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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
531

Three Dimensional Direct Print Additively Manufactured High-Q Microwave Filters and Embedded Antennas

Hawatmeh, Derar Fayez 28 March 2018 (has links)
The need for miniaturized, and high performance microwave devices has focused significant attention onto new fabrication technologies that can simultaneously achieve high performance and low manufacturing complexity. Additive manufacturing (AM) has proven its capability in fabricating high performance, compact and light weight microwave circuits and antennas, as well as the ability to achieve designs that are complicated to fabricate using other manufacturing approaches. Direct print additive manufacturing (DPAM) is an emerging AM process that combines the fused deposition modeling (FDM) of thermoplastics with micro-dispensing of conductive and insulating pastes. DPAM has the potential to jointly combine high performance and low manufacturing complexity, along with the possibility of real-time tuning. This dissertation aims to leverage the powerful capabilities of DPAM to come-up with new designs and solutions that meet the requirements of rapidly evolving wireless systems and applications. Furthermore, the work in this dissertation provides new techniques and approaches to alleviate the drawbacks and limitations of DPAM fabrication technology. Firstly, the development of 3D packaged antenna, and antenna array are presented along with an analysis of the inherent roughness of 3D printed structures to provide a deeper understanding of the antenna RF performance. The single element presents a new volumetric approach to realizing a 3D half-wave dipole in a packaged format, where it provides the ability to keep a signal distribution network in close proximity to the ground plane, facilitating the implementation of ground connections (e.g. for an active device), mitigating potential surface wave losses, as well as achieving a modest (10.6%) length reduction. In addition, a new approach of implementing conformal antennas using DPAM is presented by printing thin and flexible substrate that can be adhered to 3D structures to facilitate the fabrication and reduce the surface roughness. The array design leverages direct digital manufacturing (DDM) technology to realize a shaped substrate structure that is used to control the array beamwidth. The non-planar substrate allows the element spacing to be changed without affecting the length of the feed network or the distance to the underlying ground plane. The second part describes the first high-Q capacitively-loaded cavity resonator and filter that is compatible with direct print additive manufacturing. The presented design is a compromise between quality factor, cost and manufacturing complexity and to the best of our knowledge is the highest Q-factor resonator demonstrated to date using DPAM compatible materials and processes. The final version of the single resonator achieves a measured unloaded quality factor of 200-325 over the frequency range from 2.0 to 6.5 GHz. The two pole filter is designed using a coupled-resonator approach to operate at 2.44 GHz with 1.9% fractional bandwidth. The presented design approach simplifies evanescent-mode filter fabrication, eliminating the need for micromachining and vias, and achieving a total weight of 1.97 g. The design is fabricated to provide a proof-of-principle for the high-Q resonator and filter that compromises between performance, cost, size, and complexity. A stacked version of the two-pole filter is presented to provide a novel design for multi-layer embedded applications. The fabrication is performed using an nScrypt Tabletop 3Dn printer. Acrylonitrile Butadiene Styrene (ABS) (relative permittivity of 2.7 and loss tangent of 0.008) is deposited using fused deposition modeling to form the antenna, array, resonator, and filter structures, and Dupont CB028 silver paste is used to form the conductive traces conductive regions (the paste is dried at 90 °C for 60 minutes, achieving a bulk DC conductivity of 1.5×106 S/m.). A 1064 nm pulsed picosecond Nd:YAG laser is used to laser machine the resonator and filter input and output feedlines.
532

Design de estrutura biônica através de prototipagem e análise por elementos finitos baseada em microtomografia do bambu

