• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 359
  • 55
  • 43
  • 43
  • 37
  • 16
  • 16
  • 5
  • 4
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 737
  • 737
  • 252
  • 248
  • 244
  • 109
  • 106
  • 85
  • 57
  • 51
  • 51
  • 48
  • 48
  • 45
  • 43
  • 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.
521

The role of 3D printing in biological anthropology

Allard, Travis T. 14 September 2006 (has links)
The following work explores the role of 3D printing in biological anthropology. A case study approach is used to provide an understanding of two different applications for 3D printing and to identify a potential methodology for creating 3D models. Case study one looks at the application of 3D printing to reconstruction projects using a flowerpot to test the reconstruction methodology. The second case study uses both laser surface and CT scanning to create a replica of a human skeleton. The two methods of data acquisition are evaluated for advantages and limitations in creating the virtual model. This work shows that there is a role for 3D printing in biological anthropology, but that data acquisition and processing issues are the most significant limiting factors in producing skeletal replicas. / October 2006
522

Ubiquitous Projection: New Interfaces using Mobile Projectors

Willis, Karl D. D. 19 March 2013 (has links)
The miniaturization of projection technology has enabled a new class of lightweight mobile devices with embedded projectors. Projection engines as small as a postage stamp are currently being embedded in thousands of mobile devices. Mobile projector-based devices differ in very fundamental ways from the display-based devices we commonly use. Mobile projectors can be carried with the user and project imagery into almost any space, projected content is visible to multiple users and supports social interaction, physical objects and surfaces can be augmented with projected content, and embedded projectors can enable new form-factors for mobile displays. This research investigates the potential of mobile projectors as a new platform for human-computer interaction. I aim to demonstrate that the unique affordances created by the miniaturization of projection technology can inspire new and compelling interaction with single-users, multi-users, the environment, and projector-embedded objects. This research presents a comprehensive survey of mobile projector-based interaction – documenting interaction with historic projection devices; introducing novel interaction techniques, metaphors, and principles for mobile projector-based systems; providing implementation details of functional prototype devices using mobile projectors; presenting technical innovations, such as the development of specialized projectors and custom marker tracking algorithms; and detailing results from preliminary user testing with the prototype systems created. This research forms a systematic investigation of the past, the present, and a possible future for interaction using mobile projectors.
523

A smart wireless integrated module (SWIM) on organic substrates using inkjet printing technology

Palacios, Sebastian R. 22 May 2014 (has links)
This thesis investigates inkjet printing of fully-integrated modules fabricated on organic substrates as a system-level solution for ultra-low-cost and eco-friendly mass production of wireless sensor modules. Prototypes are designed and implemented in both traditional FR-4 substrate and organic substrate. The prototype on organic substrate is referred to as a Smart Wireless Integrated Module (SWIM). Parallels are drawn between FR-4 manufacturing and inkjet printing technology, and recommendations are discussed to enable the potential of inkjet printing technology. Finally, this thesis presents novel applications of SWIM technology in the area of wearable and implantable electronics. Chapter 1 serves as an introduction to inkjet printing technology on organic substrates, wireless sensor networks (WSNs), and the requirements for low-power consumption, low-cost, and eco-friendly technology. Chapter 2 discusses the design of SWIM and its implementation using traditional manufacturing techniques on FR-4 substrate. Chapter 3 presents a benchmark prototype of SWIM on paper substrate. Challenges in the manufacturing process are addressed, and solutions are proposed which suggest future areas of research in inkjet printing technology. Chapter 4 presents novel applications of SWIM technology in the areas of implantable and wearable electronics. Chapter 5 concludes the thesis by discussing the importance of this work in creating a bridge between current inkjet printing technology and its future.
524

The role of 3D printing in biological anthropology

Allard, Travis T. 14 September 2006 (has links)
The following work explores the role of 3D printing in biological anthropology. A case study approach is used to provide an understanding of two different applications for 3D printing and to identify a potential methodology for creating 3D models. Case study one looks at the application of 3D printing to reconstruction projects using a flowerpot to test the reconstruction methodology. The second case study uses both laser surface and CT scanning to create a replica of a human skeleton. The two methods of data acquisition are evaluated for advantages and limitations in creating the virtual model. This work shows that there is a role for 3D printing in biological anthropology, but that data acquisition and processing issues are the most significant limiting factors in producing skeletal replicas.
525

Optimization of Electron Beam Melting for Production of Small Components in Biocompatible Titanium Grades

