193 research outputs found
NASA Lewis H2-O2 MHD program
Performance and power costs of H2-O2 combustion powered steam-MHD central power systems are estimated. Hydrogen gas is assumed to be transmitted by pipe from a remote coal gasifier into the city and converted to electricity in a steam MHD plant having an integral gaseous oxygen plant. These steam MHD systems appear to offer an attractive alternative to both in-city clean fueled conventional steam power plants and to remote coal fired power plants with underground electric transmission into the city. Status and plans are outlined for an experimental evaluation of H2-O2 combustion-driven MHD power generators at NASA Lewis Research Center
H2-O2 combustion powered steam-MHD central power systems
Estimates are made for both the performance and the power costs of H2-O2 combustion powered steam-MHD central power systems. Hydrogen gas is assumed to be transmitted by pipe from a remote coal gasifier into the city and converted to electricity in a steam MHD plant having an integral gaseous oxygen plant. These steam MHD systems appear to offer an attractive alternative to both in-city clean fueled conventional steam power plants and to remote coal fired power plants with underground electric transmission into the city
Light bulb heat exchanger for magnetohydrodynamic generator applications - Preliminary evaluation
The light-bulb heat-exchanger concept is investigated as a possible means of using a combustion heat source to supply energy to an inert gas MHD power generator system. In this concept, combustion gases flow through a central passage which consists of a duct with transparent walls through which heat is transferred by radiation to a radiation receiver which in turn heats the inert gas by convection. The effects of combustion-gas emissivity, transparent-wall-transmissivity, radiation-receiver emissivity, and the use of fins in the inert gas coolant passage are studied. The results indicate that inert gas outlet temperatures of 2500 K are possible for combustion temperatures of 3200 K and that sufficient energy can be transferred from the combustion gas to reduce its temperature to approximately 2000 K. At this temperature more conventional heat exchangers can be used
Braneworlds with timelike extra-dimension
In this work, we consider a braneworld model with a timelike extra-dimension.
There are strong constraints to the parameter values of such a model resulting
from the claim that there must be a physical solution to the Friedmann equation
at least between now and the time of recombination. We fitted the model to
supernova type Ia data and checked the consistency of the result with other
observations. For parameter values that are consistent with observations, the
braneworld model is indistinguishable from a LambdaCDM universe as far as the
considered cosmological tests are concerned.Comment: 7 pages, 8 figures, matches version accepted by Phys. Rev.
Performance optimization of an MHD generator with physical constraints
A method to optimize the Faraday MHD generator performance under a prescribed set of electrical and magnet constraints is described. The results of generator performance calculations using this technique are presented for a very large MHD/steam plant. The differences between the maximum power and maximum net power generators are described. The sensitivity of the generator performance to the various operational parameters are presented
Bayesian model-independent evaluation of expansion rates of the universe
Marginal likelihoods for the cosmic expansion rates are evaluated using the
`Constitution' data of 397 supernovas, thereby updating the results in some
previous works. Even when beginning with a very strong prior probability that
favors an accelerated expansion, we obtain a marginal likelihood for the
deceleration parameter peaked around zero in the spatially flat case. It
is also found that the new data significantly constrains the cosmographic
expansion rates, when compared to the previous analyses. These results may
strongly depend on the Gaussian prior probability distribution chosen for the
Hubble parameter represented by , with . This and similar
priors for other expansion rates were deduced from previous data. Here again we
perform the Bayesian model-independent analysis in which the scale factor is
expanded into a Taylor series in time about the present epoch. Unlike such
Taylor expansions in terms of redshift, this approach has no convergence
problem.Comment: To appear in Astrophysics and Space Scienc
Field-Testing Reusable Learning Objects Related to Sensory Over-Responsiveness
Background. There is an increased need for dynamic, mobile, and relevant parent and caregiver education related to autism spectrum disorders (ASD) and Sensory Processing (SP). This need may be due to the increased incidence of the conditions’ co-morbidity and the revision of the diagnostic criteria of ASD. Reusable learning objects (RLOs) have been implemented as instructional tools as a part of, or adjunct to, formal health care education programs. However, there is a lack of knowledge regarding the appropriateness of RLOs as a part of routine patient and caregiver instruction of children with ASD.
Method. A semi-structured interview/rating scale was implemented among three practicing occupational therapists to ascertain their opinions regarding six prototype RLOs related to sensory processing for caregivers of children with ASD.
Results. The participants’ perspectives revealed that the SP-based prototype RLOs were a viable and valuable option to be included as a resource for parents and caregivers of children with ASD.
Conclusion. The findings of this study suggest that RLOs related to SP were valuable, especially related to their subject matter, accessibility, and reusability. Furthermore, the participants indirectly identified the strengths related to the foundational concepts of RLOs and how they could be applied to other therapeutic and behavioral topics for parents and caregivers of children with ASD
Model- and calibration-independent test of cosmic acceleration
We present a calibration-independent test of the accelerated expansion of the
universe using supernova type Ia data. The test is also model-independent in
the sense that no assumptions about the content of the universe or about the
parameterization of the deceleration parameter are made and that it does not
assume any dynamical equations of motion. Yet, the test assumes the universe
and the distribution of supernovae to be statistically homogeneous and
isotropic. A significant reduction of systematic effects, as compared to our
previous, calibration-dependent test, is achieved. Accelerated expansion is
detected at significant level (4.3 sigma in the 2007 Gold sample, 7.2 sigma in
the 2008 Union sample) if the universe is spatially flat. This result depends,
however, crucially on supernovae with a redshift smaller than 0.1, for which
the assumption of statistical isotropy and homogeneity is less well
established.Comment: 13 pages, 2 figures, major change
A summary of the ECAS performance and cost results for MHD systems
The potential is examined of various advanced power plant concepts using coal and coal-derived fuel. The results indicate that open cycle coal fired direct preheat MHD systems have potentially one of the highest coal-pile-to-bus-bar efficiencies and also one of the lowest costs of electricity (COE) of the systems studied. Closed cycle MHD systems may have the potential to approach the efficiency and COE of open cycle MHD. The 1200-1500 F liquid metal MHD systems studied do not appear to have the potential of exceeding the efficiency or competing with the COE of advanced steam plants
Generalized Fisher matrices
16.04.15 KB Ok to add accepted version to spira
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