des cellulaires sont développés et intégrés dans une démarche de conception-modélisation avec adaptation de maillage. Les analyses numériques effectuées utilisent un modèle de comportement thermomécanique des AMF incluant l’effet de la transformation de phase, l’orientation martensitique et les mécanismes d’accommodation de macles afin de décrire la super-élasticité et l’effet mémoire de forme. Les effets de porosité, de taille, d’orientation et de dimensions des cellules à pores ouverts ou fermés sont étudiés. La technique d’homogénéisation basée sur le modèle de Mori-Tanaka est proposée. Des comparaisons avec les modèles CAO en terme de raideur et de transformation pour des mousses de porosité relativement faible <40% sont effectuéesCellular foams structures in Shape Memory Alloys (SMAs) are particularly interesting for their potential to provide superelasticity and shape memory effect in a lightweight material. The objective of the thesis is to design the 3D structure of NiTi foams using cell units most representative of the microstructure of the representative volume element. Three reconstruction methods are proposed: A reconstruction using the Computer Aided Design (CAD) method; a reconstruction using the tomodensitometry (CT) method and a mixed method CT-CAD. Reconstruction algorithms integrating random geometric characteristics and cell distributions are developed and integrated into a design-modeling approach with adaptive mesh. The numerical analyzes are performed on the reconstructed porous structure by using thermomechanical model of SMAs including phase transformation, martensitic orientation, and twin accommodation mechanisms describing superelasticity and Shape Memory Effect. The effects of porosity, size, orientation and cell dimensions on the super-elasticity of open and closed foams SMAs are studied numerically. The homogenization technique based on the Mori-Tanaka model is proposed to simulate the superelasticity behavior of homogeneous material. Comparisons with CAD models in terms of stiffness and transformation for relatively low porosity foams < 40% are performed
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Paine, Jeffrey Steven Nelson. "Multi-functional SMA hybrid composite materials and their applications /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-162936/.
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Chan, Y. B. "Molecular study of spinal muscular atrophy (SMA) using Drosophila melanogaster." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270342.
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Pal, Anamitra. "Coordinated Control of Inter-area Oscillations using SMA and LMI." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/41229.
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The traditional approach to damp inter-area oscillations is through the installation of Power System Stabilizers (PSSs) which provide damping control action through excitation control systems of the generating units. However, study of recent blackouts has shown that the control action provided by a PSS alone is not sufficient for damping oscillations in modern power systems which operate under stressed conditions. An integrated form of control using remote measurements to coordinate the different control elements present in the system is the need of the hour.
One way of implementing such a coordinated control is through the development of a Linear Matrix Inequality (LMI)-based polytopic model of the system that guarantees pole placement for a variety of operating conditions. The size of the polytopic formulation is an issue for application of LMIs to large systems. The use of Selective Modal Analysis (SMA) alleviates this problem by reducing the size of the system. The previous attempts have used a model containing all the and modes, with SMA being used to eliminate all the other states. In practical applications the resulting system was still found to be too large to use in a polytopic model. This thesis presents an algorithm to reduce the size of the system to the relevant modes of oscillations.
A 16 machine, 68 bus equivalent model of the New England-New York interconnected power system is used as the test case with DC lines and SVCs acting as the control. The algorithm is then applied to a 127-bus equivalent model of the WECC System. The use of ESDs as a form of control is also demonstrated. The results indicate that the proposed control successfully damps the relevant modes of oscillations without negatively damping the other modes. The control is then transferred to a more detailed 4000+ bus model of the WECC system to realize its performance on real-world systems.Master of Science
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Idini, Ilaria. "Polymer stabilised phospholipid nanodiscs." Thesis, University of Bath, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629677.
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Membrane proteins are involved in several fundamental biological processes such as transport or signal transduction. Most of them are enzymes, receptors or other important biological macromolecules representing up to 70% of therapeutic targets. Despite the interest in understanding their structures and behaviour the scientific knowledge is still very limited due to several practical difficulties. In 2009 a new platform for membrane protein studies called SMALP (Styrene-Maleic Acid Lipid Particles) nanodiscs was introduced. SMALPs are self-assembled structures formed by a bilayer of phospholipids controlled in diameter by a polystyrene maleic acid (SMA) copolymer belt. The purpose of this research project herein presented was to structurally characterise SMALPs, with analyses aimed to understand the role of both the polymeric and lipid parts in the self-assembly process. A series of investigations were carried out to elucidate the specific copolymer characteristics that allow the assembly into such well-defined, stable and reproducible structures. Experiments performed via small angle X-ray (SAXS) and neutron (SANS) scattering together with nuclear magnetic resonance (NMR), gel-filtration chromatography (GPC), dynamic light scattering (DLS), allowed identification of the specific polymeric characteristics of the copolymer architecture which were revealed to be crucial for the SMALPs assembly process. Investigations performed also addressed the question whether it was possible to assemble nanodiscs with the use of different phospholipids (with different chain length and charged or non-charged heads) and what the impact of the different lipids had on the structures. Finally, further analyses were made to test the physical chemical behaviour of the SMALPs when important environmental parameters such as temperature, pH and salt concentration of the buffer were changed.
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Filho, Cláudio Luiz Dubeux Neves. "Avaliação laboratorial de misturas asfálticas SMA produzidas com ligante asfalto-borracha." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18137/tde-18122015-105039/.
