12 documents found, page 1 of 2
Versatile Video Coding of 360-Degree Video using Frame-Based FoV and Visual Att...
Carreira, J.; Faria, Sérgio M. M. de; Távora, L. M. N.; Navarro, António; Assunção, Pedro A. A.High quality omnidirectional video requires ultra high resolution formats encoded with very high bit rates to guarantee acceptable QoE in video delivery services. Since in general the full FoV, i.e., 360º, is not required at once by users, rather than agnostic encoding of the whole 360º video, this work proposes a flexible coding approach where the full FoV is mapped into video frames and efficiently encoded us...
Experimental measurement of H3+/H5 + and D3+/D5+ mobilities in their parent gases
Neves, P.N.B.; Escada, J.; Borges, F.I.G.M.; Távora, L. M. N.; Conde, C.A.N.The experimental study of the reduced mobility K0 of the molecular ions H3+/H5+ in H 2 and D3+/D5+ in D 2 was carried out using a recently developed technique, that uses a Xe VUV flash lamp and a Gaseous Electron Multiplier (GEM) microstructure with a CsI deposit to produce the molecular ions by electron avalanche ionization. For both gases, the K0 values were obtained at room temperature (295 K) and at pressur...
Experimental Measurement of the Ne+ and Ne+2 Mobilities in Ne and the Reaction ...
Neves, P.N.B.; Garcia, A. N. C.; Trindade, A. M. F.; Barata, J. A. S.; Távora, L. M. N.; Conde, C. A. N.We measured the reduced mobilities of the atomic, Ne+, and dimer, Ne2+, ions in Ne, under different pressures and reduced electric fields, at 300 K. Extrapolation to zero field yields values of 4.4 cm2 V-1 s-1 for Ne+ and 6.2 cm2 V-1 s-1 for Ne2+, which are in relative good agreement with other published data. The Ne+ ions are converted to Ne2+ by a three-body reaction with a rate constant that was also measure...
Photopeak shift effects due to the drift electric field in high pressure xenon ...
Neves, P. N. B.; Barata, J. A. S.; Távora, L. M. N.; Dias, T. H. V. T.; Borges, F. I. G. M.; Conde, C. A. N.The photopeak shift in High Pressure Xe (HPXe) gamma ray detectors due to the energy acquired/lost by the photoelectric and Compton electrons, from the electric field applied in the drift region, is calculated using the PENELOPE code for gamma rays from several radioactive sources. The implications of this effect in HPXe detectors are discussed, namely for TPCs for double beta decay of 136 Xe studies.
The X++2X→X2++X reaction rate constant for Ar, Kr and Xe, at 300 K
Neves, P. N. B.; Conde, C. A. N.; Távora, L. M. N.The X++2X → X+2X- reaction rate constants were measured for Ar, Kr and Xe, at 300 K, using a new experimental technique. The results for Ar, kAr=(1.2 ± 0.2) × 10 -31 cm6 Kr, kKr=(2.1 ± 0.9) × 10-31 cm and Xe, kxe=(1.48 ± 0.18) x 10 -31 cm6S-1 are discussed and compared with those of other authors using different techniques.
Experimental measurement of the mobilities of atomic, Ne+, and dimer, Ne2+, ion...
Garcia, A. N. C.; Trindade, A. M. F.; Oliveira, T. D. P.; Neves, P. N. B.; Barata, J. A. S.; Távora, L. M. N.; Dias, T. H. V. T.; Borges, F. I. G. M.We measured the reduced mobilities of the atomic, Ne+, and dimer, Ne2+, ions in Ne, under different pressures and reduced electric fields, at 300 K. The value obtained for the atomic ion, 4.1 cm2V1 s1, is in good agreement with other values published in the scientific literature. The value obtained for the mobility of the dimer ion, 7.3 cm2 V1 s1, is not in accordance with other published data. We discuss the m...
Experimental measurement of the mobilities of atomic and dimer Ar, Kr, and Xe i...
Neves, P. N. B.; Conde, C. A. N.; Távora, L. M. N.A new experimental technique for measuring the mobilities of positive ions in their parent gases is presented. The technique was applied to the rare gases, Ar, Kr, and Xe, and, for pressures typically below 10 Torr, two different types of positive ions were observed. The reduced mobilities of these ions in their parent gases were measured as a function of E/N, the ratio of the electric field strength to the gas...
A new experimental technique for positive ion drift velocity measurements in no...
Neves, P. N. B.; Conde, C. A. N.; Távora, L. M. N.A new technique is described for measuring the drift velocities and mobilities of noble gas ions in noble gases that makes use of a gaseous electron multiplier (GEM) and a UV flash lamp to produce the ions in a thin, well-defined, planar region. The drift velocities are determined from measurements of the transit time of the ions in crossing the drift space. We present experimental results for xenon ions in xen...
A Monte Carlo study of the electron clouds produced by polarized x-rays in xenon
Botte, G. S.; Rachinhas, P. J. B. M.; Dias, T. H. V. T.; Santos, F. P.; Távora, L. M. N.; Silva, R. M. Curado da; Conde, C. A. N.; Stauffer, A. D.Information about the polarization of x-ray photons can be determined by probing the direction of emission of photoelectrons and the profile of the electron cloud produced in the detecting medium. In this work we present Monte Carlo results for the electron clouds produced in xenon by the absorption of x-rays, considering a simple non-relativistic dipole approach to the angular differential photoionization cros...
A simulation study of the effect of drift electric fields on the response of ra...
Távora, L. M. N.; Dias, T. H. V. T.; Conde, C. A. N.The effect of the presence of a drift electric field on the response of gaseous and semiconductor radiation detectors to energetic X-rays (energies from 20 to 200 keV) is investigated using the PENELOPE code to simulate the photo-absorption and the slow-down of the electrons produced in Si, Ge, and Xe gas at 1 atm. For typical drift fields, the energy deposited in the detection media is calculated taking into a...