12,046 research outputs found
Photoionization of the valence shells of the neutral tungsten atom
Results from large-scale theoretical cross section calculations for the total
photoionization of the 4f, 5s, 5p and 6s orbitals of the neutral tungsten atom
using the Dirac Coulomb R-matrix approximation (DARC: Dirac-Atomic R-matrix
codes) are presented. Comparisons are made with previous theoretical methods
and prior experimental measurements. In previous experiments a time-resolved
dual laser approach was employed for the photo-absorption of metal vapours and
photo-absorption measurements on tungsten in a solid, using synchrotron
radiation.
The lowest ground state level of neutral tungsten is , with =0, and requires only a single dipole matrix for
photoionization. To make a meaningful comparison with existing experimental
measurements, we statistically average the large-scale theoretical PI cross
sections from the levels associated with the ground state levels and the \rm 5d^56s \; ^7S_3
excited metastable level. As the experiments have a self-evident metastable
component in their ground state measurement, averaging over the initial levels
allows for a more consistent and realistic comparison to be made.
In the wider context, the absence of many detailed electron-impact excitation
(EIE) experiments for tungsten and its multi-charged ion stages allows current
photoionization measurements and theory to provide a road-map for future
electron-impact excitation, ionization and di-electronic cross section
calculations by identifying the dominant resonance structure and features
across an energy range of hundreds of eV.Comment: 10 pages, 3 figures, accepted for publication in J Phys B: At. Mol.
Opt. Phy
Three Flavor Neutrino Oscillations in Matter: Flavor Diagonal Potentials, the Adiabatic Basis and the CP phase
We discuss the three neutrino flavor evolution problem with general,
flavor-diagonal, matter potentials and a fully parameterized mixing matrix that
includes CP violation, and derive expressions for the eigenvalues, mixing
angles and phases. We demonstrate that, in the limit that the mu and tau
potentials are equal, the eigenvalues and matter mixing angles theta_12 and
theta_13 are independent of the CP phase, although theta_23 does have CP
dependence. Since we are interested in developing a framework that can be used
for S matrix calculations of neutrino flavor transformation, it is useful to
work in a basis that contains only off-diagonal entries in the Hamiltonian. We
derive the "non-adiabaticity" parameters that appear in the Hamiltonian in this
basis. We then introduce the neutrino S matrix, derive its evolution equation
and the integral solution. We find that this new Hamiltonian, and therefore the
S matrix, in the limit that the mu and tau neutrino potentials are the same, is
independent of both theta_23 and the CP violating phase. In this limit, any CP
violation in the flavor basis can only be introduced via the rotation matrices,
and so effects which derive from the CP phase are then straightforward to
determine. We show explicitly that the electron neutrino and electron
antineutrino survival probability is independent of the CP phase in this limit.
Conversely, if the CP phase is nonzero and mu and tau matter potentials are not
equal, then the electron neutrino survival probability cannot be independent of
the CP phase
Analytical Model for the Optical Functions of Indium Gallium Nitride with Application to Thin Film Solar Photovoltaic Cells
This paper presents the preliminary results of optical characterization using
spectroscopic ellipsometry of wurtzite indium gallium nitride (InxGa1-xN) thin
films with medium indium content (0.38<x<0.68) that were deposited on silicon
dioxide using plasma-enhanced evaporation. A Kramers-Kronig consistent
parametric analytical model using Gaussian oscillators to describe the
absorption spectra has been developed to extract the real and imaginary
components of the dielectric function ({\epsilon}1, {\epsilon}2) of InxGa1-xN
films. Scanning electron microscope (SEM) images are presented to examine film
microstructure and verify film thicknesses determined from ellipsometry
modelling. This fitting procedure, model, and parameters can be employed in the
future to extract physical parameters from ellipsometric data from other
InxGa1-xN films
The innovative capacity of voluntary organisations and the provision of public services: A longitudinal approach
The prior history of voluntary and community organisations (VCOs) as pioneers of public services during the late nineteenth and early twentieth century has lead to reification of the innovativeness of these organisations. Is this reification justified – are VCOs inherently innovative, or is innovation contingent on other factors? This paper reports on a longitudinal study of this capacity conducted over 1994 – 2006. This study finds that the innovative capacity of VCOs is in fact not an inherent capacity but rather is contingent upon the public policy framework that privileges innovation above other activity of VCOs. The implications of this for theory, policy and practice are considered
On the Matter of Robot Minds
The view that phenomenally conscious robots are on the horizon often rests on a certain philosophical view about consciousness, one we call “nomological behaviorism.” The view entails that, as a matter of nomological necessity, if a robot had exactly the same patterns of dispositions to peripheral behavior as a phenomenally conscious being, then the robot would be phenomenally conscious; indeed it would have all and only the states of phenomenal consciousness that the phenomenally conscious being in question has. We experimentally investigate whether the folk think that certain (hypothetical) robots made of silicon and steel would have the same conscious states as certain familiar biological beings with the same patterns of dispositions to peripheral behavior as the robots. Our findings provide evidence that the folk largely reject the view that silicon-based robots would have the sensations that they, the folk, attribute to the biological beings in question
Implementable Wireless Access for B3G Networks - III: Complexity Reducing Transceiver Structures
This article presents a comprehensive overview of some of the research conducted within Mobile VCE’s Core Wireless Access Research Programme,1 a key focus of which has naturally been on MIMO transceivers. The series of articles offers a coherent view of how the work was structured and comprises a compilation of material that has been presented in detail elsewhere (see references within the article). In this article MIMO channel measurements, analysis, and modeling, which were presented previously in the first article in this series of four, are utilized to develop compact and distributed antenna arrays. Parallel activities led to research into low-complexity MIMO single-user spacetime coding techniques, as well as SISO and MIMO multi-user CDMA-based transceivers for B3G systems. As well as feeding into the industry’s in-house research program, significant extensions of this work are now in hand, within Mobile VCE’s own core activity, aiming toward securing major improvements in delivery efficiency in future wireless systems through crosslayer operation
A Bayesian VAR forecasting model for the Philadelphia Metropolitan Area
Vector-autoregression (VAR) forecast models have been developed for many state economies, including the three states in the Third Federal Reserve District--Pennsylvania, New Jersey, and Delaware. This paper extends that work by developing a Bayesian VAR forecast model for the Philadelphia metropolitan area and the city of Philadelphia.Forecasting ; Philadelphia (Pa.)
The Philadelphia story: a new forecasting model
Several years ago, the Philadelphia Fed developed a small forecasting model for each of the three states in the Third Federal Reserve DistrictCPennsylvania, New Jersey, and Delaware. This article introduces a similar model that forecasts major economic variables for the Philadelphia metropolitan area and the city of Philadelphia. Read this article and find out what the model predicts for the metro area and the cityForecasting ; Philadelphia (Pa.)
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