3,044 research outputs found
Steady internal flow and aerodynamic loads analysis of shuttle thermal protection system
An analytical model for calculation of ascent steady state tile loading was developed and validated with wind tunnel data. The analytical model is described and results are given. Results are given for loading due to shocks and skin friction. The analysis included calculation of internal flow (porous media flow and channel flow) to obtain pressures and integration of the pressures to obtain forces and moments on an insulation tile. A heat transfer program was modified by using analogies between heat transfer and fluid flow so that it could be used for internal flow calculation. The type of insulation tile considered was undensified reusable surface insulation (RSI) without gap fillers, and the location studied was the lower surface of the orbiter. Force and moment results are reported for parameter variations on surface pressure distribution, gap sizes, insulation permeability, and tile thickness
Comparative Study of Model-Based and Learning-Based Disparity Map Fusion Methods
Creating an accurate depth map has several, valuable applications including augmented/virtual reality, autonomous navigation, indoor/outdoor mapping, object segmentation, and aerial topography. Current hardware solutions for precise 3D scanning are relatively expensive. To combat hardware costs, software alternatives based on stereoscopic images have previously been proposed. However, software solutions are less accurate than hardware solutions, such as laser scanning, and are subject to a variety of irregularities. Notably, disparity maps generated from stereo images typically fall short in cases of occlusion, near object boundaries, and on repetitive texture regions or texture-less regions. Several post-processing methods are examined in an effort to combine strong algorithm results and alleviate erroneous disparity regions. These methods include basic statistical combinations, histogram-based voting, edge detection guidance, support vector machines (SVMs), and bagged trees. Individual errors and average errors are compared between the newly introduced fusion methods and the existing disparity algorithms. Several acceptable solutions are identified to bridge the gap between 3D scanning and stereo imaging. It is shown that fusing disparity maps can result in lower error rates than individual algorithms across the dataset while maintaining a high level of robustness
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