Fabrication and evaluation of advanced titanium and composite structural panels

Advanced manufacturing methods for titanium and composite material structures are being developed and evaluated. The focus for the manufacturing effort is the fabrication of full-scale structural panels which replace an existing shear panel on the upper wing surface of the NASA YF-12 aircraft. The program involves design, fabrication, ground testing, and Mach 3 flight service of full-scale structural panels and laboratory testing of representative structural element specimens

Random Walks and Market Efficiency: Evidence from International Real Estate Markets

This study performs tests of the random walk hypothesis for international commercial real estate markets utilizing stock market indices of real estate share prices for three geographical regions: Europe, Asia and North America. The augmented Dickey-Fuller and Phillips-Perron unit root tests and Cochrane variance ratio test find that each of these markets (as well as associated broader stock markets) exhibits random walk behavior. Moreover, a non-parametric runs test provides support for weak-form market efficiency in the real estate markets. In addition, Johansen-Juselius co-integration analysis reveals that all three markets appear co-integrated and share a common long-run stochastic trend. Results of co-integration analyses and vector error correction models suggest that diversification benefits through international real estate securities can only be achieved in the short run.

Radio Recombination Lines at Decametre Wavelengths: Prospects for the Future

This paper considers the suitability of a number of emerging and future instruments for the study of radio recombination lines (RRLs) at frequencies below 200 MHz. These lines arise only in low-density regions of the ionized interstellar medium, and they may represent a frequency-dependent foreground for next-generation experiments trying to detect H I signals from the Epoch of Reionization and Dark Ages ("21-cm cosmology"). We summarize existing decametre-wavelength observations of RRLs, which have detected only carbon RRLs. We then show that, for an interferometric array, the primary instrumental factor limiting detection and study of the RRLs is the areal filling factor of the array. We consider the Long Wavelength Array (LWA-1), the LOw Frequency ARray (LOFAR), the low-frequency component of the Square Kilometre Array (SKA-lo), and a future Lunar Radio Array (LRA), all of which will operate at decametre wavelengths. These arrays offer digital signal processing, which should produce more stable and better defined spectral bandpasses; larger frequency tuning ranges; and better angular resolution than that of the previous generation of instruments that have been used in the past for RRL observations. Detecting Galactic carbon RRLs, with optical depths at the level of 10^-3, appears feasible for all of these arrays, with integration times of no more than 100 hr. The SKA-lo and LRA, and the LWA-1 and LOFAR at the lowest frequencies, should have a high enough filling factor to detect lines with much lower optical depths, of order 10^-4 in a few hundred hours. The amount of RRL-hosting gas present in the Galaxy at the high Galactic latitudes likely to be targeted in 21-cm cosmology studies is currently unknown. If present, however, the spectral fluctuations from RRLs could be comparable to or exceed the anticipated H I signals.Comment: 9 pages; Astron. & Astrophys., in pres

General implementation of all possible positive-operator-value measurements of single photon polarization states

Positive Operator Value Measures (POVMs) are the most general class of quantum measurements. We propose a setup in which all possible POVMs of a single photon polarization state (corresponding to all possible sets of two-dimensional Kraus operators) can be implemented easily using linear optics elements. This method makes it possible to experimentally realize any projective orthogonal, projective non-orthogonal or non-projective sets of any number of POVM operators. Furthermore our implementation only requires vacuum ancillas, and is deterministic rather than probabilistic. Thus it realizes every POVM with the correct set of output states. We give the settings required to implement two different well-known non-orthogonal projective POVMs.Comment: 5 pages, newer version with minor addition

Semiclassical theory of magnetotransport through a chaotic quantum well

We develop a quantitative semiclassical formula for the resonant tunneling current through a quantum well in a tilted magnetic field. It is shown that the current depends only on periodic orbits within the quantum well. The theory explains the puzzling evolution of the tunneling spectra near a tilt angle of $30^{\circ}$ as arising from an exchange bifurcation of the relevant periodic orbits.Comment: 4 pages, RevTeX, epsf, 2 PostScript Figures (1 with color

