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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.
21

Mathematical models of superconductivity

Heron, Dale Robert January 1995 (has links)
No description available.
22

VUV laser oscillation in optically pumped nitric oxide

Hooker, Simon Martin January 1990 (has links)
No description available.
23

A study of dead-end filtration enhanced by electric and acoustic fields

Smythe, Melanie Claire January 2001 (has links)
This thesis describes the experimental procedure and results of an investigation into the effect of electric and acoustic fields on dead end vacuum filtration. The test suspension used was low concentration titanium dioxide. Ultrasound energy was applied tangentially and electrical energy parallel to the filter medium. Varying electric field gradients were applied to the filter cell, either alone or together with the constant frequency acoustic field. The filter cell was based on a Nutsche filter, and allowed samples of cake to be taken at the end of the filtration experiment. Electric and acoustic field strengths, suspension characteristics and process parameters could all be varied independently.
24

Episiotomy use at operative vaginal delivery

Macleod, Maureen January 2011 (has links)
Episiotomy, a component of operative vaginal delivery (OVD), aims to prevent anal sphincter tears and associated sequelae. Robust evidence suggests restrictive use should be adopted at vaginal delivery but poor quality contradictory evidence exists at OVD. This thesis concerns a series of studies conducted to address this gap in knowledge. Formative work established a priori views and current practice of all obstetricians in the UK and Ireland via a national survey. The majority of clinicians preferred routine use of episiotomy at forceps delivery and restrictive use at vacuum. Respondents indicated support for the planned pilot RCT. A feasibility study established the possibility of conducting a pilot RCT with its known complexities. Data collection tools were developed and found to be fit for purpose and acceptable to women. Shortcomings in the study design informed the proposed pilot RCT. Contemporaneous to the pilot RCT, we conducted a prospective cohort study (n=1360) of morbidity in relation to episiotomy use at OVD to contextualise its findings. Episiotomy was not found to be protective of anal sphincter tears, shoulder dystocia or neonatal trauma but was associated with an increased risk of postpartum haemorrhage [adjusted OR 1.72 (95%CI 1.21 – 2.45)], perineal infection [adjusted OR 4.04 (95%CI 1.44 – 11.37)] and analgesic use [adjusted OR 3.35 (95%CI 2.49 – 4.51)]. The two centred pilot RCT, while not powered to provide definitive evidence, suggested a restrictive approach to episiotomy use does not appear to reduce or greatly increase anal sphincter tears [8.1% vs 10.9%, adjusted OR 0.77, (95% CI 0.28 – 2.10)]. There may however be a difference in effect size and direction between vacuum and forceps use. Routine use was associated with an increase in PPH [36% vs 27%; adjusted OR 1.88, (95% CI 0.99 - 3.57)]. A longitudinal follow up of participants to one year postpartum suggested routine use of episiotomy may decrease rates of urinary morbidity, particularly stress incontinence; dyspareunia; and perineal pain compared to restrictive use. This pilot RCT supports current practice regarding approach to episiotomy use at OVD meantime, pending the results of a definitive study.
25

Analise de viabilidade técnica-econômica na substituição de um sistema combinado de geração de vapor-vácuo por bombas secas /

Oliva, Robson Vitor. January 2013 (has links)
Orientador: Pedro Magalhães Sobrinho / Banca: Eliana Vieira Canettieri / Banca: Christian Jeremi Coronado Rodriguez / Resumo:As tecnologias tradicionais utilizadas na geração de vácuo para fabricação de aço são ejetores a vapor, bombas de vácuo de anel líquido e sistemas combinados entre esses dois. O sistema de ejetores de vapor tem uma capacidade de gerar um vácuo médio de 101 kPa (1 atm) a 0,1 Pa (0,01 mbar), as bombas de anel líquido chegam a apenas 3 kPa (30 mbar) e as bombas secas abrangem a faixa de 101 kPa (1 atm) até 67 Pa (0,67 mbar), faixa necessária para a aplicação em metalurgia secundária e é o limite desta tecnologia. Neste trabalho foi realizado estudo de caso no setor industrial que utiliza a geração de vácuo à ejetores a vapor superaquecidos a 250°C e 1,2 MPa (12 kgf/cm2) de pressão. O vácuo é necessário para a remoção de gases indesejáveis na composição do aço, como Nitrogênio, Oxigênio, Hidrogênio e Enxofre que causam fragilidades na estrutura cristalina. Atualmente têm surgido inovações tecnológicos para geração de vácuo para aplicações em VD (desgaseificação à vácuo), vácuos até 67 Pa (0,67 mbar) e para VOD (descarburação) para vácuos de 8-20 kPa (80-200mbar). Uma dessas inovações é a combinação de bombas mecânicas secas formando três estágios de vácuo, juntando várias tecnologias, sendo a primeira e segunda com rotor Roots e a terceira com rotor parafuso. Neste estudo o objetivo foi o de mensurar os rendimentos reais oferecidos pelo sistema de ejetores a vapor, juntamente com o rendimento da Caldeira em comparação com a nova tecnologia de bomba seca em aplicações siderúrgicas, apresentaremos as vantagens, desvantagens e custo benefício para a substituição do sistema de geração de vácuo. Representando uma redução de 92,7 % no consumo energético e 81,4% de redução dos custos operacionais / Abstract: Traditional technologies used to generate vacuum for steelmaking are steam ejectors, liquid ring vacuum pumps and systems combined of them. The steam ejector system has a capacity to generate a medium vacuum 101 kPa (1 atm) a 0,1 Pa (0,01 mbar), the liquid ring pumps only reach 3 kPa (30 mbar) and dried pump cover the range of 101 kPa (1 atm) até 67 Pa (0,67 mbar), band required for use in secondary metallurgy and is the limit of this technology. In this work was realized a case study in the industrial sector that uses the vacuum generation through steam ejectors superheated at 250 ° C and 1,2 MPa (12 kgf/cm2). The vacuum is needed for removal of undesirable gases in the composition of the steel as nitrogen, oxygen, hydrogen and sulfur which causes weakness in the crystalline structure. Currently there have been technological innovations for vacuum generation in applications in VD (vacuum degassing), vacuums until to 67 Pa (0,67 mbar) and VOD (decarburization) for vacuums of 8-20 kPa (80-200 mbar). One of these innovations is mechanical pumps dried formed by three-stage vacuum, joining various technologies, the first and second rotor roots and the third screw rotor. In this study the objective was to measure the real returns offered by the steam ejector system, along with the performance of the boiler compared to the new dry pump technology in steel making industry, will present the advantages, disadvantages and cost effective to replace the vacuum generating system. Representing a 92,7% reduction in energy consumption and 81,4 % reduction in operating costs / Mestre
26

