Orientador: Vitor Baranauskas / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T22:24:59Z (GMT). No. of bitstreams: 1 Degasperi_FranciscoTadeu_D.pdf: 5413263 bytes, checksum: 7251a00fbc05d996c38d70e8417d16ae (MD5) Previous issue date: 2006 / Resumo: O principal objetivo deste trabalho foi contribuir para o cálculo, análise e modelagem de sistemas de vácuo de uso geral. As contribuições ocorreram na criação, desenvolvimento e aprimoramento de ferramentas matemáticas tanto analíticas como numéricas para modelar e analisar detalhadamente sistemas de vácuo. Foram consideradas duas maneiras de modelar sistemas de vácuo, denominadas de formulação discreta e contínua. Na formulação discreta os sistemas de vácuo são tratados de modo que a pressão em função do tempo na câmara de vácuo pode ser obtida a partir de especificações das fontes de gases e vapores, das dimensões da linha de bombeamento e das bombas de vácuo. Foram considerados nos cálculos e nas modelagens os quatro regimes de escoamento presentes nos sistemas de vácuo em geral. Foram também consideradas em detalhe as condutâncias e as fontes gasosas importantes para processos em vácuo em geral, além de obtidas as expressões matemáticas para as curvas de velocidade de bombeamento das bombas de vácuo comumente utilizadas em circuitos de vácuo. Foram utilizados nas análises numéricas os métodos de Euler-Heun e Runge-Kutta de segunda e quarta ordens. Na formulação contínua os sistemas de vácuo foram modelados de forma que a pressão possa ser determinada em todas as suas partes e em função do tempo. Foram obtidas as equações de difusão para sistemas de vácuo unidimensionais, bidimensionais e tridimensionais estacionários e transientes. Foram estudados em detalhe e exemplificados sistemas de vácuo por meio das formulações discreta e contínua. Sistemas de vácuo com geometrias tubulares e planares foram modelados com o estabelecimento preciso das definições das grandezas condutância específica e throughput específico para as fontes de gases e condições de contorno pertinentes à descrição a partir de equações diferenciais parciais. Para exemplificar os conceitos e abordagens desenvolvidas, foram tratados de casos realísticos encontrados em laboratórios e na indústria / Abstract: The main propose of this work is to toward in modeling of general vacuum systems. In addition, the aims of this work are to create, develop and improve analytic and numerical mathematical tools in order to model and to analyze vacuum systems in detail. Two different modeling ways to vacuum systems have been considered, denoted discrete and continuum formulations. In the discrete formulation the vacuum systems are treated in a way such that inside the vacuum chamber the pressure as a function of time can be obtained from the specification of the gas and vapor sources, from the pumping line dimensions and from the choice of the vacuum pumps. The conductance and the gas sources were considered important to vacuum processes in general besides the mathematical expressions obtained to pumping speed curves of the vacuum pumps. The numerical analysis was done through the Euler-Heun and the Runge-Kutta of second and fourth order methods. In the continuum formulation the vacuum systems were modeled in a way such that the pressure can be determined in all parts and as a function of the time. To perform this modeling were defined specific conductance and specific throughput to general gas sources. Vacuum systems with one-dimension or tubular forms and two-dimensions or planar forms were studied in detail and exemplified with the definitions of the quantities and the appropriate partial differential equations boundary conditions. The concepts, definitions and approach were applied in realistic cases, with typical laboratory and industry dimensions / Doutorado / Eletrônica, Microeletrônica e Optoeletrônica / Doutor em Engenharia Elétrica

The vacuum system of the Van de Graaff generator is described. Techniques in the construction of the high voltage vacuum tubes are indicated. The required performance of the system and the methods of attaining it are outlined, calculations being given in the Appendices. Vacuum pressure gauges are described and the indicated performance of the system recorded. Vacuum protection circuits are discussed. Methods of leak detection are discussed and the University of British Columbia mass spectrometer leak detector described in detail. The theory of analysis by a spectrometer with a coterminous crossed electric and magnetic field is given. An operating procedure for the spectrometer is described in detail and some results recorded and discussed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The objectives of this thesis are to characterize the plasma environment of a new vacuum chamber facility at Virginia Tech and to perform initial measurements of plasma flow field for studying spacecraft-plasma interactions using this facility. An argon plasma environment was created using a hot filament cathode plasma source. Flange plates attached to the sides of the vacuum chamber were modified in order to attach various feedthroughs both now and in the future such that a probe array DAQ system could be used to expedite measurement and analysis. A Langmuir probe array was used to measure 3-D plasma flow field in the chamber. A Matlab code was developed for automatic evaluation of the Langmuir probe traces. Two sets of measurements were preformed. The first measurement characterizes the plasma produced by the hot filament cathode in the chamber. Langmuir Probes were used to characterize the plasma environment yielding the following average characteristics: Plasma Potential = 5.5486V, Electron Saturation Current = 0.003421A, Electron Temperature = 1.505eV, and the Plasma Density = 6.806*10^14 m^-3. It was found that for both the spherical and cylindrical probes used in the test facility Rs > Debye length and thus were analyzed under the thin sheath condition. The second measurement attempts to measure the 3-D plasma flow field for plasma flow over a structure composed of 4-inch biased Al box sitting on a biased Al plate. The results show signs of the the generation of the expansion pre-sheath structure at the leading edge of the plate and the box upper surface predicted by numerical models. However, the current diagnostics system does not have the spatial resolution and range as well as the data accuracy required to reach a definitive measurement of plasma presheath and plasma wake. / Master of Science

