No 2 (2012)

Modifications of Ross and Harary algorithm to express the number ck of cycles of length k in an undirected graph in terms of its adjacency matrix are developed. The general undirected graphs as well as bipartite graphs were considered. Computer algebra implementations of the algorithms enable us to construct the formulae at least for k ≤ 12 in general case and for k ≤ 14 in case of bipartite graph. It was shown that, for any fixed value of k ≥ 8 and space complexity quadratic in order n of a graph, the time complexity of computing ck is O(n[k/2] logn). In case of bipartite graph, for k = 8,10,14 better estimations are obtained: O(n3 log2n), O(n4 log2n), O(n6 log2n).

In the paper we establish the optimal necessary conditions for guaranteeing uniquely the resolution of boundary hydrodynamic problems in a bounded domain so that they could accurately describe the studied hydrodynamic phenomenon.

K. Wodkiewicz describes Holevo-Helstrom method, and proposes his own operational model of quantum measurements as an example of using this method. It involves the quantum probability distribution function P q,p = Wψ * Wφ q,p. Here Wφ is the Wigner distribution function of the quantum state of a quantum system before measurement, Wψ is the quantum Wigner distribution function of the quantum filter before the measurement procedure. It is known that the convolution of two quantum Wigner distribution functions is positive-definite probability distribution function in phase space of a quantum system. Quantum Wigner distribution function is uniquely related to Weyl quantization rule, which says that a classical observable A q,p corresponds to a (pseudo) differential operator OW A, whose symbol is the function A q,p. The paper states that Kuryshkin quantization rule is associated with the quantum distribution Kuryshkin-Wodkiewicz function. This quantization rule corresponds to a classical observable A q,p the operator of the observable Oψ A with the symbol AG q,p = A * Φ q,p. Here Φ q,p = 2πℏ −3 2 e−ipq ℏ ψ q ˜ ψ p, where ˜ψ p is the Fourier transform of the state function ψ q of the quantum filter.

In , the fist author presented an efficient algorithm for computing involutive (and reduced Gr̈obner) bases. In this paper, we consider a modification of the algorithm which simplifies matters to understand it and to implement. We prove correctness and termination of the modified algorithm and also correctness of the used criteria. The proposed algorithm has been implemented in Maple. We present experimental comparison, via some examples, of performance of the modified algorithm with its original form described in and implemented in Maple too. In doing so, we have taken care to provide uniform implementation details for the both algorithms.

The steady numerical solution using Tikhonov functional with a stabilizer of the second order was obtained for the integral equation of the first kind, which occurs for deconvolution of thin-target bremsstrahlung spectra to determine electron energy distributions function (EEDF)

In the static cylindrically symmetric metric and cosmological metric Bianchi I we consider the interacting scalar and spinor fields with the Lagrangian of the interaction Lint = V (φ)S2, where V (φ) is arbitrary function of scalar field φ, S = ψ¯ψ is an invariant of the spinor field ψ. We obtain exact solutions of the Einstein, spinor and scalar equations and one exhibited that function V (φ) is absent in the components of the energy-momentum tensor for the interacting fields. It means that the considered type of the interaction removes the contribution of the scalar field in the geometry of the space-time.

The article considers the modern level of researches in the field of cloud computing network security. The structure and functioning principles of cloud computing security systems, as well as cloud-based security system were analyzed. The modern trends in this field were studied.