• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 7
  • 3
  • 1
  • Tagged with
  • 12
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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.
1

Synthesis and Pyrolysis of Benzoic3,5- Dimethyl-2-furoic Anhydride and 4-Quinolylmethyl Benzoate

LIN, CHI-CHENG 13 July 2000 (has links)
Synthesis and Pyrolysis of Benzoic3,5- Dimethyl-2-furoic Anhydride and 4-
2

[The analysis, design, and construction of a millimeter-wave reflex oscillator

Lafferty, J. M. January 1900 (has links)
Thesis - University of Michigan. Bibliographical footnotes. / Pt. 1 reprinted from Journal of applied physics, v. 17, no. 12, Dec. 1946, pts. 2 and 3 from Proceedings of the Institute of Radio Engineers, v. 35, no. 8, Aug. 1947 and v. 35, no.9, Sept. 1947.
3

Análise, cálculo e modelagem do sistema a vácuo / Analysis, calculation and modeling of the vacuum system

Silva, André 03 September 2018 (has links)
Submitted by Repositorio Tarefa (tarefarepositorio@gmail.com) on 2018-09-11T00:11:40Z No. of bitstreams: 2 TituloDeniseIlidio.pdf: 10074 bytes, checksum: 051a02493cf99b99197f680aeebab230 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-09-11T00:11:40Z (GMT). No. of bitstreams: 2 TituloDeniseIlidio.pdf: 10074 bytes, checksum: 051a02493cf99b99197f680aeebab230 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-09-03 / This paper deals with the analysis, calculation and modeling of the vacuum system / Este trabalho trata sobre a análise, o cálculo e a modelagem do sistema a vácuo
4

Ultrahigh Vacuum Studies of the Kinetics and Reaction Mechanisms of Ozone with Surface-Bound Fullerenes

Davis, Erin Durke 30 November 2011 (has links)
Acquiring in depth knowledge of the ozone oxidation of surface-bound fullerenes advances the understanding of fullerene fate in the environment, as well as the reactivity of ozone with carbonaceous nanomaterials. Recent ultrahigh vacuum studies of the reaction of gasphase ozone with surface-bound fullerenes have made it possible to observe the formation and subsequent thermal decomposition of the primary ozonide (PO). As the use of nanomaterials, such as C₆₀, continues to increase, the exposure of these molecules to humans and the environment is of growing concern, especially if they can be chemically altered by common pollutants. These experiments are made possible by combining ultrahigh vacuum surface analysis techniques with precision dosing using a pure O₃ gas source. The experimental setup also provides the capability of monitoring surface-bound reactants and products in situ with reflection-absorption IR spectroscopy, while gas-phase products are detected with a mass spectrometer. Our results indicate that ozone adds across a 6/6 bond on the C₆₀ cage, forming an unstable intermediate, the primary ozonide. The observed initial reaction probability for the PO is γ = 4.1 x 10⁻³. Energies of activation for the formation and decomposition of the PO were obtained via temperature-dependent studies. After formation, the primary ozonide thermally decomposes into the Criegee Intermediate which can rearrange or, upon further exposure to ozone, react with another ozone molecule to form a variety of products such as carbonyls, anhydrides, esters, ethers, and ketenes. Larger fullerenes (C₇₀, C₇₆, C₇₈, and C₈₄) were also exposed to gas-phase ozone, in order to observe the reaction rate for ozonolysis and to propose an initial mechanism for ozone exposure. The results indicate that the structure of the fullerenes has little to no impact on the rate of oxidation via ozone. Lastly, Terbium endohedral were exposed to ozone, in an effort to determine whether ozone was capable of oxidizing both the outer fullerene cage, as well as the Tb atom sequestered inside. The preliminary XPS data suggests ozone oxidizes both within an hour of continuous exposure. Understanding this atmospherically-relevant reaction from both a mechanistic and kinetic standpoint will help predict the environmental fate of fullerenes and their oxides. / Ph. D.
5

Desenvolvimento de método para medida de permeabilidade superficial de revestimentos de argamassa. / Development of method for measuring the surface permeability of coating mortar.