Palombini, Felipe Luis January 2016 (has links)
O bambu é considerado um dos materiais naturais com a melhor relação resistência por peso. Entre as características responsáveis encontram-se os feixes fibrosos do esclerênquima, que protegem os elementos de condução de água e solutos na planta, além de serem preenchidos pelo parênquima. Os feixes estão distribuídos gradual-mente, da parte interna à externa do bambu, aumentando a rigidez do colmo. Contudo, a morfologia da seção dos feixes fibrosos e a presença da matriz parenquimática no caule ainda não foram totalmente estudados, quanto à sua importância estrutural, nem aplicados em estruturas biônicas. Esse estudo trata do design de estruturas biônicas baseada na caracterização do bambu, por meio de técnicas não-invasivas, de proto-tipagem e de análise por elementos finitos. Um protocolo de amolecimento e secagem para secionamento foi seguido em uma amostra de bambu (Bambusa tuldoides Munro). A superfície da amostra foi analisada por microtomografia computadorizada de raios X de alta resolução. As imagens resultantes permitiram a segmentação dos tecidos constituintes e caracterização em nível celular. Os modelos 3D do parênquima e do esclerênquima foram discretizados para uma análise por elementos finitos não-linear. Os resultados mostraram que o parênquima é configurado como uma matriz celular de baixa densidade e que distribui as tensões em todos os elementos de re-forço na planta, sendo considerado um tecido com importante função estrutural. De mesmo modo, a geometria da seção dos feixes fibrosos apresentou um desempenho mecânico superior às seções referenciais. Ambas características foram aplicadas no desenvolvimento de duas estruturas biônicas, sendo analisadas como mais eficientes em comparação a um modelo da literatura, e impressas em 3D para análise visual. / Bamboo is considered one of the natural materials with the best strength-to-weight ratio. Among the features responsible for its properties are the sclerenchyma’s fiber bundles that protect the conducting elements of water and solutes in the plant, and are filled by parenchyma. Bamboo fibers are gradually distributed from the inner to the outer side of the plant, thus increasing the culm stiffness. However, the morphology of the section of the fiber bundles and the presence of the parenchymatic matrix in the stem have not been fully studied regarding its structural importance, neither applied in bionic structures. This study addresses the design of bionic structures based on the characterization of bamboo, by means of non-invasive techniques, rapid prototyping and finite element analysis. A bamboo sample (Bambusa tuldoides Munro) was col-lected and softening and drying protocols were followed for proper sectioning. The surface of the sample was analyzed by high-resolution X-ray microcomputed tomog-raphy. Resulting images allowed the segmentation of the sample’s constituent tissues and the characterization at a cellular level. The 3D models of the parenchyma and sclerenchyma were discretized for a non-linear finite element analysis. The results showed that the parenchyma is set as a low-density cellular matrix by distributing the stresses among all reinforcement elements in the plant, being considered a tissue with great structural importance. Likewise, the shape of the fiber bundles’ section showed superior mechanical performance compared to reference sections. Both characteris-tics were applied in the development of two bionic structures that were analyzed as more efficient than a literature model, and 3D printed for a visual analysis.
533

Contribution au potentiel de la fabrication additive dans la construction : Proposition d’une formulation cimentaire imprimable / Contribution to the potential of Additive Manufacturing : On the development of a printable cement based material.

Krimi, Imane 08 December 2017 (has links)
La fabrication additive (Impression 3D) consiste à fabriquer des objets couche par couche en utilisant un modèle 3D, un matériau approprié et une machine dédiée. Pour la construction, c’est un nouveau mode constructif qui se profile. Depuis 2010, la fabrication additive a fait un saut technique et médiatique dans ce secteur. Les projets d’impression 3D se sont multipliés et diversifiés avec les premières maisons construites entièrement au moyen de cette technologie (Winsun, D-Shape, Contour Crafting, Apis Cor…etc). Ce travail s’inscrit dans le cadre d’une thèse CIFRE démarrée en 2015 entre le laboratoire de génie civil de l’Ecole Centrale de Lille et l’entreprise Bouygues Construction. L’objectif de ce travail est d’étudier le potentiel de la fabrication additive pour la construction et plus précisément de proposer une formulation à matrice cimentaire qui sera mise en œuvre par impression 3D.La thèse est organisée en trois grandes parties.La première partie est consacrée à la définition de l’impression 3D et des matériaux cimentaires pour définir leurs interactions. La deuxième partie est dédiée à la formulation d’un matériau cimentaire imprimable. L’imprimabilité a été définie par trois indicateurs : l’extrudabilité, la buildabilté et l’adhérence. La troisième partie est destinée à la validation de la formulation proposée. Ce travail peut être considéré comme une première approche pour définir un protocole d’évaluation de l’imprimabilité des matériaux cimentaires à l’échelle du laboratoire ainsi qu’une première étape pour la conception d’une imprimante 3D destinée et adaptée à la construction. / Additive Manufacturing (3D printing) consists in building an object layer by layer following a 3D model. For this purpose an appropriate material, machine and model are needed. From Construction industry point of view, 3D printing is considered as a new building method. Since 2010, the use of 3D printing for construction has known a large evolution. More and more real construction projects are using this new technology. Some of these examples are Winsun in China, D-Shape in Italy, Contour Crafting in California or Apis Cor in Russia…etc.The work presented in this manuscript was conducted through an industrial PhD thesis (CIFRE) which was launched between “Ecole Centrale de Lille” and “Bouygues Construction” in 2015. The objective of this work was to study the potential of large scale 3D printing integration in the construction process and more precisely the development of a printable cement based mix design.The work is organized in three main parts.The first part was dedicated to 3D printing and cement based material as general concepts. Then their interactions were analyzed. The second part was devoted to the printable mix design. The printability was defined using three indicators: Extrudability, Buildability and layers adhesion. The third part was dedicated to check the printability of the proposed mix design. This work may be considered as a first approach to define a laboratory scale methodology for cement based materials printability testing. It is also a step to contribute to the development of construction 3D printers.
534

