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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.
121

Um estudo experimental sobre sopros laterais a partir da ponta de asa / Multiple lateral wingtip blowing: an experimental study

Coimbra, Rogério Frauendorf de Faria 23 August 2002 (has links)
O uso de sopro lateral a partir da ponta de uma asa, desloca para fora seus vórtices de ponta, aumentando sua envergadura efetiva. Este aumento reflete em incremento na sustentação da asa e redução em seu arrasto induzido. O presente estudo pesquisou, através de ensaios em túnel de vento, uma configuração de sopro lateral a partir da ponta de asa, cujo sopro foi efetuado através de três fendas dispostas ao longo da corda da ponta de um modelo de asa. Cada fenda era individual, ou seja, sua alimentação de ar, regulagem da intensidade do sopro e posicionamento do ângulo de saída do jato em relação ao plano da asa, eram independentes. Desta forma, ensaiaram-se vários posicionamentos angulares relativos entre as fendas e configurações com um, dois ou três sopro(s). Os resultados obtidos demonstraram que todas as configurações ensaiadas promoveram incrementos na sustentação e reduções no arrasto da asa e, geralmente, quanto maior o número de sopros, maiores foram os ganhos. Entretanto, algumas configurações com sopros duplos apresentaram benefícios aerodinâmicos superiores àqueles demonstrados pelos sopros triplos. Portanto, pode-se obter benefícios aerodinâmicos com configurações de sopro que demandem menor massa de ar e, no caso de uma aeronave equipada com tal dispositivo, significar-se-á menor sangria de ar do(s) motor(es). / Lateral wing tip blowing device displaces wing tip vortices outboard and increases the effective span of the wing. The increase in wing span increases lift and reduces induced drag. This study, which included tests in the wind tunnel, tested a lateral wing tip blowing device in which the jets flow exit was from three longitudinal slots on a wing tip model. Jet intensity and angular position could be individually regulated for each slot. Various angular positions of the slots were tested and were also tested one, two or three plenum chambers operating. Results shown that all the blowing configurations increased lift and reduced drag. Some double jet configurations, using reduced jet coefficient, demonstrated aerodynamic improvements than those with triple jets. Therefore, localized lateral wing tip blowing devices provides aerodynamic improvement than full cord lateral jets and yet, uses less engine bleed air.
122

A decisão da largada do levantador do voleibol na perspectiva de dinâmica ecológica / The volleyball setter\'s decision-making of tipping in the ecological dynamics

Denardi, Renata Alvares 14 December 2015 (has links)
O objetivo deste estudo foi investigar a decisão do levantador do voleibol de largar a bola no campo adversário no segundo toque, com base em variáveis espaço-temporais que refletem a interação jogador-ambiente de jogo. Foram filmados 20 jogos de voleibol (10 masculinos e 10 femininos) do Campeonato Paulista - divisão I (2013), dos quais foram selecionadas 172 sequências de jogadas de levantadores, sendo 86 largadas e 86 levantamentos (controle). Os deslocamentos dos jogadores foram capturados pelo software TACTO, desde o início do passe até o contato do levantador com a bola. Foram consideradas 37 variáveis (espaço-temporais) para análise por meio da MANOVA, sendo estas resultantes das seguintes medidas: (i) distância do levantador à rede; (ii) distância percorrida pelo levantador para chegar até à bola; (iii) distância do passe; (iv) área adversária; (v) distância entre os bloqueadores; (vi) distância entre o levantador e os bloqueadores; e (vii) distância dos bloqueadores à rede. Quando pertinente, foram observadas as respectivas velocidades e variabilidades dessas medidas. Uma análise complementar buscou compreender a natureza das largadas, por meio de comparações relativas à sua efetividade, sua ocorrência nas diferentes transições do rali, o tipo de largada e largadas executadas por homens e mulheres. Os resultados revelaram que largadas diferiram de levantamentos em relação às seguintes variáveis que envolviam o time atacante: distâncias inicial e final do levantador à rede, distância e velocidade de deslocamento do levantador para chegar até à bola, e velocidade do passe. Em relação ao time adversário, as variáveis foram apenas espaciais: área final e distância final entre o levantador e os bloqueadores. Concluiu-se que variáveis espaço-temporais que refletem as interações dos jogadores no jogo de voleibol foram cruciais para a tomada de decisão de largar do levantador. Foi destacada a relação entre os dois times e a importância dessas interações também nas duas fases de transição do rali. Interações espaciais foram críticas para determinar o tipo de largada que seria utilizado. E ainda, interações interpessoais e extrapessoais influenciaram a decisão de largar / This study aimed to investigate the volleyball setter\'s decision-making of tipping based on spatiotemporal variables involving the interaction between players and their game environment. Twenty volleyball games (10 male and 10 female) of the Paulista championship - division I (2013) were recorded, from which 172 actions of the setters were selected. The actions were 86 tips and 86 sets (control group). Players\' displacements were captured using TACTO software, from the beginning of the pass to the contact of the setter to the ball. Thirty-seven spatiotemporal variables were considered in a MANOVA analysis. They were extracted from the follow measures: (i) distance between the setter and the net; (ii) distance between the setter and the ball; (iii) pass distance; (iv) area between opponents; (v) distance between blockers; (vi) distance between the setter and the blockers; (vii) distance between the blockers and the net. When appropriate it was considered the velocity and variability of these measures. Complementary analysis aimed to understand the tips, comparing its effectiveness, its occurrence in different rally transitions, types of tips and tips according to sex. Results revealed that tips and sets were different according these spatiotemporal variables of the attacking team: initial and final distances between the setter and the net, distance and velocity between the setter and the ball, and pass velocity. Only spatial variables related to the defending team were significant: final area and final distance between the setter and the blockers. In conclusion, spatiotemporal interactions involving the players\' behavior in the game environment were crucial for setter\'s decision-making of performing the tip. The relation between the two teams and the importance of their interactions were highlighted also in the two phases of rally transition. Spatial interactions were critical to determine the type of tip. Moreover, interpersonal and extrapersonal interactions influenced this specific setters\' decision
123

