5,459 research outputs found
Theoretical and experimental study of AC loss in HTS single pancake coils
The electromagnetic properties of a pancake coil in AC regime as a function
of the number of turns is studied theoretically and experimentally.
Specifically, the AC loss, the coil critical current and the voltage signal are
discussed. The coils are made of Bi2Sr2Ca2Cu3O10/Ag (BiSCCO) tape, although the
main qualitative results are also applicable to other kinds of superconducting
tapes, such as coated conductors. The AC loss and the voltage signal are
electrically measured using different pick up coils with the help of a
transformer. One of them avoids dealing with the huge coil inductance. Besides,
the critical current of the coils is experimentally determined by conventional
DC measurements. Furthermore, the critical current, the AC loss and the voltage
signal are simulated, showing a good agreement with the experiments. For all
simulations, the field dependent critical current density inferred from DC
measurements on a short tape sample is taken into account.Comment: 22 pages, 15 figures; contents extended (sections 3.2 and 4); one new
figure (figure 5) and two figures replaced (figures 3 and 8); typos
corrected; title change
Magnetic structure and orbital ordering in BaCoO3 from first-principles calculations
Ab initio calculations using the APW+lo method as implemented in the WIEN2k
code have been used to describe the electronic structure of the
quasi-one-dimensional system BaCoO3. Both, GGA and LDA+U approximations were
employed to study different orbital and magnetic orderings. GGA predicts a
metallic ground state whereas LDA+U calculations yield an insulating and
ferromagnetic ground state (in a low-spin state) with an alternating orbital
ordering along the Co-Co chains, consistent with the available experimental
data.Comment: 8 pages, 9 figure
High-J v=0 SiS Maser Emission in IRC+10216: A New Case of Infrared Overlaps
We report on the first detection of maser emission in the J=11-10, J=14-13
and J=15-14 transitions of the v=0 vibrational state of SiS toward the C-rich
star IRC+10216. These masers seem to be produced in the very inhomogeneous
region between the star and the inner dust formation zone, placed at 5-7 R*,
with expansion velocities below 10 km/s. We interpret the pumping mechanism as
due to overlaps between v=1-0 ro-vibrational lines of SiS and mid-IR lines of
C2H2, HCN and their 13C isotopologues. The large number of overlaps found
suggests the existence of strong masers for high-J v=0 and v=1 SiS transitions,
located in the submillimeter range. In addition, it could be possible to find
several rotational lines of the SiS isotopologues displaying maser emission.Comment: 4 pages, 1 figure, published in the ApJ Letter
Geostatistical modelling of a coal seam for resource risk assessment
The evaluation of a coal seam for profitable extraction requires the estimation of its thickness and quality characteristics together with the spatial variability of these variables. In many cases the only data available for the estimation are from a limited number of exploration and feasibility drill holes. Spatial variability can be quantified by geostatistical modelling, which provides the basis for estimation (kriging). In cases where the spatial variability of the seam thickness and quality characteristics has a significant impact on how the coal is extracted and stored, geostatistical simulation may be preferable to geostatistical kriging methods. The aim of this paper is to present an improved approach to resource risk assessment by propagating the uncertainty in semi-variogram model parameters into the spatial variability of coal variables. We show that a more realistic assessment of risk is obtained when the uncertainty of semi-variogram model parameters is taken into account. The methodology is illustrated with a coal seam from North-western Spain. © 2012 Elsevier B.V.E. Pardo-IgĂșzquiza, P.A. Dowd, J.M. Baltuille, M. Chica-Olm
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