• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 68
  • 41
  • 38
  • 4
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 181
  • 181
  • 37
  • 24
  • 23
  • 23
  • 16
  • 16
  • 15
  • 15
  • 14
  • 13
  • 13
  • 13
  • 11
  • 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.
31

Gaseous Species Measurements of Alternative Jet Fuels in Sooting Laminar Coflow Diffusion Flames

Zabeti, Parham 31 December 2010 (has links)
The gaseous species concentration of Jet A-1, GTL, CTL and a blend of 80 vol.% GTL and 20 vol.% hexanol jet fuels in laminar coflow diffusion flames have been measured and studied. These species are carbon monoxide, carbon dioxide, oxygen, methane, ethane, ethylene, propylene, and acetylene. Benzene and propyne concentrations were also detected in CTL flames. 1-Butene has been quantified for the blend of GTL and hexanol flame. The detailed experimental setup has been described and results from different flames are compared. The CO is produced in a same amount in all the flames. The CTL flame had the largest and GTL/hexanol flame had lowest CO2 concentrations. The results indicate that GTL and GTL hexanol blend flames produce similar concentrations for all the measured hydrocarbon species and have the highest concentration among all the jet fuels. The experimental results from Jet A-1 fuel are also compared with numerical studies by Saffaripour et al.
32

Mobile Service Overlay Networks for Multimedia Applications

Tang, Yongbo 28 November 2013 (has links)
With the increasing demand on multimedia applications over the Internet, and the growing number of mobile smart devices people are using, it is helpful to develop a mobile network architecture that can support multimedia transmission without using infrastructures. We propose that service overlay networks over MANETs can serve as a supplement to the existing 3G/4G networks and Wi-Fi access point networks. In this thesis we present experiment results that show the feasibility of mobile service overlay networks to meet the requirements of multimedia streaming. And also, we improved one of the existing overlay protocols. The improved protocol takes physical location into consideration when establishing connections in the overlay network. It also limits the number of neighbors each node can have, which prevents a particular node from becoming the bottleneck of the network, when connected to too many neighbors. Evaluation results show the new protocol reduces network packet loss rate.
33

Gaseous Species Measurements of Alternative Jet Fuels in Sooting Laminar Coflow Diffusion Flames

Zabeti, Parham 31 December 2010 (has links)
The gaseous species concentration of Jet A-1, GTL, CTL and a blend of 80 vol.% GTL and 20 vol.% hexanol jet fuels in laminar coflow diffusion flames have been measured and studied. These species are carbon monoxide, carbon dioxide, oxygen, methane, ethane, ethylene, propylene, and acetylene. Benzene and propyne concentrations were also detected in CTL flames. 1-Butene has been quantified for the blend of GTL and hexanol flame. The detailed experimental setup has been described and results from different flames are compared. The CO is produced in a same amount in all the flames. The CTL flame had the largest and GTL/hexanol flame had lowest CO2 concentrations. The results indicate that GTL and GTL hexanol blend flames produce similar concentrations for all the measured hydrocarbon species and have the highest concentration among all the jet fuels. The experimental results from Jet A-1 fuel are also compared with numerical studies by Saffaripour et al.
34

Mobile Service Overlay Networks for Multimedia Applications

Tang, Yongbo 28 November 2013 (has links)
With the increasing demand on multimedia applications over the Internet, and the growing number of mobile smart devices people are using, it is helpful to develop a mobile network architecture that can support multimedia transmission without using infrastructures. We propose that service overlay networks over MANETs can serve as a supplement to the existing 3G/4G networks and Wi-Fi access point networks. In this thesis we present experiment results that show the feasibility of mobile service overlay networks to meet the requirements of multimedia streaming. And also, we improved one of the existing overlay protocols. The improved protocol takes physical location into consideration when establishing connections in the overlay network. It also limits the number of neighbors each node can have, which prevents a particular node from becoming the bottleneck of the network, when connected to too many neighbors. Evaluation results show the new protocol reduces network packet loss rate.
35

Experimental study of morphological case marking knowledge in Japanese-English bilingual children in Christchurch New Zealand

