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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Επανασχεδιασμός ρομποτικού λαπαροσκοπικού εργαλείου / Redesign of a robotic laparoscopic tool

Παπαδόπουλος, Γεώργιος Μάριος 13 January 2015 (has links)
Το θέμα αυτής της διπλωματικής εργασίας είναι ο σχεδιασμός, η παραγωγή, η κατασκευή και ο έλεγχος ενός χειρουργικού ρομποτικού εργαλείου με βελτιωμένα χαρακτηριστικά από το προηγούμενο πρωτότυπο. Το λαπαροσκοπικό εργαλείο αποτελείται από συνδέσμους σε σειρά οι οποίοι ενεργοποιούνται με μορφομνήμονα καλώδια, οι οποίοι λειτουργούν σαν δυαδικοί ενεργοποιητές με δύο πιθανές καταστάσεις. Κάθε σύνδεσμος αποτελείται από τρεις πρισματικούς ενεργοποιητές, οι οποίοι δημιουργούν μια πλατφόρμα Stewart και παρέχουν μια 3 βαθμών ελευθερίας κινητικότητα σε κάθε σύνδεσμο. Τα ηλεκτρονικά είναι ενσωματωμένα στο εσωτερικό των συνδέσμων, σε αρχιτεκτονική Master-Slave. Η επικοινωνία μεταξύ του χειρούργου και του εργαλείου επιτυγχάνεται με I2C δικτυωμένους μικρο-ελεγχτές, Στον τελευταίο σύνδεσμο του εργαλείου, υπάρχει μια στερεοσκοπική κάμερα και μια πλακέτα IMU η οποία προσφέρει πληροφορίες προσανατολισμού. Επιπρόσθετα, ένα σύστημα αντίληψης δύναμης το οποίο είναι ικανό να επικολληθεί στην επόμενη έκδοση του εργαλείου. Εν κατακλείδι, σχεδιαστικές παράμετροι καθώς και η κινηματική του δυαδικού βραχίονα παρουσιάζεται σε προσομοίωση και πειραματικές μελέτες του λαπαροσκοπικού πρωτότυπου εργαλείου. / The subject of this master thesis is the design, the fabrication, the construction and the control of a surgical robotic tool with improved characteristics than previous version. The laparoscopic tool consists of cascaded links which are powered by Shape Memory Alloys wires, acting as binary actuators with two stable states. Each link is composed of three prismatic actuators, creating a Stewart platform and providing a 3-DOF maneuverability for each joint. The electronics are embedded in the inner cavity of the links in, Master-Slave architecture. The communication between the surgeon and the tool is achieved with I2C-networked microcontrollers. In the distal link of the tool, there is a stereoscopic camera and an IMU board that offers orientation information. Moreover, a Force Sensing System, that is able to be attached to the next version of the current tool. Finally, certain design aspects as well as the kinematics of the binary manipulator are presented simulation and experimental studies on the laparoscopic tool prototype.
142

Performance-based assessments of buckling-restrained braced steel frames retrofitted by self-centering shape memory alloy braces

Pham, Huy 20 September 2013 (has links)
Concrete-filled buckling restrained braces (BRBs) was first developed in 1988 in Tokyo, Japan, to prevent the steel plates in the core portion from buckling, leading the steel core to exhibiting a more stable and fully hysteretic loop than conventional steel braces. However, past studies have shown that buckling restrained braced frames (BRBFs) have a large residual deformation after a median or high seismic event due to steel’s residual strain. In order to address this issue, innovative self-centering SMA braces are proposed and installed in the originally unbraced bays in existing BRBFs to become a hybrid frame system where the existing steel BRBs dissipate energy induced by external forces and the newly added self-centering SMA braces restore the building configuration after the steel BRBs yield. A case study of conventional three-story BRBF retrofitted by the proposed self-centering SMA braces is carried out to develop systematic retrofit strategies, to investigate the structural behavior, and to probabilistically assess their seismic performance in terms of interstory drifts, residual drifts, and brace deformation, as compared to the original steel BRB frames. Finally, the developed brace component fragility curves and system fragility curves will be further used for the assessment of downtime and repair cost.
143

Identification and Characterization of an Arginine-methylated Survival of Motor Neuron (SMN) Interactor in Spinal Muscular Atrophy (SMA)

