128,087 research outputs found
SPARKPLUS for Self- and Peer Assessment on Group-Based Honours’ Research Projects
This paper explores an application of an online tool SPARKPLUS (Self and Peer Assessment Resource Kit) for the self and peer assessment on the group-based Honours’ research projects. The Honours’ research projects in School of Civil, Environmental Engineering at University of Adelaide are running in a small group of students (typically four students or less) working with an academic supervisor in a selected area for one year. Since the research project is self-directed study, it is very difficult to fairly assess the contribution of individual students to the group-based research project. The paper-based method of self and peer assessment for the Honour’s research projects was used in the previous years. The same mark was often distributed and no feedback was given. Both the students and academic staff were not satisfied with the paper-based method of self and peer assessment. Thus an online tool SPARK PLUS together with a set of assessment criteria was used for the self and peer assessment of the Honours’ research projects in 2010. Thirty-seven groups participated in the self and peer assessment of using SPARK PLUS in semester one 2010 and a series of results from the online self and peer assessment were obtained and analysed. Feedback sessions were held and substantial feedback was received from students. Based on the feedback, suggestions were made on improving use of the online tool for self and peer assessment on the Honours’ research project.Chengqing Wu, Emmanuel Chanda and John Willisonhttp://www.adelaide.edu.au/erg
Electrochemical Studies of Redox Systems for Energy Storage
Particular attention was paid to the Cr(II)/Cr(III) redox couple in aqueous solutions in the presence of Cl(-) ions. The aim of this research has been to unravel the electrode kinetics of this redox couple and the effect of Cl(1) and electrode substrate. Gold and silver were studied as electrodes and the results show distinctive differences; this is probably due to the role Cl(-) ion may play as a mediator in the reaction and the difference in state of electrical charge on these two metals (difference in the potential of zero charge, pzc). The competition of hydrogen evolution with CrCl3 reduction on these surfaces was studied by means of the rotating ring disk electrode (RRDE). The ring downstream measures the flux of chromous ions from the disk and therefore separation of both Cr(III) and H2 generation can be achieved by analyzing ring and disk currents. The conditions for the quantitative detection of Cr(2+) at the ring electrode were established. Underpotential deposition of Pb on Ag and its effect on the electrokinetics of Cr(II)/Cr(III) reaction was studied
Persistent currents in a bosonic mixture in the ring geometry
In this paper we analyze the possibility of persistent currents of a
two-species bosonic mixture in the one-dimensional ring geometry. We extend the
arguments used by Bloch to obtain a criterion for the stability of persistent
currents for the two-species system. If the mass ratio of the two species is a
rational number, persistent currents can be stable at multiples of a certain
total angular momenta. We show that the Bloch criterion can also be viewed as a
Landau criterion involving the elementary excitations of the system. Our
analysis reveals that persistent currents at higher angular momenta are more
stable for the two-species system than previously thought.Comment: 20 pages and 7 figure
An interim reference model for the variability of the middle atmosphere H2O vapor distribution
Water vapor is an important minor constituent in the studies of the middle atmosphere for a variety of reasons, including its role as a source for active HO(y) chemicals and its use in analysis of transport processes. A number of in situ and remote techniques were employed in the determination of water vapor distributions. Two of the more complete data sets were used to develop an interim reference profile. First, there are the seven months of Nimbus 7 limb infrared monitor of the stratosphere (LIMS) data obtained during Nov. 1978 to May 1979 over the range 64S to 84N latitude and from about 100 to 1 mb in the mid-mesosphere at several fixed Northern Hemisphere mid-latitude sites. These two data sets were combined to give a mid-lattitude, interim reference water vapor profile for the entire vertical range of the middle atmosphere and with accuracies of better than 25 percent. The daily variability of stratospheric water vapor profiles about the monthly mean was also established from these data sets for selected months. Information is also provided on the longitudinal variability of LIMS water vapor profiles about the daily, weekly, and monthly zonal means. Generally, the interim reference water vapor profile and its variability are consistent with prevailing ideas about chemistry and transport
Local dynamics in high-order harmonic generation using Bohmian trajectories
We investigate high-order harmonic generation from a Bohmian-mechanical
perspective, and find that the innermost part of the core, represented by a
single Bohmian trajectory, leads to the main contributions to the high-harmonic
spectra. Using time-frequency analysis, we associate this central Bohmian
trajectory to an ensemble of unbound classical trajectories leaving and
returning to the core, in agreement with the three step model. In the Bohmian
scenario, this physical picture builds up non-locally near the core via the
quantum mechanical phase of the wavefunction. This implies that the flow of the
wavefunction far from the core alters the central Bohmian trajectory. We also
show how this phase degrades in time for the peripheral Bohmian trajectories as
they leave the core region.Comment: 7 pages, 3 figures; the manuscript has been considerably extended and
modified with regard to the previous version
The effect of supernova heating on cluster properties and constraints on galaxy formation models
Models of galaxy formation should be able to predict the properties of
clusters of galaxies, in particular their gas fractions, metallicities, X-ray
