2,896 research outputs found
Space-Enhanced Solar Power for Equatorial Regions
This paper examines the concept of solar mirrors in a Earth orbit to provide solar farms with additional solar power
during the hours of darkness. The design of the orbit is key for the purposes of the mission: the mirror needs continuous
access to the Sun and the solar farm simultaneously. Therefore, orbits with high-eccentricity will be considered to
increase the visibility time. Also, since the most convenient locations for solar power farms are about the equator,
a suitable orbit should have a low inclination. This issue can be addressed through the concept of anti-heliotropic
orbits that exploits mainly solar radiation pressure perturbations to generate highly-eccentric equatorial orbits able to
maintain the orientation with respect to the Sun. The considered configuration consists in two space mirrors in a flower
constellation rotating with the Earth to deliver a repeat ground track
The Feshbach-Kerman-Koonin multistep direct reaction theory
The multistep direct reaction theory of Feshbach, Kerman and Koonin (1980) is described in detail and compared with other theories. The results of several analyses of experimental cross-sections are described, and the validity and usefulness of the theory assessed
Spontaneous heavy cluster emission rates using microscopic potentials
The nuclear cluster radioactivities have been studied theoretically in the
framework of a microscopic superasymmetric fission model (MSAFM). The nuclear
interaction potentials required for binary cold fission processes are
calculated by folding in the density distribution functions of the two
fragments with a realistic effective interaction. The microscopic nuclear
potential thus obtained has been used to calculate the action integral within
the WKB approximation. The calculated half lives of the present MSAFM
calculations are found to be in good agreement over a wide range of observed
experimental data.Comment: 4 pages, 4 figure
Universal decay law in charged-particle emission and exotic cluster radioactivity
A linear universal decay formula is presented starting from the microscopic
mechanism of the charged-particle emission. It relates the half-lives of
monopole radioactive decays with the -values of the outgoing particles as
well as the masses and charges of the nuclei involved in the decay. This
relation is found to be a generalization of the Geiger-Nuttall law in
radioactivity and explains well all known cluster decays. Predictions on the
most likely emissions of various clusters are presented.Comment: 2 figure
Direct Observation of Large Amplitude Spin Excitations Localized in a Spin-Transfer Nanocontact
We report the direct observation of large amplitude spin-excitations
localized in a spin-transfer nanocontact using scanning transmission x-ray
microscopy. Experiments were conducted using a nanocontact to an ultrathin
ferromagnetic multilayer with perpendicular magnetic anisotropy. Element
resolved x-ray magnetic circular dichroism images show an abrupt onset of spin
excitations at a threshold current that are localized beneath the nanocontact,
with average spin precession cone angles of 25{\deg} at the contact center. The
results strongly suggest that we have observed a localized magnetic soliton.Comment: 5 pages, 3 figure
Space-Enhanced Solar Power for Equatorial Regions
This paper examines the concept of solar mirrors in a Earth orbit to provide solar farms with additional solar power
during the hours of darkness. The design of the orbit is key for the purposes of the mission: the mirror needs continuous
access to the Sun and the solar farm simultaneously. Therefore, orbits with high-eccentricity will be considered to
increase the visibility time. Also, since the most convenient locations for solar power farms are about the equator,
a suitable orbit should have a low inclination. This issue can be addressed through the concept of anti-heliotropic
orbits that exploits mainly solar radiation pressure perturbations to generate highly-eccentric equatorial orbits able to
maintain the orientation with respect to the Sun. The considered configuration consists in two space mirrors in a flower
constellation rotating with the Earth to deliver a repeat ground track
Performance of a Y-Ba-Cu-O superconducting filter/GaAs low noise amplifier hybrid circuit
A superconducting 7.3 GHz two-pole microstrip bandpass filter and a GaAs low noise amplifier (LNA) were combined into an active circuit and characterized at liquid nitrogen temperatures. This superconducting/semiconducting circuit's performance was compared to a gold filter/GaAs LNA hybrid circuit. The superconducting filter/GaAs LNA hybrid circuit showed higher gain and lower noise figure than its gold counterpart
Clustering-based measurement of dependence
A measure of the dependence of a multivariate response variable upon a categorical variable is introduced. Its characteristics are explored via simulations by referring to a specific mixture association model. Inferential aspects are investigated using a permutation test approach. We present preliminary results
Huge Seebeck coefficients in non-aqueous electrolytes
The Seeebeck coefficients of the non-aqueous electrolytes tetrabutylammonium
nitrate, tetraoctylphosphonium bromide and tetradodecylammonium nitrate in
1-octanol, 1-dodecanol and ethylene-glycol are measured in a temperature range
from T=30 to T=45 C. The Seebeck coefficient is generally of the order of a few
hundreds of microvolts per Kelvin for aqueous solution of inorganic ions. Here
we report huge values of 7 mV/K at 0.1M concentration for tetrabutylammonium
nitrate in 1-dodecanol. These striking results open the question of
unexpectedly large kosmotrope or "structure making" effects of
tetraalkylammonium ions on the structure of alcohols.Comment: Submitted to J. Chem. Phy
Global torques and stochasticity as the drivers of massive black hole pairing in the young Universe
The forthcoming Laser Interferometer Space Antenna (LISA) will probe the
population of coalescing massive black hole (MBH) binaries up to the onset of
structure formation. Here we simulate the galactic-scale pairing of MBHs in a typical, non-clumpy main-sequence galaxy embedded in a
cosmological environment at . In order to increase our statistical
sample, we adopt a strategy that allows us to follow the evolution of six
secondary MBHs concomitantly. We find that the magnitude of the
dynamical-friction induced torques is significantly smaller than that of the
large-scale, stochastic gravitational torques arising from the perturbed and
morphologically evolving galactic disc, suggesting that the standard dynamical
friction treatment is inadequate for realistic galaxies at high redshift. The
dynamical evolution of MBHs is very stochastic, and a variation in the initial
orbital phase can lead to a drastically different time-scale for the inspiral.
Most remarkably, the development of a galactic bar in the host system either
significantly accelerates the inspiral by dragging a secondary MBH into the
centre, or ultimately hinders the orbital decay by scattering the MBH in the
galaxy outskirts. The latter occurs more rarely, suggesting that galactic bars
overall promote MBH inspiral and binary coalescence. The orbital decay time can
be an order of magnitude shorter than what would be predicted relying on
dynamical friction alone. The stochasticity, and the important role of global
torques, have crucial implications for the rates of MBH coalescences in the
early Universe: both have to be accounted for when making predictions for the
upcoming LISA observatory.Comment: Accepted for publication in MNRAS; 15 pages, 10 Figures, 2 Table
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