20,556 research outputs found
Lunar landing module reflectivity model
Lunar landing module reflectivity model based on Surveyor and Orbiter photographs of lunar craters, hills, and boulder
Probable deviations in altitude reading given by the LM altimeter for the most rough surface along a certain given trajectory
Random noise calculations in altitude reading of lunar module altimeter for rough surfaces targe
Strongly modulated transmissions in gapped armchair graphene nanoribbons with sidearm or on-site gate voltage
We propose two schemes of field-effect transistor based on gapped armchair
graphene nanoribbons connected to metal leads, by introducing sidearms or
on-site gate voltages. We make use of the band gap to reach excellent
switch-off character. By introducing one sidearm or on-site gate to the
graphene nanoribbon, conduction peaks appear inside the gap regime. By further
applying two sidearms or on-site gates, these peaks are broadened to conduction
plateaus with a wide energy window, thanks to the resonance from the dual
structure. The position of the conduction windows inside the gap can be fully
controlled by the length of the sidearms or the on-site gate voltages, which
allows "on" and "off" operations for a specific energy window inside the gap
regime. The high robustness of both the switch-off character and the conduction
windows is demonstrated and shows the feasibility of the proposed dual
structures for real applications.Comment: 6 pages, 6 figure
Gravitational Lensing by Dark Matter Halos with Non-universal Density Profiles
The statistics of gravitational lensing can provide us with a very powerful
probe of the mass distribution of matter in the universe. By comparing
predicted strong lensing probabilities with observations, we can test the mass
distribution of dark matter halos, in particular, the inner density slope. In
this letter, unlike previous work that directly models the density profiles of
dark matter halos semi-analytically, we generalize the density profiles of dark
matter halos from high-resolution N-body simulations by means of generalized
Navarro-Frenk-White (GNFW) models of three populations with slopes, ,
of about -1.5, -1.3 and -1.1 for galaxies, groups and clusters, respectively.
This approach is an alternative and independent way to examine the slopes of
mass density profiles of halos. We present calculations of lensing
probabilities using these GNFW profiles for three populations in various
spatially flat cosmological models with a cosmological constant . It
is shown that the compound model of density profiles does not match well with
the observed lensing probabilities derived from the Jodrell-Bank VLA
Astrometric Survey data in combination with the Cosmic Lens All-Sky Survey
data. Together with the previous work on lensing probability, our results
suggest that a singular isothermal sphere mass model of less than about
10^{13}h^{-1}M_{\sun} can predict strong lensing probabilities that are
consistent with observations of small splitting angles.Comment: 11 pages, 2 figures, Accepted by ApJL for publication (February 10
issue 2004
Simulated LM static reflectivity data, for site P-2-6
Simulated lunar module static reflectivity data for site P-2-
Electron spectra close to a metal-to-insulator transition
A high-resolution investigation of the electron spectra close to the
metal-to-insulator transition in dynamic mean-field theory is presented. An
all-numerical, consistent confirmation of a smooth transition at zero
temperature is provided. In particular, the separation of energy scales is
verified. Unexpectedly, sharp peaks at the inner Hubbard band edges occur in
the metallic regime. They are signatures of the important interaction between
single-particle excitations and collective modes.Comment: RevTeX 4, 4 pages, 4 eps figures; published versio
A Parameterized Centrality Metric for Network Analysis
A variety of metrics have been proposed to measure the relative importance of
nodes in a network. One of these, alpha-centrality [Bonacich, 2001], measures
the number of attenuated paths that exist between nodes. We introduce a
normalized version of this metric and use it to study network structure,
specifically, to rank nodes and find community structure of the network.
Specifically, we extend the modularity-maximization method [Newman and Girvan,
2004] for community detection to use this metric as the measure of node
connectivity. Normalized alpha-centrality is a powerful tool for network
analysis, since it contains a tunable parameter that sets the length scale of
interactions. By studying how rankings and discovered communities change when
this parameter is varied allows us to identify locally and globally important
nodes and structures. We apply the proposed method to several benchmark
networks and show that it leads to better insight into network structure than
alternative methods.Comment: 11 pages, submitted to Physical Review
Precoded turbo code within 0.1dB of Shannon limit
The application of the precoding technique to turbo codes is investigated, resulting in a new class of turbo-like codes named precoded turbo codes. The introduction of a precoder provides a degree of freedom for code optimisation. As a result, an optimised rate-1/2 precoded turbo code with a threshold of 0.28 dB is designed using the EXIT chart
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