Aximo: automated axiomatic reasoning for information update

Aximo is a software written in C++ that verifies epistemic properties of dynamic scenarios in multi-agent systems. The underlying logic of our tool is based on the algebraic axiomatics of Dynamic Epistemic Logic. We also present a new theoretical result: the worst case complexity of the verification problem of Aximo

Trade Openness: An Australian Perspective

Australia’s external trade is relatively low compared with the size of its economy. Indeed, Australia’s openness ratio (exports plus imports as a proportion of GDP) in 2002 was the third-lowest among the 30 OECD countries. This paper seeks to understand Australia’s low openness by analysing the empirical determinants of aggregate country trade. We begin by estimating a standard gravity model of bilateral trade. Although the model appears to fit the bilateral data very well, it does a relatively poor job at fitting countries’ aggregate trade levels, with different methodologies sometimes providing highly conflicting results. The focus of the paper is an equation for country openness. Our equation explains a substantial amount of the variation in how much countries trade using a small number of explanatory variables. We find that the most important determinants of openness are population and a measure of distance to potential trade partners. Countries with larger populations trade less, as do countries that are relatively more remote. Furthermore, after controlling for trade policy there is little evidence of a positive correlation between openness and economic development. While gravity models suggest Australia trades much more than expected, the openness equation suggests that its level of trade is relatively close to what would be expected. The most important factors in explaining Australia’s low openness ratio are its distance to the rest of the world, and to a lesser extent its large geographic size.trade; outward orientation; economic geography; trade liberalisation

Adaptive mesh refinement computation of acoustic radiation from an engine intake

A block-structured adaptive mesh refinement (AMR) method was applied to the computational problem of acoustic radiation from an aeroengine intake. The aim is to improve the computational and storage efficiency in aeroengine noise prediction through reduction of computational cells. A parallel implementation of the adaptive mesh refinement algorithm was achieved using message passing interface. It combined a range of 2nd- and 4th-order spatial stencils, a 4th-order low-dissipation and low-dispersion Runge–Kutta scheme for time integration and several different interpolation methods. Both the parallel AMR algorithms and numerical issues were introduced briefly in this work. To solve the problem of acoustic radiation from an aeroengine intake, the code was extended to support body-fitted grid structures. The problem of acoustic radiation was solved with linearised Euler equations. The AMR results were compared with the previous results computed on a uniformly fine mesh to demonstrate the accuracy and the efficiency of the current AMR strategy. As the computational load of the whole adaptively refined mesh has to be balanced between nodes on-line, the parallel performance of the existing code deteriorates along with the increase of processors due to the expensive inter-nodes memory communication costs. The potential solution was suggested in the end

Aeroacoustic computation of sound radiation from ducts

Modern high-bypass turbofan engines produce high levels of nuisance noise that has a significant impact on the environment near airports as well as the crew and passengers inside the aircraft. Significant research is being undertaken to understand the aeroacoustic noise source mechanisms and to accurately predict engine noise levels. High-performance computers and advanced numerical techniques are now taking an active role in this research area. In this work, a numerical solver is developed to accurately and efficiently predict noise radiation from ducts. The solver is based upon a hybrid methodology whereby only the acoustic near-field is solved using the developed numerical solver, with the resultant far-field directivity determined from an integral solution of the Ffowcs Williams - Hawking equation. Particular emphasis has been placed on the radiation of duct modes from a realistic bypass engine intake geometry. The performance of the numerical schemes employed in the solver is analysed, with particular attention to the dispersion and dissipation qualities. A study into the determination of a suitable non-reflecting boundary condition for duct acoustics is also undertaken. Using a novel formulation of the linearised Euler equations, the solver is applied to noise radiation from a realistic engine intake geometry with background mean flow. The accuracy of the scheme is validated by comparison with analytic solutions for the unflanged duct case. For the unflanged duct case the effect of an acoustic liner is modelled using a time-domain impedance boundary condition. The effect of a locally supersonic inflow on radiation from the engine intake is examined. Finally, the solver is extended to determine multimode radiation from generic engine intakes, with the possibility to incorporate swirling mean flows and asymmetric duct geometries