Tadesse, Helina 19 December 2012 (has links)
Spinal Muscular Atrophy (SMA) is a neuronal degenerative disease caused by the mutation or loss of the Survival Motor Neuron (SMN) gene. The cause for the specific motor neuron susceptibility in SMA has not been identified. The high axonal transport/localization demand on motor neurons may be one potentially disrupted function, more specific to these cells. We therefore used a large-scale immunoprecipitation (IP) experiment, to identify potential interactors of SMN involved in neuronal transport and localization of mRNA targets. We identified KH-type splicing regulatory protein (KSRP), a multifunctional RNA-binding protein that has been implicated in transcriptional regulation, neuro-specific alternative splicing, and mRNA decay. KSRP is closely related to chick zipcode-binding protein 2 and rat MARTA1, proteins involved in neuronal transport/localization of beta-actin and microtubule-associated protein 2 mRNAs, respectively. We demonstrated that KSRP is arginine methylated, a novel SMN interactor (specifically with the SMN Tudor domain; and not with SMA causing mutants). We also found this protein to be misregulated in the absence of SMN, resulting in increased mRNA stability of KSRP mRNA target, p21cip/waf1. A role for SMN as an axonal chaperone of methylated RBPs could thus be key in SMA pathophysiology.
144

Interação de componentes celulares estromais e microvasculares em tumor odontogênico queratocístico: um estudo comparativo

Sousa Neto, Ernesto Santos January 2014 (has links)
Submitted by Hiolanda Rêgo (hiolandarego@gmail.com) on 2017-11-09T15:57:04Z No. of bitstreams: 1 Dissertação_ODONTO_ Ernesto Santos Sousa Neto.pdf: 4765427 bytes, checksum: ae3f93ce46ff32b7ce466869740090de (MD5) / Approved for entry into archive by Delba Rosa (delba@ufba.br) on 2017-11-17T14:44:34Z (GMT) No. of bitstreams: 1 Dissertação_ODONTO_ Ernesto Santos Sousa Neto.pdf: 4765427 bytes, checksum: ae3f93ce46ff32b7ce466869740090de (MD5) / Made available in DSpace on 2017-11-17T14:44:34Z (GMT). No. of bitstreams: 1 Dissertação_ODONTO_ Ernesto Santos Sousa Neto.pdf: 4765427 bytes, checksum: ae3f93ce46ff32b7ce466869740090de (MD5) / Fapesb / O presente trabalho teve como objetivo estudar, por meio da imunohistoquímica, a participação de componentes celulares estromais a exemplo dos mastócitos (mast cell triptase), miofibroblastos (alfa-SMA) e macrófagos (CD163) e componentes vasculares (CD34 e D2-40) em uma série de tumores odontogênicos queratocísticos (TOQ), na tentativa de fornecer subsídios para compreender a interação entre esses componentes e o comportamento biológico distinto desta lesão. Para fins comparativos, cistos radiculares (CRs) e folículos pericoronários (FPs) também foram incluídos. A amostra foi composta por 30 TOQs, 15 CRs e 07 FPs. Para a avaliação dos mastócitos, miofibroblastos e macrófagos, foram quantificadas as células imunorreativas aos marcadores mast cell triptase, alfa-SMA e CD163, respectivamente, em 10 campos (400x). Os índices angiogênico e linfangiogênico foram avaliados por meio da densidade microvascular (MVD) e densidade microvascular linfática (MVDL) dos microvasos marcados, respectivamente, pelos marcadores CD34 e D2- 40. Foi utilizado o teste ANOVA com pós-teste de correção de Tukey, para análise estatística entre os marcadores segundo o tipo de lesão. Para a análise da correlação entre os marcadores dentro da mesma lesão, utilizamos a correlação de Pearson. Para a associação, no TOQ, entre os marcadores e a presença de inflamação, utilizamos o Teste T de Student. A análise da expressão do marcador mast cell triptase revelou existir diferenças significativas (p<0,05) entre a densidade de células mastocitárias presentes nos CRs (22,7) em relação aos FPs (1,23) e TOQs (7,39), e entre a densidade de mastócitos presentes no TOQs e FPs. Houve também diferença significativa (P<0,05) entre a densidade de miofibroblastos em TOQs (29,25) em relação aos CRs (4,66) e os FPs (1,50). A diferença da densidade de miofibroblastos entre os CRs e FPs não foi significativa (p>0,05). A respeito dos macrófagos, não houve diferenças significativas (p= 0,084) entre as densidades de macrófagos presentes nos TOQs (2,31), CRs (1,42) e FPs (0,14). Na avaliação do índice angiogênico, não houve diferenças significativas da MVD entre as três lesões estudadas. No entanto, para o índice linfangiogênico, houve diferença significativa (p<0,05) entre a MVDL presentes nos TOQs (11,64) em relação aos CRs (4,19) e aos FPs (0,167). A diferença entre a MVDL dos CRs em relação aos FPs não foi estatisticamente significante (p>0,05). Não foi encontrada associação significativa (p>0,05) entre os marcadores estudados com a presença de inflamação no TOQ. No presente trabalho, encontramos uma correlação positiva e moderada entre os marcadores mast cell triptase e o CD34 nos TOQ (p = 0,025). Já nos CRs encontramos uma correlação inversa e moderada entre os marcadores SMA x CD34 (p = 0,017). Nos FPs também encontramos uma correlação inversa entre os mesmos marcadores anteriores, porém forte (p=0,049). Embora os componentes celulares estromais e microvasculares aqui representados por mastócitos, miofibroblastos, macrófagos CD163 positivos e vasos CD34 e D240, respectivamente, sejam importantes para manutenção do arcabouço estrutural do TOQ e CR, existiu uma interação significante entre mast cell triptase e CD34 no TOQ e entre CD34 e o alfa –SMA no CR.
145

