71,131 research outputs found
Core drill's bit is replaceable without withdrawal of drill stem - A concept
Drill bit is divided into several sectors. When collapsed, the outside diameter is forced down the drill stem, when it reaches bottom the sectors are forced outward and form a cutting bit. A dulled bit is retracted by reversal of this procedure
Spectral Response of the Pulsationally-Induced Shocks in the Atmosphere of BW Vulpeculae
The star BW Vul excites an extremely strong radial pulsation that grows in
its envelope and is responsible for visible shock features in the continuum
flux and spectral line profiles emerging in the atmosphere At two phases
separated by 0.8 cycles. Material propelled upwards in the atmosphere from the
shock returns to the lower photosphere where it creates a second shock just
before the start of the next cycle. We have obtained three nights of echelle
data for this star over about 5 pulsation cycles (P = 0.201 days) in order to
evaluate the effects of on a number of important lines in the spectrum,
including the HeI 5875A and 6678A lines. These data were supplemented by
archival high-dispersion IUE (UV) data from 1994. A comparison of profiles of
the two HeI lines during the peak of the infall activity suggests that
differences in the development of the blue wing at this time are due to heating
and short-lived formations of an optically thin layer above the atmospheric
region compressed by the infall. This discovery and the well-known decreases in
equivalent widths of the CII 6578-83A doublet at the two shock phases, suggests
that shock flattens the temperature gradient and produces heating in heating
the upper atmosphere. Except for absorptions in the blue wings of the UV
resonance lines, we find no evidence for sequential shock delays arriving at
various regions of line formation of the photosphere (a "Van Hoof effect").
Phase lags cited by some former observers may be false indicators arising from
varying degrees of desaturation of multiple lines, such as for the red HeI
lines. In addition, an apparent lag in the equivalent width curve of lines
arising from less excited atomic levels could instead be caused by post-shock
cooling, followed by a rebound shock.Comment: 12 pages in Latex/MNRAS format, 9 eps-format figure
Prosocial and antisocial children's perceptions of peers' motives for prosocial behaviours
This study investigated whether peer-nominated prosocial and antisocial children have different perceptions of the motives underlying peers' prosocial actions. Eighty-seven children, aged 10-12 years old, completed peer-nomination measures of social behaviour. On the basis of numbers of social nominations received, a subsample of 51 children (32 who were peer-nominated as 'prosocial', and 18 who were peer-nominated as 'antisocial') then recorded their perceptions of peers' motives for prosocial behaviours. Expressed motives were categorized predominantly into three categories, coinciding with Turiel's (1978) 'moral', 'conventional', and 'personal domains'. Results indicate that children's social reputation is associated with the extent to which they perceive peers' prosocial motives as 'personal' or 'moral', with more prosocial children attributing moral motives, and more antisocial children attributing personal motives. Although traditionally Turiel's domain theory has been used to understand 'antisocial' children's behaviour, the current findings suggest that 'prosocial' children's behaviour may also be related to domains of judgment
Torsionally rigid and thermally stable boom
Design of rigid thermally stable beryllium copper extendible boom for space application
eta - eta' - glueball mixing
We have revisited glueball mixing with the pseudoscalar mesons in the MIT bag
model scheme. The calculation has been performed in the spherical cavity
approximation to the bag using two different fermion propagators, the cavity
and the free propagators. We obtain a very small probability of mixing for the
eta at the level of $0.04-0.1% and a bigger for the eta' at the level of 4-12%.
Our results differ from previous calculations in the same scheme but seem to
agree with the experimental analysis. We discuss the origin of our difference
which stems from the treatment of our time integrations.Comment: 21 pages, 7 figure
Crystal structure, thermodynamics, magnetics and disorder properties of Be-Fe-Al intermetallics
The elastic and magnetic properties, thermodynamical stability, deviation
from stoichiometry and order/disorder transformations of phases that are
relevant to Be alloys were investigated using density functional theory
simulations coupled with phonon density of states calculations to capture
temperature effects. A novel structure and composition were identified for the
Be-Fe binary {\epsilon} phase. In absence of Al, FeBe_5 is predicted to form at
equilibrium above ~ 1250 K, while the {\epsilon} phase is stable only below ~
1650 K, and FeBe_2 is stable at all temperatures below melting. Small additions
of Al are found to stabilise FeBe_5 over FeBe_2 and {\epsilon}, while at high
Al content, AlFeBe_4 is predicted to form. Deviations from stoichiometric
compositions are also considered and found to be important in the case of
FeBe_5 and {\epsilon}. The propensity for disordered vs ordered structures is
also important for AlFeBe_4 (which exhibits complete Al-Fe disordered at all
temperatures) and FeBe_5 (which exhibits an order-disorder transition at ~ 950
K).Comment: 14 pages, 10 figures, accepted for publication in J. Alloy Compd. on
14 March 201
Resilience of multi-photon entanglement under losses
We analyze the resilience under photon loss of the bi-partite entanglement
present in multi-photon states produced by parametric down-conversion. The
quantification of the entanglement is made possible by a symmetry of the states
that persists even under polarization-independent losses. We examine the
approach of the states to the set of states with a positive partial transpose
as losses increase, and calculate the relative entropy of entanglement. We find
that some bi-partite distillable entanglement persists for arbitrarily high
losses.Comment: 5 pages, 3 figures, title changed, minor typographic errors correcte
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