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As misturas asfálticas do tipo SMA apresentam granulometria descontínua, composta por uma maior fração de agregados graúdos, uma rica massa de ligante/fíler (mastique) e aproximadamente 4% de volume de vazios. Possuem um esqueleto pétreo de alta estabilidade devido ao contato pedra-pedra, que proporciona uma maior resistência à deformação permanente. Geralmente o teor de ligante asfáltico é superior a 6%, formando uma película asfáltica mais espessa. São utilizadas fibras para evitar o escorrimento do ligante durante as etapas de produção e lançamento e, geralmente, são usados asfaltos modificados por polímero. Esta pesquisa tem por objetivo avaliar se o ligante asfalto-borracha possibilita misturas asfálticas SMA capazes de atender aos valores limites de aceitação e, por meio de ensaios de laboratório (resistência à tração, módulo de resiliência, fadiga e deformação permanente em simulador de tráfego), comparar o comportamento de misturas SMA com diferentes tipos de ligante (asfalto convencional CAP 20, modificado por polímero e asfalto-borracha) com um concreto asfáltico convencional de granulometria contínua (Faixa C do DNER). Os resultados obtidos apresentam o comportamento de uma mistura SMA com asfalto-borracha muito mais próximo de misturas SMA produzidas com um ligante modificado por polímero do que com um asfalto convencional.SMA is a gap-graded asphalt mixture with a large proportion of high quality coarse aggregate, a high content of mastic (binder/filler), and approximately 4% of air voids. The larger proportion of coarse aggregate provides a greater stone-to-stone contact, which results in a mixture more resistant to permanent deformation than the conventional Hot Mix Asphalt (HMA). The asphalt content is typically greater than 6.0 percent, which increases the film thickness. Fibers are used to prevent drainage of the asphalt binder during the HMA production and placement, and polymer-modified asphalt cements are usually used. This research aims to evaluate if an asphalt-rubber binder produces SMA mixtures able to meet the technical requirements. The behavior of SMA mixtures produced with different binders (conventional AC-20, polymermodified, and asphalt-rubber) is analyzed based on laboratory tests (tensile strength, resilient modulus, fatigue, and permanent deformation in a traffic simulator) and compared to the behavior of a conventional dense-graded HMA The results show that the behavior of SMA mixtures produced with asphalt-rubber is much closer to SMA mixtures produced with polymer-modified binder than conventional asphalts.
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Thiel, Richard A. "Development of a control system for a SMA actuated medical manipulator." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA340992.
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Thesis (M.S. in Mechanical Engineering and Mechanical Engineer) Naval Postgraduate School, December 1997."December 1997." Thesis advisor(s): Ranjan Mukherjee. Includes bibliographical references (p. 77). Also available online.
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Francis, Michael J. "Physical mapping around the SMA gene using yeast artificial chromosomes (YACs)." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259879.
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Han, L. "Shape memory alloys : numerical simulation and optimal design of SMA actuators." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603638.
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Shape memory alloys (SMAs) are particularly attractive as actuators in smart structures, due to their large actuation strain/stress, high power/weight ratio, single actuation mechanism and low noise etc. However, the lack of reliable predictive models and computational and design tools severely limits their applications. This thesis is concerned with the models appropriate for the numerical implementation, and the optimal design procedure of SMA actuators. To understand the thermomechanical characteristics of NiTi SMAs, a number of tests have been carried out, including iso-thermal tension tests under different constant temperatures, iso-thermal tension tests with different constant strain rates, iso-stress thermal cycling tests under different constant stresses, repeated iso-stress thermal cycling tests and repeated iso-thermal superelastic mechanical cycling tests. The stress-temperature phase diagrams for phase transformations are constructed. Under the framework of generalized plasticity with an internal-variable formalism, a three-dimensional phenomenological model is developed. Based on the stress-temperature phase diagram, the evolution equations of phase fractions are derived. The model reproduces the basic features of SMAs, such as the shape memory effect (SME) and superelasticity (SE), and can deal with incomplete phase transformations. Using return mapping algorithms, the incremental numerical formulation of the model is implemented into ABAQUS, through a user-defined material subroutine. Numerical examples and comparisons between the simulations and experiments have shown the capacity of the model and the feasibility of the subroutine. The design method of a typical bias SMA actuation unit is developed. The relationship of the actuation stress, strain and temperature is obtained by solving a coupled problem combining a thermomechanical constitutive model, heat conduction equations and the spring response. A novel lightweight SMA actuator integrating SMA actuation units into a truss structure is proposed, optimised and manufactured to demonstrate the possibility of SMA actuators in the application of smart structures.
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Hassan, 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.
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Garrau, Sylvain. "Estudio Analítico de una Conexión Viga Columna Usando Aleación SMA CuAlBe." Tesis, Universidad de Chile, 2007. http://repositorio.uchile.cl/handle/2250/103183.
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Se ha visto que después de ocurrido algunos eventos sísmicos, las uniones viga columna
soldadas fallan, debido a fracturas en la soldadura ó a la deformación plástica de la unión. Surge
así la posibilidad de examinar una alternativa a las uniones comunes viga columna, usando
elementos disipadores en base a SMA.
Este estudio es de carácter teórico y tiene por meta reproducir los ensayos experimentales
hechos por J.R. Sepúlveda en 2006. Estos ensayos involucraron una conexión viga columna de
acero con 4 barras SMA de CuAlBe de 3 [mm] de diámetro y 182 [mm] de largo útil trabajando
como disipadores de energía. Se impusieron giros a la conexión, según el protocolo del SAC del
97, a frecuencias de 0.25 [Hz] y 1 [Hz].
Para el desarrollo de este trabajo se determinó en un comienzo que sólo se utilizará el
programa ANSYS, teniendo presente todas las limitaciones que esto conlleva.
Con el programa de elementos finitos ANSYS, se calibró un modelo que reprodujo el
ensayo de una barra y luego se usó la geometría de la conexión, se le impusieron las mismas
solicitaciones para verificar el comportamiento de las barras y de la conexión en general.
El modelo de la conexión se comportó de manera similar a la conexión ensayada. De la
comparación de los resultados se concluye que lo que produjo las mayores diferencias es la
modelación de la curva tensión-deformación del material SMA.
La comparación teórica de la misma conexión con barras de acero muestra que la
deformación remanente debida a la fluencia de las barras, hace que la viga tenga una resistencia
al corte casi nula, lo que induce el colapso de la estructura. Aunque en el caso del acero la
disipación de energía de la conexión es mayor, la solución de ocupar un material superelástico se
recomienda por la ausencia de deformaciones remanentes.
