25,686 research outputs found
Feasibility study of inlet shock stability system of YF-12
The feasibility of self actuating bleed valves as a shock stabilization system in the inlet of the YF-12 is considered for vortex valves, slide valves, and poppet valves. Analytical estimation of valve performance indicates that only the slide and poppet valves located in the inlet cowl can meet the desired steady state stabilizing flows, and of the two the poppet valve is substantially faster in response to dynamic disturbances. The poppet valve is, therefore, selected as the best shock stability system for the YF-12 inlet
Structural Modeling of Marine Reserves with Bayesian Estimation
Structural models can assess the effectiveness of fishery management prospectively and retrospectively. However, when only fishery-dependent data are available, structural econometric models are highly nonlinear in the parameters, and maximum likelihood and other extremum-based estimators can fail to converge. As a solution to these estimation challenges, we adapt Bayesian econometric methods to estimate a dynamic structural model of marine reserve formation. Using simulated data, we find that our approach is able to recover structural biological and economic parameters that classical estimation procedures fail to recover. We apply the approach to real data from the Gulf of Mexico reef-fish fishery. We test the effects of the Steamboat Lumps Marine Reserve on population growth and catchability for gag, a species of grouper. We find that after four years, the reserve has neither produced statistically significant losses in sustainable yield nor statistically significant gains in biological production.Marine reserves, marine protected areas, Bayesian econometrics, Markov Chain Monte Carlo, Environmental Economics and Policy, C11, Q22,
Bayesian Bioeconomics of Marine Reserves
We use Bayesian econometric methods to estimate dynamic bioeconomic models of marine reserve formation using simulated data and real data from the Gulf of Mexico reef fish fishery. We test the effects of reserves on fish growth and catchability.Resource /Energy Economics and Policy,
Two-fluid behavior of the Kondo lattice in the 1/N slave boson approach
It has been recently shown by Nakatsuji, Pines, and Fisk [S. Nakatsuji, D.
Pines, and Z. Fisk, Phys. Rev. Lett. 92, 016401 (2004)] from the
phenomenological analysis of experiments in Ce1-xLaxCoIn5 and CeIrIn5 that
thermodynamic and transport properties of Kondo lattices below coherence
temperature can be very successfully described in terms of a two-fluid model,
with Kondo impurity and heavy electron Fermi liquid contributions. We analyze
thermodynamic properties of Kondo lattices using 1/N slave boson treatment of
the periodic Anderson model and show that these two contributions indeed arise
below the coherence temperature. We find that the Kondo impurity contribution
to thermodynamics corresponds to thermal excitations into the flat portion of
the energy spectrum.Comment: 7 pages, 2 figure
Growth of Intermediate-Mass Black Holes in Globular Clusters
We present results of numerical simulations of sequences of binary-single
scattering events of black holes in dense stellar environments. The simulations
cover a wide range of mass ratios from equal mass objects to 1000:10:10 solar
masses and compare purely Newtonian simulations to simulations in which
Newtonian encounters are interspersed with gravitational wave emission from the
binary. In both cases, the sequence is terminated when the binary's merger time
due to gravitational radiation is less than the arrival time of the next
interloper. We find that black hole binaries typically merge with a very high
eccentricity (0.93 < e < 0.95 pure Newtonian; 0.85 < e < 0.90 with
gravitational wave emission) and that adding gravitational wave emission
decreases the time to harden a binary until merger by ~ 30% to 40%. We discuss
the implications of this work for the formation of intermediate-mass black
holes and gravitational wave detection.Comment: 28 pages including 9 figures, submitted to Ap
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Continued evaluation of potential for geologic storage of carbon dioxide in the southeastern United States
Southern States Energy Board
Duke Energy
Santee Cooper Power
Southern CompanyBureau of Economic Geolog
Atomic Model of Susy Hubbard Operators
We apply the recently proposed susy Hubbard operators to an atomic model. In
the limiting case of free spins, we derive exact results for the entropy which
are compared with a mean field + gaussian corrections description. We show how
these results can be extended to the case of charge fluctuations and calculate
exact results for the partition function, free energy and heat capacity of an
atomic model for some simple examples. Wavefunctions of possible states are
listed. We compare the accuracy of large N expansions of the susy spin
operators with those obtained using `Schwinger bosons' and `Abrikosov
pseudo-fermions'. For the atomic model, we compare results of slave boson,
slave fermion, and susy Hubbard operator approximations in the physically
interesting but uncontrolled limiting case of N->2. For a mixed representation
of spins we estimate the accuracy of large N expansions of the atomic model. In
the single box limit, we find that the lowest energy saddle-point solution
reduces to simply either slave bosons or slave fermions, while for higher boxes
this is not the case. The highest energy saddle-point solution has the
interesting feature that it admits a small region of a mixed representation,
which bears a superficial resemblance to that seen experimentally close to an
antiferromagnetic quantum critical point.Comment: 17 pages + 7 pages Appendices, 14 figures. Substantial revision
What can we learn from Dijet suppression at RHIC?
We present a systematic study of the dijet suppression at RHIC using the
VNI/BMS parton cascade. We examine the modification of the dijet asymmetry A_j
and the within-cone transverse energy distribution (jet-shape) along with
partonic fragmentation distributions z and j_t in terms of: qhat; the path
length of leading and sub-leading jets; cuts on the jet energy distributions;
jet cone angle and the jet-medium interaction mechanism. We find that A_j is
most sensitive to qhat and relatively insensitive to the nature of the
jet-medium interaction mechanism. The jet profile is dominated by qhat and the
nature of the interaction mechanism. The partonic fragmentation distributions
clearly show the jet modification and differentiate between elastic and
radiative+elastic modes
Design of experiments for non-manufacturing processes : benefits, challenges and some examples
Design of Experiments (DoE) is a powerful technique for process optimization that has been widely deployed in almost all types of manufacturing processes and is used extensively in product and process design and development. There have not been as many efforts to apply powerful quality improvement techniques such as DoE to improve non-manufacturing processes. Factor levels often involve changing the way people work and so have to be handled carefully. It is even more important to get everyone working as a team. This paper explores the benefits and challenges in the application of DoE in non-manufacturing contexts. The viewpoints regarding the benefits and challenges of DoE in the non-manufacturing arena are gathered from a number of leading academics and practitioners in the field. The paper also makes an attempt to demystify the fact that DoE is not just applicable to manufacturing industries; rather it is equally applicable to non-manufacturing processes within manufacturing companies. The last part of the paper illustrates some case examples showing the power of the technique in non-manufacturing environments
General Solutions for Tunneling of Scalar Fields with Quartic Potentials in de Sitter Space
The tunneling rates for scalar fields with quartic potentials in de Sitter
space in the limit of no gravitational back reaction are calculated numerically
and the results are fitted by analytic formulae.Comment: (Contours in Figure 1 corrected, two-dimensional fitting coefficient
corrected, references added.), 16 pages, KUNS 124
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