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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.
1

A PERSPECTIVE ON THE NUMERICAL AND EXPERIMENTAL CHARACTERISTICS OF MULTI-MODE DRY-FRICTION WHIP AND WHIRL

Wilkes, Jason C. 16 January 2010 (has links)
The present work investigates the nature of dry-friction whip and whirl through experimental and numerical methods. Efforts of the author, Dyck, Pavalek, and coworkers enabled the design and construction of a test rig that demonstrated and recorded accurately the character of multi-mode dry-friction whip and whirl. These tests examined steady state whip and whirl characteristics for a variety of rub materials and clearances. Results provided by the test rig are unparalleled in quality and nature to those seen in literature and possess several unique characteristics that are presented and discussed. A simulation model is constructed using the Texas A and M University (TAMU) Turbomachinery Laboratory rotordynamic software suite XLTRC2 comprised of tapered Timoshenko beam finite elements to form multiple degree of freedom rotor and stator models. These models are reduced by component mode synthesis to discard highfrequency modes while retaining physical coordinates at locations for nonlinear interactions. The interaction at the rub surface is modeled using a nonlinear Hunt and Crossley contact model with coulomb friction. Dry-friction simulations are performed for specific test cases and compared against experimental data to determine the validity of the model. These comparisons are favorable, capturing accurately the nature of dryfriction whirl. Experimental and numerical analysis reveals the existence of multiple whirl and whip regions spanning the entire range of frequencies excited during whirl, despite claims of previous investigations that these regions are predicted by Black's whirl solution, but are not excited in simulations or experiments. In addition, spectral analysis illustrates the presence of harmonic sidebands that accompany the fundamental whirl solution. These sidebands are more evident in whip, and can excite higher-frequency whirl solutions. Experimental evidence also shows a strong nonlinearity present in the whirl frequency ratio, which is greater than that predicted by the measured radius-toclearance ratio at the rub location. Results include whirl frequencies 250% of that predicted by the measured radius-to-clearance ratio.
2

Stiffness Characteristics of Airfoils Under Pulse Loading

Turner, Kevin E. January 2009 (has links)
No description available.
3

THE ROLE OF AUXIN RESISTANT 1 (AXR1) IN ARABIDOPSIS CYTOKININ SIGNALING

Li, Yan 01 January 2012 (has links)
The plant hormone cytokinin plays essential roles in many aspects of growth and development. The cytokinin signal is transmitted by a multistep phosphorelay to the members of two functionally antagonistic classes of Arabidopsis response regulators (ARRs): the type-B ARRs (response activators) and type-A ARRs (negative-feedback regulators). Previous studies have shown that mutations in AXR1, encoding a subunit of the E1 enzyme in the related to ubiquitin (RUB) modification pathway, leads to decreased cytokinin sensitivity. This research shows that the cytokinin resistance of axr1 seedlings is suppressed by loss-of-function of type-A ARRs and that the cytokinin resistance caused by ectopic expression of ARR5, a type-A ARR family member, is enhanced in axr1 background. Based on the established role of the RUB pathway in ubiquitin-dependent proteolysis, these data suggested that AXR1 promotes the cytokinin response by facilitating type-A ARR degradation. Indeed, both genetic (axr1 mutants) and chemical (MLN4924) suppression of RUB E1 increased ARR5 stability, suggesting that the ubiquitin ligase that promotes ARR5 proteolysis requires RUB modification for optimal activity. In addition, ARR1, a type-B ARR family member, also accumulated in the axr1 mutant background, suggesting that AXR1 regulates primary cytokinin signaling at multiple levels.
4

A study to determine the efficacy of Deep Heat® rub combined with chiropractic adjustments on mechanical low back pain

