• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1
  • Tagged with
  • 3
  • 3
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 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

Efeito do Tipo de GÃs de ProteÃÃo Sobre o Desempenho do Arame Tubular AWS E71T-1, Utilizando Processo Convencional e Pulsado / The effect of the shielding gas type on performance of the AWS E71T-1 flux cored wire using the conventional and the pulsed process

Juscelino Chaves Sales 16 December 2002 (has links)
O arame tubular AWS E71T-1 tem sido utilizado, na grande maioria das aplicaÃÃes, com CO2 e argÃnio. No entanto, para esta mistura de gÃs, as informaÃÃes nÃo foram levantadas, de forma suficiente, com relaÃÃo ao desempenho operacional do arame. Sabe-se que o tipo de gÃs afeta tambÃm a transferÃncia metÃlica, o comportamento do arco, a geometria do cordÃo de solda, a taxa de deposiÃÃo e a eficiÃncia de fusÃo do arame, dentre outras caracterÃsticas do processo de soldagem. O objetivo do trabalho consiste em realizar um levantamento das caracterÃsticas operacionais do arame tubular AWS E71T-1 empregando CO2 puro e uma mistura de CO2 + argÃnio na soldagem convencional em tensÃo constante e na soldagem com corrente pulsada. Neste sentido, foram realizadas soldas, com arame tubular AWS E71T-1 de 1,2 mm de diÃmetro, em simples deposiÃÃo, na posiÃÃo plana, em corpos de prova de aÃo ABNT 1020 com dimensÃes de 150x50x8 mm. Empregou-se uma fonte eletrÃnica de soldagem e um sistema automÃtico de posicionamento da pistola. A tensÃo de soldagem foi mantida em 23 V. A relaÃÃo entre a velocidade de alimentaÃÃo do arame e a velocidade de soldagem foi mantida entre 20 e 23, para garantir uma Ãrea adicionada aproximadamente constante de 18 mm2. analisaram-se os efeitos do tipo de gÃs de proteÃÃo (CO2 e Ar + CO2 ), da distÃncia bico de contato peÃa (20 e 25 mm), dos nÃveis de corrente (160, 180 e 200 A) e sua natureza (convencional e pulsada) sobre o comportamento do arco, sobre a geometria da solda e sobre as caracterÃsticas econÃmicas do arame (taxa de fusÃo, taxa de deposiÃÃo e eficiÃncia de deposiÃÃo). Os resultados indicam que o tipo de gÃs de proteÃÃo afeta mais significativamente a transferÃncia metÃlica e a geometria da solda, exercendo pequena influÃncia sobre as caracterÃsticas econÃmicas do arame. Constatou-se tambÃm que o efeito da intensidade de corrente sobre a operacionalidade do arame tubular AWS E71T-1 depende sensivelmente do tipo de corrente (convencional ou pulsada). / The flux cored wire AWS E71T-1 has been used in the vast majority of its applications with pure CO2 as a shielding gas. A recent study demonstrated that it is possible to improve the metallurgical characteristics of the weld metal of the flux cored wire by the application of a mixture of CO2 and argon. However, information for this gas mixture hasnât been raised sufficiently concerning the operational performance of the wire using this gas mixture. It is known that the gas type also affects the metal transfer, the behavior of arc welding, the weld bead geometry, the deposition rate and the deposition efficiency of the wire within other characteristics of the welding process. The aim of the study consists in the realization of a survey of the AWS E71T-1 flux cored wire operational characteristics (economic characteristics of the welding consumable, geometric weld characteristics, arc stability and metal transfer). Due to this, bead on plate welding was performed using the flux cored wire AWS E71T-1 with a diameter of 1,2 mm, in flat position on samples of ABNT 1020 steel with a size of 150x50x8 mm. An electronic welding source and a positioning system were used. It was sustained a welding tension of 23 V. The relationship between the wire feed speed and the travel speed was kept constant between 20 and 23 to guarantee a deposit area of approximately 18 mm2. The influence of shielding gas (CO2 and Ar and CO2 ), the contact tube-to-work (TTW) (20 and 25 mm), the welding current (160, 180 and 200 A) and its nature (conventional and pulsed) were analyzed regarding the behavior of arc welding, the weld geometry and the economic characteristics of cored wire (fusion rate, deposition rate and deposition efficiency). The results showed that the shielding gas type has more influence on metal transfer and welding geometry and little influence on economic characteristics of the cored wire. It was also shown that the effect of the current intensity on the operationally of the flux cored wire AWS E71T-1 depends perceptibly on the current type (conventional or pulsed).
2