Shirakawa, Mineko January 2013 (has links)
This thesis presents the results of an experimental study designed to examine whether children raised bilingually in Japanese and English from birth in Christchurch, New Zealand, exhibit the same morphological case and topic marking knowledge in Japanese as monolingual children in Japan. The participants were 34 children aged between five and eleven years who have been raised in a one-person one-language environment in an English dominant community. The study replicated previous studies on monolingual Japanese children, and involved two widely used paradigms for assessing a child’s grammar: picture selection, and elicited imitation. The responses of the children in this study were different from those reported in studies of monolingual children. In the picture selection tasks, some children in this study interpreted the agent-patient relationship based on the word order cue in the object-initial types of transitive sentences, whereas previous studies have demonstrated that monolingual children five years and older are able to interpret the agent-patient relationship in the same way as adults, using the case marking cue. Moreover, in the elicited imitation tasks, many children in this study re-analysed the topic-comment construction as a genitive possessive when the particles in the stimuli were masked with noise. This pattern has not been reported in any previous study. The results also revealed that there was a great degree of individual variation. The study suggests cross-linguistic influence from English on Japanese as a possible explanation for the difference between the children in this study and monolinguals. The phenomena observed in the results satisfies two conditions for cross-linguistic influence proposed by Hulk and Müller (2000) and Müller and Hulk (2001), because (i) English and Japanese overlap at the surface level in terms of the agent position in a canonical sentence and the possessive structure, and (ii) the problematic structures for some children in this study involved the interface between syntax and pragmatics in the C-domain. The study, however, has no principled explanation for the individual variation found because of a lack of data on the Japanese input and the child’s fluency, both of which are likely to affect simultaneous bilingual development.
36

Behaviour of elliptical tube columns filled with self-compacting concrete

Mahgub, Munir January 2016 (has links)
The present research is conducted to investigate the behaviour of elliptical tube columns filled with self-compacting concrete (SCC). In total, ten specimens, including two empty columns, were tested to failure. The main parameters investigated were the length and the sections of the columns, and the concrete compressive strength. Artificial Neural Network (ANN) model was developed to predict the compressive strength of SCC using a comprehensive database collected from different previous studies. The database was used to train and test the developed ANN. Moreover, parallel to the experimental works, a three dimensional nonlinear finite element (FE) model using ABAQUS software was developed to predict the behaviour of SCC elliptical tube columns. The proposed ABAQUS model was verified against the current experimental results. The experimental results indicated that the failure modes of the SCC filled elliptical steel tube columns having large slenderness ratios were dominated by global buckling. Moreover, the composite columns possessed higher critical axial compressive capacities compared with their hollow section companions due to the composite interaction. However, due to the large slenderness ratio of the test specimens, the change of compressive strength of concrete core did not show significant effect on the critical axial compressive capacity of concrete filled columns although the axial compressive capacity increased with the concrete grade increase. The comparisons between the axial compressive load capacities obtained from experimental study and those predicted using simple methods provided in Eurocode 4 for concrete-filled steel rectangular tube columns showed a reasonable agreement. The proposed three dimensional FE model accurately predicted the failure modes, the load capacity and the load-deflection response of the columns tested. The experimental results, analysis and comparisons presented in this thesis clearly support the application of self-compacting concrete filled elliptical steel tube columns in construction engineering practice.
37

Internet Safety for Children : Stranger danger, misbehaviour and problems when online

Fergus, Seamus January 2018 (has links)
The Internet has evolved and continues to evolve rapidly and as adults we understand the need to be careful with various issues including our privacy, scams, bullying and as adults we stumble across unwanted material that might be considered inappropriate. Children also need to be protected and this thesis will research what children do when they are online, and what protection is currently given to children. The research will also include input from teachers and parents and find out what experiences they have and what they are doing to protect children. The thesis will involve software testing to evaluate how effective parental control software is, and possibilities of it being hacked. This research will concentrate on smartphones, and in particular the Android operating system, the reason is that Android phones can be purchased cheaper than an iPhone, and therefore are more likely to be used by a child. A developer’s version of Android can also be configured to run it in a virtual machine running on a PC which makes various testing possible. The thesis will also involve reviewing other organisation’s research and findings and how it compares to my own research. The thesis will give advice on how to move forward in relation to keeping children safe online.
38

