Dissertations / Theses on the topic '3DAP'

Les alliages d’aluminium de la série 7000 à hautes caractéristiques mécaniques, constitués principalement des éléments d’addition Zn, Mg, et Cu, sont notamment utilisés dans l’industrie aéronautique civile. Néanmoins, les traitements thermiques et/ou thermomécaniques appliqués pour maximiser les propriétés mécaniques de ces alliages, peuvent les sensibiliser à divers modes de corrosion structurale dont la corrosion feuilletante, dont les mécanismes sont encore mal compris. En outre, les nouvelles générations d’alliages, développées en vue d’augmenter les propriétés mécaniques, contiennent toujours plus d’éléments d’addition, ce qui est susceptible de modifier leur sensibilité à ce phénomène. Ce travail s’attache à faire progresser la compréhension des mécanismes de corrosion feuilletante des alliages 7000, en cherchant à identifier le rôle des principaux éléments d’alliage. Pour cela nous avons caractérisé finement les états de précipitation d’un grand nombre de microstructures, comme la composition des précipités durcissants nanométriques et de la matrice, par ASAXS et 3DAP. En parallèle, nous avons développé de nouvelles techniques électrochimiques permettant de quantifier la sensibilité de ces mêmes microstructures à la corrosion feuilletante. Les résultats de l’étude mettent en évidence l’existence de deux mécanismes de corrosion : endommagement par dissolution intergranulaire et par rupture intergranulaire, dont la prédominance dépend de la composition de l’alliage et du traitement thermique. Nous proposons une explication au comportement en corrosion des différentes microstructures, faisant intervenir la composition chimique des différentes entités microstructurales
High strength 7XXX series aluminium alloys, composed of the major alloying elements Zn, Mg, and Cu, are used especially for aircraft applications. However, the ageing process, maximizing the mechanical properties, returns alloys sensitive to structural corrosion, and particularly to exfoliation corrosion. New developments in high strength alloys, for strength optimization, lead an overall increase in solute saturation, which could modify their corrosion susceptibility. The objective of the study is to progress in the understanding of the exfoliation corrosion mechanisms of high-strength 7000 series aluminium alloys, by attempting especially to identify the role of the main alloying elements. By leaning on a quantitative precipitation characterisation of a large number of microstructures, we notably measured the composition of nanometric hardening precipitates and of the matrix, by ASAXS and 3DAP. In parallel, we developed new electrochemical techniques providing quantitative results on the exfoliation corrosion sensitivity of microstructuresTheses results show the existence of two operating corrosion mechanisms: damages by " intergranular dissolution " and by intergranular ruptures. The ascendancy of which depends on the composition of the alloy. We propose an explanation of the corrosion susceptibility of the various microstructures, based on the chemical composition of the microstructural entities and of the alloy

Les alliages d'aluminium de la série 7000 à hautes caractéristiques mécaniques, constitués principalement des éléments d'addition Zn, Mg, et Cu, sont notamment utilisés dans l'industrie aéronautique civile. Néanmoins, les traitements thermiques et/ou thermomécaniques appliqués pour maximiser les propriétés mécaniques de ces alliages, peuvent les sensibiliser à divers modes de corrosion structurale dont la corrosion feuilletante, dont les mécanismes sont encore mal compris. En outre, les nouvelles générations d'alliages, développées en vue d'augmenter les propriétés mécaniques, contiennent toujours plus d'éléments d'addition, ce qui est susceptible de modifier leur sensibilité à ce phénomène.
Ce travail s'attache à faire progresser la compréhension des mécanismes de corrosion feuilletante des alliages 7000, en cherchant à identifier le rôle des principaux éléments d'alliage. Pour cela nous avons caractérisé finement les états de précipitation d'un grand nombre de microstructures, comme la composition des précipités durcissants nanométriques et de la matrice, par ASAXS et 3DAP. En parallèle, nous avons développé de nouvelles techniques électrochimiques permettant de quantifier la sensibilité de ces mêmes microstructures à la corrosion feuilletante.
Les résultats de l'étude mettent en évidence l'existence de deux mécanismes de corrosion : endommagement par dissolution intergranulaire et par rupture intergranulaire, dont la prédominance dépend de la composition de l'alliage et du traitement thermique. Nous proposons une explication au comportement en corrosion des différentes microstructures, faisant intervenir la composition chimique des différentes entités microstructurales.

This thesis systematically investigates the effects of a recently developed modified ageing procedure of aluminium alloys, termed the T6I6 temper, on the microstructural development and mechanical properties of the Al ??? Mg ??? Si - Cu alloy 6061. For the T6I6 temper, a conventional single stage T6 temper is interrupted by an ageing period at a reduced temperature (65??C) to facilitate secondary precipitation, before resuming the final ageing at the temperature of the initial T6 treatment. The T6I6 temper was found to cause simultaneous increases in tensile properties, hardness, and toughness as compared with 6061 T6. Al ??? Mg ??? Si ??? Cu alloys are medium strength alloys widely used in the automotive industry and their further improvement is underpinned by stringent demands for weight reduction placed on the transportation industry in recent years. The potential for further improvement of the mechanical properties was found in the control of secondary precipitation that may take place even in some fully aged alloys when exposed to reduced temperatures. The overall improvement in the mechanical properties of 6061 T6I6 was attributed to the formation of finer and more densely dispersed precipitates in the final microstructure. The refinement of precipitates was facilitated by control of the precipitation processes and gradual evolution of the microstructure throughout each stage of the T6I6 treatment. The results indicated that the concentration and the chemical environment of the vacancies controlled the precipitation processes in this alloy. Findings also show that the proportion of the different precipitate phases present in the final microstructure, as well as the amount of the solute in these precipitates, can be controlled and modified utilizing secondary precipitation. A number of analytical techniques were used in this study. The evolution of the microstructure was studied using Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM) and Three Dimensional Atom Probe (3DAP). Vacancy-solute interactions were studied using Positron Annihilation Lifetime Spectroscopy (PALS) and 3DAP. The distribution of the solute was studied using 3DAP and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) was used to identify precipitation reactions and to determine the stability of vacancy-associated aggregates.

The demand for affordable and realistic phantoms for training, in particular for functional endoscopic sinus surgery (FESS), has continuously increased in recent years. Conventional training methods, such as current physical models, virtual simulators and cadavers may have restrictions, including fidelity, accessibility, cost and ethics. In this investigation, the potential of three-dimensional printing for the manufacture of biologically representative simulation materials for surgery training phantoms has been investigated. A characterisation of sinus anatomical elements was performed through CT and micro-CT scanning of a cadaveric sinus portion. In particular, the relevant constituent tissues of each sinus region have been determined. Secondly, feedback force values experienced during surgical cutting have been quantified with an actual surgical instrument, specifically modified for this purpose. Force values from multiple post-mortem subjects and different areas of the paranasal sinuses have been gathered and used as a benchmark for the optimisation of 3D-printing materials. The research has explored the wide range of properties achievable in 3DP through post-processing methods and variation of printing parameters. For this latter element, a machine-vision system has been developed to monitor the 3DP in real time. The combination of different infiltrants allowed the reproduction of force values comparable to those registered from cadaveric human tissue. The internal characteristics of 3D printed samples were shown to influence their fracture behaviour under resection. Realistic appearance under endoscopic conditions has also been confirmed. The utilisation of some of the research has also been demonstrated in another medical (non-surgical) training application. This investigation highlights a number of capabilities, and also limitations, of 3DP for the manufacturing of representative materials for application in surgical training phantoms.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.
In title on t.p., superscript "TM" follows "S-3DP".
Includes bibliographical references.
GRIN lenses with vertical index variation and radial index variation have been successfully fabricated using S-3DPTM. Two silica-based material systems, A1203-SiO₂ and BaO-SiO₂, have been studied and used for the fabrication of GRIN lenses. Aluminum nitrate was dissolved in water to provide the dopant salt solution for S-3DPTM. The pre-sintering treatment at 1000 ⁰Cfor 24 hours in. vacuum (-5x10-6 torr) was used to remove the hydroxyl groups that cause bubbles during sintering. The sintering condition for the A1203-SiO₂ material system was found to be 1650 ⁰C for 30 minutes in vacuum. Two alumina-doped silica GRIN lenses with vertical index variation, Design 1.63 [percent] max and Design 2.5 [percent] max, were fabricated with effective focal lengths of 10.00 cm and 6.10 cm, respectively. An alumina-doped silica GRIN lens with radial parabolic index variation also was fabricated with effective focal lengths of 63.75 cm in the x direction and 52.50 cm in the y direction. The BaO-SiO₂ material system, which has a 2.4 stronger index changing ability than the A1203-SiO₂ material system, also was developed. Barium acetate was used as the dopant source. The pre-sintering treatment was found to be 900 ⁰C for 18 hours in air to convert barium acetate to barium oxide. The sintering condition was found to be 1725 ⁰C for 10 minutes in vacuum. A barium oxide-doped GRIN lens with radial parabolic index variation was fabricated. Its effective focal length was measured to be 14.63 cm in the x direction and 11.14 cm in the y direction. The barium oxide concentration profiles were measured. The theoretical focal lengths were calculated and compared with the effective focal lengths.
by Hong-Ren Wang.
Ph.D.