Revestimento asfáltico tipo SMA para alto desempenho em vias de tráfego pesado. / SMA asphalt surface course for high performance on heavy traffic roads.

Rafael Marcal Martins de Reis 25 April 2002 (has links)
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.
146

Identification and Characterization of an Arginine-methylated Survival of Motor Neuron (SMN) Interactor in Spinal Muscular Atrophy (SMA)

Tadesse, Helina January 2012 (has links)
Spinal Muscular Atrophy (SMA) is a neuronal degenerative disease caused by the mutation or loss of the Survival Motor Neuron (SMN) gene. The cause for the specific motor neuron susceptibility in SMA has not been identified. The high axonal transport/localization demand on motor neurons may be one potentially disrupted function, more specific to these cells. We therefore used a large-scale immunoprecipitation (IP) experiment, to identify potential interactors of SMN involved in neuronal transport and localization of mRNA targets. We identified KH-type splicing regulatory protein (KSRP), a multifunctional RNA-binding protein that has been implicated in transcriptional regulation, neuro-specific alternative splicing, and mRNA decay. KSRP is closely related to chick zipcode-binding protein 2 and rat MARTA1, proteins involved in neuronal transport/localization of beta-actin and microtubule-associated protein 2 mRNAs, respectively. We demonstrated that KSRP is arginine methylated, a novel SMN interactor (specifically with the SMN Tudor domain; and not with SMA causing mutants). We also found this protein to be misregulated in the absence of SMN, resulting in increased mRNA stability of KSRP mRNA target, p21cip/waf1. A role for SMN as an axonal chaperone of methylated RBPs could thus be key in SMA pathophysiology.
147

Hydrological Modelling of Al Auja Earth Dam in the Lower Jordan Valley. / Hydrologisk modellering av Al Auja jorddammen i lägre Jordandalen.

