Generating a Condensed Representation for Association Rules

Association rule extraction from operational datasets often produces several tens of thousands, and even millions, of association rules. Moreover, many of these rules are redundant and thus useless. Using a semantic based on the closure of the Galois connection, we define a condensed representation for association rules. This representation is characterized by frequent closed itemsets and their generators. It contains the non-redundant association rules having minimal antecedent and maximal consequent, called min-max association rules. We think that these rules are the most relevant since they are the most general non-redundant association rules. Furthermore, this representation is a basis, i.e., a generating set for all association rules, their supports and their confidences, and all of them can be retrieved needless accessing the data. We introduce algorithms for extracting this basis and for reconstructing all association rules. Results of experiments carried out on real datasets show the usefulness of this approach. In order to generate this basis when an algorithm for extracting frequent itemsets—such as Apriori for instance—is used, we also present an algorithm for deriving frequent closed itemsets and their generators from frequent itemsets without using the dataset.     

Boundedness properties of the soft-constrained time-optimal control

We present a general analysis of the asymptotic behaviour of the soft-constrained time-optimal (SCTO) control of linear systems. We are essentially seeking to show that (1) this control is bounded, like its hard-constrained counterpart; and (2) there is a basic tradeoff between the control bounds and the speed of the response, and we seek to characterize this tradeoff. We show that if the 'No Infinite Manoeuvre in Finite Optimal Time' (NIMIFOT) condition holds, then the boundedness of the SCTO control can be easily checked, and that the above-mentioned tradeoff is clearly characterized. For instance, we show that the SCTO control is bounded for all stable systems and for many marginally stable systems provided that the NIMIFOT condition holds. We also show that a slight modification of the formulation of the SCTO control problem can ensure that the NIMIFOT condition holds. With this new formulation, the SCTO control can be shown to be bounded for most linear plants satisfying mild and easily checkable conditions.     

Infrared and carbon dioxide chemisorption study of Mo/ZrO2 catalysts

The interaction of Mo with zirconia has been investigated by infrared spectroscopy (IR) and carbon dioxide chemisorption. Quantitative analysis of the IR results indicated that Mo interacts preferentially with the most basic hydroxyl group (high frequency band at 3775 cm^–1). An approximately 79% decrease in the 3775 cm^–1 band is observed vs. 21% for the low frequency band at 3673 cm^–1, with increasing the Mo loading up to 1 wt%. The relative decrease of the IR band at 3775 cm^–1 was identical to that measured for the CO₂ uptake. The Mo cross-sections estimated from CO₂ chemisorption results were much higher than those typically reported for the Mo system. It was concluded that, as previously reported for the Mo/Al₂o₃ system, CO₂ chemisorption overestimates the surface coverage of Mo/ZrO₂ catalysts.     

Experimental study on the compressive resistance of stress-relieved solid round steel members

The Canadian Standard for Antenna Towers and Antenna Supporting Structures, CSA-S37-01, specifies expressions for the compressive resistance of solid rounds based on the Structural Stability Research Council (SSRC) Column Curves for non-solid-round members and the results from experimental investigations on the compressive resistance of solid rounds carried out back to 1965. Similar Standard in USA (TIA/EIA-222-G.0) specifies design criteria for such members as derived from the superseded AISC-LRFD-94 Standard, which is independent of the shape of the member cross-section. The European Standard, Eurocode 3, provides column curves for the compressive resistance of various structural steel members, and assumes the applicability of one of them to solid rounds. As such, it is necessary to conduct an experimental study on solid round stress-relieved steel members to refine the available design equations for such members. This paper provides a summary of the literature review on solid rounds as well as a recent test program conducted on stress-relieved steel solid rounds. Correlation between the results from these tests and the current practice for the design of solid rounds is investigated. The paper concludes with a proposed compressive resistance equation for economical design of such members.     

Effect of Buoyancy Ratio on Double-Diffusive Natural Convection in a Porous Rhombic Annulus

This paper reports on the effect of buoyancy ratio due to both heat and mass transfer on natural convection in a porous enclosure between two isothermal concentric cylinders of rhombic cross sections. For negative values of the buoyancy ratio, buoyancy forces due to heat and mass transfer are in opposite directions (opposing mode), while for positive values they are in the same direction (aiding mode). Numerical results demonstrate that the flow strength increases as the absolute value of the buoyancy ratio increases. In the opposing mode, the eye of the vortex flow is located in the lower half of the enclosure, while in the aiding mode it is positioned in the upper part of the annulus. The average Nusselt and Sherwood number values increase as the absolute value of the buoyancy ratio moves away from 1, with values obtained in the aiding mode being higher than corresponding values achieved in the opposing mode. A comparison is also made between the computed average Nusselt and Sherwood number values and similar ones obtained in a circular annulus having the same inner and outer perimeters as the rhombic enclosure. Predictions indicate large percent difference in values, demonstrating that circular geometries cannot be exploited to accurately predict heat and mass transfer in complex geometries.