CNPq
Este trabalho apresenta um algoritmo genético paralelo (AGP) para o problema de dobramento de proteínas, utilizando o modelo 3DHP-SC. Este modelo tem sido pouco abordado devido ao elevado grau de complexidade envolvido. Foi proposta uma função de fitness baseada na energia livre e na compacidade do dobramento. Operadores genéticos especiais foram desenvolvidos, além de estratégias para auxiliar o algoritmo no processo de busca de conformações de proteínas. Vários experimentos foram realizados para ajustar todos os parâmetros do sistema, incluindo os parâmetros básicos do AG (probabilidades de mutação e crossover, e o tamanho de torneio) e os parâmetros dos operadores especiais e das estratégias. O efeito da matriz de energias para o modelo no desempenho do algoritmo também foi estudado. Uma comparação com outra abordagem de computação evolucionária também foi realizada, a fim de verificar o desempenho do método proposto. Devido a não existir, até então, benchmarks para teste deste modelo, foi proposto um conjunto de 25 sequências baseado em outro modelo mais simplificado. Os resultados obtidos mostraram que o AGP alcançou um bom nível de eficiência e obteve dobramentos biologicamente coerentes, sugerindo a adequabilidade da metodologia proposta.
This work presents a parallel genetic algorithm (PGA) for the protein folding problem, using the 3DHP-SC model. This model has been sparsely studied in the literature due to its complexity. A new fitness function was proposed, based on the free-energy and compacity of the folding. Special genetic operators were developed, besides strategies to aid the algorithm in the search of protein conformations. Many experiments were done to adjust all the parameters of the system, including the basic parameters of the GA (mutation and crossover probability, and tournament size) and parameters of the special genetic operators and strategies. The effect of the energy matrix of the model in the performance of the algorithm was also studied. Moreover, a comparison with other evolutionary computation approach was done, to verify the performance of the proposed method. Since there is no benchmark available to date, a set of 25 sequences was used, based on a simpler model. Results show that the PGA achieved a good level of efficiency and obtained biologically coherent results, suggesting its adequacy for the problem.

