65 research outputs found
Experimental study on the influence of wall heat effect on gas explosion and its propagation
In order to understand the mechanism and the influence degree of wall heat effect on gas explosion and its propagation, the influence of wall heat effect on gas explosion and its propagation is theoretically analyzed mainly from perspectives of the heat transportation and reaction process. Results show that the influence of wall heat loss on gas explosion strength is significant. In addition, the influences of wall heat effect on explosion wave and flame propagation velocity in the gas explosion process are experimentally investigated in the adiabatic condition and heat conduction. It is found that the wall heat effect can affect gas explosion strength, flame propagation velocity, peak overpressure and the peak flame propagation velocity, and their influence degree becomes more significant with the increase of the adiabatic degree. Therefore, it can be seen that the wall heat effect has an important influence on the gas explosion and its propagation. The influence of wall adiabatic condition on gas explosion with a higher combustion level is greater than the influence on gas explosion with low combustion levels
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Effects of low-temperature catalytic pretreatments on coal structure and reactivity in liquefaction. Final technical report, Volume 2 - hydrogenative and hydrothermal pretreatments and spectroscopic characterization using pyrolysis-GC-MS, CPMAS {sup 13}C NMR and FT-IR
It has been indicated by DOE COLIRN panel that low-temperature catalytic pretreatment is a promising approach to the development of an improved liquefaction process. This work is a fundamental study on effects of pretreatments on coal structure and reactivity in liquefaction. The main objectives of this project are to study the coal structural changes induced by low-temperature catalytic and thermal pretreatments by using spectroscopic techniques; and to clarify the pretreatment-induced changes in reactivity or convertibility of coals. As the second volume of the final report, here we summarize our work on spectroscopic characterization of four raw coals including two subbituminous coals and two bituminous coals, tetrahydrofuran (THF)-extracted but unreacted coals, the coals (THF-insoluble parts) that have been thermally pretreated. in the absence of any solvents and in the presence of either a hydrogen-donor solvent or a non-donor solvent, and the coals (THF-insoluble parts) that have been catalytically pretreated in the presence of a dispersed Mo sulfide catalyst in the absence of any solvents and in the presence of either a hydrogen-donor solvent or a non-donor solvent
Non-Gaussianity from false vacuum inflation: Old curvaton scenario
We calculate the three-point correlation function of the comoving curvature
perturbation generated during an inflationary epoch driven by false vacuum
energy. We get a novel false vacuum shape bispectrum, which peaks in the
equilateral limit. Using this result, we propose a scenario which we call "old
curvaton". The shape of the resulting bispectrum lies between the local and the
false vacuum shapes. In addition we have a large running of the spectral index.Comment: 13 pages, 3 figures; v2 with minor revison; v3 final version to
appear on JCA
Quadra-Spectrum and Quint-Spectrum from Inflation and Curvaton Models
We calculate the quadra-spectrum and quint-spectrum, corresponding to five
and six point correlation functions of the curvature perturbation. For single
field inflation with standard kinetic term, the quadra-spectrum and
quint-spectrum are small, which are suppressed by slow roll parameters. The
calculation can be generalized to multiple fields. When there is no entropy
perturbation, the quadra-spectrum and quint-spectrum are suppressed as well.
With the presence of entropy perturbation, the quadra-spectrum and
quint-spectrum can get boosted. We illustrate this boost in the multi-brid
inflation model. For the curvaton scenario, the quadra-spectrum and
quint-spectrum are also large in the small r limit. We also calculate
representative terms of quadra-spectrum and quint-spectrum for inflation with
generalized kinetic terms, and estimate their order of magnitude for
quasi-single field inflation.Comment: 16 pages; v2: references added
On primordial trispectrum from exchanging scalar modes in general multiple field inflationary models
We make an complementary investigation of the primordial trispectrum from
exchanging intermediate scalar modes in multi-field inflation models with
generalized kinetic terms. Together with the calculation of irreducible
contributions to the primordial trispectrum in Ref.[103], we give the full
leading-order primordial trispectrum in generalized multi-field models.Comment: 15 pages, 1 figure; v2 references adde
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