Risk, Ambiguity, and the Klibanoff Axioms

Machina (2007) formulates a number of experiments, and shows that they can be used to test the Choquet expected utility model. We show that one of them can also be used to test the class of maxmin expected utility preferences in Klibanoff (2001). Those preferences are not consistent with Choquet expected utility preferences in Machina's experiment.maxmin expected utility

Possibility and permissibility

We generalize permissibility (Brandenburger, 1992) to allow for any suitably defined model of preference and definition of possibility. We also prove that the generalized solution concept characterizes rationality, caution, and “common belief" of rationality and caution.

A robust definition of possibility for biseparable preferences

This note presents several preference-based definitions of a likely event, and shows that they induce (in the sense of Lo 2005b) the same set of possible states for biseparable preferences.

Risk, Ambiguity, and the Klibanoff Axioms

Machina (2007) formulates a number of experiments, and shows that they can be used to test the Choquet expected utility model. We show that one of them can also be used to test the class of maxmin expected utility preferences in Klibanoff (2001). Those preferences are not Choquet expected utility preferences, and they are not consistent with Choquet expected utility preferences in Machina’s experiment.Choquet expected utility,Ellsberg Paradox,Maxmin expected utility,Stochastic independence,Uncertainty

Correlated Nash Equilibrium

Nash equilibrium presumes that players have expected utility preferences, and therefore the beliefs of each player are represented by a probability measure. Motivated by Ellsberg-type behavior, which contradicts the probabilistic representation of beliefs, we generalize Nash equilibrium in n-player strategic games to allow for preferences conforming to the maxmin expected utility model of Gilboa and Schmeidler [Journal of Mathematical Economics, 18 (1989), 141–153]. With no strings attached, our equilibrium concept can be characterized by the suitably modified epistemic conditions for Nash equilibrium.Agreeing to disagree, Correlated equilibrium, Epistemic conditions, Knightian uncertainty, Multiple priors, Nash equilibrium

Flow around an articulated lorry model

An experimental study has been conducted to investigate both the time-averaged and instantaneous flow pattern over a scale articulated vehicle model for understanding the flow physics of tractor-trailer vehicles. Fully turbulent flow was used in the study and smoke visualisation, surface oil flow visualisation and two-component particle image velocimetry were employed for flow diagnostics. Results obtained from the time-averaged and instantaneous flow fields show different flow pattern in the wake region downstream of the rear end of the trailer model. In the time-averaged flow field, a single counter-clockwise rotating vortex is presented in the wake region due to the coil-up of the lower shear layer. The instantaneous flow pattern shows that two wake vortices are presented in the wake region downstream of the trailer model. Moreover, the interactions between the wake vortex and the upper shear layer lead to the formation of the streamwise vortices within the shear layer. These streamwise vortices grow and propagate downstream which lead to the occurrence of vortex shedding in the upper shear layer downstream of the trailer model

Flow visualisation of a normal shock impinging over a rounded contour bump in a Mach 1.3 free-stream

An experimental study has been conducted to visualise the instantaneous streamwise and spanwise flow patterns of a normal shock wave impinging over a rounded contour bump in a Mach 1.3 free-stream. A quartz-made transparent shock generator was used, so that instantaneous images could be captured during the oil-flow visualisation experiments. Fluorescent oil with three different colours was used in the surface oil-flow visualisation experiment to enhance the visualisation of flow mixing and complicated flow features that present in the flow field. Experimental data showed that the rounded contour bump could split the impinging normal shock wave into a or a series of lambda-shaped shock wave structure(s). In addition, it was found that the flow pattern and the shock wave structures that appeared over the rounded contour bump depended highly on the impinging location of the normal shock wave. The flow pattern shown in this study agreed with the findings documented in literature. Moreover, it was observed from the instantaneous oil streaks that the normal shock impinging location also affected the size and the formation location of the spanwise counter-rotating vortices downstream of the bump crest. Finally, it was concluded that the terminating shock could distort the oil streaks that left over the surface of the contour bump. Therefore, the use of the transparent normal shock wave generator is recommended when conducting experiments with normal shock wave impingement involved

Flow Control Over a Tractor-Trailer Using Vortex Generators

No abstract available

Control of flow separation on a contour bump by jets in a Mach 1.9 free-stream: an experimental study

Flow separation control over a three-dimensional contour bump using jet in a Mach 1.9 supersonic free-stream has been experimentally investigated using a transonic/supersonic wind tunnel. Jet total pressure in the range of 0–4 bar was blowing at the valley of the contour bump. Schlieren photography, surface oil flow visualisation and particle image velocimetry measurements were employed for flow visualisation and diagnostics. Experimental results show that blowing jet at the valley of the contour bump can hinder the formation and distort the spanwise vortices. The blowing jet can also reduce the extent of flow separation appears downstream of the bump crest. It was observed that this approach of flow control is more effective when high jet total pressure is employed. It is believed that a pressure gradient is generated as a result of the interaction between the flow downstream of the bump crest and the jet induced shock leads to the downwards flow motion around the bump valley

Shock wave diffraction phenomena around slotted splitters

In the field of aerospace engineering, the study of the characteristics of vortical flows and their unsteady phenomena finds numerous engineering applications related to improvements in the design of tip devices, enhancement of combustor performance, and control of noise generation. A large amount of work has been carried out in the analysis of the shock wave diffraction around conventional geometries such as sharp and rounded corners, but the employment of splitters with lateral variation has hardly attracted the attention of researchers. The investigation of this phenomenon around two-dimensional wedges has allowed the understanding of the basic physical principles of the flow features. On the other hand, important aspects that appear in the third dimension due to the turbulent nature of the vortices are omitted. The lack of studies that use three-dimensional geometries has motivated the current work to experimentally investigate the evolution of the shock wave diffraction around two splitters with spike-shaped structures for Mach numbers of 1.31 and 1.59. Schlieren photography was used to obtain an insight into the sequential diffraction processes that take place in different planes. Interacting among them, these phenomena generate a complicated turbulent cloud with a vortical arrangement