3,654 research outputs found
Impact of Scottish vocational qualifications on residential child care : have they fulfilled the promise?
This article will present findings from a doctoral study exploring the impact of 'SVQ Care: Promoting Independence (level III)' within children's homes. The study focuses on the extent to which SVQs enhance practice and their function within a 'learning society'. A total of 30 staff were selected from seven children's homes in two different local authority social work departments in Scotland. Each member of staff was interviewed on four separate occasions over a period of 9 months. Interviews were structured using a combination of repertory grids and questions. Particular focus was given to the assessment process, the extent to which SVQs enhance practice and the learning experiences of staff. The findings suggest that there are considerable deficiencies both in terms of the SVQ format and the way in which children's homes are structured for the assessment of competence. Rather than address the history of failure within residential care, it appears that SVQs have enabled the status quo to be maintained whilst creating an 'illusion' of change within a learning society
Bayesian Parameter Estimation for Latent Markov Random Fields and Social Networks
Undirected graphical models are widely used in statistics, physics and
machine vision. However Bayesian parameter estimation for undirected models is
extremely challenging, since evaluation of the posterior typically involves the
calculation of an intractable normalising constant. This problem has received
much attention, but very little of this has focussed on the important practical
case where the data consists of noisy or incomplete observations of the
underlying hidden structure. This paper specifically addresses this problem,
comparing two alternative methodologies. In the first of these approaches
particle Markov chain Monte Carlo (Andrieu et al., 2010) is used to efficiently
explore the parameter space, combined with the exchange algorithm (Murray et
al., 2006) for avoiding the calculation of the intractable normalising constant
(a proof showing that this combination targets the correct distribution in
found in a supplementary appendix online). This approach is compared with
approximate Bayesian computation (Pritchard et al., 1999). Applications to
estimating the parameters of Ising models and exponential random graphs from
noisy data are presented. Each algorithm used in the paper targets an
approximation to the true posterior due to the use of MCMC to simulate from the
latent graphical model, in lieu of being able to do this exactly in general.
The supplementary appendix also describes the nature of the resulting
approximation.Comment: 26 pages, 2 figures, accepted in Journal of Computational and
Graphical Statistics (http://www.amstat.org/publications/jcgs.cfm
UK Environmental Change Network stakeholder consultation
During the Environmental Change Network (ECN) site mangers meeting feedback on the role of UK-SCAPE funding was sought. Representatives from collaborating institutions did not restrict their comments to only the period of UK-SCAPE, as this program is a continuation of previous national capability funding. The stakeholders present appreciated the role of UKCEH through the processes of co-design, co-delivery and co-development in shaping the ECN. They further commented on the co-dependency conferred by the network for their institutions and sites. While several stakeholders noted that they could not benefit directly from UK-SCAPE funding they recognised that funding was required for coordination of the network in addition to collecting monitoring data. They highlighted the risk of failure of the network and the lost opportunities in terms of collaborative working and data delivery to the research community if funding is not maintained in the network
Non-clairvoyant Scheduling of Multiple Bag-of-Tasks Applications
International audienceThe bag-of-tasks application model, albeit simple, arises in many application domains and has received a lot of attention in the scheduling literature. Previous works propose either theoretically sound solutions that rely on unrealistic assumptions, or ad-hoc heuristics with no guarantees on performance. This work attempts to bridge this gap through the design of non-clairvoyant heuristics based on solid theoretical foundations. The performance achieved by these heuristics is studied via simulations in a view to comparing them both to previously proposed solutions and to theoretical upper bounds on achievable performance. Also, an interesting theoretical result in this work is that a straightforward on-demand heuristic delivers asymptotically optimal performance when the communications or the computations can be neglected
Strain-free bulk-like GaN grown by hydride-vapor-phase-epitaxy on two-step epitaxial lateral overgrown GaN template
Crack-free bulk-like GaN with high crystalline quality has been obtained by hydride-vapor-phase-epitaxy (HVPE)growth on a two-step epitaxial lateral overgrown GaN template on sapphire. During the cooling down stage, the as-grown 270-ÎŒm-thick GaN layer was self-separated from the sapphire substrate. Plan-view transmission electron microscopyimages show the dislocation density of the free-standing HVPE-GaN to be âŒ2.5Ă10 exp 7â cm exp â2 on the Ga-polar face. A low Ga vacancy related defect concentration of about 8Ă10 exp 15âcm expâ3 is extracted from positron annihilation spectroscopy data. The residual stress and the crystalline quality of the material are studied by two complementary techniques. Low-temperature photoluminescence spectra show the main neutral donor bound exciton line to be composed of a doublet structure at 3.4715 (3.4712) eV and 3.4721 (3.4718) eV for the Ga- (N-) polar face with the higher-energy component dominating. These line positions suggest virtually strain-free material on both surfaces with high crystalline quality as indicated by the small full width at half maximum values of the donor bound exciton lines. The E1(TO) phonon mode position measured at 558.52âcm exp â1 (Ga face) by infrared spectroscopic ellipsometry confirms the small residual stress in the material, which is hence well suited to act as a lattice-constant and thermal-expansion-coefficient matched substrate for further homoepitaxy, as needed for high-quality III-nitride device applications.Peer reviewe
Optimization of a high work function solution processed vanadium oxide hole-extracting layer for small molecule and polymer organic photovoltaic cells
We report a method of fabricating a high work function, solution processable vanadium oxide (V2Ox(sol)) hole-extracting layer. The atmospheric processing conditions of film preparation have a critical influence on the electronic structure and stoichiometry of the V2Ox(sol), with a direct impact on organic photovoltaic (OPV) cell performance. Combined Kelvin probe (KP) and ultraviolet photoemission spectroscopy (UPS) measurements reveal a high work function, n-type character for the thin films, analogous to previously reported thermally evaporated transition metal oxides. Additional states within the band gap of V2Ox(sol) are observed in the UPS spectra and are demonstrated using X-ray photoelectron spectroscopy (XPS) to be due to the substoichiometric nature of V2Ox(sol). The optimized V2Ox(sol) layer performance is compared directly to bare indiumâtin oxide (ITO), poly(ethyleneoxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and thermally evaporated molybdenum oxide (MoOx) interfaces in both small molecule/fullerene and polymer/fullerene structures. OPV cells incorporating V2Ox(sol) are reported to achieve favorable initial cell performance and cell stability attributes
- âŠ