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Accurate prediction of mixing at cross junctions is important in water quality models because most of the intersecting pipes use cross junctions in water distribution systems. To describe the characteristics of complex mixing phenomena, an empirical mixing model at the cross joints is proposed based on a large number of experimental data. The orthogonal experiments by numerical simulations show that the diameter ratio of inlets and the Reynolds number ratios of inlets and outlets have a dominant effect on the solute mixing at cross junctions. These dominant parameters are then chosen to investigate the cross-joint mixing in the experimental setup. The results indicated that the cross joint connected by pipes with a large size difference has a more complete mixing than the one with a small pipe size difference, if other conditions are kept the same. The mixing formulas for solute concentrations at outlets are fitted by an improved particle swarm optimization (PSO) algorithm based on the experimental data. The interpolation method is used to obtain the mixing information for other diameter ratios of the inlets. The established mixing model can be incorporated into standard EPANET to analyze the water quality in water distribution systems. [ABSTRACT FROM AUTHOR]

Tris(8-hydroxyquinolato) aluminum (Alq3), a prototypical molecule for organic light-emitting devices, has been studied via synchrotron radiation photoemission to investigate (1) the surface electronic structure of the molecules at room temperature and at elevated temperatures, (2) adsorption onto the inorganic Si(001)-2×1 surface, and (3) doping with the alkaline metal Mg. For case (1), three chemical environments of carbon are resolved. Moreover, the shake-up satellite structures are detected in all the N 1s, C 1s, O 1s, and Al 2p core-level spectra, but with different magnitudes. Annealing allows for a charge redistribution within Alq3 itself. As to case (2), the organic molecules not only passivate the dangling bonds, but also rupture the dimer bonds. The wave function of the surface dangling bonds and of the pyridyl side of an 8-quinolinol ligand overlaps greatly so that charge is polarized towards, the organic adlayer. However, the polarization diminishes at greater coverage. With regard to case (3), the N 1s core-level spectra appear as an Mg-induced charge-transfer component with a binding energy lower than the original component. This new component grows gradually in intensity with increasing concentration of the dopant. Moreover, Mg also affects the O 1s core, as manifested by a component lying at a +1.09 eV higher binding energy than the original component. The Mg 2p core-level spectra, although rather broad, exhibit a shift toward a lower binding energy with increasing Mg vapor. Upon examining all these experimental results, we propose that Mg in the surface Alq3 molecules forms clusters. Each cluster attaches to a pyridyl ring, affecting not only the nitrogen atom at that ring, but also the oxygen atom in the adjacent phenoxide ring. The depleted charge in the affected oxygen then flows about its adherent ligand and resides on the pyridyl ring at that ligand, resulting in a high Alq3 anion state. [ABSTRACT FROM AUTHOR]