1,843 research outputs found
Influence of Course Design on Learning Approaches and Academic Performance in Physical Therapy Students
AbstractThis study investigated (1) changes in learning approaches and academic performance between courses designed according to lecture-based learning or problem-based learning, (2) the relationship between academic performance and learning approaches. 32 students participated in this study. Students’ learning approaches were ascertained by the Approaches and Study Skills Inventory for Students. Summative results from each course indicated academic performance. The results showed that approximately 50% of students changed their learning approaches for different course designs. Furthermore, choice of learning approach influenced academic performance in a course designed according to problem-based learning but not in one designed according to lecture-based learning
Oil quality in diesel engines with on line oil cleaning using a heated lubricating oil recycler
A method of cleaning the oil on line was investigatedusing a bypass fine particulate filter followed by an infra
red heater to remove water and light diesel fractions in
the oil. This was tested on a range of on road vehicles
and a Ford 1.8 litre IDI passenger car engine on a test
bed. Comparison was made with the oil quality on the
same vehicles and engines without the on-line recycler.
Test times were from 200 to 1500 hours of oil ageing and
some of the tests showed that the oil quality was still
good after 4 times the normal oil life. The results showed
that the on line oil recycler cleaning system reduced the
rate of fall of the TBN and rate of increase of the TAN.
There was a very significant reduction in the soot in oil
and the fuel dilution. There was also a consistent reduction
in all the wear metals apart from copper and a
decrease in the rate of reduction of oil additives. There
was also measured on the Ford IDI engine a 5% reduced
fuel consumption. Many of these effects were attributed
to an influence of the cleaner oil on reduced engine
deposits
Oil quality in diesel engines with on line oil cleaning using a heated lubricating oil recycler
A method of cleaning the oil on line was investigatedusing a bypass fine particulate filter followed by an infra
red heater to remove water and light diesel fractions in
the oil. This was tested on a range of on road vehicles
and a Ford 1.8 litre IDI passenger car engine on a test
bed. Comparison was made with the oil quality on the
same vehicles and engines without the on-line recycler.
Test times were from 200 to 1500 hours of oil ageing and
some of the tests showed that the oil quality was still
good after 4 times the normal oil life. The results showed
that the on line oil recycler cleaning system reduced the
rate of fall of the TBN and rate of increase of the TAN.
There was a very significant reduction in the soot in oil
and the fuel dilution. There was also a consistent reduction
in all the wear metals apart from copper and a
decrease in the rate of reduction of oil additives. There
was also measured on the Ford IDI engine a 5% reduced
fuel consumption. Many of these effects were attributed
to an influence of the cleaner oil on reduced engine
deposits
Distribution and density of the partition function zeros for the diamond-decorated Ising model
Exact renormalization map of temperature between two successive decorated
lattices is given, and the distribution of the partition function zeros in the
complex temperature plane is obtained for any decoration-level. The rule
governing the variation of the distribution pattern as the decoration-level
changes is given. The densities of the zeros for the first two
decoration-levels are calculated explicitly, and the qualitative features about
the densities of higher decoration-levels are given by conjecture. The Julia
set associated with the renormalization map is contained in the distribution of
the zeros in the limit of infinite decoration level, and the formation of the
Julia set in the course of increasing the decoration-level is given in terms of
the variations of the zero density.Comment: 8 pages,8figure
Localized surface states in HTSC: Alternative mechanism of zero-bias conductance peaks
It is shown that the quasiparticle states localized in the vicinity of
surface imperfections of atomic size can be responsible for the zero-bias
tunneling conductance peaks in high-Tc superconductors. The contribution from
these states can be easily separated from other mechanisms using their
qualitatively different response on an external magnetic field.Comment: REVTeX, 4 pages, 2 figs; to be published in PR
Spin transport of electrons through quantum wires with spatially-modulated strength of the Rashba spin-orbit interaction
We study ballistic transport of spin-polarized electrons through quantum
wires in which the strength of the Rashba spin-orbit interaction (SOI) is
spatially modulated. Subband mixing, due to SOI, between the two lowest
subbands is taken into account. Simplified approximate expressions for the
transmission are obtained for electron energies close to the bottom of the
first subband and near the value for which anticrossing of the two lowest
subbands occurs. In structures with periodically varied SOI strength, {\it
square-wave} modulation on the spin transmission is found when only one subband
is occupied and its possible application to the spin transistor is discussed.
