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《Proceedings of the Combustion Institute》2023,39(4):4365-4375
The interaction between ammonia (NH3) and nitric oxide (NO) at high temperatures is studied in this work using a shock tube combined with laser absorption diagnostics. The system simultaneously measured the NH3 and NO time-histories during the reaction processes of the shock-heated NH3/NO/CO/Ar mixtures (NH3:NO ≈ 0.9:1.0 and 1.4:1.0). The absorption cross-sections of NH3 near 1122.10 cm–1 and NO at 1900.52 cm–1 (characterized in this study) were used for measuring NH3 and NO time-histories with the temperature measured by two CO absorption lines. The measured NH3 and NO time-histories at 1614–1968 K and 2.4–2.8 atm were compared with predictions of seven recent kinetics models. The predictions that based on different mechanisms are very different and the measured profiles are within the range of the predictions. The Glarborg, NUI Galway Syngas-NOx, and Mathieu mechanisms give the closest predictions to the measurements. Kinetics analyses indicate that the NH3 and NO consumption rates are extremely sensitive to the rate constants and branching ratio of NH2 + NO = N2 + H2O and NH2 + NO = NNH + OH, which are more reliably represented in the Glarborg and NUI Galway Syngas-NOx mechanisms. The performances of Glarborg mechanisms at lower initial temperatures can be apparently improved by revising the rate constants and branching ratio of NH2 + NO = N2 + H2O and NH2 + NO = NNH + OH. These two reactions are also the primary pathways for NO reduction and NH3 is mainly consumed via NH3 + OH = NH2 + H2O and NH3 + H = NH2 + H2. Trace amounts of NO2 and N2O impurities decompose to form O radical followed by the generation of OH radical via H-abstraction reactions, which significantly affects the predictions of NH3 and NO according to kinetics analyses. 相似文献
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《Proceedings of the Combustion Institute》2023,39(1):735-743
We address the role of the linear mixing rule in the kinetics of the H2O2 decomposition system by reporting the rate constant for H2O2 + M = 2OH + M (M = Ar and CO2) in the temperature range of 1087–1234 K at low pressures in a mixture of 20% CO2 in Argon. The reaction rate constant was inferred from H2O concentrations monitored by using a laser-absorption spectroscopy-based water diagnostic. To the best of our knowledge, this is the first measurement of the rate constant of this reaction in a mixture to be reported in literature. A significant discrepancy was found between the rate constants derived using the traditional linear mixing rule and the reduced pressure linear mixing rule. This discrepancy can have serious implications on the predictive accuracy of these kinetic models, especially under conditions relevant to the operation of supercritical CO2 (sCO2) power cycles that rely on oxy-fuel combustion in a working fluid comprised almost entirely of CO2. 相似文献
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The line shape of the signals observed by intracavity absorption in an atomic beam of barium is studied as a function of absorber density. Complex structure is observed consisting of both absorption and enhancement features. Comparison is made with models of intracavity absorption, and it is concluded that the rate equation model in its present form does not explain the structure. On the other hand the super-regen model does seem able to partially account for the observed structure. The complexity of the line shape will directly affect those workers who are using intracavity absorption as a spectroscopic technique. 相似文献
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R. Alexandrescu J. Morjan C. Grigoriu I. N. Mihailescu Z. Bastl J. Tlaskal R. Mayer J. Pola 《Applied Physics A: Materials Science & Processing》1988,46(4):275-279
Infrared multiphoton decomposition of monosilane in the presence of methyl methacrylate results in the formation of gaseous methane, acetylene, butenes and carbon monoxide along with a solid polymer whose chemical mechanism of formation is discussed in line of the poly(dimethylsiloxane) structure inferred from ESCA and IR spectral analysis. 相似文献
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《Superlattices and Microstructures》2001,29(4):301-307
The time-resolved differential absorption of the ZnSe/ZnSTe superlattice is studied using femtosecond pump-probe measurements. Transient spectral hole burning due to the initial nonthermal carrier distribution is observed at zero time delay and the carriers are thermalized within 0.5 ps. The high-energy tail of the differential absorption spectra was used to deduce the effective temperature of the thermalized carriers. Rapid hot-carrier cooling from a temperature of 763 to 450 K within the first 4 ps is observed, with carrier cooling slowing down hence. This initial fast hot-carrier cooling is consistent with the strong carrier–phonon interaction in large gap II–VI semiconductors. 相似文献
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Gas exchange in fruits, in particular oxygen transport in apples, was studied non-intrusively using wavelength modulation diode laser absorption spectroscopy at about 761 nm, applied to the strongly scattering intact fruit structure. The applicability of the technique was demonstrated by studies of the influence of the skin to regulate the internal oxygen balance and of cling film in modifying it by observing the response of the signal from the internal oxygen gas to a transient change in the ambient gas concentration.Applications within controlled atmosphere fruit storage and modified atmosphere packaging are discussed. The results suggest that the technique could be applied to studies of a large number of problems concerning gas exchange in foods and in food packaging. 相似文献
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Optical absorption spectra of Cr3+ ions in calcium formate single crystals with two different dopants have been studied at room and liquid nitrogen temperatures. The observed spectra have been attributed to Cr3+ ions in octahedral environment with tetragonal distortion. The values of the crystal field and Racah parameters have been evaluated. 相似文献
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A diffusion equation for a binary mixture and spinodal decomposition in the case of phase separation are considered. It is
shown that, if the binding force between polymer chain links is weak, the diffusion equation for a binary mixture allows for
the reduction to the Burgers equation with “viscosity”; that is, the coexistence of rarefaction waves and shock density waves
is a possibility. The effect of strong bonds between polymer chain links on the spinodal decomposition dynamics is studied.
It is demonstrated that strong bonding may cause a multiflux wave system with alternate stability to arise when the viscosity
varies. 相似文献
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Methyl methacrylate (MMA)-ethyl methacrylate (EMA) copolymers of different monomer concentrations containing anhydrous ferric chloride were prepared by bulk polymerization at 70°C. TGA studies showed that inclusion of iron salt increases the thermal stability of copolymers by 50°C. Mössbauer spectra of copolymers heated at different temperatures showed the presence of Fe3+ species only, in different environments. The mechanism of thermal stabilization of copolymer has been proposed on the basis of IR, TGA and Mössbauer spectroscopy studies. 相似文献
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In this study,an improved impedance tube test method is proposed to determine the sound absorption coefficients of materials at high frequencies up to 10 kHz.Specifically,a multi-modal decomposition method is used to measure the sound absorption coefficients above the cut-off frequency of plane waves in the impedance tube.During the measurement process,an array of microphones is placed in the circumferential and axial directions of the tube.Then,the first three acoustic circumferential modes are... 相似文献
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B. E. Cole C. J. G. M. Langerak B. N. Murdin C. D. Bezant J. M. Chamberlain C. R. Pidgeon M. Henini V. Nakov 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
We present saturation absorption studies of the HH1→LH1 intersubband transition in a 70 Å p-type GaAs/AlGaAs multi-quantum well. The subband separation in this sample, with strongly non-parabolic bands, varies from 26 meV at k=0 to 16 meV at the Fermi wave vector. The absorption behaviour of this transition is studied over a range of four orders of magnitude of intensity of incident THz radiation. The results are analysed within the contexts of a simple two-level model and an instantaneous thermalization model. The results indicate that the lifetime obtained with these models is limited by the pulsewidth, i.e. is greater than 1.7 ps. This places a lower limit on the energy relaxation time for transitions below the LO-phonon energy. 相似文献