Um estudo experimental sobre sopros laterais a partir da ponta de asa / Multiple lateral wingtip blowing: an experimental study

Rogério Frauendorf de Faria Coimbra 23 August 2002 (has links)
O uso de sopro lateral a partir da ponta de uma asa, desloca para fora seus vórtices de ponta, aumentando sua envergadura efetiva. Este aumento reflete em incremento na sustentação da asa e redução em seu arrasto induzido. O presente estudo pesquisou, através de ensaios em túnel de vento, uma configuração de sopro lateral a partir da ponta de asa, cujo sopro foi efetuado através de três fendas dispostas ao longo da corda da ponta de um modelo de asa. Cada fenda era individual, ou seja, sua alimentação de ar, regulagem da intensidade do sopro e posicionamento do ângulo de saída do jato em relação ao plano da asa, eram independentes. Desta forma, ensaiaram-se vários posicionamentos angulares relativos entre as fendas e configurações com um, dois ou três sopro(s). Os resultados obtidos demonstraram que todas as configurações ensaiadas promoveram incrementos na sustentação e reduções no arrasto da asa e, geralmente, quanto maior o número de sopros, maiores foram os ganhos. Entretanto, algumas configurações com sopros duplos apresentaram benefícios aerodinâmicos superiores àqueles demonstrados pelos sopros triplos. Portanto, pode-se obter benefícios aerodinâmicos com configurações de sopro que demandem menor massa de ar e, no caso de uma aeronave equipada com tal dispositivo, significar-se-á menor sangria de ar do(s) motor(es). / Lateral wing tip blowing device displaces wing tip vortices outboard and increases the effective span of the wing. The increase in wing span increases lift and reduces induced drag. This study, which included tests in the wind tunnel, tested a lateral wing tip blowing device in which the jets flow exit was from three longitudinal slots on a wing tip model. Jet intensity and angular position could be individually regulated for each slot. Various angular positions of the slots were tested and were also tested one, two or three plenum chambers operating. Results shown that all the blowing configurations increased lift and reduced drag. Some double jet configurations, using reduced jet coefficient, demonstrated aerodynamic improvements than those with triple jets. Therefore, localized lateral wing tip blowing devices provides aerodynamic improvement than full cord lateral jets and yet, uses less engine bleed air.
124

Acquisition of a Social Problem Solving Method by Caregivers in the Foster Care System: Evaluation and Implications

