2,848 research outputs found
Donor Advisors and Philanthropic Strategy
Based on a literature review and interviews, explores how donor advisors shape the philanthropic strategies of the wealthy. Looks at the key activities and elements of effective advising, the need for training, and the potential for collaboration
A unified approach to suboptimum control
Suboptimal control based on linear changes in vicinity of optimum trajector
Design of a three-axis attitude control system for a spacecraft acted upon by random perturbations Final report
Three axis attitude control system for spacecraft under random perturbation
Stability of attitude control systems acted upon by random perturbations
Mathematical models on stability of attitude control systems acted upon by random perturbation processe
Additional studies of quasi-optimum feedback control techniques
Quasi-optimal control technique for space vehicle attitude, bounded acceleration rendezvous in free space, and aircraft landing proble
Extra dimensions, orthopositronium decay, and stellar cooling
In a class of extra dimensional models with a warped metric and a single
brane the photon can be localized on the brane by gravity only. An intriguing
feature of these models is the possibility of the photon escaping into the
extra dimensions. The search for this effect has motivated the present round of
precision orthopositronium decay experiments. We point out that in this
framework a photon in plasma should be metastable. We consider the
astrophysical consequences of this observation, in particular, what it implies
for the plasmon decay rate in globular cluster stars and for the core-collapse
supernova cooling rate. The resulting bounds on the model parameter exceed the
possible reach of orthopositronium experiments by many orders of magnitude.Comment: 13 pages, no figure
Robust autoresonant excitation in the plasma beat-wave accelerator: a theoretical study
A modified version of the Plasma Beat-Wave Accelerator scheme is introduced
and analyzed, which is based on autoresonant phase-locking of the nonlinear
Langmuir wave to the slowly chirped beat frequency of the driving lasers via
adiabatic passage through resonance. This new scheme is designed to overcome
some of the well-known limitations of previous approaches, namely relativistic
detuning and nonlinear modulation or other non-uniformity or non-stationarity
in the driven Langmuir wave amplitude, and sensitivity to frequency mismatch
due to measurement uncertainties and density fluctuations and inhomogeneities
Approximating the monomer-dimer constants through matrix permanent
The monomer-dimer model is fundamental in statistical mechanics. However, it
is #P-complete in computation, even for two dimensional problems. A
formulation in matrix permanent for the partition function of the monomer-dimer
model is proposed in this paper, by transforming the number of all matchings of
a bipartite graph into the number of perfect matchings of an extended bipartite
graph, which can be given by a matrix permanent. Sequential importance sampling
algorithm is applied to compute the permanents. For two-dimensional lattice
with periodic condition, we obtain , where the exact value is
. For three-dimensional lattice with periodic condition,
our numerical result is , {which agrees with the best known
bound .}Comment: 6 pages, 2 figure
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