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151.
Michael C. Baker Bo Kong Jesse Capecelatro Olivier Desjardins Rodney O. Fox 《American Institute of Chemical Engineers》2020,66(7):e16230
Particle-laden flows in a vertical channel were simulated using an Eulerian–Eulerian, Anisotropic Gaussian (EE-AG) model. Two sets of cases varying the overall mass loading were done using particle sizes corresponding to either a large or small Stokes number. Primary and turbulent statistics were extracted from these results and compared with counterparts collected from Eulerian–Lagrangian (EL) simulations. The statistics collected from the small Stokes number particle cases correspond well between the two models, with the EE-AG model replicating the transition observed using the EL model from shear-induced turbulence to relaminarization to cluster-induced turbulence as the mass loading increased. The EE-AG model was able to capture the behavior of the EL simulations only at the largest particle concentrations using the large Stokes particles. This is due to the limitations involved with employing a particle-phase Eulerian model (as opposed to a Lagrangian representation) for a spatially intermittent system that has a low particle number concentration. 相似文献
152.
Dieter Grschl Axel Mayer Michael Schmidt Herbert Meier 《Advanced Synthesis \u0026amp; Catalysis》1995,337(1):379-384
Synthesis of Benzo[b]thioxanthenes Benzo[b]thioxanthenes, heterocyclic compounds related to tetracenes and tetracyclines can be obtained by the reaction of 2H-benzo[b]thiete ( 1 ) and 1,4-naphthoquinones ( 3a–g ). The primary cycloadducts 4a–g undergo an autoxidation process leading to the quinones 6a–g . The dihydroxy compound 4e shows an additional isomerization by a tetrafold H transfer ( 4e → 5e ′). Another preparative route to benzo[b]thioxanthenes makes use of the cycloadditon reaction of 1 and 1,4-epoxynaphthalenes ( 7a–d ). The primary adducts can be transformed to the title compounds by catalytic dehydration processes ( 8a–d → 9a-d ). An alternate regioselective opening of the oxygen bridge can be performed by the action of trimethyliodosilane ( 8a → 10a ). Methylation of 9a furnishes the sulfonium salt 14a which rearranges in a strongly alkaline medium to 16a ; in the presence of oxygen ketone 17a is generated. 相似文献
153.
154.
The profiles of liquid velocity and gas hold-up in convection cells of bubble columns were calculated numerically. Development of a circulation cell was calculated from momentum and mass balances. Breakdown of the circulation cell was calculated taking into account the drift motion of bubbles ascending in accordance with the velocity gradient of the liquid. A limit of stability for the development of circulation cells has been obtained. 相似文献
155.
Evaporation of liquid films, not subjected to motion, and with a starting thickness of 1 mm, was tested. Solvents dichloromethane and ethanol were used as liquids. Surface temperature during evaporation was measured in a non-intrusive way using pyrometry. The employed pyrometer was calibrated against a black body radiant. Measurement accuracy in the region of the ambient temperature is 0.2 K. Since any principal stray radiation is always measured along with the thermal radiation emitting from the liquid film, the measurement results are at first distorted. A correction calculation is described. With this, the various proportions of stray radiation can be subsequently calculated. In order to do this, the dimensions of the test equipment and the spectral data of the evaporating solvents must be taken into account. The quantity of stray radiation depends mainly on the properties of the surface onto which the liquid film is applied, as well as on the spectral transmissivity of the liquid. This was measured for every tested liquid according to wavelength and layer thickness. Where the spectral transmissivity of a liquid is low, a correction calculation of the measured surface temperature is not necessary, while a high level of accuracy is still retained. 相似文献
156.
Ilse Bacaloglu Truong The Ky Carmen Boeriu Hans Horst Glatt Radu Bacaloglu Dieter Martin Heinz Graubaum 《Advanced Synthesis \u0026amp; Catalysis》1982,324(5):803-808
Acylation of Heterocycles with Carbonic Acid Derivatives. I. Kinetics and Mechanism of the Reaction of 2-Aminobenzimidazoles with Aryl Cyanates The second order rate constants for the reaction of 2-amino-benzimidazoles (2-ABI) with aryl cyanates forming 2-amino-benzimidazole aryl ester imide 3 have been determined in dependence on substituent effects by u. v. measurements. The results are interpreted by a six-membered cyclic transition state in which the electrophilic attack of the cyanate on the endocyclic N atom is catalyzed by an H bridge interaction of the exocyclic amino group of 2-ABI with the OCN group. 相似文献
157.
Jimmy Perdana Martijn B. Fox Maarten A. I. Schutyser Remko M. Boom 《Food and Bioprocess Technology》2013,6(4):964-977
The inactivation of bioactive ingredients during spray drying is often matrix specific. Therefore, the design of new processes or the optimisation of existing spray drying processes is usually highly product specific and requires numerous experiments. Rapid experimentation methods that facilitate fast data generation are therefore desired. A novel method for drying single droplets to mimic spray drying is proposed. The approach involves droplet deposition on a hydrophobic flat surface followed by controlled drying. A heat and mass transfer model is applied to predict the drying history of the single droplets. The approach is successfully evaluated through studying the inactivation of β-galactosidase during drying. The heat and mass transfer model supplemented with inactivation kinetics provided reasonable prediction of the residual enzyme activity after drying. In addition, the inactivation kinetics could be directly extracted from single droplet experiments rather than using the kinetics from separate heating experiments. Finally, it was demonstrated that the inactivation kinetics found with the single-drop experiments could satisfactorily predict the residual activity of β-galactosidase dried with a laboratory-scale spray dryer. 相似文献
158.
A polymerase chain reaction (PCR) assay based on a solution hybridization format with colorimetric end-point detection (PCR ELISA) was investigated for the specific detection of Campylobacter jejuni and Campylobacter coli in food samples following enrichment culture. One hundred fifteen samples of raw meat and offal (poultry, porcine, ovine, and bovine), raw shellfish, and artificially contaminated milk were enriched in blood-free Campylobacter Enrichment Broth for 48 h. Enrichment cultures were subcultured to Campylobacter blood-free selective agar plates, and presumptive isolates were identified by phenotypic methods. DNA was extracted from 1-ml aliquots of the enrichment cultures using a rapid extraction method, and the DNA was used as the template in a PCR ELISA. A comparison of the PCR ELISA with the enrichment culture and subculture to selective agar method showed that the results of 112 of the 115 samples tested were in agreement by both methods. Seventy-one of the various food samples were positive in the PCR ELISA, and 70 samples were positive by culture. The PCR ELISA had a sensitivity of 99% and a specificity of 96%, with a positive predictive value of 97% and a negative predictive value of 98%. The PCR ELISA is a rapid, sensitive, and specific method for the detection of C. jejuni and C. coli in foods following enrichment culture and significantly reduces the time required for their detection. 相似文献
159.
To date, the price of electricity to commercial or business energy consumers has generally increased at greater rates in the areas of Texas where retail competition has been introduced than in areas that do not enjoy competition. Trends in commercial competitive prices have largely mirrored trends in residential prices. Market restructuring has tended to increase the sensitivity of retail electricity prices to changes in the price of natural gas, the marginal fuel used for generation in Texas. Consequently, the rapid increases in the commodity price of natural gas following restructuring led to increases in competitive electric rates which exceeded the increases in areas not exposed to restructuring, where the fuel component of electric rates tend to reflect a weighted average of the utilities’ fuel costs. There is some evidence that pricing behavior by competitive retailers changed when the retailers affiliated with the incumbent utilities were permitted some pricing flexibility, resulting in a reduction in prices. 相似文献
160.