Skelton, Evan Ann 19 March 2014 (has links)
All youth are faced with many social issues and problems on a daily basis, and youth in foster care are often less equipped than their peers to make good decisions for themselves. The SODAS problem solving method is a component of the Transition to Independence Process (TIP) model and is intended for personnel to use with youth to help them make better decisions when faced with difficult situations. The SODAS method is designed to guide youth through a problem solving method for a current situation, and over time to acquire improved problem solving skills. Three caregivers at a group facility for youth in foster care were trained in the use of the SODAS method using Behavioral Skills Training (BST) and were evaluated by the researchers in their use of SODAS in simulated role plays with the researchers and with youth participants to test for generalization of the SODAS method to novel situations. Results showed substantial improvement of caregiver application of the steps on the SODAS method from baseline to the post-training condition when researchers simulated the youth's role. Results also showed that caregiver proficiency generalized to novel situations presented by youth participants during their role play probes.
125

A Service for Audio Icon and Audio Books in the Mobile Tourist Information System (TIP) via the Greenstone Digital Library

Gao, Xin January 2007 (has links)
This project provides an audio notification about nearby tourism place to visit (named sight in this thesis), a chapter based Audio Books related to the current sight and involving Digital Library to provide text for the Audio Books for the Tourist Information Provider on a mobile device (TIP). The current system plays a background sound for the sight only when the system displays the specific information for that sight after user selects it. This has been improved to provide a notification by which to receive audios from the recommendation service, and then keep sending audio data to clients on real time. So users can know the sight nearby before they look at their screen. The limitation of current Audio Books is that it only provides Audio Books when the books start from the current sight. This problem is solved by providing a list of books that has any chapter related to that sight, and users can add them into a now-playing list. The Travel Planning Service has been involved to place the Audio Books chapters into the now-playing list based on the order of the visiting sight in their plan. The TIP/Greenstone Service, which can load particular text from Greenstone Digital Library into TIP, has been involved in this project to provide related chapter-based text for those Audio Books. The implemented prototype has been evaluated on effeteness and performance based on the purpose of this project. The result has been discussed to prove it has effectively solved the problem described above. Finally, the result of the experiment on distinguishing audio, and technology for implementation and audio transfers, has been left for future study.
126

Application of fracture mechanics to predict the growth of single and multi-level delaminations and disbonds in composite structures

Mikulik, Zoltan, Mechanical & Manufacturing Engineering, Faculty of Engineering, UNSW January 2008 (has links)
The high stiffness to weight ratio and fatigue resistance make carbon fibre composites suitable for both military and large civil aircraft. The limited ability of current numerical methods to capture the complex growth of damage in laminated composites leads to a conservative design approach applied in today??s composite aircraft structures. The aim of the presented research was to develop an improved methodology for the failure prediction of laminated composites containing delaminations located between arbitrary layers in the laminate, and to extend the investigations to composite structures subjected to barely visible impact damage (BVID). The advantages of fracture mechanics-based methodologies to predict interlaminar failure in composite structures were identified, from which the crack tip element (CTE) approach and the virtual crack closure technique (VCCT) were selected for assessment. Extensive validation of these fracture mechanics methods is presented on a number of composite structures ranging from coupons to large stiffened panels. It was shown that the VCCT was relatively insensitive to the crack front mesh size, whilst predictions using the CTE methodology were significantly influenced by the element size. Based on the obtained results modelling guidelines for the VCCT and CTE were established. Significant contribution of this research to the field of the analysis of composite structures was the development of a novel test method for the evaluation of embedded single and multi-level delaminations. The test procedure of the single delamination specimen was proposed as an analogous test to conventional compression experiments. The transverse test overcame the inherent problems of in-plane compression testing and produced less scatter of experimental measurements. Quantitative analysis of numerical results employing the validated finite element modelling approaches showed that the failure load and location were in agreement with experiments. Furthermore, new modelling techniques for composite structures containing BVID proposed in this research produced good correlation with test data from the compression after impact (CAI) test. The study of BVID provided a significant contribution toward the knowledge of the applicability of implicit FE solvers to predict failure of CAI specimens as well as the criticality of centrally impacted specimens.
127