This thesis focuses on the representation and consumption of 'Asian culture' within a context of Western popular culture and specifically, 'British mainstream' and 'British Asian' magazine visual discourses. Through a critical engagement with Edward Said's Orientalism (1978) which charted Western inferiorizing cultural representations of the East as located in historical and material contexts, I aim to explore issues of 'race' and Otherness amidst a background of historical and commodification processes. This has been attempted using multiple methodologies that in addition to engaging with secondary material, has involved a reflexive use of semiotics and discourse analysis to analyse magazine images and written text respectively. Further, I have attempted to go beyond the textual focus of both Orientalism (1978) and many media studies by also gathering contextual reader responses to magazine representations. These have taken the form of the subjective interpretations of 20 British youths (men and women of Asian and white English origin) that have been analysed in conjunction with biographical narratives that I also conducted with each of them. Through the use of this rich and varied empirical data coupled with a thorough review of secondary source material, I aim to add to and question work that has been conducted in the area of 'race' and culture that appears to have moved from a concentration on the 'essential black subject' to an emphasis on ethnic unities within an uncritical celebration of 'diaspora' and 'hybridity'. I also aim to make problematic work that has been conducted in the area of orientalism through drawing attention to the limitations associated with the concept of 'self-orientalism' and practices of 'self-representation' by minorities. Overall, through conducting work on Asian representations within the popular magazine media coupled with its interrelation with varied audiences, I hope to make some inroads into these under-researched areas.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.
Includes bibliographical references (p. 79).
Three Dimensional Printing (3DP) is a rapid prototyping process that creates a three dimensional part directly from computer models by printing a sequence of two dimensional layers. In this research, the strength of 3DP parts were improved by using different "print styles" (the way binder is deposited on the powder bed in creating a 3DP part) for use in investment casting process. The print styles that were created optimized line to line interaction between the printed lines, binder overlap, and the amount of unprinted powder surrounding the printed features. The strength of the parts are measured in three different axes (X-fast, Y-slow, Z). The strength improved by factors of 2, 8, and 7 for the three different axes. A controlled strength cellular structure investment casting shell that enables the creation of a metal part without any stress related defects has been created. The ceramic shell has an open cell frame structure with thin inner shell where the metal casting is poured. The flexibility of the 3DP technology applied to controlled strength cellular structure investment casting shell will incorporate all the advantages of 3DP to investment casting (Sach 1992, ASME) as well as reduction in material consumption, controlled heat transfer, permeability, and of course controlled strength to eliminate stress related defects. The cellular structure ceramic mold is designed to withstand the pouring pressures of the molten metal and survive the handling during processing yet fail when the stresses from the contracting metal becomes excessive. The 3DP molds are usually 60% porous and cellular structure investment casting shells consist of only 35% of the 3DP material per volume. A controlled strength cellular structure investment casting shell is designed to fail when excessive stress is applied to the shell structure. The stress on the casting shell is caused by the shrinkage of the metal part. The controlled strength investment casting shell has an open cellular structure frame with a thin inner shell where the metal casting will form.
by Won B. Bang.
S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.
Includes bibliographical references (leaves 189-190).
Three-Dimensional Printing (3DPTM) is a rapid-manufacturing process originally developed at MIT for building parts directly from CAD-generated models. Parts are fabricated in "slices" by creating a complete layer of powder and then selectively joining powder particles with a polymer binder deposited using a moving printhead. Traditional 3DPTM builds layers by spreading dry powder and prints binder using a rastering scheme with a continuous-jet printhead. For smaller parts and greater accuracy, a variation on the process called slurry 3DPTM (s3DPTM) uses raster-built slurry layers and a vector-printing scheme with a drop on demand (DoD) printhead. This here thesis presents efforts to improve core technology in both dry-powder 3DPTM and slurry 3DPTM. One of the most critical steps in s3DPTM is the building of the slurry layers. To avoid intra- and interlayer defects the slurry layer must be rastered at high deposition rates to promote line merging and better layer quality. The difficulty lies in the design of a machine capable of oscillating the slurry nozzle at the required frequencies. Fortunately, such a design was completed and the machine built as part of a collaborative effort with TDK Japan to build an s3DPTM machine for manufacturing small parts. The design uses a reciprocating countermass strategy to recycle mechanical energy and eliminate troublesome vibrations. A general overview of this slurry layer forming station (LFS) is given, along with an in-depth treatment of several components, including the forcers, centering system, and interface software. And speaking of rastering, dry-powder 3DPTM relies on this strategy for printing binder, just as the LFS uses a raster method to build powder layers. Beginning with observations made during the design of the LFS, the fluid-handling system was redesigned to improve binder droplet stream stability during the carriage traverse and turnaround. The improvement was made possible by repositioning a smaller version of the "Clamshell" constant pressure vessel used to set the fluid flow rate to the printhead carriage itself and using a closed-loop control system to maintain a constant fluid level in the Clamshell. Drawings, parts lists, schematic diagrams, and assembly instructions are included for building additional fluid control systems.
by David C. Ables.
S.M.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Ao longo das duas últimas décadas, a contribuição da manufatura aditiva passou da confecção de um mero protótipo de um produto, no início de seu desenvolvimento, para a confecção de qualquer produto direto, presente em todos os setores industriais. Com este avanço, diferentes tecnologias da manufatura aditiva surgiram com o intuito de melhorar alguns parâmetros de produção. Neste meio, a tecnologia de impressão tridimensional 3DP, por consequência de suas várias características intrínsecas, se destaca para atender o setor biomédico, através da técnica de biomodelagem, que contribuem imensamente de forma didática e prática para a performance de cirurgias. Porém, há algumas limitações finais nas peças obtidas por esta tecnologia que devem ser contornadas, focando-se no tratamento adicional necessário destas peças, o pós-processamento, de modo a aprimorá-las, conferindo então sucesso ao destino destas. Neste trabalho, adotou-se a tecnologia de manufatura aditiva 3DP para estudar como a adição de diferentes agentes infiltrantes influenciam no acréscimo de densidade aparente e resistência mecânica de amostras feitas de componentes de gesso, constituídas por corpos de prova cilíndricos e prismáticos, de modo a simular a melhor composição para biomodelos. Para isto, o pós-processamento foi dividido em duas etapas. Na primeira etapa, foram aplicados separadamente nas amostras, quatro tipos de adesivos à base de etilcianocrilato, por gotejamento, e um à base de epóxi, por moldagem com pá. Já na segunda etapa, foram aplicados nas amostras, também separadamente, quatro tipos de adesivos à base de etilcianocrilato, por gotejamento e banho de imersão, e um à base de epóxi, por moldagem com pá. Além dos métodos de aplicação dos adesivos, as duas etapas se diferem também pelos binders utilizados para constituírem as amostras à base de gesso. Para ambas etapas, obteve-se o melhor resultado com o adesivo de cianocrilato de baixíssima viscosidade, capaz de provocar maiores variações de densidade aparente às amostras, além de maiores acréscimos de resistência.
Over the past two decades, the contribution of additive manufacturing has shifted from a mere prototype of a product at the beginning of its development to the production of any direct product present in all industrial sectors. With this advance, different technologies of the additive manufacturing appeared with the intention to improve some parameters of production. In this environment, three-dimensional printing 3DP technology, due to its various intrinsic characteristics, stands out to serve the biomedical sector through the biomodelling technique, which contribute immensely in a didactic and practical way for the performance of surgeries. However, there are some final limitations in the parts obtained by this technology that must be improved, focusing on the necessary additional treatment of these parts, the post-processing, in order to upgrade them, thus giving success to their destination. In this study, 3DP additive manufacturing technology was adopted to study how different infiltrating agents influence the increase in apparent density and mechanical strength of samples made of gypsum components, constituted by cylindrical and prismatic specimens, in order to simulate the best composition for biomodels. For this, the post-processing was divided in two stages. In the first stage, separately, four types of ethylcyanoacrylate-based adhesives were applied on the samples by dripping, and one epoxy-based adhesive was applied by shovel molding. In the second stage, also separately, four types of ethylcyanocrylate based adhesives were applied in the samples, by dripping and by dipping, and the epoxy-based, by shovel molding. Besides the adhesive application methods, the two stages also differ from the binders used to constitute the gypsum-based samples. For both stages, the best result was obtained by the cyanoacrylate adhesive with very low viscosity, capable of causing greater variations of apparent density and additions of strength to the samples.

Orientador: Ruis Camargo Tokimatsu
Resumo: Ao longo das duas últimas décadas, a contribuição da manufatura aditiva passou da confecção de um mero protótipo de um produto, no início de seu desenvolvimento, para a confecção de qualquer produto direto, presente em todos os setores industriais. Com este avanço, diferentes tecnologias da manufatura aditiva surgiram com o intuito de melhorar alguns parâmetros de produção. Neste meio, a tecnologia de impressão tridimensional 3DP, por consequência de suas várias características intrínsecas, se destaca para atender o setor biomédico, através da técnica de biomodelagem, que contribuem imensamente de forma didática e prática para a performance de cirurgias. Porém, há algumas limitações finais nas peças obtidas por esta tecnologia que devem ser contornadas, focando-se no tratamento adicional necessário destas peças, o pós-processamento, de modo a aprimorá-las, conferindo então sucesso ao destino destas. Neste trabalho, adotou-se a tecnologia de manufatura aditiva 3DP para estudar como a adição de diferentes agentes infiltrantes influenciam no acréscimo de densidade aparente e resistência mecânica de amostras feitas de componentes de gesso, constituídas por corpos de prova cilíndricos e prismáticos, de modo a simular a melhor composição para biomodelos. Para isto, o pós-processamento foi dividido em duas etapas. Na primeira etapa, foram aplicados separadamente nas amostras, quatro tipos de adesivos à base de etilcianocrilato, por gotejamento, e um à base de epóxi, por moldagem com... (Resumo completo, clicar acesso eletrônico abaixo)
Mestre

