Aviation Safety as a Function of Pilot Experience: Rationale or Rationalization?

Editor\u27s Note: This article originally appeared in the Spring 1992 issue. It is reprinted due to its continuing value and timeliness. This study tests the effectiveness of an experience model in predicting aviation safety behavior. The elements comprising the model include: (a) flight hours, (b) ratings and flight characteristics, (c) career status, and (d) malfunction history. Data were derived from a random sample of U.S. pilots in Fall 1990 by means of a survey instrument. Significant variance in aviation safety is not explained by the model. The key predictor of safety behavior is the career status (i.e., certificate duration) of the pilot. Flight hours, ratings, and malfunction history are negatively and non-significantly associated with aviation safety. The research: (a) questions the use of these variables in ex post facto explanations of aviation safety, and (b) suggests a topology for examining safety behavior

Aviation Safety as a Function of Pilot Experience: Rationale or Rationalization?

This study tests the effectiveness of an experience model in predicting aviation safety behavior. The elements comprising the model include: (a) flight hours, (b) ratings and flight characteristics, (c) career status, and (d) malfunction history. Data were derived from a random sample of U.S. pilots in the fall of 1990 by means of a survey instrument. Significant variance in aviation safety is not explained by the model. The key predictor of safety behavior is the career status (i.e., certificate duration) of the pilot. Flight hours, ratings, and malfunction history are negatively and non-significantly associated with aviation safety. The research: (a) questions the use of these variables in ex post facto “explanations” of aviation safety, and (b) suggests a topology for examining safety behavior

Symmetric Rotating Wave Approximation for the Generalized Single-Mode Spin-Boson System

The single-mode spin-boson model exhibits behavior not included in the rotating wave approximation (RWA) in the ultra and deep-strong coupling regimes, where counter-rotating contributions become important. We introduce a symmetric rotating wave approximation that treats rotating and counter-rotating terms equally, preserves the invariances of the Hamiltonian with respect to its parameters, and reproduces several qualitative features of the spin-boson spectrum not present in the original rotating wave approximation both off-resonance and at deep strong coupling. The symmetric rotating wave approximation allows for the treatment of certain ultra and deep-strong coupling regimes with similar accuracy and mathematical simplicity as does the RWA in the weak coupling regime. Additionally, we symmetrize the generalized form of the rotating wave approximation to obtain the same qualitative correspondence with the addition of improved quantitative agreement with the exact numerical results. The method is readily extended to higher accuracy if needed. Finally, we introduce the two-photon parity operator for the two-photon Rabi Hamiltonian and obtain its generalized symmetric rotating wave approximation. The existence of this operator reveals a parity symmetry similar to that in the Rabi Hamiltonian as well as another symmetry that is unique to the two-photon case, providing insight into the mathematical structure of the two-photon spectrum, significantly simplifying the numerics, and revealing some interesting dynamical properties.Comment: 11 pages, 5 figure

Meson vacuum phenomenology in a three-flavor linear sigma model with (axial-)vector mesons

We study scalar, pseudoscalar, vector, and axial-vector mesons with non-strange and strange quantum numbers in the framework of a linear sigma model with global chiral $U(N_f)_L \times U(N_f)_R$ symmetry. We perform a global fit of meson masses, decay widths, as well as decay amplitudes. The quality of the fit is, for a hadronic model that does not consider isospin-breaking effects, surprisingly good. We also investigate the question whether the scalar $\bar{q}q$ states lie below or above 1 GeV and find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states. Additionally, we also describe the axial-vector resonances as $\bar{q}q$ states.Comment: 29 pages, 4 figures, 3 tables. v2 is the updated version after referee remarks (dilaton field discussed, a new figure added

Bipartite Entanglement in Continuous-Variable Cluster States

We present a study of the entanglement properties of Gaussian cluster states, proposed as a universal resource for continuous-variable quantum computing. A central aim is to compare mathematically-idealized cluster states defined using quadrature eigenstates, which have infinite squeezing and cannot exist in nature, with Gaussian approximations which are experimentally accessible. Adopting widely-used definitions, we first review the key concepts, by analysing a process of teleportation along a continuous-variable quantum wire in the language of matrix product states. Next we consider the bipartite entanglement properties of the wire, providing analytic results. We proceed to grid cluster states, which are universal for the qubit case. To extend our analysis of the bipartite entanglement, we adopt the entropic-entanglement width, a specialized entanglement measure introduced recently by Van den Nest M et al., Phys. Rev. Lett. 97 150504 (2006), adapting their definition to the continuous-variable context. Finally we add the effects of photonic loss, extending our arguments to mixed states. Cumulatively our results point to key differences in the properties of idealized and Gaussian cluster states. Even modest loss rates are found to strongly limit the amount of entanglement. We discuss the implications for the potential of continuous-variable analogues of measurement-based quantum computation.Comment: 22 page

Microscopic origins of the surface exciton photoluminescence peak in ZnO nanostructures

We report photoluminescence (PL) studies of the surface exciton peak in ZnO nanostructures at ∼3.367 eV aimed at elucidation of the nature and origin of the emission and its relationship to the nanostructure morphology. PL spectra in conjunction with localized voltage application in high vacuum and different gas atmospheres show a consistent variation (and recovery), allowing an association of the PL to a bound excitonic transition at the ZnO surface, which is modified by an adsorbate. PL studies of samples treated by plasma and of samples exposed to UV light under high vacuum conditions, both well-known processes for desorption of surface adsorbed oxygen, show no consistent effects on the surface exciton peak indicating the lack of involvement of oxygen species. X-ray photoelectron spectroscopy data strongly suggest involvement of adsorbed OH species. X-ray diffraction, scanning, and transmission electronmicroscopy data are presented also, and the relationship of the surface exciton peak to the nanostructure morphology is discussed