869 research outputs found
Detection of organic materials by spectrometric radiography method
In this paper we report a spectrometric approach to dual-energy digital
radiography that has been developed and applied to identify specific organic
substances and discern small differences in their effective atomic number. An
experimental setup has been designed, and a theoretical description proposed
based on the experimental results obtained. The proposed method is based on
application of special reference samples made of materials with different
effective atomic number and thickness, parameters known to affect X-ray
attenuation in the low-energy range. The results obtained can be used in the
development of a new generation of multi-energy customs or medical X-ray
scanners.Comment: 6 pages, 2 tables, 5 figures, will be presented at the Workshop on
X-Ray Imaging, 22-24 October, 2008, Dresden, German
Direct reconstruction of the effective atomic number of materials by the method of multi-energy radiography
A direct method is proposed for reconstruction of the effective atomic number
by means of multi-energy radiography of the material. The accuracy of the
method is up to 95% . Advantages over conventional radiographic methods, which
ensure accuracy of just about 50%, are discussed. A physical model has been
constructed, and general expressions have been obtained for description of the
effective atomic number in a two-energy monitoring scheme. A universal
dependence has been predicted for the effective atomic number as a function of
relative (two-energy) radiographic reflex. The established theoretical law is
confirmed by the experimental data presented. The proposed development can find
multiple applications in non-destructive testing and related fields, including
those in the civil sphere as well as anti-terrorist activities.Comment: 15 pages LaTeX, 4 figures, the paper accepted in Nuclear Methods and
Instruments in Physics Research, Section
Horn fragments of the Halpern-Shoham Interval Temporal Logic
We investigate the satisfiability problem for Horn fragments of the Halpern-Shoham interval temporal logic depending on the type (box or diamond) of the interval modal operators, the type of the underlying linear order (discrete or dense), and the type of semantics for the interval relations (reflexive or irreflexive). For example, we show that satisfiability of Horn formulas with diamonds is undecidable for any type of linear orders and semantics. On the contrary, satisfiability of Horn formulas with boxes is tractable over both discrete and dense orders under the reflexive semantics and over dense orders under the irreflexive semantics but becomes undecidable over discrete orders under the irreflexive semantics. Satisfiability of binary Horn formulas with both boxes and diamonds is always undecidable under the irreflexive semantics
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