Iterative Reduction Procedure Research Articles

Social Rationalizability with Mediation

We propose a solution concept for social environments called social rationalizability with mediation that identifies the consequences of common knowledge of rationality and farsightedness. In a social environment several coalitions may and could be willing to move at the same time. Individuals not only hold conjectures about the behaviors of other individuals but also about how a mediator is going to solve conflicts of interest. The set of socially rationalizable outcomes with mediation is shown to be non-empty for all social environments, and it can be computed by an iterative reduction procedure. We show that social rationalizability with mediation does not necessarily satisfy coalitional rationality when the number of coalition members is greater than two.

Development of a reduced polyoxymethylene dimethyl ethers (PODEn) mechanism for engine applications

Polyoxymethylene dimethyl ethers (PODEn) features high oxygen content (>45 wt%) and cetane number (>60) and is a promising alternative fuel for diesel engines. In the current study, a reduced primary reference fuel (PRF)-PODEn chemical kinetic mechanism consisting of 145 species and 585 reactions is proposed for combustion and soot formation prediction. The PODEn sub-mechanism is reduced from a comprehensive mechanism using an iterative reduction procedure with different mechanism reduction methods (directed relation graph with error propagation, sensitivity analysis and isomer lumping), and is then incorporated into the base reduced PRF-PAH mechanism. This reduced PRF-PODEn mechanism has been extensively validated against experimental results including ignition delay times, laminar flame speeds, species concentration profiles and homogeneous charge compression ignition (HCCI) combustion. At specific operating conditions, PODE3 HCCI combustion exhibits a three-stage heat release, which is found to be caused by PODE3 decomposition, CH2O-to-CO reactions and CO-to-CO2 oxidation, respectively. Furthermore, the present mechanism is further applied in three-dimensional simulations of the engine direct injection compression ignition (DICI) combustion fueled with pure diesel (D100), gasoline/diesel blends (GD50) and gasoline/diesel/PODEn blends (GDP30). Compared to D100, the soot emissions are reduced with GD50 and GDP30 by 75% and 96%, respectively, due to the higher ratio of premixed combustion and higher fuel oxygen content. Additionally, 0-D modeling investigations with the present mechanism are conducted to clarify the chemical effects on soot formation. The A4 formation of PODE3 is three orders of magnitude smaller than that of PRF since no CC bonds exist in PODE3′s molecules. The decline of A4 formation in the n-heptane/iso-octane/PODE3 blend illustrates that oxygenated fuels like PODEn are beneficial to the soot reduction.

Quantifying the Effects of Activity Concentration at Airports on Public Transport Using an Iterative Reduction Procedure

Airport locations are increasingly the place of non-aeronautical activities. This is driven by airport operators seeking non-aeronautical revenues and real estate investors attempting to profit from major airports as high value locations. The resulting higher densities lead to more travel to and from the location. Travellers induced by non-aeronautical activity are likely to behave different than those induced by aeronautical activity. Consequently, there are potentially not only more, but also more public transport prone travellers. This can improve the viability of operating high quality public transport services. However, as demand of the different traveller groups is likely distributed differently, it also needs to be studied whether the superimposed demand affects the peaking behaviour of travel demand in a beneficial, balancing, or negative, exacerbating, way.For the analysis, an iterative reduction procedure is proposed that begins with a network of highest quality services. Considering demand elasticity and minimum loads to viably operate a service, network elements are degraded and demand is recalculated iteratively until only viable services remain. This procedure is applied to a case study of Zurich, where large scale commercial activities and a public transport hub are located at the airport. It was found that the non-aeronautical development already contributes decisively to public transport use and without it, severe service reductions might be necessary. Furthermore, the compound demand distribution is more even than that of the individual traveller groups, resulting in a landside transport hub that can be operated more efficiently than facilities in conventional locations. Future growth of the airport location will increase this effect and further service expansions may become an attractive option.It is concluded that the high connectivity of airport locations is an opportunity to drive development patterns conducive to public transport use. In addition, airports can be efficient locations for transfer centres as there, if their locations are suitable, sustained high demand with less variation throughout a day allows for a better utilisation of services and facilities.

Development of reduced and optimized reaction mechanisms based on genetic algorithms and element flux analysis

The present paper introduces an approach for the automatic development of reduced reaction mechanisms for hydrocarbon combustion. An iterative reduction procedure is adopted with the aim of gradually reducing the number of species involved in the mechanism, while still maintaining its predictiveness in terms of not only ignition delay times, but also the time evolution of important species. In particular, a global error function is defined taking into account a set of 18 ignition delay calculations at different, engine-relevant, initial mixture compositions, temperatures and pressures. The choice of the species to be deleted is performed exploiting the element flux analysis method, first introduced by Revel et al.; when a global error function of the reduced mechanism exceeds the required accuracy, the collision frequencies and activation energies of selected reactions are corrected by means of a GA-based code. The procedure is repeated until the lowest number of species at the required global error tolerance is achieved. The methodology is applied to a detailed mechanism of ethanol combustion consisting of 58 species and 383 reactions to produce an optimal reduced mechanism of 33 species and 155 reactions.

Rationalizability for social environments

Social environments constitute a framework in which it is possible to study how groups of agents interact in a society. The framework is general enough to analyze both non-cooperative and cooperative games. In order to remedy the shortcomings of existing solution concepts and to identify the consequences of common knowledge of rationality and farsightedness, we propose to apply extensive-form rationalizability to the framework of social environments. For us, the social environment is a primitive. On this social environment is defined a multistage game. An outcome of the social environment is socially rationalizable if and only if it is rationalizable in the multistage game. The set of socially rationalizable outcomes is shown to be non-empty for all social environments and it can be computed by an iterative reduction procedure. We introduce a definition of coalitional rationality for social environments and show that it is satisfied by social rationalizability.