25,933 research outputs found
Reducing Reoffending: Review of Selected Countries: Final Review for Audit Scotland
The report reviews reoffending patterns in Scotland, England and Wales, Ireland, Northern Ireland, Norway and New Zealand to establish relevant conditions for different rates of reoffending. A significant part of the report, however, is given over to a critical examination of the concept of 'reoffending' itself which is more a measure of criminal justice agency behaviour than individual behaviour. The report concludes with some suggestions for moving beyond such thin, technocratic understanding of reoffending and rehabilitation. This work was commissioned by and submitted to Audit Scotland
Derivation of the stress concentrations at holes in orthotropic plates using thermoelastic stress analysis
An experimental study of the stress distribution around holes in orthotropic composite laminates has been
conducted using thermoelastic stress analysis (TSA). Quantitative thermoelastic studies of stress
concentrations in metallic plates is a straightforward matter, all that is required is the ratio of the response
from the hole and a far-field reading. For orthotropic materials the situation is more complex as the
response is not simply proportional to the sum of the principal stresses. In general the thermoelastic
response of an orthotropic laminate is a function of the stresses in the principal surface material directions
and the associated coefficient of thermal expansion. The approach in this paper is to obtain âstress
factorsâ at the hole and identify the maxima in the plot. Specimens manufactured from a variety of
different laminate lay-ups (unidirectional (UD), cross-ply (CP), angle-ply (AP) and quasi-isotropic (QI)) are
considered. In all these cases the principal stress directions at the hole are not coincident with the
principal material directions and it is a challenging proposition to derive meaningful stress data from these
configurations. To validate the approach the experimental data are compared to analytical models. To
better understand the nature of the response finite element models are produced that mimic the
thermoelastic response
Identification of the source of the thermoelastic response from orthotropic laminated composites
In previous work, a series of theoretical considerations have been made aimed at
identifying the source and assessing prominent factors influencing the thermoelastic
response from laminated composites. In this paper four different methods of interpreting
the data are investigated and the theoretical thermoelastic response is compared to
experimental data to identify the source of the thermoelastic response
The Casimir effect for thin plasma sheets and the role of the surface plasmons
We consider the Casimir force betweeen two dielectric bodies described by the
plasma model and between two infinitely thin plasma sheets. In both cases in
addition to the photon modes surface plasmons are present in the spectrum of
the electromagnetic field. We investigate the contribution of both types of
modes to the Casimir force and confirm resp. find in both models large
compensations between the plasmon modes themselves and between them and the
photon modes especially at large distances. Our conclusion is that the
separation of the vacuum energy into plasmon and photon contributions must be
handled with care except for the case of small separations.Comment: submitted to JPhysA Special Issue QFEXT'05, replaced due to a wrong
Latex comman
Contributions of Vacuum and Plasmon Modes to the Force on a Small Sphere near a Plate
The force on a small sphere with a plasma model dielectric function and in
the presence of a perfectly reflecting plane is considered. The contribution of
both the vacuum modes of the quantized electromagnetic field and of plasmon
modes in the sphere are discussed. In the case that the plasmon modes are in
their ground state, quasi-oscillatory terms from the vacuum and plasmon parts
cancel one another, leading a monotonic attractive force. If the plasmon modes
are not in the ground state, the net force is quasi-oscillatory. In both cases,
the sphere behaves in the same way as does an atom in either its ground state
or an excited state.Comment: 7 pages, no figures, talk presented at "Quantum Fields under External
Conditions - 2005", Barcelona, Spain, September 200
Application of Chiral Lanthanide-induced Shift Reagents to Optically Active Cations: the Use of Tris[3-(trifluoromethylhydroxymethylene)-( + )-camphorato]europium(III) to Determine the Enantiomeric Purity of Tris(phenanthroline)ruthenium(II) Dichloride
In non-polar solvents, chiral europium complexes provide attractive n. m. r. shift reagents to resolve spectra of optically active cations, and, in particular, for tris(phenanthroline)ruthenium dichloride,^1H n. m. r. shift differences of up to 0.7 p.p.m. between isomers easily permit the determination of absolute enantiomeric purity
Modelling and evaluation of pulsed and pulse phase thermography through application of composite and metallic case studies
A transient thermal finite element model has been created of the pulsed thermography (PT) and pulse phase thermography (PPT) experimental procedure. The model has been experimentally validated through the application of four case studies of varying geometries and materials. Materials used include aluminium, carbon fibre reinforced plastic (CFRP) and adhesively bonded joints. The same four case studies have also formed a basis for comparison between three experimental techniques: PT, PPT and the more established ultrasonic (UT) c-scan.Results show PPT to be advantageous over PT due to its deeper probing as it is less influenced by surface features. Whilst UT is able to reveal all the defects in these case studies, the time consuming nature of the process is a significant disadvantage compared to the full field thermography methods.Overall, the model has achieved good correlation for the case studies considered and it was found that the main limiting factor of the PT model accuracy was knowledge of thermal material properties such as conductivity and specific heat. Where these properties were accurately known the model performed very well in comparison with experimental results. PPT modelling performed less well due to the method of processing the PT data which aims to emphasise small differences. Hence inaccuracies in inputted values such as material properties have a much greater influence on the modelled PPT data. The model enables a better understanding of PT and PPT and provides a means of establishing the experimental set-up parameters required for different components, allowing the experimental technique to be appropriately tailored to more complex situations including bonded joints or structures where several materials are present.The paper ends with a section on defect detectability based on thermal diffusivity contrast between the defect and the bulk material. It shows that in aluminium, because of its higher conductivity, greater thermal contrast is achieved for small differences in diffusivity. Regions where the diffusivity ratio between defect and bulk materials was insufficient to provide thermal contrast for defect identification were found. PPT phase data is shown to reduce the extent of such regions increasing the detectability of defects. Effusivity is introduced as a means of determining the thermal contrast between the defect and non-defective areas and hence establishing the defect detectability
Oil Blending: Mixing and Contamination
The Shell Company of Australia has a frequent need to blend lubricants. Blending, sometimes involving three lubricant oils and additives, takes place by jet mixing in large tanks of typically 45,000 titres capacity. The jets are driven by pumps with typical volume throughput of up to 1,000 titres per minute, and typical blending times may be as long as one or two hours.
The jet blending process was investigated in a number of ways at the Study Group. These included: simple estimates for blending times, theoretical and experimental description of jet behaviour, development of a simple compartment model for the blending process, and several large scale computer simulations of the jet-induced motion using a commercial Computational Fluid Dynamics package. In addition, the sedimentation of contaminant particles in the tanks was investigated. This overall investigation, using a variety of approaches, gave a good knowledge of the blending process
Material heterogeneity or stress concentration: the thermoelastic response from woven composite materials subjected to cyclic fatigue
A study of the growth of fatigue damage in 2 x 2 twill woven composite materials,
subjected to cyclic tensile loading are described. Thermoelastic stress analysis (TSA) is
used to monitor the stress field. As a result of the damage, a net reduction in the
thermoelastic signal is observed. Laminates are found to be more resistant to fatigue
Development of thermoelastic stress analysis as a non-destructive evaluation tool
A modified methodology is proposed in which only a single transient load is used for
the TSA measurement. Specimens with different damage severities are tested and it is
shown that the modified TSA method has the potential to be applied in the field as a
non-destructive evaluation tool
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