Sentone, Daniel Tourinho 25 May 2011 (has links)
O fenômeno de permeabilidade refere-se à capacidade com que um fluido é transportado através de um meio poroso, impulsionado por gradiente de pressão entre material e meio externo. Agentes de degradação são conduzidos ao interior de argamassas e concretos impelidos através desse tipo de fenômeno. Por isso, considera-se a permeabilidade como um dos principais parâmetros referentes à durabilidade e vida útil de materiais cimentíceos. Além disso, como esse tipo de avaliação está relacionada às condições estruturais dos vazios capilares de meios porosos, esse tipo de medida pode prover um indicativo das condições da estrutura porosa das argamassas no momento do ensaio, servindo ainda como método de controle de qualidade e avaliação dos processos de produção. Portanto, um novo procedimento de medida de permeabilidade ao ar, em regime de escoamento transiente, foi desenvolvido para avaliação de argamassas de revestimento através do método de vaccum-decay. O potencial do processo não se restringe apenas na determinação dos parâmetros clássicos de permeabilidade propostos por Henry Darcy, mas na avaliação das curvas de recuperação de pressão que fornecem um indicativo das condições microestruturais de diferentes estados da estrutura de meios porosos. Além disso, trata-se de um ensaio portátil, não destrutivo e de baixo custo de implementação para avaliação de argamassas de revestimento in situ. Para isto, neste trabalho foram avaliadas diferentes formulações de argamassas de revestimento tanto em ambiente laboratorial quanto in situ, em comparação ao método de Cembureau (referência), e se existe relação entre as duas diferentes condições apresentadas. A profundidade alcançada por esse tipo de ensaio superficial é uma dúvida recorrente deste e outros ensaios da mesma natureza, e por isso foi considerado no desenvolvimento do plano experimental. Ainda, as diferentes direções do fluxo de ar durante a medida podem influenciar as determinações das permeabilidades para diferentes configurações de experimentos realizados, e também foram considerados no desenvolvimento do método. / The phenomenon of permeability refers to the ability with which a fluid is transported through a porous medium, driven by pressure gradient between the material and the external environment. Degradation agents are conducted to the interior of mortar and concrete driven through such a phenomenon. Therefore, it is the permeability as a key parameters for durability and shelf life of cementitious materials. Moreover, as this type of evaluation is related to structural conditions of the empty capillary porous media, this type of measurement can provide an indication of the conditions of the porous structure of mortar at the time of trial, still serving as a method of quality control and evaluation production processes. Therefore, a new procedure for measuring air permeability in transient flow regime was developed for evaluation of mortar coating by the method of vacuum-decay. The potential of the process is not restricted only to the determination of the classical parameters of permeability proposed by Henry Darcy, but in assessing the recovery curve of pressure that provide a clear picture of states in different microstructural conditions of the structure of porous media. Moreover, it is a portable test, nondestructive and low cost of implementation for evaluation of mortar coating in situ. For this reason, this study evaluated different formulations of mortar coating in laboratory environment and in situ, compared to the Cembureau method (reference), and if there is a relationship between two different conditions presented. The depth reached by this type of test surface is a recurring question of this and other tests of the same nature, and so was considered in developing of this experimental plan. Still, the different directions of air flow during the measurement can influence the determination of permeability for different configurations of the experiments, and were also considered in developing the method.
6

Desenvolvimento de método para medida de permeabilidade superficial de revestimentos de argamassa. / Development of method for measuring the surface permeability of coating mortar.

