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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.
81

Scale estimation by a robot in an urban search and rescue environment

Nanjanath, Maitreyi 30 September 2004 (has links)
Urban Search and Rescue (USAR) involves having to enter and explore partially collapsed buildings in search for victims trapped by the collapse. There are many hazards in doing this, because of the possibility of additional collapses, explosions, fires, or flooding of the area being searched. The use of robots for USAR would increase the safety of the operation for the humans involved, and make the operation faster, because the robots could penetrate areas inaccessible to human beings. Teleoperated robots have been deployed in USAR situations to explore confined spaces in the collapsed buildings and send back images of the interior to rescuers. These deployments have resulted in the identification of several problems found during the operation of these robots. This thesis addresses a problem that has been encountered repeatedly in these robots: the determination of the scale of unrecognizable objects in the camera views from the robot. A procedure that would allow the extraction of size using a laser pointer mounted on the robot's camera is described, and an experimental setup and results that verify this procedure have been shown. Finally, ways to extend the procedure have been explored
82

Sequential and Localized Implicit Wavelet Based Solvers for Stiff Partial Differential Equations

McLaren, Donald Alexander 01 May 2012 (has links)
This thesis explains and tests a wavelet based implicit numerical method for the solving of partial differential equations. Intended for problems with localized small-scale interactions, the method exploits the form of the wavelet decomposition to divide the implicit system created by the time discretization into multiple, smaller, systems that can be solved sequentially. Included are tests of this method on linear and non-linear problems, with both its results and the time required to calculate them compared to basic models. It was found that the method requires less computational effort than the high resolution control results. Furthermore, the method showed convergence towards high resolution control results.
83

The Outcome of Head Injuries: The Saudi Experience

IBRAHIM, E.M., AMMAR, AHMED, CHOWDHARY, U.M., IBRAHIM, M., WAHAB, ABDEL 03 1900 (has links)
No description available.
84

Scale-up of Extrusion Foaming Process for Manufacture of Polystyrene Foams Using Carbon Dioxide

Zhang, Hongtao 31 December 2010 (has links)
An initial evaluation of the scalability of extrusion foaming technology is conducted in this thesis. Both lab- and pilot-scale foam extrusion systems along with annular dies and flat dies were used to investigate the effects of extrusion system scale on the foam expansion. The effects of the processing conditions including die temperature and blowing agent content on the volume expansion of extruded polystyrene foams blown with carbon dioxide are presented. A systematic comparison of the effects of extrusion system scale on the expansion behavior of polystyrene foams blown with carbon dioxide at the consistent pressure-drop rate, demonstrated that the scale of the foam extrusion system does not affect the principles of the foaming process, and the effects of extrusion system size on the scale-up of foam techniques, such as shear rate and temperature uniformity, could be suppressed by tailoring the processing conditions and experimental parameters.
85

Scale-up of Extrusion Foaming Process for Manufacture of Polystyrene Foams Using Carbon Dioxide

Zhang, Hongtao 31 December 2010 (has links)
An initial evaluation of the scalability of extrusion foaming technology is conducted in this thesis. Both lab- and pilot-scale foam extrusion systems along with annular dies and flat dies were used to investigate the effects of extrusion system scale on the foam expansion. The effects of the processing conditions including die temperature and blowing agent content on the volume expansion of extruded polystyrene foams blown with carbon dioxide are presented. A systematic comparison of the effects of extrusion system scale on the expansion behavior of polystyrene foams blown with carbon dioxide at the consistent pressure-drop rate, demonstrated that the scale of the foam extrusion system does not affect the principles of the foaming process, and the effects of extrusion system size on the scale-up of foam techniques, such as shear rate and temperature uniformity, could be suppressed by tailoring the processing conditions and experimental parameters.
86

Investigation of Scale Adaptive Simulation (SAS) Turbulence Modelling for CFD-Applications

Wahlbom Hellström, Victoria, Alenius, Frida January 2013 (has links)
Fluid dynamics simulations generally require large computational recourses in form of computer power and time. There are different methods for simulating fluid flows that are more or less demanding, but also more or less accurate. Two well known computational methods are the Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES). RANS computes the timeaveraged flow properties, while LES resolve the large structures (eddies) of the flow directly and model the small ones. Hybrid models are combinations of these two models which have been developed to improve the RANS solutions and shorten the simulation time compared to LES computations. One such model is the Scale Adaptive Simulation (SAS) model which uses the RANS model in steady flow regions, such as close to walls, and a LES like model in unsteady regions with large fluctuations. This study was done for evaluating the SAS model compared to Unsteady RANS (URANS) and LES and their performance compared to measurements from an engineering point of view. This was done by running simulations on two different test cases, one external and one internal flow situation. The first one was flow around a wall-mounted cylinder and the second one was flow through an aorta with a coarctation in the descending aorta. The first test case was used to thoroughly evaluate the SAS model by running many simulations with URANS, SAS and LES with different element types, element sizes and flow parameters. The element types that have been analyzed are; tetrahedral, hexahedral and polyhedral. The results were compared with experiments done by Sumner et al. [7, 8, 9, 10]. The second test case was used for evaluating the SAS model even further on another flow situation. For this test case, only two SAS simulations were performed on two different grids; a structured hexahedral and an unstructured polyhedral. These results were compared with Magnetic Resonance Imaging (MRI) measurements obtained from Linköping University. No conclusion of which one of the simulated cases gives the best overall agreement with experimental results could be concluded from the obtained results. The best prediction of the drag coefficient for the cylinder was obtained for the coarsest polyhedral mesh that was run with LES, with the disagreement 0.4 percent. The best prediction of the Strouhal number was obtained for a URANS simulation performed on the coarsest mesh with an improved grid close to the cylinder surface, generating less than one, with a disagreement of 3 percent compared to measurements. For the meshes used, it was found that the polyhedral mesh gave the best overall results and the tetrahedral mesh gave the worst results for the cylinder case. For the aorta case the SAS model produced velocity components that had acceptable agreement with the MRI-measurements, but gave very poor results for the turbulent kinetic energy. The main conclusion of this thesis was that the SAS model performed better than URANS, but took longer time to compute simulations than LES, which was the model that generated the best overall results.
87