Vacuum forming is a popular, cost effective method amongst large and small scale applications. The method is used to mold a material to the surface of a mold/pattern in order to create a negative copy for reproduction or an object in positive form. The prototype vacuum forming system developed and documented herein is of a membrane-seal type that consists of three (3) principle parts: radial platen, Hinged Frame and Platen Support Assembly, and a PVC surge tank. Each part is described in detail through design, manufacturing, and testing processes. The design supports functional versatility, small scale molding, and uses readily available materials. Functional prototype testing was performed with the thermoplastic KYDEX® and multiple objects for mold examples. Results include successful proof of concept, design pros and cons, and findings based on functional testing.

Made available in DSpace on 2015-05-08T15:00:03Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 6635361 bytes, checksum: 14da0b5d0e9d4fb2821cb495e6d9fcfa (MD5) Previous issue date: 2010-08-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents the state of the in vacuum technology which covers the fundamentals, devices for generating, measuring and major applications in precision engineering. Also, the design and development of vacuum tables applied to machine tool is shown. With regard to fundamentals, it is described the historical background, classical theories and classification of this technology by bands of applications. It is shown most widely used vacuum generators and gauges, showing their construction, operation and applications within various areas. Applications of vacuum technology in precision engineering that span the macro, micro and nano scales are presented, highlighting their importance in each application area. In addition, a methodology to design and development of vacuum tables to fixture workpieces in machine tools, is described and applied. The development of this methodology was motivated due lack of technical and scientific articles that concern the studies on vacuum tables with emphasis on its design parameters. In this work, vacuum tables with hollow, square and hexagonal cores were analyzed by considering two different magnitudes of machining forces. The displacement and stress that each vacuum table configuration is submitted were determined by using numeric simulation based on the finite element method for both machining conditions. / O presente trabalho trata do resgate da literatura sobre a tecnologia do vácuo englobando os seus fundamentos básicos, dispositivos de geração, medição e o estado da arte em aplicações na área de engenharia de precisão seguido de um projeto e desenvolvimento de mesas de vácuo aplicadas em máquinas-ferramenta. Com relação aos fundamentos, é descrito o seu contexto histórico, teorias clássicas e classificação desta tecnologia por faixas de aplicações. É mostrado os geradores e medidores de vácuo mais utilizados evidenciando a sua construção, funcionamento e aplicações dentro das mais variadas áreas. São apresentadas aplicações na engenharia de precisão que abrangem as escalas macro, micro e nano, ressaltando a importância da tecnologia do vácuo em cada aplicação. No projeto e desenvolvimento de mesas de vácuo, é descrita e aplicada uma metodologia própria que consiste em dimensionar mesas de vácuo capazes de fixar peças mediante a usinagem em máquinas-ferramenta. O desenvolvimento desta metodologia foi motivada em função da carência de artigos técnicos e científicos que concernem os estudos sobre mesas de vácuo dando ênfase aos seus parâmetros de projetos. São dimensionadas mesas de vácuo com núcleos vazados, quadrado e hexagonal em função de duas condições de usinagem que utilizam diferentes magnitudes de forças. Por meio de simulação numérica computacional, são avaliados os esforços de deslocamento e tensão em cada mesa de vácuo dimensionada, de forma a eleger uma mesa que atenda a critérios de rigidez, peso e homogeneização do fluxo de vácuo para cada magnitude de forças de usinagem.

No description available.

