Mechanisms of High Temperature Degradation of Thermal Barrier Coatings.

Thermal barrier coatings (TBCs) are crucial for increasing the turbine inlet temperature (and hence efficiency) of gas turbine engines. The thesis describes PhD research aimed at improving understanding of the thermal cycling failure mechanisms of electron beam physical vapour deposited (EB-PVD) yttria stabilised zirconia (YSZ) TBCs on single crystal superalloys. The research consisted of three different stages. The first stage involved designing a coupled one-dimensional thermodynamic-kinetic oxidation and diffusion model capable of predicting the concentration profiles of alloying elements in a single-phase γ nickel-rich Ni-Al-Cr ternary alloy by the finite difference method. The aim of this investigation was to improve the understanding of interactions between alloying species and developing oxide. The model demonstrated that in the early stages of oxidation, Al consumption by oxide scale growth is faster than Al replenishment by diffusion towards the scale, resulting in an initial Al depletion in the alloy near the scale. The second stage involved a systematic study of the life-time of TBC systems on different single crystal superalloys. The study aimed at demonstrating that the compatibility of modern nickel-based single crystal superalloys with TBC systems is influenced strongly by the content of alloying element additions in the superalloy substrate. The results can be explained by postulating that the fracture toughness parameters controlling decohesion are influenced strongly by small changes in composition arising from interdiffusion with the bond coat, which itself inherits elemental changes from the substrate. The final stage of study involved a detailed study of different bond coats (two β-structured Pt-Al types and a γ/γ’ Pt-diffusion type) in TBC systems based on an EB-PVD YSZ top coat and a substrate material of CMSX-4 superalloy. Generation of stress in the thermally grown oxide (TGO) on thermal cycling, and its relief by plastic deformation and fracture, were investigated experimentally in detail

Finding a needle in a haystack: toward a psychologically informed method for aviation security screening

Current aviation security systems identify behavioral indicators of deception to assess risks to flights, but they lack a strong psychological basis or empirical validation. We present a new method that tests the veracity of passenger accounts. In an in vivo double-blind randomized-control trial conducted in international airports, security agents detected 66% of deceptive passengers using the veracity test method compared with less than 5% using behavioral indicator recognition. As well as revealing advantages of veracity testing over behavioral indicator identification, the study provides the highest levels to date of deception detection in a realistic setting where the known base rate of deceptive individuals is low

Doomed to failure? UKIP and the organisational challenges facing right-wing populist anti-political establishment parties

Using the UK Independence Party, we examine the effects of sudden electoral success on an Anti-Political Establishment (APE) party. The pressures of aspiring to government necessitate organisational structures resembling those of mainstream parties, while this aspiration challenges APE parties because they differ not just in terms of their policy profiles, but also in their more ‘unorthodox’ organisational make-up, inextricably linked to their electoral appeal. Robert Kilroy-Silk wanted to emphasise office-seeking goals while most members wanted the party to remain true to its APE status and not sacrifice its populist nature. This inevitably resulted in internal party conflict

Improved Synthesis of 5-methylbenz(a)anthracene

A revised synthesis of 5-methylbenz(a)anthracene is reported. It involves only three simple and convenient steps starting from a commercially available compound, and gives a 82% overall yield. Bromination of 5-methylbenz(a)anthracene with N-bromosuccinimide (NBS) in carbon tetrachloride furnishes 5-bromomethylbenz(a)anthracene in a 92% yield. When bromination is carried out using dimethylformamide as the solvent, 7-bromo-5-methylbenz(a)anthracene is formed as the exclusive product

Are Choice Experiments Incentive Compatible? A Test with Quality Differentiated Beef Steaks

This study compares hypothetical and nonhypothetical responses to choice experiment questions. We test for hypothetical bias in a choice experiment involving beef ribeye steaks with differing quality attributes. In general, hypothetical responses predicted higher probabilities of purchasing beef steaks than nonhypothetical resposnes. Thus, hypothetical choices overestimate total willingness-to-pay for beef steaks. However, marginal willingness-to-pay for a change in steak quality is, in general, not statistically different across hypothetical and actual payment settings.CVM, conjoint analysis, heteroskedastic extreme value model, hypothetical bias, multinomial probit, random parameters logit.

Scheduling Optimisations for SPIN to Minimise Buffer Requirements in Synchronous Data Flow

Synchronous Data flow (SDF) graphs have a simple and elegant semantics (essentially linear algebra) which makes SDF graphs eminently suitable as a vehicle for studying scheduling optimisations. We extend related work on using SPIN to experiment with scheduling optimisations aimed at minimising buffer requirements.We show that for a benchmark of commonly used case studies the performance of our SPIN based scheduler is comparable to that of state of the art research tools. The key to success is using the semantics of SDF to prove when using (even unsound and/or incomplete) optimisations are justified. The main benefit of our approach lies in gaining deep insight in the optimisations at relatively low cost

An Object-Oriented Framework for Explicit-State Model Checking

This paper presents a conceptual architecture for an object-oriented framework to support the development of formal verification tools (i.e. model checkers). The objective of the architecture is to support the reuse of algorithms and to encourage a modular design of tools. The conceptual framework is accompanied by a C++ implementation which provides reusable algorithms for the simulation and verification of explicit-state models as well as a model representation for simple models based on guard-based process descriptions. The framework has been successfully used to develop a model checker for a subset of PROMELA

Post-communism and the abandonment of mixed-member electoral systems

Many countries adopted mixed-member (MM) electoral systems in the 1990s, but several switched to list proportional representation (PR) recently. Most switchers are post-communist countries that used the semi-proportional mixed-member majoritarian (MMM) system, often associated with dominant parties. List PR was adopted under competitive conditions in some cases (Albania, Bulgaria, Croatia, Macedonia, Ukraine), while in places where authoritarian control remains (Russia, Kazakhstan, Kyrgyzstan), list PR appears to be used as a means of reducing competition and undermining multiparty democracy