5,434 research outputs found
Method and apparatus for tensile testing of metal foil
A method for obtaining accurate and reproducible results in the tensile testing of metal foils in tensile testing machines is described. Before the test specimen are placed in the machine, foil side edges are worked until they are parallel and flaw free. The specimen are also aligned between and secured to grip end members. An aligning apparatus employed in the method is comprised of an alignment box with a longitudinal bottom wall and two upright side walls, first and second removable grip end members at each end of the box, and a means for securing the grip end members within the box
Approaches to optimization of SS/TDMA time slot assignment
Reduction techniques for traffic matrices are explored in some detail. These matrices arise in satellite switched time-division multiple access (SS/TDMA) techniques whereby switching of uplink and downlink beams is required to facilitate interconnectivity of beam zones. A traffic matrix is given to represent that traffic to be transmitted from n uplink beams to n downlink beams within a TDMA frame typically of 1 ms duration. The frame is divided into segments of time and during each segment a portion of the traffic is represented by a switching mode. This time slot assignment is characterized by a mode matrix in which there is not more than a single non-zero entry on each line (row or column) of the matrix. Investigation is confined to decomposition of an n x n traffic matrix by mode matrices with a requirement that the decomposition be 100 percent efficient or, equivalently, that the line(s) in the original traffic matrix whose sum is maximal (called critical line(s)) remain maximal as mode matrices are subtracted throughout the decomposition process. A method of decomposition of an n x n traffic matrix by mode matrices results in a number of steps that is bounded by n(2) - 2n + 2. It is shown that this upper bound exists for an n x n matrix wherein all the lines are maximal (called a quasi doubly stochastic (QDS) matrix) or for an n x n matrix that is completely arbitrary. That is, the fact that no method can exist with a lower upper bound is shown for both QDS and arbitrary matrices, in an elementary and straightforward manner
Stokes IQUV mapping of CVn & other Ap stars using ESPaDOnS and NARVAL
New spectral line polarisation observations of 7 bright Ap stars have been
obtained with the ESPaDOnS and Narval high resolution spectropolarimeters
(Silvester et al. 2012). The aim of this data set is produce a series of
surface magnetic field and surface chemistry maps for these Ap stars. We
present new magnetic maps for the Ap star CVn using these new data
and the MDI inversion code INVERS10. CVn is the first Ap star to be
observed during two separate epochs using high resolution phase resolved
spectropolarimetric observations and as such allows us an insight into
how stable the surface magnetic structure is over a decade timescale. We show
that the new maps give a magnetic field structure consistent with the previous
maps obtained by Kochukhov and Wade (2010) from lower quality MuSiCoS spectra
taken a decade ago and that the field topology cannot be described by a dipolar
or quadrupolar field.Comment: 6 pages, 3 figures. Proceedings of New advances in stellar physics:
from microscopic to macroscopic processes (Roscoff 2013
The magnetic field topology and chemical abundance distributions of the Ap star HD 32633
Previous observations of the Ap star HD 32633 indicated that its magnetic
field was unusually complex in nature and could not be characterised by a
simple dipolar structure. Here we derive magnetic field maps and chemical
abundance distributions for this star using full Stokes vector (Stokes )
high-resolution observations obtained with the ESPaDOnS and Narval
spectropolarimeters. Our maps, produced using the Invers10 magnetic Doppler
imaging (MDI) code, show that HD 32633 has a strong magnetic field which
features two large regions of opposite polarity but deviates significantly from
a pure dipole field. We use a spherical harmonic expansion to characterise the
magnetic field and find that the harmonic energy is predominately in the
and poloidal modes with a small toroidal component. At the
same time, we demonstrate that the observed Stokes parameter profiles of HD
32633 cannot be fully described by either a dipolar or dipolar plus quadrupolar
field geometry. We compare the magnetic field topology of HD 32633 with other
early-type stars for which MDI analyses have been performed, supporting a trend
of increasing field complexity with stellar mass. We then compare the magnetic
field topology of HD 32633 with derived chemical abundance maps for the
elements Mg, Si, Ti, Cr, Fe, Ni and Nd. We find that the iron-peak elements
show similar distributions, but we are unable to find a clear correlation
between the location of local chemical enhancements or depletions and the
magnetic field structure.Comment: 15 pages, 11 figures, accepted for publication in MNRA
Acoustooptic pulse-echo transducer system
A pulse-echo transducer system which uses an ultrasonic generating element and an optical detection technique is described. The transmitting transducer consists of a concentric ring electrode pattern deposited on a circular, X-cut quartz substrate with a circular hole in the center. The rings are independently pulsed with a sequence high voltage signals phased in such a way that the ultrasonic waves generated by the separate rings superimpose to produce a composite field which is focused at a controllable distance below the surface of the specimen. The amplitude of the field reflected from this focus position is determined by the local reflection coefficient of the medium at the effective focal point. By processing the signals received for a range of ultrasonic transducer array focal lengths, the system can be used to locate and size anomalies within solids and liquids. Applications in both nondestructive evaluation and biomedical scanning are suggested
On three-dimensional reconstruction of optically thin solar emission sources
Calculations are given for constructing the three dimensional distribution of optically thin EUV emission sources associated with solar active regions, from two dimensional observations (projections) recorded by the spectroheliograph on the OSO 7 satellite. The relation of the method to other image reconstruction methods is briefly discussed as well as the special requirements imposed in the solar case such as a knowledge of the true solar rotation function. A useful correlation criterion for establishing the physical validity of solutions is given
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