Karlsson, Joakim January 2015 (has links)
Additive manufacturing (AM), also called 3D-printing, are technologies where parts are formed from the bottom up by adding material layer-by-layer on top of each other. Electron Beam Melting (EBM) is an AM technique capable of manufacturing fully solid metallic parts, using a high-intensity electron beam to melt powder particles in layers to form finished components. Compared to conventional machining, EBM offers enhanced efficiency for production of customized and patient specific parts such as e.g. dental prosthetics. However, dental prosthetics are challenging to produce by EBM, as their small sizes mean that mechanical and surface properties may be altered as part sizes decreases. The aim of this thesis is to gain new insights that could lead to optimization for production of small sized components in the EBM. The work is focused to understand the process-property relationships for small size components production. To improve the surface resolution and part detailing, a smaller sized powder was used for production and compared to parts made with standard sized powder. The surface-, chemical and mechanical properties were evaluated for parts produced with both types of powders. The results indicate that the surface roughness may be influenced by powder and build layer thickness size, whereas the mechanical properties showed no influence of the layer-wise production. However, the mechanical properties are dependent on part size. The outermost surface of the parts consists of a surface oxide dominated by TiO2, formed as a result of reaction between the surface and residual gases in the EBM build chamber. The surface oxide thickness is comparable to that of a conventionally machined surface, but is dependent on build height. This work concludes that the surface resolution and component detailing can be improved by various measures. Provided that proper process themes are used, the EBM manufactured material is homogenous with properties comparable to conventional produced titanium. It has also been shown that the material properties will be altered for small components. The results point towards different ways of optimizing manufacturing of dental prosthetics by EBM, which will make dental prosthetics available for an increased number of patients.
526

The role of 3D printing in biological anthropology

Allard, Travis T. 14 September 2006 (has links)
The following work explores the role of 3D printing in biological anthropology. A case study approach is used to provide an understanding of two different applications for 3D printing and to identify a potential methodology for creating 3D models. Case study one looks at the application of 3D printing to reconstruction projects using a flowerpot to test the reconstruction methodology. The second case study uses both laser surface and CT scanning to create a replica of a human skeleton. The two methods of data acquisition are evaluated for advantages and limitations in creating the virtual model. This work shows that there is a role for 3D printing in biological anthropology, but that data acquisition and processing issues are the most significant limiting factors in producing skeletal replicas.
527

Utilisation de matériaux lignocellulosiques et d'impression 3D pour élaborer des structures contuctrices / Use of lignocellulosic materials and 3D printing for the elaboration of conductive carbon strutures

Shao, Ying 29 September 2017 (has links)
Cette thèse a pour l’objectif d’élaborer, à partir de technologie additive 3D (extrusion de gel), des structures conductrices (électriquement) et résistantes (mécaniquement) en utilisant exclusivement des matériaux lignocellulosiques. Les matériaux sélectionnés sont des microfibrilles de cellulose (MFC), du lignosulfonate de sodium (LS ou NaLS) et de la cellulose en poudre (CP). Ces trois constituants peuvent être utilisés pour élaborer des hydrogels aqueux compatibles avec l’impression 3D (extrusion). De plus, ce procédé d’impression permet la mise en forme avec une excellente définition de structures à base de précurseurs de carbone dont les géométries peuvent être adaptées aux différentes techniques de caractérisation selectionnées. / In the present work, electrically conductive and mechanically resistant carbon structures were elaborated by 3D printing and subsequent pyrolysis using microfibrillated cellulose/lignosulfonate/cellulose powder (labeled as MFC/LS/CP) blends. The processability of MFC/LS/CP slurries by 3D printing was examined by rheological tests in both steady flow and thixotropic modes. The printed MFC/LS/CP pastes were self-standing, provided a high printing definition and were proved to be morphologically stable to air drying and the subsequent pyrolysis. Pyrolysis at a slow rate (0.2°C/min) to a final temperature in the range of 400-1200°C was used to manufacture MFC/LS/CP carbons. The TGA/DTG was applied to monitor the thermal degradation of MFC/LS/CP materials in blends as well as in a separated form. The resulting carbons were further characterized in terms of morphology, microstructure and physical properties (such as density, electrical conductivity and mechanical strength). At 900°C, MFC/LS/CP carbons displayed a high electrical conductivity of 47.8 S/cm together with a low density of 0.74 g/cm3 as well as an important porosity of 0.58. They also achieved an elastic modulus maximum of 6.62 GPa. Such interesting electrical and mechanical properties would lead to a promising application of MFC/LS/CP- derived biocarbons in energy storage devices as electrode materials in close future.
528

