Multiple Steady States in Heterogeneous Azeotropic Distillation

In this article we study multiple steady states in ternary heterogeneous azeotropic distillation. We show that in the case of infinite reflux and an infinite number of trays one can construct bifurcation diagrams on physical grounds with the distillate flow as the bifurcation parameter. Multiple steady states exist when the distillate flow varies non-monotonically along the continuation path of the bifurcation diagram. We show how the distillate and bottom product paths can be located for tray or packed columns, with or without decanter and with different types of condenser and reboiler. We derive a necessary and sufficient condition for the existence of these multiple steady states based on the geometry of the product paths. We also locate in the composition triangle the feed compositions that lead to these multiple steady states. We show that the prediction of the existence of multiple steady states in the case of infinite reflux and an infinite number of trays has relevant implications for columns operating at finite reflux and with a finite number of trays

Multiple Steady States in Homogeneous Azeotropic Distillation

In this article we study multiple steady states in ternary homogeneous azeotropic distillation. We show that in the case of infinite reflux and an infinite number of trays one can construct bifurcation diagrams on physical grounds with the distillate flow as the bifurcation parameter. Multiple steady states exist when the distillate flow varies non-monotonically along the continuation path of the bifurcation diagram. We derive a necessary and sufficient condition for the existence of these multiple steady states based on the geometry of the distillation region boundaries. We also locate in the composition triangle the feed compositions that lead to these multiple steady states. We further note that most of these results are independent of the thermodynamic model used. We show that the prediction of the existence of multiple steady states in the case of infinite reflux and an infinite number of trays has relevant implications for columns operating at finite reflux and with a finite number of trays. Using numerically constructed bifurcation diagrams for specific examples, we show that these multiplicities tend to vanish for small columns and/or for low reflux flows. Finally, we comment on the effect of multiplicities on column design and operation for some specific examples

Trends in health facility deliveries and caesarean sections by wealth quintile in Morocco between 1987 and 2012.

OBJECTIVES: To examine trends in the utilisation of facility-based delivery care and caesareans in Morocco between 1987 and 2012, particularly among the poor, and to assess whether uptake increased at the time of introduction of policies or programmes aimed at improving access to intrapartum care. METHODS: Using data from nationally representative household surveys and routine statistics, our analysis focused on whether women delivered within a facility, and whether the delivery was by caesarean; analyses were stratified by relative wealth quintile and public/private sector where possible. A segmented Poisson regression model was used to assess whether trends changed at key events. RESULTS: Uptake of facility-based deliveries and caesareans in Morocco has risen considerably over the past two decades, particularly among the poor. The rate of increase in facility deliveries was much faster in the poorest quintile (annual increase RR: 1.09; 95% CI: 1.07-1.11) than the richest quintile (annual increase RR: 1.01; 95% CI: 1.02-1.02). A similar pattern was observed for caesareans (annual increase among poorest RR: 1.13; 95% CI: 1.07-1.19 vs. annual increase among richest RR: 1.08; 95% CI: 1.06-1.10). We found no significant acceleration in trend coinciding with any of the events investigated. CONCLUSIONS: Morocco's success in improving uptake of facility deliveries and caesareans is likely to be the result of the synergistic effects of comprehensive demand and supply-side strategies, including a major investment in human resources and free delivery care. Equity still needs to be improved; however, the overall trend is positive

MCMAS: an open-source model checker for the verification of multi-agent systems

We present MCMAS, a model checker for the verification of multi-agent systems. MCMAS supports efficient symbolic techniques for the verification of multi-agent systems against specifications representing temporal, epistemic and strategic properties. We present the underlying semantics of the specification language supported and the algorithms implemented in MCMAS, including its fairness and counterexample generation features. We provide a detailed description of the implementation. We illustrate its use by discussing a number of examples and evaluate its performance by comparing it against other model checkers for multi-agent systems on a common case study

Multiple Steady States in Heterogeneous Azeotropic Distillation

In this article, we study multiple steady states in ternary heterogeneous azeotropic distillation. We show that in the case of infinite reflux and an infinite number of trays, one can construct bifurcation diagrams on physical grounds with the distillate flow as the bifurcation parameter. Multiple steady states exist when the distillate flow varies nonmonotonically along the continuation path of the bifurcation diagram. We show how the distillate and bottom product paths can be located for tray or packed columns, with or without decanter and with different types of condenser and reboiler. We derive a necessary and sufficient condition for the existence of these multiple steady states based on the geometry of the product paths. We also locate in the composition triangle the feed compositions that lead to these multiple steady states. We show that the prediction of the existence of multiple steady states in the case of infinite reflux and an infinite number of trays has relevant implications for columns operating at finite reflux and with a finite number of trays