1,196 research outputs found
Modelling thermomechanical behaviour of Cr-Mo-V steel
This paper presents a mechanism-based approach for modelling the thermomechanical behaviour of a Cr-Mo-V steel. A set of unified viscoplastic constitutive equations were employed to model dislocation density, recrystallisation and grain size during deformation. The evolution of dislocation density accounts for the build-up of dislocations due to plastic strain, the static and dynamic recovery and the effect of recrystallisation. Recrystallisation occurs when a critical dislocation density is reached after an incubation time, and grain size becomes smaller after such event. Gleeble compression tests were used to obtain Stress-strain curves and evaluate the microstructural evolution at different temperature and strain rate, and the material constants for the model were determined from the experimental data. Copyright © 2010 MS&T10®
Development of a carbon fibre composite active mirror: Design and testing
Carbon fibre composite technology for lightweight mirrors is gaining
increasing interest in the space- and ground-based astronomical communities for
its low weight, ease of manufacturing, excellent thermal qualities and
robustness. We present here first results of a project to design and produce a
27 cm diameter deformable carbon fibre composite mirror. The aim was to produce
a high surface form accuracy as well as low surface roughness. As part of this
programme, a passive mirror was developed to investigate stability and coating
issues. Results from the manufacturing and polishing process are reported here.
We also present results of a mechanical and thermal finite element analysis, as
well as early experimental findings of the deformable mirror. Possible
applications and future work are discussed.Comment: Accepted by Optical Engineering. Figures 1-7 on
http://www.star.ucl.ac.uk/~sk/OEpaper_files
Unsung heroes: who supports social work students on placement?
Since the introduction of the three year degree programme in 2003, social work education has undergone a number of significant changes. The time students spend on placement has been increased to two hundred days, and the range of placement opportunities and the way in which these placements have been configured has significantly diversified. A consistent feature over the years, however, has been the presence of a Practice Educator (PE) who has guided, assessed and taught the student whilst on placement. Unsurprisingly, the role of the PE and the pivotal relationship they have with the student has been explored in the past and features in social work literature.
This paper, however, concentrates on a range of other relationships which are of significance in providing support to students on placement. In particular it draws on research to discuss the role of the university contact tutor, the place of the wider team in which the student is sited, and the support offered by family, friends and others.
Placements and the work undertaken by PE’s will continue to be integral to the delivery of social work education. It is, however, essential to recognise and value the often over looked role of others in providing support to students on placement
Technical assistance, neo-colonialism or mutual trade? The experience of an Anglo/Ukrainian/Russian social work practice learning project
Since the collapse of the Soviet Union there has been a steady stream of Western consultants ready to work in Eastern Europe and Russia and share professional and academic expertise and experience. Social work, unknown as a discrete discipline or profession in the Soviet Union, has been a growth area with funding from a variety of sources to help promote East-West partnerships.Social work theory and practice emphasises critical appraisal of policy and embraces issues of power, discrimination and oppression. Social work educators should therefore be especially alert to the complex ethical questions which these kinds of collaborations raise, and adept at finding practical solutions or workable compromises. This article explores these ethical and political issues with reference to a project to develop social work practice learning in a Russian oblast' (region). The project was an ambitious partnership of British, Ukrainian and Russian educators, involving numerous Russian social work and related agencies, and four Russian universities and colleges in one oblast'. The authors use a series of vignettes to help the reader achieve insights into these East-West transactions. The article concludes with a discussion of different interpretations of these dealings, using three prisms: technical assistance, neo-colonialism and mutual trade
GIFT-Grab: Real-time C++ and Python multi-channel video capture, processing and encoding API