[en] FROM CHISEL TO BIT: THE REVOLUTION OF DIGITAL TECHNOLOGIES IN JEWELLERY DESIGN / [pt] DO CINZEL AO BIT: A REVOLUÇÃO DAS TECNOLOGIAS DIGITAIS NO DESIGN DE JOIAS

NATASCHA SCAGLIUSI 28 March 2017 (has links)
[pt] As tecnologias digitais de fabricação por adição ou subtração têm em si um potencial ainda inexplorado pela indústria joalheira. Por isso, essa dissertação tem como objetivo avaliar as vantagens técnicas e comerciais que podem incentivar a transformação no seu uso pela indústria de joias, inclusive apontando exemplos de iniciativas internacionais e nacionais, estas últimas centradas no Estado do Rio de Janeiro, assinalando assim as razões de seus sucessos e falhas. Através de uma pesquisa bibliográfica se busca determinar as bases históricas e especificações técnicas dos principais processos de produção tradicionais (técnicas manuais tais como o repuxo, a cinzelagem, a modelagem e fundição por cera perdida, entre outras) e digitais (impressão 3D, escaneamento 3D e modelagem digital), para, nesse contexto, seguir-se à experimentação com as tecnologias mais novas, como forma de se buscar a comprovação da existência do potencial técnico e comercial destas tecnologias para o setor joalheiro fluminense que justifiquem essa inovação. / [en] The digital manufacturing technologies by addition or subtraction of material holds an unexplored potential for the jewellery industry. Therefore, this dissertation aims to assess the technical and commercial advantages that can encourage the transformation of its use by the jewellery industry, pointing out examples of international and national enterprises, the latest centered in the Brazilian State of Rio de Janeiro, thus signalizing the reasons of their successes and failures. Through a literature research this work pursuits the historical foundations and the technical specifications of the traditional manual techniques (such as repoussé, chasing, lost wax casting, among others) and digital manufacturing processes (3D printing, 3D scanning and 3D modelling), for, in this context, experimenting with the newest technologies, as a way to seek evidence of its technical and commercial potential for the jewellery industry in Rio de Janeiro that justifies the innovation.
529

Methodological proposition to evaluate polymer recycling in open-source additive manufacturing contexts / Proposition d'une approche méthodologique permettant d'évaluer le recyclage des polymères dans un contexte de fabrication additive open-source

Cruz Sanchez, Fabio Alberto 09 December 2016 (has links)
En ce début de XXIème siècle, l’époque où seul la technique transformait la société toute entière est clairement révolue. Certes, les révolutions techniques sont là : interconnexion des personnes, explosion de l’internet, apparition de nouvelles formes d’énergies, de nouveaux procédés de production, de nouveaux matériaux etc... mais l’homme n'est plus un simple consommateur sensible au prix et aux incitations de l’état. Il souhaite être acteur et participer à l’utilisation des nouvelles technologies mais de manière raisonnée et en intégrant les grands enjeux sociétaux tels que le partage et la sauvegarde des ressources et matières premières. Cette thèse s’inscrit dans cette problématique globale: en effet tout au long du manuscrit nous réfléchissons à comment une révolution technique tel que la fabrication additive (FA) est prise en main par des citoyens dans des lieux de partage de la connaissance que sont les FabLabs, et plus précisément, s’il est possible et de quelle manière introduire de la durabilité dans le contexte open-source. Nous voyons dans un premier temps, comment la problématique sociétale forte du recyclage des matériaux se développe dans le contexte de la FA en générale et plus particulièrement nous proposons une revue bibliographique systématique sur le sujet. Dans un second temps nous recentrons notre recherche sur la FA dans le contexte open source et nous montrons que les machines dans ce contexte, bien qu’à des coûts très faibles par rapport aux machines professionnelles, ont cependant des niveaux de reproductibilités suffisant pour que l’on les utilise dans le cadre d’une recherche poussée. Dans le troisième chapitre nous proposons une méthodologie générale fixant l’étude du recyclage de polymères thermoplastiques dans le contexte open-source. Dans le quatrième chapitre nous utilisons la méthodologie vu précédemment pour le recyclage de l’acide polylactique (PLA). Nous montrons le niveau de dégradation de la matière à travers l’ensemble du procédé et concluons qu’il est possible de recycler le PLA pour l’impression 3D mais dans une moindre mesure que pour les procédés d’injection. Enfin nous concluons et proposons en perspective d’étudier le recyclage en circuit court d’autres polymères thermoplastique / Since the beginning of the XXI century, we can recognize that several technical (r)evolutions have changed the way we conceived our world. New realities have appeared thanks to the information and communication technologies (e.g. Internet), peer-to-peer dynamics (e.g. open software/hardware, collaborative economy), new means of production (fablabs, hackerspaces), among others. One of the impacts of this technical ecosystem is the individual's empowerment that changes the relationship between consumer and producer. For instance, we observe an evolution of role passing from a passive consumer towards an active prosumer, where this latter considers not only economic aspects, but also social and environmental issues.This thesis is integrated in this global issue; indeed, throughout the manuscript we analyze about the impact of open-source (OS) Additive Manufacturing (AM) (also as known as open-source 3D printing or just 3D printing) in the light of the sustainability issues. The democratization of OS AM and the creation of spaces for co-creation (e.g. FabLabs) proved the interest for changes in the established roles. Therefore, we are interested in how this OS technology could develop sustainable waste management options through a polymer recycling process. In a first phase, we present the concept of additive manufacturing (AM) and its importance on sustainability issues. A systematic literature review related to the material recycling advances in the commercial and open-source (OS) AM is developed with a focus on thermoplastic polymer recycling.In a second phase, our aim is to validate open-source AM systems as a reliable manufacturing tool. We develop and test an experimental protocol in order to evaluate the dimensional performance using as case study a representative OS 3D printer: called FoldaRap. It was found that the International Standard Tolerance Grade of this machine is situated between IT14 and IT16. We conclude that the dimensional performance of this case study is comparable to the commercial AM systems, taking into account the important different in terms of machine cost. In a third phase, we center our attention on the recycling process and we propose a systematic methodology to evaluate the feasibility of the use of recycled thermoplastic polymer in OS 3D printers. A case study is developed with the evaluation of the recycling process using polylactid acid (PLA). The results allow us to conclude that the use of recycled PLA is technically feasible. Nevertheless, the degradation of the material is more important than in other traditional manufacturing systems (e.g. injection). Finally, we concludes and propose as perspectives, the study of a distributed recycling process for other type of polymers
530