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Olea, Guajardo Manfred. "Ensayo en Mesa Vibradora de Marco de Acero con Conexiones SMA." Tesis, Universidad de Chile, 2009. http://repositorio.uchile.cl/handle/2250/103620.
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Se ha observado que frente a eventos sísmicos de magnitud considerable, las uniones vigacolumna
en estructuras de acero pueden presentar fallas, debido a fracturas en la soldadura o
deformación plástica de la unión. Esto genera la posibilidad de estudiar sistemas de disipación
de energía en las conexiones viga columna. Una alternativa es la incorporación de disipadores
en base a SMA (Shape Memory Alloys).
Este estudio es de carácter teórico-experimental, donde se describe el comportamiento de un
modelo a escala reducida de una estructura de acero de un piso, en cuyas conexiones vigacolumna
se usan barras SMA. Previo a la ejecución de ensayos, se modeló la estructura y las
acciones en ella, utilizando un programa de análisis no lineal, para tener una estimación en el
orden de magnitud de la respuesta del modelo experimental.
Las conexiones viga-columna están formadas por 4 barras SMA, y el marco se sometió a ensayos
tipo pull-back y registros sinusoidales y de sismos reales en una mesa vibradora de un grado de
libertad. Se usan dos tipos de barras: de Nitinol de 2,5 mm de diámetro y de CuAlBe de 3,3 mm
de diámetro. Ambos materiales se encuentran en fase austenita a temperatura ambiente y han
sido caracterizados con anterioridad en ensayos cíclicos de tracción.
La instrumentación incluye acelerógrafos a nivel de losa y de techo, un potenciómetro para
medir desplazamiento de techo, y celdas de carga y potenciómetros para medir fuerzas y
deformaciones en las barras SMA de cada conexión.
A partir de los ensayos tipo pullback se obtiene el período fundamental y el amortiguamiento
por decremento logarítmico, resultando 0.52 [seg] y un 2.3% para el marco con barras de Nitinol
y 0.47 [seg] y 1.4% para el marco con barras de CuAlBe.
Al aplicar el registro de Llolleo N10E escalado en un 25% y 50% al marco con conexiones de
Nitinol, se observa reducciones en la aceleración del techo, comparada con la aceleración
espectral, del orden del 24% para el registro escalado a un 25% y del 49% para el registro
escalado a un 50%. Para el marco con conexiones de CuAlBe, la reducción de la aceleración es
de un 14% para el registro de Llolleo escalado en un 25%.
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Alazzawi, Sheymaa. "DESIGNING A SMART GREENHOUSE VENTILATION WINDOW BASED ON NITI SMA ACTUATOR." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1703.
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A multi-functional (sensing -actuating) greenhouse ventilation window heated/cooled naturally by convection was designed to overcome different industry challenges in terms of designing smart applications. This ventilation window design includes a three-pulley system to reduce the load on the NiTi actuator and enhance its long-life time. In addition, using the NiTi actuator allows energy saving due to natural phase transformation induction (i.e. convection) and high force generation compared to the small NiTi wire mass. Structural analysis was used to determine the force generated in the “C-shaped” NiTi wire after loading. Transient thermal and structural analysis also was used to investigate the strain rate effects on the shape memory response of “C shaped” NiTi alloy element under different thermomechanical loadings and boundary conditions. Two types of loading have been applied isothermally or at adiabatic conditions. The results showed a significant effect of the high loading rates on increasing the stress plateau which is caused by the corresponding shift in the transformation temperatures. As a result, it could be expected that the actuator life time could be reduced when a rapid, as opposed to a slow loading rate, is adopted. In addition, the dynamic loading of the NiTi leads to a decrease of the recoverable strain. Experimental work was done to validate the simulation model by testing a commercial NiTi sample dynamically and compare the macroscopic displacement during mechanical loading and the strain recovery process.
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Fernández, Villalba Omar A., and Salinas Edgardo G. Cáceres. "Evaluación del comportamiento mecánico de mezclas SMA y Superpave empleando asfalto modificado con Polímero SBS (Estireno-Butadieno-Estireno)." Bachelor's thesis, Universidad Ricardo Palma. Programa Cybertesis PERÚ, 2007. http://cybertesis.urp.edu.pe/urp/2007/fernandez_oa/html/index-frames.html.
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Li, Yinan. "Design and Analysis of Energy Harvesting with Shape Memory Alloy." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1354872782.
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Jun, Hyoung Yoll. "Development of a fuel-powered compact SMA (Shape Memory Alloy) actuator system." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1426.
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The work presents investigations into the development of a fuel-powered compact SMA actuator system. For the final SMA actuator, the K-alloy SMA strip (0.9 mm x 2.5 mm), actuated by a forced convection heat transfer mechanism, was embedded in a rectangular channel. In this channel, a rectangular piston, with a slot to accommodate the SMA strip, ran along the strip and was utilized to prevent mixing between the hot and the cold fluid in order to increase the energy density of the system. The fuel, such as propane, was utilized as main energy source in order to achieve high energy and power densities of the SMA actuator system. Numerical analysis was carried out to determine optimal channel geometry and to estimate maximum available force, strain and actuation frequency. Multi-channel combustor/heat exchanger and micro-tube heat exchanger were designed and tested to achieve high heat transfer rate and high compactness. The final SMA actuator system was composed of pumps, valves, bellows, multi-channel combustor/heat exchanger, micro-tube heat exchanger and control unit. The experimental tests of the final system resulted in 250 N force with 2 mm displacement and 1.0 Hz actuation frequency in closed-loop operation, in which the hot and the cold fluid were re-circulated by pumps.
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Lanteigne, Eric. "Design of a composite SMA actuator for a pressurized hyper-redundant manipulator." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27383.
