15,985 research outputs found
Fluidized combustion of coal
A combustion technology that permits the burning of low quality coal, and other fuels, while maintaining stack emissions within State and Federal EPA limits is discussed. Low quality fuels can be burned directly in fluidized beds while taking advantage of low furnace temperatures and chemical activity within the bed to limit SO2 and NOx emissions. The excellent heat transfer characteristics of the fluidized beds also result in a reduction of total heat transfer surface requirements. Tests on beds operating at pressures of one to ten atmospheres, at temperatures as high as 1600 F, and with gas velocities in the vicinity of four to twelve feet per second, have proven the concept. The progress that has been made in the development of fluidized bed combustion technology and work currently underway are discussed
Protective encapsulation of implantable biotelemetry units
Development of materials for encapsulating electronic devices used in biotelemetry is discussed. Chemical resistance of materials to effects of animal fluids is described. Silicone rubber is recommended as basic material with polymers applied to outer surface for protective coating
Consistent Kaluza-Klein Sphere Reductions
We study the circumstances under which a Kaluza-Klein reduction on an
n-sphere, with a massless truncation that includes all the Yang-Mills fields of
SO(n+1), can be consistent at the full non-linear level. We take as the
starting point a theory comprising a p-form field strength and (possibly) a
dilaton, coupled to gravity in the higher dimension D. We show that aside from
the previously-studied cases with (D,p)=(11,4) and (10,5) (associated with the
S^4 and S^7 reductions of D=11 supergravity, and the S^5 reduction of type IIB
supergravity), the only other possibilities that allow consistent reductions
are for p=2, reduced on S^2, and for p=3, reduced on S^3 or S^{D-3}. We
construct the fully non-linear Kaluza-Klein Ansatze in all these cases. In
particular, we obtain D=3, N=8, SO(8) and D=7, N=2, SO(4) gauged supergravities
from S^7 and S^3 reductions of N=1 supergravity in D=10.Comment: 27 pages, Latex, typo correcte
Entropy-Product Rules for Charged Rotating Black Holes
We study the universal nature of the product of the entropies of all horizons
of charged rotating black holes. We argue, by examining further explicit
examples, that when the maximum number of rotations and/or charges are turned
on, the entropy product is expressed in terms of angular momentum and/or
charges only, which are quantized. (In the case of gauged supergravities, the
entropy product depends on the gauge-coupling constant also.) In two-derivative
gravities, the notion of the "maximum number" of charges can be defined as
being sufficiently many non-zero charges that the Reissner-Nordstrom black hole
arises under an appropriate specialisation of the charges. (The definition can
be relaxed somewhat in charged AdS black holes in .) In
higher-derivative gravity, we use the charged rotating black hole in
Weyl-Maxwell gravity as an example for which the entropy product is still
quantized, but it is expressed in terms of the angular momentum only, with no
dependence on the charge. This suggests that the notion of maximum charges in
higher-derivative gravities requires further understanding.Comment: References added. 24 page
Decoupling Limit, Lens Spaces and Taub-NUT: D=4 Black Hole Microscopics from D=5 Black Holes
We study the space-times of non-extremal intersecting p-brane configurations
in M-theory, where one of the components in the intersection is a ``NUT,'' i.e.
a configuration of the Taub-NUT type. Such a Taub-NUT configuration
corresponds, upon compactification to D=4, to a Gross-Perry-Sorkin (GPS)
monopole. We show that in the decoupling limit of the CFT/AdS correspondence,
the 4-dimensional transverse space of the NUT configuration in D=5 is foliated
by surfaces that are cyclic lens spaces S^3/Z_N, where N is the quantised
monopole charge. By contrast, in D=4 the 3-dimensional transverse space of the
GPS monopole is foliated by 2-spheres. This observation provides a
straightforward interpretation of the microscopics of a D=4 string-theory black
hole, with a GPS monopole as one of its constituents, in terms of the
corresponding D=5 black hole with no monopole. Using the fact that the
near-horizon region of the NUT solution is a lens space, we show that if the
effect of the Kaluza-Klein massive modes is neglected, p-brane configurations
can be obtained from flat space-time by means of a sequence of dimensional
reductions and oxidations, and U-duality transformations.Comment: 22 pages, Late
Compactifications of Deformed Conifolds, Branes and the Geometry of Qubits
We present three families of exact, cohomogeneity-one Einstein metrics in
dimensions, which are generalizations of the Stenzel construction of
Ricci-flat metrics to those with a positive cosmological constant. The first
family of solutions are Fubini-Study metrics on the complex projective spaces
, written in a Stenzel form, whose principal orbits are the Stiefel
manifolds divided by . The second family are
also Einstein-K\"ahler metrics, now on the Grassmannian manifolds
, whose principal orbits are the
Stiefel manifolds (with no factoring in this case). The
third family are Einstein metrics on the product manifolds , and are K\"ahler only for . Some of these metrics are believed
to play a role in studies of consistent string theory compactifications and in
the context of the AdS/CFT correspondence. We also elaborate on the geometric
approach to quantum mechanics based on the K\"ahler geometry of Fubini-Study
metrics on , and we apply the formalism to study the quantum
entanglement of qubits.Comment: 31 page
Charge Carrier Transport in Metal Phthalocyanine Based Disordered Thin Films
The charge carrier transport in metal phthallocyanine based disordered thin
films has been investigated. Charge carrier mobility in these disordered thin
films strongly depends on the electric field and temperature due to hopping
conduction. The applicability of two different Gaussian disorder models has
been compared and evaluated for charge carrier transport using simple
experimental results and based on our extensive analysis, it has been found
that spatial and energetic correlation is important in explaining the
electrical transport in these organic semiconductors
Development of a 60 kW alternator for SNAP-8
Design and development testing of 60 kW alternator for SNAP
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