1,835 research outputs found
Potential markets for a satellite-based mobile communications system
The objective of the study was to define the market needs for improved land mobile communications systems. Within the context of this objective, the following goals were set: (1) characterize the present mobile communications industry; (2) determine the market for an improved system for mobile communications; and (3) define the system requirements as seen from the potential customer's viewpoint. The scope of the study was defined by the following parameters: (1) markets were confined to U.S. and Canada; (2) range of operation generally exceeded 20 miles, but this was not restrictive; (3) the classes of potential users considered included all private sector users, and non-military public sector users; (4) the time span examined was 1975 to 1985; and (5) highly localized users were generally excluded - e.g., taxicabs, and local paging
Using Online Program Development to Foster Curricular Change and Innovation
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153766/1/jddj002203372011753tb05047x.pd
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Fighting HIV/AIDS: Reconfiguring the State?
The author wishes to thank the anonymous reviewers of the article and the ESRC for funding part of this research
The Entropy of 4D Black Holes and the Enhancon
We consider the physics of enhancons as applied to four dimensional black
holes which are constructed by wrapping both D-branes and NS-branes on K3. As
was recently shown for the five dimensional black holes, the enhancon is
crucial in maintaining consistency with the second law of thermodynamics. This
is true for both the D-brane and NS-brane sectors of these black holes. In
particular NS5-branes in both type IIA and IIB string theory are found to
exhibit enhancon physics when wrapped on a K3 manifold.Comment: 23 pages. 1 figure. Minor typos corrected. Refs added. To appear in
PR
Tachyon Hair on Two-Dimensional Black Holes
Static black holes in two-dimensional string theory can carry tachyon hair.
Configurations which are non-singular at the event horizon have non-vanishing
asymptotic energy density. Such solutions can be smoothly extended through the
event horizon and have non-vanishing energy flux emerging from the past
singularity. Dynamical processes will not change the amount of tachyon hair on
a black hole. In particular, there will be no tachyon hair on a black hole
formed in gravitational collapse if the initial geometry is the linear dilaton
vacuum. There also exist static solutions with finite total energy, which have
singular event horizons. Simple dynamical arguments suggest that black holes
formed in gravitational collapse will not have tachyon hair of this type.Comment: 11 pages, 1 figure (not included), uses phyzzx, SU-ITP-93-1
Brane Baldness vs. Superselection Sectors
The search for intersecting brane solutions in supergravity is a large and
profitable industry. Recently, attention has focused on finding localized forms
of known `delocalized' solutions. However, in some cases, a localized version
of the delocalized solution simply does not exist. Instead, localized separated
branes necessarily delocalize as the separation is removed. This phenomenon is
related to black hole no-hair theorems, i.e. `baldness.' We continue the
discussion of this effect and describe how it can be understood, in the case of
Dirichlet branes, in terms of the corresponding intersection field theory. When
it occurs, it is associated with the quantum mixing of phases and lack of
superselection sectors in low dimensional field theories. We find surprisingly
wide agreement between the field theory and supergravity both with respect to
which examples delocalize and with respect to the rate at which this occurs.Comment: 26 pages, ReVTeX, 2 figures, reference added, version to appear in
PR
Het voeren van gemalen en geplette tarwe aan vleesvarkens
Vervanging van 10% van het vleesvarkensvoer door gemalen of geplette tarwe heeft geen effect op de technische resultaten van vleesvarkens. Vervanging van 40% van het vleesvarkensvoer door gemalen tarwe verslechtert de groei en voederconversie in het laatste deel van het mesterijtraject
Quantum Black Hole Evaporation
We investigate a recently proposed model for a full quantum description of
two-dimensional black hole evaporation, in which a reflecting boundary
condition is imposed in the strong coupling region. It is shown that in this
model each initial state is mapped to a well-defined asymptotic out-state,
provided one performs a certain projection in the gravitational zero mode
sector. We find that for an incoming localized energy pulse, the corresponding
out-going state contains approximately thermal radiation, in accordance with
semi-classical predictions. In addition, our model allows for certain acausal
strong coupling effects near the singularity, that give rise to corrections to
the Hawking spectrum and restore the coherence of the out-state. To an
asymptotic observer these corrections appear to originate from behind the
receding apparent horizon and start to influence the out-going state long
before the black hole has emitted most of its mass. Finally, by putting the
system in a finite box, we are able to derive some algebraic properties of the
scattering matrix and prove that the final state contains all initial
information.Comment: 37 pages (figs 2 and 3 included as uuencoded compressed tar file),
Latex, needs epsf.tex, PUPT-1395, IASSNS-HEP-93/25 (revised version has minor
corrections, one reference added
Het bijvoeren van geplette en gestructureerde tarwe aan vleesvarkens
Vervanging van 25% en 50% van het vleesvarkensvoer door geplette of gestructureerde tarwe in respectievelijk de startfase en afmestfase geeft een ongunstigere energieconversie dan voeren van volledig mengvoer
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