Van Haute, Dieter Miek Raymond 04 June 2012 (has links)
M. Tech. / This randomised, comparative study was undertaken in order to evaluate whether a menthol-containing gel (Deep Heat® Rub) combined with Chiropractic adjustments on mechanical low back pain, over a three-week period, is more effective than Chiropractic adjustments and aqueous cream only.Thirty participants who conformed to the specified inclusion and exclusion criteria, were accepted to form part of the study. The thirty participants were placed randomly into two groups of fifteen participants each. The Experimental Group received lumbar spine and/or Sacroiliac adjustment(s) over the restricted joint(s) together with the application of Deep Heat® Gel, and the Control Group received lumbar spine and/or Sacroiliac adjustment(s) over the restricted joint(s) together with the application of non-medicated aqueous cream. All participants received a total of six treatments over a three-week period, i.e. two treatments per week. Each participant was requested to come in for a follow-up consultation one day after the last treatment session used for data capturing only. The subjective data was collected by means of the Revised Oswestry Low Back Pain Disability Questionnaire, taken prior to the first, fourth and at the seventh consultations. The objective data, in the form of lumbar range of motion, was obtained by means of a Digital Inclinometer, taken prior to every consultation. Data was statistically analysed by means of the Friedman and Wilcoxon Signed Rank tests for intra-group comparisons and the Mann-Whitney test for inter-group comparisons.The results indicated that the treatment protocols used in the Control and the Experimental Group were equally effective in reducing low back pain and disability as well as increasing the lumbar range of motion. The Control Group did, however, demonstrate statistically significant differences in three out of six ranges of motion, compared to two out of six for the Experimental Group, although no statistically significant differences were found.The results of this study suggest that Chiropractic adjustive therapy (with non-medicated aqueous cream) alone or when administered with Deep Heat® Rub are equally effective in terms of subjective pain perception and objective clinical findings in the treatment of mechanical low back pain. No statistically significant difference could be seen when participants received diversified spinal adjustive therapy and application of aqueous cream, compared to receiving diversified spinal adjustive therapy and application of Deep Heat® Rub.
5

A unified tribological model for different regimes of lubrication and rub/impact phenomena in rotor dynamics

Nadian, Behrooz January 1995 (has links)
No description available.
6

A Moving Load Finite Element-Based Approach To Determining Blade Tip Forces During A Blade-On-Casing Incursion In A Gas Turbine Engine

Ferguson, Jeremy Lee 18 March 2008 (has links)
No description available.
7

Två linsrengöringsmetoders påverkan på hornhinnan i samband med användande av kontaktlinsvätskan Opti-Free® Express®

Wikander, Markus January 2013 (has links)
Syfte: Studiens syfte var att jämföra två linsrengöringsmetoders påverkan på hornhinnan. Studien jämförde tillverkarens rekommenderade användningsinstruktioner för Opti-Free® Express®, med den alternativa rengöringsmetoden att gnugga linserna, något som ofta rekommenderas av optiker. Metod: Deltagarna sågs vid två tillfällen för utvärdering av eventuell påverkan på hornhinnan. Värdena som återfanns vid första tillfället fungerade som ett utgångsvärde. Samtliga fynd dokumenterades, graderades och poängräknades efter vilken typ av staining samt utbredning. Cornea delades in i fem regioner; centralt, superiort, inferiort, nasalt och temporalt. Typen staining som återfanns poängsattes enligt; mikropunktata (25), makropunktata (50), coalesced (75) och patch (100). Medelvärden för respektive deltagares ögon räknades ut genom att muliplicera poängen given för typen funnen staining med den procentuella utbredningen i varje region. Därefter dividera med fem för att få ett medelvärde utbrett över hela ögat. Deltagarna fick ett nytt par linser och blev därefter instruerade att under två veckors tid rengöra höger och vänster lins separat. Det ena sättet att rengöra var att följa tillverkarens rekommenderade instruktioner, något som innebär sköljning i fem sekunder per linssida. Det andra sättet var genom att gnugga linserna i en L-formad rörelse fem gånger per sida och därefter skölja linsen i fem sekunder. Efter två veckors tid undersöktes deltagarna på nytt. Funna värden sammanställdes och jämfördes sedan med varandra samt utgångsvärdena. Resultat: I de ögon vars linser gnuggades minskade medelvärdet av mängden staining från ursprungligen 140179 till 12185 (p = 0,68). Ursprungsvärdet för de ögon vars linser sköljdes var 125149, något som efter två veckor ökade till 214179 (p = 0,03). Medelvärdena efter två veckor för de båda rengöringsmetoderna uppkom till 12185 för gnugg respektive 214179 för skölj, jämförelser drogs emellan grupperna (p = 0,046). Slutsats: I de ögon vars linser rengjordes genom sköljning återfanns en högre grad av påverkan på hornhinnan. Mängd funnen staining var större i dessa ögon än i de ögon vars linser rengjordes genom gnuggning. Skillnaden var av statistisk signifikans. / The aim of this study was to compare the impact of contact lens cleaning on cornea using two different methods. The study compared the manufacturer’s recommended usage for Opti-Free® Express®, with the alternative cleaning method that involves rubbing the lens, a method often recommended by Optometrists. The participants were seen twice to evaluate the cornea. The values found on the first visit were used as baseline values. The participants were given a new pair of contact lenses and were told to clean them in two different ways for the upcoming two weeks. The first method was to follow the recommended instructions by the manufacturer. A method that involves rinsing the lens for five seconds per side. The alternative method was to rub both sides in shape of the letter L. This procedure was repeated five times per side followed by rinsing for five seconds. The participants were seen for a second visit after two weeks. Evaluations were once again made. The values found were compared with the baseline values as well with each other.  In those cases where the lenses had been cleaned by rubbing, the value of found staining decreased from 140179 at the baseline to 12185 after two weeks (p = 0,68). The baseline value for the eyes where the lenses were cleaned by rinsing was 125149. Those values increased to 214179 after two weeks (p = 0,03). A comparison between the two groups later values showed that there was a statistically significant difference between the two types of cleaning, where the eyes that were only rinsed contained a higher amount of staining (p = 0,046). In those eyes where lenses had been cleaned only by rinsing there were found a higher amount of staining compared to the ones cleaned by rubbing. The difference in found staining between the two cleaning methods were statistically significant.
8