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Hyper-redundant devices are characterized by repeating independently controlled structures connected in series, much like the architecture of a snake or worm. This thesis evaluates the performance of a pressurized hyper-redundant manipulator design driven by high strain shape memory alloy actuators. The proposed design is composed of four identical modules; each providing three degrees of freedom from three symmetrically positioned actuators. The modules have an outer diameter of 31mm and a length of 33mm at full extension. The actuator return force and manipulator stiffness are controlled by an air pump connected at the base. Although connection failures between the actuator tabs and vertebrae prevented the validation of the hyper-redundant manipulator prototype, the unit module element was successfully fabricated and evaluated. The unit module could achieve linear contractions of 40% and rotations of over 50° at a frequency of 0.05Hz. Several limitations remain to be addressed in order to build a reliable device; these include: (1) The high current requirement of the actuators, (2) The inefficient actuation system, and (3) The connectivity issues between the actuators and the modules.
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Vilches, González Evelyn Andrea. "Ensayo en Mesa Vibradora de un Marco Arriostrado con Barras de SMA." Tesis, Universidad de Chile, 2010. http://www.repositorio.uchile.cl/handle/2250/103789.
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En este trabajo se ensayó un marco de acero de escala reducida de dimensiones 1,5mx1,5mx0,8m, con el objetivo de verificar la capacidad que tienen barras de NiTiNOL (aleación de Niquel y Titanio), para disipar energía sísmica.
Las barras de NiTiNOL de 48cm de longitud y 2,46mm de diámetro se incluyen como parte del sistema de arriostramientos, en el centro del vano principal de la estructura, la cual se ensaya en la mesa vibradora del Laboratorio de Dinámica de Estructuras del Departamento de Ingeniería Civil, aplicando señales sinusoidales y registros sísmicos reales escalados.
Como instrumentación se utilizan acelerómetros, celdas de carga y potenciómetros, con los cuales se obtienen aceleraciones a nivel de losa y sobre el marco, esfuerzo y deformación en barras y desplazamientos laterales del marco. La estructura sin arriostrar tiene un amortiguamiento de 1,55% y periodo de 0,44s. Al incorporar las diagonales el amortiguamiento aumenta a 2,5% y el periodo baja a 0,15s y 0,16s, dependiendo de la pretensión de las barras. Los desplazamientos y aceleraciones en el techo de la estructura se reducen con respecto al caso de la estructura sin diagonales cuando se aplica el registro de Llolleo en su componente N10E reducido al 50%.
Con la utilización de diagonales en estructuras reales es posible disminuir la magnitud de los desplazamientos frente a solicitaciones sísmicas. Además, si éstas incorporan materiales SMA (Shape Memory Alloys), se pueden controlar las aceleraciones en la estructura.
Los periodos obtenidos de manera experimental verifican analíticamente, al igual que la respuesta ante el registro sísmico escalado al 50%.
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Boza, Maria Gabriela. "Modelling SMA using induced pluripotent stem cells from a discordant affected family." Thesis, University of London, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589610.
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Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease in which low levels of survival of motor neuron (SMN) protein lead to the degeneration of alpha motor neurons (MNs) in the spinal cord. The pathological mechanism of SMA is highly controversial and until recently it was not possible to obtain human MNs to study the disease. The development of induced pluripotent stem cell (iPSC) technology has made it possible to bypass this obstacle and iPSC-based models of SMA type I have already been validated by two separate groups. Encouraged by these pioneering findings I have produced and characterized iPSCs from several members of a discordant consanguineous family in which four haploidentical siblings share the same homozygous SMNl mutation, but nonetheless show different phenotypes of the disease. I have differentiated iPSC clones from three of the siblings and the carrier unaffected mother, as well as a control unaffected clone and a clone derived from a patient with SMA type I, into ISL1+/ChAT+ MNs. No obvious phenotypic difference was observed between the MN cultures of the siblings during the period of study, but cells from the SMA type I patient did show an impaired ability to form rosettes. The study of SMN and PLS3 levels during the differentiation from iPSCs to ChAT+ MNs showed a gradual decay of these proteins during MN development in all clones. Furthermore, SMN protein levels did not correlate with the pattern of mRNA expression, c suggesting the existence of post-transcriptional and/or post-translational regulation of full-length SMN (FL-SMN) transcripts and protein. The FL/.d7-SMN mRNA ratio and total SMN (tSMN) mRNA levels were found to be possible biomarkers to distinguish unaffected individuals from SMA patients and the severity of SMA pathology, respectively. PLS3 protein level was higher in the SMA type IV/asymptomatic sibling than in two of the type III SMA siblings, but it could not be confirmed as a modifier factor in the family. These results suggest that SMN levels are regulated during MN development, and that low levels may impair the generation of rosettes but not necessarily of MNs. SMN levels in MNs only show minor differences between patients, suggesting that there may be a threshold after which reduced levels of SMN within a narrow range become suddenly and increasingly detrimental unless modifier factors can compensate for the cellular function(s) lost. 3
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Reis, Rafael Marcal Martins de. "Revestimento asfáltico tipo SMA para alto desempenho em vias de tráfego pesado." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/3/3138/tde-14112003-103348/.
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Este trabalho apresenta alguns resultados de pesquisa laboratorial compreendendo projeto de dosagem, comportamento mecânico da mistura SMA (Stone Matrix Asphalt - Matriz Pétrea Asfáltica), bem como, aspectos executivos relacionados ao desenvolvimento de um trecho experimental em SMA para revestimento de pavimentos. Os resultados de laboratório obtidos mostram que o SMA é um revestimento asfáltico que pode apresentar bom desempenho sob cargas pesadas em climas quentes, pois estas misturas são muito resistentes à deformação permanente, mas preservam a flexibilidade como os concretos asfálticos densos. O SMA é uma solução bem conhecida para tráfego pesado na Europa e mais recentemente na América do Norte. O SMA também tem sido empregado para aumento de aderência em pista molhada e para redução de ruído.This research presents laboratory test results of mixture design, mechanical behavior of SMA (Stone Matrix Asphalt), as well as some construction aspects regarding to development of Brazilian road trial section as a new bituminous surface course to pavement construction or maintenance.The laboratory results show that SMA can perform very well in hot climate under heavy load conditions due to the mixture to be very resistant against permanent deformation but still flexible like dense asphalt concrete. The SMA is a well Known solution for heavy traffic in Europe and, more recently, in North America. The SMA is also employed to increase the adherence in wet conditions and for noise reduction.