Recently, additive manufacturing (AM), or "3D printing," is expanding into civil infrastructure applications, particularly cementitious materials. To ensure the safety, health, and welfare of the public, quality assurance and quality control (QA/QC) methods via standardized testing procedures are of the upmost importance. However, QA/QC methods for these applications have yet to be established. This thesis aims to implement existing ASTM standards to characterize additive manufactured cementitious composites and to gather better information on how to tackle the challenges that are inherent when printing with cementitious materials. In this work, fresh mix properties and hardened concrete properties were investigated using current ASTM standards as a starting point for applying or adapting them for AM applications. Specifically, this project applied existing ASTM standards for fresh mix mortars to measure setting time, flow, and early compressive strength as qualitative indicators of printability, pumpability, and buildability. The fresh mix properties were investigated for 12 different mortar mixes to demonstrate the effect that moisture content, absorption, and sand type can have on these fresh mix properties. The results for setting time and compressive strength demonstrated that there was less variability in the properties when the moisture condition of the aggregate was measured and accounted. Flow was shown to be strongly influenced by the sand type. Additively manufactured mortars were used to print a box in a layer-by-layer process. To evaluate the effect of layering on the flexural strength, three-point bending tests were implemented using four different loading orientations to explore the anisotropic mechanical properties. The observed anisotropic behavior was corroborated with stereo-digital image correlation data showing the stress-strain and load-deflection relationships. Two orientations (A and B) demonstrated brittle behavior while the other two orientations (C and D) experienced quasi-brittle behavior. In addition, setting a minimum unit weight of 132 pcf enabled an analysis of the effect that defects had on the mechanical performance: specimens greater than 132 pcf demonstrated greater and less variable strengths than the specimens less than 132 pcf. The discussion of how defects impacted performance of the different orientations can be valuable when determining how to effectively model, design, and inspect 3D printed structures in the future. The findings of this thesis confirm that existing ASTM standards for mortars can be modified and applied to AM cementitious composites for QA/QC. It is recommended that mixtures used in 3D printing of cementitious composites should design and accommodate the moisture condition of the aggregate to optimize the predictability of the fresh and early-age properties. For the hardened properties, it is recommended that testing procedures such as flexural testing account for anisotropic behavior. Furthermore, for implementation of 3D printed concrete structures, it is highly recommended that design is a function of loading orientation due to the anisotropic properties of the composite.
Master of Science
Recently, additive manufacturing (AM), or "3D printing," is expanding into civil infrastructure applications, specifically cementitious materials such as mortar and concrete. Understanding and predicting the behavior of the materials when using this new technique is vital for quality assurance and quality control (QA/QC). However, standard test methods have yet to be established for this new construction technique. This thesis aims to use existing testing standards to characterize AM cementitious composites and to gather better information on how to tackle the challenges of printing with these materials. In this work, properties before and after the materials hardened were studied by adapting current testing standards. Specifically, this project applied existing testing standards for fresh mix mortars to measure setting time, flow, and early compressive strength. These properties can serve as indicators of specific printing requirements. The fresh mix properties were studied for 12 different mortar mixes to show the effect of moisture content, absorption, and sand type. The results suggest that there was less variability in the properties when the moisture condition and type of the aggregate was accounted. The fresh mix materials were printed in a layer-by-layer process and then hardened in place. The effects of the layers were explored by performing flexure tests using four orientations with respect to how the load was applied to the layers. The observed difference in behavior for the different orientations was supported by digital image correlation data. In addition, an analysis of the effect defects had on the performance was included. Understanding how defects impacted performance can be valuable for effectively designing 3D printed structures in the future. The results of this thesis confirm that existing testing standards for mortars can be adapted and applied to AM cementitious materials for QA/QC. It is recommended that mixtures used in 3D printing of cementitious materials should account for the moisture condition of the aggregate to improve the predictability of the fresh and early-age properties. For the hardened properties, it is recommended that the design is a function of loading orientation due to the difference in behavior for the different orientations of the material.

Introduction: Early diagnosis represents the best opportunity for cure of gastro-intestinal cancers; however current gastro-intestinal cancer screening programmes have low test sensitivity and low patient acceptability. It is hoped that a better understanding of carcinogenesis and the development of new biomarkers will provide answers to these clinical problems. Hypothesis and aims: This thesis examines the current understanding of gastro-intestinal carcinogenesis focusing on colorectal and oesophageal cancers. It reviews the circulating gastro-intestinal cancer biomarker literature reporting the strengths, weaknesses and successes of current approaches. The study tests the hypothesis that control patients and patients with colorectal and oesophageal neoplasia have differing plasma levels and fragmentation patterns of cell free nuclear and mitochondrial DNA, and that endoscopic removal of these lesions returns the levels and patterns to normal. We aim to show how new techniques of DNA processing can improve results, and how the application of these results could form part of a diagnostic approach in an at risk population. We compare our results to and including carcinoembryonic antigen levels. Results: Cell free DNA was isolated from 164 patients, including 71 patients with oesophageal neoplasia, 50 patients with colorectal neoplasia, 35 patients without endoscopic abnormality and 8 patients with Barrett’s oesophagus. This is the first report of statistically significant differences in circulating DNA quantities and patterns in patients with early oesophageal and colorectal neoplasia (p≤ 0.005). Logistic regression of the best DNA marker for colorectal neoplasia demonstrated a ROC of 0.888, with a sensitivity of 81.1% and specificity of 75.8%. Logistic regression of the best DNA marker for oesophageal neoplasia demonstrated a ROC of 0.778 with a sensitivity of 81.3% and specificity of 60.5%. Carcinoembryonic antigen performed poorly with a ROC of 0.547 and did not add diagnostically. There were no significant changes in markers from patients resected at endoscopy. Conclusions: These circulating markers in combination with other markers offer the prospect of a simple blood test as a possible screen for colorectal and oesophageal dysplasia and cancers in an at risk population.

