1,485 research outputs found
A statistical model for the excitation of cavities through apertures
In this paper, a statistical model for the coupling of electromagnetic
radiation into enclosures through apertures is presented. The model gives a
unified picture bridging deterministic theories of aperture radiation, and
statistical models necessary for capturing the properties of irregular shaped
enclosures. A Monte Carlo technique based on random matrix theory is used to
predict and study the power transmitted through the aperture into the
enclosure. Universal behavior of the net power entering the aperture is found.
Results are of interest for predicting the coupling of external radiation
through openings in irregular enclosures and reverberation chambers.Comment: 12 pages, 11 figures, in press, IEEE Transactions on Electromagnetic
Compatibilit
ON DEMAND: CROSS-COUNTRY EVIDENCE FROM COMMERCIAL REAL ESTATE ASSET MARKETS
Using over 25 years of quarterly U.S. and Japanese time series data, this paper examines the determinants of demand for an important class of real assets: commercial real estate. We specify a structural model of market equilibrium that considers direct effects of real investment on built asset price. Our empirical findings are consistent across countries and produce several new results. First, we find that real investment exerts a significant positive direct effect on asset price, which in turn feeds back to impact investment decisions. Second, idiosyncratic risk is found to be strongly positively related to asset price, and to complement supply effects. Third, systematic risk is priced as expected, where the strength of the relation between asset price and systematic risk is found to be higher than in previous studies of capital asset prices. Fourth, lagged values of price determinants (of up to two years) are consistently important in real asset demand estimation. Alternative explanations for our findings are analyzed and discussed. Implications for asset pricing model specification and interpretation are also considered.equity REIT; IPO; interest-rate sensitivity; risk-adjusted return performance
Sensing Small Changes in a Wave Chaotic Scattering System
Classical analogs of the quantum mechanical concepts of the Loschmidt Echo
and quantum fidelity are developed with the goal of detecting small
perturbations in a closed wave chaotic region. Sensing techniques that employ a
one-recording-channel time-reversal-mirror, which in turn relies on time
reversal invariance and spatial reciprocity of the classical wave equation, are
introduced. In analogy with quantum fidelity, we employ Scattering Fidelity
techniques which work by comparing response signals of the scattering region,
by means of cross correlation and mutual information of signals. The
performance of the sensing techniques is compared for various perturbations
induced experimentally in an acoustic resonant cavity. The acoustic signals are
parametrically processed to mitigate the effect of dissipation and to vary the
spatial diversity of the sensing schemes. In addition to static boundary
condition perturbations at specified locations, perturbations to the medium of
wave propagation are shown to be detectable, opening up various real world
sensing applications in which a false negative cannot be tolerated.Comment: 14 pages, 11 figures, as published on J. Appl. Phy
A Systematic Survey of the Effects of Wind Mass Loss Algorithms on the Evolution of Single Massive Stars
Mass loss is a key uncertainty in the evolution of massive stars. Stellar
evolution calculations must employ parametric algorithms for mass loss, and
usually only include stellar winds. We carry out a parameter study of the
effects of wind mass loss on massive star evolution using the open-source
stellar evolution code MESA. We provide a systematic comparison of wind mass
loss algorithms for solar-metallicity, nonrotating, single stars in the initial
mass range of . We consider combinations drawn from two hot
phase algorithms, three cool phase algorithms, and two Wolf-Rayet algorithms.
We consider linear wind efficiency scale factors of , , and to
account for reductions in mass loss rates due to wind inhomogeneities. We find
that the initial to final mass mapping for each zero-age main-sequence (ZAMS)
mass has a uncertainty if all algorithm combinations and wind
efficiencies are considered. The ad-hoc efficiency scale factor dominates this
uncertainty. While the final total mass and internal structure of our models
vary tremendously with mass loss treatment, final observable parameters are
much less sensitive for ZAMS mass . This indicates that
uncertainty in wind mass loss does not negatively affect estimates of the ZAMS
mass of most single-star supernova progenitors from pre-explosion observations.
Furthermore, we show that the internal structure of presupernova stars is
sensitive to variations in both main sequence and post main-sequence mass loss.
We find that the compactness parameter varies by as much as
for a given ZAMS mass evolved with different wind efficiencies and mass
loss algorithm combinations. [abridged]Comment: Accepted for publication on A&A, 22 pages + 2 appendixes, 12 figures,
online input parameters available at https://stellarcollapse.org/renzo2017
and data at https://zenodo.org/record/292924#.WK0q2tWi6W
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