13,648 research outputs found
Wear of a chute in a rice sorting machine
In a rice sorting machine, rice grains drop onto and slide down an anodised aluminium chute. The purpose of the chute is to separate the grains and provide a controlled distribution. At the bottom of the chute the grains are examined optically and contaminants or defective grains
are removed from the stream by jets of air. The machine has the ability to sort low quality rice which contains a large element of contaminants such as husk. The husk is extremely
abrasive and this, along with other factors, can lead to a reduction in the life of the chute by wear of the surface.
In this work a failure analysis process was undertaken to establish the nature and causes of the chute surface wear and the mechanisms of material removal. Wear occurs initially at the location where the grains first strike the chute and at subsequent regions down the chute where bounce occurs.
An experimental and analytical examination of the rice motion on impacting the chute was also carried out along with some friction testing of potential replacement chute materials. The evidence gathered during the failure analysis along with the experimental analysis was
used to propose possible material/design improvements
Wheel/Rail Contact Isolation Due to Track Contamination
An experimental study has been carried out to
investigate the effect of sanding on the electrical
isolation of a wheel/rail contact. Sand is applied to the
wheel/rail interface to increase adhesion in both braking
and traction. Train detection, for signalling purposes,
can be by means of track circuits. Signalling block
occupancy is triggered by the wheelset of the train
‘shorting out’ the track circuit. Sand in the wheel/rail
interface means that contact between the wheelsets and
the track may be compromised, inhibiting train
identification.
Static tests were performed using sections cut
from wheels and rail and dynamic tests on a twin disc
machine where rail and wheel steel discs are loaded
together and driven under controlled conditions of
rolling and slip. The electrical circuit used was a
simplified simulation of the TI21 track circuit.
The application of sand was carried out under a
range of mild and severe test conditions. The results
indicated that a transition exists in the amount of sand
applied, below which there is a measurable, but not
severe, change in voltage, but above which the contact
conductance decreases by an order of magnitude. A
model of electrical isolation has been developed
assuming either full disc separation by a sand layer or
partial disc contact with some sand present.
Idealisations inherent in both test methods mean
that they represent a severe case. Given these
limitations, it is likely that the test methods, at their
present stage of development, should be used as a
means to qualitatively assess the relative effects on
electrical isolation of different contaminants
Hydrogen environment embrittlement of astroloy and Udimet 700 (nickel-base) and V-57 (iron-base) superalloys
The sensitivity to hydrogen environment embrittlement of three superalloys was determined. Astroloy forgings were resistant to embrittlement during smooth tensile, notched tensile, and creep testing in 3.5-MN/sq m hydrogen over the range 23 to 760 C. The notched tensile strength of Udimet 700 bar stock in hydrogen at 23 C was only 50 percent of the baseline value in helium. Forgings of V-57 were not significantly embrittled by hydrogen during smooth tensile testing over the range 23 to 675 C; creep and rupture lives of V-57 were degraded by hydrogen. Postcreep tensile ductility of V-57 was reduced by 40 percent after creep exposure in hydrogen
Micro-simulating child poverty in 2010 and 2020
The 2008 Pre-Budget Report (PBR) said that 'the Government will take stock of progress towards its 2010 and 2020 child poverty target in the [2009] Budget'. As background to that exercise, this paper updates our previous analysis of the prospects for child poverty in the UK in 2010-11 and 2020-21
History, Sociology, Modernity : How Connect?
Special Issue on 'The State of Scottish History: Past, Present and Future'Peer reviewedPublisher PD
The Aesthetic Uncanny: Staging Dorian Gray
This article discusses my theatrical adaptation of Oscar Wilde's The Picture of Dorian Gray (1891) for the Edinburgh Festival Fringe (2008). Freud's concept of the uncanny (1919) was treated as a purely aesthetic phenomenon and related to late nineteenth century social and literary preoccupations such as Christianity, the supernatural and glamorous, criminal homosexuality. These considerations led to a conceptual ground plan that allowed for experiments during rehearsal in a form of theatrical shorthand
Supersymmetry of Noncompact MQCD-like Membrane Instantons and Heat Kernel Asymptotics
We perform a heat kernel asymptotics analysis of the nonperturbative
superpotential obtained from wrapping of an M2-brane around a supersymmetric
noncompact three-fold embedded in a (noncompact) G_2-manifold as obtained in
[1], the three-fold being the one relevant to domain walls in Witten's MQCD
[2], in the limit of small "zeta", a complex constant that appears in the
Riemann surfaces relevant to defining the boundary conditions for the domain
wall in MQCD. The MQCD-like configuration is interpretable, for small but
non-zero zeta as a noncompact/"large" open membrane instanton, and for
vanishing zeta, as the type IIA D0-brane (for vanishing M-theory cicle radius).
We find that the eta-function Seeley de-Witt coefficients vanish, and we get a
perfect match between the zeta-function Seeley de-Witt coefficients (up to
terms quadratic in zeta) between the Dirac-type operator and one of the two
Laplace-type operators figuring in the superpotential. This is an extremely
strong signature of residual supersymmetry for the nonperturbative
configurations in M-theory considered in this work.Comment: 21 pages, LaTeX; v3: several clarifying remarks added, to appear in
JHE
Wrapped brane gas as a candidate for Dark Matter
We consider brane gas models based on type II string theories and analyze the
mass, the Ramond-Ramond charge and the charge on moduli fluctuations of branes
wrapping over cycles of a compactified space in the four-dimensional Einstein
frame. A six-dimensional torus and Calabi-Yau threefolds are considered for the
Kaluza-Klein reduction. A large volume of the compactified space and a weak
string coupling gives rise to point particles of the wrapped branes which have
a light mass and a small charge of the Ramond-Ramond flux and of the moduli
fluctuations, while the particles become very heavy in the string frame. We
find that the masses and the charges satisfy the sea-saw like dual relations
which become time-independent in the four-dimensional Einstein frame.Comment: 17 pages, 2 figures, revtex4, v3: comments adde
Infrared ground-based astronomy with the Hughes 256 X 256 PtSi array
It is shown that large format PtSi Schottky diode infrared arrays, the Hughes 256 X 256 hybrid Schottky array in particular, are competitive alternatives to the smaller format photovoltaic arrays for ground-based astronomy. The modest quantum efficiency of the PtSi compared to the photovoltaic devices is more than compensated for by the larger format. The use of hybrid technology yields effective fill factors of nearly 100 percent, and the low dark current, noise, excellent imaging characteristics, cost, and solid nitrogen operating temperature add to the effectiveness of this array for ground-based imaging. In addition to discussing the characteristics of this array, researchers present laboratory test data and astronomical results achieved at Kitt Peak
Formation of the 0.511.-MeV line in solar flares
The gamma-ray line produced at 0.51-MeV was studied and is shown to be the result of either of free annihilation of positrons with electrons or of the decay of positronium by 2-photon emission. Positron annihilation from the bound state of positronium may also proceed by 3-photon emission, resulting in a continuum with energies up to 0.51-MeV. Accurate calculations of the rates of free annihilation and positronium formation in a solar-flare plasma are presented. Estimates of the positronium-formulation rates by charge exchange and the rates of dissociation and quenching are also considered. The temperature and density dependence of the ratio of 3-photon to 2-photon emission was obtained. It is shown that when the ratio of free electrons to neutral atoms in the plasma is approximately unity or greater, the Doppler width of the 0.51-MeV line is a function of the temperature of the annihilation region. For the small ion densities characteristics of the photosphere, the width is predominantly a function of the density
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