Um processo para utilizar a tecnologia de impressão 3D na construção de instrumentos didáticos para o ensino de Ciências / A process to use the 3D printing technology in the building of educational tools for Science teaching

Aguiar, Leonardo De Conti Dias [UNESP] 23 February 2016 (has links)
Submitted by LEONARDO DE CONTI DIAS AGUIAR null (leonardodeconti@feb.unesp.br) on 2016-04-09T17:29:03Z No. of bitstreams: 1 Um processo para utilizar a tecnologia de impressão 3D na construção de instrumentos didáticos para o ensino de ciências.pdf: 8779312 bytes, checksum: c2f9f1bb85c39f2ff84434217d4f73fe (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-04-12T14:30:16Z (GMT) No. of bitstreams: 1 aguiar_ldcd_me_bauru.pdf: 8779312 bytes, checksum: c2f9f1bb85c39f2ff84434217d4f73fe (MD5) / Made available in DSpace on 2016-04-12T14:30:16Z (GMT). No. of bitstreams: 1 aguiar_ldcd_me_bauru.pdf: 8779312 bytes, checksum: c2f9f1bb85c39f2ff84434217d4f73fe (MD5) Previous issue date: 2016-02-23 / Esta dissertação trata de uma pesquisa empírica sobre a utilização da tecnologia de impressão 3D na construção de instrumentos didáticos para o Ensino de Ciências. A crescente disponibilidade da tecnologia de impressão 3D abriu oportunidades de explorações em novas áreas, como a educação. Considerando as oportunidades de uso dessa tecnologia para a criação de materiais didáticos, este trabalho mostra como tal tecnologia pode ser utilizada por professores em formação e professores em serviço. Desta forma, um processo prático foi proposto e avaliado por meio de uma oficina. O processo consiste em 6 etapas distintas: identificação das necessidades de ensino por meio da seleção de conteúdos e conceitos científicos; desenvolvimento do plano de construção do instrumento didático desejado; elaboração de rascunhos considerando as dimensões físicas do objeto a ser construído; modelagem 3D do objeto utilizando softwares de desenho ou buscando por modelos prontos; preparação e impressão do modelo 3D na impressora 3D; utilização e avaliação do objeto real gerado. Esse processo foi apresentado e ensinado para alunos de licenciatura construírem instrumentos didáticos em uma oficina. A análise dos dados coletados nessa oficina por meio de observações, entrevistas e questionários mostram que: o processo pode guiar sobre quais são os passos a serem percorridos para construir instrumentos didáticos utilizando impressoras 3D; ocorrem situações estimuladoras ao aprendizado durante as construções; o uso desta tecnologia pode colaborar com o desenvolvimento da instrumentação para o Ensino de Ciências. Concluiu-se que, para se realizar o uso dessa tecnologia, é preciso que o professor desenvolva novas habilidades, como: planejar a construção de objetos levando em conta restrições técnicas das impressoras 3D, aprender a desenhar em softwares de modelagem 3D, preparar o modelo 3D para que a impressora 3D o construa (etapa denominada fatiamento) e a utilizar recursos informacionais para compartilhar e reutilizar modelos 3D de instrumentos didáticos criado por outras pessoas. Essa pesquisa contribui com o Ensino de Ciências, uma vez que: fornece uma forma sistemática para utilização da tecnologia de impressão 3D na educação; acrescenta novo conhecimento sobre o tema em uma área onde a literatura é escassa; abre oportunidades para que o conhecimento gerado por meio dos instrumentos didáticos construídos utilizando o processo proposto possa ser compartilhado com outros professores. / This thesis is an empirical research on the use of 3D printing technology in the construction of didactic tools for science teaching. The growing availability of 3D printing technology has opened exploration opportunities in new areas such as education. Considering the opportunities of this technology for the creation of teaching materials, this study shows how such technology can be used in the teacher education and by teachers in service. So, a practical process was proposed and evaluated by its use in a workshop. The process consists in 6 distinct stages: identification of educational needs through the selection of scientific content and concepts; development of the construction plan of the desired teaching tool; preparation of drafts considering the physical dimensions of the object to be built; 3D modeling of the object using drawing software or searching for 3D models created by others; preparation and printing of the 3D model in the 3D printer; use and evaluation of the real object generated. This process was presented and taught for undergraduate students for them build didactic tools during a practical workshop. The analysis of the collected data in this workshop through observations, interviews and questionnaires show that: the process can guide on which are the steps to be taken to build teaching tools using 3D printers; during the constructions occurs situations that stimulate the learning; the use of this technology can contribute to the development of instrumentation for Science Teaching. It was concluded that to do the use of this technology, it is required that the teacher develop new skills, such as planning the construction of objects taking into account technical constraints of 3D printers, learn to draw in 3D modeling software, prepare the 3D model to the 3D printer build it (step called slicing) and use IT resources to share and reuse 3D models of didactic tools created by others. This research contributes to the Teaching of Science, because: it provides a systematic way to use 3D printing technology in education; adds new knowledge on the subject in an area where the literature is scarce; It opens opportunities for knowledge generated through the teaching tools built using the proposed process can be shared with other teachers.
535

