56,884 research outputs found
The Surveyor 5, 6, and 7 Flight Paths and Their Determination from Tracking Data
Surveyor 5, 6, and 7 flight paths and tracking data for space station location
Rocketdyne's advanced coal slurry pumping program
The Rocketdyne Division of Rockwell International Corporation is conducting a program for the engineering, fabrication, and testing of an experimental/prototype high-capacity, high-pressure centrifugal slurry feed pump for coal liquefaction purposes. The abrasion problems in a centrifugal slurry pump are primarily due to the manner in which the hard, solid particles contained in the slurry are transported through the hydraulic flow passages within the pump. The abrasive particles can create scraping, grinding, cutting, and sandblasting effects on the various exposed parts of the pump. These critical areas involving abrasion and impact erosion wear problems in a centrifugal pump are being addressed by Rocketdyne. The mechanisms of abrasion and erosion are being studied through hydrodynamic analysis, materials evaluation, and advanced design concepts
Bounds on Cubic Lorentz-Violating Terms in the Fermionic Dispersion Relation
We study the recently proposed Lorentz-violating dispersion relation for
fermions and show that it leads to two distinct cubic operators in the
momentum. We compute the leading order terms that modify the non-relativistic
equations of motion and use experimental results for the hyperfine transition
in the ground state of the ion to bound the values of the
Lorentz-violating parameters and for neutrons. The resulting
bounds depend on the value of the Lorenz-violating background four-vector in
the laboratory frame.Comment: Revtex 4, four pages. Version to match the one to appear in Physical
Review
Axion hot dark matter bounds
We derive cosmological limits on two-component hot dark matter consisting of
neutrinos and axions. We restrict the large-scale structure data to the safely
linear regime, excluding the Lyman-alpha forest. We derive Bayesian credible
regions in the two-parameter space consisting of m_a and sum(m_nu).
Marginalizing over sum(m_nu) provides m_a<1.02 eV (95% CL). In the absence of
axions the same data and methods give sum(m_nu)< 0.63 eV (95% CL).Comment: Contribution to Proc. 4th Patras Workshop on Axions, WIMPs and WISPs
(18-21 June 2008, DESY
A Study of Non-Neutral Networks with Usage-based Prices
Hahn and Wallsten wrote that network neutrality "usually means that broadband
service providers charge consumers only once for Internet access, do not favor
one content provider over another, and do not charge content providers for
sending information over broadband lines to end users." In this paper we study
the implications of non-neutral behaviors under a simple model of linear
demand-response to usage-based prices. We take into account advertising
revenues and consider both cooperative and non-cooperative scenarios. In
particular, we model the impact of side-payments between service and content
providers. We also consider the effect of service discrimination by access
providers, as well as an extension of our model to non-monopolistic content
providers
Photon pair generation using four-wave mixing in a microstructured fibre: theory versus experiment
We develop a theoretical analysis of four-wave mixing used to generate photon
pairs useful for quantum information processing. The analysis applies to a
single mode microstructured fibre pumped by an ultra-short coherent pulse in
the normal dispersion region. Given the values of the optical propagation
constant inside the fibre, we can estimate the created number of photon pairs
per pulse, their central wavelength and their respective bandwidth. We use the
experimental results from a picosecond source of correlated photon pairs using
a micro-structured fibre to validate the model. The fibre is pumped in the
normal dispersion regime at 708nm and phase matching is satisfied for widely
spaced parametric wavelengths of 586nm and 894nm. We measure the number of
photons per pulse using a loss-independent coincidence scheme and compare the
results with the theoretical expectation. We show a good agreement between the
theoretical expectations and the experimental results for various fibre lengths
and pump powers.Comment: 23 pages, 9 figure
The Surveyor 3 and Surveyor 4 flight paths and their determination from tracking data
Surveyor 3 and 4 spacecraft flight path
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