Understanding the Responses of a Metal and a CMCTurbine Blade during a Controlled Rub Event using a Segmented Shroud

Langenbrunner, Nisrene A. 08 August 2013 (has links)
No description available.
9

Alcohol-based hand rub in the prevention of diarrhoea and respiratory-tract infection among children in community settings : a systematic review

Steyn, Joelynn Geraldine Rachelle 04 1900 (has links)
Thesis (MCur)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Annually more than 3.5 million children worldwide, less than five years of age die of diarrhoea and acute lower respiratory-tract infections. Over the last two decades, the care of pre-school children outside of their homes has become more common in most parts of the world and has contributed to an increased risk of respiratory-tract and gastrointestinal infections in children. Children attending day-care centres are at an increased risk for diarrhoea and respiratory-tract infections and hands are the primary vehicle for transmission of infectious diseases. Thus, hand hygiene is essential for preventing and controlling of infection in the health care and community settings. Waterless hand sanitizer as an alternative to hand washing was investigated. Rinse-free hand sanitizer programmes in the community may be effective, safe and feasible. The aim of the study was to systematically appraise evidence on the effect of alcohol-based hand rub in the prevention of diarrhoea and acute respiratory-tract infection among children aged five years and below in community settings. The primary outcome of the study was to assess the incidence of respiratory-tract infection and diarrhea. Diarrhoea is defined by the World Health Organization as the excretion of three or more loose or liquid stools per day (or more frequent excretion than is normal for the individual). The secondary outcome was to assess mortality, admission to hospital and duration of hospital stay. A comprehensive search for relevant studies was conducted on the following databases from 1990 to 2014: EMBASE, MEDLINE, CINAHL, Google Scholar and Cochrane Central Register of Controlled Trials (CENTRAL). We searched the reference lists of all relevant articles and textbooks for more studies. Unpublished data previously presented at international and scientific meetings have been included in the review. Proceedings of international conferences on diarrhoea and respiratory-tract infection among children were searched for relevant articles. Subject experts were contacted. Two reviewers, Joelynn Steyn (JS) and Oswell Khondowe (OK) selected studies following a two-step study selection process. This review considered all published randomized controlled trials and quasi-experimental designs published from January 1990 to July 2014. The first step was the selection of studies based on titles and abstracts. Both reviewers selected eligible studies which met the set criteria. During the second step, both reviewers retrieved the full-text articles of the studies and assessed the methodological quality of the studies. Four studies were included in this review. The included studies met most of the quality assessment criteria as stipulated in the Cochrane risk assessment tool. Two studies were clusterrandomized controlled trials, one was a block randomized controlled trial and one was a randomized controlled trial. Disagreements were resolved by discussion and where a lack of consensus existed, consultation with a third reviewer occurred. The use of alcohol hand rub as compared to control interventions significantly reduced the incidence of diarrhoea in children (RR 0.79, 95% CI 0.63 to 0.99). Statistical heterogeneity was observed among the included studies (I²=69, p=0.04). However this review found no significant difference in respiratory-tract infections between intervention groups versus control as observed from the confidence interval (RR 0.98, 95% CI 0.90 to 1.07, p=0.63). The results should be interpreted with caution due to the limited number of studies conducted in communities with alcoholbased hand rub used by caregivers. Due to limited studies in this review, it makes it difficult to make strong conclusions on findings and to provide sufficient evidence to guide future research. We therefore recommend that more studies with high quality methodologies, using randomized controlled trial designs be conducted especially in poor resourced communities. / AFRIKAANSE OPSOMMING: Meer as 3.5 miljoen kinders jonger as vyf jaar oud sterf jaarliks wêreldwyd as gevolg van diarree en akute laer respiratoriese lugweginfeksies. Oor die laaste dekades het die versorging van voorskoolse kinders buite hul tuiste meer algemeen geword in die meeste dele van die wêreld wat bygedra het tot ’n risiko in die toename van respiratoriese en spysverteringskanaalinfeksies by kinders. Kinders by dagsorgsentrums het ’n groter risiko vir diarree en respiratoriese lugweë infeksies want die oordra van siekte-infeksies word veral deur die hande wat as die primêre bron daarvan beskou word, gesien. Dus is hand-higiëne noodsaaklik om infeksies in gesondheidsorg en gemeenskapsentrums te voorkom en te beheer. ’n Waterlose hande-ontsmettingsmiddel as ’n alternatief om hande te was, is ondersoek. Spoelvrye hande-ontsmettingsmiddel programme in die gemeenskap mag effektief, veilig en uitvoerbaar wees. Die doel van die studie was om sistematies die geslaagdheid van bewyse op die effek van alkoholgebaseerde hande-smeermiddel in die voorkoming van diarree en akute lugweginfeksies by kinders 5 jaar en jonger in gemeenskapsentrums te ondersoek. Die primêre uitkoms van die studie was om die voorkoms van respiratoriese lugweginfeksie en diarree te asseseer. Diarree soos gedefinieer deur die WGO is die uitskeiding van drie of meer los- of waterige stoelgange per dag (of meer gereelde uitskeiding wat normaal vir die individu is). Die sekondêre uitkoms was om mortaliteit, toelating tot die hospitaal en duur van hospitaalverblyf te assesseer. ’n Omvattende soektog vir relevante studies was op die volgende databasisse van 2004-2014 uitgevoer: EMBASE, MEDLINE, CINAHL, Google Scholar en Cochrane Sentrale Register van Beheerde Toetse. Ons het die verwysingslyste van alle relevante artikels en handboeke vir meer navorsingstudies nagegaan. Ongepubliseerde data wat voorheen aangebied is by internasionale en wetenskaplike vergaderings, is ingesluit in die oorsig. Bevindings by internasionale konferensies oor diarree en lugweginfeksies by kinders was nagegaan in die soektog na relevante artikels. Onderwerpdeskundiges was gekontak. Die twee navorsers, Joelynn Steyn (JS) en Oswell Khondowe (OK) het studies geselekteer deur ’n twee-stap studieselekteringsproses te volg. Die oorsig het alle gepubliseerde, ewekansige gekontroleerde proewe en kwasi-eksperimenteerde studies oorweeg tussen Januarie 1990 en Julie 2014. Die eerste stap was die selektering van studies gebaseer op hul titels en opsommings. Beide navorsers het geskikte studies slegs geselekteer as die studie aan die bepaalde kriteria voldoen het. Tydens die tweede stap het beide navorsers die volledige artikels geneem van die studies geselekteer en die gehalte van die metodologie geassesseer. Vierstudies is in die oorsig ingesluit. Die ingeslote studies het aan die meeste vereistes soos deur die Cochrane risiko assesseringsinstrument gestipuleer voldoen. Twee studies was groep-ewekansige gekontroleerde proewe, een was ’n blok ewekansige gekontroleerde proef en een was ’n ewekansige gekontroleerde proef. Verskille is opgelos deur bespreking en waar daar onderbreking in konsensus was, het ’n konsultasie met ’n derde beoordelaar plaasgevind. Die gebruik van ’n alkohol handreiniger, soos vergelyk met kontrole-intervensies, het die voorkoms van diarree in kinders beduidend verminder (RR 0.79, 95% CI 0.63 to 0.99). Statistiese heterogeniteit is egter tussen die ingeslote studies waargeneem (I²=69, p=0.04). Hierdie studie het geen beduidende verskille in lugweg infeksies tussen die intervensiegroepe teenoor die kontrolegroep gevind nie soos waargeneem uit die vertroue interval (RR0.98, 95% CI 0.90 to 1.07, p=0.63). Die resultate moet met omsigtigheid geïnterpreteer word as gevolg van die beperkte aantal studies wat in gemeenskappe uitgevoer was met alkohol-gebasseerde handreiniger wat deur versorgers gebruik word. As gevolg van die beperkende aantal studies in hierdie studie, is dit moeilik om sterk gevolgtrekkings te maak op bevindinge en om voldoende bewyse te gee om toekomstige navorsing te rig. Ons beveel dus aan dat meer studies met hoë kwaliteit metodologie en wat ewekansige gekontroleerde proef-ontwerpe gebruik, uitgevoer word, veral in swak-toegeruste gemeenskappe. (RR0.98, 95% CI 0.90 to 1.07, p=0.63). Die resultate moet met omsigtigheid geïnterpreteer word as gevolg van die beperkte aantal studies wat gedoen is in gemeenskappe met alkohol-
10