Modelo computacional de descrição de projetos para impressão de biosistemas

Francisco, Luiz Angelo Valota 24 March 2016 (has links)
Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-10-10T20:31:55Z No. of bitstreams: 1 DissLAVF.pdf: 2396434 bytes, checksum: d18db543d45b99a8efd280285db823b0 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-21T12:05:36Z (GMT) No. of bitstreams: 1 DissLAVF.pdf: 2396434 bytes, checksum: d18db543d45b99a8efd280285db823b0 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-21T12:05:43Z (GMT) No. of bitstreams: 1 DissLAVF.pdf: 2396434 bytes, checksum: d18db543d45b99a8efd280285db823b0 (MD5) / Made available in DSpace on 2016-10-21T12:05:51Z (GMT). No. of bitstreams: 1 DissLAVF.pdf: 2396434 bytes, checksum: d18db543d45b99a8efd280285db823b0 (MD5) Previous issue date: 2016-03-24 / Não recebi financiamento / Currently, there are several studies directed to the manufacture of biosystems (biomaterials, living tissues or organs). These studies include several practice areas ranging from virtual representation of an organ or tissue to its biomanufacturing (bioprinting) itself. But for biomanufacturing a complex organ, it is still needed a long walk, because this process requires a very large wealth of information. Experiments to aid in surgical planning have been made based on medical image data and use of 3D printer rapid prototyping through STL specifications (STereoLitography). This work aims the study biomanufacturing processes of biomaterials, living tissues and organs aiming to establish the requirements for building a computer model to assist in the development of a project description framework for bioprinting living tissues and organs via STL specifications. This model was designed through research processes and parameters required for bioprinting of living tissues or organs resulting from the state of the art in this area and forms of representation in a computer model. For the evaluation of the model and the developed framework, an experiment was conducted where the data of a cartilage bioprinting experiment conducted by other authors were expressed through a bioprinting project. / Atualmente, existem vários estudos voltados para a fabricação de biosistemas (biomateriais, tecidos vivos ou órgãos). Esses estudos contemplam várias áreas de atuação que vão desde a representação virtual de um órgão ou tecido até a sua biofabricação (bioimpressão) propriamente dita. Porém, para a biofabricação de um órgão complexo, ainda é necessária uma longa caminhada, pois esse processo exige uma riqueza muito grande de informações. Experimentos para auxilio em planejamento cirúrgico têm sido feitos baseados em dados de imagens médicas e uso de impressoras 3D de prototipagem rápida, através de especificações STL (STereoLitography). Este trabalho, tem como objetivo, o estudo de processos de biofabricação de biomateriais, tecidos vivos e órgãos visando, estabelecer os requisitos necessários para a construção de um modelo computacional que auxilie no desenvolvimento de um framework de descrição de projetos para bioimpressão de tecidos vivos e órgãos por intermédio de especificações STL. Esse modelo foi concebido através da investigação de processos e parâmetros necessários para a bioimpressão de tecidos vivos ou órgãos, decorrentes do estado da arte nessa área e das formas de sua representação em um modelo computacional. Para a avaliação do modelo e do framework desenvolvido, foi realizado um experimento onde os dados de um experimento de bioimpressão de cartilagem realizado por outros autores foram expressados através de um projeto de bioimpressão.
536

