On the expressiveness of the approach to constructing PLC-programs by LTL-specification

The article is devoted to an approach to constructing and verification of discrete PLC-programs by LTL-specification. This approach provides a possibility of analysing the correctness of PLCprograms by using the model checking method. The linear temporal logic LTL is used as a language of specification of the program behavior. The correctness analysis of LTL-specification is automatically performed by the symbolic model checking tool Cadence SMV. The article demonstrates the consistency of the approach to constructing and verification of PLC programs by LTL-specification from the point of view of Turing power. It is proved that in accordance with this approach for any Minsky counter machine an LTL-specification can be built, which is used for machine implementation in any PLC programming language of standard IEC 61131-3. Minsky machines are equipollent to Turing machines, and the considered approach also has the Turing power. The proof focuses on representation of a counter machine behavior in the form of a set of LTL-formulas and matching these formulas to constructions of ST and SFC languages. SFC is interesting as a specific graphical language. ST is considered as a basic language because the implementation of a counter machine on IL, FBD/CFC and LD languages is reduced to rewriting blocks of an ST-program. The idea of the proof is demonstrated by an example of a Minsky 3-counter machine, which implements a function of squaring.     

On languages of automaton counter machines

A class of formal languages (ACML) acceptable by automaton counter machines is considered. This class is shown to be close with respect to the operations of union, regular intersection, concatenation, infinite iteration, homomorphism, and inverse homomorphism. It follows from here that this class is a full abstract family of languages [7] with all the properties following from this. Furthermore, the ACML is close with respect to intersection and substitution but is not closed with respect to complement and reverse. For the ACML class, the problems of emptiness and recognition of words of a language given by an automaton counter machine are decidable, but the problems of inclusion and equivalence of languages are undecidable. A comparison with other classes of languages (regular, context-free, context-sensitive, and Petri-net languages) is performed.     

Ab initio LCAO study of the atomic,electronic and magnetic structures and the lattice dynamics of triclinic CuWO4

The electronic, structural and phonon properties of antiferromagnetic triclinic CuWO₄ have been studied using the first-principles spin-polarized linear combination of atomic orbital (LCAO) calculations based on the hybrid exchange–correlation density functional (DFT)/Hartree–Fock (HF) scheme. In addition, the local atomic structure around both Cu and W atoms has been probed using extended X-ray absorption fine structure (EXAFS) spectroscopy. We show that, by using the hybrid DFT–HF functional, one can accurately and simultaneously describe the atomic structure (the unit cell parameters and the atomic fractional coordinates), the band gap and the phonon frequencies. In agreement with our EXAFS results, the LCAO calculations reproduce a strong distortion of both the CuO₆ and the WO₆ octahedra, which occur due to the first-order and second-order Jahn–Teller effects, respectively. We found that the HF admixture of 13–16%, which is implemented in the PBE0–13% and WCGGA–PBE-16% functionals, produces the best result for CuWO₄. The calculated properties agree well with the available experimental data provided by diffraction, optical, X-ray photoelectron and Raman spectroscopies.     

Special features of strain aging of sheet automobile IFBH steel

Strain aging of commercial sheet automobile IF steels is investigated. The aging process is studied by measuring the dynamic modulus of elasticity, the amplitude-independent dislocation internal friction, the mechanical properties, and the microhardness. Analysis of the results obtained reveals the complex mechanism of strain aging of the steels. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 38–45, January, 2007.     

Decidability of boundedness problems for Minsky counter machines

The decidability of boundedness problems for Minksy counter machines is studied. It is proved that, for Minsky machines with two counters, the boundedness problem is partially decidable and the problem of the total boundedness is not even partially decidable. For one-counter Minsky machines, these problems are decidable during a time polynomially depending on the total number of local states of the counter machine.     

Integral Algorithms to Evaluate TiO2 and N-TiO2 Thin Films’ Cytocompatibility

Titanium oxide (TiO₂) and oxynitride (N-TiO₂) coatings can increase nitinol stents’ cytocompatibility with endothelial cells. Methods of TiO₂ and N-TiO₂ sputtering and cytocompatibility assessments vary significantly among different research groups, making it difficult to compare results. The aim of this work was to develop an integral cytocompatibility index (ICI) and a decision tree algorithm (DTA) using the “EA.hy926 cell/TiO₂ or N-TiO₂ coating” model and to determine the optimal cytocompatible coating. Magnetron sputtering was performed in a reaction gas medium with various N₂:O₂ ratios and bias voltages. The samples’ morphology was studied by scanning electron microscopy (SEM) and Raman spectroscopy. The cytocompatibility of the coatings was evaluated in terms of their cytotoxicity, adhesion, viability, and NO production. The ICI and DTA were developed to assess the cytocompatibility of the samples. Both algorithms demonstrated the best cytocompatibility for the sample sputtered at U_bias = 0 V and a gas ratio of N₂:O₂ = 2:1, in which the rutile phase dominated. The DTA provided more detailed information about the cytocompatibility, which depended on the sputtering mode, surface morphology, and crystalline phase. The proposed mathematical models relate the cytocompatibility and the studied physical characteristics.     

The output window of a large-area accelerator with an increased electron-beam current density

The results of theoretical and experimental investigations of a large-area accelerator with a new type of output window are presented. With this window, it is possible to increase the current density of the extracted electron beam, reduce the operating temperature of the foil, and extend its service life. A two-level support structure with cooling of each level is used for this purpose. The heat load of the foil mounted on the second level of the support structure that carries the main mechanical load is reduced by partial interception of the thermal power due to direct loss of the electron beam, which is released on the first level experiencing no mechanical load. The current loss at the structural elements of the output window is estimated, and the hydraulic characteristics and foil temperature in the output device are calculated. A higher current density of the beam extracted over the foil is attained in comparison with the conventional design of the support structure.     

Obtaining Solid Extractants Based on Mixtures of Tributylphosphate and Molecular Iodine and Researching the Extraction of Scandium from Chloride Solutions

Theoretical Foundations of Chemical Engineering - SOLEX, a solid extractant for extracting metal chlorides from solutions, has been obtained by impregnating tributyl phosphate (TBP) and iodine into...