Investigating the use of Virtual Learning Environments by teachers in schools and colleges

Investigating the use of Virtual Learning Environments by teachers in schools and college

Radiation patterns of seismic surface waves from buried dipolar point sources in a flat stratified Earth

Explicit compact expressions were obtained for the far displacement field of Rayleigh and Love waves generated by force configurations which served to simulate shear-type faults with arbitrary dip and slip. The medium transfer functions for dipolar sources were computed for a Gutenberg flat continental earth model with 23 layers. These were then used to obtain universal radiation pattern charts for couple- and double-couple-type sources at various depths over the period range 50 to 350 sec. It was demonstrated by means of few typical examples that the radiation patterns of Rayleigh waves may depend strongly on the depth of the source, and unlike the fundamental Love mode may be rather sensitive to small variations in frequency. For a given source and frequency the radiation pattern may differ considerably from one mode to another

Social marketing: Immunizing against unethical practice

A simple approach for the catalytic conversion of primary alcohols into their corresponding esters and amides, with evolution of H2 gas using in situ formed ruthenium PNP- and PNN-pincer catalysts, is presented. The evaluation showed conversions for the esterification with turnover numbers as high as 4300, and 4400 for the amidation

Fast evaluation of source parameters from isolated surface-wave signals. Part I. Universal tables

Tables for spectral displacements of seismic surface waves from shear dislocations in flat multilayered earth models were prepared. Earth response functions for seven modes (R_(11), R_(21), R_(12), L_0, L_1, L_2, L_3) at six periods (300 sec, 250 sec, 200 sec, 150 sec, 100 sec, 50 sec) and three paths (continental, oceanic, shield) were calculated for the source-depth range of 10 to 600 km at intervals of 5 km until 200 km, and thereafter at intervals of 10 km. Ground motion is given in micron-seconds for the three fundamental shear dislocations, each of strength U_0dS = 10^3 (m × km^2) and a delta-function time-dependence. The tables provide the means for rapid evaluation of source parameters from spectral radiation patterns of amplitudes and initial phases

Determination of source parameters by amplitude equalization of seismic surface waves: 2. Release of tectonic strain by underground nuclear explosions and mechanisms of earthquakes

The radiation patterns of Love and Rayleigh waves from three nuclear explosions (Hardhat, Haymaker, and Shoal) are studied to determine the nature of the asymmetry of radiation and the mechanism of Love wave generation. From a comparative study of different explosions it is reasoned that the Love waves are generated at the source of the explosion. The source function, represented as the superimposition of an isotropic dilatational component due to the explosion and a multipolar component due to the release of tectonic strain energy, is consistent with the observed radiation patterns and the amplitude spectrums. The amount of seismic energy due to the strain release is computed. In some cases (Haymaker and Shoal) it is found that this energy may be due to the relaxation of the pre-stressed medium by the explosion-formed cavity. In the case of Hardhat it is concluded that the explosion must have triggered some other strain release mechanism, such as an earthquake. The amplitude equalization method is applied to surface waves from an earthquake to determine the source parameters. From only the amplitude spectrums and radiation patterns of Love and Rayleigh waves, the source functions, source depth, strike and dip of the fault plane, and the rake of displacement are determined for the July 20, 1964, Fallon earthquake

Slow movement of a random walk on the range of a random walk in the presence of an external field

In this article, a localisation result is proved for the biased random walk on the range of a simple random walk in high dimensions (d \geq 5). This demonstrates that, unlike in the supercritical percolation setting, a slowdown effect occurs as soon a non-trivial bias is introduced. The proof applies a decomposition of the underlying simple random walk path at its cut-times to relate the associated biased random walk to a one-dimensional random walk in a random environment in Sinai's regime

Management of trade-offs in geoengineering through optimal choice of non-uniform radiative forcing

Solar radiation management could be used to offset some or all anthropogenic radiative forcing, with the goal of reducing some of the associated climatic change. However, the degree of compensation will vary, with residual climate changes larger in some regions than others. Similarly, the insolation reduction that best compensates climate changes in one region may not be the same as for another, leading to concerns about equity. Here we show that optimizing the latitudinal and seasonal distribution of solar reduction can improve the fidelity with which solar radiation management offsets anthropogenic climate change. Using the HadCM3L general circulation model, we explore several trade-offs. First, residual temperature and precipitation changes in the worst-off region can be reduced by 30% relative to uniform solar reduction, with only a modest impact on global root-mean-square changes; this has implications for moderating regional inequalities. Second, the same root-mean-square residual climate changes can be obtained with up to 30% less insolation reduction, implying that it may be possible to reduce solar radiation management side-effects and risks (for example, ozone depletion if stratospheric sulphate aerosols are used). Finally, allowing spatial and temporal variability increases the range of trade-offs to be considered, raising the question of how to weight different objectives

Control theory for principled heap sizing

We propose a new, principled approach to adaptive heap sizing based on control theory. We review current state-of-the-art heap sizing mechanisms, as deployed in Jikes RVM and HotSpot. We then formulate heap sizing as a control problem, apply and tune a standard controller algorithm, and evaluate its performance on a set of well-known benchmarks. We find our controller adapts the heap size more responsively than existing mechanisms. This responsiveness allows tighter virtual machine memory footprints while preserving target application throughput, which is ideal for both embedded and utility computing domains. In short, we argue that formal, systematic approaches to memory management should be replacing ad-hoc heuristics as the discipline matures. Control-theoretic heap sizing is one such systematic approach