Thèse réalisée dans le cadre d'une collaboration avec UCB Pharma et la région Wallonne s'inscrivant dans le cadre du projet SAS. Le but de ce projet était de développer des implants sous-cutanés imprimés en trois dimensions pour permettre une libération d’anticorps thérapeutique de manière prolongée au cours du temps. En effet, les thérapies disponibles sont souvent administrées par voie intraveineuse, ce qui peut réduire la compliance des patients dû à l’inconfort et à la fréquence de ces administrations. Les systèmes de délivrance, tels que des implants, peuvent limiter les fréquences d’administration grâce à l’insertion d’un dispositif qui libèrera le principe actif au cours du temps durant une période donnée. Les implants s’inscrivent comme une alternative aux microsphères qui sont également des dispositifs développés et investigués en vue de favoriser l’adhésion et la compliance des patients. L’avènement du 3D dans le milieu pharmaceutique a montré une certaine frénésie liée au développement de la médecine personnalisée et à l’innovation du procédé dans ce secteur. La sélection d’un matériau biocompatible et biorésorbable tel que le PLGA représente une véritable plus-value dans le développement d’implant. Etant donné que ces implants sont biodégradables, le retrait n’est pas à envisager, ce qui limite les désagréments du patient à un seul acte chirurgical lors de l’implantation. Au cours de ce travail, une approche pragmatique a d’abord été abordée sur les procédés d’extrusion à chaud et de l’impression 3D en utilisant un polymère couramment employé dans l’impression grand public, le PLA. L’investigation des paramètres d’impressions (température d’impression, epaisseur de couche et vitesse d’impression) et l’usage de divers plastifiants (la triacétine (TA), le polyethylène glycol 400 (PEG 400), le citrate de triéthyle (TEC) et l’acétyle citrate de triéthyle (ATEC)) pour faciliter les procédés à chaud et dans l’idée de réduire les températures d’extrusion et d’impression du matériau ont été évalués. Ces essais ont démontré l’effet de la température d’impression sur la qualité de l’impression et principalement sur les propriétés du matériau comme la force de traction et la ductilité. De plus, l’ajout de plastifiant à la matrice du PLA a permis de diminuer sa température de transition vitreuse. Par exemple, la température de transition vitreuse du PLA a été diminuée de 53 °C à 34 °C par l’ajout de PEG 400. Cette approche avait pour but d’évaluer la possibilité de diminuer les températures d’impression dans l’optique d’encapsuler à chaud un anticorps sensible à la chaleur pour la suite de ce travail.Ensuite, le développement de filaments imprimables contenant des anticorps a été abordé et mis en place à l’aide d’un modèle d’anticorps polyclonal disponible en grandes quantités et à des coûts relativement faibles. Un anticorps à l’état solide a été favorisé dans le procédé car il est largement accepté que les protéines sous forme solide sont plus stables au cours du temps en comparaison aux solutions d’anticorps. De plus, cet état solide facilite les manipulations précédant l’extrusion comme l’étape de mélange. Pour la réalisation des filaments, différents types de PLGA ont été investigués afin d’atteindre les propriétés nécessaires à l’impression en termes de diamètre mais également de comportement physique. Ces dérivés étaient caractérisés par des masses moléculaires différentes comme pour le PDLG5004 (44 kDa), le RG502 (7-17 kDa) et parmis eux, un copolymère PEG-PLGA (2 kDa-20 kDa). Un PLGA de faible masse moléculaire a été sélectionné pour développer ce filament. En effet, les extrusions étaient réalisables à une température maximum de 90 °C et les impressions à 113 °C minimum. L’un des enjeux cruciaux du développement de filament imprimable contenant un anticorps à haute concentration, au minimum 15% (w/w), était d’en assurer l’homogénéité. Cependant, l’usage de températures aussi élevées lors de l’impression a induit la dégradation de l’anticorps par la formation d’agrégats et principalement de fragments. Ces derniers sont généralement produits lors de procédé à haute température ou par l’usage de conditions drastiques telles que l’acidification du milieu. Cette plateforme a été adaptée à l’encapsulation d’anticorps thérapeutique fournit par UCB Pharma. L’usage d’un anticorps monoclonal possédant une stabilité supérieure à celle du modèle initialement utilisé permettrait d’identifier l’impact du procédé sur l’intégrité de l’anticorps. La formulation de l’anticorps a été réalisée en utilisant différents stabilisants conventionnels (sucrose (Suc), trehalose (Tre), 2-Hydroxypropyl-beta-cyclodextrine (HP-β-CD), inuline (Inu) et sorbitol (Sor)) et reconnus pour la stabilisation des protéines. A côté des excipients ajoutés, différentes quantités d’excipients ont été investigués. Ces manipulations ont montré que la stabilité de l’anticorps était privilégiée à l’aide du sucrose et du tréhalose à un ratio anticorps monoclonal:excipient de 2.0:1. En gardant ce ratio, l’ajout d’un acide aminé (leucine) aux deux disaccharides précédemment cités, a amélioré la stabilité de l’anticorps vis-à-vis des procédés à chaud (extrusion et impression 3D). L’homogénéité au sein des filaments imprimables et des pièces 3D a été confirmée tout au long du procédé. En effet, les charges en anticorps étaient similaires à la charge théorique de 15% (w/w). Aucune fragmentation de l’anticorps n’a été observée à l’issue des procédés à chaud. Cependant, une augmentation des agrégats de 2.6% en solution à 3.6% après impression 3D a été constatée à la fin du processus. Après avoir stabilisé l’anticorps, le but premier étant d’en promouvoir une libération prolongée au cours du temps. Les profils ont révélé une libération en trois phases au cours du temps mais avec un relargage après 24h relativement faible (< 5%) dû à la densité des matrices polymériques. Ensuite, la dégradation du polymère représente l’élément limitant la libération de l’anticorps au cours du temps. En effet, l’érosion du polymère joue un rôle clé dans la libération de l’anticorps encapsulé. La libération au cours du temps a été démontrée sur une période allant jusqu’à 15 semaines. La stabilité de l’anticorps dans le milieu de dissolution a été évaluée et une dégradation de celui-ci au cours du temps a été observée. Cette dégradation est principalement liée à l’érosion du polymère et à l’acidification du milieu au cours du test de dissolution. Après avoir optimisé la formulation de l’anticorps et avoir démontré la libération prolongée de celui-ci, son affinité restait à être étudiée. La capacité de l’anticorps à se lier à sa cible a pu être démontrée après 24h de dissolution mais cette affinité s’est réduite au cours de la durée de la dissolution avec une augmentation de l’agrégation et de la fragmentation de l’anticorps. Une étude de stabilité a également démontré que les implants imprimés en 3D sont stables à une température 5 °C sur une durée de 6 mois. Aucun élément de dégradation n’a été observé au cours du temps et l’affinité de l’anticorps a été préservée au cours de l’étude. Finalement, cette plateforme a également été évaluée pour l’encapsulation d’une troisième molécule biologique, un fragment d’anticorps monoclonal, pour d’une part en estimer la stabilité et l’applicabilité et d’autre part envisager une prochaine étude pré-clinique sur rongeurs. Le fragment d’anticorps a montré une stabilité supérieure à celle de l’anticorps monoclonal avec une faible agrégation après l’extrusion et l’impression. La libération prolongée du fragment a été évaluée sur 8 semaines et une libération du fragment de 79% a été observée avec une formulation contenant du tréhalose et de la leucine. En effet, les fragments d’anticorps ont une demi-vie plasmatique relativement faible, de l’ordre de 28 minutes, ce qui donne tout son sens à des systèmes à libération prolongée. Pour finir, la réalisation d’une étude pré-clinique permettrait de valider le modèle. En conclusion, ce travail a démontré la faisabilité de l’usage de l’impression 3D en vue de développer des systèmes à libération prolongée contenant des anticorps et en utilisant des procédés à hautes températures. Ces implants ont été caractérisés par une stabilité favorable et une libération intéressante qui feront l’objet d’investigation lors d’études pharmacocinétiques.
Doctorat en Sciences biomédicales et pharmaceutiques (Pharmacie)
info:eu-repo/semantics/nonPublished

3DP (three-dimensional printing) technologies have become more than just a tool to help companies with prototyping and designing in the pre-production stage. Some firms have already implemented 3DP technology to produce parts and end-use products. However, there are several challenges and barriers that this technology must overcome to replace traditional manufacturing methods. One of the most significant obstacles associated with 3D printing is its low level of accuracy in variable repeatability when it comes to making separate batches of the same product. There are several arguable reasons behind this variation. Some of the factors that can influence repeatability are the type of material, the design, the type of product produced, and the orientation, or the location of the build inside the building envelope. The goal of this study was to determine whether the location of the build inside the surface area of the working envelope can affect the properties (height, width, depth, and weight) of the product. Western Kentucky University (WKU) provides students with a few 3D printers on campus. One of those printers, a Stratasys (model: BST 768/SST 768), is in the Senator Mitch McConnell Advanced Manufacturing and Robotics Laboratory. The researcher used this printer for the study to determine if the location of the printer influenced the final product. The conclusion of the research did reveal that the printing location does affect the quality of the final product.

The financial crisis which hit Southeast Asian countries in July 1997 had a significant impact on the countries' economies and forced governments in the region to undertake programmes of financial restructuring in order to reduce weaknesses in banks' balance sheets, stabilise currencies and, most importantly, to improve the soundness of the banking and financial sectors. The main aim of such policies was to restore confidence and help meet the ongoing challenges associated with financial innovation and globalisation. The causes and consequences of the Asian crisis have been studied extensively in the past decade. However, the literature on the impact of the post-crisis crisis restructuring programmes on bank efficiency, performance and competition, and their evolving relationships, remain rather limited and inconclusive. This study aims to shed some light on these interrelated aspects, with particular reference to the experience of six of the countries mostly affected by the crisis - Indonesia, Korea, Malaysia, Philippines and Thailand - during their recovery period (1999 to 2005). Results from the efficiency analysis, carried out by means of Data Envelopment Analysis (DEA), show evidence of efficiency improvements in the region thereby indicating a positive impact of the restructuring programmes on the banking sector. Between 1999 to 2005 most of the countries in our sample actively followed policies of either closing failing institutions or fostering mergers. As a consequence, bank concentration in the region increased, raising the issue of the impact of the restructuring programmes on the competitive structure of banking markets. We found that, despite increased concentration, competition (assessed by the Panzar-Rosse Hstatistic) also increased leading us to conclude that the structural changes in South East Asia improved the region's banking industry performance without resulting in banks enjoying excessive market power. These lessons from the Asian crisis may prove valuable in the light of current re-structuring of global banking systems in the light of the 2008 credit crisis.