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Silva, Patricia Barboza da. "Estudo em laboratório e em campo de misturas asfálticas SMA 0/8S." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/3/3138/tde-31082006-134522/.
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Esta pesquisa foi baseada em um projeto de Stone Matrix Asphalt - SMA na faixa 0/8S com asfalto CAP 20, feito para a execução de revestimento delgado em trecho experimental na Rodovia Presidente Dutra, ligando São Paulo ao Rio de Janeiro. A ocorrência de alguns defeitos neste trecho experimental motivou o estudo de misturas SMA 0/8S alternativas empregando dois asfaltos convencionais: CAP 20 e CAP 50/60, e dois modificados por polímeros: um com 3,0% de SBS e outro com 6,5% de SBS. Foram realizados ensaios laboratoriais para a verificação da dosagem das misturas asfálticas e determinação de propriedades mecânicas em laboratório por meio de ensaios de deformação permanente em trilha de roda, de resistência à tração por compressão diametral e de módulo de resiliência. Observou-se que o uso de asfalto modificado por polímero e do asfalto convencional CAP 50/60 acarreta uma redução significativa de afundamentos em trilha de roda. O módulo de resiliência a 25°C também apresenta redução de valor nas amostras com asfalto modificado por polímero e com CAP 50/60, em comparação com o convencional CAP 20. A resistência à tração sofre pouca variação quando se comparam os asfaltos empregados, considerando-se ensaios realizados na mesma temperatura. Foram feitos ensaios em campo para a avaliação funcional e de aderência no trecho experimental da Rodovia Presidente Dutra, tendo sido realizados monitoramentos logo após a execução do trecho e decorridos 2 anos e 7 meses de operação. Os resultados demonstraram que o revestimento do trecho experimental apresenta atualmente poucos defeitos de superfície, com fechamento da macrotextura nas trilhas de roda e pequena diminuição do conforto ao rolamento.This research was based on a Stone Matrix Asphalt SMA in the band 0/8S design made with asphalt binder AC 20, used as a thin wearing course of a test section on the Presidente Dutra Highway, that connects São Paulo to Rio de Janeiro. The occurrence of some distresses in the test section motivated the study of alternative SMA 0/8S mixtures using two conventional asphalt binders: AC 20 and AC 50/60, and two modified by polymer: one with 3.0% of SBS and other with 6.5% of SBS. Laboratory tests were conducted to verify the mix design and to determine their mechanical behavior such as the resistance against rutting, the indirect tensile strength and the resilient modulus. It was observed that the use of SBS polymer modified binders and asphalt binder AC 50/60 causes a significant reduction of rutting. The resilient modulus at 25°C also presents a reduction in the samples with SBS polymer modified binders and AC 50/60 in comparison with AC 20. The indirect tensile strength suffers little variation across the different types of asphalt binders, tested at the same temperature. Field tests related to functional evaluation and skid-resistance of the test section were carried out. The test section was monitored immediately following the construction and after 2 years and 7 months of continuous use. The results showed that the wearing coarse presented a few distresses in the surface, in particular a reduction of the macrotexture at the wheel tracks and a slight worsening of the riding quality.
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Rademacher, Sebastian [Verfasser]. "Cytoskeletal dysregulation in the motoneuron disease Spinal Muscular Atrophy (SMA) / Sebastian Rademacher." Hannover : Bibliothek der Tierärztlichen Hochschule Hannover, 2017. http://d-nb.info/1136298002/34.
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Maniscalco, Federica. "Commonalities between SMA and ALS: investigation of ribosome heterogeneity and translational defects." Doctoral thesis, Università degli studi di Trento, 2023. https://hdl.handle.net/11572/370629.
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According to the “ribosome heterogeneity hypothesis”, ribosomes are not all identical, and specialized ribosomes, capable of finely tuning translation of selected mRNAs, do exist. Multiple types of ribosomes are defined by several elements, such as their composition, and their association with different proteins, known as ribosome-associated proteins (RAPs). In particular, these proteins can exert a direct role on mRNA selection and translation efficiency. At present, some RNA-binding proteins (RBPs), such as Fragile X Messenger Ribonucleoprotein 1 (FMRP) and Fused in sarcoma (FUS) are considered putative RAPs and likely to regulate translation of specific mRNA transcripts via their binding to ribosomes. Even if dysregulation of translation has been associated with several neurodegenerative diseases, it remains unclear whether ribosome heterogeneity perturbations may be central to human pathologies. In this thesis I explored the hypothesis that disruption of ribosome heterogeneity in spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS) is a common hallmark of these devastating neurodegenerative disorders. Despite different genetic causes, they share some notable commonalities, both at clinical and molecular level. Both pathologies, characterized primarily by lower motor neuron degeneration, are caused by mutations in genes encoding for ubiquitously expressed RBPs with common functions in mRNA metabolism. Recent studies have revealed that the survival motor neuron protein (SMN), which is involved in SMA, is a RAP and that the RBPs TAR DNA binding protein 43 (TDP43) and Matrin3 (MATR3), involved in ALS, are associated with the translation machinery. In addition, translatome changes are commonly observed in both diseases and loss of SMN and dysregulation of TDP43 and MATR3 are associated with translation defects of specific mRNAs. Therefore, exploration of a direct involvement of these proteins in translation may reveal a still uncharacterized level of heterogeneity which may account for most of translational defects and may reveal common dysregulated pathways. This thesis has three specific aims: i) characterize the RNA features of mRNAs bound by SMN-primed ribosomes and of their defects in in cellulo and in vivo models of SMA; ii) investigate ribosome heterogeneity and translational defects in TDP43-dependent ALS models and iii) explore the mutual role of SMN and MATR3 in ribosome heterogeneity and the impact of their loss in ALS and SMA models of disease. The first specific aim stemmed from previous findings obtained at the Institute of Biophysics (CNR, Italy) on the role played by SMN in translation and the consequent translational defects in SMA. SMN co-sediments with ribosomes and polysomes and acts as a RAP, influencing the translation efficiency of specific mRNAs. Computational analyses identified specific features in the sequences of transcripts bound by SMN-primed ribosomes: translational enhancer sequences in the 5’ untranslated region (UTR) and rare codons at the beginning of the coding sequence (CDS). SMN loss causes translational downregulation