An Empirically Derived Three-Dimensional Laplace Resonance in the Gliese 876 Planetary System

We report constraints on the three-dimensional orbital architecture for all four planets known to orbit the nearby M dwarf Gliese 876 based solely on Doppler measurements and demanding long-term orbital stability. Our dataset incorporates publicly available radial velocities taken with the ELODIE and CORALIE spectrographs, HARPS, and Keck HIRES as well as previously unpublished HIRES velocities. We first quantitatively assess the validity of the planets thought to orbit GJ 876 by computing the Bayes factors for a variety of different coplanar models using an importance sampling algorithm. We find that a four-planet model is preferred over a three-planet model. Next, we apply a Newtonian MCMC algorithm to perform a Bayesian analysis of the planet masses and orbits using an n-body model in three-dimensional space. Based on the radial velocities alone, we find that a 99% credible interval provides upper limits on the mutual inclinations for the three resonant planets ($\Phi_{cb}<6.20^\circ$ for the "c" and "b" pair and $\Phi_{be}<28.5^\circ$ for the "b" and "e" pair). Subsequent dynamical integrations of our posterior sample find that the GJ 876 planets must be roughly coplanar ($\Phi_{cb}<2.60^\circ$ and $\Phi_{be}<7.87^\circ$), suggesting the amount of planet-planet scattering in the system has been low. We investigate the distribution of the respective resonant arguments of each planet pair and find that at least one argument for each planet pair and the Laplace argument librate. The libration amplitudes in our three-dimensional orbital model supports the idea of the outer-three planets having undergone significant past disk migration.Comment: 19 pages, 11 figures, 8 tables. Accepted to MNRAS. Posterior samples available at https://github.com/benelson/GJ87

The 55 Cancri Planetary System: Fully Self-Consistent N-body Constraints and a Dynamical Analysis

We present an updated study of the planets known to orbit 55 Cancri A using 1,418 high-precision radial velocity observations from four observatories (Lick, Keck, Hobby-Eberly Telescope, Harlan J. Smith Telescope) and transit time/durations for the inner-most planet, 55 Cancri "e" (Winn et al. 2011). We provide the first posterior sample for the masses and orbital parameters based on self-consistent n-body orbital solutions for the 55 Cancri planets, all of which are dynamically stable (for at least $10^8$ years). We apply a GPU version of Radial velocity Using N-body Differential evolution Markov Chain Monte Carlo (RUN DMC; B. Nelson et al. 2014) to perform a Bayesian analysis of the radial velocity and transit observations. Each of the planets in this remarkable system has unique characteristics. Our investigation of high-cadence radial velocities and priors based on space-based photometry yields an updated mass estimate for planet "e" ($8.09\pm0.26$ M$_\oplus$), which affects its density ($5.51\pm^{1.32}_{1.00}$ g cm$^{-3}$) and inferred bulk composition. Dynamical stability dictates that the orbital plane of planet "e" must be aligned to within $60^o$ of the orbital plane of the outer planets (which we assume to be coplanar). The mutual interactions between the planets "b" and "c" may develop an apsidal lock about $180^o$. We find 36-45% of all our model systems librate about the anti-aligned configuration with an amplitude of $51^o\pm^{6^o}_{10^o}$. Other cases showed short-term perturbations in the libration of $\varpi_b-\varpi_c$, circulation, and nodding, but we find the planets are not in a 3:1 mean-motion resonance. A revised orbital period and eccentricity for planet "d" pushes it further toward the closest known Jupiter analog in the exoplanet population.Comment: 12 pages, 5 figures, 4 tables, accepted to MNRAS. Figure 2 (left) is updated from published version. Posterior samples available at http://www.personal.psu.edu/ben125/Downloads.htm