Development, Modelling and Implementation of Cartesian Drill Bit Control

Larsen, Erik, Källquist, Mathias January 2009 (has links)
<p>Atlas Copco Surface Drilling Equipment is one of the leading manufacturers of surface drill rigs. To stay in the top segment it is of great importance to have a well functioning development strategy as well as rig functions that makes the work as easy as possible for the operator. In this master thesis one development strategy has been evaluated and a dub tip control has been developed from idea to test on rig.</p><p> </p><p>Today the conventional method to position the drill is to use two joysticks with three axes each where each axis corresponds to one hydraulic actuator on the boom and feeder structure. The dub tip control system enables the operator to position the drill in Cartesian coordinates with only one 3-axes joystick. After the definition of the desired drill angle is done, the control system makes sure that this angle is obtained throughout the positioning motion. This system makes it considerably easier for an inexperienced operator to position the drill.</p><p> </p><p>For development, simulation and verification of the control algorithms and regulators <em>Matlab/Simulink</em> has been used. To test the control system on rig, a configuration with <em>LabVIEW</em> together with a <em>compactDAQ</em> has been evaluated. <em>LabVIEW </em>is chosen because it provides the opportunity to create a user friendly graphical user interface. To use this configuration is however not recommended for persons with little or none experience from using <em>LabVIEW</em>.</p><p> </p><p>This development strategy can be used for tests and verifications of control algorithms, but since neither <em>Windows </em>nor the <em>compactDAQ </em>are real time systems, there are solutions that are better but of course to a higher price.</p><p> </p><p>The master thesis work has shown that it is possible to implement a dub tip control on a rig of this dimension. It has also concluded that compensated valves are necessary to achieve optimal performance of a velocity controlled dub tip positioning.</p>
128

Reverse genetic and cell biological approaches to the study of developmental functions of Class XI myosin in Arabidopsis thaliana

Park, Eunsook 01 March 2010 (has links)
Myosin proteins function as molecular motors that drive the ATP-dependent movement of cellular components along actin filaments. Vascular plants encode two different types of myosin, referred to as class VIII and class XI. Although class XI myosins have been suggested to function in organelle movement and cytoplasmic streaming, little is known about their cellular function in detail. The Arabidopsis genome encodes 13 class XI myosin genes. The reasons for the relatively large number of myosin XI isoforms present within a single plant species are unknown. To investigate the function of these gene products in the cell, we determined the spatial and temporal gene expression patterns by constructing promoter-reporter plants. Myosin genes are expressed in a variety of tissues with substantial overlap between family members. To study the biological function more intensively, homozygous T-DNA insertion lines were isolated for all 13 genes. Interestingly, five mutants showed phenotypes related to root hairs. mya2, xi-b, and xi-k showed shorter root hairs than in wild type while xi-h and mya1 produced a higher density of root hairs on the epidermis. MYA1 and XI-K are the most similar isoforms among the 13 myosins and their double mutant showed an additive phenotype with extremely short root hairs suggesting that these two myosins have partially redundant functions. Interestingly organelle movements, especially those of peroxisomes, were reduced in mya1 xi-k. Tip growth is the key growth mechanism in root hairs and pollen tubes. Many kinds of vesicles are trafficking toward (or backward from) the apical dome of root hairs to supply membrane and cell wall material as well as energy for growing tips. These movements along the shank of the hair occurred with velocities around 2 to 3 μm/s for Arabidopsis thaliana. In xi-k mutants, root hairs grew more slowly and terminated sooner than in wild type. Interestingly, this reduction of growth rate was correlated with a fluctuation of YFP-RAbA4b accumulation at the tip of growing root hairs. Other markers, including PI4P lipid and ER, as well as calcium and actin dynamics did not show significant differences. A YFP-XI-K construct driven by its native promoter could rescue the mutant phenotype and revealed accumulation of this myosin in the tip of growing root hairs. The distribution of YFP-XI-K in the root hair tip partially overlapped with CFP-RHD4-labeled vesicles at the subapex and YFP-RabA4b vesicles at the apex of root hairs, suggesting that myosin XI-K might be involved in the accumulation of unidentified vesicles in the tip of growing root hairs. Characterization of two mutants that showed ectopic root hair growth in the epidermis, resulting in a higher density of root hairs than wild type, mya1 and xi-h, were initiated with two analyses. At first, staining pattern of promoter-reporter constructs of three key transcription factors, WER, EGL3, and GL2 were observed in mya1. Although variation in individual samples was too large to conclude, GL2 staining patterns in mya1 occasionally were unorganized. Increasing sample population and detail study is necessary. Secondly, effects of phosphate deficiency were observed with the mya1 and the xi-h in series of phosphate concentrations ranging from 1μM to 300μM. The xi-h mutant showed insensitivity on root hair production upon phosphate deficiency, suggesting a potential function of XI-H in the response to phosphate deficiency. Confirmation of these results and further study of the MYA1 and the XI-H is essential. In summary, this study established a systematic approach to investigate the biological function of class XI myosins in plant development and significantly increases our understanding of the function of XI-K myosin in root hair tip growth.
129

