14,803 research outputs found

    Micro Fourier Transform Profilometry (Ό\muFTP): 3D shape measurement at 10,000 frames per second

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    Recent advances in imaging sensors and digital light projection technology have facilitated a rapid progress in 3D optical sensing, enabling 3D surfaces of complex-shaped objects to be captured with improved resolution and accuracy. However, due to the large number of projection patterns required for phase recovery and disambiguation, the maximum fame rates of current 3D shape measurement techniques are still limited to the range of hundreds of frames per second (fps). Here, we demonstrate a new 3D dynamic imaging technique, Micro Fourier Transform Profilometry (Ό\muFTP), which can capture 3D surfaces of transient events at up to 10,000 fps based on our newly developed high-speed fringe projection system. Compared with existing techniques, Ό\muFTP has the prominent advantage of recovering an accurate, unambiguous, and dense 3D point cloud with only two projected patterns. Furthermore, the phase information is encoded within a single high-frequency fringe image, thereby allowing motion-artifact-free reconstruction of transient events with temporal resolution of 50 microseconds. To show Ό\muFTP's broad utility, we use it to reconstruct 3D videos of 4 transient scenes: vibrating cantilevers, rotating fan blades, bullet fired from a toy gun, and balloon's explosion triggered by a flying dart, which were previously difficult or even unable to be captured with conventional approaches.Comment: This manuscript was originally submitted on 30th January 1

    Liquid Distribution from Industrial Scale Spray Jets in Fluidized Beds

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    Liquid injections via spray nozzles are used in fluidized bed reactors such as Fluid Cokers. In such industrial processes, in order to maximize the product yields it is required to optimize the performance of the nozzle. Moreover parts of the bed might become defluidized, bogged, due to high liquid load. Then optimizing the performance of the nozzle and local bed bogging detection is the primary research objectives for this thesis work. The first part of the research work was focused on developing a novel method employing electrical conductance to characterize the liquid distribution in a large scale fluid bed of about 7 tonnes of silica sand, using a commercial-scale spray nozzle. It was used to determine the effect of increasing atomization gas-to-liquid ratio on the liquid-solid contact efficiency. Electrodes have been employed to map the free moisture distribution through the entire bed. The results indicated that raising the G/L ratio improves the contact efficiency, especially at high G/L ratios. The effect of a new device, consisting of a draft tube located downstream of the nozzle, on liquid distribution inside the large fluidized bed was studied next. It not only remarkably reduced the liquid trapped within wet agglomerates, but also greatly enhanced the distribution of injected liquid feed and the jet penetration of the nozzle. Finally, the electrical conductance and several other experimental methods, such as differential and static pressure measurements, and image processing were successfully implemented to detect local bogging in a large scale pilot fluid bed

    Report by the ESA-ESO Working Group on Fundamental Cosmology

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    ESO and ESA agreed to establish a number of Working Groups to explore possible synergies between these two major European astronomical institutions. This Working Group's mandate was to concentrate on fundamental questions in cosmology, and the scope for tackling these in Europe over the next ~15 years. One major resulting recommendation concerns the provision of new generations of imaging survey, where the image quality and near-IR sensitivity that can be attained only in space are naturally matched by ground-based imaging and spectroscopy to yield massive datasets with well-understood photometric redshifts (photo-z's). Such information is essential for a range of new cosmological tests using gravitational lensing, large-scale structure, clusters of galaxies, and supernovae. Great scope in future cosmology also exists for ELT studies of the intergalactic medium and space-based studies of the CMB and gravitational waves; here the synergy is less direct, but these areas will remain of the highest mutual interest to the agencies. All these recommended facilities will produce vast datasets of general applicability, which will have a tremendous impact on broad areas of astronomy.Comment: ESA-ESO Working Groups Report No. 3, 125 pages, 28 figures. A PDF version including the cover is available from http://www.stecf.org/coordination/esa_eso/cosmology/report_cover.pdf and a printed version (A5 booklet) is available in limited numbers from the Space Telescope-European Coordinating Facility (ST-ECF): [email protected]
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