Emergence of Bulk CsCl Structure in (CsCl)nCs+ Cluster Ions

The emergence of CsCl bulk structure in (CsCl)nCs+ cluster ions is investigated using a mixed quantum-mechanical/semiempirical theoretical approach. We find that rhombic dodecahedral fragments (with bulk CsCl symmetry) are more stable than rock-salt fragments after the completion of the fifth rhombic dodecahedral atomic shell. From this size (n=184) on, a new set of magic numbers should appear in the experimental mass spectra. We also propose another experimental test for this transition, which explicitely involves the electronic structure of the cluster. Finally, we perform more detailed calculations in the size range n=31--33, where recent experimental investigations have found indications of the presence of rhombic dodecahedral (CsCl)32Cs+ isomers in the cluster beams.Comment: LaTeX file. 6 pages and 4 pictures. Accepted for publication in Phys. Rev.

Modelling of unsteady-state, heterogeneous catalytic combustion

ABSTRACT: This paper describes a set of mathematical models of a unique reactor for the total oxidation of combustible vapors in the several-percent range without supplemental fuel or expensive heat exchange. The reactor operates at slightly above atmospheric pressure with Platinum on gamma alumina catalyst at about 200 °C. The reactor operates in an unsteady-state mode with feed gas flow direction periodically reversed. The simulation results for the variation of concentration, feed flow rate and cycle time show the experimentally observed behaviour. Further simulations show that runaway can occur when the concentration is high

On the use of residence time distributions for the design of clarifiers

Use of residence time distributions (RTD's) for the design of clarifiers proposed by the senior author in 1969 and by others has been found to be based on flow pattern assumptions which are false. Since the residence time distribution depends upon the density of the feed to the clarifier, flow rate and other near‐intangibles, it is not possible to obtain RTD's which pertain to an operating settler from which reliable performance may be predicted. Finally, laboratory studies demonstrate that the combination of RTD's and quiescent settling data do not reliably predict clarifier performance.</p

On the use of residence time distributions for the design of clarifiers

Use of residence time distributions (RTD's) for the design of clarifiers proposed by the senior author in 1969 and by others has been found to be based on flow pattern assumptions which are false. Since the residence time distribution depends upon the density of the feed to the clarifier, flow rate and other near‐intangibles, it is not possible to obtain RTD's which pertain to an operating settler from which reliable performance may be predicted. Finally, laboratory studies demonstrate that the combination of RTD's and quiescent settling data do not reliably predict clarifier performance