of transcripts bound by SMN-primed ribosomes (named SMN-specific mRNAs) due to ribosome-associated defects in SMA. Here, I validated these features analyzing the translation efficiency of reporter constructs bearing c-Myc translational enhancer at the 5’UTR or rare codons at the beginning of the CDS in an in cellulo model of SMA. Results of luciferase assays indicated that the two features are required for SMN-specific mRNAs to be translationally controlled by SMN-primed ribosomes. Co-sedimentation analysis of selected SMN-specific mRNAs along sucrose gradients of control and early symptomatic SMA brain from the Taiwanese model of the disease confirmed that these transcripts are depleted from the polysomal fractions, thus leading to possible changes at the protein level. I found that SMN-primed ribosomes play a critical role in regulating translation of AChE mRNA, a neuron-specific gene encoding for Acetylcholinesterase (AChE), molecular marker of the neuromuscular junction (NMJ) impairment at early stages of SMA. The second specific aim of this thesis is focused on the role played by TDP43 in translation in the context of ALS. ALS is associated with the dysregulation of multiple RBPs that play important roles in mRNA localization, maturation and translation, similarly to SMN. Overexpression or mutations of TDP43 are major contributors to ALS. Recently, MATR3 has also been associated with ALS cases. Here, I investigated the association of TDP43 with ribosomes and polysomes in neuronal compartments by taking advantage of a tag-free polysome profiling approach applied in axonal and cell body lysates obtained from neurons cultured in microfluidic chambers. Thanks to this technique, I explored the hypothesis that the overexpression of TDP43 WT and its mutated form TDP43 A315T cause axonal specific impairment in the balance between granule- and polysome-associated mRNAs, leading to disruption of local protein synthesis in ALS. By sequencing the mRNAs associated with subcellular regions (cell body or axon) and sub-compartments (RNA granules or polysomes), I found a loss of balance between polysome-engaged transcripts and free RNA in the axonal compartment upon overexpression of TDP43 WT and TDP43 A315T. These observations, together with results of axonal puromycilation assay, suggested that the imbalance between mRNAs associated with granules and polysomes derives from robust degradation of free RNA targets of TDP43, which causes a release of ribosomes free to bind to and hyper-translate remaining mRNAs, in particular TDP43 non-target mRNAs. To test this hypothesis, I used a set of constructs in cell line models of ALS that reveled the existence of a translational burden effect caused by decreasing levels of TDP43 mRNA targets. This revealed possibly completely new mechanisms leading to axonal loss in a cell model of ALS. Finally, the third specific aim of this thesis derived from the observation that SMN-bound ribosomes are associated with specific mRNAs that are involved not only in SMA but also in ALS. Among the mRNAs targeted by SMN-primed ribosomes involved in ALS, I observed the MATR3 mRNA, suggesting the existence of a common molecular trait connecting SMN and MATR3. Interactomics analysis of SMN-primed ribosomes revealed that MATR3 protein is also a top interactor. In addition, MATR3 has recently been shown to associate with the translational machinery and control the translation efficiency of a specific subset of mRNAs involved in the maintenance of human cell pluripotency. Given these findings, I hypothesized that MATR3 acts as a RAP and that both MATR3 and SMN converge on the same subset of ribosomes. Using biochemical methods, I confirmed the association of MATR3 with ribosomes in hiPSCs and found that this association is RNA-independent. Furthermore, I found that downregulation of MATR3 decreases the association of MATR3 and SMN with the translation machinery. Conversely, downregulation of SMN causes a decrease in the co-sedimentation of MATR3 with ribosomes. These results strongly support the SMN and MATR3 mutual-dependency in converging on the translation machinery and open a new translation-centered scenario to understand common mechanisms leading to ALS and SMA. The discovery of common molecular mechanisms between SMA and ALS could prove to be pivotal to better understanding these diseases and enable the development of novel therapies.
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Boulisfane, Nawal. "Etude des bases moléculaires de l'atrophie musculaire spinale." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20113/document.
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L'Atrophie Musculaire spinale (SMA) est une maladie neurodégénérative causée par des mutations du gène SMN1 et caractérisée par la dégénérescence sélective des motoneurones alpha de la moelle épinière. les mécanismes moléculaires de la SMA ne sont aps clairs. cependant, deux hypothèses ont été retenues:D'une part, que la déficience en SMN entraine une perturbation de la biogenèse des snRNPs spliceosomales individuelles et par conséquent des défauts d'épissage. pendant ma thèse, nous avons montré que la déficience en SMN provoquait une diminution des particules tri-snRNPs majeures amis surtout mineures et que cela avait des conséquences sur l'épissage d'un sous-groupe de pré-ARNm contenant des introns mineurs.D'autre part, que la déficience en SMN entraine des altérations de transport d'ARN dans les axones, essentiels pour la survie des motoneurones. A part l'ARNm de la beta-actine et l'ARNm de cpg15 récemment identifié, ceux qui pourraient être transportés par SMN n'ont pas été décrits. nous avons donc identifié les ARN interagissant avec les isoformes a-SMN et SMN-fl dans des cellules neuronales, et montré que certains de ces ARN cibles colocalisent avec SMN dans les axones, suggérant qu'elle est impliquée dans leur transportSpinal Muscular Atrophy is a neurodegenerative disease caused by mutations in SMN1 gene. SMA is characterized by the loss of alpha-motoneurons of the spinal cord. However, the precise molecular mechanisms underlying the disease are still unkown. two hypotheses have been retained to explain SMA pathigenesis:In one hand, the fact that SMN deficiency leads to a perturbation of individual snRNPs biogenesis and consequently splicing defects. During my PhD, we have shown that SMN deficiency alters the levels of major, but mostly, minor tri-snRNPs. And that leads to splicing defects of a subset of pre-mRNA containing minor introns.In the other hand, that SMN deficiency causes alteration of axonal transport of RNAs crucial to motoneurons survival. Except beta-actin mRNA and the recently identified cpg mRNA, the RNA targets of SMN have not been described. We succeed to identify RNA targets of both a-SMN and SMN-fl isoformes in a neuronal cell line and colocalisation data of some of these targets suggested that SMN could be implicated in the transport of these RNAs
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Vargas, Olguín Javier Ignacio. "Ensayo de Placas Tipo Adas de Láminas de CuZnal." Tesis, Universidad de Chile, 2007. http://www.repositorio.uchile.cl/handle/2250/104832.