Three dimensional printing (3DP) is one of the most important solid freeform fabrication (SFF) methods that can produce any material with desired 3D shape by using suitable powder-binder formulations. It differs from the standard molding operations in that it can produce a complicated shapes by a software driven instrument in a laminated fashion and the cost is lower. This method can be applied in a very wide area including drug release operations, biomaterial production especially for bone fixation, prototype production for all purposes, wound dressing etc. It can also be used in obtaining edible objects by using natural polysaccharides with water based binders. In this study, it is aimed to understand the gelling behaviour of some of the gelling materials, which are alginates, pectins and carageenans, and effect of various factors on the production of confectionary objects by means of 3DP process. Effect of multivalent cations, especially Ca2+ ion, on the gelling behaviour of these materials are investigated. The egg-box structure obtained between the polymer segments increases the water holding capacity of the materials and much more chewy structures can be obtained. The molecular changes are followed by Fourier Transform infrared spectroscopy (FTIR). In 3DP applications, the composition of powder and binder, pH, temperature, relative humidity (RH) and machine parameters are important factors affecting the texture of the final object. The texture of the produced specimens is examined by using a texture analyzer and maximum force values are given as g/cm at failure. Alginate and carrageenans are found to be more effective in obtaining chewy textures with Ca2+ ion content in sugar based matrices and optimization of machine parameters are performed to obtain a higher resolution on the specimens.

In the Manufacturing Industry there is a subset of technologies referred to as Rapid Technologies which are those technologies that create the ability to compress the time to market for new products under development . Of this subset, Additive Fabrication (AF), or more commonly known as Rapid Prototyping (RP), acquires much attention due to its unique and futuristic approach to the production of physical parts directly from 3D CAD data, CT or MRI scans, or data from laser scanning systems by utilizing various techniques to consecutively generate cross-sectional layers of a given thickness upon the previous layer to form 3D objects. While Rapid Prototyping is the most common name for the production technology it is also referred to as Additive Manufacturing, Layer Based Manufacturing, Direct Digital Manufacturing, Free-Form Fabrication, and 3-Dimensional Printing. With over 35 manufacturers of Additive Fabrication equipment in 2006 , the selection of an AF process and material for a specific application can become a significant task, especially for those with little or no technical experience with the technology and to add to this challenge, many of the various processes have multiple material options to select from . This research was carried out in order to design and construct a system that would allow a person, regardless of their level of technical knowledge, to quickly and easily filter through the large number of Additive Fabrication processes and their associated materials in order to find the most appropriate processes and material options to create physical reproductions of any part. The selection methodology used in this paper is a collection of assumptions and rules taken from the author's viewpoint of how, in real world terms, the selection process generally takes place between a consumer and a service provider. The methodology uses those assumptions in conjunction with a set of expert based rules to direct the user to a best set of qualifying processes and materials suited for their application based on as many or as few input fields the user may be able to complete.
M.S.
Department of Industrial Engineering and Management Systems
Engineering and Computer Science
Industrial Engineering MS

Polysiloxanes represent a unique class of synthetic polymers, employing a completely inorganic backbone structure comprised of repeating –(Si–O)n– 'siloxane' main chain linkages. This results in an assortment of diverse properties exclusive to the siloxane bond that clearly distinguish them from the –(C–C)n– backbone of purely organic polymers. Previous work has elucidated a methodology for fabricating flexible and elastic crosslinked poly(dimethyl siloxane) (PDMS) constructs with high Mc through a simultaneous crosslinking and chain-extension methodology. However, these constructs suffer the poor mechanical properties typical of lower molecular weight crosslinked siloxanes (e.g. modulus, tear strength, and strain at break). Filled PDMS networks represent another important class of elastomers in which fillers, namely silica and siloxane-based fillers, impart improved mechanical properties to otherwise weak PDMS networks. This work demonstrates that proper silicon-based reinforcing agent selection (e.g. siloxane-based MQ copolymer nanoparticles) and incorporation provides a synergistic enhancement to mechanical properties, whilst maintaining a low viscosity liquid composition, at high loading content, without the use of co-solvents or heating. Rheological analysis evaluates the viscosity while photorheology and photocalorimetry measurements evaluate rate and extent of curing of the various MQ-loaded formulations, demonstrating theoretical printability up to 40 wt% MQ copolymer nanoparticle incorporation. Dynamic mechanical analysis (DMA) and tensile testing evaluated thermomechanical and mechanical properties of the cured nanocomposites as a function of MQ loading content, demonstrating a 3-fold increase in ultimate stress at 50 wt% MQ copolymer nanoparticle incorporation. VP AM of the 40 wt% MQ-loaded, photo-active PDMS formulation demonstrates facile amenability of photo-active PDMS formulations with high MQ-loading content to 3D printing processes with promising results. PDMS polyureas represent an important class of elastomers with unique properties derived from the synergy between the nonpolar nature, unusual flexibility, and low glass transition temperature (Tg) afforded by the backbone siloxane linkages (-Si-O)n- of PDMS and the exceptional hydrogen bond ordering and strength evoked by the bidentate hydrogen bonding of urea. The work herein presents an improved melt polycondensation synthetic methodology, which strategically harnesses the spontaneous pyrolytic degradation of urea to afford a series of PDMS polyureas via reactions at high temperatures in the presence of telechelic amine-terminated oligomeric poly(dimethyl siloxane) (PDMS1.6k-NH2) and optional 1,3-bis(3-aminopropyl)tetramethyldisiloxane (BATS) chain extender. This melt polycondensation approach uniquely circumvents the accustomed prerequisite of isocyanate monomer, solvent, and metal catalysts to afford isocyanate-free PDMS polyureas using bio-derived urea with the only reaction byproduct being ammonia, a fundamental raw ingredient for agricultural and industrial products. As professed above, reinforcement of polysiloxane materials is ascertained via the incorporation of reinforcing fillers or nanoparticles (typically fumed silica) or blocky or segmented development of polymer chains eliciting microphase separation, in order to cajole the elongation potential of polysiloxanes. Herein, a facile approach is detailed towards the synergistic fortification of PDMS-based materials through a collaborative effort between both primary methods of polysiloxane reinforcement. A novel one-pot methodology towards the facile, in situ incorporation of siloxane-based MQ copolymer nanoparticles into segmented PDMS polyureas to afford MQ-loaded thermoplastic and thermoplastic elastomer PDMS polyureas is detailed. The isocyanate-free melt polycondensation achieves visible melt dispersibility of MQ copolymer nanoparticles (good optical clarity) and affords segmented PDMS polyureas while in the presence of MQ nanoparticles, up to 40 wt% MQ, avoiding post-polymerization solvent based mixing, the only other reported alternative. Incorporation of MQ copolymer nanoparticles into segmented PDMS polyureas provides significant enhancements to modulus and ultimate stress properties: results resemble traditional filler effects and are contrary to previous studies and works discussed in Chapter 2 implementing MQ copolymer nanoparticles into chemically-crosslinked PDMS networks. In situ MQ-loaded, isocyanate-free, segmented PDMS polyureas remain compression moldable, affording transparent, free-standing films.
Master of Science
Polysiloxanes, also referred to as 'silicones' encompass a unique and important class of polymers harboring an inorganic backbone. Polysiloxanes, especially poly(dimethyl siloxane) (PDMS) the flagship polymer of the family, observe widespread utilization throughout industry and academia thanks to a plethora of desirable properties such as their incredible elongation potential, stability to irradiation, and facile chemical tunability. A major complication with the utilization of polysiloxanes for mechanical purposes is their poor resistance to defect propagation and material failure. As a result polysiloxane materials ubiquitously observe reinforcement in some fashion: reinforcement is achieved either through the physical or chemical incorporation of a reinforcing agent, such as fumed silica, or through the implementation of a chemical functionality that facilitates reinforcement via phase separation and strong associative properties, such as hydrogen bonding. This research tackles polysiloxane reinforcement via both of these strategies. Facile chemical modification permits the construction PDMS polymer chains that incorporate hydrogen bonding motifs, which phase separate to afford hydrogen bond-reinforced phases that instill vast improvements to elastic behavior, mechanical and elongation properties, and upper-use temperature. Novel nanocomposite formulation through the incorporation of MQ nanoparticles (which observe widespread usage in cosmetics) facilitate further routes toward improved mechanical and elongation properties. Furthermore, with growing interest in additive manufacturing strategies, which permit the construction of complex geometries via an additive approach (as opposed to conventional manufacturing processes, which require subtractive approaches and are limited in geometric complexity), great interest lies in the capability to additively manufacture polysiloxane-based materials. This work also illustrates the development of an MQ-reinforced polysiloxane system that is amenable to conventional vat photopolymerization additive manufacturing: chemical modification of PDMS polymer chains permits the installation of UV-activatable crosslinking motifs, allowing solid geometries to be constructed from a liquid precursor formulation.

