15,985 research outputs found

    Fluidized combustion of coal

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    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

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    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

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    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

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    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 D6D\ge 6.) 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

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    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

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    We present three families of exact, cohomogeneity-one Einstein metrics in (2n+2)(2n+2) 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 CPn+1CP^{n+1}, written in a Stenzel form, whose principal orbits are the Stiefel manifolds V2(Rn+2)=SO(n+2)/SO(n)V_2(R ^{n+2})=SO(n+2)/SO(n) divided by Z2Z_2. The second family are also Einstein-K\"ahler metrics, now on the Grassmannian manifolds G2(Rn+3)=SO(n+3)/((SO(n+1)×SO(2))G_2(R^{n+3})=SO(n+3)/((SO(n+1)\times SO(2)), whose principal orbits are the Stiefel manifolds V2(Rn+2)V_2(R^{n+2}) (with no Z2Z_2 factoring in this case). The third family are Einstein metrics on the product manifolds Sn+1×Sn+1S^{n+1}\times S^{n+1}, and are K\"ahler only for n=1n=1. 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 CPn+1CP^{n+1}, 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

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    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

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    Design and development testing of 60 kW alternator for SNAP
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