Electromagnetic Propagation Velocities in an Inhomogeneous or Random Atmosphere

This thesis is concerned primarily with determination of statistics for the velocities of propagation of an electromagnetic wave in a dispersive medium. The velocities of propagation are discussed in terms of a plane travelling wave solution of Maxwell\u27s equations obtained using the multiple Laplace transformation and complex inversion integrals. The types of dispersion discussed correspond to a magneto-ionic, electron displacement and polar resonances of the ionosphere and troposphere. The physical nature of the randomness of the dispersive index of refraction is derived from considerations of statistical turbulence theory. Expressions are then obtained for determining the mean, mean square and variance of the signal, group and phase velocity of an electromagnetic wave. It is proposed by S. M. Harris (IRE Trans. Vol. AP-9, No. 2, pp. 207-210, Mar., 1961) that the group velocity and phase velocity of an electromagnetic wave propagated in the ionosphere may be averaged to obtain a velocity estimate free of refraction to within second order refractive effects. The basis for this procedure is that for an operating frequency considerably above the critical frequencies of the ionospheric medium, the group velocity is slightly less than the velocity of light

Self-Defense in Kentucky: A Need for Clarification or Revision

Recent prosecutions have pushed Kentucky’s concept of self-defense beyond the limits of tolerance for complexity and confusion. There is little doubt that there exists a critical need to clarify or to revise the Kentucky law of self-defense. A demonstration of this need and a description of its nature are the principal objectives of this article. To accomplish these objectives, it is necessary to provide some information about the recent history of homicide and self-defense in Kentucky and to describe some important recent interpretations of this law by the Supreme Court of Kentucky

Paper Session III-B - Overview of the Orbiting Radio Communications Asset (ORCA) Mission

The Orbiting Radio Communications Asset (ORCA) mission is a commercial mission being designed, built and conducted by the Iowa Space Grant Consortium, supported by Rockwell Collins, and Space Industries. The mission will utilize advanced technology digital radio equipment provided by Rockwell to survey the low-earth orbit radio spectrum. This survey is of interest to both the commercial communications industry and to the scientific radio astronomy community. In addition to the survey, the spacecraft will provide an on-orbit transmit and receive test platform for advanced communications technologies that can be fully reprogrammed from the control station. A significant feature of the ORCA mission is the intimate involvement of students from Drake University, the University of Iowa, the University of Northern Iowa, and Iowa State University. These students will be involved in all aspects of the mission design, development, and staff the operations center after the initial mission

Advanced sensors technology survey

This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed

Abstracts and Citations

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138936/1/head13152.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138936/2/head13152_am.pd

Resumming the large-N approximation for time evolving quantum systems

In this paper we discuss two methods of resumming the leading and next to leading order in 1/N diagrams for the quartic O(N) model. These two approaches have the property that they preserve both boundedness and positivity for expectation values of operators in our numerical simulations. These approximations can be understood either in terms of a truncation to the infinitely coupled Schwinger-Dyson hierarchy of equations, or by choosing a particular two-particle irreducible vacuum energy graph in the effective action of the Cornwall-Jackiw-Tomboulis formalism. We confine our discussion to the case of quantum mechanics where the Lagrangian is $L(x,\dot{x}) = (1/2) \sum_{i=1}^{N} \dot{x}_i^2 - (g/8N) [ \sum_{i=1}^{N} x_i^2 - r_0^2 ]^{2}$. The key to these approximations is to treat both the $x$ propagator and the $x^2$ propagator on similar footing which leads to a theory whose graphs have the same topology as QED with the $x^2$ propagator playing the role of the photon. The bare vertex approximation is obtained by replacing the exact vertex function by the bare one in the exact Schwinger-Dyson equations for the one and two point functions. The second approximation, which we call the dynamic Debye screening approximation, makes the further approximation of replacing the exact $x^2$ propagator by its value at leading order in the 1/N expansion. These two approximations are compared with exact numerical simulations for the quantum roll problem. The bare vertex approximation captures the physics at large and modest $N$ better than the dynamic Debye screening approximation.Comment: 30 pages, 12 figures. The color version of a few figures are separately liste

Improved fidelity of triggered entangled photons from single quantum dots

We demonstrate the on-demand emission of polarisation-entangled photon pairs from the biexciton cascade of a single InAs quantum dot embedded in a GaAs/AlAs planar microcavity. Improvements in the sample design blue shifts the wetting layer to reduce the contribution of background light in the measurements. Results presented show that >70% of the detected photon pairs are entangled. The high fidelity of the (|HxxHx>+|VxxVx>)/2^0.5 state that we determine is sufficient to satisfy numerous tests for entanglement. The improved quality of entanglement represents a significant step towards the realisation of a practical quantum dot source compatible with applications in quantum information.Comment: 9 pages. Paper is available free of charge at http://www.iop.org/EJ/abstract/1367-2630/8/2/029/, see also 'A semiconductor source of triggered entangled photon pairs', R. M. Stevenson et al., Nature 439, 179 (2006