The liberal and republican traditions of political thought are commonly treated as divergent political-philosophical doctrines which existed in a state irreconcilable opposition in late eighteenth-century France and America. The present study challenges this notion through examining the concept of political neutrality as discussed and expounded in the political and constitutional writings of James Madison and Benjamin Constant. In seeking to account for not only why, but also how, both thinkers endeavoured to construct political systems geared toward securing the production of neutral laws, this thesis explores and highlights the complex interdependent relationship between the liberal and republican philosophical traditions in late eighteenth- and early nineteenth-century political theory. It is argued that in their desire to construct political-constitutional systems tailored toward guaranteeing the materialisation of neutral laws, Madison and Constant incorporated republican, or ‘Real Whig’, concepts into their respective constitutional strategies. Their shared objective, it is shown, was to form limited and neutral states through exploiting the diversity of public opinion in such a way that would render popular sovereignty self-neutralising. More specifically, this thesis suggests that both Madison and Constant placed considerable emphasis on de-legitimising particular justifications for legislative action, and that their respective efforts in this area were motivated by a desire to restrict the legislature to the promotion of objective, and impartially-conceived, accounts of the public good. Thus through examining Madison’s and Constant’s attempts to form neutral states, this thesis challenges the traditional account of the development of modern liberalism through pointing to the existence of an autonomous liberal-republican philosophy in post-revolutionary French and American political thought. It is argued that this hybrid political philosophy – which underpinned the constitutionalisms advanced by both Madison and Constant – had as its principal objective the reconciliation of the practice of popular governance with the restoration and maintenance negative individual liberty. Both thinkers, in other words, exploited republican concepts and institutions in order to realise the distinctly liberal end of forming limited and neutral states.

This research provides in depth analysis of how qualified and experienced doctoral therapists and graduates of the professional doctorate counselling programmes, understood and made sense of their experiences in working at a depth of engagement in therapy. A qualitative approach of interpretative phenomenological analysis is the methodology used. This provides rich, detailed analysis of individuals' accounts where idiographic focus and participants' lived experiences remain central. Six Doctoral counselling therapists were individually interviewed via a semi-structured interview schedule. Participants' counselling orientations varied, with most describing themselves as integrative practitioners. Six accounts were examined separately and then analysed. Clusters and themes developed. Themes were also analysed to ascertain convergence and divergence in participants' accounts. Implications are discussed with data rooted in verbatim extracts and embedded within relevant literature. The study presents super-ordinate themes of, 'the indefinable', 'spiritual in nature', 'levels of encounter', 'dissolution of boundaries', 'personally challenging', 'nourishing of the self' and 'professional questioning'. Findings show how participants called upon phenomenological perspectives, epistemological lenses, spiritual and neurobiological discourses and counselling theory, used interchangeably, to try and understand their experiences. The study also points to practitioners crossing interpersonal boundaries, their fear of being judged by the counselling community and their reluctance to take certain aspects of the phenomenon to supervision. The implications of the research highlight whole areas of experiencing that are not being supervised and show challenges on many levels for the counselling community. Such an IPA study also highlights divisions and commonalities in how participants make sense of the phenomenon and a contribution is offered indicating where further research would be helpful. Overall this research study invites a greater awareness and greater openness to understand the ripples and challenges practitioners face from working at a depth of engagement.

Il potenziale delle nuove tecnologie digitali applicate al settore industriale ha consentito di ridurre enormemente la durata dei cicli produttivi grazie alla rapida gestione di quantità di dati sempre più considerevoli attraverso l’introduzione delle Macchine a Controllo Numerico (Computer Numerical Control – CNC). Nel corso delle ultime tre decadi, l’industria manifatturiera ha subito notevoli e sostanziali cambiamenti grazie ad una sempre più forte connessione con il mondo dell’informatica. La più grande rivoluzione in tale ambito è stata segnata dall’avvento della Manifattura Additiva (Additive Manufacturing - AM), conosciuta sotto diversi nomi, tra i quali Prototipazione Rapida (Rapid Prototyping), Manifattura Rapida (Rapid Manufacturing) o Libera Fabbricazione di Forme (Free Form Fabrication). Materia di ricerca e sviluppo sin dalla fine degli anni ’80, la Manifattura Additiva consente la creazione di elementi fisici tridimensionali partendo da modelli CAD attraverso la sovrapposizione successiva di materiale strato per strato (layer by layer), offrendo i benefici di una elevata flessibilità geometrica degli elaborati, altrimenti irraggiungibile attraverso le tradizionali tecniche di Manifattura Sottrattiva operanti per asportazione di materiale. In seguito ad intensive ricerche, progressi significativi sono stati fatti nello sviluppo e nella commercializzazione di nuovi ed innovativi processi AM.

碩士
國立交通大學
資訊工程系
87
3DAF（3D Animation Framework）is a software framework developed at the Animation Laboratory of Institute of Computer Science & Information Engineering , National Chiao Tung University. With 3DAF, we try to set up a software environment, which provides rich high-level libraries which are common to various applications. So that programmers can be more productive in their development of 3D applications. In order for a computer animation to look more "real", it is desirable to make objects in the scene to possess physical properties. In this thesis I have developed a ball collision model for 3DAF. In this model, two types of objects are designed: balls and boards. Only balls are allowed to move. In its movement a ball may hit another ball or a board and bounce back. A ball is affected by the friction of the board it is rolling on. I tried to make the model concise, easy to use, and reliable. To demonstrate the usefulness and versatility of this model, a billiard game and a table tennis game were coded. The model did save a great deal of efforts. It is my wish that this model will also help other users of 3DAF when they need to included in their applications objects like balls and boards in my model.

碩士
東吳大學
資訊科學系
94
PET（Positron Emission Tomography） is an important technique in medical imaging. PET helps doctors to find the tumour early and is a great help for diagnosing cancer. The image reconstruction in PET can be divided into two categories, direct analytical methods and iterative reconstruction methods. According to the image reconstruction in PET, the quality of traditional two-dimensional image reconstruction has been efficiently improved by three-dimensional image reconstruction, but the sensitivity of the data and the quality of the image are restricted by the limit of modality physics. In analytical image reconstruction algorithm, 3DRP method compensates the unmeasured events by forward projection based on the initial direct image estimate. However, the original 3DRP method merely depends on the parallel projections without taking into account the oblique projections. In our proposed 3DRP-SSRB method, we improve the first image estimate by incorporating the rebinned oblique data. SSRB method was used to perform the rebinning operation to make use of the oblique projection data to improve the sensitivity information. And then project the improved image estimate forward and reconstruct the final image. Conflicting parameters of reconstructed image quality of 3DRP are experimented by simulated thee-dimensional phantom study with regard to both system sensitivity and image quality factors. PET simulation software package was used to conduct the experiment along with the MATLAB software to evaluate the effectiveness of two-dimensional FBP, 3DRP, and our proposed 3DRP-SSRB methods. The result demonstrated its better image quality by having better mean squared error numbers in most of output image slices. According to the concept of axial compression, different span value does not have too great influence on the quality of the reconstructed image.

