Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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.

13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg