8,819 research outputs found
Detecting degree symmetries in networks
The surrounding of a vertex in a network can be more or less symmetric. We
derive measures of a specific kind of symmetry of a vertex which we call degree
symmetry -- the property that many paths going out from a vertex have
overlapping degree sequences. These measures are evaluated on artificial and
real networks. Specifically we consider vertices in the human metabolic
network. We also measure the average degree-symmetry coefficient for different
classes of real-world network. We find that most studied examples are weakly
positively degree-symmetric. The exceptions are an airport network (having a
negative degree-symmetry coefficient) and one-mode projections of social
affiliation networks that are rather strongly degree-symmetric
Strong absorption and selective thermal emission from a mid-infrared metamaterial
We demonstrate thin-film metamaterials with resonances in the mid-infrared
wavelength range. Our structures are numerically modeled and experimentally
characterized by reflection and angularly-resolved thermal emission
spectroscopy. We demonstrate strong and controllable absorption resonances
across the mid-infrared wavelength range. In addition, the polarized thermal
emission from these samples is shown to be highly selective and largely
independent of emission angles from normal to 45 degrees. Experimental results
are compared to numerical models with excellent agreement. Such structures hold
promise for large-area, low-cost metamaterial coatings for control of gray- or
black-body thermal signatures, as well as for possible mid-IR sensing
applications.Comment: The following article has been submitted to Appl. Phys. Lett. After
it is published, it will be found at http://apl.aip.org/. 14 pages including
4 figure page
Notes on Automating Stem and Leaf Displays
The stem-and-leaf display is a natural semi-graphic technique to include in statistical computing systems. This paper discusses the choices involved in implementing both automated and flexible versions of the display, develops an algorithm for the automated version, examines various implementation considerations, and presents a set of semi-portable FORTRAN subroutines for producing stem-and-leaf displays.
Cosmology in the Randall-Sundrum Brane World Scenario
The cosmology of the Randall-Sundrum scenario for a positive tension brane in
a 5-D Universe with localized gravity has been studied extensively recently.
Here we extend it to more general situations. We consider the time-dependent
situation where the two sides of the brane are different AdS/Schwarzschild
spaces. We show that the expansion rate in these models during inflation could
be larger than in brane worlds with compactified extra dimensions of fixed
size. The enhanced expansion rate could lead to the production of density
perturbations of substantially larger amplitude.Comment: 11 pages, revte
Social Requirements for Virtual Organization Breeding Environments
The creation of Virtual Breeding Environments (VBE) is a topic which has
received too little attention: in most former works, the existence of the VBE
is either assumed, or is considered as the result of the voluntary,
participatory gathering of a set of candidate companies. In this paper, the
creation of a VBE by a third authority is considered: chambers of commerce, as
organizations whose goal is to promote and facilitate business interests and
activity in the community, could be good candidates for exogenous VBE creators.
During VBE planning, there is a need to specify social requirements for the
VBE. In this paper, SNA metrics are proposed as a way for a VBE planner to
express social requirements for a VBE to be created. Additionally, a set of
social requirements for VO planners, VO brokers, and VBE members are proposed.Comment: 10 pages, 2 figure
Who students interact with? A social network analysis perspective on the use of Twitter in language learning
This paper reports student interaction patterns and self-reported results of using Twitter microblogging environment. The study employs longitudinal probabilistic social network analysis (SNA) to identify the patterns and trends of network dynamics. It is building on earlier works that explore associations of student achievement records with the observed network measures. It integrates gender as an additional variable and reports some relation with interaction patterns. Additionally, the paper reports the results of a questionnaire that enables further discussion on the communication patterns
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