luminosity-temperature relation, temperature function and mass-deposition-rate
function. Fitting these properties places important constaints on galaxy
formation on all scales. By following gas processes in detail, our
semi-analytic model (based on that of Nulsen & Fabian 1997) is the only such
model able to predict all of the above cluster properties. We use realistic gas
fractions and gas density profiles, and as required by observations we break
the self-similarity of cluster structure by including supernova heating of
intracluster gas, the amount of which is indicated by the observed
metallicities. We also highlight the importance of the mass-deposition-rate
function as an independent and very sensitive probe of cluster structure.Comment: 5 pages, 4 figures, accepted for publication in MNRAS as a lette
The soft X-ray background: evidence for widespread disruption of the gas halos of galaxy groups
Almost all of the extragalactic X-ray background (XRB) at 0.25 keV can be
accounted for by radio-quiet quasars, allowing us to derive an upper limit of 4
\bgunit\ for the remaining background at 0.25 keV. However, the XRB from the
gas halos of groups of galaxies, with gas removal due to cooling accounted for,
exceeds this upper limit by an order of magnitude if non-gravitational heating
is not included. We calculate this using simulations of halo merger trees and
realistic gas density profiles, which we require to reproduce the observed gas
fractions and abundances of X-ray clusters. In addition, we find that the
entire mass range of groups, from to \Ms,
contributes to the 0.25 keV background in this case. In a further study, we
reduce the luminosities of groups by maximally heating their gas halos while
maintaining the same gas fractions. This only reduces the XRB by a factor of 2
or less. We thus argue that most of the gas associated with groups must be
outside their virial radii. This conclusion is supported by X-ray studies of
individual groups. The properties of both groups and X-ray clusters can be
naturally explained by a model in which the gas is given excess specific
energies of keV/particle by non-gravitational heating. With this
excess energy, the gas is gravitationally unbound from groups, but recollapses
with the formation of a cluster of temperature \ga 1 keV. This is similar to
a model proposed by Pen, but is contrary to the evolution of baryons described
by Cen \& Ostriker. (abridged)Comment: 14 pages, 14 figures, submitted to MNRA
Site-Specific Research Conducted in Support of the Salton Sea Solar Pond Project - FY 1982 Report
The design and operation of a salt-gradient solar pond power plant at the Salton Sea presents problems not encountered at small research ponds that were built in the United States. The specific characteristics of the Salton Sea site and the desire to construct the pond using the local clay as a sealant represent major deviations from previous solar pond experience. The site-specific research in support of the plant design is described. The research activity included validation of the spectrophotometric light transmission measurement technique, a search for options for clarifying the turbid and colored water of the Salton Sea, development of water clarification specifications in terms common to industry practice, quantification of gas production from microbiological reactions in the ground, a determination of the combined effects of temperature and salinity on the permeation of the local clays, and a preliminary evaluation of material corrosion
Runup and rundown generated by three-dimensional sliding masses
To study the waves and runup/rundown generated by a sliding mass, a numerical simulation model, based on the large-eddy-simulation (LES) approach, was developed. The Smagorinsky subgrid scale model was employed to provide turbulence dissipation and the volume of fluid (VOF) method was used to track the free surface and shoreline movements. A numerical algorithm for describing the motion of the sliding mass was also implemented.
To validate the numerical model, we conducted a set of large-scale experiments in a wave tank of 104m long, 3.7m wide and 4.6m deep with a plane slope (1:2) located at one end of the tank. A freely sliding wedge with two orientations and a hemisphere were used to represent landslides. Their initial positions ranged from totally aerial to fully submerged, and the slide mass was also varied over a wide range. The slides were instrumented to provide position and velocity time histories. The time-histories of water surface and the runup at a number of locations were measured.
Comparisons between the numerical results and experimental data are presented only for wedge shape slides. Very good agreement is shown for the time histories of runup and generated waves. The detailed three-dimensional complex flow patterns, free surface and shoreline deformations are further illustrated by the numerical results. The maximum runup heights are presented as a function of the initial elevation and the specific weight of the slide. The effects of the wave tank width on the maximum runup are also discussed
Surface Contribution to Raman Scattering from Layered Superconductors
Generalizing recent work, the Raman scattering intensity from a semi-infinite
superconducting superlattice is calculated taking into account the surface
contribution to the density response functions. Our work makes use of the
formalism of Jain and Allen developed for normal superlattices. The surface
contributions are shown to strongly modify the bulk contribution to the
Raman-spectrum line shape below , and also may give rise to additional
surface plasmon modes above . The interplay between the bulk and
surface contribution is strongly dependent on the momentum transfer
parallel to layers. However, we argue that the scattering
cross-section for the out-of-phase phase modes (which arise from interlayer
Cooper pair tunneling) will not be affected and thus should be the only
structure exhibited in the Raman spectrum below for relatively large
. The intensity is small but perhaps observable.Comment: 14 pages, RevTex, 6 figure
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