30,977 research outputs found
Cost and size estimates for an electrochemical bulk energy storage concept
Preliminary capital cost and size estimates were made for an electrochemical bulk energy storage concept. The electrochemical system considered was an electrically rechargeable flow cell with a redox couple. On the basis of preliminary capital cost estimates, size estimates, and several other important considerations, the redox-flow-cell system emerges as having great promise as a bulk energy storage system for power load leveling. The size of this system would be less than 2 percent of that of a comparable pumped hydroelectric plant. The capital cost of a 10-megawatt, 60- and 85-megawatt-hour redox system is estimated to be 330 per kilowatt. The other important features of the redox system contributing to its load leveling application are its low adverse environmental impact, its high efficiency, its apparent absence of electrochemically-related cycle life limitations, and its fast response
Orbital calculations and trapped radiation mapping
Flux and energy spectra code for orbital calculations and trapped radiation mappin
Observations of apparent superslow wave propagation in solar prominences
Phase mixing of standing continuum Alfv\'en waves and/or continuum slow waves
in atmospheric magnetic structures such as coronal arcades can create the
apparent effect of a wave propagating across the magnetic field. We observe a
prominence with SDO/AIA on 2015 March 15 and find the presence of oscillatory
motion. We aim to demonstrate that interpreting this motion as a magneto
hydrodynamic (MHD) wave is faulty. We also connect the decrease of the apparent
velocity over time with the phase mixing process, which depends on the
curvature of the magnetic field lines. By measuring the displacement of the
prominence at different heights to calculate the apparent velocity, we show
that the propagation slows down over time, in accordance with the theoretical
work of Kaneko et al. We also show that this propagation speed drops below what
is to be expected for even slow MHD waves for those circumstances. We use a
modified Kippenhahn-Schl\"uter prominence model to calculate the curvature of
the magnetic field and fit our observations accordingly. Measuring three of the
apparent waves, we get apparent velocities of 14, 8, and 4 km/s. Fitting a
simple model for the magnetic field configuration, we obtain that the filament
is located 103 Mm below the magnetic centre. We also obtain that the scale of
the magnetic field strength in the vertical direction plays no role in the
concept of apparent superslow waves and that the moment of excitation of the
waves happened roughly one oscillation period before the end of the eruption
that excited the oscillation. Some of the observed phase velocities are lower
than expected for slow modes for the circumstances, showing that they rather
fit with the concept of apparent superslow propagation. A fit with our magnetic
field model allows for inferring the magnetic geometry of the prominence.Comment: 10 pages, 6 figures, 1 of which consists of 3 panel
A preliminary report on energetic space radiation and dose rate analysis
Energetic space radiation and dose rate analysi
Charged particle radiation environment for the LST
Preliminary charged particle dose rates are presented for the LST orbit. The trapped proton component appears to dominate the total dose for the expected shielding available. Typical dose rates should range from 400 to 800 millirads/day
On the inverse cascade of magnetic helicity
We study the inverse cascade of magnetic helicity in conducting fluids by
investigating the detailed transfer of helicity between different spherical
shells in Fourier space in direct numerical simulations of three-dimensional
magnetohydrodynamics (MHD). Two different numerical simulations are used, one
where the system is forced with an electromotive force in the induction
equation, and one in which the system is forced mechanically with an ABC flow
and the magnetic field is solely sustained by a dynamo action. The magnetic
helicity cascade at the initial stages of both simulations is observed to be
inverse and local (in scale space) in the large scales, and direct and local in
the small scales. When saturation is approached most of the helicity is
concentrated in the large scales and the cascade is non-local. Helicity is
transfered directly from the forced scales to the largest scales. At the same
time, a smaller in amplitude direct cascade is observed from the largest scale
to small scales.Comment: Submitted to PR
Field-calibrated model of melt, refreezing, and runoff for polar ice caps : Application to Devon Ice Cap
Acknowledgments R.M.M. was supported by the Scottish Alliance for Geoscience, Environment and Society (SAGES). The field data collection contributed to the validation of the European Space Agency Cryosat mission and was supported by the Natural Sciences and Engineering Research Council, Canada, the Meteorological Service of Canada (CRYSYS program), the Polar Continental Shelf Project (an agency of Natural Resources Canada), and by UK Natural Environment Research Council consortium grant NER/O/S/2003/00620. Support for D.O.B. was provided by the Canadian Circumpolar Institute and the Climate Change Geoscience Program, Earth Sciences Sector, Natural Resources Canada (ESS contribution 20130371). Thanks are also due to the Nunavut Research Institute and the communities of Resolute Bay and Grise Fjord for permission to conduct fieldwork on Devon Ice Cap. M.J. Sharp, A. Gardner, F. Cawkwell, R. Bingham, S. Williamson, L. Colgan, J. Davis, B. Danielson, J. Sekerka, L. Gray, and J. Zheng are thanked for logistical support and field assistance during the data collection. We thank Ruzica Dadic, two other anonymous reviewers, and the Editor, Bryn Hubbard, for their helpful comments on an earlier version of this paper and which resulted in significant improvements.Peer reviewedPublisher PD
Full-time dynamics of modulational instability in spinor Bose-Einstein condensates
We describe the full-time dynamics of modulational instability in F=1 spinor
Bose-Einstein condensates for the case of the integrable three-component model
associated with the matrix nonlinear Schroedinger equation. We obtain an exact
homoclinic solution of this model by employing the dressing method which we
generalize to the case of the higher-rank projectors. This homoclinic solution
describes the development of modulational instability beyond the linear regime,
and we show that the modulational instability demonstrates the reversal
property when the growth of the modulation amplitude is changed by its
exponential decay.Comment: 6 pages, 2 figures, text slightly extended, a reference adde
Teaching Improvement Practices: New Perspectives
The movement to improve the quality of teaching and learning in higher education has gained increasing importance over the last several years. Policies and programs aimed at enhancing instruction are becoming commonplace as post-secondary institutions strive to provide a high quality educational experience for students. The impact of different teaching improvement practices varies, and decision-makers in universities and colleges need to know where best to place their efforts and resources. The experienced judgement of teaching improvement practitioners can assist others in making these decisions
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