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Bondy-Chorney, Emma. "Characterization of Novel Post-Transcriptional Events Misregulated In Disease: Implications for the Development of Future Therapies." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36034.
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The misregulation of post-transcriptional mechanisms has been linked to the development and progression of numerous human diseases, in particular neurological disorders and cancer. Investigating these misregulated RNA pathways is essential to fully understand the disease mechanisms, identify novel biomarkers, and to develop effective therapies. In this thesis, I present three manuscripts that investigate the mechanisms behind the post-transcriptional misregulation of RNA in human disease, with a focus on pre-mRNA splicing. In the first manuscript (Bondy-Chorney et al., 2016a), we investigated the role of Staufen1 (Stau1) in splicing regulation in the neuromuscular disorder Myotonic Dystrophy Type 1 (DM1). Here we report the first insights into the mechanism that Stau1 uses to regulate the alternative splicing of INSR exon 11 through an interaction with Alu elements located in intron 10. Moreover, using a high-throughput RT-PCR screen, we uncovered a number of additional Stau1-regulated alternative splicing events in both wild-type and DM1 myoblast cell lines. As Stau1 is known to be aberrantly upregulated in DM1 skeletal muscle, our findings suggest that Stau1 acts as a disease modifier in this disorder. The second manuscript (Sanchez, Bondy-Chorney et al., 2015), describes a novel role of the protein methyltransferase Coactivator-Associated Methyltransferase-1 (CARM1), a protein found to be overexpressed in Spinal Muscular Atrophy (SMA). We found that CARM1 can act as a mediator in the nonsense-mediated decay pathway (NMD) and associated UPF1 to promoted its occupancy on PTC-containing transcripts. We identified a subset of natural non-PTC containing NMD targets that were dependent on CARM1, a number of which were misregulated in SMA. This work uncovered a novel role for CARM1 in the NMD pathway and revealed that defective targeting of PTC-containing mRNAs should be included in the complex array of molecular defects associated with SMA. Finally, the third manuscript (Bondy-Chorney et al., – in prep) examines the alternative
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splicing regulation of the Protein Arginine Methyltransferase PRMT1 exon 2, an event shown to alter the growth, survival, and invasion of breast cancer cells. Here, we used an RNA interference (RNAi) RT-PCR screen to uncover several splicing proteins that regulate the inclusion of exon 2, several of which we found to be misregulated in a panel of breast cancer cell lines and patient tumours. These findings confirmed that the inclusion of PRMT1 exon 2 was regulated by alternative splicing via splicing factors that are altered in breast cancer. Moreover, depletion of one of these splicing factors, RALY, resulted in a decrease in the motility and invasive potential of an aggressive breast cancer cell line. These three manuscripts represent a collection of work focused on elucidating the mechanisms involved in post-transcriptional misregulation of RNA in three diverse human diseases. Taken together, the data presented here highlight the broad impact that proteins, such as Stau1 and CARM1, can have in neuromuscular disorders. Moreover, we also uncovered novel misregulation of splicing proteins that alter alternative splicing patterns in breast cancer. Elucidating these mechanisms is of the highest importance in order to identify potential new and effective treatment avenues.
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Hoelz, Bruno Werneck Pinto. "Metamodelo para adaptação de confiança e reputação em sistemas multiagente dinâmicos." reponame:Repositório Institucional da UnB, 2013. http://repositorio.unb.br/handle/10482/15238.
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Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2013.Submitted by Alaíde Gonçalves dos Santos (alaide@unb.br) on 2014-01-21T12:46:46Z No. of bitstreams: 1 2013_BrunoWerneckPintoHoelz.pdf: 3440475 bytes, checksum: 3084aa1ec80c1c223b65cf14f4cac8b2 (MD5)
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Modelos computacionais de confiança e reputação são elementos-chave no projeto de sistemas multiagente abertos. Eles oferecem um meio de avaliar e reduzir o risco de cooperação na presença de incerteza. No entanto, os modelos propostos na literatura não consideram os custos envolvidos na sua aplicação e como os modelos são afetados pela dinamicidade do ambiente. Neste trabalho, um metamodelo para adaptação de confiança a e reputação em sistemas multiagente dinâmicos é proposto. O metamodelo tem como finalidade complementar os modelos de confiança e reputação já existentes, permitindo que agentes deliberativos possam raciocinar sobre os componentes do modelo em uso e reagir a mudança as no ambiente. O processo de adaptação é realizado ajustando a configuração do modelo adotado para melhor se adequar às condições atuais. É demonstrado como o metamodelo pode ser aplicado a modelos propostos na literatura e como planos de adaptação podem ser utilizados para ajustar seus componentes dinamicamente para melhorar seu desempenho. Um mecanismo de aprendizagem, incluindo uma prova de conceito baseada em algoritmos genéticos, é proposto para identificar novos planos de adaptação para cenários similares. Por fim, a avaliação experimental da aplicação do metamodelo e do mecanismo de aprendizagem mostra melhorias significativas em comparação com o uso de modelos não adaptáveis, o que contribui para a melhoria do projeto de agentes autônomos para sistemas multiagente dinâmicos. _______________________________________________________________________________________ ABSTRACT
Computational trust and reputation models are key elements in the design of open multi-agent systems. They offer a way of evaluating and reducing risks of cooperation in the presence of uncertainty. However, the models proposed in the literature do not consider the costs they introduce and how they are affected by dynamic environments. In this work, a meta-model for trust and reputation adaptation in dynamic multi-agent systems is proposed. The meta-model acts as a complement to trust and reputation models, by allowing deliberative agents to reason about the components of the model being used, and to react to changes in the environment. The adaptation process is made by adjusting the model's configuration to better ft the current conditions. It is demonstrated how the meta-model can be applied to existing models proposed in the literature, and how adaptation plans can be used to adjust its components dynamically to improve its performance. A learning mechanism, along with a proof of concept implementation based on genetic algorithms, is proposed to identify new adaptation plans for similar scenarios. Finally, the experimental evaluation of the meta-model application and its learning mechanism shows significant improvements in comparison to the use of non-adaptable models. This contributes to improving the design of autonomous agents for dynamic multi-agent systems.
