Attitudes towards waste minimisation amongst labour only sub-contractors

Waste generation by the construction industry is a significant issue for the industry and for society generally. The paper examines previous studies of attitudes to waste management within the industry and by means of a small questionnaire study sets out to examine: the extent of labour only sub-contractors’ awareness and understanding of waste as an issue, their perceptions of the causes of waste and their attitudes towards the allocation of financial responsibility for waste minimisation. The survey shows that the results of previous studies can be extended to labour only sub-contractors and it identifies a willingness, beyond what might have been anticipated for this group, to accept some of the costs of waste reduction

Symbolic Computation of Polynomial Conserved Densities, Generalized Symmetries, and Recursion Operators for Nonlinear Differential-Difference Equations

Algorithms for the symbolic computation of polynomial conserved densities, fluxes, generalized symmetries, and recursion operators for systems of nonlinear differential-difference equations are presented. In the algorithms we use discrete versions of the Fréchet and variational derivatives, as well as discrete Euler and homotopy operators. The algorithms are illustrated for prototypical nonlinear polynomial lattices, including the Kac-van Moerbeke (Volterra) and Toda lattices. Results are shown for the modified Volterra and Ablowitz-Ladik lattices

Major Galaxy Mergers and the Growth of Supermassive Black Holes in Quasars

Despite observed strong correlations between central supermassive black holes (SMBHs) and star-formation in galactic nuclei, uncertainties exist in our understanding of their coupling. We present observations of the ratio of heavily-obscured to unobscured quasars as a function of cosmic epoch up to z~3, and show that a simple physical model describing mergers of massive, gas-rich galaxies matches these observations. In the context of this model, every obscured and unobscured quasar represent two distinct phases that result from a massive galaxy merger event. Much of the mass growth of the SMBH occurs during the heavily-obscured phase. These observations provide additional evidence for a causal link between gas-rich galaxy mergers, accretion onto the nuclear SMBH and coeval star formation.Comment: Accepted for publication in Science. Published by Science Express on March 25th. 17 pages, 5 figures, including supplemental online materia

Observations of fast anisotropic ion heating, ion cooling, and ion recycling in large-amplitude drift waves

Large-amplitude drift wave fluctuations are observed to cause severe ion temperature oscillations in plasmas of the Caltech Encore tokamak [J. M. McChesney, P. M. Bellan, and R. A. Stern, Phys. Fluids B 3, 3370 (1991)]. Experimental investigations of the complete ion dynamical behavior in these waves are presented. The wave electric field excites stochastic ion orbits in the plane normal (perpendicular to) to B, resulting in rapid perpendicular to heating. Ion-ion collisions impart energy along (parallel to) B, relaxing the perpendicular to-parallel to temperature anisotropy. Hot ions with large orbit radii escape confinement, reaching the chamber wall and cooling the distribution. Cold ions from the plasma edge convect back into the plasma (i.e., recycle), causing further cooling and significantly replenishing the density depleted by orbit losses. The ion-ion collision period tau(ii)similar to Tau(3/2)/n fluctuates strongly with the drift wave phase, due to intense (approximate to 50%) fluctuations in n and Tau. Evidence for particle recycling is given by observations of bimodal ion velocity distributions near the plasma edge, indicating the presence of cold ions (0.4 eV) superposed atop the hot (4-8 eV) plasma background. These appear periodically, synchronous with the drift wave phase at which ion fluid flow from the wall toward the plasma center peaks. Evidence is presented that such a periodic heat/loss/recycle/cool process is expected in plasmas with strong stochastic heating

Real-time phase-selective data acquisition system for measurement of wave phenomena in pulsed plasma discharges

A novel data acquisition system and methodology have been developed for the study of wave phenomena in pulsed plasma discharges. The method effectively reduces experimental uncertainty due to shot-to-shot fluctuations in high repetition rate experiments. Real-time analysis of each wave form allows classification of discharges by wave amplitude, phase, or other features. Measurements can then be constructed from subsets of discharges having similar wave properties. The method clarifies the trade-offs between experimental uncertainty reduction and increased demand for data storage capacity and acquisition time. Finally, this data acquisition system is simple to implement and requires relatively little equipment: only a wave form digitizer and a moderately fast computer

A Bulk-Parallel Priority Queue in External Memory with STXXL

We propose the design and an implementation of a bulk-parallel external memory priority queue to take advantage of both shared-memory parallelism and high external memory transfer speeds to parallel disks. To achieve higher performance by decoupling item insertions and extractions, we offer two parallelization interfaces: one using "bulk" sequences, the other by defining "limit" items. In the design, we discuss how to parallelize insertions using multiple heaps, and how to calculate a dynamic prediction sequence to prefetch blocks and apply parallel multiway merge for extraction. Our experimental results show that in the selected benchmarks the priority queue reaches 75% of the full parallel I/O bandwidth of rotational disks and and 65% of SSDs, or the speed of sorting in external memory when bounded by computation.Comment: extended version of SEA'15 conference pape