Infrared Behaviour of Propagators and Vertices

We elucidate constraints imposed by confinement and dynamical chiral symmetry breaking on the infrared behaviour of the dressed-quark and -gluon propagators, and dressed-quark-gluon vertex. In covariant gauges the dressing of the gluon propagator is completely specified by P(k^2):= 1/[1+Pi(k^2)], where Pi(k^2) is the vacuum polarisation. In the absence of particle-like singularities in the dressed-quark-gluon vertex, extant proposals for the dressed-gluon propagator that manifest P(k^2=0)=0 and Max[P(k^2)]~10 neither confine quarks nor break chiral symmetry dynamically. This class includes all existing estimates of P(k^2) via numerical simulations.Comment: 10 pages, 2 figure

Gauge covariant fermion propagator in quenched, chirally-symmetric quantum electrodynamics

We discuss the chirally symmetric solution of the massless, quenched, Dyson-Schwinger equation for the fermion propagator in three and four dimensions. The solutions are manifestly gauge covariant. We consider a gauge covariance constraint on the fermion--gauge-boson vertex, which motivates a vertex Ansatz that both satisfies the Ward identity when the fermion self-mass is zero and ensures gauge covariance of the fermion propagator.Comment: 11 pages. REVTEX 3.0. ANL-PHY-7711-TH-9

Assessing single helix screw pile geometry on offshore installation and axial capacity

Due to their low-noise installation and relatively large axial capacity, screw piles have been proposed as an alternative foundation solution in dense sand for offshore renewable energy applications in deeper water. For this to occur, significant upscaling of onshore dimensions is required. Furthermore, the effects of certain geometric features on installation requirements are still not well understood. In this work, using the three-dimensional discrete-element method, the effects of base geometry, shaft diameter and helix pitch were investigated by simulating the full installation process prior to conducting axial compression and tension tests. The results of the investigation showed it is possible to optimise the geometry of the screw pile to reduce installation requirements, in terms of both vertical installation force (up to 61%) and installation torque (up to 39%), without reducing the axial capacity of the pile significantly.</p

SMT-based Model Checking for Recursive Programs

We present an SMT-based symbolic model checking algorithm for safety verification of recursive programs. The algorithm is modular and analyzes procedures individually. Unlike other SMT-based approaches, it maintains both "over-" and "under-approximations" of procedure summaries. Under-approximations are used to analyze procedure calls without inlining. Over-approximations are used to block infeasible counterexamples and detect convergence to a proof. We show that for programs and properties over a decidable theory, the algorithm is guaranteed to find a counterexample, if one exists. However, efficiency depends on an oracle for quantifier elimination (QE). For Boolean Programs, the algorithm is a polynomial decision procedure, matching the worst-case bounds of the best BDD-based algorithms. For Linear Arithmetic (integers and rationals), we give an efficient instantiation of the algorithm by applying QE "lazily". We use existing interpolation techniques to over-approximate QE and introduce "Model Based Projection" to under-approximate QE. Empirical evaluation on SV-COMP benchmarks shows that our algorithm improves significantly on the state-of-the-art.Comment: originally published as part of the proceedings of CAV 2014; fixed typos, better wording at some place

Using discrete element method (DEM) to create a cone penetration test (CPT)-based method to estimate the installation requirements of rotary-installed piles in sand

Deep foundations maybe used in a range of soil types where significant foundation resistance is 10 required but their installation is often associated with disturbance due to noise and vibration. Greater restrictions on use in urban and offshore environments is now commonplace. Screw piles and rotary jacked straight shafted piles are two potential methods of silent piling that could be used as alternative foundation solution, but the effects of certain geometric and installation properties such as installation pitch i.e. the ratio between vertical displacement and rotation, on the required installation torque and force in sand are not well understood. In this paper the effects of installation pitch and base geometry on the installation requirements of a straight shafted pile are simulated in 3D using the discrete element method (DEM). The installation requirements of straight shafted piles into sand have been validated against centrifuge testing, in three different relative densities. The DEM shows reductions in installation force can be achieved by increasing the installation pitch or including a conical tip. An existing cone penetration test (CPT) based prediction method for installation requirements has been improved to include the effects of installation pitch and base geometry for rotary installed piles in sand

Physiological, perceptual and performance responses associated with self-selected versus standardized recovery periods during a repeated sprint protocol in elite youth football players: A preliminary study

As accepted for publicationPurpose: To examine the physiological and perceptual responses of youth footballers to a repeated sprint protocol employing standardized and self-selected recovery. Methods: Eleven male participants (13.7 ± 1.1 years) performed a repeated sprint assessment comprising 10 x 30 m efforts. Employing a randomized crossover design, repeated sprints were performed using 30 s and self-selected recovery periods. Heart rate was monitored continuously with ratings of perceived exertion (RPE) and lower body muscle power measured 2 min after the final sprint. The concentration of blood lactate was measured at 2, 5 and 7 minutes post sprinting. Magnitude of effects were reported using effect size (ES) statistics ± 90% confidence interval and percentage differences. Differences between trials were examined using paired student t-tests (p 0.05). Conclusion: Self-selected recovery periods compromise repeated sprint performance

The psychological-type profile of lay church leaders in Australia

A sample of 845 lay church leaders (444 women and 401 men) from a range of 24 different denominations and movements (including house churches and independent churches) completed the Francis Psychological-Type Scales within the context of the 2006 Australian National Church Life Survey. The psychological-type profiles of these lay church leaders were almost identical to the type profiles of 1527 Australian churchgoers (936 women and 591 men) published in an earlier study by Robbins and Francis. The predominant types among female lay church leaders were ISFJ (21%), ESFJ (21%), and ISTJ (18%). The predominant types among male lay church leaders were ISTJ (28%), ISFJ (17%), ESTJ (13%), and ESFJ (12%). The SJ temperament accounted for 67% of the female lay church leaders and for 70% of the male lay church leaders. The strengths and weaknesses of the SJ leadership style are discussed