Parametric analysis of runway stone lofting mechanisms

The influence of various factors affecting the severity of runway debris lofting mechanisms was investigated by performing numerical simulations and drop-weight impact experiments to assess the likelihood of a stone impact. Geometrical characterisation of stones collected from airfields led to a generic model of a tyre rolling over stones of various shape with different overlaps, orientations, and densities. In numerical simulations of a 0.4 m diameter aircraft tyre rolling at 70 m/s, a 10 mm diameter spherical stone was lofted at a maximum vertical speed of 35 m/s. For equivalent mass prolate spheroid stones, the loft speeds were 11–34% lower depending on the stone orientation. Objects with flat surfaces exhibited different lofting mechanisms and lower angular velocities. The conditions most conducive to stone lofting were very stiff, small diameter, sharp cornered tyres rolling on ground with a high friction coefficient over spherical stones such that just under half the stone diameter was covered by the tyre. The stone loft speed was approximately proportional to the square root of the tyre tread stiffness. Finally, tyre tread grooves could throw stones upwards at the tyre-ground separation speed, which was 17 m/s for the conditions mentioned earlier.     

PERIODIC CORRELATION IN STRATOSPHERIC OZONE DATA

Abstract. A 50-year time series of monthly stratospheric ozone readings from Arosa, Switzerland, is analyzed. The time series exhibits the properties of a periodically correlated (PC) random sequence with annual periodicities. Spectral properties of PC random sequences are reviewed and a test to detect periodic correlation is presented. An autoregressive moving-average (ARMA) model with periodically varying coefficients (PARMA) is fitted to the data in two stages. First, a periodic autoregressive model is fitted to the data. This fit yields residuals that are stationary but non-white. Next, a stationary ARMA model is fitted to the residuals and the two models are combined to produce a larger model for the data. The combined model is shown to be a PARMA model and yields residuals that have the correlation properties of white noise.     

Negative staining-carbon film technique: New cellular and molecular applications

Two techniques are presented which extend the original negative staining-carbon film technique into new areas of cellular and molecular application. These relate (1) to the production of negatively stained specimens of single-layer plasma membrane split from intact cells during the overall procedure that are negatively stained from the cytoplasmic face and (2) to the production of negatively stained specimens directly from glycerol-containing protein solutions, membrane or viral suspensions. In both cases in vacuo drying onto mica from glycerol is performed, prior to deposition of a carbon film. (For the cellular technique, freshly cleaved mica is firstly rendered positively charged by immersion in Alcian blue.) This is followed by release of the carbon film plus adsorbed membrane or protein by floating onto water, with subsequent negative staining. Selected preliminary applications using human erythrocyte membrane and the high molecular weight (native) human erythrocyte tripeptidyl peptidase-II complex are given and considered speculation as to the future application of the techniques is provided.     

Variability of waste copper slag concrete and its effect on the seismic safety of reinforced concrete building: A case study

Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment. Although numerous studies on waste copper slag concrete can be found in the published literature, no research has focused on the structural application of this type of concrete. In particular, the variability in the strength properties of waste copper slag concrete, which is required for various structural applications, such as limit state design formulation, reliability-based structural analysis, etc., has so far not attracted the attention of researchers. This paper quantifies the uncertainty associated with the compressive-, flexural- and split tensile strength of hardened concrete with different dosages of waste copper slag as fine aggregate. Best-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory experiments. In addition, the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building, considering the proposed distribution model. The results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand.     

Environmental flows in two highly regulated rivers: the Hawkesbury Nepean in Australia and the Durance in France

Environmental flows are waters released from storages to improve degraded ecosystems. Subsequent monitoring is then used to determine incremental benefits. These flows in the Hawkesbury Nepean and the Durance are very low compared with those advocated for other systems. In the former, water is used in Sydney and Wollongong, while the Durance water is diverted to supply 16 hydropower stations. In this system, reserved flows have been set at 2.5% of mean discharge, while in the Australian river, environmental flows have varied, but are usually 3.6% or less in the current regime. Additionally, increasing the transparencies of barrages and weirs will enhance the effectiveness of current environmental flows. Implementation of such flows imposes many problems because of structural difficulties for releasing water and compromising regulatory infrastructures. Additionally, with the onset of global warming, both systems will suffer significant water losses.