When two subbands are occupied the transmission is strongly affected by the
existence of SOI interfaces as well as by the subband mixing
Gain in a quantum wire laser of high uniformity
A multi-quantum wire laser operating in the 1-D ground state has been
achieved in a very high uniformity structure that shows free exciton emission
with unprecedented narrow width and low lasing threshold. Under optical pumping
the spontaneous emission evolves from a sharp free exciton peak to a
red-shifted broad band. The lasing photon energy occurs about 5 meV below the
free exciton. The observed shift excludes free excitons in lasing and our
results show that Coulomb interactions in the 1-D electron-hole system shift
the spontaneous emission and play significant roles in laser gain.Comment: 4 pages, 4 figures, prepared by RevTe
Finite temperature excitations of a trapped Bose-Fermi mixture
We present a detailed study of the low-lying collective excitations of a
spherically trapped Bose-Fermi mixture at finite temperature in the
collisionless regime. The excitation frequencies of the condensate are
calculated self-consistently using the static Hartree-Fock-Bogoliubov theory
within the Popov approximation. The frequency shifts and damping rates due to
the coupled dynamics of the condensate, noncondensate, and degenerate Fermi gas
are also taken into account by means of the random phase approximation and
linear response theory. In our treatment, the dipole excitation remains close
to the bare trapping frequency for all temperatures considered, and thus is
consistent with the generalized Kohn theorem. We discuss in some detail the
behavior of monopole and quadrupole excitations as a function of the Bose-Fermi
coupling. At nonzero temperatures we find that, as the mixture moves towards
spatial separation with increasing Bose-Fermi coupling, the damping rate of the
monopole (quadrupole) excitation increases (decreases). This provides us a
useful signature to identify the phase transition of spatial separation.Comment: 10 pages, 8 figures embedded; to be published in Phys. Rev.
Early stage morphology of quench condensed Ag, Pb and Pb/Ag hybrid films
Scanning Tunneling Microscopy (STM) has been used to study the morphology of
Ag, Pb and Pb/Ag bilayer films fabricated by quench condensation of the
elements onto cold (T=77K), inert and atomically flat Highly Oriented Pyrolytic
Graphite (HOPG) substrates. All films are thinner than 10 nm and show a
granular structure that is consistent with earlier studies of QC films. The
average lateral diameter, , of the Ag grains, however, depends on
whether the Ag is deposited directly on HOPG ( = 13 nm) or on a Pb
film consisting of a single layer of Pb grains ( = 26.8 nm). In
addition, the critical thickness for electrical conduction () of Pb/Ag
films on inert glass substrates is substantially larger than for pure Ag films.
These results are evidence that the structure of the underlying substrate
exerts an influence on the size of the grains in QC films. We propose a
qualitative explanation for this previously unencountered phenomenon.Comment: 11 pages, 3 figures and one tabl
SuperWIMP Dark Matter Signals from the Early Universe
Cold dark matter may be made of superweakly-interacting massive particles,
superWIMPs, that naturally inherit the desired relic density from late decays
of metastable WIMPs. Well-motivated examples are weak-scale gravitinos in
supergravity and Kaluza-Klein gravitons from extra dimensions. These particles
are impossible to detect in all dark matter experiments. We find, however, that
superWIMP dark matter may be discovered through cosmological signatures from
the early universe. In particular, superWIMP dark matter has observable
consequences for Big Bang nucleosynthesis and the cosmic microwave background
(CMB), and may explain the observed underabundance of 7Li without upsetting the
concordance between deuterium and CMB baryometers. We discuss implications for
future probes of CMB black body distortions and collider searches for new
particles. In the course of this study, we also present a model-independent
analysis of entropy production from late-decaying particles in light of WMAP
data.Comment: 19 pages, 5 figures, typos correcte
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