Daniel Tourinho Sentone 25 May 2011 (has links)
O fenômeno de permeabilidade refere-se à capacidade com que um fluido é transportado através de um meio poroso, impulsionado por gradiente de pressão entre material e meio externo. Agentes de degradação são conduzidos ao interior de argamassas e concretos impelidos através desse tipo de fenômeno. Por isso, considera-se a permeabilidade como um dos principais parâmetros referentes à durabilidade e vida útil de materiais cimentíceos. Além disso, como esse tipo de avaliação está relacionada às condições estruturais dos vazios capilares de meios porosos, esse tipo de medida pode prover um indicativo das condições da estrutura porosa das argamassas no momento do ensaio, servindo ainda como método de controle de qualidade e avaliação dos processos de produção. Portanto, um novo procedimento de medida de permeabilidade ao ar, em regime de escoamento transiente, foi desenvolvido para avaliação de argamassas de revestimento através do método de vaccum-decay. O potencial do processo não se restringe apenas na determinação dos parâmetros clássicos de permeabilidade propostos por Henry Darcy, mas na avaliação das curvas de recuperação de pressão que fornecem um indicativo das condições microestruturais de diferentes estados da estrutura de meios porosos. Além disso, trata-se de um ensaio portátil, não destrutivo e de baixo custo de implementação para avaliação de argamassas de revestimento in situ. Para isto, neste trabalho foram avaliadas diferentes formulações de argamassas de revestimento tanto em ambiente laboratorial quanto in situ, em comparação ao método de Cembureau (referência), e se existe relação entre as duas diferentes condições apresentadas. A profundidade alcançada por esse tipo de ensaio superficial é uma dúvida recorrente deste e outros ensaios da mesma natureza, e por isso foi considerado no desenvolvimento do plano experimental. Ainda, as diferentes direções do fluxo de ar durante a medida podem influenciar as determinações das permeabilidades para diferentes configurações de experimentos realizados, e também foram considerados no desenvolvimento do método. / The phenomenon of permeability refers to the ability with which a fluid is transported through a porous medium, driven by pressure gradient between the material and the external environment. Degradation agents are conducted to the interior of mortar and concrete driven through such a phenomenon. Therefore, it is the permeability as a key parameters for durability and shelf life of cementitious materials. Moreover, as this type of evaluation is related to structural conditions of the empty capillary porous media, this type of measurement can provide an indication of the conditions of the porous structure of mortar at the time of trial, still serving as a method of quality control and evaluation production processes. Therefore, a new procedure for measuring air permeability in transient flow regime was developed for evaluation of mortar coating by the method of vacuum-decay. The potential of the process is not restricted only to the determination of the classical parameters of permeability proposed by Henry Darcy, but in assessing the recovery curve of pressure that provide a clear picture of states in different microstructural conditions of the structure of porous media. Moreover, it is a portable test, nondestructive and low cost of implementation for evaluation of mortar coating in situ. For this reason, this study evaluated different formulations of mortar coating in laboratory environment and in situ, compared to the Cembureau method (reference), and if there is a relationship between two different conditions presented. The depth reached by this type of test surface is a recurring question of this and other tests of the same nature, and so was considered in developing of this experimental plan. Still, the different directions of air flow during the measurement can influence the determination of permeability for different configurations of the experiments, and were also considered in developing the method.
7

Interpretações e controvérsias nas teorias do éter e do vácuo

Santos, Marcos dos 08 July 2015 (has links)
Made available in DSpace on 2016-04-28T14:16:22Z (GMT). No. of bitstreams: 1 Marcos dos Santos.pdf: 890332 bytes, checksum: 9c64da4f57e1bd9130331efad08c9f03 (MD5) Previous issue date: 2015-07-08 / Men always have the curiosity of observe natural phenomenon and try to understand it, for simple curiosity or taking advantage of it in his life. From this, he describes his theory to explain the phenomenon, but not all have the same view and due to different influences a lot of controversies are produced about the subject. Some of them are just small discussions and others lead to big revolutions that have an influence on man. This paper is about the importance of the controversies because it stimulates the scientific and philosophical researching that are awaked by the human curiosity, by the expecting knowledge that promotes the science development by rousing searching. A special approach is dedicated to ether theory because not even with the most brilliant minds of the world help a general approval was reached, because even in the 21th century wasn t possible to proof scientifically the existence or not of this important substance to science development / O homem sempre teve interesse em observar os fenômenos naturais e tentar entendê-los, seja pela simples curiosidade ou para deles tirar proveito em sua vida. A partir disso, ele lança suas teorias para explicar tal fenômeno, mas nem todos tem a mesma visão, devido ao fato de cada um estar sujeito a diferentes influências, o que gera muita controvérsia a respeito do assunto. Em alguns casos, trata-se de meras discussões, já em outros, levam a grandes revoluções que influenciam toda a humanidade. Esta dissertação abordará a importância das controvérsias no que concerne o papel que estas desempenham enquanto incentivadoras das pesquisas científicas e filosóficas, pois elas são despertadas pela curiosidade humana, pelo arguto anseio do homem pelo conhecimento, e portanto provocam o desenvolvimento da ciência, à medida que promovem mais pesquisas. Será dado um enfoque especial à teoria do éter, devido ao fato de que, mesmo com o auxílio das grandes mentes científicas de todos os tempos, não se chegou a um consenso geral acerca dessa substância, pois mesmo no século XXI, ainda não foi possível provar cientificamente sua existência ou não, questão primordial para o desenvolvimento científico
8

