5,996 research outputs found
Limitations on the extent of off-center displacements in TbMnO3 from EXAFS measurements
We present EXAFS data at the Mn K and Tb L3 edges that provide upper limits
on the possible displacements of any atoms in TbMnO3. The displacements must be
less than 0.005-0.01A for all atoms which eliminates the possibility of
moderate distortions (0.02A) with a small c-axis component, but for which the
displacements in the ab plane average to zero. Assuming the polarization arises
from a displacement of the O2 atoms along the c-axis, the measured polarization
then leads to an O2 displacement that is at least 6X10^{-4}A, well below our
experimental limit. Thus a combination of the EXAFS and the measured electrical
polarization indicate that the atomic displacements likely lie in the range
6X10^{-4} - 5X10^{-3}A.Comment: submitted to PRB; 11 pages (preprint form) 7 figure
Detection of plant stress through multispectral photography
There are no author-identified significant results in this report
An Efficient Algorithm for Enumerating Chordless Cycles and Chordless Paths
A chordless cycle (induced cycle) of a graph is a cycle without any
chord, meaning that there is no edge outside the cycle connecting two vertices
of the cycle. A chordless path is defined similarly. In this paper, we consider
the problems of enumerating chordless cycles/paths of a given graph
and propose algorithms taking time for each chordless cycle/path. In
the existing studies, the problems had not been deeply studied in the
theoretical computer science area, and no output polynomial time algorithm has
been proposed. Our experiments showed that the computation time of our
algorithms is constant per chordless cycle/path for non-dense random graphs and
real-world graphs. They also show that the number of chordless cycles is much
smaller than the number of cycles. We applied the algorithm to prediction of
NMR (Nuclear Magnetic Resonance) spectra, and increased the accuracy of the
prediction
Evaluation Of Support Vector Machine Based Forecasting Tool In Electricity Price Forecasting For Australian National Electricity Market Participants
In this paper, we present an analysis of the results of a study into wholesale (spot) electricity price forecasting utilising Neural Networks (NNs) and Support Vector Machines (SVM). Frequent regulatory changes in electricity markets and the quickly evolving market participant pricing (bidding) strategies cause efficient retraining to be crucial in maintaining the accuracy of electricity price forecasting models. The efficiency of NN and SVM retraining for price forecasting was evaluated using Australian National Electricity Market (NEM), New South Wales regional data over the period from September 1998 to December 1998. The analysis of the results showed that SVMs with one unique solution, produce more consistent forecasting accuracies and so require less time to optimally train than NNs, which can result in a solution at any of a large number of local minima. The SVM and NN forecasting accuracies were found to be very similar
Support Vector Machine Based Electricity Price Forecasting For Electricity Markets utilising Projected Assessment of System Adequacy Data
In this paper we present an analysis of the results of a study into wholesale (spot) electricity price forecasting with Support Vector Machines (SVM) utilising past price and demand data and Projected Assessment of System Adequacy (PASA) data. The forecasting accuracy was evaluated using Australian National Electricity Market (NEM), New South Wales regional data over the year 2002. The inclusion of PASA data shows little improvement in forecasting accuracy
Numerical Investigation of a Coronal Mass Ejection from an Anemone Active Region: Reconnection and Deflection of the 2005 August 22 Eruption
We present a numerical investigation of the coronal evolution of a coronal
mass ejection (CME) on 2005 August 22 using a 3-D thermodynamics
magnetohydrodynamic model, the SWMF. The source region of the eruption was
anemone active region (AR) 10798, which emerged inside a coronal hole. We
validate our modeled corona by producing synthetic extreme ultraviolet (EUV)
images, which we compare to EIT images. We initiate the CME with an
out-of-equilibrium flux rope with an orientation and chirality chosen in
agreement with observations of a H-alpha filament. During the eruption, one
footpoint of the flux rope reconnects with streamer magnetic field lines and
with open field lines from the adjacent coronal hole. It yields an eruption
which has a mix of closed and open twisted field lines due to interchange
reconnection and only one footpoint line-tied to the source region. Even with
the large-scale reconnection, we find no evidence of strong rotation of the CME
as it propagates. We study the CME deflection and find that the effect of the
Lorentz force is a deflection of the CME by about 3 deg/Rsun towards the East
during the first 30 minutes of the propagation. We also produce coronagraphic
and EUV images of the CME, which we compare with real images, identifying a
dimming region associated with the reconnection process. We discuss the
implication of our results for the arrival at Earth of CMEs originating from
the limb and for models to explain the presence of open field lines in magnetic
clouds.Comment: 14 pages, 8 Figures, accepted to Astrophysical Journa
Redetermination of despujolsite, Ca3Mn4+(SO4)2(OH)6·3H2O
The crystal structure of despujolsite [tricalcium manganese bisÂ(sulfate) hexahydroxide triÂhydrate], the Ca/Mn member of the fleischerite group, ideally Ca3Mn4+(SO4)2(OH)6·3H2O, was previously determined based on X-ray diffraction intensity data from photographs, without H-atom positions located [Gaudefroy et al. (1968 â–¶). Bull. Soc. Fr. Minéral. Crystallogr.
91, 43–50]. The current study redetermines the structure of despujolsite from a natural specimen, with all H atoms located and with higher precision. The structure of despujolsite is characterized by layers of CaO8 polyhedra (m.. symmetry) interÂconnected by Mn(OH)6 octaÂhedra (32. symmetry) and SO4 tetraÂhedra (3.. symmetry) along [001]. The average Ca—O, Mn—O and S—O bond lengths are 2.489, 1.915, and 1.472 Å, respectively. There are two distinct hydrogen bonds that stabilize the structural set-up. This work represents the first description of hydrogen bonds in the fleischerite group of minerals
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