A meta-analysis of randomized trials of behavioural treatment of depression

Reproduced with permission of the publisher. Copyright © 2008 Cambridge University Press.Background. Depression is a common, disabling condition for which psychological treatments, in particular cognitive behavioural therapies are recommended. Promising results in recent randomized trials have renewed interest in behavioural therapy. This systematic review sought to identify all randomized trials of behavioural therapy for depression, determine the effect of such interventions and examine any moderators of such effect. Method. Randomized trials of behavioural treatments of depression versus controls or other psychotherapies were identified using electronic database searches, previous reviews and reference lists. Data on symptom-level, recovery/ dropout rate and study-level moderators (study quality, number of sessions, severity and level of training) were extracted and analysed using meta-analysis and meta-regression respectively. Results. Seventeen randomized controlled trials including 1109 subjects were included in this meta-analysis. A random-effects meta-analysis of symptom-level post-treatment showed behavioural therapies were superior to controls [standardized mean difference (SMD)-0.70, 95% CI -1.00 to -0.39, k=12, n=459], brief psychotherapy (SMD -0.56, 95% CI -1.0 to -0.12, k=3, n=166), supportive therapy (SMD -0.75, 95% CI -1.37 to -0.14, k=2, n=45) and equal to cognitive behavioural therapy (SMD 0.08, 95% CI -0.14 to 0.30, k=12, n=476). Conclusions. The results in this study indicate behavioural therapy is an effective treatment for depression with outcomes equal to that of the current recommended psychological intervention. Future research needs to address issues of parsimony of such interventions

Modelling Backward Travelling Holes in Mixed Traffic Conditions Using an Agent Based Simulation

A spatial queue model in a multi-agent simulation framework is extended by introducing a more realistic behaviour, i.e. backward travelling holes. Space corresponding to a leaving vehicle is not available immediately on the upstream end of the link. Instead, the space travels backward with a constant speed. This space is named a ‘hole’. The resulting dynamics resemble Newell’s simplified kinematic wave model. Furthermore, fundamental diagrams from homogeneous and heterogeneous traffic simulations are presented. The sensitivity of the presented approach is tested with the help of flow density contours

Service user perspectives of an early intervention in psychosis service: a service evaluation

This evaluation aimed to gather the perspectives of individuals accessing an early intervention in psychosis service (EIPS), in order to inform service development.Individual interviews (n=9) and one focus group (n=7) were conducted. Discussions focused on open questions pertaining to Service Users’ (SUs) experiences of accessing the EIPS. The results were analysed using inductive thematic analysis.Inductive thematic analysis was used and three main themes were generated; Consistency and Communication, facilitating therapeutic relationships between EIP service staff and SU’s. Pushing Boundaries, relating to the importance of services taking a graded approach to developing therapeutic relationships and (re)engaging in activities; and Normalising and Validating experiences of psychosis. Participants emphasised the importance of relationships with EIP service staff and fellow SUs and highlighted how SUs can feel fearful and vulnerable when staff are not accessible or they view their care as inconsistent. Participants further emphasised the need for practitioners to balance an approach that de-stigmatises psychotic experiences whilst validating distress.Consistency of support from EIP services can be as important as flexibility. Clinicians should carefully consider the balance between validating and normalising distressing experiences associated with Psychosis. Offering social activities with other SUs can facilitate therapeutic relationships and recovery but the results suggest that this should be facilitated in a graded way

New people: the younger informal settlements in central Durban

The report commissioned by the Department of Local Government and National Housing covers six survey areas, the first four of which are regarded as younger informal settlements closer to the city centre (Cato Manor, Kennedy Road, Briardene and Block AK). The remaining two are formal townships (Umlazi and Clermont) which have experienced informal housing areas within them. The report was completed by the Rural-Urban Studies Unit