Design de estrutura biônica através de prototipagem e análise por elementos finitos baseada em microtomografia do bambu

Palombini, Felipe Luis January 2016 (has links)
O bambu é considerado um dos materiais naturais com a melhor relação resistência por peso. Entre as características responsáveis encontram-se os feixes fibrosos do esclerênquima, que protegem os elementos de condução de água e solutos na planta, além de serem preenchidos pelo parênquima. Os feixes estão distribuídos gradual-mente, da parte interna à externa do bambu, aumentando a rigidez do colmo. Contudo, a morfologia da seção dos feixes fibrosos e a presença da matriz parenquimática no caule ainda não foram totalmente estudados, quanto à sua importância estrutural, nem aplicados em estruturas biônicas. Esse estudo trata do design de estruturas biônicas baseada na caracterização do bambu, por meio de técnicas não-invasivas, de proto-tipagem e de análise por elementos finitos. Um protocolo de amolecimento e secagem para secionamento foi seguido em uma amostra de bambu (Bambusa tuldoides Munro). A superfície da amostra foi analisada por microtomografia computadorizada de raios X de alta resolução. As imagens resultantes permitiram a segmentação dos tecidos constituintes e caracterização em nível celular. Os modelos 3D do parênquima e do esclerênquima foram discretizados para uma análise por elementos finitos não-linear. Os resultados mostraram que o parênquima é configurado como uma matriz celular de baixa densidade e que distribui as tensões em todos os elementos de re-forço na planta, sendo considerado um tecido com importante função estrutural. De mesmo modo, a geometria da seção dos feixes fibrosos apresentou um desempenho mecânico superior às seções referenciais. Ambas características foram aplicadas no desenvolvimento de duas estruturas biônicas, sendo analisadas como mais eficientes em comparação a um modelo da literatura, e impressas em 3D para análise visual. / Bamboo is considered one of the natural materials with the best strength-to-weight ratio. Among the features responsible for its properties are the sclerenchyma’s fiber bundles that protect the conducting elements of water and solutes in the plant, and are filled by parenchyma. Bamboo fibers are gradually distributed from the inner to the outer side of the plant, thus increasing the culm stiffness. However, the morphology of the section of the fiber bundles and the presence of the parenchymatic matrix in the stem have not been fully studied regarding its structural importance, neither applied in bionic structures. This study addresses the design of bionic structures based on the characterization of bamboo, by means of non-invasive techniques, rapid prototyping and finite element analysis. A bamboo sample (Bambusa tuldoides Munro) was col-lected and softening and drying protocols were followed for proper sectioning. The surface of the sample was analyzed by high-resolution X-ray microcomputed tomog-raphy. Resulting images allowed the segmentation of the sample’s constituent tissues and the characterization at a cellular level. The 3D models of the parenchyma and sclerenchyma were discretized for a non-linear finite element analysis. The results showed that the parenchyma is set as a low-density cellular matrix by distributing the stresses among all reinforcement elements in the plant, being considered a tissue with great structural importance. Likewise, the shape of the fiber bundles’ section showed superior mechanical performance compared to reference sections. Both characteris-tics were applied in the development of two bionic structures that were analyzed as more efficient than a literature model, and 3D printed for a visual analysis.
537

Towards a Democratisation of Digital Fabrication

Nihlwing, Victor January 2018 (has links)
Digital fabrication technologies such as 3D printing is predicted to have a significant impact on our future society. However, the complexity of current 3D modelling softwares  risk deterring novices from engaging with the technology. In this thesis, a series of workshops were conducted to explore the implications for novices to create models out of tangible materials such as clay, paper and LEGO, that were then scanned and printed with a 3D printer. The results show that while the tangible materials create engaging opportunities for novices to engage with digital fabrication technologies such as 3D printing, the materials also provide limitations and constraints depending on their physical properties.
538