碩士
國立中興大學
電機工程學系所
100
Video always plays an important role in entertainment. There is a need to pursue high quality videos. For that reason the display of images continues to develop higher resolution, such as HD 720p, Full HD 1080p, and QFHD for future display spec. However, the 2D video display method is difficult for viewers to have virtual reality. 3D video, therefore, becomes a popular topic in recent years. The virtual reality with 3D stereo videos is created by having the right eye and left eye seeing the right image and left image separately. Then human brain will synthesize the stereo feeling for us. To obtain the right and left image, one method is to capture it directly. This method will provide us higher quality in display. If we capture the video in 2D video’s method, we then need to process the video by some steps in order to generate the right and left images. In the definition of MPEG-2, it describes the view synthesis method of DIBR(3DAV－Advanced 3D TV), and it is the research topic of this paper. The algorithm of 3D view synthesis can be separated by three steps: preprocessing of depth map, image warping, and hole filling. The main purpose of view synthesis is to fill the holes generated by image warping. By preprocessing the depth map, we could reduce the size of holes, and relieves the difficulty of hole filling. The proposed 3D view synthesis algorithm analyzes the three steps of original view synthesis flow and adds the concept of image interpolation to improve the quality of original warping computations. We analyze the holes in different locations in one frame at the same time, and choose the most appropriate method to fill these holes. The implementation of the chip by TSMC 0.18μm technology file can generate the spec of Full HD 1080p, and 60fps of its frame rate. We also analyze the fractional problem and minimize the hardware requirements. By doing so, we wish to obtain real time display with high quality.

碩士
中原大學
化學工程研究所
105
The reaction kinetics of the CO2 absorption into aqueous solutions of 3-dimethylamino-1-propanol (3DMAP) and into mixed aqueous solutions of 3DMAP and Diethylenetriamine (DETA) were investigated by a wetted wall column at 30, 35, and 40oC. The systems studied were: 3DMAP (5, 10, 15, 20, 25, 30wt%) + H2O and 3DMAP (25%) + DETA (5%) + H2O, 3DMAP (20%) + DETA (10%) + H2O, 3DMAP (15%) +DETA (15%) + H2O. The physical properties such as density, viscosity, Henry’s law constant and diffusivity of the studied systems were also measured. Due to the reactivity of CO2 to the amine solutions, the N2O analogy was used to estimate the solubility and diffusivity of CO2 in the aqueous amine solutions. The reaction rate constants were calculated by applying a hybrid model which combines a pseudo-first order reaction mechanism for the reaction of CO2 with 3DMAP while the zwitterion mechanism for the absorption of CO2 into DETA. The results of this research data can be used to design for the absorption process of which the aqueous 3DMAP + DETA solutions used as the CO2 absorbents.

碩士
中原大學
化學工程研究所
105
Due to global warming is increasing recently, the issue of reducing carbon dioxide is much important; we could find amine that is good absorbent in the literature. Blended amines are worth exploring recent research projects, as they contribute to properties of carbon dioxide capture. In addition to absorbing carbon dioxide thermo-physical properties, molar heat capacity in carbon dioxide capture plays an important role. In this study, the heat capacities of ternary systems of polyamines (DETA, TETA)/(1DMAP, 3DMAP)/H2O were measured over the temperature range of 3080C and different solute concentrations: (1DMAP, 3DMAP)/Polyamines (5/35, 20/20, 30/10, 35/5wt%) + water (60wt%) and (1DMAP, 3DMAP)/Polyamines (10/20, 15/15, 20/10, 25/5 wt%) + water(70wt%) using a heat flux differential scanning calorimeter (DSC). For the pure systems, the temperature dependence of the molar heat capacity was represent by a second order equation. The obtained CP data were correlated as function temperature and composition using a RedlichKister expansion and a modified Söhnel and Novotný equation for the binary aqueous polyamines solutions and ternary aqueous systems, respectively. Thus, it can be said the proposed correlations in this study that can be utilized to yield reliable estimation of the heat capacities of the studied systems.

碩士
國立成功大學
機械工程學系
103
Most transtibial sockets are made by prosthetist with traditional manual process. However, the process includes lots of complicated modification skills which directly affect the quality of transtibial sockets. Moreover, a certificated prosthetist also need plenty of experience and cases. To solve these problems, our laboratory has developed a CAD/3DP transtibial socket model manufacturing process, which uses the philosophy of reverse engineering. The research developed a finite element (FE) model to predict the interface pressures between transtibial stump and the CAD/3DP socket during walking. The boundary conditions of the knee joint were measured using Motion Analysis System and a force plate in the gait laboratory. Ultimately, the FE-predicted results were compared with interface pressures of experimental measurement. The FE-predicted results showed that the average pressure of peak 1 and peak 2 at patellar tendon, tibia end and fibular end sites was 12.2% higher than that measured from Tekscan System. In addition, the pressures patterns of FE-predicted results and measurement results were similar at patellar tendon, tibia end and fibular end sites.

L’attività di ricerca presentata in questa tesi verte sullo studio di nuovi materiali, a base cementizia, utilizzabili per applicazioni di digital concrete, ovvero di stampa 3D. Si sono, infatti, testati una serie di innovativi mix design da potersi impiegare in processi robotizzati di estrusione, che spaziano da campi di applicazione non strutturali (conglomerati alleggeriti), a quelli strutturali con riferimento, in quest’ultimo caso, a prestazioni meccaniche buone ed eccellenti. Nel campo non strutturale, molteplici sono i vantaggi dell’utilizzo di miscele cementizie alleggerite con schiuma, in quanto le bolle d’aria inglobate nella matrice cementizia conferiscono ai prodotti finiti diverse importanti qualità, tra cui leggerezza, isolamento termico, resistenza al fuoco, economicità. Nel lavoro di tesi vengono investigati il comportamento a frattura e le caratteristiche meccaniche di calcestruzzi schiumati “eco-sostenibili” con aggiunta di un prodotto di scarto: il biochar. Per quanto riguarda il campo strutturale, le indagini sperimentali presentate, partono dallo studio di un mix design di una malta tradizionale di cui, dopo un attento studio delle caratteristiche meccaniche e reologiche, viene proposta una versione “stampabile”, caratterizzata cioè da proprietà reologiche che ne permettano l’applicabilità al processo di stampa 3D. Infine, per completare l’attività di ricerca, si è voluto estendere la sperimentazione anche a mix design di paste cementizie ad alte prestazioni (HPC), riuscendo ad ottenere delle nuove formulazioni, sempre con caratteristiche “green”, vista la presenza del biochar, dalle rilevanti prestazioni meccaniche e adatte alla stampa 3D.
The research activity presented in this thesis focuses on the study of new cement-based materials that can be used for digital concrete applications, i.e. 3D printing. In fact, a series of innovative mix designs, suitable for robotic extrusion processes, have been tested with possible applications ranging from non-structural purpose fields (lightweight conglomerates) to structural ones with reference, in the latter case, to good and excellent mechanical performances. In the non-structural field, there are many advantages of using lightweight cementitious mixtures with foam, as the air bubbles incorporated in the cementitious matrix give to the finished products various important qualities, including lightness, thermal insulation, fire resistance and cost-effectiveness. In the thesis, the fracture behavior and mechanical characteristics of "ecosustainable" foamed concrete with the addition of a waste product (biochar) are investigated. As regards the structural field, the experimental investigations presented start from the study of a mix design of a traditional mortar of which, after a careful study of the mechanical and rheological characteristics, a "printable" version is proposed, the printable version is characterized by rheological properties that allow its applicability to the 3D printing process. Finally, to complete the research activity, the experimental campaign was extended also to the development of mix design of high-performance cement pastes (HPC), managing to obtain new formulations, always with "green" characteristics, given by the presence of biochar, with important mechanical performance and suitable for 3D printing applications.