Estudo experimental da influência da razão de espaçamento e da intensidade de turbulência no escoamento biestável em dois cilindros paralelos

Ost, Ana Paula January 2015 (has links)
Este trabalho apresenta um estudo experimental acerca da influência da razão de espaçamento e da intensidade de turbulência no escoamento biestável. É estudado o escoamento sobre dois cilindros dispostos lado a lado, para o canal aerodinâmico com intensidade de turbulência inferior a 1%, para o canal aerodinâmico com grade promotora de turbulência com intensidade de turbulência de 8 a 7%, e para uma seção do canal aerodinâmico sem paredes laterais. A técnica experimental aplicada consiste na medição das flutuações de velocidade no canal aerodinâmico utilizando a técnica da anemometria de fio quente. As medições são realizadas com duas sondas, uma fixa e outra móvel que foi posicionada em seis pontos diferentes do escoamento. Os dados medidos são tratados através de ferramentas estatísticas, análise espectral e transformadas de ondaletas. Os resultados confirmam a existência do fenômeno da biestabilidade e mostram como o fenômeno sofre alterações quando exposto às condições de maior intensidade de turbulência e redução da razão de bloqueio pela retirada das paredes laterais em uma seção do canal. Para a condição de maior intensidade de turbulência, os resultados mostram que as trocas de modo se intensificam, e em alguns dos pontos de medição os sinais referentes à sonda móvel não apresentam características de biestabilidade. Para o caso sem paredes laterais, os sinais apresentam características de biestabilidade até o momento em que as paredes são removidas. / This work presents an experimental study, about the influence of the pitch to diameter ratio and the turbulence intensity on a bistable flow. The flow through two cylinders side-by-side is studied in an aerodynamic channel with turbulence intensity lower than 1%, in an aerodynamic channel with a turbulence grid, that increased the turbulence intensity to about 8 to 7%, and a section of the aerodynamic channel without lateral walls. The experimental technique consists in the measurements of the fluctuating velocities in the aerodynamic channel, using hot wire anemometry. The measurements are performed with two probes, one static, and one movable, positioned in six different points of the flow. The acquired data are analysed through statistical, spectral and wavelet tools. The results confirmed the occurrence of the bistable phenomenon and shows how it behaves when exposed to different conditions of turbulence intensity, and reduction of the blockage ratio aspect due to removal of the lateral walls of a channel section. The results for the higher turbulence intensity condition shows that the switches are intensified, some data resulting of the measurements of the second probe, do not show bistable characteristics. In the no-walls section case, the signals showed bistable features, until the moment the walls were removed.
39

Estudo comparativo experimental e numérico sobre o desempenho de turbinas savonius helicoidal e de duplo-estágio

