3D SLAM from stereoimages

A method of visual navigation by stereoimages for autonomous underwater vehicles is suggested. Two modifications of the method are considered. The first one is based on integration of measurement data of onboard navigation system with visual data. The second modification relies on the use of a six-cloud computation scheme. Results of computational experiments with model data are presented.     

Oxygen transport in the system niobium-uranium dioxide

Luch Technological Society. Translated from Atomnaya Énergiya, Vol. 71, No. 1, pp. 62–64, July, 1991.     

Structure formation in the heat treatment of alloy steel bar

The structure formation in 42Cr4Mo2 electrosteel on continuous cooling is studied. The results are presented in the form of a thermokinetic diagram. It follows from the diagram that bainite structure is predominantly formed in thermochemical treatment with cooling of the rolled steel at a mean-mass rate of 0.4–1.0°C/s, while ferrite-pearlite structure is mainly formed at rates less than 0.4°C/s. The influence of the treatment temperature and time on the structure and properties of the chromomolybdenum steel is investigated. If the cooling rate after hot deformation is increased by a factor of 1.6, the proportion of bainite in the metal is greater. In subsequent annealing with isothermal holding at 650–680°C, the bainite accelerates the spheroidization of the carbides. Consequently, the holding time may be reduced from 6.5 to 4 h, with consequent energy savings but without loss of metal quality.     

Synthesis of ZnO-based nanostructures for heterostructure photovoltaic cells

A model describing heterostructure solar cells based on zinc and copper oxides is developed. Seed layers of ZnO and CuO are synthesized by spray pyrolysis. To form a bulk heterojunction, ZnO nanorods are grown by hydrothermal synthesis. The morphological, electricaland optical properties of the fabricated structures are investigated.     

Thermomechanical treatment of high-carbon wire rod in the 150 high-speed wire mill at Belorussian Metallurgical Plant

The introduction of a reduction and calibration unit at a wire mill is recommended for the production of high-carbon wire rod subjected to thermomechanical treatment with controlled rolling and cooling. By this means, the fluctuation in the mechanical properties may be reduced. In addition, the decarburized layer will be thinner and uniformly distributed over the perimeter of the wire rod. As a result, the plasticity of the wire rod in subsequent processing is improved, while the formation of quench structures at the wire surface in high-speed drawing is practically eliminated.     

Thermodynamics of chemisorption of sulfur from thiocyanate on nickel during electrochemical passivation

The effect of potassium thiocyanate content in an aqueous H₂SO₄ solution on the activation potential of a passive film formed on the nickel surface is studied. Based on the results, a thermodynamic model of chemisorption in electrochemical passivation of nickel in an aqueous H₂SO₄ solution containing surface-active KSCN thiocyanate additive is proposed. In the model, the formation of a NiO-NiS film is considered as a result of the equilibrium processes at the interfaces of the Ni|NiO-NiS|H₂O, SCN^? system. The total Gibbs energy of the chemisorptive phase formation of NiO-NiS solid solution is determined by partial chemisorptive formation energies of NiO and NiS. In turn, partial formation energy of either component is estimated as a sum of the Gibbs energy of the chemical formation of the component and the surface Gibbs energy of nickel, which depends on the KSCN concentration in the solution in the case of NiS formation. The system can be controlled due to the relation between the Gibbs energy and Flade electrode potential. As was experimentally found, the latter value determines the quantitative NiO: NiS ratio in the passive film.     

Nucleotide and actin binding properties of the isolated motor domain from Dictyostelium discoideum myosin

Nucleotide and actin binding properties of the truncated myosin head (S1dC) from Dictyostelium myosin II were studied in solution using rabbit skeletal myosin subfragment 1 as a reference material. S1dC and subfragment 1 had similar affinities for ADP analogues, epsilon ADP and TNP-ADP. The complexes of epsilon ADP and BeFx or AIF4- were less stable with S1dC than with subfragment 1. Stern-Volmer constants for acrylamide quenching of S1dC complexes with epsilon ADP, epsilon ADP.AIF4- and epsilon ADP.BeFx were 2.6, 2.9 and 2.2 M-1, respectively. The corresponding values for subfragment 1 were 2.6, 1.5 and 1.1 M-1. The environment of the nucleotide binding site was probed by using a hydrophobic fluorescent probe, PPBA. PPBA was a competitive inhibitor of S1dC Ca(2+)-ATPase (Ki = 1.6 microM). The binding of nucleotides to subfragment 1 enhanced PPBA fluorescence and caused blue shifts in the wavelength of its maximum emission in the order: ATP approximately ADP.AIF4- approximately ADP.BeFx > ATP gamma S > ADP > PPi. In the case of S1dC, the effects of different nucleotides were smaller and indistinguishable from each other. S1dC bound actin tighter than S1 (Kd = 7 nM and 60 nM, respectively). The actin activated MgATPase activity of S1dC varied between preparations, and the Vmax and K(m) values ranged between 3 and 7 s-1 and 60 and 190 microM, respectively. S1dC showed lower structural stability than S1 as revealed by their thermal inactivations at 35 degrees C. These results show that the nucleotide and actin binding of S1dC and subfragment 1 are similar but there are some differences in nucleotide and phosphate analogue-induced changes and the communication between the nucleotide and actin binding sites in these proteins.     

Tabular method of calculating the critical heat flux in water-cooled triangular rod assemblies

A new method of calculating the critical heat flux in fuel-rod assemblies is presented. The method is based on a generalization of the experimental data in tabular form. The table for the critical heat fluxes is constructed for the correct macrocells of triangular bundles with relative rod spacing s/d=1/4 and a 9.36 mm heat diameter of a microcell for the following conditions: no effect due to peripheral zones and unheated rods; turbulizing influence of the entrance conditions and spacers; and, the heating along the length and across assemblies is uniform. To use the table for other, quite wide regions of the determining parameters, relations are presented for calculating the effect of the important parameters: heating diameter, relative rod spacing in the assembly, distance to the entrance (heated length), turbulizing influence of the spacers, and others. 1 figure, 1 table, 9 references. State Science Center of the Russian Federation—A. I. Leipunskii Physics and Power-Engineering Institute. Translated from Atomnaya énergiya, Vol. 87, No. 1, pp. 17–24, July, 1991.