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11.
An IR laser absorption diagnostic has been further developed for accurate and sensitive time‐resolved measurements of ethylene in shock tube kinetic experiments. The diagnostic utilizes the P14 line of a tunable CO2 gas laser at 10.532 μm (the (0 0 1) → (1 0 0) vibrational band) and achieves improved signal‐to‐noise ratio by using IR photovoltaic detectors and accurate identification of the P14 line via an MIR wavemeter. Ethylene absorption cross sections were measured over 643–1959 K and 0.3–18.6 atm behind both incident and reflected shock waves, showing evident exponential decay with temperature. Very weak pressure dependence was observed over the pressure range of 1.2–18.6 atm. By measuring ethylene decomposition time histories at high‐temperature conditions (1519–1895 K, 2.0–2.8 atm) behind reflected shocks, the rate coefficient of the dominant elementary reaction C2H4 + M → C2H2 + H2 + M was determined to be k1 = (2.6 ± 0.5) × 1016exp(?34,130/T, K) cm3 mol?1 s?1 with low data scatter. Ethylene concentration time histories were also measured during the oxidation of 0.5% C2H4/O2/Ar mixtures varying in equivalence ratio from 0.25 to 2. Initial reflected shock conditions ranged from 1267 to 1440 K and 2.95 to 3.45 atm. The measured time histories were compared to the modeled predictions of four ethylene oxidation mechanisms, showing excellent agreement with the Ranzi et al. mechanism (updated in 2011). This diagnostic scheme provides a promising tool for the study and validation of detailed hydrocarbon pyrolysis and oxidation mechanisms of fuel surrogates and realistic fuels. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 423–432, 2012 相似文献
12.
13.
If the baryon asymmetry of the Universe is produced by leptogenesis, CP violation is required in the lepton sector. In the seesaw extension of the standard model with three hierarchical right-handed neutrinos, we show that the baryon asymmetry is insensitive to the Pontecorvo-Maki-Nagakawa-Sakata phases: thermal leptogenesis can work for any value of the observable phases. This result was well known when there were no flavor effects in leptogenesis; we show that it remains true when flavor effects are included. 相似文献
14.
S.A. Scott J.F. Davidson J.S. Dennis P.S. Fennell A.N. Hayhurst 《Proceedings of the Combustion Institute》2005,30(2):2151-2159
Three chars and an activated carbon were gasified by reaction with CO2 in a fluidised bed of sand, at 800–1050 °C. The chars were produced from (i) dried sewage sludge, (ii) car tyres, and (iii) a bituminous coal. For the conditions used, the rate of CO2 + C → 2CO was largely determined by chemical kinetics; there was a small effect from mass transfer for the most reactive char, derived from sewage sludge. The rate of CO formation, r, differed greatly for these chars, but was well described by:The reactivity of a char depends on: (i) its pore structure, (ii) catalytic activity of the associated ash, and (iii) the activity of the char’s carbon. The sewage sludge char was the most reactive, on the basis of either BET area or mass by 2 orders of magnitude. The activated carbon had the lowest reactivity per unit BET surface area, indicating that the area in its micropores is comparatively unreactive. 相似文献
15.
Arwen R. Pearson Reinhard Pahl Elena G. Kovaleva Victor L. Davidson Carrie M. Wilmot 《Journal of synchrotron radiation》2007,14(1):92-98
X‐ray exposure during crystallographic data collection can result in unintended redox changes in proteins containing functionally important redox centers. In order to directly monitor X‐ray‐derived redox changes in trapped oxidative half‐reaction intermediates of Paracoccus denitrificans methylamine dehydrogenase, a commercially available single‐crystal UV/Vis microspectrophotometer was installed on‐line at the BioCARS beamline 14‐BM‐C at the Advanced Photon Source, Argonne, USA. Monitoring the redox state of the intermediates during X‐ray exposure permitted the creation of a general multi‐crystal data collection strategy to generate true structures of each redox intermediate. 相似文献
16.
Nixon M Friedman M Ronen E Friesem AA Davidson N Kanter I 《Physical review letters》2011,106(22):223901
We experimentally investigate the phase dynamics of laser networks with homogenous time-delayed mutual coupling and establish the fundamental rules that govern their state of synchronization. We identified a specific substructure that imposes its synchronization state on the entire network and show that for any coupling configuration the network forms at most two synchronized clusters. Our results indicate that the synchronization state of the network is a nonlocal phenomenon and cannot be deduced by decomposing the network into smaller substructures, each with its individual synchronization state. 相似文献
17.
D. Hojman M. A. Cardona D. Bazzacco N. Blasi J. Davidson M. Davidson M. E. Debray A. J. Kreiner S. M. Lenzi G. Lo Bianco D. R. Napoli C. Rossi Alvarez 《The European Physical Journal A - Hadrons and Nuclei》2004,21(3):383-390
High-spin states in 163,164Ho were investigated by means of in-beam
-ray spectroscopy techniques using the multidetector array GASP. Excited states in 163,164Ho were populated predominantly through the incomplete-fusion mechanism in the 160Gd (11B
reaction at a beam energy of 61 MeV. Known rotational bands in 163
Ho have been extended to higher spins and a three-quasiparticle band has been observed in this nucleus. Rotational bands have been identified in 164Ho and their configurations have been discussed. Empirical Gallagher-Moszkowski (GM) splitting energies were extracted from the
and
GM doublets. Alignments, band crossing frequencies, and electromagnetic properties have been analyzed in the framework of the cranking model.Received: 13 February 2004, Revised: 18 March 2004, Published online: 14 September 2004PACS:
21.10.Re Collective levels - 21.60.Ev Collective models - 23.20.Lv
transitions and level energies - 27.70. + q
相似文献
18.
p palan BS 《Physical review letters》1987,58(16):1597-1599
19.
20.
Malcolm R. Davidson 《Transport in Porous Media》1987,2(2):165-176
An asymptotic, one-dimensional Green-Ampt model is derived for infiltration into a soil whose surface is impermeable except for regularly spaced vertical cracks, and infiltration into a cylindrical soil column whose top surface is also impermeable except for a central hole. The model is valid at times when the wetting front has become horizontal and corresponds to one-dimensional infiltration initiated from a plane lying above or below the soil surface, depending on the crack spacing/depth ratio (or column radius/hole depth ratio). When applicable, asymptotic Green-Ampt solutions are shown to agree well, in selected cases, with corresponding finite difference solutions of the saturated-unsaturated flow equations. 相似文献