Estudo comparativo de auxiliares de audição obtidos com sistema CAD/CAM e com método convencional de pré-moldagem

Marques, Janaína Benício 25 January 2017 (has links)
Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2017-07-26T14:12:57Z No. of bitstreams: 1 PDF - Janaína Benício Marques.pdf: 14648505 bytes, checksum: d012b9258828a4761e4dc0c746b9ce9a (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2017-08-29T15:31:07Z (GMT) No. of bitstreams: 1 PDF - Janaína Benício Marques.pdf: 14648505 bytes, checksum: d012b9258828a4761e4dc0c746b9ce9a (MD5) / Made available in DSpace on 2017-08-29T15:31:07Z (GMT). No. of bitstreams: 1 PDF - Janaína Benício Marques.pdf: 14648505 bytes, checksum: d012b9258828a4761e4dc0c746b9ce9a (MD5) Previous issue date: 2017-01-25 / OBJECTIVE: To compare earmolds obtained by the CAD / CAM system and the conventional pre-molding method. METHODS: Comfort sensations and anthropometric measures were analyzed in 30 ears of 15 volunteers randomly selected from a private clinic in a Brazilian Northeast Municipality, who underwent two procedures to obtain measurements, a CT scan composing the case group and preforming, constituting the control group. After the preparation of the silicone earmolds, the physical test of the devices was performed by the blind study method, in which the participants were not aware of the origin of each mold. RESULTS: The concepts Regular (53.3%), Good (20%) and Bad (20%), in the control group prevailed, based on the self-perception of the participants, while in the method proposed by the biomodel the concepts Good (73.3%) and Optimum (26.7%). As for the anthropometric linear measurements per ear in each of the evaluation forms: Conventional Preform, Conventional Silicone, Biomodel and Mold proposed significant differences (p <0.05) were found between the evaluation forms in the variables "Intertragic Incision - Top border of the Shell "," Length of the socket "" Depth of External Acoustic Meatus "," Thickness of EAM "and" Volume "in each ear. The coefficient of standard deviation being less than half of the corresponding mean values.CONCLUSION: In view of the above, it is possible to obtain atrial molds from tomographic images with favorable results. / OBJETIVO: Comparar auxiliares de audição obtidos pelo sistema CAD/CAM e pelo método convencional de pré-moldagem. METODOLOGIA: Foram analisadas as sensações de conforto e medidas antropométricas em 30 orelhas de 15 voluntários escolhidos aleatoriamente de uma clínica particular de um município do Nordeste brasileiro, os quais foram submetidos aos dois processos de obtenção de medidas, exame de tomografia computadorizada compondo o grupo caso e pré-moldagem constituindo o grupo controle. Após a confecção dos moldes de silicone, a prova física dos dispositivos foi realizada pelo método do estudo cego, onde os participantes não tinham conhecimento acerca da origem de cada molde. RESULTADOS: Com base na avaliação de autopercepção dos participantes quanto à técnica de obtenção dos moldes prevaleceram, no grupo controle, os conceitos Regular (53,3%), Bom (20%) e Ruim (20%), enquanto no método proposto pelo biomodelo prevaleceram os conceitos Bom (73,3%) e Ótimo (26,7%). Quanto às medidas lineares antropométricas por orelha em cada uma das formas de avaliação: Pré-molde convencional, Silicone convencional, Biomodelo e Molde proposto foram verificadas diferenças significativas (p < 0,05) entre as formas de avaliação nas variáveis ―Incisura Intertrágica – Bordo superior da Concha‖, ―Comprimento do encaixe‖ ―Profundidade de Meato Acústico Externo‖, ―Espessura do MAE‖ e do ―Volume‖ em cada uma das orelhas. Estando o coeficiente de desvio padrão inferior a metade dos valores das médias correspondentes. CONCLUSÃO: Diante do exposto, verifica-se que é possível obter moldes auriculares a partir de imagens tomográficas com resultados favoráveis.
539