Nozzle Design for Vacuum Aerosol Deposition of Nanostructured Coatings

January 2017 (has links)
abstract: Nanomaterials exhibit unique properties that are substantially different from their bulk counterparts. These unique properties have gained recognition and application for various fields and products including sensors, displays, photovoltaics, and energy storage devices. Aerosol Deposition (AD) is a relatively new method for depositing nanomaterials. AD utilizes a nozzle to accelerate the nanomaterial into a deposition chamber under near-vacuum conditions towards a substrate with which the nanomaterial collides and adheres. Traditional methods for designing nozzles at atmospheric conditions are not well suited for nozzle design for AD methods. Computational Fluid Dynamics (CFD) software, ANSYS Fluent, is utilized to simulate two-phase flows consisting of a carrier gas (Helium) and silicon nanoparticles. The Cunningham Correction Factor is used to account for non-continuous effects at the relatively low pressures utilized in AD. The nozzle, referred to herein as a boundary layer compensation (BLC) nozzle, comprises an area-ratio which is larger than traditionally designed nozzles to compensate for the thick boundary layer which forms within the viscosity-affected carrier gas flow. As a result, nanoparticles impact the substrate at velocities up to 300 times faster than the baseline nozzle. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2017
9

A Numerical Investigation on VOD Nozzle Jets

Song, Zhili January 2011 (has links)
The metallurgic process, Vacuum Oxygen Decarburization (VOD) process, is used for producing stainless steels with ultra-low carbon grades. In a VOD process, an oxygen lance is equipped with a De Laval nozzle which injects high speed oxygen gas. The aim of this work is to increase the knowledge of the flow behavior in the harsh environment of VOD vessels. Two real VOD nozzles from industry were numerically studied and compared at different temperatures and ambient pressures.  Flow patterns of the oxygen jet under different ambient pressures were studied and the flow information at different positions from the nozzle was analyzed. In addition, the study compared the effects of different ambient temperatures on the jet velocity and the dynamic pressure. The predictions revealed that the modeling results obtained with the CFD modeling showed an incorrect flow expansion, which agreed well with the results from the De Laval theory. Moreover, a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry have also been studied. It has been observed that a variation in the ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature has a positive effect on the improvement of the jet dynamic pressure. For the comparison between the two nozzles concerned, the modeling results showed that one of the nozzles was more applicably proper for lower pressures, displaying a more stable flow pattern. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian curves. / QC 20110920
10

Digestibilidade de dietas e metabolismo em frangos de corte e suínos alimentados com soja integral processada / Digestibility of diets and metabolism in broilers and pigs fed with full-fat soybean