On the influence of indenter tip geometry on the identification of material parameters in indentation testing

Guo, Weichao 08 December 2010 (has links)
ABSTRACT The rapid development of structural materials and their successful applications in various sectors of industry have led to increasing demands for assessing their mechanical properties in small volumes. If the size dimensions are below micron, it is difficult to perform traditional tensile and compression tests at such small scales. Indentation testing as one of the advanced technologies to characterize the mechanical properties of material has already been widely employed since indentation technology has emerged as a cost-effective, convenient and non-destructive method to solve this problem at micro- and nanoscales. In spite of the advances in indentation testing, the theory and development on indentation testing are still not completely mature. Many factors affect the accuracy and reliability of identified material parameters. For instance, when the material properties are determined utilizing the inverse analysis relying on numerical modelling, the procedures often suffer from a strong material parameter correlation, which leads to a non-uniqueness of the solution or high errors in parameter identification. In order to overcome that problem, an approach is proposed to reduce the material parameter correlation by designing appropriate indenter tip shapes able to sense indentation piling-up or sinking-in occurring in non-linear materials. In the present thesis, the effect of indenter tip geometry on parameter correlation in material parameter identification is investigated. It may be helpful to design indenter tip shapes producing a minimal material parameter correlation, which may help to improve the reliability of material parameter identification procedures based on indentation testing combined with inverse methods. First, a method to assess the effect of indenter tip geometry on the identification of material parameters is proposed, which contains a gradient-based numerical optimization method with sensitivity analysis. The sensitivities of objective function computed by finite difference method and by direct differentiation method are compared. Subsequently, the direct differentiation method is selected to use because it is more reliable, accurate and versatile for computing the sensitivities of the objective function. Second, the residual imprint mappings produced by different indenters are investigated. In common indentation experiments, the imprint data are not available because the indenter tip itself shields that region from access by measurement devices during loading and unloading. However, they include information about sinking-in and piling-up, which may be valuable to reduce the correlation of material parameter. Therefore, the effect of the imprint data on identification of material parameters is investigated. Finally, some strategies for improvement of the identifiability of material parameter are proposed. Indenters with special tip shapes and different loading histories are investigated. The sensitivities of material parameters toward indenter tip geometries are evaluated on the materials with elasto-plastic and elasto-visoplastic constitutive laws. The results of this thesis have shown that first, the correlations of material parameters are related to the geometries of indenter tip shapes. The abilities of different indenters for determining material parameters are significantly different. Second, residual imprint mapping data are proved to be important for identification of material parameters, because they contain the additional information about plastic material behaviour. Third, different loading histories are helpful to evaluate the material parameters of time-dependent materials. Particularly, a holding cycle is necessary to determine the material properties of time-dependent materials. These results may be useful to enable a more reliable material parameter identification.
130

On failure modelling in finite element analysis : material imperfections and element erosion

Unosson, Mattias January 2005 (has links)
This dissertation concerns failure modelling with material imperfections and element erosion in finite element analyses. The aim has been to improve the element erosion technique, which is simple to use and implement and also computationally inexpensive. The first part of the dissertation serves as an introduction to the topic and as a summary of the methodologies presented in the following part. The second part consists of seven appended papers. In paper A the standard element erosion technique is used for projectile penetration. In papers B and C a methodology that accounts for size effects is developed and applied to crack initiation in armour steel and tungsten carbide. A methodology to better predict the stress state at crack tips with coarse meshes is presented and applied to armour steel in paper D. Papers E and F concern the development of selective mass scaling which allows for larger time steps in explicit methods. Finally, in paper G the previously presented methodologies are used in combination and validated against experimental results on tungsten carbide. The computations show good agreement with the experimental results on failure initiation for both materials, while the computational results on the propagation of cracks show better agreement for the armour steel than for the tungsten carbide. / On the day of the public defence of the doctoral thesis, the status of articles I, III and IV was Accepted and article VII was Submitted.

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