INVESTIGATION OF THE LOW-SUBSONIC STABILITY AND CONTROL CHARACTERISTICS OF A 0.34 -SCALE FREE-FLYING MODEL OF A MODIFIED HALF-CONE REENTRY VEHICLE

Low subsonic stability and control of a 0.34-scale free flying model of a half cone reentry vehicl

Space shuttle nonmetallic materials age life prediction

The chemiluminescence from samples of polybutadiene, Viton, Teflon, Silicone, PL 731 Adhesive, and SP 296 Boron-Epoxy composite was measured at temperatures from 25 to 150 C. Excellent correlations were obtained between chemiluminescence and temperature. These correlations serve to validate accelerated aging tests (at elevated temperatures) designed to predict service life at lower temperatures. In most cases, smooth or linear correlations were obtained between chemiluminescence and physical properties of purified polymer gums, including the tensile strength, viscosity, and loss tangent. The latter is a complex function of certain polymer properties. Data were obtained with far greater ease by the chemiluminescence technique than by the conventional methods of study. The chemiluminescence from the Teflon (Halon) samples was discovered to arise from trace amounts of impurities, which were undetectable by conventional, destructive analysis of the sample

Perceptions of Electability: Candidate (and Voter) Ideology, Race, and Gender

Previous work has shown candidate electability is an important consideration to voters in deciding who to support. However, we do not know what candidate qualities voters consider more electable, especially in the absence of polling information. While scholarship has documented general election penalties for candidates with certain demographic and ideological characteristics, we do not know whether voters actually use these factors when judging electability. Using a conjoint experimental design, we examine how candidate characteristics influence perceptions of candidate electability. We find voters perceive women and minorities as less electable and ideologically extreme candidates as more electable. However, perceptions of electability vary with voter characteristics. Our results indicate that arguments about electability, for many individuals, are based on their own ideological preferences (and to a lesser extent, their identity) rather than systematically viewing candidates with attributes that provide general election advantages as more electable

Poincar\'e Husimi representation of eigenstates in quantum billiards

For the representation of eigenstates on a Poincar\'e section at the boundary of a billiard different variants have been proposed. We compare these Poincar\'e Husimi functions, discuss their properties and based on this select one particularly suited definition. For the mean behaviour of these Poincar\'e Husimi functions an asymptotic expression is derived, including a uniform approximation. We establish the relation between the Poincar\'e Husimi functions and the Husimi function in phase space from which a direct physical interpretation follows. Using this, a quantum ergodicity theorem for the Poincar\'e Husimi functions in the case of ergodic systems is shown.Comment: 17 pages, 5 figures. Figs. 1,2,5 are included in low resolution only. For a version with better resolution see http://www.physik.tu-dresden.de/~baecker

Amplitude dependent frequency, desynchronization, and stabilization in noisy metapopulation dynamics

The enigmatic stability of population oscillations within ecological systems is analyzed. The underlying mechanism is presented in the framework of two interacting species free to migrate between two spatial patches. It is shown that that the combined effects of migration and noise cannot account for the stabilization. The missing ingredient is the dependence of the oscillations' frequency upon their amplitude; with that, noise-induced differences between patches are amplified due to the frequency gradient. Migration among desynchronized regions then stabilizes a "soft" limit cycle in the vicinity of the homogenous manifold. A simple model of diffusively coupled oscillators allows the derivation of quantitative results, like the functional dependence of the desynchronization upon diffusion strength and frequency differences. The oscillations' amplitude is shown to be (almost) noise independent. The results are compared with a numerical integration of the marginally stable Lotka-Volterra equations. An unstable system is extinction-prone for small noise, but stabilizes at larger noise intensity

Internationally trained pharmacists in Great Britain: what do registration data tell us about their recruitment?

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The fundamental solution and Strichartz estimates for the Schr\"odinger equation on flat euclidean cones

We study the Schr\"odinger equation on a flat euclidean cone $\mathbb{R}_+ \times \mathbb{S}^1_\rho$ of cross-sectional radius $\rho > 0$, developing asymptotics for the fundamental solution both in the regime near the cone point and at radial infinity. These asymptotic expansions remain uniform while approaching the intersection of the "geometric front", the part of the solution coming from formal application of the method of images, and the "diffractive front" emerging from the cone tip. As an application, we prove Strichartz estimates for the Schr\"odinger propagator on this class of cones.Comment: 21 pages, 4 figures. Minor typos corrected. To be published in Comm. Math. Phy