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

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

The Fear of Growing Old: Lessons from Nigeria

Today, in most developed countries, issues relating to aging and the elderly have continued to command the attention of policy makers. This unfortunately cannot be said for most African Nations like Nigeria which have to grapple with such crucial problems as inflation rates, unemployment, hunger, poverty, insecurity etc. Yet, the population of the elderly is increasing just as the level of hopelessness and misery has gotten to its peak. One can therefore only imagine the consequences of the massive increase in the elderly population, especially as they steadily retire from the labour force. This therefore calls for adequate social resources and programmes to help ameliorate the sufferings of the elderly and provide adequate care for them. With unfavourable policies and programmes of government in different sectors of the economy, most workers are made to retire prematurely from service and consequently age quickly due to the level of neglect experienced by Pensioners who hardly receive their gratuity and pension before they are dead. This has created a lot of destitute amongst the very old in society. Government has not been able to do much with regards to processes of resettlement and rehabilitation of the elderly, especially since most families due to high levels of poverty cannot do much for their old ones. Based on these problems, this paper sets out to examine the fear of growing old and how people should prepare for old age and what the future holds for the aged in Nigeria, most especially the role of the government, private organisations and the families concerne

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

IRAs and household saving revisited: some new evidence

The effectiveness of tax-favored savings accounts in raising national savings depends crucially upon the willingness of households to reduce consumption in order to finance contributions to these accounts. The debate over the tax deductibility of IRA's has centered on whether IRA contributions represented new savings or reshuffled assets. We devise a test to distinguish between these two hypotheses where we compare the behavior of households which just opened an IRA account with that of households which already had an IRA account. Our test accounts for any unobservable heterogeneity across the two groups. We find evidence that supports the view that households financed their IRA contributions primarily through reductions in their stocks of other assets. Our results indicate that less than 20% of IRA contributions represented addition to national savings

Advanced SPIN Tutorial

Spin [9] is a model checker for the verification of distributed systems software. The tool is freely distributed, and often described as one of the most widely used verification systems. The Advanced Spin Tutorial is a sequel to [7] and is targeted towards intermediate to advanced Spin users

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