26,481 research outputs found
The VLSI design of a single chip Reed-Solomon encoder
A design for a single chip implementation of a Reed-Solomon encoder is presented. The architecture that leads to this single VLSI chip design makes use of a bit serial finite field multiplication algorithm
Movement, materiality, and the mortuary: Adopting go-along ethnography in research on fetal and neonatal postmortem
This article explores the use of the go-along method in research that takes place âbehind closed doorsâ drawing on qualitative research on postmortem imaging. Often favored in community and urban studies, go-along consists of mobile interviews and observations with respondents in their own environments. We conducted go-alongs with various professionalsâfrom pathologists to hospital chaplainsâin a range of settings. We also tracked different forms of materiality in and out of the mortuary space. As the article seeks to show, go-along allowed us to appreciate the complex and mobile nature of postmortem, situating it within the wider landscape of bereavement and memorialization. It also enabled us to illuminate the ways in which the mortuary as a place cannot be fixed âindoors,â but rather, is continually remade through different types of practice. Our analysis emphasizes the value of using go-alongs in indoor settings, and further reinforces a fluid conceptualization of place
Observation of small scale structure using sextupole lensing
Weak gravitational lensing seeks to determine shear by measuring induced
quadrupole (elliptical) shapes in background galaxy images. Small impact
parameter (a few kpc) gravitational lensing by foreground core masses between 2
10^{9} and 2 10^{12} M_\odot will additionally induce a sextupole shape with
the quadrupole and sextupole minima aligned. This correlation in relative
orientation of the quadrupole and sextupole provides a sensitive method to
identify images which have been slightly curved by lensing events. A general
theoretical framework for sextupole lensing is developed which includes several
low order coefficients in a general lensing map. Tools to impute map
coefficients from the galaxy images are described and applied to the north
Hubble deep field. Instrumental PSFs, camera charge diffusion, and image
composition methods are modelled in the coefficient determination process.
Estimates of Poisson counting noise for each galaxy are used to cut galaxies
with signals too small to reliably establish curvature. Curved galaxies are
found to be spatially clumped, as would be expected if the curving were due to
small impact parameter lensing by localized ensembles of dark matter haloes.
Simulations provide an estimate of the total required lensing mass and the
acceptable mass range of the constituent haloes. The overdensities and
underdensities of visible galaxies and their locations in the Hubble foreground
is found to be consistent with our observations and their interpretation as
lensing events.Comment: 40 pages, 44 figure
A new result on the Klein-Gordon equation in the background of a rotating black hole
This short paper should serve as basis for further analysis of a previously
found new symmetry of the solutions of the wave equation in the gravitational
field of a Kerr black hole. Its main new result is the proof of essential
self-adjointness of the spatial part of a reduced normalized wave operator of
the Kerr metric in a weighted L^2-space. As a consequence, it leads to a purely
operator theoretic proof of the well-posedness of the initial value problem of
the reduced Klein-Gordon equation in that field in that L^2-space and in this
way generalizes a corresponding result of Kay (1985) in the case of the
Schwarzschild black hole. It is believed that the employed methods are
applicable to other separable wave equations
Multiparticle Schrodinger operators with point interactions in the plane
We study a system of N bosons in the plane interacting with delta function
potentials. After a coupling constant renormalization we show that the
Hamiltonian defines a self-adjoint operator and obtain a lower bound for the
energy. The same results hold if one includes a regular inter-particle
potential.Comment: 17 pages, Late
Universality in the merging dynamics of parametric active contours: a study in MRI-based lung segmentation
Measurement of lung ventilation is one of the most reliable techniques of
diagnosing pulmonary diseases. The time consuming and bias prone traditional
methods using hyperpolarized HHe and H magnetic resonance
imageries have recently been improved by an automated technique based on
multiple active contour evolution. Mapping results from an equivalent
thermodynamic model, here we analyse the fundamental dynamics orchestrating the
active contour (AC) method. We show that the numerical method is inherently
connected to the universal scaling behavior of a classical nucleation-like
dynamics. The favorable comparison of the exponent values with the theoretical
model render further credentials to our claim.Comment: 4 pages, 4 figure
VLSI architectures for computing multiplications and inverses in GF(2-m)
Finite field arithmetic logic is central in the implementation of Reed-Solomon coders and in some cryptographic algorithms. There is a need for good multiplication and inversion algorithms that are easily realized on VLSI chips. Massey and Omura recently developed a new multiplication algorithm for Galois fields based on a normal basis representation. A pipeline structure is developed to realize the Massey-Omura multiplier in the finite field GF(2m). With the simple squaring property of the normal-basis representation used together with this multiplier, a pipeline architecture is also developed for computing inverse elements in GF(2m). The designs developed for the Massey-Omura multiplier and the computation of inverse elements are regular, simple, expandable and, therefore, naturally suitable for VLSI implementation
A VLSI single chip (255,223) Reed-Solomon encoder with interleaver
A single-chip implementation of a Reed-Solomon encoder with interleaving capability is described. The code used was adapted by the CCSDS (Consulative Committee on Space Data Systems). It forms the outer code of the NASA standard concatenated coding system which includes a convolutional inner code of rate 1/2 and constraint length 7. The architecture, leading to this single VLSI chip design, makes use of a bit-serial finite field multiplication algorithm due to E.R. Berlekamp
Long-term measurements of flow near the Aleutian Islands
In summer 1995, the Alaskan Stream at 173.5W was very intense; the peak geostrophic speed was â125 cm sâ1, and the computed volume transport above 1000 db, referred to 1000 db, was 9 Ă 106 m3 sâ1). Flow north of the central Aleutians was shallow, convoluted and weak (2â 3 Ă 106 m3 sâ1). A sequence of CTD casts across Amukta Pass, spaced irregularly in time during 1993â1996, showed a mean northward (southward) geostrophic transport of 1.0 (0.4) Ă 106 m3 sâ1, for a net flow into the Bering Sea of 0.6 Ă 106 m3 sâ1. The source of this flow was the Alaskan Stream except in 1995, when it was Bering Sea water. Results from two 13-month current moorings west and east of the pass were quite different. To the west, flow was weak and variable and appeared to have a barotropic component. To the east, flow was stronger and unidirectional eastward
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