20,480 research outputs found
De-aliasing Undersampled Volume Images for Visualization
We present and illustrate a new technique, Image Correlation Supersampling (ICS), for resampling volume data that are undersampled in one dimension. The resulting data satisfies the sampling theorem, and, therefore, many visualization algorithms that assume the theorem is satisfied can be applied to the data. Without the supersampling the visualization algorithms create artifacts due to aliasing. The assumptions made in developing the algorithm are often satisfied by data that is undersampled temporally. Through this supersampling we can completely characterize phenomena with measurements at a coarser temporal sampling rate than would otherwise be necessary. This can save acquisition time and storage space, permit the study of faster phenomena, and allow their study without introducing aliasing artifacts. The resampling technique relies on a priori knowledge of the measured phenomenon, and applies, in particular, to scalar concentration measurements of fluid flow. Because of the characteristics of fluid flow, an image deformation that takes each slice image to the next can be used to calculate intermediate slice images at arbitrarily fine spacing. We determine the deformation with an automatic, multi-resolution algorithm
Cheryl's Birthday
We present four logic puzzles and after that their solutions. Joseph Yeo
designed 'Cheryl's Birthday'. Mike Hartley came up with a novel solution for
'One Hundred Prisoners and a Light Bulb'. Jonathan Welton designed 'A Blind
Guess' and 'Abby's Birthday'. Hans van Ditmarsch and Barteld Kooi authored the
puzzlebook 'One Hundred Prisoners and a Light Bulb' that contains other
knowledge puzzles, and that can also be found on the webpage
http://personal.us.es/hvd/lightbulb.html dedicated to the book.Comment: In Proceedings TARK 2017, arXiv:1707.0825
A simple proof of the Markoff conjecture for prime powers
We give a simple and independent proof of the result of Jack Button and Paul
Schmutz that the Markoff conjecture on the uniqueness of the Markoff triples
(a,b,c), where a, b, and c are in increasing order, holds whenever is a
prime power.Comment: 5 pages, no figure
Surveying the solar system by measuring angles and times: from the solar density to the gravitational constant
A surprisingly large amount of information on our solar system can be gained
from simple measurements of the apparent angular diameters of the sun and the
moon. This information includes the average density of the sun, the distance
between earth and moon, the radius of the moon, and the gravitational constant.
In this note it is described how these and other quantities can be obtained by
simple earthbound measurements of angles and times only, without using any
explicit information on distances between celestial bodies. The pedagogical and
historical aspects of these results are also discussed briefly.Comment: 12 pges, one figur
X-ray fluoresced high-Z (up to Z = 82) K-x-rays produced by LiNbO3 and LiTaO3 pyroelectric crystal electron accelerators
High-energy bremsstrahlung and K X-rays were used to produce nearly
background-free K X-ray spectra of up to 87 keV (Pb) via X-ray fluorescence.
The fluorescing radiation was produced by electron accelerators, consisting of
heated and cooled cylindrical LiTaO3 and LiNbO3 crystals at mTorr pressures.
The newly discovered process of gas amplification whereby the ambient gas
pressure is optimized to maximize the electron energy was used to produce
energetic electrons which when incident on a W/Bi target gave rise to a
radiation field consisting of high-energy bremsstrahlung as well as W and Bi K
X-rays. These photons were used to fluoresce Ta and Pb K X-rays.Comment: 6 pages, 6 figures, PD
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