3,026 research outputs found
The quest for rings on bipolar scales
We consider the interval and intend to endow it with an algebraic structure like a ring. The motivation lies in decision making, where scales that are symmetric w.r.t.~ are needed in order to represent a kind of symmetry in the behaviour of the decision maker. A former proposal due to Grabisch was based on maximum and minimum. In this paper, we propose to build our structure on t-conorms and t-norms, and we relate this construction to uninorms. We show that the only way to build a group is to use strict t-norms, and that there is no way to build a ring. Lastly, we show that the main result of this paper is connected to the theory of ordered Abelian groups.
The Large-scale Bipolar Wind in the Galactic Center
During a 9-month campaign (1996--1997), the Midcourse Space Experiment (MSX)
satellite mapped the Galactic Plane at mid-infrared wavelengths (4.3--21.3um).
Here we report evidence for a spectacular limb- brightened, bipolar structure
at the Galactic Center extending more than a degree (170 pc at 8.0 kpc) on
either side of the plane. The 8.3um emission shows a tight correlation with the
3, 6 and 11 cm continuum structure over the same scales. Dense gas and dust are
being entrained in a large-scale bipolar wind powered by a central starburst.
The inferred energy injection at the source is ~10^54/kappa erg for which
\kappa is the covering fraction of the dusty shell (kappa <= 0.1).
There is observational evidence for a galactic wind on much larger scales,
presumably from the same central source which produced the bipolar shell seen
by MSX. Sofue has argued that the North Polar Spur -- a thermal x-ray/radio
loop which extends from the Galactic Plane to b = +80 deg -- was powered by a
nuclear explosion (1-30 x 10^55 erg) roughly 15 Myr ago. We demonstrate that an
open-ended bipolar wind (~10^55 erg), when viewed in near-field projection,
provides the most natural explanation for the observed loop structure. The
ROSAT 1.5 keV diffuse x-ray map over the inner 45 deg provides compelling
evidence for this interpretation. Since the faint bipolar emission would be
very difficult to detect beyond the Galaxy, the phenomenon of large-scale
galactic winds may be far more common than has been observed to date.Comment: 24 pages, 6 figures, aastex. High resolution figures are available at
ftp://www.aao.gov.au/pub/local/jbh/astro-ph/GC/. Astrophysical Journal,
accepte
Aggregation on bipolar scales
The paper addresses the problem of extending aggregation operators typically defined on to the symmetric interval , where the ``0'' value plays a particular role (neutral value). We distinguish the cases where aggregation operators are associative or not. In the former case, the ``0'' value may play the role of neutral or absorbant element, leading to pseudo-addition and pseudo-multiplication. We address also in this category the special case of minimum and maximum defined on some finite ordinal scale. In the latter case, we find that a general class of extended operators can be defined using an interpolation approach, supposing the value of the aggregation to be known for ternary vectors.bipolar scale; bi-capacity; aggregation
Dusty Blue Supergiants: News from High-Angular Resolution Observations
An overview is presented of the recent advances in understanding the B[e]
phenomenon among blue supergiant stars in light of high-angular resolution
observations and with an emphasis on the results obtained by means of long
baseline optical stellar interferometry. The focus of the review is on the
circumstellar material and evolutionary phase of B[e] supergiants, but recent
results on dust production in regular blue supergiants are also highlighted.Comment: 8 pages, 2 figures. Published in "Advances in Astronomy" by Hindawi
Publishing Corporatio
Molecularly Resolved Electronic Landscapes of Differing Acceptor-Donor Interface Geometries
Organic semiconductors are a promising class of materials for numerous
electronic and optoelectronic applications, including solar cells. However,
these materials tend to be extremely sensitive to the local environment and
surrounding molecular geometry, causing the energy levels near boundaries and
interfaces essential to device function to differ from those of the bulk.
Scanning Tunneling Microscopy and Spectroscopy (STM/STS) has the ability to
examine both the structural and electronic properties of these interfaces on
the molecular and submolecular scale. Here we investigate the prototypical
acceptor/donor system PTCDA/CuPc using sub-molecularly resolved pixel-by-pixel
STS to demonstrate the importance of subtle changes in interface geometry in
prototypical solar cell materials. PTCDA and CuPc were sequentially deposited
on NaCl bilayers to create lateral heterojunctions that were decoupled from the
underlying substrate. Donor and acceptor states were observed to shift in
opposite directions suggesting an equilibrium charge transfer between the two.
Narrowing of the gap energy compared to isolated molecules on the same surface
are indicative of the influence of the local dielectric environment. Further,
we find that the electronic state energies of both acceptor and donor are
strongly dependent on the ratio and positioning of both molecules in larger
clusters. This molecular-scale structural dependence of the electronic states
of both interfacial acceptor and donor has significant implications for device
design where level alignment strongly correlates to device performance
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