3,840 research outputs found
Magnetic field topology and chemical spot distributions of the Ap star HD119419
Analysis of high-resolution spectropolarimetric observations of early-type
magnetic stars is currently the most advanced method of obtaining detailed
information on their surface magnetic field topologies and horizontal spot
distributions. In this study we analyse a new set of high-quality four Stokes
parameter observations of the magnetic Ap star HD119419 - a member of the 14
Myr old Lower Cen-Cru association - for the purpose of studying the surface
field topology and mapping the chemical abundance spots. We made use of the
circular and linear polarisation data collected for HD119419 with the HARPSpol
instrument at the ESO 3.6-m telescope. These observations were analysed with a
multi-line magnetic diagnostic technique and modelled in detail with a Magnetic
Doppler imaging code. We present a new set of mean longitudinal magnetic field
measurements and derive a revised stellar rotational period. We also
redetermine the basic stellar atmospheric parameters. Our four Stokes parameter
magnetic inversions reveal a moderately complex surface field topology with a
mean field strength of 18 kG and a maximum local strength of 24 kG. A poloidal
dipolar component dominates the magnetic energy spectrum of the surface field
in HD119419. However, significant contributions of the higher-order spherical
harmonic components are also present. We show that the dipole plus quadrupole
part of the reconstructed field geometry is incapable of reproducing the
observed amplitudes and shapes of the Stokes Q and U profiles. The chemical
abundance distributions of Fe, Cr, Ti, and Nd, derived self-consistently with
the magnetic field geometry, are characterised by large abundance gradients and
a lack of clear correlation with the magnetic field structure. This full Stokes
vector analysis of HD119419 extends the modern hot-star magnetic mapping
investigations to an open cluster Ap star with a well-determined age.Comment: 15 pages, 11 figures; accepted for publication in A&
Techniques development for whale migration tracking
Effort leading to the completion of development and fabrication of expansible whale harnesses and whale-carried instrument pods is described, along with details of the gear. Early preparative effort for a January-February 1974 field expedition is reported
Band structure approach to the resonant x-ray scattering
We study the resonance behaviour of the forbidden 600 and 222 x-ray Bragg
peaks in Ge using LDA band structure methods. These Bragg peaks remain
forbidden in the resonant dipole scattering approximation even taking into
account the non local nature of the band states. However they become allowed at
resonance if the eigenstates of the unoccupied conduction band involve a
hybridization of p like and d like atomic states. We show that the energy
dependence of the resonant behaviour, including the phase of the scattering, is
a direct measure of this p-d hybridization.and obtain quantitative agreement
with experiment. A simple physical picture involving a product of dipole and
quadrupolar transition matrix elements explains this behaviour and shows that
it should be generally true for cases where the resonating atom is not at an
inversion center. This has strong implications for the description of the
resonance behavior of x-ray scattering in materials where the resonant atom is
not at an inversion center such as V2O3 and in ferro and antiferro electric and
piezo electric materials in general.Comment: 4 pages, 5figure
Pendekatan Metode Tiga Fase dalam Optimasi Masalah Rute Kendaraan dengan Varian Jenis Kendaraan dan Jenis Produk
SClustering is a commonly system used by the distribution company. Some consumers who are in the same location but located in two different clusters as a result of a fixed and rigid area within cluster, resulting in longer delivery time and higher cost incurred to deliver the order. The purpose of this research is to determine the optimal vehicle route using three-phase method approachthat improve the clustering system. Complexity arising from the problem of this vehicle routing includes variant types of vehicles and variants of product types. The three-phase method includes a cluster-making phase with a maximum distance between consumers within 10 kilometers, a cluster adjustment phase, and a routing phase that determine shipping routes and calculate total distribution cost. Numerical examples shows that the cost of distributing goods can be minimized, from an average of IDR 1,064,408.33 to an average of IDR 775,586.46. Thus a three-phase method may improve the clustering system by reducing distribution time and cost
Probabilistic abstract interpretation: From trace semantics to DTMC’s and linear regression
In order to perform probabilistic program analysis we need to consider probabilistic languages or languages with a probabilistic semantics, as well as a corresponding framework for the analysis which is able to accommodate probabilistic properties and properties of probabilistic computations. To this purpose we investigate the relationship between three different types of probabilistic semantics for a core imperative language, namely Kozen’s Fixpoint Semantics, our Linear Operator Semantics and probabilistic versions of Maximal Trace Semantics. We also discuss the relationship between Probabilistic Abstract Interpretation (PAI) and statistical or linear regression analysis. While classical Abstract Interpretation, based on Galois connection, allows only for worst-case analyses, the use of the Moore-Penrose pseudo inverse in PAI opens the possibility of exploiting statistical and noisy observations in order to analyse and identify various system properties
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