3D Printing and Characterization of PLA Scaffolds for Layer-by-Layer BioAssembly in Tissue Engineering / Impression 3D et Caractérisation des Scaffolds en PLA pour Assemblage Couche par Couche en Ingénierie Tissulaire

Guduric, Vera 13 December 2017 (has links)
L’Ingénierie tissulaire (IT) est un domaine interdisciplinaire qui applique les principes de l'ingénierie et des sciences de la vie au développement de substituts biologiques afin de restaurer, maintenir ou améliorer la fonction tissulaire. Sa première application consiste à remplacer les tissus endommagés par des produits cellulaires artificiels. Une autre application de l’IT est basée sur la production des modèles en 2 et 3 dimensions (2D et 3D) pour des études biologiques et pharmacologiques in vitro. Ces modèles ou remplacements de tissus peuvent être fabriqués en utilisant des différentes méthodes de médecine, biologie, chimie, physique, informatique et mécanique, fournissant un micro-environnement spécifique avec différents types de cellules, facteurs de croissance et matrice. L'un des principaux défis de l'IT la pénétration cellulaire limitée dans les parties internes des biomatériaux poreux. Une faible viabilité cellulaire au centre du produit d'IT est la conséquence de la diffusion limitée d'oxygène et de nutriments du fait d’un réseau vasculaire insuffisant dans l'ensemble de la construction 3D. Le BioAssembage couche-par-couche est une nouvelle approche basée sur l'assemblage de petites constructions cellularisées permettant une distribution cellulaire homogène et une vascularisation plus efficace dans des produits d’IT.Notre hypothèse est que l'approche couche-par-couche est plus adaptée à la régénération osseuse que l'approche conventionnelle de l'IT. L'objectif principal de cette thèse était d'évaluer les avantages de l'approche couche-par-couche en utilisant des membranes de polymères imprimées en 3D et ensemencées avec des cellules primaires humaines. Nous avons évalué l'efficacité de la formation du réseau vasculaire in vivo dans toute la construction 3D en utilisant cette approche et en la comparant à l'approche conventionnelle basée sur l'ensemencement des cellules sur la surface des scaffolds massives. Il n'y avait pas de différence significative dans le nombre de vaisseaux sanguins formés en 3D au niveau des parties externes des constructions implantées en site souscutanée chez des souris. Mais dans les parties internes des implants qui n'étaient pas en contact direct avec un tissu hôte, nous avons pu observer une formation des vaisseaux sanguins statistiquement plus efficace lorsque l'approche du bio-assemblage couche-par-couche a été utilisée. Cette formation de réseau vasculaire était plus importante dans le cas de co-cultures que de mono-cultures.Il y avait plusieurs objectifs secondaires dans ce travail. Le premier était de fabriquer des constructions 3D cellularisées pour l'IT en utilisant des membranes d'acide polylactique (PLA) et des cellules primaires humaines : des cellules de stroma de moelle osseuse humaine (HBMSCs) isolées de la moelle osseuse et des cellules progénitrices endothéliales (EPCs) isolées du sang du cordon ombilical. Ensuite, nous avons comparé différentes technologies de fabrication des scaffolds: impression 3D directe à partir de poudre de PLA et impression par fil fondu en utilisant une imprimante commerciale et une autre fabriquée sur mesure. L'imprimante sur mesure a permis le plus haut niveau de résolution d'impression spécialement adaptée à la forme et la taille des pores. Par ailleurs, nous avons évalué différents systèmes de stabilisation pour l'assemblage couche par couche : l’utilisation de clips en PLA imprimés en 3D a fourni une stabilisation plus efficace pour empiler les membranes PLA couche par couche. Un autre avantage de ce système de stabilisation est qu'il peut être implanté avec des implants. Ensuite, nous avons observé une prolifération et une différenciation cellulaire plus efficaces lorsque le système de co-culture était utilisé, en comparaison avec des