3,375 research outputs found
Voice Compression and Communications: Principles and Applications for Fixes and Wireless Channels
No full textUp-to-date, expert coverage of topics in wireless voice communications Voice communication is the most important facet of mobile radio service. Even when the predicted surge of wireless data and Internet services becomes a reality, voice will remain the most natural means of human communication. Voice Compression and Communications details issues in wireless voice communications and treats compression, channel coding, and wireless transmission as a joint subject. Part I covers background material, whereas Part II provides detailed information on both proprietary and standardized analysis-by-synthesis codecs, including the speech codecs of virtually all existing wireline-based and wireless systems. Parts III and IV discuss mainly research-based wideband, audio, as well as very low-rate schemes likely to find their way into future standards. Voice Compression and Communications describes fundamental concepts in a non-mathematical way early in the book for those with only a background knowledge of signal processing and communications. More advanced readers will find detailed discussions of theoretical principles, future concepts, and solutions to various specific wireless voice communications problems
1973-10-25 Morehead State Concert and Lecture Series J.P. Donleavy
No full textRenowned author J.P. Donleavy speaks on the plight of an author and the methods to write, recorded on October 25, 1973
Entrainment and detrainment rates from the piv measurements at the top of laboratory analogs of stratocumulus and cumulus clouds
No full textWe analyze mixing at the top of laboratory analogs of convective clouds: stratocumulus and cumulus to investigate entrainment of environmental air into the cloud. We retrieve two components of air velocity using Particle Image Velocimetry technique. Suitable image processing allows to determine cloud–clear air interface. Using velocity differences between cloudy and clear sides of the interface we calculate entrainment / detrainment rates
Vortex Dynamics in The Transitional and Turbulent Wake of 6:1 Prolate Spheroid at 45-deg incidence angle
No full textThe incompressible flow past a 6:1 prolate spheroid with an inclination angle of 45o at Re = 3,000 has been studied by means of direct numerical simulations (DNS). The Reynolds number is based on the inflow velocity and minor-axis length. The preliminary results presented here are focused mainly on vortex dynamics and vortical structures in the wake. The wake behind this configuration starts almost symmetric but is soon strongly deflected and bent as it evolves to the intermediate wake. A pair of unequal-strength vortices dominates the intermediate wake, of which one exhibits the shape of a long vortex tube while the other rapidly breaks down into turbulent-like vortical structures
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The gas-phase reactions Of SiCl4 and Si2Cl6 with CH3OH and C2H5OH: an investigation by mass spectrometry and matrix-isolation infrared spectroscopy
No full textThe gas phase reactions Of SiCl4 and Si2Cl6 With CH3OH and C2H5OH have been investigated using both mass spectrometry and matrix isolation techniques. SiCl4 reacts with both CH3OH and C2H5OH upon mixing of the vapours for times in excess of 3 h to generate the HCl-elimination products SiCl3OR (R = CH3 or C2H5). The identity of these products is confirmed by deuteration experiments and by ab initio calculations at the HF/6-31G(d) level. Further products are generated when the mixture is passed through a tube heated to 750degreesC. Si2Cl6 reacts with CH3OH and C2H5OH via a different mechanism in which the Si-Si bond is cleaved to yield SiCl3OR and HCl. Other products of the type SiCl4-n(OCH3)(n) are tentatively identified by a combination of mass spectrometric and matrix isolation measurements. These latter products indicate further replacement of Cl atoms by OR groups as a result of reaction of CH3OH or C2H5OH with the initial product
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Experimental and theoretical evidence for homogeneous catalysis in the gas-phase reaction of SiH2 with H2O (and D2O): a combined kinetic and quantum chemical study