Carvalho, Amanda D'ávila 24 November 2006 (has links)
The purpose of this dissertation was to realize two studies to evaluate the nutritional value of diets containing full-fat soybean processed by vacuum (FFSvac) or by steam (FFSstm) and of FFSvac and FFSstm for broilers and pigs. The study 1 evaluated the digestibility of diets, of soybeans and the metabolism of broilers fed with diets containing processed full-fat soybean. The experimental design was completely randomized with five treatments (control diet - CD, CD with isometric substitution of 40% FFSvac or FFSstm; diet with FFSvac and diet with FFSstm). The N intake was 23 and 20% less (P<0.01) to the broilers fed with diets containing FFSvac or FFSstm in relation to control group. The excretion, digestibility and absorption of N were not influenced (P>0.05) by the diets. The excretion of energy was 19 and 22% less (P<0.01) to the broilers fed with FFSvac in the diet in relation to control group and those fed with FFSstm in the diet. The diet with FFSvac enhanced (P<0.01) the digestibility and the metabolization of energy. The apparent metabolizable energy corrected for retention of N (MEn) was 12% higher (P<0.01) to the one fed of diet with FFSstm and similar to control diet. The dry matter, protein and ether extract digestibles, the apparent metabolizable energy and MEn were similar (P>0.05) for full-fat soybean processed by vacuum or by steam. The digestibility and absorption of N are not influenced by diets containing full-fat soybean processed by vacuum or by steam. The vacuum processing for full-fat soybean improves the digestibility of gross energy and the apparent metabolizable energy of diets. For the studied soybean types, the digestible nutrients, the apparent metabolizable energy and corrected to nitrogen retention are similar. The study 2 evaluated the digestibility of diets, of soybeans and the metabolism of pigs fed with diets containing processed full-fat soybean. The experimental design was completely randomized with five treatments (control diet - CD, CD with isometric substitution of 40% FFSvac or FFSstm; diet with FFSvac and diet with FFSstm) and four replications with one animal. The intake, urinary excretion of energy and digestible and metabolizable energy were not influenced (P>0.05) by the type of FFS processing. The animals fed diet containing FFSvac excreted 56% more energy (P<0.05) in their feces than animals fed the control diet. The digestion and N metabolism were not influenced (P>0.05) by the type of FFS processing. The digestibility of P, the fecal and the retained P did not differ (P>0.05) between the diets. For FFS, the digestible contents of protein and energy were 10.4 and 4.0% higher (P<0.01) with vacuum processing. The processed soybean does not affect the digestibility of diets neither the metabolism of pigs, except the digestibility of gross energy, which is reduced. The vacuum processing improves the digestible contents of protein and energy of full-fat soybean. / O objetivo desta dissertação foi realizar dois estudos para avaliar o valor nutricional de dietas contendo soja integral processada a vácuo (SIvac) ou a vapor (SIvap) e da SIvac e SIvap para frangos de corte e suínos. O estudo 1 avaliou a digestibilidade das dietas, das sojas e o metabolismo de frangos de corte alimentados com dietas contendo soja integral processada. O delineamento experimental foi inteiramente casualizado, com cinco tratamentos (dieta controle - DC; DC com substituição isométrica de 40% de SIvac ou SIvap; dieta com SIvac e dieta com SIvap). A ingestão de N foi 23 e 20% menor (P<0,01) para as aves alimentadas com dietas com SIvac ou SIvap em relação ao grupo controle. A excreção, digestibilidade e absorção do N não foram influenciadas (P>0,05) pelas dietas. A excreção de energia foi 19 e 22% menor (P<0,01) para as aves alimentadas com SIvac na dieta em relação ao grupo controle e àquele alimentado com dieta com SIvap. A dieta com SIvac melhorou (P<0,01) a digestibilidade e a metabolização da energia. A energia metabolizável aparente corrigida para retenção de N (EMn) foi 12% superior (P<0,01) à da dieta com SIvap e similar a da dieta controle. A matéria seca, proteína e extrato etéreo digestíveis, as energias metabolizável aparente e EMn foram semelhantes (P>0,05) para a soja integral processada a vácuo ou a vapor. A digestibilidade e a absorção do nitrogênio não são influenciadas por dietas contendo soja integral processada a vácuo ou a vapor. O processo a vácuo para a soja integral melhora a digestibilidade da energia bruta e a energia metabolizável aparente das dietas. Para os tipos de soja estudados, os nutrientes digestíveis, a energia metabolizável aparente e corrigida para retenção de nitrogênio são similares. O estudo 2 avaliou a digestibilidade das dietas, das sojas e o metabolismo de suínos alimentados com dietas contendo soja integral processada. O delineamento experimental foi inteiramente casualizado, com cinco tratamentos (dieta controle - DC; DC com substituição isométrica de 40% de SIvac ou SIvap; dieta com SIvac e dieta com SIvap) e quatro repetições de um animal. A ingestão, excreção urinária de energia e energias digestível e metabolizável das dietas não foram influenciadas (P>0,05) pelo processamento da soja. Os animais alimentados com dieta contendo SIvac excretaram 56% mais energia (P<0,05) nas fezes que os alimentados com a dieta controle. A digestão e o metabolismo do N não foram influenciados (P>0,05) pelo tipo de processamento da soja. A digestibilidade do P, o P fecal e absorvido não diferiram (P>0,05) entre as dietas. Para a soja integral, os teores digestíveis de proteína e energia foram 10,4 e 4,0% superiores (P<0,01) com o processamento a vácuo. A soja processada não altera a digestibilidade das dietas nem o metabolismo de suínos, exceto a digestibilidade da energia bruta, que é reduzida. O processamento a vácuo melhora os teores digestíveis de proteína e energia da soja integral para suínos.

Page generated in 0.0372 seconds