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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.
1

Improving the Perception of Depth of Image-Based Objects in a Virtual Environment

Whang, JooYoung 29 July 2020 (has links)
In appreciation of High-Performance Computing, modern scientific simulations are scaling into millions and even billions of grid points. As we enter the exa-scale, new strategies are required for visualization and analysis. While Image-Based Rendering (IBR) has emerged as a viable solution to the asymmetry between data size and its storage and required rendering power, it is limited in its 2D image portrayal of 3D spatial objects. This work describes a novel technique to capture, represent, and render depth information in the context of 3D IBR. We tested the value of displacement by displacement map, shading by normal, and image angle interval with our technique. We ran an online user study of 60 participants to evaluate the value of adding depth information back to Image-Based Rendering and found significant benefits. / Master of Science / In scientific research, data visualization is important for better understanding data. Modern experiments and simulations are expanding rapidly in scale, and there will come a day when rendering the entire 3D geometry becomes impossible resource-wise. Cinema was proposed as an image-Based solution to this problem, where the model was represented by an interpolated series of images. However, using flat images cannot fully express the 3D characteristics of a data. Therefore, in this work, we try to improve the depth portrayal of the images by protruding the pixels and applying shading. We show the results of a user study conducted with 60 participants on the effect of pixel protrusion, shading, and varying the number of images representing the object. Results show that this method would be useful for 3D scientific visualizations. The resulting object almost accurately resembles the 3D object.
2

Estimation of Machining System Dynamic Properties - Measurement and Modelling

Österlind, Tomas January 2017 (has links)
Dynamic characteristics of machining systems are analysed for improved understanding of both structural and process properties. The thesis stresses the use of testing methods under operational like conditions as these are more representative of closed loop systems, such as machining systems, as compared to conventional testing methods. The test instrument proposed is a contactless excitation and response system, developed for testing of machine tool spindles under load and with rotating spindle. The instrument uses electromagnetic excitation and displacement sensors for analysis of rotating milling tools subject to load. A graphical tool for displaying and analysing rotor displacement was developed in conjunction with this. A modelling procedure for both off-line and on-line estimation of dynamic properties of mechanical structure and process information is presented. The proposed auto-regressive moving average models enable calculation of operational dynamic parameters and they can be estimated in a recursive manner, thus enabling real-time monitoring. The discrimination between stable and unstable processes, both in turning and milling, was performed by analysing the damping obtained from the operational dynamic parameters. / <p>QC 20170330</p>

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