Kothe, Leonardo Brito January 2016 (has links)
O presente trabalho apresenta um estudo numérico e experimental sobre o desempenho aerodinâmico de turbinas eólicas de eixo vertical envolvendo rotores Savonius convencional de duplo-estágio e helicoidal. O estudo experimental é realizado no Túnel Aerodinâmico Professor Debi Pada Sadhu, do Laboratório de Mecânica dos Fluidos da UFRGS. As simulações numéricas são realizadas com o software Fluent/ANSYS utilizando o Método dos Volumes Finitos. São comparados os coeficientes de torque estático e dinâmico, o coeficiente de potência, além de uma análise aerodinâmica das duas turbinas. As medições são realizadas empregando Tubos de Pitot, um torquímetro estático digital e um torquímetro simples construído para a medição do torque dinâmico. As turbinas são fabricadas através da técnica de prototipagem 3D, com uma semelhança de dimensões e parâmetros. As soluções numéricas são resolvidas através da equação da continuidade, das equações de Navier-Stokes com médias de Reynolds (RANS) e pelo modelo de turbulência k-ω SST. A qualidade da malha utilizada é avaliada através do método de Índice de Convergência de Malha (GCI), para três diferentes tamanhos de malha. São feitas análises dos rotores na forma estática para diferentes ângulos de incidência e com a turbina em rotação são feitas análises para diferentes razões de velocidades de ponta de pá (λ). Resultados demonstram que a turbina helicoidal apresenta um coeficiente de torque positivo para todos os ângulos do rotor, assim como a turbina convencional de dois estágios. O coeficiente de torque dinâmico da turbina helicoidal é superior ao da turbina de duplo-estágio para a maioria dos casos, e também apresenta menor oscilação de torque ao longo de cada rotação. Por consequência, o coeficiente de potência do rotor helicoidal também se tornou superior, com um valor máximo encontrado na ordem de 11,8% para um λ de 0,65 no caso experimental, e de 8,4% para o mesmo λ no caso numérico, quando comparado com o rotor de duplo-estágio. Os erros relativos entre as simulações numéricas e os resultados experimentais estão entre 2,16% e 13,4%. Uma estimativa de potência gerada é feita para ambos os casos, para uma razão de velocidade de ponta de 0,65, onde a turbina helicoidal apresenta melhores resultados em relação ao rotor de duplo-estágio, na ordem de 13,6% para uma velocidade de 10,4 m/s. / This paper presents a numerical and experimental study of vertical axis wind turbine performance comparison involving two-stage and helical Savonius rotors. The experimental study is conducted in the Aerodynamic Tunnel Professor Debi Pada Sadhu at the Fluid Mechanics Laboratory of the UFRGS. The numerical simulations are performed with the Fluent/ANSYS software using the Finite Volumes Method. The static and dynamic torque coefficients, the power coefficients, and an aerodynamic analysis of the two turbines are compared. Measurements are made using Pitot tubes, a digital static torque wrench and a simple wrench constructed for the dynamic torque measurement. The aerodynamics rotors are manufactured by 3D prototyping technique with similar dimensions and parameters. Numerical solutions are solved by the continuity equation, the Reynolds Averaged Navier-Stokes (RANS) equations and the turbulence model k-ω SST. The quality of the mesh used is evaluated used the Grid Convergence Index (GCI) method, for three different mesh sizes. The rotors analyzes are made in static form for different angles of incidence and for the rotating turbine analyzes are made for differents tip speed ratio (λ). Results show that the helical turbine has a positive static torque coefficient for any rotor angles, as well as conventional two-stage turbine. The dynamic torque coefficient of the helical turbine is higher than the two-stage turbine for most cases and also shows less torque variation along each rotation. Consequently, the power coefficient of the helical rotor also become higher, with a maximum value found on the order of 11.8% for a λ of 0.65 in the experimental case, and 8.4% for the same λ number when compared with the two-stage rotor. The relative errors between the numerical simulations and the experimental results are between 2.16% and 13.4%. A generated power estimate is made for both cases, for a tip speed ratio of 0.65, where the helical turbine provides better results compared to two-stage rotor in order of 13.6% for a velocity of 10.4 m/s.
40