Empirical Examination of the Ex ante and Ex post Determinants of the ICT Adoption

Cheng, kai-yun 13 July 2004 (has links)
Abstract This article uses the plant-level data of Taiwan manufacturing industry to study the determinants in explaining the timing of information and communication technologies (ICTs) adoption. This paper then investigates whether there exists any difference in determining the utilization of ICTs among high-tech industries and traditional industries. We find size variable has the most significant effect while there appears a different impact in different industries.
88

Scaling Marangoni Flow in Melting or Welding

Yan, Geng-huei 11 July 2005 (has links)
In this study, shapes of the molten region and transport processes affected by thermocapillary convection in melting or welding pool irradiated by a low-power-density beam are determined from a scale analysis. A low-power-density-beam heating implies no deep and narrow cavity or keyhole taking place in the pool. In this work, the complicated flow pattern in the pool is influenced by an unknown shape of solid-liquid interface, and interactions between the free surface layer, corner regions, and boundary layer with phase transition on the solid-liquid interface. Since Prandtl number is much less than unity while Marangoni and Reynolds number can be more than in melting metals, an appropriate scaling mass, momentum, and energy transport subject to a force balance between viscous stress and surface tension gradient on the free surface account for distinct thermal and viscous boundary layers in these regions of different length, velocity, and temperature scales. The results find that shapes of the fusion zone, free surface velocity and temperature profiles are determined by Marangoni, 104 i Prandtl, beam power, Peclet, and Biot numbers, and solid-to-liquid thermal conductivity ratio. The predications agree with numerical computations.
89

Gravure Printing, management, Strategy

Tsai, Kou- Ping 08 August 2005 (has links)
China's economic growth rate soars continuously in the future, what the small and medium-sized enterprises of Taiwan strengthen and carry on in China's Mainland one after another is thrown money, intaglio printing expand very much rapidly not passing most early at China's Mainland from in company, Taiwan of joint-venture, step forward about last direction Taiwan the small and medium-sized enterpriseses running. To the main shaft of intaglio printing industry, this research is dividing with SWOT analyse it for the structure, probe into and find out about the difficulty faced of small and medium-sized enterprises of Taiwan, and successful course and key factor analyse, and combine and propose discovering and suggestion , for wanting to invest in the Taiwan traders of the mainland and intaglio printing correctly in the future. 1. Make analysis and offer the scheme solved by the human resources , production management and investment environment. 2. In the face of doing the economic idea that E turn environment into the main fact in the future society , economy and culture in the 21st century. Offer investors' suggestion of to Mid- and small-scale enterprise Taiwan to the operation on China's Mainland WTO market.
90

Scale Analysis of Thermal & Fluid Flow Induced by Thermocapillary Force During Laser Melting

Yeh, Jih-Sheng 03 July 2006 (has links)
In this study, shapes of the molten region and transport processes affected by thermocapillary convection in melting or welding pool irradiated by a low-power-density beam are determined from a scale analysis for the first time. A low-power-density-beam heating implies no deep and narrow cavity or keyhole taking place in the pool. A quantitative determination of the fusion zone shape is crucial due to its close relationship with the strength, microstructure, and mechanical properties of the fusion zone. In this work, the complicated flow pattern in the pool is influenced by an unknown shape of solid-liquid interface, and interactions between the free surface layer, corner regions, and boundary layer with phase transition on the solid-liquid interface. Since Prandtl number is much less than unity while Marangoni and Reynolds number can be more than in melting metals, an appropriate scaling mass, momentum, and energy transport subject to a force balance between viscous stress and surface tension gradient on the free surface account for distinct thermal and viscous boundary layers in these regions of different length, velocity, and temperature scales. The results find that shapes of the fusion zone, free surface velocity and temperature profiles are determined by Marangoni, Prandtl, beam power, Peclet, and Biot numbers, and solid-to-liquid thermal conductivity ratio. The predications agree with numerical computations.

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