Hibridos inorganico-organicos nanoestruturados e termoquimica da interação cation-centros basicos / Inorganic-organic nanostructured hybrids and thermochemistry of cation-basic center interaction

Macedo, Thais Regi 09 October 2009 (has links)
Orientador: Claudio Airoldi / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-14T17:53:43Z (GMT). No. of bitstreams: 1 Macedo_ThaisRegi_D.pdf: 2848180 bytes, checksum: 54c8b1c12b90c47c6be6008afc371018 (MD5) Previous issue date: 2009 / Resumo: Este trabalho descreve a preparação, caracterização e aplicação de novos materiais híbridos inorgânico-orgânicos nanoestruturados, obtidos a partir do processo de funcionalização da superfície lamelar de derivados do RUB-18, a forma ácida do material, H-RUB-18, e a forma intercalada com moléculas orgânicas polares, CTA-RUB-18. Para esse processo, foram usados agentes sililantes contendo nitrogênio, enxofre e oxigênio como grupos ativos nas moléculas e dois métodos diferentes. Os difratogramas de raios X mostraram a cristalinidade dos materiais e as microscopias eletrônicas de varredura, a morfologia e o tamanho das partículas formadas. Os espectros de ressonância magnética nuclear de Si e C no estado sólido mostraram que as sínteses foram bem sucedidas. Os resultados obtidos através da análise elementar e da termogravimetria determinaram as quantidades de grupos orgânicos imobilizadas na superfície, o valor máximo obtido foi de 3,79 mmol de grupos por grama de material, um valor próximo da capacidade máxima de funcionalização do material, que é de 3,85 mmol g. Os híbridos nanoestruturados apresentaram estabilidade térmica até aproximadamente 540 K. Os materiais funcionalizados com grupos nitrogenados foram aplicados para a sorção de íons cobre, níquel e cobalto, enquanto os materiais sulfurados foram usados para a sorção de cádmio e chumbo de solução aquosa. As isotermas de sorção foram obtidas pelo processo de batelada, e os dados experimentais foram ajustados aos modelos de Freundlich e Langmuir-Freundlich, considerando superfícies heterogêneas. Esses dados forneceram subsídios para o conhecimento interativo do sistema, considerando a energética da interação. O efeito interativo cátion/centros básicos na interface sólido/líquido foi avaliado através da microcalorimetria e as grandezas termodinâmicas, obtidas nesses sistemas heterogêneos, propiciaram condições para estabelecer ordem energética favorável das interações. Os resultados obtidos mostraram a viabilidade da aplicação dos materiais como eficientes sorventes, para extrair cátions de um ecossistema. / Abstract: The present study describes the preparation, characterization and application of the new inorganic-organic nanostructured hybrid materials, prepared by the functionalization process of the layered surface of derivative RUB-18 material, its acidic, H-RUB-18 and intercalated, CTA-RUB-18 forms. For this process were used silylating agents containing nitrogen, sulfur and oxygen as active atoms on the molecules and two different methods. The X ray diffractograms showed the crystallinity of the materials and the electron scanning microscopy (SEM) the morphology and size of the particles formed. The nuclear magnetic resonance (NMR) spectra for Si and C nuclei in the solid state show that the syntheses were successfully performed. From the obtained elemental analysis and thermogravimetry (TG) results the amount of organic groups immobilized on the surface was determined. The maximum number was 3.79 mmol groups per gram of material, a value near to the maximum of its capacity, 3.85 mmol g. The nanostructured hybrids present thermal stability up to 540 K. The nitrogen functionalized materials were applied for sorption of copper, nickel and cobalt from aqueous solution, while the sulfur materials were used for cadmium and lead sorption from aqueous solution. The sorption isotherms were obtained by the batchwise process and the data were adjusted to the Freundlich and Langmuir- Freundlich models, considering heterogeneous surfaces. These data supply information for the interactive knowledge of the systems, considering the energy of interaction. The interactive effect of cation/basic centers at the solid/liquid interface was evaluated through microcalorimetry and the thermodynamic values, obtained in these heterogeneous systems, give conditions for establishment of a favorable energetic order in the interaction. The obtained results showed the viability of application of the materials as efficient sorbents to extract cations from an ecosystem. / Doutorado / Quimica Inorganica / Doutor em Ciências

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