mono-cultures.L'approche du bioassemblage couche-par-couche semble être une solution appropriée pour une vascularisation efficace dans des structures 3D entières d'ingénierie tissulaire. / Tissue Engineering (TE) is “an interdisciplinary field that applies principles of engineering and the life sciences toward development of biological substitutes that restore, maintain, or improve tissue function”. The First application of TE is to replace damaged tissues by artificial cell-materials products of tissue engineering (TE). Another TE application is to produce 2 or 3 dimensional (2D and 3D) models for biological and pharmacological in vitro studies. These models or tissue replacements can be fabricated using a combination of different interdisciplinary methods of medicine, biology, chemistry, physics, informatics and mechanics, providing specific micro-environment with different cell types, growth factors and matrix.One of the major challenges of tissue engineering is related to limited cell penetration in the inner parts of porous biomaterials. Poor cell viability in the center of engineered tissue is a consequence of limited oxygen and nutrients diffusion due to insufficient vascular network within the entire construct. Layer-by-layer (LBL) BioAssembly is a new approach based on assembly of small cellularized constructs that may lead to homogenous cell distribution and more efficient three dimensional vascularization of large tissue engineering constructs.Our hypothesis is that LBL Bioassembly approach is more suitable for bone regeneration than conventional tissue engineering approach. The primary objective of this thesis was to evaluate the advantages of LBL Bioassembly approach using 3D-printed polymer membranes seeded with human primary cells. We have evaluated the efficiency of vascular network formation in vivo within entire 3D tissue engineering construct using LBL bioassembly approach and comparing it to the conventional approach based on seeding of cells on the surface of massive 3D scaffolds. There was no significant difference in number of formed blood vessels in 3D at the outer parts of constructs implanted subcutaneously in mice 8 weeks post-implantation. But in the inner parts of implants which were not in direct contact with a host tissue, we could observe statistically more blood vessel formation when LBL bioassembly approach was used. This vascular network formation was more important in the case of co-cultures than mono-vultures of HBMSCs.There were several secondary objectives in this work. The first was to fabricate cellularized 3D constructs for bone tissue engineering using poly(lactic) acid (PLA) membranes and human primary cells: human bone marrow stroma cells (HBMSCs) isolated from the bone marrow, and endothelial progenitor cells (EPCs) isolated from the umbilical cord blood. Then, we have compared different Additive manufacturing technologies to fabricate scaffolds: direct 3D printing (3DP) starting from PLA powder dissolved in chloroform and fused deposition modelling (FDM) using a commercial or a custom-made printer with different resolutions.The custom-made printer equipped with 100 μm nozzle allowed the highest level of printing resolution concerning pores shape and size. In the meantime we evaluated different stabilization systems for layer-by-layer assembling of PLA membranes with human primary cells: the use of 3D printed PLA clips provided the most efficient stabilization to stack PLA membranes in 3D. Another advantage of this stabilization system is that it could be implanted together with LBL constructs. Then we investigated the most suitable cell culture system for such constructs and we observed more efficient cell proliferation and differentiation when co-culture system is used, comparing to mono-cultures.LBL bioassembly approach seems to be suitable solution for efficient vascularization within entire large 3D tissue engineering constructs especially when co-cultures of mesenchymal and endothelial cells are used.

Page generated in 0.0742 seconds