Weak Pseudo-Rationalizability

This paper generalizes rationalizability of a choice function by a single acyclic binary relation to rationalizability by a set of such relations. Rather than selecting those options in a menu that are maximal with respect to a single binary relation, a weakly pseudo-rationalizable choice function selects those options that are maximal with respect to at least one binary relation in a given set. I characterize the class of weakly pseudo-rationalizable choice functions in terms of simple functional properties. This result also generalizes Aizerman and Malishevski's characterization of pseudo-rationalizable choice functions, that is, choice functions rationalizable by a set of total orders

Another Approach to Consensus and Maximally Informed Opinions with Increasing Evidence

Merging of opinions results underwrite Bayesian rejoinders to complaints about the subjective nature of personal probability. Such results establish that sufficiently similar priors achieve consensus in the long run when fed the same increasing stream of evidence. Initial subjectivity, the line goes, is of mere transient significance, giving way to intersubjective agreement eventually. Here, we establish a merging result for sets of probability measures that are updated by Jeffrey conditioning. This generalizes a number of different merging results in the literature. We also show that such sets converge to a shared, maximally informed opinion. Convergence to a maximally informed opinion is a (weak) Jeffrey conditioning analogue of Bayesian “convergence to the truth” for conditional probabilities. Finally, we demonstrate the philosophical significance of our study by detailing applications to the topics of dynamic coherence, imprecise probabilities, and probabilistic opinion pooling

Morphology investigation on direct current pulsed gas tungsten arc welded additive layer manufactured Ti6Al4V alloy

The effects of pulsed gas tungsten arc weldingparameters on the morphology of additive layer manufacturedTi6Al4V has been investigated in this study. Thepeak/ base current ratio and pulse frequency are found tohave no significant effect on the refinement of prior betagrain size. However, it is found that the wire feed ratehas a considerable effect on the prior beta grainrefinement at a given heat input. This is due to the extrawire input being able to supply many heterogeneousnucleation sites and also results in a negative temperaturegradient in the front of the liquidus which blocks thecolumnar growth and changes the columnar growth toequiaixal growth

Development of a Low-Noise High Common-Mode-Rejection Instrumentation Amplifier

Several previously used instrumentation amplifier circuits were examined to find limitations and possibilities for improvement. One general configuration is analyzed in detail, and methods for improvement are enumerated. An improved amplifier circuit is described and analyzed with respect to common mode rejection and noise. Experimental data are presented showing good agreement between calculated and measured common mode rejection ratio and equivalent noise resistance. The amplifier is shown to be capable of common mode rejection in excess of 140 db for a trimmed circuit at frequencies below 100 Hz and equivalent white noise below 3.0 nv/square root of Hz above 1000 Hz

Unanimous Consensus Against AGM?

Given the role consensus is supposed to play in the social aspects of inquiry and deliberation, it is important that we may always identify a consensus as the basis of joint inquiry and deliberation. However, it turns out that if we think of an agent revising her beliefs to reach a consensus, then, on the received view of belief revision, AGM belief revision theory, certain simple and compelling consensus positions are not always available

Development of weld repair methods for Rene 80 nickel based superalloy

Nickel based superalloys are an integral material for gas turbines, where their excellent high temperature mechanical properties and corrosion resistance are utilised. Due to the increasing costs of raw materials, manufacturers are interested in repairing in-service and manufacturing defects in components. Unfortunately, superalloys such as Rene 80 are highly susceptible to welding defects such as liquation cracking and post-weld heat treatment cracking, which make repair welding highly difficult. The aim of the research in this thesis was to develop an improved understanding of welding defect production in nickel-based superalloys. In particular, the effect of repair process and its parameters were examined, with the ultimate aim to produce crack-free repair welds. The main theme of the work involved a large parametric study of the process parameter effects on welding defects in Rene 80 using a high power fibre laser. This work determined an optimised range of parameters which reduced the incidence of cracking. Furthermore, this work also identified a key relationship between the weld bead geometry aspect ratio and the incidence of cracking. This relationship was studied using neutron diffraction to determine the differences in strain and residual stresses between two welds with identical heat input but different geometry. An in-depth investigation of the cracks within the material, identified that as-welded cracks formed via liquation of secondary phases such as carbides, γ/γ’ eutectics, and secondary gamma prime. The post weld heat treatment cracks formed by the strain-age mechanism in Rene 80. From this work, a novel repair procedure avoiding the complications associated with using lower strength filler metal was developed, based on the optimised welding parameters. Finally, a number of advanced low heat input welding processes were also investigated for repair of superalloys

A Hyper-Relation Characterization of Weak Pseudo-Rationalizability

I provide a characterization of weakly pseudo-rationalizable choice functions---that is, choice functions rationalizable by a set of acyclic relations---in terms of hyper-relations satisfying certain properties. For those hyper-relations Nehring calls extended preference relations, the central characterizing condition is weaker than (hyper-relation) transitivity but stronger than (hyper-relation) acyclicity. Furthermore, the relevant type of hyper-relation can be represented as the intersection of a certain class of its extensions. These results generalize known, analogous results for path independent choice functions

Conditional choice with a vacuous second tier

This paper studies a generalization of rational choice theory. I briefly review the motivations that Helzner gives for his conditional choice construction (2013). Then, I focus on the important class of conditional choice functions with vacuous second tiers. This class is interesting for both formal and philosophical reasons. I argue that this class makes explicit one of conditional choice's normative motivations in terms of an account of neutrality advocated within a certain tradition in decision theory. The observations recorded several of which are generalizations of central results in the standard theory of rational choice are intended to provide further insight into how conditional choice generalizes the standard account and are offered as additional evidence of the fruitfulness of the conditional choice framework