Excited states of atmospheric molecules: spectra, structures and interactions : a thesis submitted for the degree of Doctor of Science of the University of Adelaide / Brenton R. Lewis.

Lewis, Brenton R. January 2000 (has links)
Includes bibliographical references. / 1 v. : / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The experimental, analytical and computational research achievements of the author, relating to the study of the interaction of vacuum ultraviolet radiation with molecules of particular atmospheric, aeronomic, or astrophysical significance are described. Elucidates details of molecular structure and dynamics through comparision between precise experimental measurements and quantum-mechanical calculations, and provides benchmark experimental molecular data and develops molecular modelling techniques intended to contribute to the solution of problems in the photochemistry of the terrestial and planetary atmospheres, aeronomy and astrophysics / Thesis (D.Sc.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 2000
27

Pyrolytic study of 2-(2-Azidoethyl)-1H-indole and 2-Azido-1-(1H-indol-2-yl)ethanone

Chou, Wei-zhen 05 August 2004 (has links)
Flash vacuum pyrolysis (FVP) of 2-(2-azidoethyl)-1H-indole, via a nitrene intermediate, gave two products, 2-methyl-1H-indole and quinoline. However, under the same route, FVP of 2-azido-1-(1H-indol-2-yl)ethanone produced indole, 1-(1H-indol-2-yl)ethanone, (1H-indol-2-yl)-[4-(1H-indol-2-yl)-1H-imidazol-2-yl]ethanone and it¡¦s isomer.
28

Pyrolytic Study of 6-Phenylfulvene and Its Derivatives

Lin, Fang-Ying 11 July 2005 (has links)
Flash vacuum pyrolysis (FVP) of cyclopenta-2,4-dienylidenemethylbenzene gave acenaphthylene¡Bacenaphthene and dimer¡G5a,5b,11b,11c-tetrahydrocyclobuta[1",2":3,4;4",3":3',4']dicyclopenta[1,2-a:1',2'-a']diindene¡CPyrolysis of 1-bromo-4-cyclopenta-2,4-dienylidenemethylbenzene gave acenaphthene¡Bdimer¡B5-bromoacenaphthylene and 5-bromoacenaphthene¡CPyrolysis of 2-cyclopenta-2,4-dienylidenemethyl-3-methylthiophene gave 5H-1-thia-s-indacene and 7H-1-thia-s-indacene¡Aand naphthalene¡CPyrolysis of 2-inden-1-ylidene-methyl-3-methylthiophene gave 5H-1-thiacyclopenta[b]fluorene and unidentified products¡C
29

Pyrolytic study of 6-benzylfulvene and its benzofuran analogues

Wang, Yuan-Heng 05 July 2006 (has links)
Flash vacuum pyrolysis (FVP) of 1-(2-(cyclopenta-2,4-dienylidene)ethyl)benzene gave 1H-benzo[e]indene, 3H-benzo[e]indene, and fluorene. Pyrolysis of 2-cyclopentadienylidenemethyl-3-methylbenzofuran gave 1H-benzofurano[2,3-d]indene and 3H-benzofurano[2,3-d]indene. Pyrolysis of 2-cyclopentadienylidenemethylbenzofuran gave 1H-benzo[e]indene, 3H-benzo[e]indene, fluorene, 2-phenylbenzofuran, and unidentified products
30

Study of the Chemistry of 5-Thiapyrido[b]cyclobuten-6-one,6-Oxapyrido[b]cyclobuten-5-one and 5-Oxapyrido[b]cyclobuten-6-one

Liu, Wei-Min 27 June 2000 (has links)
Flash vacuum pyrolysis of 3-mercaptopyridine-2-carboxylic acid(74), gave 3-mercaptopyridine(83) and di-(3-pyridyl)disulfide(84). FVP of 3-hydroxy-pyridine-2-carboxylic acid(75), gave dipyrrolo[1,2-a;1',2'-d]pyrazine-5,10-dione(91). FVP of 2-hydroxypyridine-3-carboxylic acid(76), gave di-[2]-pyridylether(101) and trimer(102).

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