Rimfors, Otto, Velichkin, Vadim January 2015 (has links)
In a populated region with very high potential evapotranspiration, where the rainwater falls only during the winter and mostly in the mountains, the need for sustainable water management and fair distribution is crucial. In the West Bank, Palestine, the main potable water source is a karst mountain aquifer system. Precipitation occurs usually in the form of rainfall in the mountainous regions during winter period and recharges the groundwater systems. The water either reaches the surface as spring water, or is extracted through pumped wells. But the scarcity of drinking water in Palestine is not due to lack of water resources or technical knowledge of water extraction but a direct consequence of Israeli policies, water management, breached water rights and the occupation of Palestinian territories. Because of such restrictions, ground water is not an option to provide more freshwater, instead it is suggested to collect rainwater runoff in reservoirs. In 2011, the first surface water dam was built in Palestine in Al Auja, just north of Ariha. It was built as an experimental project for future dams and is therefore a small earth fill dam which will be expanded to collect water also from an adjacent watershed, much larger than the current one. The purpose of this study is to determine how much bigger the reservoir needs to be to safely store the inflowing rainwater runoff in the future. This was achieved through hydrological modelling using the HEC-HMS software which is a physical based model. The data used in this study were: 25 m DEM, land use data, soil data (both from remote sense and field visit), river network map, precipitation data, location of the gauges and geological formations. Field visits and soil tests were also great contributions of insights and knowledge crucial for the project. Hourly time-series data for precipitation for the winters 2011-2012 and 2012-2013 and monthly evapotranspiration for 2010-2011 were used as input to the model. Water level data in Al Uja reservoir with 20 minutes intervals were used to evaluate the simulations. Simulations were first optimized for the current scenario to find sets of parameters that match the changes in water level in the dam reservoir. This was done both for single rainfall events as well as for the whole seasons. The parameters creating the most matching results were used in additional simulations with the adjacent watershed included. The difference in results between the simulations with the current watershed and the expanded one was used to answer how much more water the reservoir would have received during 2011-2012 and 2012-2013 if the larger watershed were included. The model results reveal that the reservoir should have been able to hold about three times as much water as today. Installation of an inflow meter is suggested for the future along with an evaluation of local climate change in precipitation and evapotranspiration.
148

Prestressing RC Beams with Near Surface Mounting (NSM) Fiber Reinforced Polymers (FRP) and/or Iron-Based Shape Memory Alloy (Fe-SMA) Rods

Raad, Janet January 2018 (has links)
No description available.
149

Native Mandarin Speakers' Production of English Fricatives as a Function of Linguistic Task Type and Word Position: A Spectral Moment Analysis

Wing, Lindsey McCall 01 March 2018 (has links)
The purpose of this study was to analyze the phonetic production of fricatives across differing word positions and task types. Further knowledge about the fricative production of second language learners of English would potentially improve the ability to teach correct pronunciation and improve the productivity of second language programs. All participants in this study were native speakers of Mandarin Chinese with English as their second language. A total of 12 subjects participated, all of whom had English proficiency ratings ranging from novice to advanced. The speakers were between 21-51 years of age, with each speaker having between 2 to 6 years of experience learning English in their country of origin. Using acoustic and spectral moment analyses, the acoustic nature of four types of fricative productions (/f/, /θ/, /s/, and /ʃ/) were analyzed as a function of linguistic task type and word position. Although a number of measures were found to differ significantly as a function of word position and task type, the majority of statistical analyses were not found to be significant. This lack of significance may be due to the specific methodology used, the speakers atypical voicing patterns, and/or decreased length of sound productions. Findings of this study may indicate that second language learners production of fricatives vary minimally across differing word positions and task types.
150

Investigation into the Hybrid Production of a Superelastic Shape Memory Alloy with Additively Manufactured Structures for Medical Implants

Hamann, Isabell, Gebhardt, Felix, Eisenhut, Manuel, Koch, Peter, Thielsch, Juliane, Rotsch, Christin, Drossel, Welf-Guntram, Heyde, Christoph-Eckhard, Leimert, Mario 05 May 2023 (has links)
The demographic change in and the higher incidence of degenerative bone disease have resulted in an increase in the number of patients with osteoporotic bone tissue causing. amongst other issues, implant loosening. Revision surgery to treat and correct the loosenings should be avoided, because of the additional patient stress and high treatment costs. Shape memory alloys (SMA) can help to increase the anchorage stability of implants due to their superelastic behavior. The present study investigates the potential of hybridizing NiTi SMA sheets with additively manufactured Ti6Al4V anchoring structures using laser powder bed fusion (LPBF) technology to functionalize a pedicle screw. Different scanning strategies are evaluated, aiming for minimized warpage of the NiTi SMA sheet. For biomechanical tests, functional samples were manufactured. A good connection between the additively manufactured Ti6Al4V anchoring structures and NiTi SMA substrate could be observed though crack formation occurring at the transition area between the two materials. These cracks do not propagate during biomechanical testing, nor do they lead to flaking structures. In summary, the hybrid manufacturing of a NiTi SMA substrate with additively manufactured Ti6Al4V structures is suitable for medical implants.

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