Dosagem de frações ativadas do sistema complemento em empiema induzido em ratos

Peterson, Guilherme Eckert January 2016 (has links)
Introdução: Empiema pleural em geral decorre de complicação de pneumonias e, se não identificado e tratado precocemente, pode ocasionar aumento morbidade ou mesmo mortalidade. A identificação de marcadores no líquido pleural de efusões parapneumônicas que mostrem a presença ou a evolução precoce para empiema tem significância clínica. Neste cenário, dosagens das concentrações de frações ativadas do complemento no líquido pleural podem ajudar no diagnóstico precoce do empiema. Objetivos: Comparar as concentrações de frações ativadas do complemento (C3a, C5a e C5b9) em efusões pleurais induzidas em ratos por inoculação intrapleural de bactérias ou por irritante químico estéril (terebentina). Métodos: Trinta e nove ratos Wistar machos, peso médio de 414g (290 a 546g), realizaram anestesia geral com isofluorano inalatório por máscara, e toracocentese no 4º espaço intercostal com abocath conectado a oscilômetro de pressão para confirmar posição intrapleural. Os animais foram divididos em 3 grupos: SA (n=17) - inoculação de Staphylococcus aureus; SP (n=12) - inoculação de Streptococcus pneumoniae; C (n=10) – inoculação de terebintina (efusão pleural estéril, controle). Doze horas após a inoculação intrapleural foi coletado liquido pleural por toracocentese, sob controle ecográfico, e realizadas dosagens de C3a, C5a e C5b9 pelo método ELISA. Resultados: A dosagem de C3a foi de 1066,82 μg/ml (937,29 – 1196,35 μg/ml) no grupo SA, 1188,28 μg/ml (1095,65 – 1280,92 μg/ml) no SP, e de 679,13 μg/ml (601,29 – 756,98 μg/ml) no C (p<0,001). A dosagem de C5a foi de 55.727 ng/ml (41,22 – 70,23 ng/ml) no grupo SA, 520.107 ng/ml (278,92-761,3 ng/ml) no SP, e de 5.268 ng/ml (1,68 – 8,85 ng/ml) no C (p<0,001). A dosagem de C5b9 foi de 15,02 ng/ml (13,1 – 16,94 ng/ml) no SA, de 16,63 ng/ml (14,37 – 18,9 ng/ml) no SP, e de 14,05 ng/ml (9,8 – 18,29 ng/ml) no C (p=0,692). A avaliação das curvas ROC demonstrou área sob a curva de 0,987 (IC95% 0,953-1) para o C3a; 1 para C5a (1-1) e 0,757 (0,523-0,990). Conclusões: As frações ativadas dos complementos C3a e C5a foram significativamente maiores nos empiemas induzidos experimentalmente por inoculação intrapleural de Staphylococcus aureus e Streptococcus pneumoniae do que com aquelas observadas após inoculação intrapleural de terebentina. A dosagem elevada destas frações ativadas do complemento foi útil para o diagnóstico do empiema pleural induzido em ratos. / Background Pleural empyema is a well-known complication of pneumonia. If treatment is delayed, empyema may increase morbidity and mortality in affected patients. Therefore, the identification of empyema biomarkers in parapneumonic pleural effusion is desirable. Previous research has suggested complement activation products as candidate empyema markers. Objective To compare the levels of complement activation products C3a, C5a, and C5b9 in pleural effusion induced by Staphylococcus aureus (SA), Streptococcus pneumoniae (SP), or turpentine (control). Method Thirty-nine male Wistar rats (mean weight 414g; 290-546g) were allocated as follows: 17 animals in the SA group, 12 in the SP group, and 10 in the control group. Bacteria or turpentine were injected into the pleural space. After 12h, intrapleural fluid was collected using ultrasound-guided thoracentesis. Levels of complement activation products were determined using ELISA kits. Results Two SA and 1 SP animals died before 12h. Mean levels were as follows: C3a: 1066.82 μg/mL (937.29-1196.35 μg/mL) in SA, 1188.28 μg/mL (1095.65-1280.92 μg/mL) in SP, and 679.13 μg/mL (601.29-756.98 μg/mL) in controls (p<0.001); C5a: 55.727 ng/mL (41.22-70.23 ng/mL) in SA, 520.107 ng/mL (278.92-761.3 ng/mL) in SP, and 5.268 ng/mL (1.68-8.85 ng/mL) in controls (p<0.001); C5b9: 15.02 ng/mL (13.1-16.94 ng/mL) in SA, 16.63 ng/mL (14.37-18.9 ng/mL) in SP, and 14.05 ng/mL (9.8-18.29 ng/mL) in controls (p=0.692). ROC analysis revealed an area under the curve of 0.987 (95%CI: 0.953-1) for C3a; 1 (1-1) for C5a; and 0.757 for C5b9 (0.523-0.990). Conclusions In the present rat model, complement activation fragments C3a and C5a accurately detected infected pleural effusion.

Page generated in 0.1382 seconds