Similarity matching in video databases is of growing importance in many new applications such as video clustering and digital video libraries. In order to provide efficient access to relevant data in large databases, there have been many research efforts in video indexing with diverse spatial and temporal features. However, most of the previous works relied on sequential matching methods or memory-based inverted file techniques, thus making them unsuitable for a large volume of video databases. In order to resolve this problem, this paper proposes an effective and scalable indexing technique using a trie, originally proposed for string matching, as an index structure. For building an index, we convert each frame into a symbol sequence using a window order heuristic and build a disk-resident trie from a set of symbol sequences. For query processing, we perform a depth-first search on the trie and execute a temporal segmentation. To verify the superiority of our approach, we perform several experiments with real and synthetic data sets. The results reveal that our approach consistently outperforms the sequential scan method, and the performance gain is maintained even with a large volume of video databases.
James Dodd, Steven Hartman, Sanghyun Park, Claudio Pellegrini, James Rosenzweig, J. Smolin, W. Barletta, David Cline, Richard Cooper, J. Kolonko, J. Davis, G. Hairapetian, Chand Joshi, Neville Luhmann, S. Ivanchenkov, A. Khlebnikov, A. Varfolomeev
A compact 20 MeV linac with an RF laser-driven electron gun will drive a high-gain (10 cm gain length), 10.6 micrometers wavelength FEL amplifier, operating in the SASE mode. FEL physics in the high-gain regime will be studied, including start-up from noise, optical guiding, sidebands, saturation, and superradiance, with emphasis on the effects important for future short wavelength operation of FEL's. The hybrid undulator, designed and built at the Kurchatov Institute of Atomic Energy in the U.S.S.R., has forty periods, each 1.5 cm long. The magnetic material is a hybrid combination of SmCo5 blocks and Nd-Fe-B blocks, with vanadium-permendur yokes. The gap distance between pole-tips is fixed at 5 mm. On axis the peak value of the completed undulator's magnetic field was measured to be 7.3 kGauss (+/- 0.25%). Measurements during the conditioning phase of the RF gun for the electron beam's peak dark-current show 6 mA without the longitudinal magnetic focusing field in the gun and 34 mA with the focusing field active. The peak current from photoemission is calculated to be 200 A.
A novel, compact S-band LINAC has been designed and is currently under construction at UCLA. It is expected to deliver high brightness, 200 A, 20 MeV electron pulses, less than 4 ps in duration from a device that is about 1 meter long. It comprises; (1) a laser photocathode driven gun that produces 4.5 MeV electron bunches from a 1 1/2 cell cavity operating in the (pi) -mode and (2) an accelerating structure known as a plane wave transformer (PWT) designed by Swenson. The design considerations of the machine and initial operating experience of the gun are discussed. The linac will be used for free electron laser, advanced accelerator research and beam-plasma experiments.
James Dodd, F. Aghamir, W. Barletta, David Cline, Steven Hartman, Thomas Katsouleas, J. Kolonko, Sanghyun Park, Claudio Pellegrini, J. Terrien, J. Davis, Chand Joshi, Neville Luhmann, David McDermott, S. Ivanchenkov, Yu Lachin, A. Varfolomeev
1407_51Saturnus is an infrared FEL operating in the 10 micrometers wavelength region, driven by a compact 20 MeV linac with a photoinjector, under construction at UCLA. The 1.5 cm period, 0.6 (Tau) peak field undulator is being built at the Kurchatov IAE. The FEL is designed to operate primarily in the self-amplified spontaneous emission mode. This paper covers the start-up from noise, optical guiding, saturation, sidebands and superradiance, with emphasis on the effects important for future short wavelength operation of FELs. The photoinjector follows closely the Brookhaven design. Electrons are injected into an accelerating section based on the plane-wave transformer design developed by Swenson at SAIC. Simulation of the linac and FEL show a gain length of 10 cm, and a saturation power of 50 MW.
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