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91.
Roe‐type Riemann solver for gas–liquid flows using drift‐flux model with an approximate form of the Jacobian matrix 下载免费PDF全文
This work presents an approximate Riemann solver to the transient isothermal drift ‐ flux model. The set of equations constitutes a non‐linear hyperbolic system of conservation laws in one space dimension. The elements of the Jacobian matrix A are expressed through exact analytical expressions. It is also proposed a simplified form of A considering the square of the gas to liquid sound velocity ratio much lower than one. This approximation aims to express the eigenvalues through simpler algebraic expressions. A numerical method based on the Gudunov's fluxes is proposed employing an upwind and a high order scheme. The Roe linearization is applied to the simplified form of A . The proposed solver is validated against three benchmark solutions and two experimental pipe flow data. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
92.
Eugénie Hunsicker Hengguang Li Victor Nistor Ville Uski 《Numerical Methods for Partial Differential Equations》2014,30(4):1130-1151
In this article, we consider the problem of optimal approximation of eigenfunctions of Schrödinger operators with isolated inverse square potentials and of solutions to equations involving such operators. It is known in this situation that the finite element method performs poorly with standard meshes. We construct an alternative class of graded meshes, and prove and numerically test optimal approximation results for the finite element method using these meshes. Our numerical tests are in good agreement with our theoretical results.Copyright © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 1130–1151, 2014 相似文献
93.
Quantitative monitoring of an activated sludge reactor using on-line UV-visible and near-infrared spectroscopy 总被引:1,自引:0,他引:1
Mafalda C. Sarragu?a Ana Paulo Madalena M. Alves Ana M. A. Dias Jo?o A. Lopes Eugénio C. Ferreira 《Analytical and bioanalytical chemistry》2009,395(4):1159-1166
The performance of an activated sludge reactor can be significantly enhanced through use of continuous and real-time process-state
monitoring, which avoids the need to sample for off-line analysis and to use chemicals. Despite the complexity associated
with wastewater treatment systems, spectroscopic methods coupled with chemometric tools have been shown to be powerful tools
for bioprocess monitoring and control. Once implemented and optimized, these methods are fast, nondestructive, user friendly,
and most importantly, they can be implemented in situ, permitting rapid inference of the process state at any moment. In this
work, UV-visible and NIR spectroscopy were used to monitor an activated sludge reactor using in situ immersion probes connected
to the respective analyzers by optical fibers. During the monitoring period, disturbances to the biological system were induced
to test the ability of each spectroscopic method to detect the changes in the system. Calibration models based on partial
least squares (PLS) regression were developed for three key process parameters, namely chemical oxygen demand (COD), nitrate
concentration (N-NO3−), and total suspended solids (TSS). For NIR, the best results were achieved for TSS, with a relative error of 14.1% and a
correlation coefficient of 0.91. The UV-visible technique gave similar results for the three parameters: an error of ~25%
and correlation coefficients of ~0.82 for COD and TSS and 0.87 for N-NO3−. The results obtained demonstrate that both techniques are suitable for consideration as alternative methods for monitoring
and controlling wastewater treatment processes, presenting clear advantages when compared with the reference methods for wastewater
treatment process qualification. 相似文献
94.
Noelia Calvar Begoña González Ángeles Domínguez Eugénia A. Macedo 《The Journal of chemical thermodynamics》2009,41(1):11-16
Measurements of osmotic coefficients of BmimCl (1-butyl-3-methylimidazolium chloride) and HmimCl (1-hexyl-3-methylimidazolium chloride) with ethanol and EmimEtSO4 (1-ethyl-3-methylimidazolium ethylsulfate) and EmpyEtSO4 (1-ethyl-3-methylpyridinium ethylsulfate) with water at T = (313.15 and 333.15) K are reported in this work. Vapour pressure and activity results of the studied binary systems are obtained from experimental measurements. The results for the osmotic coefficients are correlated using the extended Pitzer model modified by Archer and the modified NRTL (MNRTL) model. The standard deviations obtained with both models are also given. The parameters obtained with the extended Pitzer model of Archer are used to calculate the mean molal activity coefficients. 相似文献
95.
Noelia Calvar Elena Gómez Ángeles Domínguez Eugénia A. Macedo 《The Journal of chemical thermodynamics》2011,43(8):1256-1262
The osmotic and activity coefficients and vapour pressures of binary mixtures containing 1-propanol, or 2-propanol and imidazolium-based ionic liquids with bis(trifluoromethylsulfonyl)imide as anion (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C2MimNTf2, 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, C3MimNTf2, and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C4MimNTf2) were determined at T = 323.15 K using the vapour pressure osmometry technique. The experimental osmotic coefficients were correlated using the extended Pitzer model modified by Archer and the MNRTL model, obtaining standard deviations lower than 0.033 and 0.064, respectively. The mean molal activity coefficients and the excess Gibbs free energy for the mixtures studied were calculated from the parameters of the extended Pitzer model modified by Archer. Besides the effect of the alkyl-chain of the cation, the effect of the anion can be assessed comparing the experimental results with those previously obtained for imidazolium ionic liquids with sulphate anions. 相似文献
96.
Ana P. M. Tavares Rui P. Silva António L. Amaral Eugénio C. Ferreira Ana M. R. B. Xavier 《Applied biochemistry and biotechnology》2014,172(4):2132-2142
Image analysis technique was applied to identify morphological changes of pellets from white-rot fungus Trametes versicolor on agitated submerged cultures during the production of exopolysaccharide (EPS) or ligninolytic enzymes. Batch tests with four different experimental conditions were carried out. Two different culture media were used, namely yeast medium or Trametes defined medium and the addition of lignolytic inducers as xylidine or pulp and paper industrial effluent were evaluated. Laccase activity, EPS production, and final biomass contents were determined for batch assays and the pellets morphology was assessed by image analysis techniques. The obtained data allowed establishing the choice of the metabolic pathways according to the experimental conditions, either for laccase enzymatic production in the Trametes defined medium, or for EPS production in the rich Yeast Medium experiments. Furthermore, the image processing and analysis methodology allowed for a better comprehension of the physiological phenomena with respect to the corresponding pellets morphological stages. 相似文献
97.
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Sans résumé 相似文献
100.