No full textTime-resolved kinetic studies of the reaction of silylene, SiH2, with H2O and with D2O have been carried out in the gas phase at 297 K and at 345 K, using laser flash photolysis to generate and monitor SiH2. The reaction was studied independently as a function of H2O (or D2O) and SF6 (bath gas) pressures. At a fixed pressure of SF6 (5 Torr), [SiH2] decay constants, k(obs), showed a quadratic dependence on [H2O] or [D2O]. At a fixed pressure of H2O or D2O, k(obs) Values were strongly dependent on [SF6]. The combined rate expression is consistent with a mechanism involving the reversible formation of a vibrationally excited zwitterionic donor-acceptor complex, H2Si...OH2 (or H2Si...OD2). This complex can then either be stabilized by SF6 or it reacts with a further molecule of H2O (or D2O) in the rate-determining step. Isotope effects are in the range 1.0-1.5 and are broadly consistent with this mechanism. The mechanism is further supported by RRKM theory, which shows the association reaction to be close to its third-order region of pressure (SF6) dependence. Ab initio quantum calculations, carried out at the G3 level, support the existence of a hydrated zwitterion H2Si...(OH2)(2), which can rearrange to hydrated silanol, with an energy barrier below the reaction energy threshold. This is the first example of a gas-phase-catalyzed silylene reaction
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Time-resolved gas-phase kinetic and quantum chemical studies of the reaction of silylene with nitric oxide
No full textTime-resolved kinetic studies of the reaction of silylene, SiH2, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with NO. The reaction was studied in the gas phase over the pressure range 1-100 Torr in SF6 bath gas at five temperatures in the range 299-592 K. The second-order rate constants at 10 Torr fitted the Arrhenius equation log(k/cm3 molecule-1 s-1) = (-11.66 ± 0.01) + (6.20 ± 0.10 kJ mol-1)/RT ln 10 The rate constants showed a variation with pressure of a factor of ca. 2 over the available range, almost independent of temperature. The data could not be fitted by RRKM calculations to a simple third body assisted association reaction alone. However, a mechanistic model with an additional (pressure independent) side channel gave a reasonable fit to the data. Ab initio calculations at the G3 level supported a mechanism in which the initial adduct, bent H2SiNO, can ring close to form cyclo-H2SiNO, which is partially collisionally stabilized. In addition, bent H2SiNO can undergo a low barrier isomerization reaction leading, via a sequence of steps, ultimately to dissociation products of which the lowest energy pair are NH2 + SiO. The rate controlling barrier for this latter pathway is only 16 kJ mol-1 below the energy of SiH2 + NO. This is consistent with the kinetic findings. A particular outcome of this work is that, despite the pressure dependence and the effects of the secondary barrier (in the side reaction), the initial encounter of SiH2 with NO occurs at the collision rate. Thus, silylene can be as reactive with odd electron molecules as with many even electron species. Some comparisons are drawn with the reactions of CH2 + NO and SiCl2 + NO
Experimental characterisation of large scale structures in a high Reynolds number turbulent boundary layer
No full textA very large field of view (4δ x 1δ) with a good spatial resolution owing to the use of four 2k x 2k pixel cameras was conducted in a flat plate boundary layer at two Reynolds numbers (Reθ ≈7,500 and 20,000). Comparing the flow statistics with previously obtained hot-wire data under similar flow conditions show good agreement. The goal of this experiment is to detect and characterise the large scale motions which develop in the log region of a high Reynolds number turbulent boundary layer
Letter from J.P. Bradley to Mr. [William] S. Martin The Dominguez Estate Company, June 28, 1940
No full textRegarding attached payment by Mr. K.L. Schaap settling his account
The Calorimetric Electron Telescope (CALET) on the International Space Station: Results from the First Six Years on Orbit
No full textCALET Collaboration authors: - O. Adriani, Y. Akaike, K. Asano, Y. Asaoka, E. Berti, G. Bigongiari, W.R. Binns, M. Bongi, P. Brogi, A. Bruno, J.H. Buckley, N. Cannady, G. Castellini, C. Checchia, M.L. Cherry, G. Collazuol, K. Ebisawa, A. W. Ficklin, H. Fuke, S. Gonzi, T.G. Guzik, T. Hams, K. Hibino, M. Ichimura, K. Ioka, W. Ishizaki, M.H. Israel, K. Kasahara, J. Kataoka, R. Kataoka, Y. Katayose, C. Kato, N. Kawanaka, Y. Kawakubo, K. Kobayashi, K. Kohri, H.S. Krawczynski, J.F. Krizmanic, P. Maestro, P.S. Marrocchesi, A.M. Messineo, J.W. Mitchell, S. Miyake, A.A. Moiseev, M. Mori, N. Mori, H.M. Motz, K. Munakata, S. Nakahira, J. Nishimura, G.A. de Nolfo, S. Okuno, J.F. Ormes, S. Ozawa, L. Pacini, P. Papini, B.F. Rauch, S.B. Ricciarini, K. Sakai, T. Sakamoto, M. Sasaki, Y. Shimizu, A. Shiomi, P. Spillantini, F. Stolzi, S. Sugita, A. Sulaj, M. Takita, T. Tamura, T. Terasawa, S. Torii, Y. Tsunesada, Y. Uchihori, E. Vannuccini, J.P. Wefel, K. Yamaoka, S. Yanagita, A. Yoshida, K. Yoshida, and W. V. ZoberCOSPAR 2022 44th Scientific Assembly; Athens, Greece; 16-24 July 2022https://calet.jp/wp-content/uploads/2022/07/COSPAR22_akaike_pub.pd
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