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Souza, Daniel da Silva. "Uma ferramenta multiagente baseada em conhecimento para anotação de proteínas : um estudo de caso para o Fungo Saccharomyces cerevisiae." reponame:Repositório Institucional da UnB, 2014. http://repositorio.unb.br/handle/10482/18225.
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Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciências da Computação, 2014.Submitted by Ana Cristina Barbosa da Silva (annabds@hotmail.com) on 2015-03-26T16:59:05Z No. of bitstreams: 1 2014_DanieldaSilvaSouza.pdf: 2076331 bytes, checksum: a87184e0f162b276c6b8666762b41e35 (MD5)
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Identificar funções biológicas das sequências é uma atividade chave em projetos genomas. Esta tarefa é realizada na etapa de anotação, que possui duas fases. Na fase manual, biólogos utilizam seu conhecimento e experiência determinar a função de cada sequência, baseada nos resultados produzidos pela fase automática, onde ferramentas e bancos de dados são utilizados para predizer uma anotação funcional. Esta dissertação propõe BioAgents-Prot, uma ferramenta multiagente baseada em conhecimento, que simula o conhecimento e experiência dos biólogos para anotação de proteínas. BioAgents-Prot foi definido com uma abordagem de agentes cooperativos, onde diferentes agentes especializados trabalham em conjunto na tentativa de sugerir uma anotação manual adequada. A arquitetura proposta em três camadas foi desenvolvida com Java Agent DEvelopment Framework - JADE e Drools, um motor de inferência baseado em regras. Para avaliar o desempenho do BioAgents-Prot, as anotações dos transcritos do fungo Saccharomyces cerevisiae foram comparadas com as anotações sugeridas pelo sistema. Usando regras básicas que representam o raciocínio de anotação, obtemos 95.84% de sensibilidade, 93.22% de especificidade, 98.40% de F1-score e 0.80 de MCC, que demonstram a utilidade do BioAgents-Prot na etapa de anotação em projetos transcritoma. ______________________________________________________________________________________________ ABSTRACT
Identifying biological function of sequences is a key activity in genome projects. This task is done in the annotation step, which has two phases. In the manual phase, biologists use their knowledge and experience to determine the function for each sequence, based on the results produced by the automatic phase, where tools and data bases are used to predict functional annotation. This dissertation presents BioAgents-Prot, a knowledge based multiagent tool, which simulates biologists expertise to annotate proteins. BioAgents-Prot is defined with an approach of cooperative agents, where specialized intelligent agents work together to suggest proper manual annotation. The proposed three-layer architecture was implemented with Java Agent DEvelopment Framework-JADE and Drools (a rule-based inference engine). To assess performance, transcript annotations of the Saccharomyces cerevisiae fungus were compared to the annotations suggested by BioAgents-Prot. Using basic rules that represents the annotation reasoning, we obtained 95.84% of sensitivity, 93.22% of specificity, 98.40% of F1-score and 0.80 of MCC, which shows the usefulness of BioAgents-Prot in annotation step of transcriptome projects.
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Eggert, Christian. "Untersuchungen zur Biogenese spleissosomaler UsnRNPs und ihrer Bedeutung für die Pathogenese der SMA." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978830261.
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Zaidi, Mohammed. "Experimental Testing and Reliability Analysis of Repaired SMA and Steel Reinforced Shear Walls." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35357.
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Superelastic Shape Memory Alloys (SMAs) are being explored as alternative reinforcing materials to traditional deformed steel reinforcement for seismic applications. The main advantage is the ability of the SMA to recover large nonlinear strains, which promotes the self-centering phenomenon. The primary objective of this research is to present the performance, before and after repair, of slender reinforced concrete shear walls, one reinforced internally with SMAs in the boundary zones within the plastic hinge region and other control wall reinforced with conventional steel only. The repair procedure included removal of damaged concrete within the plastic hinge region, replacing fractured and buckled reinforcement, followed by shortening of the SMA reinforcement in the boundary zones of SMA wall. The removed concrete was replaced with self-consolidating concrete, while the concrete above the plastic hinge region remained intact.
The SMA reinforced concrete shear wall (before and after repair) exhibited stable hysteretic response with significant strength, and displacement and energy dissipation capacities. In addition, the walls exhibited pinching in the hysteretic response as a result of minimizing the residual displacements due to the restoring capacity of the SMA reinforcement. The results demonstrate that SMA reinforced components are self-centering, permitting repairing of damaged areas. Furthermore, the SMA reinforcement is re-usable given its capacity to reset to its original state. The length of the SMA bars in the original and repaired wall, in addition to the presence of starter bars in the original wall, were significant factors in the location of failure of the walls.
The conventional steel wall prior to repair was unstable due to large residual displacements experienced during the original test. After repair the wall exhibited ratcheting in hysteretic response but with significant strength. The conventional wall, before and after repair, dissipated more energy than the SMA wall. This was the result of the wider hysteretic loops with reduced punching, but at the cost of large residual displacements. The starter bars in the conventional wall before repair controlled the location of failure, while the presence of couplers in the plastic hinge region was the main factor in determining the failure location in the repaired conventional wall.