46,804 research outputs found
Alignment Theory of Parallel-beam CT Image Reconstruction for Elastic-type Objects using Virtual Focusing Method
X-ray tomography has been studied in various fields. Although a great deal of
effort has been directed at reconstructing the projection image set from a
rigid-type specimen, little attention has been addressed to the reconstruction
of projected images from an object showing elastic motion. Here, we present a
mathematical solution to reconstruct the projection image set obtained from an
object with specific elastic motions: periodically, regularly, and elliptically
expanded or contracted specimens. To reconstruct the projection image set from
expanded or contracted specimens, we introduce new methods; detection of
sample's motion modes, mathematical re-scaling pixel values and converting
projection angle for a common layerComment: 30 pages, 11 figure
Network Marketing on a Small-World Network
We investigate a dynamic model of network marketing in a small-world network
structure artificially constructed similarly to the Watts-Strogatz network
model. Different from the traditional marketing, consumers can also play the
role of the manufacturer's selling agents in network marketing, which is
stimulated by the referral fee the manufacturer offers. As the wiring
probability is increased from zero to unity, the network changes from
the one-dimensional regular directed network to the star network where all but
one player are connected to one consumer. The price of the product and the
referral fee are used as free parameters to maximize the profit of the
manufacturer. It is observed that at the maximized profit is
constant independent of the network size while at , it
increases linearly with . This is in parallel to the small-world transition.
It is also revealed that while the optimal value of stays at an almost
constant level in a broad range of , that of is sensitive to a
change in the network structure. The consumer surplus is also studied and
discussed.Comment: 12 pages, to appear in Physica
Thermodynamic arrow of time of quantum projective measurements
We investigate a thermodynamic arrow associated with quantum projective
measurements in terms of the Jensen-Shannon divergence between the probability
distribution of energy change caused by the measurements and its time reversal
counterpart. Two physical quantities appear to govern the asymptotic values of
the time asymmetry. For an initial equilibrium ensemble prepared at a high
temperature, the energy fluctuations determine the convergence of the time
asymmetry approaching zero. At low temperatures, finite survival probability of
the ground state limits the time asymmetry to be less than . We
illustrate our results for a concrete system and discuss the fixed point of the
time asymmetry in the limit of infinitely repeated projections.Comment: 6 pages in two columns, 1 figure, to appear in EP
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