Large Deployable Space Antennas Based on Usage of Polygonal Pantograph

This paper describes large space antenna projects based on application of a closed polygonal pantograph truss used for transforming, deploying, and prestressing the reflector structure. Their reflecting surfaces represent a flexible mesh fabric. Two means of maintaining the surface are discussed herein. The first technique is associated with employment of forces of the gravity field gradient. The second is based on the use of a flexible carcass prestressed by internal forces applied to the pantograph. Reflectors of the second kind have a rather complicated mechanical structure depending on the way of their attachment to a carrier. Provisions are made for supporting the reflector by an articulated arm linked with its central interface and through the use of tube beams, supporting the reflector periphery structures. During the design of the reflectors, special attention was paid to the problems of their structural simulations at the stages of their launching, deployment, and orbital motion. The deployable antennas considered can be enabling elements for many space missions ranging from communications to other satellite systems, including radar, remote sensing, interferometry, wireless power transmission, etc. They exhibit an enhanced stiffness of structure, required for the digit tele- and radio-communication and navigation, which makes it possible to diminish ray scattering, to raise the power of the accepted signals, and to prevent frequency losses.     

Hydraulic resistance of plane channels and annulus with different roughness on opposite walls

A new method for prediction of hydraulic resistance for a turbulent flow in plane channels and annulus is proposed. In spite of the importance of this issue, only very few publications devoted to the investigation into hydrodynamics in these channels are available, and there are no methods for predicting hydraulic resistance of a flow in these channels at all. The flow in channels with different roughness on the walls is described using the Prandtl semiempirical theory of a turbulent boundary layer. The flow in a channel cross-section is divided into two noninteracting layers of different thickness flowing along the walls with different roughness. The basic balance correlations are derived for a plane channel. To match the velocity profiles of both layers at the interface point, a logarithmic velocity profile is used. This yields a closed system of equations for predicting hydraulic resistance in plane channels with a given different roughness on opposite walls. It is demonstrated that the obtained correlation may be used for predicting hydraulic resistance in annulus as well. Experiments were carried out with a water flow in an annulus. Each annuli consisted of a pipe having a smooth wall into which a rod with artificial roughness on the surface was inserted coaxially. Two types of roughness were investigated: trapezoid and threadlike ones. Comparison of the predictions with the experimental data confirmed the validity of the proposed method. It can be used in designing flowpaths of various power installations.     

Determination of the Complex Permittivity of Materials by a Modified Resonator Method Based on the Theory of Small Perturbations Using a Resonator of the Reflective Type

Journal of Communications Technology and Electronics - A modified resonator method for determining the complex permittivity of materials based on the theory of small perturbations where a resonator...     

Aspects of Topological Superconductivity in 2D Systems: Noncollinear Magnetism,Skyrmions, and Higher-order Topology

Journal of Superconductivity and Novel Magnetism - The review is aimed at highlighting the aspects of topological superconductivity in the absence of spin–orbit interaction in two-dimensional...     

Oxidation of Np(IV) with hydrogen peroxide in carbonate solutions

Oxidation of Np(IV) with hydrogen peroxide in NaHCO₃-Na₂CO₃ solutions was studied by spectrophotometry. In NaHCO₃ solution, Np(IV) is oxidized to Np(V) and partially to Np(VI). It follows from the electronic absorption spectra that Np(IV) in 1 M Na₂CO₃ forms with H₂O₂ a mixed peroxide-carbonate complex. Its stability constant β is estimated at 25–30. The Np(IV) bound in the mixed complex disappears in a first-order reaction with respect to [Np(IV)]. The first-order rate constant k’ is proportional to [H₂O₂] in the H₂O₂ concentration range 2.5–11 mM, but further increase in [H₂O₂] leads to a decrease in k′. The bimolecular rate constant k = k′/[H₂O₂] in solutions containing up to 11 mM H₂O₂ increases in going from 1 M NaHCO₃ to 1 M Na₂CO₃ and significantly decreases with a further increase in the carbonate content. The activated complex is formed from Np(IV) peroxide-carbonate and carbonate complexes. Synchronous or successive electron transfer leads to the oxidation of Np(IV) to Np(V). Large excess of H₂O₂ oxidizes Np(V) to Np(VI), which is then slowly reduced. As a result, Np(V) is formed in carbonate solutions at any Np(IV) and H₂O₂ concentrations.     

Systems Analysis of the Efficiency of Imitation Processes of the Chemical Immobilization of Mercury in Waste Using Multivariant Visualization Tools

Theoretical Foundations of Chemical Engineering - A methodology has been proposed and multifactor experiments have been performed to determine the effectiveness of simulation processes of the...     

Radiation-Chemical Behavior of Plutonium in the Heterogeneous System PuO2-Ground Water

Radiation-chemical behavior of plutonium in the heterogeneous system PuO₂-ground water from the Red forest in the vicinity of Chernobyl NPP was studied. It was found that, in nonirradiated and irradiated ground water, Pu(IV) passes into the aqueous phase with subsequent transformation into Pu(V) and Pu(III). The degree of plutonium leaching is governed by the amount of organic substances, particularly fulvic and mellitic acids, in the ground water, and the degree of conversion of Pu(IV) to Pu(III) and Pu(V), by the ionizing radiation dose. The physicochemical and radiation-chemical behavior of plutonium in the systems was judged from the spectral characteristics of the irradiated and nonirradiated solutions.     

Heat treatment and durability of punching dies

Conclusion Quenching of 7KhG2VM dies in air from 860°C produces minimal distortion and substantially increases the durability.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 62–63, February, 1968.