Vacuum assisted delivery (VAD) is a common procedure used in the final stage of labor in the situation of a difficult natural delivery. Since the only biomechanical studies concerning the clinical safe traction force were conducted during 70s using simplified models to mimic the fetal head, concerns remain regarding the side effects of this medical intervention when applying high levels of traction forces. For experimental evaluation of VAD, a tissue-mimicking accurate fetal head phantom, having the same skull and brain dimension as a newborn, as well as, proper mechanical and acoustic properties of materials, can be used as a useful resource in terms of establishing safe levels of traction forces. The goal of this project is to develop a realistic patient-specific fetal head phantom that will be used to investigate the relation between applied traction force and imposed brain deformation in VAD in an experimental setting. A realistic fetal head phantom was developed using geometry accurate segmented meshes of pediatric skull and brain from a CT fetal head dataset. The fetal skull was 3D printed while the segmented mesh of the brain was used to create a fetal brain mold. The fetal brain phantom was developed using a PVA and graphite solution (10% and 3% mass concentration), whereas the sutures and fontanels, the scalp and the cerebrospinal fluid were mimicked using silicone, surgical latex and water, respectively. All the tissue-mimicking materials used corresponded with the biomechanical properties of the fetal head tissues. After the construction of the fetal head phantom, grey-scale long- and short- axis ultrasound images as well as the fetal brain phantom elasticity map were obtained. Furthermore, using sonomicrometry crystals, the reference strain values during manual hand pressure and VAD experimental procedures were acquired. The results showed negative strain values (compression) reaching 15% in the manual pressure experimental procedure, and higher positive strain values (stretching) reaching over 40% in the VAD experimental procedure. However, due to experimental limitations only one measurement using clinically realistic levels for both vacuum pressure (65 kPa) and traction force (70 N) was achieved. The developed fetal head phantom has potential to provide trustful biomechanical evidence to guide safe vacuum assisted delivery as well as to provide useful resource in terms of defining the clinical effective force of the vacuum extractor (VE). / I slutskedet av svåra vaginala förlossningar är assistans med sugklocka vanligt förekommande. Eftersom de enda biomekaniska studierna om kliniskt säkra dragkrafter genomfördes under 70 -talet med hjälp av förenklade modeller för att efterlikna fostrets huvud, finns det fortfarande oro om vilka skador användandet av sugklocka kan leda till när höga dragkrafter används. För att kunna fastställa en säker nivå av dragkrafter skulle en modell av fosterhuvudet, med realistiska dimensioner samt liknande mekaniska och akustiska egenskaper som en nyfödd, kunna användas.  Målet med detta projekt är att utveckla en realistisk patientspecifik modell av fosterhuvudet och sedan använda den för att experimentellt undersöka sambandet mellan applicerad dragkraft och hjärndeformation.  En realistisk fosterhuvudsmodell utvecklades från segmenterade datortomografibilder på ett fosterhuvud. Skallbenet tillverkades med en 3D-skrivare medan hjärnans gjöts i PVA och grafit (10% och 3% masskoncentration) i en 3D-utskriven form. Suturerna och fontanellerna, skalpen och cerebrospinalvätskan efterliknades med silikon, kirurgisk latex respektive vatten. Alla vävnadsimiterande material som användes motsvarade de biomekaniska egenskaperna hos ett fosters huvud.  När modellen var färdigkonstruerad togs ultraljudsbilder i gråskala i både lång- och kortaxel. Även hjärnmodellens elasticitet mättes med ultraljudsbaserad skjuvvågselastografi. Sonomikrometri –kristaller användes för att samla in referensvärden på hjärndeformation vid manuellt handtryck och experimentell rekonstruktion av förlossning med sugklocka. Resultaten visade att negativ deformation (kompression) på 15% i experimentella rekonstruktionen av förlossning. På grund av experimentella begränsningar uppnåddes dock endast en mätning med kliniskt realistiska nivåer för både vakuumtryck (65 kPa) och dragkraft (70 N).  Den utvecklade fosterhuvudsmodellen har i vidare studier potential att tillhandahålla tillförlitliga biomekaniska bevis för att vägleda säker vakuumassisterad förlossning samt för att definiera kliniska effektiva krafter i en sugklocka.

Call number: LD2668 .T4 1958 M17

Published Article / This article looks at the role that vacuum casting plays in the rapid prototyping and rapid manufacturing process. The accuracy to which components can be reproduced, by looking at the controllable factors in the casting process and the different types of materials that are available, were investigated and the process was also compared to other rapid prototyping and manufacturing processes in terms of cost effectiveness. Castings were made from a typical component under different operating conditions and the characteristics of the cast component, dimensions strength and surface hardness, were measured and plotted to determine the characteristics and accuracy of the process.

No description available.