A Study of Digital RF Phase Shifters Fabricated With Additive Manufacturing

Vega, Yaniel 30 October 2015 (has links)
Digital RF phase shifters fabricated using additive manufacturing processes are presented and studied. The purpose is to explain the performance differences between phase shifters fabricated using additive manufacturing and those fabricated with conventional subtractive techniques. All phase shifters are designed to operate at a center frequency of 2.45 GHz with a 100 MHz bandwidth. The 1-bit 45° switched line phase shifters have an average insertion loss of 1.3 dB and a 220 mm2 footprint, while the 1-bit 180° high-pass low-pass phase shifters have an insertion loss 1.56 dB and a 180 mm2 footprint. The 4-bit high-pass low-pass, switched line hybrid phase shifters on the other hand show an average state insertion loss of 5.4 dB and have a 660 mm2 foot print. By carefully analyzing the performance of the various phase shifter designs it is shown that the limiting factors of additive manufacturing technology are the low conductivity of CB028 silver ink in comparison to copper, and the inability to print dielectrics with low surface roughness. Finally, parallel plate capacitors and a spiral inductor designed to be fabricated using additive manufacturing techniques are studied. This is done in order to better understand the advantages and disadvantages of such a design. By analyzing the component’s simulated performance it is shown that 3D printed capacitors and inductors are feasible as long as the capacitance or inductance values needed are low. Large value 3D printed components are impractical for RF applications due to their large size.
540

Design and additive manufacture for flow chemistry

Capel, Andrew J. January 2016 (has links)
This thesis aims to investigate the use of additive manufacturing (AM) as a novel manufacturing process for the production of milli-scale chemical reaction systems. Five well developed additive manufacturing techniques; stereolithography (SL), selective laser melting (SLM), fused deposition modelling (FDM), ultrasonic additive manufacture (UAM) and selective laser sintering (SLS) were used to manufacture a number of miniaturised flow devices which were tested using a range of organic and inorganic reactions. SL was used to manufacture a range of functioning milli-scale flow devices from Accura 60 photoresin, with both simple and complex internal channel networks. These devices were used to perform a range of organic and inorganic reactions, including aldehyde and ketone functional group interconversions. Conversion of products within these reactors, were shown to be comparable to commercially available milli-scale coil reactors. More complex designs, which allowed SL parts to be integrated to existing flow and analytical instrumentation, allowed us to develop an automated reaction analysis and optimisation platform. This platform allowed precise control over the reaction conditions, including flow rate, temperature and reagent composition. We also designed a simplex type reaction optimisation software package that could input data in the form of reaction conversions, peak intensities, and thermocouple data, and generate a new set of optimal reaction conditions. SL parts which incorporated embedded analytical components were also manufactured, which allowed us to perform inline reaction analysis as a feedback method for input into the optimisation platform. Stereolithography was shown to be a highly versatile manufacturing method for designing and producing these flow devices, however the process was shown to be still limited by the range of processable materials currently commercially available. SLM was also used to manufacture a number of functioning milli-scale flow devices from stainless steel and titanium, which had simplistic internal channel designs of diameters ranging from 1 to 3 mm. Again, SLM parts were manufactured which incorporated embedded analytical components, which could be integrated into an automated reaction platform. These devices, unlike parts produced via SL, could be attached to heating platforms to allow us to perform high temperature reactions. This control over the reaction temperature formed an essential part of the reaction optimisation platform. These parts were again used to perform a ketone functional group interconversion. Internal structures of these SLM parts were also visualised via micro computed tomography (μCT or microCT) scanning as well as optical microscopy. FDM was used throughout the project as an inexpensive method of prototyping parts which were to be manufactured via more expensive manufacturing processes. This prototyping allowed the optimisation of intricate design features, such as the manufacture of an inline spectroscopic flow cell for integration with a commercially available LC system. FDM was also proposed as a customisable approach to designing and manufacturing flow devices with embedded components, however the current limitations in build resolution and materials choices severely limited the use of FDM for this application. UAM was also proposed as a novel manufacturing process whereby the build process would allow discrete components to be embedded directly into a flow channel. This was demonstrated by embedding a type-k thermocouple across a 2 mm channel. The data from this thermocouple was monitored during a heated reaction, and used as a method of determining the exact reaction conditions the reaction medium was being exposed to. SLS was also proposed as a possible manufacturing method for milli-scale flow devices, however it proved difficult to remove un-sintered powder from parts with internal channel diameters as high as 5 mm. It was shown that this powder was forming a dense semi solid, due to the large degree of shrinkage upon cooling of the SLS parts, which was compressing the powder. More research into optimum processing conditions is required before SLS could be used for the production of intricate channel networks.

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