14,913 research outputs found
The Shape of Australian Real Estate Return Distributions and Comparisons to the United States
Investment risk models with variance provide a better description of distribution of individual property returns in the Property Council of Australia data base from 1985 to 1996 than normally distributed risk models. The shape of the distribution of Australian property returns is virtually indistinguishable from the shape of United States property returns in the NCREIF Property Index for the years 1980 to 1992. Australian real estate investment risk is heteroscedastic, like its US counterpart, but the characteristic exponent of the investment risk function is constant across time and property type. It follows that portfolio management and asset diversification techniques that rely upon finite-variance statistics are as ineffectual for the Australian real estate market as they have been found to be for the United States.
Thrust performance of isolated 36-chute suppressor plug nozzles with and without ejectors at Mach numbers from 0 to 0.45
Plug nozzles with chute-type noise suppressors were tested with and without ejector shrouds at free-stream Mach numbers from 0 to 0.45 and over a range of nozzle pressure ratios from 2 to 4. A 36-chute suppressor nozzle with an ejector had an efficiency of 94.6 percent at an assumed takeoff pressure ratio of 3.0 and a Mach number of 0.36. This represents only a 3.4 percent performance penalty when compared with the 98 percent efficiency obtained with a previously tested unsuppressed plug nozzle
Dynamics of Surface Roughening with Quenched Disorder
We study the dynamical exponent for the directed percolation depinning
(DPD) class of models for surface roughening in the presence of quenched
disorder. We argue that for dimensions is equal to the exponent
characterizing the shortest path between two sites in an
isotropic percolation cluster in dimensions. To test the argument, we
perform simulations and calculate for DPD, and for
percolation, from to .Comment: RevTex manuscript 3 pages + 6 figures (obtained upon request via
email [email protected]
Thrust performance of isolated, two-dimensional suppressed plug nozzles with and without ejectors at Mach numbers from 0 to 0.45
A series of two-dimensional plug nozzles was tested with and without ejector shrouds at free stream Mach numbers from 0 to 0.45 and over a range of nozzle pressure ratios from 2 to 4. These nozzles were also tested with and without chute noise suppressors. A two-dimensional plug nozzle has an efficiency of 96.1 percent at an assumed takeoff pressure ratio of 3.0 and Mach 0.36. A 12-chute suppressed nozzle with sidewalls has an efficiency of 81.0 percent (15.1 percent below the unsuppressed nozzle)
Calorons and BPS monopoles with non-trivial holonomy in the confinement phase of SU(2) gluodynamics
With the help of the cooling method applied to SU(2) lattice gauge theory at
non-zero we present numerical evidence for the existence of
superpositions of Kraan-van Baal caloron (or BPS monopole pair) solutions with
non-trivial holonomy, which might constitute an important contribution to the
semi-classical approximation of the partition function.Comment: 3 pages, 6 figures, contribution to Lattice2002(topology
Monte Carlo Simulation of Lyman Alpha Scattering and Application to Damped Lyman Alpha Systems
A Monte Carlo code to solve the transfer of Lyman alpha (Lya) photons is
developed, which can predict the Lya image and two-dimensional Lya spectra of a
hydrogen cloud with any given geometry, Lya emissivity, neutral hydrogen
density distribution, and bulk velocity field. We apply the code to several
simple cases of a uniform cloud to show how the Lya image and emitted line
spectrum are affected by the column density, internal velocity gradients, and
emissivity distribution. We then apply the code to two models for damped Lya
absorption systems: a spherical, static, isothermal cloud, and a flattened,
axially symmetric, rotating cloud. If the emission is due to fluorescence of
the external background radiation, the Lya image should have a core
corresponding to the region where hydrogen is self-shielded. The emission line
profile has the characteristic double peak with a deep central trough. We show
how rotation of the cloud causes the two peaks to shift in wavelength as the
slit is perpendicular to the rotation axis, and how the relative amplitude of
the two peaks is changed. In reality, damped Lya systems are likely to have a
clumpy gas distribution with turbulent velocity fields, which should smooth the
line emission profile, but should still leave the rotation signature of the
wavelength shift across the system.Comment: 19 pages, 17 eps figures. One panel is added in Fig.1 to show the
recoil effect. Revisions are made in response to the referee's comments.
Accepted for publication in Ap
On Characterizing Spector Classes
We study in this paper characterizations of various interesting classes of relations arising in recursion theory. We first determine which Spector classes on the structure of arithmetic arise from recursion in normal type 2 objects, giving a partial answer to a problem raised by Moschovakis [8], where the notion of Spector class was first
essentially introduced. Our result here was independently discovered by S. G. Simpson (see [3]). We conclude our study of Spector classes by examining two simple relations between them and a natural hierarchy to which they give rise
A Basis Result for Σ^0_3 Sets of Reals with an Application to Minimal Covers
It is shown that every ∑^0_3 set of reals which contains reals of arbitrarily high Turing degree in the hyperarithmetic hierarchy contains reals of every Turing degree above the degree of Kleene's O. As an application it is shown that every Turing degree above the Turing degree of Kleene's O is a minimal cover
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