Observing multiple behaviors

Most experimental kinetic curves are rather smooth, i.e, the concentration of adsorbate in solution monotonically decreases, but some kinetic curves reported in the literature have multiple minima and maxima, which are rather unlikely to be reproducible. Such minima and maxima represent probably the scatter of results due to insufficient control over the experimental conditions. For instance use of a specific type of shaker or stirrer at constant speed and amplitude does not necessarily assure reproducible conditions of mass transfer. Some publications report only kinetic data—results of experiments aimed merely at establishing the sufficient equilibration time in equilibrium experiments. Other authors studied adherence of the experimentally observed kinetic behavior to theoretical kinetic equations derived from different models describing the transport of the adsorbate. Design of a kinetic experiment aimed at testing kinetic models is much more demanding, and full control over all parameters that potentially affect the sorption kinetics is hardly possible. 

Rathousky and Hlavacek (1981) presented two mathematical models to illustrate the fact that the influence of adsorbed species on the rate of an isothermal catalytic reaction may lead to a complex dynamic pattern including multiplicity of steady states and oscillatory states. Multiple oscillations and horatian behavior can not be calculated from the models. Rathousky and Hlavacek (1982) studied CO oxidation on Pt/Al203 catalyst and observed changes in oscillations due to the variations in inlet temperature. For a narrow range they observed horatian behavior. Experiments show that interaction of two oscillatory processes cause horatian behavior. 

For the H2/O2 reaction it was found that structure insensitivity occurs for low H2/O2 ratios (313), whereas for the C0/02 reaction it occurs (319) for relatively high CO/O2 ratios. However, CO competes with 02 for surface sites more strongly than H2. We recall the already-mentioned observed surface reconstruction of Pt as the C0/02 ratio on the surface changes (315). This behavior, as well as the related formation of bulk and surface Pt02, is connected to observed multiple steady states and isothermal oscillations (320). 

The three solution branch dominating the nonlinear behavior of the process can also be observed in a conventional process with a reactor-separator recycle as recently reported by Blagov et al. [12]. This flowsheet is analogous to a column with one reactive and one non-reactive column section with a single product stream, the multiplicity behavior of which has been studied Cerafimov and coworkers [49, 83]. In these papers it is shown that this type of output multiplicity is a generic phenomenon for reaction systems with competing irreversible reactions and a similar distribution of volatUities between reactants and products. 

Abstract. Snip is a tool that allows a user to constrict the view onto any window. We report on a controlled study of the snip tool in the context of a multiple-monitor environment. The study was designed based on observed user behavior in a field study of multiple-monitor users snipping habits. Analysis provided results that indicate that users can expect to reference information approximately 15% to 30% faster from snipped windows than from non-snipped windows. Further, users need to pay only a small overhead cost to perform the snip operation. The result extends to other recently presented region-based interface tools that aim to assist multiple-monitor users interact effectively and employ additional monitor space for information-referencing activities. 

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