GIFT-Grab is an open-source API for acquiring, processing and encoding video streams in real time. GIFT-Grab supports video acquisition using various frame-grabber hardware as well as from standard-compliant network streams and video files. The current GIFT-Grab release allows for multi-channel video acquisition and encoding at the maximum frame rate of supported hardware – 60 frames per second (fps). GIFT-Grab builds on well-established highly configurable multimedia libraries including FFmpeg and OpenCV. GIFT-Grab exposes a simplified high-level API, aimed at facilitating integration into client applications with minimal coding effort. The core implementation of GIFT-Grab is in C++11. GIFT-Grab also features a Python API compatible with the widely used scientific computing packages NumPy and SciPy. GIFT-Grab was developed for capturing multiple simultaneous intra-operative video streams from medical imaging devices. Yet due to the ubiquity of video processing in research, GIFT-Grab can be used in many other areas. GIFT-Grab is hosted and managed on the software repository of the Centre for Medical Image Computing (CMIC) at University College London, and is also mirrored on GitHub. In addition it is available for installation from the Python Package Index (PyPI) via the pip installation tool
Correlation between Infrared Colors and Intensity Ratios of SiO Maser Lines
We present the results of SiO millimeter-line observations of a sample of
known SiO maser sources covering a wide dust-temperature range. A cold part of
the sample was selected from the SiO maser sources found in our recent SiO
maser survey of cold dusty objects. The aim of the present research is to
investigate the causes of the correlation between infrared colors and SiO maser
intensity ratios among different transition lines. In particular, the
correlation between infrared colors and SiO maser intensity ratio among the
J=1-0 v=1, 2, and 3 lines are mainly concerned in this paper. We observed in
total 75 SiO maser sources with the Nobeyama 45m telescope quasi-simultaneously
in the SiO J=1-0 v=0, 1, 2, 3, 4 and J=2-1 v=1, 2 lines. We also observed the
sample in the 29SiO J=1-0 v=0 and J=2-1 v=0, and 30SiO J=1-0 v=0 lines, and the
H2O 6(1,6)-5(2,3) line. As reported in previous papers, we confirmed that the
intensity ratios of the SiO J=1-0 v=2 to v=1 lines clearly correlate with
infrared colors. In addition, we found possible correlation between infrared
colors and the intensity ratios of the SiO J=1-0 v=3 to v=1&2 lines. Two
overlap lines of H2O (i.e., 11(6,6) nu_2=1 -> 12(7,5) nu_2=0 and 5(0,5) nu_2=2
-> 6(3,4) nu_2=1) might explain these correlation if these overlap lines become
stronger with increase of infrared colors, although the phenomena also might be
explained by more fundamental ways if we take into account the variation of
opacity from object to object.Comment: 49 pages, 7 figures, 3 tables, accepted for publication in ApJ. Full
resolution version available at
http://www.asiaa.sinica.edu.tw/~junichi/paper
The Coupled Cluster Method in Hamiltonian Lattice Field Theory
The coupled cluster or exp S form of the eigenvalue problem for lattice
Hamiltonian QCD (without quarks) is investigated. A new construction
prescription is given for the calculation of the relevant coupled cluster
matrix elements with respect to an orthogonal and independent loop space basis.
The method avoids the explicit introduction of gauge group coupling
coefficients by mapping the eigenvalue problem onto a suitable set of character
functions, which allows a simplified procedure. Using appropriate group
theoretical methods, we show that it is possible to set up the eigenvalue
problem for eigenstates having arbitrary lattice momentum and lattice angular
momentum.Comment: LaTeX, no figur
Two-dimensional model of dynamical fermion mass generation in strongly coupled gauge theories
We generalize the Schwinger model on the lattice by adding a charged
scalar field. In this so-called model the scalar field shields
the fermion charge, and a neutral fermion, acquiring mass dynamically, is
present in the spectrum. We study numerically the mass of this fermion at
various large fixed values of the gauge coupling by varying the effective
four-fermion coupling, and find an indication that its scaling behavior is the
same as that of the fermion mass in the chiral Gross-Neveu model. This suggests
that the model is in the same universality class as the
Gross-Neveu model, and thus renormalizable and asymptotic free at arbitrary
strong gauge coupling.Comment: 18 pages, LaTeX2e, requires packages rotating.sty and curves.sty from
CTA
Level Crossing for Hot Sphalerons
We study the spectrum of the Dirac Hamiltonian in the presence of high
temperature sphaleron-like fluctuations of the electroweak gauge and Higgs
fields, relevant for the conditions prevailing in the early universe. The
fluctuations are created by numerical lattice simulations. It is shown that a
change in Chern-Simons number by one unit is accompanied by eigenvalues
crossing zero and a change of sign of the generalized chirality \tGf=
(-1)^{2T+1} \gf which labels these modes. This provides further evidence that
the sphaleron-like configurations observed in lattice simulations may be viewed
as representing continuum configurations.Comment: Latex file, 29 pages + 13 figure
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