Human-scaled personal mobility device performance characteristics

Ballard, Lance Dale 14 November 2012 (has links)
Today, numerous alternative modes of mobility are emerging to provide a solution to the problems created by the automobile. This research envisions a future where transportation in urban areas will be dominated by small personal mobility devices (PMDs) instead of automobiles. This Intelligent Mobility System (IMS) would be a car-free zone where people travel by a shared-system of PMDs providing levels of mobility greater than walking but less than a car. This research effort focuses on the operational aspects of this future system by studying PMD performance characteristics as inputs for a computer simulation model of an IMS environment. Therefore, the primary objective of this research is to evaluate the operations of PMDs that are currently used in a variety of settings. GPS recorders are used to log speed and location data each second of pedestrian, bicycle, Segway, and electric cart trips. Segway speed and acceleration are analyzed using three factors, sidewalk width, surface quality, and pedestrian density to study their effect on Segway speed. Pedestrians have the lowest mean speed and the most narrow speed distribution. Segways, bicycles and electric carts have increasingly faster mean speeds and wider speed distributions, respectively. Segways and bicycles were found to have similar acceleration distributions. Segways seem to provide a level of speed and mobility between that of pedestrians and cyclists, meaning that Segways might capture new users by providing a level of mobility and convenience previously unseen. Narrow sidewalk widths, poor sidewalk quality, and heavy pedestrian density all decreased Segway speeds. The researchers suspect that surface quality is likely an independent constraint for Segway speed and that sidewalk width and pedestrian density interact to limit Segway speeds under certain conditions. This research concludes that these external factors may affect PMD speed and should be considered when analyzing PMD mobility, especially in an IMS setting.
3

ONE CONSORTIUM, TWO POPULATIONS: WHAT IT TAKES TO SUCCEED

Sipes, Susan Diane 01 December 2010 (has links)
AN ABSTRACT OF THESIS OF Susan D. Sipes, for the Masters of Science degree in Workforce Education and Development, presented on October 11, 2010, at Southern Illinois University Carbondale. TITLE: ONE CONSORTIUM, TWO POPULATIONS: WHAT IT TAKES TO SUCCEED MAJOR PROFESSORS: Dr. Marcia Anderson and Dr. Beth Winfrey-Freeburg University consortia have existed for over 50 years as a practical solution to increase regional access to higher education and control costs. The challenge has been to determine how to measure the effectiveness of consortia in order to predict their success. The goal was to apply a business case to UCLC, treating students as customers, and administrators as business owners. Throughout the literature, much has been written to define the critical operational characteristics of successful consortia, but little has been done to explore the needs of consortia's customers. This work presents a compilation of operational characteristics with services desired by students in order to predict the success of one newer consortium, the University Center of Lake County in IL (UCLC). The characteristics and services of existing successful consortia were gleaned from the literature and a written survey instrument was developed. Students and administrators at UCLC were surveyed; their responses were compared to data extracted from other research using descriptive statistics and a chi-squared test. Results showed that UCLC exhibits many of the most important operational characteristics to be successful. Practical recommendations are provided to UCLC to further explore how to improve student services. For example, UCLC needs to increase its marketing and advertising efforts. Other consortia will be able to repeat the surveys to learn more about their operations and service levels.

Page generated in 0.3571 seconds