7,093 research outputs found
Student experiences of virtual reality - a case study in learning special relativity
We present a study of student learning through the use of virtual reality. A
software package is used to introduce concepts of special relativity to
students in a game-like environment where users experience the effects of
travelling at near light speeds. From this new perspective, space and time are
significantly different to that experienced in everyday life. The study
explores how students have worked with this environment and how these students
have used this experience in their study of special relativity. A mixed method
approach has been taken to evaluate the outcomes of separate implementations of
the package at two universities. Students found the simulation to be a positive
learning experience and described the subject area as being less abstract after
its use. Also, students were more capable of correctly answering concept
questions relating to special relativity, and a small but measurable
improvement was observed in the final exam
Long-range ferromagnetism of Mn12 acetate single-molecule magnets under a transverse magnetic field
We use neutron diffraction to probe the magnetization components of a crystal
of Mn12 single-molecule magnets. Each of these molecules behaves, at low
temperatures, as a nanomagnet with spin S = 10 and strong anisotropy along the
crystallographic c axis. Application of a magnetic field perpendicular to c
induces quantum tunneling between opposite spin orientations, enabling the
spins to attain thermal equilibrium. Below approximately 0.9 K, intermolecular
interactions turn this equilibrium state into a ferromagnetically ordered
phase. However, long range ferromagnetic correlations nearly disappear for
fields larger 5.5 T, possibly suggesting the existence of a quantum critical
point.Comment: 4 pages, 4 figure
Spin gaps and magnetic structure of NaxCoO2
We present two experiments that provide information on spin anisotropy and
the magnetic structure of NaxCoO2. First, we report low-energy neutron
inelastic scattering measurements of the zone-center magnetic excitations in
the magnetically ordered phase of Na0.75CoO2. The energy spectra suggest the
existence of two gaps, and are very well fitted by a spin-wave model with both
in-plane and out-of-plane anisotropy terms. The gap energies decrease with
increasing temperature and both gaps are found to have closed when the
temperature exceeds the magnetic ordering temperature T_m~22 K. Secondly, we
present neutron diffraction studies of Na0.85CoO2 with a magnetic field applied
approximately parallel to the c axis. For fields in excess of ~8T a magnetic
Bragg peak was observed at the (0,0,3) position in reciprocal space. We
interpret this as a spin-flop transition of the A-type antiferromagnetic
structure, and we show that the spin-flop field is consistent with the size of
the anisotropy gap.Comment: 9 pages, 7 figure
Managing Grassy Woodlands: Balancing Production and Conservation of Resources
Eastern Australian eucalypt woodlands are important agricultural areas that have been widely modified during two centuries of European-style use. Despite this they contain important natural resources including significant biodiversity. Long term sustainability of production depends on maintaining resources and management must be for both production and conservation. A research program on four properties in south east Queensland showed the properties were in generally good condition although all had some problems, and has highlighted a number of significant costs and barriers to adopting a more balanced approach to production and conservation
TB85: A New Potato Scab Problem in Maine
The scientific literature is filled with conflicting reports on the development of the common scab disease of potatoes and its causal organism. One unresolved question is soil reaction, once thought to be the answer in controlling this disease. Scientific studies an d practical experience over a long period had shown that acid soils having a pH of approximately 5.3 or below usually did not support common scab development, though sporadic and unexplained reports of disease occurrence in these soils were observed. In the late 1950s, however, such reports became more frequent in Maine and before the mid-1960s, losses relate d to scabb y potatoes growing in acid soils were common. Throughout this period overall crop losses from the disease were minimal even though individual growers sometimes lost a large par t of their crop. During the dry 1970 growing season, however, a disease survey estimated that up to 5% of the Maine crop was scabby. Studies of this new form of scab and observations on its development within the state are reported herein.https://digitalcommons.library.umaine.edu/aes_techbulletin/1114/thumbnail.jp
Exploring the influence of workplace trust over health worker performance: Preliminary national overview report South Africa
Field induced magnetic order in the frustrated magnet Gadolinium Gallium Garnet
Gd3Ga5O12, (GGG), has an extraordinary magnetic phase diagram, where no long
range order is found down to 25 mK despite \Theta_CW \approx 2 K. However, long
range order is induced by an applied field of around 1 T. Motivated by recent
theoretical developments and the experimental results for a closely related
hyperkagome system, we have performed neutron diffraction measurements on a
single crystal sample of GGG in an applied magnetic field. The measurements
reveal that the H-T phase diagram of GGG is much more complicated than
previously assumed. The application of an external field at low T results in an
intensity change for most of the magnetic peaks which can be divided into three
distinct sets: ferromagnetic, commensurate antiferromagnetic, and
incommensurate antiferromagnetic. The ferromagnetic peaks (e.g. (112), (440)
and (220)) have intensities that increase with the field and saturate at high
field. The antiferromagnetic reflections have intensities that grow in low
fields, reach a maximum at an intermediate field (apart from the (002) peak
which shows two local maxima) and then decrease and disappear above 2 T. These
AFM peaks appear, disappear and reach maxima in different fields. We conclude
that the competition between magnetic interactions and alternative ground
states prevents GGG from ordering in zero field. It is, however, on the verge
of ordering and an applied magnetic field can be used to crystallise ordered
components. The range of ferromagnetic and antiferromagnetic propagation
vectors found reflects the complex frustration in GGG.Comment: 6 pages, 7 figures, HFM 2008 conference pape
Design of test flows to investigate binary scaling in high enthalpy CO2-N2 mixtures
Binary scaling is a similitude law that facilitates the study of hypersonic flows around blunt bodies. It conserves the Reynolds number and the binary (two-body) reaction rates, which are mainly present in the nonequilibrium layer, and scales properly the convective heat transfer. It requires duplication of the product of density and a length scale of the flow, σL, as well as the free-stream enthalpy, H . Its use for ground-to-flight extrapolation depends on the fractional extent of regions of the flow where higher order reactions become important. This paper presents the design of flow conditions relevant to the study of binary scaling for the X2 super-orbital expansion tube. Flows conditions with similar free-stream enthalpy but distinct free-stream densities were obtained. With the help of numerical simulation, it was confirmed that those conditions were suitable to isolate the effect of binary scaling from the uncertainties and scattering of free-stream conditions
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